Heat spreader for IC package, and IC package clamper having the heat spreader

According to one aspect of the present invention, there is provided a heat spreader to be mounted on an IC package, the IC package including: a circuit board; an IC chip mounted on one surface of the circuit board; and a plurality of connection terminals formed on the other surface of the circuit board, the heat spreader including: a top wall formed into a rectangular shape; a circumferential wall formed continuously from the top wall, the circumferential wall and the top wall defining a block-like cavity for enclosing the IC chip when the heat spreader is mounted on the IC package; and ear portions formed at lengthwise central portions of a facing pair of side walls of the circumferential wall so to extend outwardly from bottom edges of the facing pair of side walls, respectively.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priorities from Japanese Patent Application No. 2010-247685 filed on Nov. 4, 2010, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a heat spreader for spreading heat generated from an integrated circuit (IC) chip mounted on an IC package, and an IC package clamper having the heat spreader.

BACKGROUND

There are proposed various heat spreaders for spreading heat generated from an IC chip mounted on an IC package.

For example, JP-2563182-B describes a heat sink attaching apparatus in which a gate array is mounted inside a space (cavity) defined by a frame, and a finned heat sink is provided to make contact with a top surface pad of the gate array, thereby spreading heat generated from the gate array.

While the heat spreading efficiency of the above-mentioned heat sink is good as it is provided with plural fins laminated along a post, such structure is complicated, and the operation (catching the post with a hole formed in a heat sink clip by inserting the heat sink clip between two of the fins) required for attaching the heat sink is cumbersome.

Thus, there is a demand for a heat spreader which has a simple structure, and can be easily attached. For example, a so-called hat type heat spreader as shown inFIGS. 10A and 10Bis proposed.

As illustrated inFIGS. 10A and 10B, a heat spreader100has a top wall101, a circumferential wall102formed continuously from the entire circumference of the top wall101, and a flange103extended outwardly from the bottom edge of the circumferential wall102.

For example, it is assumed that an IC chip is mounted on a circuit board as an IC package, and the circuit board is mounted on a motherboard together with a socket. The above-mentioned heat spreader100is mounted on the circuit board to surround the IC chip, and then, the heat spreader100is attached to the socket together with the circuit board. At that time, the flange103of the heat spreader100is pressed by a turnable lid member of the socket. Consequently, plural connection terminals formed on the bottom surface of the circuit board are electrically connected to plural connection bumps formed on a base substrate of the socket, respectively.

Here, while the flange130is formed on the entire circumference of the circumferential wall of the heat spreader100, only a part of the whole area of the flange130is to be pressed by the lid member of the socket, and the remained non-pressed part is a waste.

On the other hand, in an IC package, the number of chips mounted on a circuit board has been recently increased due to the advance of the implementation of a multichip structure, and the size of the circuit board is correspondingly increased.

Sometimes, the multichip structure is restrained, depending upon the shape of a heat spreader. Thus, it is requested to increase the cavity volume of the heat spreader so that it can cover each IC chip in the IC package, in order to assure the flexibility of the implementation of the multichip structure.

SUMMARY

According to an aspect of the present invention, there is provided a heat spreader to be mounted on an IC package, the IC package including: a circuit board; an IC chip mounted on one surface of the circuit board; and a plurality of connection terminals formed on the other surface of the circuit board, the heat spreader including: a top wall formed into a rectangular shape; a circumferential wall formed continuously from the top wall, the circumferential wall and the top wall defining a block-like cavity for enclosing the IC chip when the heat spreader is mounted on the IC package; and ear portions formed at lengthwise central portions of a facing pair of side walls of the circumferential wall so to extend outwardly from bottom edges of the facing pair of side walls, respectively.

According to another aspect of the present invention, there is provided an IC package clamper including: an IC package including: a circuit board; an IC chip mounted on one surface of the circuit board; and a plurality of connection terminals formed on the other surface of the circuit board; a heat spreader mounted on the IC package including: a top wall formed into a rectangular shape, a bottom surface of the top wall contacting a top surface of the IC chip; a circumferential wall formed continuously from the top wall, a bottom edge of the circumferential wall contacting a top surface of the circuit board, the circumferential wall and the top wall defining a block-like cavity in which the IC chip is enclosed; and ear portions formed at lengthwise central portions of a facing pair of side walls of the circumferential wall so to extend outwardly from the bottom edges of the facing pair of side walls, respectively; and a socket clamping the IC package together with the heat spreader, the socket including: a socket body configured to receive the circuit board; a plurality of connection bumps formed in the socked body, the connection bumps being electrically connected to the connection terminals, respectively; a lid member turnably attached to one side of the socket body so as to be openable/closable with respect to the socket body, the lid member and the socket body clamping the IC package and the heat spreader therebetween; and a pair of pressing portions formed on the lid member and configured to elastically press the ear portions, respectively, in a state where the IC package and the heat spreader are clamped between the lid member and the socket body.

