PATENT DOCUMENT

Publication Number: US-9985345-B2
Application Number: US-201514971791-A
Country: US
Kind Code: B2

Title: Methods for electrically isolating areas of a metal body

Abstract:
Unitary structures having conductive portions electrically separated by non-conductive portions are described. In some embodiments, the non-conductive portions are made of metal oxide. In some embodiments, the method involves an oxidizing process adapted to convert an entire thickness at a selected portion of a metal substrate to a metal oxide, thereby creating metal portions that are electrically isolated from one another. In some embodiments, the thickness of the metal substrate is reduced at certain regions prior to oxidizing in order to provide a sufficiently thin metal for complete oxidization through the entire thickness. In some embodiments, the oxidizing process involves a plasma electrolytic oxidation process. In some embodiments, the plasma is concentrated at certain regions of the substrate for preferential oxidation. Applications for the substrate include enclosures and electrical components for electronic devices that use radio frequency communication.

Claims:
What is claimed is: 
     
       1. An enclosure for an electronic device, the enclosure comprising:
 a unitary body including:
 a metal substrate having a first thickness and formed of an oxidizable metal, the metal substrate having a first external surface separated from a second external surface by a channel, wherein the channel is defined by lateral walls that extend away from the first and second external surfaces to a bottom wall of the channel that has a second thickness that is less than the first thickness; and 
 a metal oxide layer that covers at least a portion of the bottom wall of the channel, the metal oxide layer separating the metal substrate into first and second metal portions that correspond to the first and second external surfaces, respectively, wherein the metal oxide layer has the second thickness and an external surface corresponding to a surface of the bottom wall. 
 
 
     
     
       2. The enclosure of  claim 1 , wherein the enclosure includes an electronic component, and the metal oxide layer is generally radio frequency transparent such that electromagnetic signals generated by the electronic component are transmittable through the metal oxide layer while being blocked by the first and second metal portions. 
     
     
       3. The enclosure of  claim 1 , wherein the first and second metal portions border the metal oxide layer, and the first and second metal portions have the second thickness. 
     
     
       4. The enclosure of  claim 1 , wherein the first and second metal portions are electrically conductive. 
     
     
       5. The enclosure of  claim 1 , wherein the metal oxide layer is isolated within the channel. 
     
     
       6. An enclosure for an electronic device, the enclosure comprising:
 a unitary metal substrate having a channel that defines a first metal portion having a first thickness and a second metal portion having a second thickness, the channel defined by sidewalls that extend into the unitary metal substrate and terminate at a bottom wall, the bottom wall having a thickness that is less than either of the first or second thicknesses, and wherein the bottom wall includes a metal oxide layer having the thickness of the bottom wall and a length of the channel. 
 
     
     
       7. The enclosure of  claim 6 , wherein the bottom wall further includes a non-oxidized metal layer in addition to the metal oxide layer. 
     
     
       8. The enclosure of  claim 7 , wherein the metal oxide layer is confined within the channel by the non-oxidized metal layer. 
     
     
       9. The enclosure of  claim 6 , wherein the metal oxide layer has a size and shape that corresponds to a shape and size of the channel. 
     
     
       10. The enclosure of  claim 6 , wherein the first and second metal portions are electrically conductive. 
     
     
       11. The enclosure of  claim 6 , wherein the enclosure includes an antenna capable of generating radio frequency (RF) signals, and the metal oxide layer is transparent to the RF signals. 
     
     
       12. The enclosure of  claim 6 , wherein an anodized layer covers the first metal portion, the second metal portion, and the metal oxide layer. 
     
     
       13. The enclosure of  claim 12 , wherein an external surface of the anodized layer includes dyed color particles. 
     
     
       14. A method of forming an enclosure for an electronic device, the enclosure including a metal substrate having a first metal portion and a second metal portion, the method comprising:
 forming a metal oxide layer over a bottom wall of the metal substrate that defines a channel that separates the first metal portion having a first thickness and the second metal portion having a second thickness, the channel defined by walls that extend from the first and second metal portions into the metal substrate and terminate at the bottom wall, wherein the bottom wall has a thickness that is less than either of the first or second thicknesses, and the metal oxide layer has an external surface corresponding to a surface of the bottom wall. 
 
     
     
       15. The method of  claim 14 , wherein, prior to forming the metal oxide layer over the bottom wall, the method further comprises:
 masking the first and second metal portions while leaving the bottom wall unmasked; 
 immersing the metal substrate in an electrolytic solution; and 
 applying an electric potential to the metal substrate. 
 
     
     
       16. The method of  claim 15 , further comprising:
 prior to applying the electric potential to the metal substrate, thinning the metal substrate at a location corresponding to the channel. 
 
     
     
       17. The method of  claim 14 , wherein the metal oxide layer includes metal oxide material that is radio frequency (RF) transparent. 
     
     
       18. The method of  claim 14 , wherein the first and second metal portions are electrically conductive. 
     
     
       19. A metal substrate, comprising:
 separate metal portions and channels that are arranged according to a pattern, such that at least one channel is disposed between at least two of the metal portions, wherein the at least one channel is defined by (i) peripheral metal portions, and (ii) a dielectric metal oxide portion bordered by the peripheral metal portions, thereby effectively electrically isolating the metal portions from each other such as to enable operation of an antenna that is enclosed by the metal portions. 
 
