|
|
|
|
|
|
Ask the Experts | |||||||
|
|||||||
September 25, 2006 - Updated July 4, 2007 - Originally Posted 0201 capacitors creating process problemWe are having process problems with 0201 devices in the new lead free-line. We did not experience these problems with tin lead process. Could this be a problem with too much or too little paste, we are using the same stencils we had for tin lead process? Or could this be an issue with the reflow profiles? P.D. |
|||||||
Expert Panel Responses | |||||||
What is the issue? Tomb stoning? Or not wetting? Tomb stoning can be profiled out to some extent with a hot soak at 200C. Then a slow ramp to 220C. Alloys also have an effect, SN100C eliminates tomb stoning as compared to SAC305. Stencil apertures can also be modified. Home plate or reverse home plate will also show some differences. If it is wetting check to see what finish you are receiving, sometimes if there are thick film terminations there is a high glass frit in them or a Palladium oxide content. This would have to be investigated. Then a proper profile would need to be implemented to over come some of the termination issue, however some may not be capable of profiling out. 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.
We have run several comparison tests between different stencil technologies (AMTX Electroform and Laser-Cut) for Lead-Free solder paste. We fine a large difference in print performance for small apertures (AMTX provides better paste transfer for small apertures like 0201's than Laser-Cut stencils). One good reference is "Choosing a Stencil" which appeared in July issue of SMT Magazine. I have attached an example of the performance difference for 0201's, 0210_Electroform_vs_Laser.pdf. Please call and I will be happy to discuss aperture and stencil design. 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.
The types of process problems that you are having aren't clear, but I will guess that you are experiencing problems with poor wetting and/or poor coalescence as these are the most common issues with 0201s in general. It isn't surprising that these issues would become more prominent with the conversion to lead-free. It is mostly a function of a few factors:
General Manager - Electronic Assembly Americas DEK International 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.
|
|||||||
Submit A Comment | |||||||
Comments are reviewed prior to posting. You must include your full name to have your comments posted. We will not post your email address. |
Free Newsletter Subscription
Circuitnet is built for professionals who bear the responsibility of looking ahead, imagining the future, and preparing for it. Insert Your Email Address |
|
|
|
|