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Opps, solder joins 2 traces. Now what?

Discussion in 'Troubleshooting and Repair' started by Mac29, Apr 6, 2014.

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  1. Mac29

    Mac29

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    Apr 6, 2014
    Sorry gents, I searched and looked for 'soldering issue', 'bridge' etc. and waded thru 6 out of 9 pages. No luck.

    I finally got my caps for an LCD repair (power board) but made 2 mistakes: some solder joined the cap lead to another silver trace. So I scraped as gently as I could but then some of the green layer came off exposing copper. There seemed to be enough silver left on the long trace so hoping that's not compromised.

    Quick and dirty, I covered the exposed copper between the 2 areas with ... wait for it: whiteout. Too hard to work w/super glue. Should've researched first but...

    So finished my caps (using 50/50 and no flux and other uneducated techniques) and now hope everything works. Have done these repairs before successfully.

    Is that whiteout going to be an issue? I'm not even sure I needed to 'patch' anything as I don't know where the copper extends in the lower layer. Figure if not connected on the surface I see it isn't supposed to touch.


    Appreciate any feedback. Just a Nube fighting crapitalist bean counter corporate behavior.


    Thanks,

    Mac
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Show us a photo, but the general solution is to drag the soldering iron tip between the two bridged traces, parallel to the traces and (obviously) at right angles to the bridge.

    If your iron has no excess solder on it, it will normally both pick up a little of the solder and push the remainder back where it should be.

    If there's a lot of solder, some desoldering wick (or in extreme cases a desoldering "sucker") will help.
     
  3. Mac29

    Mac29

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    Apr 6, 2014
    (*steve*),

    Thanks but the space between the two was so small I couldn't pick up all the solder, using iron or sucker. Therefore the knife. Got the solder I think but then the exposed copper... Will have to get some desolder if there's a next time.

    Main Q was if the copper underneath constitutes an electrical connection between the solder around the cap lead and the other silver trace, as well as whether white out is a bad solution.

    I'm about to put it all back together right now but would like to know what the pros use to 'patch' exposed copper.


    Thanks for the help,

    Mac
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    The "pros" don't pull out a knife.

    We get narrower solder wick.

    I'm not sure how close is too close. I've used both methods on tracks with less than 0.2mm spacing on boards without solder mask.

    The only time I have resorted to a knife is when I actually want to cut a track.

    Repair? Get a short length of wire and use it to bridge the slice you've made in the track. In a pinch you can bridge it with solder, although I tend not to recommend that because whilst accidental solder bridges are always 100% effective, deliberate ones are not! (Murphy's law in practice)

    If the trace is really narrow, you need to unwind a single conductor from a stranded wire (leaving it 30 to 40mm long). Tin this, then solder one end carefully on one side of the break, then the other. If both sides are tinned and your tip is wet, you may not even need any more solder. Finally cut off the free end.

    Solder bridges on tracks with narrow spacing is almost always caused by using too much solder. You can minimise this by using thinner solder (I have some 0.3mm solder I use for *very* fine work) and mostly by wiping the tip of the soldering iron to remove excess solder between joints.

    The tip doesn't have to be really small. The tip I use often covers three or more pins of a device at once and this doesn't cause any real problems. (we're talking about devices with pins with centres a fraction of a mm apart).
     
  5. davenn

    davenn Moderator

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    Sep 5, 2009
    that's where solder wick as steve suggested REALLY comes into its own
    couldn't live without that stuff in my workshops

    Without seeing a pic of what you are talking about its really hard to give an answer to that


    Dave
     
  6. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    Really good advice here. I also find solder wick is very good for tricky jobs. For cutting stuff on PCBs I use a very sharp scalpel, and I hold it near the point and push my hand down firmly on the board so I have accurate control. Like when a dentist rests his hand on your jaw as he's using a hand tool.

    Sometimes a good way to remove solder bridges is to turn the board upside down and apply the iron pointing straight upwards so gravity pulls the melted solder onto the tip.
     
  7. Mac29

    Mac29

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    Apr 6, 2014
    1. I've read on a number of sites about using a knife, obviously these guys weren't the 'pros'. Others recommend dental pick. Somehow Steve read that I cut a track. Didn't cut a track, bridged it because of too much solder/ very small space.

    Solder wick - good to know. Well, davenn & KrisBlueNZ sorry no pic. Save 1,000 words.... Good tips.

    Didn't work so I may order a whole module or try it again. Thought I got the 3 bad caps found. Could be something I can't ID w/the eye.

    Hope to keep learning ; ) so thanks for the input. It's a lot more interesting doing it than reading a textbook.


    Thanx,

    Mac
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    It depends what you're trying to fix. If you have a solder whisker, or some loose solder, you can often scrape it away with whatever you have handy -- even a brush in some cases.

    If you have a major solder bridge, there's no way you're using a knife to fix it -- you stand to damage more than you fix. Perhaps the sites suggest using a knife on melted solder? Sure. But why not use the soldering iron (unless you're using hot air)?

    But without pictures we can't tell.

    I read this as you actually did something that allowed you to see the copper - i.e. the colour of copper, not the colour of solder. It's practically impossible to do this without damaging the copper. It's reasonable to suggest that if you can see reddy, orangy, brown instead of silver then something has happened. You may have even completely removed a track.

    Again, without pictures it's very hard to tell.

    The copper provides a far better conducting path than solder. Up to a point, more current will flow in the copper than in a layer of solder on it. Exposed copper will go brown, but in most cases doesn't need protection. In more hostile environments, to make soldering easier, and for aesthetics it may be covered in anything from a clear layer to an opaque black coat (translucent green is a traditional colour).

    Covering the track in liquid paper probably won't hurt. Coating it in solder is often the easiest for a short run if you've removed the coating. And maybe that is what you removed. However, removing it with a knife risks damaging the track. Whilst the copper is pretty tough, deep scratches can be a real issue if the track carries a high current relative to its size.

    The picture doesn't cost 1000 words, it saves them -- actually it saves far more. :)

    Good/better luck with your future endeavours.
     
  9. Mac29

    Mac29

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    Apr 6, 2014
    OK for the last time, let me try to be crystal clear. The area I scraped was the space between the cap lead and a trace. I didn't do anything to the trace. The problem was the connectivity between the cap and the trace.

    When the excess solder was removed it exposed copper underneath the green layer which vy possibly caused connectivity between......? The cap lead and the trace. So figuring I needed to do something about that, I covered the copper area with what I had handy. Again, didn't do anything to the trace/"track".

    And yeeesssss a picture obviously saves a thousand words. Never said anything about a cost. Guess the operative word is Worth. Looks like I'm replacing the rest of the caps, a fuse and a transistor. Hopefully it will go smoothly.

    Thanks for the tips.
     
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    I answered that exact issue in my last post.

    And the lack of a picture is COSTING ME a lot more time than it should.
     
  11. daddles

    daddles

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    Jun 10, 2011
    For folks unfamiliar with solder wick, it's a chunk of flat-braided copper wire (see attached image).

    If you don't have any solder braid, you can substitute a piece of fine-stranded copper wire. Strip off a 5-10 mm portion and use it like solder wick (put the copper onto the solder you want to remove, then heat the copper with your soldering iron). Cut off the wire/solder, strip the insulation, and you're ready to go again.
     

    Attached Files:

  12. Thedarkb123

    Thedarkb123

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    Apr 15, 2014
    When I was a beginner I used a hacksaw to get rid of bridges lol
     
  13. debe

    debe

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    Oct 15, 2011
    I use clear nail varnish for covering bare tracks. Looks neat & is clear.
     
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