     
     
       20. The metal substrate of  claim 19 , wherein the operation of the antenna includes at least one of transmitting or receiving a radio-frequency signal.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority under 35 U.S.C § 119(e) to U.S. Provisional Application No. 62/146,155, entitled “METHODS FOR ELECTRICALLY ISOLATING AREAS OF A METAL BODY,” filed on Apr. 10, 2015, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     FIELD 
     The described embodiments relate generally to methods of forming unitary structures by rendering portions of a metal substrate non-conductive, thereby creating conductive regions that are electrically isolated from each other. The methods can be use in various applications, including forming electrically isolated portions of electronic devices, such as enclosures and housing for electronic devices. 
     BACKGROUND 
     Many computing devices have outer enclosures and coverings with metallic surfaces that give the device enclosures an aesthetically pleasing look and feel, as well as a high durability. Computing devices also generally include any of a number of complex functional components. For example, many mobile phones, tablets and laptops have radio frequency antennas that allow communication via radio frequency transmission. 
     One design challenge associated with computing devices is maintaining a sleek and consistent appearance of a metallic enclosure for housing the various complex internal components. Since metal is not radio frequency transmissive, metal is generally a poor choice of material when the devices utilize radio frequency transmission for communication. In addition, metal is generally a high capacitive material, and as a result, not used to cover capacitive touch pads, touch screens and other capacitive sensors. Accordingly, portions of the enclosures that cover antennas and touch sensors are typically made of a non-metallic material such as plastic or glass. Unfortunately, plastic surfaces and glass surfaces can have different visual and tactile qualities than metallic surfaces, which can result in a visible and tactile break in the metallic surface of the enclosures. These visible breaks can detract from the smooth and continuous look of the metallic enclosures. 
     SUMMARY 
     This paper describes various embodiments that relate to forming metallic structures having electrically isolated portions that are separated by non-conductive portions. In particular embodiments, oxidation techniques are used to form metal oxide portions within a bulk metal substrate. 
     An enclosure for an electronic device is described. The enclosure includes a unitary structure. The unitary structure includes a substrate formed of a metal and having a first portion electrically isolated from a second portion by an insulating portion formed of the metal having been rendered electrically insulative. 
     According to another embodiment, an enclosure for an electronic device is described. The enclosure includes a substrate defined by a thickness. The substrate has a first metal portion, a second metal portion and an intervening portion positioned between the first and second metal portions. An entirety of the thickness of the substrate at the intervening portion is comprised of metal oxide material such that the first metal portion is electrically separated from the second metal portion. 
     According to another embodiment, a method of oxidizing a metal substrate is described. The method includes masking a first portion and a second portion of the metal substrate with a mask such that an intervening portion between the first portion and the second portion is unmasked. The method also includes immersing the metal substrate in an electrolytic solution. The method further includes applying an electric potential to the metal substrate while immersed in the electrolytic solution. The electric potential is sufficiently high to cause electrical discharge and formation of an associated plasma that converts the intervening portion of the metal substrate to a metal oxide material. An entire thickness of the metal substrate at the intervening portion is converted to the metal oxide material such that the first portion is electrically separated from the second portion. 
     According to a further embodiment, a substrate characterized has having a thickness is described. The substrate includes a first metal portion, a second metal portion and an intervening portion positioned between the first and second metal portions. The intervening portion is characterized as being non-electrically conductive. An entirety of the thickness of the substrate at the intervening portion is comprised of metal oxide material such that the first metal portion is electrically separated from the second metal portion. 
     These and other embodiments will be described in detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements. 
         FIGS. 1A-1C  show a back view of an enclosure of an electronic device that can be formed using methods described herein. 
         FIG. 2  shows a structure that can be formed using methods described herein. 
         FIGS. 3A-3D  show cross section views of a portion of a substrate undergoing an oxidation process in accordance with some embodiments. 
         FIGS. 4A and 4B  show an apparatus that can be used to perform a PEO process, in accordance with some embodiments. 
         FIG. 5  shows a perspective view of a substrate after undergoing an oxidizing process, in accordance with some embodiments. 
         FIGS. 6A-6D  show cross section views of a portion of a substrate undergoing pre-oxidizing and oxidizing processes to achieve metal oxide portions that look similar to metal portions of the substrate, in accordance with some embodiments. 
         FIG. 7  shows a substrate, which includes a translucent metal oxide portion formed using an oxidizing process, in accordance with some embodiments. 
         FIGS. 8A-8C  show perspective cross section views of portions of a substrate having undergone a pre-oxidizing thinning process, in accordance with some embodiments. 
         FIG. 9  shows a flowchart indicating an oxidizing process for forming electrically isolated areas within a part, in accordance with some embodiments. 
