Patent Application
20210043997
The present disclosure relates generally to window assemblies, and more specifically to a window assembly with an electrically insulated, solderless electrical connector.
Window assemblies for vehicles are often functionalized to include one of more electrical components disposed on the transparent substrate. These electrical components may include, for example, RF antennae or resistive heating elements. An external electrical connection is typically made with these electrical components via a wiring harness that is connected to a printed silver circuit on the glass via an electrical connection element. In typical applications, the electrical connection element is both mechanically and electrically bonded to the printed silver circuit and underlying transparent substrate through a solder joint that is formed between the connection element and the silver circuit.
While lead-based solder has typically been the standard material used to create solder joints, various corporate practices and international agreements have restricted the use of lead-based solders. Unfortunately, lead-free alternative solders generally have lower mechanical strength and thermal stability than comparable lead-based solders. Furthermore, better performing lead-free solders typically are composed of one or more rare earth metals, such as Indium, that are, at times in scarce supply.
As such, there is a need for a means of reliably attaching an electrical connection element to a silver circuit on a glass window substrate that does not rely on lead-free solders.
While this provided background description attempts to clearly explain certain electrical-connector-related terminology, it is meant to be illustrative and not limiting.
The present embodiments discussed below are directed to a solderless electrical connector that may supply electrical power to a circuit disposed on a transparent substrate such as a window. Instead of solder, the present design utilizes a strong adhesive to mechanically bind a connector body to the substrate. Between the body and the substrate is a compressed, electrically conductive, metallic connector, such as a foam or a spring, that applies a contact pressure to force an electrically conductive surface (e.g., an electrically conductive metal connector) against the substrate. In doing so, the compliant, metal connector is held in firm mechanical contact with the substrate, thus maintaining a persistent electrical contact with the conductor. Furthermore, the present design addresses upcoming prohibitions on leaded solder without the need to rely on exotic rare earth metals or the need to compromise strength.
“A,” “an,” “the,” “at least one,” and “one or more” are used interchangeably to indicate that at least one of the item is present; a plurality of such items may be present unless the context clearly indicates otherwise. All numerical values of parameters (e.g., of quantities or conditions) in this specification, including the appended claims, are to be understood as being modified in all instances by the term “about” whether or not “about” actually appears before the numerical value. “About” indicates that the stated numerical value allows some slight imprecision (with some approach to exactness in the value; about or reasonably close to the value; nearly). If the imprecision provided by “about” is not otherwise understood in the art with this ordinary meaning, then “about” as used herein indicates at least variations that may arise from ordinary methods of measuring and using such parameters. In addition, disclosure of ranges includes disclosure of all values and further divided ranges within the entire range. Each value within a range and the endpoints of a range are hereby all disclosed as separate embodiment. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated items, but do not preclude the presence of other items. As used in this specification, the term “or” includes any and all combinations of one or more of the listed items. When the terms first, second, third, etc. are used to differentiate various items from each other, these designations are merely for convenience and do not limit the items.
The terms “first,” “second,” “third,” “fourth,” and the like in the description and in the claims, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms “include,” and “have,” and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, device, or apparatus that comprises a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such process, method, system, article, device, or apparatus.
Other features and aspects will become apparent by consideration of the following detailed description and accompanying drawings. Before any embodiments of the disclosure are explained in detail, it should be understood that the disclosure is not limited in its application to the details or construction and the arrangement of components as set forth in the following description or as illustrated in the drawings. The disclosure is capable of supporting other embodiments and of being practiced or of being carried out in various ways. It should be understood that the description of specific embodiments is not intended to limit the disclosure from covering all modifications, equivalents and alternatives falling within the spirit and scope of the disclosure. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
Referring to the drawings, wherein like reference numerals are used to identify like or identical components in the various views,
In most embodiments, the transparent substrate 18 may include a pane of silica glass. In some embodiments, a glass substrate 18 may include various additives to alter the transmissivity of the pane, for example, to provide various levels of tint or coloration. Furthermore, in some embodiments, the transparent substrate 18 may be a laminate that includes one or more layers of both a silica glass and of a polymeric material such as polymethyl methacrylate, polycarbonate, polyvinyl butyral, or the like. In some embodiments, the substrate 18 may alternatively be a polymeric substrate that is entirely made from a transparent polymeric material such as polymethyl methacrylate, polycarbonate, polyvinyl butyral, acrylic, or the like.
