Patent Publication Number: US-11380603-B2

Title: Method for making a heat dissipation structure

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a divisional application of patent application Ser. No. 15/615,065 filed on Jun. 6, 2017, which is based on and claims priority to China Patent Application No. 201610830252.6 filed on Sep. 18, 2016, the contents of which are incorporated by reference herein. 
    
    
     FIELD 
     The subject matter herein generally relates to a method for making a heat dissipation structure, and an electronic device having the heat dissipation structures. 
     BACKGROUND 
     Electronic devices usually comprise electronic elements (such as central processing units (CPUs)) which may generate heat when in operation. Heat sinks are usually used in the electronic devices for dissipating the heat generated by the electronic elements. However, the temperature of a portion of the heat sink near a heat source of the electronic element is always larger than temperatures of other portions of the heat sink away from the heat source, causing the electronic device to have uneven temperatures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Implementations of the present technology will now be described, by way of example only, with reference to the attached figures. 
         FIG. 1  is a flowchart of a first exemplary embodiment of a method for making a heat dissipation structure. 
         FIG. 2  is a cross-sectional view of a flexible substrate used in the method of  FIG. 1 . 
         FIG. 3  is a cross-sectional view showing at least one groove being defined in the flexible substrate of  FIG. 2 . 
         FIG. 4  is a cross-sectional view showing a first adhesive layer being formed on the flexible substrate of  FIG. 3 . 
         FIG. 5  is a cross-sectional view showing a phase changing material being filled in each groove of  FIG. 4 . 
         FIG. 6  is a cross-sectional view of a cover plate used in the method of  FIG. 1 . 
         FIG. 7  is a cross-sectional view showing each groove with the phase changing material being sealed by the cover plate of  FIG. 5 . 
         FIG. 8  is a cross-sectional view of a graphite sheet with at least one lower recess. 
         FIG. 9  is a cross-sectional view showing a second adhesive layer being formed on the graphite sheet of  FIG. 8 . 
         FIG. 10  is a cross-sectional view showing the graphite sheet of  FIG. 9  being connected to the flexible substrate of  FIG. 7  to form a heat dissipation structure. 
         FIG. 11  is similar to  FIG. 3 , but showing a plurality of microgrooves being defined at a bottom of each groove. 
         FIG. 12  is a cross-sectional view of a second exemplary embodiment of a heat insulating structure, using the flexible substrate of  FIG. 11 . 
         FIG. 13  is similar to  FIG. 3 , but showing at least one upper recess being defined in the flexible substrate. 
         FIG. 14  is a cross-sectional view of a third exemplary embodiment of a heat insulating structure, using the flexible substrate of  FIG. 13 . 
         FIG. 15  is a cross-sectional view of a fourth exemplary embodiment of a heat insulating structure. 
         FIG. 16  is a cross-sectional view of an electronic device using a heat insulating structure. 
     
    
    
