Emerging Interconnection Technology and Pb-Free Solder Materials for Advanced Microelectronic Packaging

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Welding and Joining".

Deadline for manuscript submissions: closed (31 August 2021) | Viewed by 33678

Special Issue Editor

Department of Materials Science and Engineering, Ajou University, Suwon 16499, Korea
Interests: high entropy alloys; additive manufacturing; bulk nanostructured materials; advanced powder metallurgy; electron microscopy; lead-free solders and packaging
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The evolution of microelectronic devices towards miniaturization, fast signal transmission, and multi-functionality undoubtedly encourages the development of novel, advanced, and reliable soldering materials. Sn-Pb solders have a long history of applications in electronics due to their superior wetting, melting, and satisfactory mechanical properties. However, due to the environmental concern and legislation, i.e., the Restriction of Hazardous Substances (RoHS), Waste Electrical and Electronic Equipment (WEEE), and End-of-Life Vehicles (ELV) directives across the globe, toxic Pb has been eliminated from electronic products. The issue of Pb-free soldering has triggered the research and development of advanced Pb-free solders in all areas of electronic materials research, including micro–nano joining, flexible electronics, etc., in the last few decades.

Recent advancements in high-density packaging and low-cost portable and wearable packages have encouraged the wide use of flip-chip packages and transparent conductors. The decreasing form factor for smartphones, tablets, and portable notebooks requires package substrates to be as thin as possible. For example, the detailed functioning of various electronic appliances is critical to the design of and cost-effective approaches to material fabrication. Further, the bonding of each component is crucial for the robustness, high reliability, and successful commercialization of electronic appliances.

This Special Issue will cover a wider scope of novel soldering/joining materials and advanced methodologies and their understanding for advanced high-density packaging devices. It is my great pleasure to cordially invite original research articles, including full papers, communications, and reviews, on the recent progress on the following subjects of electronic packaging, including but not limited to the keywords/topics below.

Prof. Dr. Byungmin Ahn
Guest Editor

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Keywords

  • Lead-free solders
  • Conductive adhesives
  • Die attach materials
  • Screen printing
  • Brazing
  • Plating and surface finishing
  • Micro-nano joining
  • Flip chip packaging
  • Flexible electronics packaging
  • Microelectromechanical systems and packaging

Published Papers (6 papers)

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Editorial

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3 pages, 158 KiB  
Editorial
Emerging Interconnection Technology and Pb-Free Solder Materials for Advanced Microelectronic Packaging
by Byungmin Ahn
Metals 2021, 11(12), 1941; https://doi.org/10.3390/met11121941 - 01 Dec 2021
Cited by 6 | Viewed by 1533
Abstract
In the field of electronics packaging, Pb-bearing solder alloys are mostly used as robust interconnecting materials [...] Full article

Research

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10 pages, 7446 KiB  
Article
Effect of Cr Addition on Microstructure and Properties of AuGa Solder
by Yu Tao, Songbai Xue, Han Liu, Weimin Long and Bo Wang
Metals 2020, 10(11), 1449; https://doi.org/10.3390/met10111449 - 29 Oct 2020
Cited by 5 | Viewed by 1616
Abstract
In order to meet the service requirements of electronic devices working at 300 °C in the fields of energy resource prospecting and space exploration, Cr element was added to modify AuGa solder to improve its high-temperature performance. The results showed that the addition [...] Read more.
In order to meet the service requirements of electronic devices working at 300 °C in the fields of energy resource prospecting and space exploration, Cr element was added to modify AuGa solder to improve its high-temperature performance. The results showed that the addition of 0.3 wt.% Cr element reduced the loss of Ga element in the smelting and casting process, and effectively improved the problem of the inhomogeneous microstructure of the solder matrix. On the basis of maintaining the good wettability of the solder, the addition of trace chromium effectively restrains the excessive flux of the solder, and the presence of chromium improves the oxidation resistance of the solder. Furthermore, Cr element optimized the interface morphology and improved the mechanical properties of the solder joint. The shear strength of the AuGa-0.3Cr/Ni joint was 87.2 MPa, which was 13.1% higher than that of the joint without Cr element. After 240 h of aging, the shear strength of the AuGa-0.3Cr joint was still the peak value at 84.1 MPa, which was 16.3% higher than that of the AuGa joint. Full article
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17 pages, 8141 KiB  
Article
Shear Strength and Aging Characteristics of Sn-3.0Ag-0.5Cu/Cu Solder Joint Reinforced with ZrO2 Nanoparticles
by Sri Harini Rajendran, Seung Jun Hwang and Jae Pil Jung
Metals 2020, 10(10), 1295; https://doi.org/10.3390/met10101295 - 28 Sep 2020
Cited by 21 | Viewed by 4580
Abstract
This study investigates the shear strength and aging characteristics of Sn-3.0Ag-0.5Cu (SAC 305)/Cu joints by the addition of ZrO2 nanoparticles (NPs) having two different particle size: 5–15 nm (ZrO2A) and 70–90 nm (ZrO2B). Nanocomposite pastes were fabricated by [...] Read more.
This study investigates the shear strength and aging characteristics of Sn-3.0Ag-0.5Cu (SAC 305)/Cu joints by the addition of ZrO2 nanoparticles (NPs) having two different particle size: 5–15 nm (ZrO2A) and 70–90 nm (ZrO2B). Nanocomposite pastes were fabricated by mechanically mixing ZrO2 NPs and the solder paste. ZrO2 NPs decreased the β-Sn grain size and Ag3Sn intermetallic compound (IMC) in the matrix and reduced the Cu6Sn5 IMC thickness at the interface of lap shear SAC 305/Cu joints. The effect is pronounced for ZrO2A NPs added solder joint. The solder joints were isothermally aged at 175 °C for 24, 48, 144 and 256 h. NPs decreased the diffusion coefficient from 1.74 × 10–16 m/s to 3.83 × 10–17 m/s and 4.99 × 10–17 m/s for ZrO2A and ZrO2B NPs added SAC 305/Cu joints respectively. The shear strength of the solder joints decreased with the aging time due to an increase in the thickness of interfacial IMC and coarsening of Ag3Sn in the solder. However, higher shear strength exhibited by SAC 305-ZrO2A/Cu joints was attributed to the fine Ag3Sn IMC’s dispersed in the solder matrix. Fracture analysis of SAC 305-ZrO2A/Cu joints displayed mixed solder/IMC mode upon 256 h of aging. Full article
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Review