The conductive circuit 16 disposed on the transparent substrate may comprise one or more electrical conductors 24 or wires that are bonded to or integrally formed as an outer layer of the substrate 18. The one or more electrical conductors 24 may include, for example, a conductive layer of silver. In other embodiments, the electrical conductor 24 may be made of other conductive metals and/or other conductive or nonconductive materials in addition to, or instead of, silver. The electrical conductor 24 may be a film, a coating, and/or may take any other form so long as the electrical conductor 24 is conductive and serves any function known in the art for such electrical conductors. The electrical conductor 24 may be porous and/or nonporous. In various embodiments, the electrical conductor 24 is a porous silver film. In other embodiments, the electrical conductor 24 may be printed, for example, a screen printed silver film or printed silver circuit.
The conductive circuit 16 and electrical conductor 24 may be an electrical extension of, or may be electrically coupled with the electrical component 22. The conductive circuit 16 may further include one or more bus bars (not shown), resistors, or similar electrical components. It should be appreciated that the wire harness 14 may transfer power from a separate power supply (not shown) to the conductive circuit 16.
As further shown in
It has been found that the present design produces favorable results (robust, low resistance connection) when the metal connector 34 is formed from a flat sheet of metal that has a uniform thickness of about 0.4 mm. In one embodiment, this flat sheet material may have a single thickness throughout the compressible portion 40, though may be folded over to have a double thickness in the connection portion 42. Doing so would enable a better connection with standard spade-type connectors. When formed from this gauge of metal (e.g., copper), the convex protrusion may desirably have an undeformed aspect ratio (length—measured along the connector body 30, to height—measured normal from the connector body 30) of between about 2:1 and about 9:1 or more preferably between about 2.5:1 and about 5.5:1.
Referring to
In the present designs, the adhesive may be provided on the body 30 in the form of a tape. In one configuration, the adhesive/tape may have an undeformed thickness of between about 0.5 mm and about 0.8 mm. Once a protective layer is removed, the adhesive portion of the tape may be flashed with an initiator, such as ultraviolet light, and the connector body 30 and metal connector 34 may be simply placed or adhered to the surface. This greatly decreases both the cycle time and the sensitivity of the assembly (i.e., where the assembly tolerances with a press-on connector are not nearly as tight as with solder). For example, in typical solder applications, forming a joint may have about a 15-20 second cycle time, whereas with the present adhesive-based designs, the cycle time may be reduced to around 10 seconds or less.
In addition to simply being a faster means of forming an electrical connection (when compared to traditional solder joints), the present design is also advantageous over solder for not requiring tightly controlled temperature parameters. More specifically, to form a solder connection on a glass substrate, the time, temperature, and heat flux must be carefully controlled within narrow parameter windows to avoid thermally shocking the glass or inducing excess residual stress on the connection upon cooling (i.e., due to differing coefficients of thermal expansion). Conversely, the present designs may be adhered at room temperature (i.e., without the application of thermal energy), and without the need for down-stream thermal curing.
In one embodiment, such as shown in
As illustrated in
In some embodiments, the channel 52 or other internal concavity may define an internal connector volume. Functionally, in such embodiments, the body 30 may encapsulate the electrical connection formed with the circuit 16 to both protect the integrity of the connection and inhibit foreign objects or fluids from contacting and/or degrading the interface.
Regardless of whether the connector body is solid, or hollow/concave, in some embodiments, the body 30 may be formed from a polymer or polymeric material, which may provide electrical insulation about the joint. The polymer body may comprise one or more thermoplastic materials and/or thermoset materials. Non-limiting examples of suitable polymers include thermoplastic elastomers (TPE), thermoplastic vulcanizates (TPV), polyphthalamides (PPA), and thermoplastic polyolefins (TPO). Specific non-limiting examples include thermoplastic styrene (TPS), polyurethane, polyvinyl chloride (PVC), Acetal, acrylic, polyamide (PA6 or PA66), Polytetrafluoroethylene (PTFE), and ester based thermoplastic elastomers (E-TPE). It should also be appreciated that the body 30 may be made of non-polymeric materials.
As noted above, the body 30 may be secured in place over the compressible connector 34 by directly adhering it to the substrate 18 via the adhesive 32. More specifically, as shown in
A method of making a solderless electrical connection with an electrical conductor 24 disposed on a transparent substrate 18 may generally begin by preparing the transparent substrate 18 to include an integral electrical conductor 24 and a circuit 16. This step may include any needed heat-treating processes, laminating processes, autoclaving processes, tempering processes, screen printing of circuitry, and any other such processes that may necessarily be performed to the substrate 18 and/or circuit 16.
