Effects of crystallographic orientation of Sn on electromigration behavior

2010 ◽  
Vol 2010 (1) ◽  
pp. 000792-000797 ◽  
Author(s):  
Kiju Lee ◽  
Keun-Soo Kim ◽  
Kimihiro Yamanaka ◽  
Yutaka Tsukada ◽  
Soichi Kuritani ◽  
...  
Keyword(s):  
Crystallographic Orientation ◽  
Flip Chip ◽  
Current Flow ◽  
Electron Flow ◽  
Test Sample ◽  
Microstructural Change ◽  
Cathode Side ◽  
Fast Diffusion ◽  
Applied Current ◽  
Current Stressing

Electromigration behavior of SAC flip-chip joints with respect to the crystallographic orientation of Sn grains was investigated. The test sample had direct contact of Sn-3.0wt% Ag-0.5wt% Cu on Cu-OSP (organic surface preservative) and the applied current density was 15 kA/cm2 at 160 °C. Without current stressing, no microstructural change depending on the crystallographic orientation of Sn was observed. With current stressing, however, the bumps showed the substantial microstructural changes with respect to the crystallographic orientation of Sn. When the orientation of the current flow was parallel to the c-axis, fast failure of the bumps occurred due to the massive dissolution of the Cu electrode on the cathode side caused by the fast diffusion of Cu atoms along the c-axis of Sn grains while only a slight microstructural change was observed when the c-axis of Sn grains was perpendicular to the electron flow.

Effect of electromigration on mechanical shear behavior of flip chip solder joints

2006 ◽  
Vol 21 (3) ◽  
pp. 698-702 ◽  
Author(s):  
Jae-Woong Nah ◽  
Fei Ren ◽  
Kyung-Wook Paik ◽  
K.N. Tu
Keyword(s):  
Flip Chip ◽  
Shear Failure ◽  
Solder Joints ◽  
Electron Flow ◽  
Shear Behavior ◽  
Cathode Side ◽  
Current Stressing ◽  
Large Growth ◽  
Electroless Ni ◽  
Solder Interface

Effect of electromigration on mechanical shear behavior of flip chip solder joints consisting of 97Pb3Sn and 37Pb63Sn composite solder joints was studied. The under bump metallurgy (UBM) on the chip side was TiW/Cu/electroplated Cu, and the bond pad on the board side was electroless Ni/Au. It was found that the mode of shear failure has changed after electromigration and the mode depends on the direction of electron flow during electromigration. The shear induced fracture occurs in the bulkof 97Pb3Sn solder without current stressing, however, after 10 h current stressing at 2.55 × 104 A/cm2 at 140 °C, it occurs alternately at the cathode interfaces between solder and intermetallic compounds (IMCs). In the downward electron flow, from the chip to substrate, the failure site was at the Cu–Sn IMC/solder interface near the Si chip. However, in the upward electron flow, from the substrate to chip, failure occurred at the Ni–Sn IMC/solder interface near the substrate. The failure mode has a strong correlation to microstructural change in the solder joint. During the electromigration, while Pb atoms moved to the anode side in the same direction as with the electron flow, Sn atoms diffused to the cathode side, opposite the electron flow. In addition, electromigration dissolves and drives Cu or Ni atoms from UBM or bond pad at the cathode side into the solder. These reactions resulted in the large growth of Sn-based IMC at the cathode sides. Therefore, mechanical shear failure occurs predominantly at the cathode interface.

Electro-migration Behavior in Micro-joints of Sn-57Bi solder and Cu Post Bumps

2011 ◽  
Vol 2011 (1) ◽  
pp. 000997-001006 ◽  
Author(s):  
Kei Murayama ◽  
Taiji Sakai ◽  
Nobuaki Imaizumi ◽  
Mitsutoshi Higashi
Keyword(s):  
Low Temperature ◽  
Flip Chip ◽  
High Reliability ◽  
Electron Flow ◽  
Organic Substrate ◽  
Cathode Side ◽  
Migration Behavior ◽  
Low Temperature Bonding ◽  
Electroless Ni ◽  
Interconnect Resistance

The bonding technique for high density Flip Chip(F.C.) packages requires a low temperature and a low stress process to achieve high reliability of the micro joining. Sn-Bi solder has been noted as a low temperature bonding material. Electromigration behavior of Sn-57wt%Bi flip chip interconnection with Cu post bumps was investigated. The flip chip bumps used for this experiments consisted of Cu post formed with plating and Sn-57wt%Bi solder. Two types of under bump metal(UBM) of organic substrate were studied, that is, electroless Ni(6μm)/Au(0.5μm) on Cu pad and Cu pad. Electron flow to induce the electro-migration was from organic substrate side (Cu pad) to chip side (Cu post) with current density of 40000A/cm2 at 125 degree C. At both types of the UBM, Bi migrated and accumulated to the anode side (Cu post) and Sn migrated to the cathode side (substrate pad). Each interconnect resistance has increased to about 25% and 46% within 100 hours, respectively. However, after more than 3000 hours, they were stabilized. With Ni/Au UBM pad, Cu3Sn/Cu6Sn5 intermetallic compounds (IMCs) were formed at the Cu bump side. And under the Bi layer Cu6Sn5/Ni-Sn compounds were formed. But we didn’t observe the failure like cracks or voids at the Ni layer. With Cu pad, only Cu3Sn IMC at the Cu bump side and under the Bi layer Cu6Sn5/Cu3Sn compounds were formed after 4000 hours. Although the voids were observed at Cu3Sn/Cu interface, good electrical connection was obtained.

