Reliability drive for vehicle connectors

Rugged connectors are meeting the rapidly changing requirements of the modern motor vehicle platform. Today’s vehicles are heading into new territory, due to smart and adaptable interconnect products.

There is one requirement in the industry that remains steadfast - reliability. While consumer demands drive many trends in the dynamic motor vehicle industry, including cost, comfort, size, style, safety and functionality, the need for advanced, rugged components in this harsh environment application, remains a constant.

Many connecters were developed based on industrial connector designs. The original industrial designs were developed to address many of the same environmental factors that are found in the vehicle environment, including high temperatures, vibration, shock, and fluid exposure.

Engineers adapted the industrial designs to meet vehicle requirements. However, the increasing complexity of vehicle electronics - particularly control systems and sensors - has created demands for interconnects that vary greatly from the traditional pin-and-socket connectors.

Designers using the latest technologies to enhance systems, such as safety features, user interfaces and electric vehicle charging, must implement high-performance, ultra-dependable connectors.

In addition to meeting reliability and quality standards, connectors in today’s vehicles are required to have an increased I/O count and density, while reducing their PCB footprint and cost.

A significant challenge in the evolution of these connectors is meeting reliability and durability standards. Today’s vehicles rely heavily on electronics to control critical systems, including steering, braking, airbags and GPS.

This means that electronic components used in safety-critical systems must be ultra-reliable and durable. Failures in any critical system could have disastrous results.

While today’s electronic systems have demonstrated reliability, they cannot be visually inspected and physically tested like traditional rod-and-gear mechanics.

As electronic designs continue to replace mechanical control systems, connectors must evolve to eliminate reliability concerns.

Temperature: Under-the-bonnet applications must perform at both ends of the temperature spectrum, from sub-freezing temperatures before ignition to high operating temperatures when an engine is running.

Temperature stresses are common in vehicle applications and these require connectors that can operate at temperatures between -55 to +125°C, but these aren’t the only concerns.

Current electronic fabrication processes require connectors that can withstand processing temperatures for RoHS compliance up to +260°C (for a limited time during processing).

This elevated processing temperature requirement has emerged in response to the European initiatives that eliminated lead from soldering, elevating the processing temperatures during electronics fabrication.

Shock and vibration: Interconnects for vehicle electronics have incorporated much of the experience from industrial applications with regard to shock and vibration.

It can be challenging to find interconnect solutions that are able to withstand both low and high frequency vibrations typical of motor vehicle applications.

So there is critical need to find an interconnect partner with the ability to work on a project from the beginning to ensure that a reliable solution ends up in the finished product.

Examples of vibration include low frequency sources caused by out of balance wheels on a vehicle to high frequency vibration caused by engines.

Shock loads vary, with some extreme, undampened shock resulting in hundreds of Gs of force on impact surfaces.

Sealing: Many electronics traditionally used in vehicles were developed for environments not typically subjected to moisture and chemicals.

Fortunately, some manufacturers have been able to use their industrial experience to implement sealing techniques designed to meet IP65 (splash), IP67 (submersion) and IP69 (spray) specifications.

Manufacturers have employed anti-corrosive materials to ensure connectors survive in wet and corrosive environments for applications found on vehicle engines, batteries and on systems exposed to the external environment.

Beyond the performance and environmental exposure issues for connectors, there are important quality concerns as well.

Conditions, such as bent pins from connector misalignment during assembly, are an old problem that affects reliability, raises assembly costs and leads to production delays.

However, even this issue is being addressed through the latest plug-only landed contact designs, which minimise these types of quality issues.

There has been a significant move away from traditional pin-and-socket connectors towards newer pressure contacts that can be better controlled in under-bonnet environments.

These plug-only landed contact systems include pressure contacts designed to mate directly to pads on a PCB, yet are able to withstand the thermal shock, vibration and hostile environments common in vehicles.

In these systems, all the contacts are in a plug-side connector, so OEMs can have receptacles integrated into their housing with essentially no connectors and no contacts. The advantages include:

• Increased density (due to requiring only a pad on the PCB);
• Cost reduction (from the removal of contacts);
• Simplification of the connection in the plug-side to provide the total solution.

New connector designs provide a plug-only solution that is scalable, sealed, rugged, high-density, smaller and has lower total installed costs.

Environmental concerns and the rising cost of oil have spurred consumer demand for more compact, fuel-efficient vehicles.

Technological advancements have enabled motor vehicle manufacturers to address this demand with the mass-production of environmentally friendly vehicles, such as hybrid and electric cars.

Since the introduction of electric vehicles, a primary concern from many sceptical consumers has been the reliability of charging. Not only is the operating life of the rechargeable lithium-ion battery being questioned but the lengthy battery recharging process is also an issue.

These obstacles have undoubtedly delayed the mass-production of electric vehicles by major manufacturers. With recent interconnect technology advancements, however, the charging of a lithium-ion battery can be reduced from the standard eight hours down to four hours.

With the release of the SAE Electric Vehicle J1772 charging specification in January 2010 (a standard adopted in both the US and Japan for Level 1 and Level 2 electric vehicle charging), the market needed a robust coupler capable of passing the UL 2251 certification.

In addition, the application required a high amperage charging solution that could provide fast, easy and safe charging of any electric vehicle.

Manufacturers have provided a high amperage solution that reduces the Level 2 charge time by 50%. With a single inlet design that allows for Level 1 and Level 2 charging, this interconnect system has proved its ability to meet both electrical and mechanical UL specifications.

It features high-efficiency power contact to provide flexible functionality, with minimal modifications, across a power curve ranging from a low of 15 A/120 V to a high of 75 A/240 V. The interconnect solution uses standard ITT VEAM CIR series backshells, flange gaskets and mounting plates, providing an enhanced cable management system that incorporates robust technology and ground pin contacts on the inlet side.

Anti-freeze drain holes enable outdoor use in extreme environments.

Manufacturers are continuously developing new connector designs and technologies to keep pace with vehicle demands.

When designing for the industry, engineers must always take into account the severe environmental conditions that connectors are subjected to every day.

As electronics are increasingly used in safety-critical applications, it is even more important that connectors are rugged and reliable.

Robin Pearce, Bishop & Associates

rpearce@bishopinc.com