The automotive industry standards QC/T 1067.4-2023, Connectors for automobile wiring harnesses and electrical equipment, Part 4: Types and dimensions of equipment connectors (plugs), and QC/T 1067.5-2023, Part 5: Types and dimensions of equipment connectors (receptacles), came into force on 1 November 2023, providing strong technical support for the domestic automotive connector industry.

The interface types in the new edition were drawn up after thorough research into vehicle models used in China and abroad, with reference to technical material from leading overseas automotive organisations, and were agreed with vehicle makers and connector manufacturers on the basis of actual test experience with domestic and overseas products.

About the QC/T 1067 standard

The QC/T 1067 series was proposed and is administered by the National Technical Committee of Auto Standardization (SAC/TC114). It was drafted jointly by leading companies in the industry including Henan THB Electric, China Automotive Technology and Research Center, Changsha Automotive Electrical Research Institute, Chongqing Changan Automobile, FAW Haima Automobile, FAW Jiefang, Geely Automotive Research Institute, SAIC Volkswagen, Pan Asia Technical Automotive Center, Anhui Jianghuai Automobile Group, Chongqing Lifan Passenger Vehicle, BAIC Motor, Zhengzhou Yutong Bus, Changchun Bulb and Wire, Shanghai Forsin Cable, SAIC Volkswagen and SAIC Motor Technical Center.

Important and widely followed

In the automotive connector industry, the QC/T 1067 series is one of the standards currently in force in China. When selecting connectors, vehicle makers first consider the particular requirements of automotive connectors and are expected to refer increasingly to the QC/T 1067 series, which is divided into five parts:

Part 1: definitions of test methods and general performance requirements.

Part 2: types and dimensions of plug terminals.

Part 3: types, dimensions and special requirements of wire connections.

Part 4: types, dimensions and special requirements of equipment connectors (plugs).

Part 5: types, dimensions and special requirements of equipment connectors (receptacles).

With the rise of domestic brands in the Chinese automotive industry, and with demand for independent development and cost control, domestic connector manufacturers have greatly improved both cost and performance, opening a new era for domestic connector companies entering the automotive industry.

Key requirements of the standard

1. How QC/T 1067 defines the connector operating environment

The QC/T 1067 series defines specifications such as operating ambient temperature, current carrying capability, ingress protection rating and vibration resistance grade. Selection engineers need to understand the requirements of different operating environments and refer to Tables 1 to 3 of QC/T 1067 when choosing.

Table 1 Temperature grades

Table 2 Vibration grades

Table 3 Sealing grades

Table 4 Vibration grades

2. How QC/T 1067 defines mechanical performance

The mechanical performance items in current connector standards are mainly: bending strength of the terminal itself; insertion and withdrawal force between terminals; insertion force, retention force, push-back force and polarisation testing between terminal and connector; insertion force, separation force, unlocking force and polarisation testing between connectors; assembly force and retention force of the terminal position assurance (TPA); assembly force and retention force of the connector position assurance (CPA); mechanical strength of connector assist structures; mechanical strength of connector mounting structures; retention force of seals; and retention force of board-end pins.

Mechanical performance test items are shown below.

3. How QC/T 1067 defines electrical performance

Connector electrical performance mainly covers low level contact resistance and voltage drop between terminals, and the insulation resistance and dielectric strength of the connector itself. These are verified together with the combined environmental tests described later. For the merits of the terminal itself, the standard also defines maximum current carrying capability and 1,008 h current cycling performance, which serve as an important reference for terminal durability.

4. Contact resistance and voltage drop in the standard

Whatever the connector terminal specification, the standard requires that after effective contact between plug and receptacle the voltage drop shall not exceed 50 mV.

Definitions of contact resistance and voltage drop

Note: under no circumstances may the total resistance of a connector exceed 20 mΩ.

5. Insulation resistance and dielectric strength in the standard

Insulation resistance ensures a certain electrical insulation between two adjacent terminals inside the connector, and dielectric strength verifies the electrical insulation performance of the connector itself. (1) Insulation resistance: at 500 V, the insulation resistance between adjacent terminals shall be at least 100 MΩ. (2) Dielectric strength: at 1,000 V AC or 1,600 V DC for one minute, there shall be no dielectric breakdown or puncture between adjacent terminals or between terminals and the plastic housing, with leakage current not exceeding 1 mA.

6. Combined thermal ageing test

The high temperature ageing test verifies how the metal material of the terminals, the plastic material of the connector and the rubber material of the seal change after 1,008 h at the maximum operating temperature, and how those changes affect sealing, electrical and mechanical performance. Of particular interest are the compression set of the seal and plastic deformation of the terminal cantilever, which affect key connector performance.

Sequence of the thermal ageing test for waterproof connectors

7. Combined chemical resistance test

Chemical resistance testing evaluates whether the sealing performance and material compatibility of a sealed connector assembly meet requirements when immersed in the various liquids commonly found in and around vehicles.

Sequence of the combined chemical resistance test (numbers show test order)

8. Combined thermal shock test

An in-vehicle connector assembly is normally made from several materials: the housing from plastics such as PBT and PA66 with reinforcing fillers, conductive parts such as terminals from brass, bronze and copper alloys, and seals from silicone rubber. These materials expand and contract with temperature change through thermal expansion, causing wear and fretting on the terminal contact surfaces. Rapid temperature change testing simulates in-vehicle conditions to verify whether such changes after thermal shock cause the connector assembly to fail.

Sequence of the combined thermal shock test (numbers show test order)

To learn about the latest requirements and test methods of the QC/T 1067 standard for automotive wiring harness and electrical equipment connectors, and to understand how vehicle makers select and test automotive connectors, please contact our laboratory for a technical exchange covering connector standards and the testing challenges they present.