Patent Publication Number: US-9409379-B2

Title: Method and apparatus for bonding metals and composites

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of U.S. application Ser. No. 12/715,702, filed Mar. 2, 2010, and entitled “METHOD AND APPARATUS FOR BONDING METALS AND COMPOSITES,” which is hereby incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure relates generally to assembly processes for components that include different materials and, more particularly, to creating components that include a metal and a composite material. 
     BACKGROUND OF THE INVENTION 
     Devices, e.g., small electronic devices, often include components that are formed by assembling sections made from different materials. Metal is used in many devices, as for example portable media players and cell phones, because of the structural strength of metal and/or the aesthetic qualities of metal. Thus, in many devices, it becomes necessary to create bonds between metal on materials such as composites. 
     When sections of components are formed from the same material, bonding the sections is generally not difficult. However, when sections of components are formed from different materials, bonding sections becomes more challenging. For example, bonding a metal section to a section formed from a composite material such as a hard plastic is difficult to accomplish especially when there are space constraints. In other words, creating a joint between a metal piece and a plastic piece that provides a desired bond strength and substantially minimizes the size of the joint is difficult. Often, joints are larger than desired and effectively become macro features of a component, as achieving a desired bond strength may require relatively large joints. 
     Therefore, what is desired is a method and an apparatus for achieving a relatively strong bond between components of different materials. More specifically, what is needed is a method and an apparatus for creating a relatively strong joint between a metal part and a part formed from a composite material. 
     SUMMARY 
     The invention pertains to apparatus, systems and methods for providing facilitating bonding between a metal part and a composite part. 
     The invention may be implemented in numerous ways, including, but not limited to including, as a method, system, device, or apparatus (including computer readable medium). Several embodiments of the invention are discussed below. 
     According to one aspect, a layer stack includes a metal layer with a first surface, the first surface including at least one protruding feature. The layer stack also includes a non-metal layer molded to the first surface of the metal layer, wherein the non-metal layer is molded over and/or around the at least one protruding feature. In one embodiment, the at least one protruding feature is a flange machined onto the metal layer. In another embodiment, the at least one protruding feature is formed by adding a wire bond or a solder ball to the metal layer. In still another embodiment, the non-metal layer is a thermoplastic layer. 
     According to another aspect, an assembly includes a substrate arrangement and a non-metal layer. The substrate arrangement includes a metal substrate and a prongle component. The prongle component includes at least one protruding feature. The non-metal layer is formed over the protruding feature, and the non-metal layer engages the protruding feature. 
     In accordance with yet another aspect, an electronic device includes a bezel and a composite component. The bezel is formed from a metal material, and includes at least one flange with a first surface. The first surface has at least one protruding feature formed thereon and extending therefrom. The composite component is formed over the protruding feature and the flange. The composite component engages the at least one protruding feature and the flange to engage the bezel. In one embodiment, the protruding feature is a wire or a solder ball. 
     According to still another aspect, a method for bonding a composite material to a metal material includes obtaining a metal substrate and obtaining a prongle piece that has at least one protruding feature. The method also includes bonding the prongle piece to the metal substrate and forming a composite piece over the protruding feature to bond the composite piece with the at least one protruding feature. In one embodiment, the metal substrate includes a flange, and bonding the prongle piece to the metal substrate includes bonding the prongle piece to the flange. 
     In accordance with another aspect, a method for bonding a composite material to a metal material includes obtaining a metal substrate and forming a plated surface on the metal substrate. The plated surface includes at least one plated feature. The method also includes forming a prongle piece over the plated surface. The prongle piece has at least one protruding feature that is formed over the at least one plated feature. A composite piece is formed over the protruding feature to bond the composite piece with the protruding feature. 
     Other aspects and advantages will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated into and constitute a part of this specification, illustrate one or more example embodiments and, together with the description of example embodiments, serve to explain the principles and implementations associated with the specification. 
         FIG. 1A  is a diagrammatic representation of a substrate assembly, e.g., a metal substrate assembly, in accordance with one embodiment. 
