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Part 1 discussed the automotive electronic distribution system problem due to growing electronic features and functions and a MOSFET/IP concept for a reliable junction box design without any fuses or relays.
A look at the enablers: EDS connection systems
Electrical distribution system (EDS) connectors used in production today are remnants of connectors designed for multi-layered fret and bus bar EDS designs. Adapting these through-hole connectors to PCB based EDS designs is neither efficient nor cost effective.
PCB based EDS designs typically require multi-layer, high-density (weight) copper boards. Through-hole EDS connectors restrict and interfere with PCB trace routing and actually prevent heat (thermal power dissipation) from being naturally transferred (flowing) from the module.
EDS connector systems have evolved and can use either stitched or stamped terminals with the connector shell and mounting features molded into the module housing. These terminal designs tend to provide the lowest cost connection system even though the assembly process and equipment costs are more demanding than those imposed by purchased assembled connectors. The average cost for stitched or stamped terminals are less than a penny in production versus the cost of a purchased connector assembly that may cost several dollars.
SMD (surface mount device) terminals are more efficient in PCB trace routing since they physically impact only one side or one layer of the board. Furthermore, by designing an SMD connector that can be mated (same geometry) to semiconductor power packages enables improving module level thermal dissipation.
The capability to place output drivers in close proximity to the connector allows almost zero length PCB traces. Experimentation has shown that 10 mm of extra trace length in a 3 oz copper PCB can lead to a 6C temperature rise in the junction temperature of a MOSFET HSD (high side driver).
Consequently, the advantage of an SMD style connector are too numerous to fully discuss, but the capability to use the connector and vehicle wiring to effectively conduct heat from the module creates some new design concepts to explore. Furthermore, the target price for the SASE-Lear co-developed SMD terminals can approach the economies of stitched or stamped terminals.
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