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 metals 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.

an example of paste flux

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 joints 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.

Courtesy of American Beauty Tools


See also:
Flux, an introduction
Fluxes, a description
The Purpose of flux
The action of fluxes
Soldering fluxes

Use of Sal Ammoniac block

A block of sal ammoniac is an excellent aid to keeping your soldering iron tip (or bit) clean and able to hold a small blob of solder.

A description of what sal ammoniac is and the safety precautions in its use are here. 

You should place the block in such a way that it cannot slide around as you rub your iron over it.

Place your hot soldering iron tip on the block until it begins to smoke. Then move your iron slowly back and forth along the block.  Initially, the block will be black from the contaminants coming from the soldering iron bit.  As you rub the bit along the block, it will begin to clear. As it does, you can add a touch of solder and turn the bit over to check whether there are still any black spots on the face of the bit. 

If there are still black spots, return to rubbing on the block for a time.  If these spots are persistent, you can use a brass wire brush to help clean the contaminants off.  Then add a touch of solder and return to rubbing along the block.  Repeat this check until the whole bit is bright and holding a small blob of solder.

Repeat this process for the other side too.

Leave a small blob of solder on each side of the bit to protect the bit from oxidising.  This cleaning process should be done at the end of each soldering session if the bit is not clean.  But it does not substitute for the frequent wiping of the bit on a damp sponge to clean the bit as you work.  The sal ammoniac block is for cleaning persistent contaminants off the bit.

Soldering old lead

This is normally only a requirement when repairing old windows. Usually either to join new lead to the old, or to repair breaks at the original solder joint.

You will need to clean the lead down to the bright metal at the joints. This is more than a rub with steel wool. You need a glazing nail to scratch through the oxidisation layer, the corner of your lead knife, or in cases of mild oxidisation, a brass wire brush might do. But not a steel one as that may scratch the glass and any painting.  

Do not clean the oxidisation off the lead elsewhere. That is a protective layer already formed which leads to the longevity of the came. It is best to leave oxidised lead alone rather than expose the metal to further oxidisation.

Getting to the bright metal where you want to solder the joint means the flux can act appropriately and help the solder form a secure joint.  Otherwise only a weak, cold joint is possible.

Note that you always need to use dust masks or other breathing protection.  You need to have the work area well ventilated and need to do a damp wipe down of surfaces to reduce the amount of lead oxide in the work space.

Soldering Iron Maintenance

“How do I maintain my soldering iron?  I see so many different methods online that I find it confusing.”

Regular cleaning

There at least two reasons for regular cleaning of the solder bit.

The first is to avoid the build-up of carbon and other contaminants which impedes the transfer of heat from the soldering bit to the solder and surfaces to be joined.

Many soldering stations come with a sponge which, when wet, is used to quickly swipe the iron's tip clean. A small amount of fresh solder is usually then applied to the clean tip in a process called tinning.

The second is to maintain the soldering bit in good condition.

The copper that forms the heat-conducting bulk of the soldering iron's tip will dissolve into the molten solder, slowly eroding the tip if it is not properly cleaned. As a result of this, most soldering iron tips are plated to resist wearing down under use. To avoid damaging the plating, abrasives such as sand paper or wire brushes should not be used to clean them. Tips without this plating or where the plating has been broken-through may need to be periodically sanded or filed to keep them smooth.

To avoid using abrasives, cleaning with sal ammoniac is recommended. This comes in a block. You rub the hot 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 longer and will be ready for soldering immediately when you next need to use it.

Turn off the Iron

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. If you will not be using the iron for a while turn it off until you are ready again.

Tinning

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 will 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.

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 can cause a layer of oxides to form, which will inhibit the transfer of heat through the bit.

These factors are reasons why keeping a film of solder on the bit (tinning) is important in maintaining the long life of the soldering bit.

Courtesy of American Beauty Tools

Cleaning the whole Bit.

Each soldering bit has a shank which fits into a heating collar of one kind or another.  The bit should be removed at periodic intervals and the build-up of oxides should be cleaned from the shank.  The oxides inhibit the transfer of heat from the elements to the soldering bit.  This cleaning work, of course should be done when the iron is cool.  You can use fine abrasives on the shank to remove the oxides.  You can also make a tube of fine sand paper to clean the inside of the heating collar.  This should not be done on ceramic heated soldering irons such as the Hakko.

