The Deformation Mechanism Of The IMCs’ Growth On The Solder/Substrate Interface

Currently, the portability and the high-integrity are becoming important issues in thedevelopment of electronic devices. Electronic Packaging is also developing in the directiontoward the high density interconnect.Solder joint of Micro-connect is gradually reduced.Intermetallic compound as a connection is used as an intermediate function between solderand substrate The poor heat dissipation of High density packaging would lead to increasingVolume ratio of the whole Intermetallic compound in the whole Encapsulation solderjoints.So it is urgent to solve the deformation mechanism of the IMCs’ growth on thesolder/substrate interface.Adding the element of Zinc into the solder and copper substrate, With the increase ofZinc element content in the solder, Wettability of solder on the copper substrate will becomeworse, When the content is0.8%, the solder in the substrate is almost no wetting,If Addingthe element of Zinc into the copper substrate have little Impacting on the wettability, Butwhen the high zinc element content in the copper substrate will also Suppress wettingspreading.In Sn-Cu binary thermodynamic calculations, The formation of Cu6Sn5needs lessGibbs free energy than Cu3Sn in the initial stages of Soldering. Therefore, Cu6Sn5is the firststable phase precipitation to separate out. In the Sn-Zn-Cu ternary system, When the zinccontent in the solder is less than0.7%, as the content is lower, The driving force of Cu6Sn5becomes larger with the first formation of stable phase. But if the zinc content higher than0.7%, Cu5Zn8will stay positive, the formation of phase driving force is always above theCu6Sn5, Become a priority generating phase. After several days’ aging of Sn-XZn/Cu andSn/Cu-XZn,IMC of Sn-0.8Zn/Cu needs largest growth activation energy, The thickness ofthe IMC is the thinnest, IMC of Sn/Cu needs least growth activation energy. When the Zn isadded to the substrate from the solder,IMC of Sn/Cu-2.27Zn needs larger growth activationenergy than IMC of Sn/Cu,but clearly Less than IMC of Sn-0.5Zn/Cu. IMC growthactivation energy of Sn/Cu-4.87Zn is between Sn-0.5Zn/Cu and Sn-0.8Zn/Cu.Sn-3.0Ag-0.5Cu/Cu soldering joints is studied under different strain rate and differentcombination morphology by the finite element method, In the layered combinationmorphology. The thickness of IMC is10μm,under0.01s-1strain rate, when the thickness ofthe solder is increasing from30μm to80μm, Fracture mode of solder joints will changefrom mixed fracture to brittle fracture, While the strain rate is1s-1or30s-1, the fracturemode of solder joints are all of ductile fracture, and when combined morphology ofsolder/IMC interface is from layer into scallop shape,in three different strain rates, fracture mode is All plastic fracture. We consider that there exists some connection between Serratedflow behavior in low loading rate and shear band, and each shear band is not correspondingto single pop-in event but to multiple pop-in events.