Repairing pulled Genesis PCB pad (easy fix? pictures inside)

[sofakng]

Last night I was replacing all of the Sega Genesis 2 capacitors (there are 30+ !!) and the while desoldering I accidentily pulled one of the PCB pads. (I was using the lowest temp on my Hakko FR-300 but this PCB seems extremely sensitive)

Anyways, there is a via right next to the pad and I think I traced the path on the other side of the PCB to a resistor. Can anybody tell me the best way to repair this?

I’ve tried lightly scraping the via on the bottom of the board using a fiberglass brush but it wasn’t removing the PCB silkscreen too easily.

Here are some pictures:

Bottom of PCB (view of pulled PCB pad)


Top of PCB:


Highlighted area where I THINK the trace goes:

[ASDR]

Ugh, not your lucky day.

How much heat a PCB can take largely depends on how much heat the copper can dissipate. If you're attached to a giant ground plane you can set your iron to 400C and might get away with it, but that small pad can only sink heat through the tiny via and hence will heat up very quickly and the epoxy will come off. The easiest pads to rip off are the not-connected ones that are only there for some extra mechanical stability.

It's hard to tell from your pictures, but is even the plating in via completely gone? If not, you should be able to use your DMM, stick the probe tip in there and check continuity to where you think it goes and the run a jumper wire. But from the pictures it looks like you found the right spot. You might want to just solder the jumper to the new cap leg topside so you don't have to run across the board.

I once ripped a pad off and was able to solder some tiny magnet wire to the via. It's a pain, but can be done.

[sofakng]

Thanks for the reply.

I'll have to take a look to see if the plating in the via is gone, but running a jumper on the top side of the board sounds good. It's also unfortunate that the Genesis PCB doesn't have copper on the top side of the board for the capacitors. (I thought it was common to have copper plating on the top and bottom of the board for through-holes?)

Will I need to scrape away the solder mask on the top of the via before I use my DMM probe? I don't see any copper exposed.

[ASDR]

Most PCBs have pads at the top and bottom for some extra stability. But this makes desoldering actually easier for you. A cap can be connected to a ground plane topside, but you have to work with your desoldering gun from the bottom. The big ground plane removes all the heat and you have a hard time getting the solder in the via and topside molten.

Internally a via looks like a hollow cylinder, the walls of the hole are plated. So if you have a decent fine tip DMM probe you might be able to just stick it in there and make contact. You can dig a bit into PCB to expose the via if you want to solder a jumper to it on the bottom. Might not be the best idea on a many-layer PCB but I think this one is only 2, so you should be fine.

But I also found these older boards to be much more fragile. I don't know if it's just age or if they were made worse back then. The kind of PCBs you find in a modern console or computer can wick away a lot of heat with all their layers but are also generally very robust. They're very hard to destroy with soldering or hot air. But on some types old boards it's often kinda scary. I was desoldering some ports from an old VCR and thought I'd just use hot air. Wasn't even set very high but you could immediately hear popping sounds and the entire PCB came apart. You could've put that kind of hot air on a modern console logic board for like 5min and would've likely not damaged anything.

[sofakng]

Yeah, I know what you mean about the ground plane. I’ve desoldered about 5 NES PPUs and a bunch of pins are connected to the ground plane and are always difficult. However, I’ve never pulled a pad (except my first time because I was too agressive) even with higher heat so I was suprised the Genesis PCB was damaged even on the lowest heat.

Anyways, I really appriciate your help!

[ASDR]

Sure, let us know if you can make it work

Did you recap your Genesis because it's broken or stuff looks like it's about to go bad or just as a preventative measure? I got an old MD Mk1, works fine and the caps look good, so I haven't touched it yet.

[sofakng]

It worked fine before I did the recap and I was only doing it as a preventative measure, lol.

I'll post back with an update and pictures of the fix, if it works.

[Taiji_Mods]

A quick continuity check on my Genesis 2 confirms your theory. CE7 connects directly to that pad of R28. I agee with @ASDR just run a wire from the leg of the cap on the topside to the resistor. Good luck.

[ChuChu Flamingo]

I would wager age also has a lot to do with it + joints being slightly oxidized. Even a joint that looks decent can still be slightly oxidized and make it a pia to desolder. That extra second can sometimes be the difference between a pulled trace or not.

From what I've seen though stuff that gets hot is more susceptible to pulling pads (crt chassis boards for example). The thermal cycles seems to wreck havoc on the glue that holds the trace in place.

It might seem backwards but reflowing/adding new solder/flux before desoldering can sometimes prevent this from happening. It is why you often see Lord Voultar recommend this before desoldering a NES PPU. This crucial step can be the difference between a pulled trace or not.

Most of the time when I desolder I do it out of habit. I find it helps on stubborn through holes.

[sofakng]

@Taiji_Mods - Thanks so much for checking this!! I really appreciate you going out of your way to check it.

@ChuChu Flamingo - Yeah, I usually do add some liquid flux and then additional solder before I desolder (and then increase temperature as needed).

Anyways, I scraped a bit of the via on the bottom of the board to expose the copper and then I was able to solder the capacitor leg to it. It was such a small amount of copper that I wasn't sure if it would work but I tested with my multimeter and it's definitely connected properly.

Here is a picture of the repair:

[maxtherabbit]

@Taiji_Mods - Thanks so much for checking this!! I really appreciate you going out of your way to check it.