         FIG. 10  shows a flowchart indicating a high level process for forming electrically isolated areas within a part, in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to representative embodiments illustrated in the accompanying drawings. It should be understood that the following descriptions are not intended to limit the embodiments to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as can be included within the spirit and scope of the described embodiments as defined by the appended claims. 
     The following disclosure relates to forming a non-electrically conductive portion within a metal substrate such that electrically isolated conductive portions are formed within a unitary structure. In some embodiments, the unitary structures are formed by co-extruding and/or molding a non-electrically conductive material with an electrically conductive material. In some embodiments, the non-electrically conductive portions are metal oxide portions formed by oxidizing select portions of a metal substrate. In some cases, the non-electrically conductive portions are radio frequency (RF) transmissive or transparent, meaning they allow RF waves to pass though substantially uninterrupted. In some applications, the unitary structures are used to form enclosures for electronic devices that include RF antennas. The non-electrically conductive portions of the enclosure can allow RF communication to and/or from the RF antennas housed within the enclosures. 
     In embodiments where the non-electrically conductive portions are made of metal oxide, the metal oxide material can be formed using any suitable technique. In some embodiments, the metal oxide is formed using one or more anodizing processes. In general, anodizing is an electrolytic process that involves converting a portion of a metal substrate, typically a top layer of the metal substrate, to a corresponding metal oxide layer. The anodizing methods described herein can be adapted to anodize select portions of a metal substrate through an entire thickness of the metal substrate instead of only providing a top coating to the metal substrate. This way, adjacent metal portions can become electrically isolated from one another. In some embodiments the oxidizing process involves plasma electrolytic oxidation (PEO) techniques. Like anodizing, PEO is an electrochemical process. However, PEO usually involves applying higher potentials to a metal substrate compared to conventional anodizing processes. The high potential causes discharged to occur, which results in the formation of plasma that oxidizes the metal substrate to a corresponding metal oxide. This generally allows for formation of metal oxide with greater thicknesses compared to metal oxides using anodizing. In some embodiments, an anodizing and a PEO process are used in combination. 
     In some embodiments, portions of the metal substrates are masked prior to exposure to an oxidizing process (e.g., anodizing or PEO). The portions of the metal substrate that are not masked are oxidized and converted to corresponding metal oxide material, while the masked portions remain in metal form. The unmasked portion of the metal substrate can be oxidized through an entire thickness of the substrate, thereby electrically separating the metal portions. In some PEO embodiments, the plasma is concentrated at certain regions of the substrate such that specified portions of the metal substrate are oxidized. This can be done in addition to or instead of masking the substrate. 
     Methods described herein are well suited for providing cosmetically appealing and/or functional portions of consumer products. For example, the methods described herein can be used to form metal enclosures or portions of metal enclosures for electronic devices, such as computers, portable electronic devices, wearable electronic devices and electronic device accessories, such as those manufactured by Apple Inc., based in Cupertino, Calif. 
     These and other embodiments are discussed below with reference to  FIGS. 1A-10 . 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. 
     Methods described herein can be used to form metal structures having electrically isolated metal portions separated from each other by intervening non-metal portion. In some embodiments, the non-metal portions are made of metal oxide, which is substantially non-electrically conductive. Note that as used herein, the terms “oxide,” and “metal oxide,” “metal oxide material,” and “oxide material” can be used interchangeably. The metal structures can serve as cosmetic and/or functional members for any of a number of suitable applications. 
     In some applications, the metal structures serve as housings or enclosures of electronic devices. For example,  FIG. 1A  shows a back view of enclosure  101  of an electronic device  100 , such as a mobile phone, prior to treatment in accordance with some methods described herein. Enclosure  101  can be made of any suitable electrically conductive material, such as metal. In some embodiments, enclosure  101  is made of a metal material, such as aluminum or aluminum alloy, that can be oxidized to form a durable metal oxide. Electronic device  100  can include one or more RF antennas (not shown) positioned within enclosure  101  and configured to transmit and/or receive RF signals. For example, RF antennas may be positioned proximate to ends  103  and  105  of electronic device  100 . In some embodiments, enclosure  101  is anodized such that a protective and cosmetically appealing metal oxide layer is formed on exposed surfaces of enclosure  101 . 
       FIGS. 1B and 1C  show enclosure  101  after portions of enclosure  101  are electrically separated.  FIG. 1B  shows a back view and  FIG. 1C  shows cross section A-A view of enclosure  101 . As shown, electrically conductive or metal portions  102 ,  104  and  106  are separated from one another by non-electrically conductive or non-metal portions  108  and  110 . Non-metal portions  108  and  110  can also be referred to as an electrically insulating portion. Non-metal portions  108  and  110  can be RF transparent in order to allow transmission of RF signals to and/or from antenna(s) housed within enclosure  101 . In this way, non-metal portions  108  and  110  can sometimes be referred to as RF windows, segments or lines. RF transparent materials can be non-conductive materials such as glass, plastic or ceramic (e.g. metal oxide). Methods described herein can be used to form non-metal portions  108  and  110  that are unitarily formed with metal portions  102 ,  104  and  106 . For example, non-metal portions  108  and  110  can co-extruded with metal portions  102 ,  104  and  106  using an extruding process. In some embodiments, non-metal portions  108  and  110  and metal portions  102 ,  104  and  106  are molded together using a molding process. In some embodiments, a co-extrusion and molding operation are used in combination. The co-extruding and/or molding process can be customized such that any seams between non-metal portions  108  and  110  and metal portions  102 ,  104  and  106  are visually and tactilely unperceivable to a user of electronic device  100 . For example, enclosure  101  can be finished after the co-extrusion and/or molding process to smooth out thickness variations of non-metal portions  108  and  110  and metal portions  102 ,  104  and  106 . 
