Connect with us

Desoldering Grief

Discussion in 'General Electronics Discussion' started by Greg J., May 2, 2014.

Scroll to continue with content
  1. Greg J.

    Greg J.

    24
    0
    Oct 8, 2013
    I'm a soldering newb. I have quite a few old computer PC boards that I thought I would scavenge for discrete components before sending them to the great recycling center in the sky. I discovered that the components appear to be well attached to the boards without solder. I tried both a heat gun (set way hotter than I thought it should take) and an iron on the backside of a board and more often than not that I could not pull the component off with pliers even with the solder (presumably) melted. I discovered once that a capacitor would rather melt than let me pull it off. Can anyone explain why I am having trouble and how I can get these components off without destroying them? Thanks!
     
  2. Supercap2F

    Supercap2F

    550
    150
    Mar 22, 2014
    Well it sounds like the solder got hard before you could pull the components off. The way I take two legged components off of a circuit board is I bridge there legs together with a blob of solder and put the soldering iron in the blob and pull the component off with my fingers. Another way is to use desoldering braid. I have a hakko 808 desoldering tool that has a cylinder that gets real hot and you push the trigger and it just sucks the solder off.

    Hope I have helped

    Dan
     
  3. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,271
    Nov 28, 2011
    RoHS-compliant boards use lead-free solder which has a higher melting point than standard solder. Multi-layer boards have high thermal mass and it is difficult to heat up the pads under large components because the heat travels to the inner layers very quickly. Sometimes, the glue that components are stuck down with before the board is reflowed in the oven can be pretty strong. These factors can all contribute to the difficulty you're having.

    You can buy low-melting-point solder that you can add onto the board to reduce the overall melting point of the solder, for cases where you need to remove a large component intact. There are also desoldering systems with wide flat pieces of metal that can simultaneously heat up all wires of quad flatpack ICs.

    Scavenging components from motherboards is a bit of a losing battle. I try to salvage crystals, but this is increasingly difficult. Inductors and through-hole electrolytics can sometimes be salvaged, but electrolytics should be checked visually and electrically before re-use. Anything with more than 20 pins, or more than 2 sides with pins on them, is impractical without special equipment.
     
  4. daddles

    daddles

    443
    3
    Jun 10, 2011
    For a hobbyist without a lot of cash, a solder sucker (look up e.g. "Soldapullt") might be something you want to try. They're a simple, reliable design (I've been using mine for decades) and they can suck up a goodly amount of solder as long as you melt it. I consider them more handy than e.g. desoldering braid, which is occasionally useful in situations where a solder sucker can't be used (e.g., where there's not enough clearance).
     
  5. Greg J.

    Greg J.

    24
    0
    Oct 8, 2013
    Thanks for all the helpful replies. I usually can't get the solder to melt. I think I need to try a tip other than a pencil-type. The iron is only 35W; hopefully that is enough for the higher temp solders. The idea of putting some solder on so better contact is made is clever.

    I am amazed at all the things there are to know about soldering, and how little information there is on any given web page, lol. Seeing some Youtube videos of people soldering on (or taking) off super-fine pin ICs is amazing. I shudder to think what it would be like if solder wasn't cohesive.
     
  6. Greg J.

    Greg J.

    24
    0
    Oct 8, 2013
    Responsibility comes with knowledge. Responsibility to acquire knowledge comes with ignorance.
    ;)
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-