Before you start selling your new-found treasures, you want to look for scrap metal buyers that will make the selling process as quick and easy as possible while offering you the best pricing. What you don’t know about the industry can hurt you; so it is important to understanding the following:

• Scrap metal is now selling for more than it ever has but some metals are particularly in demand
• Not every scrap metal buyer will offer you top price. Prices continuously fluctuates so it is important to keep up with their current value. That way you will know immediately if a buyer is giving a reasonable deal or not.
• Anything metallic will have some value but what you earn will depend on the type and weight of the metals you have to sell
• Not all dealers accept all types of metal. It’s particularly important to understand the difference between ferrous and non-ferrous metals.
• Not all dealers accept small quantities. Usually it’s dealers that only work locally that will be interested in quantities under 500. So ask up front.
• You should get the terms of the sale in writing prior to delivering the metal. Quality dealers will do this and if for some reason, your metal shipment doesn’t turn out to match the specifications the dealer expected, he should promptly let you know why.

Another important factor to consider is whether or not the scrap metal company you are planning to sell to will pick up your material or if you will have to provide delivery with your own transportation. Some scrap recycling companies will be more choosy than others when it comes to shipping the metals and accepting mixed shipments compared to sorting each individual metal out. Researching these small details prior to the sale, will mean a more successful outcome for you and the dealer. Another way to make sure you are not wasting your time or the dealer’s: give them a good description of what you have to sell or send a sample.

After you have positioned yourself to understand the basics of the scrap metal business, your next move should be figuring out more ways to gather scrap from others who have no need for it. Some methods of increasing your metal load include:

• telling people you know of your new endeavor – they are more most apt to contact you to dispatch their junk
• post an ad on Craigslist offering to pick up people’s junk in your area
• search the “free stuff” section of Craiglist to see if people are giving away any junk metals
• contact local businesses (plumbing, electricians, demolition services, etc.) and offer to take away scrap metals they accumulate

As mentioned previously, metal prices are fluctuating on a daily basis simply due to supply and demand. With that being said, the third and final step in familiarizing yourself with the scrap metal world involves staying up-to-date with the latest pricing details of each metal. Most important is knowing what metals will bring you the highest exchange value. One way of determining current pricing is through signing up for a free-trial at recycleinme.com, a website that is currently being used by scrap metal industries for price assurance. Many professionals turn to Peony. They also offer a free trial period.

Understanding how to classify the metals, ferrous and non-ferrous, will be a determining factor in who you will be able to sell to, as some scrap metal buyers only accept non-ferrous metals. Here’s the difference: A non-ferrous metal is any metal which is not iron or any alloy of metals which does not contain iron. Non-ferrous generally sells for a higher price than ferrous metals.

One way to tell if a metal has any ferrous content in it: use a magnet. Ferrous is magnetic due to its iron content, but non-ferrous does not contain any iron and is therefore not magnetic.

In order to ensure that you get the most out of the the work you put in scrapping, be sure to keep this in mind: to optimize pricing for non-ferrous scrap metals be sure to remove any attached materials like screws and/or rubber coating.

Heavy melt is a type of ferrous metal that includes piping. Plate and structural steel is the other category of ferrous metal and it contains metal beams used in construction. It is important to note that junkyards, machine shops and garages may have quite a bit a material leftover or lying around.

Scrap metal is everywhere – more places than you thought possible. With cautious observation you will discover a considerable amount of potential cash in places you never would have previously thought! As you go along, you will learn tricks of the trade to surely help you with selling scrap metal at a profit.

Sell scrap metal to Hirsch Metals. We are always in “buy” mode and are always looking for large quantities of non-ferrous scrap metals.

In the article “Selecting the best Flux for the Job” we briefly discussed the way that “No Clean” (NC) fluxes came into general use. While there is nothing complicated in the procedures for using these fluxes, from time to time problems arise because of a lack of understanding of the factors involved. This article provides answers to most of these questions.

