Homebrew PCBs

Hi Robin, I use Kinsten precoated board from Kalex and find it excellent, 
the difference being it is positive acting resist!. Look in the Kalex 
catalogue for the sizes and prices. I use 7 grams of caustic soda to 1 litre 
of warm water to dissolve the caustic as a developer and acrylic thinners to 
clean it off after exposure. Exposure is with 4 15w black lights for approx 
80 seconds. They also have polyester translucent sheets which I use to print 
the pattern with a laser printer and contact expose directly on to the 
sensitisized board sandwiched between 2 pieces of 0.25" glass and the lamps 
are about 3" above the glass. I have never had a failure yet after a couple 
of tries initially to get the settings right.
My 2 cents worth. Been there and done that and now would not even give 
Riston a second look!

Don VK3YV  ......
----- Original Message ----- 
From: "Robin Whittle" <rw@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Friday, May 18, 2012 1:12 AM
Subject: [Homebrew_PCBs] Riston precoated FR4 in Australia, Riston sheets 
and rolls


>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.html
>
> 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/
>
>
>
>
>
>
> ------------------------------------
>
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> Photos:
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>
>
>
>