The design requirement of COB
In the previous article, we have introduced what is the COB process, wire bonding, and wire pull test. In this article, we’re going to talk about the design requirements of COB.
1.The surface finish should be either gold plating or ENIG to provide the requirement of Die Bonding, and the thickness of gold plating is usually larger than general.
2. The consistency of length of wire should be considered. In other words, to spread the risk of short circuit, the manufacturer have to keep the same distance from solder joint to Die and PAD. Shorten the spacing can avoid the appearance of diagonal PADs, and designing elliptical PAD also be helpful to equally divide the bonding wires into the relative positions.
3. Additionally, one wafer should have more than two positioning points, and replace the round hole with a cross shape. Wire Bonder is automatic-control, due to the restriction of the machine, the engineer should consider the function while setting the positioning points.
4. The Die Pad of the PCB should be bigger than the actual size, not only can control the shift of the die but also avoid the over-revolve in the die pad. The suggestion is every die pad on the board should be larger than the actual size.
5. It would be better not set vias in the potting area, or require the PCB manufacturer to plug those vias completely. The purpose is to avoid epoxy filters with the other side of the board.
6. For the convenience of dispensing and dispensing control, it is suggest to print the silkscreen on the areas which need epoxy.
*Related Article:
COB1:What is COB (Chip On Board)? Introduce the Evolution History of COB
COB2:Brief Introduction Process of COB (Chip On Board)
COB3:Introduce COB's bonding wire and its pulling force
1.The surface finish should be either gold plating or ENIG to provide the requirement of Die Bonding, and the thickness of gold plating is usually larger than general.
2. The consistency of length of wire should be considered. In other words, to spread the risk of short circuit, the manufacturer have to keep the same distance from solder joint to Die and PAD. Shorten the spacing can avoid the appearance of diagonal PADs, and designing elliptical PAD also be helpful to equally divide the bonding wires into the relative positions.
3. Additionally, one wafer should have more than two positioning points, and replace the round hole with a cross shape. Wire Bonder is automatic-control, due to the restriction of the machine, the engineer should consider the function while setting the positioning points.
4. The Die Pad of the PCB should be bigger than the actual size, not only can control the shift of the die but also avoid the over-revolve in the die pad. The suggestion is every die pad on the board should be larger than the actual size.
5. It would be better not set vias in the potting area, or require the PCB manufacturer to plug those vias completely. The purpose is to avoid epoxy filters with the other side of the board.
6. For the convenience of dispensing and dispensing control, it is suggest to print the silkscreen on the areas which need epoxy.
*Related Article:
COB1:What is COB (Chip On Board)? Introduce the Evolution History of COB
COB2:Brief Introduction Process of COB (Chip On Board)
COB3:Introduce COB's bonding wire and its pulling force