PATENT DOCUMENT

Publication Number: US-8339787-B2
Application Number: US-87721910-A
Country: US
Kind Code: B2

Title: Heat valve for thermal management in a mobile communications device

Abstract:
A thermal valve for controlling heat transfer between two electronic components is disclosed. The thermal valve includes a first thermally conductive strip that is secured to the first electronic component and a second thermally conductive strip that is secured to the second electronic component. The first strip and the second strip are located between the two electronic components. The first strip changes its shape toward making contact with the second strip in response to a temperature increase of the first electronic component, and the second strip changes its shape away from making contact with the first strip in response to a temperature increase of the second electronic component. Other embodiments are also described and claimed.

Claims:
1. A thermal valve, comprising:
 a first thermally conductive strip secured to a first electronic component and located between the first electronic component and a second electronic component; and 
 a second thermally conductive strip secured to the second electronic component and located between the first electronic component and the second electronic component, the first strip to change its shape toward making contact with the second strip in response to a temperature increase of the first electronic component, the second strip to change its shape away from making contact with the first strip in response to a temperature increase of the second electronic component. 
 
     
     
       2. The thermal valve of  claim 1  wherein the first strip includes two different thermally conductive materials laminated together, wherein the second strip includes the same two different thermally conductive materials laminated together, and wherein the two different thermally conductive materials have different coefficients of thermal expansion. 
     
     
       3. The thermal valve of  claim 1  wherein the first strip does not contact the second strip when essentially no heat is being generated by the first electronic component and by the second electronic component. 
     
     
       4. The thermal valve of  claim 1  wherein the first strip does not contact the second strip when a temperature of the second electronic component is above a threshold temperature. 
     
     
       5. The thermal valve of  claim 1  wherein the first strip does not contact the second strip when a temperature of the first electronic component is below a threshold temperature. 
     
     
       6. The thermal valve of  claim 1  wherein the first strip contacts the second strip when a temperature of the first electronic component is above a threshold temperature while a temperature of the second electronic component is below the threshold temperature. 
     
     
       7. The thermal valve of  claim 6  wherein the second strip separates from the first strip in response to the temperature of the second electronic component increasing to a temperature that is above the threshold temperature. 
     
     
       8. The thermal valve of  claim 6  wherein the first strip separates from the second strip in response to the temperature of the first electronic component decreasing to a temperature that is below the threshold temperature. 
     
     
       9. The thermal valve of  claim 1  further comprising a plurality of said first strips arranged in a linear array and a plurality of said second strips arranged in a linear array. 
     
     
       10. A apparatus, comprising:
 a mobile communications handset housing having integrated therein 
 a camera module, 
 a main logic board having an applications processor and memory installed thereon, and 
 a thermal valve having a plurality of states responsive to a temperature of the camera module and a temperature of the main logic board, the plurality of states including a coupled state where the thermal valve thermally couples the camera module and the main logic board and a decoupled state where the thermal valve thermally decouples the camera module and the main logic board. 
 
     
     
       11. The apparatus of  claim 10  wherein the thermal valve is in the decoupled state when essentially no heat is being generated by the camera module and the main logic board. 
     
     
       12. The apparatus of  claim 10  wherein the thermal valve is in the decoupled state when the temperature of the main logic board is above a threshold temperature. 
     
     
       13. The apparatus of  claim 10  wherein the thermal valve is in the decoupled state when the temperature of the camera module is below a threshold temperature. 
     
     
       14. The apparatus of  claim 10  wherein the thermal valve is in the coupled state when the temperature of the camera module is above a threshold temperature while the temperature of the main logic board is below the threshold temperature. 
     
     
       15. The apparatus of  claim 10  wherein the thermal valve includes a first thermally conductive strip secured to the camera module and a second thermally conductive strip secured to the main logic board, the first strip to curve in response to the temperature of the camera module increasing, the second strip to curve in response to the temperature of the main logic board increasing. 
     
     
       16. The apparatus of  claim 15  wherein the thermal valve is in the decoupled state when the first strip is straight. 
     
     
       17. The apparatus of  claim 15  wherein the thermal valve is in the decoupled state when the second strip curves away from the first strip. 
     
     
       18. The apparatus of  claim 15  wherein the thermal valve is in the coupled state when the first strip curves toward the second strip and makes contact with the second strip while the second strip is straight. 
     
     
       19. The apparatus of  claim 15  wherein the thermal valve includes a plurality of said first strips arranged in a linear array and a plurality of said second strips arranged in a linear array. 
     
