Product
1: The finished surface treatment of the PCB board must be electroplated gold or ENIG, and the gold plating layer must be thicker than that of the general PCB board to provide the energy required for Die Bonding and form gold-aluminum or gold-gold co-gold.
2: In the wiring position of the pad circuit outside the COB Die Pad, try to consider that the length of each welding line has a fixed length, that is, the distance from the wafer to the PCB pad should be as consistent as possible, so that the position of each welding line can be controlled and the problem of intersecting short circuits of welding lines can be reduced. Therefore, the design of the welding pad with diagonal lines does not meet the requirements. It is recommended to shorten the spacing between the PCB welding pads to eliminate the appearance of diagonal welding pads. It is also possible to design an elliptical welding pad position to evenly disperse the relative positions between welding wires.
3: It is recommended that a COB wafer should have at least two or more positioning points. It is best not to use the traditional SMT circular positioning points, but to use cross-shaped positioning points instead, because the Wire Bonding machine will basically grab a straight line for positioning when doing automatic positioning. It is recommended to refer to the machine performance to make a design.
4: The size of the PCB Die Pad should be slightly larger than the actual wafer, which can limit the offset when placing the wafer and prevent the wafer from rotating too much in the die pad. It is recommended that the wafer pads on each side be 0.25~0.3mm larger than the actual wafer.
5: It is best not to have vias in the area where COB needs to be glued. If it cannot be avoided, the vias should be 100% plugged to prevent the epoxy from penetrating from the vias to the other side of the PCB during glue dispensing, causing unnecessary problems.
6: It is recommended to print the Silkscreen mark on the area where glue is required, which can facilitate the glue dispensing operation and the glue dispensing shape control.