First of all we must always remember this is a “No Clean” (NC) flux not a “No Residue” flux. In other words there will always be some residues left on the board. By carefully setting the fluxing and soldering parameters these residues will be minimal, and will generally cause no electrical failures, However it is wise to carry out testing to assure that the material left on the assembly causes neither short term or long term failure.

If the assembly contains very high impedance circuits, or it will operate in a high temperature/humidity environment, some form of reliability testing becomes absolutely necessary. The two most prevalent forms of circuit failure are caused by ionic flux residues that pick up moisture from the environment and form a conductive path on the board surface. If this path is a very high resistance, or if the circuits involved are all low impedance then it is unlikely that any failure will occur.

However if the conductive path is of a lower resistance, or the circuits are very high impedance, then the tiny current that will flow through the ionic materials can change the operation of the circuit. If the conductive path lies between two closely spaced terminations with a potential difference of more than a few volts, it is quite possible that sufficient current will eventually flow to “plate” a metallic path from one conductor to the next, (“dendrite’ growth). This of course will produce a catastrophic failure, shorting out the power supply and often causing a fire and destruction of the PWB.

The most practical form of testing is to thermally cycle the assembly, with power applied, over the range of temperatures for which it is designed to operate. The assembly must be held at the maximum and minimum temperatures a sufficient time for the entire assembly to stabilize at that temperature. The humidity must be maintained at a minimum of 85% for the entire cycle, care being taken to prevent any liquid moisture from condensing on the assembly. The assembly must be continuously monitored for performance during the entire test. It is generally found that if the assembly is going to fail it will do so during the first few days of testing.

However we want to be sure that no long term jeopardy exists, so the testing is usually continued for four weeks. This testing will demonstrate that any similar assembly, processed in exactly the same way, will not fail in the field because of the use of the particular NC flux involved. In turn this means that every detail of the wave soldering set up used to solder the test samples, must be very carefully recorded and then used as the standard with no variations of any kind. The following are the most important items.

1). The amount of flux applied must remain constant, which in turn means that the flux density or “solids content” must not vary. With the very low solids content fluxes used with the NC process, it is impractical to attempt to monitor and make additions to maintain the solids content, and the only practical alternative is to use a “total loss” fluxer in which fresh flux is always used.
2). The foam fluxer circulates the flux and cannot be used in a “total loss” system, therefore the spray fluxer has become the standard when using these fluxes. There are several types on the market, and each have their own advantages. Remember that maintenance and cleaning are important in maintaining control of the process.
3). The flux is rapidly broken down by the heat of soldering, and therefore the preheat temperature and the contact time with the solder are both vitally important. Once the machine set up has been determined and the test sample has successfully completed the thermal cycling, then the parameters must not be changed in any way.

In setting up the wave soldering process, the amount of flux applied to the assembly must be held to the practical minimum. It is not difficult to know when this level is reached as the incidence of solder shorts and bridging will increase dramatically as the amount of flux is reduced. More flux must then be applied until these defects are minimized, and this will determine the correct amount for that particular assembly. The flux has to clean the surfaces to be joined, but it must also prevent the formation of oxides on the wave surface, and on the joints until they solidify. Any film of oxide will prevent the solder from draining from the joints and generate the solder shorts and bridges. Inevitably this means that more flux must be applied than is actually required for making the joint, and will leave some residues on the assembly.

This is where the advantages of a nitrogen blanket over the wave become obvious. Now only sufficient flux has to be applied to form the joint, the nitrogen then eliminates the formation of oxides on the wave and the solder fillet. This in turn means that much less flux has to be applied and the result is a cleaner assembly. Note that the addition of a nitrogen blanket will not improve the quality or reliability of the joints, but will often produce brighter, shinier, solder fillets as well as a cleaner assembly. Many clients claim that the improved appearance of the product and the reduced consumption of flux, more than pay for the nitrogen.

