[Bob 256]

Maybe there is one of you out there who can help me with an issue not related to a Pentax product.

I do printed circuit work using photosensitized boards. These are copper clad boards with a thin photo-polymer coating which responds to light by polymerizing and retaining a pattern which protects copper beneath in a subsequent etching process which removed unprotected copper and produces the copper pattern for the finished product.

Previously, I've had a local service drop the pattern to an azo negative from a digital file for the master to expose the board (in a contact frame). About a year ago, this service went out of business so now I'm looking for someone who has that capability at a reasonable cost (typical cost was $15 for a 12" x12" azo). It has to be a fairly high resolution master (600 dpi or higher) and high contrast. Files are PSD.

Anyone know of a service like that who does mail-order work? I know they're hard to find because even high contrast film is disappearing from the market.

Thanks.

[UncleVanya]

Not the answer you wanted but here's some info you may or may not already have:

Making excellent printed circuit boards

In this he discusses the issues with losing access to negative film and local printing resources.

[Bob 256]

Thanks UncleVanya.

I still have a stock of litho film but no way to transfer digital files to it (no film writer). The shop that used to do it with azo film did a great job at 1000dpi and the azo was excellent media for this (high maxD and contrast) but I note that even azo products are disappearing not to mention equipment to write to them.

It's sad to see these hobbyist resources disappear as many younger folks have cut their teeth on such hobbies which have led them into technical careers. If we look 20 years ahead, it gives me wonder where we are going to find people with technical skills other than using a cell phone and texting. I understand technology marches on but the trend removes easy exposure to technical skills through hobbies and backyard experimenters out of the picture. Just my observations.

Anyway - anyone have a good resolution film writer - cheap and one that can do 5x7s?

[AstroDave]

Wacko idea(?)(!): use a laser printer to print on a transparent plastic sheet. We made overhead projector viewgraphs this way in the "olden days" (10-15 years ago).

Don't know if the resolution or contrast would be adequate. I have an old LaserJet II which still works and prints at 1200 dpi, and some of those old plastic sheets if you want to experiment. If you need a negative, you can just invert the image before printing (may use up toner in a hurry!).

Wanna try it? Just PM me. I could print a file you send me, or send you some of my plastic.

[Bob 256]

Thanks AstroDave. I've tried that but the results are disappointing. I actually got better results from an inkjet print on film than with a laser printer. The resolution is adequate, but laser transparencies tend to have a lot of pinholes and often aren't dense enough which leads to poor patterning on the photoresist. I probably was spoiled by the results I got with film since they usually provided excellent results with little effort. I appreciate your offer though. I'm contemplating building an x-y scanner which would print directly to the printed circuit board from a file - just haven't had the time yet. Would hope that there is still a shop out there which could print to film products litho or azo.

[AstroDave]

I'm contemplating building an x-y scanner which would print directly to the printed circuit board from a file - just haven't had the time yet.

Check out an HP7470 plotter? Not sure how good the pens would be for this (and they may be hard to find these days). IIRC, you'll need a vector graphics file to start with, and ultimately an HPGL (HP graphics language) file (which isn't all that hard to create - I've made them from scratch with a BASIC program).

[SSGGeezer]

I was thinking about the laser cutters that are small sized for sale at Bang Good that can be modded to cut patterns????

[Bob 256]

AstroDave: I think a good ink jet pattern would work better than a pen plotter. Around here, a pen plotter (and its pens) is about as hard to get as a box of Kodalith. All my patterns are in regular image formats and they would need to be changed to vector files - just not too practical if I can get them to film instead.

SSGGeezer: A bit harsh for etching the thin copper film on a printed circuit board. They actually have x-y router systems for that purpose, but they take forever to route a single board and require vector files to work. Ofttimes, I make multiple boards (the same), and a photo process is real quick at that. I did, however, look at the Bang Good laser engraver and it might work as a direct to board writer for the photoresist. It uses a blue laser and that could probably be pulsed on a pixel level to get what I want. Will explore that one further - and the price is right. Thanks for that tip!

I might just farm out my board making to one of the firms that does that - a few around. Would have to overcome the raster to vector graphics issue in that case.

Thanks anyways folks for all the suggestions.

[SSGGeezer]

Both happy and slightly surprised that my suggestion may have some value! I was just tossing out a SWAG there!

[Bob 256]

Both happy and slightly surprised that my suggestion may have some value! I was just tossing out a SWAG there!

You never know where those SWAGs are going to take someone. I was going to build a contraption very similar to what your site offers - Arduino control on the steppers and also using the micro-controller to read a bitmap file from an SD card for controlling laser firing to blast the photoresist directly (might have to tame a 1 Watt + laser). Some technical issues with the arrangement in terms of spot size and power that have to be worked out. Having a fully assembled unit would save some time so will look into it for sure.

Boards are always available and I can coat them myself if needed so those materials won't be extinct for a while.

Thanks again SSGGeezer.