3D Hot Spot Localization via Lock-in Thermography
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Solution Overview
Problem
Current methods for localizing thermal defects in 3D system-in-package devices are limited by the opaque material layers, making it difficult to access and analyze buried heat sources, and existing non-destructive techniques like Lock-in Thermography lack depth localization capabilities.
Innovation Solution
The method employs Lock-in Thermography with multiple frequency excitation and time-resolved thermal response measurements to analyze phase shifts and thermal time delays, enabling three-dimensional localization of hot spots within electronic devices by understanding heat wave propagation through material layers, using finite element modeling to simulate and optimize the thermal diffusion process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Lock-in Thermography is used to detect thermal defects, then spatial resolution and sensitivity are improved, but depth localization capability is lost
Solution Approach 1:
The patent applies periodic thermal excitation at multiple frequencies to the device under test. By measuring the phase shift of the thermal response at different frequencies, the system can determine the depth of buried hot spots. The periodic action enables differentiation between thermal responses from different depths through frequency-dependent phase analysis.
Solution Approach 2:
The patent changes the excitation frequency parameter to extract depth information. By performing Lock-in Thermography measurements at multiple frequencies and analyzing how the phase shift varies with frequency, the system can calculate the depth of thermal defects. This parameter change approach transforms a 2D surface measurement technique into a 3D localization capability.
2Measurement precision
If de-capsulation is performed to access buried structures, then failure analysis capability is improved, but additional defects are introduced and analysis time increases
Solution Approach 1:
The patent replaces mechanical de-capsulation methods with a non-contact thermal measurement system. By using infrared detection combined with periodic thermal excitation and phase shift analysis, the system can locate buried hot spots through opaque encapsulation layers without physically opening or damaging the device.
Solution Approach 2:
The patent uses thermal waves as an intermediary to penetrate opaque encapsulation layers. The periodic thermal excitation generates heat waves that propagate through the encapsulation material, and the phase-modulated thermal response carries depth information about buried defects to the surface for non-contact detection.
3Measurement precision
If multiple frequency excitation is used for depth profiling, then depth measurement accuracy is improved, but measurement time increases
Solution Approach 1:
The patent employs periodic thermal excitation at multiple frequencies simultaneously or in sequence. By using the phase shift characteristics of periodic thermal waves at different frequencies, the system can determine depth information efficiently. The periodic nature of the excitation allows for synchronized detection and rapid phase analysis.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for fast and secure detection of thermally active structures in all three dimensions, reducing analysis time significantly and improving depth measurement accuracy, enabling precise localization of hot spots without de-capsulation, even through hundreds of microns of opaque material layers.
Implementation Method 1
heat wave propagation through material layers
Implementation Method 2
periodic thermal excitation generates heat waves that propagate through the material layers
Implementation Method 3
an infrared detector is used to measure temperature modulations at the device surface
Data Source
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AI summary
A non-destructive approach for the 3D localization of buried hot spots in electronic device architectures by use of Lock-in Thermography (LIT). The 3D analysis is based on the principles of thermal wave propagation through different material layers and the resulting phase shift/thermal time delay. With more complex multi level stacked die architectures it is necessary to acquire multiple LIT results at different excitation frequencies for precise hot spot depth localization. Additionally, the use of multiple time -resolved thermal waveforms, measured in a minimized field of view on top of the hot spot location, can be used to speed up the data acquisition. The shape of the resulting waveforms can be analyzed to further increase the detection accuracy and confidence level.