JP2007305761A - Semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device with higher reliability than in prior art by restraining mechanical stress from being applied to a semiconductor chip owing to a difference of thermal expansion between a heat dissipation plate and a package substrate. <P>SOLUTION: A heat sink 37 includes a center lower surface side bonded to a semiconductor chip 32, and an edge upper surface side brought into contact with a heat sink press 36a and is held and sandwiched between the semiconductor chip 32 and the heat sink press part 36a. The heat sink 37 and the heat sink press part 36a are not joined with a gap provided between the heat sink 37 and a frame 36. Consequently, the frame 36 does not suffer from stress applied owing to thermal expansion of the heat sink 37, even though the heat sink 37 is thermally expanded owing to heat produced in the semiconductor chip 32. It is therefore possible to avoid mechanical stress caused by the thermal expansion of the heat sink 37 and applied to a circumferential junction of the semiconductor chip 32 through the package substrate 31. This improves the reliability of the semiconductor device. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductor device having a structure in which a semiconductor chip is mounted on a package substrate with its element formation surface facing down, and more particularly to a semiconductor device in which a semiconductor chip that generates a large amount of heat is flip-chip connected to the package substrate. .

  A flip-chip type semiconductor device in which a semiconductor chip is flip-chip connected to a package substrate has the advantage that the package can be downsized, the number of pins can be easily increased, and high-density mounting is possible.

  2. Description of the Related Art In recent years, the amount of heat generated by a semiconductor chip has increased with the improvement in performance of electronic devices. Since a malfunction occurs when the temperature of the semiconductor chip rises, it is necessary to provide a means for quickly releasing the heat generated in the semiconductor chip to the outside in a semiconductor device that generates a large amount of heat. In the flip chip type semiconductor device, heat generated in the semiconductor chip is transmitted to the heat sink from the heat radiating plate attached to the back surface (surface opposite to the element forming surface) of the semiconductor chip, and is released from the heat sink to the atmosphere. It has become.

  FIG. 1 is a cross-sectional view showing an example of a conventional flip-chip type semiconductor device. In the flip chip type semiconductor device shown in FIG. 1, a package for sealing the semiconductor chip 12 is composed of a package substrate 11, a frame body 16, and a heat radiating plate 17. The semiconductor chip 12 is mounted on the package substrate 11 with its element formation surface facing down. A plurality of electrodes (not shown) are formed on the element forming surface of the semiconductor chip 12, and these electrodes and electrodes (not shown) formed on the upper surface of the package substrate 11 are electrically connected via bumps 13. Connected. A sealing resin 14 is filled between the element formation surface of the semiconductor chip 12 and the package substrate 11 in order to protect the elements formed on the semiconductor chip 12.

  An electrode formed on the upper surface of the package substrate 11 is electrically connected to an electrode (not shown) formed on the lower surface of the substrate 11 through a connection portion (not shown) inserted through the package substrate 11. A ball 15 is formed under the electrode on the lower surface side. In the semiconductor device shown in FIG. 1, these balls 15 are bonded to the electrodes of the mounting board and mounted on the mounting board.

  On the other hand, a frame 16 surrounding the periphery of the semiconductor chip 12 in a wall shape is bonded on the package substrate 11 with an adhesive 18. A heat radiating plate 17 is bonded on the frame 16 by an adhesive 19. A heat conductive paste 20 is applied to the back surface (the upper surface in FIG. 1) of the semiconductor chip 12, and the heat radiating plate 17 is attached to the semiconductor chip 12 with the heat conductive paste 20.

  A heat sink (not shown) is attached on the heat radiating plate 17. The heat generated in the semiconductor chip 12 is quickly transmitted to the heat radiating plate 17 through the heat conductive paste 20, and is further transmitted from the heat radiating plate 17 to the heat sink and released from the heat sink to the atmosphere. If the heat generated in the semiconductor chip 12 is large, a cooling fan is attached in addition to the heat sink. As shown in FIG. 1, a package constituted by a frame body 16 and a heat radiating plate 17 is called a two-body type.

  FIG. 2 is a cross-sectional view showing another example of a conventional flip-chip type semiconductor device. In FIG. 2, the same components as those in FIG.

