JPH10209352A - Radiation fin for lsi package - Google Patents

Abstract

PROBLEM TO BE SOLVED: To removably mount a radiation fin on a package, by providing protrudent downward and opposed claws for gripping the side edges of an LSI package at the opposite side ends of a bottom plate of the fin. SOLUTION: A corrugated fin 30 comprises a flat bottom plate and a corrugated radiation plate 15a to be a radiator. The plate 15a is a corrugated Al or Al allay sheet bonded with blaze, etc., to the top face of the bottom plate with claws. A BGA package 14 has a flat plate, i.e., heat conductive base 16 and epoxy resin plates 17, 18 which are inserted into from the no-claw side end of the bottom plate of the fin 30 to grip the end edge of the resin plate 18 with the top ends 31c of claws 31b. If using the radiation fin for the LSI package, the fin can be very easily mounted on the package with the assembling process automated to raise the productivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiating fin mounted on an LSI (Large Scale Integrated Circuit) package for cooling an LSI chip (hereinafter referred to as a chip) mounted on the package.

[0002]

2. Description of the Related Art An LSI package (hereinafter simply referred to as a package) is the most basic electronic device containing a chip. In the history of high performance and miniaturization of electronic devices, the degree of integration of chips has been increasing year by year, and it is important to take cooling measures to prevent malfunctions due to heat generation of chips and electrical destruction of packages. It is getting. The most widely adopted measure to suppress the temperature rise of the chip is to attach heat radiation fins to the package and remove the heat of the chip by natural air cooling or forced air cooling by a fan.

Various methods have been proposed for mounting the radiation fins on the package as described below. FIG.
Shows an example in which a pin-type radiation fin is attached to a ceramic pin grid array type package (hereinafter referred to as a PGA package). FIG. 4A is a plan view from the pin fin side, and FIG. 4B is a PG with the pin fin attached.
FIG. 3C is a cross-sectional view of the A package, and FIG. 3C is a plan view of the lower surface of the PGA package.

[0004] A pin-shaped heat radiating fin (hereinafter referred to as a pin fin) 2 has a plurality of heat radiating pins 2a serving as heat radiating portions.
The shape is vertical to b. In the present invention, the radiating fin means a radiating portion and a bottom plate.

[0005] As shown in FIG. 4, the chip 3 is joined to a heat transfer substrate 16 and housed in an airtight space S composed of frame-shaped ceramic plates 5, 6 and a lid 7. The heat transfer substrate 16 and the ceramic plate 5, the lid 7, and the ceramic plate 6 are joined by a method such as brazing, and the mating surface of the ceramic plates 5 and 6 is sealed with a glass layer. A large number of pins 8 serving as external terminals inserted into the ceramic plate 6 and the chip 3 are connected via bonding wires 9 and a conductive circuit (not shown) connected to a terminal portion drawn on the lower surface 5a of the ceramic plate 5. And are electrically connected.

At the time of mounting, the pins 8 are inserted into a printed circuit board (not shown). The heat transfer substrate 16 to which the chip 3 is bonded is required to be made of a material having a coefficient of linear expansion close to that of the chip 3 in order to prevent the chip 3 from being broken by thermal stress when the temperature rises.

For example, copper-containing tungsten in which tungsten is impregnated with copper is used. The heat generated in the chip 3 is transmitted to the heat transfer substrate 4 and further transmitted to the pin fins 2a and dissipated.

In the example shown in FIG. 4, the radiation fins are PGA
It is attached to the package with screws. That is, the male screw 10 fixed to the heat transfer board 4 by brazing or the like is passed through the bottom plate portion 2b of the radiating fin, and the counterbore portion 4 of the bottom plate portion 2b is tightened with the nut 11, so that the radiating fin is fixed to the package. Have been. The reason for the tightening is that if an air layer exists between the bottom plate portion 2b and the heat transfer substrate 4, the heat transfer resistance increases, so that the cooling performance of the radiation fins 2 is not utilized.

However, this fixing method has the following problems. First, it is necessary to braze the male screw 10 to the heat transfer board 16 and to process a hole or a counterbore portion for penetrating the male screw into the pin fin, which is troublesome. Second, in order to secure a space for fastening the nut 11 to the pin fins, it is necessary to thin out the heat radiation pins 2a, and the heat radiation performance is reduced accordingly. Third, the tightening work of the nut 11 is complicated, and the productivity of the assembling work is hindered. Fourth, PG
Male screw 10 is on the upper surface of A package, and pin 8 is on the lower surface.
Are protruding, so that they obstruct the transportation of the package in the manufacturing stage.