     In some embodiments, non-metal portions  108  and  110  are formed by converting selected portions of enclosure  101  to a corresponding metal oxide using an oxidizing process, such as anodizing or PEO. Metal oxide is generally non-conductive and sufficiently RF transparent to allow RF signals to pass therethrough, and therefore can be used as a suitable RF window or segment material for device  100 . Since the oxidizing process is a conversion process, non-metal portions  108  and  110  can be integrally formed with metal portions  102 ,  104  and  106  such that transitions between non-metal portions  108  and  110  and metal portions  102 ,  104  and  106  are virtually seamless. This can improve the look and feel of enclosure  101 . In addition, the manufacturing process for forming enclosure  101  can be simplified since enclosure  101  can be formed from a single metal piece instead of three separate pieces. That is, conventional methods for forming enclosure  101  can include forming metal portions  102 ,  104  and  106 , then coupling metal portions  102 ,  104  and  106  together with non-metal portions  108  and  110 . In contrast, the oxidizing processes can involve starting with a single metal substrate, and oxidizing portions of enclosure  101  without cutting metal portions  102 ,  104  and  106  into individual pieces. This can also eliminate problems related to mismatched looking metal portions  102 ,  104  and  106 . 
     Note that the shapes of RF transparent non-metal portions  108  and  110  and metal portions  102 ,  104  and  106  are not limited to those shown in  FIGS. 1A-1C . That is, the shapes of non-metal portions  108  and  110  and metal portions  102 ,  104  and  106  can vary depending on design requirements. For example, non-metal portions  108  and  110  can encompass portions  102  and  106  such that portions  102  and  106  are non-conductive and/or RF transparent. 
     The methods described herein can also be used to form other types of metal structures. For example, the methods described herein can be used to form an arrangement of metal portions isolated from each other by metal oxide.  FIG. 2  shows part or structure  200  that can be formed using methods described herein. Structure  200  can be part of an electronic component of a larger electronic device. Structure  200  includes metal substrate  201 , which can correspond to a metal material that can form a durable oxide, such as aluminum or aluminum alloy. In some embodiments, metal substrate  201  is treated such that portions  202  are oxidized to a corresponding non-electrically conductive metal oxide material. Non-conductive portions  202  can be formed through an entire thickness of metal substrate  201 , and can surround metal portions  204  such that metal portions  204  are electrically isolated from one another. Metal portions  204  can be arranged in a predetermined pattern, such as an array or grid. For example, metal portions  204  can be arranged in accordance with a sensor array with each metal portion  204  corresponding to a position of a sensor. Non-conductive portions  202  electrically isolate each metal portion  204  such that the sensor array can function independently. In some embodiments, metal portions  204  can function as button sensors. The shapes, sizes and spacings between metal portions  204  can vary depending on design choice. 
     Note that  FIGS. 1A-1C and 2  are provided as exemplary implementations of the techniques described herein and are not meant to limit the scope of possible applications and types of unitary structures that can be formed using the techniques described herein. For example, metal oxide portions of a substrate having larger areas can be used to cover capacitive touch pads, touch screens or other capacitive sensors of an electronic device. 
       FIGS. 3A-3D  show close up cross section views of a portion of substrate  300  undergoing an oxidation process in accordance with some embodiments.  FIG. 3A  shows substrate  300 , which can be made of an electrically conductive material, such as metal. In some embodiments, substrate  300  is made of aluminum or aluminum alloy. Substrate  300  includes first side  302  and opposing second side  304 . At  FIG. 3B , select portions of substrate  300  are covered with mask  306 . In the embodiment of  FIG. 3B  select portions of first side  302  and second side  304  of substrate  300  are covered with mask  306 , which leaves portions  308  and  310  exposed. In other embodiments, one side (e.g., first side  302  or second side  304 ) is completely masked. Mask  306  can be made of any suitable type of material that can protect the selected portions of substrate  300  covered by mask  306  from oxidizing in a subsequent oxidizing process. In some embodiments, mask  306  is made of polymer material. Mask  306  can be applied to substrate  300  using any suitable technique, including painting on, spraying on, spinning on, taping/gluing on using adhesive, or using heat-shrink methods. 
     At  FIG. 3C , exposed portions  308  and  310  are oxidized and converted to a corresponding metal oxide  312 . Mask  306  prevents metal portions  314  and  316  from being oxidized and, therefore, remain in metal form. The oxidizing process can convert an entire thickness  318  of substrate  300  to metal oxide  312 , thereby electrically separating metal portions  314  and  316 . In some embodiments, the oxidizing process is an anodizing process. This involves immersing substrate  300  in an electrolytic solution and applying a voltage such that substrate  300  acts as an anode to a counter electrode. This causes conversion of metal material of substrate  300  on first side  308  and second side  310 . Note that in embodiments where one side (e.g., first side  308  or second side  310 ) is completely masked, the oxidizing will occur from one side only. In some embodiments, the process can modified to provide a sufficiently thick metal oxide  312  to embody the entire thickness  318 . For example, thickness  318  of substrate  300  can be made to be sufficiently thin to allow complete conversion using anodizing. Additionally, the anodizing process parameters (e.g., type of electrolyte, voltage and/or current density) can be adjusted to create a thick oxide. 
