Homebrew PCBs

Steve

Have you thought about starting a dbase list. It would be good to 
have Toms offer where it was easily found.

Garry


--- In Homebrew_PCBs@yahoogroups.com, "twb8899" <twb8899@y...> wrote:
> 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