Solid Electrolytic Capacitor Bonding Structure for ESR Stability

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Solution Overview

Problem

Conventional solid electrolytic capacitors experience fluctuations in equivalent series resistance (ESR) due to moisture intrusion and expansion during high-temperature processes, leading to increased resistance and variability in ESR values.

Innovation Solution

The capacitor design incorporates a substrate with a roughened surface and an adhesive layer with specific surface roughness characteristics, ensuring deep penetration and close contact, thereby reducing moisture ingress and stabilizing ESR.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a smooth substrate surface is used, then the manufacturing process is simpler, but moisture intrusion occurs leading to ESR fluctuation

Engineering Contradiction:

ImproveESR stabilityVSAvoidsubstrate surface preparation

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The substrate surface is pre-roughened before adhesive application to create a surface structure that will later provide mechanical interlocking and moisture barrier functions. This preliminary surface preparation ensures that when the adhesive is applied, it will penetrate deeply and form a robust moisture-resistant interface, preventing ESR fluctuation caused by moisture intrusion.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The substrate surface is intentionally created with a porous or rough structure having Rz≥5μm. This porous surface structure allows the adhesive to penetrate deeply, creating a mechanically interlocked bond that also serves as a moisture barrier. The rough surface topology provides capillary channels for adhesive infiltration while the resulting structure blocks moisture pathways.

Inventive Principle:

Principle #31Porous materials

2Reliability

If the adhesive layer has low surface roughness, then the application process is easier, but moisture penetration increases

Engineering Contradiction:

Improvemoisture resistanceVSAvoidadhesive layer formation

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The adhesive layer is designed with differentiated surface roughness characteristics: the interface with the substrate has high roughness (Rz≥3μm) to ensure deep penetration and moisture resistance, while the upper surface maintains appropriate smoothness for subsequent processing. This local quality differentiation optimizes both moisture barrier performance and manufacturability.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The controlled roughness of the adhesive layer, which might seem to complicate manufacturing, is actually converted into a benefit by creating a surface structure that enhances moisture resistance. The rough texture with Rz≥3μm creates tortuous paths for moisture diffusion while the adhesive material itself fills the valleys to create a continuous barrier.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Object-affected harmful factors

If the substrate surface roughness is increased, then moisture intrusion is reduced, but the manufacturing complexity increases

Engineering Contradiction:

Improvemoisture intrusionVSAvoidsurface roughness control

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The invention specifies a quantitative parameter threshold (Rz≥5μm) for substrate surface roughness and (Rz≥3μm) for adhesive layer surface roughness. By defining clear parameter boundaries, the complex task of surface roughness control is transformed into a measurable and controllable manufacturing specification, making the process manageable while ensuring effective moisture protection.

Inventive Principle:

Principle #35Parameter changes

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 minimizes moisture penetration and stabilizes ESR fluctuations, maintaining consistent performance under high-temperature conditions.

Implementation Method 1

At an interface between the first surface and the adhesive layer, a maximum height Rz1 of surface roughness of the first surface is 5 μm or more, and a maximum height Rz2 of surface roughness of the adhesive layer is 3 μm or more

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Data Source

PatentUS20260004970A1Solid electrolytic capacitor and method for manufacturing same

Publication Date: 2026.01.01 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

A solid electrolytic capacitor includes: a capacitor element including an anode part and a cathode part; a substrate that supports the capacitor element; a sealing body that seals the capacitor element; a first external electrode electrically connected to the anode part; a second external electrode electrically connected to the cathode part; and an adhesive layer disposed between the capacitor element and a first surface of the substrate. At an interface between the first surface and the adhesive layer, a maximum height Rz1 of surface roughness of the first surface is 5 μm or more, and a maximum height Rz2 of surface roughness of the adhesive layer is 3 μm or more.