A stretchable thermal conductive patch with adjustable thermal conductivity and a preparation method thereof

Abstract

The application aims to provide a stretchable heat-conducting patch with adjustable heat-conducting coefficient and a preparation method thereof, and belongs to the technical field of flexible heat-conducting patches. The heat-conducting patch is provided with a through hole on a silicone rubber layer, and a heat-conducting metal layer is plated on the inner wall of the through hole by electroplating. Meanwhile, the heat dissipation area to the outside and the stretchability of the heat-conducting patch are increased by the design of a serpentine grid structure on the surface of the silicone rubber layer away from the device. The heat-conducting coefficient of the heat-conducting patch is adjusted by adjusting the density of the through hole. The heat-conducting coefficient of the application can reach 5-20 W / m.k, which is much higher than the heat-conducting coefficient (about 2 W / m.k) of the existing heat-conducting silicone rubber patch.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of flexible heat-conducting patches, and particularly relates to a stretchable heat-conducting patch with adjustable heat-conducting coefficient and a preparation method thereof. BACKGROUND

[0002] With the wide application of stretchable electronic devices, the heat management problem is increasingly prominent. Especially the electronic components of wearable electronics, if they cannot be effectively and quickly cooled down when in use, the heat generated by the electronic components will potentially cause skin burns. Moreover, the heat generated by different components varies significantly, for example, the heat generated by light-emitting components is much greater than that generated by other components. In addition, the increase of the heat-conducting coefficient of the existing heat-conducting silicone is often achieved by increasing the heat-conducting filler, which results in the decrease of the stretchability of the heat-conducting silicone. Therefore, the adjustable heat-conducting coefficient can realize the heat dissipation of local high-heat components and avoid the significant decrease of the stretchability of the entire circuit caused by the increase of the overall heat dissipation coefficient.

[0003] At present, most of the heat dissipation patches achieve heat dissipation through a metal layer, such as the heat dissipation patch of patent CN103805082B, which includes a graphite layer, a heat-conducting adhesive layer, a release material layer, a copper layer and an aluminum layer. Through the matching of the multi-layer structure, the uniformity of heat dissipation of the heat-conducting patch is improved. However, this method has two shortcomings: first, the preparation process is complex; second, the addition of the metal layer seriously limits the stretchability of the heat dissipation patch, affecting its use in wearable devices. The commonly used flexible heat dissipation patch is mainly composed of polymers doped with high-heat-conducting particles (Zhu Ningning. Influence of BN and AlN particles on the performance of heat-conducting silicone [D]. Harbin Institute of Technology, 2012.), in which the high-heat-conducting particles are mainly boron nitride and aluminum oxide. However, the heat-conducting coefficient of the composite heat-conducting silicone sheet doped with the above particles does not exceed 4wmk. The above heat-conducting coefficient is difficult to cope with the heat dissipation problem in the application process of wearable electronics, and the doping of too many heat-conducting particles will also limit the stretchability of the heat-conducting silicone sheet.

[0004] Therefore, how to simply realize the preparation of the stretchable and heat-conducting patch with adjustable heat-conducting coefficient has become a problem to be solved in the field of stretchable electronic devices. SUMMARY

[0005] In view of the problems existing in the background art, the purpose of the present application is to provide a stretchable heat-conducting patch with adjustable heat-conducting coefficient and a preparation method thereof. The heat-conducting patch is provided with through holes on the silicone rubber layer, and a layer of heat-conducting metal layer is plated on the inner wall of the through holes by electroplating. At the same time, the structure of the serpentine grid is designed on the surface of the silicone rubber layer far from the device to increase the heat dissipation area and the stretchability of the heat-conducting sheet. The density of the through holes is adjusted to adjust the heat-conducting coefficient of the heat-conducting patch.

[0006] To achieve the above object, the technical scheme of the present application is as follows:

[0007] A stretchable heat-conducting patch with adjustable thermal conductivity, comprising a top contact layer, a silicone rubber layer and a bottom contact layer; a through hole is arranged on the silicone rubber layer, and a heat-conductive metal layer is attached to the inner wall of the through hole; the top contact layer and the bottom contact layer are the same serpentine structure, and the two ends of the through hole are connected with the serpentine lines respectively; the thermal conductivity of the stretchable heat-conducting patch is changed by adjusting the density of the through hole.

