JP2005012166A - Ceramic wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic wiring board, which can dissipate a heat generated from a mounted electronic part or the like efficiently to the outside and has excellent heat-dissipating properties. <P>SOLUTION: In the ceramic wiring board, a plurality of insulating layers composed of ceramics are laminated, a plurality of wiring conductors 2 are formed inside and a plurality of connecting pads 3 electrically connected to the wiring conductors 2 are formed to a main surface on the lower side. In the ceramic wiring board, the wiring board has an insulating base body 1, in which through-holes 1a penetrating between upper-lower main surfaces and having stepped sections A extending over the whole periphery between an internal side face and the lower-side main surface are formed at a central section; ball-shaped terminals 5 mounted on the pads 3 and metal plates 6, which have projecting sections at the centers of the top faces of tabular sections and in which the top faces of the tabular sections in the peripheries of the projecting sections are joined with the undersides of the stepped sections A. In the wiring board, the top faces of the projecting sections of the metal plates 6 and the upper-side main surface of the insulating base body 1 are formed on the same plane, and the undersides of the metal plates 6 and the lower ends of the terminals 5 are formed in the same height. <P>COPYRIGHT: (C)2005,JPO&amp;NCIPI

Description

  The present invention relates to a ceramic wiring board having a metal plate for heat dissipation, and more particularly to a ceramic wiring board having excellent heat dissipation characteristics due to a metal plate for heat dissipation.

  Conventionally, a ceramic wiring board on which electronic components such as semiconductor elements and capacitive elements are mounted has a mounting portion on which an electronic component is mounted on the upper surface of an insulating base made of ceramics such as an aluminum oxide sintered body. In this configuration, a wiring conductor is formed over the lower surface of the insulating substrate.

  An example of such a conventional ceramic wiring board is shown in FIG. In FIG. 3, reference numeral 11 denotes an insulating base formed by laminating a plurality of insulating layers made of ceramics such as an aluminum oxide sintered body, and an electronic component is mounted on the upper surface. Reference numeral 12 denotes an electronic component on the upper surface of the insulating base 11. It is a wiring conductor formed from the part to be mounted to the lower surface of the insulating base 11. A connection pad 13 for external connection is formed on the lead-out end portion of the wiring conductor 12 on the lower surface of the insulating base 11.

  A semiconductor element 14 such as an IC or LSI is mounted on the upper surface of the insulating base 11, and the electrode of the semiconductor element 14 is connected to an exposed portion of the wiring conductor 12 via a bonding wire 15 so that the semiconductor element 14 is sealed with a sealing resin 18 or the like. A semiconductor device is formed by covering and sealing with. The solder balls 16 are joined to the connection pads 13 by soldering with, for example, solder 17 made of the same material as the solder forming the solder balls 16.

  Then, by connecting the connection pads 13 to the circuit conductors of the external circuit board via the solder balls 16, the semiconductor device is mounted on the external circuit board, and the semiconductor element 14 is electrically connected to the external electric circuit.

  In a semiconductor device using such a conventional ceramic wiring board, heat generated in the semiconductor element 14 is transmitted to the lower surface side of the insulating base 11 through the insulating base 11 and externally connected via the solder balls 16. Released to a circuit board or the like.

  Since the sealing resin that covers the electronic component such as the semiconductor element 14 generally has a large thermal resistance, the amount of heat released through the resin is larger than the amount of heat released through the insulating substrate 11 and the solder balls 16. Therefore, it does not contribute much to the release of heat usually generated in electronic parts.

  However, in such a conventional ceramic wiring board, the heat generated from the semiconductor element is transmitted through the insulating base 11 made of ceramics having a large thermal resistance, and is released to the external circuit board or the like via the solder balls 16. There was a problem that heat could not be released effectively.

  To solve such a problem, a through hole penetrating between the upper and lower main surfaces is formed in the central portion of the insulating base, and a metal plate is placed on the lower main surface of the insulating base so as to close the lower side of the through hole. A ceramic wiring board having an attached structure has been proposed (see, for example, Patent Document 1).

