Lead Terminal Concave Joint Structure for Crack-Resistant Wiring Bases
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Solution Overview
Problem
Conventional lead terminals with inclined side surfaces do not adequately prevent the spread of joining members, leading to heat stress and potential cracks in the wiring substrate when joined to signal or grounding conductors, which affects the reliability of high-frequency signal transmission.
Innovation Solution
The lead terminal design features a first portion in contact with the joining member and a continuous second portion with two concave surfaces opposite each other across the center line, increasing the joint contact area and reducing thermal stress, thereby enhancing the strength and stability of the joint and minimizing the likelihood of cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a lead terminal with inclined side surfaces is used, then the joining member is prevented from spreading, but the joint strength is insufficient and heat stress causes cracks
Solution Approach 1:
The lead terminal incorporates concave curved surfaces instead of inclined straight surfaces. The concave surfaces increase the contact area with the joining member, distributing thermal stress more evenly and preventing crack formation while maintaining prevention of joining member spread.
Solution Approach 2:
The lead terminal has different surface geometries in different regions: concave surfaces at the joining member contact area to increase contact area and reduce stress, while maintaining the inclined side surfaces in other regions to prevent spreading. This local differentiation optimizes both joint strength and reliability.
2Ease of manufacture
If the lead terminal has a simple inclined surface design, then the manufacturing is simple, but the contact area with joining member is small leading to heat stress
Solution Approach 1:
The concave curved surfaces are formed using standard ceramic processing techniques such as grinding or molding, which are commonly used in the industry. This maintains manufacturing simplicity while significantly increasing the contact area to reduce thermal stress concentration.
3Force
If the lead terminal uses inclined side surfaces, then the joining member spread is reduced, but the joint contact area is insufficient
Solution Approach 1:
The lead terminal combines two different surface geometries: inclined side surfaces that prevent joining member spread, and concave surfaces at the contact area that increase the joint contact area. This local differentiation allows both functions to coexist without compromising either.
Solution Approach 2:
The concave curved surfaces increase the contact area with the joining member while the inclined side surfaces maintain the prevention of spreading. The combination of curved and inclined surfaces optimizes both contact area and spread prevention.
Data Source
AI summary
A wiring base includes a base having a first surface, at least one metal layer positioned on the first surface, at least one lead terminal positioned on the metal layer, and a joining member that is positioned on the metal layer and joins the lead terminal to the metal layer. The lead terminal has a first portion to be in contact with the joining member and also has a second portion being continuous with the first portion. In a cross section of the lead terminal orthogonal to a longitudinal direction of the lead terminal, the first portion has two concave surfaces that are formed near the metal layer so as to be disposed opposite to each other across a center in a transverse direction of the lead terminal.