[0008] Further, the heat-conductive metal layer attached to the inner wall of the through hole is arranged by electroplating.

[0009] Further, the heat-conductive metal is preferably copper, aluminum or the like.

[0010] Further, the greater the density of the through hole, the higher the thermal conductivity; the diameter of the through hole is 0.1-0.5mm, and the hole density is 1-5 / cm 2 .

[0011] A method for preparing a stretchable heat-conducting patch with adjustable thermal conductivity, comprising the following steps:

[0012] Step 1. Coating liquid silicone on the surface of copper foil by coating process, and then heating and curing;

[0013] Step 2. Coating liquid silicone on the surface of the silicone cured in step 1 again, and rolling and pasting another copper foil on the surface of the liquid silicone, and then curing under pressure and temperature; the curing under pressure and temperature is to remove the air bubbles between the copper foil and the silicone rubber, and to ensure the flatness, so as to obtain a double-sided copper-clad plate;

[0014] Step 3. Preparing a through hole on the double-sided copper-clad plate by laser drilling, and the diameter of the through hole is 0.1-0.5mm; then electroplating a heat-conductive metal layer on the inner wall of the through hole by black hole-electroplating process;

[0015] Step 4. Processing the upper and lower copper layers of the sample obtained in step 3 to obtain the top contact layer and the bottom contact layer with serpentine structure, and the two ends of the through hole are connected with the serpentine lines respectively, so as to obtain the required stretchable heat-conducting patch.

[0016] Further, the coating process in step 1 can use doctor blade coating, slot coating, etc.; the curing temperature is 60-80℃, and the time is 3h.

[0017] Further, the specific parameters of the curing under pressure and temperature in step 2 are: the pressure is 10-14Mpa, the temperature is 60-80℃, and the time is 1-3h.

[0018] Further, in step 3, the through holes are arranged in a uniform array or a non-uniform array; when the through holes are arranged in a uniform array, the hole density is 1-5 per cm 2 .

[0019] Further, in step 3, the black hole-electroplating process comprises the following steps: cleaning, hole finishing, black hole, micro-etching and electroplating; the cleaning is used to remove residues generated in the laser processing process and clean the hole wall; the hole finishing is used to change the charge characteristics of the hole wall surface, so that the carbon black in the black hole liquid can be more effectively attached to the inner side of the hole wall; the black hole is that the plate after hole finishing is soaked in the carbon black aqueous dispersion liquid and dried, so that a conductive carbon black layer is formed on the inner side of the hole wall for subsequent electroplating process; the micro-etching is used to remove excess carbon black on the surface of the copper foil to improve the electroplating quality of the surface; the electroplating is used to electroplate a layer of heat-conducting metal on the inner wall of the through hole.

[0020] Further, if the conductive metal layer is a copper layer, the electroplating is that the plate after micro-etching is placed on the anode of a copper sulfate electroplating ruler for electroplating, the electroplating current density is 2 A / dm 2 , and the electroplating time is 1-6 h.

[0021] Further, in step 4, the processing technology is etching or laser engraving.

[0022] In summary, due to the adoption of the above technical solutions, the present application has the following advantages:

[0023] The present application realizes high thermal conductivity coefficient without loss of the stretchability of the thermal conductive patch by preparing through holes on the silicone rubber layer and cooperating with the structure of the serpentine grid line. More specifically, the heat-conducting metal layer is arranged on the inner wall of the through hole to realize high thermal conductivity coefficient in the thickness direction; through the structural design of the serpentine grid, the heat dissipation area of the device and air is improved while the stretchability of the thermal conductive silicone rubber plate is guaranteed. Experimental results show that the increase of the hole density can significantly improve the thermal conductivity coefficient of the patch. The thermal conductivity coefficient of the present application can reach 5-20 W / m.k, which is much higher than the thermal conductivity coefficient of the existing thermal conductive silicone rubber sheet (about 2 W / m.k). BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Fig. 1 is a structural schematic diagram of the thermal conductivity coefficient adjustable stretchable thermal conductive patch of the present application;

[0025] In the figure, 1 is a top contact layer, 2 is a silicone rubber layer, 3 is a bottom serpentine grid layer, and 4 is a through hole.

