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Subject: Re: [Homebrew_PCBs] Setting exposure with a step gauge

From: Philip Pemberton <ygroups@...>
Date: 2009-06-02

Marc Sulfridge wrote:
> The problem is one of units. The first number you calculated is the lamp
> intensity in W/cm^2=J/(s∗cm^2). Your dry film dose is specified in
> mJ/cm^2= 0.001 J/cm^2. You need to convert this to J/cm^2 to keep your
> units consistent. 42.5 mJ/cm^2 = 0.0425 J/cm^2.
>
> Thus: time = 0.0425 J/cm^2 / 0.065 J/(s∗cm^2) = 0.654 s
>
> doubling this gives 1.31 seconds.

Which seems even more off than my estimates -- other types of photoresist I've
looked at specify an exposure time of between two and three minutes.

The only time I can see a one-second exposure working is if the light source
was an arc lamp...

--
Phil.
ygroups@...
http://www.philpem.me.uk/