Overview
IEC 61189-3-302:2025 specifies a standardized, non‑destructive test method for the detection of plating defects in unpopulated circuit boards using computed tomography (CT). Applicable to metallized holes (vias and through-holes), the standard defines the CT test principle, required equipment, test steps, image reconstruction and reporting requirements to reliably identify plating voids, fills and related defects.
Key technical topics and requirements
- Test principle: Cone‑beam X‑ray CT acquires multiple angular projections and uses reconstruction software to produce a 3D grayscale representation of the board interior. The minimum detectable defect is three times the device imaging resolution (3× pixel size).
- Equipment:
- X‑ray CT scanner with stable X‑ray source; select smaller focal size for smaller defects. Table examples link source focal size to spatial resolution (e.g., focus size 1 μm → spatial resolution ~0.5 μm).
- Detector system and imaging resolution definition (detector pixel size divided by magnification).
- Mechanical scanning system with minimum displacement steps ≤ 0.01 mm and angular rotation step ≤ 0.01°.
- Shielding facilities and appropriate software for reconstruction and visualization.
- Imaging parameters:
- Radiation penetration rate should exceed 20% (typically 20–70%).
- Parameter setup includes X‑ray source settings, scanning method, field of view, number of frames and scan time to optimize image quality.
- Analysis and reporting:
- 3D reconstruction, visualization, image analysis and data saving.
- Report items: device and sample information, sweep parameters and measurement results.
- Defect identification & statistics: Annexes provide typical images for plating voids, blind‑via filling defects, nodulation, folds and interlayer coincidence, plus void identification and statistical methods (void counts, void/board thickness ratios, filled hole void rate).
Practical applications and users
Who benefits:
- PCB manufacturers and contract electronics assembly (PCBA) houses performing quality control.
- Reliability engineers assessing interconnect integrity.
- Non‑destructive testing (NDT) labs and inspection service providers.
- X‑ray/CT equipment vendors and software developers validating system capabilities.
Typical uses:
- Detecting and quantifying plating voids, incomplete via fills, and internal anomalies without destroying boards.
- Process qualification, failure analysis, incoming inspection and supplier audits.
- Supporting corrective actions in plating and drilling processes by providing statistically robust defect metrics.
Related standards
- ISO 15708-3: Radiation methods for computed tomography - Operation and interpretation (normative reference).
- Other parts of the IEC 61189 series (test methods for electrical materials and printed boards).
Keywords: computed tomography, CT inspection, plating defects, unpopulated circuit boards, metallized holes, non‑destructive testing, X‑ray CT scanner, imaging resolution, void identification.