42V: The new automotive molding challenge

Automotive electronics molders are getting ready for a major system shift that will push products such as lighting, switches, and connectors to the limit. We're talking about the planned conversion from 12 to 42V electrical systems, which automakers believe will allow them to create more efficient engines and more intelligent vehicles. First expected among high-end models from automakers such as BMW and DaimlerChrysler, initial 42V vehicles may appear as early as 2003. 

While it is a boon for engine design, the new electrical system will tax existing molded parts to a certain extent. IMM asked Tricon Industries, a Tier Two automotive lighting and electronics supplier, to explain how the new electrical systems will impact molders in this industry. Tricon is already meeting the challenge head-on with innovative concept designs. 

Jeff Terrell, product development manager for Tricon, explains that customers such as Delphi are developing components based on these concepts. "Our customers will ultimately do the design work for these products," he adds, "but we have been researching 42V systems and creating some preliminary concepts to make the transition easier." 

New Demands 
One of the new requirements for a 42V system will be that connectors and lighting components must exhibit a high degree of arc resistance. Under heavy load, the higher-voltage system can develop severe arcing that may erode metal contacts. "Any power system under 16V has no sustainable arcing," Terrell says, "but anything over 16V has a known arc for a specified distance. With 42V systems, if you unplug a connector that is under power, it will arc." 

Arcing can occur even if the components are only slightly disconnected. As a result, new products will need to incorporate locking mechanisms as well as a way to eliminate arcing. Tricon is looking at an insert molding method that combines two magnets in the connector to disrupt the arc. In addition, designs that have molded-in locking mechanisms are being investigated. 

Incandescent light bulbs are another area that must be addressed in the new systems. As voltage goes up, bulb life decreases significantly. While research is under way to produce a longer-lasting incandescent bulb, Tricon is investigating systems that use LEDs. "Each LED bulb requires only 2 to 4V of electricity," Terrell says. "We are working on designs that use multiple LEDs that will provide the amount of light needed." LED bulbs can be connected in a series with a voltage step-down resistor. 

By comparison, materials are predicted to remain the same. "Existing base plastic materials should be able to meet flammability and temperature resistance requirements," Terrell says, "mainly because the heat generation will be the same." Although higher voltages are being used, the amps or current will decrease so that the temperatures the parts see will remain constant. 

Higher-voltage Concepts
With a 42V system, off-the-shelf items such as standard switches, connectors, and lighting components may become obsolete. "More of these parts will require a custom approach," he says. "For example, encapsulation will likely become more common as a way to protect higher-voltage components from arcing or shorting." Tricon is investigating the MuCell process (microcellular foam molding) as a means of encapsulating sensitive electronics such as PC boards and solid-state switches.

Another concept under development is a longer-life CHMSL (center high mounted stop lamp, pronounced chim-sul). It incorporates LEDs for greater life span in a 42V system. According to Terrell, heat issues are being addressed through design innovation. "One downside of new, high-intensity LEDs is that the hotter they are, the less light is transmitted. We are working on designs that incorporate a metal heat sink to draw heat away from the bulb." He estimates that Tricon could have an LED-based CHMSL in production within one year. 

Finally, a drop-in LED replacement for incandescent bulbs in stop lamps, called a Universal Wedge, is also on the drawing board. The design works with all existing backplate and socket configurations, eliminating the need for any retooling.