JPH11111897A - Multi-chip type semiconductor device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] A plurality of semiconductor elements or chip carriers of varying heights are cooled by contact with a single heat transfer body, capable of coping with thermal deformation during ON / OFF, and further improving long-term reliability. Secure. A flat plate is provided on a contact surface of a heat transfer member via a frame-shaped resin, and grease is sealed in an area formed by the contact surface of the frame-shaped resin, the flat plate, and the heat transfer member. And apply oil to the chip carrier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a plurality of semiconductor devices,
Alternatively, the present invention relates to a multi-chip semiconductor device in which chip carriers are mounted at high density.

[0002]

2. Description of the Related Art With high-speed operation and high performance of electronic devices,
2. Description of the Related Art High-speed operation and high-density semiconductor devices used in electronic devices are being developed. As a result, the number of external connection terminals of the semiconductor element increases, and high-density mounting on a semiconductor mounting substrate is required.

In order to meet this demand, there has been adopted a method in which a protruding projection electrode is protruded on an electrode terminal of a semiconductor element or a chip carrier, and the semiconductor element is bonded to a semiconductor mounting substrate via the projection electrode. I have.

However, in this method, the contact area between the semiconductor element and the mounting board is reduced, so that the thermal resistance between the semiconductor element and the mounting board is increased. It was necessary to provide a special heat dissipation path.

Therefore, a method has been devised in which a heat transfer member or a cooling member is brought into close contact with the back surface of the semiconductor element to create a new heat radiation path. However, the following problems have been found in a method in which one heat transfer body or a cooling body is brought into close contact.

First, there is a variation in height of a semiconductor element or a chip carrier. Since a large number of semiconductor elements or chip carriers are mounted in electronic equipment, the height of the semiconductor element surface bonded to the mounting board due to the unevenness in the height of the projecting projection electrodes and the unevenness in the thickness of the semiconductor element,
The inclination varies and does not form a single plane. As a result, when cooling is performed by a single heat transfer element or cooling element, not all elements are in close contact with the heat transmission element or cooling element. If the height of the semiconductor device is low, the device will not be cooled sufficiently. On the other hand, if the height of the semiconductor element is too high, an excessive force is applied due to the pressing of the heat transfer body, and there is a possibility that the above-mentioned convex projection electrode is deformed or broken.

As another problem, thermal deformation of the semiconductor element during operation may be considered. The semiconductor element is thermally deformed due to heat generation when it is turned on and off. At this time, if the cooling body or the heat transfer body that is in close contact is a rigid body, a compressive or tensile stress is generated in the semiconductor element or the protruding electrode, and the electrode may be broken by long-term operation.

Various cooling structures have been devised to solve these problems.

A cooling structure in which a concave portion is provided on the surface of a heat transfer body in contact with a semiconductor element, a spherical material having thermal conductivity and elasticity is filled in the concave portion, and a thermosetting resin excellent in thermal conductivity is further filled. It is disclosed in Kohei 5-235213. This structure maintains excellent thermal conductivity and forms a good adhesion state with all the semiconductor elements having different heights by means of a heat conductor having elasticity.

Japanese Patent Application Laid-Open No. Hei 7-245362 discloses a cooling structure in which a semiconductor element having a variable height is connected to a heat transfer body by a brazing material via an elastic metal sponge. In this structure, the metal sponge acts as a cushion and cancels the height variation of the semiconductor element.

Further, a method has been put into practical use in which grease having high thermal conductivity is applied to a contact surface of a semiconductor element having a variable height, and the grease is brought into contact with a heat transfer surface via the grease. In this structure, the grease acts as a cushion to cancel the height variation of the semiconductor element.

[0012]

As described above, in the conventional structure, a layer having thermal conductivity and elasticity is formed on a cooling surface or a heat transfer surface to cancel a variation in the height of a semiconductor element and to maintain a certain level. It was able to cope with heat generation and height variations.

However, in the method disclosed in Japanese Patent Application Laid-Open No. 5-235213, the elastic body is composed of a spherical elastic body and a thermosetting resin. Therefore, the bonding with the semiconductor element is in point contact with the spherical elastic body or in surface contact with the thermosetting resin.
Point contact has a small contact area and a large contact thermal resistance. Also, thermosetting resins generally have undulations and irregularities on the surface, and similarly have high contact thermal resistance. As a result, the thermal conductivity is relatively low due to the contact thermal resistance, and it is difficult to apply the present invention to a semiconductor device having a higher heat generation.

