Determination of interface fracture parameters by shear testing using different theoretical approaches

Abstract

Simple adhesion tests like the pull-out test or the button shear tests have been used in industry for decades. They offer a great potential for comparison of different molding compounds, encapsulants, or adhesives on different types of sub-strates with or without surface treatment. However, for theoretical prediction purposes, interface fracture mechanics parameters are needed. Quantitative evaluations of the test applied to molding compound (MC)-button on Cu-leadframe by different fracture- and damage mechanical approaches are the subjects of the paper. Defect tolerant methodologies like the "virtual crack closure technique" (VCCT), which consider the interface initially delaminated, are compared to the damage methodology "cohesive zone modelling (CZM)", which needs no initial crack and can track the delamination progress. Calculated fracture parameters, in particular the energy release rates and mode mixity are compared. Effects on these parameters are discussed for d ifferent button shapes. In-situ tracking of delamination progress for a cubic button is shown using the optical correlation technique microDAC

Determination of adhesion and delamination prediction for semiconductor packages by using Grey Scale Correlation and Cohesive Zone Modelling

“…The adhesion of material combinations can be measured by Button-Shear-Test (BST) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] . Fig.…”

“…In the CZM a ratio of 5:1 between shear and traction mode was fixed. A cooling-down step from 165°C to À65°C was applied as load (chemical shrinkage of moulding compound was not considered) [18][19][20]. Simulation with CZM approach and experimental results after temperature cycling show same kind of delamination on the die pad near the chip edges for TO220 package.…”

“…Fig. 16 shows the strategy to built-up a FEM model with cohesive zone elements in a semiconductor package at the interfaces which have to be investigated [18][19][20].…”

“…17a-c show the delamination prediction by using CZM on the example of a TO220 package and the comparison to experimental results after temperature cycling (À65/150°C, 500Â, ultrasonic scan) (done by ABAQUS). For the simulations a minimum fracture energy of E PreCrack = 10 J/m 2 was used (visco-elastic simulation for moulding compound, solder as die attach with creep model) [18][19][20]. In the CZM a ratio of 5:1 between shear and traction mode was fixed.…”

Integration of intra chip stack fluidic cooling using thin-layer solder bonding

“…Table I summarizes the results. Although other experiments have shown that the onset of shear failure can occur before the maximum load reaction [15], usually the maximum force reading serves the shear strength calculation. The crucial detail is to which sheared area the force relates to.…”