Laser Ablation of Thin Films on LTCC

摘要

Direct Digital Manufacturing techniques such as laser ablation are proposed for the fabrication of lower cost, miniaturized, and lightweight integrated assemblies with high performance requirements. This paper investigates the laser ablation of a Ti/Cu/Pt/Au thin film metal stack on fired low temperature cofired ceramic (LTCC) surfaces using a 355 nm Nd:YAG diode pumped laser ablation system. It further investigates laser ablation applications using unfired, or 'green', LTCC materials: (1) through one layer of a laminated stack of unfired LTCC tape to a buried thick film conductor ground plane, and (2) in unfired Au thick films. The UV laser power profile and part fixturing were optimized to address defects such as LTCC microcracking, thin film adhesion failures, and redeposition of Cu and Pt. An alternate design approach to minimize ablation time was tested for efficiency in manufacture. Multichip Modules (MCM) were tested for solderability, solder leach resistance, and wire bondability. Scanning electron microscopy (SEM) as well as cross sections and microanalytical techniques were used in this study.