Power Electronics

Packaging Propels Developments in Automotive Power Management

Semiconductor vendors have been creating a variety of power management components for a host of automotive subsystems. Some of these components are intended to replace existing electromechanical functions, while others integrate formerly discrete electronic functions. But as evidenced by recent announcements at the Convergence 2004 conference in the Detroit, power IC packaging is playing a major role in the development of automotive-oriented power management devices. This trend has implications not only for those working in automotive electronics, but also for those pursuing power management designs in other performance-driven markets.

Companies such as Fairchild Semiconductor, Freescale Semiconductor and International Rectifier have turned to multi-chip package development to extend integration beyond the limits of monolithic IC design. Fairchild Semiconductor has introduced a packaging technology called Smart Power Switch that co-packages multiple control and power MOSFET die in PQFNs, DPAKs and other standard chip packages.

This approach, which the company is using to develop custom devices, such as a dual integrated solenoid driver, allows Fairchild to optimize control and power functions by using the appropriate process technologies for each. Putting multiple die in an IC package enables the company to accommodate higher power levels than would be possible with monolithic power chips. There are a number of other benefits as well, including isolation of power and control circuitry, the ability to integrate more control functions, and layout flexibility.

Similarly, Freescale Semiconductor has exploited the capabilities of its SMARTMOS and HDTMOS processes to develop its MC33981, a self-protected 4-mΩ high-side MOSFET switch that replaces electromechanical relays and discrete devices. As is the case with Fairchild’s solenoid driver, Freescale’s high-side switch takes advantage of the PQFN’s capabilities, including its easily configurable die attach pads.

Meanwhile, International Rectifier has introduced a die-on-leadframe (DOL) packaging technology for medium- to high-power applications of power inverters. This technology offers better electrical and thermal conductivity than existing packaging techniques like insulated metal substrate (IMS), direct-bonded copper (DBC) to a ceramic substrate and thick-film substrates or PCB-based modules.

A DOL power module includes silicon die directly soldered to a copper leadframe within an injection-molded shell. The internal components are connected directly to outside terminals, eliminating intermediate insulation and conductive layers. DOL accommodates higher current levels and achieve lower costs than the packaging alternatives. It is these benefits that make DOL an enabling technology for new applications in electric power steering.

Although these packaging developments take place in the automotive realm, power designers working in other areas should take note. It’s well known that automotive product development is driven by rigorous performance and reliability requirements, as well as by extreme cost sensitivity. Thus, the packaging techniques now being exploited for automotive power management may be able to meet the needs of power management designs in other less cost-sensitive and less environmentally challenging areas such as computing, networking and communications. Considering that the semiconductor companies mentioned above are also active in those non-automotive areas, such spin-off activities seem very likely.

For more information, visit www.fairchildsemi.com, www.irf.com or www.freescale.com/analog.

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