In the method disclosed in Japanese Patent Application Laid-Open No. 7-245362, a semiconductor element is bonded to a metal sponge body via a brazing material.
Therefore, it is considered that there is no contact thermal resistance, and good heat transfer characteristics can be obtained. However, since the semiconductor element is bonded on both the back surface and the electrode surface, heat generation during operation and stop, and thermal deformation during cooling are restricted. Therefore, an excessive force is applied to the electrode connection surface having relatively low rigidity, and there is a possibility that the electrode portion may be creeped or broken / ruptured due to long-term operation. A metal sponge has elasticity as compared with a metal body, but is rigid as compared with a resin and is inferior in deformation absorbing ability, so that it is difficult to absorb the thermal deformation.

Grease is a liquid having high viscosity, but has very low contact resistance. Further, since it is a liquid, it has low rigidity and can sufficiently cope with heat generation during operation and stop of the apparatus and thermal deformation due to cooling. However, grease has the following problems. Normal high thermal conductivity grease is
Fine particles having high thermal conductivity, for example, metal particles such as Ag, Cu, and Al, or non-metal gas particles such as C, AlN, and SiO ₂ are dispersed in oil at high density. As the oil, a silicon-based oil is usually used.

If the grease is repeatedly pressurized or heated / cooled for a long period of time, the oil in the grease may evaporate or escape, causing the grease to deteriorate and solidify. In this case, the viscosity of the grease is lost, so that the grease cannot cope with the deformation of the semiconductor element, and further, a gap is formed in an applied portion, and the contact resistance is significantly increased. In this state, it becomes difficult to cool the semiconductor element.

SUMMARY OF THE INVENTION The object of the present invention has been made in view of the above, and even when the amount of heat generated by a semiconductor element is increased, heat generated from a semiconductor can be sufficiently radiated and thermal deformation of the semiconductor element can be absorbed. It is an object of the present invention to provide a multi-chip semiconductor device having a highly reliable electronic circuit device.

[0018]

In order to achieve the above object, the present invention uses the following configuration as a multi-chip type semiconductor device.

A flat plate is provided on the contact surface of the heat transfer body in contact with the semiconductor element or the chip carrier with a frame-shaped resin interposed therebetween, and is further provided in an area formed by the contact surface of the frame-shaped resin, the flat plate and the heat transfer body. Enclose grease or oil, apply grease or oil to the flat plate,
The structure was such that the semiconductor element or the chip carrier was in close contact with the semiconductor element.

The following configuration is used as another means.
A frame-shaped resin is provided on a contact surface of the heat transfer body in contact with a semiconductor element or a chip carrier.
Grease or oil is sealed in the area formed by the contact surfaces of the heat transfer bodies, and the frame-shaped resin and grease,
Alternatively, the structure is such that the semiconductor element or the chip carrier is brought into close contact with the semiconductor via oil.

According to the present invention, the following effects are produced by the above-mentioned means, and the above-mentioned problems are solved. A substantially sealed area is formed by a frame-shaped resin, a flat plate, or a semiconductor element attached to the heat transfer body contact surface, and grease or oil is sealed in the inside, thereby preventing escape of oil in the grease. The frame-shaped resin itself is an elastic body having low rigidity, and serves as a wall that absorbs deformation of the semiconductor element and prevents escape of oil. The flat plate is used when the contact surface of the semiconductor element is not flat and it is difficult to make good contact with the frame-shaped resin, and acts as a sealing surface instead of the semiconductor element.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic perspective view of a multi-chip type semiconductor device according to the present invention, in which some components are cut to explain the inside. Reference numeral 1 denotes a chip carrier, and a plurality of chip carriers are arranged on the wiring board 3 in a grid pattern. Reference numeral 31 denotes a frame joined to four sides of the wiring board 3. Reference numeral 32 denotes a pin connected to the semiconductor element connected to the wiring board 3.
Reference numeral 2 denotes a heat transfer body having a coolant passage 22 therein, and a coolant inflow / outlet 21 is provided on the upper surface. Heat transfer body 2
And the frame 31 are bolted together at the brim portions protruding on the four sides to form a module. Here, the liquid cooling is taken as an example, but in the case of air cooling, the heat transfer body 2 is used.
Instead, a radiation fin may be attached, and the present invention is not limited to the cooling method.

FIG. 2 is a longitudinal sectional view showing the detailed structure. In the figure, reference numeral 4 denotes a ball-shaped electrode for connecting the chip carrier 1 and the wiring board 3, and a large number of electrodes are arranged in a grid on the joining surface between the chip carrier 1 and the wiring board 3. Normal electrode 4
Is made of solder, and serves to electrically connect the semiconductor elements in the chip carrier 1 to the wiring board 3 and to fix and bond the chip carrier 1 on the wiring board 3.

