Electronic Packaging and Interconnection: Pb Free Solder Alloys II
Sponsored by: TMS Functional Materials Division, TMS: Electronic Packaging and Interconnection Materials Committee
Program Organizers: Kazuhiro Nogita, University of Queensland; Mohd Arif Mohd Salleh, Universiti Malaysia Perlis; Dan Li, Beijing University of Technology; David Yan, San Jose State University; Fan-Yi Ouyang, National Tsing Hua University; Patrick Shamberger, Texas A&M University; Tae-Kyu Lee, Cisco Systems; Christopher Gourlay, Imperial College London; Albert T. Wu, National Central University
Wednesday 8:30 AM
March 22, 2023
Room: Sapphire E
Location: Hilton
Session Chair: Albert Wu, National Central University; Fan-Yi Ouyang, National Tsing Hua University
8:30 AM Introductory Comments
8:35 AM Invited
Effect of Joint Length Scale on Creep Deformation of Sn-rich Dissimilar Metallic Joints: Praveen Kumar1; Anwesha Kanjilal1; 1Indian Institute of Science
This study analyzes the joint-scale effect on creep and failure of Sn-rich dissimilar joints. Sn-Cu and Sn-Ag-Cu(SAC)/Cu joints of varied thicknesses were fabricated and creep tested in tension. In both systems, at given stress, the secondary creep rate reduced with a reduction in joint thickness, and crystallographic texture varied with length scale. In thinner joints, creep rate and strain during tertiary decreased, with transition in failure from necking to cavitation. The synergistic approach of continuum-based finite element analysis and microstructure-based crystal plasticity modeling captured the dimensional and microstructural constraints on size-dependent reduction of creep rate. At the same time, necking-cum-cavitation-based model explained the role of joint size-dependent stress state and varying length of neck on tertiary creep. The effect of electric current and precipitates as well as the interfacial intermetallic compounds on the size-dependent creep of joints were also analyzed and correlated with the aforementioned behavior.
9:00 AM
Properties of Sn-3wt%Ag-5wt%Cu Alloys with Cu6Sn5 Intermetallic Grain Refined by Mg: Chiying Tan1; Mohd Arif Anuar Mohd Salleh1; Xin Fu Tan2; Hideyuki Yasuda3; Norainiza Saud1; Tetsuro Nishimura4; Kazuhiro Nogita2; 1CEGeoGTech; 2NS CMEM; 3Kyoto University; 4Nihon Superior Co. Ltd
The influence of Mg addition was investigated on the microstructure, thermal, electrical properties and joint strength of bulk and ball grid array (BGA) reflowed Sn-3wt%Ag-5wt%Cu solder alloy. The addition of Mg effectively triggered the grain refinement of primary Cu6Sn5 IMCs in the bulk solder alloys. In addition, the thickness of the interfacial Cu6Sn5 IMCs layer was suppressed. Synchrotron tomography images reveal that the grain refinement of primary Cu6Sn5 IMCs is also effective even in BGA scale solder joint at normal reflow conditions. These primary Cu6Sn5 IMCs showed a non-faceted morphology. 0.10wt%Mg addition reduced the number and size of the Cu6Sn5 IMCs. The undercooling values was significantly reduced to the minimum with 0.10wt%Mg addition, which increased when the amount of Mg increased to 0.15wt%. The mechanical properties showed that the ductility of the solder joint at high shear speed was improved.
9:20 AM
Ball Drift in SnAgCu/SnBi Hydrid Joints during Thermal Cycling: Jingwei Xian1; R.J. Coyle2; L. Wentlent3; J. Wilcox3; Christopher Gourlay1; 1Imperial College London; 2Nokia Bell Labs; 3Universal Instruments Corporation
There is an ongoing desire to reduce the solder processing temperature to reduce cost and emissions while minimising dynamic warpage. One approach is to use hybrid joints that combine high temperature solder balls with a low temperature solder paste in two-step reflow. During thermal cycling of SnAgCu/SnBi hybrid joints it has been found that some joints are sheared significantly out of position, a phenomenon termed ball drift. In this presentation, we will quantify the ball drift phenomenon, measure the microstructure evolution that occurs during drift, investigate the mechanisms that cause the pronounced shear, and explore how crystallographic orientation affects ball drift.
