On Wednesday, 17 June 2015 11:58:03 UTC-4, Phil Hobbs wrote:
On 06/17/2015 10:20 AM, Ralph Mowery wrote:
"Matthew Connor" wrote in message
...
Good morning, all! While technically minded, I am brand new to repairing
PCBs. I'd therefore greatly appreciate relatively simple explanations and
your indulgence of my ignorance.

I recently obtained a Geiger counter which was in need of being rebuilt.
Because it was manufactured in 1962, the components are large and provide
me with plenty of working room. After desoldering all components, I took a
locksmith's file (very small and fine) and took off just the immediate
outer layer of the leads of the components. My intention was to remove
existing solder and any other "gunk". As soon as I began to see the copper
color of the lead showing through, I stopped and moved on to the next.
After doing this for all .components, I soldered them back in and
everything is working perfectly...for now.

I ran across some information AFTER doing this that tells me that might
have been a bad idea. Are .component leads coated with something
protective that I should have left on? Should I expect earlier-than-usual
failure from any of my components since I filed off this outer layer? Any
insight is much appreciated.

Most component leads are tinned. That is the copper wire is coated with a
thin layer of solder. This makes it easier for soldering. Copper will
oxidise very fast, so don't scrape the tinned wires to bare copper. It will
not hirt anything,but just make soldering more difficult. When repairing
circuits use some 60/40 solder with rosin core flux. That is unless you run
across some of the newer lead free stuff. You might alos want to get a
bottle of the liquid flux to use. Just make sure the flux is for electronic
work. There is some acid flux that is made mainly for plumming. It will
tend to draw moisture out of the air and corrode the copper in electronics.

If you think there is a lot of crud on the wires, use one of the Scotch
Bright typw pads to just shine them up, but not enought to remove the old
solder.
It is often recommended to tin the bare copper wires before soldering them.

I doubt you will get any failure because you scraped off the coating.


You can get RA flux (rosin, activated) in solder or in a bottle. It
cleans off oxidized leads very well. Kester 44 solder is RA, and you
can get the same stuff as Kester 1544 (only in gallons or pails
unfortunately). However, MG Chemicals 835 RA flux is available from
Digikey or Amazon in much smaller quantities for about 10 bucks. I use
a small bottle with a stainless steel needle.

When the needle clogs up (as it will), just touch it with the iron and
it magically clears out.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

Dr. Hobbs: Thank you very much for your insight, sir! It's greatly appreciated! -Matthew