PATENT DOCUMENT

Publication Number: US-10280516-B2
Application Number: US-201414280462-A
Country: US
Kind Code: B2

Title: Encapsulation of a stiffener layer in aluminum

Abstract:
The described embodiments relate to methods and apparatus for increasing rigidity of a metal housing while maintaining or reducing a wall thickness of the metal housing. More particularly a method for embedding a stiffener layer within an aluminum substrate is discussed. In one exemplary embodiment the stiffener layer can be a carbon fiber sheet applied to an inside surface of an unfinished housing and then subsequently covered by depositing a layer of aluminum over the carbon fiber in a solid-state deposition process. The deposited aluminum can adhere to the unfinished housing around or through the carbon fiber layer to bond with the unfinished housing. Deposition parameters can be controlled to prevent damage to the carbon fiber sheet.

Claims:
What is claimed is: 
     
       1. An apparatus, comprising:
 an aluminum substrate having a first surface; 
 a stiffener layer comprising carbon fiber abutting the first surface of the aluminum substrate, wherein the stiffener layer includes a plurality of openings; and 
 an aluminum layer deposited over the stiffener layer and through the plurality of openings to adhere to and directly contact the aluminum substrate, wherein the aluminum layer and the aluminum substrate encapsulate the stiffener layer. 
 
     
     
       2. The apparatus of  claim 1 , wherein the stiffener layer includes a plurality of rows of openings. 
     
     
       3. The apparatus of  claim 2 , wherein the aluminum layer resides within the openings of each of the plurality of rows of openings. 
     
     
       4. The apparatus of  claim 1 , wherein a cross-section of the stiffener layer includes pyramidal shapes. 
     
     
       5. The apparatus of  claim 1 , wherein a thickness of the aluminum substrate at a portion where the stiffener layer abuts the aluminum substrate is thicker than the stiffener layer. 
     
     
       6. The apparatus of  claim 1 , wherein a cross-section of the stiffener layer includes right angles. 
     
     
       7. The apparatus of  claim 1 , wherein the first surface comprises at least one pocket or cavity for receiving the stiffener layer and subsequently the aluminum layer. 
     
     
       8. A method for making the apparatus of  claim 1 , the method comprising:
 applying the stiffener layer comprising carbon fiber and including a plurality of openings against the first surface of the aluminum substrate by using an adhesive to bond the stiffener layer to the first surface of the aluminum substrate; 
 depositing the aluminum layer over the stiffener layer such that the aluminum layer adheres to and directly contact the aluminum substrate through the plurality of openings of the stiffener layer; and 
 machining material away from a second surface of the aluminum substrate that opposes the first surface of the aluminum substrate, wherein the stiffener layer reinforces the second surface of the aluminum substrate during the machining. 
 
     
     
       9. The method of  claim 8 , wherein the plurality of openings are filled by the deposited aluminum layer. 
     
     
       10. The method of  claim 8 , further comprising anodizing the aluminum substrate. 
     
     
       11. The method of  claim 8 , wherein the stiffener layer has a plurality of rows of openings therethrough. 
     
     
       12. The method of  claim 8 , further comprising:
 arranging additional components adjacent to the stiffener layer for embedding with the stiffener layer.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Application No. 61/901,221, entitled “ENCAPSULATION OF A STIFFENER LAYER IN ALUMINUM” filed Nov. 7, 2013, the content of which is incorporated herein by reference in its entirety for all purposes. 
    
