30 Dec
2008
30 Dec
'08
9:09 p.m.
I was perusing some topics on Wikipedia and came across this enlightening
tidbit of information in the article on "Gold plating":
"With direct gold-on-copper plating, the copper atoms tend to diffuse
through the gold layer, causing tarnishing of its surface and formation of
an oxide and/or sulfide layer.
"A layer of a suitable barrier metal, usually nickel, is usually deposited
on the copper substrate before the gold plating. The layer of nickel
provides mechanical backing for the gold layer, improving its wear
resistance. It also reduces the impact of pores present in the gold
layer."
http://en.wikipedia.org/wiki/Gold_plating
So this is why a re-seating of certain cards, connectors and ICs
oftentimes cures a fidgety system.
Just thought I'd share this. It was novel to me at least.
P.S. I'm assuming this information is accurate :)
--
Sellam Ismail Vintage Computer Festival
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30 Dec
30 Dec
10:18 p.m.
On 30 Dec 2008 at 21:09, Sellam Ismail wrote:
So this is why a re-seating of certain cards,
connectors and ICs
oftentimes cures a fidgety system.
Maybe the scrappers know this, but how often is pure gold used as the
contact material on edge connectors? I thought that an alloy was
plated as pure gold is very soft and doesn't withstand too many
insertion cycles. Anyone?
Cheers,
Chuck
10:41 p.m.
From: cclist at sydex.com
To: cctalk at classiccmp.org
Date: Tue, 30 Dec 2008 22:18:45 -0800
Subject: Re: Why it is sometimes necessary to re-seat a board or chip
On 30 Dec 2008 at 21:09, Sellam Ismail wrote:
Hi
To my knowledge, it is pure gold. It is difficult to plate
alloys.
Another reason why boards need to be resetted is because
there are differences in the materials. Gold to solderplate
will cause problem over time.
Keeping air and moisture away from the contacts will avoid
problems. This is why I have been using things like DC#4
on contacts for my machines for years. I've never had to
reset any of my machines boards or ICs that I've applied
the grease to( not ever ).
But back on the plating, it is done very thin. 15 or 30
micro inches are common. The nickel ( as well as a barrier
to the copper ) provides the stiffness.
The gold is so thin that a few minutes with a pencil
eraser will remove most of it.
That is why I hate to see people using this method to
clean boards. I find that this can more properly be done
with some damp lense paper. The eraser often leaves a
little of the rubber as well that will eventually release
the sulfur, causing the need for more cleaning.
Dwight
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So this is why a re-seating of certain cards,
connectors and ICs
oftentimes cures a fidgety system.
Maybe the scrappers know this, but how often is pure gold used as the
contact material on edge connectors? I thought that an alloy was
plated as pure gold is very soft and doesn't withstand too many
insertion cycles. Anyone?
Cheers,
Chuck
31 Dec
31 Dec
12:13 a.m.
On 30 Dec 2008 at 22:41, dwight elvey wrote:
To my knowledge, it is pure gold. It is difficult to
plate
alloys.
Not really that hard, depending on the alloy. For instance, I can
plate brass in my own shop--it's not difficult; just an acid bath
process. (Tin-lead) Solder has been electroplated onto PCBs for
decades.
Some people have pointed to their college chemistry texts and told me
definitively that it was impossible to electrodeposit an alloy. I
don't know where that one got started.
I'll agree that cooking up a plating bath can be a black art. Stuff
you'd never think would affect the outcome such as sugar sometimes
winds up in them and I know a retired fellow who ran a plating shop
who swore that he got better results than anyone else because he
urinated in his tanks.
From: http://www.pfonline.com/articles/pfd0022.html
Hard, Bright Gold
Platers who gold plate contacts and connectors generally use bright
acid gold formulations. These baths contain complexed cobalt or
nickel in small quantities, to improve hardness and brightness of the
deposit. Such gold electroplates will be 99.7 to 99.9 pct pure, and
hardness can be 120 to 300 Knoop. The small amount of nickel or
cobalt will interfere with die bonding, so these baths cannot be used
for semiconductor plating. Hard, bright gold baths, if operated with
good housekeeping and chemical control, have very long life-often
three years and more.
Cheers,
Chuck
7:01 a.m.
----------------------------------------
From: cclist at sydex.com
On 30 Dec 2008 at 22:41, dwight elvey wrote:
Hi Chuck
I only meant that is wasn't 18K gold and not that is was impossible.
speed is important, as mentioned in the article you point to.
It is harden some but it is still quite close to 24K.
Dwight
_________________________________________________________________
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To my knowledge, it is pure gold. It is difficult
to plate
alloys.
Not really that hard, depending on the alloy. For instance, I can
plate brass in my own shop--it's not difficult; just an acid bath
process. (Tin-lead) Solder has been electroplated onto PCBs for
decades.
