Soldering Help

Discussion in 'General Electronics Chat' started by Steve55, Feb 11, 2013.

  1. Steve55

    Thread Starter New Member

    Nov 30, 2008
    I am trying to solder four 28AWG wires onto a USB PCB. The PCB has four plated thru holes. The board is about .095" thick and I am using lead free solder @ 650 degrees F with a HAKKO FX951 and a heavy tip. I cannot get the solder to flow all the way through the thru holes with out having the wire insulation melting back up the wires. Will I need to preheat the boards? Thank you.
  2. #12


    Nov 30, 2010
    1) use wire that has insulation that doesn't melt back.
    2) add shrink tubing over the bare part.
    3) don't worry about it. They aren't going to melt back far enough to cause a short.
    4) pre-solder the board and insert the wire end later.
  3. Steve55

    Thread Starter New Member

    Nov 30, 2008
    Thanks for the ideas. I will try #2 but will probably end up using #3. I should have mentioned that the wires are in a jacket. It looks like regular USB extension cable. They would also like me to keep the distance from the cable jacket to the board at 5/16". I tried pre-soldering the holes and it worked great for the first wire, but I don't have the skill to get the other three wires in with out butchering up the insulation.
  4. takao21203

    AAC Fanatic!

    Apr 28, 2012
    There are some things you can do.

    Pretin the wire, so the soldering goes faster.

    Often not neccessary but add some flux.

    Use a lead solder for lower temp.

    Use a broad tip.

    All this should work.
  5. KJ6EAD

    Senior Member

    Apr 30, 2011
    Clip a heat sink or hemostat to the wire just above the joint area prior to soldering to prevent heat damage to the insulation.

    Remember that heat rises. Sometimes you can gain some advantage by orienting the work with the most heat sensitive parts to the side or below the heat source.
  6. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    You absolutely do not need 100% solder hole fill (that's high reliability/mil spec stuff). Just enough to keep/attach the wires there.
  7. Steve55

    Thread Starter New Member

    Nov 30, 2008
    Thanks to everyone who replied with their comments and advice. This is what I ended up doing. I applied heat with an Aoyue hot air tool to the cable side of the board after the wires were installed. I had to shield the wires with tin foil to keep the insulation from receding. I am very happy with the way it turned out. The company I'm doing this work for wanted to see at least some solder on the destination side of the board.

    I used a PanaVise to hold the board and duct taped the hot air tool to the side of the bench. Again, thanks for all the great input.
  8. sheldons

    Well-Known Member

    Oct 26, 2011
    you could solder some pcb pins and solder the wire to the pin and sleeve it.....