Laser soldering with light-intensity patterns reconstructed from computer-generated holograms

We describe a laser soldering technology with diffractive optics. This technology provides efficient one-step laser illumination for components to be soldered. A phase-only computer-generated hologram set in a variable-focal-length optical configuration generates a diffraction pattern with the dimensions required for processing solder. We verified the effectiveness of the proposed scheme by sealing a ceramic package such that it could house a quartz device. The factors for successful soldering include alignment of the diffraction pattern to the work piece, the thermal properties of the materials involved, and the wavelength of the laser used to process the solder. The beam intensity across the diffraction pattern influences the process, and the Oth-order intensity should be minimized to prevent damage to the work piece. (C) 2001 Optical Society of America.