JP2012015372A - Cooling structure of electronic component, electronic component device, and heat sink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cool electronic components such as LSI chips stably by limiting production of bubbles in thermal grease.SOLUTION: An cooling structure of an electronic component comprises: an electronic component 10 mounted on the surface of a wiring board 30; a heat sink 20 provided to cover the electronic component 10; and a thermal grease 40 having semi-fluidity and filling the gap between the electronic component 10 and the heat sink 20. The heat sink 20 has a peripheral wall 25 projecting from the surface on the electronic component 10 side and housing the electronic component 10 in the inside space. The peripheral wall 25 has open parts 22 formed at positions corresponding to corners of the electronic component 10 and interconnecting the inside space and the outside. The thermal grease 40 fills the inside space and is stored in the open parts 22.

Description

  The present invention relates to a cooling structure for an electronic component such as an LSI (Large Scale Integration) chip, an electronic component device, and a heat sink.

  In recent years, with the increase in integration and speed of semiconductor circuits mounted on LSI chips, the heat generation of LSI chips has become extremely large. For this reason, a large heat sink is attached to the LSI chip to promote heat dissipation of the LSI chip.

FIG. 4 is a schematic diagram of a cooling structure for a general electronic component.
The LSI chip 1 is mounted at a predetermined position on the wiring board 2. A heat sink 3 having a larger area than the LSI chip 1 is disposed on the top surface 1 a of the LSI chip 1. The heat sink 3 is fixed to the LSI chip 1 so as to be pressed by using a coil spring or a plate spring (not shown), whereby the lower surface side 3a is pressed against and contacted with the top surface 1a of the LSI chip 1.

However, the contact surface between the heat sink 3 and the LSI chip 1 is not completely smooth but has fine irregularities. Further, the heat sink 3 cannot be strongly pressed against the LSI chip 1 due to the strength of the LSI chip 1. Therefore, even if the heat sink 3 and the LSI chip 1 are in direct contact, the substantial contact area between the LSI chip 1 and the heat sink 3 is small, and the thermal resistance of the heat conduction path from the LSI chip 1 to the heat sink 3 is increased. End up.
As a result, in terms of thermal design, the contact surface between the LSI chip 1 and the heat sink 3 is the portion with the highest heat density in the heat conduction path from the LSI chip 1 to the heat sink 3. Therefore, in a general electronic component cooling structure, as shown in FIG. 4, in order to reduce the thermal resistance between the LSI chip 1 and the heat sink 3, thermal grease 4 is provided between the LSI chip 1 and the heat sink 3. (See, for example, Patent Document 1 below).

JP 2002-93962 A

Incidentally, it is known that such an LSI chip 1 has a problem of pumping out. Each of the LSI chip 1 and the heat sink 3 on the wiring board 2 has a difference in thermal expansion coefficient. For this reason, when the amount of strain on the surface of the LSI chip 1 increases or decreases with the temperature change, the gap dimension between the LSI chip 1 and the heat sink 3 changes as shown in FIG. Bubbles are mixed while being repeatedly pushed out and pulled in from the gap with the heat sink 3.
FIG. 5 shows a case where the gap dimension between the LSI chip 1 and the heat sink 3 changes from (a) standard gap (room temperature) to (b) narrow gap (high temperature) to (c) standard gap (room temperature) due to temperature change. The state change of the thermal grease 4 is shown. When the temperature increases from the state shown in FIG. 5A and the gap dimension between the LSI chip 1 and the heat sink 3 becomes a narrow gap as shown in FIG. Extruded from the range of the top surface to the outer periphery. Then, as shown in FIG. 5C, when the temperature decreases again and the gap dimension between the LSI chip 1 and the heat sink 3 becomes the standard gap, a part of the thermal grease 4 once pushed out is part of the LSI. It does not return to the range of the top surface 1 a of the chip 1, and as a result, the bubbles 5 are taken into the thermal grease 4.
If the bubbles 5 are generated in the thermal grease 4 in this manner, the bubbles 5 have a large thermal resistance, which causes a problem that the LSI chip 1 cannot be stably cooled.

  Such a pump-out phenomenon is caused by the fact that the thermal grease 4 is less in the vicinity of the corner 1c of the LSI chip 1 than the four sides 1b of the LSI chip 1 and around the LSI chip 1. to cause. More specifically, as shown in FIG. 6A, in the assembly process, the thermal grease 4 is supplied from the nozzle that supplies the thermal grease 4 to the center of the top surface 1a of the LSI chip 1. Then, due to the surface tension, the thermal grease 4 remains on the top surface 1a of the LSI chip 1 in a substantially circular shape in plan view. 6B and 6C, when the heat sink 3 is pressed onto the LSI chip 1, the thermal grease 4 spreads to the outer peripheral side. Even in the spread state, since the thermal grease 4 is circular in plan view, the amount of the thermal grease 4 existing in the vicinity of the corner 1c of the LSI chip 1 is naturally reduced.

