Analysis of the use of automotive connectors and comparison of automotive connector standards

With the rapid development of China's automobile industry, automobiles have expanded from satisfying the initial transportation function to having many safety and comfort functions. With the increase of functions, automobile connectors, as key components of automobiles, have developed from dozens of connectors used in one car to hundreds of connectors used in one car today, with more than one hundred varieties.

Its types can be classified into six levels: electrical equipment function, installation location, buckle structure, appearance specification model, specification model, and output power. The details are as follows:

By electrical equipment function: electronic device module (driving computer), headlight socket, temperature sensor, intermediate electrical equipment box, central air conditioning car wiring harness, speaker game entertainment

According to the installation location: automobile braking system, vehicle dashboard, automobile engine system software, safety management system

According to the buckle structure: line to line, line to board, board to board, flexible circuit board FPC, integrated circuit chip (IC pin type)

According to specifications: rectangular frame, ring

By specification: annular connector (ordinary, coaxial), rectangular frame connector (sealed, non-sealed)

By output power: low frequency and high frequency (with 3MHz as the boundary)

For other types of automotive connectors, they can be divided into other categories according to their main purpose, unique structure, installation method, unique characteristics, etc., but generally just to better highlight a certain feature and main purpose, the basic classification is still acceptable and does not exceed the above zoning standards.

From the previous 6.3 specification to the current 0.64 specification. These more than 100 connectors are distributed in the cab, body, door, engine compartment, transmission and other places. Because the use temperature and vibration level of connectors in different places are different, the requirements for the protection level of connectors are different, so different use environments have different performance requirements for connectors.

1

Analysis of the usage status of automotive connectors

Taking two foreign and domestic car models as examples, the connector usage specifications and manufacturer distribution are analyzed.

1) The proportion of connector specifications for a certain foreign brand of automobile is shown in Figure 1.

This model has a total of 205 connectors, of which 90 are 0.64-size connectors, accounting for 43.9% of the total number of connectors developed; 25 are 1.2-size connectors, accounting for 12.2% of the total number of connectors developed; 30 are 1.5-size connectors, accounting for 14.63%; 20 are 2.8-size connectors, accounting for 9.76%, etc. These connectors are from different brands, including TE, THB, Molex, JAE, YAZAKI, APTIV, Bosch, SUM, etc.

Figure 1 List of connector specifications for a certain foreign vehicle model

2) The proportion of connector manufacturers in a domestic joint venture brand car is shown in Figure 2.

Figure 2 List of connector specifications for a certain domestic vehicle model

This model has a total of 265 connectors, of which 93 are 0.64-specification connectors, accounting for 35.09% of the total; 12 are 1.2-specification connectors, accounting for 4.53% of the total; 41 are 1.5-specification connectors, accounting for 15.47%; 23 are 1.8-specification connectors, accounting for 8.68%; 33 are 2.2-specification connectors, accounting for 12.45%; 16 are 2.8-specification connectors, accounting for 6.04%, etc.

3) From the above data, we can judge that there are more than 10 connector suppliers currently used in domestic and foreign models, and the specifications used range from 0.5 specifications, 0.64 specifications to 9.5 specifications, and more than 8 specifications. From the data analysis, when the OEM selects and develops connectors for new models, it is necessary not only to consider the specifications, usage locations, and protection level requirements of the selected connectors, but also to select a connector that best suits the model and function from different products of different manufacturers. This requires a standard to support and guide the corresponding engineers of the connector manufacturer to select the most cost-effective and most suitable functional connector.

Analysis of automotive connector usage standards

2.1 Current Distribution of Automotive Connector Standards

There are many connector standards at present, from the earlier international standard ISO 8092, SAE standard USCAR-2, to the latest revised industry standard QC/T-1067-2017 (replacing QC/T-417) in China. At the same time, many automobile companies have also defined their own connector standards, such as Volkswagen's VW 75174, GM's GMW-3191, SAIC's SMTC 3 862 001, Geely's Q/JLY J7110195C, etc. Because there are so many standards, and there are many similarities and differences between different standards, this article focuses on the three most widely used standards in the world, namely USCAR-2-6, QC/T-1067-2017, and GMW 3191-2012.

