Fabrication Of High Temperature Solder Based On Cu@Sn Core Shell Structured Powder And The Study Of Cu-Sn IMCs Growth On Curved Surface

With the development of electronics industry toward miniaturization and multi-functionalization,the power density of microelectronic devices is increased dramatically,which results in high current frequency and a significant amount of heat release.As a result,the maximum working temperature of solder joint interconnections needs to be improved.Most chips in microelectronic devices are made of silicon(Si)that can't maintain high working stability above 150 ?.Recently,silicon carbide(Si C)and gallium nitride(Ga N)known as wide band gap,high saturated electron driftvelocity,large critical breakdown strength and high thermal conductivity become the most promising materials for power semiconductor devices.The most important is that Si C can maintain good performance above 600 ?.So there is an urgent demand for die attach material in the field of power device packaging which can make the most of the excellent properties of the wide bandgap semiconductors.Cu@Sn core-shell powder is a new high temperature filler,meeting the demands of low-temperature reflow and high-temperature operation.This paper first to optimize the preparation processing of Cu@Sn core-shell powder,made a detailed experimental study of essential parameters in electroless plating,then summarized the relationship between process parameters and particle size to meet the requirements of electroless plating for different size Cu particles.In comparison with TLP soldering,Cu@Sn core-shell powder soldering has two advantages in Cu-Sn reaction area and Cu diffusion source,which confirmed by theoretical calculation and experiment data.The vast reaction area and more diffusion sources make Cu@Sn core-shell powder soldering have a shorter reflow time.It helps for the protection of die attachment process.Through the research of morphology and mechanical properties of different Cu@Sn core-shell powder bondlines during different reflow time,the relationship between Cu@Sn core-shell powder size and shear strength of bondlines has been discovered.Thevolume change of Cu-Sn IMCs in reflow soldering has been confirmed by theoretical calculation and experimental results which led to the failure of bondlines.The Cu@Sn core-shell powder solder paste has been fabricated,and the properties have been tested in the last chapter of this paper.This newly solder paste has the advantage to adjust weld thickness flexibly that contributed to meeting the requirements of realistic production.