Underfill adhesion to Cyclotene/sup TM/ (BCB) dielectrics

The adhesion of several underfills (Dexter Hysol FP4511, FP4527 and CNB775-34) to BCB (Cyclotene/sup TM/ 4022, 4024) has been studied through die shear testing and subsequent failure analysis. Die shear values range between 69 and 90 MPa. Failure analysis indicates that this spread in data probably results from the mixed mode nature of the fracture surfaces. From the die shear data collected before and after 24 hr water boil for Cyclotene 4022 and 4024 (with AP3000 adhesion promoter) and FP 4511 and 4527 underfillers, we find that the die shear strength decreases by an average of 11% for the 4 comparisons.