Central issue:
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Friction corrosion and plating problems
Electrical fault problem
Connector plugging problem
Automakers are increasingly demanding their supply bases, which is already well known for auto parts suppliers. In the case of connector suppliers, this means more stringent requirements for product performance, stability and cost. Suppliers can only be in a dominant position by constantly innovating products and processes to meet these needs of customers.
A typical light vehicle has approximately 1,500 connection points, of which 50% to 60% are used for critical power distribution functions. Automotive connectors are used in increasingly harsh environments, including temperatures (down to minus 40 ° C, up to minus 155 ° C), vibration, oxidation, and frictional corrosion, and we are beginning to recognize the importance of design challenges.
In fact, this thing is not easy to do. Most commercial electronic components are most troublesome when they fail. However, if there is a problem with the connection of key auto parts, it will cause the fire alarm, brake or airbag to malfunction. Lead to serious consequences.
Connector manufacturers must identify and analyze physical and mechanical phenomena in the environment that may affect connector performance. In order to evaluate the stability of the connector, the connector manufacturer implemented a detailed test procedure in accordance with the application conditions specified by the car manufacturer. In the event of a connector failure, it can be determined to be one of three failure modes: friction corrosion, electrical failure, and connector insertion problems.
Friction corrosion and plating problems
Corrosive gases, high humidity and strong oscillations are the three conditions that cause oxidation and frictional corrosion and lead to connector failure. These environmental factors can have a significant impact on tin and lead-tin contact surfaces, as is the case with 90% of connector surfaces.
Usually, people use electroplated precious metals, such as gold plating or silver plating, because these metals do not oxidize. The thickness of these coatings varies from 0.5 μm to 1.27 μm. However, unfortunately, such electroplating processes are used at a low cost because of the high price of such precious metals and their processing. In automotive electrical harness applications, only about 10% of the connection points use this type of metal.
As a result, some major connector suppliers, such as FCI, have other alternative plating solutions (such as pure tin plating, tin-Teflon TinTeflon, NXT, and press-fit technology) that not only meet OEM requirements. Cost requirements, and the product has the same performance.
The press-fit terminal technology (connector to board) from the telecom market has attracted attention because it must meet high standards of automotive specifications. Since automotive PCBs are thinner than PCBs used in the telecommunications industry, operating temperatures (125oC) are much higher and vibrations are used in the environment, it is not an easy task to introduce this technology into automotive systems.
This technology brings significant process cost benefits by pressing a solderless pin into the metal PCB hole. Designed for demanding automotive applications, FCI press-fit terminals are specifically designed to provide fully controllable force when inserted into the PCB, minimizing drag and strain and ensuring a secure interface to the PCB.
FCI butterfly solutions (and related application tools) are increasingly favored by automakers because they are more cost effective than wave soldering, and the process is fully automated, reducing PCB costs. In addition to superior performance (compatible with SMT processes and excellent component integrity), it also adds additional process quality due to the absence of thermal shock to the PCB and the risk of solder bridges.
In addition, FCI found that when the correct plating process and pins are used in the press-fit application, the contacts are subject to various external conditions (eg, sharp temperature changes, relative humidity changes, long-term dry conditions, and gas corrosion). At the time of the contact resistance, the contact resistance has remained small. However, as the number of pins increases, the pressure becomes very large, so be careful when inserting the connector into the base.
FCI has developed a new electroplating process called "NXT". Based on the chemistry of an amorphous nickel, it provides a very smooth and uniform plating surface that significantly reduces the thickness of the gold coating (approximately 80% reduction). In safety critical applications, this technology can support very low signal currents.
Multi-pin connectors present another test for connecting electroplating systems. For ergonomic considerations, the connector insertion force should be as small as possible, but as the circuit count increases, the force required to insert the connector will increase proportionally. However, electrical performance often indicates that each contact achieves high contact pressure (usually causing high insertion forces), which is incompatible with the goal of achieving low connector insertion force.
To solve this problem, a new type of contact surface has been developed. Teflon microparticles are treated identically in a common tin bath and selectively plated onto the contact surface. Microparticles reduce the insertion force of a typical tin-plated terminal by more than 40%. This solution allows the connector to have more pins without the need to plug in an auxiliary device - enhancing ergonomics and improving connector stability. In addition, the Tin-Teflon surface has a better anti-friction effect than any other tin-plated contact when the terminal is susceptible to vibration.
