# Development Status of Key Technologies for Optoelectronic Integrated Circuit Manufacturing
## 4 Packaging of Optoelectronic Integrated Circuits
### Optical Co-Package  
Optical co-packaging encapsulates optical transceiver modules/chips and integrated circuit chips in one package [83]. The packaging structure is divided into 2D, 2.5D, and 3D packaging (Figure 3). The packaging process includes COB, TAB, and FC. Furthermore, 2D packaging is typically directly interconnected by wire bonding, which is realized through COB packaging technology. The COB packaging process is a packaging technology in which the chip is directly bound to the PCB board or metal-based printed circuit board through a COB solid-state machine, and the chip and the circuit board are electrically connected through wire bonding. Dozens or even hundreds of chips are packaged in the area. In 1987, Siemens disclosed a hybrid packaging structure for electro-optical components [84], which was the earliest patent involving hybrid packaging, using a 2D packaging structure to achieve a high-precision and correct assembly of optoelectronic component circuits in a metal housing containing optical components without the use of gluing and brazing. Although the assembly of 2D packaging is easy, the high-speed signal interconnection of optical and electrical devices is long, and the occupied area is relatively large, which considerably reduces the integration density and bandwidth. Here, 2.5D packaging includes co-packaging the optical transceiver module and the integrated circuit chip on a carrier board, with higher interconnection density and lower power consumption. In 1995, Canon Japan disclosed an optoelectronic hybrid packaging method using a TAB packaging process and 2.5D packaging structure [85], which can be applied to produce various types of equipment, suitable for mass production, low manufacturing cost, and easy-to-solder chips to the circuit board. TAB involves mounting and connecting the integrated circuit chip on a soft, film-like polymer carrier tape and automatically soldering the inner lead end of the carrier tape to the chip integrated circuit, whereas the outer lead end is connected to the conventional package or printed board PWB soldering, a highly automated surface  
Figure 2: Schematic of the quantum cascade laser packaging structure. mount technology, and provides numerous terminal interconnects, typically used for mass production greater than 500 pieces. In 2002, the Industrial Technology Research Institute of Taiwan, a consortium, disclosed a packaging method for optoelectronic components using a 2.5D packaging structure [86], consisting of an optical transceiver package, a driver circuit bonding, a microlens bonding package, and a plug-in connector, which enables the effective alignment of optical transceivers, reduces costs, improves yields, and is suitable for high-volume production. In 2014, China's Huajin Semiconductor revealed an optical component packaging method using a 2.5D package combined with a stop-hole packaging method for optical communication devices [87], which can reduce the temperature of VCSEL arrays under normal operation by approximately 20 \({}^{\circ}\)C while maintaining a smaller size and lower manufacturing cost and can reduce space while directly coupling optical fibers and optoelectronic devices. In 2020, Infineon from Germany developed a semiconductor packaging method using the FC packaging process [88], which provides semiconductor packaging technology with component stacking arrangement that allows components to communicate over very short distances, reducing parasitic inductance, for applications requiring low-inductance electrical connections between package components, such as LIDAR systems and power semiconductor modules. Next, 3D packaging is a three-dimensional stacking of integrated circuit chips and optical chips to achieve the shortest electrical interconnection with low losses, the highest interconnection density, and lower power consumption than the 2.5D solution.