Cold solder joints in DME
07-14-2002, 12:41 PM
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Join Date: May 2001
Location: Paramus, NJ
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Cold solder joints in DME
Listers,
Last week my 951 wouldn't start. I was able to eliminate everything as a cause except the computer. Finally I removed the wood panel and gave the computer a couple of hard taps and the car started. I suspect the infamous "cold solder joints" have finally struck.
My question is, which joints have been suspect and how do I identify a cold joint.
Thanks for all the help,
Steve '86 951 (164,000 miles)
Last week my 951 wouldn't start. I was able to eliminate everything as a cause except the computer. Finally I removed the wood panel and gave the computer a couple of hard taps and the car started. I suspect the infamous "cold solder joints" have finally struck.
My question is, which joints have been suspect and how do I identify a cold joint.
Thanks for all the help,
Steve '86 951 (164,000 miles)
07-14-2002, 01:21 PM
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Join Date: Aug 2001
Location: Denver CO
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A cold solder joint may exhibit a hairline crack between the solder and the component lead. It may also simply be a frosty appearance to the solder or the solder may not have flowed up the components leads. Most of the time I have to have a large magnifing glass to actually see the problem, remember you asked. There is as much written about solder, soldering techniques and equipment as there is about oil and just as many opinions!
The best way to fix the problem is to purchase a GOOD soldering, NOT the 40W pencil sold by Radio Shack. A good one will run a $100 or more. And get good quality electronic solder. When I was doing techie work I used 63-37 mix but 60-40 is OK. Get a hot tip 800F and probably a mid size as well. Once the iron is hot, clean the tip (wet sponge) and place it against the joint, add a lttle bit of solder and let the solder puddle flow. Repeat this for each and every joint on the board! Pay attention around the connectors and large components.
A simplier way would be to find a local TV repair shop and have them do it for you. Probably cheaper if you have to buy an iron. Or contact me and I'll see what one of the techs at work would charge you to do it during his lunch break.
The best way to fix the problem is to purchase a GOOD soldering, NOT the 40W pencil sold by Radio Shack. A good one will run a $100 or more. And get good quality electronic solder. When I was doing techie work I used 63-37 mix but 60-40 is OK. Get a hot tip 800F and probably a mid size as well. Once the iron is hot, clean the tip (wet sponge) and place it against the joint, add a lttle bit of solder and let the solder puddle flow. Repeat this for each and every joint on the board! Pay attention around the connectors and large components.
A simplier way would be to find a local TV repair shop and have them do it for you. Probably cheaper if you have to buy an iron. Or contact me and I'll see what one of the techs at work would charge you to do it during his lunch break.
07-14-2002, 02:48 PM
#3
Nordschleife Master
A couple items. If you go in and hit all the solder joints, don't leave the iron on longer than to remelt the tin/lead. You don't want to cook the component on the other side. A wet sponge applied afterwards will suck off the extra heat.
Also, a "frosty" finish to the solder doesn't necessarily mean a cold joint, but is a good indication. For some reason the solder I'm currently using is flashing to frost finish on cool down (it is 37-63 electronic rosin core) on Molex terminals. I think it has something to do with what Molex is using in their tinning process as these joints are plenty hot and not moved on cool down. I even cut a couple apart and looked under microscope. Good joints. And if you scrape the solder with your fingernail you get the smooth silver finish you always like to see. Something is floating up to the surface.
Also, a "frosty" finish to the solder doesn't necessarily mean a cold joint, but is a good indication. For some reason the solder I'm currently using is flashing to frost finish on cool down (it is 37-63 electronic rosin core) on Molex terminals. I think it has something to do with what Molex is using in their tinning process as these joints are plenty hot and not moved on cool down. I even cut a couple apart and looked under microscope. Good joints. And if you scrape the solder with your fingernail you get the smooth silver finish you always like to see. Something is floating up to the surface.
