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November 15, 2018

Mixing Different SAC305 Solders

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

M.K.

Experts Comments

If both of the manufacturers certify that their products conform to the requirements of J-STD-006, then the solders should be interchangeable. There may still be differences between different manufacturers' products with regard to the amounts of certain contaminants present, based on the source materials and processes used to manufacture the bar, but unless you have specific concerns/knowledge that lead you to conclude you need lower contamination limits than specified in J-STD-006, this should not be an issue.

If you are producing high-reliability electronics (class 3), you will want to have independent testing 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.
Provided the new material meets the requirements of the appropriate JSTD, I would see no issues in mixing the SAME alloy from two suppliers.
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 two different vendors materials are of the same chemical levels there should be no issues.
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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 than your 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.
Greg York
Technical Sales Manager
BLT Circuit Services Ltd
Greg York has twenty two years of service in Electronics industry. York has installed over 350 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 elemental specifications from one manufacturer to the other, so they are normally identical in composition. Adding one SAC305 to another manufacturer's SAC305 is not usually a problem.  

Some manufacturers may use some recycled materials to make the bar solder but because of the high tin content this is done to a lesser extent than tin-lead solder. If it is recycled you want to pay attention to the impurities but also it may create more dross in use at times. Creation of more dross or oxides during use will not impact quality of the solder joint but increase operating costs.  

The other factor is the quality and consistency of the solder itself, composition at times depending on the method used to make each bar, the tin or silver content may be higher or lower. Process consistency is key, so dealing with a reliable supplier is important.  

It is important to have the lowest lead content and copper within limits since this may go up in use 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 would recommend you to check the certificate of conformity (CoC) or the certificate of analysis (CoA) of the new suppliers alloy: does it conform to J-STD-006 ? are the maximum levels of impurity the same or even better compared to your current supplier?

Second, check the quality of your current solder bath: is it in the specification or close to the limits? If necessary, adjust it first. Then, you can add the new 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 patents on solder alloys, I would doubt there would be a problem. To verify this make sure you review the certificate of analysis which comes in with every lot of solder you buy. The analysis should be very similar, if they are not something is wrong and I would not mix them, but if the percentages are exactly the same then I see no problem in mixing them in the wave.

If this is the first time you are thinking about doing this due to the cost of solder from one supplier to another, this raises a red flag. I would recommend an independent analysis of the alloys to make sure they are in fact compatible. Additionally make certain the analysis also checks for sulfur and other types of salts as these are sometimes used to clean impurities from reclaim solder and this could lead to increase dross in the wave.

Finally I would recommend working with reputable firms in the purchase of bar solder for the wave as there is no such thing a low cost solder. It may be less expensive to buy, but the quality of the solder joint and the quality of the product 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  SAC305 bar from different suppliers is fine.  However, keep in mind that some solder manufacturers use virgin raw metals and some use reclaimed metals. Putting reclaimed SAC305 bar into a solder pot with virgin SAC305 can cause contamination and excessive drossing.  Contamination, depending on the type and amount, can affect solder joint strength and reliability.  

In the distant past, OEMs and CMs would test a supplier's solder materials for purity and consistency and would only purchase from approved suppliers. Many still do, but the volatility of the metals market is pushing price to the forefront. The pressure to switch, or add solder suppliers, without proper testing is growing.  

Ultimately you want your customers to have confidence in the quality and durability of your products. Your suppliers play a very important role in helping gain that confidence. The best answer is to test the composition of a few different lots from your prospective solder supplier. The process is quick and painless and will give you the data you need to make the best choice.
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.
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