    
     FIELD 
     The described embodiments relate generally to reducing a weight of a device housing without adversely affecting its structural integrity. More specifically a method for embedding a stiffening layer within a metal substrate is disclosed. 
     BACKGROUND 
     As makers of electronic devices attempt to continually make devices increasingly smaller, innovative ways of reducing the weight of devices has become progressively more difficult to achieve. For example, while the overall weight of a device enclosure can be reduced by commensurably reducing the thickness of device enclosure walls, the reduction in wall thickness can reduce the ability of the enclosure to withstand normal handling. Accordingly, the walls will require a certain minimum wall thickness or rigidity to maintain a minimum structural integrity of the enclosure. 
     SUMMARY 
     This paper describes various embodiments that relate to reducing the weight of a device housing without adversely affecting the structural integrity of the device housing. In one embodiment, an apparatus is set forth as having a metal substrate and a stiffener layer made of carbon fiber that abuts the metal substrate. Additionally, the apparatus includes a cold sprayed layer, wherein the cold sprayed layer and metal substrate encapsulate the stiffener layer. 
     In another embodiment, a computing device housing is set forth. The computing device housing can include an aluminum substrate comprising a recess. Further, the computing device housing can include a stiffener layer made of carbon fiber residing within the recess of the aluminum substrate. Additionally, the computing device housing can include a cold sprayed layer residing within the recess of the aluminum substrate, wherein the aluminum substrate and cold sprayed layer completely encapsulate the stiffener layer. 
     In yet another embodiment, a method is set forth for encapsulating a stiffener layer within an aluminum substrate of a device housing to improve rigidity of the device housing. The method can include a step of applying the stiffener layer against a first surface of the aluminum substrate. The method can further include a step of depositing a layer of material over the stiffener layer such that the aluminum substrate and the layer of material cooperate to encapsulate the stiffener layer. Additionally, the method can include machining material away from a second surface of the aluminum substrate that opposes the first surface of the aluminum substrate. In this way, the stiffener layer can reinforce the second surface of the aluminum substrate during the machining operation. 
     Other aspects and advantages of the invention 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 described embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The described embodiments may be better understood by reference to the following description and the accompanying drawings. Additionally, advantages of the described embodiments may be better understood by reference to the following description and accompanying drawings in which: 
         FIGS. 1A-1C  show a series of cross-sectional views illustrating a method for embedding a composite material in a metal substrate; 
         FIGS. 2A-2C  show a series of cross-sectional views illustrating an alternative method for embedding a composite material in a metal substrate; 
         FIGS. 3A-3G  show various patterns of a composite layer that can be utilized with the described embodiments; 
         FIGS. 4A-4B  show various embodiments for machining a pattern of pockets from an inside surface of the enclosure to reduce weight of an enclosure; 
         FIGS. 5A-5B  show how a composite matrix can be laminated across a number of pockets; and 
         FIG. 6  shows a flow diagram illustrating a method for embedding a composite material within a metal substrate. 
     
    
    
