Solid Electrolytic Capacitor with Straight Lead Terminals
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Solution Overview
Problem
Conventional chip-type solid electrolytic capacitors face limitations in reducing Equivalent Series Inductance (ESL) due to the lead connections required for mounting, which restricts the increase of resonant frequency and capacitance, especially in high-frequency noise removal applications.
Innovation Solution
The design features a solid electrolytic capacitor with a sintered body of valve metal powder, where the anode and cathode leads extend straight from the package, reducing the lead length and ESL by eliminating bent lead portions and using a mount structure with a hole or recess on the printed board for direct terminal connection to minimize inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional chip-type solid electrolytic capacitors use leads to connect the capacitor element to terminals, then the capacitor can be mounted on a board, but the lead length increases the equivalent series inductance (ESL)
Solution Approach 1:
The invention extracts and eliminates the unnecessary bent portions of the leads. The lead structure is simplified to extend substantially straight from the capacitor element through the resin package to the terminal, removing the bending sections that contribute to inductance while maintaining the mounting function.
Solution Approach 2:
Instead of having leads that bend and extend outward from the package for mounting, the invention inverts the approach by having the terminal itself serve as the mounting interface. The lead extends straight through the package and the terminal makes direct contact with the mounting board, eliminating the traditional bent-lead mounting structure.
2Reliability
If the lead length is reduced to decrease ESL, then the resonant frequency increases, but the capacitance value decreases
Solution Approach 1:
The invention segments the lead structure into distinct functional portions: a first lead member extending straight from the capacitor element, and a terminal portion that provides the mounting interface. This segmentation allows optimization of each portion independently - the first lead member is minimized for low inductance while the terminal is designed for proper capacitance formation and mounting.
Solution Approach 2:
The invention applies local quality by making the lead extension substantially straight in the region where it passes through the resin package, specifically optimizing this local region to minimize inductance. The terminal portion at the end has different properties - it is designed to form the capacitor's capacitance and provide mounting surfaces, allowing it to have the necessary dimensions for electrical performance while the lead path remains minimized.
3Ease of operation
If bent lead portions are used for mounting, then the capacitor can be connected to the board, but the inductance increases due to the bent path
Solution Approach 1:
The invention extracts and removes the bent lead portions that were traditionally used for mounting. Instead of bending the leads to achieve mounting connectivity, the design uses a substantially straight lead extension that passes through the resin package, eliminating the harmful bent sections while maintaining mounting capability through the terminal structure.
Solution Approach 2:
The invention changes the mounting approach from a planar bent-lead connection to a three-dimensional straight-through structure. The lead extends substantially straight from the capacitor element through the resin package to the terminal, utilizing the vertical dimension for direct connection rather than horizontal bending, thereby minimizing the inductance-contributing path length.
Data Source
AI summary
A solid electrolytic capacitor 1 includes a capacitor element 2 and a resin package 9 enclosing the capacitor element. The capacitor element includes a sintered body 3 of valve metal powder, an anode 4a provided by embedding an anode wire 4 in the sintered body, and a cathode 5 provided by forming a metal layer on the sintered body. A first lead member 6 in the form of a plate is connected to the anode wire 4. The end of the first lead member projects from a side surface 9a of the resin package 9 to provide an anode terminal T1. A second lead member 7 in the form of a plate is connected to the cathode 5. The end of the second lead member projects from a side surface 9b of the resin package 9 to provide a cathode terminal T2. By extending the first and the second lead members 6 and 7 generally horizontally at the substantially same height from the lower end of the resin package and making the portions projecting from the resin package 9 serve as the anode terminal T1 and the cathode terminal T2, the lead length between the anode 4a of the capacitor element 2 and the anode terminal T1 and the lead length between the cathode 5 and the cathode terminal T2 is made as short as possible, whereby ESL is reduced.