JP2000174186A - Semiconductor device and method for mounting the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid lowering of mounting workability and wiring density of a mounting board for raised heat-radiation performance. SOLUTION: BGA.LSI comprises a wiring board 20 where a chip 10 is CCBed(controlled collapse bonding), a heat-radiation fin 30 coated on the wiring board 20, a thermal conductive material layer 19 formed between the heat-radiation fin 30 and the chip 10, a stopper 33 which, protruded below the lower surface of the heat-radiation fin 3, hits the upper surface of the wiring board 20, and a leaf spring 35 which connects the heat-radiation fin 30 and the wiring board 20, with the wiring board 20 CCBed to a mounting board 40 with a connection terminal 45 of a solder bump. Since the heat-radiation fin is positioned on the wiring board by a stopper, the thickness of thermal conductive material layer is kept constant for its stable thermal conductivity capability, so no hole is required to be opened on the mounting substrate wherein a specified heat- radiation performance is assured at all trmes, avoiding lowering of mounting workability and wiring density of the mounting board.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device mounting technology, and more particularly to a package heat radiation technology. Hereinafter, LS
It is called I. )) That are effective for the manufacturing technology.

[0002]

2. Description of the Related Art In the mounting technology of general-purpose computers and supercomputers, it is necessary to reduce the mounting delay as much as possible while increasing the number of I / Os in order to reduce the mounting delay as much as possible. For this reason, a package using a flip chip connection capable of area connection has been developed.

A conventional package of this type is a BGA
There is. That is, the BGA is a semiconductor chip (hereinafter, referred to as a chip) in which an integrated circuit including a semiconductor element is built.
To control collapsed bonding on the wiring board
ding. Hereinafter, it is called CCB. Flip by
This is a package connected to a chip. BGA I /
Since the number of Os is generally set to be large, B
LSI with GA (hereinafter referred to as BGA LSI)
The calorific value becomes extremely large.

In order to improve the heat radiation performance, a BGA
In a mounting structure in which the LSI is mounted on a mounting board (hereinafter, referred to as a board) such as a motherboard of a computer, a heat radiating fin is formed on a chip by heat conductive grease or Ag.
It is bonded by a heat conductive material having heat conductivity such as a paste. That is, after a heat conductive material is applied to the upper surface of the BGA / LSI chip mounted on the board by CCB, the radiating fins are covered on the BGA / LSI, and the legs of the radiating fins are provided in the mounting holes formed in the boat. And is fixed. In this state, the space between the upper surface of the BGA / LSI chip and the lower surface of the heat radiation fin is filled with a heat conductive material, so that the heat generated from the chip is thermally conducted to the heat radiation fin through the heat conductive material layer having good heat conductivity. Therefore, the heat radiation performance of the mounting structure is extremely high.

[0005] As an example describing BGA, 1
May 31, 993 Published by Nikkei BP Co., Ltd. "Practical Course VLSI Packaging Technology (2)" P173-P17
There are four.

[0006]

SUMMARY OF THE INVENTION The aforementioned BGA LS
There are the following problems in the mounting structure of I.
The first is the thickness of the board and the C
The point is that the thickness of the heat conductive material layer varies due to the variation in the amount of sinking of the solder bump during CB, so that the heat conductive performance of the heat conductive material layer becomes unstable. Secondly, since the radiation fins are fixed to the mounting holes formed in the board, not only the workability is reduced but also the wiring density of the board is reduced.

An object of the present invention is to provide a semiconductor device and a method of mounting the same, which can secure a desired heat radiation performance while avoiding a reduction in mounting workability and a reduction in wiring density of a mounting substrate.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0009]

The outline of a typical invention among the inventions disclosed in the present application is as follows.

That is, the semiconductor device comprises a wiring board to which the semiconductor chip is mechanically and electrically connected, a radiator covered by the wiring board, and a radiator formed between the radiator and the semiconductor chip. A heat conductive material layer having thermal conductivity, a stopper protruding from a lower surface of the heat radiator and abutting against an upper surface of the wiring board, and connecting the heat radiator to the wiring board. Connection means.

