Elucidation of Adhesive Interaction between the Epoxy Molding Compound and Cu Lead Frames

Abstract

Clarification of adhesive interactions in semiconductor packages can improve reliability of power electronics. In this study, the adhesion interfaces between the epoxy molding compound and Cu-based lead frames were analyzed using the density functional theory. A resin fragment was prepared based on the polymer framework formed in the curing reaction of epoxy cresol novolac (ECN) and phenol novolac (PN), which are typical molding materials. The resin fragment was optimized on the surfaces of Cu and Cu 2 O. We calculated the charge density differences for adhesion structures and discussed the origin of adhesive interactions. The ECN–PN fragment’s adhesion to the Cu surface relied mainly on dispersion forces, whereas in the case of Cu 2 O, the resin bonded chemically to the surface via (1) σ-bonds formed between the ECN–PN’s OH group oxygen and coordinatively unsaturated copper (Cu CUS ) and (2) hydrogen bonds between resin’s OH groups and coordinatively unsaturated oxygen (O CUS ) located close to to Cu CUS , resulting in a stable adhesive structure. The energy required to detach the resin fragment from the optimized structure was determined using the nudged elastic band method in each model of the adhesive interface. Morse potential curve was used to approximate the obtained energy, and the energy differentiation by detachment distance yielded the theoretical adhesive force. The maximum adhesive stress was 1.6 and 2.2 GPa for the Cu and Cu 2 O surfaces, respectively. The extent to which the ECN–PN fragment bonded to the Cu 2 O surface stabilized was 0.5 eV higher than in the case of the Cu surface.

Peel Adhesion Strength between Epoxy Resin and Hydrated Silica Surfaces: A Density Functional Theory Study

“…The potential energy curve is plotted in 0.1 Å increments. As in many previous studies, − ,,,,− there is one inflection point in the curve. The curve was fitted using the Morse potential shown in eq .…”

“…The tensile adhesion strength was obtained by differentiating the potential energy curve, which represents the energy change during the process of the entire adhesive molecule being pulled vertically away from the surface. − ,,,,− To obtain the potential energy curve, we gradually displaced the entire epoxy molecule upward from the silica surface in increments of 0.1 Å, as shown in Figure a. The structures of the epoxy molecule and silica were fixed when the displacement was applied, and a single-point calculation was performed at each point to obtain the energy.…”

“…Since it is known that the adhesion force varies greatly depending on the direction of force application, different adhesion tests are conducted according to the application of the product. Although theoretical studies on adhesive forces have been conducted, − ,,,− ,− many of these studies are related to tensile adhesive forces; theoretical methods to estimate the adhesive forces corresponding to other adhesive tests and molecular understandings for the adhesive interfaces are needed.…”

Shear adhesive strength between epoxy resin and copper surfaces: a density functional theory study

“…Although theoretical studies on adhesive strength have also been conducted, most of them are related to tensile adhesive strength. [7][8][9][10][11][12][13][14][15]19,21,23,24,27,28 Theoretical studies on adhesion forces for different directions have recently been conducted, 18,20,30 but further theoretical analysis of adhesion forces in various directions and its molecular understanding are required.…”

Effects of Moisture Diffusion on a System-in-Package Module by Moisture–Thermal–Mechanical-Coupled Finite Element Modeling

“…In the literature, various methodologies were reported to characterize the effects of moisture absorption on the mechanical performance of bulk EMC and EMC/substrate interfaces, such as piezoresistive stress sensor chips for strain measurements [ 4 ], and micro-digital image speckle correlation (μ-DiSC) for interfacial fracture toughness [ 5 ]. Finite element modeling and molecular dynamics were also frequently used to study the influences of moisture absorption on the device reliability [ 6 , 7 , 8 , 9 , 10 , 11 ]. It was found that the interactions between water molecules and the chain structure of epoxy polymer during moisture diffusion can alter the mechanical and thermal performance of EMCs [ 7 , 12 , 13 ].…”