After the chip is completed, we still need to make a device to truly understand the performance of the chip and face the problem of how to weld the electrical performance chip. The welding of the chip and the packaging body refers to the solid formation, conduction or insulation connection method between the semiconductor chip and the carrier (packaging shell or substrate). In addition to providing mechanical and electrical connections for equipment, the welding layer also needs to provide a good heat dissipation channel for the equipment.

The welding method of the chip BA3884S conductive electricity is as follows:

1) Use conductive glue, that is, glue can conduct electricity, and metal is added to the polymer. The bonding and curing can be used, but thermal conductivity and conductivity are average.

2) Common crystal welding

Common crystal welding is a very interesting phenomenon that can welded two different metals at low temperatures.

Also known as low melting point alloy welding. The basic characteristic of common crystal alloys is that two different metals can form a certain percentage of alloys at a far lower melting point temperature. The most commonly used common crystal welding in microelectronics equipment is to weld the silicon chip to the gold-plated base or wire framework, that is, "gold-silicon co-crystal welding". As we all know, the gold melting point is 1063 ° C, and the melting point of silicon is higher, which is 1414 ° C. However, if the gold combination of silicon with a weight ratio of 2.85%and 97.15%can form a 363 melting point ℃ common crystal alloy body. This is the theoretical basis of gold silicon co -welding.

The metal type of common crystal welding has a great impact on connection. At present, the main alloys of Gongjing welding are AUGE, AUSN, AUSI, Snin, SNAG, etc. It can be achieved through vacuum/controllable atmosphere. It has a thermal conductivity, small resistance, fast heat transfer, strong reliability, and large shear force after bonding. It is suitable for welding in high -frequency, chip and substrates in high -power devices. For power devices with high heat dissipation requirements, common crystal welding must be used.

There are generally the following common crystal processes in the industry:

;

(2) Ultrasonic thermal pressure welding process adopts golden ball key;

(3) Jinxihe alloy co -crystal backstalling welding process.

Common crystal reflux welding is mainly aimed at the common crystal reflux welding PBSN, pure SN, and SNAG waiting for welding metal materials. The characteristics of these metals are relatively low flow temperature. This method is characterized by simple craftsmanship, low cost, but low return temperature, which is not conducive to secondary return.

The common crystal refurbishment process of Jinxin alloy is 280 gold tin alloy (20%tin) ℃. The above temperature is liquid. When the temperature drops slowly, a common reaction occurs, forming a good connection. The advantage of the co -crystal of Jinxi is that its common crystal temperature is higher than the second return temperature, generally 290 ~ 310 ° C. The entire alloy return time is short. It can form a firm connection within a few minutes. Silver can be combined well.

Vacuum return welding furnace

1. The vacuum return furnace can provide low oxygen concentration and proper restoration atmosphere, greatly reducing the oxidation level of the weld;

2. Due to the decrease in the degree of weld oxidation, the gas of the oxide and the reaction of the welds is greatly reduced, thereby reducing the possibility of the cavity;

3. Vacuum can make melting welds have better liquidity and smaller flow resistance. Therefore, the bubble buoyant in the melting weld is far greater than the flow resistance of the solder.

4. Due to the pressure difference between the bubbles and the external vacuum environment, the buoyancy of the bubbles will be very large, making the bubbles easily get rid of the restrictions of the melting welded. After the vacuum reflux welding, the reduction rate of the bubbles can reach 99%, the hollow rate of a single solder joint can be less than 1%, and the empty hole rate of the entire board can be less than 5%. On the one hand, it can enhance the reliability and combined intensity of the solder joints, enhance the wetting performance of the solder joints, and on the other hand, it can reduce the use of the welding paste during use, and improve the requirements of the welding joints to adapt to different environments, especially high temperatures, high humidity, and humidity. Low temperature and high humidity environment.