JP3392593B2 - Heat sink mounting structure - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mounting structure of a heat sink. 2. Description of the Related Art In recent years, portable electronic devices such as a laptop personal computer have been widely marketed as electronic devices that require miniaturization and high reliability. In order to improve the performance of this type of electronic device, it is necessary to use one or more integrated circuit packages that generate a large amount of heat. For this reason, a heat sink is used to secure the heat radiation of the integrated circuit package that generates a large amount of heat.
Optimization of the mounting structure and the mounting method is being sought. 2. Description of the Related Art Conventionally, as shown in FIG. 11, an integrated circuit chip 2 is hermetically housed in a package 4 and the integrated circuit chip 2 is mounted on a printed wiring board 8 by leads 6 attached to the package 4. Connect and glue 1 on package 4
A structure is known in which the heat sink 12 is fixed with a zero. In this structure, the one in which the integrated circuit chip 2 is built in the package 4 corresponds to the above-described integrated circuit package. [0003] However, FIG.
In the conventional heat sink mounting structure shown in
Since the package 4 is interposed between the integrated circuit chip 2 and the heat sink 12, the thermal resistance between the integrated circuit chip 2 and the heat sink 12 increases, and there is a problem that a high heat radiation effect cannot be obtained. Accordingly, an object of the present invention is to provide a mounting structure of a heat sink which can enhance a heat radiation effect. Accordingly, in the present invention, a heat sink is directly mounted on an electronic component represented by an integrated circuit chip. That is, according to the present invention, a substrate having a wiring layer, an electronic component fixed on the substrate by a first adhesive and electrically connected to the wiring layer, and a second component on the electronic component are provided. And a heat sink fixed by an adhesive, wherein the second adhesive has a thermal conductivity higher than that of the first adhesive. Here, the softening temperature of the hardened second adhesive is hardened.
Lower than the softening temperature of the first adhesive. According to another aspect of the present invention, a heat sink having an opening at a substantially central portion is suction-supported by a suction nozzle having a suction port at a position facing the opening, and the electronic component is sucked through the opening. Then, the upper surface of the electronic component is brought into close contact with the heat sink via the first adhesive, and the lower surface of the electronic component is brought into close contact with the substrate via the second adhesive by moving the suction nozzle. , The first
And a method for mounting a heat sink for solidifying the second adhesive. According to the heat sink mounting structure of the present invention,
Electronic components such as integrated circuit chips are directly fixed on the substrate with a first adhesive in order to electrically connect to a wiring layer of the substrate (for example, a printed wiring board). Further, the heat sink is directly fixed on the electronic component by the second adhesive. As described above, the heat sink is directly fixed on the electronic component with the second adhesive, and the thermal conductivity of the second adhesive is higher than the thermal conductivity of the first adhesive. Therefore, the heat radiation effect is enhanced. Also cured
Softening of the first adhesive cured at the softening temperature of the second adhesive
Since the temperature is set lower than the temperature, the heat sink
After obtaining the mounting structure of the metal, only the second adhesive is softened.
The heat sink can be replaced. In the method of mounting a heat sink according to the present invention, a suction nozzle having a specific configuration is used to handle the heat sink and the electronic circuit components. Therefore, the mounting structure of the present invention can be easily obtained. An embodiment of the present invention will be described below. FIG. 1 is a side view of a mounting structure of a heat sink showing an embodiment of the present invention. For example, a lower surface of an integrated circuit chip 2 as an electronic component is fixed on a substrate 8 formed of a printed wiring board having a wiring layer by a first adhesive 14. A heat sink 12 is provided on the upper surface of the integrated circuit chip 2 with a second adhesive 16.
