JP2003282771A - Wiring board with heat sink plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board with a heat sink plate which is composed of the wiring board and the heat sink plate that are firmly bonded together through a conductive adhesive layer, and enables a semiconductor element mounted on the heat sink plate to operate stably and normally for a long term. <P>SOLUTION: The heat sink plate 2 made of copper is bonded on the undersurface of an insulating board 1 through the conductive adhesive layer 15 composed of a conductive filler and a thermosetting resin to form the wiring board with the heat sink plate, and a large number of micro projections 2a which are formed of laminated copper crystals are formed on the top surface of the heat sinking plate. <P>COPYRIGHT: (C)2004,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board with a heat radiating plate used for a semiconductor element housing package for housing a semiconductor element such as a semiconductor integrated circuit element. 2. Description of the Related Art Conventionally, a wiring board with a heat radiating plate used for a semiconductor element housing package for housing a semiconductor element such as a semiconductor integrated circuit element is, for example, as shown in a sectional view of FIG. A wiring board 21 having a stepped through hole 21a for accommodating the semiconductor element 20 in the center, and a bonding made of a thermosetting resin such as an epoxy resin on the lower surface of the wiring board 21 so as to cover the through hole 21a. It is mainly composed of a flat heat dissipation plate 22 having a mounting portion 22a on which the semiconductor element 20 is mounted at the center of the upper surface. In this conventional wiring board with a heat sink, the wiring board 21 is composed of two insulating plates 2 made of glass cloth impregnated with a thermosetting resin such as an epoxy resin.
4 and 25 are also laminated via an adhesive layer 26 made of glass cloth impregnated with a thermosetting resin such as an epoxy resin. In the insulating plate 24, a through hole 24a slightly larger than the semiconductor element 20 is formed at the center thereof, and the wiring conductor layer 27 and substantially the entire lower surface thereof extend from the periphery of the through hole 24a on the upper surface to the outer peripheral portion. Is grounded or a power supply conductor layer 28 is applied to the insulating plate 25.
A through hole 25a larger than the through hole 24a is formed at the center thereof, and an external connection conductor 29 is attached on the upper surface. A plurality of through holes 30 are provided in the outer peripheral portions of the insulating plates 24 and 25 and the adhesive layer 26, and the inner wall of the through hole 30 has a wiring conductor layer 27, a ground or power supply conductor layer 28, A through conductor 31 that electrically connects the connection conductor 29 is provided. Further, an insulating layer 32 made of a thermosetting resin such as epoxy resin is applied to the lower surface of the wiring board 21 so as to cover the ground or power supply conductor layer 28 and the through conductor 31.
2 and the adhesive layer 23 are joined to each other to
And the radiator plate 22 are joined via the adhesive layer 23. On the other hand, the heat radiating plate 22 is a substantially rectangular flat plate made of copper. Usually, the heat radiating plate 22 is subjected to a blackening process in which an oxide film is formed on the upper surface thereof in order to strengthen the bonding with the adhesive layer 23. It has been subjected. According to the conventional wiring board with a heat sink, the semiconductor element 20 is mounted on the mounting portion 22a of the heat sink 22 and each electrode of the semiconductor element 20 is connected to the wiring conductor layer 27 by a bonding wire 33 or the like. Electrically connected via the electrical connection means, and then the external connection conductor 2
An external connection member 34 made of a solder ball or the like is joined to 9 and the through hole 21a is filled with a sealing resin (not shown) to hermetically seal the semiconductor element 20 to obtain a semiconductor device as a product. [0006] However, recently,
In order to stabilize the operation of the semiconductor element 20, a wiring board with a heat radiating plate, in which the heat radiating plate 22 is electrically connected to the ground or the power supply conductor layer 28, has been required. In such a case, an opening for exposing the grounding or power supply conductor layer 28 is provided in a part of the insulating layer 32 adhered to the lower surface of the wiring board 1, and the upper surface of the heat sink 22 is not blackened. Further, as the adhesive layer 23 for joining the wiring board 21 and the heat sink 22 to each other, a conductive adhesive made of an epoxy resin containing a metal powder of good conductivity such as copper or silver is used to make the insulation. A method of connecting the ground or power supply conductor layer 28 exposed from the opening of the layer 32 and the heat sink 22 made of copper without an oxide film via a conductive adhesive layer 23 is adopted. However, the upper surface of the heat radiating plate 22 is not subjected to the blackening treatment, and the heat radiating plate 22 is
