Nalin Jain asked whether it is necessary to bake an assembled board before PBGA rework, and if yes what the recommended temperature & humidity condition would be. Gordon Davy responded with issues associated with damaging the board that the PBGA is soldered to. Another concern is damage to the removed PBGA due to moisture absorption in the package, itself. We must remember that the PBGA construction consists of an overmolded laminate substrate (usually BT resin) to which the silicon is mounted on one side and solder-balls are mounted on the other. I ALWAYS bake assembled boards prior to hot-air removal of PBGAs if I plan to save the PBGA (I am not certain that they are electrically dead). I ALWAYS bake the PBGA I plan to put back on the board (unless I'm certain it has not absorbed moisture). PBGAs are classified according to moisture sensitivity just like other packages (e.g. Level 1 - Level 6). I don't believe there are any Level 1 PBGAs on the market (Level 1 implies that you won't get PBGA delamination, popcorning, when soldering/desoldering the part even if you haven't kept the assembly dry). To be scientific about it, one would need to know the diffusion rates of the overmold plastic and the BT resin substrate. My rule-of-thumb baking procedure is: 24 hours at 125 degrees C ... I start with a cold oven and let the parts come up to temperature with the oven. Although I doubt you could heat the assembly fast enough in an oven to popcorn any parts even if the oven were up to temperature when you put the assembly into it. Check the PBGA package for moisture sensitivity Level X and baking instructions for drying parts that have been subjected to moist environments out of the sealed package. Gary P. --- Gary D. Peterson _/_/_/ _/ _/ _/ SANDIA NATIONAL LABORATORIES _/_/_/ _/ _/_/ _/ _/ P.O. Box 5800, M/S 0503 _/_/ _/_/_/ _/ _/ _/ _/ Albuquerque, NM 87185-0503 _/_/_/_/_/_/ _/ _/ _/_/ _/ Phone: (505)844-6980 _/ _/_/ _/ _/_/_/ _/ _/ _/_/_/_/ FAX: (505)844-2925 _/ _/_/ _/ E-Mail: [log in to unmask] _/_/_/ *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************