Soldering

Soldering Techniques

This article deals with soldering of lead came, copper foiled projects and zinc.   

Lead Came

Tools

A soldering iron of sufficient power and temperature is required – soldering tools. This will normally be a 100 watt rated iron with a 700F degree bolt (or soldering tip). An additional rheostat is not required or desirable.

Usually, 40/60 solder/tin alloy solder is appropriate for soldering lead, although 50/50 also works well. The differences in melted and solid states is given in the table here.

The lead needs to be clean and bright to start with. If it's fairly new lead it should be solder-able without more than a scrubbing of the joints with a brass wire brush. However, if the lead is dull and oxidized, you should scrape the lead in the area to be soldered with the blade of a lead knife or leading nail until the bright metal is revealed. This is required because the oxidised surface interferes with the adhesion of the solder to the metal.

The iron is held over-handed (as you would a tennis racquet) in order to get the handle low enough to have the tip flat on the lead. Allow the weight of the soldering iron to do the work for you. Let it rest briefly both edges of the joint and apply the solder at the front of the iron's bit. Take the solder away from the iron so it doesn't become attached to the joint. As soon as the solder spreads, lift the iron straight up.

Avoid "painting" or dragging the iron over the solder. The object is to have a shiny, smooth, slightly rounded solder joint. There should be no points sticking up from the solder joint. If a solder joint is not satisfactory you can reflux and re-heat. Don't apply too much solder. It's easier to add more solder than to remove excess.

The most common concern is whether there is enough solder on the joint. Very little solder is required to stick the joints together. Often a securely soldered joint will still show the ends of the cames. You can sweat a joint and get as good (and in some way a more lasting) joint as by having a bead. That is because by adding the minimum of solder (sweating) you will have to get the base metal hot for the thin layer of solder to flow. For cosmetic reasons it is usual to use enough solder to disguise the ends of the cames. It is not a structural requirement.

Copper Foil

I Tools and Materials

Iron

The iron temperature needs to be higher than for lead because so much more solder is being melted for the beads that are the feature of copper foiled projects. Temperature controlled irons have interchangeable bits with different temperatures indicated. An 800F rated tip (noted by the number 8 stamped on the base) is the most common tip used for running beads. For decorative work you may wish to use a 600F or a 700F tip to achieve effects requiring lower temperatures.

Tip size

Some people recommend a smaller tip size for copper foil work. This is done on the basis that the width of the solder bead is narrow and that with a smaller tip less of the heat will get to the glass. This is a common sense idea that is not borne out by the studies.

The glass will get hot under the solder whether a wide or narrow tip is used, because the solder needs a minimum temperature to melt.

The narrower the tip is the less heat it has stored, and so the soldering will be slower than with a wider tip. A 6 mm tip is tempting, but a 10 mm tip is better because the frequency of pausing for the temperature of the iron to catch up is reduced.

Since the solder has a surface tension, the bead will form appropriately whether a small or large tip is used. The bead can become too large if too much solder is applied, but that is not due to the size of the tip.

Solder

The solder used for copper foil is commonly a 60/40 tin/lead composition or even 63/37, as its melting and solid states are almost the same temperature. The table given in the section on soldering materials gives the melting and solidifying temperatures. 

II Techniques

Smooth solder joints

Good smooth soldering occurs when the temperature of the iron is correct for the job and the solder being used.

The problem of bunched up solder or peaks as you lift the iron from the solder is caused by the iron being slightly too cool for the job and the solder being used. Looking at the conditions causing the problems may lead to a better solution.

If the problem is caused by the iron being slightly too cool to let the solder flow properly, this can be caused by a number of things.

If your iron is too low power, you may start out well and have the problem develop as you solder.

If your iron is high enough power and you're using a 'rheostat' or dimmer controller, this has the effect of lowering the iron's power and the problem will occur as above.

50/50 (tin/lead) solder requires a hotter iron than 60/40 (tin/lead) solder to keep the molten metal flowing properly.


The best possible soldering iron controller is a genuine temperature controlled iron, where the iron’s controller maintains the tip temperature by applying full power to the heater when the tip cools slightly, but otherwise just 'idles'. If you can't get (or afford) one of these, possibly the best would be to get a higher power iron or throw away the 'rheostat' or dimmer 'controller'.


If the problem still occurs, then use 60/40 solder – which melts and solidifies in a narrower range than 50/50 - or perhaps do the soldering in shorter 'bursts', letting the iron recover for a half a minute before starting again.


In any case you need to match the speed of movement and the speed of feeding the solder to the iron according to the capability of the iron to adequately melt the solder.

Flux


Also you have to ensure that the foil has been properly fluxed. This is done by applying a thin film of flux. This is an area where little is good and a lot is bad. Over fluxed foil leads to a lot of sputtering as the excess flux boils and breaks through the hot solder.

Tinning

Tinning is the application of a film of solder over the fluxed foil. This helps protect the foil from oxidisation while working on the project. I fit and foil all the pieces for the project. Then I tin each piece separately on all edges. I re-assemble the project and add a very thin film of flux before tack soldering everything into place. Some people tin the whole project without taking any pieces out of the panel as I do. This seems to work well too.

The object of tinning is to make the running of the bead as simple and quick as possible, knowing that you will have made it easy for the solder to flow through to the other bead.

Soldering Techniques

My experience leads me to say that the tip of the iron should be in contact with the surface of the material being soldered. If the metal is not hot, it will not take the solder well. In the case of copper foil, the metal is so thin it will heat up almost instantaneously. The solder should be added to the heated metal to obtain a good joint. All the advice to hover just above the surface and allow the molten solder to heat the metal below seems to make for hard work suspending the iron, and for possible cold joints.

The principle is that both metals should be hot for a good join. In leaded work you can sweat a joint and get as good (and in some way a more lasting) joint as by having a bead. That is because by adding the minimum of solder (sweating) you will have to get the base metal hot for the thin layer of solder to flow. I feel that many people do not understand the principles of soldering, but look only to the finish. It is possible to have a beautiful joint, or bead and have the joining of the metals technically weak.

The strength of a copper foil panel comes from the glass of course, but also the formation of a “came” with a fin of solder connecting the top and bottom beads. This means the glass should be fitted together with a tiny gap between each piece. The Tiffany method allows for fine detail and yet at the same time it is imitating the creation of lead came. If you tightly pack the pieces together you are only soldering a bead top and bottom and no "heart" is created. By creating a bead on top and bottom it is possible to enclose flux within the panel.

It is important to reiterate that a bead is required on both sides of the panel for strength, even though the bottom may never be seen as on a lamp. It is only by having a top and bottom bead joined by a “heart” that you produce a strong panel.

Solder application

The solder is applied in one of two ways. The quickest method is to feed solder in on the thicker part of the shiny soldering iron tip and let it flow down to the foil. The iron is held against the foil and pulled along the foil (which has been fluxed) at the rate that allows the solder being fed to the iron to produce a slightly rounded, shiny solder bead. Don't try and "float" the iron on top of the solder, be gently resting against the foil. This requires practice to match the speed of movement and the amount of solder fed to the iron.

