Wave Solder Pot Contaminated with Lead

Richard Boyle is a Global Product Champion at Henkel Electronics. He has over 25 years experience in the electronics assembly industry and is responsible for the global technical service of all of Henkel's solder materials.

Mr. Smith has been supporting customers in the electronics assembly industry since 1994. His expertise is focused on solder paste printing and reducing soldering defects. He holds a BS in Chemical Engineering and an MBA in Marketing. He has authored several papers in trade magazines and at industry conferences. He is an SMTA Certified Process Engineer.

Mike Scimeca created FCT Assembly after the purchase of Fine Line Stencil, Inc., and consists of two major operations: stencil manufacturing and the manufacturing of electronic assembly products such as solder paste, flux and solder bar.

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.

Dr. Poole is a Senior Applications Chemist in Henkel Technologies, electronics assembly materials application engineering group. He is responsible for all of Henkel's assembly products including soldering products, underfills, PCB protection materials, and thermally conductive adhesives.

Kevin is part of the Sunstone Management team. In his role as Quality Assurance Manager, Beattie’s 25+ year background in Printed Circuit Board manufacturing is a tremendous asset to the Sunstone team. In addition, he brings valuable experience from his previous roles in the following areas: process engineering, new process introductions, support of nearly every manufacturing process, and extensive knowledge of Continuous Improvement, ISO, IPC, and various other industry requirements.

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.

Mr. Feinberg is a 52 year industry veteran and President and founder of Fein-Line Assoc, a consulting group serving the Global Interconnect and EMS industries.

Ed Zamborsky is a Regional Sales & Technical Support Manager for Thermaltronics, located in New York. His position requires frequent customer visits throughout North America and the Caribbean and his position encompasses not only sales but the role of trainer and master applications engineer for all of Thermaltronics products. His expertise includes such specialties as hand soldering, convection and conduction reflow techniques, array rework, fluid dispensing equipment, and fume extraction. Ed has authored many articles and has presented many papers on topics such as; Low Volume SMT Assembly, Solder Fume Extraction, SMT Rework, BGA Rework, Lead-Free Hand Soldering, High Thermal Demand Hand Soldering, Lead Free Visual Inspection and Lead Free Array Rework.

Richard D. Stadem is an advanced engineer/scientist for General Dynamics and is also a consulting engineer for other companies. He has 38 years of engineering experience having worked for Honeywell, ADC, Pemstar (now Benchmark), Analog Technologies, and General Dynamics.

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.

I agree that find the root causes of the Pb contamination is the first action. I do not know what your lead-free alloy solution is, but maybe you should check also if concentration of copper andiron are above of 0.30% and 0.020%, respectively. In past I was working as consultant and I was presented to a contamination case.

In the first approach the customer told me that the issue was only about 0.50% of lead concentration.When I got access to the machine and the chemical analysis reports and I could see that copper and iron limits were also above the limits. For the iron contamination a quick examination show some machine parts were eroded...

Some parts were changed, others not, remained in the state. They don't tell me but the machine was retrofitted (a bad one) from SnPb to lead-free. For the copper, I could see that machine was dedicated to run OSP mother boards (thousands and thousands boards per week) and they never had controlled copper concentration in the bath. Also they didn't want fully replace solder in the pot. So, I did the calculations and I recommended they should remove 80% of soldering in the pot (about 560kg) putting melted solder into minor molds with capacity of 20kg each.

After solder cooling, each mold produced a contaminated solder bar with 20kg each. So, I asked to complete the machine solder pot with new solder (SN100 alloy), since I could not use SAC305 due to copper be above the limits.When the machine was completed with melted solder (about 700kg) they sent samples to external chemical analysis in the solder supplier lab. After the analytical results, all the concentrations were within the limits again (as expected) and the machine was released to restart production.

No major changes in the yields or line quality indicators were observed in during the week I was there. The contaminated solder bar were used following the rule: for each 100kg of new SAC305 solder bar disposed into the pot a 20kg contaminated solder bar could be used to feed the solder pot. As well, the chemical analysis frequency changed from once per month to once per week (the solder bar supplier did this without cost!).

Also we created a SPC for the chemical elements inside the machine to make easier take decision to abandon use of contaminated solder bar in the pot (if necessary). For my happiness they used all the contaminated solder (split in 20kg minor bars) without cause a new contamination of solder pot. In terms of root cause, I gave them some directions, but I did not take part of the investigation team.

And the best answer goes to Richard Stadem from General Dynamics. He mentioned the Pb will stratify at the bottom of a still pot held at a minimal temperature, the material with the lead concentrate will be more liquid and heavier, so use the bottom port to decant with still solder.

This would best be done after a minimal soak temp over a 12 hour period to obtain the concentration of lead at the lowest possible layer of stratification in the pot.

David Bao has more than fifteen years of experience in developing new solder paste, wave soldering fluxes and other SMT consumables. He currently serves as the Director of New Product Development at Metallic Resources Inc. He received a Ph.D. in Chemistry at Oklahoma State University.