What is the encapsulation process of optical components in an optical module?

COB package is short for chip on board. It is a butterfly package and is widely used in optical modules of Ethernet data centers. COB refers to attaching bare die chips such as TIA and LDD directly to the copper foil of PCB, and then bonding the gold wire for electrical connection, and finally adding a cover or glue protection on the top of the chip.

TO can package is commonly used in SFP small package optical module. The full name of TO CAN package is Transistor Outline. According to the diameter of the base size to divide, the common TO56, TO42, TO52, TO38 several, more is the manufacturer customized size specifications.

Butterfly encapsulation shell usually a cuboid in appearance, structure and realization of function is usually complicated, can be a built-in refrigerator, heat sink, ceramic base, chips, thermistors, backlight control, and can support all of the above parts of bonding wire, housing area is big, good heat dissipation, can be used for various rate and 80 km long distance transport.

Optical modules with 25G or lower speed are usually single-channel TO can or butterfly packaging, equipped with standard manufacturing and automation equipment, and with low technical barriers. However, for high-speed optical modules with a speed of 40G or higher, it is mainly implemented through multiple channels in parallel due to the laser rate limit. For example, 40G is implemented by 4*10G, while 100G is implemented by 4*25G. The packaging of high-speed optical modules puts forward higher requirements for parallel optical design, high rate electromagnetic interference, heat dissipation under the condition of volume reduction and power consumption increase. With the increasing rate of optical modules, the baud rate of a single channel has already faced a bottleneck. In the future, the design of parallel optics will become more and more important when it reaches 400G and 800G.