In the ceramic wiring board having such a structure, the upper surface of the metal plate (heat sink) is exposed at the lower end side of the through hole (through slot), and an electronic component (semiconductor) such as a semiconductor element is exposed on the exposed upper surface of the metal plate. Since the chip) is directly mounted, the heat generated in the electronic component is transmitted directly to the metal plate and effectively absorbed, and is released from the lower surface side of the metal plate to the external circuit board, etc. to improve heat dissipation. Can do.
JP-A-9-186272

  However, a ceramic wiring board having a structure in which a through hole is formed in the central portion of the insulating base and a metal plate is attached to the lower main surface of the insulating base so as to close the lower side of the through hole is also conventionally used. Although the heat dissipation is improved compared to the ceramic wiring board having a structure in which heat is transmitted through an insulating base made of ceramic, the metal plate is flat and joined to the lower surface of the insulating base. In order to reduce the thickness of the wiring board, the height of the metal plate cannot be increased too much. For this reason, the volume of the metal plate cannot be increased so much that the absorption and release of heat by the metal plate correspond to the large amount of heat generated by electronic components that have recently become highly integrated and highly functional. There was a problem that it was still difficult to do well.

  The present invention has been completed in order to solve such conventional problems, and its purpose is to dissipate heat generated from the mounted electronic components efficiently to the outside. It is to provide an excellent ceramic wiring board.

  The ceramic wiring board of the present invention is formed by laminating a plurality of insulating layers made of ceramics, and has a plurality of wiring conductors formed therein, and is electrically connected to the plurality of wiring conductors on the lower main surface, respectively. Insulation in which a plurality of connection pads are formed and a through hole having a stepped portion is formed between the inner side surface and the lower side main surface through the center portion between the upper side surface and the lower side main surface. A base, a ball-like terminal attached to each of the connection pads, and a convex portion at the center of the upper surface of the plate-like portion, and the upper surface of the plate-like portion around the convex portion is a lower surface of the step portion. The upper surface of the convex portion of the metal plate and the upper main surface of the insulating base are on the same plane, and the lower surface of the metal plate and the ball-shaped terminal The lower end of the .

  The ceramic wiring board of the present invention is preferably characterized in that the side surface of the metal plate and the inner side surface of the through hole are bonded via a resin adhesive in the above configuration.

  In the ceramic wiring board of the present invention, preferably, the resin adhesive has a higher thermal conductivity than the insulating base.

  The ceramic wiring board of the present invention is formed by laminating a plurality of insulating layers made of ceramics, a plurality of wiring conductors are formed therein, and the lower main surface is electrically connected to the plurality of wiring conductors, respectively. An insulating base formed with a plurality of connection pads and having a through hole having a stepped portion around the entire circumference between the inner side surface and the lower side main surface penetrating between the upper and lower main surfaces in the central portion; A ball-like terminal attached to each connection pad, and a metal plate having a convex portion at the center of the upper surface of the plate-like portion, and the upper surface of the plate-like portion around the convex portion being joined to the lower surface of the step portion Since the upper surface of the convex portion of the metal plate and the upper main surface of the insulating base are on the same plane, the electronic component can be directly mounted on the upper surface of the convex portion of the metal plate, The heat generated by the mounted electronic components is transferred directly to the metal plate, It can be effectively released through the high conductivity metal plate.

  Further, the metal plate is attached with the convex portion on the upper surface entering the through hole having the step portion formed on the insulating base, so that the volume is increased by the height of the step. Therefore, the heat generated in the electronic component can be efficiently absorbed and released to the lower surface side. As a result, the heat dissipation of the ceramic wiring board can be improved.

  In addition, since the lower surface of the metal plate and the lower end of the ball-shaped terminal are the same height, the ceramic wiring board of the present invention has a lower surface of the metal plate when connecting the ball-shaped terminal to the circuit conductor of the external circuit board. Can be easily and reliably bonded to the external circuit board, and heat transfer from the metal plate to the external circuit board can be ensured. Thereby, it is possible to configure a highly functional and highly reliable electronic device that does not degrade the performance of the electronic component to be mounted.

  In the ceramic wiring board of the present invention, preferably, the side surface of the metal plate and the inner side surface of the through hole are bonded to each other through a resin adhesive in the above configuration. Since heat can be transferred to the insulating base via the metal plate, heat conduction from the metal plate to the insulating base becomes more reliable.

  Furthermore, the ceramic wiring board of the present invention preferably has the above-described configuration, and the resin adhesive has a higher thermal conductivity than the insulating base, and therefore is insulated from the side surface of the metal plate via the resin adhesive. Since heat can be more efficiently transmitted by the base, the conduction of heat from the metal plate to the insulating base is further ensured.

