Abstract

Micro metal PIN pins are widely used in various precision connectors and are prone to fracture failure during service. Optical microscopes are limited by depth of field and magnification, making it difficult to analyze microscopic fracture characteristics. Scanning electron microscopy (SEM), with its advantages of large depth of field and wide magnification range, has become a common tool for failure analysis of PIN pin fractures. This paper takes a fractured PIN pin with a diameter of approximately 400 μm as a case study. SEM was employed to observe the fracture morphology, revealing that the pin exhibited a mixed fracture mode, predominantly brittle fracture with localized ductile features characterized by a few dimples. The findings provide a basis for product process improvement.

Introduction to Metal PIN Pins

Metal PIN pins are core basic components of connectors, wire harness terminals, and plugs. As key carriers for electrical signal and current transmission, they are widely used in consumer electronics, automotive electronics, industrial control, communication equipment, and other fields. With the trend toward lightweight and miniaturization in electronic products, PIN pins are increasingly designed with finer specifications, with diameters of several hundred micrometers becoming mainstream. The sample analyzed in this study is a micro PIN pin with a diameter of approximately 400 μm.

The production of PIN pins involves multiple processes, including wire drawing, stamping, surface plating, and others. In actual service conditions, the finished products are subjected to repeated insertion and extraction, alternating stresses, thermal cycling stresses, and instantaneous impact loads. Due to multiple factors such as raw material metallurgical defects, abnormal grain structure, residual stress from stamping, hydrogen embrittlement from plating, and excessive assembly loads, micro PIN pins are highly susceptible to sudden fracture failures, which directly lead to open circuits, complete equipment failure, and consequent production and after-sales losses.

Case Study

(I) Testing Background

Signal interruption occurred in an electronic component during operation. After preliminary investigation, it was suspected that the failure was caused by internal PIN pin fracture. The submitted sample was a fractured metal PIN pin with a diameter of approximately 400 μm. The fracture morphology was observed using a SuperSEM scanning electron microscope to determine the fracture type and analyze the possible causes.

(II) Experimental Conditions

Testing Equipment: SuperSEM N10eV Desktop Scanning Electron Microscope

Imaging Mode: Backscattered Electron (BSE) mode, which is sensitive to atomic number contrast and helps distinguish different phases or contaminants on the fracture surface

Accelerating Voltage: 15 kV

(III) Detection Images

(IV) Test Results

The overall morphology of the fracture can be clearly observed. The fracture surface exhibits distinct cleavage steps and river patterns, which are typical microscopic features of brittle fracture, indicating that the fracture propagated rapidly in a brittle manner. At the same time, a small number of dimple-like features can be observed in local areas.

Based on comprehensive judgment: the fracture of this PIN pin is predominantly a brittle crystalline fracture, accompanied by localized ductile features. Brittle crystalline fracture is generally associated with high material brittleness, improper heat treatment, or service stresses exceeding the material's load-bearing capacity.

Conclusion

Currently, the semiconductor and precision electronics industry is rapidly advancing toward miniaturization, high precision, and high reliability. The structure of components is becoming increasingly refined, and traditional macroscopic inspection methods can no longer meet the quality control requirements of high-end electronics manufacturing.

As a core precision instrument for microstructural characterization, scanning electron microscopy has completely broken through the observational limitations of traditional inspection techniques. It can not only efficiently perform fracture failure analysis and defect tracing on metal PIN pins but also be widely applied to the microstructural inspection and process verification of semiconductor wafers, chip leads, precision packaging devices, and electronic plating structures. Throughout the entire production chain—from raw material inspection, in-process inspection, failure analysis, to process optimization—scanning electron microscopy can precisely capture micro- and even submicron-scale defects, providing intuitive and accurate microstructural data support for determining failure mechanisms, optimizing production processes, and improving product reliability.