In a semiconductor device mounting method, a wiring board to which a semiconductor chip is mechanically and electrically connected is mechanically and electrically connected to a mounting board by solder bumps, and a heat is applied to an upper surface of the semiconductor chip. A heat conductive material having conductivity is applied, a radiator is placed on the wiring board, and a stopper protruding from a lower surface of the radiator is brought into contact with an upper surface of the wiring board. Are connected by connecting means.

According to the first means, since the radiator is positioned on the wiring board by the stopper, the thickness of the heat conductive material layer is always kept constant.
Therefore, since the heat conduction performance of the heat conduction material layer is stable,
The expected heat dissipation performance is always ensured.

According to the second means, since the heat radiator is connected to the wiring board by the connecting means, the mounting board does not need to be perforated. Therefore, a reduction in mounting workability and a reduction in wiring density of the mounting board can be avoided.

[0014]

FIG. 1 is a front sectional view showing a BGA / LSI mounting structure according to an embodiment of the present invention.
FIG. 2 is an enlarged partial cross-sectional view of the BGA LSI. 3A and 3B show a chip, wherein FIG. 3A is a bottom view and FIG.
It is an expanded sectional view which follows a bb line. 4A and 4B show a wiring board, wherein FIG. 4A is a plan view of the left half, a bottom view of the right half, and FIG. 4B is an enlarged cross-sectional view taken along line bb of FIG. 5A and 5B show a radiation fin, wherein FIG. 5A is a front sectional view and FIG. 5B is a bottom view.

In the present embodiment, the semiconductor device according to the present invention is a BGA / LS used in a general-purpose computer or a supercomputer (hereinafter, referred to as a computer).
It is configured as an LSI which functionally requires high heat radiation performance. Then, as shown in FIG. 1, the BGA LSI 1 is mounted on a motherboard (hereinafter, referred to as a board) 40 of the computer.

The BGA LSI 1 includes a semiconductor chip (hereinafter, referred to as a chip) 10 in which a semiconductor integrated circuit is built. As shown in FIG. 3A, the chip 10 includes a substrate 11 formed of a square thin plate-shaped piece using a silicon wafer, and a large-scale integration is performed in an active area of the substrate 11. A circuit (hereinafter, referred to as an integrated circuit) is built. The active area in which the integrated circuit is built is arranged on one main surface side of the substrate 11, and the integrated circuit is externally mounted on the main surface on the active area side (hereinafter, sometimes referred to as a first main surface). Electrode pad 1 for electrically pulling out
2 are arranged in a matrix at a distance from each other.

As shown in FIG. 3B, a passivation film 13 is formed on the first main surface of the substrate 11.
Is formed, and a through hole 14 is formed at a position corresponding to each electrode pad 12 in the passivation film 13. In each of the through holes 14, a barrier metal film 15 is selectively deposited. Each electrode pad 12 is provided with a solder bump 16 for forming a connection terminal 17 via a barrier metal film 15.

The BGA LSI 1 has a wiring board 20. The main body 21 of the wiring board 20 is made of alumina ceramic or BT (Bismaleimide-triazin).
e) An insulating material such as a resin or a glass-impregnated epoxy resin is used, and as shown in FIG. A plurality of CCB pads 22 are arranged on one main surface (hereinafter, referred to as an upper surface) of the main body 21 so as to correspond to the respective solder bumps 16 protruding from the chip 10. The solder resist film 2 is formed on the upper surface of the main body 21.
3 is attached, and each CCB of the solder resist film 23 is
A through hole is opened at a position corresponding to the pad 22 for use. A barrier metal film 24 is selectively applied to each through hole.

The lower surface of the main body 21 of the wiring board 20 has a CCB
External terminals 25 connected to the pads 22 via the electric wiring 29 are arranged in a plurality of rows in an annular frame shape or a grid pattern on the entire periphery of the main body 21. A solder resist film 26 is adhered to the upper surface of the main body 21, and through holes are opened at positions of the solder resist film 26 corresponding to the external terminals 25. A barrier metal film 27 is selectively applied to each through hole, and a mounting bump 28 is provided on the barrier metal film 27 so as to project in a substantially hemispherical shape. The melting point of the solder material of the mounting bumps 28 is set to be lower than the melting point of the solder material of the solder bumps 16 of the chip 10 described above. Each external terminal 25 is connected to each CC
The B pads 22 are connected to each other via respective electric wirings 29 so as to be electrically independent from each other.

