With the development of hybrid integrated circuits in the direction of high performance, high density, high reliability, miniaturization and low cost, higher requirements are put forward for the packaging and welding process of chips. There are two methods of conductive adhesive bonding and eutectic welding. Today we mainly study the eutectic welding process.
01 What is a eutectic? Advantages of eutectic
Eutectic welding is an important method in microelectronics assembly, also known as low melting point alloy welding. A eutectic alloy sheet (eutectic solder) is placed between the chip and the carrier, heated to the eutectic point of the alloy in a certain protective atmosphere to melt it, and filled between the die and the carrier, while the back of the die and the surface of the carrier A small amount of gold will enter the molten solder, and after cooling, an interatomic bond between the alloy solder and the gold layer will be formed, thereby completing the welding of the chip to the case or other circuit carriers.
Eutectic welding has the advantages of low connection resistance, high heat transfer efficiency, uniform heat dissipation, high welding strength, and good process consistency, and has gradually become one of the mainstream methods of semiconductor packaging welding.
02 Factors Affecting Eutectic Quality and Solutions
During the eutectic process, the wettability of the solder and the amount of applied pressure affect the soldering quality, resulting in problems such as excessive void ratio and chip cracking, which lead to the failure of the eutectic.
The void ratio after eutectic is an important detection index, and how to reduce the void ratio is the key technology of eutectic.
The main methods for eliminating voids are:
(1) Before eutectic, microwave PLASMA can be used to clean the surface of the substrate and the solder to increase the wettability of the solder;
For the cleaning scheme of substrate and solder, it is recommended to use Shengding's microwave PLASMA cleaning machine, which can be directly imported into microwave PLASMA cleaning in the existing process, which is simple and convenient, and can quickly improve the yield.
(2) When eutectic, place a pressure device on the device to directly apply positive pressure;
The setting of eutectic pressure parameters requires many experiments to obtain appropriate values. Too large or too small pressure is not conducive to process control and welding reliability.
03 Sindin microwave PLASMA cleaning solution
Sindin microwave PLASMA product advantages
? The plasma is not charged and does not damage precision components
? Keep the temperature low during the process
? Fast response and short response time
? No electrode, no pollution source, long life
? Ability to maintain plasma at high pressure
? Has a high degree of ionization and decomposition
? Microwave junction and magnetic circuit are compatible
? Low self-bias requirement
? The microwave generator is stable and easy to control
? High voltage source and generator are isolated from each other, safe
Sindin's microwave PLASMA cleaning machine adopts self-developed microwave plasma generator, which is highly efficient and uniform, and can completely remove impurities on the substrate and oxide film on the solder, thereby reducing the generation of eutectic voids and improving the reliability and yield of the eutectic.
After understanding the core technology of Sindin microwave PLASMA cleaning machine, are you more interested?
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