1. secretstep

    Thread Starter Member

    Jun 27, 2008
    I'm having a trouble by doing a real project with digital system design.
    Basically I ordered the Cyclone II TQFP 144 pin, but then it says "BAKE" the chip. The moisture sensitivity strip became pink from blue when the seal is opened. So I guess I have to bake the chip before soldering.... but what does it mean by "BAKE" the chip? How can we BAKE the chip? I'm pretty sure we don't cook these.

    Also, why do we need a socket for TQFP or any other FPGAs?
    What are the "burn-in socket" and "test socket"?
    What are the advantages of using the sockets?
    Will the FPGA be damaged if I just solder them on a PCB?
    and the sockets seem to be very expensive.. anyone know a good cheap socket?

    It's my first time buying FPGA and putting it into a digital system. Please help me!
  2. yubyub


    Aug 13, 2008
    I'd like to know the same stuff really, I have to work with an fpga soon. I assume a socket is just an easy way to have a removable chip, soldering it should be fine.
  3. roddefig

    Active Member

    Apr 29, 2008
    Actually, that is literally what you need to do ;). The issue is that if there is moisture inside the chip it could damage it when you heat it to the temperatures needed to reflow solder. So, before you solder it you need to "cook" the moisture out of the chip. The datasheet should have a recommended temperature and time. Any oven should do the trick, but I find toaster ovens work well...

    As far as your questions regarding sockets go, you shouldn't need to use them because you're not mass producing anything. Soldering the FPGA directly to the board will not harm it.
  4. secretstep

    Thread Starter Member

    Jun 27, 2008
    wow that was very clear. So, I really bake the chip, haha. Thank you very much.
  5. dwurmfeld

    New Member

    Apr 27, 2008
    It is true that if you are reflowing the chip onto a board with a reflow oven moisture could be a problem. Yes, baking the chip for an hour at 85 - 100C alleviates that problem. But we unsolder and resolder TQFP packages by hand (a few hundred a week) and we do not bake the chips before hand. Even at Pb-Free temperatures solderability is not a problem.

    I use TQFP development boards and hand solder 144 pin FPGA packages to build test fixtures using VHDL. I wouldn't worry. If you are, it will not hurt the chip to bake it, it is just very difficult to handle the chip hot, and if you are in a humid climate, the newly baked chip will capture any moisture back within two hours out of the oven. I live in humid Florida and have no issues just using the chip as is.

    Have fun, report on what you ended up doing and the results.

  6. secretstep

    Thread Starter Member

    Jun 27, 2008
    Thanks for the opinion! I'll let you know when things end up =)