Effect Of Micron-sized Zn Particles On Cu/Al(Cu) Joints Adding SAC0307 Powders With Solid-state Interconnection By Ultrasound-assisted And Its Thermal Reliability

With the development of electronic products towards integration and high density.Aluminum alloys was used to replace copper because its inherent excellent performance and price advantage.Therefore,it was imperative to accomplish low-temperature and high quality interconnection of Cu/Al in the field of electronic encapsulation.In this paper,SAC0307 powders with No.4 and Zn particles with 1?m diameter(contents are 0%,10%,20%,30%,40%,50%)were mixed to fill the Cu/Al(Cu)joints with ultrasound-assisted under 180?to 210?.The studied thermal reliability of homogeneous and heterogeneous soldering joints at 75?,100?,125?and 150?,the conclusion was shown as:(1)Sn-Zn solid solution was formed by adding Zn particles into SAC powder and ultrasound-assisted at low temperature,which could accomplished the interconnection between the SAC0307 powders.The Cu₅Zn₈ intermetallic compound(IMC)was formed at the interface between the solder and Cu,which could accomplish realize the solder/Cu solid interconnection.With the increase of Zn content,IMC was transformed from Cu₆Sn₅ to Cu₅Zn₈ and gradually thickened.When the content of Zn was 40%,the shear strength reached the maximum of 29.76 MPa because continuous and stable solid solution could be formed around the SAC0307 powders and Zn particles,which was 62.6%higher than that of 0%Zn.(2)The shear strength of Cu/SAC0307+40%Zn/Cu joints at 125?and below had little change and the reliability of the joints was good with the extension of aging time.When the aging temperature reached 150?,the shear strength of the joints decreased as an inverse proportional function,and the shear strength decreases by 39.4%at 24h.The thickness of IMC at the upper/lower interface did not fluctuate much at 75?with the aging time.At100?,125?and 150?for 24h,the thickness of the upper/lower interface IMC increased by 35.5%and 94.8%,199.0%and 300.5%,404.7%and 505.5%,respectively.With the increase of aging temperature and time,the fracture changed from ductile fracture to ductile-brittle mixed fracture.(3)The IMC of Cu interface was Cu₅Zn₈ when the soldering temperature of Cu/Al joint was 180?.When the soldering temperature was 190?,200?,210?,the Cu interface IMC had two layers,was Cu₅Zn₈ and CuZn₅.The Cu interface IMC had two layers of Cu₅Zn₈ and CuZn₅ when the soldering temperature is 190?,200?and 210?.Brittle fracture occured on the Al side because no solid solution or solid solution discontinuity was formed on the Al side at 180?.The fracture occurred ductile fracture in the Zn layer with partial tearing of the Zn-Al solid solution because the formation of obvious Zn-Al solid solution on the Al side at 190-210?.The shear strength of the joint reached the maximum 38.07MPa at 200?,which was 153.6%higher than that at 180?.(4)With the increased of aging time,the thickness of CuZn₅ at the Cu interface of the Cu/Al joints gradually decreased to completely disappeared,while the thickness of Cu₅Zn₈increased gradually.The solid solubility of Zn in the Al interface of Cu/Al joints was increasing,and the bonding of Sn-Zn layer was strong.Fracture between Zn particles and Zn particles was easy to occur in Cu/Al joint,because the oxidation degree of Zn particles increased and the space between Zn particles and Zn particles increased.The shear strength of the joints has fluctuates little at 75?.When the aging temperature was 100?,125?and150?,the shear strength of the joints decreased rapidly with the increased of aging time and aging temperature.After aging for 24h,the shear strength of the joints was 20.63MPa,11.37MPa and 6.41MPa,respectively.It decreased by 45.8%,70.1%and 83.2%compared with non-aging joints,respectively.