Alternatively, you can do the patting method. This is easier to control and is done by soldering one tip-length, lifting the iron and soldering the next tip-length, barely re-heating the section just soldered.

Another variation is to place blobs of solder at regular intervals along the foiled and fluxed joint and then move the iron along the joint melting the blobs as you go. This avoids the tide marks at the cooling ends of the solder bead.

Even Solder Beads on Edges

Running an even bead on the edges of copper foiled projects is often difficult, but several things can help.

Ensure the edges have been tinned all around. Add a thin film of flux to the tinned edges. Then hold the panel vertically and ensure the edge you are applying solder to is horizontal. This means that you have to keep moving anything that is not rectangular.

To apply solder and move the piece ideally needs three hands – one for the solder, one for the iron, and one to manipulate the piece. Failing such an evolutionary leap, you can use a small vice to continually alter the angle of the edge; you can get a friend or colleague to manipulate the panel; or you can place the solder so that you can pick up little drops of solder and place them on the edge. With practice, you can pick up some solder and transfer it to the edge before the previous dot of solder has cooled, so leaving a smooth bead by the joining of the dots.

Alternatively, you can place dots of solder near each other around the piece. You then come back and with one hand manipulating the piece the other can use the soldering iron to heat and join the dots.

You do have to be careful that you do not move the panel before the solder has hardened, or it will run down the newly created slope to the new horizontal edge.

I find that it is much more difficult to run a bead on an edge than it is to “pat” the solder dots. This patting motion allows the solder to join together, but does not heat such a long line that it flows as you turn the piece to keep the edge currently being soldered horizontal.

Building up the edge of sun catchers helps the foil from being ripped off accidentally, or just peeling back on its own from being damaged during the cleaning process. This edge soldering will also allow you to bury a length of fine wire around the outer edge of the sun catcher. This provides reinforcement, especially if the sun catcher has a design that has a part of it sticking out on its own, unsupported by the main body of the piece.

Tack Soldering

Tack soldering is the placing of a small amount of solder on the foil to hold two or more pieces together, so the main soldering can be performed without disturbing any placing of the remaining pieces. It is particularly important in 3D projects.

The advantage of tack soldering is it can allow you to completely eliminate framing if you are in a hurry. You can just hold two pieces together with one hand and spot a dab of solder to hold them together. You don't have to do this for all pieces - just enough of the outside pieces to hold the whole project together. Although it is more certain to have everything placed just as you want throughout the process by tack soldering the whole project. Once you've tack soldered, everything will be held in place and you can just run the beads without further considering the placing of the pieces.

For free form shapes, tack soldering the whole is always quicker. You may want to use nails or tacks to hold all the glass in place while you tack solder.

With big foil projects or ones that have to fit into a predetermined dimension, tack soldering ensures there is no growth through movement of the pieces.

It's also a quick way to avoid having to fiddle with each piece to make sure each is exactly lined up before starting with the running of the beads.

Soldering 3-D Pieces

When soldering 3-D pieces together, first tack the panels together with a single tack at each end. If it later turns out that there is an alignment problem, it is much easier to dis-assemble a few tacks, with a piece of paper or thin aluminium inserted into the space between the pieces of glass and moved up into the molten solder while your iron is at the tack joint. The paper will strong enough to move through the solder, separating the two piece of glass as will the metal.

Once your 3-D piece is tacked together, turn the piece over on its side, and, using 50/50 or 40/60 solder, fill in the inner seams, moving the piece around. Be careful to support the piece with boxes or blocks and by holding it at the top part above where you are soldering, to prevent the piece collapsing.

Once the inside of the piece, say a panel lamp, has been soldered smoothly with 50/50, turn the lamp over. Get a few boxes or similar supports to prop the lamp up against, and make it so that there will be a level solder seam. Using the 50/50 solder again, fill in the seam. It doesn't have to be perfect, at first. Do all of the seam filling first, to ensure the stability of the piece. Then go back with 60/40 solder and, again making sure the lamp seams are level, finish by smoothly soldering each seam. Both the solders have the same melting point, but because the 60/40 solder solidifies only one or two degrees below the melting point, there is not enough time and heat for the solder below to liquefy and drip, if your rate of soldering is sufficiently rapid.

Even Solder Beads

Getting even solder beads is a lot about where you look while you solder. Unlike drawing or cycling looking at where you are going is not so useful when soldering. You need to see the effects of what you are doing so looking behind the solder bit will help you understand what you are doing. If the bead begins to get small or narrow you either slow down the forward movement of the solder bit or add solder to it more quickly. If the bead begins to get too thick, you do the opposite. You can move the bit faster, or reduce the speed of feeding the solder to the bit.

Another element in getting an even bead is the heat being delivered. If you use a wide soldering bit you are delivering more heat to the joint. You hold the chisel bit so that it runs along the foil. The bigger the bit, the more heat is being held. And the more heat held in the bit, the more heat is applied to the soldering. Small bits are for getting into tight spots and for decorative soldering. Big wide bits of about 10 mm are best for running beads.

Moving Pieces

To keep pieces from moving about as you solder them, use pins or nails to keep them in place. The best is to assemble the whole panel and then keep them in place with a frame or lots of nails/pins around the outside. This keeps pieces from moving and also keeps the panel to the original size.

The type of nail or pin will depend on the work board you are using. Softer boards allow push pins of various sorts to be used. Harder boards will need nails.

If you don’t like assembling the whole before soldering, you can confine the pieces you are currently soldering with nails/pins in the same fashion as for the whole panel.

It also helps to do a little tack soldering before the process of running a bead begins. A small amount of solder on the copper foil where pieces join will keep the pieces in exact alignment while you are running a bead.

It must be emphasised that assembling the whole and tack soldering the pieces produces the best result in terms of having all the pieces aligned correctly throughout the panel.

III Special Conditions

Soldering small pieces

No-foil approach

One approach is to have some of the pieces held by over-beaded solder without foil, but it is patchy at best and likely to lose pieces in the long term.

Bevel approach


The best approach is to partially 'bevel' the edges of each piece on both faces. Grind at 45 degrees until the very edge is only 1 mm thick. Then use foil that is 4 mm wide for 3mm thick glass. For 4 mm glass, you will use 5.4 mm foil. Make sure that the foil covers only the bevelled edges and does not extend outside them by trimming if necessary.

You solder into the 'V' formed by the bevelled edges. Don't over- fill the joints as you don't want solder outside the 'V'. It also is best if the panel is supported underneath the area being soldered.

With the solder contained by the 'V', the solder lines will be of constant width throughout the entire panel. It is best to practise this technique on some scraps before you start the main job.

This approach will minimise the amount of light blocked by the foil - important with tiny pieces - while still providing the strength of fully foiled pieces.

Trimming approach

If you have to have really small pieces, just foil them as you would any other piece, and burnish it as normal. Then take a very sharp craft knife and trim the foil so that just a little tiny bit of foil is on the front and back of the piece.