Wattage

Another element in the maintenance of soldering irons is to have an iron of high enough wattage to readily melt the solder and be able to reheat fast enough to maintain the necessary melting temperature. An iron with enough power will reduce the strain on the heating element of the iron and the strain on the user while waiting for the iron to catch up.

For example, an 80-watt iron is sufficient to solder with, but it will continue to get hotter, as it has no temperature control until it becomes too hot for stained glass soldering, often causing breaks in the glass. An iron of this type is often used with a rheostat in order to prevent overheating while it is idling. However, this reduces the power to the iron and so increases the time needed to recover sufficient heat to continue soldering.  Also, a rheostat only slows the heat up, it does not limit it, so eventually the iron will still become too hot if left to idle.

Most temperature-controlled irons seem to be produced in 100 watts or higher. These irons attempt to maintain a constant temperature. Their ability to do so depends on the wattage and the amount of heat drained from the bit during soldering. The temperature-controlled irons are normally supplied with a 700°F bit (identified by the number 7 stamped on the internal end of the bit) and is sufficient to melt solder without long recovery times. You can obtain bits of different temperature ratings, commonly 800°F and 600°F. The 800°F bit is particularly useful when doing a lot of copper foil soldering, because it recovers to a higher temperature, allowing much more continuous soldering action.

You can also get several sizes of tips for different detail of work.  Upon first sight a fine tip would be useful for fine copper foil work.

But fine tips loose heat quickly, requiring the user to wait while the tip regains the required heat.  A 6mm to 8mm wide bit is useful to maintain the heat during the running of a long bead.  Of course, the bit is wider than the bead being run, but the solder has enough surface tension, while molten, to draw up into a bead the copper foil without spreading – unless too much solder is being applied. Really big bits of 12mm or larger are not practical – long initial heat up times, and too much area is covered, even though there is enough heat stored for really long solder beads.

Patina

The successful application of patina to solder or zinc depends on an understanding of what patina is, how it works and the methods of applying it.

What is it?

Definition:

Patina is a thin layer that variously forms on the surface of copper, bronze and similar metals (tarnish produced by oxidation or other chemical processes), or certain wooden furniture (a sheen produced by age, wear, and polishing), or any similar acquired change of a surface through age and exposure.

The chemical process by which a patina forms or is deliberately induced is called patination, and a work of art coated by a patina is said to be patinated.

The word "patina" comes from the Latin for "shallow dish". Figuratively, patina can refer to any fading, darkening or other signs of age, which are felt to be natural or unavoidable (or both).

https://en.wikipedia.org/wiki/Patina

A description of patination and the industrial process:

“In their natural state, most metals combine with chemicals in the earth or air to create metallic compounds that change their surface colour, which appear as rust or tarnish. These thin layers of corrosion are nature's patinas.”

“Among the most common procedures [to patinate] are immersion and spraying. During immersion, a piece is cleaned with sandblasting or chemicals, then dipped into a prepared liquid compound, creating an immediate change in colour. Alternatively, a piece is sprayed or brushed with a patina solution, allowed to air dry, and spritzed again. This oxidation process creates corrosion on the metal's surface that forms a layer of patina. Other methods include heat, dabbing and wiping, anodizing, and random contact patina.”

Source: Triple-S Chemical Products

A product – Black on Solder – is described and the industrial process illustrated:

“DESCRIPTION: Black on Solder is a chemical formula developed to achieve a black antique finish on Tin/Lead or Solder areas (60-40 or 50-50). This solution is a non-chromate, non-cyanide liquid solution widely used on lighting fixtures, tin wares, sculptures, gift items and other decorations. The surface will not chip, flake or peel.

“PREPARATION: Parts must be free of grease, alkalinity or acid when Black on Solder is applied. Parts must be thoroughly cleaned and deoxidized prior to blackening. … Do not use petroleum degreasing solvents that leave a residue on the surface. Rinse thoroughly with over flowing cold water to remove residual cleaners and dust. It is important that alkaline cleaners are completely rinsed off prior to blackening.

“IMPORTANT: Triple- S does NOT recommend using any sort of alcohol, solvent, acid or degreaser to clean parts prior to solution application. … Powdered cleaners such as Ajax or Comet can also be used. Use the cleaner in conjunction with a scotch brite pad and apply medium strength scrubbing to prepare the part then thoroughly rinse with fresh water. ….