9:40 AM
Effects of Different Surface Finish to the Microstructure and Properties of Sn-Ag Solder Joints: Mohd Arif Anuar Salleh1; Siti Farahnabilah Muhd Amli1; Mohd Izrul Izwan Ramli1; Mohd Mustafa Al Bakri Abdullah1; Mohd Sharizal Abdul Aziz1; Hideyuki Yasuda1; Jitrin Chaiprapa1; Kazuhiro Nogita1; 1Universiti Malaysia Perlis
The effects of Cu-OSP, ENIG, ImmAg and ImmSn surface finishes to the microstructure and properties of Sn-Ag solder joints were investigated. Besides conventional characterisation methods, in-situ synchrotron X-Ray imaging technique were utilised to analyse and quantify the growth kinetics of microstructure during soldering in the solder joints. High speed shear test were also conducted to understand the correlation of microstructure formation to the solder joint strength. In addition, the growth kinetics of intermetallic compounds (IMCs), morphology and activation energy had been investigated after multiple reflows. Experimental results were then correlated with the numerical finite element (FE) modelling using FE software ANSYS to investigate the effects of primary intermetallics to the reliability of solder joint. It was observed that the formation of (IMCs) were strongly dependent on the types of surface finish applied on Cu substrate which could effect to the properties of the solder joint.
10:00 AM Break
10:20 AM
New Insights into the Nucleation and Growth of Ag3Sn Plates in Solder Joints: Christopher Gourlay1; Yi Cui1; Athanasios Zois1; 1Imperial College London
The nucleation and growth of Ag3Sn is studied in 500um balls of Sn-Ag and Sn-Ag-Cu solders cooled in a differential scanning calorimeter (DSC) with and without copper substrates. The droplets undercooled to 1 - 50 K with respect to the Ag3Sn liquidus, enabling a study of Ag3Sn crystal morphology versus undercooling. It is found that the Cu6Sn5 reaction layer has a strong influence on the nucleation of Ag3Sn, and consequently also on its growth. The results provide new insights that allow us to understand the wide range of Ag3Sn morphologies in solder joints.
10:40 AM
Thermomigration of Liquid Indium and Nickel Thin Film During Bonding Process: Po-Hsun Yang1; Fan-Yi OuYang1; 1National Tsing Hua University
The internet of things (IOT) has been developed over the past decade. However, most sensors in IOT system have a low heat tolerance. Therefore, indium-based solder, which have a lower melting temperature, is regarded as the substitute for traditional tin-based solder during solid liquid interdiffusion bonding (SLID) process. In this study, we investigate thermomigration behavior between liquid-state Indium and nickel under bump metallization (UBM) thin film under a temperature gradient. The microstructure evolution of intermetallic compounds (IMCs) under thermomigration would be examined and compared to isothermal cases. In addition, through the marker experiment, the dominant diffusion species in In/Ni system would be found. The growth mechanism of IMCS at hot end and cold end during SLID process would be discussed.
11:00 AM
The Effect of Ni Microalloying on the Microstructure Evolution of In-35wt.% Sn Solder Alloy: May Shin Chang1; Mohd Arif Anuar Mohd Salleh1; Dewi Suriyani Che Halin1; Hideyuki Yasuda2; Tetsuro Nishimura3; Kazuhiro Nogita4; 1Centre of Excellence Geopolymer & Green Technology (CeGeoGTech); 2Department of Materials Science and Engineering; 3Nihon Superior Co. Ltd.; 4Nihon Superior Centre for the Manufacture of Electronic Materials (NS CMEM)
In-35wt.% Sn alloy is a potential Pb-free solder alloy for low temperature electronic packaging interconnect of quantum computing due to the superconductive properties. Such properties are highly dependent on the properties of the β-phase. This paper studies the effect of Ni microalloying on the microstructural changes of β-phase in an In-35wt.% Sn alloy during the solidification process by using the in-situ real-time synchrotron radiography technique. The β-phase preferably formed a columnar dendritic structure that made a transition to cellular-dendrite structure with a unique morphology after addition of 0.05wt% Ni into the In-35wt.% Sn alloy. The findings provide detailed observations of microstructure evolution, specifically β-In3Sn phase, and examine the effects of Ni addition during solidification of the In-35wt.% Sn alloy. The results are of relevance to the development of superconductive Pb-free solder alloys for electronic applications at extreme low temperature.