The working principle and packaging method of mobile phone camera module

A mobile phone camera is a shooting device capable of shooting still pictures or short videos on a mobile phone, and is also an additional function of the mobile phone. The mobile phone camera module is composed of PCB board, FPC, lens, lens holder, holder, color filter, sensor and other components. All parts of the components are packaged together, and then can be directly applied to the camera components of smartphones.

The working principle of the mobile phone camera module: the scene is shot through the lens, and the generated optical image is projected onto the sensor, and then the optical image is converted into an electrical signal, and the electrical signal is converted into a digital signal through analog-to-digital conversion, and the digital signal is processed by DSP. , and then sent to the processor of the mobile phone for processing, and finally converted into an image that can be seen on the screen of the mobile phone.

There are two types of packaging modes for mobile phone camera modules: COB (ChipOnBoard) and CSP (ChipScalePackage). COB (Chip on Board) means that the photosensitive chip is bonded to the substrate through gold wires, and then the lens and the bracket (or motor) are bonded together. On the substrate, CSP (ChipScalePackage), that is, the photosensitive chip is welded to the substrate by SMT, and then the lens and bracket (or motor) are bonded to the substrate. Although they are both used as two packaging modes, they have different advantages and disadvantages in the application of mobile phone camera modules.

Advantages of COB packaging: COB packaging involves multiple assembly, packaging and testing of image sensors, lenses, mirror mounts, filters, motors, circuit boards, front and rear covers, etc., and can be directly delivered to the assembly plant. It has the advantages of good packaging cost, low module height and effective space saving.

Disadvantages of COB packaging: The disadvantage of COB packaging is that it is easy to be polluted during the production process, has high environmental requirements, high cost of process equipment, large fluctuations in yield rate, long process time, and cannot be repaired, etc. The problem of Particle shaking. The production process is shortened, but this also means that the technical difficulty of making modules will be greatly increased, which will affect the performance of yield rate.

Advantages of CSP packaging: CSP-packaged chips have lower requirements for cleanliness, better yield, low cost of process equipment, and short process time due to their glass coverage.

Disadvantages of CSP packaging: poor light penetration, more expensive, higher height and other phenomena.

In fact, the biggest difference between CSP and COB is that the photosensitive surface of the CSP package chip is protected by a layer of glass, while COB does not, which is equivalent to a bare chip. Compared with CSP packaging, COB packaging has many advantages, especially in reducing the height of the camera module. In the case of smart terminals generally pursuing ultra-thin, major module manufacturers have chosen COB packaging. However, due to the very high dust-free requirements of the COB packaging environment, the current product yield is very low. Therefore, in order to ensure the yield rate, a considerable number of domestic manufacturers still use CSP packaging technology, and many companies use both technologies at the same time.