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

Hi,

it's been years since I made my first circuit boards the old fashioned way, carefully tracing over the artwork with a sheet of carbon paper underneath onto the bare copper board and retracing again over the pattern left from the carbon paper using an etch resist pen and then using a #11 xacto to gently scribe any excess ink from the edges of the traces, touch up with pen, scribe, etc. until perect and then etch.

ok that was 30 years ago and I want to make some new boards now so looking at products ranging from DIY hobby to industrial production, youtube videos and websites I am in a better position to understand the processes now. basically from what I gather the first step is the one with the most variation, applying the etch resist to the board. etching is still pretty much the same all around.

there are 2 ways to go, either positive or negative photoresist,

the former seems more straight forward considering the artwork is unchanged, but the chemicals to apply positive resist are expensive and not as readily available I am discovering.

There is a discontinued positive resist spray that was made by MG Chemical, and various liquid positive like Kodak KPR, and POSITIV 20 photoresist lacquer spray available by mail order from UK distributors. These all need to be applied in dark room conditions and fully cured before developing, possibly with heat from an oven.
the nice thing I think is that no laminating machine is needed, since looking into that I find that "hot roller" is the way to go and that can get expensive.


next is the dry film negative that must be applied with a laminator, I see many videos showing DIYers running boards through the laminators several times in an attempt to compensate for low or uneven heat, something a more expensive 4 Hot Roller laminator (Tamerica / Tashin TCC6000) would be needed for even light production.

when comparing the 2 methods it's possible to see pros and cons in both, positive must have a dedicated darkroom to work and negative is an investment into equpiment, namely a reasonable quality laminator that new might run over $400

both need uv exposure but the latter need less power so maybe the cost is offset somewhat not having to absolutly have UV.

then it comes to what brand of dry negative resist?

there are several including:

MG Chemical

Dupont Riston

Kolon

eBay nameless brands, etc.

and then there are different types, thichnesses intended for different processes, electroplating, sandblasting, etc.

I'm skipping the part where the transparency is made, guessing that would be fine just bringing the pcb file to Kinko's or an Office Box store on a flash drive, or buying at least a 600dpi, maybe even 1200dpi laser black and white printer, ok for cad art, a scanner also for magazine or other art. either pos or neg transparency for either spray on/chemical or dry film, that I get.

so my questions then are,

anyone with any experience either with the positive resist chemicals and/or the various brands of negative dry resist films?

I'm looking for information beyond manufacturers claims and DIY videos or websites to help in comparison of these 2 photoresist methods and the various processes and products required.

Many thanks and happy holidays to all,

Robert