Thanks for all the input!
So then avoid KPR even though it works well, is that because it's toxic? explosive? staining? if it works then maybe using proper precautions, but then on the other hand if there are safer alternatives that work as well (or better?) then of course that would be the logical preference.
I see that some commercial equipment use dispensing pumps and "spinners" to apply the stuff, I've been a painter by trade most of my adult years so I have plenty of airbrushes, small detail guns and a supply of clean dry air I could use, possibly, for even distribution of material...
actually on that note I should mention that I have an account with Paasche, they make a lot of custom spray heads for use in automation, I can get them at cost, about 40-60% off, if anyone wants.
wishing it were so with MEGA Electronics, as they have the nicest UV units I've seen (in pictures) so far. perhaps modeling a homeaid unit something like their products would be the best alternative to buying outright.
Mega has everything for producing quality boards, through hole rivit kits, pcb drills and routers, a lot of ancillary items that are very specialized, and very expensive...
http://www.megauk.com/http://www.megauk.com/uv_exposure_units.phphttp://www.megauk.com/pcb_drilling_machines.phphttp://www.megauk.com/through_hole_rivets.phpthere seems a certain "drool" factor in considering their products, but alas I fear they are all far to expensive for mua!
one item I do think is very reasonable however is a small drill press from Micro-Mark, it appears to be a spot on copy of the German proxxon at about $100 less cost, and comes in "cleanroom" white.
http://www.micromark.com/MicroLux-3-Speed-Mini-Drill-Press,7797.htmlI'm interested in the possible use of a photoplotter for making the positive or negative transparency plate also,
not really too familiar with them and trying to understand the benifit, I have some idea now, thanks!
still, I was looking at some used equipment like that on ebay but determined that it was too bulky, expensive, (and maybe even possibly could become somewhat antiquated as things tend to go, new technolgy and what all coming around so fast these days), it just seems easier to have just a decent printer to check the actual size of the board for parts fit, errors missed on screen (computer), etc. and bringing a flash drive somewhere (where they might have a photoplotter?) to have a transparency made. I saw a video where someone taped 2 identical overlapping transparencies together and thought sure that will work but there is a chance to distort if not perfectly aligned and so such methods can introduce greater possibility for error, but novel in it's simplicity and using far less expensive equipment.
As a painter I used to use a lot of leaded enamels (glad that's passed), lacquer and acrylic urethanes (Dupont Chromabase), and working at a factory that produced surfboards I worked with polyester resins, epoxys, acetone, etc. and much later ended it all with a move completly to waterbased material or I wouldn't take the job.
for hobby in small quantity or even very light limited production though I can't see a big problem with chemicals, though again I would prefer any safer alternatives, so I'm interested in the elmers glue resist mentioned also!
I'd like to try both methods for myself anyway but want to hear any thoughts or suggestions in any case, I might have better luck succeeding that way I reckon maybe...
Thanks again!
Very Kind regards,
Robert
--- In Homebrew_PCBs@yahoogroups.com, "Jeff Heiss" <jeff.heiss@...> wrote:
>
> I have been researching and have found that making your own resist looks
> possible. The ingredients are polyvinyl alcohol (PVA) and ammonium
> dichromate. An alternative is Elmers glue and ammonium dichromate. Baxter,
> a member on here was performing experiments in this area. Maybe he can
> chime in if he is reading?
>
>
>
> Jeff
>
>
>
> _____
>
> From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
> On Behalf Of Harvey White
> Sent: Monday, December 26, 2011 8:00 PM
> To: Homebrew_PCBs@yahoogroups.com
> Subject: Re: [Homebrew_PCBs] Photoresist
>
>
>
>
>
> On Mon, 26 Dec 2011 20:32:02 -0000, you wrote:
>
> >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.
>
> I never got that to work.
> >
> >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.
> >
>
> DIY is one thing, professional gets nasty.
>
> >there are 2 ways to go, either positive or negative photoresist,
>
> also toner transfer, which can be surprisingly decent.
> >
> >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.
> >
>
> Take your word, presensitized boards are expensive, say 6 to 8 USD for
> a 4 x 6 board.
>
> >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.
> >
>
> Avoid KPR like the plague. Works really well, but nasty chemicals,
> really.....
>
> Problem with these is that unless you manage to get the coating even,
> the exposure can vary a bit.
>
> >
> >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.
>
> I hear good results if you are careful.
>
> >
> >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
>
> negative may need that same darkroom. However, a bathroom with some
> towels across the door bottom can be just fine. I wouldn't worry
> about the cost of the darkroom that much.
>
> >
> >both need uv exposure but the latter need less power so maybe the cost is
> offset somewhat not having to absolutly have UV.
>
> Generally, three or four Blacklight tubes will do well enough, unless
> you use something that needs shortwave UV (which gets nasty, really).
>
> Longwave is not all that bad, tubes are easy enough. The MG chemicals
> uses pretty much 6500 degrees K daylight fluorescents. Slightly
> difficult to find, but not expensive.
>
> >
> >then it comes to what brand of dry negative resist?
>
> no ideas here.
>
> >
> >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.
>
> Not really, the more opaque the negative, the better you get.
> Sometimes you need red ink from an inkjet, laser may not be
> sufficient. Some experimentation is needed. Not opaque enough, you
> start to expose the wrong regions.
>
> Ideal would be a photolith film, which is pretty much opaque black and
> transparent. Sadly, Kodak Photolith is not made (IIRC) and it still
> requires a good photoplotter (ideally), otherwise it's negative on
> transparency.
>
> >
> >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?
>
> Only the MG boards and KPR.
>
> >
> >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,
>
> And to you.
>
> Harvey
>
> >
> >Robert
> >
> >
> >
> >
> >
> >------------------------------------
> >
> >Be sure to visit the group home and check for new Links, Files, and Photos:
> >http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
> >
> >
> >
>
>
>
>
>
> [Non-text portions of this message have been removed]
>