WO2008100004A1

WO2008100004A1 - Method and apparatus for bonding case of flat plate heat spreader based on brazing

Info

Publication number: WO2008100004A1
Application number: PCT/KR2007/005622
Authority: WO
Inventors: Hyuck-Jin Kwon; Hyun-Tae Kim; Su-Hyeon Kim; Hwan-Hee Oh; Yong-Duck Lee
Original assignee: LS Cable Ltd; LS Mtron Ltd
Current assignee: LS Mtron Ltd; LS Cable and Systems Ltd
Priority date: 2007-02-15
Filing date: 2007-11-08
Publication date: 2008-08-21
Anticipated expiration: 2009-08-15
Also published as: KR100826052B1

Abstract

An apparatus for bonding a case of a flat plate heat spreader based on brazing, the case being formed of a case assembly including an upper case and a lower case such that a space for receiving a heat spread medium in the case assembly is formed and a welding material is secured along a bonding portion therebetween, the apparatus comprises a lower flat plate having a flat upper surface, on which the case assembly is placed; an upper flat plate formed in the shape of a plate of a predetermined thickness and having a high frequency coil arranged uniformly therein; and an adhering means for adhering closely the lower flat plate and the upper flat plate with the case assembly interposed therebetween in such a state that the upper flat plate is heated by applying a high frequency power to the high frequency coil.

Description

METHOD AND APPARATUS FOR BONDING CASE OF FLAT PLATE HEAT SPREADER BASED ON BRAZING

Technical Field

[1] The present invention relates to method and apparatus for manufacturing a flat plate heat spreader, in particular, to a method for bonding a case of a flat plate heat spreader and a bonding apparatus used in the method. Background Art

[2] Recently, with development of high density packaging techniques, electronic equipments such as notebook computers or PDAs get smaller and thinner. Further, as the demands for high responsibility and function improvement of the electronic equipments increase, power consumption increases.

[3] For this reason, electronic components installed in the electronic equipments emit much heat during operation of the electronic equipments. To radiate the heat outwards, various flat plate heat spreaders are used.

[4] The flat plate heat spreader comprises a case assembly including a lower case and an upper case, and a heat spread medium interposed between the lower case and the upper case, such as a screen mesh, and the lower case and the upper case are bonded together except a refrigerant inlet. Next, a refrigerant is injected into the case assembly and the refrigerant inlet is tightly sealed, and thus the flat plate heat spreader is completely manufactured. At this time, a technique for bonding the lower case and the upper case includes mainly TIG (Tungsten Insert Gas) welding, laser welding, soldering or brazing.

[5] FIGs. 1 to 3 are views illustrating a conventional apparatus for bonding a case based on brazing.

[6] In describing the conventional case bonding apparatus and a case bonding method using the apparatus with reference to FIGs. 1 to 3, first, as shown in FIG. 1, the case bonding apparatus comprises a lower mold 30 having a groove 10 for receiving a case assembly. The lower mold 30 has a high frequency coil 20 surrounding the groove 10 where the case assembly will be mounted. As shown in FIG. 2, a case assembly 40 is mounted in the groove 10 of the lower mold 30, and the apparatus is ready for a case bonding process. Next, as shown in FIG. 3, an upper mold 50 and the lower mold 30 are adhered closely together, and a high frequency induction heating is performed on a welding material 45 of the case assembly 40 through the high frequency coil 20 to melt the welding material 45. The melted welding material 45' is cooled and solidified to bond the case assembly 40. [7] However, a case bonding method using the above-mentioned conventional case bonding apparatus requires different grooves of the lower mold depending on shape of the case assembly. Thus, the prior art requires much cost, and is not suitable for application to various shapes of case assemblies. And, the prior art has difficulty in promoting uniform thermal distribution of the lower mold, and consequently in bonding uniformly the case assembly, thereby increasing the defect rate. Disclosure of Invention Technical Problem

[8] The present invention was designed to solve the above-mentioned conventional problems, and an object of the present invention is to provide a case bonding apparatus, in which cases of various shapes of flat plate heat spreaders can be bonded, and a bonding method using the same.

