JP2806622B2 - Heat sink mounting structure - Google Patents

Description

The present invention relates to a heat sink mounting structure for mounting a heat sink on an LSI case on which a semiconductor element is mounted.

[Conventional technology]

FIG. 5 shows a conventional structure for mounting a heat sink to this type of LSI case. In FIG. 5, an LSI case 41 on which a semiconductor element 43 is mounted is mounted on a printed board 42, and a heat sink 46 is bonded to the LSI case 41 with an adhesive 47 containing a good heat conductive filler such as silver particles.

FIG. 6 (a) shows another conventional heat sink and mounting structure. An LSI case 51 on which the semiconductor element 53 is mounted is mounted on a printed board 57, a stud 54 is provided on a heat transfer plate 52 of the LSI case 51, and a heat sink 56 is provided on a side surface of the stud 54.
(For example, JP-A-58-25249). FIG. 4B is a plan view of the heat sink 56. In some cases, the studs were threaded and the heat sink was screwed.

[Problems to be Solved by the Invention] In the conventional heat sink mounting structure described above, the heat sink cannot be removed in the case of bonding shown in FIG. 5, so that a surface mount type component such as a flat pack is mounted on both sides of a printed board. In the assembling process, it is difficult to hold the printed board due to the unevenness of the heat sink when mounting the back surface after mounting the components on one side, and the heat sink becomes an obstacle when mounting and soldering the components.

In addition, the heat sink has been increased in size due to an increase in the amount of heat generated by high integration and high speed of the semiconductor element, and the heat capacity of the heat sink has become large, causing uneven heating in the soldering process, which is an obstacle to soldering.

Even when the wiring pattern of the printed circuit board is remodeled after the assembly, the work of pattern cutting and wiring is difficult due to the presence of the heat sink.

In the case of a flat pack type LSI case, it was necessary to visually observe the leads for soldering and inspection, and it was not possible to attach a large heat sink that concealed the leads larger than the LSI case.

As shown in FIG. 6, even when studs and screws are provided on the LSI case, unevenness due to the studs and screws can be an obstacle to assembling when mounting both sides of the printed board. Also, for surface mount components such as flat packs, mounting on the printed circuit board is performed by an automatic mounting machine in order to reduce the lead pitch, and the automatic mounting machine performs suction and clamping to handle the LSI case. In both cases, studs and projections of screws hinder the holding of the LSI case.

[Means for solving the problem]

The mounting structure of the heat sink of the present invention includes an LSI case on which a semiconductor element is mounted, a heat sink having a lower end abutting on a heat dissipation surface of the LSI case, and a claw hooked on an eave provided on the LSI case. A fixing plate that covers the heat sink, and a screw that is screwed into a screw hole provided in the fixing plate and whose tip presses the upper end of the heat sink to abut and fix the lower end of the heat sink to the heat radiation surface of the LSI case. .

〔Example〕

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

 FIG. 1 is a longitudinal sectional view of a first embodiment of the present invention.

A convex portion of a metal heat transfer plate 2 is embedded in an LSI case 1. The lead 11 of the LSI case 1 is a printed board 12
Soldered to. The semiconductor element 3 is directly bonded to the heat transfer plate 2, and transfers heat generated in the semiconductor element 3 to the heat transfer plate 21. The surface of the heat transfer plate 2 opposite to the surface on which the semiconductor element 3 is mounted is flat and protrudes outside the LSI case 1, and serves as a heat dissipation surface 4 of the heat transfer plate 2. Eaves 5 protruding in a direction parallel to the heat radiation surface 4 are provided on the side surfaces of the heat radiation surface 4. The heat sink 6 is placed on the heat radiating surface 4, and has a flat surface facing and contacting the heat radiating surface 4 so as to easily contact the heat radiating surface 4. The fixing plate 7 has a substantially U-shape and has a shape that covers the heat transfer plate 2 and the heat sink 6.
Claws 8 are provided so as to catch on the eaves 5 of the heat transfer plate 2. A screw hole 9 is provided in the fixing plate 7.

The fixing plate 7 is put on the heat transfer plate 2 of the LSI case 1 and the heat sink 6 placed thereon, so that the claw 8 catches on the eaves 5. When the screw 10 is screwed into the screw hole 9 of the fixing plate 7, the tip of the screw 10 pushes the heat sink 6 and presses the heat sink 6 against the heat radiation surface 4 of the heat transfer plate 2. When the screw 10 is screwed in, the fixing plate 7 is pushed up. On the contrary, the fixing plate 7 is caught by the eaves 5 so that the heat sink 6 can be brought into close contact with the heat radiation surface 4. Fixed.

The heat generated by the semiconductor element 3 passes through the heat transfer plate 2, is transmitted to the heat sink 6 in contact with the heat radiation surface 4, and is radiated into the air.

The heat sink 6 can be easily removed because it is only fixed by the screws 10. In addition, heat sinks of various sizes can be attached according to the amount of heat generated by the semiconductor element 3.

