Hello all,
This is my first post here so dont hesitate to correct me if post in the wrong section. All the thread on this subject are at least 5 years old so I thought I would make a new one.

I recently purchased the CircuitWriter product on Amazon to perform some much needed repairs to a vehicle circuit board. I needed to bypass three traces that were in close proximity to each other. In order to get nice clean lines I used scotch tape on top of plastic board and cut the tape away from the damaged traces essentially leaving a stencil. Once cured, I would just remove the tape and be left with nice clean traces. This technique worked well when I tested it on some plastic. However, I found cutting the tape over the actual PCB traces to be Impossible. The traces are just too close together. I instead opted to put a layer a scotch tape down and cut a small hole over the beginning and ending point for the traces to be bypassed. I then made new traces on top of the tape using the circuit writer pen. Then pen does not really flow like I imagined even after cleaning. It works better when putting lots of tiny dots together as each time the tip is depressed a little bit squirts outs. I have now done away with using the tip and have found that using a toothpick dipped in the silver solution and carefully dabbing little dots to be much more effective in making a trace. my new problem is when making "touch ups" to certain areas. I didnt realize how thin the layer of silver would be on a surface after curing and it seems that as the product cures, the height different between the tape and PCB board is enough to cause a disconnect of the trace. Im getting decent continuity on top of the tape but nothing when I test the continuity at the trace sites. I have dabbed some more layers at those areas to try and build up the silver to over come the thickness of the tape. Does anyone have any suggestions on how I could accomplish this better?

Thanks, -Z

 

Get rid of the CircuitWriter pen and instead solder point-to-point using single strand insulated wire, 30AWG wire-wrap wire for low current signals or 24AWG or 22AWG cable. Scrap telephone wire works well.
For heavy traces, run tinned copper wire along the bare copper PCB traces and solder directly to the trace.

 

Solder wires along the traces, or between contact points on either side of the breaks. This will make a much more reliable and long lasting repair, especially when subject to vibration in the vehicle.

 

Get rid of the CircuitWriter and instead solder point-to-point using single strand insulated wire, 30AWG wire-wrap wire for low current signals or 24AWG or 22AWG cable. Scrap telephone wire works well.
For heavy traces, run tinned copper wire along the bare copper PCB traces and solder directly to the trace.

That is what I wanted to do in the first place. I wanted to bypass with wires or trying to lay down small copper filaments. These traces are ridiculously close together. Im also more of a novice at soldering. I have had a lot of problems like solder refusing to stick or flow. I cant even seem to tin the iron properly. I wanted to try soldering a wire directly to one of the pin point ends of the trace but the end of the trace is almost the same size of the trace itself. Im really just trying to patch it until Christmas when I can get actual supplies. If it helps, let treat this as a hypothetical experiment with the Circuit Writer pen.

 

Do you know exactly where the break is and is there only a narrow gap between the ends?
If so, then you might be able to clean the ends to bare copper (emery paper, carefully) and then blob some solder across the ends.

 

Yes, I know exactly where the breaks are and confirmed with multi meter tests. Here is a picture from before I started playing with silver solutions. There are 6 traces in question. I have numbered them 1 - 6. Traces 2, 3, and 5 are the ones that failed the continuity test. Blue areas are where I cut throught the tape to apply the silver solution.

 

Get "trace" out of your mind. Solder small insulated wires point to point.

You need an electric "soldering pen", some small scraps of fine wire (like phone wires), a bit of new clean fine sandpaper, and fine rosin core solder.

You need to heat those "beads" of solder at the ends of those traces just enough to add a small amount of new solder. Then cut pieces of wire to go point to point (not tight, but don't make a tangle either), tin the ends, then put the end of the tinned wire on the bead, quickly heat it to melt the solder bead so it fuses to that tinned wire end, then repeat.

The sandpaper is to get your wire ends shiny clean, and your soldering pen tip shiny clean. Melt that flux core solder onto the pen tip frequently, and wipe it off with a very damp cotton cloth.

There may well be YouTubes of soldering. It's not difficult, but you must have enough heat, good flux core solder, AND KEEP EVERYTHING CLEAN!!!

CLEAN SHINY CLEAN SHINY SHINY SHINY SHINY CLEAN!!!!!!!

Those traces are trash. Not a chance. Forget them totally.

CLEAN SHINY CLEAN!!!!!

Oh yeah, I know of no tech that has any use for those pens.

 

There are silver repair solutions that work quite well. They are expensive and the product you used is not one of them.

As for cleaning small areas and removing solder mask, I prefer a pointed scalpel (#11 blade) and/or a fiber glass sander made for detail paint repair on cars. They generally are called spot sanders and are available at autoparts places or for more money at Amazon. I use the sander to get the general area clean and bright -- great for removing solder mask -- then the scalpel for detail.


John

 

The sandpaper is to get your wire ends shiny clean, and your soldering pen tip shiny clean.

