Cross-section analysis under a microscope is important for solder joints because it reveals internal defects and bonding conditions that cannot be seen from the outside. By cutting and polishing a solder joint, engineers can use microscopy to identify microcracks, voids, porosity, poor wetting, incomplete bonding, and abnormal intermetallic layers. This helps determine the quality and reliability of the joint, understand why a solder connection may have failed, and improve manufacturing or reflow processes. In automotive electronics, such as ECUs and sensors, this analysis is especially valuable for preventing microscopic defects from developing into electrical or mechanical failures.

 

1. Detect hidden solder-joint cracks

Role: Cross-section microscopy exposes cracks that may not be visible on the surface of a solder joint.

Case scenario:
An automotive ECU passes visual inspection but later develops an intermittent electrical connection after thermal cycling. Engineers cross-section the solder joint and discover a fine crack propagating through the solder or along the solder/metal interface.

Suitable Meiji microscope: MT7530H — trinocular metallurgical microscope with brightfield/darkfield observation and 5×, 10×, 20×, and 50× objectives. Darkfield can be useful when trying to emphasize small surface or structural discontinuities.

---

2. Evaluate solder bonding and wetting

Role: The microscope allows engineers to examine the interface between the solder and PCB/component termination to determine whether the joint formed properly.

Case scenario:
An automotive sensor intermittently loses its electrical connection. A cross-section shows that the solder did not properly wet or bond to part of the pad, leaving an abnormal interface.

Suitable Meiji microscope: MT7100H — an upright trinocular brightfield metallurgical microscope with 5×–50× Plan EPI objectives. It is designed for high-magnification observation of metallurgical specimens using incident light.

---

3. Find voids and porosity inside the solder

Role: Cross-section analysis can reveal internal voids and pores and allow engineers to examine their size, location, and distribution.

Case scenario:
A solder connection in an automotive electronic module experiences reliability problems. Cross-sectioning reveals multiple voids concentrated in the solder region. Engineers can then investigate whether the manufacturing/reflow process contributed to the defect.

Suitable Meiji microscope: IM7520H — an inverted metallurgical microscope offering brightfield and darkfield observation with 5×, 10×, 20×, and 50× objectives. Its inverted configuration can be particularly useful for examining prepared metallographic specimens.

---

4. Examine the solder/metal interface and microstructure

Role: Higher magnification allows engineers to examine the fine structure of the solder joint and the interface between solder and the underlying metal.

Case scenario:
An automotive electronics manufacturer changes its solder alloy or PCB surface finish. Engineers cross-section sample joints before and after the change and compare the interface, solder microstructure, and intermetallic region.

Suitable Meiji microscope: MT7500 series, such as the MT7530H. The series provides brightfield/darkfield observation and is designed for industrial metallurgical inspection of metals, alloys, coatings, and solid specimens.

---

5. Perform failure analysis and document the results

Role: Cross-section microscopy provides visual evidence for determining where a solder joint failed and what physical features are associated with the failure.

Case scenario:
An ECU fails during environmental testing. Engineers cross-section several solder joints and find cracks concentrated at a particular interface. Images are captured and compared between failed and good samples to support the failure-analysis investigation.

Suitable Meiji microscope: MT7100H + HD2500T camera. The MT7100H provides 5×–50× metallurgical observation, while the HD2500T configuration allows the microscopic findings to be captured for documentation and comparison.

---

Summary

The main idea: the cross-section preparation exposes the internal solder joint, while the metallurgical microscope provides the magnification, contrast, and illumination needed to identify and document the microscopic features responsible for joint quality or failure.

---

Cross Section Analysis

INDUSTRY

---

Cross Section Analysis

UNIVERSITY