High-volume shrinkage nanoporous gold microspheres fabricated by non-wetting liquid-solid interface and chemical dealloying for high-reliability electronic packaging

Nanoporous gold (NPG) offers promise in electronic packaging due to its high compressibility, excellent conductivity, and high thermal conductivity. However, fabricating ultrafine (1–10 μm) conductive NPG microspheres presents a challenge. Herein, we report a novel method for preparing high-volume shrinkage NPG microspheres (NPGMS) with a particle size range of 2.3–8 μm (average 5.06 μm, calculated by ImageJ software). The method involves preparing gold-copper precursors via spray freeze-drying, achieving spheroidization through non-wetting effects at the liquid-solid interface, and fabricating NPGMS by chemical dealloying. Statistical analysis shows a 79 % average volume shrinkage upon dealloying. By using these high-volume shrinkage NPGMS, we fabricated an NPGMS anisotropic conductive film (NPGMS-ACF) and demonstrated its superior performance in 500-micron pitch Flex-on-Glass (FOG) bonding. Remarkably, at only 5 wt% powder loading, the NPGMS-ACF exhibited significantly improved connection reliability compared to commercial ACFs. In cyclic thermal shock testing, NPGMS-ACF packaged devices displayed exceptional stability, with a resistance change of 0.468 Ω (18.4 % change) after 5 cycles. In contrast, commercial ACF packaged devices failed after one cycle, with resistance changes exceeding 100 MΩ. The improved performance of NPGMS-ACF stems from: (1) NPGMS’s excellent thermal and electrical conductivity; (2) enhanced chip-substrate bonding due to the porous structure’s high compressibility, effectively reducing thermal stress. These findings establish NPGMS-ACF as a promising candidate for advanced liquid crystal display (LCD) packaging, providing enhanced thermal shock resistance and adhesive reliability.