Newsgroups: sci.electronics
Path: cantaloupe.srv.cs.cmu.edu!magnesium.club.cc.cmu.edu!news.sei.cmu.edu!cis.ohio-state.edu!zaphod.mps.ohio-state.edu!saimiri.primate.wisc.edu!ames!olivea!sgigate!sgiblab!munnari.oz.au!metro!dmssyd.syd.dms.CSIRO.AU!megadata!swanee
From: swanee@megadata.mega.oz.au (Geoff Swan)
Subject: Re: Why circuit boards are green?
Message-ID: <1993Apr27.051830.14545@mega.com.au>
Sender: news@mega.com.au
Organization: Megadata P/L, North Ryde, Sydney, Aust.
References: <1993Apr23.105152.20155@news.cs.tut.fi> <1993Apr23.102039.1720@mala.bc.ca>
Date: Tue, 27 Apr 1993 05:18:30 GMT
Lines: 35

In article <1993Apr23.102039.1720@mala.bc.ca>, wagner@mala.bc.ca (TOM WAGNER, Wizzard of old Audio/Visual Equipment........Nanaimo Campus) writes:
> 
> The color of the board shows the composition of it, hence the use of it.
> 
> Original and older boards were bakelite composition, and were brown.
> Phenolic (spelling) was a tan
> Most "non filled" fiberglass boards used in computers are green.
> Filled fiberglass is blue.
> Teflon is white.
> 

Rubbish. The reason for the colour of the boards depends on the solder
mask that is used. Older boards (bakelite and phenolic) rarely used
a solder mask (these boards are not suited well to automatic stuffing
and soldering techniques) and hence are the colour of the compound
used to make them. These days boards are made of fibreglass for most
general purpose uses and have a solder mask applied to them to prevent
close traces shorting to one another during soldering (and also to prevent
the decomposition of traces under harsh environments). The light and dark
green boards ofter seen have a "dry film" mask applied to them (usually
applied as a complete film photographically produced). The blue (and red
or orange) boards are a two-part epoxy or a liquid-imageable resist
formulation and are applied in a different manner. There's a lot of info
about the pro's and con's of each, but that's another story...

    Sla/n go fo/ill,
                    Risky B.
--------------------------------------------------------------------------
Geoff Swan (research & development)   _--_|\         swanee@mega.com.au
Megadata Pty Ltd                     /      \ 
2/37 Waterloo Rd, North Ryde,        \_.--._/               +61 2 805 0899
NSW 2113, Australia.                       v          (Fax) +61 2 887 4847