     DETAILED DESCRIPTION 
     It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related relevant feature being described. Also, the description is not to be considered as limiting the scope of the embodiments described herein. The drawings are not necessarily to scale and the proportions of certain parts may be exaggerated to better illustrate details and features of the present disclosure. 
     Several definitions that apply throughout this disclosure will now be presented. 
     The term “substantially” is defined to be essentially conforming to the particular dimension, shape or other word that substantially modifies, such that the component need not be exact. For example, substantially cylindrical means that the object resembles a cylinder, but can have one or more deviations from a true cylinder. The term “comprising” when utilized, means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in the so-described combination, group, series and the like. 
       FIG. 1  illustrates a flowchart is presented in accordance with a first exemplary embodiment. The first exemplary method for making a heat dissipation structure  100  (shown in  FIG. 10 ) is provided by way of example only, as there are a variety of ways to carry out the method. Each block shown in  FIG. 1  represents one or more processes, methods or subroutines, carried out in the first exemplary method. Furthermore, the illustrated order of blocks is by example only and the order of the blocks can be changed. Additional blocks may be added or fewer blocks may be utilized, without departing from this disclosure. The first exemplary method can begin at block  301 . 
     At block  301 , referring to  FIGS. 2 and 3 , a flexible substrate  10  is provided, and at least one groove  11  is defined in the flexible substrate  10 . 
     The flexible substrate  10  comprises a first surface  101  and a second surface  102  facing away from the first surface  101 . 
     In the first exemplary embodiment, the flexible substrate  10  is made of copper, and has a thickness of about 18 μm to about 175 μm. In another exemplary embodiment, the flexible substrate  10  may be made of other materials which are resistant to thermal deformation, such as aluminum or silver. A thickness of the flexible substrate  10  can be selected according to the specific need of a particular application. 
     Each groove  11  is defined from the first surface  101  toward the second surface  102  by, for example, etching. In another exemplary embodiment, each groove  11  can be defined by mechanical cutting, laser cutting, or punching. 
     In the first exemplary embodiment, each groove  11  is substantially square when seen from a top plan view. In another exemplary embodiment, each groove  11  may be substantially circular, rectangular, polygonal, or trapezoidal when seen from a top plan view. 
     In another exemplary embodiment, an inner surface of each groove  11  can be micro-etched to form wick structures. 
     At block  302 , referring to  FIG. 4 , a first adhesive layer  20  is formed on the first surface  101  to surround each groove  11 . The first adhesive layer  20  is made of materials having a heat conducting capability, and is formed on the first surface  101  by coating, fluid dispensing, or printing. 
     At block  303 , referring to  FIG. 5 , a phase changing material  30  is filled in each groove  11 . The phase changing material  30  may include paraffin, polyethylene glycol 1000 (PEG 1000), lauric acid, or any combination thereof. 
     At block  304 , referring to  FIGS. 6 and 7 , a cover plate  40  is provided, then the cover plate  40  and the flexible substrate  10  with the phase changing material  30  are pressed, causing the cover plate  40  to be connected to the flexible substrate  10  by the first adhesive layer  20 . As such, each groove  11  is sealed by the cover plate  40  to define a sealed cavity  50 . The phase changing material  30  is filled in each sealed cavity  50 . 
     In the first exemplary embodiment, the cover plate  40  is made of copper. In another exemplary embodiment, the cover plate  40  may be made of other materials which are resistant to thermal deformation, such as aluminum or silver. 
     At block  305 , referring to  FIG. 8 , a graphite sheet  60  is provided which defines at least one lower recess  62  on a third surface  61  of the graphite sheet  60 . The heat insulating material may include air, polyimide resin, polyester resin, asbestos, polypropylene resin, or any combination thereof. 
     Each lower recess  62  can be defined by etching, mechanical cutting, or laser cutting. In the first exemplary embodiment, each lower recess  62  is substantially circular when see from a top plan view. In another exemplary embodiment, each lower recess  62  may be substantially square, rectangular, polygonal, or trapezoidal when see from a top plan view. 
     At block  306 , referring to  FIGS. 9 and 10 , a second adhesive layer  63  is formed on the third surface  61  of the graphite sheet  60  to surround the lower recess  62 , and a heat insulating material is filled in each lower recess  62 , then the graphite sheet  60  and the flexible substrate  10  are pressed, causing the graphite sheet  60  to be connected to the second surface  102  of the flexible substrate  10  by the second adhesive layer  63 . Each lower recess  62  is sealed by the flexible substrate  10  to define a containing cavity  64 . It should be noted that a heat insulating material is filled in the containing cavity  64  to form a heat insulating structure  65 . The adhesive layer  63  is made of materials having a heat conducting capability. 
     Referring to  FIGS. 11 and 12 , in a second exemplary embodiment, at block  301 , a plurality of microgrooves  113  is further defined at a bottom  111  of each groove  11 . Sizes and/or shapes of the microgrooves  113  may be the same or be different. 
     Referring to  FIGS. 13 and 14 , in a third exemplary embodiment, at block  301 , at least one upper recess  12  is further defined at the second surface  102  which extends toward the first surface  101 . Each upper recess  12  faces one lower recess  62  when the graphite sheet  60  and the flexible substrate  10  are pressed at block  306 . In this embodiment, the containing cavity  66  is formed by the upper recess  12  and the lower recess  62 . The heat insulating material is filled in the containing cavity  66  to form the heat insulating structure  65 . 