According to the above-mentioned structures, ear portions are respectively formed at lengthwise central portions of facing side walls of the circumferential wall, to extend outwardly from bottom edges of the side walls, respectively, without forming a flange over the entire circumference of the circumferential wall of the heat spreader. The ear portions are elastically pressed by a pair of the pressing portions of the socket. Thus, the other pair of side walls of the circumferential wall having no ear portions can be shifted outwardly by the ear portion's width as compared with a case where an ear portion or flange would be formed thereon. According to the above-mentioned aspects of the present invention, there is provided a heat spreader suitable for the implementation of the multichip structure of an IC package by increasing a cavity area/volume without changing the overall size thereof, and an IC package clamper having such a heat spreader.

DETAILED DESCRIPTION

A heat spreader according to a first embodiment will be described with reference toFIG. 1.

As illustrated inFIG. 1, a heat spreader1is formed into a rectangular-box-like shape by performing press working or the like onto a metal plate obtained by plating a copper surface with nickel. The heat spreader1has a substantially rectangular-shaped top wall2, a circumferential wall3, and rectangular ear portions4and5. The circumferential wall3is formed continuously from the entire circumference of the top wall2. The circumferential wall3includes a pair of side walls3A and3B which face each other. The ear portions4and5are respectively formed at lengthwise central portions of the side walls3A and3B, to extend horizontally and outwardly from the bottom edges of the side walls3A and3B.

Widths of the ear portions4and5extending outwardly from the wall surfaces of the side walls3A and3B are set at t (e.g., 1.5 millimeters (mm)). And, the width (or thickness) of the circumferential wall3is set at t (e.g., 1.5 mm).

On a pair of side walls3D and3E of the circumferential wall3, which respectively adjoin the side walls3A and3B and face each other, no ear portions are formed. Since no ear portions are formed on the side walls3D and3E, each of the side walls3D and3E can be shifted outwardly by the ear portion's width as compared with a case where an ear portion or flange would be formed thereon, without increasing the overall size of the heat spreader1.

A degassing hole H for discharging organic solvent gas generated from adhesive layers9and10which is used to bond the heat spreader1to an IC package6(a circuit board7and a chip8) is provided at a corner portion of the heat spreader1, as will be described below.

Next, a clamper for using the heat spreader1as a heat spreader for an IC chip of the IC package and for connecting such an IC package to a motherboard is described hereinafter with reference toFIGS. 2 to 4.

In this embodiment, the IC package6includes the circuit board7and the IC chip8mounted thereon. As illustrated inFIGS. 2 to 4, first, the heat spreader1is bonded to the circuit board7to surround the IC chip8.

As illustrated inFIGS. 5A to 5C, the heat spreader1is fixed to the circuit board7such that a bottom edge3C of the circumferential wall3is bonded to the top surface of the circuit board7via the adhesive layer9. Similarly, the ear portions4and5on the side walls3A and3B of the circumferential wall3are bonded to the top surface of the circuit board7via the adhesive layer9. In addition, the back surface of the top wall2is bonded to the top surface of the IC chip8via the adhesive layer10. Thus, the heat spreader1is bonded and fixed to the IC package6.

Plural connection terminals11are formed on the bottom surface of the circuit board7. Plural connection bumps16are formed on a base substrate17provided in a socket12so as to be connected to the motherboard (not illustrated), and the connection terminals11are pressure-bonded and connected to the connection bumps16, respectively.

The IC package6is connected and fixed to the motherboard (not illustrated) via the socket12serving as the clamper together with the heat spreader1. The socket12has a socket body13and a lid member14turnably supported at one side (i.e., a left side, as viewed inFIG. 2) of the socket body13.

In the top surface of the socket body13, an opening15is formed to have substantially the same size as that of the circuit board7. The base substrate17having the plural connection bumps16thereon is provided in the opening15. Each of the connection bumps16is generated by forming an Au-plating layer on the top surface of a solder bump.

The base substrate17also has connection terminals at the bottom surface correspondingly with the connection bumps16formed on the top surface. Each of the connection bumps16is connected to an associated one of the connection terminals, and each of the connection terminals is connected to an associated one of connection terminals of the motherboard (not illustrated). Thus, the connection terminals11of the circuit board7are respectively connected to the motherboard (not illustrated). Since such a connection structure has been known, the description thereof is omitted.

