Abstract
An epoxy-based solder paste (ESP) is a promising alternative to conventional solder pastes to improve the reliability of fine-pitch electrical joining because the epoxy encapsulates the solder joint. However, development of an appropriate epoxy formulation and investigation of its reaction mechanism with solder powder is challenging. In this study, we demonstrate a newly designed ESP consisting of diglycidyl ether of bisphenol F (DGEBF) resin, Sn-3.0 Ag-0.5 Cu (SAC305) solder powder, and L-glutamic acid (Glu), which is a proteinogenic amino acid for biosynthesis of proteins in living systems. The mechanism of the thermochemical reaction was explored and tentatively proposed, which reveals that the products of the reaction between SAC305 and Glu function as catalysts for the etherification of epoxides and alcohols produced by chemical bonding between DGEBF and Glu, consequently leading to highly crosslinked polymeric networks and an enhancement of impact resistance. Our findings provide further insight into the mechanism of the reaction between various formulations comprising an epoxy, amino acid, and solder powder, and their potential use as ESPs for electrical joining.
Highlights
Accepted: 18 March 2021Solder paste, mainly consisting of a solder alloy, a flux, an activator, and a solvent, plays an important role as an electrical joining material in the field of surface mount technology of electronic packaging for interconnection between semiconductor chips and substrates [1]
We studied the thermochemical reactions between diglycidyl ether of bisphenol F (DGEBF), glutamic acid (Glu), and SAC305, which revealed that the number of reactive groups of Glu that participate in chemical bonding mainly depends on the critical temperature owing to their inherent zwitterionic nature
Glu and SAC305 could function as catalysts for the etherification of epoxides and alcohols
Summary
Mainly consisting of a solder alloy, a flux, an activator, and a solvent, plays an important role as an electrical joining material in the field of surface mount technology of electronic packaging for interconnection between semiconductor chips and substrates [1]. Generation of harmful fumes during solder reflow, which can be mainly ascribed to the flux and solvent, does not conform to the emerging requirement for eco-friendly manufacturing processes [4]. Over the last few decades, epoxy-based solder pastes (ESPs) have generated considerable interest as a leading option to overcome the disadvantages of commercial solder pastes. Eom et al have conducted extensive research on the mechanism of the reaction between epoxy-based resins and solders [5,6,7,8] and their thermomechanical and electrical
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