capabilities of its newest generation of power switches, IR’s COOLiR2 packaging platform utilizes a proprietary Solderable Front Metal (SFM) process on ultra-thin die to minimize wafer warpage, enabling the utilization of the same standard and cost effective wafer processing lines used for non-SFM devices.
SFM die technology eliminates the need for
bond wires and the inherent failure mechanism that limits reliability and shortens operational life times. At the same time, SFM technology enables dual-sided cooling capability to increase thermal performance by 30-40 percent and eliminate bond wire related parasitic impedances which typically increase system level costs and footprint. The COOLiR2DIE package is as a “power module building block”, which is a fully tested Surface Mount Device (SMD) that can be handled and assembled utilizing standard pick-and-place and solder reflow equipment (See Figure 1). It eliminates the need for die attach, wire-bonding and significantly reduces costly assembly yield- losses on module substrates. This innovative package allows configuration of half-bridge or multi-phase modules on commonly used substrate materials with fewer design constraints than traditional die-attach and bond-wire assemblies. This enables more flexible form factors for close integration with other system components, so called “Mechatronics”, referring to Motor and Power Electronics integration in one assembly. Closer integration of electric motors and power electronics is required to reduce system footprint, eliminate cost and weight of wiring and eliminate consequential cost and detrimental performance caused by electrical parasitics associated with high current wiring harnesses.
The COOLiR2DIE package platform supports all of IR’s SFM capable technologies including IGBT, MOSFET and Diodes and scales to large die sizes also supporting multi-die attach outlines. Because of the solderable front metal, current spreading
resistance present on die surfaces with wire bonds or clips is virtually eliminated reducing losses and increasing die temperature uniformity which is important for reliability. Wide copper tracks on the carrier allow for Die Free Package Resistance (DFPR) of typical 50uOhm. Parasitic inductance is reduced compared to wire bonds and mostly determined by the module substrate layout. The package outline has been optimized to enable
Figure 3: Passive and Active cooled assembly examples
module layouts with very low parasitic loop inductances of 10-15uH utilizing common and proven assembly techniques.
Even better performing 3-D assembly techniques are under development and promise to further significantly reduce parasitic impedances on module level while at the same time allowing for even smaller module form factors and increased power densities.
When assembled on a substrate, the COOLiR2DIE provides an electrically isolated copper surface for top-side cooling with low thermal resistance. Topside cooling has been demonstrated to lower thermal resistance by 35 percent in real-world applications (~70% in lab
assemblies which don’t have to take volume manufacturing tolerances into account). Depending on system requirements, the dual sided cooling capability can be utilized and optimised to increase current ratings for a particular module outline (reduce overall size of the system by increasing power density). It can also reduce constraints and cost in the cooling system by allowing for higher case temperatures or increase thermal robustness for peak power requirements. Furthermore the topside cooling interface allows the module or system designer to strike a balance between Rth and Zth optimisation meeting the exact requirements of the application. The new COOLiR2DIE package provides a versatile and scalable building block that optimises the performance of the latest generation of power switch devices. COOLiR2DIE devices are fully tested, eliminating costly yield losses usually associated with multi die attach and wire bonding on expensive substrates. Instead COOLiR2DIE devices are mounted with standard SMD pick & place equipment. The elimination of bondwires increases reliability while at the same time allowing for dual-sided cooling, another major system design advantage. In summary, IR’s new COOLiR silicon and advanced COOLiR2 packaging technology provides a new power management platform approach for H(EV) vehicles that helps address the requirements for reducing the size, weight and system cost of electric power train components while at the same time increasing system reliability for long lifetime, low maintenance and low warranty cost.
International Rectifier |
www.irf.com Michael Wittmann is Director Automotive Modules, Automotive Products Business Unit at International Rectifier
CIE electronica 2012
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