[9] Another object of the present invention is to provide a case bonding apparatus which can maintain uniformly a thermal distribution applied to a welding material when bonding a case, and a bonding method using the same.

[10] The other features, advantages and benefits of the present invention will be understood by the following description, and be explained more clearly through embodiments of the present invention. And, it should be known that the features, advantages and benefits of the present invention will be realized by configurations recited in the claims and combinations thereof. Technical Solution

[11] In order to achieve the above-mentioned objects, an apparatus for bonding a case of a flat plate heat spreader, the case being formed of a case assembly including an upper case and a lower case such that a space for receiving a heat spread medium in the case assembly is formed and a welding material is secured along a bonding portion between the upper case and the lower case, comprises a lower flat plate having a flat upper surface on which the case assembly is placed; an upper flat plate formed in the shape of a plate of a predetermined thickness and having a high frequency coil arranged uniformly therein; and an adhering means for adhering closely the lower flat plate and the upper flat plate with the case assembly interposed therebetween in such a state that the upper flat plate is heated by applying a high frequency power to the high frequency coil.

[12] Preferably, the apparatus further comprises a cooling means for cooling and solidifying the welding material after the welding material included in the case assembly is melted.

[13] Moreover, the cooling means injects a cooling gas between the upper flat plate and the lower flat plate to cool the melted welding material in the case assembly. [14] And, preferably, the apparatus further comprises an atmosphere creating means for creating an atmosphere by providing an oxidation preventing gas to prevent oxidation of the surface of the case assembly caused by the high frequency induction heating when bonding the case assembly, and the oxidation preventing gas is an argon gas or a nitrogen gas.

[15] Further, preferably, the adhering means moves the upper flat plate or the lower flat plate vertically by a press cylinder located above the upper flat plate or below the lower flat plate.

[16] In particular, the high frequency coil in the upper flat plate is arranged uniformly on the same level as a plane horizontal to the upper flat plate.

[17] According to another aspect of the present invention, a method for bonding a case of a flat plate heat spreader based on brazing, the case being formed of a case assembly including an upper case and a lower case such that a space for receiving a heat spread medium in the case assembly is formed and a welding material is secured along a bonding portion between the upper case and the lower case, the method comprises (a) placing the case assembly on a lower flat plate having a flat upper surface; (b) applying power to an upper flat plate formed in the shape of a plate of a predetermined thickness and having a frequency coil arranged uniformly therein to heat the upper flat plate; and (c) adhering closely the lower flat plate and the heated upper flat plate with the case assembly interposed therebetween and melting the welding material of the case assembly to bond the lower case and the upper case of the case assembly together.

[18] Preferably, the method further comprises injecting a cooling gas between the upper flat plate and the lower flat plate to cool and solidify the welding material after melting the welding material.

[19] And, preferably, an atmosphere is created by providing an oxidation preventing gas to prevent oxidation of the surface of the case assembly caused by the high frequency induction heating when bonding the case assembly, and the oxidation preventing gas is an argon gas or a nitrogen gas. Brief Description of the Drawings

[20] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to the description, it should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present invention on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation.

[21] FIGs. 1 to 3 are views illustrating a conventional apparatus for bonding a case based on brazing.

[22] FIG. 4 is a perspective view illustrating an apparatus for bonding a case of a flat plate heat spreader according to an embodiment of the present invention.

[23] FIGs. 5 to 7 are cross-sectional views illustrating the operation of the apparatus for bonding a case of a flat plate heat spreader according an embodiment of the present invention.

[24] FIG. 8 is a flow chart illustrating steps of a method for bonding a case of a flat plate heat spreader according to an embodiment of the present invention. Best Mode for Carrying Out the Invention

[25] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to the description, it should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present invention on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. Therefore, the description proposed herein is just a preferable example for the purpose of illustrations only, not intended to limit the scope of the invention, so it should be understood that other equivalents and modifications could be made thereto without departing from the spirit and scope of the invention.

