[sdiy] DIY PCBs

[Scott Bernardi]

Schematic printing on transparencies:
I use 3M transparencies that are made to withstand the heat of a laser
printer.
I use an old HP Laserjet 4L that I've had for years.  I use the manual
paper feed that passes the transparency directly through the printer
without bending it.
I've just been using whatever toner was available locally. Lately it's
been Xerox cartridges. These are whole cartridges including drum and
toner powder, not liquid toner.  You need a fairly fresh cartridge to
print schematics. I also take the cartridge out and shake it (to
redistribute the toner evenly) if the cartridge has been used a while.
I examine the transparency closely after printing. Sometimes it is
necessary to darken traces with a permanent marker. My layouts use 40mil
traces as the standard, which are pretty fat compared to a lot of
commercial boards.
I also don't use a super high intensity UV box that exposes a board in
90 seconds.  My exposure lamp is basically just a fluorescent light
fixture with a lamp that puts out a bit more UV than standard (I
purchased the fixture and lamp from http://www.web-tronics.com/). My
exposure times are typically 9-10 minutes.
Now that I've worked out the details, I have a very high success rate in
making acceptable boards.  My failures usually had to do with using
presensitised PCBs I bought in an auction that were probably pretty old.
There were areas of the board that just didn't develop and etch
correctly.
This doesn't count the obvious screwups I've done, like exposing with
the transparency backwards, or putting what should have been a double
sided board on a single sided PCB (fortunately that one didn't have too
many top traces and was salvageable by using wires).


Brockr0 at cs.com wrote:

> In a message dated 7/25/01 CHoaglin at aol.com writes:
>
>
>
>> Now I remember somebody mentioning quite some time ago some site
>> that had
>> plans for home made PCB etching gear that was pretty high
>> grade...anybody
>> recall what site that might have been (I have all the plastic tanks,
>> flow
>> switches, heating elements, liquid/temperature sensors, etc, etc I
>> need to
>> build a lot of this stuff just lying around, thanks to a lot of
>> scrounging
>> in
>> the bin behind a local medical dye laser manufacturer.)
>>
>> -Chris
>
> Perhaps http://www.thinktink.com/pcbfram.htm
> DIY pcbs including plated through holes and solder plating.
>
>
> Might as well ask a couple of questions since I'm posting...
>
> For those who have had success with printing to transparencies, what
> brands
> of  transparencies, printer, and toner are you using?
> I have tried many kinds of film and toner in a Raven laser printer and
> have
> never had any success. The toner is seldom opaque and if it is, the
> film is
> sufficiently distorted from the heat of the fuser that it can no
> longer be
> forced into flat contact with the board.
>
> I have also tried using translucent vellum but have never achieved
> adequate
> resist exposure, even with very long exposure times. Is there a trick
> to this?
>
> For people milling boards, what kind of tool life are you achieving?
> Milling
> seems like an attractive option to etching but small end mills are
> expensive
> and re-pointing them seems impossible in a home shop.
>
> Brock

--
Scott Bernardi
sbernardi at home.net