Lasers at Liverpool

Laser removal of oxides and particles from copper surfaces for microelectronic fabrication
: Opt Express 2000; 7(2): 68}76. http://www.opticsexpress.org/oearchive/source/22798.htm.
: J. M. Lee and K. G. Watkins
Laser Group, Department of Engineering, University of Liverpool: Brownlow Street, Liverpool L69 3GH, UK
: Abstract: Laser removal of surface oxides and small particles from copper surfaces was carried out using a Q-switched Nd:YAG laser. Oxide layers and small particles on copper surfaces should be removed for the improvement of solder quality on printed circuit boards (PCBs) and for the prevention of circuit failure or loss of production yield during the fabrication of microelectronic devices. A selective removal of surface oxides from a copper surface was achieved by the laser treatment, which was confirmed by on-line acoustic monitoring of the process. An angular laser cleaning technique in which the laser irradiates the surface at a glancing angle was used for effective removal of the particles from the surface. The unique characteristics of this technique and the cleaning mechanism are discussed. . 2000 Optical Society of America