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24 pages, 2286 KiB  
Review
Recent Advances in Brazing Fillers for Joining of Dissimilar Materials
by Byungmin Ahn
Metals 2021, 11(7), 1037; https://doi.org/10.3390/met11071037 - 29 Jun 2021
Cited by 26 | Viewed by 5383
Abstract
Brazing fillers for joining applications are essential for manufacturing and designing advanced materials. Several types of brazing fillers have been developed in recent decades to join similar or different engineering materials. Important parts of automotive and aircraft components, including steel, are often joined [...] Read more.
Brazing fillers for joining applications are essential for manufacturing and designing advanced materials. Several types of brazing fillers have been developed in recent decades to join similar or different engineering materials. Important parts of automotive and aircraft components, including steel, are often joined by brazing. In addition, ceramic components in microwave devices and circuits have been joined with a high level of integration in microelectronic devices. Similarly, in the medical field, metallic implants have been brazed to ceramic dental crowns. These advances have made human life more convenient. However, in brazing, there are certain issues with intermetallic compound (IMC) formation and residual stresses in joints at high temperatures. Nanoparticle-reinforced fillers have been proposed to control IMCs, but there are other dispersion and particle segregation issues at the joints. In this study, various types of brazing fillers, joint fabrication processes, and brazing technologies developed in recent decades are reviewed. Furthermore, new developments in brazing materials and their specific applications are presented. Finally, the emerging areas in brazing, including the recent entropy-modified brazing fillers for various structural and technological fields, are discussed. Full article
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25 pages, 5258 KiB  
Review
Low Melting Temperature Sn-Bi Solder: Effect of Alloying and Nanoparticle Addition on the Microstructural, Thermal, Interfacial Bonding, and Mechanical Characteristics
by Hyejun Kang, Sri Harini Rajendran and Jae Pil Jung
Metals 2021, 11(2), 364; https://doi.org/10.3390/met11020364 - 22 Feb 2021
Cited by 46 | Viewed by 9880
Abstract
Sn-based lead-free solders such as Sn-Ag-Cu, Sn-Cu, and Sn-Bi have been used extensively for a long time in the electronic packaging field. Recently, low-temperature Sn-Bi solder alloys attract much attention from industries for flexible printed circuit board (FPCB) applications. Low melting temperatures of [...] Read more.
Sn-based lead-free solders such as Sn-Ag-Cu, Sn-Cu, and Sn-Bi have been used extensively for a long time in the electronic packaging field. Recently, low-temperature Sn-Bi solder alloys attract much attention from industries for flexible printed circuit board (FPCB) applications. Low melting temperatures of Sn-Bi solders avoid warpage wherein printed circuit board and electronic parts deform or deviate from the initial state due to their thermal mismatch during soldering. However, the addition of alloying elements and nanoparticles Sn-Bi solders improves the melting temperature, wettability, microstructure, and mechanical properties. Improving the brittleness of the eutectic Sn-58wt%Bi solder alloy by grain refinement of the Bi-phase becomes a hot topic. In this paper, literature studies about melting temperature, microstructure, inter-metallic thickness, and mechanical properties of Sn-Bi solder alloys upon alloying and nanoparticle addition are reviewed. Full article
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21 pages, 5093 KiB  
Review
Recent Progress in Transient Liquid Phase and Wire Bonding Technologies for Power Electronics
by Hyejun Kang, Ashutosh Sharma and Jae Pil Jung
Metals 2020, 10(7), 934; https://doi.org/10.3390/met10070934 - 11 Jul 2020
Cited by 24 | Viewed by 9747
Abstract
Transient liquid phase (TLP) bonding is a novel bonding process for the joining of metallic and ceramic materials using an interlayer. TLP bonding is particularly crucial for the joining of the semiconductor chips with expensive die-attached materials during low-temperature sintering. Moreover, the transient [...] Read more.
Transient liquid phase (TLP) bonding is a novel bonding process for the joining of metallic and ceramic materials using an interlayer. TLP bonding is particularly crucial for the joining of the semiconductor chips with expensive die-attached materials during low-temperature sintering. Moreover, the transient TLP bonding occurs at a lower temperature, is cost-effective, and causes less joint porosity. Wire bonding is also a common process to interconnect between the power module package to direct bonded copper (DBC). In this context, we propose to review the challenges and advances in TLP and ultrasonic wire bonding technology using Sn-based solders for power electronics packaging. Full article
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