There is nothing wrong with dryfilm. Only side effect can be its thickness.
It is thicker than liquid photoresist. I've used dichromated PVA in order to avoid shelf life limitation. Whenever you need photoresist you can mix PVA with dichromate and it is ready, the problem is dichromate is not an environmentally safe chemical. Now I'll try AQ 3000.
I used dryfilm before and faced a lot of problems to protect PTH holes but it was ~8 years before may be new ones are better.
I added laser to the side of inkjet head and I'm using raster scanning method to expose photoresist.
I've the same idea to use polygon mirrors of a old laser printer. I've one Brother printer which has an aluminum mirror (most of them have a copper or gold plated mirror on aluminum because of IR laser) and plastic lenses it seems it is possible to use with blue laser. I did some rough measurements and I saw that on optical path I'm loosing ~30% of the power most of it is because of diagonal mirrors because of that I left it for a future project.
Volkan
--- On Fri, 11/13/09, Adam Seychell <a_seychell@...> wrote:
From: Adam Seychell <a_seychell@...>
Subject: Re: [Homebrew_PCBs] Making PCB using these new 405nm LASER Diodes
To: Homebrew_PCBs@yahoogroups.com
Date: Friday, November 13, 2009, 2:26 AM
Volkan Sahin wrote:
>
>
> I've a working prototype. I'm using 150mw 405nm blue ray laser diode.
> Without complicated optics I can get ~3 mil trace width/space.
> Currently, I'm using Dichromated PVA based homemade photoresist. The
> problem is without polygon mirror scanner, it is very slow but result
> is impressive. The exposure time required for 1.5 mil spot is ~20
> microseconds.
> Volkan
>
What's wrong with using dry film photoresist ?
Its relatively cheap (under 10% cost of FR4 PCB material per unit area)
easy to apply, fairly sensitive to 405nm, highly uniform and the ability
to tent holes for the PTH panel plating method.
How are you positioning the laser ?
Would it be difficult to use parts off an laser printer to make a
polygon mirror scanner. In that case only 1 axis movement is needed for
the PCB. My inkjet printer is currently the limiting factor for
line/space widths, although 0.2mm (8mil) are quite reliable and adequate.
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