scholarly journals The In-Situ Observation of Grain Rotation and Microstructure Evolution Induced by Electromigration in Sn-3.0Ag-0.5Cu Solder Joints

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5497
Author(s):  
Xing Fu ◽  
Min Liu ◽  
KeXin Xu ◽  
Si Chen ◽  
YiJun Shi ◽  
...  
Keyword(s):  
Solder Joints ◽  
Flow Direction ◽  
Electron Flow ◽  
Critical Role ◽  
In Situ Observation ◽  
Fast Diffusion ◽  
Electron Backscattered Diffraction ◽  
Grain Rotation ◽  
Current Stressing

The in-situ observation of Sn-3.0Ag-0.5Cu solder joints under electromigration was conducted to investigate the microstructure and grain orientation evolution. It was observed that there was a grain rotation phenomenon during current stressing by in-situ electron backscattered diffraction (EBSD). The rotation angle was calculated, which indicated that the grain reorientation led to the decrease of the resistance of solder joints. On the other hand, the orientation of β-Sn played a critical role in determining the migration of Cu atoms in solder joints under current stressing migration. When the angle between the electron flow direction and the c-axis of Sn (defined as α) was close to 0°, massive Cu6Sn5 intermetallic compounds were observed in the solder bulk; however, when α was close to 90°, the migration of the intermetallic compound (IMC) was blocked but many Sn hillocks grew in the anode. Moreover, the low angle boundaries were the fast diffusion channel of Cu atoms while the high grain boundaries in the range of 55°–65° were not favorable to the fast diffusion of Cu atoms.

Damages and Microstructural Variation of High-lead and Eutectic SnPb Composite Flip Chip Solder Bumps Induced by Electromigration

2005 ◽  
Vol 20 (8) ◽  
pp. 2184-2193 ◽  
Author(s):  
Yeh-Hsiu Liu ◽  
Kwang-Lung Lin
Keyword(s):  
Flip Chip ◽  
Solder Bump ◽  
Electron Flow ◽  
Electron Probe Microanalyzer ◽  
Current Stressing ◽  
Solder Bumps ◽  
Underbump Metallization ◽  
Current Polarity ◽  
High Lead ◽  
Eutectic Snpb

The electromigration behavior of the high-lead and eutectic SnPb composite solder bumps was investigated at 150 °C with 5 × 103 A/cm2 current stressing for up to 1711 h. The diameter of the bumps was about 125 μm. The underbump metallization (UBM) on the chip side was sputtered Al/Ni(V)/Cu thin films, and the Cu pad on the board side was plated with electroless Ni/Au. It was observed that damages occurred in the joints in a downward electron flow (from chip side to the substrate side), while those joints having the opposite current polarity showed only minor changes. In the case of downward electron flow, electromigration damages were observed in the UBM and solder bumps. The vanadium in Ni(V) layer was broken under current stressing of 1711 h while it was still intact after current stressing of 1000 h. The electron probe microanalyzer (EPMA) elemental mapping clearly shows that the Al atoms in the trace migrated through the UBM into the solder bump during current stressing. Voids were found in the solder bump near the UBM/solder interface. The Sn-rich phases of the solder bumps showed gradual streaking and reorientation upon current stressing. This resulted in the formation of uniaxial Sn-rich phases in the middle of the solder bump, while the columnar and fibrous Sn-rich phases were formed in the surrounding regions. The formation mechanism of electromigration-induced damage to the UBM structure and solder bump were discussed.

Precise Chip Joint Method with Sub-micron Au Particle for High-density SiC Power Module Operating at High Temperature

2013 ◽  
Vol 2013 (HITEN) ◽  
pp. 000254-000259 ◽  
Author(s):  
Fumiki Kato ◽  
Fengqun Lang ◽  
Simanjorang Rejeki ◽  
Hiroshi Nakagawa ◽  
Hiroshi Yamaguchi ◽  
...  
Keyword(s):  
Shear Strength ◽  
High Temperature ◽  
Flip Chip ◽  
Stress Test ◽  
High Density ◽  
Cathode Side ◽  
Module Structure ◽  
Power Devices ◽  
Power Module ◽  
Joint Method