“APPLICATION: Clean the part with [your chosen material]. Rinse thoroughly with water and dry. Apply [the patina] solution with a brush or spray evenly and let it react. Rinse with water and air dry or wipe with a cloth to dry the surface. [Repeat this as necessary.] It is recommended to protect the finish with a clear [varnish]”

Source: Triple-S Chemical Products

Take note:

The above quote is from a company that works with metals exclusively and is an illustration of how important cleaning is for good results in patina application.  When cleaning in proximity or on glass different processes must be used to protect the glass.

1. I never would use abrasive or corrosive materials to clean solder lines holding glass.  The most aggressive cleaner I use is that intended for fibreglass baths.
2. I never use abrasive methods in conjunction with painted glass.
3. Do not use metal or scouring pads when cleaning
4. I never use patina on any part of a panel that has painting on any of the glass. The acid will remove or damage the painting.
5. I never use patina on leaded panels at all.

I suggest these precautions should always be followed.

Cleaning

These sources indicate that a patina solution is used to form a thin layer of corrosion to the material.  To do this, the metal must be cleaned of oils, and be acidically neutral.  Cleaning is to be done with household cleaners such as powdered or cream cleaners applied with moderate pressure by synthetic scrubbing materials such as a dish scrubbing pad (sometimes called a green scrubby). The metal then needs application of running water (not a bath of water) to rinse off any residues. 

Application

The clean metal needs to be dried before application of the patination solution.  Apply with a brush or sponge, or spray and allow time for the patina to react with the metal.  Rinse with water and allow to air dry.  If wanted, the drying can be aided by wiping with a soft cloth or absorbent paper.  Often a second or third application is required to achieve the depth of colour desired.

Protect

You can then apply a varnish or wax to shine and protect the colour of the patination.  This protective process must not involve scrubbing, as that will remove the patination layer from the metal.

Do it Yourself Colourations

Goran Budija has listed a wide variety of patination formulas and methods in his publication.  What follows is a reworking of his data.

Patination of Tin

Black 1

Method:

Immerse objects in heated solution(70C). When colour is developed rinse well, dry and wax.

Formula:

5 gms Bismuth nitrate

50cc Nitric Acid

80gms Tartaric acid

1 litre water

Black 2

Method:

Immerse objects in the hot (70C) solution.

Formula:

30gms Ammonium chloride

7.5gms Molybdenum acid

1 litre water

Greyish black

Method:

Immerse objects in the room temperature solution.

Formula:

200gms Iron III chloride

1 litre water

Bronze brown

Method:

Dissolve ingredients in water acidified with nitric or hydrochloric acid. Apply to the surface(s).

Formula:

3 gms Ammonium chloride

12gms copper acetate

20ml vinegar

500ml water

Bronze colour.

Method:

Mix diluted solution of copper sulphate and cream of tartar, Rub it on an object.

Formula: equal parts of:

Copper sulphate

Potassium hydrogentartarate/cream of tartar

Patination of Zinc

Black. 1

Method:

Ingredients must be dissolved in hot water, then filtered and used.  Immerse objects and take them out immediately. Colour develops after contact with air.  Repeat if needed, rinse well and dry.

Formula:

125gms copper sulphate

60gms potassium chlorate

1 litre water

Black. 2

Method:

Immerse objects in heated solution (90 C).

Formula:

12gms copper sulphate

15gms potassium permanganate

1 litre water

Black. 3

Method:

Immerse objects in the solution. (room temperature)

Formula:

20gms ammonium molybdate

5gms sodium acetate or sodium thiosulphate

1 litre water

Greyish black.

Method:

Immerse objects in the solution (approximately 20 minutes).

Formula:

200gms Iron III chloride

1 Litre water

 

From:

Collection of formulas for the chemical, electrochemical and heat colouring of metals, the cyanide free immersion plating and electroplating, by Goran Budija.  March 2011.  Zagreb, Croatia

Summary of applicable DIY formulas and methods

Tin

Goran Budija recommends hot application to get a black patination, but this is not usually suitable for stained glass work.  Cold application will also work but needs more time and repeated applications to have the same effect as hot immersion.  Whether you choose Black 1 or 2 will depend largely on the availability of the chemicals.

A cold method of patination is the Greyish Black using iron III chloride, which is easily available. More applications and drying will intensify the colour.

To get a bronze patination of solder equal parts of copper sulphate and cream of tartar made into a paste and rubbed onto the solder will be effective, although not a copper colour.

