PCB Cross-Section Analysis and OrCAD X

July 17, 2024

Cadence PCB Solutions

Key Takeaways

IPC-TM-650 gives the complete testing manual for PCB boards and specifies how to verify electronic assemblies.
In PCB cross-section analysis, the PCB material is characterized and the failure analysis is conducted.
PCB cross-section analysis can be performed at different stages of the PCB fabrication or on the assembled electronic boards.

PCB cross-section analysis is one method to ensure the reliability and quality of the PCB board under test

Analyzing PCB failures is an essential step for successful PCB design. In PCB failure analysis, problems are identified using a variety of methods. PCB cross-section analysis is one method used to ensure reliability. This type of analysis measures the quality of a PCB board under test. Even though PCB cross-section analysis damages the PCB board under test, it helps engineers ensure future designs avoid the same issues.

In PCB cross-section analysis, the PCB material is characterized and failure analysis is conducted, focusing on any interconnection defects. PCB cross-section analysis is particularly helpful in spotting internal failures in a PCB. Compared to tests such as visual inspection or X-ray inspection, PCB cross-section analysis is a destructive test.

Let’s take a look at the steps involved.

PCB Cross-Section Analysis Steps

Step	Description
Step 1: Cut and Mount a Section	A section of the PCB measuring around one square inch is cut out and mounted into potting material. The potting material hardens around the PCB cutout and provides support and protection to the sample from the subsequent processes of polishing and etching.
Step 2: Polish or Etch and Optical Microscopy	The sample is polished until the target plane is reached. The PCB specimen is then examined under an optical microscope. The optical microscope helps show the microstructure of the PCB cross-section. Instead of polishing, the PCB specimen can be etched before viewing it under the optical microscope.
Step 3: Use a Scanning Electron Microscope	The scanning electron microscope helps examine the PCB specimen surface or cross-section. Neither polishing nor etching is required before microscopy for scanning electron microscopy (SEM) examination. Various modes of SEM are used to gather different information. Secondary electron mode: Topographic information of the sample surface Back-scattered electron mode: Topographic information and elemental contrast of the sample Energy dispersive spectroscopy: Direct qualitative and semi-quantitative elemental analysis on localized areas in the PCB specimen

What Can PCB Cross-Section Analysis Identify?

PCB cross-section analysis reveals information unavailable from X-ray inspection or visual inspection, including:

Solder grain structure
Cracks or voids
Composition of tiny inclusions
Intermetallic boundary conditions between the conductor pad and solder
Solder build-up
Through-hole filing
Wetting conditions
Ball-grid array solder joints

With PCB cross-section analysis, the root cause of failure can be identified. Since this type of analysis provides information on the thickness and distribution of copper plating and intermetallic boundaries, process checks are also possible.

IPC Standards Involved When Performing Cross-Section Analysis

Standard	Description
IPC-TM-650	Provides a complete testing manual for PCBs, specifying procedures for electrical testing, inspection, environmental testing, and verification of electronic assemblies. It ensures consistent and repeatable performances for all PCBs in electronic products. Also includes inspection, environmental testing, and required equipment.
IPC-TM-650 2.1	Describes guidelines for PCB cross-section analysis, evaluating internal structure and quality. It includes quality checks based on the thickness and distribution of coating and metallization, as well as solder joints and interconnects, to identify process deviations.

When to Conduct PCB Cross-Section Analysis

PCB cross-section analysis can be performed at different stages of the PCB fabrication processor on the assembled electronic boards. It is the go-to test for failure analysis of PCBs. PCB reliability can be guaranteed once the specimen passes the PCB cross-section analysis successfully.

OrCAD X cross-section editor

OrCAD X Aids in Creating Reliable Boards

To ensure the creation of reliable boards, it's best to use advanced PCB software. Below, we've compiled features from OrCAD X that aid in creating reliable boards.

OrCAD X Tool	Description
HDI (High-Density Interconnect) and Via Arrays	Helps create compact designs by using blind, buried, or micro vias, enabling more parts per board area and more routes per layer. Provides a versatile tool to add vias in various patterns and configurations, significantly enhancing design flexibility and efficiency.
Cross-Section Editing	Allows setting up the stack-up for the PCB, including layer thickness, material, and surface finish. This helps ensure the design meets signal integrity and cost constraints.
3D Engine	Improves visualization of rigid/rigid-flex designs and includes MCAD-ECAD integration for better manufacturability.
Constraint Management	Provides real-time constraint-driven feedback, ensuring a manufacturable and functional PCB.
Design for Manufacturing (DFM)	Offers a suite of powerful DFM checks to ensure fabrication and production reliability, including design for fabrication, assembly, and test constraints.
Design for Assembly (DFA)	Enables setting up specific rules for component spacing and placement, ensuring that components can be efficiently assembled using automated or manual processes.
Signal Integrity Analysis	Provides tools for impedance and coupling analysis, allowing designers to identify and resolve signal integrity issues.

PCB cross-section analysis is crucial for identifying and resolving internal defects, ensuring the reliability of your PCB designs. With OrCAD X, designers can streamline this process and achieve superior results. These tools help you build reliable, high-quality PCBs. Learn more about how Cadence can support your design process by exploring our PCB Design and Analysis Software and OrCAD X offerings.

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