Vibration Measurement of a Printed Circuit Board (PCB)

Full-Field Out-of-Plane Measurement with a Scanning Vibrometer

Objective

The aim of this measurement is to visualize the full-field out-of-plane vibration behavior of a populated automotive PCB under controlled excitation. Instead of measuring a single point, the entire PCB surface is scanned to identify where the vibration amplitudes perpendicular to the surface are greatest—at both board and component level. The resulting operating deflection shapes (ODS) reveal which areas and components are exposed to the highest dynamic loads.

1 Measurement setup

The PCB is mounted on an electrodynamic shaker. The scanning vibrometer is installed on a portable aluminum-profile frame above the test specimen, with a perpendicular view of the PCB surface. This configuration provides the optimal measurement angle for out-of-plane vibration measurements.

The Optomet scanning vibrometer combines a vibrometer, data acquisition, signal generator, and camera in a single instrument. No additional external hardware is required for this measurement. The excitation signal for the shaker is generated directly by the integrated signal generator.

2 Define measurement points in SMART Lab

The SMART Lab software displays a live image of the test specimen via the integrated camera. The measurement area and scan grid are defined directly on this camera image. Area selection tools, mesh generators, and component-based assignment enable precise placement of measurement points—from a coarse full-board grid to dense grids on individual components.

Both images show the component side of the PCB from slightly different perspectives. The measurement areas and boundary tools are defined in the image on the left, while the image on the right shows the completed measurement-point grid. SMART Lab supports multiple layers, allowing different measurement areas—such as a coarse full-board grid and dense grids on individual components—to be managed within a single project.

3 Configure measurement parameters

The vibrometer settings are configured in the Acquisition module. For this PCB measurement, the upper cutoff frequency is 100 kHz—sufficient to capture both the board's fundamental resonances (typically below 5 kHz) and higher-frequency component modes. With more than 13 million FFT lines and a frequency resolution of 6.4 mHz, even closely spaced modes are clearly resolved.

4 Automatic scanning

Once the scan grid and settings have been defined, the vibrometer automatically scans all predefined measurement points. The laser moves from point to point, readjusts the focus as needed, records the vibration signal, and proceeds to the next position. No manual intervention is required during the scan.

The measurement is entirely non-contact. No sensors on the PCB, no cables, and no additional mass on the structure. The results reflect the assembly's actual vibration behavior.

5 Visualization and analysis

Once the scan is complete, SMART Lab offers various visualization options in the Analysis tab. The vibration data can be displayed as color-coded points overlaid on the camera image, as an interpolated color map, or as a wireframe model with animated deformation. Damping information can also be incorporated into the visualization.

The color-map visualization makes the global plate modes immediately apparent: In this case, a higher-order mode shape is visible, with several pronounced amplitude maxima distributed across the PCB. The location of these maxima relative to the component positions is directly relevant to reliability assessment—components near a vibration maximum experience the highest dynamic loads.

6 Detailed component analysis and video export

In addition to the overall view, SMART Lab lets users zoom in on individual components to visualize their local mode shapes. The integrated video recording feature produces 4K videos of the animated vibration data—including tracking shots that move the virtual camera across the PCB surface. Ideal for presentations and reports.

The detailed view shows how each individual component responds to the excitation. In this close-up, each electrolytic capacitor exhibits its own vibration pattern—some tilt laterally, while others show vertical displacement. This level of detail is only possible with the spatial resolution of a scanning vibrometer and remains undetected by conventional accelerometer measurements.

3D vibration analysis (SMART 3D-Scan)

Real measurement data, not a simulation – The visualization shows an actual 3D vibration measurement of the populated PCB, acquired using SMART 3D-Scan. The measurement data can be projected directly onto the PCB's 3D model, making it immediately apparent which components and areas are affected.

Three synchronized SMART Scan+ vibrometers measure simultaneously from different angles.

From the three velocity components, the software calculates the complete motion in the X, Y, and Z directions at each measurement point. The measurement workflow in SMART Lab is essentially the same as for 1D measurements: define measurement points on the 3D model or camera image, scan them automatically, and visualize the results. The key difference lies not in the workflow, but in what the results reveal.

Thermal expansion: the same system, a different application

In addition to vibration analysis, the same SMART 3D-Scan vibrometer can also measure the thermal expansion of the PCB and its components. Differences in the coefficients of thermal expansion of the FR4 substrate, copper traces, solder joints, and housing materials cause localized deformation as temperatures change, potentially resulting in fatigue damage.

For temperature cycling tests (TCT) and thermomechanical reliability assessments, 3D measurement of thermal expansion provides spatial evidence that strain gauges could only capture at a few locations—all without contact and across the entire surface.

3D single-point measurement with SMART 3D-Fiber

Not every PCB analysis requires a full-field scan grid. For shaker testing of electronic control units (ECUs), qualification of individual assemblies, or monitoring defined measurement points in production testing, a single measurement point is sufficient—provided all three spatial directions are captured.

SMART 3D-Fiber does exactly that: three laser beams converge on the same point on the surface to capture the complete 3D vibrational motion. The compact Fiber Head is particularly well suited to confined installation spaces—for example, when measuring directly on a PCB inside an enclosure.

The X, Y, and Z velocity components are available directly via the digital and analog outputs. SMART 3D-Fiber can be operated either through SMART Lab or directly via an external DAQ system—no proprietary software is required for integration into existing test benches.

Which system is right for which measurement task?

All three measurement approaches presented in this report use Optomet laser Doppler vibrometry and SMART Lab software. The choice of system depends on the information required:

The basic measurement process is similar for all four systems. The choice depends on the measurement task: full-field or point-based, 1D or 3D—or both, as the SMART systems can be combined and expanded incrementally.

Summary

This application report presents three approaches to vibration analysis of populated printed circuit boards using Optomet laser Doppler vibrometers.

Full-field out-of-plane measurement: A single scanning vibrometer captures the vibration component perpendicular to the PCB surface. Six steps, from setup to detailed component analysis, demonstrate the complete workflow. The results identify spatial vibration hotspots, visualize mode shapes at PCB level, and reveal the individual vibration behavior of specific components.

3D vibration analysis: Three synchronized SMART Scan+ vibrometers capture the complete motion in X, Y, and Z. This reveals lateral motion, tilting motion, and coupled modes that remain hidden in out-of-plane measurements. The same system also captures thermal expansion—relevant to assessing thermomechanical reliability.

3D single-point measurement: The SMART 3D-Fiber provides complete 3D vibration data at a defined measurement point. The compact Fiber Head is ideal for shaker testing of electronic control units, component qualification, and integration into existing test rigs.

All three approaches provide spatial evidence for informed design decisions: component relocation, local reinforcement, adjustment of mounting conditions, or FEM validation against measured real-world data.