[SI-LIST] Re: IC package
- From: steve weir <weirsp@xxxxxxxxxx>
- To: a.ingraham@xxxxxxxx, <si-list@xxxxxxxxxxxxx>
- Date: Tue, 17 Aug 2004 18:14:10 -0700
Andy, well I admit that my sense of humor is a bit strange. Yes, that was
my second post pointing to the P/E effect as the main reason for black
encapsulant. I thought that virtually everyone who had two or more
semesters of physics knew this and was quite surprised to see the various
theories about BBRs as the primary reason for an opaque black encapsulant
and such, hence the dancing molecules reference.
Micron was in the DRAM image sensor business for awhile. When I was a
teenager, Radio Shack was notorious for selling transistors with bad
encapsulant. Circuits would work fine indoors, but don't expose those
parts to sunlight!
Alpha particles have always emitted from encapsulant, there is substantial
historical literature on the subject. All the way back to the early 1980's
DRAMs had problems with this. Ironically, now it is SRAM's that are more
vulnerable. It is going to be a serious problem for SRAM based FPGA's as
single event upsets do more than cause a bit error, in configuration RAM
they alter function. This makes a very interesting reliability challenge.
Steve.
At 08:50 PM 8/17/2004 -0400, Andrew Ingraham wrote:
>[OK, this is try number 3. I don't know what's blocking my mail.]
>
>Steve Weir wrote:
>
> > Stefan, Dr. Photoelectric is a lot more concerned with photons that
> > dancing
> > molecules.
>
>Translation: I think what you're saying (in your strange way) is that opaque
>packages are best, so that light doesn't reach the die, where photo-electric
>effects would otherwise occur and disturb the electronics. (Yes, it
>happens, I've seen it.)
>
>My guess is that's one of the big reasons, but others like cost and
>mechanical considerations are there too. And then there's radiation (Alpha
>particles), but I think that mostly comes from the metal in the solder,
>leadframe, or pins.
>
>Years ago there were some white IC packages. I think they may have been
>ceramic, not plastic. They were opaque too, or at least reasonably so.
>
>Regards,
>Andy
>
>
>
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