Reference numeral 5 denotes a flat plate. In the present invention, aluminum nitride (AlN) having excellent thermal conductivity and a small coefficient of thermal expansion was used. The flat plate 5 has a square shape slightly larger than the chip carrier 1 and has a thickness of 0.3 mm in this embodiment. Reference numeral 6 denotes a frame-shaped resin. In this embodiment, a thermosetting and adhesive silicone resin is used. Although this resin is cured by heating, the rigidity after curing is low, and it becomes a good elastic body.

The thickness of the resin 6 is determined by the thermal conductivity of the grease to be enclosed, the amount of heat generated by the semiconductor element, the amount of deformation of the semiconductor element, the elastic modulus of the resin, and the deformability of the resin. In the case of this embodiment, the film thickness is 0.05 mm, and the frame width (line width) is 0.1 mm. The flat plate 5 is adhered to the heat transfer body 2 by the frame-shaped resin 6, so that a closed space having the frame-shaped resin 6 as a frame and the flat plate 5 and the heat transfer body 2 on both surfaces is formed. Highly heat-conductive grease 7 poured in advance is sealed in this sealed space. In the case of this embodiment, a silicon-based grease containing a large amount of silver (Ag) fine particles dispersed therein was used.

The frame-shaped resin 6 containing the high thermal conductive grease 7 has good thermal conductivity, and can sufficiently cope with the thermal deformation of the chip carrier 1 at the time of starting and stopping the apparatus by the elasticity of the resin. Form a contact state.

Further, oil 71 is applied to the flat plate 5 and the oil applied surface thereof comes into contact with the chip carrier 1, so that the contact thermal resistance can be extremely low. Further, since the grease is sealed in the closed space, the oil in the grease is prevented from evaporating or escaping, and solidification of the grease can be prevented for a long time. As a result, high reliability is obtained in the long term.

Next, the manufacturing procedure of this embodiment will be described with reference to FIGS. First, a flat plate 5 is coated with a frame-shaped resin 6.
In this embodiment, a paste-like resin is applied to a flat plate 5 by a printing method.
Formed. A sufficient amount of high thermal conductive grease 7 is poured into the frame-shaped resin 6. Next, as shown in FIG. 4, the heat transfer body 2 is placed and heated with an appropriate load applied. In this example, the temperature was maintained at about 150 ° C. for 1 hour in an electric furnace. When the heat value of the semiconductor element is small, oil may be sealed instead of the high thermal conductive grease 7. If silicon oil is used as the oil, the viscosity is lower than that of grease, and therefore, the chip carrier 1 can respond quickly to thermal deformation. In the present invention, the encapsulant may be high thermal conductive grease or oil, and is not limited.

First, with the heat transfer body 2 placed thereon and a load applied thereto,
The frame-shaped resin 6 before thermosetting contacts the contact surface of the heat transfer body 2 and is deformed in the thickness direction. That is, at the time of this load application, the frame-shaped resin 6 before solidification is deformed in accordance with the height of the chip carrier 1 whose height varies, thereby eliminating the height variation. When heated in this state, the frame-shaped resin 6 solidifies, and at the same time, adheres to the heat transfer body 2 and the flat plate 5 to seal the grease 7. The high thermal conductive grease 7 used in this example has a high heat resistance temperature,
It does not change at a heating temperature of about 150 ° C.

After cooling, the heat transfer body 2 is removed again, and oil 71 is applied to the flat plate 5 adhered by the frame-shaped resin 6.
Next, the heat transfer body 2 to which the frame-shaped resin 6 and the flat plate 5 are adhered and the wiring board 3 are bolted. When the heat generated by the semiconductor element provided in the chip carrier 1 is large, high thermal conductive grease may be applied instead of the oil 71 in order to reduce the thermal resistance as much as possible.

(Embodiment 2) Another embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 5, in the present embodiment, there is no flat plate 5, and the sealing space of the grease 7 is constituted by the frame-shaped resin 6, the heat transfer body 2 and the contact surface of the chip carrier 1. The resin and the high thermal conductive grease used in this embodiment are the same as those in the first embodiment.