Zinc

Black 1 seems the most useful method and formula for zinc framing of stained glass panels.  It is a cold application and immersion can be substituted by painting or brushing on the chemical solution.  Note the multiple applications required to get the depth of colour required, and the thorough cleaning and rinsing noted in the industrial process.

Sal Ammoniac

There are sometimes concerns expressed about the use of sal ammoniac to clean the tips of soldering irons.  My conclusion is that there are no elements of the block that will affect the copper plating of the soldering iron bolt.  It is safe to use this as an occasional cleaning method of soldering iron bolts. This is based on the following information.

What it is

The common term, sal ammoniac, refers to the chemical ammonium chloride.  Sal ammoniac is the archaic name for it. The Romans named it from the ammonium chloride deposits that they collected from near the Temple of Jupiter Amun in ancient Libya.  It is found as encrustations around volcanic fumaroles, guano deposits and in burning coal seams. Notable occurrences include Tajikistan; Mount Vesuvius, Italy; and Parícutin, Michoacan, Mexico.

Wikipedia

Ammonium chloride is the product from the reaction of hydrochloric acid and ammonia.  Ammonium chloride is obtained as a by-product in different chemical processes.  It consists of white crystals that are also available in rods or lumps.  The substance changes directly from being solid to gas with no intermediate liquid state. The gas does not consist of ammonium chloride molecules but ammonia and hydrogen chloride. This shows that the salt decomposes easily. When stored, ammonia is continuously emitted and the substance gradually becomes more acidic.

https://www.fishersci.co.uk/shop/products/ammonium-chloride-99-6-analysis-acs-acros-organics-3/p-3586389

Safety

It is widely used in human medicines as an expectorant, diuretic, etc. and in veterinary medicines to reduce gallstones, so it is a relatively benign material in relation to human health. 

There are some hazards though.  It can cause serious eye irritation on prolonged exposure, and is harmful if swallowed.  The precautions are to avoid eating, smoking, and drinking when using it.  Use gloves and eye protection if you are using it for extended periods. If it gets into your eyes, rinse with water for several minutes. https://www.fishersci.co.uk/shop/products/ammonium-chloride-99-6-analysis-acs-acros-organics-3/p-3586389

It is highly soluble in water, and forms a slightly acidic solution. Its main characteristic that you need to protect yourself against is that it vaporizes without melting at 340 °C to form equal volumes of ammonia and hydrogen chloride gas. https://www.britannica.com/science/ammonium-chloride

The amounts of the gas are small when used to clean soldering irons, but as the gas forms hydrochloric acid in contact with moisture, you should use dust masks rated for inorganic acids.  The amounts are small and generally only cause sneezing and coughing upon contact.

The primary hazard is the threat posed to the environment. Immediate steps should be taken to limit its spread to the environment.

https://pubchem.ncbi.nlm.nih.gov/compound/ammonium_chloride#section=Top

Uses

In addition to medicine, it is used to clean soldering irons. It has uses in jewellery-making and the refining of precious metals.  Sal ammoniac has also been used in the past in bakery products to give cookies a very crisp texture.  In some areas, particularly Nordic countries and the Netherlands, it is still widely used in the production of a salty licorice candy known as Salmiak, or Salmiakki.  Formerly it was used as the electrolyte in dry batteries.  It has uses in fertiliser as a source of nitrogen mostly for rice and wheat crops in Asia. It is also an ingredient in fireworks, safety matches, contact explosives, cosmetics and many other applications.

https://thechemco.com/chemical/ammonium-chloride/

Conclusion

Although there are some mild safety precautions that need to be followed, there is nothing in the sal ammoniac block that can harm the copper coating of the soldering iron tip.

Foiling Space

There are a lot of views on what amount of space is required between copper foiled glass pieces.  Some say the pieces should be tight, others that a consistent space is needed, and some who say that variable spaces are fine.

It is necessary to consider what holds a foiled panel together.

Adhesive

The foil is supplied with an impact adhesive which helps keep the foil attached to the glass before soldering.  However, the heat of soldering deteriorates the adhesion of the glue.  If you must take a foiled piece apart you will find that the adhesive is sticky rather than firm. Also, the adhesive will continue to degrade during the life of the object.

Solder

The solder bead is significant in creating the matrix required to hold the panel in one piece.  The bead on each side holds the glass in place and resists deformation away from a single plane. This resistance is significantly reduced if there is not a fin of solder connecting the two beads.  The beads and the fin of solder form an “I” beam which together resists movement of the glass.

