[Technology Sharing] LED chip-on-board (COB) packaging process
The chip on board (COB) packaging process firstly covers the silicon wafer with a thermally conductive epoxy resin (usually an epoxy resin doped with silver particles) on the surface of the substrate, and then indirectly places the silicon wafer on the surface of the substrate. Heat treatment until the silicon wafer is firmly fixed in the substrate, and then wire bonding is used to indirectly establish an electrical connection between the silicon wafer and the substrate. The process of its closure is as follows:
The first step: the crystal expansion uses the expansion machine to evenly spread the zero-chirping LED wafer film provided by the manufacturer, so that the LED die which is tightly displayed on the surface of the film is opened, which is convenient for puncturing.
The second step: the adhesive will spread the crystal expansion ring on the surface of the adhesive machine that is not scraping the silver paste layer, and the silver paste is placed on the back. Point silver paste. Suitable for disassembling LED chips. Use a dispenser to place the right amount of silver paste on the PCB printed circuit board.
The third step: placing the crystallized crystal expansion ring into the thorn crystal frame, the operator is under the microscope, the LED chip is punctured on the PCB printed circuit board with a lancet.
Step 4: Put it into the thermal cycle oven and put the punctured PCB printed circuit board into the heat cycle oven for a period of time. After the silver paste is solidified, take it out (not long-time, otherwise the LED chip coating will be baked yellow, ie Oxidation, forming difficulties for bonding). If there is no LED chip bonding, the above steps are required; if the IC chip is bonded, the above steps are cancelled.
Step 5: Stick the chip with the dispenser. Put the appropriate amount of red glue (or vinyl) on the IC position of the PCB printed circuit board, and then put the IC die accurately in the anti-static device (solid air pen or female). Red or black glue.
Step 6: Drying Put the bonded die into the heat cycle oven and put it on the large flat heating plate for a period of time. It can also be naturally cured (longer time).
Step 7: Bonding (wire-bonding) The aluminum wire bonding machine is used to bridge the wafer (LED die or IC chip) to the pad aluminum wire on the PCB board, that is, the inner lead of the COB is soldered.
Step 8: The pre-test uses the common detection tool (the COB is different according to different uses, the simple one is the high-precision steady-state current) to detect the COB board, and the unqualified board girl is repaired.
Step 9: Dispensing the dispenser with a suitable amount of AB glue to the bonding LED die. The IC is sealed with black rubber and then sealed according to customer requirements.
Step 10: Curing The PCB printed circuit board with the glue is placed in a thermostatic oven and placed at a constant temperature. The drying time can be set according to the requirements.
The eleventh step: After the test, the sealed PCB printed circuit board is then tested for electrical performance by using a common inspection tool to distinguish between good and bad. With advances in technology, it is packaged in an aluminum substrate COB package, a COB ceramic COB package, and an aluminum substrate MCOB package.
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