     
       20. A method for modifying a thermal connection between a camera module and an active electronic component inside a housing of an electronic device, comprising:
 creating increased thermal conductance from the camera module to the active electronic component when a temperature of the camera module is above a threshold temperature while a temperature of the active electronic component is below the threshold temperature; and 
 creating decreased thermal conductance from the camera module to the active electronic component when the temperature of the active electronic component is above the threshold temperature. 
 
     
     
       21. The method of  claim 20  further comprising creating decreased thermal conductance from the camera module to the active electronic component when essentially no heat is being generated by the camera module and the active electronic component. 
     
     
       22. The method of  claim 20  further comprising creating decreased thermal conductance from the camera module and the active electronic component when the temperature of the camera module is below the threshold temperature. 
     
     
       23. The method of  claim 20  wherein creating decreased thermal conductance comprises creating a separation between a first thermally conductive strip that is secured to the camera module and a second thermally conductive strip that is secured to the active electronic component. 
     
     
       24. The method of  claim 20  wherein creating increased thermal conductance comprises creating contact between a first thermally conductive strip that is secured to the camera module and a second thermally conductive strip that is secured to the active electronic component. 
     
     
       25. The method of  claim 24  wherein the first strip includes two different thermally conductive materials laminated together, wherein the second strip includes the same two different thermally conductive materials laminated together, and wherein the two different thermally conductive materials have different coefficients of thermal expansion to allow the first strip and the second strip to curl in response to an increase in temperature.

