JP2012160688A - Heat sink and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a down-sized heat sink which is easily manufactured and has high reliability, and to provide a method for manufacturing the same.SOLUTION: The heat sink comprises: a plurality of metal thin sheets which have a line of a meandering through hole that becomes a passage for a cooling medium and are stacked each other; sealing sheets which are provided at both sides of the stacked metal thin sheets and serve as a sealing face of the passage; and inlet and outlet ports for the cooling medium, which are provided at the sealing sheets or the metal thin sheets and connected to the passage for the cooling medium. Each of the metal thin sheets has a low-melting-point metal layer formed on at least whole one side surface, which has a melting point lower than that of the metal thin sheet. In addition, each of the metal thin sheets has embossed parts which have a recess part on one side and a convex part on the opposite side respectively and are formed at a plurality of positions except the positions of the through hole. The sealing sheets also have a plurality of embossed parts which have a recess part on one side and a convex part on the opposite side respectively and can be fitted with the embossed parts on the metal thin sheets. The sealing sheets and each of the metal thin sheets are fitted and connected at the embossed parts and jointed by the melting of the low-melting-point metal layer.

Description

  The present invention relates to a heat sink used for a cooling device such as a computer CPU periphery, various laser devices, various motors, and the like, and a manufacturing method thereof.

  In electrical and electronic equipment such as a computer CPU, various laser devices, and various motors, cooling is indispensable because heat generation reduces the performance of the equipment. Cooling methods include cooling the metal material by providing fins etc. to increase the surface area, cooling by forcibly blowing air with a fan, etc., cooling the heat by circulating the refrigerant Various methods are known, such as a method of cooling using a Peltier element.

  For example, Patent Document 1 discloses a process of punching an aluminum brazing sheet to produce a flow path plate in which a part of the refrigerant flow path and a part of the refrigerant inlet / outlet are formed. Forming a refrigerant flow path and the refrigerant inlet / outlet; inserting and fitting a pipe joint into the refrigerant inlet / outlet; and brazing the plurality of laminated flow path plates and the pipe joint together. A heat sink manufacturing method is disclosed.

  In the method of the above document, an aluminum brazing sheet having a brazing material clad on the side to be joined is punched by a turret punch press to create a refrigerant flow path and a refrigerant inlet / outlet, and a plurality of the flow path plates are laminated. Then, the upper plate and the lower plate to be the lid are stacked. In this state, the pipe joint is inserted and the temperature is raised and brazing is performed. Therefore, it is necessary to perform a process of inserting the pipe joint while maintaining the positions of the plurality of flow path plates before joining, and there is a problem that the position of the flow path plates is likely to be shifted. In addition, means for holding the flow path plate, the upper plate, and the lower plate together is also required. Furthermore, since the refrigerant inlet / outlet port is located on the side surface of the flow path plate, the pipe joint connection processing cannot be performed unless the heat sink is laminated and assembled.

  Although it is easily conceivable to manufacture the thin flow path plate as described above by a casting mold, there is a problem that the material is likely to be distorted during shrinkage due to cooling after casting.

In addition, it is possible to manufacture the thin flow path plate as described above by a cutting method, but there is a problem that if the flow path becomes longer, processing takes time and costs increase.

JP 11-87584 A

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a small heat sink that is easy to manufacture and highly reliable, and a method for manufacturing the same.

  In order to solve the above problems, the heat sink according to the present invention is formed by laminating a plurality of thin metal plates having a series of meandering through-holes serving as refrigerant flow paths, and sealing plates serving as sealing surfaces of the flow paths are disposed on both sides. In the heat sink in which the coolant inlet / outlet connected to the coolant channel is provided in the sealing plate or the metal thin plate, a low melting point metal layer having a melting point lower than that of the metal thin plate is formed on each of the metal thin plates at least on one surface. Further, each of the thin metal plates is formed with an embossed portion having a concave portion on one side and a convex portion on the opposite side at a plurality of locations other than the through hole, and the sealing plate has a concave portion on the other side and an opposite side. A plurality of embossed portions that can be fitted with the embossed portions on the metal thin plate in a convex shape are provided, and each of the sealing plates and the metal thin plates are fitted and joined at these embossed portions, Characterized in that it is joined by the melting of the low melting point metal layers.

  It is preferable that a part of the plurality of embossed portions on the thin metal plate is formed in a remaining partition wall portion for forming the meandering through hole on the thin metal plate.

