JPH01264295A - Cooling fin of electronic device - Google Patents

Abstract

PURPOSE:To obtain highly accurate cooling fins having a uniform size and accuracy, by dividing cooling fins into plate members that are simple configuration elements and combining these elements by junction. CONSTITUTION:When a base plate 1 consisting of AlN and vertical plates 6 and 7 are joined by a laminate 3, the laminate 3 is set at the side of a junction face between the vertical plates 6 and 7 and the base plate 1, that is, at a part protruding from a jig 8 after the vertical plates 6 and 7, first of all, are inserted in the prescribed positions of grooves 9 of the jig 8. Further, after the base plate 1 is placed on the top of the junction face side, the whole body is pressed by a jig 10. AlN is used as the jig 8 to prevent the generation of differential thermal expansion in comparison with the thermal expansion of a junction member. After performing these preparations, the laminate 3 is heated in an atmosphere of a vacuum of 10<-4>Torr or less up to a temperature of 600 deg.C and it is pressurized under pressure of 0.5kgf/mm<2>. Such a state is maintained for fifteen min. and then, it is cooled. In such a junction process, only both surface layers of the laminate 3 consisting of Al-Si-Mg alloy having a melting point of about 583 deg.C change to a melting state and join to AlN of the base plate 1 and the vertical plates 6 and 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a structure of a fin made of a ceramic member or a sintered metal member and a method for manufacturing the same, and particularly to a cooling fin suitable for cooling electronic devices.

[Conventional technology]

Conventional cooling fins for electronic devices are disclosed in Japanese Patent Application Laid-Open No. 60-1268.
As described in Publication No. 53, in order to cool the heat generated in the chip, the base surface of one cooling fin is directly pressed against the back of the chip, and the other cooling fin is fitted with a small gap between the two cooling fins. It was used in the structure for arranging fins.

[Problem to be solved by the invention]

The semiconductor chip targeted in the above-mentioned prior art generates a large amount of heat and requires forced cooling means. Therefore, the temperature of the cooling fin itself, which is pressed against the back surface of the chip as a cooling member, increases when the heat generated by the chip is conducted.

Therefore, the cooling fins thermally expand depending on the thermal expansion coefficient depending on the material of the cooling fins. Regardless of whether the material of the cooling fin is the same or different from the chip material (Si), a temperature difference will occur between the chip and the cooling fin, and a relative displacement will occur due to the difference in thermal expansion on the pressed surface, causing heat generation and cooling of the chip. is repeated accordingly.

In this case, when the material of the cooling fin is a metal such as Cu or AQ, there is a problem in that the corners on the back side of the chip have sharp notches, and pressing the cooling fin against the back side of the chip damages the surface.

As a means to solve this problem, a method may be considered in which the cooling fins pressed against the back of the chip are made of ceramics with high thermal conductivity, sintered alloy with good thermal conductivity, or the like.

However, as shown in the above-mentioned conventional technology, the cooling fins that are fitted together with minute intervals require high precision in shape, and when formed from difficult-to-cut materials such as ceramics, it is difficult to process them as an integral structure. Moreover, even if machining is possible, the tools are subject to severe wear and tear, making it difficult to produce large quantities of products with the same dimensions.

(Means for solving problems) The object of the present invention is to address the problems of the prior art.

This can be achieved by changing the manufacturing method to only machining to a manufacturing method in which the cooling fins are divided into plate-like members, which are simple components, and then assembled by joining.

Examples of embodiments of the invention are as follows.

(1) 0.25can/em・s・” as a plate member
A ceramic material having a thermal conductivity of 0 or more was used.

(2) High thermal conductivity SiC, high thermal conductivity AAN, BeO, etc. were used as the ceramic member.

(3) A sintered alloy material having a thermal conductivity of 0.25CaQ/Cm-8.degree. C. or higher was used as the plate member.

(4) Copper tungsten and copper molybdenum sintered alloy materials were used as the sintered alloy materials.

(5) As a method for joining both plate-like members, a laminated material was used in which the core material was pure AM or AQ alloy 2 and the skin material was AQ alloy whose melting temperature was lower than that of the core material.

