Ag@Sn Core‐Shell Powder Preform with a High Re‐Melting Temperature for High‐Temperature Power Devices Packaging

Abstract

In this paper, the authors propose a highly conductive die attach material based on Ag@Sn powder for power devices operating at high temperatures or in other harsh environments. The preform can be reflowed at 250 C (18 C above the T m of Sn, 232 C), but the resulting bondline can sustain high temperatures up to 400 C with a high shear strength due to the high re-melting temperature of the formed Ag 3 Sn (T m ¼ 480 C) after the complete consumption of the outer Sn layers. In addition, the formed bondline exhibits excellent electrical and thermal conductivities due to the embedded Ag particles in the interconnections. The interconnections also exhibit excellent reliability under thermal shock cycling from À55 to 200 C because of the increased bondline thickness and inherent ductility of the Ag particles embedded in the Ag 3 Sn.

Electrical/thermal behaviors of bimetallic (Ag–Cu, Ag–Sn) nanoparticles for printed electronics

“…The endothermic peak at 482 °C is thought as the melting of Ag3Sn phase [27,44], whereas an exothermic peak at 597 °C is ascribed to the oxidation of Sn produced by the decomposition of SnO Mass (wt.%) - (3.94×10 -6 Ω•cm); meanwhile Ag-Sn NPs are 4.24×10 -5 Ω•cm in the resistivity, ~4 times lower than that of Sn NPs (2.04×10 -4 Ω•cm) and one order higher than that Ag NPs or Ag nanowires (3.25×10 -6 Ω•cm) [47].…”

Electrochemical Processing and Thermal Properties of Functional Core/Multi-Shell ZnAl/Ni/NiP Microparticles

“…Additional small endothermic peaks in the range of 282-289 °C can be attributed to the latent heat during the eutectic phase transformation of the ZnAl alloy core. Several characteristics of the core-shell material were calculated according to Equations (12) to (14) [83][84][85], and are summarized in Table 3. Thermal energy capability = × 100% (14) where ΔHm,core and ΔHm,core-shell are the melting heat capacities, and ΔHc,core and ΔHc,core-shell are the solidification heat capacities of the core material and the core-shell material, respectively.…”

“…The outer shell may be used to protect the core material in various ways: (1) Thermal barrier at elevated temperatures [ 3 ]; (2) physical barrier which provides a proper encapsulation of the core (in both solid and liquid states) [ 4 ]; (3) diffusion barrier which is designed to inhibit elemental segregation or interdiffusion between the core material and any material in its surrounding [ 5 ]; and (4) reflective/absorptive surface, e.g., to either reduce or increase laser absorbance in the metal powder during additive manufacturing (AM) [ 6 , 7 ]. In addition, the functionality of the outer shell may be beneficial when it reacts with its surrounding to: (1) Enhance metallurgical bonding with the matrix in a composite material [ 8 , 9 ]; (2) promote specific desired reaction [ 10 ]; and (3) enhance properties of the end material, e.g., corrosion resistance [ 11 ], increased re-melting temperature [ 12 ], density, or mechanical properties.…”

“…Various applications of metal/metal core-shell materials have been explored, such as core-shell Sn-Cu anodes for Li rechargeable batteries [ 13 ], surface modification of Zn-based electrode (made of Zn granulated powder) in zinc-air batteries [ 14 ], enhancement of powder metallurgy processability [ 15 , 16 , 17 ], AM applications [ 9 , 10 , 18 , 19 , 20 ], phase change materials (PCMs) for thermal energy storage [ 3 , 21 , 22 ], die-attach materials with high remelting temperature [ 4 , 12 , 23 , 24 , 25 ], corrosion resistance enhancement of Fe-based coating processed by plasma spraying [ 11 ], sensors [ 26 , 27 ], and catalysis [ 28 ] applications. The selection of the encapsulation process is highly dependent on the selected core and shell chemistries, shell thickness, the final quantity of coated powder, and the overall desired functionality.…”

Effects of Outer Shell Layer on the Electronic Transport Behaviors of Sn@SnOx Nanoparticles

“…In recent years, the core/shell metal nanoparticles have attracted extensive interest due to their unique structure and properties. [1][2][3][4] The core/shell structure can provide an opportunity to combine their respective advantages or special properties, perfectly compounding on the nanometer scale, to achieve structure and performance regulations to meet various application requirements. [5] Meanwhile, the physical and chemical properties of core/shell nanoparticles are strongly dependent on the composition and the state of the core/shell interface, giving them new properties.…”