  The ceramic wiring board of the present invention will be described in detail below. FIG. 1 is a sectional view of an electronic device using a ceramic wiring board of the present invention. In FIG. 1, 1 is an insulating substrate, 2 is a wiring conductor, 3 is a connection pad, 5 is a connection pad 3 via a bonding material 4. A ball-shaped terminal 6 attached to the metal plate 6 is a metal plate. A ceramic wiring board on which an electronic component 7 is mounted is mainly constituted by the insulating base 1, the wiring conductor 2, the connection pad 3, and the ball-shaped terminal 5.

  The insulating substrate 1 in the present invention is formed by laminating a plurality of insulating layers made of ceramics such as an aluminum oxide sintered body and a glass ceramic sintered body. For example, each insulating layer is made of an aluminum oxide sintered body. It is produced as follows. An appropriate organic binder and solvent are added to and mixed with raw material powders such as aluminum oxide, silicon oxide, calcium oxide, and magnesium oxide to produce a slurry in the form of a slurry. Thus, a plurality of ceramic green sheets (ceramic raw sheets, hereinafter also referred to as green sheets) are obtained. These green sheets are laminated in a predetermined order to form a green sheet molded body, and the green sheet molded body is manufactured by firing at a high temperature of about 1600 ° C. in a reducing atmosphere.

  In the insulating base 1, a plurality of wiring conductors 2 are formed, for example, from the upper main surface to the lower main surface. In addition, connection pads 3 that are electrically connected to the plurality of wiring conductors 2 are formed on the lower main surface of the insulating base 1. The wiring conductor 2 and the connection pad 3 function as a connection conductor for leading and connecting the electrode of the electronic component 7 mounted on the ceramic wiring board to the outside, and are formed of a metal such as tungsten, molybdenum, copper, or silver. Has been. That is, the wiring conductor 2 and the connection pad 3 are made of, for example, the same kind of metal. When both are made of tungsten, a metal paste obtained by adding and mixing an appropriate organic binder and solvent to tungsten powder is used as the insulating base 1. It is formed by previously printing and applying a predetermined pattern on the surface of the green sheet to be obtained by screen printing or the like.

  Further, the ball-shaped terminals 5 are attached to the connection pads 3 by means such as bonding via the bonding material 4. The ball-shaped terminal 5 functions as an external connection terminal for electrically connecting the ceramic wiring board to an external electric circuit, and is formed of a metal such as iron-nickel alloy or iron-nickel-cobalt alloy. Note that the bonding material 4 is preferably a silver brazing similar to the silver brazing that bonds the metal plate 6 to the insulating base 1. If the same silver brazing is used, the ball-shaped terminal 5 and the metal plate 6 can be joined at the same time by the same brazing operation, so that the productivity of the ceramic wiring board can be improved.

  Further, the ceramic wiring board of the present invention has a through-hole having a stepped portion A over the entire circumference between the inner side surface and the lower main surface, which penetrates between the upper and lower main surfaces of the insulating substrate 1 in the central portion of the insulating substrate 1. 1a is formed. A metal plate 6 is inserted and joined inside the through hole 1a. The metal plate 6, which is a plate-like portion, is made of a metal having good thermal conductivity such as a copper-tungsten alloy, aluminum, copper, an aluminum alloy, or a copper alloy, and has a shape having a convex portion at the center of the upper surface of the plate-like portion. is there.

  In the present invention, the metal plate 6 is attached to the insulating substrate 1 by bonding the upper surface of the plate-like portion around the convex portion of the metal plate 6 to the lower surface of the stepped portion A in the through hole 1a of the insulating substrate 1. The upper surface of the convex portion of the metal plate 6 and the upper main surface of the insulating base 1 are on the same plane, and the lower surface of the metal plate 6 and the lower end of the ball-shaped terminal 5 are the same height.

  In addition, the upper surface of the plate-shaped portion around the convex portion of the metal plate 6 and the lower surface of the stepped portion A in the through hole 1a are bonded to, for example, the lower surface of the stepped portion A from the same metal as the connection pad 3 in advance. A metallization layer for brazing is formed, and this metallization layer and the metal plate 6 can be brazed via a brazing material such as silver brazing.

  A through hole 1a is formed in the central portion of the insulating base 1, and the metal plate 6 is joined in the through hole 1a so that the upper surface of the convex portion and the upper main surface of the insulating base 1 are on the same plane. Thus, the upper surface of the convex portion of the metal plate 6 can function as a mounting portion for the electronic component 7, and heat generated by the mounted electronic component 7 is directly transmitted to the metal plate 6, and the metal plate 6 having high thermal conductivity. Can be effectively released.