     DETAILED DESCRIPTION 
     Representative applications of methods and apparatus according to the present application are described in this section. These examples are being provided solely to add context and aid in the understanding of the described embodiments. It will thus be apparent to one skilled in the art that the described embodiments may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order to avoid unnecessarily obscuring the described embodiments. Other applications are possible, such that the following examples should not be taken as limiting. 
     In the following detailed description, references are made to the accompanying drawings, which form a part of the description and in which are shown, by way of illustration, specific embodiments in accordance with the described embodiments. Although these embodiments are described in sufficient detail to enable one skilled in the art to practice the described embodiments, it is understood that these examples are not limiting; such that other embodiments may be used, and changes may be made without departing from the spirit and scope of the described embodiments. 
     Thin-walled metal housings of computing devices can be susceptible to denting and can in certain cases show machining artifacts where housing walls are cut overly thin. Structural weakness of this sort can cause undesirable blemishes to appear on an outside surface of the computing device and in severe cases can cause internal damage to components within the housing. One way to alleviate such concerns is to add a stiffening layer to the housing. Unfortunately, stiffening layers can cause other problems such as additional fabrication complexities, and in some cases problems with finishing processes. In housings made of solid aluminum, conventional anodization produces predictable results; however, if an internal stiffening layer such as carbon fiber is exposed to the chemical bath used to create an anodization layer, the chemicals can have an adverse reaction with the stiffener layer, that can contaminate the bath and/or reduce structural integrity of the internal stiffening layer. One way to eliminate these kinds of surface treatment problems is to embed the stiffener layer within the metal housing. 
     The stiffener layer can be embedded within the metal housing (e.g., aluminum) by utilizing a solid-state deposition process, such as cold spray. Cold spraying involves accelerating and cooling small metal particles that plastically deform against a substrate to form a metal layer. Since finishing processes can be applied to the formed metal layer created by a cold spray process, the stiffener layer can be applied along an outside or inside surface of the enclosure to abut the surface, and then be subsequently covered by cold spray to match a look and feel of the enclosure. A material makeup of the cold spray can be adjusted to match a cosmetic look of the housing. When the stiffener layer is lighter and/or stronger than the metal to which it is affixed, a wall thickness of the enclosure can be reduced and/or strengthened. It should be noted that many forms of physical vapor deposition are also compatible with the disclosed embodiments. For example, sputter deposition, pulsed laser deposition, and evaporative deposition can all be utilized in lieu of cold spray. In other embodiments, an anodization resistant layer of epoxy or plastic can be used to cover the stiffener. Regardless of the manufacturing method, additional components can be added between the enclosure and the deposited layer. For example, cable runs, chip mounts, grounding paths or even antenna windows can be encapsulated along with the stiffener layer. 
     These and other embodiments are discussed below with reference to  FIGS. 1A-6 ; however, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes only and should not be construed as limiting. 
       FIGS. 1A-1C  show illustrations depicting a process for embedding a stiffener layer within a metal housing of a computing device (e.g., laptop, personal computer, cellular phone, media player, etc.). The stiffener layer can be a composite along the lines of carbon fiber or carbon fiber reinforced plastic and the housing can be formed from an aluminum alloy. It should be noted that these examples are for explanatory purposes only and the described embodiments can be applied to multiple configurations. For example, another composite material such as fiberglass could also be utilized in lieu of carbon fiber or carbon fiber reinforced plastic.  FIG. 1A  shows a housing  100  having stiffener layer  102  in contact with an inside layer of housing  100 . In some embodiments, stiffener layer  102  can be adhesively coupled to housing  100 .  FIG. 1B  shows cold spray layer  104  covering stiffener layer  102 . Portions of cold spray layer  104  can adhere to portions of housing  100  with which it is in direct contact. In some cases, cold spray layer  104  can adhere to housing  100  through stiffener layer  102 . A temperature, particle size, and velocity of the cold spray deposition method can be adjusted to prevent damage to stiffener layer  102  during deposition of the cold spray. For example, larger particle sizes are less likely to deform, higher temperatures are better for plastic deformation, and high velocities, in some cases, can cause damage to stiffener layer  102 .  FIG. 1C  shows how an outside surface of housing  100  can be machined away, thereby leaving a thin housing wall thickness supported by stiffener layer  102 . Stiffener layer  102  can provide increased rigidity and reduced weight for housing  100 . Furthermore, stiffener layer  102  can provide increased rigidity to housing  100  allowing housing  100  to be thinned to a thickness that would not otherwise be achievable without the added stiffness introduced by carbon fiber layer  102 . In one specific embodiment, the resulting housing can have the following dimensions: a thickness A of housing  100  can be between 0.3-0.4 mm, a thickness B of stiffener layer  102  can be about 0.3-0.4 mm, and a thickness C of cold spray layer  104  can be about 0.1-0.2 mm. 