Two axial support portions18are formed on one side (i.e., a left side, as viewed inFIG. 2) of the socket body13. An engaging portion21configured by a semispherical concave groove19and a bar-like portion20is provided on the other side of the socket body13.

A lid member14is formed of an elastic metal thin plate. An opening22is formed in a central portion of the lid member14to be slightly larger in size than the heat spreader1. Such a lid member14is provided with a pair of pressing portions14A and14B that are formed on both sides (i.e., left and right sides, as viewed inFIG. 2) of the opening22to face each other. A pressing projection23having a V-shape in side view is formed at a lengthwise central portion of each of pressing portions14A and14B.

An engaging piece24to be engaged with the engaging portion21of the socket body13is formed at a central portion on one side (i.e., an upper side, as viewed inFIG. 2) of the lid member14. Three axial support portions25are provided on the other side (i.e., a lower side, as viewed inFIG. 2) so as to respectively sandwich the axial support portions18of the socket body13therebetween. A support shaft26is inserted through the axial support portions18and25, thereby turnably attaching the lid member14to the socket body13so that the top surface of the socket body13is opened/closed.

Before attaching the IC package6to the socket12, as described above, the heat spreader1is bonded to the IC package6such that the bottom edge3C of the circumferential wall3is bonded to the top surface of the circuit board7via the adhesive layer9, while the ear portions4and5are bonded to the top surface of the circuit board7via the adhesive layer9. At this time, the top surface of the IC chip8mounted on the circuit board7and the back surface of the top wall2are bonded to each other via the adhesive layer10. Thus, the heat spreader1is bonded and fixed to the IC package6.

Then, as illustrated inFIG. 3, the IC package6to which the heat spreader1is bonded and fixed is fit into the opening15provided in the top surface of the socket body13. In this state, the connection terminals11on the circuit board7are respectively aligned with the connection bumps16on the base substrate17, the top surface of the circuit board7is flush with that of the socket body13, and the ear portions4and5are upwardly positioned with respect to a common flush surface of the circuit board7and the socket body13.

Then, the lid member14is turned in a direction (i.e., a direction to a near or right side, as viewed inFIG. 3) in which the socket body13is closed, and the engaging piece24is engaged with the bar-like portion19of the engaging portion21, as illustrated inFIG. 4.

As illustrated inFIG. 4, in a state where the socket body13is closed by the lid member14, the V-shaped pressing projections23and23on the pressing portions14A and14B elastically press the ear portions4and5of the heat spreader1. Consequently, the connection terminals11on the circuit board7are respectively electrically connected to the connection bumps16on the top surface of the base substrate17which is provided on the socket body13of the socket12.

According to the first embodiment, in the heat spreader1, and the clamper for connecting the IC package6to the motherboard (not illustrated), which uses the heat spreader1, the ear portions4and5are formed to each extend horizontally and outwardly from the bottom edge3C of an associated one of the facing pair of side walls3A and3B at the lengthwise central portion thereof, without forming a flange along the entire circumference of the circumferential wall3of the heat spreader1. Each of the ear portions4and5is elastically pressed by a pair of the pressing projections23and23formed on the lid member14of the socket12. Thus, positions of the other facing pair of the side walls3D and3E of the circumferential wall3having no ear portions can be shifted outwardly by the width t of each ear portion as compared with a case where an ear portion or flange would be formed thereon. Accordingly, the first embodiment can realize the heat spreader1suitable for the implementation of the multichip structure of an IC package by increasing a cavity area/volume without changing the overall size thereof. In addition, the first embodiment can realize the clamper for connecting the IC package6to a motherboard, which has the heat spreader1.

Hereinafter, why the cavity area/volume can be increased according to the heat spreader1according to the first embodiment will be described with reference toFIGS. 5A to 5C.

As illustrated inFIG. 5B, in a case where a flange is formed on the entire circumference of the circumferential wall3of the heat spreader1, a flange is also formed on the bottom edge of a pair of the side walls3D and3E, as indicated by dotted lines. If the flange's width is set at t without changing the overall size of the heat spreader1, there is no choice but to form each of the side walls3D and3E to an inner side (i.e., the left side corresponding to the side wall3D, and the right side corresponding to the side wall3E, as viewed inFIG. 5B) of the heat spreader1by the flange's width t, as indicated by the dotted lines inFIG. 5B.

On the other hand, in the heat spreader1according to the first embodiment, the ear portions4and5are formed only on the side walls3A and3B, respectively, as illustrated inFIG. 5C. In this case, while a flange on each of the side walls3D and3E can be eliminated, a region to be pressed by the pressing projections23and23of the lid member14of the socket12can be assured. As a result, each of the side walls3D and3E can be formed to an outer side of the heat spreader1by the flange's width t, as indicated by sold lines inFIG. 5B.