  In the flip chip type semiconductor device shown in FIG. 2, a lid 21 is bonded onto the package substrate 11 with an adhesive 22. The lid 21 has a structure in which a frame body portion 21a that surrounds the periphery of the semiconductor chip 12 in a wall shape and a heat radiation portion 21b that closes the top of the frame body portion 21a are integrally formed. On the other hand, a heat conductive paste 20 is applied to the back surface (the upper surface in FIG. 2) side of the semiconductor chip 12, and the semiconductor chip 12 is connected to the heat radiating portion 21 b of the lid 21 through the heat conductive paste 20. Yes.

  A heat sink (not shown) is attached on the heat radiating portion 21 b of the lid 21. The heat generated in the semiconductor chip 12 is promptly transmitted to the heat radiating portion 21b of the lid 21 through the heat conductive paste 20, and further transmitted from the heat radiating portion 21b to the heat sink and released from the heat sink to the atmosphere. As shown in FIG. 2, the package constituted by the lid 21 is called a lid type.

As prior art considered to be related to the present invention, there are those described in Patent Documents 1 to 3. Patent Document 1 describes a heat sink including a heat transfer pin that is biased by a spring and contacts a semiconductor chip. In Patent Document 1, a plurality of semiconductor chips having different thicknesses are collectively cooled by the heat sink. FIG. 4 of Patent Document 2 describes a heat sink having a structure in which a cooling fan is locked by a protrusion. Patent Document 3 describes a semiconductor device provided with a pressing metal fitting for pressing a substrate.
JP 2000-174182 A Japanese Patent Laying-Open No. 2003-188564 (FIG. 4) JP-A-7-249734

  However, the present inventors consider that the conventional semiconductor device described above has the following problems. That is, in the semiconductor device shown in FIG. 1, since the heat sink 17 is joined to the frame 16, an organic substrate such as glass epoxy (a composite material in which a glass fiber is impregnated with an epoxy resin) is used as the package substrate 11. In this case, in addition to the mechanical stress due to the difference in thermal expansion coefficient between the semiconductor chip 12 and the package substrate 11, the mechanical stress due to the difference in thermal expansion coefficient between the heat sink 17 and the package substrate 11. Acts on the peripheral junction of the semiconductor chip 12 through the package substrate 11, causing a reduction in the reliability of the semiconductor device.

  In the semiconductor device shown in FIG. 2 as well, since the frame portion 21a and the heat radiating portion 21b of the lid 21 are integrated in the same manner, the difference in the thermal expansion coefficient between the heat radiating portion 21b and the package substrate 11 is caused. The resulting mechanical stress acts on the peripheral joint portion of the semiconductor chip 12 through the package substrate 11 to reduce the reliability.

  In view of the above, an object of the present invention is to provide a semiconductor device in which the application of mechanical stress to the semiconductor chip due to the difference in thermal expansion between the heat sink and the package substrate is suppressed, and the reliability is higher than in the past. It is.

  According to an aspect of the present invention, a package substrate, a semiconductor chip mounted on the package substrate, a heat dissipation plate connected to the semiconductor chip and transmitting heat generated in the semiconductor chip, and the package substrate A frame that is fixed on and surrounds the periphery of the semiconductor chip in a wall shape, and is fixed to the frame and is held by the heat sink sandwiched between the semiconductor chip and the edge of the heat sink A semiconductor device, wherein the heat sink is not joined to the heat sink holding portion, and a gap is provided between the heat sink and the frame. Is provided.

  In the present invention, the heat radiating plate is held between the semiconductor chip and the heat radiating plate holding portion, and the heat radiating plate and the heat radiating plate holding portion are not joined. Further, a gap is provided between the heat radiating plate and the frame so that the heat radiating plate and the frame are not in contact with each other even if the heat radiating plate is thermally expanded by heat generated in the semiconductor chip. Thereby, it is avoided that mechanical stress resulting from the thermal expansion of the heat radiating plate is transmitted to the package substrate through the frame, and the reliability of the semiconductor device is improved.

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

(First embodiment)
FIG. 3 is a cross-sectional view showing the semiconductor device according to the first embodiment of the present invention. In the semiconductor device according to the present embodiment, a package for housing the semiconductor chip 32 is constituted by a package substrate 31, a frame body 36, and a heat radiating plate 37.

  That is, the semiconductor chip 32 is mounted on the package substrate 31 with its element formation surface facing down. A plurality of electrodes (not shown) are formed on the element formation surface of the semiconductor chip 32, and these electrodes are electrically connected to electrodes (not shown) formed on the upper surface of the package substrate 31 via bumps 33. It is connected to the. A sealing resin 34 for protecting elements formed on the semiconductor chip 32 is filled between the element formation surface of the semiconductor chip 32 and the package substrate 31.

