Cold solder joint example

[dingy]

I had an opportunity to resolder the circuit board in a spare CMOS unit from my original MKI instrument cluster.

 

I was able to get a fairly good close up picture of an example of some cold solder joints that I thought I would post. This may be helpful to someone that has never seen a cold solder joint.

 

There are 8 large connections in picture that all show some signs of a cold joint.

 

The circular ridge around the base of the soldered joint is the sign of a cold joint.

 

The worst case is the far right joint.

 

The smaller connections in the upper right corner are good solder joints.

 

For a size relationship, the large row of 4 joints is 3/4" in length.

 

Gary

[Dano]

Thanks Gary, that's a nice pic for those that need to know what we're talking about.

[FROG MAN]

I'd like to have a dollar for every connection I've heat treated at 1:00 in the morning. Nothing like a power amp down on some 911 gear due to faulty solder connections.

[mbrood]

I don't really think these are cold solder joints, those look like fatigue fractures where years and years of vibration weaken the solder and corrosion creaps in.

 

A cold solder joint is where one piece is heated sufficiently and the other (pad or pin) isn't, the solder flows around but there's no real electrical connection. Cold solder joints are EXTREMELY hard to visually detect.

 

Still the rule of thumb is to heat the harder, more substantial material and let THAT item transfer the heat... so only touch the iron to the pin tip, then let THAT heat and transfer the heat to the solder and the pad, THEN adding just a "bit" of new solder to let the flux in the solder help clean the joint.

[Flyinfool]

I don't really think these are cold solder joints, those look like fatigue fractures where years and years of vibration weaken the solder and corrosion creaps in.

 

A cold solder joint is where one piece is heated sufficiently and the other (pad or pin) isn't, the solder flows around but there's no real electrical connection. Cold solder joints are EXTREMELY hard to visually detect.

 

Still the rule of thumb is to heat the harder, more substantial material and let THAT item transfer the heat... so only touch the iron to the pin tip, then let THAT heat and transfer the heat to the solder and the pad, THEN adding just a "bit" of new solder to let the flux in the solder help clean the joint.

 

That was my thought also.

The one real bad joint may have been a partly cold joint, but it looks mostly like fatigue fractures.

Whenever I have to repair a joint on a PCB I always use solder with a little silver in it. The silver makes the joint a little stronger than just plain solder. I also add some NON corrosive flux in addition to the flux core of the solder, the flux and solder are both available at Radio Shack.

 

If like in the Pic there is fatigue cracking I would add a small dab of either electrical grade RTV or hot melt glue to keep that component from moving and breaking your new solder joint.