Type C Connector Core Structure and Key Design Considerations

A connector may look simple from the outside, but its performance depends heavily on the design of its internal components. Among them, the terminal and housing are two of the most critical elements.

Their material selection, structural design, plating, mechanical properties, and manufacturing tolerances directly affect electrical performance, reliability, durability, and service life.

This article introduces the basic structure of connectors and highlights several key considerations in terminal and housing design.

1. Terminal Design

What Is the Function of a Terminal?

The terminal is the primary conductive component of a connector. Its main function is to establish and maintain a stable electrical connection between two circuits.

A well-designed terminal should provide:

• High electrical conductivity

• Stable contact force

• Good elasticity and fatigue resistance

• Wear resistance

• Corrosion resistance

• Reliable performance over repeated mating cycles

Common Terminal Types

Depending on the application, connector terminals can generally be divided into wire-side terminals and PCB-side terminals.

Wire-Side Terminals

Wire-side terminals are designed to connect with electrical wires or cables.

Common termination methods include:

Crimp TypeThe terminal is mechanically crimped onto the wire, typically including both conductor crimping and insulation crimping areas. This method is widely used in automotive, industrial, and appliance applications.

Solder TypeThe conductor is soldered directly to the terminal. This method is suitable for applications where a permanent electrical connection is required.

Insulation Displacement Contact (IDC)The terminal penetrates the wire insulation and makes direct contact with the conductor without requiring the insulation to be stripped first. IDC technology can improve assembly efficiency and is commonly used in communication and signal applications.

PCB-Side Terminals

PCB terminals connect the connector directly to a printed circuit board.

Common mounting methods include:

• Through-Hole (THD/THT) – terminals are inserted through PCB holes and soldered on the opposite side.

• Surface Mount Technology (SMT) – terminals are soldered directly onto PCB pads.

• Hybrid Mounting – combines SMT signal contacts with through-hole or mechanical mounting tabs to improve PCB retention.

2. Terminal Material Selection

The base material of a terminal has a significant influence on conductivity, elasticity, mechanical strength, fatigue life, and overall connector cost.

Beryllium Copper (BeCu)

Beryllium copper offers excellent elasticity, fatigue resistance, and mechanical strength.

It is commonly used in applications requiring:

• High mating-cycle durability

• High contact reliability

• Strong spring characteristics

• Small and precision contact structures

Phosphor Bronze

Phosphor bronze provides a good balance between electrical conductivity, elasticity, mechanical properties, and cost.

It is one of the most widely used terminal materials in consumer electronics, industrial equipment, communication devices, and general-purpose connectors.

Brass

Brass offers good electrical conductivity, excellent formability, and relatively low material cost.

It is often used in terminals where extremely high spring performance or mating-cycle durability is not required.

3. Terminal Plating

Plating protects the terminal surface and plays an important role in contact resistance, corrosion resistance, solderability, and mechanical durability.

Gold Plating – Au

Gold provides excellent corrosion resistance and stable contact performance with low contact resistance.

It is commonly used in:

• High-speed data connectors

• High-frequency applications

• Low-level signal connections

• Automotive electronics

• Industrial equipment

• Harsh operating environments

Tin Plating – Sn

Tin offers good solderability at a relatively low cost, making it one of the most commonly used plating materials for general-purpose connectors.

Nickel Plating – Ni

Nickel is frequently used as an underplating layer beneath gold or tin. It provides a diffusion barrier and can improve wear resistance and plating durability.

Silver Plating – Ag

Silver has excellent electrical conductivity and is often used in high-current and power connector applications.

However, silver surfaces require appropriate design consideration because they may tarnish when exposed to certain environmental conditions.

4. Key Terminal Design Parameters

Contact Normal Force

Normal force refers to the force applied by the terminal contact against the mating contact surface.

Adequate normal force helps maintain a stable electrical interface and low contact resistance.

If the force is too low, the connector may experience:

• Increased contact resistance

• Intermittent electrical connection

• Sensitivity to vibration

If the force is too high, it may result in:

• Excessive insertion and withdrawal force

• Accelerated plating wear

• Mechanical damage to the mating interface

The required normal force should therefore be determined according to connector size, contact geometry, plating system, electrical requirements, and mating-cycle specifications.

Elastic Deformation

The spring section of the terminal must deform during mating while remaining within its intended elastic working range.

If the terminal exceeds the material's allowable stress range, permanent deformation may occur, reducing contact force and ultimately causing connection failure.

Contact Geometry

The contact interface should be designed to provide a stable electrical contact area while maintaining sufficient contact pressure.

Depending on the application, engineers may use line-contact, multi-point-contact, or surface-contact structures to optimize electrical and mechanical performance.

Terminal Retention

After being inserted into the housing, the terminal must remain securely locked in position.