  The electrode formed on the upper surface of the package substrate 31 is electrically connected to the electrode (not illustrated) formed on the lower surface of the substrate 11 through a connection portion (not illustrated) that passes through the package substrate 31. Yes. A ball 35 is formed under the electrode on the lower surface side of the package substrate 31. In the semiconductor device of this embodiment, these balls 35 are bonded to the electrodes of the mounting board and mounted on the mounting board. As the package substrate 31, for example, an organic substrate formed of a ceramic substrate or glass epoxy is used. In the present embodiment, it is assumed that an organic substrate is used as the package substrate 31.

  On the other hand, as shown in FIG. 3, a frame body 36 that surrounds the periphery of the semiconductor chip 32 in a wall shape is bonded onto the package substrate 31 by an adhesive 38. On the upper part of the frame body 36, a heat radiating plate pressing portion 36a protruding substantially horizontally toward the inside is provided. The frame body 36 and the heat sink holding portion 36a are formed of a metal material such as copper or stainless steel, an organic material such as resin, an inorganic material such as ceramic, or a composite material of metal and inorganic material. In this embodiment, the frame body 36 and the heat sink holding part 36a are integrally formed of the same material, but the frame body 36 and the heat sink holding part 36a are individually made of the same material or different materials. It may be formed.

  Thermal conductivity is not required for the frame body 36 and the heat sink holding portion 36a. However, in the semiconductor device of this embodiment, since the heat sink 37 is held by the heat sink holding part 36a and the semiconductor chip 32 as described later, if the rigidity of the frame body 36 and the heat sink holding part 36a is low, some cause When the stress is applied, the heat radiating plate 37 may be detached from the heat radiating plate pressing portion 36a. Therefore, the frame body 36 and the heat radiating plate pressing portion 36a are required to have a certain degree of rigidity.

  The heat radiating plate 37 is attached to the semiconductor chip 32 by a heat conductive paste 39 applied to the back surface (upper surface in FIG. 3) of the semiconductor chip 32. The heat dissipating plate 37 is held by being sandwiched between the heat dissipating plate holding portion 36 a and the semiconductor chip 32, with the upper surface of the edge contacting the heat dissipating plate holding portion 36 a and the lower surface of the central portion adhered to the semiconductor chip 32. In addition, although the heat sink 37 and the heat sink press part 36a are contacting, it has not joined. Further, in the present embodiment, as shown in FIG. 3, a gap is provided between the heat radiating plate 37 and the frame body 36, so that the heat radiating plate 37 does not come into contact with the frame body 36 even when thermally expanded. It has become.

  The heat radiating plate 37 is required to have a high thermal conductivity, and is usually formed of a metal material such as copper or aluminum. However, the heat radiating plate 37 may be formed of an inorganic material such as alumina or a composite material of metal and ceramic.

  A heat sink (not shown) is attached on the heat radiating plate 37. The heat generated in the semiconductor chip 32 is quickly transmitted to the heat radiating plate 37 via the heat conductive paste 39, further transmitted from the heat radiating plate 37 to the heat sink, and released from the heat sink to the atmosphere. When much heat is generated in the semiconductor chip 32, a cooling fan is attached in addition to the heat sink.

  In the semiconductor device according to the present embodiment configured as described above, the heat radiating plate 37 and the heat radiating plate pressing portion 36a are in contact with each other but are not joined, and a gap is provided between the heat radiating plate 37 and the frame body 36. Therefore, even if the heat radiating plate 37 is thermally expanded by the heat generated in the semiconductor chip 32, stress due to the thermal expansion of the heat radiating plate 37 is not applied to the frame body 36. Thereby, application of mechanical stress from the frame body 36 to the peripheral joint portion of the semiconductor chip 32 through the package substrate 31 is avoided. As a result, the reliability of the semiconductor device is improved.

(Second Embodiment)
FIG. 4 is a sectional view showing a semiconductor device according to the second embodiment of the present invention. The difference between this embodiment and the first embodiment is that the shape of the heat sink is different, and the other basic configuration is the same as that of the first embodiment. Are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the first embodiment shown in FIG. 3, the heat sink that can be used is limited because the upper surface of the heat radiating plate 37 is lower than the upper surface of the frame body 36. For example, in order to use a large heat sink having a flat bottom surface. However, there is a drawback that it is necessary to arrange a heat conduction plate or the like between the heat radiating plate 37 and the heat sink.

