Electronics > Projects, Designs, and Technical Stuff
Mylar Stencil thickness
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Bassman59:

--- Quote from: zapta on January 28, 2016, 07:38:29 pm ---From my experience, metal stencils such as the ones from electrow are more accurate and better for small pads (0402, QFN, etc). It also helps to have fine paste, e.g. T5 rather than T3.

--- End quote ---

The metal stencils from OSH Stencil work well.
texaspyro:
I cut prototype stencils out of red "vellum" from Hobby Lobby or Michaels using a 1 watt 405 nm laser diode mounted on a small CNC mill. The laser kerf is less than 10 microns.   The vellum is a plasticized translucent paper, not true sheep skin vellum.  I've never worn out a stencil, but I don't usually make more than 10 boards.

I use assist air from a small air pump blowing down a 3D printed tube with a nozzle on the end.  The laser shines down the tube and exits the nozzle.  The assist air produces a very clean cut and eliminates any invisible threads that can keep the cutouts from releasing from the body of the stencil.
Kasper:

--- Quote from: texaspyro on February 20, 2019, 04:07:19 am ---I cut prototype stencils out of red "vellum" from Hobby Lobby or Michaels using a 1 watt 405 nm laser diode mounted on a small CNC mill. The laser kerf is less than 10 microns.   The vellum is a plasticized translucent paper, not true sheep skin vellum.  I've never worn out a stencil, but I don't usually make more than 10 boards.

I use assist air from a small air pump blowing down a 3D printed tube with a nozzle on the end.  The laser shines down the tube and exits the nozzle.  The assist air produces a very clean cut and eliminates any invisible threads that can keep the cutouts from releasing from the body of the stencil.

--- End quote ---

That's pretty impressive. Whats the smallest pitch components you've soldered with it?
texaspyro:
I've done 0402, but always try to use 0805 if possible.  I've also done tiny wafer scale solder bump chips.

BTW, mylar tends to be a very poor material for stencils.  When cut by a laser the edges of the cuts tend to swell.   Some lasers are better than others.   I can also cut Kapton, but the edges of the cuts tend to char.   The vellum works very well and a 12x12" sheet costs around a dollar.
Kasper:
Ok, thanks, I'll try to find some vellum
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