  On the other hand, by increasing the amount of thermal grease 4, the range in which thermal grease 4 spreads is increased, and the amount of thermal grease 4 present in the vicinity of the corner 1 c of LSI chip 1 is reduced. It can also be prevented. However, this leads to an increase in material costs.

  By the way, a part of the heat generated in the LSI chip 1 is also radiated to the wiring board 2, thereby taking part of the cooling function of the LSI chip 1. However, the LSI chip 1 with high integration and high speed tends to have high power consumption and low voltage, and the current value supplied to the LSI chip 1 is large. As a result, the electrical resistance value of the conductor of the wiring board 2 rises due to heat generation of the wiring board 2, and a failure occurs such that necessary power feeding cannot be performed. There is a limit to doing it. Therefore, the LSI chip 1 needs to be reliably cooled by the heat sink 3.

  Accordingly, an object of the present invention is to provide an electronic component cooling structure, an electronic component device, and a heat sink that can suppress the generation of bubbles in the thermal grease and stably cool electronic components such as LSI chips. is there.

The present invention employs the following means in order to solve the above problems.
That is, the electronic component cooling structure of the present invention is filled between the electronic component mounted on the surface of the wiring board, the heat sink provided so as to cover the electronic component, and the electronic component and the heat sink. Thermal grease having fluidity, and the heat sink has a peripheral wall that protrudes from the surface on the electronic component side and accommodates the electronic component in an inner space, and the peripheral wall is formed at a corner of the electronic component. An opening portion is formed at a corresponding position and communicates the inner space and the outer side, and the thermal grease is filled in the inner space and stored in the opening portion. .

  According to another aspect of the present invention, there is provided an electronic component device including the above-described electronic component cooling structure.

  In addition, the present invention is a heat sink provided so as to cover the electronic component and dissipating heat generated by the electronic component, wherein the heat sink protrudes from the surface and forms an inner space for accommodating the electronic component. A peripheral wall, the peripheral wall is formed at a position corresponding to a corner of the electronic component, and has an open portion that allows the inner space to communicate with the outside, and the inner space can be filled with the thermal grease. The open portion can be stored.

According to the present invention, the thermal grease is stored in the open portion corresponding to the corner of the electronic component in the peripheral wall that accommodates the electronic component, so that the gap dimension between the electronic component and the heat sink varies as the temperature changes. Even if the thermal grease is repeatedly pushed out or pulled in between the electronic component and the heat sink, a sufficient amount of thermal grease is present on the outer peripheral side of the corner of the electronic component. Thereby, it is possible to prevent air bubbles from being mixed when the thermal grease is drawn. Therefore, the heat dissipation by the heat sink can be prevented from being lowered, and the electronic component can be stably cooled.
In addition, the peripheral wall restricts the expansion of the thermus grease to the outside in the part corresponding to the corner other than the corner of the electronic component. Excellent.

FIG. 1 is a schematic configuration diagram of an electronic component device according to the present embodiment, in which FIG. 1A is a plan view, and FIG. 1B is a vertical cross-sectional view (a cross-sectional view taken along a line II in FIG. 1A). It is. In FIG. 1A, illustration of the plate body 20A of the heat sink 20 is omitted, and only the peripheral wall 25 is illustrated. FIG. 3 is an enlarged cross-sectional view of a main part showing a protrusion 21 that the heat sink 20 has. FIG. 4 is a process diagram when attaching the heat sink 20 on the LSI chip 10. FIG. 4A is a schematic configuration diagram of a cooling structure for a general electronic component, FIG. 4A is a plan view, and FIG. 4B is a longitudinal sectional view (a sectional view taken along line II-II in FIG. 4A). It is. In addition, illustration of the heat sink 3 is abbreviate | omitted in Fig.4 (a). It is a figure which shows a general electronic component, Comprising: The mode when the gap dimension of an electronic component and a heat sink fluctuate | varied with the temperature change is shown. It is a figure which shows a general electronic component, Comprising: It is process drawing which attaches a heat sink on a LSI chip.

  Hereinafter, an embodiment for carrying out an electronic component cooling structure according to the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited only to these examples.

