kicad-developers team mailing list archive

[Vesa Solonen <vsolonen@xxxxxxxxx>]

On Tue, 31 Aug 2010, Lorenzo Marcantonio wrote:

> On Tue, 31 Aug 2010, Vesa Solonen wrote:

> > digital age and also replacing SCRs with synthetic mosfet ones to cut 300W 
> > from the losses. Fortunately I got my sanity back a few minutes later :)
>
> Strange, at that those current usually losses from SCR are minimal
> compared to the RDSon (unless you use IGBTs, of course).

It's 200A 8V design :D so 1.5V SCR on state drop _is_ significant. 
Something to consider for low voltage high current switching: 
http://www.irf.com/product-info/datasheets/data/irf1324s-7ppbf.pdf

Those are way better even one has to use two back to back and some in 
parallel for 200A. I'd bet the combination is also cheaper than a 250A 
SCR.

> the trick usually is the vacuum adesion of the photofilm to the focal
> plane.

Yes, someone doing demanding work would easily afford a small vacuum 
system, be it an aspirator or compressor from an old fridge.

> > I'm mostly doing toner transfers for prototypes with 12mil minimum width.
>
> Never got a decent direct transfer. 12mil is usually feasible at home
> with a little practice (never tried it, anyway).

I had to practise somewhat too. Few important points are proper paper 
(matt coated thin ~80g/m2) and a laminator with good temperature control. 
(PD-contoroller for fast response) Proper cleaning of the substrate is 
also a must and many amino alcohol based detergents work great on copper 
as they bond organic hooks to the copper chemically, making good friends 
with polymer based ink.

> We call it flash-etch since it's faster :D We bought a cheap bubbling
> tank with heater (70EUR, was an offer on RS) and it works fine with
> traditional ferric stuff. But, that said, I dont do more than 4-5 etches
> a year.

If fumes don't matter then HCl peroxide is even more flash :D No storge 
possibilities though... It seems ferric is the easiest, if you don't count 
the stains :)

-Vesa