The pre-bake consideration is also dependent on the components residing on the board. You can check the various IPC standards for this. Remember that increased reflow temperatures for lead-free solders have shortened the typical floor life for components and boards.

The MSL levels can vary, but in general 80 to 125 deg. C is a common range for up to 24 hours. There are also "bake and bag" dry storage solutions out there, depending on your rework backlog.

The rule of thumb used by us in our rework area for FR4 and Kapton based materials is 105 degrees C for 8 to 12 hours to insure that all moisture absorbed into the pcb materials are driven out and we also bake out the components that will be used as well during the rework.

Same profile unless the parts are not rated for that temperature bake out. Then one must increase the length of bake out at a lower temperature but most parts can be baked out at a higher temperature without compromise.

BGA's are the most susceptible but other overmolded qfn style packages are also susceptible. Good question and good luck. Rework requires patience.

Pre-bake prior to rework is highly recommended. This is especially the case for BGA and PTH, less so for SMT resitistors. The requirements should be based on the materials, not the fact that you are going to perform rework since the thermal excursions should be no more agressive than your original reflow profile.

Do not forget to pre-bake your BGAs too. We have seen many cases where PBGA components delaminate due to moisture.

I would recommend IPC/JEDEC J-STD-033B which is a specification for handling, packing, shipping and use of moisture/reflow sensitive surface mount devices. It is available on the JEDEC website after logging in.

We follow their recommendations for our manufacturing process.

In my experiences and experiments it never hurts to pre bake epoxy with ED copper being heated at high temperatures. Prevents heat shock and helps eliminate pad lifting.

250 degree F for 2 hours

IPC also has these instruction that you should follow so you comply for your reliability.

I cannot answer your specific question, but I would like to point out that if you are subcontracting, you are doing it to save money. If you are doing rework, you are not saving money. You are spending more.

I would carefully review your vendor and possibly either select an alternate or bring it all in house. You should be able to eliminate this rework altogether. Obviously I do not have all the details, but those are some thoughts to consider.

No, it is not a common practice to pre-bake an assembled PCB prior rework, unless the PCB storage conditions (eg high humidity over long period of time) are bad.