  In addition, it is preferable that at least one of the sealing plates is provided with the refrigerant inlet / outlet, and it is preferable that a screw hole is formed in the refrigerant inlet / outlet.

The low melting point metal layer preferably has a lower melting point than both the metal thin plate and the sealing plate, the material of the metal thin plate and the sealing plate is copper, and the low melting point metal layer is silver or its Alloys are particularly preferred. The purpose of the heat sink is to efficiently absorb heat from the heating element and conduct it to the refrigerant in the refrigerant flow path of the heat sink. Therefore, the metal thin plate and the sealing plate should be made of copper with good thermal conductivity. In this case, a material having a good thermal conductivity is required as a material for joining the laminated plates in that case, and a material having a lower melting point and a better thermal conductivity than the joining material is generally a solder alloy or a silver material. . However, since an internal pressure for circulating the refrigerant liquid is generated in the refrigerant flow path, a silver material that is stronger than the solder alloy in strength is used, and this is good from the viewpoint of thermal conductivity. Usually, the melting point of pure copper is 1080 degrees, and the melting point of silver is 960 degrees. If the melting temperature for bonding is around 1000 degrees, it is close to the melting temperature of the metal thin plate, and it is easy to cause shape deformation etc. I can't. Therefore, in order to solve these problems, when the metal thin plate 1 is a copper material, the low melting point metal layer 21 can be prevented by interposing silver plating or silver foil.
The reason is that the laminated surface of the metal thin film 1 and the sealing plates 2A and 2B made of a copper material are in close contact with each other through the embossed portion with the low-melting point metal layer 21 interposed therebetween. When the temperature is gradually raised, the intermetallic diffusion phenomenon on the contact surface starts and eutectic formation of the silver alloy occurs, and the alloyed state is realized at a relatively low temperature. The melting temperature of the silver alloy is determined by the contents of copper and silver, and from the existing alloy phase diagram, even if the content is half and half, it melts at around 800 degrees. (In the existing copper-silver alloy phase diagram, the melting temperature is 780 ° C for 40% silver and 60% copper) Deformation of the laminated member occurs because the bonding temperature can be lowered by lowering the bonding temperature relative to the melting temperature of the copper material. Good bonding conditions can be set.

As the metal thin plate, an iron material can be used in consideration of applications, costs, etc., but copper is preferable as the low melting point metal layer in that case. Compared to a combination of iron and tin, the combination of iron and copper can dramatically increase the strength of interlaminar bonding and increase the reliability.

  In the method of manufacturing a heat sink according to the present invention, a step of forming a set of copper sealing plates serving as a sealing surface of a refrigerant flow path including an outer shape and a plurality of embossed portions, and a series of meanders serving as a refrigerant flow path A step of forming a predetermined shape including a through hole and an embossed portion having a concave surface on one side and a convex surface on the opposite side from a copper thin metal plate; and silver or silver on at least one surface of the sealing plate and the thin metal plate A step of forming a low-melting-point metal layer made of an alloy, a step of bonding the pair of sealing plates and the thin metal plates by fitting the embossed portions, and thermally melting the low-melting-point metal layer. And the step of joining the sealing plate and the metal thin plate, and the step of forming a refrigerant inlet / outlet on the sealing plate or the metal thin plate.

  According to the present invention, an embossed portion is provided on each of the sealing plate and the thin metal plate, and the embossed portions are fitted and connected to each other at the time of stacking, thereby easily and reliably positioning each other and further holding them integrally. Is possible. Thereby, when joining a sealing plate and each metal thin plate, it is only necessary to raise the temperature and melt the low melting point metal layer without applying pressure. Therefore, it is possible to provide a small heat sink that is easy to manufacture and highly reliable, and a manufacturing method thereof. Further, by providing a through hole on the sealing plate and cutting the screw, it is possible to perform joint connection processing before assembly. Furthermore, since the embossed part is formed so that one side is a concave part and the opposite side is a convex part, it can be formed by simple press working.

  Hereinafter, preferred embodiments of a heat sink according to the present invention will be described with reference to the drawings. FIG. 1 shows a main part assembly diagram of an embodiment of a heat sink according to the present invention. This heat sink is intended to dissipate heat from the CPU for the workstation. Three thin metal plates 1 (copper material having an outer diameter of 80 mm square and a thickness of 1 mm) are arranged in the center, and each thin metal plate 1 is formed with a meandering through hole 4 (width 6 mm). Each metal thin plate 1 is formed with two embossed portions 5 at a total of 10 locations, two at the top and bottom, and six inside including the partition wall 3 separating the through holes 4.

