As is well known, semiconductor devices feature extremely delicate internal structures, diverse package types, and complex manufacturing processes. For IDMs, OSATs, design houses, and end-product manufacturers, the ability to rapidly and accurately detect packaging defects and process risks—without damaging the device—has become a core requirement for quality control and reliability validation.

The X-ray Nondestructive Inspection System was developed under this demand and has become an essential tool in IC packaging quality control and failure analysis (FA). The following sections introduce its working principles, application scenarios, detectable defect types, and value to enterprise users.

1. Principles and Advantages of X-Ray Inspection

1.1 X-ray Penetration and Imaging Mechanism

X-rays possess strong penetration capability. When passing through an IC package (molding compound, solder balls, lead frames, substrates, etc.), different materials absorb and attenuate X-rays at varying degrees. A detector converts the transmitted radiation into grayscale images, revealing internal structural differences and enabling visualization of hidden defects.

• High-density, high-Z materials (Pb, Sn, Au, Cu) appear darker due to stronger absorption.

• Low-density materials (molding compound, resin, voids, air) appear brighter due to weaker absorption.

• Adjusting tube voltage, current, exposure time, and magnification optimizes imaging for different packages and thicknesses.

1.2 Key Advantages of X-Ray Inspection

• Nondestructive analysis: Internal structures and packaging quality can be inspected without damaging samples.

• Wide inspection coverage: Solder joints, wire bonds, solder balls, internal structures, and substrates can all be evaluated.

• High efficiency: Supports batch inline sampling or offline rapid analysis for production quality monitoring.

• Quantitative measurement: Dimensions, positional deviation, void ratio, and geometric parameters can be accurately measured.

• Applicable to multiple package types: BGA, CSP, QFN, QFP, SOP, Flip Chip, SiP, 3D packaging, etc.

2. Typical Applications of X-Ray in IC Packaging

For manufacturing, incoming inspection, R&D, and reliability engineering, X-ray inspection is used in the following key areas:

2.1 Internal Packaging Defect Detection

• Delamination: Separation between die, substrate, or molding compound, highly correlated with thermal cycling and mechanical stress reliability issues.

• Popcorn / Cracks: Moisture expansion during reflow or high-temperature processes leads to internal cracks, which X-ray can reveal through abnormal structural patterns.

• Voids and Gas Bubbles: Voids weaken mechanical and thermal conduction performance. X-ray visualizes void size, location, and distribution, and enables void ratio analysis.

2.2 Wire Bonding Integrity and Quality Assessment

• Electrical continuity: Open wires, broken wires, missing or misaligned bonds; shorts caused by wire sag or crossover.

• Wire loop profile: Adequate loop height, correct loop shape, and no interference or sagging.

• Ball/Wedge Bond Quality: Correct size, shape, and bond position; early indicators of "necking", "lifted bonds", or weak bonding.

2.3 Solder Ball / Bump and Joint Quality Inspection

• Missing balls, misalignment, bridging, ball collapse, abnormal deformation.

• Void ratio analysis within solder balls and interfaces (IPC compliance).

• Evaluation of solder wetting, fillet formation, and metallurgical connection to pads.

2.4 Dimensional and Geometric Measurements

• Die size, die centering, and offset relative to lead frames or substrates.

• Wire length, diameter, loop height.

• Solder joint spacing, pad alignment, structural overlap in SiP/MCP/3D stacks.

2.5 Solder Coverage Ratio Measurement

X-ray grayscale and geometric analysis evaluate solder coverage on pads, supporting process tuning, reflow optimization, and FA correlation.

3. Key Value for Enterprise Users

• Quality control & yield improvement: Early detection of process drift and defect trends reduces scrap and rework.

• Failure analysis & reliability validation: Faster root-cause tracing and before/after comparison for HTS, TCT, reflow simulation, etc.

• Supply chain & incoming inspection: Vendor quality evaluation, traceability via stored X-ray reports and images.

• NPI & process optimization: Structural verification during development accelerates ramp-up and reduces trial-and-error cycles.

4. How to Select the Right X-Ray Solution

1. Resolution & penetration capability: Match to package thickness and defect size requirements.

2. 2D vs. 3D capability: 2D for screening; CT/layered tomography for complex structures and depth localization.

3. Automation & integration: AXI automation, MES/SPC connectivity, and inline deployment readiness.

4. Analysis software features: Measurement tools, void ratio calculation, reporting, and defect classification.

5. Expert application support: Vendor experience in semiconductor packaging and FA methodology.

Thanks to its strong penetration imaging capability, X-ray inspection enables nondestructive detection of internal defects such as delamination, cracks, and voids. It also provides precise measurement of wire bonding integrity, solder ball quality, die dimensions, loop geometry, and solder coverage. For semiconductor manufacturers, design houses, and OSATs, a properly deployed X-ray inspection solution significantly enhances product quality, yield, reliability analysis, supply chain management, and NPI efficiency.