Strength

To form that “I” beam there does need to be space between the foiled pieces. It does not need to be wide, but it does need to be enough to wiggle the pieces.  This will allow the solder to flow from one bead to the one on the other side, forming a strong “I” beam.

In vertical panels, the glass is the strong element.  The solder lines serve to hold the matrix together.  Where people indicate the strong border will keep the whole panel from falling apart, they are correct in part. But, if there is not a sufficient “I” beam between each piece, the whole panel is subject bowing, either from wind pressure, vibration or mechanical pressure from handling.  Therefore, you cannot rely on the border to make your panel strong and long lasting.

Dissent

Some take the view that there will be enough unintentional spaces created between pieces to allow the fin form between beads intermittently.  But the gaps in the “I” beam due to tight fiting pieces will make it much weaker than a continuous bridge between beads.  The existence of gaps puts greater pressure on the solder that does bridge between beads.

An example was provided for me in a lamp brought in by client which spontaneously fell apart one evening.  (Not made by me, I add). The upper band of glass remained attached to the vase cap, but separated from the rest of the shade.  Fortunately, it fell straight down and only a little of the bottom edge was broken.  Investigation showed there was very little solder between pieces, although there was a good bead on each side of the lamp.  The lamp pieces separated, in different places, at the foil-glass interface and elsewhere at the foil to foil interface.  This indicates there was little or no solder where the foil remained on the glass, as the adhesive is much weaker than even a thin fin of solder running between the inner and outer beads. This case is an example of the need for a fin of solder to be formed between the beads on either side to provide a strong, long lasting object.

Heat Cracks

There is sometimes a fear expressed that tight fitting of foiled pieces can lead to heat fractures when soldering due to expansion.  Yes, when soldering pieces with a lot of variation in width, you do need to move reasonably quickly. Come back later to improve a bead if you need, to avoid overheating the glass.  Even the thin copper foil can transmit heat along its length, which reduces direct heat transfer to the glass.  Mostly, breaks occur from dwelling too long in one place with the soldering iron. It may be better to tin the foil all around the suspect piece just before running the bead.  This will warm the glass around the edges in preparation for the greater heat of laying down the bead.

The main point is that the solder needs to connect the beads on either side of the glass to provide a stable, strong and long-lasting piece.

Soldering Fumes

Exhausting Soldering Fumes

Health and Safety

The health and safety of working with lead and solder are a great concern of many people.  Greg Rawls, the acknowledged expert in glass working health and safety, puts soldering and lead work in perspective.

Soldering lead came for stained glass does not usually present an inhalation hazard if the area is well ventilated and you are using an iron and not a torch. With normal soldering, you are melting the lead at temperatures that are NOT hot enough to create a fume.
Lead fume is the inhalation exposure issue. Fumes are very small respirable particulates that are made with heat. Liquid chemicals give off vapours.

Avoid exposure by ventilating the area when soldering, especially if using a torch instead of an iron. Open a window and turn on a fan!  Wash your hands thoroughly when finished working with lead. There are specific products for this purpose.

Use a P95 or P100 respirator when concerned about lead exposure. 

http://www.gregorieglass.com/chemicals.html

There are commercially made fume traps which often have an activated charcoal filter and can be effective.  A simple desk top fan blowing away from you can be effective in well ventilated areas, if you are working on your own. (otherwise it blows the smoke toward others.)

An example of a fan drawing fumes away from the person soldering

Making a fan

Exhausting fumes while soldering is a safety issue. 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 charcoal filter (as used for cooker hoods) to the front of the fan. This removes particles and some fumes.

Positioning

Always set a fan 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. A very large fan doesn't always do the job alone, since the fumes seem to rise and find your nose. However, with an additional small fan sitting right next to where you are currently soldering, the fumes just move away.

Wearing an appropriate dust mask as illustrated by the Bohem Stained Glass Studio is the best solution.

Foiling and Soldering Small Pieces

There are several approaches to dealing with small pieces in copperfoiling:

No-foil approach
One approach is to have some of the pieces held in place by over-beaded solder without foil on the tiny piece, but it is patchy at best and likely to lose pieces in the long term.

Bevel approach
A very good and strong 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.

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 by a wet sponge to more quickly cool the solder.

With the solder contained by the 'V', the solder lines will be of constant width throughout the piece. Best to practice 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.

Triming 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 (Exacto or similar) 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.

