Homebrew PCBs

At 12:46 PM 12/22/2011, Steve wrote:
>This homebrew PCB holder
><http://www.qrpbuilder.com/downloads/pcb_holder_you_can_build.pdf> was
>referenced on another email reflector. It is constructed mostly of
>polyethylene and nylon.

I personally would not build it from the plastic materials that you 
mention.  However, unfinished wood is a reasonable choice so long as 
you keep your humidity levels at 30% or higher.  Adding any coating 
to the wood is a bad idea because that coating is liable to 
accumulate high levels of static charge.

Someone else suggested just ignoring the possible effects of ESD 
damage.  My experience is that is a bad suggestion.  You don't need 
to be anal about ESD protection but keeping materials that can hold 
extremely high levels of static charge far away from your sensitive 
parts just makes sense.

We keep a couple of ESD field-strength meters in our shop for testing 
new materials coming into our premises.  It is absolutely astonishing 
just how much static field some materials can absorb and hold - I've 
seen readings as high as 75KV on some materials.


The PCB holder design in the above PDF file is simple and 
basic.  However, I would find it difficult to use because the board 
is parallel with the bench surface.  I have a couple of Panavise PCB 
holders that I use all the time - two long arms with a V-groove on 
each arm (facing each other).  The arms are spaced apart by the width 
of the PC board.

The great advantage of the Panavise setup is that the arm assembly 
can be rotated both left and right as well as tilted up and 
down.  That makes it easy to get the surface of the PCB in the best 
orientation for soldering or whatever.  I find that I usually have 
the board sitting at somewhere between 30 to 60 degrees from 
vertical, depending on exactly what I'm doing at that point in time.

You could make your own version: use 3/4" wood dowel for the 
arms.  Use a router table to route a V-groove down the length of each 
arm, then drill a 3/8" hole crosswise on each arm right near the end 
of the dowel.  Drill and tap a 10-32 screw hole into the end of the 
arm for a locking screw.  Use 3/8" dowel rod to hold the arms.  You 
could route a flat surface on one side of the 3/8" dowel rod if you 
want to stop the 3/4" dowels from rotating (the flat surface gives a 
good place for the 10-32 screw to register against.

dwayne

-- 
Dwayne Reid   <dwayner@...>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax
www.trinity-electronics.com
Custom Electronics Design and Manufacturing