Is fixed. The heat sink 12 has a plurality of radiating fins 12A on its upper surface for increasing the radiating area. Integrated circuit chip 2 using first adhesive 14
The bonding portion between the substrate and the substrate 8 will be described with reference to FIG. The integrated circuit chip 2 has a plurality of bits 16 made of a conductor for connection to an external circuit on the lower surface. The shape of the bit 16 is, for example, hemispherical. On the other hand, a wiring layer 18 made of a conductor pattern is formed on the substrate 8 corresponding to the position of the bit 16. After the alignment between the bit 16 and the wiring layer 18 is performed, the integrated circuit chip 2 is fixed on the substrate 8 with the first adhesive 14. At this time, by applying an appropriate pressure, the contact state between the bit 16 and the wiring layer 18 is obtained, and the electrical connection between the integrated circuit chip 2 and the wiring layer 8 is made. Referring again to FIG. 1, the second adhesive 16
Has a thermal conductivity greater than the thermal conductivity of the first adhesive 14. The reason for this is to minimize the thermal resistance of the solidified second adhesive 16 interposed between the integrated circuit chip 2 and the heat sink 12, thereby enhancing the heat radiation effect. In this embodiment, since the heat sink 12 is directly fixed on the upper surface of the integrated circuit chip 2, a higher heat radiation effect can be obtained as compared with the conventional heat sink mounting structure described with reference to FIG. As the second adhesive 16, for example, an adhesive obtained by mixing powder of at least one substance selected from a substance group including gold and diamond into a resin can be used. Since the thermal conductivity of gold or diamond is generally higher than the thermal conductivity of a resin, the thermal conductivity of a resin-based adhesive mixed with such a powder of a specific substance can be increased. Preferably, the main resin of each adhesive is selected such that the softening temperature of the cured second adhesive 16 is lower than the softening temperature of the cured first adhesive 14.
Since the softening temperature (curing temperature) of the cured adhesive is set as described above, the heat sink 12 can be replaced by softening only the second adhesive 16 in the structure of FIG. By using a thermosetting adhesive as each adhesive, a stable adhesive force after the start of driving of the integrated circuit chip 2 can be guaranteed. On the other hand, by using a thermoplastic adhesive as each adhesive, the exchange of the integrated circuit chip 2 and / or the heat sink 12 can be easily performed. FIG. 3 is an explanatory view of a suction nozzle which can be used in the mounting method of the present invention. When carrying out the method of the present invention, an opening 12
B is formed. The suction nozzle 20 has a suction port 20A at a position opened to the opening 12B of the heat sink 12.
Further, the heat sink 12 has a concave portion 20B at a position facing the heat radiation fin 12A where the heat radiation fin A is seated. The suction nozzle 20 is connected to a suction means such as a vacuum pump (not shown).
Thereby, the heat sink 12 can be suction-supported. Since the opening 12B is formed in the heat sink 12, the integrated circuit chip 2 can be further suction-adsorbed to the lower surface of the heat sink 12 while the heat sink 12 is suction-supported by the suction nozzle 20. Then, by moving the suction nozzle 20 in this state, the lower surface of the integrated circuit chip 2 can be arranged at a predetermined position on the substrate, and the integrated circuit chip 2 can be mounted on the substrate. . The integrated circuit package 2 is mounted on the heat sink 12.
In order to make the adhesive adhere, the adhesive is applied to one or both of the lower surface of the heat sink 12 and the upper surface of the integrated circuit chip 2 so that the adhesive is interposed therebetween.
