Re: Homemade PCBs!

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Mitchell" <Electrontube-at-sbcglobal-dot-net> 

There can be more then two sides!  Its just that the middle layer(s) is/are
just connections and do not house any components.

Regards - Jim Mitchell
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Wednesday, April 28, 2004 7:13 PM
Subject: Re: Homemade PCBs!


 > Original poster: Fucian-at-aol-dot-com
 >
 > In a message dated 4/28/2004 10:15:26 AM Eastern Standard Time,
 > tesla-at-pupman-dot-com writes:
 > Layers are exactly what the name says, 'layers'. Sort of a 'paper sheet'
 > which contains something. The PCB is then stacked/sandwiched together from
 > these layers.
 >
 > A typical single sided pre-UV-resist-coated DIY PCB:
 > 1 photoresist layer
 > 2 copper layer
 > 3 glue layer
 > 4 epox&fiberglass lamination layer (the "circuit board")
 >
 > If you order commercially produced single sided PCBs, typical order of
 > layers might be:
 > 1 silk screen (component names and other text printed on the PCB)
 > 2 solder mask layer (the often deepgreen protective coating you see on
 >     PCBs, it helps against corrosion and prevents solder flowing onto
 >     copper tracks where you don't want it)
 > 3 copper layer (this is where the signal traces are)
 > 4 glue
 > 5 epoxy&fiberglass board
 >
 > Then there are a bunch of additional "non-physical" or "info" layers that
 > are defined in the software PCB file. For example, where the automatic
 > drill should be drilling, to what dimensions the board should be cut, etc.
 >
 > You could have a try on Eagle (www.cadsoft.de) and wonder at how many
 > layers the PCB board editor contains  ;-)
 >
 > If you meant what the use of multiple copper layers is -
 > oversimplified, they reduce the number of jumper wires you need. If you
 > look inside cheap TV, video or stereo sets, there's LOTS of jumper wires
 > there, a real mess. Nearly all those jumpers could be replaced with copper
 > traces on a new, added second copper layer. Much cleaner result and less
 > work, but it costs a bit more.
 >
 > OTOH if you look at your PC motherboard, there are thousands of component
 > pins that should be connected together. A single copper layer
 > obviously isn't enough, and jumper wires are a really bad idea.
 > Additionally taking into account RF layout requirements (>100MHz to
 >  >10GHz signals there, needs ground and DC supply planes), you end up with
 > at least a 4-layer board. I don't know exactly where PC computer boards
 > are going nowadays, but I'd think they typically use from 8 up to 16
 > layers.
 >
 > To keep this even remotely TC related: if you build SSTC or flyback
 > boards, it is a good design practice (IMHO) to use two layers. For
 > example, one larger combined ground and power plane on the bottom layer,
 > and logic and RF signals on the top layer. That way the circuit is, for
 > one, much less susceptible to HV RF interference (e.g. more bullet-proof).
 >
 > cheers,
 >    - Jan
 >
 > --
 > ****************************************************
 >    Helsinki University of Technology
 >    Dept. of Electrical and Communications Engineering
 >    http://www.hut.fi/~jwagner/ -
 >
 > Ahhhh it is clear now! :-) I was thinking layers were copper layers...I
was
 > thinking, " how could there be more than 2 sides to a pcb?"
 >
 > I didnt know layers were just like a part of the design...
 > Matt
 >