What is COB?
The concept of on-board chip package ( COB ) is one of the bare chip mount technology. It is one of the microelectronic packaging technologies developed after SMT surface packaging technology. It is the bare chip of the integrated circuit, which is directly attached to the epoxy resin adhesive with silver on the circuit board, and through the pin " wire " ( Wire Bonding ), and then appropriate anti-vertical flow of epoxy resin or silane ( Silicone ) tree grease will seal the COB area. This technology can save the package cost of integrated circuits. At present, some consumer electronic pens or electronic watches and various timers can be manufactured in this way.
Brief Introduction of COB Package and Bonding Technology
1.The expansion machine uses the expander to expand the whole LED chip film evenly, the LED crystal grains which are tightly arranged on the surface of the film are opened, which is convenient for thorn crystal.
2. The expanded crystal ring is placed on the surface of the gum machine which has a good silver paste layer, and the silver paste and silver paste on the back are suitable for bulk LED chips, apply proper amount of silver paste on the printed circuit board.
3. The crystal will prepare the silver paste in the crystal frame of the expanding crystal ring, and the LED chip will be stabbed on the PCB by the operator under the microscope.
4. Curing. The PCB printed circuit board with good stab crystal is put into the heat circulating oven for a period of time, and then the silver paste is solidified and removed, otherwise, the LED chip coating will bake yellow, that is, oxidation, which make the binding difficult. Note : if you have LED chip binding, you need the above steps; if only the IC chip is bound, the above steps are cancelled.
5. Stick the chip on the PCB printed circuit board on the IC location point on the right amount of red glue ( or black glue ), and then anti-static equipment ( vacuum suction pen) will be IC naked the tablets are correctly placed on red or black glue.
6. Drying will stick to the bare piece of hot cycle oven, and then placed on the big plane heating plate, static temperature for a period of time, can also be natural curing ( time is longer ).
7. Binding ( wire ) uses aluminum wire bonding machine to bridge the wafer ( LED grain or IC chip ) with the corresponding pad aluminum wire on the PCB board, that is, the internal lead welding of COB.
8. Pretest. The use of special detection tools ( different uses of COB have different equipment, the simplest is the high precision voltage regulator ) to detect COB board, rework the unqualified board.
9. Dispensing the use of dispensing machine will be the deployment of a good AB glue points to the binding good LED crystal, IC is sealed with black glue, and then according to customer requirements view encapsulation.
10. Solidify the PCB printed circuit board with good adhesive and put the constant temperature in the hot circulation oven, and set different drying time according to the requirement.
11. Post-test will be packaged PCB printed circuit board and then use a dedicated testing tool for electrical performance testing, to distinguish between good and bad. Because there will be some bad phenomena in the binding process, such as disconnection, winding, and false welding, which lead to chip failure, so the chip and package should be tested for performance.
This article is from Allicdata Electronics.