Does Your Assembly Need a PCB Microsection Analysis?

There is no shortage of reasons to test a PCB assembly, and there is no shortage of ways to do it. Out of the many functional tests available, PCB microsection analysis has a pretty specific purpose.

Is it a test your electronics project needs? Quite possibly.

Let’s look at how a PCB microsection analysis works and what it tests for:

The Whats, Hows & Whys of PCB Microsection Analysis

Functional testing, as opposed to some other tests, checks the entire assembly, helping prevent failure and shortened service life. It’s performed at the end of the manufacturing process.

Specifically, microsection analysis (also called a PCB cross section procedure) is the first choice for checking PCB plated through-hole integrity. It takes place in these five steps:

• Identifying and marking the test area
• Removing parts, as necessary
• Prepping and staining the area
• Recording and analyzing image-based findings
• Optical microscopy

Microsection analysis is a destructive test. So it’s performed on a sample of PCBs, not the entire manufacturing run. The test allows evaluation of the plated through-holes and the lamination. It also examines a part of an assembled PCB for problems such as such as:

• Thermo-mechanical failures
• Solder reflow-related failures
• Shorts
• Opens
• Defective components

In other words, microsection analysis provides a rather comprehensive picture that helps identify and compensate for potentially costly imperfections.

Defective components can be removed, exposed by abrasion and compared to components that are performing the way they should.

Challenges of Microsectioning

Microsection analysis is not easy. The materials that make up a PCB are of different hardnesses, as are the media used for mounting.

Additionally, the prep work is exacting. It must be completed no more than 10% beyond the plated through-hole's center. This level of precision requires specialized equipment and trained personnel who should be IPC-A-600 and IPC-A- 610 certified. Consequently, it’s often performed in a laboratory.

Don’t forget this type of PCB testing is destructive, so you’ll have to factor those destroyed boards into your cost considerations.|

Who Should Specify PCB Microsectioning?

Class 1, Class 2, and Class 3 electronics manufacturers can all benefit from microsection analysis, but for many Class 1 and Class 2 applications, it might be unnecessary. This is not the case for Class 3 electronics, such as those used in medical and military applications.

Microsectioning can also be used in SEM (scanning electron microscope) analysis. In SEM analysis, an electron beam scans the sample’s surface to dig up information about topography and composition.

The best way to decide whether your electronic products and your company will benefit from microsection analysis is to talk with your ECM (electronics contract manufacturer).

Combining or Replacing With Other PCB Testing

Besides PCB microsection analysis, functional PCB tests include:

• X-ray inspection, which provides an inner look at the entire board
• PCB contamination testing, to find sources of corrosion, degradation and metallization, among other problems
• Solderability test, for solder, PCB coating, and flux evaluation
• Time-domain reflectometer testing, to discover high-frequency board failures
• Peel testing, to measure how much strength is required to peel the board’s laminate
• Solder float testing, to reveal how much thermal stress board’s holes can take

Your ECM can determine whether one test is enough or you should explore other options.

Testing Varies by Manufacturer

Find out which tests your ECM offers and whether they fit your specific project requirements. Then discuss the most economical and efficient way to accommodate for testing.

The right testing choices can actually improve your bottom line. Not to mention your company’s reputation of delivering a great product!