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Measuring PCB Stress during the assembly process

Justin

#18277

Measuring PCB Stress during the assembly process | 27 November, 2001

We are currently looking for a way to measure pcb stress during our assembly process. We would like to get an idea of what amount of stress (flex) the boards are undergoing. We would also like to use this to compare a few different processes--for example router depaneling compared to cutter / press depaneling. We're just starting to look into this, but already we have a couple of 'starter' questions: 1. How much "stress" (or flex) is too much? 2. What equipment could be used to make this an easy but accurate measurement?

Thanks, Justin

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#18292

Measuring PCB Stress during the assembly process | 27 November, 2001

Stress is meaningful if it affects the long term reliability in a product's end-use environment.

I don�t believe that things are that straight forward, although it would be nice if they were. Consider that differences in materials, number of layers, thickness of copper, etc may cause boards flexibility as much as your processing methods.

Get started understanding reliability testing of board by looking at SM-785 - Guidelines For Accelerated Reliability Testing Of SM Solder Attachments. Buy it from IPC [http://www.ipc.org]

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#18293

Measuring PCB Stress during the assembly process | 28 November, 2001

Justin, you will find measuring equipment at http://www.omega.com All sensor signals are in uV or mV and require a signal amplifier. If you get an amplifier with display, you can program a conversion factor for mV to board stretch and it will show a peak value every time you touch the board. Stefan

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#18294

Measuring PCB Stress during the assembly process | 28 November, 2001

Contact Cemal Basaran at the University at Buffalo Electronic Packaging Laboratory http://www.packaging.buffalo.edu. They develop Laser inspection technologies and use Moire Interferometry that may be able to do the things you want to do.

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