Lost my solder pads need help

This is the place for any magazine-related discussions that don't fit in any of the column discussion boards below.
Post Reply
enochsmoken
Posts: 22
Joined: Thu May 19, 2011 8:39 pm
Contact:

Lost my solder pads need help

Post by enochsmoken » Fri Jul 06, 2012 12:30 pm

I was doing some desoldering and a couple of solder pads came off. Is there away to put new ones on? Or some other idea?

Thanks,
Brad

User avatar
Externet
Posts: 1869
Joined: Fri Feb 01, 2002 1:01 am
Location: Mideast USA
Contact:

Re: Lost my solder pads need help

Post by Externet » Fri Jul 06, 2012 3:13 pm

Who needs stinking solder pads? Just use tiny wires and restore the connections. Watch for pads that are also vias and take goodl care when rewiring.

Perhaps this fits the type of damage and helps ========> http://home.comcast.net/~machrone/bjr/mistakes.htm
- Abolish the deciBel ! -

User avatar
haklesup
Posts: 3063
Joined: Thu Aug 01, 2002 1:01 am
Location: San Jose CA
Contact:

Re: Lost my solder pads need help

Post by haklesup » Fri Jul 06, 2012 6:14 pm

You can get trace repair kits and you can send it out to sepcialists but the pad still needs to be connected to something (usually). If it's a 1 or 2 layer board then use the "blue wire" repair method with wire wrap wire (solder tacked) to just replace the whole trace with the wire. If its a multi layer board, you will want to determine if any inner layer connections were made at that thru hole and use a multimeter to verify the proper continuity to all other components on the same node.

Personally I would not put a via at a thru hole component land unless I really needed to for this very reason. Its better reliability to make any vias away from the component thru holes but sometimes that's how you save space or holes. Even simple a top to bottom via connection I would avoid. This simple design rule can reduce the number of opens sustained by rework or harsh assembly.

enochsmoken
Posts: 22
Joined: Thu May 19, 2011 8:39 pm
Contact:

Re: Lost my solder pads need help

Post by enochsmoken » Mon Jul 09, 2012 8:45 am

What are vias? This is a MPU from a 1978 Bally Pinball machine. Had some corrosion from a leaky battery.
What about the silver epoxy? http://sra-solder.com/product.php/6500/8 Anyone used this before.
Brad

enochsmoken
Posts: 22
Joined: Thu May 19, 2011 8:39 pm
Contact:

Re: Lost my solder pads need help

Post by enochsmoken » Mon Jul 09, 2012 8:47 am

I forgot: what kind of solvent should i get to clean the board?
Brad

User avatar
haklesup
Posts: 3063
Joined: Thu Aug 01, 2002 1:01 am
Location: San Jose CA
Contact:

Re: Lost my solder pads need help

Post by haklesup » Mon Jul 09, 2012 1:02 pm

A via is any point where the trace changes layers on the PCB. A plain via is usually just a hole in the board with the traces at different layers leading to it. It is always a plated thru hole and if damaged can cause open circuits. A via may also exist at the same place as a thru hole component is solered on.. A conponent thru hole may or may not also be a via.

Isopropyl alcohol (not rubbing alcohol) is usually the best cleaner. Often soap and water can be used first. A board from 1978 is probably 1 or 2 layer so all traces should be visible.

User avatar
Bob Scott
Posts: 1192
Joined: Wed Nov 20, 2002 1:01 am
Location: Vancouver, BC
Contact:

Re: Lost my solder pads need help

Post by Bob Scott » Mon Jul 09, 2012 6:19 pm

enochsmoken wrote:What are vias? This is a MPU from a 1978 Bally Pinball machine. Had some corrosion from a leaky battery.
Oh wow, corrosion is bad news. I would not have to much confidence in a successful repair. Battery acid contamination in the PCB is probably present and will continue to corrode any new repairs.

If this was a repair to be done for a paying customer, I would definitely call this thing "Not Worth Repair." You don't want to get married to it.

It this thing is of some value to you and you want to try anyway, spend lots of time cleaning the PCB with water and a damp rag. I have actually soaked rainwater contaminated PCBs from a mobile TV station video production switcher in fresh water for a few minutes with success. -but that was just rainwater contamination. (BTW, you want to let it dry thoroughly for a couple of days before you reapply power!) If it was dipped into Lake Ontario, forget it! I've tried one and the contamination is impregnated into the PCBs, and slowly corrodes clean through transistor leads over time.

Dry if off quickly. Replace missing traces with fine solid Kynar wire and a lot of skill. It's the kind of skill usually the exclusive specialty of a factory "rework technician".

That's just general the general advice I can recommend with the information you supplied.
-=VA7KOR=- My solar system includes Pluto.

enochsmoken
Posts: 22
Joined: Thu May 19, 2011 8:39 pm
Contact:

Re: Lost my solder pads need help

Post by enochsmoken » Mon Jan 28, 2013 1:33 pm

Is there an adhesive product that will attach a solder pad or a trace to the board, and be able to take the heat of soldering?

User avatar
MrAl
Posts: 3862
Joined: Fri Jan 11, 2002 1:01 am
Location: NewJersey
Contact:

Re: Lost my solder pads need help

Post by MrAl » Tue Jan 29, 2013 10:28 am

Hi,

As others have said, you dont really need an actual pad. You can do other things.

The simplest is to use a light gauge solid wire like #24 and make a small circle at the end with long nose pliers. Place the circle over the component lead that is already through the hole, then solder. Cut the length of wire and solder it to the line trace that already (still) there, or if not there, run the wire to the next hole and do the same there then solder.

The pads are only there to make things simpler for the assembler.

If you are working a double sided board, make sure the component lead of each component sticks through the board completely and that it is soldered on both sides of the board. Sometimes the holes themselves actually conduct using plating in the hole itself, so we want to make sure that the connection from one side of the board to the other side is still maintained when a pad is lost.
LEDs vs Bulbs, LEDs are winning.

enochsmoken
Posts: 22
Joined: Thu May 19, 2011 8:39 pm
Contact:

Re: Lost my solder pads need help

Post by enochsmoken » Tue Jan 29, 2013 10:52 am

OK I got it now.

User avatar
dacflyer
Posts: 4578
Joined: Fri Feb 08, 2002 1:01 am
Location: USA / North Carolina / Fayetteville
Contact:

Re: Lost my solder pads need help

Post by dacflyer » Thu Jan 31, 2013 11:39 am

i have repaired many mpu boards from vintage pinball machines.
if all fails there is a generic mpu replacement board available..i think all you have to do is set the proper selection switches, and your good to go...
but battery acid is a big problem on them boards, i usually remount a battery pack later on after repairs.
oxidation was another big problem for them boards as well. i have replaced hundreds of headers and pin sets in order to get the boards back into operation.

but many times if a via or thru hole pad was damaged, i'd just use some really thin "wire wrap" wire or larger if needed, and repair the traces this way. if i remember them boards are just 2 sided. so it should be a easy fix for you..

good luck

Post Reply

Who is online

Users browsing this forum: No registered users and 29 guests