Russ: To add a little more to the early history of soldermask.
Early electronics such as PCA's were encapsulated to protect them from the
environment, vibration, abrasion, etc. Epoxies proving to be the best at the
time for the application. The Navy was one of the forerunners in this due to
the severe conditions electronics were exposed to on ships in salt water.
The potted assemblies worked but the problem was they were nearly impossible
to repair. In the late forties early fifties they then began applying the
epoxy as a surface coating instead of potting the entire unit. This provided
repairability along with most of the advantages of potting. It was actually
more of a conformal coating than soldermask as we know it today. This in
combination with a need to reduce weight(minimize solder pickup on circuits)
for avionics then evolved into the more common mask applied to the bare
board. Hence the use of epoxy coating on circuit boards as soldermask.
Michael Barmuta
Staff Engineer
Fluke Corp.
Everett WA
425-446-6076
-----Original Message-----
From: Smith, Russell (US LA) [mailto:[log in to unmask]]
Sent: Monday, April 07, 2003 1:08 PM
To: [log in to unmask]
Subject: Re: [TN] New Topic: Why are most solder mask requirements,for
GREENmask???
I just wanted to add the story I heard ; hope you all don't mind
Many years ago I asked the same question , why is solder mask green? I
finally got what I consider an answer the closest to the actual reason. TO
wit: in the beginning before solder mask , there was nothing and since the
geometries were very large , it was not needed, but as the scale began to
decrease and transistors replaced tubes something to stop solder from
shorting out the traces was needed, hence solder mask. The earliest
references I could find dealt with various shellacs, waxes, and varnishes.
Then what was the first solder mask appeared, it's exact origins are
somewhat clouded in mystery, but I was told it begins with the old
Kollmorgen company, Any way the original mask was a green. The base resin
itself had a brownish yellow color and the hardener was very muddy brown.
When mixed the material was a honey brown to darker color. If you try and
color brown, red becomes rusty adobe colored, blue becomes dark. Since a lot
of the laminate at the time was actually a green color, the natural choice
of color was to add a little more yellow and some blue to make green, and
thus the standard color became green. Then as the industry grew, everyone
made green, because they always did. Soon everyone got used to it , and it
was the norm. Even the consumer expected to see green solder mask.)
As for Clear, it never really took off for two reasons: you can't
inspect for mask on pads, before you cure and put on the final finish.(
remember before about 1988 almost all of the mask applied was screened with
a pattern and thermally cured), and second you can't hide any discoloration
of the copper , or laminate!.
On the Blue for halogen free. If you have a company that says they
can give you a blue halogen free. I want to say like that's a no brainer,
one of largest sources of halogen in solder mask is the yellow pigment!
(just in case you wanted to know) They can make green but it is more of a
challenge.
-----Original Message-----
From: Kathy Kuhlow [mailto:[log in to unmask]]
Sent: Monday, April 07, 2003 12:12 PM
To: [log in to unmask]
Subject: Re: [TN] New Topic: Why are most solder mask requirements,for
GREENmask???
We currently have customers with green, bright red, and sky blue. The
legibility of the silkscreen is not hard with any of the colors. It is nice
to quickly look for an off color in manufacturing. I also worked for a
company who used red for prototype boards and then switched to green for
production builds.
Kat
---------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
ext.5315
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
ext.5315
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------
|
