Large thin organic PTFE substrates for multichip applications

Very high performance computer applications have created a demand for large organic substrates capable of interconnecting one or a few ASIC semiconductor devices with packaged memory devices. The electrical advantages offered by the use of a thin PTFE composite substrate were coupled with intrinsic mechanical advantages to create very high performance applications. The application development required interactions of design, fabrication, and new manufacturing technology to obtain rapid prototype production and allow a successful ensuing manufacturing ramp. One such package application involved using a 0.47mm thick PTFE substrate in a 65mm size format, having 8 memory devices surrounding a central ASIC, with numerous capacitors, in double-sided format. The application was developed as a pluggable module by using SMT attached pin/socket, and has a heatspreader which is in thermal contact with all devices and further provides flatness control once attached using thermal and electrically conductive adhesives. Assembly procedures to successfully handle the thin flexible substrate in volume were developed. Other applications are being developed in both pinned and BGA connection formats, and will have similar characteristics. This advanced packaging technology allows the ASIC devices to rapidly communicate with the memory devices through the use of low-k materials in conjunction with the substrate´s stripline format. This avoids the need for PWB complexity, and provides for a very compact, lightweight application. The composite substrate also includes low thermal expansion layer materials to provide for high reliability to the die, the memory devices, and the interconnection. Because of the attractive packaging characteristics, applications in high performance military data processors as well as commercial telecom switches are being qualified for high volume production and assembly, with more than one application currently in high volume ramp. The integrated design, fabrication, and assembly facilities at Endicott Interconnect Technology allowed several large multichip applications to go from paper concept to ramp in approximately one year, showing that synergistic use of proven, existing substrate technology in new complex applications can be very successful.