Effects of the anchoring polymer layer (APL) material properties and surface modification of conductive particles on the ultra-fine pitch chip-on-glass (COG) interconnection

Abstract

In this study, a new concept of anisotropic conductive films for a next-generation display with high resolution was introduced, and mechanical, chemical, and electrical properties were evaluated when it was used. In order to realize high resolution, the bump pitch of the display driver IC is decreased, which causes an electrical short circuit between adjacent bumps when implementing an electrical interconnection using an anisotropic conductive films. By selecting a material having high tensile strength, the movement of the conductive particles occurred during the bonding process is completely suppressed, the dispersion degree of the conductive particles is increased, and finally, it is manufactured as a proto-type to evaluate electrical properties and reliability.

In Part 2, in order to suppress the movement of the conductive particles during the bonding process, APL structures using thermoplastic polymers (PBS, PVDF, Nylon and PAN) having different tensile strengths were fabricated, and surface and cross-section analysis was performed through SEM. Each APL ACFs was evaluated for conductive particle capture rate, electrical insulation properties, and contact resistance. In addition, it was analyzed by measuring FTIR that a specific functional group of nylon and PAN among APL materials reacted with a curing agent of NCF. Accordingly, it was found that the curing agent in the NCF did not participate in the curing reaction and reacted with specific functional groups of Nylon and PAN, resulting in a significantly low curing degree.

In Part 3, the surface of the conductive particles in the PAN APL structure having 95% of capture rate due to high tensile strength was exposed by SAM treatment. Since the conductive particles in the PAN APL structure are surrounded by a thin polymer skin, stable contact cannot be achieved during the interconnection process. The conductive particle surface was modified with a SAM solution to produce a structure in which the surface was naturally exposed while the PAN APL structure was fabricated. Finally, proto-type PAN APL ACFs having a length of about 10 m was produced, and electrical properties and reliability evaluations were conducted.

In Part 4, while producing a PAN APL structure with self-exposed surface of conductive particles, a magnetic field was applied to increase the distribution of the conductive particles. Electrical insulation properties of PAN APL ACFs having a high degree of dispersion of conductive particles were evaluated at ultra-fine pitch. Electrical insulation properties were evaluated by I-V curve measurement and 100% insulation properties were realized in all pitch areas.