|Ask the Experts|
January 15, 2021
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?
|Expert Panel Responses|
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.
Provided the new material meets the requirements of the appropriate JSTD, I would see no issues in mixing the SAME alloy from two suppliers.
S T and S Testing and Analysis
As long as the assay reports on the two different vendors materials are of the same chemical levels there should be no issues.
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.
Technical Sales Manager
BLT Circuit Services Ltd
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.
Senior Market Development Engineer
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.
Inventec Performance Chemicals
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.
Vice President, Technical Director
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.
V.P. Technology & Engineering
Fine Line Stencil, Inc.
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.
In theory yes you can mix suppliers, however we have had issues where compliant SAC305 actually had various 'anti-dross' agents added. For wave soldering this may be okay, but for selective can cause issues.
Pillarhouse International Ltd
I wouldn't have solder joint reliability concerns, but there can be performance differences between vendors due to material inputs and manufacturing processes. And as Simon points out, selective soldering processes cannot have dross reducing agents incorporated into the alloy as they will dramatically reduce soldering nozzle life.
Director of Product Management
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