Sunday, 29 January 2012

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

1 comment:

  1. Very nice post, impressive. its quite different from other posts. Thanks for sharing.

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