Solid crystal solder paste replaces silver glue into the new favorite in the field of flip-chip

[Source: Gaogong LED's "LED Good Products" March 2015 issue (Total Issue 63) Wen | Gan Qin] In recent years, flip-chip technology has attracted many companies to get involved by virtue of its high density and high current characteristics. The field. From a market perspective, flip-chips are currently an important branch of high-reliability products, occupying a certain market share in high-power packaged devices.

In the packaging process, flip chip puts higher demands on the chip and package manufacturers. First of all, due to the active layer of the chip facing down, in the process of chip preparation and packaging, if the process is improperly processed, it is easy to cause large stress damage, which requires chip splitting, sorting, crystal expansion, solid crystal, and total Crystal and other aspects are optimized to ensure a better product.

In the solid phase of the package, the flip-chip process is not ideal for the soldering effect of the chip and the substrate, and there are often problems such as non-melting tin, poor adhesion, and residual residue, and the appearance of the solid crystal solder paste may be solved. problem.

“Solid-solid solder paste has high thermal conductivity, low resistance and fast heat transfer, which can meet the heat dissipation requirements of LED chips, and the solid crystal quality is stable, and the welding mechanical strength is high, which can effectively ensure the reliability of solid crystal.” Hongli Optoelectronics Engineering Technology The director of the center, Weng Ping, said that the thermal conductivity of the die-cast solder paste can also ensure that the current or the chip or product it is in contact with will be higher.

According to the reporter's understanding, some packaging companies that are currently doing flip-chip processing have used solder paste as a solid crystal material.

As for why the die-casting paste is more used in the flip-chip process, the technical director of the morning technology, Wang Benzhi, explained that the traditional dressing chip is connected to the substrate by wire bonding, the electrical side of the chip is facing up, and the electrical face of the flip chip is facing. Next, it is equivalent to flipping the traditional wafer. “Because the electrical surface is facing down, if silver paste is used, it will cause leakage, and the solid crystal solder paste material is insulated. After the solid crystal is melted, it will not be compatible with the pad, so there will be no short circuit.”

Wang Benzhi said that the current technology of solder paste used in the flip chip process as a solid crystal material has been relatively mature. Domestic manufacturers including Guoxing Optoelectronics, Ruifeng Optoelectronics and Zhaochi have begun to use solid crystal solder paste for packaging.

However, Zhou Xiaoyang, the head of Meiya Optoelectronics Engineering Department, believes that the selection of flip chip technology, especially solid crystal materials, should be cautious. "Although many companies in the market are using solder paste reflow soldering, I think that because of the various industries The production equipment is not uniform and the chip structure is different. For the packaging enterprises, there is no real confirmation of the way to use the flip-chip technology, and the production yield needs to be improved."

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