Suggestions on how to fix a broken trace? - Page 1
Forum section: electronics / general

author: Ampera
author_rank: Super Contributor
timestamp: October 19, 2017, 03:19:33 am
content: A few months ago I purchased an ATI Mach 64 PCI from E-Bay. The card was DOA with corrupted graphics. The card looked like it was used as the puck in a game of hockey over solid concrete, but miraculously there was only one broken trace. All the metal has been carved away from it, and it's a fairly small trace (see picture linked). It was repaired previously via bodge wire, but the holes going through the board where it was attached are so small, even my dad who has way more EE experience than I do couldn't make a join to last forever. It has the same issue as previous, and continuity testing shows there to be a break I can't fix by idle poking.So my question is how should I go about repairing this trace? I have an pen with conductive ink (as part of a small kit which was essentially snap circuits on paper). Could this be used to fill in the trace very carefully? I do not dare solder directly into the trace as I do not believe it will work, especially with my less than professional soldering skills.Linked here are pictures of the break and the bodge wire (with Super Mario duct tape used to hold it down as a bonus, was all I had) and the gouged out trace as best as my tablet can photograph it (doesn't focus with stuff any closer). It's not massive, but I have no idea of what to use to fix it. As a warning these ARE large images, so I do not post them here half because of people in the past who screech like rabid chimps when there is a large image posted, and half out of actual respect and understanding for those people (don't hit me).https://drive.google.com/open?id=0Bx-7TCgzh8ITczhrSHJBNERNbHchttps://drive.google.com/open?id=0Bx-7TCgzh8ITaFRfS3VxemVlOG8Thanks for any suggestions.

author: ajb
author_rank: Super Contributor
timestamp: October 19, 2017, 03:29:28 am
content: A job like that, ideally you'd carefully scrape away some of the solder mask to expose part of the copper track on either side of the break, flux, tin, and solder a piece of fine magnet wire across it. Actually since it's a relatively small break and you can run straight across it without crossing any other exposed copper you could use a single strand out of a piece of stranded wire. As board repairs go, that's actually a pretty easy one, but it's definitely a solution that requires careful soldering. It doesn't strictly require fancy equipment, but it would definitely be worth practicing on scrap boards first if you've never done it before.You could try the conductive ink, but you'd still probably need to scrape away some mask to get a good connection to the track, and take care to not get it anywhere it shouldn't go. Even then it may not work, as conductive ink has a fairly high resistance compared to copper. Without knowing what that trace is for it's impossible to say what the chances of it working are.

author: Gregg
author_rank: Super Contributor
timestamp: October 19, 2017, 03:46:10 am
content: Your bodge wire is awfully thick; something like 30ga or finer magnet wire may work better. If it does, glue it down with liquid solder mask.I personally would try to patch the trace where it is broken. Since it is the outer one of the group, you have a little more working room. Get your best magnifier, borrow a microscope or whatever you have to do to see it clearly; lots of light from several directions helps a lot. Put Kapton tape over the adjacent traces to protect them and warm up the board to soften the solder mask. Reshape an old Exacto knife blade into a chisel type scraper about the same width as the trace and carefully scrape off the solder mask on both sides of the break. I have some old style pencil shaped ink erasers that are perfect for cleaning traces for solder prep; these are wood jacketed rubberized abrasive that can be sharpened in a pencil sharpener. (There is a big clue as to how old I am) If you can get enough of the trace clean, tin it and jump it with a strand from a stranded wire.

author: Brumby
author_rank: Unknown
timestamp: October 19, 2017, 04:18:48 am
content: It is a fine trace, for sure, but it's not impossible to repair. You have the advantage of there being nothing to worry about on one side.The key to such a repair is care.* First, scrape away a couple of millimetres of the solder mask (1/8") from either side of the break. Make sure there are no patches of solder mask in this area, otherwise it will repel the solder. Also, don't gouge the copper - there's not much there to lose!* Next, apply a generous amount of flux over the area.* Then, very carefully, tin the exposed sections of track. Do this one at a time, so you can be quick, but effective. Your iron needs to be clean, tinned and at temperature. With clean copper, flux and a prepared iron, you should be able to do each side in less than a second.* Get yourself a bare strand of fine wire and tin about half an inch.* Lay this alongside the track and cut a length that will reach across the break and well along the tinned sections on both sides of it.* Place this piece over the gap and use something to hold it in place. Touch one side with the iron and hopefully there will be enough solder between the track, the wire and the iron to make a nice solder fillet. Repeat on the other side of the break.With the vacant board real estate on one side, I would approach from that side - and if the repair makes good connection but sticks out a bit on that side, it won't matter.Oh yes ... very important ... PRACTICE FIRST on a board that doesn't matter.Onlywhen you feel you have the confidence to repeat such a repair consistently should you turn to the important board.

