What is the complete chip packaging process?

Chips are a very high-tech and professional field, and the entire production process is particularly complicated. Commodities on the market generally go through three stages from scratch, design, manufacture, and packaging. The chip industry is no exception. The chip production process is divided into three major components, namely design, manufacturing, and packaging, and testing. Many companies only participate in a certain part of chip manufacturing. For example, Huawei, Qualcomm, Apple, and MediaTek only design chips; TSMC, SMIC, and Huahong Semiconductor only manufacture chips, while ASE and Changjiang Electronics Technology only package and test chips. China's packaging and testing share of the global share will also jump from 22% in 2018 to 32% in 2025. The design and manufacture of chips have attracted people's attention. Today, I will introduce to you the last process of chip production-chip packaging technology in chip packaging and testing.

Package refers to the case for mounting semiconductor integrated circuit chips. Using a series of technologies, the chip is laid out on the frame, fixed and connected, and the wiring terminals are drawn out and fixed by potting and fixing with a plastic insulating medium to form an overall three-dimensional structure. This concept is a narrow definition of encapsulation. In layman's terms, it is to add a shell to the chip and fix it on the circuit board.

Packaging in a broader sense refers to packaging engineering, which connects and fixes the package body and the substrate to assemble a complete system or electronic device, and ensures the overall performance of the entire system. Combine the previous two definitions to form a broad concept of encapsulation.

Why encapsulate?

Packaging is of great significance. Obtaining an IC chip requires a long process from design to manufacturing. However, a chip is quite small and thin, and if no external protection is applied, it will be easily scratched and damaged. In addition, because the size of the chip is small, it is not easy to manually install it on the circuit board if a larger-sized housing is not used. At this time, packaging technology comes in handy.

The package has the functions of placing, fixing, sealing, protecting the chip, and enhancing the electrothermal performance. It is also a bridge between the internal world of the chip and the external circuit. The contacts on the chip are connected to the pins of the package shell with wires, and these pins pass through The wires on the printed circuit board establish connections with other devices. Therefore, packaging plays an important role in integrated circuits.

1. The role of chip packaging

1. Protection

The semiconductor chip production workshop has very strict production conditions control, constant temperature, constant humidity, strict air dust particle size control, and strict electrostatic protection measures. The bare chip is only under such strict environmental control. Will not fail. However, the surrounding environment we live in is completely impossible to have such conditions. Low temperature may be -40°C, high temperature may be 60°C, and humidity may reach 100%. If it is an automotive product, its working temperature may be as high as 120 ＾C above. At the same time, there will be various external impurities, static electricity, and other issues that will invade the fragile chip. Therefore, the packaging is needed to better protect the chip and create a good working environment for the chip.

2. Support

The support has two functions. One is to support the chip and fix the chip to facilitate the connection of the circuit. The other is to form a certain shape to support the entire device after the packaging is completed so that the entire device is not easily damaged.

3. Connect

The function of the connection is to connect the electrodes of the chip with the external circuit. The pins are used to communicate with the external circuit, and the gold wire connects the pins with the circuit of the chip. The slide table is used to carry the chip, the epoxy resin adhesive is used to stick the chip on the slide table, the pins are used to support the entire device, and the plastic package plays a role in fixing and protecting.

4. Heat dissipation

Enhancing heat dissipation is to consider that all semiconductor products will generate heat when they are working, and when the heat reaches a certain limit, it will affect the normal operation of the chip. In fact, the various materials of the package itself can take away a part of the heat. Of course, for most chips with a large amount of heat, in addition to cooling the temperature through the packaging material, it is also necessary to consider installing an additional metal heat sink or fan on the chip In order to achieve a better heat dissipation effect.

5. Reliability

Any packaging needs to form a certain degree of reliability, which is the most important measurement index in the entire packaging process. The original chip will be destroyed after leaving the specific living environment and needs to be packaged. The working life of the chip mainly depends on the choice of packaging materials and packaging processes.

Second, the type and process of packaging

There are currently thousands of independent package types and there is no unified system to identify them. Some are named after their design (DIP, flat type, etc.), some are named after their structural technology (plastic packaging, CERDIP, etc.), some are named after their volume, and others are named after their application.

Chip packaging technology has undergone several generations of changes. The technical indicators are more advanced from one generation to the next, including the ratio of chip area to package area getting closer and closer, the frequency of use is getting higher and higher, the temperature resistance performance is getting better, and the number of pins The increase, the reduction of the lead spacing, the reduction of weight, the improvement of reliability, and the more convenient use, etc., are all visible changes. This article will not do too much description here. Those who are interested can find and learn package types by themselves.

The main process of encapsulation is explained below:

The packaging process can generally be divided into two parts. The process step before plastic packaging becomes the front-end operation, and the process step after the molding becomes the back-end operation. The basic process flow includes: wafer thinning, wafer cutting, chip mounting, molding technology, flash removal, rib cutting and forming, soldering and coding, etc. The following steps are specific to each step:

1. The first paragraph:

Backgrinding: The wafer that just came out on the backside is thinned to reach the required thickness of the package. When grinding the backside, stick tape on the front side to protect the circuit area. After grinding, remove the tape.

WaferSaw: Paste the round mirror on the blue film, then cut the round mirror into individual dices, and then clean the dices.

Light inspection: check for waste

Dietrich: die-attach, silver paste curing (to prevent oxidation), wire bonding.

2. The latter part:

Injection molding: To prevent external impact, seal the product with EMC (plastic compound) and heat it to harden at the same time.

Laser typing: Engrave the corresponding content on the product. For example production date, batch, etc.

High temperature curing: protect the internal structure of the IC and eliminate internal stress.

To flash: trim the corners.

Electroplating: improve electrical conductivity and enhance weldability.

Check the scrap for slice forming.

This is the process of complete chip packaging. my country's chip packaging technology has been at the forefront of the world, which provides a good foundation for us to vigorously develop chips. In the next few years, the overall growth rate of the chip industry will remain above 30%. This is a very impressive growth rate, which means that the size of the industry will double in less than three years. Such rapid growth will benefit the three major segments of the chip industry-design, manufacturing, packaging, and testing (referred to as "P&T"). I believe that with the efforts of the Chinese people, our design and manufacturing level will one day be able to go to the world and lead the times.