Thornton

I don't know the answer to your question about bulbs, but I'd like to
warn you about Visible and IR effects.  In some cases, you're statement
about these wavelengths not assisting in exposure might be correct, but
I have found that certain resists (including soldermasks) are sensitive
to longer wavelengths, especially the IR component.  I've seen some
pretty bizarre results on expose energy and apparent photospeed of
photoresists until I looked at the resist, exposure unit, bulb and
photometer as a unique combination and used step-wedge testing to
calibrate the performance.

> ----------
> From:         Thornton White[SMTP:[log in to unmask]]
> Reply To:     TechNet E-Mail Forum.;Thornton White
> Sent:         Sunday, March 28, 1999 12:54 PM
> To:   [log in to unmask]
> Subject:      [TN] Exposure Lamps
>
> Dear Technetters
>
> I have a question about UV exposure lamps. We currently use mercury
> capillary lamps to expose our dry film photoresist and our
> photoimageable
> soldermask. The exposure specification for both these materials is for
> a
> light wavelength between 360 and 380 nanometres.
>
> I have been shown the spectral distribution for our lamps - only 20%
> of the
> radiated energy is in the 320 - 400nm radiation band, over 50% is in
> the
> higher visible and infared bands (which do not assist exposure).
>
> Are mercury capillary lamps the norm for exposure work or are there
> more
> appropriate lamps for this sort of application.
>
> Any information would be appreciated.
>
>  Best Regards
>
> Thornton White
>
>

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