The BGA LSI 1 has a radiating fin 30 shown in FIG. 5 as a radiator. Radiation fin 30
The main body 31 is made of a material having good thermal conductivity such as aluminum nitride (AlN) and is formed in a substantially square dish shape having an inner diameter equal to the outer diameter of the main body 21 of the wiring board 20. Stoppers 33 are provided at four corners of the hole 32 of the main body 31.
Are respectively projected downward in the vertical direction, and the height S of each stopper 33 is set as shown in FIG. That is, the height of the connection terminal 17 for connecting the chip 10 and the wiring board 20 is f, the thickness of the wiring board 20 is t,
Assuming that the thickness of the heat conductive material layer 19 is h, the height S of the stopper 33 is set so as to satisfy S = f + t + h.

As shown in FIG.
A mounting portion 34 is formed on the inner surface of one side wall of the 0 hole 32, and a leaf spring 35 as a connecting means is mounted on the mounting portion 34 in a bow shape so as to protrude radially inward in a natural state. ing. Radiation fins 3
A fin portion 36 is integrally formed on the upper surface of the main body 31 so as to protrude so as to enhance the heat radiation effect.

As shown in FIG. 1, a board 40 as a mounting substrate has a main body 41, and the main body 41 is made of an insulating material such as alumina ceramic, BT resin or glass impregnated epoxy resin, and is made of BGA. -It is formed in a plate shape sufficiently larger than the LSI 1. Body 41
A plurality of mounting pads 42 are arranged on one principal surface (hereinafter, referred to as an upper surface). On the upper surface of the main body 41, a solder resist film 43 is adhered.
A through-hole is formed at a position corresponding to each mounting pad 42 of No. 3. A barrier metal film 44 is selectively formed in each through hole.

Next, one embodiment of the BGA
An LSI mounting method using the chip 10, the wiring board 20, the heat radiation fins 30, and the board 40 according to the above configuration will be described.

The chip 10 is mechanically and electrically connected to the wiring board 20 by CCB. That is, FIG.
As shown by imaginary lines in FIG. 2B, each solder bump 16 of the chip 10 is connected to each CCB pad 22 of the wiring board 20.
In the face-down state that matches the
The reference numeral 0 is aligned with the wiring board 20 and temporarily bonded with a flux or a solder cream (not shown). Thereafter, by performing a reflow process using a heating furnace or the like in an inert gas (eg, nitrogen gas) atmosphere, each solder bump 16 is simultaneously melted at a preset temperature. By this reflow process, each solder bump 1
Each connection terminal 17 according to 6 is formed as shown in FIG.

When the connection terminals 17 are formed, the chip 1
0 indicates a state in which the integrated circuit is mechanically connected to the wiring board 20 by the group of connection terminals 17 and the integrated circuit is connected to the wiring board 20.
Of each electrode pad 12, connection terminal 17,
It is in a state of being electrically connected via the CCB pad 22 and the electric wiring 29.

A gap corresponding to the height of the connection terminal 17 is formed between the chip 10 and the wiring board 20 which are mechanically and electrically connected by the connection terminal 17 group. This gap is filled with an underfill 18. The connection terminals 17 are sealed by the underfill 18 with resin, and the chip 10 is mechanically fixed to the wiring board 20.

The wiring board 20 is connected to the board 40 by connecting terminals 45.
Connected mechanically and electrically. That is, in a face-down state in which the mounting bumps 28 of the wiring board 20 are aligned with the mounting pads 42 of the board 40, the wiring board 20 is aligned with the board 40, and the flux or solder cream (not shown) is used. Are temporarily bonded together. Thereafter, the mounting bumps 28 are simultaneously melted at a preset temperature by performing a reflow process using a heating furnace or the like in an inert gas (eg, nitrogen gas) atmosphere. By this reflow process,
Each connection terminal 45 by each mounting bump 28 is formed as shown in FIG.

