Epoxy Over-Molded Capacitor Assembly for Delamination Control

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Solution Overview

Problem

Existing ceramic capacitors used in power line communications (PLC) systems face issues with thermal expansion mismatch, delamination, and electrical stress due to sharp corners, leading to partial discharge and insulation breakdown, especially in underground medium voltage applications, and require complex manufacturing processes.

Innovation Solution

A capacitor assembly is molded in epoxy with annular conductive shields and O-rings to match thermal expansion and cover sharp edges, reducing electrical stress and ensuring a robust interface with the epoxy insulator.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If ceramic capacitors are directly molded into epoxy insulation, then a self-contained insulator with PLC capability is achieved, but thermal expansion mismatch and delamination occur at the interface

Engineering Contradiction:

ImprovePLC communication capabilityVSAvoidinterface bonding

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

A conformal coating layer is applied to the ceramic capacitor surface to act as an intermediary between the ceramic and epoxy materials. This coating has thermal expansion properties that bridge the gap between ceramic and epoxy, preventing delamination while maintaining the PLC communication functionality of the direct mold configuration.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The solution uses a composite material structure where the ceramic capacitor is coated with a conformal material that combines properties of both ceramic and epoxy. This composite approach allows the assembly to withstand thermal expansion differences while maintaining structural integrity and electrical performance.

Inventive Principle:

Principle #40Composite materials

2Reliability

If ceramic capacitors are cold shrunk and separately potted into pre-molded epoxy body, then interface delamination is prevented, but manufacturing complexity and labor steps increase

Engineering Contradiction:

Improveinterface bondingVSAvoidmanufacturing process

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The conformal coating application and epoxy molding operations are merged into a simplified sequential process. The conformal coating is applied to the ceramic capacitor before insertion into the mold, allowing the capacitor to be both protected and integrated in a streamlined manufacturing flow that reduces labor steps compared to separate cold shrink and potting operations.

Inventive Principle:

Principle #5Merging (Combining)

3Ease of manufacture

If sharp corners are present on capacitor terminals, then manufacturing is simplified, but electrical stress concentrates leading to partial discharge and insulation breakdown

Engineering Contradiction:

Improvecapacitor geometryVSAvoidelectrical stress

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The conformal coating is applied beforehand to the ceramic capacitor surface, including the terminal regions. This coating acts as a cushioning layer that redistributes electrical stress before it reaches the sharp corners, preventing partial discharge and insulation breakdown while allowing the capacitor to maintain its manufacturable geometry with minimal modification.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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

The solution provides a reliable and cost-effective interface that withstands temperature extremes and reduces electrical stress, preventing delamination and partial discharge, while maintaining communication integrity.

Implementation Method 1

CypoxyTM and ceramic have significantly different coefficients of thermal expansion (CTE)

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

A capacitor assembly is molded in epoxy

Methodology Applied

Scientific EffectViscoelasticity: Viscoelasticity

Implementation Method 3

annular conductive shields and O-rings to match thermal expansion and cover sharp edges, reducing electrical stress

Methodology Applied

Scientific EffectElectrical stress distribution: Electric Field

Data Source

PatentUS12593701B2Epoxy over-molded capacitor assembly

Publication Date: 2026.03.31 S&C ELECTRIC CO

AI summary

An electrical device including a first cylindrical capacitor, a first terminal electrically coupled to one end of the first capacitor, a first electrical line electrically coupled to the first terminal and a first annular conductive end shield formed over the first terminal and being electrically coupled to the first terminal and the one end of the first capacitor, where the first end shield has a greater diameter than the diameter of the first capacitor. The device also includes a second cylindrical capacitor, a second terminal electrically coupled to one end of the second capacitor, a second electrical line electrically coupled to the second terminal and a second annular conductive end shield formed over the second terminal and being electrically coupled to the second terminal and the one end of the second capacitor, where the second end shield has a greater diameter than the diameter of the second capacitor.