Heavy Al Ribbon Interconnect: An Alternative Solution for Hybrid Power Packaging Bryan Ong 1 , Mohd Helmy 1 & Shirley Chuah 2 R&D2 1 /Reliability Engineering 2 , STATS ChipPAC Ltd 73, Lorong Enggang, Ulu Kelang FTZ, 54200 KL, Malaysia bryan.ong@statschippac.com, mohd.helmy@statschippac.com & shirley.chuah@statschippac.com Christoph Luechinger & Garrett Wong Orthodyne Electronics Corporation 16700 Red Hill Avenue Irvine, California, U.S.A. 92606-4802 christoph.luechinger@orthodyne.com & garrett.wong@orthodyne.com Abstract While the semiconductor industry roadmap for IC/ASIC packaging clearly depicts an ever-decreasing pitch between wire bonds, packaging of power devices is heading the opposite way to accommodate larger Al wire with multiple stitches. Such direction is delineated with the development of heavy interconnect designs to meet the stringent requirement of low RDS ON . As placement of larger wire wedge bonds requires sufficient tool navigation space, limitations arise when it comes to accommodating multiple large wires on a single source lead for conventional TO251/2, TO262/3 & TOXXX packages. An alternative solution is to replace the current Al wire with heavy Al ribbon. This replacement works perfectly in particular for a thin lead frame based sawn type CSP package (LFCSP) that requires high current carrying capacity with better heat dissipation capability. The key advantage of this replacement is seen in the manufacturing throughput improvement on the order of 2.0× minimum, with its reliability performance surpassing current standard wire wedge bonding. Other benefits seen are some improvements in electrical performance, manufacturing yield and assembly cost reduction. This paper encompasses the development of ribbon bonding in a 12×12 hybrid LFCSPs-TE TM package: its defacto bonding requirements for replacing round Al wire, ribbon welding microscopic level analysis, its reliability performance and moisture resistance study. A form factor relationship in terms of electrical resistivity correlation is established based on RDS ON measurements. This relationship can then be applied to other conventional lead form or non-leaded power packages towards determining electrical performance of a specific device as well as process cycle time. Keywords: Spreading resistance, low RDS ON , heavy Al ribbon bond. Introduction Increasing demand for high power dies with larger current carrying capacity has propelled the development of more efficient interconnect designs to meet the requirements of dense I/O and low on- state resistance (RDS ON ) [1]. Revolutionary advances in chip-within-chip integration are one of the main drivers behind these developments. The introduction of low k dielectric materials, ultra thin wafer metalization and non-passivated die top are some of the initiatives recently realized for the performance improvement of power devices. Lower loss of dielectrics and a faster current transmission rate are the main improvements seen. Cost, however, remains the absolute factor for technology trade-offs, though in many circumstances silicon technology is priced equally or is a far more important cost factor. In addition to cost factor consideration, package interconnect design complexity continues to advance while the market intensifies the need for high design confidence with shorter cycle times. One of the key design considerations is to simplify the bond diagram and its bonding process. For power electronics applications, large Al ribbon bonding may become a technique to address current and future interconnect requirements. While it offers the same advantages as large Al wire bonding, it also eliminates, or at least alleviates, some of the wire bonding limitations, like the need for bonding a significant number of parallel wires per device to fulfill the necessary resistance or current requirements. Table 1 shows the number of round Al wires that can be replaced by one large Al ribbon of specific dimensions. As a potential drop-in replacement for the established large Al wire bonding, heavy Al ribbon bonding may be more attractive to its end-users. Ribbon raw material quality and equipment capability are two key contributors to the robustness - 1 - Presented at IMAPS 2004, November 14-18, Long Beach, CA