Ask the Experts
August 15, 2017 - Updated
July 4, 2007 - Originally Posted

Lead-free bar solder for wave soldering

We are about to switch over to lead-free wave soldering. I was wondering if there are any technical articles comparing the quality of bar solders from different companies? What is the most widely used product for lead free bar solder?

Del Iacobucci

Expert Panel Responses

Can't help with the solder bar issue but Lead Free Intrusive Reflow is a process which eliminates the need for wave soldering. I can email you a copy of a recent article presented at APEX 2007 on this subject.

Bill Coleman
Vice President Technology
Photo Stencil
For over 18 years, Dr. Coleman has been the vice president of technology for Photo Stencil, working closely with customers to understand their printing requirements. His efforts have resulted in several new stencil products.

There is not any testing that I am aware of comparing brands of lead free solder. However there are a lot of test comparing alloys. The first lead free wave solder used was SAC305 however there is a trend to move away from high silver alloys to no silver of low silver alloys. There are several conditions that need to be prioritized, copper dissolution rates, appearance ( grain structure), wetting, voiding, and maximum temperature requirements. All of these come into play to choose a lead free alloy. The largest move has been to Sn/Cu + alloys. Additives (+) can be Ni, Co, Bi, Ag to mention the most popular additives. I have my favorites as do most of the people responding to your question.

Karl Seelig

Deck Street Consultants
In his 32 years of industry experience, Mr. Seelig has authored over 30 published articles on topics including lead-free assembly, no-clean technology, and process optimization. Karl holds numerous patents, including four for lead-free solder alloys, and was a key developer of no-clean technology.

At this time, the solder with increasing market share in wave applications is tin-nickel-copper, such as SN100C from Nihon Superior. I don't know if there is any published data on which lead-free solder is the most widely used.

Dr. Craig D. Hillman
CEO & Managing Partner
DfR Solutions
Dr. Hillman's specialties include best practices in Design for Reliability, strategies for transitioning to Pb-free, supplier qualification, passive component technology and printed board failure mechanisms.

Although I've seen many companies who have switched to lead-free soldering in their wave solder machines, I've not seen any internal comparative analysis results from these operations. This phenomenon of comparative analysis used to be a common occurrence during the Tin/Lead soldering operations however I would imagine that with the various patented alloys today, the comparison is not so much evaluating the differences between suppliers but understanding the differences between the alloys. Since many of the lead-free alloys are patented, one would have to contact the vendors or suppliers directly to get any information about their particular alloy combinations and operational profiles. As for which of the alloys is most widely used, IPC and iNEMI have recommended the use of SAC 305 alloy, while the Japanese manufacturers are recommending the use of Sn100C solder. They both work fine, but users have to do the reliability work to determine which is best for their process and products. Hence, experiments are still being conducted and the results are still being developed to create an overall industrial application of these alloys.

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.
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