Description:
An embodiment of the invention relates to thermal management of a camera module within a mobile device. Other embodiments are also described and claimed. 
     BACKGROUND 
     A camera module contains an image sensor that may produce a lot of heat when capturing many images, for example, in a video mode of operation. If the heat cannot be dissipated in time, the temperature of the image sensor will rise beyond its rated temperature, which degrades the quality of the image captured by the image sensor and shortens the life of the image sensor. Heat generated by the image sensor must therefore be dissipated to improve the quality of the image captured by the image sensor and to prevent premature failure. Heat sinks are often used to transfer heat from a heat load to a cold source. Transferring heat from the heat load to the cold source through the heat sink cools the heat load and may maintain the temperature of the heat load within a specified range. Mobile devices, however, have very confined spaces thus limiting the heat sink option. 
     SUMMARY 
     A thermal valve for controlling heat transfer between two electronic components, such as a camera module and a main logic board in a mobile device, is described. The thermal valve includes two thermally conductive strips. One thermally conductive strip may be secured to the camera module along an edge and extends toward the main logic board. The other thermally conductive strip may be secured to the main logic board along an edge and extends toward the camera module. The strips are positioned so that they are separated but able to make contact with each other under certain temperature conditions. 
     The thermal valve may have two states, including a decoupled state and a coupled state. In the decoupled state, the two thermally conductive strips do not contact each other. The thermal valve may be in the decoupled state under three different temperature conditions: one such condition may be when essentially no heat or insufficient heat is being generated by both the camera module and the main logic board; another such condition may be when the temperature of the camera module is low and the temperature of the main logic board is high; and a third condition may be when the temperature of both the camera module and the main logic board are high. In the coupled state, the two thermally conductive strips contact each other so that heat may be transferred between the camera module and the main logic board in an effort to cool the camera module using the main logic board as a heat sink. The thermal valve may be in the coupled state when the temperature of the camera module is high while the temperature of the main logic board is low. 
     The thermally conductive strip may include two different thermally conductive materials that are laminated together. The two thermally conductive materials have different coefficients of thermal expansion so that the strip may change its shape in response to temperature changes. For example, the strip may be straight at room temperature and curved at a temperature that is above a certain threshold. This threshold may be the rated temperature of the camera module (which is higher than room temperature). When the camera module and the main logic board are essentially at room temperature (i.e., essentially no heat is being generated), the strips may be straight so that the thermal valve is in the decoupled state. When the temperature of the camera module becomes high while the temperature of the main logic board remains low, the strip that is secured to the camera module may curve towards and make contact with the strip that is secured to the main logic board, to thermally couple the camera module to the main logic board and enhance heat transfer from the camera module to the main logic board (to help cool the camera module). When the temperature of the main logic board becomes high, the strip that is secured to the main logic board may curve away from the strip that is secured to the camera module to reduce thermal coupling of the camera module and the logic board. This may represent the understanding that the main logic board is too hot to act as a heat sink for the camera module. 
     The thermal valve may have multiple pairs of such strips arranged in an array. For example, a set of multiple strips may be secured to the camera module in a linear array. Another set of multiple strips may be secured to the main logic board. Each strip on the camera module may curve to contact a corresponding strip on the main logic board. The arrangement of strips in a linear array may provide increased heat transfer between the camera module and the main logic board using the board as a heat sink for the camera module. 
     The above summary does not include an exhaustive list of all aspects of the present invention. It is contemplated that the invention includes all systems and methods that can be practiced from all suitable combinations of the various aspects summarized above, as well as those disclosed in the Detailed Description below and particularly pointed out in the claims filed with the application. Such combinations have particular advantages not specifically recited in the above summary. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention will now be described with reference to the drawings summarized below. The embodiments of the invention are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment of the invention in this disclosure are not necessarily to the same embodiment, and they mean at least one. 
         FIG. 1  shows a thermal valve when essentially no heat is generated by a camera module and a main logic board. 
         FIG. 2  shows the thermal valve when heat is being generated so that the temperatures of the camera module and the main logic board are high. 
         FIG. 3  shows the thermal valve when the temperature of the camera module is high and the temperature of the main logic board is low. 
         FIG. 4  shows the thermal valve when the temperature of the camera module is low and the temperature of the main logic board is high. 
         FIG. 5  shows an embodiment of the invention where the camera module and the logic board are positioned back-to-back and separated by a thermal valve. 
         FIG. 6  shows the embodiment of  FIG. 5  when the temperatures of the camera module and the logic board are both high. 
         FIG. 7  shows another embodiment of the invention where the camera module and the logic board are positioned side-by-side separated by a thermal valve. 
         FIG. 8  is a cross-sectional view of the embodiment of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION 
     Several embodiments of the invention with reference to the appended drawings are now explained. Whenever the shapes, relative positions, and other aspects of the parts described in the embodiments are not clearly defined, the scope of the invention is not limited only to the parts shown, which are meant merely for the purpose of illustration. Also, while numerous details are set forth, it is understood that some embodiments of the invention may be practiced without these details. In other instances, well-known circuits, structures, and techniques have not been shown in detail so as not to obscure the understanding of this description. 