     In some embodiments, a PEO process is used instead of or in addition to an anodizing process. As described above, PEO techniques can form metal oxides having greater thickness compared to conventional anodizing processes. Like anodizing, PEO is an electrolytic process. However, PEO generally uses higher voltages compared to anodizing, thereby allowing more of substrate to be converted to its corresponding metal oxide. Details of some PEO techniques are described in detail further below. 
     At  FIG. 3D , mask  306  is removed. Metal oxide portion  312  can not only be electrically non-conductive but can also be RF transparent. Therefore metal oxide portion  312  can act as an RF window or segment of a larger structure or part, such as an enclosure for an electronic device, as described above. 
     In some embodiments, the metal oxide portions of the metal structures are formed using plasma electrolytic oxidation (PEO). PEO is an electrochemical process that involves creating plasma that oxidizes metal material of a metal substrate to a corresponding metal oxide. PEO is similar to anodizing in that a metal substrate is electrochemically oxidized. However, PEO generally uses higher electrical potentials compared to anodizing so that discharges occur, resulting in formation of plasma that oxidizes the metal substrate. The higher potentials of PEO processes generally allow for growth of greater thickness of metal oxide compared to anodizing processes. For example, PEO processes can be used to grow metal oxides having a thickness of tens or hundreds of micrometers or more, compared to anodizing which generally grows metal oxides with thicknesses of tens of micrometers or less. 
       FIG. 4A  shows apparatus  400  used to perform a PEO process in accordance with some embodiments. Apparatus  400  includes tank  402  configured to hold an electrolytic bath or solution  404 , such as an alkaline solution. Fixture  406  is configured to hold substrate  408  while substrate  408  is immersed in electrolytic solution  404 . Power supply  410  provides electric current to substrate  408 , i.e., via fixture  406  and to electrolytic solution  404 . Substrate  408  can be made of any suitable anodizable material, such as aluminum, titanium and/or alloys thereof. Substrate  408  acts as an electrode and the walls of tank  402 , which can be made of an inert material such as stainless steel, can act as a counter electrode. During the PEO process, the outer surface of substrate  408  is converted to a corresponding layer of metal oxide. For example, aluminum and aluminum alloys are converted to aluminum oxide. 
     Power supply  410  generally provides a relatively high potential, such as 200 V or greater, such that discharges occur. These discharges result in localized plasma reactions that oxidize and cause conversion of some of the metal to a corresponding metal oxide. The metal oxide layer has different properties than the base metal of substrate  408 . For example, metal oxides are generally harder than its corresponding metal. In addition, metal oxides generally have good corrosion and wear resistance, and are non-electrically conductive. In some cases, the resulting metal oxide is in crystalline form and can therefore be harder than metal oxides formed using anodizing methods. The resultant metal oxide layer can generally be grown to a greater thickness than those grown using anodizing methods. For example, a metal oxide layer having a thickness of ten or hundreds of micrometers can be grown. In some cases, a metal oxide layer having a thickness of about 1 millimeter can be achieved. 
     Typical PEO processes involve forming a metal oxide layer on a metal substrate. In contrast, methods described herein can involve oxidizing entirely through, or nearly entirely through, a thickness of a metal substrate. In addition, selected portions of the metal substrate can be oxidized as opposed to an entire surface of a metal substrate.  FIG. 4B  shows apparatus  400  adapted to form metal oxides in accordance with some embodiments. For simplicity, power supply  410  is not shown. Fixture  406  holds substrate  408  within electrolytic solution  404  and can be electrically grounded. Select portions of substrate  408  are covered with mask  412 , which is generally a non-conductive material that is resistant to substantial degradation during the PEO process. In some embodiments, mask  412  is made of a polymer material. Mask  412  can be applied onto substrate  408  using any suitable technique, such as painting on, spraying on, spinning on, taping/gluing on using adhesive, or applied using heat-shrink methods. 
     Mask  412  is applied to all surfaces of substrate  408  except for first surface  414   a  and opposing second surface  414   b  of substrate  408 , which are exposed to electrolytic solution  404 , and the portion of substrate  408  attached to fixture  406 . During a PEO process, when the power supply is turned on, a potential is created between electrolytic solution  404  and substrate  408 . Exposed first and second surfaces  414   a  and  414   b  of substrate  408  undergo oxidation and are converted to corresponding metal oxide portion  416 . For example, substrate  408  made of aluminum or aluminum alloy will be converted to an aluminum oxide material. Portions  418  of substrate  408  covered by mask  412  do not undergo the oxidation process and therefore remain in metal form. The oxidation process is an inward growing process in that metal oxide material grows inward from opposing surfaces  414   a  and  414   b  of substrate  408 . 
