I made my first pcb recently and everything turned out fine, except one or two traces are 'pitted' or hollow looking, so I'd like to see if I can beef them up a little bit.
I was thinking of possibly trying to solder over them but its an easy-vibe and some of those traces are pretty close together :icon_confused:
what can I use and where can I get it?
Thanks
Here's an idea.
Solder over the traces that are broken or have holes in them and don't worry about connecting traces.
Then, use desoldering braid. This will remove most of the solder but will leave the broken traces mended by "tinning" them.
I've done this in the past and it has worked......as unusual as it may seem. :)
Or just run a wire to bypass the defective trace.
I ussually use a leg froma a transistor that I have a lot of and, after sanding the traces on both sides, I lay the wire down upon the trace and place a little solder along the top and sides. Works great but you have to be really carefull and use pliars so you dont burn yourself.
Quote from: Paul Perry (Frostwave) on July 16, 2006, 08:45:34 PM
Or just run a wire to bypass the defective trace.
Absolutely, you should see some of my boards!
A bit of pitting is nothing to worry about so long as the trace conducts (measure its resistance/use a continuity meter). When I have hairline breaks I run a little wire over them (cut off leg of a component is ideal, as Jimbob mentions). Treat the wire as you would a surface mount device: tiny bit of solder on the trace one side of the break, reflow it and position the wire with tweezers, remove iron until joint is cold then solder the other end.
Alternatively you can apply some flux to the trace then run an iron over it as you melt solder onto its tip. Not very good for fixing breaks, but fills in pits.
There are a few common ways in which this sort of "trace erosion" happens.
One, of course, is a poor transfer of the pattern to the board itself. This can be further subdivided into:
- insufficient ironing or heat application to get the pattern to transfer fully
- insufficient toner thickness when the pattern is printed to the transfer medium (PnP or glossy paper)
- poor adhesion of the pattern to the board due to copper surface imperfections (grease, rough finish, "finger juice", tarnish, etc.)
- impatience and premature removal of the paper/plastic backing before the toner pattern has properly cooled
At another level, though, trace erosion occurs when the etchant starts to eat at the sides of the traces. We are normally accustomed to thinking of etchant as working "vertically". That is, from the top surface of the copper, towards the phenolic/fibreglass//etc. - the "bottom". But etchant has no sense of direction whatsoever, and simply goes where there is copper, and time to chew it up. As a result, when etches starts to get particularly slow, and the etchant has already eaten down to the substrate of the PCB in some places, and left the copper traces isolated from each other, it will start to eat inwards, from the outside edges of the traces. Keep in mind that whatever you transferred to the surface of the copper ONLY covers the surface, and does not wrap itself over the edges of the traces to protect against sideways etching. That "unprotected edge" may only be a few mils in thickness, but to the etchant, it is like a sandy cliff along a shoreline that can be easily eroded away despite how huge the surface area is from those cliff-sides inland. These things will help to reduce sideways etching of traces:
- Use the freshest etchant you can. It doesn't have to be flawless, but it should be relatively powerful. If have used your current batch for a lot of boards, let it sit for awhile and after the sediment has formed, transfer the relative clear still-potent stuff at the top to another container. I find that sometimes I even need to add a bit of hot water to mine when it has evaporated and thickened after prolonged disuse.
- Whatever the state of the etchant, find a way to warm it up, since that will hasten the etch. The faster the etch, the more exclusively vertical it will be and the less horizontal it will be. You can do this by warming the whole etchant bath, or by simply heating up the etchant that comes into contact with the board. Some gentle motion to circulate the etchant also helps int hat regard.
- The surface cleanliness that helps to produce a good transfer of the pattern also helps to bring the etchant into better contact with the bare copper. A mirror shine is what you want to see before the board enters the etchant bath. That also means handling it properly from the point the transfer has been applied until the moment the board hits the etchant. You'd be surprised how many ways there are for finger juice to accidentally get on the board. Which reminds me: washing your hands isn't such a bad idea.
- Avoid trapping air bubbles. I etch my boards face down, floating on top of the etchant. That works out quite well as long as an air bubble doesn't get trapped underneath. Trapped air will leave you with unetched areas where traces are linked by solid copped surface. It is often during the prolonged immersion in etchant to get rid of these areas that the sideways etching of already-etched traces starts to occur. If you are stuck in that situation, you can consider rinsing the board with water(making sure as much of the etchant has dripped off back into the container as possible - etchant is not good for household plumbing), gently drying it off with a hair dryer or fan and "protecting" the edges of already-etched traces with a bit of judiciously applied waterproof pen along the sides of the traces to be protected. Ideally, though, you don't get to that point.
Sometimes, the traces in a pattern just need to be a bit thicker. What I do in those instances is to thicken them with software. I'll take the GIF, JPG, PNG or whatever (or a screen shot of a PDF), import it into Paint Shop Pro (though I gather many other programs will work), convert it into 256-shade greyscale, and "soften" (smudge/blur) the edges. Procedurally, what this does is to add a kind of graded grey edge to the existing pattern. Once you have some mid-greys added to the perimeter of the pattern, simply darken those midgreys through whatever tools your software has (PSP has a highlight/mid/shadow tool, which I set to 93-highlight and 30-mid for a couple of passes). Once you feel the traces have been thickened enough, convert the image back to 1-bit B&W to make it a crisper image. You may have to touch up some traces that come too close together, but that's easier to do in software than with a utility knife post-etch. One of the advantages of this is that you end up having more coper protected and your etchant will stretch farther as a result.
thanks guys, I'll let you know how it turns out