  On the other hand, in the present embodiment, as shown in FIG. 4, a step is provided between the center portion and the edge portion of the heat radiating plate 41 so that the upper surface of the heat radiating plate 41 and the upper surface of the frame body 36 have the same height. It is trying to become. However, in the present embodiment as well, as in the first embodiment, the heat radiating plate 41 and the heat radiating plate pressing portion 36a are in contact with each other, but not joined, and between the heat radiating plate 41 and the frame body 36. In order to prevent the heat radiating plate 41 from coming into contact with the frame body 36 even if it is thermally expanded.

  As a result, the semiconductor device according to the present embodiment can obtain the same effects as those of the first embodiment, and the restriction of the heat sink is relaxed, and a large heat sink with a flat bottom surface can be used. The effect of becoming can be obtained.

  Hereinafter, various aspects of the present invention will be collectively described as supplementary notes.

(Appendix 1) a package substrate;
A semiconductor chip mounted on the package substrate;
A heat radiating plate connected to the semiconductor chip to transmit heat generated in the semiconductor chip;
A frame that is fixed on the package substrate and surrounds the periphery of the semiconductor chip in a wall shape;
A heat sink holding part that is fixed to the frame and that holds the heat sink sandwiched between the semiconductor chip and the edge of the heat sink;
The semiconductor device, wherein the heat radiating plate is not joined to the heat radiating plate pressing portion, and a gap is provided between the heat radiating plate and the frame body.

  (Supplementary Note 2) A step is provided between a portion of the heat sink that contacts the semiconductor chip and a portion that contacts the heat sink holding portion, and the upper surface of the heat sink and the upper surface of the frame body have the same height. The semiconductor device according to appendix 1, wherein:

  (Supplementary note 3) The semiconductor device according to supplementary note 1, wherein the frame body and the heat sink holding part are integrally formed of the same material.

  (Additional remark 4) The semiconductor device of Additional remark 1 characterized by the heat conductive paste interposing between the said semiconductor chip and the said heat sink.

  (Supplementary note 5) The semiconductor device according to supplementary note 1, wherein the heat dissipation plate is formed of any one of a metal, an inorganic material, and a composite material of a metal and an inorganic material.

  (Additional remark 6) The said heat sink holding | suppressing part is formed with either the metal, the organic material, the inorganic material, and the composite material of a metal and an inorganic material, The semiconductor device of Additional remark 1 characterized by the above-mentioned.

FIG. 1 is a cross-sectional view showing an example of a conventional flip-chip type semiconductor device. FIG. 2 is a cross-sectional view showing another example of a conventional flip-chip type semiconductor device. FIG. 3 is a cross-sectional view showing the semiconductor device according to the first embodiment of the present invention. FIG. 4 is a sectional view showing a semiconductor device according to the second embodiment of the present invention.

Explanation of symbols

11, 31 ... package substrate,
12, 32 ... semiconductor chip,
13, 33 ... Bump,
14, 34 ... sealing resin,
15,35 ... ball,
16, 36 ... frame,
17, 37, 41 ... heat sink,
18, 19, 22, 38 ... adhesive,
20, 39 ... heat conductive paste,
21 ... Lid,
36a ... Radiator holding part.

Claims (3)

A package substrate;
A semiconductor chip mounted on the package substrate;
A heat radiating plate connected to the semiconductor chip to transmit heat generated in the semiconductor chip;
A frame that is fixed on the package substrate and surrounds the periphery of the semiconductor chip in a wall shape;
A heat sink holding part that is fixed to the frame body and holds the heat sink sandwiched between the semiconductor chip in contact with the edge of the heat sink;
The semiconductor device, wherein the heat radiating plate is not joined to the heat radiating plate pressing portion, and a gap is provided between the heat radiating plate and the frame body.   A step is provided between a portion of the heat radiating plate that contacts the semiconductor chip and a portion that contacts the heat radiating plate pressing portion, and the upper surface of the heat radiating plate and the upper surface of the frame body have the same height. The semiconductor device according to claim 1.   The semiconductor device according to claim 1, wherein the frame body and the heat sink holding portion are integrally formed of the same material.

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