From: "Barry L. Ornitz" <ornitz@dpnet.net>
Subject: Re: chemical compounds to "tin" copper traces??
Date: 14 Dec 1998
Newsgroups: sci.electronics.design

Usually stannous chloride, sulfamic acid, and a few other things.  Stannous
chloride is not difficult to find in the typical chemistry department
storeroom, but sulfamic acid might be.

Might I suggest silver plating instead.  There is an excellent product
called Cool-Amp that does this beautifully.  While expensive, a pound of
the product will last a lifetime.

         Dr. Barry L. Ornitz     ornitz@dpnet.net


robpeterson@iname.com wrote in message
<3675bb49.11153047@news.flash.net>...
>One commercial product is "Tinnit" which is two white powders to be
>mixed with hot water.  Then, a cleaned copper PC board is dropped in
>the solution and a silver-colored deposit is put on the copper traces.
>This allows easy soldering.
>
>Question: can anyone tell me what these chemicals are?  They are
>probably easily-obtained if I just knew what they were.

From: "Barry L. Ornitz" <ornitz@dpnet.net>
Subject: Re: chemical compounds to "tin" copper traces??
Date: 16 Dec 1998
Newsgroups: sci.electronics.design

Thiourea was the other chemical I could not think of at the time when I
wrote this.
>> Usually stannous chloride, sulfamic acid, and a few other things.


KMEERES wrote:
>Silver should not be used for plating pcb's despite its higher
>conductivity.
>
>I cannot remember the details but istr that the combination of
>silver/lead/tin/copper at a joint causes microscopic metallic crystals
>to grow over a period of time causing shorts.

I have used the Cool-Amp plating technique on printed circuit boards for
over 30 years.  It does not cause this problem because the coating
thickness is quite thin, only a few molecular thicknesses.
The process is an immersion plating process, not an electroless process, so
once the copper is coated, no additional silver plates out. These boards
have been used at voltages up to 60 KV without problems.  It is very
important to wash the boards thoroughly after either tin or silver plating.
Residual electrolytes CAN cause problems.

Microscopic silver needles shorting out circuit boards and especially
Tektronix ceramic terminal strips is certainly possible but most of the
stories are urban myth.  The silver must have a conducting electrolytic
path for the "whiskers" to form.

There was a long discussion about this with respect to the silver-plated
ceramic terminal strips in old Tektronix oscilloscopes (on the Boatanchors
mailing list).  Two former Tek employees with a combined experience of over
80 years, one a designer and the other a repairman, claimed to have never
seen this.  The only person who had noted that the scope had been stored in
a damp environment and the terminal strips were caked with moist dirt.
Both men noted that ordinary solder could eventually ruin these terminal
strips; you need to use solder with a small amount of silver in it.

        Dr. Barry L. Ornitz     ornitz@dpnet.net

From: "Barry L. Ornitz" <ornitz@dpnet.net>
Subject: Re: Cool-Amp Powder, was: Re: chemical compounds to "tin" copper 
	traces??
Date: 19 Dec 1998
Newsgroups: sci.electronics.design

Mark D. Braunstein wrote in message
<367c009c.5293339@news.mindspring.com>...
>If you need a silver plating compound for PC boards, check out
>www.dynaart.com. They sell a rub-on powder that plates the board and
>costs far less than the below-mentioned price.


$29 for how much material.  Remember I said a pound of Cool-Amp ($143)
lasts a LONG time.  Three engineers in our prototype lab used the same
bottle for 15 years and we only used four ounces.  The amount needed for a
typical single printed circuit board is only a few cents worth.  [Buying a
pound of Cool-Amp and selling it in 5-gram packages would probably be a
very profitable business.]

          Dr. Barry L. Ornitz     ornitz@dpnet.net

From: "Barry L. Ornitz" <ornitz@dpnet.net>
Subject: Cool-Amp Powder, was: Re: chemical compounds to "tin" copper traces??
Date: 15 Dec 1998
Newsgroups: sci.electronics.design

Dave Harris wrote in message <36772fb4.192417541@news.videotron.ab.ca>...
>>Might I suggest silver plating instead.  There is an excellent product
>>called Cool-Amp that does this beautifully.  While expensive, a pound of
>>the product will last a lifetime.
>>
>Where can I get this, Barry?


Cool-Amp/Conductolube
15834 Upper Boones Ferry Road
Lake Oswego, OR  97035

503/624-6426, FAX 503/624-6436

Just another satisfied customer..., but WOW the price has gone up since I
bought a pound 15 years ago.  It's a good thing I still have about 12
ounces left!   :-)

                   Barry L. Ornitz     ornitz@dpnet.net