Growth Control Of Full Compound Solder Joints In 3D Packages

The development of microelectronics industry depend on improvement of two factors:one is chip technology and the other is packaging technology.The development of chip technology has always followed the MOORE's law,which states that the density of2-dimensional integrated circuits on Si chip will double every 18-24 months.Over the past20 years,the amount of memory integrated on silicon chips has increased from 1 million to1billion.The feature size of 22 nanometers today is ready approaching the physical limit which has brought difficulties to package and increased costs have constrained the development of electronic industry.The microelectronics industry began to look for new packaging structures,and people began to focus on the 3D package.The 3D package brings smaller interconnect dimensions,and solder joints can be fully converted into complete compounds in a very short time?Due to the low temperature formation and high temperature load characteristics of compound solder joints,chip stacking becomes more simple and easy.This needs to understand the formation rules of compound solder joints,realize the control of the formation of compound solder joints,and provide a basis for industrial production.Based on the experiments,this article proposes a method for rapid preparation of fully compound solder joints.By controlling the temperature,current density,time parameters,and the orientation of the metal under the solder joint,the growth of the compound within the solder joint was investigated.By observing the interface reaction and morphology changes at different temperatures?250°C,280°C,310°C?.The diffusivity and diffusion activation energy of the compound?Cu6Sn5?are summarized.The growth of Cu₆Sn₅ is controlled by the diffusion of Cu,and the growth thickness of the compound is proportional to the open square of the time.When the solder joint is in a liquid state,a current density of 200 A/cm² is loaded,and the compound growth is promoted by the electromigration effect.Experiments show that:at200°C,200A/cm² current density appears as a chemical potential gradient controlled Cu diffusion growth.When the temperature is increased to 300°C and the current density is maintained at 200A/cm²,the Cu atom flux caused by electromigration is controlled to grow,showing that the solder joint exhibits a polarity effect.At 400°C.and 200 A/cm ²,the brazing material is electrified in a liquid state,and the thickness of the cathode compound appears to increase first and then decrease with time.The anode is presented as the thickness increases with time.For the controlling full compound solder joints structural,we intend to use electroplating copper film with a certain preferred orientation to control the orientation of the compound according to the phenomenon of a strong orientation relationship between Cu₆Sn₅ and the copper pad.By investigating the relationship between the current density and the copper film texture,it was found that at low current density,the copper film exhibits?110?texture;at high current density,the film exhibits?111?texture.we obtained copper films with?111?preferred orientation and?110?preferred orientation respectively,and the interface reaction and compound morphology of compound growth on copper thin films were investigated.It was found that the preferred orientation of the copper film affects the copper diffusion ability.