No glass approach

Tiny pieces are really tedious to work with. So if the piece is going to be black or really dark, for example, a small hummingbird's beak, or a bird’s eye, don't bother with glass but just fill the space with foil and solder.

Tinning Brass

Brass transmits heat much more quickly than lead, so a considerable length or the whole of the piece, e.g., a vase cap needs to be heated to avoid the cap acting as a heat sink and so not allowing even tinning of the object.

When tinning any brass pieces, like a lamp cap, rub it with fine grade steel wool, wash the residue off and dry. Then apply flux with a fresh flux brush, and hold the piece with a pair of pliers.

At this point you can heat the vase cap with a low heat blow torch to warm the whole piece. When warm, turn off the blow torch and begin applying the solder with the soldering iron.

Alternatively you can work without the blow torch. Apply a bit of solder to the tip of the iron. Touch the piece with your hot soldering iron, let the piece heat up a little, and then start moving the iron slowly and smoothly over where you have applied the flux.

When the whole piece has been covered, wash it, dry, and then inspect for any missed spots or unsightly solder blobs. Apply a little bit more flux and touch with your soldering iron. If you are doing a lot of this kind of work, an 800 degree iron tip will speed up your work.

Soldering Fragile Pieces of Glass

Heat transfers to the glass during soldering. Normally this does not produce any difficulties. However with slender pieces, deep curves, or band saw cuts, the heat generated by soldering can crack or break the glass. This means that you need to ensure that you do not linger for a long time on the solder beads along these kinds of pieces.

You can do several things:

• Solder roughly at first, and then continue soldering somewhere else on your piece, to let the heat of the solder dissipate before finishing soldering by filling the gaps in the bead. The glass does not need to be cold before coming back to solder. Glass breaks because it is hot in one place and not throughout the piece. So, soldering warm glass has less chance of breaking due to heat shock.

• Create the bead in a single relatively swift pass. It has to be slow enough to produce a bead, but not linger in any area. The bead should not be so large as to turn over on itself. It should produce a dome shaped bead and be similar to a quarter or at most a third of a circle.

• Build the bead up with a series of “pats” along the copper foil joint. This involves putting a dot of solder to the copper foil tape and resting long enough for the solder to spread to its natural dimensions, and then place another dot at the leading edge of the first and so on until you reach the end of the line. This provides a relatively cool method of soldering. Its disadvantage is that it leaves a number of “tide” marks at the cool end of the bead. These can be changed to a single tide mark by re-melting the solder at that end.

Soldering Radiating Lines

Some times no matter how you try to avoid it in the design, you end up with multiple solder lines joining at one point.

In copper foil work, I find it best to tin all the copper foil before assembly, as this means you can use a minimum of solder to solder the pieces to one another.

You will be left with less solder at the joint if you start from the joint and move away from it while soldering. This drags the solder into the bead line rather than letting the solder build up at the joint of the multiple lines and give a resulting high point resulting from the accumulation of solder there.

Soldering Zinc

Brass, copper and zinc are heat sinks. That is, the metal conducts the heat rapidly so more heat has to be applied than for lead and tin to keep the soldering site hot enough to accept the solder.

The important elements are:

Use a hot iron. If you use a rheostat, turn it up to full. If you can, change the tip/bit to one rated at 800F – it will have an “8” stamped on the end that goes into the barrel of the iron.

Ensure the joint is really clean. Zinc develops a film of oxidisation very quickly.

Apply the flux liberally at the soldering point to ensure the area is “wetted” and kept free of corrosion products.

Keep the iron in contact with the zinc came for a few seconds to heat the metal.

When the came is hot, apply the solder to the bit. Keep the bit on the metal until you see the solder begin to flow, then gently lift directly up. 


IV Problem Solving

Foil pulling away from the glass on perimeter

If this is happening to you, there are several things to remember.

Clean all the edges and surfaces just before foiling. This ensures there are no oils or oxidisation to interfere with the contact adhesive of the foil. Avoid hand creams just before foiling as this increases the amount of oils getting onto the glass.

Remember that lots of heat breaks down the adhesive. So do not remain in one place too long while soldering. However the adhesive is not the element that keeps the foil attached to the glass in the long term. Instead, think about whether the bead on the edge is thick enough to provide the rigidity required without relying on the adhesive of the foil. Also, does the bead curve around to the face of the panel?

Finally, think about whether an edging came would provide better support and finish to the piece.

Foil Lifting While Soldering

There are several possible reasons for this.

The main one is that the soldering is too slow. This causes the adhesive on the foil to fail before the solder has a chance to become rigid.

The foil may not have stuck to the glass firmly. Reasons for this are many, but some are:

• Dirty glass. Make sure the glass is washed and polished clean, especially if you have been grinding, when you need to get all the glass dust out of the pits on the edges.
• Oil from the cutter.
• Oils from your hands. The oils can be natural or from hand creams. If you have oily skin or need to use hand creams consider cotton gloves for use when handling the glass prior to and during foiling.
• Inadequate contact between the foil and the glass. This can be from both the above, but can also be that the foil was not pressed firmly to all the sides and edges of the glass pieces.

The foil adhesive may be inadequate through manufacture or age. If a test piece does not feel tacky to your finger tips, it is not going to stick to the glass very well.

Exposed Foil

After soldering, inspect the solder seams for small areas or strips of copper foil edges that aren't covered with solder.

If this exposed foil is where you want the solder bead to be, you need to clean the foil and re-apply solder. Usually scrubbing with “000” steel wool is sufficient. If, after scrubbing and applying flux, the solder still does not stick, you need to wash the piece and after drying, scrub the exposed foil, re-apply flux and solder again.

If the exposed foil is surplus or where you do not want any solder, take a craft knife, and carefully trim off the exposed foil.

Filling Gaps Between Glass Pieces

Gaps along the bead line

When you have a significant gap between pieces of foiled glass, fill the gap with small pieces of lead or copper foil tape that has the adhesive side folded together. These will have to be cut to a width of just less than 3mm to keep them from projecting above the surface of the glass. This material helps to fill the gap and reduce the amount of “melt through”. Put a bit of masking tape on the top surface of the gap and turn the panel over.

Solder the back first. You can do this with 50/50 or 40/60 solder as it does not change from solid to liquid and back so quickly as 60/40. However the masking tape will keep the solder from dripping through if you apply too much heat. When you have finished soldering the back, apply masking tape to the now filled gap and turn over.

When completing the soldering of the top, you will need to take care to avoid over-heating the solder filling the gap. Over heating will allow the solder to melt through the existing solder and flow along the back. Usually, an application of dots of solder next to each other avoids transmitting as much heat as running a bead will. When you have passed the gap area, you can continue running the bead in the normal way.


Gaps between pieces

When you have gaps between glass that cannot be cut or re-cut, such as between globs, fill the gap with a piece of lead or copper foil sheet cut to the size and shape of the gap. This is better than folded up pieces of lead or foil as it carries the solder over the gaps to the foiled pieces of glass. It allows for a smoother surface, and uses less solder.