  On both sides of the three thin metal plates 1, sealing plates 2A and 2B functioning as a ceiling portion and a bottom portion for sealing the through hole 4 serving as a refrigerant flow path (copper material having an outer diameter of 80 mm square and a thickness of 1 mm). Is arranged. The sealing plate 2A is provided with through holes at positions corresponding to both end portions of the through hole 4 formed in the thin metal plate 1, and functions as a refrigerant inlet 7 and a refrigerant outlet 8, respectively. It is desirable to form screws in these through holes 7 and 8 so that the connection joints 11 and 12 can be connected.

  As shown in FIG. 4, the sealing plates 2A and 2B and the three metal thin plates 1 are respectively provided at 10 embossed portions so that the convex portions 5B and the concave portions 5A are fitted to each other as shown in FIG. Each material is positioned and bonded simultaneously. A silver layer having a thickness of 5 microns is plated as the low melting point metal layer 21 between the materials.

  The bonded sealing plates 2A and 2B and the three metal thin plates 1 are completely joined to each other by melting the low melting point metal layer 21 disposed between the materials.

  FIG. 2 shows a front view of the completed heat sink according to the present invention, with joints 11 and 12 connected to the refrigerant inlet 7 and the refrigerant outlet 8, respectively. Further, attachment holes 6 are formed at the four corners of the heat sink so that the heat sink can be attached or fixed to the device. FIG. 3 is a side sectional view of the heat sink taken along the AA ′ plane. Since the through holes 4 of the respective thin metal plates 1 are formed at the same position, the partition wall 3 and the upper and lower sealing plates 2A and 2B are shown. Is formed in a sealed space and serves as a refrigerant flow path.

  In addition, since five places are formed in the front-end | tip part of the partition part 3 among the ten embossing parts 5, the intensity | strength of the partition part 3 itself is reinforced by the metal plate 1 fitting mutually.

  Next, the manufacturing method of the Example of the said heat sink is demonstrated. First, the sealing plates 2A and 2B are formed by press punching or the like. At this time, in the above-described embodiment, through holes serving as the refrigerant inlet 7 and the refrigerant outlet 8 are formed only in the sealing plate 2A. At this time, if screws are formed in these through holes, it becomes easy to connect the joint later. Depending on the design, it is possible to form one through hole in each sealing plate to form the refrigerant inlet 7 and the refrigerant outlet 8.

  Next, the through holes 4 and the outer shape of the three metal thin plates 1 are punched out, and the embossed portion simultaneously forms a concave portion and a convex portion by projecting a dowel or the like. Since all three sheets have the same shape, the same mold can be used. The metal thin plate 1 can be provided with a low melting point metal layer in advance on at least one side.

  Subsequently, the three metal thin plates 1 and the two sealing plates 2A and 2B are overlapped and pressed, and the embossed portions are fitted and joined to be integrated. The steps up to here can be performed continuously by using a progressive die, for example.

  The integrated heat sink assembly is put in a high temperature bath of, for example, about 830 ° C., and the low melting point metal layer is melted and then cooled. In this example, silver is used as the low melting point metal layer, but other materials such as other silver alloys or solders can be selected according to the type of the sealing plate or metal thin plate.

In this heat sink prototype, the metal thin plate was made of copper and the low melting point metal layer was plated with silver. However, considering other heat dissipation applications, the metal thin plate was made of iron, which is compatible with iron. The types of melting point metal layer materials and melting furnaces for joining them were also examined in parallel. Two types of tin and copper were studied as low melting point metal layer materials having a melting point lower than that of iron and can be easily implemented, and a joining test was carried out with two types of melting furnaces, an electric furnace and a non-oxidizing furnace.
The following is the joint tensile strength test data performed.
* Low melting point material is tin, thickness 3μ, electric furnace 0.8kg-1kg / mm ^ 2
* Low melting point material is tin, thickness 5μ, 1kg / mm ^ 2 for electric furnace
* Low melting point material is tin, thickness 3μ, non-oxidizing furnace 6kg-7kg / mm ^ 2
* Low melting point material is tin, thickness 5μ, non-oxidizing furnace 4kg ~ 5Kg / mm ^ 2
* Low melting point material is copper, thickness 3μ, 25kg-30Kg / mm ^ 2 for electric furnace
* Low melting point material is copper, thickness 5μ, 20kg to 25kg / mm ^ 2 for electric furnace
From the above results, when the same electric furnace is used for both tin and copper, the strength is higher when copper is used. Considering the original tensile strength of copper and tin, copper = 25kg / mm ^ 2, tin = 8kg / mm ^ 2, tin has poor flowability due to surface oxidation during melting, resulting in insufficient bonding. I know that. Even in the case of using a non-oxidizing furnace, in the case of tin, the flowability due to the surface oxidation phenomenon is poor at the time of melting, and a stable joining state cannot be obtained.
Regarding the thickness, the strength is slightly more stable at 3 μ than at 5 μ.
As a result, when the metal thin plate material was iron, the copper material could be stably secured as the low melting point metal layer.