         FIG. 1B  is a diagrammatic representation of an overall assembly that includes a substrate assembly, e.g., substrate assembly  104  of  FIG. 1A , and a composite piece bonded to a prongle piece of the substrate assembly in accordance with one embodiment. 
         FIG. 2  is a diagrammatic representation of a substrate assembly, e.g., a metal substrate assembly, that includes a prongle piece bonded to a substrate in accordance with one embodiment. 
         FIG. 3  is a diagrammatic representation of a substrate assembly, e.g., a metal substrate assembly, that includes a prongle piece formed onto a substrate in accordance with one embodiment. 
         FIG. 4  is a process flow diagram which illustrates a first method of forming a substrate assembly that include prongles in accordance with one embodiment. 
         FIG. 5  is a process flow diagram which illustrates a second method of forming a substrate assembly that include prongles in accordance with one embodiment. 
         FIG. 6  is a diagrammatic representation of a joint formed between a metal piece, which includes prongles on one surface, and a composite piece in accordance with one embodiment. 
         FIG. 7  is a diagrammatic representation of a joint formed between a metal piece, which includes prongles on a plurality of surfaces, and a composite piece in accordance with one embodiment. 
         FIG. 8  is a diagrammatic representation of a joint formed between a metal piece, which includes prongles that are individually bonded to the metal piece, and a composite piece in accordance with one embodiment. 
         FIG. 9  is a diagrammatic perspective representation of a device which includes a metal piece with prongles and a composite piece that is bonded to the metal piece through the prongles in accordance with one embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS 
     The invention pertains to apparatus, systems and methods for providing a bond between parts formed from different materials. In one embodiment, a bond may be formed between a metal piece and a piece formed from a composite material, i.e., a composite piece, by providing protrusions on the metal piece to which the composite piece may be bonded. The protrusions, e.g., protruding features or prongles, may be formed from a material that is easier to bond to the metal piece than the composite material, and the composite piece may be bonded to the protrusions. By sizing the prongles to provide a significant amount of surface area, a relatively strong bond between the composite piece and the prongles and, hence, the metal piece, may effectively be promoted. The prongles enable a relatively strong joint between the overall metal piece, i.e., the metal piece and the prongles, and a composite piece to be formed. 
     An overall assembly, or a layer stack, may generally include a metal layer with a surface with at least one prongle. The layer stack may also include a non-metal layer, e.g., a layer formed from a composite material such as a thermoplastic or a hard plastic, that is substantially molded to the surface of the metal layer with the prongle such that the composite material essentially interlocks with the prongle. In other words, a layer formed from a non-metal such as a composite is molded around or otherwise bonded to the prongle. 
     The configuration of a prongle may vary depending upon the requirements of a device in which the prongle is included. A prongle may be a flange, protuberance, protruding feature, or projection machined onto a metal part. It should be appreciated, however, that a prongle may instead be a flange or the like formed on the metal part, e.g., through a plating process, or a flange or the like that is bonded to the metal part, e.g., through a wire bond or solder process. 
     In general, prongles are sized to provide a surface to which a composite material may be bonded. The size, e.g., dimensions, of prongles may be dependent upon a variety of factors including, but not limited to including, the size of the parts on which the prongles are essentially bonded and the materials from which the parts are made. Prongles may, in one embodiment, effectively be wire pieces that are bonded, e.g., soldered, to a surface of a substrate. In another embodiment, prongles may be solder balls which are soldered onto a surface of a substrate. 
     The apparatus, systems, and methods of the invention allow for the formation of prongles, as well as to the assembly of a component that includes the prongles and a composite part bonded to the prongles. In one embodiment, prongles may be included on a metal bezel, and a composite part may be bonded to the metal bezel. A metal part such as a bezel with prongles and a composite part that is bonded to the metal part through the prongles may be included in small form factor electronic devices such as handheld electronic devices, as for example mobile phones, media players, user input devices (e.g., mouse, touch sensitive devices), personal digital assistants, remote controls, etc. The apparatus, systems, and methods may also be used with relatively larger form factor electronic devices such as portable computers, tablet computers, displays, monitors, televisions, etc. 