     Referring to  FIG. 1 , a thermal valve  100  according to an embodiment is shown. The thermal valve  100  may include two thermally conductive strips  110  and  120 . The thermal valve  100  is positioned between two electronic components. The electronic components may be active electronic components. An active electronic component requires power to operate and generates heat during operation. Examples of active components include image sensor arrays, transistors, amplifiers, logic gates, and logic boards (including memory modules). 
     Strip  110  of the thermal valve  100  may be secured to one electronic component, such as a camera module  150 . Strip  120  of the thermal valve  100  may be secured to another electronic component, such as a main logic board  170 . The thermal valve  100 , the camera module  150 , and the main logic board  170  may be integrated within the housing of a mobile device. A mobile device is an electronic portable device that can be used as intended while being carried in the user&#39;s hand. Examples of a mobile device include a smart phone, an MP3 player, a digital camera, and a tablet computer. 
     Strip  110  may include two layers  111  and  112  of two different thermally conductive materials that are laminated together to form the strip  110 . The materials of layer  111  and  112  of strip  110  have different coefficients of thermal expansion to cause the strip  110  to change its shape, such as curving and straightening, in response to temperature changes of the camera module  150 . For example, when the camera module  150  increases in temperature, layer  112  expands more than layer  111 , causing the strip  110  to curve. When the camera module  150  decreases in temperature, the strip  110  straightens. 
     Similarly, strip  120  may include two different layers  121  and  122  of two different thermally conductive materials that are laminated together to form strip  120 . The materials of layers  121  and  122  of strip  120  have different coefficients of thermal expansion to cause the strip  120  to change its shape, such as curving and straightening, in response to temperature changes of the main logic board  170 . For example, when the main logic board  170  increases in temperature, layer  122  expands more than layer  121 , causing the strip  120  to curve. When the main logic board  170  decreases in temperature, the strip  120  straightens. 
     Layer  111  of strip  110  and layer  121  of strip  120  may be the same material, and layer  112  of strip  110  and layer  122  of strip  120  may be the same material, such that the strips  110  and  120  behave similarly under similar temperature ranges. Alternatively, layer  111  of strip  110  may be a different material from layer  121  of strip  120 , and layer  112  of strip  110  may be a different material from layer  122  of strip  120 , such that the strips  110  and  120  behave similarly but under different temperature ranges. 
     Strip  110  may be secured to the camera module  150  along one of its edges and extends toward the main logic board  170 . Strip  120  may be secured to the main logic board  170  along one of its edges and extends toward the camera module  150 . Strip  110  and strip  120  may be positioned such that they are separated (i.e., do not touch each other). In the example shown here, this occurs when strip  110  and strip  120  are both essentially straight, as shown in  FIG. 1 , and when strip  110  and strip  120  are both curved, as shown in  FIG. 2 . Strip  110  and strip  120  are oriented so that they curve, bend, or curl in the same direction in response to temperature increases, as shown in  FIG. 2 . In  FIG. 2 , strip  110  curves toward strip  120 , and strip  120  curves away from strip  110  (with increasing temperature). Strip  110  and strip  120  are at a distance such that strip  110  makes contact with strip  120  only when strip  110  is hot enough to curve toward strip  120  while strip  120  is cool enough to remain essentially straight, as shown in  FIG. 3 . 
     The thermal valve  100  may have two operating states responsive to temperatures of the camera module  150  and the main logic board  170 , including a decoupled state and a coupled state.  FIG. 1 ,  FIG. 2 , and  FIG. 4  show the thermal valve  100  in the decoupled state. The thermal valve  100  is in the decoupled state when the strips  110  and  120  are separated and do not contact each other. In the decoupled state, the thermal valve  100  thermally decouples the camera module  150  and the main logic board  170 . The camera module  150  may need to be thermally decoupled from the main logic board  170  when the temperature of the camera module  150  is low or when the temperature of the main logic board  170  is high. Thermally decoupling the camera module  150  from the logic board  170  creates decreased thermal conductance between the camera module  150  and the logic board  170 . This reduces heat transfer between the camera module  150  and the logic board  170 . 
       FIG. 3  shows the thermal valve  100  in the coupled state. The thermal valve  100  is in the coupled state when strip  110  makes contact with strip  120 . In the coupled state, the thermal valve  100  thermally couples the camera module  150  and the main logic board  170 . Thermally coupling the camera module  150  and the logic board  170  creates increased thermal conductance between the camera module  150  and the main logic board  170 . This enhances heat transfer from the camera module  150  to the main logic board  170  through the thermal valve  100 . When the temperature of the camera module  150  is high and the temperature of the main logic board  170  is low, heat is transferred from the camera module  150  to the main logic board  170  to cool the camera module  150 . Transferring heat from the camera module  150  to the main logic board  170  may help bring the camera module  150  and the main logic board  170  into thermal equilibrium with each other and may help maintain the temperature of the camera module  150  within a specified range. 
     As shown in  FIG. 1 , the thermal valve  100  may be in the decoupled state when essentially no heat is being generated by the camera module  150  and the main logic board  170 . For example, this may occur when both the camera module  150  and the main logic board  170  are either in the off mode or sleep mode of operation. Under this condition, the strips  110  and  120  are straight and do not contact each other. This creates decreased thermal conductance from the camera module  150  to the main logic board  170 . While the temperature of the camera module  150  remains low, such as a temperature below its rated temperature, the strip  110  that is secured to the camera module  150  may remain straight and not make contact with strip  120 , and the thermal valve  100  may remain in the decoupled state, regardless of whether strip  120  is straight or curved, as shown in  FIG. 1  and  FIG. 4 . 
     Referring to  FIG. 2 , when the temperature of the camera module  150  and the temperature of the main logic board  170  are both high, such as temperatures above the rated temperature of the camera module  150 , strip  110  may curve toward strip  120 , and strip  120  may curve away from strip  110 . Strip  110  and strip  120  thus do not contact each other, and the thermal valve  100  is in the decoupled state. This creates decreased thermal conductance between the camera module  150  and the main logic board  170 . 
