[SI-LIST] Re: IC package
- From: Christopher Jakubiec <Christopher.Jakubiec@xxxxxxx>
- To: reanderson@xxxxxxxxxxxxx
- Date: Tue, 17 Aug 2004 10:04:29 -0700
Certainly during low current (leakage) wafer level testing that I have
performed in the past, the effects of having the fluorescent lights on
in the lab are real. The light does in fact excite electron-hole pairs
that contribute to the current due to the photoeletric effect.
-Chris
Ray Anderson wrote:
> Hal Murray wrote:
>
>
>>>Black was also cheaper to make before, (remember mostly black and grey
>>>plastics only)
>>>
>>>
>>
>>I assume the basic answer is cost.
>>
>>Clear plastic is available for LEDs and photo receptors - other
>>colors/filters too. Anybody have an estimate as to how much more non-black
>>costs?
>>
>>
>>
>>
>
> Another reason for black (or other photo opaque color) other than clear
> is that ambient light shining on the die can have 'unintended
> consequences' . I remember a couple cases a long time ago where in one
> instance ambient light shining through the 'erase' window on an EPROM
> somehow changed timing enough to crash a system (covering the window
> with black tape restored normal functionality). In another case 120Hz
> noise was modulated onto some driver outputs in a de-lidded chip we were
> working on in the lab. Shielding the die from the ambient fluorescent
> lighting made the 120Hz nose on the outputs go away.
>
> -Ray
>
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