Advanced Microelectronic Packaging, Emerging Interconnection Technology and Pb-free Solder: Advanced Microelectronic Packaging Materials
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
Monday 2:30 PM
February 24, 2020
Room: Palomar
Location: Marriott Marquis Hotel
Session Chair: Albert Wu, National Central University, Taiwan; Fan-Yi OuYang , National TsingHua University, Taiwan
2:30 PM Invited
Pressureless Silver Sintering of SiC MOSFET Power Module for Vehicle: Won Sik Hong1; Mi-Song Kim1; Chulmin Oh1; 1Korea Electronics Technology Institute
We developed pressureless silver sintering process of SiC MOSFET module with silver finish Si3N4 AMB substrate for 1200V/200A automotive power module. Pressureless sintering condition was 240 ℃, 90 min in vacuum and nitrogen gas. As-sintered bonding strength, bonding layer thickness (BLT), void content and densification were 39 MPa, 71.4㎛, 2% and 90.5%, respectively. The shear strength, BLT, densification and microstructure of silver sintered layer were observed before/after thermal cycling test (-40-125 ℃, 700 cycles, TCT) and high temp storage test (200 ℃, 1000h, HTST). The shear strength and densification after TCT and HTST were 35 MPa and 40.5 MPa, and 92.8% and 94.8%. On resistance and switching efficiency were 7.2 mΩ and 10.7mJ, Ag sintering was superior to soldering interconnets in power module characteristics.
2:50 PM
Si and Ag Particles Sintering Technology For Die Attach: Minoru Ueshima1; Motoharu Haga1; Tomoaki Mototsuji2; Yusuke Isono2; 1Daicel Corp.; 2Osaka University
Ag sintering technology is one of the best candidates for SiC die attach. However cracks propagates into SiC dies or DBC substrates in severe reliability tests because of the high strength and CTE of Silver. In this study, a method to coat Si particles with Ag layer and its sintering properties are researched. Si particles coated with Ag layer are prepared by utilizing high-speed 3D motion of a patented 3D Ball Mill producted by Nagao System Inc.. Their Si-Ag particles are mixed with a solvent to formulate into pastes. These pastes are printed onto Ag electroplated Cu plats, and then the bonding experiments are carried out at temperatures of 250℃ for 60 min without pressure at air atmosphere. It is revealed that some Ag layers are jointed on the surface of Si particles.
3:10 PM
Bonding and High-temperature Storage Performance of Die Attachment with Ag Paste Sintering on Bare Direct Bonding Aluminum (DBA) Substrate: Zheng Zhang1; Chuantong Chen1; Shijo Nagao1; Katsuaki Suganuma1; 1Osaka University, Institute of Scientific and Industrial Research
Sintering Ag paste is an important interconnection technique for power electronics due to its low-temperature sinter-ability, high-temperature stability, and high thermal and electrical conductivity. To get a reliable die attach via sintering Ag paste, it is required substrates to get a metallization layer for matching the Ag sintering process, which allows Ag bond with metallization layer via interdiffusion process. However, the metallization layer requires noble metals such as Ag or Au, which will inevitably increase the cost. In this work, we report a robust Ag sinter joining on bare DBA substrate, one of the mostly used substrates in power electronics, and whole sintering processes are accomplished at a pressureless, low-temperature, and atmospheric condition. The bonding mechanism is discussed in detail. In addition, high-temperature storage performance of the die attach specimens is investigated by 250 °C storage up to 1000 hours.
3:30 PM
Die-bonding Performance and Mechanism of Ag Micron Paste with Pressure-less Sintering: Tetsu Takemasa1; Shingo Ishihara2; Junya Kano2; Katsuaki Suganuma3; 1Department of Adaptive Machine Systems, Graduate School of Engineering, Osaka University; 2Institute of Multidisciplinary Research for Advanced Materials, Tohoku University; 3Institute of Scientific and Industrial Research, Osaka University
Wide-bang gap semiconductors such as SiC and GaN have many advantages including energy saving and high-power capability and are expected as the new semiconductors substituting traditional Si. To bond these SiC/GaN dies to substrates securely, the die-bonding materials are required to stand high-temperature environment and possess superior heat and electronic-conducting properties as well as excellent reliability. Recently, Ag micron particle paste has been developed to show good performance such as high-temperature reliability and high electronic conductivity.In this study, the Ag micron paste was used to connect Si dies to Ag metallized substrate. The die-loading process cause fine and rough density structure in the Ag sintered joint and the joint quality was affected by the die-loading speed and push-in height. The fluid simulation indicates that the Ag paste flow which is caused by the die-loading is not uniform, and nonuniform flow makes nonuniform joint structure.
