Chip-on-Board, or COB, applications consist of die directly attached to its circuit board. COB assemblies improve package performance as a result of the shorter interconnection paths and are a preferred application by process engineers.
COB technology is actually 'direct chip attachment', or DCA. Direct Chip Attachment assemblies can be called different names depending on substrate material. For example chip-on-glass (COG), chip-on-flex (COF), among others.
The COB process often has 3 steps:
The flip chip process incorporated with COB enables successful attachment without using wire bonding; it does so by bumping the bond pads on the correct side (via flipping the chip) and directly attaching the chip. With Flip Chip on Board (FCOB), underfilling the chip is required to protect the chip's active surface from damage.