Laser dicing of chip scale and silicon wafer scale packages

Abstract

Singulation of PCB based chip scale packages as well as the dicing of silicon based flip chip or wafer scale packaging is becoming critical. With the use of batch processes for PCB circuit fabrication and chip mounting, it becomes highly desirable to move away from standard diamond blade dicing techniques. The advent of silicon based packaging and wafers with a variety of odd form factor silicon chips and custom ASIC devices have caused further limitations to be encountered during dicing. It was inevitable that the inherent limitations of fixed row and column diamond saws would lead to the development and acceptance of free form trepanning capabilities offered by laser dicing and/or singulation. This paper will cover laser dicing and/or singulation of both chip scale and wafer scale-packaging materials. Initially the paper will outline material types with an emphasis on laser materials interactions and the selection of appropriate laser wavelengths for optimum process performance. Further explanations, formulas and basic laser nomenclature will also be discussed to familiarize those individuals who do not have experience with laser technology. The main body of the paper will focus on process parameters, processing rates, debris mitigation techniques, beam delivery configurations, substrate mounting, lasers types and cut quality achieved in the various materials outlined in the first section of the paper. The final section of the paper will summarize the quality of the process and the associated costs of using laser technology as compared to diamond saw technology.