       FIGS. 2A-2C  show illustrations depicting another process for embedding stiffener layer  202  disposed along an inside surface of housing  200 .  FIG. 2A  shows a stiffener layer  202  disposed along an inside surface of housing  200 . Stiffener layer  202  has a number of apertures  204  disposed there through.  FIG. 2B  shows cold spray layer  206  deposited over stiffener layer  202 . Portions of cold spray layer  206  lodged within apertures  204  can enhance adhesion between cold spray layer  206  and housing  200 . Furthermore, adverse effects on overall conductivity of housing  200  can be reduced by creating electrically conductive pathways arranged through the portions of the cold spray layer  206  disposed through apertures  204 . In some cases, this can increase an effectiveness of chassis ground of housing  200 . Electrical components can also be arranged in apertures  204  prior to cold spray layer  206  being deposited, thereby improving the functionality of the housing  200 . In some embodiments, cavities or pockets can be created in housing  200  for receiving stiffener layer  202 , and subsequently receiving cold spray layer  206 . 
       FIGS. 3A-3F  show alternate configurations for a stiffener layer suitable for use with the described embodiments. In these configurations, each of the depicted stiffener layers can be a carbon fiber layer having a modulus of elasticity of between about 200-300 GPa. Furthermore, the depicted layers can be constructed from multiple carbon fiber sheets oriented in an isotropic alignment (e.g. 0-45-0). In some embodiments, an overall thickness of the depicted carbon fiber layers can be about 0.3-0.4 mm.  FIG. 3A  shows a carbon fiber layer  300  without holes having a width W and length L. In some embodiments, W can be about 22 mm while L can be about 152 mm. It should be appreciated that the carbon fiber layers can have greatly varying sizes and shapes depending on a substrate with which they are designed to be used.  FIG. 3B  shows a carbon fiber layer  310  having a grid of openings. Openings  312  can be arranged in rows at a pitch P 1  of about 7.6 mm. Openings  312  can have a diameter of about 2 mm.  FIG. 3C  shows a carbon fiber layer  320  having openings  322  having a diameter of about 2 mm with a pitch P 2  of about 30 mm.  FIG. 3D  shows a carbon fiber layer  330  having a number of openings  332  with a diameter of about 5 mm and a pitch P 3  of about 20 mm.  FIG. 3E  shows a carbon fiber layer  340  having a number of rectangular openings  342  creating a rib structure. In some embodiments, a size of rectangular openings  342  can be adjusted to tune a stiffness of carbon fiber layer  340 .  FIG. 3F  shows top and side views of carbon fiber layer  350  having a three dimensional geometry with pyramid style embossments. In some embodiments, the three dimensional geometry or the cross section thereof can resemble a sphere, pyramid, semi-circle, rectangle, right angles, sinusoidal plane, exponential plane, and the like. The pyramid style embossments can enhance stiffness of carbon fiber layer  350 . The three dimensional geometry of carbon fiber layer  350  can cause a height H of carbon fiber layer  350  to vary. In some embodiments, a maximum height H of carbon fiber layer  350  can be between about 0.3 mm and 0.4 mm. As depicted, a top surface of carbon fiber layer  350  can be substantially planar to allow for bonding of carbon fiber layer  350 .  FIG. 3G  shows top and side views of carbon fiber layer  360  arranged in a grid pattern with a carbon fiber top sheet  364  disposed over a top portion of the layer. In some embodiments, top sheet  364  can be about 0.1 mm thick. Moreover, the shapes and patterns illustrated in  FIGS. 3A-3F  can be combined or arranged in any suitable configuration for purposes of strengthening a housing while reducing the weight of the housing. 
       FIG. 4A-4B  show various embodiments of housings having a number of pockets machined from an inside surface of the housing.  FIG. 4A  shows a triangular pattern of pockets etched from an inside surface of housing  400 . By etching the triangular pattern, an overall weight of the housing can be reduced while structural integrity of housing  400  can be substantially maintained.  FIG. 4B  shows a rectangular pattern of pockets etched from housing  410 . The rectangular pattern can also be operable to reduce a weight while maintaining structural integrity of housing  410 . In other embodiments, a number of circular patterns could be etched in an exemplary housing to achieve a similar weight reduction purpose. In some embodiments, the pattern of pockets can be etched by way of a chemical etching process.  FIGS. 5A-5B  show another embodiment in which the pocket patterns in  FIGS. 4A-4B  are overlaid by a stiffener layer. In some embodiments, the stiffener layer can be laminated to an inside surface of the housings, such that it overlays the pockets and improves an overall structural integrity of the housing. 