Note:

Remember to avoid moving the panel for a while, as the large solder bead will require longer to become solid, whether along a bead or filling gaps.

Glass Breaking While Soldering

Some report breaking pieces of glass while soldering. This may happen more on pieces that have big differences in width or taper to thin points. What is happening is that the glass is being heated too much locally in relation to the rest of the piece.

The solution is to solder at a steady pace. This allows the solder to cool without transferring so much heat to the glass as to break it. Some recommend that you do not rest your soldering iron on the foil while soldering. However it is the solder which is the heat sink, so the effort of holding the iron above the foil is not really necessary if you move at a reasonable pace. This means that you do not stop with the iron on the seam. It is best to solder in one continuous movement along the seam, leaving an even bead behind.

Sometimes the bead is not even. This may be because of wider parts to the seam, or inadequate flux, or many other reasons. Do not try to repair this before going on to the rest of the seam as this builds up heat in the adjoining glass. Since glass cannot dissipate heat well, the glass breaks when the temperature differential between the hot and cold parts of the glass is too great. Instead, complete the soldering of the seam before coming back to it. This gives you time to decide why the bead is not as good as you want it to be. It also gives time for the heat to even out through the piece of glass.

As you become experienced you will find a pace that suits the kind of bead on the joint that you want to achieve. If the seam is too flat, slow your pace or increase the rate at which add the solder to the iron. If the seam has too big a bead, increase your pace or reduce the rate at which you feed the solder. It is also possible to consider other methods of soldering ad described earlier.

You also need consider the usual problems relating to cleanliness and insufficient flux as noted above. Sometimes the soldering iron is not hot enough, but you should notice this early as the solder will not be melting at its usual rate and will be grainy in appearance.

Foil not sticking on edge
The adhesive is an impact type that requires a smooth, clean and dry surface to stick well.  The foil sticks to cleanly broken edges better than to ground edges.  So ground edges need to be thoroughly cleaned before foiling.

The adhesive on copper foil tape is not a permanent one. It only sticks to the glass long enough to apply the solder to the foil. The heat of soldering often degrades the adhesive so much that it no longer sticks. What holds the solder down is the solder bead. So if the foil lifts, you probably do not have a full bead on the edge. Placing a bead on the edges of pieces is difficult but a method is given above in the section "even solder beads on edges”.

You can make the edge beading a bit easier by putting thin copper wire around the edge of the piece. This also strengthens the whole piece. It allows you to attach a hanger without risk of pulling the whole sun catcher apart. It also allows you to form a bead on the edge more easily.

The bead formed on the edge curves around to the front and back faces allowing the solder to hold the copper tape more firmly to the glass.

Bubbles in the bead

Bubbles appearing in the bead, or more dramatically, flux bursting through the molten solder is most often the consequence of applying too much flux. Flux should be only a thin film whether paste or liquid. To reduce this boiling effect, reduce the amount of flux used and make sure all the materials are clean and free of oxidisation.






Other articles in this series are:
Processes
Materials
Tools

Soldering

Soldering Tools

General


Historically soldering tips were copper, placed in braziers. One tip was used; when the heat had transferred from the tip to the solder (and depleted the heat reserve) it was placed back in the brazier of charcoal and the next tip was used.

Much later gas irons were in common use. These used a gas jet to heat the soldering bolt/tip. They are very fast, but require significant amounts of experience to properly regulate the temperature.

Currently, electric soldering irons are used; they consist of coil or ceramic heating elements, which retain heat differently, and warm up the mass differently, internal or external rheostats, and different power ratings - which change how long a bead can be run.

Soldering Irons

The iron used to solder must be of a high enough wattage to readily melt the solder and be able to reheat fast enough to maintain the necessary melting temperature. The tip can't be so small it can't maintain the heat nor so big it covers more area than wanted.

For example a 75 or 80 watt iron is sufficient to begin soldering with, but it will continue to get hotter, as it has no temperature control. An iron of this type should be used with a rheostat in order to prevent overheating while it is idling. You should be aware that even with a rheostat, it will eventually reach its maximum temperature, so cannot be left on for long. Also leaving an iron idling will contribute to the rapid deterioration of the tip.

Most temperature controlled irons seem to be produced in 100 watts or more. These internally temperature controlled irons maintain a constant temperature. These are normally supplied with a 700F° bit (number 7) and are sufficient to melt the solder without long recovery times. You can obtain bits of different temperature ratings, commonly 800F° and 600F°. You can also use several sizes of tips for different detail of work.

For soldering leaded panels a 100w iron with a 10 mm temperature controlled tip that maintains a constant 370°C (700° F) is suitable.

For copper foil a higher temperature controlled tip is used. This normally runs at 425°C (800°F). Sometimes a tip of 6 mm is used where more delicate beads are being run, but be aware that the tip will cool off much more quickly than 10 mm tips.

If a lot of soldering is required that has sustained heat requirements, you might consider a 200W iron. These can deliver heat more quickly and evenly than those with lesser wattage.

People often want to have variable temperatures for decorative soldering.

It is recommended to use a rheostat in circumstances where the soldering iron does not have an internal temperature control.

Action of a Rheostat

A rheostat is NOT a temperature controller.

A rheostat actually reduces the power supplied to the iron, thereby making it take longer to heat or re-heat after a period of soldering. With or without a rheostat, if an iron is left idle, it will eventually reach its maximum temperature. This is usually too hot for soldering lead, but OK for joining other metals. With a rheostat, if an iron is left idle with the rheostat set to (say) '6', it will still reach its maximum temperature but very much slower than the one without a rheostat.

Action of a Temperature Controlled Iron


Temperature controlled soldering irons attempt to maintain a set temperature. This is controlled by the combination of the microchip in the iron and the tip. So to adjust your temperatures all you need is a few different tips. For example, a number 7 tip lets your iron heat to 700F degrees. For decorative soldering your need tips of lower temperatures, usually a number 6 or 600F degree is enough of a reduction for most decorative stuff. A number 8 tip (800F) will let you work more quickly.

Differences in Soldering Speed


Using an iron without a rheostat, provided you work relatively quickly, you will probably be able to solder all the joints in a small or medium panel without stopping to let the iron 'catch up'. In this case the temperature is controlled by the heating power of the iron balanced by the cooling effect of making the soldered joints.

Using an iron with a rheostat, you will need to slow down a little if you are to do that same panel without stopping to let the iron re-heat. In this case the temperature of the iron is controlled by the (reduced) heating power of the iron balanced by the same cooling effect of making the soldered joints.

This difference is caused by the fact that a temperature-controlled iron, if it is left idle, it will quickly reach its maximum operating temperature - just as quickly as an uncontrolled iron of the same power. When you start soldering, the cooling effect will trigger the temperature controller to provide full power until the operating temperature is reached again.