In this work, a novel precise chip joint method using sub-micron Au particle for high-density silicon carbide (SiC) power module operating at high temperature is proposed. A module structure of SiC power devices are sandwiched between two silicon nitride-active metal brazed copper (SiN-AMC) circuit boards. To make a precise position and height control of the chip bonding, the top side (gate/source or anode pad side) of SiC power devices are flip-chip bonded to circuit electrodes using sub-micron Au particle with low temperature (250°C) and pressure-less sintering. The accuracy of the bonding position of chips was less than 10 μm and the accuracy of the height after bonding chips was less than 15 μm. Mechanical shear fatigue tests for flip-chip bonded SiC Schottky barrier diode (SBD) were carried out. As a result, initial shear strength of the joint was 36 MPa. The shear strength of 43 MPa is obtained after storage life test (500 hours at 250°C), and also 35 MPa is obtained even after thermal cycle stress test (1000 cycles between −40°C and 250°C). The flip-chip bonding of SiC-JFET is successfully realizedon the substrate without short or open failure electrically. Finally we joint the backside of the SiC-JFET (drain side) and the SiC-SBD (cathode side) to each circuit electrodes at once by means of reflow process with Au-12%Ge solder. The structured sandwich SiC power module was also successfully formed.

In-situ observation of material migration in flip-chip solder joints under current stressing

2006 ◽  
Vol 35 (10) ◽  
pp. 1781-1786 ◽  
Author(s):  
C. M. Tsai ◽  
Yi-Shao Lai ◽  
Y. L. Lin ◽  
C. W. Chang ◽  
C. R. Kao
Keyword(s):  
Flip Chip ◽  
Solder Joints ◽  
In Situ Observation ◽  
Current Stressing ◽  
Material Migration

Failure Mechanism of Electromigration in Solder Joint

2008 ◽  
Vol 44-46 ◽  
pp. 905-910 ◽  
Author(s):  
Yu Dong Lu ◽  
Xiao Qi He ◽  
Yun Fei En ◽  
Xin Wang
Keyword(s):  
Solder Joint ◽  
Flip Chip ◽  
Solder Joints ◽  
High Current Density ◽  
Electron Flow ◽  
Design Rule ◽  
Bottom Surface ◽  
Constant Density ◽  
Linear Change ◽  
Void Migration

In advanced electronic products, electromigration-induced failure is one of the most serious problems in fine pitch flip chip solder joints because the design rule in devices requires high current density through small solder joints for high performance and miniaturization. The failure mode induced by electromigration in the flip chip solder joint is unique, owing to the loss of under bump metallurgy (UBM) and the interfacial void formation at the cathode contact interface. In this study, Electromigration of flip chip solder joints has been investigated under a constant density of 2.45×104 A/cm2 at 120 °C. The in-situ marker displacements during the electromigration test was measured and found to show a rough linear change as a function of time. Scanning electron microscopic images of the cross section of samples showed the existence of voids at the interface between Al interconnection and under bump metallurgy. The void movement was matched with the marker displacements during the electromigration test, and voids moved to the cathode interface between Al interconnection and under bump metallurgy in the downward electron flow (from chip to substrate) joint. The mechanism of electromigration-induced void migration and failure in the flip chip are discussed. During electromigration, a flux of atoms is driven from the cathode to the anode or a flux of vacancies in the opposite direction. It can lead to two possible mechanisms of void migration. First, if we regard the void as a rigid marker of diffusion, it will be displaced towards the cathode by the atomic flux in the electromigration, Second, if we consider surface diffusion on the void surface, electromigration will drive atoms on the top surface of the void to the bottom surface of the void, and consequently the void will move towards the cathode.

Effects of electromigration on the growth of intermetallic compounds in Cu/SnBi/Cu solder joints

2008 ◽  
Vol 23 (10) ◽  
pp. 2591-2596 ◽  
Author(s):  
X. Gu ◽  
D. Yang ◽  
Y.C. Chan ◽  
B.Y. Wu
Keyword(s):  
Activation Energy ◽  
Solder Joint ◽  
Intermetallic Compounds ◽  
Direct Current ◽  
Solder Joints ◽  
Cathode Side ◽  
Anode Side ◽  
Kinetics Parameters ◽  
Ambient Temperatures ◽  
Current Stressing

In this study, the effects of electromigration (EM) on the growth of Cu–Sn intermetallic compounds (IMCs) in Cu/SnBi/Cu solder joints under 5 × 103 A/cm2 direct current stressing at 308, 328, and 348 K were investigated. For each Cu/SnBi/Cu solder joint under current stressing, the IMCs at the cathode side grew faster than that at the anode side. The growth of these IMCs at the anode side and the cathode side were enhanced by electric current. The growth of these IMCs at the cathode followed a parabolic growth law. The kinetics parameters of the growth of the IMCs were calculated from the thickness data of the IMCs at the cathode side at different ambient temperatures. The calculated intrinsic diffusivity (D0) of the Cu–Sn IMCs was 9.91 × 10−5 m2/s, and the activation energy of the growth of the total Cu–Sn IMC layer was 89.2 kJ/mol (0.92 eV).

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