FIG. 5 is a view showing an example in which pin fins are fixed to a package with clips, and FIG.
(B) is a side view. This fixing method is disclosed in, for example, JP-A-02-298053. Flange 16a of heat transfer board 16 having T-shaped cross section and bottom plate 2 of pin fin 2
b is clamped between the claws 13a of the clip 13 and fixed.

However, in this method, the process of providing the flange 16a on the heat transfer board 16 is troublesome, and the clip 13
The problem is that it is necessary to thin out the heat radiating pins 2a at the ends due to the space for hanging. In addition, since dust and the like easily accumulate on the clip 13, it is necessary to periodically clean the clip 13.

FIG. 6 is a view showing another clip fixing method disclosed in JP-A-63-133557. FIG. 6 (a)
As shown in a perspective view of FIG. 2, a tower-type heat radiation fin (hereinafter, referred to as a tower fin) 124 is placed on a PGA package 1 fitted in a resin frame 132, and teeth 142 provided on a peripheral portion of the frame 132. Of the tower fin 124 with the clip 150 having the spring property with the both ends
Pressed and fixed to the package.

FIG. 6B is a partial sectional view. A step 136 is provided on the inner periphery of the
A tower fin 124 having a fin 124 a is fixed on the heat transfer board 16, supporting the periphery of the A package 1. However, this clip fixing method has a problem that the operation of mounting and fixing the clip 150 is complicated, and mass production by automatic assembly is difficult.

Meanwhile, with the demand for smaller and lighter electronic devices, the size and weight of packages have also been rapidly reduced, and plastic packages are becoming the mainstream among high-performance products. In the case of a highly-integrated chip even in a plastic package, a cooling measure is required, and a radiation fin is used.

FIG. 7 shows a ball grid array package 14 (hereinafter, referred to as a typical plastic package).
An example is shown in which a corrugated radiating fin 15 (hereinafter referred to as a corrugated fin) described in Japanese Patent Application No. 7-91525 is attached to a BGA package. There are various forms of the corrugated fin corrugated heat radiating plate 15a, and the one shown here is an example. 7A is a plan view from the corrugated fin side, FIG. 7B is a cross-sectional view of a BGA package to which the corrugated fin is attached, and FIG. 7C is a plan view of the lower surface of the BGA package.

The corrugated fin 15 has a structure in which a corrugated radiator plate 15a formed by bending a thin plate and a bottom plate portion 2b are joined by brazing, and can be manufactured with a light weight, so that it is suitable for a radiator fin of a plastic package.

The BGA package 14 includes a heat transfer board 16,
With a laminated adhesive structure of frame-shaped epoxy resin plates 17 and 18,
The overall lamination thickness is around 1 mm. The chip 3 is electrically connected to solder balls 21 as external terminals arranged on the lower surface of the epoxy resin plate 18 via a conductive circuit (not shown) connected to a terminal portion on the epoxy resin plate 17 by bonding wires 9. And are sealed with an injection epoxy resin 19. A soft thermal compound 20 is sandwiched between the chip 3 and the heat transfer substrate 16.
Heat passes through the thermal compound 20 and the heat transfer substrate 16
, And further transmitted to the corrugated fins 15 for radiation. The thermal compound 20 is used because the chip 3 made of silicon and the heat transfer substrate 16 made of copper or copper alloy are used.
This is because the difference in the coefficient of linear expansion is too large, and if they are firmly joined, the chip 3 is broken by thermal stress. That is, the thermal compound 20 has a role as a buffer material for absorbing a difference in linear expansion. Of course, it also has a role of electrically insulating the metal heat transfer board 16 and the chip 3.

The corrugated fins 15 are attached to the BGA package 14 by an adhesive method. That is, the bottom plate portion 2b of the corrugated fin is joined to the upper surface of the heat transfer substrate 16 of the BGA package with a heat conductive adhesive. The bonding method is adopted because the thickness of the heat transfer substrate 16 is extremely thin (0.1 to 0.2 mm), so that the screwing method or the clip fixing method as in the case of the PGA package cannot be adopted. It depends on the reason. Of course, one of the reasons is that it is necessary to avoid an increase in weight due to screws, nuts, clips, and the like in plastics, which are one feature of being lightweight.

However, this method of bonding and fixing makes it difficult to remove the radiating fins after they are once adhered. For example, it is difficult to replace the radiating fins that have been deformed during handling.

[0020]

SUMMARY OF THE INVENTION An object of the present invention is to provide a radiation fin which can be detachably mounted on a package without using any components such as screws and clips.

