Homebrew PCBs

I went down a similar track a few years ago Robin, as I had a stock of 
Riston pre-coated board inherited from a closed major electronics 
workshop. The problem I struck was that the box of 3M reversing film 
that I had bought some 20+ years earlier had "gone-off" and would no 
longer function. I was unable to locate a source of the film, as by then 
3M had ceased production.

I guess I might have been able to overcome the absence of a negative by 
using one of the PC packages that can produce a negative print from 
positive artwork but I ran out of time to experiment along those lines. 
At that point I switched over to Kinsten positive board, which you will 
see is also stocked by Kalex in Melbourne.

Sorry I cant be of help with your specific questions but I have read 
reports that one of the Chinese eBay sources you mention has a reliable 
product in his negative film. I don't have the source on this machine 
but I can probably find it and post later.

Bill
On 18/05/2012 3:54 AM, Boman33 wrote:
> Thanks for a detailed post with good information.
>
> A quick question:  Why not also consider positive resist?
>
> =============================
>
> From:  Robin Whittle  Sent: Thursday, May 17, 2012 11:12
> I am a newbie to this list and am keen to set up for using Riston
> (negative) photoresist for making small quantities of relatively small
> PCBs. I used it in mid-1980s but then I had a process camera and could
> make really good phototools.
>
> The developer and stripper chemicals are cheap and easy - sodium
> carbonate (washing soda) and caustic soda respectively.
>
> My initial tests with a novel exposure technique are encouraging - I
> will describe this in another message.
>
> It is possible to buy Riston coated single-sided 1.6mm FR4 PCB material
> in Australia: (Asterisks added to force indents in the Yahoo Groups
> archives, which gobble leading spaces.)
>
> * http://www.jaycar.com.au/productView.asp?ID=HG9970
>
> but it is expensive: $24.95 for 152 x 152mm (6 inches square). This is
> what I used for tests. According to the instructions in the pack, this
> material comes from http://www.rcsradio.com.au, a business established
> in 1943 but which has ceased trading since the proprietor Bob Barnes died:
>
> * http://www.thebackshed.com/forum/forum_posts.asp?TID=3574
>
> so it would not be surprising if Jaycar discontinued this.
>
> Kalex in Melbourne: http://www.kalex.net.au advertise 1.6mm single-sided
> Riston-coated PCB material in their pricelist. I called them and was
> told that this is only for large quantity - they don't keep any in stock.
>
> I couldn't find any other sources of FR4 already coated with Riston, so
> this lead me to buying the Riston film itself, and looking at techniques
> for laminating it to the PCB material. This will allow me to choose
> 1.6mm and 0.8mm material with normal (1 ounce) copper or thinner (0.5
> oz) copper. I understand the finer tracks can be achieved with the
> thinner copper because the etch time is reduced, leaving less time to
> undercut the photoresist, and I guess with the copper being thinner and
> less accessible to the etchant. If I get adventurous I may even try
> double-sided PCBs.
>
> This is for prototyping - and for the satisfaction of making things at home.
>
> The Riston information is at:
>
> *
> http://www2.dupont.com/Imaging_Materials/en_US/tech_info/product_selector.ht
> ml
>
> I found 3 sources of Riston film. I also found some Chinese sources of
> generally un-named dry negative photoresist film. The last one mentions
> it is Hitachi photoresist:
>
> * http://stores.ebay.com/Led-Light-Bulb-World/_i.html?_nkw=photoresist
> * http://stores.ebay.com/Digole-Digital-Solution/_i.html?_nkw=photoresist
> * http://stores.ebay.com/oneworldonedream2010/_i.html?_nkw=photoresist
> * www.ebay.com/sch/dr_ho_000/m.html
>
> The first Riston source is Think and Tinker in the USA. They sell rolls
> of "M115", which I assume means Riston MM115 or MM115i. This is 50
> microns thick. However, I don't need such large quantities.
>
> http://www.thinktink.com/products/Photopolymers.asp
>
> The second source is in Sweden. They sell sheets of Riston FX515 which
> is 15 microns thick.
>
> * http://www.ebay.com/sch/karass/m.html
>
> The third source is in the Czech Republic. They sell A5 sheets of
> Riston MM540. This is 38 micron. I ordered some sheets today.
>
> * http://www.ebay.com/sch/gaminn/m.html
>
> Can anyone comment on the merits of Riston or alternative brands of
> negative photoresist, or on the three thicknesses: 15um, 38um and 50um?
>
> - Robin Melbourne Australia http://www.firstpr.com.au/rwi/dfish/
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
>
> ------------------------------------
>
> 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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