Advantages of a Temperature Controlled Iron

You can buy an iron (not temperature controlled) and a rheostat but buying tips for the temperature controlled iron is cheaper. The big advantage of the temperature-controlled iron is that you know it will never get too hot for the work you are doing, and that it truly provides that 100 watts (or whatever) power to keep it hot even when you are soldering at top speed.

Soldering Bit Composition

Most bits are made of copper, which is suitable because of its excellent thermal conductivity and high heat content per volume. Some bits are plain copper, while others incorporate various additives or have a protective plating applied.

One of the most common problems associated with plain copper bits, is that tin-lead alloys (more specifically the tin in the alloy) will attack the copper, dissolving it away. This makes it necessary to continually file the bits to maintain the required shape, giving these bits a shortened working life. Another concern is the amount of impurity that is imparted to the solder joint when using bare copper bits.

Adding tellurium to the copper improves both wear and oxidation resistance, but does not protect the tip from rapid deterioration. It has been determined that both iron and nickel, despite their low conductivity, are wet-able, offer a high level of resistance to erosion and their heat per volume is close to that of copper.

Because of these facts it is possible to maintain good conductivity, while increasing the erosion resistance by plating copper bits with either nickel or iron. These plated bits are generally referred to as nickel-clad, or iron-clad and make up a large majority of the bits in use for modern soldering applications.

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Soldering Bits

Type

The bit type is determined by the soldering iron it is used on. There are screw type bits (bits that screw onto, or into the solder iron element), slip on bits that slip over the element and plug type bits that slide inside of the element. There are even bits that are a permanent part of a replaceable element/bit assembly. Regardless of the type of bits required it is always important to have them fully seated to the element and periodically cleaned, in order to maintain proper heat transfer from the element into the bit.

Configuration


The bit configuration to use should be determined by the intended application requirements. Some of the basic bit configurations available include ballpoint, conical, diamond (pyramid), chisel, and spade. You will find that there are usually a variety of styles, or modifications available, within each of these basic configuration families, to accommodate specific application requirements. Although less efficient, a more narrow configuration is sometimes required to obtain accessibility, or to achieve the desired results.

Size


The bit size to use (regarding the working portion) should also be determined by the intended application requirements. The bit body, or shank must be matched to the iron it will be used with (always select a bit that was designed, or approved for the soldering iron you intend to use on the application being considered). As with bit configuration though, there are usually a variety of modified working diameters available within each family of standard bit sizes that are available. These modified bits are generally referred to as turned down bits, because the working area of the bit has been turned down to a smaller diameter than the body, or shank diameter. Turned down bits are not as efficient, but are sometimes required to solder in otherwise inaccessible areas.

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Choosing the Soldering Bit

An important consideration, when choosing the most appropriate bit, is that thick, short bits will store more heat and deliver it more efficiently than long, narrow ones. This makes the standard chisel configuration the usual bit of choice. The chisel shaped bit is often used for joining flat seems together. The working edge of the chisel bit should be about the same width as (or slightly wider than) the seam that is being soldered.

Usually a solder connection is made in one to three seconds. If the connection takes longer than three seconds, you may need a larger bit, a higher wattage iron or a completely different type of soldering equipment altogether. It is a good idea to familiarize yourself with other soldering methods and equipment that are available in order to ensure that you are utilizing the best, safest, most efficient and economical means available to perform your soldering application.

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Soldering Bit Maintenance

If a bit has not been properly tinned, solder will not wet to it. Without solder on the bit heat transfer from the bit to the work surface may become extremely difficult and time consuming, or even impossible.

You must understand that proper wiping and continuous wetting is important and a lot easier than continually having to clean and re-tin the bit, especially at the risk of damage to the plated surface because of accidentally scratching, or over abrading it. [Many soldering stations come with a sponge which, when wet, is used to wipe the iron's tip clean. A small amount of fresh solder is usually then applied to the clean tip in a process called tinning.]

When you notice that an iron is not performing as well as it did when it was new you will find that poor thermal transfer from the element to the work is usually the cause. Improper care and maintenance and the lack of a periodic cleaning of the bit's shank can cause a layer of oxides, which will inhibit the transfer of heat through the bit. Always ensure plug style bits are properly seated into the elements before heating the iron. If a bit is not inserted fully into the element there may be a gap behind the bit. This gap can cause a hot spot within the element causing a premature failure of the soldering iron.

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To avoid using abrasives, cleaning with sal ammoniac is recommended. This comes in a block. You rub the soldering iron bit on the surface. As the surface becomes hot, it begins the cleaning process, noted by the smoke rising from the block. When the block under the bit becomes clear, the bit will be clean and can be tinned as above. If this is done at the end of each session of soldering, the bit will last and will be ready for soldering immediately when you next need to use it.

Tinning

Introduction

Proper care and maintenance of your soldering iron bit involves tinning, wiping (and wetting) and also periodic cleaning of the bits shank. These actions are very important and quite simple to perform, but are often neglected. When performed properly they will not only ensure the longest possible working life for your soldering iron bits, but they will also have positive effects on the overall performance of your soldering iron.

Tinning


Tinning may not be necessary if the bit you are using is new and arrives pre-tinned from the manufacturer, or has been used previously and been properly maintained. When a bit does need to be tinned (or re-tinned) it must be clean and free of any surface oxidation before it will accept any solder. Once the bit is properly tinned, care should be taken to prevent bit de-wetting by occasionally cleaning and adding small amounts of fresh solder, especially if the bit is being subjected to long periods of inactivity or idling.

If the bit to be tinned is unplated copper it should be cleaned and dressed with a single cut, flat file. After filing the bit it should be heated in the iron. When the bit reaches the lowest temperature required to melt solder, a rosin core solder should be fed onto the bit. Do not allow the iron temperature to rise too high before applying the solder, because excess heat will cause the bit surface to re-oxidize and no longer accept the solder.

If the bit is plated it should never be filed, or heavily abraded. Care should be taken to ensure the plating is not damaged or removed, as this will shorten the working life of the bit dramatically. When pre-cleaning is necessary for plated bits, they should be cleaned with a mildly abrasive emery cloth and may require an acid flux to remove the oxides before tinning, or re-tinning.

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Wiping the Bit

During use a bright, thin, but evenly tinned surface must be maintained on the working portion of the bit. Oxidation and contaminants must be continually removed from the bit surface to achieve maximum performance. This will help to ensure the proper transfer of heat from bit to work and will eliminate the possibility of impurities being transferred into the solder joint.

Between each solder application simply wipe the working area of the bit clean on a damp cellulose sponge to remove the dross and oxides that will accumulate and add small amounts of fresh solder to the bit as needed. A gentle wiping is all that is required and care must be taken not to over wipe the bit, because oxidation will occur on the surface quite rapidly if all of the solder has been removed. Once this oxidation occurs it becomes difficult, or even impossible for solder to wet to the bit. It then becomes necessary to properly clean and re-tin the bit in order to regain the appropriate wetting action required for adequate performance. When you have finished the soldering application, you should wipe any contaminates from the bit's surface and add a small amount of fresh solder to it before allowing the iron to cool. This layer of solder ensures protection from oxidation of the bit between uses and will help to extend the bit's working life.