Following this, the connector 12 may be loosely assembled with the metal connector 34 provided in an abutting relationship with the body 30 portion of the connector 12. In the embodiment described above, this may include providing the body so that the metal connector 34 extends to opposing sides of the body 30.
Depending on the specific configuration, an adhesive 32 may be applied to the body 30 either before the assembly of the connector 34 and the body 30. In some embodiments, the adhesive 32 may be applied in a liquid form, such as being screened or printed onto the body 30. In other embodiments, the adhesive 32 may be applied by sticking it onto the body as would occur with a structural bonding tape.
While in this form, the connector 12 may be stored for a period of time prior to final assembly. Once final assembly is desired, crosslinking/curing of the adhesive 32 may be initiated by applying a stimulus that is designed to activate the plasticizer compounded into the adhesive. In one embodiment, the curing is photoinitiated, such as by exposing the adhesive momentarily to an ultraviolet light source. In such an embodiment, the curing process should be self-sustaining once externally initiated, yet should be slow enough to provide some minimum amount of working time (e.g., greater than about 20 seconds) so that an assembly technician can perform the remaining steps. In one example, this self-sustaining curing may be facilitated by providing one or more of a catalyst and an initiator within a plurality of photo-sensitive micro capsules that may release the catalyst and/or initiator upon exposure to a light source such as an ultraviolet lamp.
The connector 12 is then positioned in a contacting and abutting relationship to the substrate such that the compressible connector 34 includes a portion disposed between the body 30 and the substrate 18, and such that the adhesive 32 makes contact with the substrate 18 or an element that is integral with the substrate, such as the electrical conductor 24 or a ceramic coating.
Force may then be applied to the connector body 30 to compress the compressible portion 40 of the connector 34 in a direction normal to the surface of the substrate 18 until the adhesive 32 contacts the substrate 18. In one embodiment, the force may be maintained for a sufficient amount of time until the adhesive can resist the elastic expansion of the compressible portion 40. In a more preferred embodiment, however, the green strength of the adhesive (i.e., the initial contact bonding strength) should exceed the amount of force exerted by the compressible portion 40 of the connector 34 such that the compressible connector 34 may be held in an elastically deformed state upon initial contact between the adhesive 32 and the substrate 18. In such an embodiment, the body 30 of the connector 12 need not be held in place or externally fixtured after initial assembly, which may reduce the cost and complexity of assembly.
In other embodiments, the cure-initiating stimulus may be applied continuously throughout the curing process after the body 30 is applied to the substrate 18. Such a technique has additional limitations since it may only be applicable if the location of the adhesive was on a transparent portion of the substrate (i.e., transparent to whatever stimulus is being applied) so that the stimulus may reach the adhesive through the substrate 18. This may not be feasible in many cases due to typical black masking layers that are used to improve the aesthetics by eliminating the ability to see circuitry and connections. If the adhesive is visible through the substrate, however, then the method may include applying the body 30 to a portion of the substrate 18 that is transparent to ultraviolet light, and exposing the adhesive to the stimulus to the ultraviolet through the opposite side of the substrate 18 to cure the adhesive 32.
As discussed above, in a preferred embodiment, the chosen adhesive 32 should have a green strength that is sufficient to maintain the compressible portion 40 of the metal connector 34 in the elastically deformed state without the need for external fixturing during the curing process.
The present solderless connector 12 advantageously eliminates the need for solder by applying an elastic contact pressure between both the substrate 18 and the metal connector 34. It relies on a robust adhesive to mechanically secure the connector 12 to the substrate (i.e., where the adhesive may provide an even superior and simpler bond to solder). Such a design both eliminates the need for expensive and/or performance-compromised lead-free solders, while not introducing any thermal expansion concerns that may damage the window due to differing thermal expansion rates (since the metal connector 34 is not rigidly attached to the substrate 18).
Benefits, other advantages, and solutions to problems have been described with regard to specific embodiments. The benefits, advantages, solutions to problems, and any element or elements that may cause any benefit, advantage, or solution to occur or become more pronounced, however, are not to be construed as critical, required, or essential features or elements of any or all of the claims, unless such benefits, advantages, solutions, or elements are expressly stated in such claims.
Moreover, embodiments and limitations disclosed herein are not dedicated to the public under the doctrine of dedication if the embodiments and/or limitations: (1) are not expressly claimed in the claims; and (2) are or are potentially equivalents of express elements and/or limitations in the claims under the doctrine of equivalents.
