A brief analysis of DA glue for camera module chip packaging

The camera module is a complex system integrating light, mechanics, electricity, software and hardware. Its working principle is that the light of the scene to be photographed passes through the lens to project the generated optical image onto the image sensor SENSOR, and the light signal is converted into an electrical signal through the photodiode. signal, and then through the analog-to-digital conversion circuit (A/D), the obtained analog signal is converted into a digital signal and the signal is initially processed and output, then the data is processed through the ISP, and finally converted into a readable image on the electronic screen . With the extreme involution of the camera module industry, camera modules are not only required to meet higher camera functions, but also continue to develop in the direction of thinner and shorter, which has also become the main driving force for the evolution of camera module packaging technology and packaging materials. one.

1. Camera module SENSOR and chip introduction 1. SENSOR introduction Camera module image sensor (SENSOR) mainly refers to a method that converts external light into electrical energy, and then converts the obtained image signal into digital through the analog converter on the chip. Signal output, and then the core components of the camera module that perform a series of calculations such as light perception analysis, color restoration, and impurity removal. Currently, the CCD of Dongying and the CMOS of Laomei appear on the market.

2. Introduction of the SENSOR chip The digital signal processing chip in the image sensor of the camera module is actually the brain of the SENSOR and the camera module. Its function is mainly to perform a series of complex mathematical calculations on the digital image signal transmitted by the CMOS sensor. It is the core component of SENSOR and camera module to optimize the processing and transmit the processed signal to PC and other equipment through USB interface.

2. SENSOR chip packaging technology COB chip packaging technology (Chip on Board) is widely used in camera module chip packaging technology because of its lower operating temperature, lower cost and better reliability. COB packaging The technology is mainly to directly mount the bare chip on the printed circuit board with thermally conductive epoxy resin glue, and then bond it to the printed circuit board through a gold wire to establish an electrical connection.

3. Challenges of SENSOR chip packaging SENSOR chip packaging is an extremely important process in camera module packaging. The choice of packaging process and packaging adhesive directly affects the working quality of the chip, which in turn affects the reliability and operation stability of the camera module. In particular, high-definition pixels put forward higher requirements for camera assembly and the chips used for large-bottom, high-pixel image sensors. With the gradual upgrading of pixels, the matching degree of chips, lenses, and modules is required to be higher in the assembly process, and no slight error is allowed. At the same time, the area of chips brought by high-definition pixels is enlarged, and the photosensitive area is increased. Image sensor chips are heated during assembly. More prone to problems such as warping and deformation.
4. Requirements for SENSOR chip packaging materials With the continuous development of camera modules in the direction of thinner and shorter, the performance of camera modules is constantly breaking through limitations, but large-size image sensors often have chip warping and difficulty in matching lenses and lens barrels in traditional packaging. And so on, choosing the most suitable DA glue solution becomes the key to solve the problem. Generally, the performance requirements of DA glue are as follows.
1. Low-temperature rapid curing In traditional camera module packaging, chip packaging mainly adopts heat-baking packaging technology. As camera modules become thinner and shorter, traditional packaging technology can no longer meet the packaging requirements of sensor chips with large bottom and high-definition pixels. And effectively avoid the impact of thermal process on the overall module. Therefore, the DA glue of the camera module chip needs to control the curing temperature environment to solve the deformation problem of the chip from the source, thereby improving the reliability of the chip in the subsequent manufacturing process and the overall operation stability of the camera module.

2. During the packaging process of the low curing shrinkage camera module, the chip and the printed circuit board are pasted with DA glue (Die Attach Adhesive, chip attachment adhesive). During the assembly process, it is necessary to control chip warping and match different scenarios Lens requirements to avoid virtual focus, deformation and other undesirable phenomena. Therefore, the camera module DA adhesive needs low curing shrinkage to effectively control chip warpage and achieve perfect packaging.

3. The high thermal conductivity camera module will generate a lot of heat when it runs for a long time, especially the large-size chip will have a high fever during long-term work, so that the module under operation needs to dissipate heat and relieve the high fever. Therefore, the camera module chip DA adhesive needs to have high thermal conductivity, which can meet the heat dissipation requirements of the image processing chip, and at the same time, no particle precipitation will occur during the cleaning step of the assembly process.