Three-dimensional hot spot localization

A method for detecting the location of buried heat sources using lock-in-thermography (LIT) system, comprising:

• placing a device under test (DUT) on a test system;
• applying test signal to the DUT;
• while the test signal is applied to the DUT, imaging the DUT using an infrared (IR) camera;
• detecting lateral temperature distribution on a surface of the sample to thereby locate the heat-source laterally;
• reducing the operational area of the IR camera to obtain a reduced field of view;
• subsequently applying electrical excitation signals at multiple different lock-in frequencies to the DUT;
• while the test signals are applied to the DUT, imaging the DUT using the reduced field of view;
• detecting lateral temperature distribution on a surface of the DUT;
• detecting and analyzing a resulting phase shift between the electrical excitation signal and the thermal response in correlation to the thermal heat propagation within the DUT;
• and,
• analyzing the resulting phase shift to thereby obtain depth location of the electrical active heat source.

A method for time-resolved localization of buried heat sources inside a device under test (DUT) using lock-in-thermography (LIT) system, comprising:

• applying test signal to the DUT;
• while the test signal is applied to the DUT, imaging the DUT using an infrared camera;
• detecting lateral temperature distribution on a surface of the sample to thereby locate the heat-source laterally;
• reducing the operational area of the IR camera to obtain a reduced field of view;
• subsequently applying electrical excitation signals at multiple different lock-in frequencies to the DUT;
• while the excitation signals are applied to the DUT, imaging the DUT using the reduced field of view;
• using thermal imaging to detect time-resolved thermal waveforms at the variable lock-in frequency and displaying the time-resolved thermal waveform on a monitor;
• and,
• analyzing the time-resolved thermal waveform to determine the phase shift between the electrical signal and related thermal waveform.

A system for localizing a defect within an encapsulated device under test (DUT), comprising:

• a bench for mounting the encapsulated DUT and connecting the DUT to receive excitation signals from an excitation source;
• an infrared camera positioned to obtain IR images of the DUT;
• a processor generating a sync signal at frequency ft and sending the sync signal to the excitation source;
• a frequency selector varying the frequency ft over time;
• wherein the processor reads data from the infrared camera and uses thermal imaging of the infrared camera to generate time-resolved thermal waveforms at the variable lock-in frequency and display the time-resolved thermal waveform on a monitor