@ChuChu Flamingo - Yeah, I usually do add some liquid flux and then additional solder before I desolder (and then increase temperature as needed).

Anyways, I scraped a bit of the via on the bottom of the board to expose the copper and then I was able to solder the capacitor leg to it. It was such a small amount of copper that I wasn't sure if it would work but I tested with my multimeter and it's definitely connected properly.

Here is a picture of the repair:

Nice save

[ASDR]

Nice repair

And yes, always start by adding solder. Removes oxidation, more solder gives a larger contact surface and better heat transfer. Also, a better alloy lowers the melting point. Lead-free is >200C, standard 60/40 is like 190C, eutectic 63/37 is 183C and a silver alloy (Sn62Pb36Ag2) is even 179C.

[sofakng]

Thanks! I ran the system for about an hour (just letting it idle at the intro to Sonic) and it didn't freeze or have any issues. Next time I'll have to be more careful but at least I got a little more experience at both desoldering and repairing

[Hoagtech]

Awesome. Now that the op is satisfied I was wondering If you guys could recommend good equipment.

Iron or station - ??

Desolder - Hakko FR-300

Solder - type and size

If you use a solder sucker do you still use a wick for cleanup?

Do you guys use mechanical arms or magnetic basins or is that overkill.

What do I need for easier soldering?

I would love to get back to capacitor replacement but I keep failing.

[ASDR]

Hey, I just fixed my old router:



What else could've been the culprit...

Some random tips since you asked:

- You need solder wick for cleaning up pads. Get rid of that lead-free crap or flatten pads before you solder SMD components back on. Make sure to get different widths! There's 1mm wide wick, it's super handy since it's so tiny and so easy to heat up
- FLUX!!! Make sure to get both alcohol based NoClean (low solids, 3-5%) and flux gel (syringe). The alcohol based is real easy to apply and clean but doesn't have much staying power. It's best for single joints or quick rework etc. The paste is useful with hot air (stuff doesn't blow away, doesn't immediately evaporate/burn up) and when you have a more complicated job like clearing bridges from a 100 pin QFP package
- Sn62Pb36Ag2 solder. Slightly stronger, shinier joints and slightly lower melting point. Not a huge difference, but there's no real reason not to (the 2g of silver in a 100g spool is literally 1USD...)
- Get a modern soldering iron with the heater in the cartridge. You'll otherwise either tear your hair out working with modern multilayer boards or burn everything to death since you need to set temp to >=400C to get anywhere. Cheapest option is a TS-100 or those T12 tip Hakko clones.
- Hot air stations are amazing. You don't have to spend a fortune but don't buy the total cheapo ones with the blower in the handle

And most important, watch other people work (Voultar, Louis Rossmann, etc.) to get an idea of how things are supposed to look like and work out. Then, just get all the junk electronics you can find and practice. Everything from and old VCR to a dead mothrboard. Just try to desolder and re-solder random stuff. Figure out why you fail and get a gut feeling for it. If things aren't working, you should be able to tell if you need to turn up the heat, are using the wrong solder tip, is this a job for the hot air or the desoldering gun etc. etc.

[sofakng]

- Get a modern soldering iron with the heater in the cartridge. You'll otherwise either tear your hair out working with modern multilayer boards or burn everything to death since you need to set temp to >=400C to get anywhere. Cheapest option is a TS-100 or those T12 tip Hakko clones.

I'm glad that you were able to fix it! It's awesome fixing something yourself that was broken. I feel like a hero whenever I can fix one my kids electronic toys.

Anyways, what do you mean by a soldering iron with a heater in the cartridge? I'm using a Hakko FX-888D which I think included the FX-8801 soldering iron. Can I replace the iron and still use the FX-888D base?

EDIT: It looks like I'll need a completely new station (i.e. the Hakko FX-951). I've checked eBay but it's hard to determine what's Official Hakko versus possible clones.

[ASDR]

- Get a modern soldering iron with the heater in the cartridge. You'll otherwise either tear your hair out working with modern multilayer boards or burn everything to death since you need to set temp to >=400C to get anywhere. Cheapest option is a TS-100 or those T12 tip Hakko clones.

I'm glad that you were able to fix it! It's awesome fixing something yourself that was broken. I feel like a hero whenever I can fix one my kids electronic toys.

Anyways, what do you mean by a soldering iron with a heater in the cartridge? I'm using a Hakko FX-888D which I think included the FX-8801 soldering iron. Can I replace the iron and still use the FX-888D base?

EDIT: It looks like I'll need a completely new station (i.e. the Hakko FX-951). I've checked eBay but it's hard to determine what's Official Hakko versus possible clones.

Yeah, you need a new station. Basically, with the old type irons there's quite some thermal delay between the tip of your iron and the heater/sensor. So if you soldered against a huge ground plane it would dissipate all the heat and it would take quite some time before the sensor even noticed and then it would again take a while for the heat from the heating element to warm the tip. The only real way to make soldering work in such conditions would be to crank up the heat a lot, which then again makes it likely to destroy something that doesn't have much ability to dissipate heat. Fortunately, the Chinese clones have gotten quite good so I don't think you really need to spend the money a major brand like Hakko/Pace/JBC costs. The TS100 and T12 stations are quite good and a full setup is going to cost you less than a hundred bucks.