Reflow ovens and electrolytic capacitors

Discussion in 'General Electronics Chat' started by DMahalko, Oct 5, 2013.

  1. DMahalko

    Thread Starter AAC Fanatic!

    Oct 5, 2008
    Hobbyist reflow question:

    In the electronics industry, is there some special handling required for using electrolytic capacitors with a reflow oven?

    Are boards usually reflowed without electrolytics and they are installed in a second manufacturing step?

    Apparently most other solid-state board components are tolerant of high heat (including most plastic connectors) but electrolytic capacitors are not, probably because they have a liquid electrolyte that will vaporize/boil and rupture the canister.

    I just fixed an HP LaserJet P3005 main board (formatter) by putting it in a household convection oven at 350 degrees F on a cookie sheet for exactly 8 minutes. There are a huge number of people cooking these boards to fix manufacturing defects.

    It boots now rather than hanging during initialization, though I'm not sure how long it will be stable. It may have needed more heat or longer heating, but apparently the electrolytics have a habit of going poof if heated much more.

    Some people doing this are insulating the capacitors with small crinkled foil shells to keep away the heat during reflow.

    Another option I can see is to put about a 5-10mm cubical chip of dry ice in the foil shell before putting it on the electrolytic capacitor, to provide a cooling atmosphere around the cap while the rest of the board reflows.
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
    Seems to depend on the reflow method and the capacitor. Some datasheets say they can't withstand it, others say they can, for up to 40sec.

    So the answer is: It depends. :)