Improvements in Solid State Lighting Applications with the use of Traditional Thick Film Technology.

Abstract

As the LED market continues to grow and overtake many other lighting technologies such as incandescent and compact fluorescent bulbs (CFL), there are many challenges that LED manufacturers face. As demand for higher power and longer life continue to drive LED adoption in lighting applications, manufacturers must be able to find ways to increase thermal efficiency while reducing cost for LED package designs. In this paper, the benefits of a new Pb Free smooth-print thick film Ag conductor are examined in comparison to more traditional die attach methods, which include plated thin films, and polymer based die attach adhesives. A smooth print thick film conductor can offer the best of both worlds as cost and process simplicity are comparable to a polymer system, while thermal efficiency and solderability are comparable to plated thin film systems. As surface smoothness increases, there is also the benefit of reduced solder voiding and material usage; solder voiding is a major contributor to thermal inefficiency. In the case of high cost solders such as Au/Sn, the reduction in material usage can translate to significant cost savings. Thermal efficiency, solderability, and manufacturing complexity must all be considered as new LED package designs are sought that reduce overall cost while increasing thermal efficiency and effective operational life. This paper evaluates these benefits as they apply to wire bonding, thermal dissipation, surface smoothness, and voiding at the die-package interface. Each of these properties can affect thermal efficiency of the package, which in turn affects the light output and effective operational life of the LED. A new option for LED package design is presented, and this packaging can allow for cost-effective manufacturing while keeping up with industry demands of higher power, maximum efficiency, and greater effective operational life.