If it is assumed that the length and the width of the cavity within the heat spreader1are1and w, respectively, the cavity area of the embodiment heat spreader1having no flange on the side walls3D,3E is given by l×w. On the other hand, in a conventional heat spreader having a flange on each side wall, the length l is reduced by 2 t, and the cavity area thereof is given by (1−2 t)×w. That is, the cavity area of the embodiment heat spreader1is increased, as compared with the cavity area of the conventional heat spreader. Also, if it is assumed that the height of the heat spreader1is h, the cavity volume of the embodiment heat spreader1is given by l×w×h. On the other hand, the cavity volume of the conventional heat spreader is given by (1−2 t)×w×h. Thus, the cavity volume of the embodiment heat spreader1is also increased, as compared with the cavity volume of the conventional heat spreader.

Next, a heat spreader according to the second embodiment and an IC package clamper having the heat spreader according to the second embodiment are described hereinafter with reference toFIGS. 6 to 9C.

In the heat spreader1according to the first embodiment, the rectangular ear portions4and5extend horizontally and outwardly from the bottom edges of the facing side walls3A and3B at the lengthwise central portions thereof, respectively. A heat spreader31according to the second embodiment differs from the heat spreader1according to the first embodiment in that, as illustrated inFIGS. 6 to 9C, circular arcwise ear portions32and33not only extend outwardly and horizontally from the bottom edges of the side walls3A and3B, respectively, but also inwardly retract into the side walls3A and3B like circular arcs, respectively.

Basically, an IC package clamper using the heat spreader31according to the second embodiment has a configuration similar to that of the clamper for connecting the IC package6to a motherboard according to the first embodiment. In the following description, the same component as that of the first embodiment is designated with the same reference numeral used to designate the associated component in the first embodiment, and the description of such a component is omitted. Components differing from those of the first embodiment are mainly described hereinafter.

In the second embodiment, the heat spreader31is formed into a rectangular-box-like shape by performing press working or the like onto a metal plate obtained by plating a copper surface with nickel, as illustrated inFIG. 6. The heat spreader31has a rectangular-shaped top wall2, a circumferential wall3formed continuously from the entire circumference of the top wall2. The heat spreader31also has ear portions32and33respectively formed at the lengthwise central portions of the facing side walls3A and3B of the circumferential wall3. The ear portions32and33extend horizontally and outwardly from the bottom edges of the side walls3A and3B.

Each of the ear portions32and33has a first circular arcwise portion34extending outwardly from an outer wall surface of an associated one of the side walls3A and3B, and a second circular arcwise portion35retracting inwardly into the outer wall surfaces of an associated one of the side walls3A and3B.

As illustrated inFIGS. 9B and 9C, the first circular arcwise portion34outwardly extends from the outer wall surface of each of the side walls3A and3B by a width t, which is the same as the width t of each of the ear portions4and5of the heat spreader1according to the first embodiment. On the other hand, the second circular arcwise portion35inwardly retracts from the outer wall surface of each of the side walls3A and3B by a width 0.5 t, which is the same as half the width t of each of the ear portions4and5of the heat spreader1according to the first embodiment, as illustrated inFIG. 9C.

Then, the bottom edge3C of the heat spreader31according to the second embodiment is bonded to the top surface of the circuit board7via the adhesive layer9, as illustrated inFIGS. 9A to 9C, as in the first embodiment. Similarly, the ear portions32and33on the side walls3A and3B of the heat spreader31are bonded to the top surface of the circuit board7via the adhesive layer9. In addition, the back surface of the top wall2is bonded to the top surface of the IC chip8via the adhesive layer10. Thus, the heat spreader31is bonded and fixed to the IC package6.

Then, as illustrated inFIG. 7, the IC package6to which the heat spreader31is bonded and fixed is fit into the opening15provided in the top surface of the socket body13. In this state, the connection terminals11on the circuit board7are respectively aligned with the connection bumps16on the base substrate17, the top surface of the circuit board7is flush with that of the socket body13, and the ear portions32and33are upwardly positioned with respect to a common flush surface of the circuit board7and the socket body13.

Then, the lid member14of the socket12is turned in a direction (i.e., a direction to a near or right side, as viewed inFIG. 7) in which the socket body13is closed, and the engaging piece24of the lid member14is engaged with the bar-like portion19of the engaging portion21of the socket body13, as illustrated inFIG. 8.

