Chlorosulfonated Polyethylene Primer for Insert Molding Adhesion

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Solution Overview

Problem

The existing insert molding methods face challenges in achieving reliable adhesion between metal conductors and resin insulators, particularly in automotive electrical components, due to thermal stress and moisture infiltration issues, which can lead to peeling and waterproofing failures.

Innovation Solution

A method involving the formation of a thin film layer made of chlorosulfonated polyethylene (CSM) on the metal conductor surface, which is crosslinked during injection molding, providing a strong adhesive interface and preventing thermal contraction-induced gaps between the metal and resin.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If a metal conductor with small linear expansion coefficient is used with a resin insulator having large mold shrinkage factor, then miniaturization and weight reduction are achieved, but large thermal stress is generated causing peeling at the interface

Engineering Contradiction:

Improveelectrical component sizeVSAvoidadhesion at interface

Core Design Contradiction:

Volume of moving objectVSStrength

Solution Approach 1:

A primer coating is applied to the metal conductor surface before resin injection. This primer acts as an intermediary layer between the metal conductor and resin insulator, improving adhesion and reducing peeling caused by thermal stress during cooling. The primer coating specifically addresses the interface bonding issue while allowing the use of thin-wall molding for miniaturization.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the resin insulator thickness is increased to prevent moisture infiltration, then waterproofing is improved, but the component size increases contradicting miniaturization goals

Engineering Contradiction:

Improvewaterproofing performanceVSAvoidelectrical component size

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The metal conductor surface is treated with a primer coating before resin injection. This preliminary action creates a hydrophobic or moisture-resistant surface layer that prevents moisture infiltration at the interface, eliminating the need for increased resin thickness for waterproofing purposes and enabling thin-wall molding.

Inventive Principle:

Principle #10Preliminary action

3Volume of moving object

If the resin insulator thickness is reduced for miniaturization, then component size is reduced, but moisture can infiltrate through small gaps at the interface

Engineering Contradiction:

Improveelectrical component sizeVSAvoidwaterproofing performance

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The primer coating serves as a protective intermediary layer on the metal conductor surface, preventing moisture from infiltrating through potential gaps at the interface. This allows the use of thin resin insulators for miniaturization while maintaining waterproofing reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Strength

If thermal stress between metal and resin is reduced by material selection, then adhesion is improved, but the ability to absorb thermal contraction strains is reduced

Engineering Contradiction:

Improveadhesion at interfaceVSAvoidthermal contraction strain absorption

Core Design Contradiction:

StrengthVSStability of the object's composition

Solution Approach 1:

The primer coating acts as a flexible intermediary layer that can absorb thermal contraction strains while maintaining strong adhesion between the metal conductor and resin insulator. This resolves the contradiction by providing both strong bonding and strain absorption capability.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 ensures robust adhesion and waterproofing by absorbing thermal contraction strains, maintaining the bond between the metal conductor and resin insulator, and preventing moisture infiltration, thus enhancing the reliability of electrical components.

Implementation Method 1

a thin film layer mainly made of a chlorosulfonated polyethylene (CSM) is formed on a surface of a portion of the insert component to be covered with the thermoplastic resin, and the thin film layer is crosslinked in the mold during injection molding

Methodology Applied

Scientific EffectCrosslinking:

Implementation Method 2

a metal having a small linear expansion coefficient contacts a resin or a resin composition having a large mold shrinkage factor or a large linear expansion coefficient, and therefore, a large thermal stress is generated between the metal conductor and the resin insulator during injection molding and cooling

Methodology Applied

Scientific EffectThermal contraction: Thermal Contraction

Data Source

PatentUS9962871B2Insert molding method and insert molded article

Publication Date: 2018.05.08 SHINSEI KAGAKU INDS

AI summary

An insert molding method includes: integrally molding a thermoplastic resin with an insert component, by setting the insert component, which is a metal conductor, in a mold; clamping the mold; and injection-filling the thermoplastic resin in a cavity. The insert component is made of copper or a copper alloy. Prior to injection molding, a thin film layer mainly made of a chlorosulfonated polyethylene is formed on a surface of a portion of the insert component to be covered with the thermoplastic resin, and the thin film layer is crosslinked in the mold during injection molding.