Homebrew PCBs

Has anyone measured the UV transmissive density of their artwork? One would 
think Laserjet toner should be opaque "enough", and dye-based ink jets will 
have difficulty achieving the required density. Is it a for sure certainty 
that laser printers should have no difficulty?


----- Original Message ----- 
From: "DJ Delorie" <dj@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Sunday, June 22, 2008 11:34 AM
Subject: Re: [Homebrew_PCBs] UV LED box


>
> "Bertho Boman" <boman01@...> writes:
>> I am a little surprised at the long discussions about selecting
>> exposure for just the photo resist.  To me that is artificial and
>> not real life.  To make PCBs, there needs to be an artwork and a
>> hold down vacuum frame or glass.  Both will absorb some UV so that
>> will affect the result and the "opaque" sections of the artwork are
>> not really perfect, they will let through unintentional UV that also
>> will affect the outcome.
>
> If you had been following the discussion, you would have known that I
> *included* those items in the test exposures, so I *am* compensating
> for loss through the glass, artwork, etc.  That's the whole point of
> calibrating with a step gauge - it tells you exactly what exposure you
> need for YOUR SETUP.
>