Ceramic Electronic Device Lead Terminal Recess Design
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Solution Overview
Problem
Ceramic electronic devices with lead terminals often experience cracks due to shrinkage stress during solder solidification, leading to compromised moisture resistance and mechanical strength.
Innovation Solution
The design incorporates a lead terminal with an electrode facing portion, an extension unit, and a step surface, featuring a recess that directs molten solder away from the ceramic element body, reducing the fillet angle and minimizing stress concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead terminals are soldered to terminal electrodes using conventional methods, then connection is achieved, but cracks occur inside the ceramic element body due to shrinkage stress during solder solidification
Solution Approach 1:
The patent applies preliminary action by forming a recess in the electrode facing portion before soldering occurs. This pre-formed structural feature guides the solder to flow into the recess during the soldering process, thereby preventing shrinkage stress from concentrating at the corner of the ceramic element body and reducing crack formation.
Solution Approach 2:
The patent converts the harmful shrinkage stress of solder into a beneficial force by designing the recess to capture and redirect the solder flow. The solder's natural tendency to shrink and solidify is harnessed to fill the recess, creating a stress-absorbing structure that protects the ceramic element body from cracking.
2Strength
If a fillet is formed between lead terminal and terminal electrode, then connection strength is improved, but stress concentration occurs at the corner of the ceramic element body
Solution Approach 1:
The patent applies local quality by creating a recess specifically at the electrode facing portion where solder contact occurs. This localized structural modification concentrates the solder fillet formation in the recess area, away from the ceramic element body corners, thereby maintaining connection strength while eliminating stress concentration at vulnerable locations.
3Manufacturing precision
If solder is allowed to flow freely during solidification, then complete wet spread is achieved, but cracks generate due to uncontrolled shrinkage stress
Solution Approach 1:
The recess acts as an intermediary structure between the solder and the ceramic element body. It provides a designated zone for solder accumulation and solidification, mediating the interaction between solder shrinkage and the ceramic structure. This intermediary feature enables controlled solder distribution while protecting the ceramic from crack-inducing stress.
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
This configuration effectively reduces the occurrence of cracks within the ceramic element body by minimizing the fillet angle and enhancing the stability of the solder joint, making the device more suitable for mass production.
Implementation Method 1
a fillet is formed between the lead terminal and the terminal electrode due to wet spread of solder
Implementation Method 2
generation of shrinkage stress during solidification of solder
Data Source
AI summary
A ceramic electronic device includes a ceramic element body, a terminal electrode, and a lead terminal. The ceramic element body has an end surface and a lateral surface. The terminal electrode is formed on from the end surface to a part of the lateral surface of the ceramic element body. The lead terminal is connected to the terminal electrode by a connection member. The lead terminal includes an electrode facing portion disposed correspondingly to an end-surface electrode of the terminal electrode, an extension unit extending downward from a lower end of the electrode facing portion, and a step surface located between the electrode facing portion and the extension unit. The electrode facing portion has a recess dented in a direction away from the terminal electrode. A center of the recess is located below a center of the electrode facing portion in a height direction.