MSL control

Subscribe to Thread

I have a double sided PCBA setup. I have MSL components on ... - Mar 15, 2017 by scotceltic

First, reflow does not reset the clock for MSL exposure. The... - Mar 16, 2017 by DeanM

scotceltic

#77266

MSL control | 15 March, 2017

I have a double sided PCBA setup. I have MSL components on both assembly sides. When I run Assy Side one I am within the allotted hours remaining on the MSL component. I then wait 40 hours before running 2nd Assy side. By then the hours on the 1st assy side msl component have expired. Did the 1st assy side component regenerate due to the 1st reflow cycle ? or do I need to worry about slowly baking the PCBA prior to 2nd assy side ? If so, are there any documents out there that explain the concern between 1st and 2nd assy side and the time allowed between reflow cycles for MSL components ?

reply »

DeanM

#77277

MSL control | 16 March, 2017

First, reflow does not reset the clock for MSL exposure. The best solution is to run the second side before the exposure time expires. I am curious to know why they must sit for 40 hours.

If that cannot be done, then store the assemblies in a dry cabinet until the second side can be run. This will stop the clock but not reset it.

Least preferred is baking the assemblies prior to the second side run. The default bake temperature is 125C and it wouldn't take that long (bake times increase dramatically with lower bake temps).

Get a copy of IPC/JEDEC STD-033C. This will explain everything.

reply »