[26] FIG. 4 is a perspective view illustrating an apparatus for bonding a case of a flat plate heat spreader according to an embodiment of the present invention.

[27] Referring to FIG. 4, the apparatus 100 for bonding a case assembly 200 of a flat plate heat spreader according to the present invention comprises a lower flat plate 110 on which the case assembly 200 of the flat plate heat spreader is placed, an upper flat plate 120 having a high frequency coil 122 arranged uniformly therein, a cooling means (not shown) for injecting a cooling gas, an atmosphere creating means (not shown) configured to prevent oxidation of the case assembly 200, and an adhering means 130 for adhering closely the lower flat plate 110 and the upper flat plate 120.

[28] First, in the apparatus 100 for bonding a case of the flat plate heat spreader according to the present invention, the case assembly 200 to be bonded includes an upper case and a lower case such that a space for receiving a heat spread medium in the case assembly 200 is formed and a welding material is secured along a bonding portion between the upper case and the lower case. And, the case assembly 200 may further include a medium injecting tube for injecting the heat spread medium inside.

[29] The lower flat plate 110 is a support having a flat upper surface, on which the case assembly 200 is placed, and is movable vertically by the adhering means 130 to be mentioned below. And, the lower flat plate 110 does not have a separate mold, and thus various shapes of case assemblies can be placed on the lower flat plate 110, and the lower flat plate 110 has such a sufficient area that case assemblies of various sizes can be placed.

[30] The upper flat plate 120 has the high frequency coil 122 arranged therein, and is formed in the shape of a plate having a predetermined thickness. The upper flat plate 120 is also movable vertically by the adhering means 130 to be mentioned below. The upper flat plate 120 has a flat surface, which is contacted with the case assembly 200 when the upper flat plate 120 is adhered to the lower flat plate 110. And, when a high frequency current is applied to the high frequency coil 122, the high frequency coil 122 in the upper flat plate 120 emits heat, and thus the upper flat plate 120 is heated.

[31] The high frequency coil 122 is arranged uniformly in the upper flat plate 120, which allows to heat and melt uniformly the welding material of the case assembly 200 even though the welding material has any form. For example, as shown in FIG. 4, the high frequency coil 122 may be arranged uniformly on the plane in the form of a square coil. However, the present invention is not limited in this regard, and the high frequency coil 122 may be arranged in the form of a circular coil, a polygonal coil or a zigzag coil.

[32] The adhering means 130 is configured to move the lower flat plate 110 or and the upper flat plate 120 vertically to adhere closely the case assembly 200 located on the lower flat plate 110 and the upper flat plate 120. The adhering means 130 may be realized to various kinds of adhering means, for example a press cylinder installed below the lower flat plate 110 as shown in the drawings. The press cylinder 130 is operated to move upward or downward so that the lower flat plate 110 is moved vertically. Although the drawings show the press cylinder 130 installed below the lower flat plate 110 only, the present invention is not limited in this regard, and the press cylinder may be installed above the upper flat plate 120 only so that the upper flat plate 120 is moved vertically, or the press cylinder may be installed below the lower flat plate 110 and above the upper flat plate 120 together so that the upper flat plate 120 and the lower flat plate 110 are moved downward and upward, respectively, and the flat plates 110 and 120 are adhered closely together.

[33] The cooling means (not shown) is configured to inject a cooling gas between the lower flat plate 110 and the upper flat plate 120. After the case assembly 200 is heated and the welding material is melted, the cooling means injects a cooling gas to cool the case assembly 200, and consequently solidify the melted welding material.

[34] The atmosphere creating means (not shown) is configured to provide an oxidation preventing gas to create an atmosphere in the case bonding apparatus 100 so as to prevent oxidation of the surface of the case assembly 200 in the high frequency heating. The oxidation preventing gas may be an argon gas or a nitrogen gas. However, the present invention is not limited in this regard, and various gases may be used as the oxidation preventing gas to prevent oxidation of the surface of the case assembly 200 caused by the heating.

