Electricity: conductors and insulators – Boxes and housings – Hermetic sealed envelope type
Reexamination Certificate
2000-05-25
2001-11-20
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Boxes and housings
Hermetic sealed envelope type
C174S050510, C257S682000, C257S693000, C257S789000, C257S712000, C361S749000, C361S752000, C439S077000
Reexamination Certificate
active
06320128
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to electronic assemblies adapted to operate in relatively harsh service environments.
2. Background Art
Modern electronic assemblies must often operate in relatively harsh environments. For example, in some automotive applications, electronic assemblies must be able to withstand severe vibration, drastic temperature fluctuations (e.g., between about −40° C. and about 125° C.), corrosive and/or particle-laden exhaust fumes, high atmospheric moisture, and so forth. In response, the prior art teaches providing mechanical protection for an electronic assembly by placing the electronic assembly within a protective housing. The prior art also teaches providing an electronic assembly with a measure of resistance to moisture and/or chemical attack by potting the entire assembly, or portions thereof, in a relatively moisture-impervious potting material, such as an epoxy or silicone material.
In accordance with another prior art approach, as disclosed in U.S. Pat. No. 5,317,478, a hermetically-sealed electronics package includes an electronic element located on a multilayer flexprint substrate. A cover, which may itself form the top layer of the multilayer flexprint or a separate flexprint, is supported above the electronic element by a frame structure, whereupon a periphery of the cover is sealingly attached to the substrate. The frame structure provides support for the flexprint cover to prevent deformation of the cover and resulting damage to the underlying circuit. The electronics package is thereafter itself attached to a suitable mounting structure within the vehicle.
However, these and other previously-known approaches often suffer from one or more drawbacks. For example, even when generally well-sealed against water penetration, known protective housings typically fail to protect the assembly's electronic components against long-term moisture penetration, e.g., due to the diffusion of moisture through a given potting material, whereupon the penetrated moisture will likely detrimentally affect the performance, functionality and/or service life of the assembly's electronic components. And, in the event that certain contaminants are either trapped within the potted assembly or, alternatively, form a portion of the service environment within which the assembly is operated, the moisture and contaminants can often combine within the assembly to form a corrosive solution, thereby further deteriorating the performance, functionality and service life of the assembly's components. Moreover, the requirement of separate supporting structures upon which to mount each sealed prior art electronics package will be seen to substantially increase manufacturing and assembly complexity and cost.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an environmentally-sealed electronic assembly, preferably produced by a relatively low-cost process, featuring protection against harmful environmental operating conditions without the aforementioned drawbacks.
Under the invention, an electronic assembly is provided for use in a service environment that is characterized by at least one penetrant, wherein the term “penetrant” is understood to encompass substances present in the service environment which penetrate and/or permeate into the assembly over time; substances formed within the assembly as the result of such penetration and/or permeation of substance constituents, or the combination of either such substances or substance constituents; with other constituents, e.g., process contaminants, which are internal to the assembly upon manufacture thereof. The electronic assembly of the invention includes a thin, flexible substrate having a first face, a first portion of which includes a pattern of electrically-conductive traces; at least one electronic component mounted on the substrate's first portion such that the electronic component is electrically interconnected with the pattern of traces; a filler material over at least one mounted component, wherein the filler material is operative to neutralize a predetermined quantity of the penetrant; and a thin barrier member having a peripheral portion sealingly attached to the first face such that the electrical component and the filler material are encapsulated between the substrate and the barrier member.
The barrier member includes a first metal foil or other similar, highly-moisture impervious film to thereby render the barrier member relatively impervious to moisture diffusion, as well as to reduce the likelihood of penetration/permeation of other substances or substance constituents in the service environment into the assembly. Preferably, the electronic assembly's substrate similarly includes, as one of the substrate's lowermost layers, a second metal foil or other similar, highly-moisture-impervious film, whereby the mounted electronic components and the filler material are further fully encapsulated within metal foil or film. And, in a preferred embodiment, the barrier member is integrally formed with the substrate, for example, as an adjacent portion of the substrate which is folded over the first portion to thereby encapsulate the assembly's electronic components and the filler material.
In accordance with a further feature of the invention, the assembly preferably includes a relatively-rigid polymeric material formed in touching contact with at least one of the substrate and barrier member, as by overmolding or insert-molding the polymeric material about the substrate after the barrier member has been sealingly attached. In this manner, the molded polymeric material may define a plastic part associated with the resulting electronic assembly, with the plastic part providing such additional structural features as mounting structures for use with the electronic assembly. As a further benefit, at least one heat sink may be attached to the substrate, for example, on a second face opposite its first face, during overmolding/insert molding.
In accordance with another feature of the invention, in another preferred embodiment, the filler material is preformed to a first shape, wherein the first shape includes recesses adapted to receive mounted electronic components. In this manner, the preformed filler material may include sections having different thickness which, when applied over the mounted electronic components, provides a relatively constant height to the resulting assembly.
Under the invention, a method for making an electronic assembly, adapted for use in a service environment characterized by at least one such penetrant, includes mounting at least one electronic component on a first face of a thin flexible substrate, wherein the first face of the substrate includes a first surface portion having a pattern of electrically-conductive traces, and wherein mounting includes electrically interconnecting the pattern and the electronic component; and applying a filler material over at least one mounted component, the filler material being operative to neutralize a predetermined quantity of the penetrant.
By way of example only, a preferred method for practicing the invention includes preforming the filler material into a first shape, wherein the first shape preferably includes a first side having at least one recess adapted to receive at least one of the mounted components. Preferably, the preform's first shape includes a first section having a first thickness and a second section having a second thickness, with the first thickness being greater than the second thickness, whereby a generally flat preform surface is provided for juxtaposition with the barrier member as described below. In this manner, the resulting electronic assembly may be advantageously provided with a generally flat upper surface.
The method further includes sealingly attaching a peripheral portion of a thin barrier member, which itself includes a first metal foil, to the substrate's first face so as to encapsulate the electrical components and
Baker Jay DeAvis
Dailey Daniel Phillip
Glovatsky Andrew Zachary
Goenka Lakhi Nandlal
Kneisel Lawrence Leroy
Ngo Hung V
Reichard Dean A.
Shelton Larry I.
Visteon Global Technology, Inc.
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