Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

Brian and the group,

I spent over twenty years in the circuit board business and probably
tried every method that came along. The most difficult part for the
hobby board producer seems to be good artwork generation and etching.
With this in mind you might want to spend some of your money on a
used process camera for making negatives.

Most circuit board films are now made with photoplotters and this has
put many of these cameras on the used equipment market not to mention
the ones that were thrown in the dump. If you print your designs with
a laser or inkjet printer at 2:1 scale and photograph it at 50% on
the camera a very accurate film negative can be produced. A film made
this way will not have the print density problems that arise when
trying to expose through paper artwork from printers and plotters.

Dry film photoresist is one of the best ways to sensitize the copper
panel. This film is put on the panel with a roll laminator but I have
had excellent results by gently laying it on the clean copper surface
and using a clothes iron to heat the resist for proper adhesion to
the copper. A small glass contact printing frame can be purchased at
most camera or photographic supply stores. This contact frame will
give the proper contact between the negative film and the photo
resist. A sunlamp works good as a UV exposure source.

Developing of the exposed resist can be performed in a small tray of
1% sodium carbonate (soda ash). I have also used Tide laundry soap as
a developer but it seems to take a bit longer.

Ferric chloride is a good etchant for hobby boards. It will last for
a long time and can be used in a tray, bubble, or spray etcher.
Other etchants are available but many of them have a limited tank
life. Ferric chloride does not have this problem and is stable for a
long time, just heat it up and start etching.

A small high speed drill press with carbide bits will do a good job
for making the holes. KBC Toools sells a small drill press like this
for less than $150. I have one of these and I like it much better
than any of the Dremel drills. The Dremel Tool drills have way too
much spindle runout and their drill press stand is very flimsy.

I only make circuit boards for the instruments that I produce and no
longer make boards as a merchant shop. When I got out of the
commercial business I kept just enough equipment to perform the
processes discussed in this message.

The following equipment is what I'm using for my board production:

CAD system
Photoplotter
Vertical camera
Template (stylus) drills
Pin router
Small spray etcher
Various silk screening equipment

Some of this equipment can be built in the home shop or picked up at
auctions or on eBay.

Concerning photoplotters, I saw a table top photoplotter just like
the one I use on eBay. This was about a year ago and it never got one
bid! This unit could have been picked up for less than $500 and it
would have been a bargain. This type of plotter makes the whole
process very easy so it would be a wise move to latch onto one of
these units.

If anyone is interested, I would be willing to make photo plots for a
nominal price. The plot data would have to be supplied as a Gerber
plot file with aperture list or file. The films would be made on
Kodak 7 Mil film with a negative or positive image. Email me off list
if there is any interest in this.

Tom