Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Ryan Jennens

#12995

Thermoplastic Casing? | 12 January, 1999

How is everybody?

I was asked about any problems that would be associated with having a plastic casing injection molded around an assembled PCB. I am not sure if injection molded plastic has to be hot, I am assuming so (can they use epoxies?). If they use hot plastic, I beleive there would be an issue with the speed at which the parts would be heated. Wouldn't they be heated faster than the max recommended ramp rate (4 deg/sec)? There might also be issues with the different CTEs of board and parts. Can you pre-heat assembled PCBs before the casing is applied? Are there any other issues? Is anybody doing this? I am sure I will need to supply more info, just let me know what it is. Thanks, gang!

Ryan Jennens Phoenix Engineering Design, Inc.

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Dave F

#12996

Re: Thermoplastic Casing? | 13 January, 1999

| How is everybody? | | I was asked about any problems that would be associated with having a plastic casing injection molded around an assembled PCB. I am not sure if injection molded plastic has to be hot, I am assuming so (can they use epoxies?). If they use hot plastic, I beleive there would be an issue with the speed at which the parts would be heated. Wouldn't they be heated faster than the max recommended ramp rate (4 deg/sec)? There might also be issues with the different CTEs of board and parts. Can you pre-heat assembled PCBs before the casing is applied? Are there any other issues? Is anybody doing this? I am sure I will need to supply more info, just let me know what it is. Thanks, gang! | | Ryan Jennens | Phoenix Engineering Design, Inc. | Ryan: Injection molding a case around a PCA would put a fairly severe stress on the assembly. If you need the assembly needs to function after getting it into the case, you might consider Paraline or some other encapsulant. TTYL Dave F

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