author: Ampera
author_rank: Super Contributor
timestamp: October 19, 2017, 05:18:37 am
content: Perhaps I should have clarified that since this is a free board, I do wish to repair this without buying anything extra, as I might as well just buy another card. I got to work before, so I do not believe the thickness of the bodge wire is much of an issue. It's just gotten slightly disconnected at the end.I have a soldering iron, a wide range of magnification tools, and I could probably scrape some stuff off, but my area is largely legacy computing at the moment. I do not have the skill, nor the resources to make a professional grade repair. I am more looking for a poor man's suggestion.All the suggestions are great, but the best suggestion in the world isn't that great for me if I can't use it.The ink DOES have a higher resistance than regular copper, which could be a problem, A larger problem may even be application as it's a ballpoint pen, and the ink dries upon contact with the air immediately.I can mask off some parts of the board if needed (not with any Kapton cape, I do not have any), but there is a reason why I do not think I can make solder repair, at least with my bulky iron and no flux (outside of the rosin core). I would most likely end up cooking the board to the point of absolutely no repair. I also do not have any spare board with a break like that, and I am not entirely sure I can break a board in such a manner (or if I would want to, as my supply of junk boards is not immense).I have fiddled with the bodge wire a bit and I have gotten it to make contact again, but it's a very loose fix. I am up for suggestions, but if it remains as such I might just end up using it in this state.

author: Shock
author_rank: Super Contributor
timestamp: October 19, 2017, 10:35:29 am
content: If you are going to use a bodge wire to the vias, which might not be ideal if the trace length is important. Use kynar wire, or fine magnet/enameled wire which can be salvaged from coil windings.Clear nail varnish can be used like a conformal coating to glue and protect the repair, test it first to ensure it's not conductive. Not the proper way but if you have no alternatives.Fixing a trace though is dead easy as long as you tin before soldering.

author: Old Don
author_rank: Regular Contributor
timestamp: October 20, 2017, 08:51:13 pm
content: The way you were attempting to repair the trace you are lucky you don't short to adjacent traces and really mess up the board. If all you have is wire that large in dia. then you will have one hard job repairing the trace. Perhaps rather than attempting to "patch" the broken trace you can find the two components at the opposite ends of the trace and solder directly to them and leave the trace broken. Or cut up an old MDMI/USB cable and salvage on 30 awg wire from the bundle of wires inside. Still too big, IMHO, but better than what you used. Flux is your friend when repairing traces! That and a good magnifier.Good Luck

author: Ampera
author_rank: Super Contributor
timestamp: October 23, 2017, 02:58:09 pm
content: As an update, there were two small solder pads (by normal they were connected) right next to where the bodge wire came out. I just soldered the bodge wire to that instead, and it works perfectly fine now. The wire isn't too thick, it just wasn't making good connection.I on the other hand do have an unrelated problem. What would be the best way to bend back very thing QFP pins so I can reflow them back onto the board with an iron? I have another card that has some pins, still attached to the package, but detached and bent from the board. I tried a small pin, but it wasn't all that helpful.

author: Shock
author_rank: Super Contributor
timestamp: October 24, 2017, 12:27:44 pm
content: Quote from: TwoOfFive on October 23, 2017, 02:58:09 pmPhoto of it?Not the professional way but if it was lifted without the pad (meaning the pcb pad is still intact) first remove the solder and then gently manipulate it back into position with tweezers or a blunt needle to poke it at the bend.Avoid breaking it but if it does you can carve out enough of the package sometimes to solder a wire from a broken pin to the pad.