Lead Pin Plated Layer Design for Visual Inspection Accuracy
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Solution Overview
Problem
Current visual inspection methods for lead pins on wiring boards lack accuracy, often misclassifying satisfactory connections as defective due to incomplete wetting or excessive conductive material, leading to reduced yield and the need for costly reinspection.
Innovation Solution
The lead pin design includes a shaft portion with a head portion having a tin-based first plated layer and a second plated layer with higher reflectivity and conductivity, allowing for improved visual inspection accuracy by distinguishing between correct and defective connections using visible light reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single plated layer is used on the lead pin, then the manufacturing process is simple, but the visual inspection accuracy is insufficient because reflected light from different materials cannot be distinguished
Solution Approach 1:
The lead pin surface is segmented into multiple plated layers with different materials (tin-based first plated layer and silver-based second plated layer). Each layer has distinct reflectivity characteristics, allowing the visual inspection apparatus to distinguish between satisfactory and defective connections by analyzing the reflected light patterns from different layers.
Solution Approach 2:
Different regions of the lead pin are plated with different materials to create local quality variations. The tin-based layer provides baseline reflectivity while the silver-based layer provides higher reflectivity. This local differentiation enables the inspection system to detect connection quality by comparing reflectivity signals from specific regions.
2Measurement precision
If visible light is irradiated perpendicular to the wiring board surface for inspection, then the inspection process is simple, but the inspection accuracy is insufficient because tilted or deformed lead pins cannot be reliably detected
Solution Approach 1:
The patent uses reflectivity changes (analogous to color changes in optical inspection) of the plated layers to indicate connection quality. The tin-based and silver-based layers have different reflectivity characteristics, creating distinct optical signatures. When light is irradiated perpendicular to the board surface, the reflected light intensity and pattern vary based on the lead pin's connection state, enabling detection of tilted or deformed pins without complex inspection equipment.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances the accuracy of visual inspection by maintaining satisfactory judgments even with excessive conductive material and detects defects such as bending or tilting, reducing reinspection needs and improving electrical conductivity.
Implementation Method 1
the second plated layer has a reflectivity with respect to visible light and a conductivity higher than a reflectivity with respect to the visible light and a conductivity of the first plated layer, respectively
Data Source
AI summary
A lead pin includes a shaft portion, a head portion formed on one end of the shaft portion, and having a diameter greater than a diameter of the shaft portion, a tin-based first plated layer exposed at a surface of the head portion visible from the other end of the shaft portion, and a second plated layer exposed at an end surface of the shaft portion visible from the other end of the shaft portion. The second plated layer has a reflectivity with respect to visible light and a conductivity higher than a reflectivity with respect to the visible light and a conductivity of the first plated layer, respectively.