An adhesive is applied to one or both of the lower surface of the integrated circuit chip 2 and the upper surface of the substrate. After the integrated circuit chip 2 and the heat sink 12 are mounted on the substrate, the suction by the suction nozzle 20 is stopped, the suction nozzle 20 is removed, and the adhesive is solidified by an ordinary method. According to this method, the integrated circuit chip 2 and the heat sink 12 can be simultaneously mounted on the substrate by using the suction nozzle 20, so that only one hardening step of the adhesive by heating, for example, is required, and The manufacturing process is simplified. Further, according to this method, the mounting structure of the heat sink of the present invention can be easily obtained. FIG. 4 is an explanatory view of another suction nozzle that can be used in the mounting method of the present invention. The embodiment of FIG. 4 is characterized in that the suction nozzle 20 has at least one other suction port 20C in addition to the suction port 20A in comparison with the embodiment of FIG. That is, in this embodiment, the heat sink 12
For example, a plurality of (two in the figure) suction ports 20C are provided in the suction nozzle 20 in addition to the suction port 20A formed at a position facing the opening B. By adding such a suction port 20C, even a relatively large and heavy heat sink can be suction-supported by the suction nozzle 20. By forming a slit on the bottom surface of the heat sink, the adhesive strength between the heat sink and the integrated circuit chip can be increased. This will be described with reference to FIG. In the example of FIG. 5A, the heat sink 12
A plurality of slits S are formed on the bottom surface of the fin in parallel with the radiation fins 12A. In the example shown in (B), (A)
In addition to the slits parallel to the radiating fins 12A shown in FIG. Further, in the example shown in FIG.
A radial slit S is formed on the bottom surface of the second member 2. By forming the slit S on the bottom surface of the heat sink 12 in this manner, the adhesive enters the slit S, and the heat sink 12 and the integrated circuit chip 2
Between them can be increased. Further, since each slit S is formed up to the edge of the bottom surface of the heat sink 12, for example, in the mounting method described with reference to FIG. 3, an adhesive is not interposed between the integrated circuit chip 2 and the heat sink 12. In both cases, the adhesive interposed between the integrated circuit chip 2 and the substrate can be wrapped between the integrated circuit chip 2 and the heat sink 12, and the mounting method can be simplified. By using a heat sink shaped to cover the side surface of the integrated circuit chip, the adhesive strength between the heat sink and the integrated circuit chip can be increased. This will be described with reference to FIGS. In the example shown in FIG. 6A, a pair of protrusions 12C are provided at both ends of the heat sink 12 on the side opposite to the heat radiation fins 12A, and the heat sink 12 is fixed to the integrated circuit chip 2. , The projection 12C covers part or all of the side surface of the integrated circuit chip 2. In the example shown in FIG. 3B, a projection 12C is provided on the entire outer periphery of the surface of the heat sink 12 on the side opposite to the radiation fins 12A.
Is fixed to the integrated circuit chip 2 so that the side surface of the integrated circuit chip 2 is covered by the projection 12C. FIG. 7 is a side view of a mounting structure using the heat sink shown in FIG. Heat sink 1
Since the opposite side surface of the integrated circuit chip 2 is covered by the two protrusions 12C, the adhesive 16 can easily flow between the heat sink 12 and the integrated circuit chip 2, and the adhesive strength can be increased. In this example, the integrated circuit chip 2 and the heat sink 12 are adhered by an adhesive 16 different from the adhesive 14 that adheres the substrate 8 and the integrated circuit chip 2. However, when the respective members are adhered using the same adhesive. Of course, this effect can be obtained. Also, in this embodiment, by increasing the amount of the adhesive 14, the integrated circuit chip 2 and the protrusion 12C of the heat sink can be covered with the adhesive 14 on the side surface of the integrated circuit chip 2. The adhesive strength between the substrate 8, the integrated circuit chip 2, and the heat sink 12 can be increased. The heat sink 1 is formed using the same adhesive.
When the integrated circuit chip 2 and the integrated circuit chip 2 are simultaneously fixed on the substrate 8, the integrated circuit chip 2 is set at a predetermined position on the substrate 8, and then the heat sink 12 is temporarily (for example, several hundreds μm). By floating from the chip 2, the adhesive can easily flow around between the heat sink 12 and the integrated circuit chip 2. For a heat sink having a protrusion on the side opposite to the heat radiation fin as described with reference to FIG. 6, the slit as shown in FIG. Can be. This will be described with reference to FIG. The heat sinks shown in FIGS. 8A, 8B, and 8C have various slits S shown in FIGS. 5A, 5B, and 5C, respectively. By forming such slits S on the contact surface of the heat sink 12 with the integrated circuit chip, the adhesive force between the heat sink 12 and the integrated circuit package 2 can be increased, and the gap between the heat sink 12 and the integrated circuit package 2 can be increased. Of the adhesive to the adhesive can be improved.
