Development and characterization of single mode microwave cured adhesives for electronics packaging application

The use of microwave radiation for curing of adhesives has received increasing interest due to significant advantages of this technique (rapid, uniform and selective heating) over conventional thermal curing in the electronics and microelectronics industries. The objective of this study is to formulate epoxy-based adhesives which can be rapidly cured by single mode microwave radiation and to investigate the effects of different curing agents, amounts of the curing agent and addition of carbon black on the microwave curing rate. With an epoxy, diglycidyl ether of bisphenol F as basic resin, five adhesives were formulated. The microwave radiation was performed with single mode microwave equipment (2.54 GHz, 300 W). The cure kinetics of the adhesives was studied with differential scanning calorimetry. It was found that among the five formulated adhesives with different curing agents and diluents, only one with Imidazole I as curing agent has a more efficient coupling of single mode microwave radiation. The curing degree of this adhesive, after radiated for 60 seconds, reached the same level (90%) as that of thermal curing at 150°C for 90 seconds. Three adhesives with 5, 10 and 15 wt.% of Imidazole I as curing agent were examined and the results showed that the curing rate of the adhesives increased as increasing of the amount of Imidazole I. The effects of the addition of carbon black on curing rate were investigated with the adhesives (15 wt.% Imidazole I) mixed with 5 and 10 wt.% of carbon black. The curing rate enhancement was observed. The adhesive with 10 wt.% of carbon black reached 100% of curing degree after radiated for 20 seconds.