MEASUREMENT OF INTERFACIAL FRACTURE TOUGHNESS FOR MICROELECTRONIC PACKAGES

Interfacial adhesion plays an important role in the reliability of plastic encapsulated microelectronic (PEM) devices. Moisture that penetrates through the PEM devices and stays in the weak adhesion location vaporizes when the IC devices are subjected to thermal loading such as solder reflow in the assembly process. Device failures result due to pop-corning and cracking. Reliable PEM devices can be manufactured if there is good adhesion strength between packaging materials. In this paper, measurement and determination of interfacial fracture toughness between electronic materials are addressed. Interfacial fracture toughness between commercially available glob-top material and copper substrate is characterized. Laminated specimens with center pre-crack configuration are prepared and tested using four-point bending (FPB) configuration. The aim is to quantify the critical fracture load during crack initiation. Critical strain energy release rate and its corresponding mode mixity are determined from the measured critical load. Copper/glob-top material (Cu/GT) interface is selected as a case study and it is found that its interfacial fracture energy increases from 4 to 18J/m2 for loading phase angle ranging from 0° (pure mode I) to a mode mixity of 40°. The results will be presented in this paper.