What Is Causing Connectors to Bow?

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.

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.

Kay Parker is a Technical Support Engineer based at Indium Corporation's headquarters in Clinton, N.Y. In this role she provides guidance and recommendations to customers related to process steps, equipment, techniques, and materials. She is also responsible for servicing the company's existing accounts and retaining new business.

Mr. Dimock is the manager of Process Technology at BTU International. His extensive experience in thermal processing includes positions at Corning, GE, and Sylvania. He has authored numerous articles on lead free processing and process control, taught classes at SMTAI, and participated in the IPC Reflow Oven Process Control Standard committee.

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.

Looks like CTE issues like everyone else is saying. I would look at the profile and perhaps PCB fixturing. I'm guessing the PCB is thermally unbalanced in terms of layer stack-up and you may have to address this by finding a profile that mitigates this situation, or if not possible, back-add the connector in a secondary process. A hold-down on the connector will likely provide insufficient pressure to overcome the forces that are causing this.

Georgian Simion is an independent consultant with 20+ years in electronics manufacturing engineering and operations.
Contact me at georgiansimion@yahoo.com.

I agree that the issue is he different thermal expansion coefficients of the material involved. In addition to the fine ideas others have presented here.

I would suggest you refer to the connectors data sheet and be sure that your lay-out follows the recommended design and that your profile does not exceed any of the manufacturers recommendation. If any discrepancies are noted think about following the manufacturers recommendation.

If all is well with your lay out then I'd look hard at your profile. I'd try a bit of soak before you hit reflow to try to get everything hot and stable as far as expansion goes. From there get your profiler out and grind until you get it.

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.

I would like to know what solder alloy Mr. York switched to that enabled a reduction of 40 deg. C, without compromising the overall SJ strength and reliability? Was it from SAC305 to Sn63 or Tin/bismuth? A reduction of 40 deg. C is pretty significant, and if the switch was to Sn63 then you do get something for nothing, but not if the switch was to tin/bismuth or some other alloy.

Was this in a Hi-Rel application? But I do understand that while there may be a reduction in reliability from a number of cycles to failure standpoint, this may well be within the reliability requirements of the product, for the application used. If the product was exempt from RoHS requirements that is understandable also.

I would like to know what solder alloy Mr. York switched to that enabled a reduction of 40 deg. C, without compromising the overall SJ strength and reliability? Was it from SAC305 to Sn63 or Tin/bismuth? A reduction of 40 deg. C is pretty significant, and if the switch was to Sn63 then you do get something for nothing, but not if the switch was to tin/bismuth or some other alloy. Was this in a Hi-Rel application? But I do understand that while there may be a reduction in reliability from a number of cycles to failure standpoint, this may well be within the reliability requirements of the product, for the application used. If the product was exempt from RoHS requirements that is understandable also.