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Old 01-13-2011, 01:04 PM
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Default Soldering Problems?

Trouble with your wiring? If you soldered your connections...

Originally Posted by Jim McDougall View Post
you probably have one of three common problems:

1) Cold solder joint -- did not let enough heat build up to properly melt solder. If the solder looks dull this is the usual visualization of this. A good joint should be somewhat shiny. What commonly happens here is that the lack of heat has not completely vaporize the rosin in the solder and this insulates the wire from the connection. This can create a resistance instead of a short or if the wire moved during the process, an open connection that may get made when you move the wire around.

2) A bridged solder joint. The spacing between connections is quite tight and you can easily bridge across two terminal connections. You can check this with a multimeter by testing for shorts between each connection or use a magnifying glass to visually examine the connections. I always do one or the other just to verify I haven't accidentally bridged ajoining terminals

3) Break a solder pad. This is a common problem, especially when re-doing wiring. A combination of heat and the physical stress of removing a wire can cause the copper pad to break away from the copper trace leaving a fine gap between the two. The best way to check this is to use a multimeter and check for a short between the pad and the destination of the connection. Follw the trace from where the pad connects to another visible connection point. Most will end on another chip or cpu pin and then verify that you have a short between the two points. These can usually be repaired by taking a ink eraser and rubbing down the trace right by the pad to expose base copper and then heating the exisiting solder and use the iron's tip to drag the molten solder out over the exposed copper of the trace to make the connection. Recheck with the multimeter to validate that you not have a connection from pad to destination of trace. If the gap is significant, I use a piece of fine bared wire to bridge the gap -- solder to trace and joint. Worst case, I have used a piece of insulated wire from the joint to the trace destination -- bypassing the trace completely.

Moving the wire and having the connection made and not made is a symtom of this problem. Since the pad has lift from the board, there is no physical bond between the wire/pad and the board and this allows the wire/solder pad some degree of movement. In certain positions, this moveable joint can contact the trace and you get a connection but if the wire is moved or disturbed the connection can be lost. Definitely unreliable.

If you don't have one already, I would recommend that you invest in a cheap multimeter.($10 - $20) Use it to determine what your current problems are caused by and try to fix them. Good practice before you start another board and you probably will be able to fix the current one!

If something does not work at all then 1,2 and 3 are possiblilities. If it works when you move wires then it iw usually 1 or 3.
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Old 04-13-2011, 08:32 PM
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