Chips Galore

[floppy]

I had to post some pics of theses boards I found today. These things are loaded with chips. From more old telecom stuff, sure wish I knew how to process chips cause I got chips like these coming out my ears.

 

[dherik]

You need to get yourself a weller model wha-300 hotair tool, ours goes up to about 1050 F. I usually run it around 650 to take off chips without damaging the board, if you're not worried about damaging the board, crank it up to 900 and use a mechanics pick along with a good pair of leather gloves and pop them buggers off.

 

[midge]

What do you do with eprom chips? i ahve a few of them but cant see any gold on the legs, so wheres the Precious metal? inside?

 

[macfixer01]

What do you do with eprom chips? i ahve a few of them but cant see any gold on the legs, so wheres the Precious metal? inside?

They're a sandwiched package design with usually a brown or purple ceramic slab on the bottom and top. For an EPROM the top slab will have a clear glass window used to erase the chip. You can generally scrape away any label and look through that window before opening it to see if there is gold around the chip or not. If it's a mask programmed ROM or EEPROM or SRAM it won't have a window. There are also other non-memory types of chips made with that same type package that will not have a window such as older Intel processors like the 8085, also military and industrial grades of common 14 or 16 pin TTL chips like the 74xx series. The bottom slab is solid but has a recessed pocket in the center of it that the actual silicon wafer (chip) is mounted inside. It may or may not have a layer of gold in the pocket between that silicon wafer and the bottom ceramic. In the middle of the sandwich between the top and bottom ceramic slabs is where the pins enter the package. The two slabs are stuck together with a layer of powdery glass between and around the pins, that's the gray looking center layer if you look at the edge of one of those eproms. So you may have a bit of gold under the chip, the tiny wires that connect the internal ends of the pins to the chip may contain some gold. What other PM's they may contain in place of gold or in addition to it all depend upon the manufacturer. You can generally split the two ceramic layers apart pretty easily. I use a wide mouthed pair of end-cutters. You could stand the package on one end and lightly tap at the grey layer with a hammer and chisel (safety glasses are a good idea as bits of glass and pins can fly). Some people here have mentioned using heat shock to open them, I believe boiling then throwing them in cold water. Personally I don't save any EPROMS that don't have gold visible inside but that's just me and maybe that's my mistake. Unless it has gold plated pins then the pins are probably junk. Actually I think I've only ever seen gold pins on EPROMs with a side brazed package design like the white and gold chip in your picture, never on the sandwiched type package. Those side brazed packages would need to be broken into pieces to process them chemically after removing the plate.

macfixer01