     The growth of metal oxide material at metal oxide portion  416  can be controlled by adjusting the applied voltage and/or current density, as well as the time period of performing the PEO process. The thickness of metal oxide portion  416  can also depend, in part, on the geometry of the substrate. In some embodiments, the PEO process is performed such that substantially the entire thickness  420  of substrate  408  corresponding to metal oxide portion  416  is converted to metal oxide material. This can be achieved because the PEO process enables relatively large areas of metal to be converted to metal oxide, in some cases up to about 1 millimeter or more. One can determine when metal oxide portion  416  is fully converted by measuring the current density flowing from fixture  406  during the PEO process. In particular, metal oxide portion  416  is generally fully converted when the current density measured at fixture  406  reaches zero or near zero. 
     In some embodiments, the thickness  420  of substrate  408  is made sufficiently thin to allow for full conversion to metal oxide material. For example, in some embodiments substrate  408  has a thickness  420  of about 0.3 millimeters or less. In other embodiments, thickness  420  can be greater than 0.3 millimeters. In these embodiments where metal oxide portion  416  is fully converted, substrate  408  includes conductive and RF opaque metal portions  418  that are separated by non-conductive and RF transparent metal oxide portion  416 . In addition to having different electrically conductive and RF transparency properties, metal oxide portion  416  has different mechanical properties than metal portions  418 , such as greater hardness and corrosion/wear resistance. Furthermore, metal oxide portion  416  may have a different appearance than metal portions  418  since metal oxide material can have a translucent quality. However, in some embodiments, metal oxide portion  416  is altered to appear less translucent and more like metal portions  418 , which will be described in more detail below. After the PEO process is complete, substrate  408  can undergo one or more post-PEO processes, such as machining and surface finishing operations, to create a final part. 
     Note that apparatus  400  shown in  FIGS. 4A and 4B  are exemplary and other suitable PEO arrangements can be used in order to selectively oxidize areas of a substrate. For example, in addition to or instead of masking portions of a substrate, the PEO apparatus  400  can be arranged to concentrate the plasma in certain regions of the substrate, such as by placing electrically conductive items proximate to specified surfaces of substrate  408 . 
       FIG. 5  shows a perspective view of substrate  500  after undergoing an oxidizing process in accordance with some embodiments. Substrate  500  can be part of an enclosure for an electronic device, such as a mobile telephone. Substrate  500  includes metal portions  502 ,  504 ,  506 ,  508  separated by intervening metal oxide portions  510 ,  512 ,  514 . If metal oxide portions  510 ,  512 ,  514  are formed through an entire thickness  515  of substrate  500 , metal portions  502 ,  504 ,  506 ,  508  will be electrically isolated from each other. In addition, metal oxide portions  510 ,  512 ,  514  can be electrically non-conductive and RF transparent. Thus, in some embodiments, metal oxide portions  510 ,  512 ,  514  can serve as RF windows or RF transparent segments/lines. Since metal portions  502 ,  504 ,  506 ,  508  can be electrically isolated from one another, different electrical components can be electrically connected with each of metal portions  502 ,  504 ,  506 ,  508  without themselves being electrically connected. For example, an electrical component can be electrically grounded with metal portion  502  without being electrically connected metal portions  504 ,  506  and  508 . 
     Metal oxide portions  510 ,  512 ,  514  that are formed all the way through thickness  515  of substrate  500  can be accomplished a number of ways. In one embodiment, surfaces of substrate  500  corresponding to metal portions  502 ,  504 ,  506 ,  508  are masked, including surfaces on first side  516  and opposing second side  518 , which is not visible in the view of  FIG. 5 . Substrate  500  is then exposed to an oxidizing process such that portions of substrate  500  are converted to metal oxide portions  510 ,  512 ,  514 . For anodizing and PEO processes, substrate  500  is immersed in an electrolytic solution. When voltage is applied, metal oxide material grows inward from both first side  516  and second side  518  until metal oxide portions  510 ,  512 ,  514  are fully converted. This is similar to what is described above with reference to  FIG. 4B . In other embodiments, surfaces of substrate  500  corresponding to metal portions  502 ,  504 ,  506 ,  508  are masked at first side  516  while the entirety of second side  518  is masked. This way, when substrate  500  is immersed in the electrolytic solution, only portions of substrate at first side  516  are exposed to the oxidizing process. This causes metal oxide material to grow inward from only first side  516  and not from second side  518 . After the oxidizing process is complete, any non-converted metal material on second side  518  can be machined or abraded off of substrate  500  such that metal oxide portions  510 ,  512 ,  514  are formed all the way through thickness  515 . 
     As described above, metal oxide material can have a different appearance than metal. In particular, metal oxide material can have a more translucent quality compared to metal. In some applications, however, it is desirable for intervening metal oxide portions  510 ,  512 ,  514  to appear similar to metal portions  502 ,  504 ,  506 ,  508 . Thus, in some embodiments, metal oxide portions  510 ,  512 ,  514  can be dyed or colorized to appear similar in color to metal portions  502 ,  504 ,  506 ,  508 . Alternatively or additionally, substrate  500  can undergo one or more pre-oxidizing processes in order to achieve metal oxide portions  510 ,  512 ,  514  with similar coloration as metal portions  502 ,  504 ,  506 ,  508 . 
