JPH09205166A - Multi-chip module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-chip module of a structure which can reliably and efficiently radiate heat generated in semiconductor elements mounted face- down on a board. SOLUTION: The multi-chip module includes a lid 4 which is formed therein with holes having female threaded parts 4a at positions corresponding to semiconductor elements 2 mounted face-down on a board 1. The module also includes metallic members 7 of a cone or semi-spherical shape having a bottom surface whose size can cover an outer diameter of the associated element 2. The module further includes screws 6 which are each formed in its inner surface with a fitting hole having nearly the same shape as an outer surface of the associated metallic member 7 to push down the outer surface of the member 7. Each screw 6 is formed in its outer surface a male threaded part which is engaged with the associated threaded part of the lid 4. Thereby, the elements 2 are joined to the lid 4 by means of the metallic members 7 and screws 6, thus realizing efficient heat radiation from the elements 2.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a multi-chip module in which a plurality of semiconductor elements are mounted face down on a substrate. In particular, the present invention relates to a multi-chip module having a structure for efficiently radiating heat generated by a semiconductor element.

[0002]

FIG. 7 is a longitudinal sectional view of an example of a conventional multi-chip module, FIG. 8 is a longitudinal sectional view of a second conventional example, and FIG. 9 is an exploded view of a third conventional example. It is a perspective view.

A module in which a plurality of semiconductor elements are mounted on a substrate and functions are combined is called a multi-chip module, and is often used recently as a means for increasing the degree of integration of semiconductor elements. As a method for mounting a semiconductor element, there are a face-up structure in which the circuit surface of the semiconductor element is mounted upward on the substrate and a face-down structure in which the circuit surface of the semiconductor element is mounted facing the substrate (backward). . Recently, a face-down structure has been frequently used for the purpose of higher density mounting.

As shown in FIG. 7, a face-down structure of a semiconductor device has a metal projection (bump) 3 on an external connection terminal.
The semiconductor element 2 subjected to the above operation has its circuit surface facing the substrate 1, and is electrically connected to a circuit pattern (not shown) provided on the substrate 1. The heat generated from the semiconductor element 2 mounted in this manner has no means other than being thermally conducted from the metal projection 3 to the substrate 1 or radiated from the back surface of the semiconductor element 2 to the outside air by radiation or the like. In a multi-chip module on which a semiconductor element having a large amount of heat is mounted, it is required to provide a means for radiating heat structurally.
As a structure of a multi-chip module on which such a semiconductor element generating a large amount of heat is mounted, as shown in FIG. 7, a metal lid 15 is provided on the substrate 1 and an adhesive 16 or the like is provided on the back surface of the semiconductor element 2. The heat is dissipated by heat conduction. (For example, JP-A-60-241240).

FIG. 8 shows an example of a heat dissipation structure of a multi-chip module on which semiconductor elements having different thicknesses are mounted.
As shown in the figure, the lid 20 having an opening at a position corresponding to the arrangement of the semiconductor element 2 mounted on the substrate 1 is provided with a leg 17b of the heat radiating member 17 provided with a heat radiating fin 17a at an upper portion thereof. , And bonded to the back surface of the semiconductor element 2 with the solder 18 to dissipate heat. (Japanese Patent Laid-Open No. 4-2
No. 63457).

As another example of the heat dissipation structure, the disassembled perspective view of FIG. 9 shows a heat dissipation structure of a package of a single semiconductor element, although not the whole structure of the multichip module. Heat dissipating fin 21 having external thread portion 22
Has been reported to contact the back surface of a semiconductor element and dissipate heat. Although this publication does not specifically refer to a method of mounting a semiconductor element, a method of using a lead frame, mounting a circuit surface of the semiconductor element face-up with respect to a base, and adopting a method of wire bonding is adopted. JP-A-57-162353).

