PCB developing

[Mike]

I came across a PCB called a Pre-Sensitized Positive Acting Printed Circuit Board. After reading the instructions, it says to print your design on a transparency, then put a sheet of glass over the board and expose to light. It then says to develop and etch the board. Could anybody explain to me how to do this starting from a copy of the PCB layout on paper? Also, where do I get the developer solution? <p>Thanks, Mike

[russlk]

Injectorall supplies the boards, chemicals and equipment: http:://www.injectorall.com
Take the paper layout to a copy shop and have it copied onto a transparent film. Tell them to make it dark, otherwise your PC board may look like lace. The developer is a common chemical, but I don't know where to get it other than Injectorall. Radio shack sells the etchant.

[Mike]

Russ, transparency film as in an overhead projector sheet, right? Or special film?<p>-Mike

[russlk]

Right!

[toejam]

if you want to try it. you will have to make a pc layout. I have done this using paper with .1 grid.i used etch rub off transfers from radio shack to make the pinouts for ic's and connected them with a pencel.I than transfered this to a sheet of acrylic using a photocopy machine.
Now for the fun part you will first expose the pc board to a light source I used a tanning lamp the best way to determine exposure time is to cut a long piece of the board and make a test strip by holding a piece of cardboard on top of it and moving it down a quarter inch every 30 seconds you can also use sunlight but the exposure increments will have to be longer this will get you to the neccessary exposure time.Once you know the exposure time by developing the test strip, cover the plate with the acrylic sheet expose and develope.

[bruinbear714]

There are two types of pre-sensitized pcbs, positive and negative. The positive pre-sensitized pcb is just what it says - what you see on the transparency is what you are going to get on your pcb after it is developed. The negative works vice-versa.<p>Now, with that said, you can print out your pcb on a regular transparency using a laser printer that's capable of printing on transparency. Set it to darkest setting to eliminate any possible minute holes.<p>Expose it to UV light for about a minute (or 2) and then drop it in the developer tank. The developer strips the exposed area of the photo-resist, leaving the traces protected. Then drop it in the etching tank and wait for it to be etched.<p>You can buy the pre-sensitized pcb, developer, and etchant everywhere, including radio shack. The hardest part will be obtaining a good UV source and figuring out how long to expose the board. Exposure times can range from less than a minute using a professional unit to over a few minutes using a DIY unit.

[k7elp60]

I have a good luck printing transparency film on my injet printer. I got my recent positive developer from parts express, and I see in the latest catalogue from [url=http://www.CircuitSpecialists.com,]www.CircuitSpecialists.com,[/url] that they have the positive developer. The recent positve pre-sensitized circuit boards that I got were by DATAK and only required a 100 W bulb about 6 inches above the board to expose them. I recently did a 4"X 6" with the technique.
Ned