     Embodiments are described herein in the context of forming prongles on a metal part and bonding a composite part to the prongles and, thus, effectively bonding the composite part to the metal part. The following detailed description is illustrative only, and is not intended to be in any way limiting. Other embodiments will readily suggest themselves to skilled persons having the benefit of this disclosure. Reference will now be made in detail to implementations as illustrated in the accompanying drawings. The same reference indicators will generally be used throughout the drawings and the following detailed description to refer to the same or like parts. 
     In the interest of clarity, not all of the routine features of the implementations described herein are shown and described. It will, of course, be appreciated that in the development of any such actual implementation, numerous implementation-specific decisions must be made in order to achieve the developer&#39;s specific goals, such as compliance with application and business related constraints, and that these specific goals will vary from one implementation to another and from one developer to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking of engineering for those of ordinary skill in the art having the benefit of this disclosure. 
     Referring initially to  FIG. 1A , a substrate assembly, e.g., a metal substrate assembly or arrangement, which includes prongles will be described in accordance with an embodiment of the invention. In one embodiment, a substrate assembly  104  may include a substrate  108  and a prongle piece  112  that is bonded to, or otherwise coupled to, substrate  108 . Substrate  108  is typically formed from metal. Prongle piece  112  may be formed from substantially any material that may maintain a relatively strong bond with substrate  108  on a first surface  109 . By way of example, prongle piece  112  may be formed from any suitable material which forms a stronger bond with substrate  108  than substrate  108  would likely form with a composite material (not shown). Although prongle piece  112  may be formed from metal, prongle piece  112  is not limited to being formed from metal. 
     Prongle piece  112  generally includes at least one prongle  116  on a second surface  111 . Although prongles  116  are illustrated as being integrally formed as a part of prongle piece  112 , it should be appreciated that prongles  116  are not limited to being integrally formed as part of prongle piece  112 . In one embodiment, prongle piece  112  may effectively be a single prongle  116 . That is, prongle piece  112  may essentially comprise a single prongle. 
     Prongle piece  112  is arranged to effectively bond to or otherwise engaged with a composite material (not shown). Prongle piece  112  or, more specifically, prongles  116  on prongle piece  112  provide surfaces to which a composite material (not shown) may bond. Through prongle piece  112 , such a composite material (not shown) may bond to substrate assembly  104 .  FIG. 1B  is a diagrammatic representation of an overall assembly that includes substrate assembly  104  and a composite piece bonded to prongle piece  120  of the substrate assembly in accordance with an embodiment of the invention. An overall assembly  100  includes a composite piece  120  that is essentially formed over, or molded over and/or around, prongle piece  112 . Composite piece  120  bonds with prongle piece  112  such that composite piece  120  interlocks with prongle piece  112 . 
     Because prongle piece  112  includes prongles  116  which provide a larger surface area or mechanical interlock for bonding than substrate  108 , the bond between composite piece  120  and prongle piece  112  is generally relatively strong. Further, prongle piece  112  may be formed from a material that is more conducive to the formation of a strong bond between composite piece  120  and prongle piece  112  than the material from which substrate  108  is formed. 
     A substrate piece may include a prongle piece that is integral with a substrate. Alternatively, however, a prongle piece such as prongle piece  112  of  FIGS. 1A and 1B  may be substantially bonded on a substrate, e.g., substrate  108 , to create a substrate assembly, e.g., substrate assembly  104 . For instance, a separate, substantially pre-formed prongle piece may be bonded to a substrate in order to form a substrate assembly, or a prongle piece may effectively be molded onto a substrate. 
       FIG. 2  is a diagrammatic representation of a substrate assembly, e.g., a metal substrate assembly, that includes a separate, substantially pre-formed prongle piece bonded to a substrate in accordance with an embodiment of the invention. A substrate assembly  204  includes a substrate  208  which, in the described embodiment, may be a metal substrate or layer. A prongle piece  212 , which includes at least one prongle  216  or protruding feature, may be bonded to substrate  208  by a bonding layer  224 . 
