FLIP-CHIP ON BOARD CONNECTION TECHNOLOGY - PROCESS CHARACTERIZATION AND RELIABILITY

As the consumer demand for small, lightweight electronic communication s products continues to grow, manufacturers must search for new and in novative connection technologies that will enable product miniaturizat ion to accelerate. These connection technologies must meet several cha llenging criteria. For example, increased functionality must be achiev ed in less board area and with lower board profile at a lower total sy stem cost. While silicon integration assists product designers in acco mplishing these aggressive goals, new electronic assembly methods also are essential in maintaining a competitive edge in the marketplace. U ltrafine pitch attachment methods are geared toward driving mass reflo w connection methods toward the pitch capabilities of silicon. The mos t promising of these ultrafine pitch attachment methods is Flip Chip o n Board (FCOB). This technique is capable of connecting unpackaged int egrated circuits directly to organic printed circuit boards (PCBs), ac complishing the ultimate in assembly miniaturization. The process util izes solder bumped I/O pads on the chips that are bonded to mating sol der bumped sites on the board. In order to produce high quality electr onic products in volume with FCOB, characterization of the assembly pr ocess is essential. Thorough characterization reveals the critical pro cess variables that must be controlled in production, allowing cost-ef ficient manufacturing to occur. This paper describes the process chara cterization of FCOB, and demonstrates the compatibility of the technol ogy with conventional surface mount processes. Key failure mechanisms are identified and discussed with respect to the degree of process con trol required to eliminate them.