The manufacturing method will be described below. As shown in FIG. 6, a frame-shaped resin 6 is applied to the contact surface of the heat transfer body 2. The printing method was also used in this embodiment. In this embodiment, since there is no thermal resistance equivalent to that of the flat plate 5, the thickness can be increased accordingly, and the dimensions are set to 0.1 mm and the frame width (line width) to 0.1 mm. In this example, after printing, the heat transfer body 2 was held at about 150 ° C. for 1 hour in an electric furnace to cure the frame-shaped resin 6.

Next, the heat transfer body 2 is turned over, and a sufficient amount of the high thermal conductive grease 7 is poured into the frame-shaped resin 6. Next, the wiring boards 3 joined to the chip carrier 1 were stacked on the heat transfer body 2 and integrated by bolting. As in the first embodiment, when the heat value of the semiconductor element is small, oil may be sealed instead of the high thermal conductive grease 7.

After the assembly, the frame-shaped resin 6
And the high thermal conductive grease 7 contacts. As a result, the frame-shaped resin 6 is deformed in the thickness direction, and is deformed according to the height of the chip carrier 1 whose height varies, thereby eliminating the height variation. Further, the elasticity of the frame-shaped resin 6 can sufficiently cope with thermal deformation of the chip carrier 1 at the time of starting and stopping the device, and forms a good contact state. Furthermore, since the high thermal conductive grease 7 comes into direct contact, the contact resistance becomes extremely low. In addition, since the grease is sealed in the closed space, evaporation or escape of the oil in the grease is suppressed, and solidification of the grease can be prevented for a long time. As a result, high reliability is obtained in the long term.

Opening and closing of a multi-chip type semiconductor device is indispensable for repairing a chip carrier. Therefore, the chip carrier 1 cannot be bonded to the heat transfer body 2, and the frame resin 6 and the chip carrier 1 are not bonded in this embodiment. Therefore, the space for holding the high thermal conductive grease 7 is not a completely closed space.

However, if the thickness of the frame-shaped resin 6 is set to be equal to or more than the height variation of each chip carrier, the frame-shaped resin 6 has a sufficient force when fastening the wiring board 3 and the heat transfer body 2 by bolts. , And the sealing between the frame-shaped resin 6 and the chip carrier 1 becomes sufficient. In the case of the structure of this embodiment, since there is no thermal resistance equivalent to the flat plate 5, the thickness can be increased by that amount, and the spring constant of the frame-shaped resin 6 in the compression direction can be reduced.

[0037]

According to the present invention, since the high thermal conductive grease comes into direct contact with the chip carrier, the contact resistance becomes extremely small, and good heat transfer characteristics can be achieved. Further, the frame-shaped resin has a small area in contact with the chip carrier, and can be sufficiently deformed even with a small load. In addition, since the frame-shaped resin, the flat plate, and the heat transfer body are in close contact with each other, a good hermetically sealed space is provided, and the oil of the sealed grease does not flow out and escape, and the deterioration and solidification of the grease are suppressed for a long term.

Therefore, according to the present invention, a semiconductor device having a variable height or a chip carrier thereof can be cooled by a single heat conductor, and solidification of grease can be prevented, and a highly reliable multi-chip type. A semiconductor device can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view including a partial cut of a multi-chip type semiconductor device according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a part of FIG. 1;

FIG. 3 is a schematic diagram showing a manufacturing and assembling procedure of the multi-chip semiconductor device of FIG. 1;

FIG. 4 is a longitudinal sectional view of the multi-chip semiconductor device of FIG. 1;

FIG. 5 is a longitudinal sectional view showing a part of a multi-chip type semiconductor device according to another embodiment of the present invention.

FIG. 6 is a schematic perspective view of a heat transfer body showing a manufacturing and assembling procedure of a multi-chip type semiconductor device according to another embodiment of the present invention.

FIG. 7 is a longitudinal sectional view of a multi-chip type semiconductor device according to another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Chip carrier, 2 ... Heat transfer body, 3 ... Wiring board, 4 ...
Electrodes, 5: flat plate, 6: frame resin, 7: high thermal conductive grease, 31: frame, 32: pin, 71: oil.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tadakatsu Nakajima 502 Kandachicho, Tsuchiura-shi, Ibaraki Pref.

Claims (1)

[Claims] 1. A multi-chip type semiconductor device having a semiconductor element or a substrate on which a plurality of chip carriers are mounted, and a heat conductor in contact with the semiconductor element or the chip carrier. A flat plate is attached to the contact surface of the body via a frame-shaped resin, and grease or oil is sealed in a region formed by the contact surface of the frame-shaped resin, the flat plate, and the heat transfer body. Further, the multi-chip type semiconductor device is characterized in that the flat plate is in contact with a semiconductor element or a chip carrier via grease or oil.