Patent Application
20080053700
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
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In accordance with certain aspects of the invention, housing base 12 and/or housing cover 14 are configured to define a groove or recess in the interior walls at opposite ends of the housing for securely retaining opposite edges of substrate 16. For example, in the embodiment illustrated in
In the illustrated embodiment, an inner corner of wall portion 38 of housing cover 14 is notched out to define a groove or recess 44, which preferably extends around an inner perimeter of the housing, and is defined between housing base 12 and housing cover 14. Groove or recess 44 is configured to receive and retain edges of substrate 16 to hold substrate 16 and electrical component 18 attached to substrate 16 in a fixed position within the housing. While, in the illustrated and preferred embodiments, groove or recess 44 is defined by a notched-out region of housing cover 14, it will be appreciated that as an alternative, groove or recess 44 may be defined by a notched-out region in housing base 12, or by a combination of notched-out regions in both housing base 12 and housing cover 14.
It will be appreciated that the terms “cover” and “base” are relatively arbitrary terms which refer to the orientation of the housing components in the illustrated embodiments, it being understood that the illustrated assembly may be mounted in a vehicle or other environment in generally any orientation, such that housing component 12 is on top of housing component 14, in which case housing component 12 may be regarded as a cover, and housing component 14 maybe regarded as a base. Further, it should be understood that electronic component 18 may be mounted on either or both sides of substrate 16.
Housing components 12 and 14 may be composed of generally any metal or metal alloy. However, in the preferred embodiments, housing base 12 is a die cast aluminium or aluminium alloy component, and housing cover 14 is a stamped aluminium or aluminium alloy sheet material.
Aluminium and aluminium alloy housing components are preferred because these materials can be easily and inexpensively bonded together using a friction stir welding technique. However, generally any metallic material, such as metals, metal alloys or metal composites (e.g., fiber-reinforced metals and/or alloys) can be employed. Further, it is conceivable that the housing components can be made of the same or different metallic materials, and that these compounds can be fabricated using the same or different techniques, such as die casting, sand casting, lost mold casting, forging, stamping, etc.
In a preferred embodiment, housing base 12 and housing cover 14 are joined and sealed together along seam 20 with weld joint 22 that is produced by a friction stir welding technique. In friction stir welding, a tool with a probe attached to its tip is rotated at a high speed while being pushed against the butt sections of the pieces of metal to be welded. The frictional heat generated by this process softens the metal to produce a plastic flow that effectively stirs the metal from the sections on both sides and melts the pieces together to create a weld. Unlike fusion welding, friction stir welding is a solid phase welding method which produces a weld joint having excellent mechanical properties. Friction stir welding has several advantages. First, it creates a hermetic seal between a stamped aluminium or aluminium alloy housing component and a die cast aluminium or aluminium alloy housing component. Further, unlike with fusion welding techniques, weld joints having excellent mechanical properties can be achieved between components composed of different metals or metal alloys. The strong and durable weld joint between the housing components eliminates the need for mechanical fasteners such as threaded screws or the like. It also eliminates the need for dispensing adhesives and for curing adhesives, thereby reducing capital equipment and energy costs. Friction stir welding also produces a reliable weld joint that is not susceptible to failure, and which provides improved electromagnetic compatibility. In fact, the high reliability of the weld joint produced by friction stir welding is expected to eliminate the need for leak testing after assembly.
Electronic component 18 may be generally any type of electronic device, such as semi-conductor devices (e.g., flip chips).
Substrate 16 is generally any substantially flat sheet of material on which conductive paths can be provided and electronic components can be mounted. Examples include printed circuit boards, silicon wafers, etc. By configuring the housing components to define a groove or recess for receiving and firmly holding substrate 16 in place within the housing, the need for mechanical fasteners or other devices for holding substrate 16 in place is eliminated.
In accordance with another aspect of the invention, substrate 16 is grounded to the housing without mechanical fasteners, such as threaded screws, rivets or the like. This objective may be achieved by electrically connecting a ribbon conductor, such as at one end, to substrate 16, and deposing another end of ribbon conductor 46 in seam 20 between outer wall surface 40 of housing component 14 and inner wall surface 42 of housing component 12. The expression “ribbon conductor” refers to an electrically conductive thin strip of material that can be electrically connected, such as by soldering, to circuitry on substrate 16.
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It will be understood by those who practice the invention and those skilled in the art, that various modifications and improvements may be made to the invention without departing from the spirit of the disclosed concept.
The scope of protection afforded is to be determined by the claims and by the breadth of interpretation allowed by law.
