Characterization and Modeling of Moisture Absorption of Underfill for IC Packaging

Abstract

Underfill is a highly particle filled epoxy polymer Teflon foil and ti used in flip chip to fill the gap between the leadframe and die about 300pm. or between die and die. In order to be able to flow in the thin 12.5*4.89*0.385i gap, the silica filler particle must have a diameter below moisture absorpti 10ptm. This epoxy underfill material mechanically couples the as possible. chip and substrate and decreases the stress in the solder joints, therefore enhancing solder fatigue life. Good adhesion 2.2 Equipment of between the epoxy underfill and the surface of solder ball, silicon chip, and substrate is necessary to minimize stress in a A program package. Use of the non-hermetic material does raise a humidity chamb( potential concern, i.e. moisture induced interfacial Fig. 1) delamination and moisture expansion may cause failure. In this study, moisture absorption and desorption properties were investigated, such as moisture absorption equilibrium weight gain and diffusion coefficients at different temperature and different humidity are tested and characterized, moisture absorption and desorption kinetics are tested and fitted

A new method to measure the moisture expansion in plastic packaging materials

“…The moisture properties of die attach, underfill, and molding compound are characterized in our previous papers [7,8]. C sat of different materials are listed in Table 1.…”

“…Experiments show that moisture desorption is difficult at low temperatures and moisture can be not completely dried out at these temperatures. Sometimes this small amount is called "strong bounded water [7,8]" because this small portion of moisture molecule exists between the polymer molecules. Therefore our new DMA moisture method can be considered as a more reliable method for CME determination of packaging materials.…”

“…Moisture absorption time should be long enough to ensure that moisture equilibrium is reached. According to our model [7,8], moisture absorption equilibrium time can be calculated. For thin strip sample, such as thickness from 0.3 to 0.4 mm, 300 to 600 minutes is sufficient enough for reaching moisture absorption equilibrium.…”

Moisture effects on a system in package carrier

“…The moisture properties of these three kinds of packaging materials are listed in Table 1 [4,5]. In Table 1, D is the diffusion coefficient and Csat is the moisture saturation level.…”

“…Therefore it is very important to characterize, model the moisture uptake and study moisture effect on the mechanical properties of packaging materials used in the electronic industry. Moisture diffusion properties are modeled in our previous studies and these models are proved reliable [4][5]. Polymer materials swell when moisture is absorbed.…”