Some people have pointed to their college chemistry texts and told me
definitively that it was impossible to electrodeposit an alloy. I
don't know where that one got started.
I'll agree that cooking up a plating bath can be a black art. Stuff
you'd never think would affect the outcome such as sugar sometimes
winds up in them and I know a retired fellow who ran a plating shop
who swore that he got better results than anyone else because he
urinated in his tanks.
From: http://www.pfonline.com/articles/pfd0022.html
Hard, Bright Gold
Platers who gold plate contacts and connectors generally use bright
acid gold formulations. These baths contain complexed cobalt or
nickel in small quantities, to improve hardness and brightness of the
deposit. Such gold electroplates will be 99.7 to 99.9 pct pure, and
hardness can be 120 to 300 Knoop. The small amount of nickel or
cobalt will interfere with die bonding, so these baths cannot be used
for semiconductor plating. Hard, bright gold baths, if operated with
good housekeeping and chemical control, have very long life-often
three years and more.
Cheers,
Chuck 
7:12 a.m.
I always thought this was because of "chip-creep"
over time chips (ICs) will work their way out of sockets...
From: dkelvey at hotmail.com
To: cctalk at classiccmp.org
Date: Wed, 31 Dec 2008 07:01:10 -0800
Subject: RE: Why it is sometimes necessary to re-seat a board or chip
----------------------------------------
_________________________________________________________________
From: cclist at sydex.com
On 30 Dec 2008 at 22:41, dwight elvey wrote:
Hi Chuck
I only meant that is wasn't 18K gold and not that is was impossible.
speed is important, as mentioned in the article you point to.
It is harden some but it is still quite close to 24K.
Dwight
_________________________________________________________________
Suspicious message? There?s an alert for that.
http://windowslive.com/Explore/hotmail?ocid=TXT_TAGLM_WL_hotmail_acq_broad2…
To my knowledge, it is pure gold. It is difficult
to plate
alloys.
Not really that hard, depending on the alloy. For instance, I can
plate brass in my own shop--it's not difficult; just an acid bath
process. (Tin-lead) Solder has been electroplated onto PCBs for
decades.
Some people have pointed to their college chemistry texts and told me
definitively that it was impossible to electrodeposit an alloy. I
don't know where that one got started.
I'll agree that cooking up a plating bath can be a black art. Stuff
you'd never think would affect the outcome such as sugar sometimes
winds up in them and I know a retired fellow who ran a plating shop
who swore that he got better results than anyone else because he
urinated in his tanks.
From: http://www.pfonline.com/articles/pfd0022.html
Hard, Bright Gold
Platers who gold plate contacts and connectors generally use bright
acid gold formulations. These baths contain complexed cobalt or
nickel in small quantities, to improve hardness and brightness of the
deposit. Such gold electroplates will be 99.7 to 99.9 pct pure, and
hardness can be 120 to 300 Knoop. The small amount of nickel or
cobalt will interfere with die bonding, so these baths cannot be used
for semiconductor plating. Hard, bright gold baths, if operated with
good housekeeping and chemical control, have very long life-often
three years and more.
Cheers,
Chuck
7:50 a.m.
----------------------------------------
From: dgahling at hotmail.com
I always thought this was because of "chip-creep"
over time chips (ICs) will work their way out of sockets...
Hi
It is interesting that you mentioned this. This was
a real problem at one time, created by automatic
chip insetion.
When one puts a chip into a socket with tention spreading
the legs, it will tend to pop out of the socket.
Why it does this I'm not sure because you'd think that
with the lead spread out they'd tend to pull the chip
into the socket.
The solution for this is to straighten the leads so
that they go straight into the socket without side
tention.
Those nice little insertion tools that keep some
tention on the leads should only be used for soldered
in parts and if used for sockets, one should straighten
the leads first. It doesn't hold nicely in the tool
but part won't work out of the socket over time.
Dwight
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8:17 a.m.
dwight elvey wrote:
When one puts a chip into a socket with tention
spreading
the legs, it will tend to pop out of the socket.
Why it does this I'm not sure because you'd think that
with the lead spread out they'd tend to pull the chip
into the socket.
I suppose you can ignore the outside edge of the socket, which results in an
IC leg at an angle pressing against the inside edge:
XXXXXXXXXXXXXXXXX
IC leg -> / \
|/| <-- sockets --> |\|
... if the IC legs are under tension and trying to pull inwards, it generates
a lifting effect against the inner edges of the IC socket's pins.
It wouldn't surprise me if heat doesn't make this worse, and vibration almost
certainly will.
in parts and if used for sockets, one should
straighten
the leads first.
I've got a nice little tool for doing that somewhere...
cheers
Jules
5616
days inactive
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7 comments
5 participants
participants (5)
-
cclist＠sydex.com -
dgahling＠hotmail.com -
dkelvey＠hotmail.com -
jules.richardson99＠gmail.com -
sellam＠vintagetech.com