Papers by Keyword: Electromigration

Abstract: The effect of electrolytic Ni plating on the Cu electrode on electromigration in the Sn-3.0Ag-0.5Cu (mass%) solder joint was investigated. The energization test was conducted using Ni-plated Cu/Sn-3.0Ag-0.5Cu/Ni-plated Cu joints. For comparison, the same test was done using joints without Ni plating. The scalloped Cu₆Sn₅ layer formed at the joint interface without Ni plating. In the joint with Ni plating, granular (Cu,Ni)₆Sn₅ and (Ni,Cu)₃Sn₄ formed at the joint interface on the solder side and on the Ni side, respectively. Crack propagation was observed on the cathode side in both joints by current load. Crack propagated at the Cu₆Sn₅/solder interface in the joint without Ni plating and at the (Cu,Ni)₆Sn₅/solder interface in the joint with Ni plating, respectively. The Ni plated layer inhibited the diffusion of Cu facilitated by current load so that the growth of the reaction layer on the anode side was also inhibited. Therefore, the Ni plating is expected to improve the EM life.

Abstract: In this paper, the effect of thermal aging to the Sn-Zn and Sn-Zn-Bi solders on Cu substrate was studied. Sn-Zn was chosen and the effect of addition of Bi was investigated in this work. In this research, Sn-9Zn and Sn-6Zn-4Bi were subjected to thermal aging for 24h, 72h, 120h at 75°C and 100°C respectively. Both solder shown increased of thickness intermetallic layer with increasing time. However, Sn-9Zn recorded higher increment of intermetallic layer compared to Sn-6Zn-4Bi. The hardness of solder joint on Cu substrate was decreased for both solders with increasing aging time.

Abstract: This paper aims at investigation of possibilities and effectiveness of chloride extraction from concrete and nanoparticle injection into existing reinforced concrete structures by means of electromigration technique. Concrete specimens are exposed to accelerated chloride penetration tests in order to simulate a natural chloride exposure. The developed chloride profile is removed by electroextraction by reversing the polarity in the testing chamber. In a similar manner, concrete specimens are injected with different concentrations of colloidal nanosilica particles. It was shown in the paper that chlorides can be effectively extracted from the concrete using small voltage lasting for several days. Higher concentration solutions of nanosilica can also be effectively transported into concrete via the electric field. Once injected nanosilica can act as microstructure densifier and further reduce chloride penetration as demonstrated by decreased diffusivity of the treated concrete.

Abstract: The interface microstructure and shear strength weakening of eutectic SnAgCu (SAC)/FeNi-Cu connection after current stressing for 0~12 h were investigated to discuss the stability of the FeNi layer as UBM film layer for Sn base solder. The experiments showed that the FeNi layer separated to two layers with different Fe/Ni ratio rather than intermetallic compound (IMC) thickness variation between the cathode and anode. The IMCs became rougher with a bulk amount of (Cu,Ni)₆Sn₅ emerging in the regains near to interfaces. The shear failure mode exhibited a ductile manner companied by a fracture surface rougher and even grain boundary weakening with the current exposure time increasing.

Abstract: Electromigration (EM) is the phenomenon of atomic diffusion in a metallic film with a high-density electron flow. Our group used EM to fabricate Al micro-materials. The EM technique can be used to fabricate micro-materials with a high aspect ratio, pure metal components, an arbitrary form, and a single-crystal structure. Recently, two micro-materials have been simultaneously fabricated using an array pattern consisting of parallel or series connections. However, multiple micro-materials have not been fabricated simultaneously thus far. In this study, a new comb sample pattern was used with a conductive passivation film to produce multiple Al micro-materials.

Abstract: The technique for fabricating Al micro-materials using a conductive passivation film by electromigration (EM), which is the physical phenomenon of atomic transport with high-density electron flow, has been reported. Conductive passivation film precludes the unplanned hillock formation and substantially simplifies the sample preparation time for fabricating Al micro-materials by EM. To date, TiN that is electrical conductive material has been used as a passivation film. However, the TiN passivation oxidizes during heat and current test for fabricating Al micro-materials by EM because of inherent poor oxidation resistance of TiN. Oxidation of passivation causes a problem that applying current occasionally becomes difficult. The present paper proposes a new conductive passivation made of CrN for fabricating Al micro-materials by EM. CrN is used as a countermeasure against the oxidation problem. Additionally, the growth of Al micro-materials by EM is investigated in the relation with the experimental conditions of current and substrate temperature. As a result, we report that the fabrication of Al micro-materials using the CrN passivation is successfully demonstrated in the relation with the experimental conditions.

Abstract: This work presents the studies of wettability Sn-6Zn-4Bi lead-free solder alloy in electronic applications. A reference solder Sn-3.1Ag-0.9 Cu lead-free solder alloy is used to compare the properties of both solders. Differential Scanning Calorimeter (DSC) profile, wettability and the microstructure of the solder were investigated. The melting temperature of Sn-Zn-Bi (Tm=194.97°C) is lower than Sn-Ag-Cu (Tm=220.40°C). Further, the wettability between molten solder and copper substrate was measured at different reflow temperature. The contact angle for Sn-Ag-Cu was decreasing from 28.23º to 24.97º and for Sn-Zn-Bi solder alloys were decreasing from 48.92º to 29.78º as the temperature increased from 230°C to 250°C. A significant increment of contact angle for Sn-Zn-Bi at 270°C and the contact angle did not change at 270°C for Sn-Ag-Cu. The result of spreading area is inversed with the contact angle. The layers of intermetallic compound were examined by energy-dispersive X-ray. The Sn-Zn-Bi solder exhibits a mixture of Cu-Sn+Cu-Zn phase and ϒ-Cu₅Zn₈ phase. The Sn-Ag-Cu solder exhibits Cu6Sn5 (η-phase) and Cu3Sn (ε-phase). As a conclusion, Sn-Zn-Bi is a potential lead-free solder to develop based on its wettability properties than previous available solder materials.

Abstract: This paper investigates the electromigration (EM) induced void and hillock generation in IC interconnect structures. The driving force for electromigration induced failure considered here includes the electron wind force, stress gradient, temperature gradient, as well as the atomic density gradient, which were neglected in many of the existing studies on eletromigration. The comparison of void/hillock formation and the time to failure (TTF) life through numerical example of the SWEAT structure with the measurement results are studied and discussed.

Abstract: 4H-SiC crystallization from Si-C solution in electric current-controlled liquid phase epitaxy was investigated. The dependence of growth speed on a DC current shows that dissolution/growth is controlled by the electric current without altering temperature gradient in the furnace. Application of an electric current leads to reduction of growth speed with negative polarity and enhancement of growth speed with positive polarity. The variation of the growth speed with a DC current density has been explained by the combination of the effects of electromigration of C solute and Joule heating.

Abstract: Fabrication techniques for Metal-molecule-metal junction electrodes suitable to study electron tunneling through metal junctions are reviewed. The applications of current technologies such as mechanical break junction, electromigration, shadow mask lithography, focused ion beam deposition, chemical and electrochemical plating, electron-beam lithography, in fabricating vacant junction electrodes are briefly described. For biomolecular sensing applications, the size of the junction electrodes must be small enough to allow the biomolecule inserted into the junction space to connect both leads to keep the molecules in a relaxed and undistorted state. A significant advantage of using Metal-molecule-metal junction electrodes devices is that the junction can be characterized with and without the molecule in place. Any electrical artifacts introduced by the electrode fabrication process are more easily deconvoluted from the intrinsic properties of the molecule.