Novel test prototype for the determination of mode I fracture parameters: application to adhesively bonded electronics

Structural adhesives are commonly used in space electronics particularly for bonding ceramic quad flat packages to printed circuit boards (PCB). In such application, adhesive joints are subjected to high loads due to the PCB bending under severe acceleration of the launch. It is thus mandatory to figure out the adhesive mechanical resistance in order to achieve a safe design. The present paper is concerned with the determination of the cohesive properties of an aerospace adhesive in tensile fracture mode. For this purpose, a novel test prototype consisting of a ceramic component adhesively bonded to a PCB plate is designed and tested subsequently in quasi-static loading. In parallel, a finite element (FE) model of the assembly is developed using ABAQUS software. The adhesive joint is modelled by user-defined cohesive elements. The latter are implemented using a FORTRAN user subroutine (UEL) capable of simulating the geometrical and material nonlinearities of the adhesive. A good agreement is obtained between experimental and numerical results after updating. This finding permitted to successfully find out the cohesive parameters of the tested adhesive.