As illustrated inFIG. 8, in a state where the socket body13is closed by the lid member14, the V-shaped pressing projections23and23on the pressing portions14A and14B elastically press the ear portions32and33of the heat spreader31. Consequently, the connection terminals11on the circuit board7are respectively electrically connected to the connection bumps16on the top surface of the base substrate17which is provided on the socket body13of the socket12.

According to the second embodiment, in the heat spreader31, and the clamper for connecting the IC package6to the motherboard (not illustrated), which uses the heat spreader31, the ear portions32and33are formed to each extend horizontally and outwardly from the bottom edge3C of an associated one of a facing pair of side walls3A and3B at the lengthwise central portion thereof, without forming a flange along the entire circumference of the circumferential wall3of the heat spreader31. Each of the ear portions32and33is elastically pressed by a pair of the pressing projections23and23formed on the lid member14of the socket12. Thus, positions of the other facing pair of the side walls3D and3E of the circumferential wall3having no ear portions can be shifted outwardly by the width t of each ear portion as compared with a case where an ear portion or flange would be formed thereon. Accordingly, the second embodiment can realize the heat spreader31suitable for the implementation of the multichip structure of an IC package by increasing a cavity area/volume without changing the overall size thereof. In addition, the second embodiment can realize the clamper for connecting the IC package6to a motherboard, which has the heat spreader31.

Each of the ear portions32and33of the heat spreader31according to the second embodiment has the first circular arcwise portion34outwardly extending by a width t from the outer wall surface of the associated one of the side walls3A and3B, and the second circular arcwise portion35inwardly retracting by a width 0.5 t into the outer wall surfaces of the associated one of the side walls3A and3B. Thus, when the socket body13is closed by the lid member14of the socket12, a region to be pressed by the pressing projections23and23of the lid member14can be enlarged. For example, by increasing the width of each of the pressing projections23and23for pressing the ear portions32and33, the magnitude of a pressing force for pressing the circuit board7of the IC package6against the base substrate17of the socket12can be increased, thereby enhancing the reliability of the pressure-connection between the connection terminals11of the circuit board7and the connection bumps16of the base substrate17.

Hereinafter, why the cavity area/volume can be increased according to the heat spreader31according to the second embodiment will be described with reference toFIGS. 9A to 9C.

As illustrated inFIG. 9B, in a case where a flange is formed on the entire circumference of the circumferential wall3of the heat spreader31, a flange is also formed on the bottom edge of a pair of the side walls3D and3E, as indicated by dotted lines. If the flange's width is set at t without changing the overall size of the heat spreader31, there is no choice but to form each of the side walls3D and3E to an inner side (i.e., the left side corresponding to the side wall3D, and the right side corresponding to the side wall3E, as viewed inFIG. 9B) of the heat spreader31by the flange's width t, as indicated by the dotted lines inFIG. 9B.

On the other hand, in the heat spreader31according to the second embodiment, the ear portions32and33are formed only on the side walls3A and3B, respectively, as illustrated inFIG. 9C. In this case, while a flange on each of the side walls3D and3E can be eliminated, a region to be pressed by the pressing projections23and23of the lid member14of the socket12can be assured. As a result, each of the side walls3D and3E can be formed to an outer side of the heat spreader1by the flange's width t, as indicated by sold lines inFIG. 9B.

If it is assumed that the length and the width of the cavity within the heat spreader1are1and w, respectively, the cavity area of the embodiment heat spreader1is given by l×w. On the other hand, in a conventional heat spreader having a flange on each side wall, the length l is reduced by 2 t, and the cavity area thereof is given by (1−2 t)×w. That is, the cavity area of the embodiment heat spreader31is increased, as compared with the cavity area of the conventional heat spreader. Also, if it is assumed that the height of the heat spreader31is h, the cavity volume of the embodiment heat spreader31is given by l×w×h. On the other hand, the cavity volume of the conventional heat spreader is given by (1−2 t)×w×h. Thus, the cavity volume of the embodiment heat spreader31is also increased, as compared with the cavity volume of the conventional heat spreader.

According to the second embodiment, the ear portions32and33of the heat spreader31includes the second circular arcwise portions35inwardly retracting into the outer wall surfaces of the side walls3A and3B. Each of the second circular arcwise portions35inwardly retracts with respect to the outer wall surface of an associated one of the side walls3A and3B by 0.5 t which is about half of the thickness of the heat spreader31. On the other hand, an inner width of the heat spreader31is w that is the same as that of the heat spreader1according to the first embodiment. Thus, the cavity area and the cavity volume of the heat spreader31are the same as those of the heat spreader1according to the first embodiment.

The invention is not limited to the above-described embodiments. Apparently, various improvements and modifications can be made without departing from the scope of the invention.