Product Code: ICAL06_P532

Laser Drilling of PET-backed Unfired Ceramic
Authors:
Leonard Migliore, Coherent Laser Group; Santa Clara CA USA
Presented at ICALEO 2006

Thin (50 to 100 micron) ceramic spacers for multi-layered electronic devices such as flash RAM require large numbers of small via holes drilled in them to perform their function. The preferred hole diameter is currently in the range of 100 microns but is expected to become smaller. These ceramics may be easily drilled prior to firing. So called "green" ceramic is comprised of fine refractory particles in an organic binder. The binder, which burns off during firing, gives the material the consistency of a weak flexible tape. Sheets of green ceramic, consequently, are backed with polyethylene terephthalate (PET) film for ease of handling. Drilling of PET-backed green ceramic with conventional CO2 lasers causes severe melting of the PET backing, making it impossible to separate the ceramic from the backing. We have examined the use of a 9.4 micron CO2 laser for this process. The 9.4 micron wavelength is absorbed more strongly in the PET than is 10.6 micron light, reducing the dimensions of the heat-affected zone in the PET. Drilling with this type of laser produces greatly improved results in this process.