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Cleaning

It is important to periodically clean the shank of the plug style bits as well as the inner surface of the element. This is done to keep the bit from seizing in the element and also to keep from building a layer of oxides and contaminates that would obstruct the transfer of heat from the element to the bit. After allowing the iron to completely cool the bit should be removed and the bit shank and inner walls of the element should be wiped clean with a mildly abrasive emery cloth or soft wire brush. This cleaning process should be done as often as needed, depending on the work environment, but not less than once a week.

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Care in the operation of irons

The most important element in the deterioration of soldering iron bits is long idle times. This is where you leave the iron on, and not in use, for a long time.

Have everything ready when you start soldering, so the iron will be used continuously, and will not sit there building up heat, while you get ready to use it again. An idle iron will keep heating to its maximum capacity, and without anything to transfer the heat to, it will start burning off the tinning, after a short while. So if you will not be using the iron for a while turn it off until you are ready again.

The other elements leading to deterioration in performance come from lack of cleaning and tinning of the tip. When the coating of solder burns off or is coated with carbon you get poor heat transfer from tip to working surface making it appear that the iron is not heating properly.

Soldering Ingredients and Methods

The soldering process may be accomplished in a wide variety of ways, but the four primary ingredients required will remain the same. They are; the base metal (or metal items being joined) a type of flux (or a method of cleaning and maintaining the surface to be soldered), the solder and a source of heat. It is important to match the soldering method and the equipment that will be used, to the soldering application that is being considered.

Base Metal


The base metal is the metal that is in contact with the solder and forms an intermediate alloy. There are many metals that will react willingly with solders to form a strong chemical and physical bond, while others can be very difficult, or even impossible to solder.

Flux

Flux is used to eliminate minor surface oxidation and to prevent further oxidation of the base metals surface during the heating process. Although there are many types of flux, each will include two basic parts, chemicals and solvents. The chemical includes the active portion, while the solvent is actually the carrying agent. It is the solvent that determines the cleaning method required to remove the remaining residue after soldering.

Solder

Solder is the alloy used to create the solvent action, which generates the bond between the base metals. The type and form of the solder is very important and must be determined by the individual application being performed, as well as the base metals and soldering method being employed.

Methods

There are several methods, as well as a wide variety of tools available to perform the task of soldering. Some of the current methods that are available include induction, conduction, ultrasonic, flame, dipping, resistance, oven and wave soldering. Some of these methods involve the use of small inexpensive hand tools, while others may require large and expensive machinery, equipment and tools. It is a good idea to become educated on the various methods and tools that are available, in order to insure that you are utilizing the best, safest, most efficient and economical means available for your specific soldering application.

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Soldering

Soldering Materials

Solder

Solder Alloys

There are a wide variety of solder alloys for varying uses as shown by this table below, which also gives the solidification and liquifaction points together with their uses.

Ag = Silver

Cd = Cadmium

Cu =Copper

PB = Lead

Sn = Tin

Sb = Antimony

2%Sn/2%Sb/96%Pb Solidus 305°C Liquidus 315 °C Uses: High Temperature, High Creep Strength

5%Sn/93.5%Sb/1.5%Pb Solidus 296 °C Liquidus 301°C Uses: High Melting Point

95/5%Sn/4.5%Pb Solidus 236°C Liquidus 243°C Uses: High Melting Point

100%Sn Solidus 232°C Liquidus 232°C Uses: Lead Free

15%Sn/85%Pb Solidus 225°C Liquidus 290°C Uses: Lamps

96% Sn/4%Ag Solidus 221°C Liquidus 221°C Uses: Stainless Steel, Bright, Strong Non Toxic

20%Sn/80%Pb Solidus 183°C Liquidus 275°C Uses: Lamps

30%Sn/70%Pb Solidus 183°C Liquidus 255°C Uses: Lamps, Motors

31.2%Sn/67Pb/1.8%Sb Solidus 185°C Liquidus 243°C Uses: Radiators, General Purpose Non Electrical

40%Sn/60%Pb Solidus 183°C Liquidus 234°C Uses: General Purpose

45%Sn/55%/Pb Solidus 183°C Liquidus 224°C General Purpose

50%Sn/48.5%Pb/1.5%Cu Solidus 183°C Liquidus 215°C Uses: Saves Copper Erosion

50%Sn/49.7%Pb/0.3%Sb Solidus 183°C Liquidus 212°C Uses: General Purpose

50%Sn/50%Pb Solidus 183°C Liquidus 212°C Uses: General Purpose

60%Sn/39.7%Pb/0.3%Sb Solidus 183°C Liquidus 188°C Uses: General Purpose

60%Sn/40%Pb Solidus 183°C Liquidus 188°C Uses: Electrical

63%Sn/36.7%Pb/0.3%Sb Solidus 183°C Liquidus 183°C Uses: Electrical

62%Sn/35.7%Pb/2%Sb/0.3%Ag Solidus 179°C Liquidus 179°C Uses: Silver - Plated Surfaces

62%Sn/36%Pb/2%Ag Solidus 179°C Liquidus 179°C Uses: Silver - Plated Surfaces

18%Sn/80.1%Pb/1.9%Ag Solidus 178°C Liquidus 270°C Uses: Aluminium

50%Sn/32%Pb/18%Cd Solidus 145°C Liquidus 145°C Uses: Low melting point, Soldering on Gold

70%Sn/30%Zn Solidus 196°C Liquidus 307°C Uses: Spray Wire for Metal Film capacitors

80%Sn/20%Zn Solidus 196°C Liquidus 268°C Uses: Spray Wire for Metal Film capacitors

30%Sn/70%Cd Solidus 176°C Liquidus 240°C Uses: Low Thermal EMF Solder

Common Solder Compositions for Stained Glass

The table above shows what a large variety of compositions there are for various soldering purposes.

The common solders for stained glass are mixtures of tin and lead, respectively:

63/37: melts at 183°C (362°F)

60/40: melts between 183°C (362°F) and 188°C (376°F)

50/50: melts between 183°C (362°F) and 212°C (421°F)

40/60: melts between 183°C (362°F) and 234°C (454°F)

lead-free solder (useful in jewellery, eating containers, and other environmental uses): melts between 118°C (245°F) and 220°C (428°F), depending on composition.

The 63/37 and 60/40 solders are most often used in copper foil work because of their narrower melting range. This allows the solder to set more quickly than the solders with higher lead content. They tend to give smoother beads also.

 50/50 and 40/60 solders are more often used in leaded panel work. Their wider range of melting temperatures allows the solder to spread and become flat.

Hard Solder

As used for brazing, hard solder is generally a copper/zinc or copper/silver alloy, and melts at higher temperatures than tin/lead compositions.

