Structure control and comprehensive properties study of UV-curable epoxy resins

With the rapid development of high-performance computing, artificial intelligence and internet of thing etc, flip-chip ball grid array (FCBGA) has been an important package type to support these high-end applications. Thereinto, solder resist (SR) with good Cu migration resistance, excellent photo lithography resolution as well as outstanding comprehensive performance of high Tg, Low CTE, high thermal resistance and superior mechanical performance has been widely employed in FCBGA. Typically, SR consists of photosensitive resin, photo-initiator, active diluent, fillers, and other additives. The photosensitive resin in UV-curable SR is a polymer with unsaturated functional groups, usually derived from epoxy resin, and modified with unsaturated and alkaline-soluble groups. It is one of the main components of SR and plays a decisive role in the lithographic, thermal, and mechanical properties of the solder resist ink. As a result, it is quite important to deeply understand the comprehensive properties of photosensitive and alkaline developable epoxy. Herein, the effects of the controlled modification of photosensitive resin on the lithographic performance, thermal, and mechanical properties of SR are carefully explored. Firstly, a series of modified epoxy resins were prepared by introducing acrylic groups to phenolic epoxy resin at a molar ratio of 1:1 and subsequently incorporating different amounts (50%, 75%, 100%, and 125%) of anhydride to achieve various degrees of modification. Then, the modified resins were dissolved with photoinitiator, reactive diluent, and other additives to obtain solder resist ink, by characterizing its properties, a solder resist ink with better comprehensive performance is obtained, the asprepared acid-modified epoxy resin is a promising choice for the application in high-performance solder resist of FCBGA.