Solder paste has improved dramatically in performance and consistency over the past ten years. That does not mean that all the problems of applying and reflowing paste are eliminated, but that with care consistent results are not difficult to obtain. The following suggestions can help in producing sound results.

Consistency. Develop a sound process and stick to it rigidly. Although the performance of the paste has been improved this is no excuse to allow variations to creep into the process. For example do not permit stenciled boards to sit around for varying lengths of time before placing the components. Our pastes do not vary much in tack during the first few hours after stenciling, but there is inevitably a small variation. Try to eliminate all the variables from the process, no matter how small. Look very carefully for the not so obvious variations. In one case opening the cover to the stenciling machine changed the process characteristics.

Stenciling. In a similar manner you can leave today’s paste on the stencil without the properties changing very much. But why make life more difficult? The variations are small, but inevitably there will be small changes, and by setting up the process carefully they can be avoided. It is so often the small things that collectively cause problems and are individually extremely difficult to find. Eliminate the variables in every part of the process. Develop good processing parameters for the stencil machine and then make sure they are followed at all times. Check the machine routinely for accuracy, and also remember that the boards must also comply with the processing accuracy required.

Stencil Cleaning. If the stencil is correctly designed, and the boards are flat, there should be little paste on the bottom of the stencil. But with time some paste will find it’s way there and transfer to the board surface. The result, —- solder balls. Whenever they are found after reflow, look at the bottom of the stencil for paste. If it has to be cleaned every few boards then check the stencil design. It should seal tightly onto the pad during stenciling.

Reflow. The reflow parameters are given only as a guide. The design of the assembly, and the sizes of the various joints all affect the thermal profile. The reflow oven has to be set to reflow the most thermally massive joints. A good rule of thumb is to keep the solder molten for the shortest time that will form a sound joint, and cool as quickly as possible without thermally shocking the assembly. There is no way that the optimum parameters can be calculated they must be developed from practical testing. However they must also be developed in a careful and controlled manner. They will not be found by haphazardly changing the machine parameters.

Hirsch Metals sells a variety of solder pastes including No Clean� Contact Paste and “Water Soluble” Contact Paste

We all recognize the environmental advantages of lead-free solders. Since January 1999 Hirsch Metals has been developing “easy to use” lead-free alloys for use with copper foil technology that have the additional advantages of greater strength and superior finish. Once development was completed, I had to persuade the stained glass artists to at least try these new alloys. I found that this could be a “hard sell” because of the unhappy experiences of using other lead free systems.

First I felt that I should gain some personal and practical experience in the use of these materials and I enrolled in a class given by Bob and Evelyn at “Glass by Design”. I soon found that it was not as easy as it looked, but it was not long before I had my design assembled and the copper foil fitted ready to solder.

I had to learn the “tricks of the trade” but then progressed quickly. I found out for example that the iron had to run at a higher temperature, (the lead-free solder melts at 630F instead of the 374F for the usual 60/40 lead based solder). I had to feed the solder smoothly to the iron tip, and form a continuous bead of solder rather than attempting to smooth it out later.

At first I was concerned that when the solder solidified, about 2 inches from the iron, it had a frosty appearance, but soon learned that this was the flux crystallizing on the surface, and after cleaning and waxing it had a brilliant smooth finish.

I was excited, and my classmates were eager to see the results. They had heard so much against lead-free alloys, and were surprised at how simple this was to use, and how excellent were the results. I experimented with different finishes and patinas, such as the black and pewter finishes but I personally prefer the beautiful smooth shine of the natural finish. The absence of lead of course also allows the use of these alloys for products that may come in contact with food or drink.

I would like to thank all of the many artists who helped me in the development and introduction of these alloys. Unfortunately space only allows me to pass on a few of their comments.

Bob & Evelyn of Glass by Design.
“Hirsch silver lead-free flowed like the Porsche of lead free solders. Evelyn made a candle shelter that looked like the crown jewels”

Jeremy Pitz of Centerville Architectural Glass.
“Filled gaps without any flow through. We were impressed by its strength and luster. We totally underestimated how far the solder would go.

