Innovations in Fault Isolation Methods for 3D Packages with 10X Improvement in Accuracy

摘要

3D package technology has become a product differentiator to be competitive in the market place by delivering better performance with smaller footprint at a cost-effective way. It integrates multiple functional components into one device thus reducing development effort of product manufacturers and enabling faster time-to-market. As more components are stacked together and planar features decrease at the same time, 3D package technology brings many new challenges for electrical fault isolation and failure analysis. First of all, since the stacked components are often owned by different suppliers, it is critical to be able to non-destructively isolate the failure to the defective component so that issues can be addressed by the component owners. Secondly, defect localization accuracy has become increasingly challenging because the defect is now deeply buried inside the package, and it becomes more difficult for the conventional fault isolation tools to "see" them. Adding to these technical challenges are the ever demanding volume and through-put time requirements. These challenges require more capable fault isolation tools and techniques with better accuracy, resolution and sensitivity. Lock-in thermography (LIT) is a powerful, non-contact and non-destructive technique that has been successfully applied for electrical fault isolation of 2D packages. Yet its success in 3D packages has been limited because of its accuracy, extensive data collection and in-consistent results as reported by many cases, studies and our own use experience. This paper discusses the challenges LIT faces with respect to its application to 3D packages, examines the key elements that affect its effectiveness from a fundamental way, and presents some new developments that improves its accuracy and efficiency as demonstrated by successful case studies.