Removing cheap solder mask from PCBs

I just sent in a JLC PCB order for 10 PC boards and then realized that I’d not checked the solder mask layer. When I did check, I found out that the manufacturer-supplied footprint lacked paste and mask holes on the pads of a 64-lead QFP package.
left_side_of_board
My intention is to reflow solder this part myself (JLC didn’t have it) using a stencil cut from the full-size steel stencil they provided.
I’ll be using leaded solder paste and either a modified toaster oven or a hot air pencil.

I was thinking about using my Glowforge to blast off the solder mask over the pads.

Has anyone done this?

If so, how did you do it?

And what power/speed settings would be good?

I can experiment with the engraving power, and I can try to use the proper solder mask pattern to avoid damaging the board. But it might be hard to perfectly align. Easier would be to make four stripes over the pad areas:
left_side_of_board_masked
I was wondering whether a power level adequate to vaporize the solder mask would damage the PCB material between the pads.

Also, is the result clean enough to easily solder? I figured I could use Scotchbrite pads to remove the remaining junk.

From info at Universal Laser’s site it doesn’t sound like the materials used for PCB masking are particularly harmful to the laser optics.

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popcorn3

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:smile: You might be the first to conceive of it…if it works be sure to let the folks here know how it went. (Might open up a new rabbit hole for some.)

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I for one am VERY interested in the results.

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Add me to the “no experience to contribute, but very interested” pile.

A web search certainly suggests it might be possible. And the ChiliPeppr guy has a video where he does it with a little 7W blue laser. https://youtu.be/tTKNvCmdWvc

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