Meaning
Destructive testing procedures in the electronics industry involve cutting a sample to reveal the internal structure of a component for microscopic inspection and measurement. This microsection analysis is the most reliable way to check the quality of the internal connections in a printed circuit board. It allows a technician to see the thickness of the copper plating, the integrity of the solder joints and the alignment of the different layers within the board.
In the context of manufacturing in China, this test is a standard requirement for qualifying a new production line or for investigating a failure in the field. The boundary of the analysis is the specific cross section that has been prepared for the microscope.
Sample Preparation
Creating a high quality cross section is a multi-step process that requires a great deal of skill and the right equipment. To perform a microsection analysis, the technician first cuts a small piece of the circuit board that contains the area of interest. This sample is then placed in a plastic mold and filled with a hard resin that supports the delicate structures as they are being ground down.
The technician uses a series of abrasive papers and polishing cloths to create a surface that is as smooth as a mirror. This surface is then etched with a mild acid to highlight the different layers of metal and glass fibre. If the preparation is not done correctly, the image under the microscope will be blurry or distorted, making it impossible to take accurate measurements.
This step is the most time consuming part of the entire process.
Observation Criteria
Once the sample is ready, it is placed under a metallurgical microscope where it can be viewed at very high magnification. During the microsection analysis, the inspector looks for specific features that indicate the quality of the manufacturing process. They check the thickness of the copper in the via holes to ensure it meets the minimum requirements.
They also look for any signs of cracks, voids or delamination between the layers. The shape of the solder joints is another important criterion, as a poor shape can lead to an electrical failure over time. The inspector compares what they see with the industry standards, such as those set by the IPC.
Any deviations from these standards are recorded and reported to the engineering team. This information is then used to adjust the production parameters and improve the yield of the factory.
Compliance Standard
The results of the inspection are used to prove that the manufacturer is following the agreed upon specifications for the project. A microsection analysis report is often a required part of the documentation that a supplier must provide to its customers in China and abroad. The report includes high resolution photographs of the cross section and a table of the measurements that were taken.
This provides a permanent record of the quality of a specific production lot. If a customer experiences a failure in their product, they can use these reports to determine if the fault lies with the circuit board or with some other component. The transparency provided by this testing helps to build trust between the manufacturer and the customer.
It also encourages the factory to maintain a high level of quality in all its operations. Continuous improvement is the goal of every quality manager in the industry. By using this technique, they can identify the root causes of problems and take the necessary steps to fix them.
