I'm not sure if it has tremendously improved over the past two years;
however, most PWB shops will try to strip LPI masks (even after final cure)
in preference to scrapping out the boards.

The basic requirements for stripping cured LPI solder masks after final cure
are:
   1. High pH (>13.0)
   2. High temperature (150-180 deg F)
   3. Patience (it could take up to 48 hours)

A number of companies have proprietary solder mask strippers on the market
which work well. Examples would include: Alpha Metals, Oliver Sales, Dexter
Electronic Materials, etc.

Hope this helps

Larry Fisher
Dexter Electronic Materials
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