Interesting...
I can recall reading something about Dupont having been reported as lobbying to ban hemp (not forming any opinions here, just saying I read this) farming in the US during the 30s just as they had patented then new wood pulp processing chemicals. we pretty much have all nylon or cotton rope now, I don't know the specifics or if there may be any similarity to the banning of resist chemical (in favor of Riston dry film resists by Dupont), it might be stretching beyond I mean, but then there are circumstances I am sure not at all uncommon where a company has many pronged efforts to secure it's place, beyond just making a really good product.
Irony, if any, here is that Riston isn't too easy to be found, I remember about a month ago seeing some from a seller in Australia but that's it, no online catalog distribution, nothing but data sheets from Dupont. A lot of this probably has to do with the shift in electronics manufacturing to Asia, India, etc., at least that's my guess why there seem to be more products advertized online from over yonder way.
Who knows, really?
from what I read in the last hour or so online wiki and others that positive resist is not as good at either adhearing to the substrate (pcb) or developing later, and cost, a really big factor when all is said and done, by comparison of modern available chemicals and dry films, so that might be why there aren't so many positive resist options too. Still though one would think there would be more dry laminate offerings online then? again, I have found some, but to order them the shipping cost is high and the $ is denominated in Rupies or something that wouldn't work with my info, guess they don't have paypal in parts of Asia and India either.
Not complaining about this at all, just making some observations.
Robert
--- In Homebrew_PCBs@yahoogroups.com, Roland Harriston <rolohar@...> wrote:
>
> Kodak KPR and similar materials:
>
> If I recall correctly, the main problem with Kodak KPR and similar
> compounds was that the EPA (or an equivalent federal agency) did not
> like it.
>
> I used KPR both at work and at home for many years without a single
> incident. The feds claimed that it was an air polluter and banned it.
> Dyna-Chem and others made similar compounds, and everyone had to stop
> manufacturing it.
>
> I used to purchase the Dyna-Chem material in an aerosol spray can. This
> really drove the feds up the wall.
>
> The feds did the same with Freon, although Freon is still available and
> used outside of the States.
> But I believe the Freon ban was more political than environmental.
>
> At work we would either spin coat KPR (small boards) or dip coat it for
> large, or double sided work.
>
> We had the complete Kepro PC fab lab setup with a dip coater, IR drying
> box, UV exposure box, and heated spray etcher,
> and a shear for cutting .
>
> Some artwork was on lithographic film, and some made on Rubylith cut
> and peel
> material on a coordinatograph-type apparatus. The Rubylith jobs were
> mostly stripline RF circuits.
>
> These techniques are obsolete nowadays.
>
> Everything worked fine......never any problems.
>
> Roland F. Harriston, P.D.
> ∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗
>
>
> Robert wrote:
> >
> >
> > 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.
> >
>
>
>
>
> [Non-text portions of this message have been removed]
>