Quote:
Originally Posted by JamesDean
Cold Solder Joints
The second problem comes from cold solder joints. Solder connects all the points on the board. I've been told that solder can have a life span of about 20 years or so before it starts to show signs of failure like cold solder joints. The cruise control boards are partially coated with a special type of polyurethane coating. This helps prevent moisture and other outside elements from oxidizing and corroding solder points. Several boards I've worked on have failed to come back to life after a simple capacitor replacement. They needed a full-on resolder of every point on the board to come back to life.
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Obviously you know a great deal more about cruise control amps than I do, however I just want to point out one minor inaccuracy. The term 'cold solder joint' refers to a solder joint that was made with the solder not reaching the appropriate temperature. On lead based solders, this is pretty obvious as the joint will be dull and pitted rather than shiny and smooth. The failure I see on MB module solder joints is not this type of failure, it's a stress related failure on otherwise good solder joints which is caused by both vibration as well as thermal expansion/contraction. The result is more or less the same, but not the cause. Even a perfectly formed solder joint will crack and fail if subjected to enough stress. That is the failure mode I see most often in MB modules. I have never encountered an actual 'cold solder joint' in one.
Most often I see cracks forming around the base of the solder joint, typically where a large pin (usually the module's header pins) pass through the circuit board. Sometimes these can be hard to see, but reveal themselves when you flex or move the board or pins and the gap suddenly appears before your eyes.
I point this out because when looking for a cold solder joint you are looking for something that looks completely different than a cracked solder joint.