FIG. 1 shows a configuration of an electronic component device according to the present embodiment.
As shown in FIG. 1, the LSI chip (electronic component) 10 is mounted at a predetermined position on the wiring board 30 in, for example, a rectangular plate shape. On the top surface 10 a of the LSI chip 10, a plate-shaped heat sink 20 made of metal having excellent heat dissipation and having an area larger than that of the LSI chip 10 is disposed. The heat sink 20 is fixed to the LSI chip 10 so as to be pressed by using a coil spring or a plate spring (not shown), whereby the lower contact surface 20a is pressed against the top surface 10a of the LSI chip 10. The electronic component device includes the LSI chip 10, the heat sink 20, and the wiring board 30.

The heat sink 20 includes a heat sink body 20A formed in a plate shape, and a peripheral wall 25 that protrudes from the contact surface 20a of the heat sink body 20A facing the LSI chip 10 and accommodates the LSI chip 10 in the inner space. ing.
The peripheral wall 25 is configured by arranging four protrusions 21 extending continuously along the four sides of the outer peripheral edge of the LSI chip 10 in a rectangular shape. More specifically, two protrusions 21 adjacent to each other among the four protrusions 21 are arranged so as to extend in directions orthogonal to each other via an opening 22 that communicates the inner space and the outer side. Thus, the overall configuration is rectangular. That is, the peripheral wall 25 is configured such that the open portion 22 is positioned corresponding to the corner portion 10 c of the LSI chip 10.
As shown in FIG. 2, each protrusion 21 has a predetermined distance from the side surface 10 b located on the outer peripheral edge of the LSI chip 10 to the outer peripheral side so as not to contact the LSI chip 10 when the heat sink 20 is placed on the LSI chip 10. They are spaced apart by more than the dimensions. Each protrusion 21 is formed at such a height that the tip 21 a of the protrusion 21 does not contact the wiring board 30 in a state where the contact surface 20 a of the heat sink 20 is pressed against the top surface 10 a of the LSI chip 10. . Further, in the present embodiment, the protrusion 21 is formed in a trapezoidal shape in a sectional view in which the width gradually decreases as the heat sink 20 approaches the wiring board 30.

  The peripheral wall 25 (projection 21) may be formed of a material different from that of the heat sink 20. However, if the peripheral wall 25 (projection 21) is formed of the same material as the heat sink 20, the projection 21 can be formed simultaneously when the heat sink 20 is formed. Part of the heat dissipation of the heat sink 20 can be taken. Furthermore, if the peripheral wall 25 (projection 21) is formed of a material having higher thermal conductivity than the heat sink 20, heat can be efficiently conducted to the heat sink 20 via the projection 21.

When the cooling structure of the LSI chip 10 is realized using the heat sink 20 having such a configuration, the heat sink 20 is attached as follows.
First, as shown in FIG. 3A, thermal grease 40 is placed on the top surface 10 a of the LSI chip 10 mounted on the wiring board 30.
Then, the heat sink 20 is pressed against the top surface 10 a of the LSI chip 10. Then, as shown in FIGS. 3B and 3C, the thermal grease 40 is pushed and spread between the top surface 10 a of the LSI chip 10 and the heat sink 20. Then, the place of thermal grease 40 is limited by the LSI chip 10 and the heat sink 20, and the thermal grease 40 is filled between the contact surface 20 a and the protrusion 21 of the heat sink 20 and the top surface 10 a and the four side surfaces 10 b of the LSI chip 10. Is done.

  At this time, as shown in FIG. 3C, since the protrusion 21 is not provided in the vicinity of the corner portion 10c of the LSI chip 10 in which air is easily mixed into the thermal grease 40, the thermal grease 40 is opened. It is pushed out from the part 22 and flows out to the outer peripheral side of the LSI chip 10. Thereby, the thermal grease 40 is stored in the open part 22 and the outside. That is, a sufficient amount of thermal grease 40 is present on the outer peripheral side of the corner 10 c of the LSI chip 10.

  According to such a configuration, when the gap size between the LSI chip 10 and the heat sink 20 becomes high due to the operation of the LSI chip 10 from the standard gap at normal temperature and becomes a narrow gap as the temperature changes, the thermal grease 40 Then, it is pushed out from the gap between the top surface 10a of the LSI chip 10 and the contact surface 20a of the heat sink 20 to the outer peripheral side. When the operation of the LSI chip 10 stops and the temperature decreases and the gap dimension between the LSI chip 1 and the heat sink 3 becomes the standard gap, the top surface 10a of the LSI chip 10 and the contact surface 20a of the heat sink 20 are in contact with each other. The gap is in a negative pressure state, and a part of the thermal grease 40 pushed out once is drawn into the gap between the top surface 10 a of the LSI chip 10 and the contact surface 20 a of the heat sink 20. At this time, since a sufficient amount of thermal grease 40 exists on the outer peripheral side of the corner portion 10c of the LSI chip 10, the gap between the top surface 10a of the LSI chip 10 and the contact surface 20a of the heat sink 20 is The thermal grease 40 is securely pulled.