[0007]

There are two problems with the conventional heat dissipation structure as described above. One of them is that it cannot be said to be a structure for surely dissipating heat from a semiconductor element that generates heat. The thermal design of a semiconductor element having such a heat dissipation structure is designed in consideration of the maximum used junction temperature of the semiconductor element. In a multi-chip module using face-down mounting, first, a semiconductor element is mounted on a substrate. Thereafter, the whole is assembled by surrounding members related to heat radiation. In the first structure example shown in FIG. 7, the difference in height of the semiconductor element 2 causes the distance between the lid 15 and the space to vary, so that an adhesive or It is necessary to control the amount of the solder 16. If the amount is small, a gap is generated between the lid 15 and the back surface of the semiconductor element 2, and the thermal resistance for conducting heat from the semiconductor element 2 increases. If the amount of the adhesive or the solder 16 is too large, there is a risk that the adhesive or the like flows into the substrate side and impairs the reliability of connection between the substrate and the semiconductor element.

The second structural example shown in FIG. 8 corresponds to the semiconductor elements 2 having different heights. A hole is formed in the cover 20 at a position facing each of the semiconductor elements 2, and the radiation fins 17 are formed.
The gap between the back surface of the semiconductor element 2 and the lid 20 is joined by solder 18 by changing the length of the leg 17b of the heat radiating member 17 attached with a to the semiconductor element 2. In this case as well, it is difficult to control the amount of the solder 18 for bonding, which is interposed between the lid 20, the back surface of the semiconductor element 2, and the heat radiating member 17, and to control the temperature for bonding. When the soldering property between the lid 20 and the heat radiating member 17 is extremely good, the amount of the solder 18 is reduced on the back surface of the semiconductor element 2 and the heat radiating member 17, and a gap is easily generated. Also, depending on the speed at which the solder 18 solidifies,
This includes the possibility that the heat radiating member 17 and the back surface of the semiconductor element 2 cannot be completely joined due to the difference in thermal expansion coefficient between the members. A common problem of the conventional structures shown in FIGS. 7 and 8 is that the reliability of the bonding surface with the back surface of the semiconductor element cannot be confirmed.

Another problem is that the mechanical stress on the semiconductor device cannot be controlled. In the third structural example shown in FIG. 9, since the male screw portion 22 is directly joined to the back surface of the semiconductor element by rotation, a rotational stress of the semiconductor element is applied. Materials such as silicon and gallium arsenide forming a semiconductor element are susceptible to mechanical stress, and may crack due to local stress. Therefore, it is necessary to maintain the flatness and parallelism of the surface of the screw joined to the back surface of the semiconductor element, which causes a great obstacle in terms of productivity. Similarly, the structures shown in FIGS. 7 and 8 have a high possibility that a mechanical stress is applied to the semiconductor element when the adhesive or the solder for securing the bonding is hardened.

Therefore, an object of the present invention is to generate heat generated by a semiconductor element mounted face down on a substrate.
An object of the present invention is to provide a multi-chip module having a structure for reliably and efficiently discharging.

[0011]

According to a first aspect of the present invention, there is provided a multi-chip module comprising: a plurality of semiconductor elements mounted face-down on a substrate; and a plurality of semiconductor elements mounted on the substrate and corresponding to the arrangement of the semiconductor elements. In a multi-chip module having a metal lid provided with a female screw portion in each of the openings, a truncated-cone-shaped metal piece having a bottom surface large enough to cover the outer shape of the semiconductor element, and a truncated-cone-shaped In order to press the outer surface of the metal piece, a fitting portion having a truncated cone shape having substantially the same shape as the outer surface of the metal piece is formed, and a male screw engaging with the female screw part of the metal lid is formed on the outer surface. And a screw in which a portion is formed, wherein the back surface of the semiconductor element and the metal lid are joined via a metal piece having a truncated cone shape and the screw.

According to the second aspect of the present invention, a hemispherical metal piece having a bottom surface large enough to cover the outer shape of the semiconductor element and an outer surface of the hemispherical metal piece are pressed against the inner surface. A screw having a hemispherical inner surface shape or a hemispherical band inner surface shape having substantially the same shape as the outer surface of the metal piece, and a male screw portion formed on the outer surface engaging with the female screw portion of the metal lid; The semiconductor device is characterized in that the back surface of the semiconductor element and the metal lid are joined via a hemispherical metal piece and a screw.