     Bonding layer  224  may be an adhesive layer which effectively affixes prongle piece  212  to substrate  208 . In lieu of being an adhesive layer, bonding layer  224  may instead be formed by substantially fusing prongle piece  212  to substrate  208 . By way of example, a bottom surface of prongle piece  212  and a top surface of substrate  208  may be heated and then pressed together such that bonding layer  224  is formed. 
       FIG. 3  is a diagrammatic representation of a substrate assembly, e.g., a metal substrate assembly, that includes a prongle piece that is effectively molded onto a substrate in accordance with an embodiment of the invention. A substrate assembly  304  includes a substrate  308 , e.g., a metal substrate, onto which a layer of features  328  are formed. Feature layer  328  may be molded onto substrate  308 , and may effectively provide a template for the formation of a prongle piece  312 . Prongle piece  312 , which includes at least one prongle  316  may be overmolded onto feature layer  328 . A mold (not shown) may be placed over feature layer  328 , and a material such as metal may be introduced into the mold such that prongle piece  312  may be created. 
     In general, as previously mentioned, prongles may be substantially integral to substrate. That is, prongles may effectively be machined onto a metal substrate. For example, etching processes may be used to create prongles on of a metal substrate. However, as discussed above, prongles may instead be associated with an external structure that is bonded to a surface of a metal substrate, or may be otherwise created on a surface of a metal substrate. With reference to  FIGS. 4 and 5 , methods of bonding prongles to the surface of a metal substrate and otherwise creating prongles on a surface of a metal substrate will be described, respectively. 
       FIG. 4  is a process flow diagram which illustrates a method of forming a substrate assembly, e.g., substrate assembly  204  of  FIG. 2 , that include prongles in accordance with an embodiment of the invention. A method  401  of forming a substrate assembly that includes prongles begins at step  405  in which a metal substrate is obtained. The metal substrate may be a metal bezel suitable for use as part of a portable electronic device or a cellular phone device. In one embodiment, the metal substrate may be configured such that the metal substrate includes a flange. 
     After the metal substrate is obtained, a prongle piece is then obtained in step  409 . The prongle piece may be a structure that includes a plurality of prongles or the prongle piece may be a structure that is effectively a single prongle. When the prongle piece is a structure that includes a plurality of prongles, the prongle piece may include a substrate that supports the plurality of prongles. The prongle piece may be formed from metal, e.g., the same metal that forms the metal substrate. It should be appreciated, however, that the prongle piece is not limited to being formed from metal, and may generally be formed from substantially any material which is relatively easily bonded to, and may form a relatively strong bond with, the metal substrate. A prongle piece may be formed, for example, from adhesive materials such as epoxy. In general, prongle piece may be formed from any material which bonds more easily to the metal substrate than a composite material, i.e., the composite material from which a composite piece that is to be molded over the prongle piece is formed. 
     Once the prongle piece is obtained, the prongle piece is bonded to the metal substrate in step  413 . Bonding the prongle piece to the metal substrate may include, but is not limited to including, essentially gluing the prongle piece to the metal substrate using an adhesive material, soldering the prongle piece to the metal substrate, and heating the prongle piece and/or the metal substrate to effectively fuse the prongle piece to the metal substrate. 
     In step  417 , a composite piece may be formed over the prongle piece, e.g., to create an overall structure. The composite piece may be formed over the prongle piece such that the composite piece bonds with the prongles on the prongle piece. When the metal substrate is a bezel of a device, the composite piece may be a thermoplastic piece that is arranged to effectively be bonded to the bezel. The method of forming a substrate assembly is completed after the prongle piece is bonded to the metal substrate or, if an overall structure that includes the substrate assembly is formed, the method is completed after the composite material is formed over the prongle piece. 
       FIG. 5  is a process flow diagram which illustrates a second method of forming a substrate assembly, e.g., substrate assembly  304  of  FIG. 3 , that include prongles in accordance with an embodiment of the invention. A method  501  of forming a substrate assembly begins at step  505  in which a metal substrate is obtained. Once the metal substrate is obtained, a plated surface with features is formed on the metal substrate in step  509 . The plated surface, e.g., an electroformed surface, may be formed using a mold. As will be appreciated by those skilled in the art, electroforming allows parts to be made by plating electroformed material, e.g., nickel or copper, onto surfaces. The features in the plated surface are typically configured to enable prongles to be formed thereon. 