[0021]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the problems caused by the above-mentioned conventional mounting means, and as a result, it has been found that the bottom plate portion of the radiating fin has a function of holding a package. It came to the knowledge that it was good. The present invention has been made based on such knowledge, and the gist is as follows.

"LS composed of a flat bottom plate and a heat radiator
An LSI package, comprising: a radiating fin for mounting an I package, wherein the radiating fin has a claw for protruding downward at opposite side end portions of a bottom plate portion of the radiating fin to grip a peripheral edge portion of the LSI package. Here, the lower surface of the bottom plate portion refers to the surface of the bottom plate opposite to the heat radiation portion.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram of a corrugated fin 30 with claws (hereinafter referred to as a corrugated fin with claws) showing an example of a radiating fin of the present invention.
(B) is a plan view of the lower surface of the bottom plate portion, and (c) is a front view.
Is a partially enlarged view.

This corrugated fin 30 is shown in FIG.
As shown in the figure, the bottom plate portion 2b is formed of a flat plate, and a radiating plate 15a having a waveform as the radiating portion 2c. A radiator plate 15a formed by bending a thin plate of aluminum or an aluminum alloy into a waveform at a pitch s and a height h forms an upper surface 3 of a bottom plate 31 with claws.
1a by brazing or the like.

Claws 31b having a height q protrude downward and are provided facing each other at the opposite side ends of the bottom plate 2b, ie, at 32a1 and 32a2 shown in FIG. 1B. The position where the claw is provided may be on the side end portions 32b1 and 32b2 shown in FIG. 1B, and the effect is the same.

In the example of FIG. 1, the claws 31b are provided over the entire side length f1 of the bottom plate, but a plurality of claws having a short width may be intermittently arranged on the left and right. The nailed bottom plate 2b can be manufactured by extrusion or cutting. In the case of cutting, the claws 31b may be machined after joining the corrugated heatsink 15a.

Alternatively, the claws and the bottom plate may be separately formed and processed, and the claws may be joined to the bottom plate by brazing or the like. Nail 3
The shape of 1b is not limited to that shown in FIG.
Any shape can be used as long as it can grip the package as described below, and can grip the package periphery so that it does not come off except by sliding the package between the opposing claws and removing it from the radiation fins. No problem.

Further, the fin shape of the heat radiation fin of the present invention is not limited to the one shown in FIG. 1. For example, a pin fin or a channel fin in which plate-shaped heat radiation plates stand in parallel may be used.

The material of the heat radiation fin of the present invention is preferably aluminum or an aluminum alloy from the viewpoint of lightness and economy, similarly to the conventional heat radiation fin. Also,
As described later, aluminum or an aluminum alloy is also recommended because excellent electrical insulation performance and corrosion resistance can be imparted by alumite treatment.

Next, a method of attaching the heat radiation fin of the present invention to a package will be described. 2A and 2B are views showing a state in which the corrugated fins 30 with claws are attached to the BGA package 14. FIG. 2A is a front view, and FIG. 2B is a partially enlarged view.

The flat portion of the BGA package 14, that is, the heat transfer board 16, and the epoxy resin plates 17 and 18 are inserted from the claw-free side end of the bottom plate portion of the claw corrugated fin 30 with the claw. It is gripped by the tip 31c of the claw 31b.

In addition, when inserting the flat plate portion of the package between the claws, a corner portion on the entry side between the claws, that is, FIG.
It is preferable to chamfer the part indicated by the arrow (b) because the flat part can be easily inserted.

FIG. 3 shows an example in which the BGA package 14 is attached to a corrugated fin 30 having a claw 31b having another shape. In this case, the claw 31b is provided with a slope 31e at the tip 31c, and the epoxy resin plate 18 is gripped by the slope 31e.

If the claws 31b have a spring property, the heat transfer board 16 can be pressed against the bottom plate bottom 31d.
For example, elasticity may be imparted by making the thickness t of the nail 31b thin. Further, by providing the slope 31e at the tip of the claw, the dimensional tolerance of the grip portion of the package is increased.

2 and 3, the heat transfer board 16 is in contact with the bottom plate bottom 31d, and the heat from the heat transfer board 16 is transmitted to the claw bottom plate 31 and dissipated from the corrugated heat sink 15a. Therefore, the distance m between the bottom plate bottom surface 31d and the claw tip portion 31c in FIG. 1C is substantially the same as the thickness hb of the BGA package flat plate portion (see FIG. 7B).