2.2 Definition of connector use environment in connector standards

For a connector, the ambient temperature, current carrying capacity, protection level, vibration resistance and other specifications of the connector will be defined in its specification sheet at the beginning of research and development. Connector selection engineers need to understand the different requirements of connectors in different use environments, which is also defined in detail in the current use standards. The standard definition of QC/T-1067 is shown in Table 1 to Table 3, the standard definition of GMW-3191 is shown in Table 4 to Table 6, and the standard definition of USCAR-2 is shown in Table 7 to Table 9.

Table 1 QC/T-1067 temperature grades

Table 2 QC/T-1067 vibration levels

Note: The elastic part refers to the part on the vehicle body that is supported by the suspension system. The elastic part does not include tires, wheels, brake discs (drums), etc.

Table 3 QC/T-1067 sealing grade

表4 GMW-3191 Temperature Class

Table 5 GMW-3191 Vibration Class

表6 GMW-3191 Sealing Class

表7 USCAR-2 Temperature Classification

表8 USCAR-2 Vibration Classification

表9 USCAR-2 Sealing Classification

From the definitions of the above standards, it is clear that the current definitions of the three major standards for connector protection levels are consistent according to different usage locations, and they define the S1 unsealed area, S2 sealed area, and S3 high-pressure water jet area respectively.

In the definition of temperature grade, we found that the three major standards divide the operating temperature into five levels according to the different use positions of the connector; at the same time, QC/T-1067 and USCAR-2 both clearly state that the temperature grade of -40~85℃ is not recommended, but this temperature grade is recommended in GMW-3191 for connectors installed in the cab as the experimental ambient temperature.

In the definition of vibration levels, by comparing the detailed vibration frequency and power spectral density (PSD) of the standards, it is known that the vibration levels V3, V4, and V5 defined in QC/T-1067 and USCAR-2 correspond to and are equivalent to levels 2/4/3 in GMW-3191 respectively.

At the same time, GMW-3191 defines the vibration level and applicable parameters of the transmission connector, which are not defined in USCAR-2 and QC/T-1067. However, USCAR-2 and QC/T-1067 define the vibration level and applicable parameters of the connector installed on the engine but not on the parts with severe vibration, which are not defined in GMW3191. See Tables 10 and 11.

Table 10 Summary of information on the same vibration level of QC/T-1067, USCAR-2, and GMW-3191

Regarding vibration tests, we mainly verify whether the performance of the connector system meets the requirements under simulated actual vehicle vibration conditions. Because under vibration or vibration impact conditions, it will cause plating wear on the terminal contact surface, positive pressure attenuation, and mechanical failure of supporting plastic materials. Therefore, it is necessary to continuously monitor the contact resistance in the vibration test and ensure that the contact resistance in the circuit exceeds 7Ω (or 1Ω) for no more than 1 microsecond.

Through the definition and analysis of the connector usage environment in the above different standards, we understand that when selecting a connector for a certain function, we must first understand the location where the function is used, and then determine the temperature level, vibration level, and protection level that the connector needs to withstand based on the location of use, and make the best selection.

2.3 Definition of connector mechanical properties in connector standards

Currently, USCAR-2 defines 18 items of connector mechanical properties, QC/T-1067 defines 20 items of connector mechanical properties, and GMW-3191 defines 21 items of connector mechanical properties, as shown in Table 12, Table 13, and Table 14 respectively.

By comparing the mechanical properties of the three standards, we understand that the mechanical properties in the current connector standards are mainly concentrated in the following points: the bending strength of the terminal itself; the plug-in and pull-out force between the terminal; the insertion force, retention force, thrust force, and polarization test between the terminal and the connector; the insertion force, separation force, unlocking force, and polarization test between the connector and the connector; the assembly force and retention force of the connector terminal secondary lock (TPA); the assembly force and retention force of the connector secondary locking structure (CPA); the mechanical strength of the connector assisting structure; the mechanical strength of the connector fixing structure; the retention force of the sealing ring; and the retention force of the board end pin.