[0026] Figure 2 Fig. 4 is a thermal conductivity coefficient diagram of the thermal conductive patch under different hole densities. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is described in further detail below with reference to the embodiments and drawings.

[0028] A stretchable thermal conductive patch with adjustable thermal conductivity, a structural schematic diagram of which is shown in Figure 1 The stretchable thermal conductive patch comprises a top contact layer 1, a silicone rubber layer 2 and a bottom contact layer 3. A through hole 4 is arranged on the silicone rubber layer 2, and a thermal conductive metal layer is attached to the inner wall of the through hole. The top contact layer 1 and the bottom contact layer 3 are in the same serpentine line structure, and the two ends of the through hole 4 are connected with the serpentine line respectively. The thermal conductivity of the stretchable thermal conductive patch is changed by adjusting the density of the through hole.

[0029] Embodiment 1

[0030] A preparation method of a stretchable thermal conductive patch with adjustable thermal conductivity, comprising the following steps:

[0031] Step 1. A liquid silicone rubber is coated on the surface of a first copper foil by a doctor blade coating process, and then cured at 60℃ for 3h. The thickness of the first copper foil is 15μm, and the thickness of the silicone rubber coating is 100μm. The silicone rubber used is a thermal conductive silicone rubber.

[0032] Step 2. Liquid silicone rubber is again coated on the surface of the cured silicone rubber in step 1, and a second copper foil is roll-bonded on the surface of the liquid silicone rubber, and then pressure and heat curing is performed to remove the air bubbles between the copper foil and the silicone rubber and ensure flatness, thereby obtaining a double-sided copper-clad plate. The pressure is 10Mpa, the temperature is 60℃, and the time is 3h.

[0033] Step 3. Array through holes are prepared on the double-sided copper-clad plate by laser drilling, with a diameter of 0.5mm and a hole density of 5 / cm 2 . Then a layer of copper layer is electroplated on the inner wall of the through hole by black hole-electroplating process, with an electroplating current density of 2A / dm^2, an electroplating time of 3h, and a thickness of the electroplated copper of 15μm.

[0034] The double-sided copper-clad structure is for electroplating. The prerequisite for electroplating in the hole is that the hole must be linked with a conductive object to be able to electroplate. If the hole is drilled first and then the copper is coated, the hole will be blocked by the copper foil, thereby failing to achieve the effect of electroplating.

[0035] Step 4. The upper and lower copper layers of the sample obtained in step 3 are laser engraved to obtain a serpentine line structure of the top contact layer and the bottom contact layer, and the two ends of the through hole are connected with the serpentine line respectively, thereby obtaining the required stretchable thermal conductive patch.

[0036] The copper serpentine grid on the contact surface between the heat-conductive patch and the component is to increase the contact area between the heat-conductive patch and the component, and then increase the heat-conductive path from the component to the heat-conductive patch; the serpentine grid realizes the purposes of stretchability and increasing the heat-conductive contact area. The serpentine grid on the contact surface between the heat-conductive patch and air is to increase the heat-dissipating area of the heat-conductive patch and air, and also to ensure the overall stretchability of the heat-conductive patch.

[0037] Example 2

[0038] The stretchable heat-conductive patch was prepared according to the procedure of Example 1, only the density of the holes in Step 3 was adjusted to 0, 6.7, 10 and 20, and other steps were unchanged.

[0039] The heat-conductive coefficient diagrams of the stretchable heat-conductive patches obtained in Example 1 and Example 2 are shown in FIG. 1 and FIG. 2, respectively. Figure 2 As can be seen from the diagrams, the heat-conductive coefficient of the heat-conductive patch is greater with the increase of the hole density per unit area; however, too many holes will result in the decrease of the stretchability of the heat-conductive patch, because the proportion of the copper area will increase and the proportion of the silicone area will decrease with too many holes; the decrease of the proportion of the silicone area will result in the decrease of the stretchability.

