General > General Technical Chat
Why are ICs/Semis black?
PStevenson:
I was showing my young nephew some PCBs (trying to get him into electronics) and he asked me why are all of the square things black?
I just said that it's probably because it helps it work (light can mess with the operation) and that it's easier to print visible text on it.
but does anyone actually know why they're (mostly) black?
Brumby:
Light shining on a silicon die can affect operation of circuits. Think solar cells.
EPROMs are a classic example where a clear window allows for erasure of stored data. Photons can mess with circuit operation.
Black plastic or other opaque material (such as ceramic) block light.
newbrain:
--- Quote from: Brumby on May 03, 2021, 12:10:18 pm ---Light shining on a silicon die can affect operation of circuits. Think solar cells.
--- End quote ---
When the world football cup was hosted in Italy, in 1990, a brand new telephone xchange was installed close to the stadium.
Since it was quite an advanced (for the times) model, various foreign dignitaries were invited and shown it.
Every time an official visit was going on, a complete restart (an event that should happen at most 3 times in a year) happened.
After much head scratching, it was found that:
* Journalists and visitors used flashes to take pictures
* Some of the DC/DC boards were mounted on board extender, to show them off.
Well, on those boards there were some diodes, and they had a glass enclosure.
The flash light was enough to start an avalanche and kill the power for a short time.
G7PSK:
Red or brown and blue plastic would do the job but I think there are two reasons for using black plastic.
For a start it tends to be cheaper or at least in the past it was as carbon black is used to make the plastic black and that is cheaper than the plastic or was in days gone by second reason is in days gone by pitch was used for encapsulating electrical and electronics so black is familiar, in the 60's there were some transistors and other semiconductors in both red and blue packaging.
NiHaoMike:
--- Quote from: newbrain on May 03, 2021, 12:20:55 pm ---When the world football cup was hosted in Italy, in 1990, a brand new telephone xchange was installed close to the stadium.
Since it was quite an advanced (for the times) model, various foreign dignitaries were invited and shown it.
Every time an official visit was going on, a complete restart (an event that should happen at most 3 times in a year) happened.
After much head scratching, it was found that:
* Journalists and visitors used flashes to take pictures
* Some of the DC/DC boards were mounted on board extender, to show them off.
Well, on those boards there were some diodes, and they had a glass enclosure.
The flash light was enough to start an avalanche and kill the power for a short time.
--- End quote ---
Or more recently, a design flaw with the Raspberry Pi 2:
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