Advanced Microelectronic Packaging, Emerging Interconnection Technology and Pb-free Solder: Solder Joint Intermetallics
Sponsored by: TMS Functional Materials Division, TMS: Electronic Packaging and Interconnection Materials Committee
Program Organizers: Christopher Gourlay, Imperial College London; Kazuhiro Nogita, University of Queensland; David Yan, San Jose State University; Mike Wolverton; Babak Arfaei, Ford Motor Company; Andre Delhaise; Mehran Maalekian, Mat-Tech; Mohd Arif Salleh, Universiti Malaysia Perlis
Thursday 8:30 AM
February 27, 2020
Room: Palomar
Location: Marriott Marquis Hotel
Session Chair: Kazuhiro Nogita, The University of Queensland; Sergey Belyakov, Imperial College London
8:30 AM
The Growth and Coarsening Kinetics of Ag3Sn in SAC305 Solders: Jingwei Xian1; Sergey Belyakov1; Christopher Gourlay1; 1Imperial College London
Primary and eutectic Ag3Sn are important in the performance of SAC305 solders. By coupling real-time synchrotron radiography with EBSD, it is shown that primary Ag3Sn can grow in simple or dendritic plates depending on Ag contents. Higher Ag levels tend to form more dendritic Ag3Sn plates with measured crystallography. Here we also present the coarsening kinetics of eutectic Ag3Sn at various temperatures. The result is discussed with the influence of beta-Sn nucleation undercooling and can be used to predict the eutectic size after thermal cycling. It is further shown that bigger eutectic Ag3Sn size will deteriorate the shear performance of the solder joints.
8:50 AM
Potential for Improving Sn-Cu Alloys as High-temperature Solders by the Suppression of Cu3Sn Phase: Syeda Mehreen1; Kazuhiro Nogita1; Stuart McDonald1; David StJohn1; Hideyuki Yasuda2; 1The University of Queensland; 2Kyoto University
Developing Sn-Cu alloys as potential candidates for Pb-free high-temperature solders requires increased Cu content. Beyond 7.6 wt.% Cu, Sn-Cu alloys undergo peritectic solidification whereby needle-shaped primary Cu3Sn phase is formed, surrounded by secondary Cu6Sn5. Suppressing Cu3Sn in the bulk solder is considered to be a potential strategy to achieve mechanically favourable high-temperature Pb-free solders. Alloying additions and cooling rate can have a significant effect on the nucleation and growth of Cu3Sn in these peritectic Sn-Cu alloys. Ternary Ni additions alloyed to Sn-10Cu have resulted in complete Cu3Sn suppression. This work further investigates the effect of (i) alloying with Ni additions and (ii) cooling rate on the suppression of the Cu3Sn phase in Sn-10Cu alloys via directional solidification and real-time in situ synchrotron X-Ray imaging.
9:10 AM
Effects of Secondary Reflow on Solder Joint Microstructure and Lifetime: Alyssa Yaeger1; Travis Dale1; Ganesh Subbarayan1; John Blendell1; Carol Handwerker1; 1Purdue University
Electroless Nickel Immersion Gold (ENIG) coatings are common in electronics for pads on circuit boards and surface mounted components. The Au in these coatings diffuses easily into SnPb solder during reflow and can form brittle intermetallics. With aging, these intermetallics coarsen and migrate to the Ni3Sn4 interface to form an additional intermetallic layer. Due to the diffusion of Ni into the intermetallic, a porous phosphorous-rich Ni-P layer forms between the electroless Ni coating and the intermetallic layer. Brittle fracture along the P-rich layer occurs in aged SnPb solder joints containing as little as 1wt% Au with ENIG coatings. The effects of secondary reflow as a form of mitigation for this brittle fracture will be discussed, with a focus on microstructural evolution and mechanical properties.
9:30 AM
Intermetallic Compound Analyses Provide Interfacial Reliability for Solder Connections in Electronics: Mike Wolverton1; 1Raytheon
We report numerous combinations of solders and plated metals on components and circuit boards. A common finding is that the growth of diffusion compounds, at the solder-to-plating interface, is a precursor indicator of solder connection interfacial failure. The precursor is associated with vacancy accumulation and observation of Kirkendall voiding. Diffusion between plating and precipitation compounds leads to connection separation. Vacancy content accumulates into area voids as the diffusion compounds grow. The diffusion compounds occur concurrent with, or subsequent to, the precipitation compounds. The diffusion compounds are stoichiometrically richer in the plated metal than are the precipitation compounds. We show cross-sectional microstructures, and compound chemistry identifications, from the following solder-to-plating systems: tin-lead-to-gold, tin-lead-to-copper, indium-lead-to-gold, gold-germanium-to-nickel, tin-lead-to-iron-nickel, tin-lead-to-palladium, and lead-free solder connections to copper and iron-nickel. This document does not contain technology or technical data controlled under either the U.S. International Traffic in Arms Regulations or the U.S. Export Administration Regulations
9:50 AM Break
10:10 AM
Influence of Substrates and Microalloying Additions on the Primary Intermetallic Growth of Lead-free Solder Joints: Mohd Arif Mohd Salleh1; Kazuhiro Nogita2; Mohd Izrul Izwan Ramli1; Flora Somidin2; Yasuda Hideyuki3; 1Universiti Malaysia Perlis; 2University of Queensland; 3Kyoto University
This paper investigates the influence of several substrates and microalloying additions on the microstructure of lead-free solder joints. The microstructure were mainly analysed using in-situ synchrotron imaging coupled with conventional microstructure observation techniques. Growth kinetics of primary intermetallics in the solder joints were also analysed and compared. Results shows that the substrate plays a significant role in the microstructure development in a lead-free solder joint.
10:30 AM
Effect of Bi and Zn Addition to the Properties of Sn-0.7Cu and Sn-0.7Cu-0.05Ni Solder Coating: Mohd Izrul Izwan Ramli1; Mohd Arif Anuar Mohd Salleh1; Hideyuki Yasuda2; Kazuhiro Nogita3; 1Universiti Malaysia Perlis; 2Kyoto University; 3University of Queensland
This paper investigates the effect of Bi and Zn addition on Sn-0.7Cu and Sn-0.7Cu-0.05Ni solder coating properties for surface finish application. This solder coating has two essential functions, to protect the exposed copper and to provide a solderable surface when soldering the component. This understanding of the interfacial intermetallic kinetic and free solder thickness between the solder and substrate is important for maximizing the service life of solder joints. The IMC thickness and the growth rate of solder coating of Sn-0.7Cu and Sn-0.7Cu-0.05Ni solder coating have been studied. This research also explores the formation and the growth kinetics of primary intermetallics by using real-time imaging technology to study the influence of Bi and Zn on the primary IMCs in Sn-0.7Cu and Sn-0.7Cu-0.05Ni solder coating during the solidification process. The morphology and distribution of the IMC formed during the soldering process will dramatically affect the solderability properties of the solder joints.