Common retention structures include:

• Terminal barbs

• Locking lances

• Retention tabs

• Secondary locking mechanisms

These structures help prevent terminal back-out caused by wire pulling, vibration, assembly operations, or repeated mating.

5. Connector Housing Design

What Is the Function of the Housing?

The connector housing supports and protects the terminals while providing electrical insulation and mechanical positioning.

Its primary functions include:

• Terminal positioning

• Electrical insulation

• Mechanical protection

• Connector polarization

• Mating guidance

• Locking and retention

• Protection against incorrect mating

Housing design must therefore consider electrical properties, mechanical strength, temperature resistance, environmental resistance, dimensional stability, and manufacturability.

6. Housing Material Selection

PA66 – Nylon 66

PA66 provides good mechanical strength, wear resistance, and cost performance.

It is widely used in consumer electronics, appliances, industrial equipment, and general-purpose electrical connectors.

PBT

PBT provides good dimensional stability, electrical insulation properties, chemical resistance, and relatively low moisture absorption.

It is widely used in automotive, appliance, and industrial connector applications.

LCP – Liquid Crystal Polymer

LCP provides excellent high-temperature resistance, dimensional stability, flow characteristics, and electrical insulation performance.

It is particularly suitable for:

• SMT connectors

• Fine-pitch connectors

• High-speed connectors

• Miniature connectors

• High-temperature reflow soldering applications

High-Temperature Polyamides

Materials such as PA9T are frequently selected for SMT and other high-temperature applications because of their good heat resistance, mechanical properties, and dimensional stability.

Flame-Retardant Materials

For electrical and electronic applications, connector housings are often required to meet flame-retardant standards such as UL 94 V-0, depending on the product and application requirements.

UV-resistant materials may also be selected for outdoor equipment exposed to long-term sunlight.

7. Key Housing Design Parameters

Terminal Cavities

The terminal cavity must accurately match the terminal geometry.

Excessive clearance may allow terminal movement, while insufficient clearance may make assembly difficult or damage the terminal.

Tolerance design should consider:

• Terminal dimensions

• Plastic shrinkage

• Mold manufacturing tolerances

• Assembly requirements

• Operating temperature

• Terminal retention force

Creepage Distance and Clearance

Creepage distance and electrical clearance are critical safety parameters, especially in power and high-voltage connectors.

The required values depend on factors including:

• Working voltage

• Pollution degree

• Insulation material group

• Overvoltage category

• Operating environment

• Applicable safety standards

Therefore, creepage and clearance distances should be determined according to the relevant IEC, UL, automotive, or industry-specific requirements rather than using a single fixed value for all connectors.

Polarization and Keying

Polarization features prevent incorrect or reverse mating.

Common designs include:

• Key-and-slot structures

• Asymmetric housing geometry

• Different cavity dimensions

• Mechanical coding

• Color coding

Proper polarization can significantly reduce assembly errors in production and field installation.

Locking Structure

Locking mechanisms help maintain a secure connection after mating.

Depending on the application, connectors may use:

• Snap locks

• Latches

• Locking arms

• Secondary locks

• Screw locks

• Lever-assisted locking mechanisms

Required retention force and mating-cycle durability should be defined according to the actual application, connector size, and relevant industry standards.

8. Housing Design for Injection Molding

A good connector design must not only meet electrical and mechanical requirements—it must also be suitable for stable mass production.

Wall Thickness

Large variations in wall thickness should be avoided whenever possible because they may cause:

• Sink marks

• Voids

• Warpage

• Uneven cooling

• Dimensional instability

A relatively uniform wall thickness helps improve injection molding consistency.

Draft Angle

Appropriate draft angles should be incorporated into the housing design to facilitate smooth mold release.

The required draft depends on factors such as surface texture, material, mold structure, and part depth.

Corner Radius

Sharp internal corners should generally be avoided.

Adding suitable radii can:

• Reduce stress concentration

• Improve material flow

• Improve mold filling

• Reduce cracking risk

• Improve mechanical durability

9. Connector Design Is a System Engineering Process

A reliable connector is not created by optimizing a single component.

Terminal material, plating thickness, contact force, housing material, cavity tolerance, locking structure, PCB mounting method, operating temperature, current rating, voltage rating, and manufacturing process all interact with each other.

For example, increasing terminal contact force may reduce contact resistance, but it can also increase insertion force and plating wear. Increasing housing strength may improve mechanical reliability, but improper material or wall-thickness selection can create injection molding problems.

Therefore, connector development requires a balance between:

Electrical Performance + Mechanical Reliability + Material Selection + Manufacturing Process + Cost + Application Environment

At Homyet, connector design and manufacturing are evaluated from both performance and production perspectives—from terminal stamping and plating to plastic injection molding, assembly, testing, and mass production.

A well-designed connector is not simply one that can make an electrical connection. It must maintain that connection reliably throughout its intended service life.

Shenzhen Homyet Parts Electronics Co., Ltd.Reliable Connectors for Every Application