UV curing and electrical characterization of chip on flex for smart card application

Abstract

Recently, anisotropic conductive adhesive (ACA) has found applications in the flip chip on flex interconnection process and captures more and more attention due to its ease of application, reduction in investment expenditure, and also, the lower processing temperature which is more environmentally compatible. Conventionally, the adhesives are cured under a certain temperature for a corresponding time period. In other words, heat is used as the energy source. In this project, a new curing method was applied, that is the UV curing of the chip on flex for smart card application. The first part of the project inspects the feasibility of this new method by completing the whole manufacturing process. Principal parameters affecting the final curing effects include the UV intensity, UV wavelength, heat temperature and the curing duration. It is concluded from the experimental results that properly handled, the manufacturing cycle can be greatly reduced due to an instant curing process which lasts for only 5 seconds. Also, smart card samples were made under different UV intensity settings in order to investigate the impacts on the smart card performance brought by UV intensity during curing process. The second part of the project focuses on the investigation of the electrical characteristics of smart cards. Reading-distance, the major characteristic of this kind of contact-less smart card is measured under different parameter settings. In summary, the use of UV curable ACA makes low-cost, reliable and environmentally compatible production possible, which is a very promising technology for fine-pitch flip chip packaging.