Maszara model DCB test (surface fracture energy)
Wafer bonds are commonly characterized by three important encapsulation parameters: bond strength, hermeticity of encapsulation and bonding induced stress.
The bond strength can be evaluated using double cantilever beam or chevron respectively micro-chevron tests. Double cantilever beam test, is a method to define the strength of the bond. This is achieved by determine the energy of the bonded surfaces. A blade of a specific thickness is inserted between the bonded wafer pair. This leads to a split-up of the bond connection. The crack length equals the distance between the blade tip and the crack tip and is determined using IR transmitted light. The measured crack length determines surface energy in relation to a rectangular, beam-shaped specimen. The Maszara model neglects shear stress as well as stress in the un-cleaved part for the obtained crack lengths. The compliance of a symmetric DCB specimen is determined out of the crack length , the width and the beam thickness. The surface fracture energy is depended and on the load-point displacement too.
|The surface fracture energy (J/m2)
|Modulus of elasticity ( Young's modulus) (Pa)
|The load-point displacemen (m)
|The thikness of the beam (m)
|The crack length (m)