Exposing a Chip on Board (COB)

In a previous post I had described my efforts to build (or should I say extract) a DCF77 clock radio receiver from an old radio clock. The remaining part of the board has undergone another surgery to take a look at the chip on board (COB) technology (German Wikipedia entry). The process of removing the covering epoxy resin with a scalpel was rather destructing, but I did not want to use aggressive chemicals. As a result, the bonding wires (between the silicon chip and the conductor tracks) were destroyed.

The following video shows the process of removing the epoxy resin using a scalpel and a heat gun (fired up to 200°C). The whole process took about 10 Minutes. The last minute of the video also shows some close-ups done with a cheap webcam, which was modified for magnification.

I also added some close-up pictures of the exposed silicon die, taken with my DSLR and a reverse-mounted lens.

One Reply to “Exposing a Chip on Board (COB)”

  1. Hi Mr. Kai,
    Thank you for the nice post, really! I also had torn some parts, but never did it like that. I used to just bend the PCB close to the breaking point, and usually the COB part jumps out, exposing the pads. However, the chip itself was still protected by the die attach used to glue the IC to the PCB. Never seen anything the way you did, but it was pretty cool.
    I am also interested in designing my own PCB with a COB. Do you have any tutorial or good reference?
    Best,
    Sergio

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