A Review of Sintering-Bonding Technology Using Ag Nanoparticles for Electronic Packaging

Abstract

Metal nanoparticles (NPs) have attracted growing attention in recent years for electronic packaging applications. Ag NPs have emerged as a promising low-temperature bonding material owing to their unique characteristics. In this study, we mainly review our research progress on the interconnection of using polyol-based Ag NPs for electronic packaging. The synthesis, sintering-bonding process, bonding mechanism, and high-temperature joint properties of Ag NP pastes are investigated. The paste containing a high concentration of Ag NPs was prepared based on the polyol method and concentration. A nanoscale layer of organic components coated on the NPs prevents the coalescence of Ag NPs. The effects of organic components on the bondability of the Ag NP paste were studied. Compared to the aqueous-based Ag NP paste, the polyol-based Ag NP with the reduction of organic component can improve the bondability, and the coffee ring effect was successfully depressed due to the increased Marangoni flow. The sintering behaviors of Ag NPs during the bonding process were investigated using the classical sphere-to-sphere approach. The mechanical property of joints using this Ag paste was better than that using Pb₉₅Sn₅ solders after storage at high temperatures. The sintering-bonding technology using polyol-based Ag NPs was helpful to the low-temperature interconnection for electronic packaging applications.

Keywords: Ag NP pastes; electronic packaging; joint performances; low-temperature interconnections; sintering mechanisms.

Figure 1

Illustration of the sintering-bonding process using polyol-based Ag NPs.

Figure 2

(a–c) SEM images of synthesized Ag NPs. (d–f) Optical images of the fractured bonded joints. (g–i) SEM images of the joints containing Ag NP pastes with PVP concentrations of 0.045 M, 0.45 M, 1.35 M. Reprinted/Adapted with the permission from Yan, J (2012). Copyright 2012 IOP Publishing [27].

Figure 3

(a) SEM and (b) TEM image of Ag NPs. (c) SEM image of the Ag NP paste. (d) TEM image of the bonding interface. (e) Thermogravimetric analysis (TGA) of the Ag NP paste in air. (f) Shear strength of Ag pastes as a function of sintering temperature with external pressure. Reprinted/Adapted with the permission from Yan, J (2012). Copyright 2012 Elsevier Ltd. [8].

Figure 4

(a–c) Optical images of the joint cross-sections, and (d–f) SEM images of the shear joints using aqueous-based Ag NP paste, Ag NP powders, and polyol-based Ag NP paste. Reprinted/Adapted with the permission from Yan, J (2012). Copyright 2012 Springer Nature [61].

Figure 5

(a,b) TEM images and (c) SEM image of the sintering of two adjacent Ag NPs. (d) Schematic of the sphere model, where D is the diameter of the NP and X is the diameter of the interparticle neck. (e) Neck growth kinetics at different temperatures. (f) The relationship between the joint strength and the square of the neck size ratio (x/r)². Reprinted/Adapted with the permission from Yan, J (2015). Copyright 2015 Springer Nature [71].

Figure 6

(a) Comparison of the joint strength using Ag NP paste and Pb₉₅Sn₅ solder after storage at different temperatures for 50 h. SEM fracture surfaces of the joints using Ag NP paste at different temperatures of (b) 200, (c) 250, (d) 300 and (e) 350 °C. Reprinted/Adapted with the permission from Yan, J (2016). Copyright 2016 Hindawi Publishing [82].