(6) The material of the joining jig for the cooling fins is the same as that of the plate member.

(7) In the cooling fin manufacturing method, the bonding jig structure has a laminated structure of plate-like parts.

[Effect]

The cooling fin of the present invention shown in FIG.
It is composed of a laminated plate 3 that joins the two.

As shown in FIG. 2, the laminate 3 has a three-layer structure including a core material 4 made of pure AQ or an AQ alloy, and a surface layer 5 made of an AQ-8i-Mg alloy.

When joining the base board 1 and the vertical board 2, only both surface layers 5 of the laminate board 3 are melted and joined.

When the method of the present invention is used, both the base plate 1 and the vertical plate 2 serving as the fins are formed of flat plates that can easily be machined with high accuracy in thickness, which is an important dimensional accuracy. The thickness of the vertical plate 2 corresponds to the thickness of the cooling fins, and the fin thickness is highly accurate. The spacing between the fins, that is, the groove width, is a dimension that depends on the assembly precision of the assembly jig used for joining, and by using a jig machined with high precision, high precision cooling fins can be manufactured.

In addition, since the cooling fin of the present invention requires high thermal conductivity, the laminated plate 3 that joins the base plate 1 and the plurality of vertical plates 2
High thermal conductivity is also required for this, but there is no problem because the laminate a is made of AQ alloy with high thermal conductivity.

Therefore, (1) the cooling fin of the electronic device of the present invention has a thermal conductivity equivalent to that of a cooling fin having a monolithic structure, and is formed of a plate-like member that is easy to process. The groove width and fin width of the cooling fins gradually change depending on the wear of the grinding wheel, making it difficult to mass-produce cooling fins with the same precision.However, it is easy to mass-produce cooling fins with the same precision. [Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 3 to 6.

Figures 3 to 5 show a specific method of manufacturing a cooling fin having a discontinuous part in the center fin.
A laminated plate 3 consists of a base plate 1 having a thermal expansion coefficient of QN C: approximately 4.4 x 10-'/''C) and a vertical plate A6° and a vertical plate B7.
Figure 4 shows the arrangement before joining when joining by
These cooling fin members are shown set on a jig.

Jig A8 is a vertical plate A6 which becomes a fin. It has a groove A9 slightly wider than the thickness of the vertical plate B7. First, insert the vertical plate A6 into the groove A9 of the jig A8. After fitting the vertical plate B7 into the predetermined position, the laminate plate 3 is attached to the vertical plate A6. Base Fi1 of vertical plate B7
It is placed on the joint surface side with the jig A8, that is, on the part protruding from the jig A8.

Furthermore, after stacking the base plate 1 on top of it, jig B]-0
AQN was used for the jig A8, which holds the whole together, so as not to cause a difference in thermal expansion with the joining member.

After such preparation, heat to 600°C in a vacuum atmosphere (below 10'-'Torr) L;'=I1.0.5kgf
/mwm'' pressure, maintained for 15 minutes, and then cooled.

In this bonding process, the laminate 3 is bonded to A of melting point approximately 583°C.
Only both surface layers made of l-81-Mg alloy are in a molten state, and the base plate 1. Vertical board A6. Connected to AQN of vertical plate B7.

According to this example, a flat plate that is easy to process and has good dimensional accuracy is used, and furthermore, the occurrence of shape defects due to the difference in thermal expansion coefficient between jig A8 and the joining member during the heating and cooling process during joining is prevented. In order to do this, the jig A was made of the same material AQN as the joining member, which has the effect that cooling fins with good dimensional accuracy can be easily manufactured.

In addition to the AQN material explained in the example, high thermal conductivity S
Similar effects can be obtained by using a C@CuMo sintered alloy or a CuW sintered sintered alloy.

Another embodiment will be explained with reference to FIG. FIG. 6 shows cooling fins of a vertical plate 2 that is joined to a base plate 1 made of high thermal conductivity SiC via a laminated plate 3, with high thermal conductivity S3. This is an example of a cooling fin using two types of members: a vertical plate D12 made of AQN at the center of a vertical plate C1l made of C; The bonding preparation, jig, heating, and pressure conditions are the same as before.

