Surface Mount International Conference Proceedings


Author: Rick Godin
Company: MPM Corporation
Date Published: 9/10/1996   Conference: Surface Mount International

Abstract: Printing and plating are commonly used methods for applying solders and other low melt point metals to wafers, ceramics, PCBS and other substrates. However, printing these metals into vias for interconnect, fine lines, wafer bumping and other applications requiring less than 125 micron dots, lines, etc. is not available. Also, plating requires disposal of materials and is not well suited for small runs or location in a IC fabrication facility. This article describes a new method for applying these low melt temperature metals to address the problems described above. With this new method solder, other alloys and metals can be applied with a system similar in principle to an ink jet printer. This new method is called Solder Jetting Technology (SJT). Using this method, pressure is applied to a vessel of molten metal. The material is mechanically vibrated and a continuous droplet stream is created. Using electrostatic deflection the droplet trajectory is controlled while in flight toward the substrate. As a continuous system, material is applied accurately but at higher speeds than with droplet-on-demand systems. Solder ball sizes, in a controllable range, from 49 to 189 microns have been jetted using this method. Utilizing CAD driven data files, patterns are jetted at rates of up to 44,000 dots per second, depending on ball size. This CAD data driven system permits patterns to be changed instantaneously from wafer to wafer or substrate to substrate. The variety of application is impressively diverse including wafer bumping for flip chip, DCA substrate bumping, substrate via fill, fine line interconnect, fine pattern generation, chip-on-glass bumps, BGA ball formation, 3-D substrates, hybrids, metal cladding and many other processes. SJT will become an industry standard, enabling improvements for small, lightweight packages and other electronic products.

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