After a heat conductive material such as conductive grease or Ag paste is applied to the upper surface of the chip 10, FIG.
As shown in FIG. 2, the radiation fin 30 is concentrically placed on the wiring board 20 with the opening side of the hole 32 facing downward. At this time, the wiring board 20 is inserted into the hole 32 of the radiating fin 30 while the leaf spring 35 of the radiating fin 30 is pushed radially outward by the side surface of the main body 21 of the wiring board 20, and the upper surface of the wiring board 20 is Are in contact with the stoppers 33 at the four corners of the hole 32. Thereby, between the opposing surfaces of the chip 10 and the radiation fin 30,
The heat conductive material layer 19 having the thickness h defined by the height S of the group of the stoppers 33 is formed as shown in FIG. The thickness h of the heat conductive material layer 19 is
Further, since the thickness t of the chip 10 and the thickness f of the connection terminal group 17 are almost constant, the thickness is always kept constant.

The BGA LSI 1 mounted on the board 40 as described above is in a state of being mechanically and electrically connected to the board 40 via the connection terminals 45 formed by the mounting bumps 28. In this state, the BGA
Since the heat radiation fins 30 are thermally connected to the LSI 1 by the heat conductive material layer 19, the BGA · L
SI1 will be cooled very effectively.

According to the above embodiment, the following effects can be obtained.

1) By covering the heat radiation fins on the BGA LSI, the heat generated from the chip can be efficiently dissipated by the heat radiation fins, so that the BGA LSI can exhibit the expected performance.

2) By defining the thickness of the heat conductive material layer for thermally connecting the radiating fins to the BGA LSI by the stopper, the heat conductive performance of the heat conductive material layer is reduced by the BGA LSI.
Of the BGA / LSI mounting structures can be constantly maintained at a constant level between the mounting structures.

3) By connecting the radiating fins to the wiring board by leaf springs, it is not necessary to make a hole in the board, so that a reduction in mounting workability and a reduction in the wiring density of the board can be avoided.

Although the invention made by the present inventor has been specifically described based on the embodiment, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the invention. Needless to say, there is.

For example, the connecting means for connecting the radiation fins 30 to the wiring board 20 may be configured as shown in FIGS.

In FIG. 6, at the lower end of the radiating fin 30, an engaging claw 37 as a connecting means is provided so as to protrude radially inward, and when the radiating fin 30 is covered on the wiring board 20, The engaging claw 37 is engaged with the lower end surface of the wiring board 20.

In FIG. 7, one side wall at the lower end of the radiation fin 30 is provided with a male screw member 38 as a connecting means.
Are screwed, and the male screw member 38 is abutted on the side surface of the wiring board 20 in a state where the radiation fin 30 is put on the wiring board 20.

The heat radiator is not limited to the heat radiating fin having the fin portion, but may be configured such that the fan portion 39 is attached to the main body 31 as shown in FIG.

As shown in FIGS. 9 and 10, the radiating fins 30 are BGA / LSI 1 on the board 40.
Before being mounted on the wiring board 20.
That is, as shown in FIG.
The radiating fins 30 are put on the CB wiring board 20, and the BGA LSI 1 is manufactured. Thereafter, the BGA LSI 1 is mounted on the board 40 as shown in FIG.

In the above description, the case where the invention made by the present inventor is mainly applied to a semiconductor device used for a computer, which is a background of application, has been described. However, the present invention is not limited to this. The present invention can be applied to general semiconductor devices such as equipment and other electric products. In particular, the present invention can provide excellent effects when used in semiconductor devices that require high heat dissipation performance.

[0041]

The effects obtained by typical aspects of the invention disclosed in the present application will be briefly described as follows.

By attaching the heat radiator to the semiconductor chip via the heat conductive material layer having a constant thickness, the heat generated by the semiconductor chip can be always conducted to the heat radiator with a constant heat conduction performance. Can exhibit the heat radiation performance.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing a mounting structure of a BGA / LSI according to an embodiment of the present invention.

FIG. 2 is an enlarged partial cross-sectional view of a BGA LSI.

FIG. 3 shows a chip, (a) is a bottom view, (b)
FIG. 4 is an enlarged cross-sectional view taken along line bb in FIG.