The nail 31b and the BGA package 1
In the case where there is a possibility that a gap is generated between the heat transfer board 16 and the bottom plate bottom 31d from the point of the dimensional accuracy of 4 and heat transfer is not effectively performed, the gap is formed by interposing a heat conductive grease or the like therebetween. Should be eliminated. It goes without saying that the thinner the heat conductive grease to be interposed, the better the thickness is in order to reduce the heat transfer resistance.

In any case, the mounting and dismounting of the BGA package 14 and the corrugated fins 30 with claws is easy, and the above-mentioned problems in the conventional mounting method of the package and the radiation fins can be solved.

In FIG. 2, the claws 31b hold the BGA package 14 outside the solder balls 21 on the lower surface of the BGA package 14, and the solder balls 21
It is necessary to have a dimension and shape that protrudes by g from b.

The solder ball 21 is pressed against a printed circuit board or the like with its temperature raised, and soldering is performed. The protrusion amount g is set in consideration of the collapse of the solder ball 21 at that time. For example, if the diameter of the solder ball 21 is 0.4 mm, g must be at least about 0.2 mm. The gap between the printed board and the nail 31b in the state where the soldering is performed is only about 0.1 mm at most, so that there is a possibility that an electric short circuit occurs in a use state. Therefore,
It is essential that at least the claws 31b have electrical insulation properties. It is effective to manufacture the corrugated fins 30 with claws of aluminum or an aluminum alloy and to perform anodizing.

It goes without saying that the above-described method of attaching the corrugated fins with claws to the BGA package can be similarly applied to other packages and other radiation fins with claws.

[0041]

EXAMPLE An aluminum alloy having a thickness of 0.3 mm (JIS)
3003) 8.5 mm height obtained by bending a thin plate
(H) An aluminum alloy having a plane size of 32.0 mm (f1), a thickness of 36.0 mm (f2), a thickness of 2.0 mm (T), a thickness of 2.0 mm (T) and a thickness of 50 μm on one side is formed by a corrugated heat sink having a pitch of 4.2 mm (s). Corrugated fins were prepared by vacuum brazing a bottom plate made of an aluminum alloy (JIS 3003) having a braze (JIS 4004).

On the bottom plate of the heat radiation fins, q = 0.95 mm, p = 31.4 mm, m = 0.75 m shown in FIG.
After cutting the claws 31b of m, n = 1.8 mm, the entire surface was anodized. After applying a grease-like thermal compound (SH340, manufactured by Dow Corning Toray Silicone Co., Ltd.) to the bottom surface of the bottom plate of the corrugated fin with claws, the external dimensions w1 = w2 shown in FIGS.
= 32 mm, thickness hb = 0.7 mm, diameter 0.4 mm
A plastic BGA package 14 having a large number of solder balls 21 arranged on the bottom surface was inserted into the claws 31b and mounted. Furthermore, the package with the heat radiation fin was mounted on a printed circuit board, and it was confirmed that the package had a sufficient cooling function.

[0043]

According to the heat radiation fin for an LSI package of the present invention, the attachment of the heat radiation fin to the package becomes extremely simple, and the productivity is improved by automating the assembly process.

As high-performance packages on which high-integration chips are mounted are increasingly used, it is important to easily attach heat-dissipating fins for cooling chips to the package. The radiation fin of the present invention has a great effect for such needs.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of a heat radiation fin for an LSI package of the present invention.

FIG. 2 shows a heat radiation fin for an LSI package according to the present invention as BG.
It is a figure showing the state where it attached to A package.

FIG. 3 is a diagram showing a state in which a heat radiation fin for an LSI package according to another embodiment of the present invention is attached to a BGA package.

FIG. 4 is a view showing a conventional example in which pin fins are mounted on a ceramic PGA package by screws.

FIG. 5 is a view showing a conventional example in which a pin fin is mounted on a ceramic PGA package using a clip.

FIG. 6 is a view showing a conventional example in which a tower fin is mounted on a ceramic PGA package using a clip.

FIG. 7 is a view showing a conventional example in which a corrugated fin is adhesively fixed to a plastic BGA package.

[Explanation of symbols]

 14 Ball grid array package 15 Corrugated fin type heat radiation fin 15a Corrugated fin 15b Corrugated fin bottom plate 16 Heat transfer board 17, 17 Epoxy resin plate 21 Solder ball 31 Claw

Claims (1)

[Claims] 1. An LS comprising a flat bottom plate portion and a heat radiating portion.
A heat radiation fin for mounting an I package, wherein the heat radiation fin protrudes downward at opposite side ends of a bottom plate portion of the heat radiation fin;
A heat radiation fin for an LSI package, comprising a claw for gripping a peripheral portion of the SI package.