       FIGS. 6A-6D  show close-up cross section views of substrate  500  undergoing pre-oxidizing and oxidizing processes to achieve metal oxide portions  510 ,  512 ,  514  that look similar to metal portions  502 ,  504 ,  506 ,  508 , in accordance with some embodiments.  FIG. 6A  shows substrate  500  after a pre-oxidizing process is performed. In particular, substrate  500  is anodized such that exposed surfaces of metal  600  are converted to anodized layers  602 . Any suitable anodizing process can be used. In some embodiments, an anodizing process known in the art as a type II anodizing process is used, which generally results in anodized layers  602  having acceptable corrosion/wear resistance and cosmetic qualities for many consumer product applications. The thicknesses of anodized layers  602  can vary depending on application requirements. In some embodiments, anodized layers  602  are each in tens of micrometers in thickness or less. Anodized layers  602  can be dyed to give anodized layers  602  a pre-determined color. In some embodiments, anodic pores of anodized layers  602  are filled with dye or other type of colorant in order to impart the pre-determined color to anodized layers  602 . In other embodiments, the dyeing process is performed later, such as after a subsequent PEO process is performed. 
     At  FIG. 6B , mask  604  is applied to portions of substrate  500  to prevent exposure to a PEO process. As shown, mask  604  can cover surface portions of anodized layers  602 . At  6 C, substrate  500  is exposed to a PEO process such that metal oxide portion  512  is formed between metal portions  504  and  506 . Metal oxide portion  512  can be referred to as a PEO oxide layer to distinguish it from anodized layers  602 . The thicknesses of anodized layers  602  can be thin enough such that PEO oxidation occurs through anodized layers  602 . Since the PEO process involves conversion of metal material inward, anodized layers  602  remain as exterior layers to metal oxide portion  512  and metal portions  504  and  506 . In addition, if anodized layers  602  are dyed, the color imparted to anodized layers  602  by dyeing may also be retained. 
     At  FIG. 6D , mask  604  is removed from substrate  500 . Since metal oxide portion  512  is completely converted to metal oxide material, metal oxide portion  512  is electrically non-conductive. Both sides of metal oxide portion  512  have anodized layer  602 , which are also electrically non-conductive. Thus, an entire thickness  515  of substrate  500  corresponding to metal oxide portion  512  is electrically non-conductive, thereby electrically separating metal portions  504  and  506 . If anodized layers  602  are dyed, the color imparted to anodized layers  602  can be retained. However, in some case where it may be difficult to retain the dye within anodized layers  602  during the PEO process, a post-PEO dying process can be performed on anodized layers  602 . If anodized layers  602  are dyed, substrate  500  can then have a uniformly colored appearance, which may be desirable in some applications. 
     In some embodiments, the translucent quality of metal oxide material is exploited. For example,  FIG. 7  shows substrate  700 , which includes a translucent metal oxide portion  702  formed using an oxidizing process, in accordance with some embodiments. Metal oxide portion  702  can be formed through an entire thickness  706  of substrate using any suitable oxidizing process described above, such as anodizing, PEO or a combination thereof. For example, metal portion  704  can be masked prior to the oxidizing process such that metal portion  704  remains unconverted to metal oxide material. In some embodiments, outer surfaces of substrate  700  include a thin anodized layer, as described above with reference to  FIGS. 5A-5D . Some metal oxide materials can have a translucent quality in that visible light can at least partially shine through. Thus, metal oxide portion  702  can remain undyed so as to retain this naturally translucent quality. In some applications, a light emitter, such as a light emitting diode, is positioned proximate to second side  708  of substrate  700  near translucent metal oxide portion  702 . Some of the light emitted from the light emitter can pass through metal oxide portion  702  and be visible from first side  710  of substrate  700 . In this way, metal oxide portion  702  can act as a light window. For example, substrate  700  can be a portion of an enclosure for an electronic device, and the light emitter can be positioned within the enclosure. Metal oxide portion  702  can then be a cosmetically appealing lighted design on the enclosure. In some embodiments, metal oxide portion  702  is in the shape of a logo, lettering or other design. In some embodiments, a number of metal oxide portions  702  are formed within substrate  700 . 
     In some cases, it may be advantageous to reduce the thickness of portions of the substrate prior to the oxidizing process. This can assure that the thickness of the substrate is thin enough to accomplish oxidation through an entire thickness of the substrate, while leaving other portions of the substrate thicker for structural and/or other functional purposes. To illustrate,  FIGS. 8A-8C  show perspective cross section views of portions of substrate  800 . Substrate  800  includes metal portions  802 ,  804 ,  806 ,  808 , electrically isolated from one another by metal oxide portions  810 ,  812 ,  814 . As shown, substrate  800  at metal oxide portions  810 ,  812 ,  814  is thinner than at metal portions  802 ,  804 ,  806 ,  808 . In particular, substrate  800  has a first thickness  822  at metal oxide portions  810 ,  812 ,  814  and a second thickness  824  at metal portions  802 ,  804 ,  806 ,  808 . In other embodiments, the thicknesses of metal oxide portions  810 ,  812 ,  814  vary from one other, and/or the thicknesses of metal portions  802 ,  804 ,  806 ,  808  vary from one another. 
     Any suitable technique, such as machining and/or etching portions of substrate  800  prior to the oxidizing process can achieve this varied thickness. Specifically, channels  816 ,  818 ,  820  are formed within substrate  800  that are in the shape of metal oxide portions  810 ,  812 ,  814 , respectively. Channels  816 ,  818 ,  820  can be formed such thickness  822  of substrate  800  within channels  816 ,  818 ,  820  have a pre-determined thickness that is sufficiently thin to provide full oxidation within channels  816 ,  818 ,  820  during the oxidizing process. In some embodiments, thickness  822  is about 0.3 millimeters or less. In other embodiments, thickness  822  is greater than 0.3 millimeters. In some embodiments, channels  816 ,  818 ,  820  are curved or tapered, as shown in  FIGS. 8B and 8C . Thickness  824  of metal portions  802 ,  804 ,  806 ,  808  can vary depending on design choice, such as required for adequate structural integrity of substrate  800 . 
