[chbot] Unusual package

Helmut Walle helmut.walle at gmail.com
Mon Dec 14 10:21:23 GMT 2020

The speculation about it being something photo-electric based on seeing the resin filling is
reasonable. Conversely, letting light get into the package of any semiconductor that does not
use the light for its intended operation would be counterproductive, exactly because the
photo-electric effect would cause substantial interference... For that reason, semiconductor
packages are generally opaque, except for components that are meant to either emit or receive
light (or, back in the old days, that were erased using light).
Or to put it in a different way again, you can easily make your own photo-transistor by filing
the top off the metal can of a metal-packaged bipolar transistor, then filling the cavity with
resin to protect the component against environmental influences.

On 14/12/2020 21:14, Mark Atherton wrote:
> Just in case someone recognises this part...
> 4 pin, TO-92 type ceramic package
> Two chambers, each filled with epoxy
> Vertical slot to the left.
> It is possible that the part is an IR TX/RX, and the dark epoxy is only opaque at the visible
> spectrum.
> Never seen anything like this before.
> - Mark

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