Time-temperature transformation (TTT) cure diagram of a fast cure non-conductive adhesive

The conductivity of a non-conductive adhesive (NCA) interconnect is completely dependent on the direct mechanical contact between the IC bump and the substrate pad. According to our previous research, the evolution of the cure shrinkage, cure stress and even the interfacial adhesion strength are highly related to the curing process and the phase transformation of NCA. Therefore, a good understanding of curing process which involves time-temperature transformation (TTT) is of great importance for providing an optimal cure schedule. In this paper, multiple frequency rheological technique to detect the gelation point at lower temperature was used and the data was subsequently extrapolated to higher temperatures based on the principles of cure kinetics to determine the gelation line as a function of temperature. Vitrification was determined based on the T_g-conversion relationship and isoconversional lines. Vitrification times were also directly measured by rheological experiments. Based on the gelation and vitrification times, a complete TTT cure diagram ranging from sol, gel, fully cured, glassy, and rubber states was constructed for the fast cure non conductive adhesive.