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Are these solder joints bad?

I'm attempting to locate a problem on my Dell D1025TM UltraScan (Trinitron) monitor. I posted about it a week and a half ago. I got the D board out and am checking for bad solder joints.

I'm not sure if these should be re-soldered or not. If so, what's the best way to get the crud off the pads and surrounding areas? Will acetone do it?

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Is the residue rosin that has seeped out of the solder itself as a result of thermal cycling over a period of years? I notice that all of these solder joints are for components that get hot while the monitor is on.

I realize there may be other cold solder joints that don't appear to have anything wrong with them at first glance, unlike these, but these got my attention first. I realize these may not be "cold" at all.

Appreciate any and all comments. Thanks!

VCS

Reply to
Van Chocstraw
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on.

The rosin will not seep out of the solder later on. It does look like the joints got hot and sort of melted and burnt. This hapens when the design is slightly wrong and the components get the joint too hot over the years. Try to clean off the solder and put on some new solder. You may have to scrape the leads and pads to get them clean enough.

Reply to
Ralph Mowery

FWIW, they look fine to me. I'd look elsewhere for the problem.

I wouldn't worry about the rosin unless you're in an extremely high humidity area, and maybe not even then.

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Reply to
CJT

Dirty component leads exposed to RF at high voltages can eventually isolate themselves from their solder connections. This also happens with gold-plated leads.

#5 looks like a cold joint to me, but it is hard to tell from the photo; it could just be too much solder. The top one in #2 also looks bad, but it looks like a filter cap from your description and you'd probably know if it was bad.

Rosin left on the circuit board will eventually corrode exposed metal, but it happens over a period of decades.

The easiest way to re-do these (should you decide to go that route) is probably to just add a little liquid flux, reheat the joint, and then clean up afterward with IPA or flux remover. Acetone works great, but it can take off the conformal coating and silkscreens too.

I once worked on a monitor I knew had a cold joint (it was losing deflection and beating on it made the problem appear and disappear). The one that was bad was one I'd looked at half a dozen times. I only found it by tapping around the board with a dowel.

Reply to
stickyfox

Ignore this poster. It's a troll.

Van Chocstraw wrote:

Reply to
9lnilnli080wdrd

Most computer manufacturers are using a no clean solder flux. It's OK to have it and if you attempt to remove it, it reactivates and can become corrosive to the PC board traces.

b.

Reply to
<barry

" snipped-for-privacy@gmail.com" bravely wrote to "All" (25 Sep 05 18:45:13) --- on the heady topic of "Re: Are these solder joints bad?"

st> From: " snipped-for-privacy@gmail.com" st> Xref: core-easynews sci.electronics.repair:343123 [,,,] st> Rosin left on the circuit board will eventually corrode exposed metal, st> but it happens over a period of decades. [,,,]

Acid flux will certainly corrode metal but rosin flux made for electronics is pretty inert. I've seen older circuits with a lot of residue rosin and they worked just fine.

The main problem I have experienced with rosin was in a high impedance application because rosin will absorb and trap humidity thus lowering circuit resistance. Perhaps this trapped humidity might explain the corrosion you have seen on metal?

A*s*i*m*o*v

... Who's got the Thermonuclear Welding Set? - ToddS

Reply to
Asimov

I personally don't believe it either.. but I was first told this when I was certified for mil-2000a soldering, and all of my research on the topic has confirmed it. It's the residue, which consists of flux and various other substances, some of which were formed during soldering, that are considered corrosive. Most QA programs specify that all flux residue has to be removed. However, there are different kinds of flux. Plain old rosin is supposed to be totally benign. RA and RMA are more chemically aggressive, and are not recommended for no-clean applications. No-clean fluxes have the benefit of omitting the cleanup step, but they are bad for soldering iron tips (go figure).. and my iron was pretty expensive so I use RMA and scrub it off when I'm done.

This is all going to change really soon because of the industry push to RoHS anyway.

And was this really a troll post? How can you tell? Somehow I just don't feel properly burned...

Reply to
stickyfox

I have to agree. I've got stuff here that I made 50 years ago, soldered with rosin core electronic solder that is still fine with no sign of corrosion. That was point-to-point wiring. I have plenty of later stuff that is PC board done 30 years ago that is also fine.

But I don't know what kind of flux was used in standard elecronic rosin core solder. Was it RMA?

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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Reply to
Jim Adney

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