Recent advances in anisotropic conductive adhesives (ACAs) materials and processing technology

This paper deals with three recent advances in the area of ACA materials and processing technologies, (1) wafer-level ACA, (2) ultrasonic ACA bonding, and (3) Solder ACAs. Patented idea of Wafer level package (WLP) ACA/NCA was introduced earlier as one of the promising ACA packaging technologies due to its advantages such as fewer processing steps, lower cost, and enhanced device performance compared to conventional single chip ACA packaging. WLP ACA can be widely used for flat panel display (FPD), general semiconductor packaging, and 3D-TSV applications because of cost and performance advantages. In addition, another patented novel anisotropic conductive film (ACF) bonding process using vertical ultrasonic vibration was also introduced in flex-on-board (FOB) and Touch Screen Panel(TSP) applications. The ACF temperature was precisely controlled by adjusting both U/S power and bonding pressure. The significant meaning of this technique are (1) significantly reduced ACF bonding time typically 1/3 ~ 1/5 of conventional T/C bonding times in FOB applications, (2) less thermal damages especially for TSP assembly, and (3) compact and energy saving machine. Lastly, newly developed solder ACFs combined with Ultrasonic processing can increase twice the current handling capability of conventional Ni ACFs and show excellent reliability performance in FOB applications because of metallurgical bonding at the joint rather than physical contact of conventional ACAs.