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November 15, 2018

Mixing Different SAC305 Solders

We have been using SAC305 bar solder from onesupplier. We now want to source itfrom a different supplier. Should we be concerned if wemix the new bar solder in with the current solder in our wave soldering systems? Are there any reliability concerns?

M.K.

Expert Panel Responses

If both of the manufacturers certify that their products conformto the requirements of J-STD-006, then the solders should be interchangeable.There may still be differences between different manufacturers' products withregard to the amounts of certain contaminants present, based on the sourcematerials and processes used to manufacture the bar, but unless you havespecific concerns/knowledge that lead you to conclude you need lowercontamination limits than specified in J-STD-006, this should not be an issue. If you are producinghigh-reliability electronics (class 3), you will want to have independenttesting done on incoming lots to verify the manufacturers' data.

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Fritz Byle
Process Engineer
Astronautics
Fritz's career in electronics manufacturing has included diverse engineering roles including PWB fabrication, thick film print & fire, SMT and wave/selective solder process engineering, and electronics materials development and marketing. Fritz's educational background is in mechanical engineering with an emphasis on materials science. Design of Experiments (DoE) techniques have been an area of independent study. Fritz has published over a dozen papers at various industry conferences.

Providedthe new material meets the requirements of the appropriate JSTD, I would see noissues in mixing the SAME alloy from two suppliers.

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Gerard O'Brien
President
S T and S Testing and Analysis
Gerald O'Brien is Chairman of ANSI J-STD 003, and Co Chairman of IPC 4-14 Surface Finish Plating Committee. He is a key member of ANSI J-STD 002 and 311 G Committees Expert in Surface finish, Solderability issues and Failure analysis in the PWA, PWB and component fields.

As long as the assay reports on the twodifferent vendors materials are of the same chemical levels there should be noissues.

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Jerry Karp
President
JSK Associates
Based in. Northern California since 1971. Founded JSK Associates in 1979. Actively involved in soldering, cleaning, chemistries. 30 years experience in EOS/ESD control.

As long as the impurities are the same or less thanyour existing Alloy with the exceptions of Bi then you should be fine. HOWEVER,many companies claim various impurities so it is best to get it independently analyzed on a reliable analysis machine designed for solder alloys.

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Greg York
Technical Sales Manager
BLT Circuit Services Ltd
Greg York has over thirty two years of service in Electronics industry. York has installed over 600 Lead Free Lines in Europe with Solder and flux systems as well as Technical Support on SMT lines and trouble shooting.

SAC305 bar solder normally follows similar elementalspecifications from one manufacturer to the other, so they are normallyidentical in composition.Adding one SAC305 to another manufacturer's SAC305 is notusually a problem. Some manufacturers may use some recycled materials to make thebar solder but because of the high tin content this is done to a lesser extentthan tin-lead solder.If it is recycled you want to pay attention to the impuritiesbut also it may create more dross in use at times.Creation of more dross or oxides during use will not impactquality of the solder joint but increase operating costs. The other factor is the quality and consistency of the solderitself, composition at times depending on the method used to make each bar, thetin or silver content may be higher or lower.Process consistency is key, so dealing with a reliable supplieris important. It is important tohave the lowest lead content and copper within limits since this may go up inuse and require pot adjustments.

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Peter Biocca
Senior Market Development Engineer
Kester
Mr. Biocca was a chemist with many years experience in soldering technologies. He presented around the world in matters relating to process optimization and assembly. He was the author of many technical papers delivered globally. Mr. Biocca was a respected mentor in the electronics industry. He passed away in November, 2014.

First, I wouldrecommend you to check the certificate of conformity (CoC) or the certificateof analysis (CoA) of the new suppliers alloy: does it conform toJ-STD-006 ? are the maximumlevels of impurity the same or even better compared to your current supplier? Second, check thequality of your current solder bath: is it in the specification or close to thelimits? If necessary, adjustit first. Then, you can add thenew bars, there will no concern of reliability.

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Emmanuelle Guene
Application Manager
Inventec Performance Chemicals
Emmanuelle Guene began her career as an R&D Technician with Promosol, which later became Inventec Performance Chemicals, France. Upon obtaining her Masters of Chemistry degree in Organic Synthesis from CNAM in Paris in 2003, Emmanuelle became a Development Engineer where she has been involved in formulating leading edge solder pastes and fluxes as well as providing training and technical support to customers worldwide. Since 2011, she is worldwide Application Manager.

Based upon all the patentson solder alloys, I would doubt there would be a problem. To verify this makesure you review the certificate of analysis which comes in with every lot ofsolder you buy. The analysis should be very similar, if they are not somethingis wrong and I would not mix them, but if the percentages are exactly the samethen I see no problem in mixing them in the wave. If this is the first timeyou are thinking about doing this due to the cost of solder from one supplierto another, this raises a red flag. I would recommend an independent analysisof the alloys to make sure they are in fact compatible. Additionally makecertain the analysis also checks for sulfur and other types of salts as theseare sometimes used to clean impurities from reclaim solder and this could leadto increase dross in the wave. FinallyI would recommend working with reputable firms in the purchase of bar solderfor the wave as there is no such thing a low cost solder. It may be lessexpensive to buy, but the quality of the solder joint and the quality of theproduct cannot be put in jeopardy, due to buying low cost materials.

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Leo Lambert
Vice President, Technical Director
EPTAC Corporation
At EPTAC Corporation, Mr. Lambert oversees content of course offerings, IPC Certification programs and provides customers with expert consultation in electronics manufacturing, including RoHS/WEEE and lead free issues. Leo is also the IPC General Chairman for the Assembly/Joining Process Committee.

In most circumstances mixing SAC305bar from different suppliers is fine. However, keep in mind thatsome solder manufacturers use virgin raw metals and some usereclaimed metals. Putting reclaimed SAC305 bar into a solder pot with virgin SAC305 can cause contamination andexcessive drossing. Contamination, depending on the type and amount, can affect solderjoint strength and reliability. In the distant past, OEMs and CMs would test asupplier's solder materials for purity and consistency and would only purchase from approved suppliers. Many stilldo, but the volatility of the metals market is pushing price to the forefront. The pressure to switch, or add soldersuppliers, without proper testing is growing. Ultimately you want your customers to have confidence in thequality and durability of your products. Your suppliers play a very important role in helping gain thatconfidence. The best answer is to test the composition of a few different lots from your prospective soldersupplier. The process is quick and painless and will give you the data you need to makethe best choice.

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Robert Dervaes
V.P. Technology & Engineering
Fine Line Stencil, Inc.
Robert Dervaes has worked in the electronics industry since 1992 in both design and manufacturing. Over the past 11 years he has established the technical foundation of Fine Line Stencil, Inc. - a premier stencil supplier to the electronics industry.

Yes, you can mix, but ensure the alloys are from 100% virgin materials, as more and more offers on the market are based on recycled material that makes uneasy the respect of tight impurities range. The better is to check the items as per J-STD-006 make assembly trial in your process. You can perform a lab analysis if required, or an end to line IPC-A-610 inspection should be sufficient to validate first batch.

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Swaroop Pawar
PCBA Industrialization
Schneider Electric
Have 18 years of experience in electronic Industrialization. Specialties in PCB Design & manufacturing process, PCBA Process Development and Continuous Improvement.