In silversmithing or jewellery making, special hard solders are used that will pass assay. They contain a high proportion of the metal being soldered and lead is not used in these alloys. These solders also come in a variety of hardnesses, known as 'enamelling', 'hard', 'medium' and 'easy'. Enamelling solder has a high melting point, close to that of the material itself, to prevent the joint de-soldering during firing in the enamelling process. The remaining solder types are used in decreasing order of hardness during the process of making an item, to prevent a previously soldered seam or joint de-soldering while soldering a new joint. Easy solder is also often used for repair work for the same reason. Flux or rouge is also used to prevent joints de-soldering

Flux Core Solder

A tube of multi-core electronics solder is used for manual soldering in the electronics industry - the flux is contained in cores within the solder itself.

Solder often comes pre-mixed with, or is used with, flux, a reducing agent designed to help remove impurities (specifically oxidised metals) from the points of contact to improve the electrical connection. For convenience, solder is often manufactured as a hollow tube and filled with flux. Most cold solder is soft enough to be rolled and packaged as a coil, making for a convenient and compact solder/flux package.

The two principal types of flux are acid flux, used for metal mending; and rosin flux, used in electronics, where the corrosiveness of the vapours that arise when acid flux is heated could damage components. Due to concerns over atmospheric pollution and hazardous waste disposal, the electronics industry has been gradually shifting from rosin flux to water-soluble flux, which can be removed with de-ionised water and detergent, instead of hydrocarbon solvents.

Lead-Free Solder

Most of the advice in the stained glass community about lead free solder is to avoid using it. However, lead-free solder is essential for making jewellery (which may have skin contact) or any project that may be in contact with food.

Lead-free solder does require a hotter iron than lead bearing solders, plus it does not flow easily. It has a pasty state between solid and liquid that is prone to lumps and spikes. If this is not bad enough, it also does not take patina designed for lead bearing solders well.

Those using rheostats with their soldering irons, should get rid of the rheostat, as they limit the ability of the iron to recover the soldering temperature. The best iron to use with lead free solders is a temperature controlled iron of 100W or 200W. You can get tips that run at 800F to replace the standard 700F tips. This helps with the higher temperatures needed for the lead free solder. But you should not be vaporizing the solder as the fumes are a health hazard.

Consider the effects of the flux that you are using. Experimenting with various kinds (see below) can lead you to one that works better than the others.

As always, good hygiene and good ventilation are required when soldering. Also you should wash your hands well and frequently, and eat in a separate room.

Flux

An Introduction

Flux is a key contributor to most soldering applications. It is a compound that is used to lift tarnish films from a metal's surface, keep the surface clean during the soldering process, and aid in the wetting and spreading action of the solder. There are many different types and brands of flux available on the market; check with the manufacturer or reseller of your flux to ensure that it is appropriate for your application, taking into consideration both the solder being used and the two metals involved in the process. Although there are many types of flux available, each will include two basic parts, chemicals and solvents.

The chemical part includes the active portion, while the solvent is the carrying agent. The flux does not become a part of the soldered joint, but retains the captured oxides and lies inert on the joint's finished surface until properly removed. It is usually the solvent that determines the cleaning method required to remove the remaining residue after the soldering is completed. It should be noted that while flux is used to remove the tarnish film from a metal's surface, it will not (and should not be expected to) remove paint, grease, varnish, dirt or other types of inert matter. A thorough cleaning of the metal's surface is necessary to remove these types of contaminates. This will greatly improve the fluxing efficiency and also aid in the soldering methods and techniques being used.

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The Action of Fluxes

All common untreated metals and metal alloys (including solders) are subject to an environmental attack in which their bare surfaces become covered with a non-metallic film, commonly referred to as tarnish. This tarnish layer consists of oxides, sulphides, carbonates, or other corrosion products and is an effective insulating barrier that will prevent any direct contact with the clean metal surface which lies beneath. When metal parts are joined together by soldering, a metallic continuity is established as a result of the interface between the solder and the surfaces of the two metals. As long as the tarnish layer remains, the solder and metal interface cannot take place, because without being able to make direct contact it is impossible to effectively wet the metal's surface with solder.

The surface tarnishes that form on metal are generally not soluble in - and cannot be removed by - most conventional cleaning solvents. They must, therefore be acted upon chemically, or mechanically, in order to be removed. The required chemical reaction is most often accomplished by the use of soldering fluxes. These soldering fluxes will displace the atmospheric gas layer on the metal’s surface and upon heating will chemically react to remove the tarnish layer from the fluxed metals and maintain the clean metal surface throughout the soldering process.

Chemical reactions


The chemical reaction that is required to remove the tarnish layer will usually be one of two basic types.

It can be a reaction where the tarnish and flux combine forming a third compound that is soluble in either the flux or its carrier.

An example of this type of reaction takes place between water-white rosin and copper oxides. Water-white rosin, when used as a flux is usually in an isopropyl alcohol carrier and consists mainly of abietic acid and other isomeric diterpene acids that are soluble in several organic solvents. When applied to an oxidized copper surface and heated, the copper oxides will combine with the abietic acid forming a copper abiet (which mixes easily with the un-reacted rosin) leaving a clean metallic surface for solder wetting. The hot molten solder displaces the rosin flux and the copper abiet, which can then be removed by conventional cleaning methods.

Another type of reaction is one that causes the tarnish film, or oxidized layer to return to its original metallic state restoring the metals clean surface.

An example of this type of reaction takes place when soldering under a blanket of heated hydrogen. At elevated temperatures (the temperature that is required for the intended reaction to take place is unique to each type of base metal) the hydrogen removes the oxides from the surface, forming water and restoring the metallic surface, which the solder will then wet. There are several other variations and combinations that are based on these two types of reactions.

Flux as a temporary protective coating

Once the desired chemical reaction has taken place (lifting or dissolving the tarnish layer) the fluxing agent must provide a protective coating on the cleaned metal surface until it is displaced by the molten solder. This is due to the elevated temperatures required for soldering causing the increased likelihood that the metal’s surface may rapidly re-oxidize if not properly coated. Any compound that can be used to create one of the required types of chemical reactions, under the operating conditions necessary for soldering, might be considered for use as a fluxing material. However, most organic and inorganic compounds will not hold up under the high temperature conditions that are required for proper soldering. That is why one of the more important considerations is a compounds thermal stability, or its ability to withstand the high temperatures that are required for soldering without burning, breaking down, or evaporating.

When evaluating all of the requirements necessary for a compound to be considered as a fluxing agent, it is important to consider the various soldering methods, techniques and processes available and the wide range of materials and temperatures they may require. A certain flux may perform well on a specific surface using one method of soldering and yet not be at all suitable for that same surface using a different soldering method. When in doubt it never hurts to check with the flux, or solder manufacturer for recommendations.

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Flux Categories

A. Rosin Fluxes

Rosin based fluxes are made from rosin which is extracted from pine sap. The purified product is known as "Water White Rosin". The active ingredient is an organic acid, abietic acid and may contain homologues such as dehydro abietic acid and leviopmaric acid.

