Drilling a PCB

[KP11520]

I like the wisdom in that paragraph!

At 47, I am hoping to catch up with some solid ideas but nothing replaces the experience so I need to do and learn so many thhings!

NO worries, I have lots of unused apace in my head! In fact, so much space, the "Defragmentation Utility" says Defragmenting is not necessary! (see below)

[gootee]

Originally posted by AndrewT

Hi,
I'm no chemist, but I think this statement is referring to the liquid phase of the soldering or tin plating process.
Some months ago J Neutron gave us a comprehensive review of what happens here.

Hi Andrew,

OK. But there are also apparently-serious potential problems when mating gold- and tin-plated metals in sockets. Intel had a white paper about it. You can search for something like "gold tin pin socket plated", at http://groups.google.com , and find lots of discussions about it. Apparently, certain motherboards using dissimilar metals (gold and tin in that case) in either SIMM sockets or CPU sockets started having major problems, within a matter of months in some cases.

From the little I have read about it, I think that the slight potential difference, plus a little moisture in the air, causes some kind of galvanic reaction, and corrosion or oxidation of the tin, at least, resulting in a much higher contact resistance.

Any two dissimilar metals, being in contact, can cause some kind of "corrosion" problem. How much of a problem it might become depends on the properties of the two metals. I'm not a chemist, either. But I did find and read some of the explanations, at one time, back when I was specifying all of the sockets and Molex connectors for my Curve Tracer product, and became concerned about it. At the time, I decided it would be safer to avoid mixing metal types in sockets, if possible.

- Tom Gootee

http://www.fullnet.com/~tomg/index.html

[AndrewT]

Hi Tom,
thanks for clarifying that.
Corrosion between dissimilar metals will always happen.
Even slight composition differences between apparently similar alloys will generate that electrochemical voltage.
If all the chips are using solder coated (=tinned) pins then similar coated sockets would be better than choosing another metal.
If however tin plated pins are used then that equals a different requirement for the sockets.

[KP11520]

Hi Everybody,

Just to let you know, if you also get to a point where you need to drill a PCB for whatever reason, I found this place to have quality bits at great prices and great service too: http://drillcity.stores.yahoo.net/sitemap1.html

Thanks to all of you who helped!

Regards//Keith

[ak_47_boy]

Just melt the solder then blow it out of the hole with 100 psi from an air gun.