In the example shown in FIGS. 8B and 8C, a slit is also formed on the surface of the protrusion 12C of the heat sink 12 facing the side surface of the integrated circuit chip. When carrying out the method of the invention according to FIG.
A mechanism for mechanically supporting the heat sink may be provided in the suction nozzle. An example will be described with reference to FIG. FIG.
In the suction nozzle 20 shown in FIG. 1, a holding metal (clip) 22 is provided in a concave portion 20B in which a heat radiation fin 12A (see FIG. 3) of a heat sink is seated. When the radiating fins 12A of the heat sink 12 are inserted into the concave portions 20B of the suction nozzle 20, the holding metal 22 is elastically deformed, and the heat sink 12 is supported by the suction nozzle 20 by the frictional force generated thereby. By providing such a holding member in the suction nozzle, the method of the present invention can be applied to a relatively heavy heat sink. In the example shown in FIG. 9, the holding members 22 are individually provided in the respective recesses 20B of the suction nozzle 20, but a device for holding the heat sink from the side is provided at the end of the suction nozzle 20. Is also good. Such a device includes, for example, a block fixed to the suction nozzle 20,
It can be composed of a pressing spring having one end fixed to the block and a pressing member attached to the other end of the pressing spring. As shown in FIG. 10, a split type heat sink 12 'can be used. In this example, FIG.
, A plurality of heat sinks 12 ′ divided corresponding to the respective recesses 20 B are seated in the respective recesses 20 B by the respective holders 22. Thus, the integrated circuit chip 2 is suction-supported by the suction nozzle 20. Then, the suction nozzle 20 is moved to mount the integrated circuit chip 2 at a predetermined position on the substrate. According to this embodiment, it is not necessary to form an opening at the approximate center of the heat sink unlike the method of FIG. The heat sink is moved by the suction nozzle 2 by elastic force.
Instead of being supported at zero, the heat sink may be supported by the suction nozzle 20 by the adhesive force of an adhesive tape or the like. As described above, according to the present invention,
There is an effect that a mounting structure of a heat sink having a high heat radiation effect can be provided. According to the present invention,
Provide a heat sink mounting structure that allows easy replacement of the sink
There is also an effect that it becomes possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of a mounting structure of a heat sink showing an embodiment of the present invention. FIG. 2 is an explanatory diagram of a bonding portion between a chip and a substrate. FIG. 3 is an explanatory diagram of a suction nozzle used in a mounting method. FIG. 4 is an explanatory diagram of another suction nozzle used in the mounting method. FIG. 5 is a perspective view of a heat sink according to the embodiment of the present invention. FIG. 6 is a perspective view of a heat sink according to the embodiment of the present invention. FIG. 7 is a side view of a mounting structure showing an embodiment of the present invention. FIG. 8 is a perspective view of a heat sink according to the embodiment of the present invention. FIG. 9 is an explanatory diagram of still another suction nozzle used in the mounting method. FIG. 10 is an explanatory diagram of a mounting method showing an embodiment of the present invention. FIG. 11 is a sectional view of a conventional heat sink mounting structure. [Description of Signs] 2 Electronic circuit components (integrated circuit package) 8 Substrate (printed wiring board) 12 Heat sinks 14, 16 Adhesive

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/60 H01L 23/34-23/40

Claims (1)

(57) Claims 1. A substrate having a wiring layer, an electronic component fixed on the substrate with a first adhesive and electrically connected to the wiring layer, and the electronic component and a heat sink which is secured by a second adhesive on said second adhesive have a thermal conductivity greater than the thermal conductivity of the first adhesive, cured the second adhesive The softening temperature of the agent is
A mounting structure for a heat sink, wherein the mounting temperature is lower than a softening temperature of the adhesive .