Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

Slavko Kocjancic <eslavko@...> writes:

> Does someone know what energy is nedded to develop photoresist?

Here's an example:
http://www.thinktink.com/stack/volumes/voli/store/specs/m115spec.htm

The key parameter is "energy" in mJ/cm2 (millijoules per square centimeter)

To truly calibrate a system, though, you need to do a test exposure
through a transmission step wedge, like:

http://www.stouffer.net/TransPage.htm
http://www.thinktink.com/stack/volumes/volvi/filmimag.htm#Calibration

The wedge allows you to do a range of "exposures" at one time, and since
it's calibrated(ish) the results tell you what actual exposure to use.

For example, if you do a test run at 10 cm/sec laser travel, and the
results are "held at step 10" but the resist says it wants step 8, and
you're using a 21-step wedge (1.414x per step), you need to double the
laser speed to 20 cm/sec or cut the energy in half.