Homebrew PCBs

I found this link to a database of most commonly used photoresist:

http://www.smartfabgroup.com/photoresists.php


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
> >
> >
> >
> 
> 
> 
> 
> 
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>