Fixing Cold Joints
 

When Is The Best Time To Pull The Cpu And Have The Joints Redone? When The Car Is Cold Or After Warmup, Or Do It Really Matter?

... first, don't post in all caps.

Second, you're resoldering joints in the CPU. Electrical connections. They don't care if the car is warm, cold, or not there. "Cold solder joints" has *nothing* to do with engine temperature.

-=Russ=-

understood, thanx!

To do this properly, you need to get rid of the old stuff.
I used to have a $400 Hakko desoldering gun, which was nice but very expensive.
The original solder is acid core and eats soldering gun tips like mad. :(


-Ted

Yeah it does... I go through a tip every month

Good info.. I wonder if I desoldered one on the PRC 2000, if it would damage it..

Acid core? When is this *ever* used in electronics??

Anyway, completely removing and re-solding all the joints might be best, but I can't imagine how you could go wrong with just heating the existing solder and letting it re-flow. You should be able to see it change to liquid. If it doesn't look right, then you can remove it and re-solder. I just did my logicon and added a bit of solder to a couple of points, but that's about it. If you don't have a decent amout of soldering (and especially de-soldering) experience, you're more likely to destroy it by trying to de-solder.

Just re-heating does not remove the corroded joint... it suspends it into the joint leading to another cold solder joint a year or so down the road.

You must remove all the old solder (and its accompaning fluxes) before flowing new solder in. If you don't the joints will fail again. Maybe not this week, but as someone that repairs these Mazda ones (denso/Imanson) and Porsche (bosch), and Toyota/lexus (denso/Imanson) cold solder joints for a living, I can tell you it will fail again.

Isn't a corroded joint different from a cold solder joint? I always thought a cold solder joint was one that was never quite right to begin with, and works itself loose after numerous heat/cold cycles. But then I imagine if air can get in, it would corrode, so I guess I see your point.

But you gotta agree with me on one point....de-soldering is a very different "art" from soldering!

A cold solder joint that fails, fails due to corrosion building up in the joint. The corrosion grows in the cracks in the solder.

The corrosion can start from too much flux, not enough heat, (joint was not hot enough when solder was flowed in to force the flux to rise out of the joint), from stress cracks (most common on Japanese cold solder joints) caused by vibration, insufficent solder (most common on Bosch electronics), too much heat (solder metals form a internal structure when cooling, etc.

The idea of heat and cold effecting a joint is a old wives tale. There never is enough heat to re melt the solder unless the circuit is damaged itself.

And part of soldering is de-soldering- so, no I do not agree with you that it is a different art. That is like saying checking the oil is different than adding gas to a car. Both are required if you want the car to continue running.

And both de-soldering and soldering are required if you want to fix cold solder joints and the part keep working.

Apparently when these cars were made. I'm just glad I used cheapo 10 dollar desoldeing guns from frye's. I dont really care if it screws them up.
On a side note, I'm about to start a major resoldering campaign on my car now that its got a blown apex seal, so I might be on with some questions for in the next few months, icemark.

Be happy to help were I can

I've been soldering since I was like 10 or something crazy like that, and I'm 39 now. Shows that you're never too old to learn!

Anyway, soldering was never difficult for me, but de-soldering took much more "trial and error" to perfect, hence my comment.

I never really had that much problems with it. Just heat, suck, repeat. Sometimes I'll get some solder wick for pesky clumps, but not too often.

[QUOTE=Syonyk]... first, don't post in all caps.

And just why not? You've all these three dollar bills on this site that can't/won't puntuate much less use a single capital letter. That is an Idiot RULE.

Wow, you're older than I am.
That's a surprise! :)


-Ted

Why is it a surprise? 'Cause I know so little? ;)

Nah, its because there are not very many older members like us (+35), here.

You mean most here didn't see brand new '87 TII's sitting on the Mazda dealer's showroom floor? Pity! :)

Man, I clearly remember that! I was going to buy a brand new '88 GXL, but the price went from 18,500CDN in 1986 to 24,000 in '98! Ended up with a Daytona Shelby Z instead. Fun car, but not a '7.

Hell, half the kids here are only as old as their cars. Some were not even born when their cars were made.

Crap...I meant '88 up there...not '98.