When electronic or mechanical components fail, identifying the root cause is critical. One of the most precise and revealing techniques available to engineers is mechanical cross sectioning — a cornerstone of failure analysis used across industries like aerospace, automotive, medical devices, and consumer electronics.
In this guide, we’ll walk through what mechanical cross sectioning is, why it’s used, how the process works, and when to use it in your failure analysis workflow.
What Is Mechanical Cross Sectioning?
Mechanical cross sectioning is a destructive failure analysis technique that involves cutting into a component or material to expose its internal structure. This allows analysts to inspect microscopic features and identify defects not visible on the surface.
It’s especially valuable when investigating:
- Solder joint integrity
- Voids in vias or plating
- Cracked die or delamination
- Cold solder joints
- Manufacturing process defects
Once exposed, the cross sectioned surface is prepared, polished, and analyzed under an optical microscope or SEM (scanning electron microscope) to evaluate structural quality and potential failure modes.
Why Use Cross Sectioning for Failure Analysis?
Mechanical cross sectioning gives engineers direct access to a component’s internal layers, making it ideal for root cause analysis. Unlike non-destructive techniques like X-ray or CSAM, it allows for:
- Precise localization of defects (e.g., layer separation in PCBs)
- Visual evidence of failure modes like voids, cracks, or poor bonding
- Dimensional measurements (e.g., copper plating thickness, solder fillet height)
- Metallurgical assessment of materials, interfaces, and welds
When failure has already occurred—or when you need definitive insights into the integrity of a sample—mechanical cross sectioning delivers unmatched clarity.
The Mechanical Cross Sectioning Process (Step-by-Step)
At Cross Section Lab, we follow a rigorous cross section process to ensure every sample yields accurate, actionable data.
- Sample Selection & Mounting
The failed component is selected and embedded in epoxy resin to secure it for precise grinding. - Grinding
The sample is carefully ground down using progressively finer abrasive media to expose the area of interest (e.g., solder joint, via, die attach). - Polishing
A mirror-like polish is applied to the surface to eliminate scratches and prepare it for high-resolution imaging. - Etching (Optional)
In metallic systems, chemical etchants may be used to reveal grain boundaries or interface layers. - Imaging & Documentation
The polished cross section is inspected under an optical microscope or SEM. Defects are documented with high-resolution images and measurements. - Reporting
A detailed failure analysis report is created, often including root cause hypotheses, dimensional analysis, and recommendations.
Common Applications for Mechanical Cross Sectioning
- Printed Circuit Boards (PCBs): Evaluate via quality, delamination, copper plating thickness, internal shorts.
- IC Packages & Semiconductors: Identify die cracks, poor bond wire connections, voids in encapsulants.
- Capacitors & Resistors: Inspect internal electrode alignment, cracking, or swelling due to overvoltage.
- Automotive Electronics: Assess vibration or thermal fatigue damage in high-reliability environments.
When Should You Use Cross Sectioning?
- When non-destructive testing is inconclusive
- During failure root cause investigations
- For manufacturing process validation
- In supplier quality audits
- When preparing FA reports for customers, regulators, or internal QA
If your goal is definitive evidence of a failure mechanism or process defect, mechanical cross sectioning is the gold standard.
Trust the Experts at Cross Section Lab
At Cross Section Lab, we specialize in precision mechanical cross sectioning and failure analysis services for high-reliability industries. Our fast turnaround, detailed reports, and expert interpretation make us a trusted partner for OEMs, contract manufacturers, and quality teams nationwide.
Need to evaluate a failed part? We’re here to help.