Homebrew PCBs

----- Original Message ----- 
From: "Radra" <infositeus@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Friday, February 24, 2006 5:23 PM
Subject: [Homebrew_PCBs] Re: Photolithography - resolution


> Have you had the opportunity to examine your artwork transparency
> (mask) using a microscope?  I wonder if it is better than mine.  Wish
> I had some way to take a photomicrograph so I could post a photo.
>
> I was having some difficulty during the developing process.  Some
> areas where the resist was supposed to dissolve away were not
> becoming completely clean.  Assumed it might be due to the dark areas
> of my mask not being sufficiently opaque to UV.  The dark areas
> actually appear grey, not black, when held up to a light.  So I
> overlaid two masks to increase effective opacity.  Placed the toner
> side of one mask against the toner side of a mirror image mask.  The
> down side of this technique is that the toner image is now 4 mils
> away from the PCB due to the transparency thickness which, as you
> observed, will degrade resolution; but the resulting PCB was
> acceptable.  In retrospect, I now suspect I did not have to overlay
> the masks, but instead only needed to improve the developing process.
>
> So the question I now have is "Does an inkjet printer produce better
> masks than does a laserjet printer?".

It's a lot better than the laser printers I have. I haven't compared it with 
anything expensive, though. The laser printing process is inherently 
granular, with a lot of variation in the 'blobs' produced by the toner 
particles. The sizes of inkjet droplets are much better controlled, I would 
think.

Leon