In the present embodiment, the eaves 5 are provided by protruding the side surfaces of the heat transfer plate 2 in the horizontal direction with respect to the heat radiating surface 4, but grooves are cut on the side surfaces of the heat transfer plate 2 to have the same role as the eaves 5. You can also. In this embodiment, the heat radiating surface 4 and the heat sink 6 are in direct contact with each other. However, heat may be transferred between the heat radiating surface 4 and a heat conductive silicone compound or a silicone rubber sheet.

FIG. 2 is a longitudinal sectional view of a second embodiment of the present invention, showing a case where a heat sink 26 is attached to a PGA type LSI case 21. FIG. In the embodiment shown in FIG. 1, the eaves 5 are provided on the heat transfer plate 2, but in the embodiment shown in FIG.
Can be used as the eaves 25,
The heat sink 26 can be fixed by the fixing plate 27 regardless of the presence or absence of the heat transfer plate 2.

In FIG. 2, leads 31 of an LSI case 21 on which a semiconductor element 23 is mounted are soldered to a printed board 32. A heat sink 26 is attached to the upper surface of the LSI case 21, and a screw 30 is screwed into a screw hole of a fixing plate 27 on which a claw 28 is hooked on an eave 25, so that the heat sink 26 is
It is fixed on the I case 21.

FIG. 3 is a longitudinal sectional view of a third embodiment of the present invention. The heat sink 6 is placed on the heat radiating surface 4, and the fixing plate 13 has a U-shape, has a shape that covers the heat transfer plate 2 and the heat sink 6, and has a claw that catches on the eaves 5 of the heat transfer plate 2. 8 are provided. The fixed plate 13 is provided with a spring 14.

The fixing plate 13 is put on the heat transfer plate 2 of the LSI case 1 and the heat sink 6 placed thereon, so that the claw 8 catches on the eaves 5. At this time, the spring 14 of the fixing plate 13 presses the heat sink 6 against the heat radiating surface 4 of the heat transfer plate 2 and presses the claw 8 against the eaves 5, so that the heat sink 6 is fixed on the LSI case 1 and the heat sink 6 And close contact.

The heat generated in the semiconductor element 3 passes through the heat transfer plate 2, is transmitted to the heat sink 6 in contact with the heat radiation surface 4, and is radiated into the air.

Since the heat sink 6 is only pressed by the spring 14 of the fixing plate 13, the removal can be performed easily.

FIG. 4 is a longitudinal sectional view of a fourth embodiment of the present invention, in which a heat sink is attached to a PGA type LSI case 21. In this embodiment, the fixing plate 33 is provided with the claws 28 and the springs 34, and the outer peripheral portion of the LSI case 21 can be used as the eaves 25, regardless of the presence or absence of the heat transfer plate 2.
The claw 28 of 33 can be hooked on the eave 25, and the heat sink 26 can be fixed by the pressing force of the spring 34 of the fixing plate 33.

〔The invention's effect〕

As described above, the present invention simplifies the removal of the heat sink by fixing the heat sink to the LSI case with the fixing plate in which the claw is hooked on the eaves provided on the LSI case.

Since the heat sink can be easily removed, LSI
The heat sink does not become an obstacle when soldering the case to the printed board, during inspection, or when modifying the pattern of the printed board. Also, a large heat sink that can hide the leads can be attached to a surface mount component such as a flat pack.

Since the LSI case used in the present invention has a flat surface and no protrusions, there is no obstacle when mounting a semiconductor element to the LSI case or when mounting the LSI case to a printed circuit board. It is easily possible.

[Brief description of the drawings]

FIGS. 1 to 4 are longitudinal sectional views of first to fourth embodiments of the present invention, respectively. FIG. 5 is a longitudinal sectional view of a conventional heat sink mounting structure using an adhesive, and FIGS. (B) is a longitudinal sectional view of a conventional heat sink mounting structure using studs and a plan view of the heat sink 56. 1 ... LSI case, 2 ... Heat transfer plate, 3 ... Semiconductor element,
4 ... heat dissipation surface, 5 ... eaves, 6 ... heat sink, 7
... Fixing plate, 8 ... Claw, 9 ... Screw hole, 10 ... Screw, 11
…… Lead, 12 …… Printed board, 13 …… Fixed board, 14 ……
Spring, 21 LSI case, 23 Semiconductor element, 25 Eave, 26 Heat sink, 27 Fixing plate, 28 Claw,
29: Screw hole, 30: Screw, 31: Lead, 32: Printed board, 33: Fixed plate, 34: Spring, 41: LSI case, 43: Semiconductor element, 46: Heat sink, 47: adhesive, 51: LSI case, 52: heat transfer plate, 53: semiconductor element, 54: stud, 56: heat sink.

Claims (1)

(57) [Claims] An LSI case on which a semiconductor element is mounted, a heat sink having a lower end abutting on a heat dissipation surface of the LSI case, and a claw hooked on an eave provided on the LSI case to cover the heat sink. And a screw that is screwed into a screw hole provided in the fixing plate, a tip of which presses an upper end of the heat sink to abut and fix a lower end of the heat sink and a heat radiation surface of the LSI case. Heat sink mounting structure.