  In this case, since the upper surface of the convex portion of the metal plate 6 and the upper main surface of the insulating base 1 are on the same plane, the insulating base 1 is mounted when the electronic component 7 is mounted on the upper surface of the convex portion of the metal plate 6. It is too expensive to interfere with installation. In addition, when the electronic component 7 is covered and sealed with a sealing resin or the like, the convex portion is not too high and it is not difficult to seal the electronic component 7. As a result, it is possible to easily and reliably produce an electronic device in which the electronic component 7 is mounted on the ceramic wiring board.

  Further, since the through hole 1a has the stepped portion A over the entire inner surface, the volume of the metal plate 6 entering the through hole 1a can be increased by the amount of the stepped portion A. The heat generated in the component 7 can be efficiently absorbed by the metal plate 6 and released to the lower surface side, so that the heat dissipation of the ceramic wiring board can be improved.

  Then, the electronic component 7 is bonded to the upper surface of the convex portion of the metal plate 6 bonded to the insulating base 1 with a resin adhesive such as an epoxy resin, and is exposed to the electrode of the electronic component 7 and the upper main surface of the insulating base 1. After the wiring conductor 2 is electrically connected via a bonding wire 8 such as an aluminum wire or a gold wire, the exposed surface of the electronic component 7 and the surrounding metal plate 6 and the insulating base 1 is epoxy resin, silicone resin or the like. By covering with a sealing resin 9 made of the above resin, an electronic device is completed. In addition to covering the electronic component 7 with the sealing resin 9, a lid made of metal, ceramics, or the like may be bonded to the upper main surface of the insulating base 1 so as to cover the electronic component 7.

  As shown in FIG. 2, the electronic device in which the electronic component 7 is mounted on the ceramic wiring board in this way has a lower end portion of the ball-like terminal 5 attached to the connection pad 3 on the lower main surface of the insulating base 1. Is connected to a circuit conductor (not shown) of the external circuit board 30 via solder 40 or the like, so that the electronic component 7 is externally connected via the bonding wire 8, the wiring conductor 2, the connection pad 3, and the ball-shaped terminal 5. It is electrically connected to an electric circuit and mounted on an external circuit board.

  When the ceramic wiring board is mounted on the external circuit board 30, the lower surface of the metal plate 6 joined in the through hole 1 a of the ceramic wiring board and the lower end of the ball-shaped terminal 5 are at the same height. The terminal 5 can be connected to the circuit conductor of the external circuit board 30 and the lower surface of the metal plate 6 can be easily and reliably joined to the external circuit board 30 via the solder 40 or the like. Heat transfer to 30 can be ensured. Thereby, a highly functional and highly reliable electronic device that does not deteriorate the performance of the electronic component 7 to be mounted can be manufactured, and a highly reliable mounting structure on the external circuit board 30 can be obtained.

  The solder 40 for mounting the electronic device using the ceramic wiring board of the present invention on the external circuit board 30 has a lower melting point than the bonding material 4 for bonding the ball-shaped terminal 5 to the connection pad 3 of the insulating base 1. Use things. If the melting point of the bonding material 4 is lower than that of the solder 40, the bonding material 4 is melted by heating when the ball-shaped terminals 5 and the metal plate 6 are connected to the external circuit board 30, and the ball-shaped terminals 5 are connected to the connection pads 3. There is a risk of leaving.

  In the present invention, the lower surface of the metal plate 6 and the lower end of the ball terminal 5 do not have to be completely the same height. The difference in height to some extent can be absorbed by the thickness of the solder 40 or the like for connecting the ball-shaped terminal 5 or the metal plate 6 to the external circuit board 30, so that a difference in height of about 200 μm is acceptable. .

  As described above, when a difference in height occurs between the lower surface of the metal plate 6 and the lower end of the ball-shaped terminal 5, the height of the ball-shaped terminal 5 (height from the ground) is higher than that of the lower surface of the metal plate 6. It is preferable that the lower end, that is, the lower end of the ball-shaped terminal 5 protrudes below the lower surface of the metal plate 6. When the lower surface of the metal plate 6 is lower than the lower end of the ball-shaped terminal 5, it is difficult to connect the ball-shaped terminal 5 to the circuit conductor of the external circuit board 30 normally and reliably due to the metal plate 6.

  In the ceramic wiring board of the present invention, the side surface of the metal plate 6 and the inner side surface of the through hole 1a are preferably bonded via a resin adhesive.