Electrical failure: enhanced new crimping technology
The problem of cable and terminal connections is one of the main causes of warranty and connector system failure. For automotive wiring systems, crimping is a very common method for connecting terminals to cables. This process has proven to be reliable. Compared with the welding method, it is more economical and simple to operate in terms of improving the crimping reliability. To improve the terminal chuck geometry, connector manufacturers have put a lot of effort into it. Through a wide range of analytical and experimental studies, FCI not only developed a new analytical tool for crimp optimization, but also proposed a new innovative crimp geometry.
FCI's "two-step" crimping solution proposes a crimping method that can be produced at a typical high-speed crimping rate on a conventional crimping press. When the "two-step method" is completed, two impacts will occur inside the mold.
In the first step, a normal crimping operation is performed on either side of the terminal chuck region. As with any other crimp, the press and the anvil are separated after the end of the compression stroke and the crimp is slightly loose. The strands are no longer compactly combined as before, and the resistors have a higher resistance.
This problem is solved in the second step of the crimping process. The crimping die impacts the chuck area a second time. There is a collet portion between the previously crimped positions, this time impacting the intermediate position of the collet portion. Extensive testing has shown that the best, long-term strand compression can be achieved with the "two-step" process. Since the compression rebound is eliminated, the cold welding generated by the pressure grounding belt is strengthened and stabilized, and the crimping has high reliability. Two-step crimping is ideal for all applications that require very low current and transition resistance. Airbag sensors and controllers are examples of such applications.
Connector plugging problem
Improper plugging of the connector may cause connector failure when wiring is installed in the vehicle at the assembly plant. To overcome this problem, design engineers have developed a variety of connector locking devices, an example of which is the spring lock (Spring-Lock) developed by FCI. When the two halves of the connector are plugged together, the spring device is compressed. If properly plugged in, the connector spring lock will function to bring the two connectors together. If the connector is not fully plugged in, the spring will spring open the two halves (when the installer releases the connector), indicating a failed connection.
Another option is to use a patching aid to simplify the insertion process of larger connectors. FCI's new ErgoMateTM technology uses a geared cam and slider unit. This slider assembly allows the fluid to be obtained from the assembler when the connector is plugged in, thus eliminating the need for a typical connector to drive the secondary lever or slider. Compared to other methods, the connector insertion force can be reduced by 40% because of the cam. FCI's latest APEX24-wayHybrid connector uses this technology. When the ergonomic design is improved, the assembly becomes simple and the connection stability increases.
FCI addresses another issue related to the cable connection of the airbag ignition module. In the past 20 years, a large number of pyrotechnic signal devices (airbags and seat belt pretensioners) have been produced, but some of them have been difficult to reach during assembly, which requires the connection of a safety squib connector. jack.
FCI's solution proposes a new anti-slant plug connector interface - MCCAK-2. (Burst connector is an electrical connector designed for in-vehicle pyrotechnic signaling devices. These connectors are very compact and usually have signal filtering devices such as ferrites or coils for signal processing. When the connector is plugged in Or when removing the airbag, use special short contact points to prevent inadvertent airbag triggering due to parasitic signal input.) Due to the use of advanced security applications (such as pedestrian protection), this connection is more complicated, so A sealed squib connector solution is required.
It is important to seal the electrical contacts of the connector when applied to the exterior of the car and under the hood. For connector manufacturers, providing a low-cost, high-stability, easy-to-assemble submersible connector solution is a challenging task. In high-density or multi-pin systems, it is standard practice to use gasket seals or porous seal rings. There are two major issues that must be addressed when designing such seals.
First, it is necessary to insert the terminal through the sealing hole, which means that a square or rectangular terminal is to pass through a circular sealing hole. This necessitates control of the combined insertion force of the terminals to prevent cable bending.
Second, the requirements of different wire diameters for sealing. Typically, this forces the use of smaller, more flexible seals for different wire diameters, which increases the likelihood of seal damage or tear.
FCI's approach to submarine technology, the CMC series of connectors designed for engine management systems is an innovative sealing method. The seal cable (with terminals) is fitted into the connector, and the wiring cover further compresses the seal. In this way, only a small sealing pressure or force is generated during the assembly process, and a large sealing pressure or force can be obtained in practical application.
All of these innovations demonstrate the determination of connector designers and manufacturers to continuously deliver new products to increasingly demanding markets. As a global leader in the automotive connector industry, FCI has a long history of innovation, and it will continue to strive to improve the reliability of its vehicles and ultimately satisfy customers.
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