Nancy Grant of Stained Glass Kaleidoscope.
“It was not prone to �run through� as regular solder. Nowhere as difficult as I anticipated. I have no problem in recommending the silver solder”

Sandy Seff of Colorful Vision.
“Very excited about the lead free silver solder, smooth running with a nice shiny finish. Not only user friendly but the additional strength will be a real benefit with some of the sculptural pieces we do.

Jo Stanley of The Stained Web.
“Either the lead free silver solder goes further than 60/40 or I�m a better solderer than I thought. Great to work with.

Carol Shrout Stain Glass.
“Did not like it. — could not get the solder to flow easily” (But would like to try it again).

Gloria Fohr of Expressions in Stained Glass.
“Your lead free silver solder works like a charm. Knowing there is a workable lead free is a wonderful thing”.

Carolyn of Carolyn’s Creations.
“Quite workable with absolutely no ripple effect, flowed best with higher temperature setting”

Dale Riddle of Stained Glass Concepts.
“Flows a little different but seems fine.” (Dale evaluated various blends of solder for strength and appearance)

Ray Crawford of Accent in Glass.
” Works well during tacking. At first tricky but the results are worth it. Solder is very strong and polishes to a silver sheen”

David and Gloria Lieb.
They said they were impressed with the solder and sent a 3 piece candle shelter that emphasized the beauty of the solder and their work.

Rick Wolf of Seattle Stained Glass.
“Ran smooth and evenly on every seam. I would definitely recommend the solder for any copper foil project”

Michael Straub of Ambient Stained Glass
“The solder has some fabulous potential. Thank you for developing new products for our industry”.

In summary, I found the lead free silver solder easy to use, even for a novice. Certainly it requires adapting to the higher soldering iron temperature, and different rate of melting, but this did not prove at all difficult and the advantages of a beautiful finish and greater joint strength made it well worth the effort. I had no difficulty in using any flux, and carried out all my work with a 100watt iron.

The success of the Hirsch Wizard A/G solder has led to the development of a new version of this product containing a core of water soluble flux.

I wish to thank Lisa Swiman of Venture Tape for donating copper foil for these tests, and to Jack Spangler of Esico Triton for the soldering irons that were used. These excellent products were invaluable for our testing and evaluation.

Check out our lead-free solders. GO WITH THE FLOW.

The Solder Alloy

In any soldering procedure a mechanically reliable joint is essential, but for Stained Glass work the appearance of the completed joint is also vitally important.

1). The solder joint must blend into the shape of the material being soldered.
2). The surface of the completed joint must be smooth and free of any bumps or grittiness.
3). As the solder oxidizes from exposure to the air, or the application of any metal coloring agents, the fillet should develop the same patina as the remainder of the metals.

The standard 63/37 tin/lead alloy remains the easiest solder to use. It melts at 183C and has no pasty phase, changing directly from solid to liquid and back to a solid. This means that the solder solidifies instantly producing a very smooth fillet, with no ridging or other marking which may be caused if the joint moves during solidification. The 60/40 alloy produces almost similar results at a slightly lower cost, but with a slightly higher melting point and a small pasty phase.

When cost is a major concern, solders with a lower tin content can offer some savings. However as the tin content is reduced, the solders have a higher melting point and as they cool, they pass through a pasty phase. This can produce a frosty appearance to the solder fillet and of course will leave striations or cracks if the joint moves during cooling. The higher meting point also means that soldering has to be carried out at a higher temperature. In general therefore, the 63/37 eutectic tin/lead solder is easier to use and produces a better looking joint. Solders with a higher proportion of lead are cheaper but less forgiving. .

Lead-Free Solders

Several lead-free alloys are available, and are similar in performance to the lower tin content solders mentioned above. With normal care there is little or no jeopardy to the operator in the use of lead bearing solders. (Click for article “Lead-Free”) Their chief environmental threat lies in the disposition of scrap metals which should always be returned for recycling.

