Solder Alloy Investigation

Is there a test to confirm the precise solder alloy used on an assembled PCB? We need to rework components on assembled circuit boards but have no reference for the solder alloy, so we are not sure what rework temperatures will be needed.

R.A.

Expert Panel Responses

XRF (X-ray Fluorescence) equipment can provide detailed composition results without harm to the product. Circuit Technology Center, Inc in Haverhill MA. is a source that can support this service.

David Cormier
Engineering Manager
Circuit Technology Center, Inc.

Manufacturing Engineer of 20+ years. Involved in Industries relating to all sectors of defense, Commercial product Industries, RF - Microwave and Semiconductor industries. Vast knowledge and experience relating Mil-STD’s, IPC-STD’s, EAI-STD’s, GEIA-STD’s, J-STD’s and MIL-PRF-STD’s.

The best non-destructive method for determination of the alloy used would be XRF (X-ray Fluorescence Spectroscopy). Many labs that service the PCBA assembly industry will have this capability as well as PCB fabricators. There are small handheld unit available by you would need to investigate the accuracy. If the product is labeled RoHS it is more likely than not that the alloy is SN100 or SAC305, but you can’t be sure without a test.

Kevin Mobley
PCBA Engineering Liaison
General Atomics Electromagnetic Systems Group

Kevin has over 30 years of experience in process and manufacturing engineering serving in both EMS and OEM companies. Expertise includes all aspects of SMT as well as wave solder and CCA materials such as PCBs, solder material, and component finishes. Kevin has developed processes for thousands of assemblies from stencil printing to conformal coating and testing.

The precise alloy may be difficult to determine without sending a sample out to be analyzed. I believe it would be more important to determine if the solder is leaded or lead-free. This would allow you to solder within the ball park temperatures without risking damage to the board or components. Depending on what type of rework operation you are performing, you may try using just enough heat required until you see the solder starting to flow. If this is a circuit board with a large amount of ground plan, you should consider pre-heating the board prior to rework.

Brien Bush
Manufacturing Applications Specialist
Cirtronics Corp.

Mr. Bush has 20 years experience in electronics contract manufacturing. Major areas of expertise include through hole, SMT, wave and selective soldering.

I do not know if there is a test you can do to determine the precise solder alloy unless you send a sample to a lab. For a quick test I’d recommend the following:

Determine if the solder contains lead or if it is lead-free. There are several lead testing kits in the market. If the solder contains lead, you will either have 63/37 or 60/40 tin-lead alloy. These two alloys are the most common when it comes to lead solder.
If the solder is lead-free, there is a high probability that it is a SAC 305 alloy. Again, I’m applying the same principle as I did with the lead solder. SAC 305 is the most used for lead-free solder.

Edithel Marietti
Senior Manufacturing Engineer
Northrop Grumman

Edithel is a chemical engineer with 20 year experience in manufacturing & process development for electronic contract manufacturers in US as well as some major OEM's. Involved in SMT, Reflow, Wave and other assembly operations entailing conformal coating and robotics.

XRF can be used to identify the major constituents of an alloy without damaging the solder joints. The solder could be physically removed, dissolved, and analyzed using ICP or AAS techniques. That would destroy at least 1 solder joint, but is a very accurate method of identifying the metallic constituents.

Tony Lentz
Field Applications
FCT Assembly

Tony has worked in the electronics industry since 1994. He worked as a process engineer at a circuit board manufacturer for 5 years. Since 1999, Tony has worked for FCT Companies as a laboratory manager, facility manager, and most recently a field application engineer. He has extensive experience doing research and development, quality control, and technical service with products used to manufacture and assemble printed circuit boards. He holds B.S. and M.B.S. degrees in Chemistry.

Yes, there are several test, but the easy and simple way to know the alloy and the elements of the solder joints is the XRF analysis. We can help to you on this and other test in our laboratory.

Andres Rojas
Engineering Director / Master IPC Trainer (MIT)
AMMSA Solutions

More than 20 years of technical experience in the electronics industry in roles ranging from Process & Project Engineer to engineering manager and Technical Applications Engineer for Latin Americas. IPC Master Trainer, International speaker and consultant.

XRF testing can be used to determine the composition, or to detect the presence of a certain element in the alloy.

Amit Bahl
Director of Sales and Marketing
Sierra Circuits

Amit Bahl started to work at Sierra Circuits in 2006 where he formed strong relationships with his customers working with them on flex PCBs, HDI, controlled impedance, etc. In 2009, he was promoted Director of Sales and Marketing.

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