       FIG. 6  shows a flow chart depicting a method  600  for embedding a stiffener layer in a metal housing (e.g., an aluminum housing). At a first step  602 , a billet of aluminum is obtained. The aluminum billet can be formed by an extrusion process. The aluminum can also be produced in other manners such as by rolling, casting, stamping, forging, or electrochemical machining. In step  604 , a stiffener layer is arranged against a first surface of the aluminum billet. In some embodiments, the stiffener layer is arranged across an inside surface of the aluminum billet. In some embodiments, the stiffener layer is adhesively coupled to the surface of the aluminum billet. It should be noted that the stiffener layer could have various embodiments. In some implementations, the stiffener layer can be made up of a number of carbon fiber sheets having fibers aligned in various different directions. In other implementations, the stiffener layer can have a pattern of holes disposed there through. The stiffener layer could be made of a number of different materials, such as plastic, or metal (e.g. steel, stainless steel, titanium, etc.). The stiffener layer can also include a hollow or foam layer in some embodiments that reduces an overall density of the stiffener. 
     In step  606 , a layer of aluminum is deposited over the carbon fiber layer, such that the carbon fiber is embedded between the deposited layer of aluminum and the aluminum billet. The aluminum can be deposited by any number of different solid-state deposition methods. In some embodiments, a finishing operation such as buffing, polishing or lapping operations can be applied to the deposited aluminum. The finishing operation can be operable to expose portions of the carbon fiber, or even to allow additional materials to be welded to the encapsulated carbon fiber layer. In step  608 , machining aluminum away from a second surface of the aluminum billet can reduce a thickness of the aluminum billet. The second surface of the aluminum billet can be disposed opposite the first surface. The thickness reduction of the aluminum billet can be a portion of a forming process to produce a device housing from the aluminum billet. Inclusion of the stiffener layer within the housing can produce a housing having improved rigidity when compared with an aluminum alloy housing of similar shape and size. It should also be noted that a subsequent anodization process could cause 10-20 microns of an outside surface of the resulting device housing to be converted to an Aluminum Oxide layer. In some embodiments, a portion of the deposited aluminum layer can undergo a finishing process. In some cases, portions of the aluminum can be removed to uncover portions of the stiffener layer. Furthermore, in some cases additional material or components can be welded to the composite layer. 
     The various aspects, embodiments, implementations or features of the described embodiments can be used separately or in any combination. Software, hardware or a combination of hardware and software can implement various aspects of the described embodiments. The described embodiments can also be embodied as computer readable code on a computer readable medium for controlling manufacturing operations or as computer readable code on a computer readable medium for controlling a manufacturing line. The computer readable medium is any data storage device that can store data, which can thereafter be read by a computer system. Examples of the computer readable medium include read-only memory, random-access memory, CD-ROMs, HDDs, DVDs, magnetic tape, and optical data storage devices. The computer readable medium can also be distributed over network-coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of specific embodiments are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the described embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.

Metadata:
Filing Date: 20140516
Publication Date: 20190507
Grant Date: 20190507
Priority Date: 20131107
Inventors: CHAN, Collin D.
CROWLEY, MATTHEW W.
RUNGE, JUDE MARY
Assignee: APPLE INC
CPC Classifications: [{"code": "Y10T428/24331", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/30", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/2495", "inventive": false, "first": false, "tree": "[]"}, {"code": "C25D11/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/022", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T428/13", "inventive": false, "first": false, "tree": "[]"}, {"code": "C23C24/04", "inventive": true, "first": true, "tree": "[]"}, {"code": "C25D11/022", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/022", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T428/30", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/24331", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/181", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1656", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T428/13", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/2495", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/30", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/24331", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/13", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/2495", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/181", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1656", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C24/04", "inventive": true, "first": true, "tree": "[]"}, {"code": "C25D11/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C24/04", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 53007254