Selecting the Soldering Iron

Ideally the iron should always operate at the same temperature. This is almost impossible to achieve, as the moment the tip touches the joint the temperature begins to fall rapidly. With an uncontrolled iron this means you will be soldering at varying tip temperatures. Minimize the variation by using a reliable temperature controlled soldering iron.

Buy an iron with a chisel bit, as large in diameter, and as short as is convenient to use. If you will be soldering many joints at a time make sure the iron wattage is sufficient to maintain a constant temperature. The tip should stay at least 100C above the solder melting temperature during the entire soldering process.

Patina

Make the joint quickly and try to avoid an “second soldering”. The objective must be to use the right iron and the right technique so that the joint is made correctly the first time with the solder flowing smoothly into the overall shape of the design. When this can be achieved and the solder is made from clean, pure base metals, there is seldom any problem in developing an excellent appearance.

Hirsch metals sells a variety of solders for the stained glass artist.

The Danger of Lead

Lead poisoning has been the subject of many investigations, from the danger to children of eating peeling lead based paint, to the jeopardy from handling lead products. The danger of poisoning from ingesting lead certainly exists and caution must be taken whenever lead is open to the environment. The danger however is often exaggerated, and with reasonable caution any jeopardy can be controlled. The main danger of lead poisoning comes from three areas.

1). Ingesting lead from contacting the metal with hands and fingers and then transferring the lead contamination to food, cigarettes or other items that contact the mouth or tongue. There is the less likely possibility of absorbing lead through the skin.
2). Breathing tiny particles of lead from dust in the air. These usually arise from such operations as grinding or sanding items containing lead. Molten lead which is violently disturbed as for example air blasting the solder from joints during repairs is also a source of danger.
3). Eating or drinking food or liquid contaminated with lead . For example water from pipes joined with lead bearing solders, or food prepared on lead bearing metal surfaces.

The Precautions

Simple precautions can virtually eliminate this danger. For example anyone exposed to lead must thoroughly wash their hands before any eating, drinking or smoking. If exposed to lead dust shower thoroughly immediately the work is finished. Good air filtration in the working place is absolutely necessary, effective for the particle sizes being generated. Grinding under a water spray, and similar techniques that are readily available should also be applied. Masks should be used when ever there is a danger of lead contaminated air.

Good housekeeping is mandatory including changing clothes at the end of a shift, showering and washing the hair to remove all lead particles. Item three is more complex but all water and food processing equipment should be checked for the presence of lead. Some old buildings still retain lead pipes, but in many cases hard water lines them with calcium and renders them harmless. Soft water on the other hand may be slightly acidic and can pick up a dangerous amount of lead from contact with lead pipes or lead bearing solders.

Lead Free Solders

There are no lead-free “drop in” substitutes for tin/lead solders, the process will usually have to be modified in such areas as soldering temperatures and techniques. The questions of strength, ease of use and cost must also be considered. It is pointless changing to lead-free solders if the products being worked on contain lead. For example one radiator repair shop was concerned at the high lead level found in the blood of their employees, as they had changed over completely to lead-free solders. They forgot that the radiators they were repairing had been made using lead based solders and therefore they could not relax their environmental precautions.

A Caution

The greatest jeopardy to the general health of the public lies in the disposal of lead bearing products in land fill which may eventually leach into the water supply. If we follow a recycling policy in our manufacturing plants we can avoid this danger. Any use of lead therefore must be sensibly controlled, using good housekeeping practices, and ensuring that any lead bearing materials are properly disposed of and not allowed to get into the environment.

Hirsch Metals is a top supplier of solders including ones that are lead free. Browse our site or give us a call at 800-521-0352.

When wave soldering was first developed, rosin based fluxes were almost universal and the types RMA (Rosin Mildly Active) or the more aggressive RA (Rosin Active), were used in almost every fluxer. They were alcohol based and generally around 25% solids content. They produced thick stable foam heads in the foam fluxers that were then in use, and were easily maintained.