     After channels  816 ,  818 ,  820  are formed, metal portions  802 ,  804 ,  806 ,  808  are masked. In some embodiments, portions of surfaces of substrate  800  within channels  816 ,  818 ,  820  are also masked. Then, substrate  800  is exposed to an oxidizing process resulting in metal oxide portions  810 ,  812 ,  814  that can be formed through entire thickness  822  of substrate  800 . The oxidizing process can include an anodizing, PEO or a combination of anodizing and PEO processes, such as described above. 
       FIG. 9  shows flowchart  900  indicating a process for forming electrically isolated areas within a part using one or more oxidizing processes, in accordance with some embodiments. At  902 , one or more pre-oxidizing treatments are optionally performed on a metal substrate. The metal substrate can include any suitable material capable of forming a durable metal oxide, such as aluminum and/or titanium. In some embodiments, machining operations and/or finishing operations are performed to provide a shape to the metal substrate. In some embodiments, portions of the metal substrate are thinned so that the thinned portions can be fully oxidized during a subsequent oxidizing process. For example, channels that are shaped in accordance with shapes of subsequently formed metal oxide portions can be formed within the metal substrate. In some embodiments, portions of the metal substrate to be oxidized are thinned to about 0.3 millimeters or less. In some embodiments, one or more anodizing processes are performed on the metal substrate prior to the oxidizing process to form an outer anodized layer on the metal substrate. The anodized layer can be dyed to a pre-determined color. After surface treatment processes are complete, some surface portions of the metal substrate can be masked using a mask configured to withstand a subsequent oxidizing process. The masked portions of the substrate will correspond to portions of the metal substrate that will remain in metal form, while unmasked portions of the metal substrate will be converted to a corresponding metal oxide during the oxidizing process. 
     At  904 , an oxidizing process is used to convert exposed portions of the metal substrate to a metal oxide portion. If portions of the metal substrate are masked, the unmasked portions are converted to metal oxide while the masked portions remain in metal form. In some embodiments, a PEO process is used since PEO generally allow for greater thicknesses of the metal substrate to be converted to a metal oxide compared to anodizing methods. If exposed portions of the metal substrate are thin enough, the oxidizing process can convert an entire thickness of the exposed portions to a metal oxide material. In this way, the metal oxide portions can function as non-conductive and/or RF transparent portions between the conductive metal portions. In some PEO embodiments, tools can be used during the PEO process to concentrate plasma generation at selected areas of the metal substrate such that those selected areas are oxidized to a greater extent than areas that do not have the concentrated plasma. This plasma concentration technique can be performed in addition to or instead of using a mask. 
     In some embodiments where the metal substrate is anodized prior to the oxidizing process, the metal oxide portion is formed beneath the anodized layer. Thus, if the anodized layer is dyed, the dyed anodized layer can cover both the metal oxide and the metal portions giving the part a uniform color and appearance. In other embodiments, the anodized layer and the metal oxide are undyed and have an inherently translucent quality. This translucent quality can be exploited in some applications where the metal oxide acts as a light window. 
     After the oxidizing process is complete, at  906  a post-oxidizing treatment can optionally be performed on the metal substrate. For example, in some cases a post-oxidizing dyeing process is performed. The dyeing process can dye the metal oxide portion and/or an anodized layer positioned over the metal oxide portion. This can give the part a uniform color and appearance. Other post-oxidizing treatments can include machining (e.g., cutting and/or shaping) and/or surface finishing processes to from a final part. 
       FIG. 10  shows flowchart  1000  indicating a high-level process for forming electrically isolated areas within a part, in accordance with some embodiments. At  1002 , an optional pre-treatment is performed on a substrate. The pre-treatment can include machining operations to shape the substrate to a take on a pre-determined shape. In some cases, a surface finishing process is performed, such as an anodizing, polishing, and/or dyeing process, is performed. 
     At  1004 , a unitary structure is created by forming a non-electrically conductive portion between electrically conductive portions of the substrate. In some embodiments, this involves a co-extrusion process where a non-conductive material, such as glass, plastic, or ceramic (e.g., a metal oxide) is co-extruded with a conductive material, such as a metal material. In some embodiments, an oxidizing process (e.g., anodizing and/or PEO) is used to convert a portion of a metal substrate to a corresponding metal oxide. At  1006 , an optional post-treatment is performed on the unitary structure. For example, one or more machining or surface finishing processes can be performed. In some embodiments, portions of the unitary structure are dyed. 
     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 the specific embodiments described herein are presented for purposes of illustration and description. They are not meant to be exhaustive or to limit the 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: 20151216
Publication Date: 20180529
Grant Date: 20180529
Priority Date: 20150410
Inventors: FERRETTI, FRANCESCO
MARCINKOWSKI, JOSEPH B.
CHAN, Collin D.
ENGBERSEN, TOM H.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q1/42", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04M1/0202", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M1/0202", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q1/42", "inventive": true, "first": true, "tree": "[]"}, {"code": "C25D11/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/022", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K5/0273", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04M1/0202", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/026", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 57112166