[SI-LIST] Re: IC package

  • From: Wyland <dcwyland@xxxxxxxxxxxxx>
  • To: s.raja@xxxxxxxxxxxxx
  • Date: Tue, 17 Aug 2004 10:19:17 -0700

The packages are black partly to avoid sensitivity to light.
This was a problem in the early days.

The transistors in ICs are photoelectric.
The transistors are composed of PN junctions, the same kind of junctions 
in solar cells.
Light shining on a PN junction creates photocurrent in the junction.
Solid black absorbs the most light.
Light sensitive devices such as photocells and photo transistors
use clear plastic packages. See TI, etc.

In the early days, some tried different colored packages for marketing.
Fairchild had some red plastic packages for a while.
However since black worked well and was cheap, it became the default.

Black is a better radiator of heat than other colors,
but the effect is very small at normal IC temperatures.
Remember that the heat flow goes up (and down) proportional
to the fourth power of the temperature. Wearing black clothes
in the sun draws heat because the sun is at 10K degrees.
IC case temperatures seldom achieve 70 degrees C.


s.raja wrote:

>why all IC packages are Black in colour?.
>Regards
>Raja
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