Simple hand held hydrometers were quite satisfactory for determining how much alcohol to add to make up for evaporation, although automatic flux density controllers quickly became available. Similarly the rosin fluxes were almost universally used in the early solder pastes.

Initially the flux residues were left on the board and with the circuitry used in those days they did not affect the operation or long term reliability. The hard rosin effectively encapsulated the active ingredients in the flux and prevented corrosion, or a reduction in in surface resistance. Cleaning at first was carried out solely for cosmetic reasons, but it was soon found that partial cleaning was worse than no cleaning at all. It removed the protective rosin and left the activators which could then pick up moisture, degrade surface resistance and corrode metal surfaces.

Eventually cleaning using solvents became the standard system, in particular the use of the Freon mixtures. The Freon easily dissolved the rosin and the additive, for example alcohol, removed the activators. It was very easy to obtain sparkling clean boards using a simple vapor degreaser and a minute or so immersion. Ultrasonic agitation was often added to the machine to speed up the cleaning cycle. For several years this was the industry standard, although in line machines quickly superseded the batch cleaner.

The oil shortage in the 70’s made the cost of solvents rocket and triggered the use of water soluble fluxes. When the effect of Freon on the environment became known, it was soon banned together with many other of the solvents then in use, and effectively killed this method of removing flux residues.

Organic Acid (OA) or water soluble fluxes were not new, they had been around for many years but had never gained much popularity while solvent cleaning was so easy and cheap. Now they were regarded as the savior of the industry, indeed for a while they became the preferred method of fluxing.

There are many advantages in using OA fluxes. They are highly active, and therefore permit the solder to wet easily even if the materials have less than excellent solderability. They foam well, they use the same method of density control as RMA and the change to an OA flux was simple in both wave and reflow technologies. Finally the residues can easily be removed with nothing more than hot water.

The negative effects are tied to the cleaning process. If boards are left sitting around after soldering or reflow and before cleaning, corrosion can occur. The assembly must be designed in such a way that it does not contain areas that cannot be completely washed. Being extremely acidic, residues that are not completely removed can cause major damage, often after months or even years in the field.

As the circuitry has grown more complex and more tightly packaged it has become more difficult to maintain the degree of cleanliness required. The OA fluxes have been dramatically improved, but water cleaning has become more complex and expensive. In most cases a final deionized water wash is necessary to arrive at the required cleanliness, the wash water must be heated, softened and of high resistivity. In other words the cleaning off of the flux residues is no longer the cheap simple process it was when OA fluxes were first used.

Some simple rules for using OA fluxes:

1). The design must not have places that will retain flux, e.g. Flush components, braided or stranded wire.
2). The cleaning system must be tightly controlled and monitored for temperature, water cleanliness and volume.
3). Sample assemblies must be checked for cleanliness routinely during the cleaning cycle.
4). The manufacturing process must be such that soldered boards do not sit around before cleaning.

Flux manufacturers will tell you that their fluxes permit assemblies to wait after soldering and before cleaning, but for the sake of process control it is wise to minimize the wait and maintain a constant time.

So we changed from Rosin to OA fluxes because of the cleaning problems. Then water cleaning became more expensive and complicated and the very tight packaging and the use of flush mounted components made its use ineffective in many designs. This triggered the revival of a very old idea, the use of “No Clean” (NC) fluxes, that is fluxes that leave a harmless residue after soldering.

They first came into being around the time the PWB was developed, fluxes that did not leave residues that had to be cleaned off. The idea worked but required a very tight control of many of the wave soldering functions and as solvent cleaning was readily available, why bother? So NC fluxes blossomed but soon withered and almost died. They lay dormant until the newer designs stretched the capability of the OA and rosin fluxes. Today it is probably the most widely used method of fluxing and together with the OA fluxes make up 95% of the fluxes used in our industry. NC fluxes have improved tremendously since the early days, but there are still some facets of their use that must be remembered.