Lead free Solder

There are some problems to overcome when using lead free solders. 

One is that all, except for expensive compositions, lead-free solders have a higher melting temperature than tin/lead compositions.  The table in this link shows the melting temperatures.

Most lead-free solders have a wide pasty range, so careful attention needs to be paid when selecting the composition, if you want a eutectic, or nearly so, solder.

Some eutectic solders are:

65% tin, 25% silver with a eutectic temperature of 233C.  It is known as “Alloy J” and patented by Motorolla.

99.3% tin, 0.7% copper has a eutectic temperature of 227C. It is expensive.

96.5% tin, 3.5% silver has a eutectic temperature of 221C.  This is slightly lower than the tin/copper composition but more expensive.  It is also likely to rob copper from the soldering bit, although it is easier to solder with as it has excellent wetting properties.

Lower eutectic temperature solders are available:

91% tin, 9% zinc has a eutectic temperature of 199C.  It corrodes easily and has a high level of dross.  This makes it a poor choice for copper foil work.

42% tin, 58% bismuth has a low eutectic temperature of 138C.  It is a well-established solder, but it is expensive.

48% tin, 52% indium has the lowest eutectic temperature of 118C, but it is very expensive.

Copper bearing solders

Another problem is that a solder without lead, robs copper from the soldering bit/tip, and even more so at the higher temperatures lead-free solders normally require.  One means of avoiding the rapid deterioration of the soldering bit is to use solder with a small amount of copper included in the composition. As little as 0.5% can be useful.  Normally, nothing greater than 1% is required to extend the life of the soldering bit.

Eutectic copper bearing solder

However, only one of the commonly available solders is eutectic. This is 99.3% tin and 0.7% copper with a melting temperature of 227C.

Copper bearing solders and pasty ranges

Other copper bearing solders are available. Most of them have high temperatures and wide pasty ranges making them less useful for copper foil work.

  

Near eutectic solders

97.25% tin, 2% Silver, 0.75% copper has a small pasty range of 217C – 219C, making it a nearly eutectic solder and suitable for copper foil, except for its high melting temperature.

91.8% tin, 3.2% Silver, 0.5% copper has a pasty range of 217 – 218C, also making it a near eutectic solder suitable for copper foil; again, except for its high melting temperature.  With its high silver content, the solder is expensive.

95.5% tin, 3.8% silver, 0.7% copper has a pasty range of 217-220C.  This also has a small pasty range, but may be similar in cost to the 91.8% tin composition.

95.5% tin, 4% silver, 0.5% copper has a pasty range of 217 – 225C.

95.5% tin, 4% silver, 1% copper has a smaller pasty range of 217 – 220C, but may be more expensive.

Other copper bearing solders 

94.6% tin, 4.7% silver, 1.7% copper has a wide pasty range of 217 – 244C.

96.2% tin, 2.5% silver, 0.8% copper, 0.5% antimony has a

smaller pasty range of 217 – 225C and may be slightly cheaper because of the reduced silver content.

  

95.5% tin, 4% Copper, 0.5% Silver has a pasty range of 217 – 350C and is the usual lead-free plumbing solder.  The high melting temperature of 350C makes it unsuitable for most copper foil applications.

97% tin, 0.2% silver, 2% copper, 0.8% antimony has a high melting temperature and wide pasty range of 287 – 318C., which makes it unsuitable for copper foil.  It is known as “Aquabond”. 

95.5% tin, 4% silver, 0.5% copper has a pasty range of 217 – 225C.

95.5% tin, 4% silver, 1% copper has a smaller pasty range of 217 – 220C, but may be more expensive.

94.6% tin, 4.7% silver, 1.7% copper has a wide pasty range of 217 – 244C.

96.2% tin, 2.5% silver, 0.8% copper, 0.5% antimony has a

smaller pasty range of 217 – 225C and may be slightly cheaper because of the reduced silver content.

Lower temperature copper bearing solders

94.25% tin, 2% silver, 3% bismuth, 0.75% copper has a pasty range of 205 – 217 which is smaller than many of the other copper bearing solders.

90.7% tin, 3.5% silver, 5% bismuth, 0.7% copper, with a pasty range of 198 – 213C, has a lower melting point than many other copper bearing solders.

93.4% tin, 2% silver, 4% bismuth, 0.5% copper, 0.1% germanium has a relatively small pasty range of 202 – 217C, but because of the incorporation of rare earth metals may be expensive.