Smart cards and smart labels-high volume applications of adhesive flip-chip technologies

Adhesive FC technologies have proven to be very competitive to classic solder FC technologies. Smart card and applications require chip connections with thickness of the entire card or label. Only FC technologies can meet these low cost, high throughput and thin packaging demands. The use of isotropic conductive adhesive (ICA) for bumping and assembly for smart cards results in a number of advantages such as a simple versatile process, lower temperatures and environmental friendliness. Using an anisotropic conductive adhesive (ACA) or an nonconductive adhesive (NCA) for smart label production allows a high throughput from reel to reel. All technologies require suitable bond pads. The commonly used aluminum alloys results in unstable contacts for the conductive adhesives and hence there´s an urgent need for an additional under bump metallization for these technologies. KSW Microtec has developed a technology which is based on electroless deposition of palladium. This metallization is performed as backend process. An homogeneous film of palladium with the required thickness of about 1 μm for the ICA process and about 15 μm for metallic bumps is deposited. In this article an introduction to adhesive FC technologies is given. Several bumping technologies used for the assembly process are shown. The authors explain their mass production experiences in KSW Microtec and advantages and disadvantages of each of the technologies. Detailed reliability tests performed on some adhesive FC technologies are shown. Practical experiences in mass production of smart cards and smart label especially in a reel to reel assembly process are discussed