Through Package Defect Localization by Lock-In Thermography

Abstract

Root cause analysis for package defects is currently performed by de-processing the package until such defects can be physically seen. However, many such defects within the package are removed, or are confused with defects created during de-processing itself. 3D X-ray has been used to analyze such physical defects within a packaged device in a non-destructive manner. However, the increasing density and associated shrinkage of components such as multi-layered substrates require significantly higher resolutions, which translates to longer times. High resolution X-ray is impractical when searching for a defect over a wide area due to the time to acquire detailed 3D images (~24 hrs). Thermal emission analysis has been widely used for localizing defects on ICs. Recent advancement in thermal emission camera technology coupled with lock-in thermography has allowed orders of magnitude better sensitivity ( < 1μW) and improvement in localization resolution (x,y to < 3 um). However, the application of lock-in thermography has been primarily limited to defect localization at the die level [1]. A a highly sensitive MWIR camera combined with a real time lock-in technique demonstrates the capability to localize defects within packaged devices, even through its mold compound. The technique accurately predicts the depth (z) of a thermal defect within the device (< + 5%) This paper will demonstrate multiple examples of the successful combination of advanced lock-in thermography analysis and high resolution 3D X-ray for totally non-destructive defect location within a packaged device. This initial accurate thermal localization in x, y and z enables the high resolution 3D X-ray system to focus analysis to a few microns so that the defect can be seen quickly (< 1 hr), enabling detection and analysis of previously undetected defects with highest throughput.