[0040] The above is only a specific embodiment of the present application, any feature disclosed in the specification can be replaced by other equivalent or similar purpose features unless specifically stated; all features disclosed, or steps in all methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A stretchable thermal patch with adjustable thermal conductivity, characterized in that, The stretchable thermal conductive patch comprises a top contact layer, a silicone rubber layer and a bottom contact layer; a through hole is arranged on the silicone rubber layer, and a thermal conductive metal layer is attached to the inner wall of the through hole; the top contact layer and the bottom contact layer are in the same serpentine structure, and the two ends of the through hole are connected with the serpentine lines respectively; the thermal conductivity of the stretchable thermal conductive patch is changed by adjusting the density of the through hole; The stretchable thermal conductive patch is prepared according to the following steps: Step 1: liquid silicone rubber is coated on the surface of a copper foil by coating process, and then heated and cured; Step 2: liquid silicone rubber is coated again on the surface of the silicone rubber cured in step 1, and another copper foil is laminated on the surface of the liquid silicone rubber by rolling, and then pressure and heat curing is performed to obtain a double-sided copper-clad plate; Step 3: a through hole is prepared on the double-sided copper-clad plate by laser drilling, and the diameter of the through hole is 0.1-0.5mm; then a thermal conductive metal layer is electroplated on the inner wall of the through hole by black hole-electroplating process; Step 4: the upper and lower copper layers of the sample obtained in step 3 are processed to obtain the top contact layer and the bottom contact layer in the serpentine structure, and the two ends of the through hole are connected with the serpentine lines respectively, so that the required stretchable thermal conductive patch is obtained.

2. The stretchable thermal patch of claim 1, wherein, The thermal conductive metal layer attached to the inner wall of the through hole is arranged by electroplating method.

3. The stretchable thermal patch of claim 2, wherein, The thermal conductive metal is copper or aluminum.

4. The stretchable thermal patch of claim 1, wherein, The greater the hole density, the higher the thermal conductivity; the hole density is 1-5 per cm 2 .

5. The stretchable thermal patch of claim 1, wherein, The coating process in step 1 adopts doctor blade coating or slot coating; the curing temperature is 60-80℃, and the time is 3h.

6. The stretchable thermal patch of claim 1, wherein, The specific parameters of pressure and heat curing in step 2 are as follows: the pressure is 10-14Mpa, the temperature is 60-80℃, and the time is 1-3h.

7. The stretchable thermal patch of claim 1, wherein, In step 3, the through holes are arranged in a uniform array or a non-uniform array; when the through holes are arranged in a uniform array, the hole density is 1-5 per cm 2 .

8. The stretchable thermal patch of claim 1, wherein, In step 3, the black hole-electroplating process comprises the steps of cleaning, hole finishing, black hole, micro-etching and electroplating; wherein the cleaning is used to remove the residues generated in the laser processing process and clean the hole wall; the hole finishing is used to change the charge characteristics of the hole wall surface, so that the carbon black in the black hole liquid can be more effectively attached to the inside of the hole wall; the black hole is to immerse the plate dried after the hole finishing in the aqueous dispersion liquid of carbon black and dry, so that a layer of conductive carbon black layer is formed on the inside of the hole wall for the subsequent electroplating process; the micro-etching is used to remove the excess carbon black on the surface of the copper foil to improve the electroplating quality of the surface; the electroplating is used to electroplate a layer of heat-conducting metal layer on the inner wall of the through hole; if the conductive metal layer is a copper layer, the electroplating is to place the plate treated by the micro-etching on the anode of the copper sulfate electroplating ruler to electroplate, the electroplating current density is 2 A / dm 2 , and the electroplating time is 1-6 h.

9. The stretchable thermal patch of claim 1, wherein, The processing technology in step 4 is etching or laser engraving.

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