     Referring to  FIG. 15 , in a fourth exemplary embodiment, the graphite sheet  60  defines no lower recess  62 , so that the containing cavity  67  is formed by the sealing the upper recess  12  by the graphite sheet  60  at block  306 . The heat insulating material is filled in the containing cavity  67  to form the heat insulating structure  65 . 
       FIG. 10  illustrates that in the first exemplary embodiment, the heat dissipation structure  100  comprises a flexible substrate  10 , a phase changing material  30 , a cover plate  40 , and a graphite sheet  60 . 
     The flexible substrate  10  comprises a first surface  101  and a second surface  102  facing away from the first surface  101 . At least one groove  11  is defined at the first surface  101  toward the second surface  102 . 
     In the first exemplary embodiment, the flexible substrate  10  is made of copper, and has a thickness of about 18 μm to about 175 μm. In another exemplary embodiment, the flexible substrate  10  may be made of other materials which are resistant to thermal deformation, such as aluminum or silver. A thickness of the flexible substrate  10  can be selected according to the specific need of a particular application. 
     In the first exemplary embodiment, each groove  11  is substantially square when seen from a top plan view. In another exemplary embodiment, each groove  11  may be substantially circular, rectangular, polygonal, or trapezoidal when seen from a top plan view. 
     The cover plate  40  is connected to the first surface  101  of the flexible substrate  10  by a first adhesive layer  20 , the first adhesive layer  20  surrounding each groove  11 . Each groove  11  is sealed by the cover plate  40  to define a sealed cavity  50 . The first adhesive layer  20  is made of materials having a heat conducting capability, and is formed by coating, fluid dispensing, or printing. 
     In the first exemplary embodiment, the cover plate  40  is made of copper. In another exemplary embodiment, the cover plate  40  may be made of other materials that are resistant to thermal deformation, such as aluminum or silver. 
     The phase changing material  30  is filled in each sealed cavity  50 . The phase changing material  30  may include paraffin, polyethylene glycol 1000 (PEG 1000), lauric acid, or any combination thereof. 
     In another exemplary embodiment, wick structures can be formed at an inner surface of each groove  11 . 
     At least one lower recess  62  is defined at a third surface  61  of the graphite sheet  60 . The third surface  61  of the graphite sheet  60  is connected to the second surface  102  of the flexible substrate  10  through a second adhesive layer  63 , so that the recess  62  is sealed by the flexible substrate  10  to define a containing cavity  64 . A heat insulating material is filled in each containing cavity  64  to form a heat insulating structure  65 . The heat insulating material may include air, polyimide resin, polyester resin, asbestos, polypropylene resin, or any combination thereof. 
     Each lower recess  62  is substantially circular when seen from a top plan view. In another exemplary embodiment, each lower recess  62  may be substantially square, rectangular, polygonal, or trapezoidal when seen from a top plan view. 
       FIG. 12  illustrates a second exemplary embodiment of a heat dissipation structure  200 . Different from the first exemplary embodiment, a plurality of microgrooves  113  is defined at a bottom  111  of each groove  11 . Sizes and/or shapes of the microgrooves  113  may be the same or be different. 
     In the second exemplary embodiment shown in  FIG. 12 , areas of the microgrooves  113  on the bottom  111  decrease along a direction from a position at the bottom  111  near the containing cavity  64  to other positions at the bottom  111  away from the containing cavity  64 . More specifically, the widths of the microgrooves  113  are the same. Distribution densities of the microgrooves  113  decrease from a position at the bottom  111  near the containing cavity  64  to other positions at the bottom  111  away from the containing cavity  64 . 
       FIG. 14  illustrates a third exemplary embodiment of a heat dissipation structure  300 . Different from the first exemplary embodiment, at least one upper recess  12  is defined at the second surface  102  which extends toward the first surface  101 . Each upper recess  12  faces a corresponding lower recess  62  to define the containing cavity  66 . 
       FIG. 15  illustrates a fourth exemplary embodiment of a heat dissipation structure  400 . Different from the third exemplary embodiment, the graphite sheet  60  has no lower recess  62 , so that each upper recess  12  is sealed by the graphite sheet  60  to define the containing cavity  67 . 
     As shown in  FIG. 16 , when in operation, the graphite sheet  60  contacts an electronic element  501  (such as CPU) of an electronic device  500 , which needs to dissipate heat. The heat insulating structure  65  contacts a heat source  503  (such as circuit board) of the electronic element  501 . The graphite sheet  60  absorbs the heat from the heat source  503 . The absorbed heat is dissipated towards different directions by the graphite sheet  60 , and is conducted to the flexible substrate  10  through the heat insulating structure  65  and the graphite sheet  60 . Then, the heat is dissipated to an ambient environment through the flexible substrate  10 , the phase changing material  30 , and the cover plate  40 . Because the heat insulating structure  65  contacts the heat source  503  of the electronic element  501 , a conducting speed of the heat is reduced at the heat insulating structure  65 , to cause most of the absorbed heat to be conducted along an extending (e.g., longitudinal) direction of the graphite sheet  60 . Therefore, the heat can be dissipated uniformly, to cause a temperature of the electronic device  500  to be uniformly decreased. 
     It is to be understood, even though information and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the present embodiments, the disclosure is illustrative only; changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the present embodiments to the full extent indicated by the plain meaning of the terms in which the appended claims are expressed.