[35] Hereinafter, the operation of the apparatus 100 for bonding a case of a flat plate heat spreader according an embodiment of the present invention is described with reference to FIGs. 5 to 7.

[36] FIGs. 5 to 7 are cross-sectional views illustrating the operation of the apparatus 100 for bonding a case of a flat plate heat spreader according an embodiment of the present invention.

[37] Referring to FIGs. 5 to 7, first, as shown in FIG. 5, the case assembly 200 to be bonded is placed on the lower flat plate 110. A welding material 210 for bonding the upper case and the lower case together is secured along a bonding surface between the upper case and the lower case of the case assembly 200. Next, a high frequency power is applied to the high frequency coil 122 in the upper flat plate 120 to heat the upper flat plate 120. Here, the high frequency coil 122 in the upper flat plate 120 is arranged on the same level as a plane (A) horizontal to a lower surface of the upper flat plate 120. As a result, the lower surface of the upper flat plate 120 is uniformly heated in the high frequency heating. Accordingly, uniform heating is allowed regardless of shape of the case assembly 200 and form of the welding material 210 included in the case assembly 200.

[38] Next, as shown in FIG. 6, the lower flat plate 110 is moved using the press cylinder

130, so that the lower flat plate 110 is adhered closely to the upper flat plate 120. At this time, the case assembly 200 interposed between the upper flat plate 120 and the lower flat plate 110 is heated by the high frequency coil 122 of the upper flat plate 120, and the welding material 212 included in the case assembly 200 is melted. Here, the melted welding material 212 is drawn into the bonding surface between the upper case and the lower case by a capillary force. And, subsequent to the state shown in FIG. 6, a cooling gas is injected into the heated case assembly 200 between the upper flat plate 120 and the lower flat plate 110 using the cooling means.

[39] As shown in FIG. 7, after the welding material 210 is cooled and solidified by the cooling means, the lower flat plate 110 is moved downward by the press cylinder 130, so that the lower flat plate 110 and the upper flat plate 120 are spaced away. At this time, the case assembly 200 located on the lower flat plate 110 is completely bonded by solidification of the welding material 210.

[40] Hereinafter, a method for bonding a case of a flat plate heat spreader according to an embodiment of the present invention is described with reference to FIG. 8.

[41] FIG. 8 is a flow chart illustrating steps of the method for bonding a case of a flat plate heat spreader according to an embodiment of the present invention. [42] Referring to FIG. 8, first, a case assembly to be bonded in the case bonding process is prepared. At this time, the case assembly includes an upper case and a lower case such that a space for receiving a heat spread medium in the case assembly is formed and a welding material is secured along a bonding portion between the upper case and the lower case. (1)

[43] The prepared case assembly is placed on the lower flat plate of the case bonding apparatus. Here, the lower flat plate has a flat upper surface, on which various shapes of case assemblies can be placed. (2)

[44] Next, power is applied to the high frequency coil included in the upper flat plate to heat the upper flat plate. Here, the upper flat plate also has a flat lower surface, and the high frequency coil in the upper flat plate is arranged on the same level as a plane horizontal to a lower surface of the upper flat plate. (3)

[45] The oxidation preventing gas is provided into the case bonding apparatus simultaneously with heating, which prevents oxidation of the surface of the case assembly caused by the heating. At this time, an argon gas or a nitrogen gas is provided to create an atmosphere. (4)

[46] After the oxidation preventing gas atmosphere is created, the lower flat plate is moved upward, so that the lower flat plate is adhered to the upper flat plate. At this time, the case assembly interposed between the upper flat plate and the lower flat plate is heated by the upper flat plate contacted therewith. Here, the case assembly of any shape can be heated uniformly by the high frequency coil arranged uniformly in the upper flat plate, and accordingly, the welding material included in the case assembly can be melted uniformly. And, after the welding material is melted, the melted welding material is drawn into the bonding portion between the upper case and the lower case of the case assembly by a capillary force (5)

[47] After the heating step, a cooling gas is injected between the upper flat plate and the lower flat plate to cool the case assembly. The case assembly is cooled, and accordingly, the melted welding material in the case assembly is also cooled and solidified. The case assembly is bonded by solidification of the welding material. (6)

[48] After the cooling step, the lower flat plate is moved downward, so that the lower flat plate is spaced away from the upper flat plate, and the case assembly located on the lower flat plate is completely bonded. (7)

[49] It should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present invention on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation.