  As described above, according to the present invention, it is possible to provide a small heat sink that is easy to manufacture and highly reliable and a method for manufacturing the same, and thus can greatly contribute to the field of cooling electrical and electronic equipment.

The present invention is an assembly view showing the configuration of the main part of the heat sink according to the present invention. It is a front view of the heat sink by this invention. It is side surface sectional drawing of the heat sink shown in FIG. It is a figure which shows the coupling | bonding state of the heat sink main part by this invention shown in FIG.

DESCRIPTION OF SYMBOLS 1 Metal thin plate 2A, 2B Sealing plate 3 Partition part 4 Through-hole 5 Embossed part 5A Concave part 5B Convex part 6 Mounting hole 7 Refrigerant inlet 8 Refrigerant outlet 11 Joint 12 Joint 21 Low melting-point metal layer

Claims (10)

A plurality of thin metal plates having a series of meandering through-holes serving as refrigerant flow paths are stacked, and sealing plates serving as sealing surfaces of the flow paths are disposed on both sides, and the refrigerant flow is applied to the sealing plate or the thin metal sheets. In the heat sink provided with the refrigerant inlet / outlet connected to the passage, each of the metal thin plates has a low melting point metal layer having a melting point lower than that of the metal thin plate at least on one surface, and each of the metal thin plates has Embossed portions having a concave portion on one side and a convex portion on the opposite side are formed at a plurality of locations other than the through hole, and the sealing plate has a concave portion on one side and a convex portion on the opposite side, and an embossed portion on the metal thin plate. A plurality of embossed portions that can be fitted are provided, and each of the sealing plates and the metal thin plates are fitted and joined at these embossed portions, and are joined by melting the low melting point metal layer. Heat sink to. The heat sink according to claim 1, wherein a part of the plurality of embossed portions on the thin metal plate is formed in a remaining partition wall portion for forming the meandering through hole on the thin metal plate. The heat sink according to claim 1 or 2, wherein the refrigerant inlet / outlet is provided on at least one of the sealing plates. The heat sink according to any one of claims 1 to 3, wherein a screw hole is formed in the refrigerant inlet / outlet. 5. The heat sink according to claim 1, wherein the low-melting-point metal layer has a lower melting point than any of the metal thin plate and the sealing plate. The heat sink according to any one of claims 1 to 5, wherein the metal thin plate and the sealing plate are made of copper. The heat sink according to any one of claims 1 to 6, wherein the low melting point metal layer is silver or an alloy thereof. The heat sink according to any one of claims 1 to 5, wherein a material of the metal thin plate and the sealing plate is copper, and the low melting point metal layer is silver or an alloy thereof. The heat sink according to any one of claims 1 to 5, wherein a material of the metal thin plate and the sealing plate is iron, and the low melting point metal layer is copper or an alloy thereof. A step of forming a set of copper sealing plates to be a sealing surface of the refrigerant flow path including the outer shape and the plurality of embossed portions; a series of meandering through holes to be the refrigerant flow paths; A step of forming a predetermined shape including an embossed portion whose surface is a convex portion from a copper metal thin plate, and a step of forming a low melting point metal layer made of silver or a silver alloy on at least one surface of the sealing plate and the metal thin plate And joining the set of sealing plates and the metal thin plates by fitting the embossed portions, and thermally melting the low melting point metal layer to form the sealing plates and the metal thin plates. A method of manufacturing a heat sink, comprising: a step of joining; and a step of forming a refrigerant inflow / outlet in the sealing plate or the metal thin plate.

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