A Multi-Protocol Module To Provide An External Trigger For Dynamic Lock-In Thermography

Abstract

Lock-in thermography (LIT) is a firmly established and powerful technique for IC defect localization. The standard approach is to detect and analyze the device temperature fluctuation between two bias conditions using an infrared thermal imaging camera and check for any anomalous heat response. For the most straightforward setup, these bias conditions would be achieved by the modulation of a supply voltage provided by the LIT system. This allows for synchronization to the internal camera frame rate. In addition to this method, the ability to provide an external trigger may be an option, as it is for the ELITE system by Thermo Fisher Scientific. This expands the LIT arena to failures that may only be observable by, for example, setting different register contents at a constant supply voltage. Though IC testers can be used to provide the stimulus and a trigger signal for these situations, often a simpler, more compact solution would be beneficial for the failure analyst. This paper presents such an alternative: the application of a low-cost, USB-based module which can emulate various communication protocols (for example, I2C, SPI) while providing a synchronized timing pulse to externally trigger the ELITE, thus facilitating dynamic LIT investigations. The efficacy of this solution is demonstrated by a case study in which dynamic LIT produced a single hot spot at the defect site that was undetected by the voltage modulation approach.