Fixing solder pads?

AAirhart

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Any suggestions on how to replace solder pads on a Space Invaders board?
Appears this one I'm working on was operated on by someone who hates solder pads. Could be why i'm having ram issues... that and I found a short in the power board between the -5 and +12, assuming most are probably toast.
 
EEEK!

Yeah, that short probably toasted a few things.

You can buy replacement pads that have an epoxy glue on the bottom. They stick on nicely as long as the surface is clean/smooth. You'll have to get the solder to flow from the pad to the trace which can be a bit tricky at times.

RJ
 
At work we use a variety of methods to fix pads. First is the aforementioned replacement pads. We typically use extra epoxy to keep them on.

We also will use donor boards. The process feels odd because you have to cut a trace, scrape the masking off part to get the copper exposed and to free the trace, then heat the pad and trace and nudge them around to remove the part. Then epoxy the new pad on and flow solder to it. Since you're not in a production environment, you could even put a piece of wire to patch between the pad and the old trace to make sure the connection is very good.

Finally, there have been cases where I used thin copper strip-wire. This stuff comes in a kit made for trace repair, but it's basically thin copper ribbon. A little epoxy holds it down then solder it together.

In all of these cases it's a good idea to cover the new pad-trace solder joint with some epoxy so if you need to touch it in the future you don't accidentally unsolder the new pad.
 
I used to use a pen that used a silver based ink. I wish I could remember where I got it or what it was called. It was about the size of a magic marker and left a silvery line that was conductive. You had te be very careful to coat it because it scratched very easily. But if you built up three or four layers you could actually solder to it and use it as a solder pad.

ken
 
EEEK!

Yeah, that short probably toasted a few things.

You can buy replacement pads that have an epoxy glue on the bottom. They stick on nicely as long as the surface is clean/smooth. You'll have to get the solder to flow from the pad to the trace which can be a bit tricky at times.

RJ

Can you tell me where these pads and epoxy are sold?

I've never seen them, thanks.
 
Can't you just use some 30ga wire wrap wire and patch it up? That's generally what I do when I've got a couple destroyed pads. If you've got a missing feedthrough, you can even feed the wire up through the hole, to rejoin the trace on the other side of the board.

-Ian
 
Great ideas and some are more aesthetically pleasing. The real functional key here is to ensure that you have a good and permanent electrical connection to each pin. If the board is double sided and the through-hole copper from the component side to the solder side is gone, I've had luck using a piece of wire wrap wire inserted through the hole and bent over to make contact with the component side trace before re-inserting the socket for the replacement chip. Carefully tack the wire to the component side trace ( pre-tin the wire with solder and you may have to scrape off some of the solder mask and pre-tin the component side trace). After the socket is in place, loop the wire around and solder that wire to the socket pin on the solder side of the board.

Bill
 
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That's pretty much what I do as well. One other thing I would add, before you tack the hookup wire to the old trace, be sure to cut enough of the loose piece away from the old trace so you're not soldering to something flimsy.
 
Many of the solder pads on the solder side of a Space Invaders board are not connected to anything. For those, the traces are on the other side of the board. The isolated little pads come up quite easily with a little heat.

Electrically, it doesn't matter if the isolated pad is on the underside of the board. You just have to get a good solder joint on the side with the attached traces.

It LOOKS a lot better to have the pad down there and it probably helps prevent the cooking of the board too.
 
Many of the solder pads on the solder side of a Space Invaders board are not connected to anything. For those, the traces are on the other side of the board. The isolated little pads come up quite easily with a little heat.

Electrically, it doesn't matter if the isolated pad is on the underside of the board. You just have to get a good solder joint on the side with the attached traces.

It LOOKS a lot better to have the pad down there and it probably helps prevent the cooking of the board too.

Well, the isolated pad helps solder flow through the plated thru hole and up to the upper pad.

The problem is that when you put a new pad on the bottom all you are doing is helping with creating a stronger mechanical bond that holds the IC to the board. The pad isn't connected to the plate thru so when you solder to the pad on the bottom you STILL need to solder the pad on the top of the board as the solder typically will not flow to the plate thru and up to create the electrical connection to the circuit.
 
Well, the isolated pad helps solder flow through the plated thru hole and up to the upper pad.

The problem is that when you put a new pad on the bottom all you are doing is helping with creating a stronger mechanical bond that holds the IC to the board. The pad isn't connected to the plate thru so when you solder to the pad on the bottom you STILL need to solder the pad on the top of the board as the solder typically will not flow to the plate thru and up to create the electrical connection to the circuit.

The Midway 8080 system boards didn't have plated thru-holes. I think that's what he's talking about.
 
There's also brass eyelets designed for use in circuit boards. I've used those on some fried power supplies before with good success. Tricky to install though, and IIRC the place I bought them from had a $60 minimum order.

You also need to get the right size, and there's a lot of sizes.

-Hans
 
I'm interested in the pad replacements, anyone know where to get them?

I've looked at a few places, even channelmanic's site and no luck... Thanks,
 
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Personally, I will either patch the trace with appropriate-gauge wire, or I'm a big fan of 3M's copper EMI Shielding tape. Cut up, it makes great traces and pads, it's even adhesive-backed.
 
Personally, I will either patch the trace with appropriate-gauge wire, or I'm a big fan of 3M's copper EMI Shielding tape. Cut up, it makes great traces and pads, it's even adhesive-backed.

Just googled it! Looks great.

I'm a huge fan of 3M products too.
 
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