Medical Device Wafer Singulation

Singulation can be the most damaging step in electronic manufacturing where individual dice are freed from a brittle silicon wafer. So much torque and force is applied to the silicon during this process that if precautionary steps are not taken, the freed die may exhibit low strength due to chipping damage. For medical devices, this is particularly a problem because medical devices must be specially shaped and assembled so that they can fit into small implantable or insertable units for the human body. Insertable medical products require that dice have unusually high aspect ratios in order to fit into tubular shaped instruments. For this paper, we have emulated a medical device using blank silicon wafers cut to >3.60 mm long 0.36 mm wide and 0.100 mm thick. The aspect ratios of 10:1 will be compared with lower as well as high aspect ratios for dicing quality and die integrity. With standard dicing parameters with standard blades, the singulation yield would be as low as zero. Even the use of step cut which in most cases would alleviate chipping, but for such high aspect ratio dice, the yield improved to only 50%. This paper will present comparative yield results of various dicing setups to find the process with the best yield on singulated dice. 100% yield for singulation resulting in higher strength devices can be obtained using properly selected blades with the correct dicing parameters. Newer, stronger and narrower blades are allowing dice with high aspect ratios to be sawn without chipping yield loss. Also special dicing programs are required to produce chip-free dies without resorting to laser saws.