Tag Archives: photomask

Photomask Mirrors


At our local Silicon Valley electronics surplus shops and electronics flea market, we frequently come across all sorts of bizarro semiconductor manufacturing paraphernalia. Here is one of those types that we have written about before, in our coaster project:

Photolithographic masks, or photomasks are clear templates used in semiconductor manufacturing. Typically, they are made of UV-grade fused silica and have a highly intricate chrome metal film pattern on one side.

The most commonly available masks are test patterns used for calibration, as production masks are guarded carefully. This particular one dates back to 1983!


Now looking inside at it, it’s hardly a mask at all. It’s nearly fully silvered—perhaps a mask pulled out before the etching step of its process.


If you look at an oblique angle, you will find a few incredibly detailed patterns, and some printed on markings. This one is marked “5.1 INCH ARRAY” across the top and “1447 3-OCT-83-13. 5” across the bottom.


So, what to do with them? Since they don’t have the neat patterns that made those coasters so cool, we used some truss-head screws to mount them to the wall.


And here we are then, using a couple of photolithographic mask as bathroom mirrors! (With a couple of units at different heights for different-height people.) It solves a couple of problems at once: how to display the beautiful ephemera of semiconductor manufacturing, and what to do about a soulless little extra bathroom at our shop that didn’t come with a mirror.


Manufacturing art: Photomask

Masking plate1

After seeing our photomask coasters, a friend gave us this giant photomask as an art piece. While we’re not certain what this was for, our best guess is that it is a mask for the lead frame for some device in an SO-20 package. The overall size is about 18″ x 24″ and about 1/8″ thick.

Masking plate3

Shown with an SO-24 device on the edge of the plate for comparison. (Didn’t happen to have a correctly sized 20 pin device handy.)

Masking plate5

The transparent lines show where the metal will be after processing and the black portions are where the metal will be removed. When you line up the 24 pin device on the plate it is a bit misleading, as it obscures the fact that those two outer transparent lines aren’t actually for device leads. It does confirm that it is sized correctly for a 1:1 mask for a device with a 0.050″ pin spacing, and the central square looks like the right width for a device in an SO-20 package as well.

Tangentially related: CCD wafer

Photomask coasters


Photolithographic masks, or photomasks are clear templates used in semiconductor manufacturing. Typically, they are made of UV-grade fused silica and have a highly intricate chrome metal film pattern on one side. These remarkable objects are exactly the sort of wonderful thing that occasionally pops up at good electronics surplus stores. We recently found a few, took some pictures (see below) and, in the spirit of re-use, made them into some classy coasters.
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