Re: 'Solder Rot'


greenboxmaven
 

I am very surprised at Tektronix having this sort of problem. I worked a few years at a vintage sound equipment botique as a retirement job, and aged solder joints were a very common and serious problem. Kenwood gear, both sound and ham, was the worst for this problem, but it occurred elsewhere as well. Reheating all of the connections and adding a small dab of well fluxed solder was all that was needed in many cases to bring a dead or poorly performing rig back to life. For through hole solder joints, I like to warm them up, push a piece of small stranded wire through, flow the solder well, and then trim the wire. Over 40 years ago, I was given a couple dozen Monroe/ Litton desktop calculators with Nixie tube displays. They all had unreal faults, and all but one were fully restored by putting wires in the through hole connections and reheating the others.

Bruce Gentry, KA2IVY

On 1/6/20 8:10 AM, EricJ via Groups.Io wrote:
It absolutely does. I was just reading a paper about this the other day. Several factors contribute to circuit failure due to aging. One being that the solder bond weakens apparently due to inter-metallic layer growth over time. There was a whole section dedicated to testing shear strength of aged surface mount joints. Leaded solder did much better than lead-free at retaining bond strength in those cases.

Several other factors mentioned and tested were the weakening of foil layers' (tracks and pads) adhesion to the boards (roughly halved over time), vias coming loose and separating from the fiberglass surface of the boards (apparently very common on heavy copper sections of the board due to thermal expansion of the copper and vias during soldering) and cracking and "tearing" of aged through-hole solder joints.

--Eric

On Jan 6, 2020 6:32 AM, Tim Phillips <timexucl@...> wrote:



from Tim P (UK)
The posts re '465M junker' remind me of a post I sent a couple of years
ago. I had a 1S1 plug-in that was intermittent, sometimes OK, sometimes
just would not sample.
Did the usual things, re-seat transistors, clean switches, check sampling
bridge etc. Finally, I lifted the PCBs, thinking maybe a wire-clipping or
solder blob had got between the PCB and the chassis. Close examination
with
a jewellers loupe and bright light showed a bad joint, where the solder
seemed to have parted from a transistor socket - there was a visible gap
between the solder fillet and the pin, not broken but as if the solder had

'shrunk'. Found a few other cases also. I guess solder ages like most
things, or sort-of-crystallises.
Tim





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