Electronic Packaging and Interconnection: Emerging Interconnection Technology
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
Tuesday 8:00 AM
March 21, 2023
Room: Sapphire D
Location: Hilton
Session Chair: Patrick Shamberger, Texas A&M University; Dan Li, Beijing University of Technology
8:00 AM Introductory Comments
8:05 AM Invited
Flexible Packaging by Microwave Bonding for Flexible Electronics: Tae Ik Lee1; Minjeong Sohn1; Min-Su Kim1; Dongyurl Yu1; So Jeong Lee1; 1Korea Institute of Industrial Technology
As research on developing electronic devices for simultaneous implementation of flexibility and conductivity has been continuously conducted, ensuring stable and high reliability of devices against various mechanical deformation is becoming important. When various mechanical forces are applied, the bonding area between substrates should ensure stability due to high stress generation. In this study, a flexible bonding process between polymer substrates was developed by heating carbon nanotubes through microwave irradiation. Carbon nanotubes were coated on a bonded PET polymer substrate, and then local heating was performed by microwaves to induce mechanical entanglement between the CNTs and the PET. For the analysis of the bonding mechanism in the area where mechanical entanglement formed, the CNT-PET bonding interface was analyzed through electron scanning microscope measurement, and further analysis was performed for each process condition. In addition, a fracture mechanism analysis that occurred at the junction was performed after the overlapping shear strength test.
8:30 AM
Effect of Synthesized Variables on Characteristics for Cu Nanoparticle: Ping-Hsuan Chen1; Albert T. Wu1; 1National Central University
Developing green approach for synthesizing Cu nanoparticles that can be sintered at low temperature for Cu-to-Cu direct bonding joints is crucial. In this study, Cu nanoparticles are synthesized by eco-friendly reduction method in ambient atmosphere. The particle size and distribution are controlled by experimental parameters such as pH value and reaction time of reducing process. The relationship between the synthesized variable and the characteristic of the particles is discussed. The synthesized Cu nanoparticles are mixed with organic solvent to form Cu paste, and the Cu paste are bonded with Cu substrates and pillars. The study discusses the reduction mechanism of Cu nanoparticles in detail.
8:50 AM
Low Temperature Direct Bonding in Atmosphere by Nanocrystalline Ag: Cheng Jie Yang1; Fan-Yi OuYang1; 1National Tsing Hua University
In recent years, Moore's law is approaching physical limit. Using metal-to-metal direct bonding to develop 3D integrated circuits is an effective way to scale and improve performance of devices. In this study, we performed Ag-to-Ag direct bonding in atmosphere using nanocrystalline Ag thin films and bumps. With the help of nanocrystalline grains, we successfully developed the low temperature metal to metal bonding process at 185 ℃ for 5 minutes by thermo-compressive bonding under the pressure of 5 MPa. The results of shear test show the bonding strength could reach 67.6 MPa. The average resistance of Ag microbump in a diameter of 40 μm was 1.84mΩ and the average specific contact resistance was 2.9 × 10-8 Ω. The corresponding bonding mechanism and reliability will be discussed in this talk.
9:10 AM
Pad Connectivity Induced Capacitance Effect in Electroless Copper Plating Interconnection: Yu Chun Lin1; Po-Shao Shih1; Jeng-Hau Huang1; Simon Johannes Gräfner1; Chang-Hsien Shen1; C. Robert Kao1; 1National Taiwan University
Surface defects after ENIG in PCB manufacturing have long been considered to be highly correlated with pad size and pad connectivity. In this research, similar issues are found in chip interconnection using electroless copper plating. The connectivity between copper pillars and pads triggers skip plating or etching of pillars during electroless copper plating interconnection. Area ratio between pillars and pads exist a threshold value to determine whether electroless plating may take place. An overall mechanism is proposed based on concentration cell induced potential shift. The result provides a reference standard for chip layout design to avoid defects and improve yield.
9:30 AM Break
9:50 AM
Impact of Non-linear Phase Change Processes on Thermal Impedance of an Electronics Package: Patrick Shamberger1; Alison Hoe1; Juan Carlos Lago1; Colton Brietzke1; Veronica Gonzalez1; 1Texas A&M University
Phase change materials (PCMs) can provide thermal buffering to systems that experience transient heat loads, including high power electronics and optoelectronics packaging. However, the impact of high cooling power PCMs on the thermal impedance of an electronics package subject to periodic unsteady heating and convective cooling boundary conditions remains relatively poorly understood. Here, we clarify the interaction between the non-linear phase change process and the linear behavior of heat transfer from an electronics package using both numerical and experimental simulations. In particular, we investigate the impact of PCM thermophysical properties, location in the package, and the specific characteristics of a pulsed heat train. We demonstrate that all of these elements are critical in introducing non-linear thermal buffering into the electronics package. However, when certain criteria are satisfied, introduction of PCMs can provide a powerful tool to regulate temperature rise in cases where the anticipated heat load is well defined.
10:10 AM
Sintered Ag-In Alloy Paste as Die-attach Material for Power Electronic Packaging: Chin-Hao Tsai1; Wei-Chen Huang1; C. R. Kao1; 1National Taiwan University
With the rising utilization of electric vehicles, power electronic packaging becomes important in the next decade. It’s necessary to develop reliable die-attach materials which can withstand high temperatures generated due to high-power applications. Ag pastes attract much attention in recent years because Ag pastes sintering has the merits of low processing temperature and high melting temperature after sintering. However, sintered Ag joints encounter unavoidable reliability issues, such as sintered pores coarsening and oxidation problems. The addition of indium (In) has proved to significantly improve the reliability of sintered Ag joints. However, current methods for introducing In are not fully compatible with large-scale industrial manufacturing. Therefore, this research develops novel Ag-In alloy pastes by ball milling for die-attach applications. The results demonstrate the Ag-In alloy joints exhibit excellent shear strength up to 80 MPa. In addition, the Ag-In alloy joints show more outstanding mechanical reliability than Ag joints in high-temperature surroundings.
10:30 AM
Microstructural Effect of Cu Substrate on Join Properties for Cu-to-Cu Direct Bonding: Hung Wang1; Albert T. Wu1; 1National Central University
Cu nanoparticle paste has the possibility to become a joint that can be sintered at low temperature. It has the potential to be applied in high power device packaging owing to its outstanding electrical conductivity and mechanical properties. Although numerous approaches have been proposed for sintering the Cu nanoparticle, there are not many studies on microstructural relationship between the Cu substrate and the sintered Cu joint. In this study, Cu layers are electroplated on Cu substrates by adjusting the current density. The electroplating Cu is annealed at various temperature for observing the evolution of grain size and the relaxation of residual stress. To further understand the microstructural effect on the joining properties, the electroplating Cu substrates are bonded by Cu nanoparticle paste. The shear strength of the joints is measured and evaluated. A model that includes the calculation of chemical potential of Cu nanoparticles and the substrates is proposed.