Strength Evaluation of Plastic Packages During Solder Reflow Process Using Stress Intensity Factors of V-Notch

Abstract

A crack initiated from a V-notch corner in the molding resin, such as a corner of die pad, is one of the main causes of the failure in plastic packages. The stress intensity factors of the asymptotic solution of a corner of jointed dissimilar materials are utilized for the evaluation of a solder reflow crack in a quad flat package (QFP). First, we estimate the critical vapor pressure, which causes a crack from a corner in the molding resin, using the critical stress intensity factor of a V-notch corner. This critical factor was measured by V-notched three-point bending tests and the displacement extrapolation method along with the three dimensional (3-D) finite element method (FEM). Moisture concentration in the QFP after absorption is analyzed, and vapor pressure caused by the solder reflow process is estimated. The critical moisture absorption time, which results in crack occurrence during the solder reflow process, can be predicted using this evaluation technique. Furthermore, we perform infrared solder reflow tests of the QFP for verifying the present failure evaluation technique.

Evaluation of the Delamination in a Flip Chip Using Anisotropic Conductive Adhesive Films Under Moisture/Reflow Sensitivity Test

“…Then an equilibrium condition expressed by Henry's law could be assumed to hold between the vapor pressure in the gap and the moisture concentration in the ACF. The vapor pressure in the gap during the solder reflow process was predicted from Henry's law as at at (12) where is the maximum moisture concentration, C is the reflow temperature, is the saturated vapor pressure, and is the predicted vapor pressure in the gap. Fig.…”

“…12. The stress intensity factors and were given by Kassir and Bregman [25], as follows: (13) where is the uniform tension applied to the crack surface, is the radius of a penny-shaped crack, is the gamma function, and . The bielastic constant is given in terms of the shear moduli and Poisson's ratios ( 1,2) of the materials 1 and 2 by (14) We calculated the stress intensity factors of a penny-shaped crack at the interface between the ACF and the Si chip (or the Al pattern or the substrate) from (13) and (14) when vapor pressure was applied to the crack surface.…”

Experimental and Numerical Approaches for Reliability Evaluation of Electronic Packaging

“…Residual stress of resin-molded integrated circuit (IC), which is one of the critical factors in their reliability, was evaluated. (9) Humidity effects on the delamination in a flip chip using anisotropic conductive adhesive films (ACFs) (10) and the solder reflow crack in a quad flat package (11) were evaluated. Hygrothermal properties of ACF package were experimentally obtained and moisture concentration distribution was obtained using FEM by Yoon et al (12) In this paper, experimental methods and numerical approaches are briefly reviewed, which were performed in the Computer Aided Reliability Evaluation (CARE) laboratory in KAIST for reliability evaluation of electronic packaging.…”

Reliability of Interfaces Between Components in Advanced Electronic Packages under Solder Reflow Process

“…The vapor pressure in a small gap between materials during the solder reflow process is predicted by (4) where P V is predicted vapor pressure in the gap, P SV is saturated vapor pressure, C max is the maximum moisture concentration, H is Henry's law coefficient, T R C is solder reflow temperature [2].…”