The Western Research Laboratory (WRL) is a computer systems research group that was founded by Digital Equipment Corporation in 1982. Our focus is computer science research relevant to the design and application of high performance scientific computers. We test our ideas by designing, building, and using real systems. The systems we build are research prototypes; they are not intended to become products. There is a second research laboratory located in Palo Alto, the Systems Research Center

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... ). Other Digital research groups are located in Paris (PRL) and in Cambridge, Massachusetts (CRL). Our research is directed towards mainstream high-performance computer systems. Our prototypes are intended to foreshadow the future computing environments used by many Digital customers. The long-term goal of WRL is to aid and accelerate the development of high-performance uni-and multi-processors. The research projects within WRL will address various aspects of high-performance computing. We believe that significant advances in computer systems do not come from any single technological advance. Technologies, both hardware and software, do not all advance at the same pace. System design is the art of composing systems which use each level of technology in an appropriate balance. A major advance in overall system performance will require reexamination of all aspects of the system. We do work in the design, fabrication and packaging of hardware; language processing and scaling issues in system software design; and the exploration of new applications areas that are opening up with the advent of higher performance systems. Researchers at WRL cooperate closely and move freely among the various levels of system design. This allows us to explore a wide range of tradeoffs to meet system goals. To obtain more details on ordering by electronic mail, send a message to one of these addresses with the word "help" in the Subject line; you will receive detailed instructions. Abstract Acoustic scanning and infrared imaging are two non-invasive die attach inspection techniques. Acoustic scanning provides information by emitting an acoustic pulse into a sample and analyzing the reflected waves. Based on the geometry and physical properties of the materials, details of the interior of the sample can be seen. Voids, delaminations and heterogeneities can be detected. Infrared imaging is used to examine the temperature of the chip surface while dissipating power. Depending on the geometry and thermal properties, areas with large voids or delaminations can often be detected. It is useful to compare the two techniques to understand the limits of detection capability. Samples were examined with both techniques and the resulting images compared. The acoustic technique could find small voids and heterogeneities, but infrared imaging could not. However, delaminations of the epoxy appeared in the infrared images as hot regions on the chip surface.