What’s the difference between COG and COB of LCD dot matrix screen?

As we all know, there are two types of modules of LCD dot matrix screen, COB and COG, so what are the differences between this two in terms of technology and use?

COB, Chip On Board packaging technology, is to adhere the bare chip to the interconnect substrate with conductive or non-conductive adhesive;

COG, Chip On Glass technology, directly binds the driver chip to the glass.

Features of LCD using COB packaging technology.

The bare chip packaged with COB technology is the chip and I/O terminals above the crystal. When soldering, the bare chip is bonded to the PCB with conductive/thermally conductive adhesive. After solidification, the metal wire is ultrasonically and hot-pressed with a Bonder machine. Under the action of hot pressing, they are respectively connected to the I/O terminal pads of the chip and the corresponding pads of the PCB. After passing the test, they are sealed with resin glue.

COB technology has the following advantages: low price; space saving; mature technology.

COB technology also has shortcomings, that is, it needs to be equipped with a welding machine and packaging machine, and sometimes the speed cannot keep up; PCB patch has stricter environmental requirements; cannot be repaired, etc.

Features of LCD using COG packaging technology.

1. The process is simplified. Directly paste the IC on the conductive electrode of the LCD screen, reducing the welding process;
2. The volume ratio is greatly reduced, making it easier to miniaturize, simplify and highly integrate. The PCB circuit is directly fabricated on the LCD screen, which is widely used in small portable products.
3. There are no problems such as IC deformation, because the IC is directly flipped and attached to the LCD screen.
4. The cost is relatively high because the chip has to be pressed onto the glass.