In addition to rosin other activators may be present at different levels to increase the ability to clean and de oxidise. Activators are compounds that decompose at soldering temperatures yielding ammonia or hydrochloric acid in the process. Flux activity is categorised as R (rosin only), RMA (rosin mildly activated) and RA (rosin activated). A low boiling solvent such as isopropanol is used as the vehicle so they are flammable.

Type R containing only rosin is the least active and is recommended for surfaces very clean to start with. It leaves virtually no residue behind. Thus this is the best rosin based flux for copper foil and lead cames.

Type RMA contains a small amount of additional activator to enhance cleaning and de-oxidisation leaving only a minimum amount of inert residue behind. A characteristic of RMA fluxes is that the remaining residue be non-corrosive, tack free, and exhibit a high degree of freedom from ionic contamination after cleaning. These fluxes are acceptable, but more difficult to clean. They are not acceptable for conservation work.

Type RA are most active of the rosin fluxes, and leave the most residue, however the residues can be removed with appropriate flux cleaners. The residues are really difficult to remove in decorative glass work circumstances and should not be used.

B. Water Soluble Fluxes

These are called water-soluble, as the residue left after soldering is water soluble, although the flux is not. The so-called water-soluble fluxes are divided into two categories, organic and inorganic based on composition. Organic fluxes are more active than RA rosin, and inorganic are the most active of all. Both of these are the best of all fluxes to use in decorative glass work, as the residues are water soluble making clean-up easier, and they are more effective in wetting and keeping the copper and lead free from oxidisation at soldering temperatures.

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Soldering Techniques

Soldering Techniques 

Soldering - how it works

Soldering is a well known and widely used process where two or more metal items are joined together using a fusible alloy with a melting temperature that is lower than their own. The most commonly used solder is a fusible alloy consisting essentially of a tin and lead mixture.

The solder actually dissolves a small amount of the metal’s surface, at a temperature that is well below its melting point and joins with it. It is this solvent action of the solder alloy that causes it to fuse with and attach to the surface of the metal items being joined.

The solvent action that takes place, between the solder and the metal, makes the joint chemical (not just physical) in nature and causes the properties of the joint to differ from the original solder’s properties and from those of the surface of the metal items being joined. When metal parts are joined by solder, a metallic continuity is established as a result of the interfaces where the solder is bonded to the metallic surfaces.

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Soldering vs. Welding

The metal joining process that is generally referred to as soldering (or soft soldering) requires temperatures between 183 to 445°C. The joining of metals at temperatures above 445°C (and below the melting point of the metals being joined) is more commonly referred to as brazing (or hard soldering). The actual melting and fusing of the metal items that are being joined together is considered welding. There are, of course overlapping situations that may occur when classifying a process.

The actual joining characteristics that take place are physically different in each of these processes. Soft solders attach to metals by what is referred to as a solvent action that takes place at relatively low temperatures. Hard solders, or brazing alloys contain metals that require higher temperatures to cause the solvent action to take place and fuse the alloy with the metal being joined. Because welding involves actually melting and fusing the surface of the metals that are being joined together, a filler, or fusible material is not always used.

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Creating a Quality Solder Joint

Soldering is the process that uses solder (a metal alloy usually consisting of tin mixed with other metals) for the metallurgical joining of metal components to form an electrical, mechanical or hermetically sealed bond at temperatures (less than 449°C) that are well below the melting temperature of the individual components that are being joined. The soldering equipment used to create the required heat and other materials (solder, fluxes, heat sinks, fixtures, etc.) should always be properly matched to the intended soldering application. The equipment and materials used may vary, but the basic soldering techniques that are required will usually remain the same.

One of the most important rules to remember about soldering is "keep it clean". This includes, not only the items being soldered, but also the materials used. Choose quality solders and fluxes without unnecessary impurities. Surface oxidation, contaminants and other impurities are some of the most common reasons for poor quality solder joints. The use of fluxes does not eliminate the need for pre-cleaning the surfaces you are joining, especially if heavy oxidation or large amounts of grease, oil or dirt are present. The stages of soldering are:

Clean: Thoroughly clean all surfaces to be joined, removing any dirt, grease, oil, oxidation, paint, coatings or other impurities that may exist before attempting to solder. Proper wetting can only occur when the intended solder joint area has been properly cleaned. Soldering should be performed as soon as possible after cleaning to eliminate the possibility of re oxidation or contamination of the items being soldered. [So leaving pieces fluxed overnight is not good practice. Flux only the area that can be soldered in the next few minutes.]

Flux: Apply flux sparingly to each of the intended joint surfaces. Flux is primarily used for the removal of light oxidation and to protect against re-oxidation during the actual soldering process. Make sure you have the right flux for the application being performed.

Heat: Apply heat directly to the intended joint area. The correct application of heat is important and should be consistent with the operating requirements determined by the type of equipment being used. Fast and accurate heating will minimize the risk of thermal damage.

Solder: Add solder to the heated surfaces you are joining (do not apply solder directly to the tip, or other heat source being used). The solder should flow uniformly over all of the surfaces that are being connected. Stop feeding solder as soon as you have applied an adequate amount and then remove the heat source. The amount of solder is important because too much will create unnecessary waste, while too little can affect the mechanical strength and conductivity of the finished solder joint.

Cool: Allow the finished solder joint to remain undisturbed until it has completely cooled. You should never attempt to speed up the cooling process by blowing on the solder joint. Even minor vibrations or disturbances during cooling, can cause micro fractures or other types of damage that may severely weaken the solder joint.

Inspect: Check all finished joints for proper wetting, the right amount of solder, a good physical appearance, and the required mechanical strength.

Skills


A quality solder joint is not achieved solely by the equipment and techniques being used, but also by the operator being trained to use them properly. An operator should know how the physical appearance of a finished solder joint helps to determine possible flaws that may exist.

A quality solder joint appears bright, shiny and smooth with all components appearing well soldered. The surface of a finished joint should never look rough, grainy, dull, or flaky (these are signs of what is commonly referred to as a cold solder joint). Problems with proper wetting (solder balling up and not adhering to the components surface) are sometimes associated with too much heat, but are more often related to cleanliness issues.

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Exhausting Soldering Fumes

Making a fan


Exhausting fumes while soldering is a safety issue of some importance. If you happen to have an outdoor screened-in studio a simple fix can be had with a computer fan You can scavenge such a fan from an older used computer ready for disposal. Simply cut four timbers 50mm square or 25mm x 100mm to fit around it as a box. Attach a long electrical cord to it with an approved plug;. Attach a screen to both sides. Plug in. An additional feature is to attach an activated carbon filter (as used for cooker hoods) to the front of the fan. This removes particles and some fumes.

Positioning

Always set it to draw fumes away you, generally pointing it so that it is blowing the fumes in the same direction as the larger air flow in the studio. In general a very large fan doesn't always do the job alone, since the fumes always seem to rise up and find your nose. However, with the additional tiny computer fan sitting right next to where you are currently soldering, the fumes just move away.

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Materials
Tools