What Is Cross-Sectioning and Why It Follows SAM in Failure Analysis

At CSAM Lab, we often explain to customers that Scanning Acoustic Microscopy (SAM) is just the beginning of the failure analysis journey. While SAM excels at non-destructive internal imaging, it often leads to a need for physical verification and deeper structural insight. That’s where cross-sectioning comes in.

Cross-sectioning is one of the most powerful and precise techniques in failure analysis—especially when used in combination with acoustic imaging. Here’s what it is, how it works, and why it’s a common next step after SAM.

What Is Cross-Sectioning?

Cross-sectioning is a destructive sample preparation technique that physically exposes the internal structure of a device by cutting and polishing it along a targeted plane. The goal is to reveal internal features—such as layers, interfaces, and defects—for visual inspection under optical, SEM (Scanning Electron Microscopy), or EDS (Energy Dispersive X-ray Spectroscopy).

Cross-sectioning is often used to:

Pinpoint and visually confirm anomalies (voids, cracks, delaminations)
Measure layer thicknesses and materials
Investigate corrosion, fracture, or process defects
Correlate findings from non-destructive techniques like SAM

Why SAM and Cross-Sectioning Go Hand-in-Hand

1. SAM Localizes the Problem, Cross-Sectioning Confirms It

SAM provides a real-time, internal map of a package without opening it. But acoustic contrast alone can’t always tell you the exact nature of the defect—for example, whether it’s a crack, a void, or corrosion. Cross-sectioning physically exposes the suspected area to:

Validate SAM findings
Capture high-resolution images for reports
Enable material characterization (e.g., metal migration or oxidation)

Example: SAM reveals a delamination at the die attach layer. Cross-sectioning shows it’s caused by voids in the epoxy leading to thermal stress failure.

2. SAM Guides the Cut

Rather than blindly sectioning a device and hoping to intersect the defect, SAM helps precisely target the area of interest. This improves efficiency, conserves sample integrity, and avoids missing the failure site.

Result: Fewer samples needed. More meaningful data collected.

3. Cross-Sectioning Unlocks Detail at the Micron Level

While SAM visualizes internal structures, cross-sectioning can expose material interfaces and micro-defects at sub-micron resolution. This is crucial for root cause analysis of:

Microcracks in silicon or metals
Layer delamination in complex stack-ups
Die attach voids or underfill issues
Electro-migration and corrosion in traces

When to Use Cross-Sectioning

Cross-sectioning is typically performed:

After SAM reveals a potential defect
When confirmation or deeper inspection is required
For failure mode documentation (e.g., for RMA, yield loss, or customer reports)
As part of qualifying new materials, packages, or assembly processes

Types of Devices We Cross-Section at CSAM Lab

We provide high-precision cross-sectioning for:

BGA, QFN, QFP, LGA, and other plastic packages
Ceramic and hermetic components
PCB assemblies with embedded components
Advanced semiconductor packages (2.5D, 3D ICs)

Our team ensures that sample preparation is accurate, repeatable, and documented, with optional imaging under SEM, optical microscopy, or EDS upon request.