Electrolytic Capacitor Electrode Structure to Prevent Solder Explosion
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Solution Overview
Problem
Solid electrolytic capacitors experience solder explosion during reflow treatment due to expansion of organic components and water in the silver paste layer, which cannot be completely prevented by adjusting their amounts alone, as the insulating resin and solid electrolyte layer also contain these components.
Innovation Solution
The electrolytic capacitor design includes a resin molded body with a stack of capacitor elements sealed in a resin, featuring external electrodes with a resin electrode layer and a Ni plating layer, where the ratio of the resin electrode layer thickness to the Ni plating layer thickness is 5 or less, preventing solder explosion by ensuring the Ni plating layer remains intact during heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amounts of organic components and water in the silver paste layer are reduced, then solder explosion is prevented or reduced, but the insulating resin and solid electrolyte layer still contain these components causing solder explosion to occur
Solution Approach 1:
A Ni plating layer is introduced as an intermediary protective barrier between the resin electrode layer containing organic components and water, and the external environment. This Ni plating layer prevents the expansion of organic components and water during reflow treatment from causing solder explosion, while allowing the resin electrode layer to maintain its functional properties.
Solution Approach 2:
The external electrode is designed as a composite structure combining a resin electrode layer (containing conductive component and resin component) with a Ni plating layer. This composite material structure provides both the electrical conductivity needed for electrode function and the protective barrier needed to prevent solder explosion by containing the expansion of organic components and water.
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 design effectively prevents solder explosion and stress-induced peeling by maintaining the integrity of the Ni plating layer, even when organic components and water in the resin electrode layer expand during reflow treatment.
Implementation Method 1
a Ni plating layer on a surface of the resin electrode layer, wherein a ratio of a thickness of the resin electrode layer to a thickness of the Ni plating layer is 5 or less
Data Source
AI summary
An electrolytic capacitor that includes a resin molded body including a stack that includes a capacitor element with an anode exposed at a first end surface, a dielectric layer on a surface of the anode, and a cathode opposite to the anode and exposed at a second end surface; a first external electrode on the first end surface and electrically connected to the anode; and a second external electrode on the second end surface and electrically connected to the cathode, wherein the first external electrode and the second external electrode each include: a resin electrode layer containing a conductive component and a resin component; and a Ni plating layer on a surface of the resin electrode layer, wherein a ratio of a thickness of the resin electrode layer to a thickness of the Ni plating layer is 5 or less.