Drilling a PCB

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KP11520

KP11520

Member
Joined 2007
Hi Nordic,

I can FEEL your pain! I guess this is just one of the realities of DIY!

The Kitten with the frog helmet! Is this little guy, yours too? He (or she) is real cute. But what happened to his leggs? My wife loves your cat pictures! It is the only thing she pays attention to on this web-site!

Regards//Keith
 
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gootee

Member
Joined 2006
fullnet.com/~tomg/index.html
KP11520 said:
Hi Gajanan,

Good idea, in fact I have a can of "Duster II" right here for blowing off/out dust from PCBs and Motherboards.

I will use glasses. Flying Solder is better than a flying PCB (like when I throw it across the room out of frustration).

Now, what about the sockets. Is there something better than Gold, both in the short term and over the long run (doesn't tarnish)? I haven't ever seen Rhodium Sockets (I like Rhodium for RCAs and Binding Posts because of great conductivity and minimal tarnishing).

Also, it seems the Machined Sockets are the way to go!

Thanks!

Regards//Keith
Click to expand...

Hi Keith,

Dis-similar metals in contact with each other can do bad things. The best bet is to have the same metal/plating for both the pins and the socket.

To clear solder from holes, I often just use a rubber squeeze-bulb (aka a cheap solder-sucker), and blow it out the bottom, while heating it with a small, pointed tip.

- Tom Gootee

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

Member
Joined 2007
conradhoffman.com
IMHO, most of what people know about sockets is just what marketing people tell them. In reading some actual studies on reliability, the best sockets were double leaf, not machined contacts. Gold only accomplishes something when the IC leads are also gold plated, and I haven't seen one of those in years. OTOH, any decent quality socket seems to work fine, and I haven't had any trouble with the gold flashed machined ones from Digikey (ED3308-ND). I do avoid single leaf, and any socket that doesn't leave plenty of room underneath for cleaning, or that tends to trap liquids.
 
KP11520

KP11520

Member
Joined 2007
Here is an article from a respected and reputable source that may or may not shape some of our opinions: http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel6/33/25250/01135481.pdf?arnumber=1135481

Conrad, I, like you, like to dig a little deeper, past the jargon, to really understand the truth. This has gotten me into trouble around here on occasion, so forgive me everybody if I keep at it and every once in a while what I present asks anybody to re evaluate their belief system.

We will all have better systems as a result by keeping each other honest!

Tom, do you feel that way even if all the metals are inert and don't change much regardless of physical conditions or voltage passing through them? I can see if they are arcing and sparking that a breakdown of plating can happen, but with a solid contact too?

Thanks all!

Regards//Keith
 
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gmphadte

Member
Joined 2003
When I open any equipment, first thing I do is raise those socketed ICs and push them back in. This rubs the two metals and cleans them at the place of contact. Most of the times this makes the repairs. I never advocate for any socket. It is only good for prototyping.

The second repair tool is the hot air blower. Most of the problems in teh rainy season are due to pcb laminate absorbing the moisture.

Gajanan Phadte
 
G

gootee

Member
Joined 2006
fullnet.com/~tomg/index.html
KP11520 said:
Here is an article from a respected and reputable source that may or may not shape some of our opinions: http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel6/33/25250/01135481.pdf?arnumber=1135481

Conrad, I, like you, like to dig a little deeper, past the jargon, to really understand the truth. This has gotten me into trouble around here on occasion, so forgive me everybody if I keep at it and every once in a while what I present asks anybody to re evaluate their belief system.

We will all have better systems as a result by keeping each other honest!

Tom, do you feel that way even if all the metals are inert and don't change much regardless of physical conditions or voltage passing through them? I can see if they are arcing and sparking that a breakdown of plating can happen, but with a solid contact too?

Thanks all!

Regards//Keith
Click to expand...

Hi Keith,

I don't know what an inert metal is. :)

From what I have read, gold can diffuse into tin coatings (and tin-lead solder) and form non-conductive, brittle, intermetallic compounds. It's a recipe for long term failure.

- Tom Gootee

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

R.I.P.
Joined 2004
gootee said:

From what I have read, gold can diffuse into tin coatings (and tin-lead solder) and form non-conductive, brittle, intermetallic compounds. It's a recipe for long term failure.
http://www.fullnet.com/~tomg/index.html
Click to expand...
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.
 
C

Conrad Hoffman

Member
Joined 2007
conradhoffman.com
IMO, life is far easier if one can develop the ability to move between different, sometimes contradictory, belief systems. I sometimes build things with leads fully wrapped around lugs and component leads bent flat against circuit boards, with no sockets, and tout the great reliability of the project. Five minutes later I might tack solder everything, breaking every rule of good soldering, because I want to quickly make changes, test ideas, or even reclaim the parts when the exercise is over. Class A, discrete, op-amps, batteries, super regulators, whatever. You have to try a large variety of different designs, techniques, parts, and philosophies, if you want to learn anything.:clown:
 
KP11520

KP11520

Member
Joined 2007
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)
 
G

gootee

Member
Joined 2006
fullnet.com/~tomg/index.html
AndrewT said:

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.
Click to expand...

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
 
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AndrewT

R.I.P.
Joined 2004
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.
 
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