The sandpaper is fine for wires, but you shouldn't sandpaper a soldering iron tip or you risk removing the plating and then your tip won't last long. Stick to the damp cotton for the iron. And make sure it is cotton - plenty of others will melt at soldering temperatures.

 

Ok, guys

Here's what I have, 60/40 rosin core solder, flux braid wire, solder sucker, 65watt POS frys soldering iron, a few tips that refuse to tin. Im ok with the tips becoming sacrificial. I can buy more when Im back in the states. I cant believe I never thought about before but I do have a roll of CAT6 cable sitting in the closet. Would a strand of twisted pair wire from that work? Assuming I can get a ball of solder to actually stick to the board, how do I approach resistors? I followed trace #3 and it ends on the other side of the board ar a teeny tiny resistor. I guess I could heat it up and drop a ball of solder on the side and then fuse a tinned wire to it.

 

That is probably not sufficient to make the repair. You need tinned tips. A ball of solder resting on top the board does not an electrical joint make.
How are you going to clean the board?
Cat6 wire may be too big. A single strand of wire from a section of 22 awg stranded wire (often 7x30) would probably work better. Stranded wire made with 26 to 28 awg would probably be OK too, particularly if it is tinned.

John

 

CLEAN SHINY CLEAN SHINY SHINY SHINY SHINY CLEAN!!!!!!!

What little soldering experience I have, I always make sure my work has a mirror finish

 

That is probably not sufficient to make the repair. You need tinned tips. A ball of solder resting on top the board does not an electrical joint make.
How are you going to clean the board?
Cat6 wire may be too big. A single strand of wire from a section of 22 awg stranded wire (often 7x30) would probably work better. Stranded wire made with 26 to 28 awg would probably be OK too, particularly if it is tinned.

John

Some of these traces literally just end at a pin point. My plan was to put some solder on top of these "points" and then solder a pre tinned wire to them.

 

Solder wires along the traces, or between contact points on either side of the breaks. This will make a much more reliable and long lasting repair, especially when subject to vibration in the vehicle.

I second that - cleaning and tinning the traces sometimes shows up previously missed breaks, and sometimes it actually bridges very trivial cracks.

Laying wire strands onto pre-tinned tracks does a lot to stabilise a cracked PCB, but it also fixes it in whatever state of preparation you bothered to do. Its worth the effort to get a cracked PCB as back to flat and level as possible. If it didn't crack cleanly, it may be necessary to carefully chisel away some rough bits to make the edges fit back together.

 

A not very good video of how to mend a PCB trace.
1. Flux does not cause overheating and melt the soldering iron tip!
2. He recommends using a file to clean the tip and that's why his tips are wrecked!
But the basic idea is right.

 

I second that - cleaning and tinning the traces sometimes shows up previously missed breaks, and sometimes it actually bridges very trivial cracks.

Laying wire strands onto pre-tinned tracks does a lot to stabilise a cracked PCB, but it also fixes it in whatever state of preparation you bothered to do. Its worth the effort to get a cracked PCB as back to flat and level as possible. If it didn't crack cleanly, it may be necessary to carefully chisel away some rough bits to make the edges fit back together.

The PCB is not cracked. Assuming Im able to get solder to stick to my soldering tip, will it just coat the traces and not attach to the PCB? There is no way i could drag a bead across 1 trace and not the other since they are a hairs width apart.

 

I keep a bottle of nail polish for that, really!
If you remove the green solder mask off of traces that need no repair, take the nail polish brush and cover the bare traces with nail lacquer.
Allow to dry before tackling the broken trace.

 

I got some strange looks in out local shop when I bought a bottle of nail polish but it is very useful stuff. Apart from solder mask it also makes a quick setting glue which can be easily removed later (if you buy the remover too) and mine is bright orange and I use it to make very visible marks for all kinds of things. I have a clock with the tips of the pointers highlighted in bright orange...

 

The PCB is not cracked. Assuming Im able to get solder to stick to my soldering tip, will it just coat the traces and not attach to the PCB? There is no way i could drag a bead across 1 trace and not the other since they are a hairs width apart.

If the soldering tip is iron plated; you have to be careful not to damage it - if you expose the copper core; it literally dissolves into the solder.

The Antex (that I know of) isn't pre-tinned, so you have to tin it as it heats up before it oxidises.

Cleaning an oxidised iron plated tip isn't easy - possibly easier to start over with a new tip and tin it properly from the start.

 

Happy Sunday everyone,

I followed your advice and was able to get solder to stick to the iron. Within minutes I was solder things down. I bypassed the 3 traces using wire from a Cat6 cable. I known this was ill advised but it worked. I was able to solder that wire to sever all links point locations. Some of the joints are shiny, some are not. I thought I did pretty well for a novice. Unfortunately the vehicle still isn't starting. I'm getting no ignition at all so I may have a seperated problem or more board issues. Here are some pics of my progress.





Thanks, -Z