Chip-on-board (COB) is an assembly technique in electronics production in which a bare semiconductor chip (die) is mounted and contacted directly on a printed circuit board (PCB). In contrast to the classic assembly of an already moulded housing, there is no intermediate step via a separate chip housing.
Process: The chip is first mechanically attached to the PCB substrate using die bonding (usually with conductive adhesive or solder). The contact surfaces of the chip are then connected to the conductive tracks of the board using gold wire bonding or aluminium wire bonding. To protect against environmental influences and mechanical damage, the chip and wires are then encapsulated with a drop of synthetic resin (glob top).
Features:
- Space saving: COB assemblies are extremely flat and compact due to the absence of a housing.
- Cost advantage: Elimination of the housing and faster production with high quantities.
- Heat management: The chip lies more directly on the substrate, which can improve heat dissipation.
- Typical applications: Pocket calculators, LED strips (LED-COB), smart cards, low-cost electronics or sensors.
Flip-chip COB technology
Flip-chip COB technology represents a significant advance. Here, the chip is turned over (flip chip) and applied directly to the substrate, which means that its contacts are in direct contact with the substrate contact surfaces.
This direct mounting has several advantages: Gold wire bonding between the chip and the housing is completely eliminated, which reduces energy losses and heat generation. At the same time, the structure is much simpler and enables a more compact design - in other words: finer pixel pitches and a higher pixel density. Flip-chip COB also offers better heat management, as the heat can be efficiently dissipated via the solder beads and the back of the chip, thereby reducing thermal resistance.
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