I have some PCBs with a Chip-On-Board (COB) chip that I was curious about. A website stated that this COB contained a QX5252F chip but it was not stated how this was determined. I didn’t really believe it and decided that I would sacrifice the board to see if the chip had any markings. I planned on examining the chip with my grandfather’s microscope – he was a medical doctor.
I used Kai Bader’s YouTube video as a guide for COB exposure using an SMD Hot-Air rework station, It worked like a charm and exposed the chip under the COB Goop – EXCEPT that my chip didn’t stay on the board like Kai Bader’s. My, smaller than expected, chip came off of the board, embedded within a piece of goop. I could only see the bottom of the chip. I reheated the piece of goop and tried to pop the chip out of the goop – FAIL – the fragile chip broke into hopelessly useless fragments. See the photo below.
I may try another COB exposure but first I’ll practice on some other boards. Hey, it was my first try at this!