MPX-16 census

[Jeff Walther]

>Date: Wed, 12 Oct 2005 15:25:03 +0000
>From: Gordon JC Pearce <gordonjcp at gjcp.net>
>Subject: Re: MPX-16 census

>der Mouse wrote:
>>>I've never heard of anybody making more than double-sided PCBs at
>>>home (I would love to be proved wrong!).
>>
>>
>>  I can't *prove* you wrong.  But I've spoken with someone who claimed to
>>  have done it, and when I started asking questions, talked a good enough
>>  line that I found it believable.  As she described it, you need
>>  epoxy/fibreglass mix, which you cast a thin sheet of.  You then sand it
>>  smooth, copper-plate it, and etch.  Slap on another coat of epoxy and
>>  fibreglass, let it cure, sand it smooth, copper-plate, and etch.
>>  Lather, rinse, repeat.
>>
>>  The hard part is of course quality control (and plated-through vias,
>>  which you can get somewhere with by drilling holes before doing the
>>  last copper-plating).  And registration of the layers.  But with
>>  patience and attention to detail...after all, anyone doing this is
>>  considering time to be worth a great deal less than money, or the job
>>  would simply be shipped off to a commercial pcb fab house. :)
>
>It's the sort of thing I can see our Mr Duell doing though.

This is a topic that interests me.  The most useful sounding site 
I've found so far is this one 
<http://www.thinktink.com/stack/volumes/volvi/pcbproto.htm>

IIRC, they recommend drilling your boards before etching so that you 
can use the hole locations to help with your layer registration. 
They also have an interesting ink and electroplating system to create 
plated-through vias.

(As an aside, I found another site one time where a fellow had 
replaced the pen in a plotter with a drill and was using it to drill 
boards with an Apple II(?) driving the thing. 
<http://rich12345.tripod.com/PCB/>  It would be an interesting 
project if one could make it interpret Excellon drill files.)

However, the information on greater than 2 layer boards is thin. 
They seem to imply that you can etch seperate thinner boards and then 
laminate them together, but there's no detail on what kind of board 
would work for this.  There's an obscure reference to not fully cured 
fiberglass or some such.

The implication is that, e.g. one could make a total .062" thick 
board with four layers out of three boards laminated 
together--perhaps three .020" boards.  The two outer boards would be 
double sided circuit boards and the center would be a separator with 
plated-through vias and "doughnuts" at the plated-through holes to 
make contact from one board to the next.

I'm curious about what one would need in terms of board or additives 
to laminate multi-layer boards together.   A standard fully cured 
board isn't going to stick, I don't think.

Building multi-layer boards out of raw fiberglass/epoxy mix and 
copper plating it oneself does not sound like a viable home project. 
At least, not for me.

Jeff Walther