Table According to this embodiment, as is clear from the physical constants shown in the table, the thermal conductivity of the vertical plate D12 made of AQN placed at the center of the cooling fin is higher than that of the vertical plate D12 made of AQN placed at the center of the cooling fin.
The thermal conductivity of iC is high, and the thermal conduction of the entire cooling fin is A
It exhibits a value approximately intermediate between cooling fins made only of QN or only high thermal conductivity SiC. The difference in thermal expansion between AQN and high thermal conductivity SiC is small as shown in Table 1, and deformation due to bonding is extremely small.

In this example, two types of materials selected from among the low thermal expansion and high thermal conductivity materials shown in the table were explained, but cooling fins having any heat conductivity can be manufactured by various combinations of the materials in the table.

Still other embodiments will be described with reference to FIGS. 7 to 9.

FIG. 7 shows the assembly order of the jig and the AQN cooling fin material onto the jig.

First, groove B1 accommodates plate jig A1-7 and plate jig B18.
5, and a plate jig A17 and a plate jig B18 in the groove B15 of the jig base 13 having the groove C16 for guiding the pushing jig 14.
and are laminated alternately. The stacking direction is the direction pushed by the pushing jig 14.

The heights of plate jig A1-7 and plate jig B18 are hi and h2.
The difference hx-ha between the two is the vertical plate 2 of the cooling fin.
be smaller than the height a. Furthermore, the plate thickness tt of plate jigs A and B
, tz and the plate thickness t of the vertical plate 2 is set as tz > t, and tl is an arbitrary dimension since it depends on the pitch of the cooling fins. In this example, h = 12 m, hz = 6
m, h=8w, ti=2, 0 m, t, z
= 2, 30 m, t = 2, 28 m
And so.

Further, the length a of the vertical plate 2 was set to 25+s.

In this embodiment, the number of vertical plates 2 of the cooling fins is five. Therefore, as shown in FIG. 7, the plate jig is plate jig A1.
7 and five plate jigs 818 were used. Each plate jig is placed in close contact with the bottom of the groove B15 of the jig base 13, and is pressed in the stacking direction of the plate jig by the pressure piece 14 loaded in the groove 016. The pressurizing piece 14 is pressurized using a pressurizing bolt 25 attached to a push plate 24 fixed to the end face 23 of the jig base 13 with a bolt 26. The pressing position of the plate jig is the plate jig B1 pressed against the bottom of the groove B15.
The pressure piece 14 was shaped as shown in FIG. 8 to prevent the laminated plate jigs from lifting up due to pressure. In other words, the end surface side that the bolt 26 contacts is
A component of the pressure applied by the bolt 26 moves the pressure piece 14 into the groove C.
The inclined portion 27 is provided so as to also occur in the direction in which it is pressed against the portion 16.

Next, we will discuss the thermal expansion coefficient and length of the jig material in the jig used in this example.1 The water bonding jig has a structure in which plate-like members are laminated, and in bonding. Exposure to high temperatures (approximately 600°C). Therefore, it is necessary to construct a jig so that the stacked plate members do not move from a predetermined position even under high temperature conditions. Regarding the dimensions and thermal expansion coefficients of the jig constituent members shown in FIG. 9, the following relational expression must hold true.

Lxax+Lzax>CLx+Lz>as −(1
) Here, Ll is the laminated thickness of plate jig A17 and plate jig B18 after lamination, Lx is the length of pressure piece 14, α1 is the thermal expansion coefficient of plate jig A17 and plate jig B18, α2 is the pressure piece, and α3 is the jig-based thermal expansion coefficient.

In this example, the plate jig A17 and the plate jig B18 were made of AQN, which is the same material as the cooling fin, the jig base was made of carbon steel, and the pressure piece was made of austenitic stainless steel. αz=4.4X10 as each thermal expansion coefficient
-'/"C, ax = 18X10-6/'C, αg =
Using 13xlO-'/'C, the pressure piece length Lz is determined by equation (1).

