Effects of the complexed moisture in metal acetylacetonate on the properties of the no-flow underfill materials

A potential no-flow (compression filling of encapsulant) underfill encapsul ant for simultaneous solder joint reflow and underfill cure has been report ed by the authors. The encapsulant is based on a cycloaliphatic epoxy/organ ic anhydride/Co(II) acetylacetonate system. The key of this no-flow encapsu lant is the use of a latent metal acetylacetonate catalyst that provides th e solder reflow prior to the epoxy gellation and fast cure shortly after th e solder reflow. However, most of the metal acetylacetonates can easily abs orp moisture as their ligand. Therefore, it is of practical importance to u nderstand the effect of the complexed water on the properties of the no-flo w material before and after cure. In this paper, differential scanning calo rimetry, thermal gravimetric analysis, thermal mechanical analysis, dynamic mechanical analysis, and Fourier transform infrared spectrometry were used to validate the existence of complexed moisture in the Co(III acetylaceton ate. The effects of the complexed water on the curing profile, glass transi tion temperature, and storage modulus of the cured no-flow underfill materi al were studied. A possible catalytic mechanism of the metal acetylacetonat e in the cycloaliphatic epoxy/anhydride system was subsequently discussed a nd proposed. (C) 1999 John Wiley & Sons, Inc.