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Tips for soldering wire onto PCB "pads"

Discussion in 'Homebrew and Kit Projects' started by KJ6ZOL, Feb 21, 2019.

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  1. KJ6ZOL

    KJ6ZOL Ham Member QRZ Page

    I'm gradually getting parts together to build a homebrew GPS clock. I am using the W8BH Arduino based design. Instead of the juice hungry LED display he used, I bought a 20 character/2 line LCD display off Ebay. I noted that it is one of those components that have "pads" to solder the wire directly onto the PCB. I haven't done this before. I used Google and didn't find anything other than really basic info. Any tips for doing this, such as soldering station temperature? I will use silver plated 26awg wire.
  2. N1OOQ

    N1OOQ Ham Member QRZ Page

    Do the pads have holes, or just flat pads?
  3. W4KJG

    W4KJG Subscriber QRZ Page

    I'm going to assume flat pads. Strip the wire insulation back about 1/8 inch, maximum. Tin the wire heavily with solder. Tin the pad. Put the wire on the pad and apply heat to the top of the wire until the solder starts to flow and gives a decent looking bond. Add solder if necessary.

    Depending on the soldering tip size, I would generally suggest 700 F degrees.
    KI7HSB likes this.
  4. KJ6ZOL

    KJ6ZOL Ham Member QRZ Page

    Yes, Ken, flat pads. Pin-through-hole assembly is *so* 1995. :p;) Then again, PTH or point-to-point is mostly what I've done, so this is new. Thanks.
  5. W4KJG

    W4KJG Subscriber QRZ Page

    If you have a flux pen, swab the wires and the pads with it before tinning.

    Good luck.
  6. N1OOQ

    N1OOQ Ham Member QRZ Page

    Other stuff...
    Don't move the assembly much until it cools. The wires have leverage and will pull a hot pad right off the board.
    Don't flex the wires much... They will want to weaken and break right above the solder joint. With something like this I usually bundle all the wires together with a zip tie or two to give it some stress relief. This works better if you have multi-colored wires!
  7. WB0RIO

    WB0RIO Ham Member QRZ Page

    A good trick is to strip the end of the wire about 1/8", then bend the end of the wire into a U shape, that
    will cause a blob of solder to wick into the center of the U and create a larger contact point with the PCB pad.
    The soldering iron tip will also fit nicely into the center of the U.
    KD2ACO and AD5HR like this.
  8. KD2ACO

    KD2ACO Platinum Subscriber Life Member Platinum Subscriber QRZ Page

    I also paint a thin layer of clear nail polish on top of the connection and 1/4” onto the wire for strain relief. Those pads are pretty easy to tear off of the board. Use thin, flexible wire to keep the torque low on the connection when you’re moving the other end of the wire around.
  9. K6BSU

    K6BSU Ham Member QRZ Page

    If you worry about wire flexing after assembly, it would help to use small stranded wire (like 28 ga.) After soldering, put a dab of 5 minute epoxy on the joint and onto the wire to prevent any movement close to the solder pad.
  10. KJ6ZOL

    KJ6ZOL Ham Member QRZ Page

    K6BSU, the wire I will use is 26 gauge stranded with real silver plating. I have a roll of it I bought off Ebay from a guy in Israel. The pix he posted of the original roll core indicated that the wire was made in the US in the 80s and was apparently sold originally to the Israeli military. The guy was cutting 100 foot lengths and selling them.

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