In these multichip modules, a highly thermally conductive sheet is interposed between the back surface of a semiconductor element mounted face down on a substrate and a metal piece pressing the semiconductor element. Preferably
Further, a thermosetting resin is respectively interposed in the joint portion between the back surface of the semiconductor element and the metal piece, the joint portion between the metal piece and the screw, and the joint portion between the screw and the metallic lid, and after joining the joint portions, It is also preferable that it is cured by heating.

[0014]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a longitudinal sectional view of an embodiment of the multichip module of the present invention, FIG. 2 is a perspective view of FIG. 1, and FIG. It is a perspective view.

In FIG. 1, a semiconductor element 2 having a metal projection 3 on a connection terminal (not shown) for connection to the outside is mounted on a substrate 1.
And is electrically connected to a circuit pattern (not shown) formed on the surface of the substrate 1. Although the description of the connection method at this time is omitted, as the metal projection, a method of plating solder or the like on the external connection terminal of the semiconductor element 2 or a method of forming a soft metal such as gold Au by thermocompression bonding or the like, The connection is established by melting with the formed solder. After the semiconductor element 2 is mounted on the substrate 1, a lid 4 for heat dissipation is bonded to the substrate. As a joining method, a method of providing a pattern on a portion corresponding to a leg portion of the lid 4 on the substrate 1 and joining with a solder or the like or a method of joining with an adhesive or the like is adopted. The lid 4 is provided with an opening at a portion corresponding to the semiconductor element 2, and a female screw 4a is provided inside the opening. As shown in FIGS. 1 and 3, a frustum-shaped metal piece 7 having a bottom surface larger than a circle covering the back surface of the semiconductor element 2 is provided with an opening of a lid 4 on the back surface of the semiconductor element 2 attached to the substrate 1. Put on from the department. From above, a semiconductor element is formed by a screw 6 having a fitting surface having the same shape as the truncated-cone-shaped metal piece 7 as shown in FIGS. 2 is fixed with a fixed torque to fix it. At this time, the rotation of the screw 6 is performed by a rotation groove 6b provided above the screw 6. The difference in the height of the semiconductor element 2 attached to the substrate 1 is adjusted by adjusting the screw 6 into the cover 4. At this time, the metal piece 7 bonded onto the semiconductor element 2 is pressed with a constant pressure, so that no rotational stress is applied to the semiconductor element 2 and the substrate 1 is brought into contact with the lid 4 only by a vertical force. Joining can be performed. The fins 5 provided on the lid 4 need not consider the amount of heat generated by the semiconductor element 2 as long as the amount of heat generation is low.

FIG. 4 is a longitudinal sectional view of a second embodiment of the present invention, FIG. 5 is a longitudinal sectional view of a third embodiment of the present invention,
FIG. 6A is a partially enlarged longitudinal sectional view of a part of one element junction in FIG. 5, and FIG. 6B is a partially enlarged longitudinal section of another element junction in FIG. 5. It is.

In the second and third embodiments, the screw 1 of the metal piece 9 which is planarly bonded to the back surface of the semiconductor element 2 is formed.
The joints with 0 and 11 are hemispherical. The semicircular metal piece 9 has a high degree of freedom at the joint with the screws 10 and 11,
As shown in FIG. 6 (a), even if the semiconductor element 2 is mounted on the substrate 1 and there is a difference in the height direction in one semiconductor element, an angular displacement.
And the screw 11 can absorb the displacement. FIG.
The screw 10 on the right side of FIG. 5 and the screw 12 on the right side of FIG.
This is an example of the case where fins for heat dissipation are provided. In the semiconductor element 2 on the left side of FIG. 5, a heat conductive sheet 13 is interposed between the semiconductor element 2 and the semi-spherical metal piece 9. This sheet is suitable as a strong cushioning material when the semiconductor element 2 having a low mechanical strength is mounted and securely joined to the back surface of the semiconductor element. FIG. 6B shows a state where the heat conductive adhesive (resin) 14 is poured into the respective joints between the back surface of the semiconductor element 2, the hemispherical metal pieces 9, the screws 11, and the lid 4. It is an enlarged view of a similar example. In particular, it is used when the heat value is large and the thermal resistance at each joint is more reliably performed. Since the gap between the joints is about several tens of μm, the amount to be poured is very small, and it is sufficient to apply the resin 14 to each joint. Therefore, the mechanical stress when the resin is cured is very small.

