Abstract: This disclosure relates to a process for laser soldering surface mount components on a printed circuit board using the continuous wave laser scanning technique. The process involves factoring together the scan rate, the beam diameter, and the laser power level, in order to determine what these specific process variables should be. In addition, the process also involves taking account of the depth of a metallic layer, such as a reference plane, inside the printed circuit board to determine its effect on other process variables. On the other hand, if the board does not have a metallic layer, the process takes account of the thickness of the board being processed. Preferred ranges for process variables are identified, as well as optimization techniques which further refine the process variables to achieve production efficiency or bonding pull strength.

Abstract: This disclosure relates to laser bonding electrical components having conductive elements which are naturally reflective of the laser beam wavelength. Component leads or pads which are made of copper or have a gold coating, for example, will reflect the wavelength of an Nd:YAG laser, making it difficult to form physical and electrical bonds using the laser bonding technique. In preferred embodiments, the conductive elements are coated with a non-flux, non-metallic, coating material which is less reflective of the laser energy than the conductive elements, making it possible to efficiently use a laser to accomplish bonding.

Abstract: An atmospheric pressure gaseous flux-assisted laser reflow soldering system provides a means of finely controlled soldering while eliminating post-soldering cleanup with environmentally damaging cleaning agents.

Abstract: The present invention involves a hold-down fixture which is usable in connection with bonding an integrated circuit package to a printed circuit board in a surface mount environment. The purpose of the fixture is to hold each of the leads of the package in intimate contact with corresponding contact pads on the printed circuit board during the bonding process. The fixture includes a base with two bars for each group of leads extending from the perimeter of the housing of the package. Together the bars compressively force the entire foot of each lead to set flatly against its pad. The bars are spaced such that an aperture, which is defined by an opening through the base and positioned between the bars, can admit a bonding means, such as a laser beam, to reflow a solder composition at the lead/pad junction. Accordingly, with the leads compressed against the pads by the bars of the fixture, and with the reflow of the solder composition by means of the laser, a good bond between each lead and pad will be formed.

Abstract: A system for continuously supplying solid silicon particles to an apparatus for growing hollow, tubular crystalline bodies. The system includes a container for storing solid silicon particles, a vibratory, pneumatic, or other device for causing the particles to exit the container through an aperture in the bottom thereof, a receiving chamber coupled with the container for receiving the particles which are dispensed from the container, and means for providing a jet of pressurized fluid in the receiving chamber. The latter is coupled with the crucible of the crystal growth apparatus via a conduit extending up through the center of the crucible.In operation, silicon particles are dispensed from the container, travel into the receiving chamber where they are entrained by the jet of pressurized fluid which drives the particles out of the receiving chamber, through the conduit, and into the crystal growth furnace where they fall back into the molten silicon supported in the crucible.

Abstract: A method of reflow soldering an electrical lead to a solder pad using a laser in which the solder pad, rather than the terminal, is irradiated by the laser beam. The pad becomes hot enough to melt the solder which efficiently transfers the thermal energy to the lead. Upon removal of the laser beam, the solder sets forming an intimate electrical and mechanical connection between the common areas of the lead and pad. To practice the process, the solder pad should extend out beyond the portion of the lead in contact with the pad by a distance equal to or exceeding the diameter of the laser beam used in the bonding process.