Multichip module testing methodologies: what's in; what's not

The multichip module (MCM) is rapidly finding its way into the design of commercial electronic systems. The MCM offers this market opportunities for increasing performance, lowering size and weight, lowering power requirements, lowering costs, and improving the functionality per unit area. These characteristics are much too attractive to pass up and thus has begun a headlong rush to create designs using this wonderful new invention. Therefore, the most important element in the cost-effective manufacturing of multichip modules is the accurate diagnosis of defects. This must include the location and cause of manufacturing defects (shorts, opens, wrong component, etc.), functional defects, and performance or timing defects. Surprisingly, such test methods exist and are being used today. The only difficulty with these techniques is that the module designers must be willing to sacrifice some freedom in their designs to meet the testability requirements of the diagnostic methods chosen. Admittedly, this can be a difficult hurdle to overcome; but overcome it we must in order to produce truly high-quality, low-cost modules.