1. What is Flip Chip?
Flip chip, also known as controlled collapse chip connection or its acronym, C4, is a method for interconnecting semiconductor devices, such as IC chips and micro electromechanical systems (MEMS), to external circuitry with solder bumps that have been deposited onto the chip pads.
The solder bumps are deposited on the chip pads on the top side of the wafer during the final wafer processing step. In order to mount the chip to external circuitry, it is flipped over so that its top side faces down, and aligned so that its pads align with matching pads on the external circuit, and then the solder is reflowed to complete the interconnect. This is in contrast to wire bonding, in which the chip is mounted upright and wires are used to interconnect the chip pads to external circuitry.
2. What is C.O.B.?
COB (Chip-on-boar) is a technology where uncoated semiconductor elements (dice, die, chip) are mounted directly on a PCB or a substrate of e.g. glasfibre epoxy, typically FR4 and die bonded to pads of gold or aluminum.