With the increasing number of packaged devices such as Flip-Chip and BGA, the number of spherical pins of this type of device has increased, forcing the size of the solder joints for circuit interconnection to shrink, although the size of the electronic products we produce is getting smaller and smaller, The weight is getting lighter and lighter, but the connection strength between the device and the printed circuit board and the insulation between the pins are becoming more and more fragile. Therefore, potting or filling the bottom of the BGA packaged device with glue is necessary for the long-term reliability of flip-chip assembly. The potting or filling at the bottom of the device can reduce the stress of the solder joints, evenly disperse the stress on the packaging surface of the flip chip, and at the same time can increase the mechanical and electrical insulation strength of the device.

In the current information age, with the rapid development of the electronics industry, products such as computers and mobile phones have become increasingly popular. People have more and more functional requirements and stronger performance requirements for electronic products, but the volume requirements are getting smaller and the weight requirements are getting lighter and lighter. This promotes the development of electronic products in the direction of multi-function, high performance, miniaturization and light weight. In order to achieve this goal, the feature size of IC chips will become smaller and smaller, and the complexity will continue to increase. Therefore, the number of I/Os in the circuit will increase, and the density of packaged I/Os will continue to increase. In order to meet the requirements of this development, some advanced high-density packaging technologies have emerged, and BGA packaging technology is one of them. The development trend of integrated circuit packaging is shown in the figure. It can be seen from the figure that the current BGA packaging technology occupies a major position in small, light and high-performance packaging.

 

 

 

    BGA packaging appeared in the early 1990s and has now developed into a mature high-density packaging technology. Among all packaging types of semiconductor ICs, BGA packaging has the fastest growth rate during the five-year period from 1996 to 2001. In 1999, the output of BGA was about 1 billion, and it is expected to reach more than 8 billion in 2008. However, so far this technology is limited to the packaging of high-density, high-performance devices, and the technology is still developing in the direction of fine pitch and high I/O terminal count. BGA packaging technology is mainly applicable to the packaging of devices such as PC chipsets, microprocessors/controllers, ASICs, gate arrays, memories, DSPs, PDAs, and PLDs.

    Although the BGA package has good performance and near-ideal packaging density, there are still a series of problems that have not been well solved for a long time, such as the fragility of the chip solder ball and pad connection after the chip is mounted, and the solder joint stress. , Mechanical strength, moisture resistance, repair and other issues.

 

 

 

    In the 1980s, IBM invented the underfill technology, which used underfill to fill the gap between the chip and the substrate, thereby greatly increasing the thermal fatigue solder joint life caused by the mismatch of the expansion coefficient of the chip and the substrate. Therefore, this article draws on the idea of ​​chip underfilling technology, and proposes that after the BGA device is mounted, the bottom of the BGA should be filled with glue to improve the vulnerability of solder balls and pad connections and solder joints in the chip after the chip is mounted. Problems such as stress, mechanical strength, moisture resistance, repairing, etc. Below we explain the application of the potting process in the bottom potting of BGA devices from several aspects such as the characteristics of the BGA package, the structure type of the BGA package, the characteristics and requirements of the bottom potting material, and how to perform the bottom potting.