Water-jet guided laser: possibilities and potential for singulation of electronic packages

摘要

Singulation of packages is an important step in the manufacturing of IC devices. Presently, the most widely used technique is abrasive sawing. Due to the combination of different materials used in packages such as copper and mold compound, the saw rapidly blunts and also conventional laser cutting is no alternative. Since 3 years, a new process is available for high precision material processing: the water-jet guided laser. This process combines the advantages of cold cutting by a water-jet with the high precision and speed of a laser cut and is now applied into electronic package singulation. We show that complete mold compound removal inbetween the copper contacts in a first step is important. The following step of copper cutting is usually the speed-determining step of the singulation process. The mold compound can be ablated due to the reflected or diffused light. Thus care has to been taken in order not to alter too much the good mold compound edge quality during the copper cutting step. Flipping the sample between the two steps, and using different nozzle sizes for mold compound and copper cutting, give the best results. In all cases however, the copper cut is wear free and without burrs, which is an important advantage compared to mechanical sawing. Typical cutting speeds for different copper thicknesses will be given and the possibilities for further speed enhancements will be briefly discussed.