     When the temperature of the camera module  150  is high, the strip  110  that is secured to the camera module  150  may curve toward strip  120 . As shown in  FIG. 3 , the strip  110  may make contact with the strip  120  while the temperature of the main logic board  170  is low such that the strip  120  is straight. When strip  110  makes contact with strip  120 , the thermal valve  100  is in the coupled state and creates increased thermal conductance from the camera module  150  to the main logic board  170 . However, if the temperature of the main logic board  170  the rises to a high level, strip  120  may curve away from strip  110 , as shown in  FIG. 2 , so that strip  110  no longer is in contact with the strip  120 . The thermal valve is now in the decoupled state, as described above in the previous paragraph. Here, it may be that the main logic board  170  has become too hot to adequately dissipate the heat being generated by the camera module  150 . 
     In  FIG. 4 , the temperature of the camera module  150  is low so that the strip  110  is straight and the strips  110  and  120  do not contact each other. The thermal valve  100  is now in the decoupled state, to create decreased thermal conductance between the camera module  150  and the main logic board  170 . This may represent the understanding that the camera should not be made any warmer (by the heat from the board). 
       FIG. 5  shows an embodiment of the invention where a camera module  550  and a main logic board  570  are positioned back-to-back within the housing (not shown) of a mobile device and separated by a thermal valve  500 . The camera module  550  includes an image sensor chip  551  and may include a heat bridge  560 . The top surface  561  of the heat bridge  560  is thermally connected to the image sensor chip  551 . The heat bridge  560  extends through the base  552  of the camera module  550 . The heat bridge  560  may protrude out of the bottom of the camera module  550  and extend along the bottom surface of the base  552 . The bottom surface  562  of the heat bridge  560  may be thermally joined or connected to an edge of a strip  110  of the thermal valve  500 . The heat bridge  560  allows heat to transfer from the image sensor chip  551  that is inside the camera module  550  to the thermal valve  500  that is outside the camera module  550 . A strip  120  of the thermal valve  500  may be thermally joined or connected to the main logic board  570 . The main logic board  570  may have an applications processor and memory installed on it. 
     As shown in  FIG. 5 , the thermal valve  500  may include a set of strips  110  arranged in a linear array that is secured to the camera module  550  and a set of strips  120  arranged in a linear array that is secured to the main logic board  570 . For example, the set of strips  110  may be arranged along the edge of the bottom surface  562  of the heat bridge  560 , and the set of strips  120  may be arranged around the strips  110 , as shown in  FIG. 5 . Referring to  FIG. 6 , the strips  110  and  120  may be positioned so that they curve outwardly away from the center of the array in response to a high temperature. Each strip  110  that is secured to the camera module  550  curve toward making contact with a corresponding strip  120  that is secured to the main logic board  570 , and each strip  120  curves away from making contact with the corresponding strip  110 . The arrangement of strips in a linear array may provide increased heat transfer between the camera module  550  and the main logic board  570  when the thermal valve  500  is in the coupled state. 
       FIG. 7  and  FIG. 8  show another embodiment of the invention where the camera module  750  and the main logic board  770  are positioned side-by-side within a housing (not shown) of a mobile device and separated by a thermal valve  700 . The camera module  750  includes an image sensor chip  751  and may include a heat bridge  760 . The top surface  761  of the heat bridge  760  is thermally connected to the image sensor chip  751 . The heat bridge  760  extends through the base  752  of the camera module  750 . The heat bridge  760  may protrude out of the bottom of the camera module  750  and extend along the bottom surface of the base  752 . The side surface  763  of the heat bridge  760  may be thermally joined or connected to a strip  110  of the thermal valve  700 . The heat bridge  760  allows heat to transfer from the image sensor chip  751  that is inside the camera module  750  to the thermal valve  700  that is outside the camera module  750 . A strip  120  of the thermal valve  700  may be thermally joined or connected to the main logic board  770 . The main logic board  770  may have an applications processor and memory installed on it. 
     The thermal valve  700  may include a set of strips  110  arranged in a linear array that is secured to the camera module  750  and a set of strips  120  arranged in a linear array that is secured to the main logic board  770 , as shown in  FIG. 7 . For example, the strips  110  may be arranged around the side surface  763  of the heat bridge  760 , and the strips  120  may be arranged around an edge of the main logic board  770 , as shown in  FIG. 7  and  FIG. 8 . Each strip  110  that is secured to the camera module  750  curve toward making contact with a corresponding strip  120  that is secured to the main logic board  770 , and each strip  120  curves away from making contact with the corresponding strip  110 . The arrangement of strips in a linear array may provide increased heat transfer between the camera module  750  and the main logic board  770  when the thermal valve  700  is in the coupled state. 
     For purposes of explanation, specific embodiments were described to provide a thorough understanding of the present invention. These should not be construed as limiting the scope of the invention but merely as illustrating different examples and aspects of the invention. It should be appreciated that the scope of the invention includes other embodiments not discussed in detail above. Various other modifications, changes, and variations which will be apparent to those skilled in the art may be made in the arrangement, operation, and details of the systems and methods of the present invention disclosed herein without departing from the spirit and scope of the invention as defined in the appended claims. For instance, while the figures show the strips  110  and  120  of the thermal valve being secured directly to the electronic components, an alternative is to have the strips  110  bonded to a thermally conductive base that is then secured to the camera module and the strips  120  bonded to another thermally conductive base that is then secured to the main logic board. Therefore, the scope of the invention should be determined by the claims and their legal equivalents. Such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure. Furthermore, no element, component, or method step is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims.

Metadata:
Filing Date: 20100908
Publication Date: 20121225
Grant Date: 20121225
Priority Date: 20100908
Inventors: TSAI RICHARD
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F1/206", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/206", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 45770585