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Complete guide to PCB cross-section analysis or micro-sectional analysis

Complete guide to PCB cross-section analysis or micro-sectional analysis

A PCB is a printed circuit board. It is used in electronics to connect components and other electronic devices. The main purpose of PCB is to house the electronic parts, connectors, and other electronic components of an electronic device.

PCB cross-section analysis is mainly used to check the thickness of the internal traces, the number of layers, the size of the through hole, and the quality of the through hole. Slice analysis is an important technique for PCB/PCBA failure analysis, and the quality of slices will directly affect the accuracy of failure location confirmation.

What is a PCB cross-section analysis?

What is a PCB cross-section analysisCross-section, also called X-section, is the most commonly used sample preparation and analysis method to observe the cross-sectional structure of the sample. Slice analysis technology is one of the most common and important analysis methods in PCB/PCBA, parts and other manufacturing industries. Find the cause and solution of failure, evaluate process improvement, and use it as the basis for objective inspection, research and judgment.

A PCB is made up of many layers, each of which has a specific purpose. The layers are stacked together to form a circuit that converts electrical signals into radio waves or light waves, or vice versa. A PCB cross-section analysis is a visual representation of the physical characteristics of a printed circuit board. It is often used to show how the circuit board was constructed, which components are on which layers, and what kind of materials were used in their construction.

What is another name for cross-section analysis?

PCB microsectional analysis is a method used to study the characteristics and properties of thin films, such as printed circuit boards. It is a common technique in industry and research, because it allows researchers to study the chemical composition of thin films without having to create a sample that is too large or tedious to handle.

The micro sectional analysis involves cutting the PCB into thin slices, measuring the thickness and composition of each slice, and then analyzing how these properties change as the slice gets thinner. The technique has been used to study the effects of temperature and humidity on electrical properties, as well as how PCBs degrade in soil over time.

What’s the way of PCB cross-section analysis?

What’s the way of PCB cross-section analysis1. Longitudinal section: Cut the board in the direction perpendicular to the board surface, grind and observe the section of the section. This method is usually used to observe the condition of the hole after copper plating and the internal bonding surface, such as the confirmation of the copper thickness of the hole, the internal disconnection and the internal connection, copper particles, and electroplating sag. It is the most commonly used method in PCB cross-section analysis.

2. Horizontal section: grind down layer by layer along the stacking direction of the board and analyze it. This method is often used to aid longitudinal sectioning for abnormal analysis of boards.

Why PCB cross-section analysis are needed?

The PCB cross-section analysis is needed because it is necessary to determine the dimensions of the PCB. They are needed to determine the overall shape of a PCB. It helps in identifying the number of layers and the size of each layer. This information is essential for the designer to create an efficient layout.

● Understanding the PCB’s physical properties
● It helps in designing the PCB as well as in manufacturing the PCB.
● It helps in testing various components.
● The cross-section also helps in identifying defects on the surface of the PCB, which might not be visible to the naked eye.
● Preventing electrical shorts between components and other conductive materials.

What’s the PCB cross-section analysis procedure?

The PCB cross-section analysis or microsection analysis is a method for determining the thickness of a piece of the printed circuit board. The cross-sectional shape of the PCB can be determined by cutting out a sample from the board and measuring its thickness from one edge to another. The sample can then be used to create an image on a computer screen. This image can be compared with known standards to determine whether the board has been accurately measured.

The procedure for PCB cross-section analysis involves several steps:
① Sample culling
Cut out the part of the board you want to analyze. Confirm the position, and select the cutting part with the appropriate thickness of hole copper and the number of holes according to the needs of the analysis.

② Cleaning
When cutting the board, there will be a lot of debris on the surface, which needs to be cleaned first for better grinding below.

③ Grinding
Grind the cross-section evenly and forcefully with sandpaper to the point where the condition can be observed.

④ Polish
Since the sandpaper is too rough, scratches may affect the effect of observing the slices, so it needs to be polished again to prepare for the follow-up observation.

⑤ Microetch
Uses the micro-etching solution to leak out the various metal interfaces of the cross-section, which is convenient for the following observation.

⑥ Analyze(OM inspection, SEM inspection, EDS analysis, EBSD analysis…)
The cross sections after microetch are placed under a microscope for observation and quality analysis, so as to quickly and accurately find board defects.

What’s the PCB cross-section analysis equipment and material?

In the PCB cross-section analysis process, SEM/EDS, 3D digital optical microscope, stereo microscope, grinding/polishing machine, precision cutting machine, abrasive paper, polishing cloth/polishing liquid, epoxy resin glue + curing agent are used.

What’s the standard and items of PCB cross-section analysis?

The standards for cross-section analysis are IPC-TM 650 2.1.1, IPC-TM 650-2.2.5, IPC A 600, IPC A 610, etc.

Items inspected include:
1. PCB structural defects: PCB delamination, hole copper fracture, etc.

2. PCBA welding quality inspection:
a. BGA air soldering, virtual soldering, holes, bridges, tin area, etc.
b. Product structure analysis: capacitor and PCB copper foil layer number analysis, LED structure analysis, electroplating process analysis, internal structural defects of materials, etc.
c. Small size measurement (generally greater than 1um): pore size, tin height, copper foil thickness, etc.

Conclusion

The PCB cross-section analysis shows all of the layers of a printed circuit board, as well as the layers between them. It helps you understand what material your circuit board is made of and where those materials are located in relation to each other.

There are a number of ways to improve the performance of PCBs. While it is important not to lose sight of the fact that this analysis was performed on a single sample of PCBs, it nonetheless provides valuable insight into how different types of PCBs perform at different stages in their life cycle.

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