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Board Talk
At Board Talk, the Assembly Brothers cut through the marketing hype, the platitudes and incompetent un-scientific baloney with a search for the truth.
This episode features:
Phil Zarrow, ITM ConsultingPhil has been involved with hybrid and PCB assembly for more than 30 years including equipment design for pcb fab and assembly. 
Jim Hall, ITM ConsultingJim has a wealth of knowledge in soldering and thermal technology, equipment and process basics and is a pioneer in the science of reflow technology. |
Is There A Thermal Cycle Limit?
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Comments and Questions At my company we qualify PCB suppliers based in part on HATS or IST via reliability testing. For the test, we specify 6 preconditioning cycles, which simulates the manufacturing process for a complex board (2 reflow cycles, 1 wave solder, 1 BGA rework - it adds up fast). Then we limit our assemblers to 6 thermal cycles at any one site. Thus we maintain the validity of the reliability qualification. J.K. There IS a limit, but there are so many variables that its hard to define. Too long at the Td and the resin degrades. Too long at Tg and delam occurs. Too much Z axis movement and the interconnects separate from the barrel and the pads rise breaking the "knee" of the hole wall/pad interface. The only way to understand the limits for your own process is to perform DOE's and destructive analysis as part of the validation of the reflow and rework processes. Too often CCA assemblers are enthusiastic about throwing the PWB supplier under the bus and unwilling to examine their own processes. I have been on both sides of the business. Is there a thermal cycle limit ... no. Michael Nadreau, Henkel Corp. Thermal Cycles - tough question to answer - as you stated there is no set number of cycles, it will be dependent on temperature and the component, board material etc.. Keep up the program very informative. Randy Bock, Pitney Bowes "Board Talk" is very informative. Keep the articles coming. Dan Pereira, GBE |
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