  If the side surface of the metal plate 6 and the inner side surface of the through hole 1 a are bonded via the resin adhesive 20, heat can be transferred from the side surface of the metal plate 6 to the insulating substrate 1 via the resin adhesive 20. Therefore, heat conduction from the metal plate 6 to the insulating substrate 1 is more reliable.

  The resin adhesive 20 is made of an organic resin such as epoxy resin, glass epoxy, or polyimide. For example, before the ceramic wiring board is mounted on the external circuit board 30, the side surface of the metal plate 6 and the inner side surface of the through hole 1a are formed. It is formed by injecting and filling the resin adhesive 20 between them.

  In the ceramic wiring board of the present invention, the resin adhesive 20 preferably has a higher thermal conductivity than the insulating substrate 1.

  If the thermal conductivity of the resin adhesive 20 is higher than that of the insulating base 1, heat can be more efficiently transmitted from the side of the metal plate 6 to the insulating base 1 via the resin adhesive 20. Heat conduction from the metal plate 6 to the insulating substrate 1 is further ensured.

  As the resin adhesive 20 having a higher thermal conductivity than that of the insulating substrate 1, an organic resin such as epoxy filled with filler particles made of a highly thermally conductive inorganic substance or metal having a thermal conductivity of 12 W / m · ° C. or higher is used. be able to.

  For example, if the insulating substrate 1 is made of an aluminum oxide sintered body (thermal conductivity of about 14 W / m · ° C.), the thermal conductivity of the resin adhesive 20 is preferably 15 W / m · ° C. or more. It is preferable to use a material filled with a highly heat conductive filler.

  Such a resin adhesive 20 having a higher thermal conductivity than that of the insulating base 1 is prepared by mixing filler particles such as metal in advance with a resin adhesive such as an epoxy resin, for example, and using this mixture as a through hole 1a. It is formed by filling between the metal plates 6.

  Note that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. For example, the metal plate 6 may be bonded more firmly to the insulating substrate 1 by bonding the side surface of the convex portion on the upper surface of the metal plate 6 to the inner surface of the through hole 1 a of the insulating substrate 1. Further, if a protruding portion such as a bowl-shaped portion is formed at the lower end portion of the side surface of the metal plate 6 with a width equal to or less than the height of the ball-shaped terminal 5 over the entire circumference, heat dissipation by heat radiation of the metal plate 6 is performed. And heat dissipation by heat transfer to the external circuit board 30 can be enhanced, and the bonding strength of the metal plate 6 to the external circuit board 30 can be improved. Further, in this case, if the protruding portion formed at the lower end portion of the side surface of the metal plate 6 is a hook-shaped portion, and the surface of the hook-shaped portion is an inclined surface that spreads outward as it goes downward, the protruding portion Even if the lower surface of the portion is widened and the protruding portion is enlarged, the protruding portion is less likely to come into contact with the lower main surface of the insulating base 1, and the heat dissipation by heat radiation of the protruding portion can be improved. The bonding strength of the metal plate 6 to the external circuit board 30 can be further improved.

It is sectional drawing which shows an example of embodiment of the electronic device using the ceramic wiring board of this invention. It is sectional drawing which shows the state which mounted the ceramic wiring board of this invention in the external circuit board. It is sectional drawing of the conventional ceramic wiring board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Insulation base | substrate 1a ... Through-hole 2 ... Wiring conductor 3 ... Connection pad 4 ... Bonding material 5 ... Ball-shaped terminal 6 ... Metal plate 7 ... Electronic component A ..Step part 20 ... Resin adhesive

Claims (3)

A plurality of insulating layers made of ceramics are laminated, a plurality of wiring conductors are formed inside, and a plurality of connection pads electrically connected to the plurality of wiring conductors are formed on the lower main surface. In addition, each of the connection pads is provided with an insulating base that has a through hole formed between the inner side surface and the lower main surface, and has a stepped portion around the entire circumference. An attached ball-shaped terminal, and a metal plate having a convex portion at the center of the upper surface of the plate-like portion, and the upper surface of the plate-like portion around the convex portion being joined to the lower surface of the step portion The upper surface of the convex portion of the metal plate and the upper main surface of the insulating base are on the same plane, and the lower surface of the metal plate and the lower end of the ball-shaped terminal are at the same height. A ceramic wiring board characterized by being. 2. The ceramic wiring board according to claim 1, wherein a side surface of the metal plate and an inner side surface of the through hole are bonded via a resin adhesive. The ceramic wiring board according to claim 2, wherein the resin adhesive has a thermal conductivity higher than that of the insulating base.

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