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I was trying to flash OpenWrt onto my BT HH5 wireless router and it involves soldering wires to very tiny balls of solder, which in the guides I've been following are referred to as pads. I've tried putting a small amount of solder in the little caveat hole but it doesn't stay in place. I known this would have been produced in a factory by a machine but is there any way I can repair the broken pad?

first image

second image

UPDATE

I've put a 1p coin in the corner for a scale comparison to show how small the pads really are. The blue circles represent the pad I have been referring to.

Scale of the PCB

As there is a hole wear the pad was, is there nothing I can use to refill the hole? I knows this sounds stupid but is there a conductive glue that the solder can stick to?

I've been using a battery powered soldering iron, but should I be using a temperature controlled iron with a low temperature and maybe using a smaller head on the iron?

N.B I only usually solder leads for audio equipment so moving down to micro PCB components isn't too much for my hand in terms of keeping it steady, but the fact that I think I need to invest a decent soldering station possibly?

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  • \$\begingroup\$ Is the missing pad a via ? In that case, what's on the other side to solder upon? Else, this means that some track used to go to that pad, so you can connect on those. You should use some glue when you have checked your work is done and functional to avoid similar problem in the future. \$\endgroup\$
    – xryl669
    Apr 2, 2019 at 13:59
  • \$\begingroup\$ I remember during my first ever experiment with soldering small pitch components on newly manufactured PCBs. I burned out pad an routing path due to high temperature setting. I always keep soldering iron temperature settings within 200C since then. \$\endgroup\$
    – Prasan Dutt
    Apr 2, 2019 at 14:00

2 Answers 2

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One thing I have tried and works, but requires good precision is the following:

Drill small hole near the ripped pad and insert a piece of copper. Twist the ends of the copper so that they form 2 loops on both ends of the board. Then solder it to the track and on top of that solder any component that was there.

If the pcb has mask or paint, scrape them off. If it is a 4 board layer, the above technique is doable, but the piece of copper must be insulated so that it does not short-circuits the 2 mid layers.

Here are some pictures, in which we managed to fix the destroyed "via", but the technique is the same for destroyed pads.

enter image description here

enter image description here

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    \$\begingroup\$ Drill a hole nearby? Got to be something lucky for that to work. Likely outcome is you short out all the internal layers. \$\endgroup\$
    – Curious Diode
    Apr 20, 2019 at 19:55
  • \$\begingroup\$ As I said in the initial post, this is possible, but the wire has to be insulated. It is a little bit painful, because it requires delicate manipulation of the drill/board/wire, but totally doable. If the board has only 2 layers it's way easier. \$\endgroup\$
    – thece
    Apr 21, 2019 at 10:57
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It's hard to be sure with all the flux, but it looks an awful lot like that pad connected to the via just below it (circled); you can see the clearance in the surrounding plane where the track ran.

enter image description here

First thing to do is clean up the area with a cotton-bud dipped in IPA (or acetone, probably if you don't have any IPA to hand). Do it very carefully, as it'll be easy to snag one of the other pads with solder sticking up and rip that off too, especially if it's been overheated.

You should then be able to see evidence of the track going from the missing test-pad to the via (it'll probably look like a brown line).

If you decide to solder onto the via, you'll need to (with a round-bladed scalpel), scrape the green solder-resist off the top of the via, until you see bare copper. Then you can solder your wire to this.

Aside: It's a good idea, if you can, to solder to these pads etc. with very thin enamelled wire, which can be tacked down somewhere with hot glue, etc, and then solder the wires to your programmer onto those. You're much less likely to rip pads off.

I would caution against drilling the board, unless as an absolute last resort.

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