In this way, it is possible to prevent bubbles from entering the thermal grease 40 in the vicinity of the corner 10c of the LSI chip 10.
Here, when the thermal grease 40 is pushed out due to a temperature change, the thermal grease 40 is restricted from spreading to the outer peripheral side by the protrusions 21 in the portion along the four side surfaces 10b of the LSI chip 10, and the LSI. It spreads intensively from the opening 22 near the corner 10c of the chip 10. Therefore, the amount of the thermal grease 40 in the vicinity of the corner portion 10c of the LSI chip 10 can be effectively increased at a low cost without increasing the amount of the thermal grease 40.
Further, the direction in which the thermal grease 40 spreads by the protrusions 21 is limited to the wiring board 30 side rather than the outer peripheral side, so that not only between the top surface 10a of the LSI chip 10 and the contact surface 20a of the heat sink 20 but also the LSI. Thermal grease 40 can be filled between the heat sink 20 and the surface of the wiring board 30 along the four side surfaces 10 b of the chip 10. As a result, the efficiency of heat conduction from the LSI chip 10 to the heat sink 20 can be increased, heat dissipation can be improved, and the LSI chip 10 can be prevented from coming into contact with air.
At this time, since the protrusion 21 provided on the heat sink 20 can be brought into contact with the wiring board 30 via the thermal grease 40, heat generated in the wiring board 30 caused by power feeding to the LSI chip 10 is released to the heat sink 20. In this respect, the heat dissipation can be improved. In this case, the tip 21 a of the protrusion 21 is preferably a flat surface parallel to the surface of the wiring board 30. This is because the thermal grease 40 can be reliably interposed between the tip 21 a of the protrusion 21 and the wiring board 30.

The present invention is not limited to the above-described embodiment described with reference to the drawings, and various modifications can be considered within the technical scope thereof.
For example, the shape of the protrusion 21 formed on the heat sink 20, the position of the opening 22, the opening size, and the like can be changed as appropriate.
Further, the protrusion 21 may be a separate component from the heat sink 20 and may be attached to the heat sink 20 by various fixing means such as soldering or screws.
Further, the plate-like heat sink 20 may have a structure in which fins that enhance the heat dissipation effect are formed.
Further, not only the LSI chip 10 but also other electronic components can improve the heat dissipation performance by applying the same configuration.
In addition to this, as long as it does not depart from the gist of the present invention, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate.

10 LSI chip (electronic component)
10a Top surface 10b Side surface 10c Corner portion 20 Heat sink 20a Contact surface 21 Projection 21a Tip portion 22 Open portion 30 Wiring board 40 Thermal grease

Claims (7)

Electronic components mounted on the surface of the wiring board;
A heat sink provided to cover the electronic component;
A thermal grease filled between the electronic component and the heat sink and having semi-fluidity,
The heat sink has a peripheral wall that protrudes from the surface on the electronic component side and accommodates the electronic component in an inner space,
The peripheral wall includes an open portion that is formed at a position corresponding to a corner of the electronic component and communicates the inner space with the outer side,
The cooling structure for electronic parts, wherein the thermal grease is filled in the inner space and stored in the open portion.   2. The electronic component cooling structure according to claim 1, wherein the peripheral wall is made of the same material as the heat sink.   The cooling structure for an electronic component according to claim 1, wherein the peripheral wall is formed of a material having a higher thermal conductivity than a material forming the heat sink.   4. The electronic component according to claim 1, wherein a tip portion of the peripheral wall facing the wiring board is formed by a flat surface parallel to a surface of the wiring board. 5. Cooling structure.   5. The electronic component cooling structure according to claim 1, wherein the thermal grease is stored outside the peripheral wall through the open portion. 6.   An electronic component device comprising the electronic component cooling structure according to claim 1. A heat sink provided to cover the electronic component and dissipating heat generated in the electronic component,
The heat sink has a peripheral wall that protrudes from the surface and forms an inner space that accommodates the electronic component,
The peripheral wall is formed at a position corresponding to a corner portion of the electronic component and includes an open portion that allows the inner space to communicate with the outside. The thermal grease can be filled into the inner space and stored in the open portion. A heat sink characterized by being capable.

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