Interfacial adhesion of nano-particle silver interconnects for electronics packaging application

Rapid package prototyping (RPP) technology based on a data-driven chip-first approach using nano-particle silver (NPS) interconnects has been developed to promptly assess novel package designs, new packaging materials, and performance of new devices. A potential limitation of rapid package prototyping with NPS interconnects is the adhesion between NPS and polymer substrates such as LCP, Polyimide, and BCB. Improving the adhesion strength of NPS is a key issue for reliable package prototypes with NPS interconnect. Qualitative measurement of the adhesion strength of NPS is necessary to investigate the adhesion improvements of NPS. A new adhesion test method is developed to estimate the interfacial fracture energy of NPS films. It has been found that most of the existing adhesion test methods are not directly applicable to NPS films. The newly developed adhesion test method is called Modified Button Shear Test (MBST) because it modifies the conventional button shear test and integrates the generally known die shear test. The MBST is used for measuring the interfacial fracture energy of NPS interconnect material. The interfacial fracture energy varies depending on physical, mechanical, and chemical states of the interface between NPS and polymer substrates. A mechanical interlocking adhesion model will be validated using MBST to demonstrate that the contribution of surface roughness to the interfacial fracture energy can be identified. It will show that the Yao´s model is an applicable mechanical interlocking model for NPS film adhesion model.