Ll is L L = 2, 3 X 5 + 2, O
From X 4 = 19, 5 wm, Lz>33.5mm
Therefore, in this embodiment, Lx is set to 35 cabinets.

Based on this preparation, the vertical plate 2 of the cooling fin is inserted into the groove 19 formed by the plate jig A17 and the plate jig B18. The longitudinal position within the groove 19 of the vertical plate 2 is
The length of the plate jig A17 and the plate jig 18 is the length a of the vertical plate 2.
The height h2 of the plate jig A17 and the plate jig B18 are higher than the height h2 of the plate jig B18, and
A workpiece fixing piece having a width approximately equal to the stacking thickness of the stacked plate jigs is arranged and fixed.

Next, the laminated plate 3 is placed on the joint surface of the vertical plate 2 protruding from the plate jig with the base plate, and the base plate 1 is placed on top of the laminated plate 3. Furthermore, a fixing plate 2 is provided for stabilizing the relative positions of the vertical plate 2, the laminated plate 3, and the base plate 1 during the joining operation.
1 was fixed to the screw hole 20 of the jig base 13 with a bolt through a hole 22 in which a fixing plate 21 was formed.

After the above preparations, the heating and pressurizing processes described above were performed, and the base plate 1 and the vertical plate 2 were joined by the laminated plate 3 to create a cooling fin made of AQN.

According to this embodiment, since the jig used for bonding is made of the same material as the base plate 1 of the cooling fin, there is no difference in thermal expansion between the jig and the base plate 1 due to heating during bonding, resulting in dimensional accuracy. Good quality cooling fins can be manufactured.

Furthermore, since the jig into which the vertical plate 2 is inserted has a laminated structure of plate-like members, the mold release operation after the bonding process is facilitated. That is, if the vertical plate 2 of the cooling fin is joined to the base plate at a slight angle with respect to the perpendicular line of the base plate 1, a frictional force is generated at the contact portion with the jig, and mold release may not proceed smoothly. In such a case, by relaxing the pressure on the pressure piece 14, the plate jig A17 and the plate jig B1
Since 8 exists independently, it can be easily removed from the cooling fin.

〔Effect of the invention〕

According to the present invention, as a method for manufacturing high-precision cooling fins used for cooling electronic devices from ceramics or sintered alloys with good thermal conductivity, a diffusion bonding method using AQ insert material is applied, and processing is easy. By using the method of combining flat plates, it is possible to obtain cooling fins with high dimensional accuracy.

[Brief explanation of the drawing]

1 is a perspective view of a cooling fin according to an embodiment of the present invention, FIG. 2 is a sectional view of a bonding laminate, FIG. 3 is an exploded perspective view of a cooling fin according to an embodiment of the present invention, and FIG. 4 is a perspective view of a cooling fin according to an embodiment of the present invention. 5 is a perspective view of a cooling fin example similarly obtained, FIG. 6 is a perspective view of a cooling fin according to another embodiment, and FIG. 7 is an assembly of another embodiment. FIG. 8 is an exploded perspective view of the cooling fins and the jig, FIG. 8 is a perspective view explaining the shape of the jig parts, and FIG. 9 is a side sectional view explaining the dimensions of the jig. 1... Base board, 2... Vertical board, 3... Laminated board,
4... Heartwood, 5... Surface layer, 6... Vertical plate A, 7
... Vertical plate B, 8... Jig A, 9... Groove A, 10
... Jig B, 11... Vertical plate C112... Vertical plate D, 13... Jig base, 14... Pressure piece, 1
5...Groove B, 16...Groove C117...Plate jig A,
18...Plate jig B, 19...Groove, 21...Fixing plate, 24...Press plate, 25...Pressure bolt. etc. 1 ■ Kaya Z 圀S Surface layer Gi 6 Figure Kayaotsu ``''J-&I)

Claims (1)

[Claims] 1. A cooling fin for an electronic device comprising a plate-like member and a plurality of plate-like members formed in a direction perpendicular to the plate-like member, wherein both plate-like members are joined.