Compact and robust connectors for automotive electronics
Electromobility and autonomous driving mean increased requirements
The implementation of electromobility requires close cooperation between component manufacturers and OEMs. In parallel to electromobility, the trend toward self-driving cars is the second major challenge. For the various driver assistance systems, the data has to be collected and processed by numerous sensors and actuators have to be controlled accordingly. Only with a reliable, secure network or connection is a perfect interaction of the various systems possible. In harsh and often near-engine environments, connector systems not only have to be as compact as possible, but must also exhibit high vibration resistance, tightness, temperature resistance, high current carrying capacity and ease of handling. A wide variety of connector solutions optimized for the automotive sector are available for this purpose.
Ultimately, the implementation of electromobility and autonomous driving requires unprecedented connectivity in automobiles, which in turn calls for high-performance, space-saving and reliable connector solutions. Compact, reliable and robust connector solutions are required for this field of applications. Applications range from highly sensitive front and rear camera solutions to sophisticated headlamp systems with dynamic cornering lights and airbags that can precisely adjust to the weight of the occupants. Connectors available as robust Koshiri variants are used in electronically controlled steering systems and headlamp range adjustment systems. Space-saving cable connectors can also be found in reversing cameras and parking assist sensors.
In many cases, the corresponding connectors not only have certifications such as ISO TS16949 or meet Koshiri specifications, but also offer sufficient design margins to handle higher currents or voltages with small pitches. MiniBridge (1.27 mm pitch), MaxiBridge (2.54 mm) and MicroBridge (1.27 mm) cable connectors also meet the applicable LV 214 specifications. In 29 test groups, the LV 214 specification defines electrical, climatic, mechanical and corrosive stress scenarios that a contact system must withstand.
Battery management systems and the corresponding power electronics (inverters) play a key role in electromobility (Fig. 1). The BMS ensures safe charging/discharging of the battery and monitors the battery cells. It is not usually installed directly in the high-voltage battery, but is connected via decoupled bus systems (for example CAN). Fundamentally, the contact resistance at the charge input must be kept as low as possible. This is why connectors are required that have the lowest possible contact resistance that remains largely constant even with rising temperatures. This can be achieved by a suitable contact design.
Another growth driver for automotive lighting systems is the increasing market penetration of LED technology. Especially for front lights, the trend is clearly towards LEDs. Corresponding connector systems tested according to automotive standards must guarantee that the assemblies function perfectly in all weather and road conditions. Robust interlocking and SMD solder joints resist even severe vibrations and shocks. Even high temperatures (150 °C), which occur in the tight spaces in front headlamps, should not pose a problem. Flexible, miniaturized cable-to-board solutions and a high degree of mating reliability are the key criteria here.
LED systems are often wired or modularly connectable with printed circuit boards. With appropriately assembled MiniBridge cable connectors, which can accommodate both ribbon cables and single wires, a particularly simple, flexible and cost-effective installation is possible. For such compact lighting tasks, the MiniBridge connectors are also available with “white” insulation (Fig. 2). Connectors with non-colored insulation prevent the shadowing effects in lighting applications, e.g. LED strips with transparent diffusing lens. This ensures uniform light distribution.
The automotive industry places high demands on the process reliability of connectors. It must be ensured that no damage occurs to the male connector, especially if the male and female connectors are mated skewed. The Koshiri version of MiniBridge connectors ensures that this requirement is met during the mating process.
With dimensions of only 10 mm x 10 mm x 3 mm (4-pin version), a very high current carrying capacity (when using appropriate cables) is achieved over a wide temperature range of – 55 °C to + 125 °C due to a special contact material. Straight and angled male connectors and female connectors with angled and straight cable outlets can be used to address a wide range of applications. The male connectors have SMT terminals for economical processing, while the female connectors use insulation displacement contact (IDC) technology. Female connectors with reliable interlocking for particularly high vibration/shock loads are also available.
Designed for automotive applications right from the start
In developing the MicroBridge cable connector, ERNI has consistently implemented the requirements of customers from the automotive sector (Fig. 3). Right from the start, the cable-to-board connector has been developed in accordance with the demanding automotive test specifications VW75174 and USCAR-2. Koshiri security, an optional electrical CPA (connector position assurance) and possible colour and mechanical codings for any number of pins ensure safe, reliable and correct connections. With the MicroBridge, tongues on the female connector and grooves on the male connector allow the pre-alignment of the connector housings, thus ensuring a precise mating process. The contact pins of the male connector are not damaged by improper, skewed mating. The electrical CPA makes it possible to test for a secure contact between the female and male connector even during the mating process. A shortened test pin (without signal and power supply function) is used on the male connector for this purpose. All the above-mentioned functional features for a high degree of mating integrity and reliable contacting help to reduce possible failures in production and in the field.
Despite the small pitch of 1.27 mm, the MicroBridge is very robust. This means that the connector can withstand the harsh environmental conditions with vibrations or shock loads (as specified in VW75174, for example) and high temperatures in the vehicle. This is ensured, among other things, by the latching mechanism on both sides and the high temperature resistance. The housing latching mechanism on both sides provides acoustic and haptic feedback of the interlocking during the mating. The latching mechanism can be released without tools. The solder clips of the male connectors absorb mechanical stress and resist high shock and vibration loads. The high temperature resistance of up to 150 °C allows the connectors to be used in areas exposed to demanding temperature conditions, e.g close to LEDs in the headlamps. The current rating per contact is specified at 9.0 A at 20 °C (2-pin version).
The MicroBridge is available as a single-row male connector in straight and angled SMT versions. The male connectors are supplied in tape on reel packaging for automatic assembly. The single-row female connectors are available as insulation displacement contact (IDC) versions. They are currently available with a 90° cable outlet and are qualified according to internationally recognized standards. The double design of the insulation displacement terminal ensures a particularly reliable contact. In addition, the integrated strain relief protects the insulation displacement connection from mechanical stress caused by cable movements.
The SMC family with a 1.27 mm pitch is also recommended for demanding, often spatially confined applications in the automotive sector. For example, the SMC connector family also offers 50-pin versions with Secure Lock locking (Fig. 4). The highly reliable electrical contact of the Secure Lock versions is provided when mated by the proven dual-beam female contact. The wire-to-board solution (connector system with IDC female connector and SMT male connector) has been modified and optimized accordingly for the secure, mechanical connection of two assemblies. This means that even the most demanding applications, such as in inverters of electric/hybrid vehicles, can be addressed. Reliability in the locked state (e.g. under vibration and shock loads) is just as important as the precise and error-free mating process.
The special geometry of the angled IDC female connector and the straight SMT male connector requires a defined force to lock the wire-to-board connection. The user thus receives a clear acknowledgement (audible, tactile) that the connection has been securely made. With additional guides and widened locking levers, contact damage when mating is practically impossible. The connection is released using a cost-effective unlocking tool.
Author: After training in electrical engineering and further qualification as a Stated-Certified Engineer, Markus Breitenbücher is now Team Leader Marketing & Product Data Manager at ERNI in Adelberg.
Section Power Electronics