[50] As such, the preferred embodiments of the present invention were described in detail. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. Industrial Applicability

[51] The case bonding apparatus of the present invention can bond a case regardless of shape of the case, and thus reduces time and cost in comparison with a conventional apparatus that requires different molds depending on shape of the case.

[52] And, the present invention can maintain uniformly a thermal distribution when bonding a case, thereby resulting in a high yield and the reduced defect rate of the case bonding process.

Claims

[1] An apparatus for bonding a case of a flat plate heat spreader based on brazing, the case being formed of a case assembly including an upper case and a lower case such that a space for receiving a heat spread medium in the case assembly is formed and a welding material is secured along a bonding portion therebetween, the apparatus comprising: a lower flat plate having a flat upper surface, on which the case assembly is placed; an upper flat plate formed in the shape of a plate of a predetermined thickness and having a high frequency coil arranged uniformly therein; and an adhering means for adhering closely the lower flat plate and the upper flat plate with the case assembly interposed therebetween in such a state that the upper flat plate is heated by applying a high frequency power to the high frequency coil.

[2] The apparatus for bonding a case of a flat plate heat spreader based on brazing according to claim 1, further comprising: a cooling means for cooling and solidifying the welding material after the welding material included in the case assembly is melted.

[3] The apparatus for bonding a case of a flat plate heat spreader based on brazing according to claim 2, wherein the cooling means injects a cooling gas between the upper flat plate and the lower flat plate to cool the melted welding material in the case assembly.

[4] The apparatus for bonding a case of a flat plate heat spreader based on brazing according to any one of claims 1, further comprising: an atmosphere creating means for creating an atmosphere by providing an oxidation preventing gas between the upper flat plate and the lower flat plate to prevent oxidation of a surface of the case caused by the high frequency induction heating in bonding of the case assembly.

[5] The apparatus for bonding a case of a flat plate heat spreader based on brazing according to claim 4, wherein the oxidation preventing gas is an argon gas or a nitrogen gas.

[6] The apparatus for bonding a case of a flat plate heat spreader based on brazing according to claim 1, wherein the adhering means moves the upper flat plate or the lower flat plate vertically by a press cylinder located above the upper flat plate or below the lower flat plate.

[7] The apparatus for bonding a case of a flat plate heat spreader based on brazing according to claim 1, wherein the high frequency coil in the upper flat plate is arranged uniformly on the same level as a plane horizontal to the upper flat plate.

[8] A method for bonding a case of a flat plate heat spreader based on brazing, the case being formed of a case assembly including an upper case and a lower case such that a space for receiving a heat spread medium in the case assembly is formed and a welding material is secured along a bonding portion therebetween, the method comprising:

(a) placing the case assembly on a lower flat plate having a flat upper surface;

(b) applying power to an upper flat plate formed in the shape of a plate of a predetermined thickness and having a frequency coil uniformly therein to heat the upper flat plate; and

(c) adhering closely the lower flat plate and the heated upper flat plate with the case assembly interposed therebetween and melting the welding material of the case assembly to bond the lower case and the upper case of the case assembly together.

[9] The method for bonding a case of a flat plate heat spreader based on brazing according to claim 8, wherein, in the step (c), after the welding material is melted, a cooling gas is injected between the upper flat plate and the lower flat plate to cool and solidify the melted welding material. [10] The method for bonding a case of a flat plate heat spreader based on brazing according to claim 8 or 9, wherein an atmosphere is created by providing an oxidation preventing gas to prevent oxidation of a surface of the case assembly caused by the high frequency induction heating in bonding the case assembly. [11] The method for bonding a case of a flat plate heat spreader based on brazing according to claim 10, wherein the oxidation preventing gas is an argon gas or a nitrogen gas.