Section 1: Connector Basics

Section 2: Why Connectors Are Needed

Take a car battery as an example. Suppose the battery cables are permanently soldered to the battery. This increases the workload for the car manufacturer during battery installation, leading to longer production times and higher costs. When the battery needs to be replaced due to damage, the car must be taken to a repair shop, where the old battery must be unsoldered and removed, and the new one soldered in place—a process that incurs significant labor costs. Connectors eliminate much of this hassle. Simply purchase a new battery from a store, disconnect the connector, remove the old battery, install the new one, and reconnect the connector. This simple example illustrates the benefits of connectors: they make the design and production processes more convenient and flexible, while reducing production and maintenance costs.

第三节：连接器的优点

第四节：连接器的基本要求:

Section 5: A Brief Classification of Connectors:

第六节：连接器的简要应用:

第七节：连接器的构成:

The connector shown in the figure below is an in-line connector; in-line connectors are characterized by wires entering through one half of the connector and exiting through the other half. These two parts of the connector are called the plug (male) and the socket (female), respectively.

The connector housing serves the following functions:

■ Supports the contact elements (pins, springs, etc.) and ensures they are securely and correctly positioned;

■ Protects the contact elements and conductors from dust, dirt, and moisture;

■ Insulates the circuits from one another

Connectors mounted on printed circuit boards use a housing known as a header, also referred to as a base or wafer. The main difference between a header and a housing is that a header is always assembled with circuit pins, whereas a housing is merely an empty shell. Headers come in two forms: shielded and unshielded. A shield refers to a protective cover formed by the housing or a skirt around the mating area of the connector’s pins and sockets. There are also friction-lock-style headers, which are a type of shielded header but feature a locking mechanism that secures the header to the housing.

Contacts:

The contacts in a connector join the two conductors (or wires) to be connected. Once joined, the circuit is closed, and current flows through the connector. There are two main types of contacts: terminals and pins. Their actual shapes vary widely. Illustrations of both are shown below.        Terminals (or pins) have two ends: a front end and a rear end. The front end is always the mating end, which engages with another terminal to form a contact. The rear end always serves as the termination point, either crimping or connecting to a wire (conductor) (see the figure below).

连接器接触部份采用的金属

The contact parts of connectors are plated to improve electrical conductivity, corrosion resistance, and wear resistance, as well as to enhance weldability. Metals with good mechanical properties (such as formability and elasticity) often lack excellent electrical conductivity, corrosion resistance, wear resistance, and weldability. These metals are plated—either entirely or selectively—to improve their performance. The table below summarizes the most commonly used plating metals and their characteristics.

Section 7: Electrical Performance of Connectors:

The primary electrical performance characteristics of connectors include contact resistance, insulation resistance, and dielectric strength.

▶ Contact Resistance: High-quality electrical connectors should have low and stable contact resistance. Contact resistance in connectors ranges from a few milliohms to tens of milliohms.

▶ Insulation Resistance: A metric that measures the insulation performance between the connector’s contacts and between the contacts and the housing; its value ranges from several hundred megohms to several thousand megohms.

 ▶ Dielectric Strength, also known as voltage withstand or dielectric breakdown voltage, characterizes the ability of the connector’s contacts or the contacts and housing to withstand a rated test voltage.

 ▶ Other Electrical Performance Characteristics

 Electromagnetic interference (EMI) leakage attenuation is used to evaluate a connector’s EMI shielding effectiveness; it is typically tested within the 100 MHz to 10 GHz frequency range.

For RF coaxial connectors, other electrical parameters include characteristic impedance, insertion loss, reflection coefficient, and voltage standing wave ratio (VSWR). Due to the development of digital technology, a new type of connector—the high-speed signal connector—has emerged to connect and transmit high-speed digital pulse signals. Accordingly, in terms of electrical performance, in addition to characteristic impedance, several new electrical parameters have emerged, such as crosstalk, transmission delay, and skew.

Section 8: Physical Properties of Connectors:

Common environmental performance tests include low-temperature testing, constant humidity and heat testing, cyclic humidity and heat testing, salt spray testing, sulfur dioxide testing, and hydrogen sulfide testing

▶ Temperature Resistance: Currently, the maximum operating temperature for connectors is 200°C (with the exception of a few specialized high-temperature connectors), and the minimum temperature is -65°C. Since current flowing through the contact points generates heat during operation, leading to a temperature rise, it is generally accepted that the operating temperature should equal the sum of the ambient temperature and the contact temperature rise. Some specifications explicitly stipulate the maximum allowable temperature rise for connectors under rated operating current.

▶ Moisture Resistance: Moisture intrusion can affect the connector’s insulation performance and cause corrosion of metal parts. The constant humidity and heat test conditions are 90%–95% relative humidity (up to 98% depending on product specifications) and a temperature of +40±20°C. The test duration is specified by the product and is at least 96 hours. The cyclic humidity and heat test is even more rigorous.

▶ Salt Fog Resistance: When connectors operate in environments containing moisture and salt, their metal structural components and the surface treatment layers of the contacts may undergo electrochemical corrosion, affecting the connector’s physical and electrical performance. To evaluate an electrical connector’s ability to withstand such environments, a salt fog test is specified. In this test, the connector is suspended in a temperature-controlled test chamber, where a sodium chloride solution of a specified concentration is sprayed using compressed air to create a salt fog atmosphere. The exposure time is specified by the product standard and must be at least 48 hours.

▶ Vibration and Shock Resistance to vibration and shock are critical performance characteristics of electrical connectors, particularly in specialized application environments such as aerospace, rail, and road transportation. These characteristics serve as key indicators for assessing the robustness of the connector’s mechanical structure and the reliability of its electrical contacts. Relevant test methods provide explicit specifications. For shock testing, the peak acceleration, duration, and shock pulse waveform must be specified, as well as the duration of any interruption in electrical continuity.

▶ Other Environmental Performance Requirements Depending on usage requirements, other environmental performance characteristics of electrical connectors include sealing performance (air leakage, liquid pressure), liquid immersion (resistance to degradation by specific liquids), and low-pressure environments.