CHIP ID PLEASE

[oldgoldman]

Curiosity killed the cat. I have an old board that has this chip on it. It had a grey soft rubbery cover on it .. I peeled it off to see the goodies underneath. it reads "3" on the left side of the chip .. and "25" on the other. Thoughts ? Thanks

 

[Barren Realms 007]

Get the gold out of it.

 

[Claudie]

What did the board come out of?

 

[oldgoldman]

i'll post picture later .. gotta tun to airport .. off light brownish board with "WORD GEN" on back .. 18 chips on board ...ED3C342-30 .. 840116040 .. Regards

 

[macfixer01]

i'll post picture later .. gotta tun to airport .. off light brownish board with "WORD GEN" on back .. 18 chips on board ...ED3C342-30 .. 840116040 .. Regards

I've seen some chips designed similar to that before except mine were in DIP packages with pins going through the board or into sockets, not a flat pack like you have there. They were made on a very thin white ceramic wafer and the bottom side where the gold traces were was covered with a thin gray rubbery coating. I can't recall now if they were made by Western Electric or ATT, but were definitely from some old telephony boards of some kind.

macfixer01

 

[macfixer01]

i'll post picture later .. gotta tun to airport .. off light brownish board with "WORD GEN" on back .. 18 chips on board ...ED3C342-30 .. 840116040 .. Regards

I've seen some chips designed similar to that before except mine were in DIP packages with pins going through the board or into sockets, not a flat pack like you have there. They were made on a very thin white ceramic wafer and the bottom side where the gold traces were was covered with a thin gray rubbery coating. I can't recall now if they were made by Western Electric or ATT, but were definitely from some old telephony boards of some kind.

macfixer01

I believe the white chips shown in this auction (second photo from the bottom) are the same type I had that I was referring to. They're made by Western Digital, part number 267AE. They have gold traces on the ceramic substrate with a thin grey rubber coating over them, similar to what he's showing in the other picture a little higher up on the page.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=270686655594


macfixer01

 

[Militoy]

Limited production IC potted with silicone or polybutadiene RTV. This kind of construction Isn't extremely uncommon when only a few of a new IC type are being built - when it doesn't make sense to tool up a production line for a regular ceramic or plastic package. You'll find a similar kind of construction sometimes when a DIP IC has become obsolete. A DIP carrier/adapter is designed to accept a newer SMT version of the chip. The adapter can then be installed into the older style PCB without re-spinning the board. Nothing magic - just go for the gold.

 

[Drewbie]

This look like a "thick film" module.

My very first job back in the early 80's was designing and building thick film circuits for low production run electronics.

You would lay out the design of the tracks at a larger scale using the usual thin black sticky tape (like how PCB's were done), with a film negative produced BUT it wouldn't be 1:1, it would be 10:1 or less, then that much smaller negative would be used to produce a screen to screen print a metallic paste onto the ceramic substrate. Then you would wait for it to dry, then you would screen print on layers of resistors (using different pastes of different resistive values).

Later you would glue silicon chips directly to the ceramic substrate and under a microscope, hook the IC's up to the tracks with hair-thin gold wire using a special machine.

Google images "thick film paste" gives some examples. I dare say the pastes would have good silver content.

 

[oldgoldman]

Many Thanks for the great insight

 

[HowitzerMan]

Here's a couple of the Western Electric with grey rubberized coating on back.
these are out of an old Dataphone (1973)

 

[HowitzerMan]

pretty though