Printed Circuit Boards (PCBs) serve as the fundamental platform for electronic devices, fulfilling the dual roles of electrical interconnection and physical support: they facilitate circuit connectivity while securing electronic components such as resistors, capacitors, and microchips. Thanks to their significant advantages in terms of lightweight and compact design, PCBs are integral to virtually all electronic devices.
Under high-temperature operating conditions, PCBs and soldered components are prone to thermal deformation caused by mismatches in the Coefficient of Thermal Expansion (CTE), which can lead to reliability issues such as solder joint fatigue and connection failure. Consequently, thermal load testing has become a critical step in evaluating the in-service performance of PCBs. In this case study, the XTOP3D XTDIC 3D full-field strain measurement system is utilized to quantitatively analyze the impact of thermal loads on the deformation of the PCB and its mounted components, thereby providing data to support reliability-focused design.
I. Measurement Bottlenecks in Conventional DIC
Refraction Interference from Hot Air Turbulence
Heated air convection and temperature gradients around the PCB cause non-uniform air refractive indices. This leads to "virtual" or noise-induced displacements in the speckle images captured by DIC cameras, resulting in distorted strain and warpage data.
Thermal Environment Interference
High-temperature air disturbances cause image distortion, thermal radiation degrades speckle coating performance, and the equipment itself is subject to thermal drift errors.
Refraction-Induced Distortion
Installing heat-insulating glass in conventional DIC setups introduces refraction distortion, further increasing matching errors and distorting the calculated strain and warpage data.
Thermal Expansion Errors from Temperature Fluctuations
Rapid heating and cooling rates within the oven cause thermal expansion and contraction in the support structures, fixtures, and mounting stages. Conventional DIC struggles to distinguish between the overall displacement of the tooling and the actual deformation of the PCB itself.
II. DIC Measurement Solution
The XTDIC 3D full-field strain measurement system employs technologies such as high-temperature resistant speckle patterning, algorithms for the automatic elimination of rigid-body displacement, and distortion correction modules for observation windows. It accurately analyzes in-plane displacement, in-plane strain, and out-of-plane (Z-axis) warpage displacement on the circuit board. It extracts data on maximum deflection, overall twist, and localized bulging or depression, enabling the analysis of mechanisms by which warpage induces component placement shifts.
Ensuring Measurement Accuracy in Thermal Environments
3. Test Results and Analysis
Displacement Distribution at Critical PCB Locations
The XTDIC 3D strain measurement system captured the full-field 3D displacement distribution of the PCB under the following four temperature conditions:
Room temperature (baseline)
Serving as the zero-displacement reference, the displacement map below shows the initial flat state, with a single-point displacement standard deviation of <0.3 μm.
At a temperature of 85°C, significant thermal expansion and warping occur upon heating; the central region of the panel bulges into a "bowl" shape, with a maximum displacement of approximately 15 μm.
At a temperature of 125°C (the maximum temperature), warpage reaches its peak; the displacement in the central region increases to approximately 35 μm, while the edge regions exhibit reverse bending due to constraints.
Upon returning to room temperature, partial deformation recovery occurred; however, a residual permanent deformation of approximately 5 μm remained in the central region, indicating that viscoelastic creep had occurred in the substrate.
Out-of-Plane Displacement Analysis Along the Diagonal Section Line
Extract out-of-plane displacement data along the diagonal section line of the PCB:
|
Temperature |
Maximum warpage along the diagonal cut line |
Deformation features |
|
Room temperature |
0 μm（Benchmark） |
Approximately straight |
|
85℃ |
~15 μm |
The center is raised, exhibiting a parabolic distribution. |
|
125℃ |
~35 μm |
The protrusion intensifies, and a slight depression appears at the margin. |
|
Return to room temperature |
~5 μm |
Irreversible residual deformation; the distribution pattern is similar to that at high temperatures, but the magnitude is reduced. |
Analysis Conclusion: PCB warpage increases non-linearly with rising temperature, and irreversible residual warpage persists after cooling back down from high temperatures; this indicates that the material is approaching its viscoelastic transition zone at 125°C.
IV. Summary of PCB Thermal Deformation Testing
Using the XTOP3D XTDIC 3D full-field strain measurement system combined with a thermal stage, a "hardware isolation + software compensation + image enhancement" integrated thermal drift correction system was established. Through these technologies, the measurement accuracy of the microscopic DIC system regarding PCB thermal warpage was elevated to the micrometer level, meeting the rigorous demands for high-precision thermal deformation measurement in the field of electronic packaging.
1. Multi-level thermal drift correction technology system: A comprehensive technical scheme comprising "hardware isolation + software compensation + image enhancement" was developed. This controlled system thermal drift in high-temperature environments to the sub-micrometer level, overcoming the accuracy bottleneck of high-temperature microscopic DIC measurements.
2. Traceability of the full-process temperature history: Through stepped temperature control and synchronized image acquisition—combined with real-time drift correction—the true deformation data of the PCB across the entire cycle (room temperature → high temperature → room temperature) was fully recorded.
3. Quantitative warpage assessment capability: By analyzing displacements along diagonal cross-sections and employing single-point tracking, the magnitude of PCB warpage and residual deformation at various temperatures was precisely quantified, providing critical data support for the thermal reliability design of electronic products.
This technical scheme offers a reliable, precise, and scalable solution for high-temperature deformation measurement in fields such as electronic packaging, power devices, and MEMS, holding significant value for both engineering applications and academic research.
