Hi all, I had some old stock of CEM1 pcb: a. How long & under what temp. condition shall I bake it to eliminate the trapped moisture ? b. Is the baking time & temp. different for 3 yrs old stock, 2yrs old stock & 6 month old stock ? c. For CEM1 pcb, what is the safe manual soldering temp. and duration without side effect to the pcb ?
The time and temperature required for baking moisture from your boards varies according to the conflicting desires to: * Remove enough entrapped moisture. * Desire to retain solderability of solderable surfaces.
Search the fine SMTnet archives for suggested board bake recipes. Unfortunately [for you] most of these recipes are for FR-4, but this is not rocket science. Something makes me want to say CEM-1 boards should require less bake than FR-4, because of the lower resin content, but I�m not sure. Your fabricator is probably the best source of advice.
Bake time should be a function of the amount of mosture retained in the boards. So, bake time is a function of weight gain. Weight gain is a function of the substrate and available moisture, with the boards saturating at some time or another. Odds are all your boards are saturated.
Safe manual soldering temperature and duration without side effect to the PCB: 580-650�F, depending on pad size; 63/37 solder; liquid flux; 2 seconds, depending on pad size