     After the plated surface is formed on the metal substrate, a prongle piece which includes at least one prongle extending therefrom is formed over the plated surface in step  513 . In one embodiment, a composite piece may be formed over the prongle piece, e.g., to create an overall structure, in step  517 . The composite piece may be formed over the prongle piece such that the composite piece bonds with the prongles on the prongle piece. When the metal substrate is a bezel of a device, the composite piece may be a thermoplastic piece that is arranged to effectively be bonded to the bezel. The method of forming a substrate assembly is completed after the prongle piece is bonded to the metal substrate or, if an overall structure that includes the substrate assembly is formed as discussed with respect to step  517 , the method is completed after the composite material is formed over the prongle piece. 
     As previously mentioned, a metal substrate may include a flange. A flange may be arranged to be a part of a lap joint, or an overlapping joint, such that the flange effectively interlocks with a composite piece to form a lap joint. Prongles may be formed on a surface of the flange to facilitate the interlocking of metal substrate to the composite piece.  FIG. 6  is a diagrammatic representation of a joint, e.g., a lap joint, formed between a metal substrate assembly, which includes a flange with prongles on one surface, and a composite piece in accordance with an embodiment of the invention. A joint is formed to effectively bond a metal substrate assembly  604  and a composite piece  620 . The joint, as shown, may be a lap joint in that a portion of composite piece  620  effectively overlaps a flange portion  632  of metal substrate assembly  604 . 
     Prongles  616  are present on a surface of flange portion  632 . Prongles  616  may be bonded to flange portion  632 , or otherwise formed on a surface of flange portion  632 , as for example using the method described above with respect to  FIG. 5 . Alternatively, prongles  616  may be substantially machined onto flange portion  632 . 
     The number of prongles  616 , as well as the size and shape of prongles  616 , may vary widely. In general, prongles  616  have a height that extends from a top surface of flange portion  632  to approximately a top of metal substrate assembly  604 . For example, the height of prongles  616  may be approximately 0.2 millimeters (mm), and the height of flange portion  632  as measured from a bottom surface to a surface at which prongles  616  substantially begin may be approximately 0.2 mm. The overall height of metal substrate assembly  604  may be approximately 0.5 mm. In one embodiment, the length of flange portion  632  may be approximately 3.0 mm. 
     It should be appreciated, however, that the relative heights of prongles  616 , flange portion  632 , and metal substrate assembly  604  may vary widely. By way of example, prongles may have a height of approximately 0.125 mm while flange portion  632  has a height of approximately 0.25 mm and metal substrate assembly  604  has an overall height of approximately 0.5 mm. 
     When a metal substrate assembly includes a flange, prongles are not limited to being formed on a single surface of the flange. By way of example, prongles may be formed on a top surface of a flange as well as on a bottom surface of the flange.  FIG. 7  is a diagrammatic representation of a joint formed between a metal substrate assembly, which includes a flange portion with prongles on a plurality of surfaces, and a composite piece in accordance with an embodiment of the invention. A joint, e.g., a lap joint, is formed to effectively bond a metal substrate assembly  704  and a composite piece  720 . In the embodiment as shown, the joint includes a flange portion  732  of metal substrate assembly  704  and a portion of composite piece  720 . 
     Prongles  716  are present on a top surface and a bottom surface of flange portion  732 . Prongles  716  may be substantially integral with flange portion  732 , e.g., machined onto flange portion  732 , bonded to flange portion  732 , or otherwise formed on flange portion  732 . 
     In one embodiment, prongles may be formed from individual pieces of wire that are bonded, as for example through wire bonding or soldering, to a surface of a metal substrate. Referring next to  FIG. 8 , a joint formed between a metal substrate assembly, which includes prongles that are individual wires bonded to the metal substrate assembly, and a composite piece will be described in accordance with an embodiment of the invention. A joint, which may be a lap joint, is effectively formed as a junction between a metal substrate assembly  804  and a composite piece  820 . The joint may include, as shown, a flange portion  832  of metal substrate assembly  804  and a portion of composite piece  820 . 
