Hongtao Chen

Driven by the rapid development of deep-space exploration, artificial intelligence, and new energy vehicles, the integration density of power devices has been significantly improved, creating an urgent demand for electronic packaging interconnection materials with low thermal resistance, high reliability, and thermomechanical stress resistance. Porous metals have become a major research focus for packaging interconnection materials owing to their high specific surface area; controllable porous structure; and excellent thermal, electrical, and mechanical properties. Among various porous metals, porous metal has attracted extensive attention in the field of electronic packaging interconnection due to its low cost, high thermal conductivity, superior wettability, and good processability. This paper systematically reviews the research progress of porous copper (Cu)-based interconnection materials in electronic packaging, covering the preparation methods, interconnection methods and reliability of porous Cu-based interconnection materials. In addition, the existing challenges in the preparation, interconnection processes, and reliability evaluation are summarized, which provides clear research directions for the structural optimization and engineering application of such materials in the future.

With the trend towards high-frequency, high-power-density packaging, through-glass vias (TGV) are considered a promising alternative to TSVs. However, their reliability under high current density, a critical concern for practical application, remains insufficiently studied. This work systematically investigates the failure mechanisms of TGV interconnect structures under electrical loads. In-situ electromigration experiments were conducted on daisy-chain TGV samples at current densities of 2.3×105, 2.8×105, and 3.0×105 A/cm2, with real-time resistance monitoring and cross-sectional SEM analysis. Distinct failure modes were identified: at the lowest density, failure was dominated by RDL/glass interfacial delamination with negligible resistance change; at the medium density, electromigration became apparent, accelerating void nucleation/growth and causing a linear resistance increase; at the highest density, severe thermo-mechanical coupling led to glass cracking at the TGV-RDL corner and RDL plastic deformation, resulting in an accelerated resistance rise. Complementary electro-thermo-mechanical finite element simulations revealed significant current crowding at the TGV-RDL corners, with local current density exceeding that at the narrowest via cross-section. The combined temperature field and geometric features jointly determined the stress concentration locations. This study clarifies the failure mechanisms of TGV and provides insights for the reliable design of high-current-density glass interposer packages.

In response to the increasing packaging density and operating temperature requirements of wide bandgap power devices (e.g., SiC, GaN), a novel SAC305-infiltrated Ag-reinforced porous Cu (SAPC) composite solder was fabricated via a screen-printing and reduction sintering method using CuO as the matrix, NaCl as the pore-forming agent, and Ag as the reinforcing additive. After reflow at 250 ℃ for 15 min, the interconnect layer consisted of a Cu-Sn intermetallic compound (IMC) framework embedded with residual Cu and dispersed Ag3Sn particles, achieving an average shear strength of 53.80 MPa. At 250 ℃, shear strength of the 3 wt.% Ag samples was 37.17 MPa, improved by 74.10 % compared to that of the sample without Ag. After 1000 hours of aging at 250 ℃, the shear strength of the 3 wt.% Ag samples was 45.10 MPa, decreased by only 16.17 % compared with as-bonded samples. Ag3Sn particles improved long-term operating reliability through pinning effect, and Kirkendall voids were constrained by Cu skeleton. SAPC-packaged SiC diode maintained stable electrical performance up to 300 °C. After 15000 cycles of power cycling at 25~175 ℃, and the devices maintained stable, while SAC305-packaged devices failed, which proved that it meets the long-term reliability requirements of high temperature power devices.

Oxidation of copper nanoparticles during bonding in air severely limits the formation of dense Cu-Cu joints. In this work, oxidation-resistant copper nanoparticles were developed by surface modification with L-ascorbic acid and 2-pyridinemethanol, forming a protective shell of about 1.7 nm. TG-DSC results demonstrated their excellent oxidation resistance and good low-temperature sinterability. After mixing with glycerol to form a nanocopper paste, Cu-Cu bonding could be achieved directly in air. Molecular dynamics simulations further revealed that oxide removal is critical for atomic diffusion and dense sintering between adjacent particles. Dense Cu-Cu joints were obtained at 260 °C under 8 MPa for 40 min, with a shear strength as high as 109 MPa. This work provides a low-cost and high-performance route for power device packaging.

Through silicon via (TSV) and through glass via (TGV) are critical for advanced chip packaging, enabling vertical interconnections and improving bandwidth. The increase in chip density leads to a dramatic rise in heat generation, which induces the significant coefficient of thermal expansion (CTE) mismatch in TSV and TGV and further induces internal stresses, potentially degrading electrical performance and reliability. This work presented a study of TSV and TGV interconnect structures, focusing on their electrical transmission characteristics under thermal loading, evaluating the reliability differences between TGV and TSV by using electrical transmission characteristics as the metric. The findings reveal that the electrical transmission characteristics of TGV generally outperform those of TSV. Especially, when optimized by increasing signal via spacing and adding additional grounding vias, the characteristics of TGV significantly enhance high-frequency performance. Furthermore, thermal shock measurements indicate that TSV experience rapid transmission characteristics degradation at lower shock cycles, while TGV degrade more slowly even at higher cycles. Based on microstructural analysis, we observe that TSV suffers from cracked insulation layers, leading to current leakage and transmission performance loss; TGV exhibits only minor delamination issues between the RDL and PI that do not significantly impact transmission characteristics. Under high temperature, TSV initially shows improved transmission performance due to air gap formation, but later degrade sharply as copper extrudes and bridges with the silicon substrate. In contrast, under high temperature, TGV exhibit a gradual increase in impedance due to crack expansion within the copper, but this effect remains minimal. TGV not only offers superior transmission performance but also demonstrates greater reliability under thermal loading compared to TSV.