3:50 PM Break
4:10 PM
Fatigue and Creep Properties of Sintered Ag Paste from Room Temperature to High Temperature: Chuantong Chen1; Chanyang Choe1; Aiji Suetake1; Katsuaki Suganuma1; 1Osaka University
Sintered silver (Ag) paste has been considered as a promising joint material for SiC and GaN power modules due to its excellent thermo-stability and high electrical/thermal conductivity. Here, we investigated the mechanical properties of sintered Ag paste including fatigue and creep from room temperature to high temperature (≥200℃), which strongly related with reliability and lift time of power modules. At the room temperature, the sample did not break even at 10 to the 8th power when the stress amplitude was less than 4MPa. From the S-N curve, the fatigue is close to the Morrow equation but not is the Coffin-Manson law. In addition, in the case of high temperature test (200℃), the fracture behavior is different with room temperature, large deformation appeared at the necking part of the sintered Ag paste for the both fatigue and creep test.
4:30 PM
On the Adhesion of a Sintered Ag Joint on a Cu Substrate using Laser Shocks Influence of Aging: Anna Gordun Peiro1; Thibaut De Resseguier1; Loic Signor1; Eloic Ferdinand1; Jacques Baillargeat1; Hadi Bahsoun2; Xavier Milhet1; 1Prime Institute CNRS ENSMA; 2Prime Institute CNRS Université Poitiers
Ag paste sintering, is a promising candidate for die bonding in the next generation of power electronic modules. In order to model the behavior of the system, there is a need for a fine characterization of the joint itself as well as those of the interface, especially during aging. In this study, we have explored an alternative route to test the adhesion of the Ag film on a Cu substrate using laser driven shocks: a laser pulse is calibrated to induce a tensile stress at the interface between the substrate and the film, and time-resolved velocity measurements complemented by post-recovery observations provide quantitative information on the adhesive strength. This method presents the advantage over other techniques to really focus on the interface properties. The results are used to explore the relationship between adhesion, aging and the underlying microstructure.
4:50 PM
Low Temperature Cu-Cu Bonding by Copper-based Paste with Small Amount Sn Additive: Kuo-Shuo Huang1; Wei Liu1; Albert T. Wu1; 1National Central University
The increasing demand of wide-bandgap semiconductors power devices prompts the development of high temperature bonding methods. Because the conventional solder joints are not allowed to operate over 150 oC, the bonding by sintering micro- or nano-sized particles become the most promising way for requirements. Silver sintering technique has been proposed but the high cost and poor electromigration resistance limit its applications. In addition, the densification issue by sintering that would affect the electrical and mechanical properties of joints remains unsolved. In this study, by means of high diffusion rate between Cu and Sn atoms, small amount of Sn would be added into copper-based paste that is composed of Cu particles and organic solvent. The Cu-Sn paste would be used to bond two Cu plates. The microstructure and mechanical properties of the bonding are investigated. The optimized conditions are studied by varying the amount of additive, the bonding temperature and time.
5:10 PM
Low Temperature Polyimide-to-polyimide Direct Bonding with Low Curing Temperature Polyimide Films: Hung-Che Liu1; 1Chih Chen
Nowadays, the requirement of the performance on microelectronic device become higher while the size of joints need to be shrunk. Cu direct bonding appears to be the solution for ultra-fine pitch packaging, in which hybrid bonding with passivation has been carried out simultaneous with Cu direct bonding. Cu/polyimide hybrid bonding is a promising technology to fabricate 3D integrated microsystems with ultra-fine pitch. Low temperature hybrid bonding need not only low temperature copper direct bonding but also dielectric layer direct bonding. Polyimide is a commonly-used dielectric material. However, surface activation needs to be done for the fully cured polyimide.In this study, we use partially cured polyimide films for direct bonding, so that no surface activation is needed. We use thermal bonding to finish bonding process. We successfully bond polyimide films at 250℃ for 30 min.