Due to the susceptibility of micro nano devices to external environmental damage such as moisture, dust, mechanical vibrations, etc., it is necessary to package the chip in order to provide connectivity and heat dissipation functions, and protect the chip from external factors

Adhesive bonding refers to firmly connecting a chip to a selected packaging structure, ensuring normal operation in terms of electrical connections, heat dissipation, and mechanical support.

After the bonding is completed, it is necessary to use metal wires to connect the reserved pads on the chip to the circuit board, providing input and output of electrical signals for the chip. This step is called wire bonding or pressure bonding. Leads are an important factor affecting the reliability and stability of devices, and suitable metal wires should have stable chemical properties, good conductivity and conductivity, and strong bonding strength. The commonly used lead materials are gold and aluminum.

An important method to improve the stability of pressure welding process is to use plasma cleaning. While cleaning and removing dirt, it can also change the surface properties of the material itself, such as improving the wetting performance of the surface, improving the adhesion between different materials, etc., making the bonding surface more firm.

Due to the susceptibility of micro nano devices to external environmental damage such as moisture, dust, mechanical vibration, etc., it is necessary to package the chip in order to provide connection and heat dissipation functions, and protect the chip from external factors. The process flow is as follows:

Packaging process flow

Figure 1 Packaging Process Flow

Adhesive bonding refers to firmly connecting a chip to a selected packaging structure, ensuring normal operation in terms of electrical connections, heat dissipation, and mechanical support.

After the bonding is completed, it is necessary to use metal wires to connect the reserved pads on the chip to the circuit board, providing input and output of electrical signals for the chip. This step is called wire bonding or pressure bonding. Leads are an important factor affecting the reliability and stability of devices, and suitable metal wires should have stable chemical properties, good conductivity and conductivity, and strong bonding strength. The commonly used lead materials are gold and aluminum.

An important method to improve the stability of pressure welding process is to use plasma cleaning. While cleaning and removing dirt, it can also change the surface properties of the material itself, such as improving the wetting performance of the surface, improving the adhesion between different materials, etc., making the bonding surface more firm.

Plasma cleaning

(1) Plasma cleaning effect

Plasma is an ionized gas with roughly the same density of positive ions and electrons. A plasma cleaning machine ionizes argon gas, and the generated plasma is accelerated by an electromagnetic field, hitting the surface of the silver plating layer and the aluminum pad of the chip. It can effectively remove organic matter, epoxy resin, oxides, micro particles and other contaminants on the surface of the silver plating layer and the aluminum pad, effectively improving the activity of the surface of the silver plating layer and the aluminum pad, thus facilitating the bonding of pressure welding.

(2) Plasma cleaning method

Using a mixture of Ar and H2 gas for plasma cleaning of the surface of the lead frame can effectively remove impurities and oxide layers on the surface, thereby improving the activity of silver and copper atoms, significantly enhancing the bonding strength between the solder wire and the lead frame, and improving product yield. In practical production, plasma cleaning has become a necessary process for copper wire technology.

(3) Verify the impact of plasma cleaning on the pressure welding process

As shown in Table 1, under the same process conditions, one group did not undergo plasma cleaning after core solidification, while the other group underwent plasma cleaning using a mixture of Ar and H2 gas after core solidification. After the wire bonding is completed, two sets of samples are subjected to push ball value measurement, and a set of comparative data is obtained.

Table 1 Effect of plasma cleaning on push ball value

The measurement results in Table 1 show that plasma cleaning has a significant impact on improving the push ball value of solder joints, with a value increase of about 10% compared to the unwashed group. The test conclusion indicates that plasma cleaning can effectively improve bonding quality and increase packaging yield.