0
\$\begingroup\$

I've seen several similar topics where people have torn off PCB pads, but in my case, I managed to tear off a pad from an SMD component (a sealed pressure sensor). It was one of the communication (I2C) pads. Since I didn't have a PCB nor means to make one, I thought I could get away by soldering wires to the pads, and then immediately sealing the whole thing (except the sensor hole) with epoxy for strength. Unfortunately, the pad came off as I was soldering. Here is a pic, the best one I could make, because the component is just 4 mm in size:

enter image description here

Unfortunately the component is extremely expensive and very hard to get, so I absolutely need to fix this one somehow. Solder doesn't stick to the place where the pad used to be. The datasheet does not provide any info on the inner structure of this component either. Can someone give any advice on how to get a connection to whatever that pad was connected to?

\$\endgroup\$
16
  • \$\begingroup\$ Apparently you have a datasheet, so please post a link to it, or to a scan or photo of the datasheet. \$\endgroup\$ Feb 28, 2023 at 21:43
  • 1
    \$\begingroup\$ First of all you will need to remove the three remaining wires (avoiding further damage!), then take a better picture. But I'm afraid you might have one irreparably damaged component – this indeed doesn't look like copper, but maybe like primer/glue used to affix the metal to the ceramic substrate, in which all that was connected to the pad is gone as well. \$\endgroup\$ Feb 28, 2023 at 21:43
  • \$\begingroup\$ @MarkLeavitt - sorry! Updated the post and added the datasheet. MarcusMüller - This is the best photo I was able to take with my camera, but I will remove the rest of the wires. Unfortunately there is not much else to see, really. It's just a white rectangle base with 4 pads, one of which is torn off. There are no tracks or anything. I believe whatever glue was connecting the pad, is gone too. But there must be something conductive there, right? \$\endgroup\$ Feb 28, 2023 at 21:48
  • 1
    \$\begingroup\$ @MarcusMüller yes, that is my country. Shipping this component took a month when I ordered it. And like I said, price becomes triple, which is a lot of money here. I can't afford another sensor. Anyway, my question is about trying to repair this one... It is not like I have much to lose now. \$\endgroup\$ Feb 28, 2023 at 22:00
  • 1
    \$\begingroup\$ Easy there, @MarcusMüller, you're really hounding the point and the poor OP :-) Question's on fixing, not buying, so let's take if for now that the OP happens to know their life and situation somewhat better than we do and get back to the question. \$\endgroup\$
    – TonyM
    Feb 28, 2023 at 23:06

2 Answers 2

3
\$\begingroup\$

The best engineering approach is to consider this a lesson learned, and order a replacement part ($12 and in stock).

If you want to try again, you can solder wires to an SMT part, but they need to be very fine so they don't exert significant force on the pad. Strip that wire you were using, separate the strands, and use just one strand. Use the smallest tip on the soldering iron, some flux, and if possible fine-gauge solder. Then route those fine wires to another, stable tie point to connect to normal-gauge insulated wires.

\$\endgroup\$
3
  • 1
    \$\begingroup\$ I live in a remote location, and getting that part here means paying 3 times than that base price when taxes and shipping are added (ant it is A LOT of money here), and shipping takes a month, which I don't have. Good advice on the wire soldering... But I need to get this sensor working somehow \$\endgroup\$ Feb 28, 2023 at 21:58
  • 1
    \$\begingroup\$ @JustinasRubinovas If you can get some conductive epoxy or other adhesive, it might be possible to put some on the part where the small via is, and hope that it makes contact. A little heat might help the material seep into the via. But I think it would be better to find some extremely thin copper or silver wire to insert into the hole. You might use a really tiny drill or a sharp needle to remove any solder mask or other coating in the hole, to expose the copper. \$\endgroup\$
    – PStechPaul
    Feb 28, 2023 at 23:33
  • \$\begingroup\$ @PStechPaul, thank you, that is good advice, I will try this. \$\endgroup\$ Mar 1, 2023 at 0:03
1
\$\begingroup\$

It really depends on how the pad connected to the component. I can think of a few ways: A via and a wire around the outside of the component.

If it's a small wire, you could find the wire and solder to that.

If it's a a via, you should also be able to solder to that.

The picture isn't great but I can't tell if either is available

One problem with looking at the device is there is no strain relief for the wiring, which means any force on the wires will not be relieved and translate to the part. Heatshrink or tape around the wires could help considerably in avoiding damage to the part.

It's a 12$ part, it would be much easier to order one than repair it.

\$\endgroup\$
6
  • \$\begingroup\$ The component is completely sealed - there are no exposed connections anywhere, because this component is designed to be waterproof, except for these 4 pads, which have to be waterproofed after soldering. As for relief, yes, I was planning to do that, but the pad broke off before I had a chance to do it. You can check the datasheet for better images of the part (I added it to my post), because my camera sucks. \$\endgroup\$ Feb 28, 2023 at 21:51
  • 1
    \$\begingroup\$ The conductor either has to go through the PCB or around it, it's there somewhere, it might be small but it's there. You might have to get an exacto and dig around and find it in the PCB. \$\endgroup\$
    – Voltage Spike
    Feb 28, 2023 at 22:00
  • \$\begingroup\$ I think the conductor is somewhere under that pad, but I can't seem to access it with exacto, the material is very hard. I will try to drill it. \$\endgroup\$ Feb 28, 2023 at 22:02
  • 1
    \$\begingroup\$ @JustinasRubinovas You'll need a microscope \$\endgroup\$
    – Voltage Spike
    Feb 28, 2023 at 22:19
  • 1
    \$\begingroup\$ @VoltageSpike I just discovered that there is actually an extremely small via hole right next to the pad. It is smaller than any strand of copper wire that I can insert into it, and solder doesn't want to stick to it either. I think there was a wire going through that via that was attached to the pad. I think when I ripped off the pad, I also pulled out that wire. \$\endgroup\$ Feb 28, 2023 at 22:21

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.