     Prongles  816 , in one embodiment, may be formed from lengths of wire that are joined to at least one surface of flange portion  832 . As shown, solder joints  834  effectively couple prongles  816  to two surfaces of flange portion  832 . It should be appreciated that a solder joint  834  and a length of wire may, together, be considered as an overall prongle  816 . 
     As previously mentioned, prongles may be used to efficiently join a metal frame to a composite piece, e.g., a plastic piece, in a portable electronic device. For example, an electronic device may include a metal frame that is to be interfaced with a composite piece.  FIG. 9  is a diagrammatic perspective representation of a device which includes a metal piece with prongles and a composite piece that is bonded to the metal piece through the prongles in accordance with an embodiment of the invention. A device  900  includes metal bezel pieces  904   a ,  904   b , as well as a composite piece  920 . Composite piece  920  is configured to substantially interlock with prongles  916  formed on surfaces of metal bezel pieces  904   a ,  904   b . In one embodiment, composite piece  920  is arranged to be molded or otherwise formed over prongles  916  such that composite piece  920  is essentially joined with both metal bezel piece  904   a  and metal bezel piece  904   b.    
     When prongles  916  are included in metal bezel pieces  904   a ,  904   b , the joint formed by joining composite piece  920  to bezel piece  904   a  and the joint formed by joining composite piece  920  to bezel piece  904   b  are relatively strong due, at least in part, to the amount of surface area associated with the bonds associated with the joints. Further, as shown, composite piece  920  is bonded to metal bezel pieces  904   a ,  904   b  within the thickness of metal bezel pieces  904   a ,  904   b . Bonding composite piece  920  to metal bezel pieces  904   a ,  904   b  within the thickness of metal bezel pieces  904   a ,  904   b  allows joints that are formed to occupy substantially no internal volume of device  900  and substantially no external volume of device  900 . Although only a few embodiments of the invention have been described, it should be understood that the invention may be embodied in many other specific forms without departing from the spirit or the scope of the invention. By way of example, the size and shape of prongles, as well as the number of prongles formed on a substrate, may vary widely. A prongle may be, in one embodiment, a ball of solder provided on a substrate. In general, the size, shape, and number of prongles may be dependent on a number of factors including, but not limited to including, the size of an assembly that includes a metal piece bonded to a composite piece. 
     While a metal substrate with prongles has been described as being a metal bezel of an electronic device such s a portable electronic device, and a composite piece has been described as a thermoplastic piece of the device that is to be bonded to the metal bezel, it should be appreciated that a metal substrate with prongles is not limited to being a part of an electronic device. Prongles may generally be used to efficiently join two different pieces in any device or structure. 
     A composite piece or layer has been described as molded over or interlocked with prongles of a substrate assembly. When the composite piece is molded over or interlocked with prongles, composite piece is effectively formed over and around prongles, as shown for example in  FIG. 1A . Generally, a composite piece may be cast over and around, shaped over and around, sculpted over and around, and/or positioned over and around prongles. 
     In general, the steps associated with the methods of the invention may vary widely. Steps may be added, removed, altered, combined, and reordered without departing from the spirit or the scope of the invention. 
     The various aspects, features, embodiments or implementations of the invention described above may be used alone or in various combinations. 
     While this specification contains many specifics, these should not be construed as limitations on the scope of the disclosure or of what may be claimed, but rather as descriptions of features specific to particular embodiment of the disclosure. Certain features that are described in the context of separate embodiments may also be implemented in combination. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. 
     In one embodiment, the components, process steps, and/or data structures may be implemented using various types of operating systems, computing platforms, computer programs, and/or general purpose machines. In addition, those of ordinary skill in the art will recognize that devices of a less general purpose nature, such as hardwired devices, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), or the like, may also be used without departing from the scope and spirit of the inventive concepts disclosed herein. 
     While embodiments and applications have been shown and described, it would be apparent to those skilled in the art having the benefit of this disclosure that many more modifications than mentioned above are possible without departing from the inventive concepts herein.