[0019]

As described above, according to the present invention, it is possible to radiate heat flexibly and surely by coping with the difference in height and size between the semiconductor elements mounted on the substrate and the angular displacement of one semiconductor element. The structure of being joined to the lid has an effect of providing a highly reliable multi-chip module in which heat is efficiently and surely radiated from the semiconductor element.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of a multichip module according to the present invention.

FIG. 2 is a perspective view of FIG.

FIG. 3 is a perspective view of the screw and the truncated conical metal piece of FIG. 2;

FIG. 4 is a longitudinal sectional view of a second embodiment of the present invention.

FIG. 5 is a longitudinal sectional view of a third embodiment of the present invention.

6 (a) is a partially enlarged longitudinal sectional view of a part of one element junction in FIG. 5, and FIG. 6 (b) is a partially enlarged longitudinal sectional view of a part of another element junction in FIG. 5; FIG.

FIG. 7 is a longitudinal sectional view of an example of a conventional multi-chip module.

FIG. 8 is a longitudinal sectional view of a second conventional example.

FIG. 9 is an exploded perspective view of a third conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Semiconductor element 3 Metal protrusion 4,15,20 Lid 4a, 25 Female screw part 5,17a, 21 Heat radiation fin 6,10,11,12 Screw 6a, 22 Male screw part 6b Rotation groove 7 Frustoconical metal piece 8, 24 terminal 9 semicircular metal piece 13 heat conductive sheet 14 heat conductive adhesive (resin) 16 adhesive or solder 17 heat dissipation member 17b leg 18 solder 19 spacer 23 semiconductor package

Claims (4)

[Claims] 1. A metal lid having a plurality of semiconductor elements mounted face-down on a substrate and a plurality of female threads mounted on the substrate and having a plurality of openings corresponding to the arrangement of the semiconductor elements. A multi-chip module having a truncated-cone-shaped metal piece having a bottom size large enough to cover the outer shape of the semiconductor element; and an inner surface, for pressing an outer surface of the frusto-conical-shaped metal piece, A screw having a truncated cone-shaped fitting portion having substantially the same shape as the outer surface of the metal piece and having a male screw portion engaged with the female screw portion of the metal lid formed on the outer surface. A multi-chip module, comprising: a back surface of the semiconductor element and the metal lid joined to each other via the truncated cone-shaped metal piece and the screw. 2. A plurality of semiconductor elements attached face-down to a substrate, and a metal lid attached to the substrate and having female threads in a plurality of openings corresponding to the arrangement of the semiconductor elements. A multi-chip module comprising: a hemispherical metal piece having a bottom surface large enough to cover the outer shape of the semiconductor element; and A fitting portion having a hemispherical inner surface shape or a hemispherical band inner surface shape having substantially the same shape as the outer surface of the piece was formed, and a male screw portion engaging with the female screw portion of the metal lid was formed on the outer surface. A multi-chip module, comprising: a screw; and a back surface of the semiconductor element and the metal lid are joined via the hemispherical metal piece and the screw. 3. The multi-chip module according to claim 1, wherein a sheet having high thermal conductivity is interposed between the back surface of the semiconductor element and the metal piece. 4. A thermosetting resin is interposed at a joint between the back surface of the semiconductor element and the metal piece, at a joint between the metal piece and the screw, and at a joint between the screw and the metallic lid, respectively. 2. After the joining, the joining portions are joined and then cured by heating.
Or the multichip module according to 2.