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|BD-HDI: New Substrate technology for integrated Transmission Control Units|
|Keywords: Transmission Control, Substrate Technology, BD-HDI technology|
|The market for automatic transmissions continues to grow. In addition to what originally attracted interest in the product was enhanced driver convenience. Now the prospect of greater fuel efficiency is another factor in their favor. Continental has been offering transmission controls since 1982 , starting with simple three-gear conventional automatic transmissions (Renault), followed by all-wheel applications (Ford) in 1985, truck applications (Eaton) in 2000 and CVT applications (Audi Multitronic) in 1999, and arriving at double clutch transmissions in widespread use today. At present Continental Business Unit Transmission is a technology leader worldwide in the market for transmission controls for the full spectrum of automatic drives. Depending on the installation situation of the control units, a basic distinction is made between stand-alone, attached-to and integrated control units. Stand-alone control units are installed in the vehicle as a separate electronic box away from the transmission under relatively moderate ambient conditions. The maximum ambient temperatures are typically limited to +105°C. The attached-to control units are attached the transmission itself and are designed to withstand vibration loads comparable to those of the transmission itself. They can also withstand higher ambient temperatures up to +125°C. Usually standard PCBs with soldered packaged components are used for stand-alone and transmission mount applications. Integrated control units, which are installed inside the transmission, have even higher demands in terms of vibration and, above all, high temperatures. The temperature on the substrate may get as high as +180°C, therefore special substrates, typically a ceramic-based material, are used. The semiconductor components themselves are bonded directly onto such substrates as chips, without any package, by electrical conductive adhesives. The selection of the best substrate, electrical components, and the interconnection technologies – is mandatory to satisfy the customer’s requirements. A general distinction is made between organic substrates (printed circuit boards, PCBs) and ceramic substrates. Typically organic substrates are used for applications with maximum junction temperatures of (in special cases) up to +150°C, whereas ceramic substrates can operate up to +180°C. Continental has made a big step to change the rules of the game: With the idea to combine the advantages of both organic and ceramic substrate types, a new substrate type was created: BD-HDI PCBs (Bare Die HDI PCBs). The selection of special high temperature PCB base materials, combined with optimal design of PCBs and the best performing surface finish was the basis for a PCB that is reliable in harsh environments with operating temperatures up to +180°C. The usage of electrically conductive glued and wire bonded bare dies instead of soldered packaged components was a mandatory step to ensure the electrical functionality of the circuit in that temperature range. The successful combination of the high temperature substrate and the high temperature assembly technologies is today a serious competition to ceramic substrates and has been implemented in integrated transmission control units for different automotive OEMs. For this innovative substrate technology, Continental is a PACE AWARD 2015 finalist!|
|Wolfgang Gruebl, Development Engineer
Conti Temic microelectronic GmbH
Nuremberg , Bavaria