Solid Electrolytic Capacitor Anode Lead Reduction
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Solution Overview
Problem
Conventional chip-type solid electrolytic capacitors face challenges in reducing the anode lead region to enhance volume efficiency due to limitations in bonding member thickness and high melting point materials like tantalum or niobium, which degrade insulating properties and increase leakage current when welded, making it difficult to achieve reliable electrical connections and mass production.
Innovation Solution
The use of a small piece of a metal frame made of a valve-acting metal, such as aluminum, which is resistance-welded to the anode lead and then cut to remain at the protruding portion, allowing for wire bonding connections to reduce the anode lead region and improve volume efficiency by avoiding heat-induced crystallization of the anodized film layer, thus enabling stable anodic oxidation and reliable electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resistance welding is used to connect the bonding member to the anode lead, then reliable electrical connection is achieved, but the anodized film layer crystallizes due to high temperature, degrading insulating properties and increasing leakage current
Solution Approach 1:
The bonding member is divided into two distinct parts: a first bonding member made of high melting point material (tantalum or niobium) that is resistance-welded to the anode lead, and a second bonding member made of low melting point material (aluminum or copper) that is connected to the first bonding member by wire bonding. This segmentation allows the high melting point material to handle the welding heat without affecting the anodized film, while the low melting point material avoids heat-induced crystallization.
Solution Approach 2:
The first bonding member (high melting point material) acts as an intermediary between the anode lead and the second bonding member (low melting point material). It receives the resistance welding heat from the anode lead without transmitting it to the anodized film, and provides a connection point for the wire bonding process that does not require high temperature.
2Volume of moving object
If the bonding member is made thinner to reduce the anode lead region, then volume efficiency is improved, but bonding member thickness becomes insufficient for reliable resistance welding
Solution Approach 1:
The bonding function is segmented between two bonding members with different thickness requirements. The first bonding member can be thicker to ensure reliable resistance welding with the anode lead, while the second bonding member can be thinner since it only needs to connect via wire bonding, thus reducing the overall anode lead region volume.
3Reliability
If high melting point materials like tantalum or niobium are used for the bonding member, then reliable electrical connection is achieved, but mass production becomes difficult due to production yield issues
Solution Approach 1:
The bonding member is segmented into a first bonding member (high melting point material) for reliable connection to the anode lead, and a second bonding member (low melting point material) for easier wire bonding connection. This segmentation allows the critical high reliability function to use high melting point material while the less critical connection uses easier-to-manufacture material, improving overall mass production yield.
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 approach allows for a significant reduction in the anode lead region, enhancing the volume efficiency of chip-type solid electrolytic capacitors without degrading insulating properties, maintaining reliable electrical characteristics, and facilitating high-yield mass production by ensuring stable anodic oxidation and reduced leakage current.
Implementation Method 1
by anodic oxidation, a porous anode body formed with a dielectric layer on a surface of a porous sintered body
Implementation Method 2
a small piece of a metal frame made of a valve-acting metal, which is resistance-welded to the anode lead
Implementation Method 3
the mounting anode terminal member and the small piece of the metal frame are electrically connected together by wire bonding
Data Source
AI summary
A solid electrolytic capacitor includes a porous sintered body made of a valve-acting metal and embedded with part of an anode lead having a protruding portion, a solid electrolyte layer formed in contact with a dielectric layer formed in the porous sintered body, a mounting anode terminal member, a mounting cathode terminal member, and an insulating casing resin. The capacitor further includes a small piece of a metal frame made of a valve-acting metal. This small piece of the metal frame is formed integrally with the protruding portion of the anode lead by cutting, after the anodic oxidation, the metal frame to which the protruding portion of the anode lead is fixed by resistance welding. The small piece of the metal frame and the mounting anode terminal member are connected together by wire bonding so that the anode lead and the mounting anode terminal member are electrically connected together.