1). They are “no clean” fluxes not “no residue” fluxes. There will always be some residues left on the assembly.
2). The active ingredients that could cause corrosion or low surface resistance are broken down into harmless gasses by the heat of soldering.
3). This infers that the amount of flux applied must be tightly controlled as well as the pre-heat and dwell time at soldering temperature.
4). As no cleaning will be done, special care must be taken during manufacture to avoid other contaminants from handling and storage.

The foam fluxer was incapable of the tight control required with NC fluxes in wave soldering and the “total loss” spray fluxer has become the standard. Liquid NC fluxes have a very low solids content, (1 – 2%), and the old type of density control is no longer effective . With the “total loss” fluxer fresh flux is always supplied and no flux density control is necessary. See the article Using “No Clean” fluxes in the Wave Solder Machine.

With tight control of the soldering parameters such as pre-heat, dwell time in reflow and contact time with the solder wave in wave soldering it is possible to produce soldered boards that have the cleanliness requirements for today’s products. Process control is the secret, very tight control of every facet of the soldering process.

So which flux to use? Each has its advantages and disadvantages, which are primarily concerned with the degree of cleanliness demanded by the circuitry and the environment in which the product will be used. Each flux will produce sound soldered joints, all require close control of the soldering parameters, and a sound understanding of the soldering process.

Hirsch Metals sells a variety of fluxes to meet almost any need.

The broken oxide particles become wetted with solder and float to the surface forming the thick silvery slush we call “dross”. This is more than 90% clean solder and in the early days of wave soldering, we pressed dross in a perforated spoon to force the free solder out and and returned it to the pot.

Now there are machines that will do this and they can salvage a high percentage of the solder. Similarly the use of a “dross reducing agent” which is sprinkled over and mixed into the dross will return much of the free solder to the pot, leaving only a small amount of gray oxide floating on the surface which can easily be removed.

There is a common belief that contaminants in the solder increase the rate of dross production. This is a complex subject but at the temperatures normally used in wave soldering, (around 260C) and the degree of contaminants normally found in a wave solder machine, they have little or no effect. In fact of the 8 most common contaminants, small amounts of six of these, actually reduce the amount of dross formed.

The addition of Phosphorus to the solder will reduce the amount of dross produced, and is the addition found in many “low dross” solders. However excessive amounts of Phosphorus can cause grittiness in the joints and dewetting, and it is generally not a recommended additive. The degree of turbulence in the wave is the prime factor in determining the rate of dross production and everything should be done to maintain this to a minimum.

A) Set the wave height as low as possible.
B) Keep the solder level in the pot as high as possible.
C) See that any “solder chutes” or guide plates in the pot are adjusted correctly.
D) Make sure there are no cracks of missing screws in the nozzle.

If the the oxide on the solder surface can be eliminated so is the formation of dross. In practice there are only two ways to achieve this.

1). Maintain a layer of tinning oil on the solder surface. This will have to be replaced routinely, about every 40 operating hours, and many users find this increases the amount of maintenance on the pot. Some of the oil may find it’s way onto the PWBs which can be a problem if soldering with the No Clean process.

2). The use of a nitrogen blanket over the entire solder surface, is probably the most practical method of eliminating dross. Many users claim that the reduction in maintenance and the lower solder consumption pays for the cost of the nitrogen. In addition it permits a reduction in the amount of flux applied when using the No Clean process and thus reduces the residues left on the soldered assembly.

It is extremely difficult to measure the rate of dross production accurately, unless carried out over several weeks There are so many variables that can affect the results. The excellent paper published in 1980 by the Tin Research Institute is probably the definite document on the subject, and says the following
“When these considerations are taken together, the various and contradictory opinions as to the effect of particular impurities on dross formation are readily explained. For example, aluminum at the 01% level would produce 25% more oxide or oxidation than pure 60/40 alloy at 245C, while at about 265 C it would produce 15% less.”