FIGS. 4A and 4B show a wiring board, wherein FIG. 4A is a plan view of the left half, a bottom view of the right half, and FIG. 4B is an enlarged sectional view taken along line bb of FIG.

5A and 5B show a radiation fin, in which FIG. 5A is a front sectional view and FIG. 5B is a bottom view.

FIG. 6 is a front sectional view showing a BGA / LSI mounting structure according to a second embodiment of the present invention;

FIG. 7 is a front sectional view showing a BGA / LSI mounting structure according to a third embodiment of the present invention.

FIG. 8 is a front sectional view showing a BGA / LSI mounting structure according to a fourth embodiment of the present invention.

FIG. 9 is a front sectional view showing a BGA / LSI mounting structure according to a fifth embodiment of the present invention.

FIG. 10 is a front sectional view showing the mounting structure of the BGA / LSI.

[Explanation of symbols]

1 BGA LSI (semiconductor device), 10 chip (semiconductor chip), 11 substrate, 12 electrode pad, 13 passivation film, 14 through hole,
Reference numeral 15: barrier metal film, 16: solder bump, 17: connection terminal, 18: underfill, 19: thermal conductive material layer, 20
... Wiring board, 21 body, 22 CCB pad (pad), 23 solder resist film, 24 barrier metal film, 25 external terminal, 26 solder resist film, 27
... Barrier metal film, 28 ... Bump for mounting, 29 ... Electrical wiring, 30 ... Heat radiating fin (heat radiator) 31 ... Main body, 32 ... Hole, 33 ... Stopper, 34 ... Mounting part, 35 ... Leaf spring (connection means) , 36 fins, 37 engaging pawls (connecting means), 38 male screw members (connecting means), 39
Fan unit, 40: board (mounting board), 41: body, 4
2. Mounting pads 43 Solder resist film 44 Barrier metal film 45 Connection terminals

Claims (11)

[Claims] 1. A wiring board to which a semiconductor chip is mechanically and electrically connected, a radiator covered by the wiring board, and a heat formed between the radiator and the semiconductor chip. A heat conductive material layer having conductivity, a stopper protruding from a lower surface of the heat radiator and abutting on an upper surface of the wiring board, and a connecting means for connecting the heat radiator to the wiring board. A semiconductor device, comprising: 2. The semiconductor device according to claim 1, wherein said connecting means is a spring sandwiched between said heat radiator and said wiring board. 3. The connector according to claim 1, wherein said connecting means is an engaging claw projecting radially inward from a lower end portion of said heat radiator and engaged with a lower end surface of said wiring board. 13. The semiconductor device according to claim 1. 4. The semiconductor device according to claim 1, wherein said connecting means is a male screw member screwed into said heat radiator and abutting against said wiring board. 5. The semiconductor device according to claim 1, wherein the radiator has a fin. 6. The semiconductor device according to claim 1, wherein a fan is attached to the radiator. 7. A method for mounting a semiconductor device, wherein the semiconductor device according to claim 1 is mechanically and electrically connected to a mounting substrate by solder bumps. 8. A heat conductive board having a heat conductive property, wherein a wiring board to which a semiconductor chip is mechanically and electrically connected is mechanically and electrically connected to a mounting board by solder bumps, and an upper surface of the semiconductor chip has thermal conductivity. A material is applied, a radiator is placed on the wiring board, and a stopper protruding from a lower surface of the radiator is brought into contact with an upper surface of the wiring board, and the radiator and the wiring board are connected by connecting means. A method for mounting a semiconductor device, comprising: 9. The mounting of the semiconductor device according to claim 7, wherein the connecting means is constituted by a spring, and the radiator is placed on the wiring board in a state where the spring is forcibly deformed. Method. 10. The connecting means is constituted by an engagement claw projecting radially inward from a lower end of the heat radiator, and after the heat radiator is put on the wiring board, the engagement claw is attached to the wiring board. The method according to claim 7, wherein the lower surface of the semiconductor device is engaged with the lower surface of the semiconductor device. 11. The connecting means is constituted by a male screw member screwed into the radiator, and the male screw member is abutted on the wiring board after the radiator is put on the wiring board. Or the mounting method of the semiconductor device according to 8.