Reliability Design of Conductive Adhesive Connection in Electronic Packages

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Conductive adhesive connection for electronic packaging using anisotropic conductive adhesive film (ACF) and conductive resin are expected to increase year after year due to its easiness for downsizing, manufacturing process under low temperature and including no lead and so on. However, the reliability of adhesive connection is currently lower than that of soldering which has the developed reliability technologies. Developing the evaluation and the design technique for the reliability of adhesively connected electronic packages is very important for the promotion of the adhesive connection technique for electronic packages.Flip chips are often used with other surface mount devices, and are connected with a circuit board using solder joints. During a solder reflow process, a circuit board is heated to the range from 150℃ to 200℃ for the pre-heating, and reached to the peak temperature around, the range from 240℃ to 245℃. During the solder reflow process, some flip chip using adhesive connection are broken or unconnected.In this study, we developed a new design technique for a flip chip using the ACF against the solder reflow sensitivity test. At first, the coefficient of diffusion, and Henry's low coefficient were measured, then the finite element analysis of the moisture absorption was performed to estimate the vapor pressure induced in a flip chip during solder reflow process after moisture absorption in an atmosphere. The stress intensity factors around assumed cracks in a flip chip caused by the estimated vapor pressure were compared with the delamination toughness of an interface between the ACF and the material of a component part (Aluminum terminal, Cu terminal or Si chip). Estimated critical absorption time that causes the delamination during the solder reflow process corresponds well with experimental result.