Most likely silver sulphide from the sulphur in your fingerprints. It is conductive, but not quite as good as silver. However, it is soft and contact pressure may break through the film.
Old WWII transmitters often used silver plate on the tank coils, especially for VHF and UHF. They used sliding or roller contacts to adjust the tank. The discoloration had little or no effect on the power output.
Mike Monett
Hello Keith,
I found ECL to be better than that but we soon abandoned it anyway for discretes and FPGA because it gulped so much power.
The real name slipped my mind because I never ordered any and never will. It's the white experimenter's boards where you stick components into.
Yes, it can be. What I saw in these mainframes was that it all turned black over time. On prototype it was even worse because people touched it with their hands a lot. With solder that wasn't a problem.
I wasn't either but we had techs that received training it WW. They did a pretty neat job but for boards I never authorized WW.
WW still was much superior to another technique. Forgot what it was called but you pushed wires into IDC slots. Once in a while you heard a faint "ping", had no idea where it came from and the board would refuse to work. That was often a real pain.
Regards, Joerg
Why do you care? Yes, silver oxide is black and tin-lead oxide is gray, but in neither case is the oxide in the path that the electrons take - wire-wrap connections are gas-tight. Besides, Silver oxide conducts electricity just fine.
Vero wire is better:
The trick is to bend all IC socket-legs "outwards" beforehand (see photo) otherwise the vero-wire will slip off.
When wiring the MCU sockect,
1) Pre-tin the vero-wire (don't melt the tool tip). 2) wrap a couple of turns around the MCU socket pin and solder it. 3) Then you can run the wire around all other nodes (don't solder untill board complete).Wiring up memory is a snip... d0 to d0 to d0 to d0 ad infinitum takes seconds *and* you don't solder anything until the end.
You can make ten or twenty connections to one node (you can only get three or four with wire-wrap).
Wire-wrap ends up about an inch thick and looks ugly Vero-wire only adds 0.1 inch thickness and looks neat.
Cheers Robin
All the WW pins we used were gold plated. I don't think there was any silver-oxide or sulfate in there. ;-)
In the case of wire-wrap, there isn't even a need for the film to conduct or for any breaking through of the film. Every wire-wrap has multiple gas-tight connections in parallel. Neither oxygen from the air or sulpher from finger oils can reach the contact point.
I don't think so, but I don't have any around anymore. Silver was a no-no after many major disasters.
MIL-STD-1130B says that it isn't.
Not when I do it.
Slit-N-Wrap wire wrapping is faster than vero wire, and you don't have to solder at all.
I believe that if you checked, you would find that the wires were all silver-plated copper.
Hadco sounds familiar. This was 1997-2000 when I was in MA.
Cheers Terry
Just put a via on every ball, used or not.
John
That's what I did. It was easier leaving the via, since it came with the image.
Have something to add? Share your thoughts — no account required.
Ask the community — no account required