Is bonded via an adhesive layer 23 made of a conductive adhesive, the bonding strength between the heat radiating plate 22 made of copper and the bonding layer 23 made of the conductive resin is weak, and therefore, the semiconductor substrate is connected to the wiring board 21 and the heat radiating plate 22. When the heat generated during the operation of the element 20 is repeatedly applied for a long period of time, the wiring board 21 and the heat radiating plate 22 adhere to the heat radiating plate 22 due to the thermal stress generated due to the difference in the coefficient of thermal expansion between the two. Separation occurs with the layer 23, and as a result, the airtightness of the semiconductor element 20 mounted on the heat sink 22 is impaired, and the electrical connection between the heat sink 22 and the ground or the power supply conductor layer 28 becomes unstable. Therefore, there is a problem that the semiconductor element 20 cannot be normally and stably operated for a long period of time. The present invention has been devised in view of such a conventional problem, and has as its object to reliably and firmly join a wiring board and a heat sink through an adhesive layer made of a conductive resin. It is an object of the present invention to provide a wiring board with a heat sink, which can make the semiconductor element mounted on the heat sink operate normally and stably for a long period of time. A wiring board with a heat sink according to the present invention has an insulating substrate having a through hole for accommodating a semiconductor element in a central portion, and an outer peripheral surface from an upper surface around the through hole of the insulating substrate. A plurality of wiring conductor layers applied toward the portion, a ground or power supply conductor layer applied to substantially the entire lower surface of the insulating substrate, and the ground or power supply conductor layer provided on the lower surface of the ground or power supply conductor layer. An insulating layer made of a thermosetting resin applied so as to expose a part of the conductive layer, and a conductive layer formed on a lower surface of the insulating layer and an exposed portion of the ground or power supply conductor layer so as to cover the through hole. And a heat sink made of copper joined via a conductive adhesive layer made of a filler and a thermosetting resin, wherein the heat sink has a plurality of copper on its upper surface. Many formed by stacking crystals of Characterized by having the fine projections described above. According to the wiring board with a heat sink of the present invention, since a plurality of fine protrusions formed by stacking a plurality of copper crystals on the upper surface of the heat sink, these fine protrusions are conductive. The heat sink and the conductive adhesive layer are extremely strongly mechanically and electrically bonded to the conductive adhesive layer. Next, a wiring board with a heat sink according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a sectional view showing an example of an embodiment of a wiring board with a heat sink of the present invention. In the drawing, reference numeral 1 denotes a wiring board, and 2 denotes a heat radiating plate. These mainly constitute a wiring board with a heat radiating plate for mounting the semiconductor element 3. In this example, a through hole 4a for forming a space for accommodating the semiconductor element 3 in the center is provided.
An insulating plate 4 having a wiring conductor layer 5 on the upper surface and a grounding or power supply conductor layer 6 on the lower surface, a through hole 7a larger than the through hole 4a in the center, and an external connection conductor 8 on the upper surface. This shows an example in which the wiring board 1 is formed by bonding the attached insulating plate 7 through an adhesive layer 9.
A plurality of through holes 10 are formed in the outer peripheral portion of the wiring board 1, and a through conductor 11 is attached to an inner wall of the through hole 10. Note that the ground or power supply conductor layer 6 is electrically connected to either the ground electrode or the power supply electrode of the semiconductor element 3 and thereby functions as a ground conductor layer or as a power supply conductor layer. The insulating plates 4 and 7 constituting the wiring board 1 are in a substantially rectangular frame shape formed by impregnating a thermosetting resin such as an epoxy resin or a bismaleimide triazine resin into a cloth of glass fiber or aramid fiber, for example. In addition to functioning as a support for the wiring conductor layer 5, the ground or power supply conductor layer 6, and the external connection conductor 8, a space for accommodating the semiconductor element 3 is formed in the through holes 4a and 7a. The insulating plates 4 and 7 are formed by impregnating, for example, a glass cloth with a thermosetting resin such as an uncured epoxy resin, and then thermosetting the sheet to form a through hole. 4a and 7a are formed by cutting the cured insulating plates 4 and 7. The adhesive layer 9 for bonding the insulating plates 4 and 7 is formed by impregnating a cloth made of glass fiber or aramid fiber with a thermosetting resin such as epoxy resin or bismaleimide triazine resin. , Function as an adhesive member for adhering the insulating plates 4 and 7. The insulating plates 4 and 7 sandwich a sheet for the adhesive layer 9 formed by impregnating a cloth made of glass fiber or the like with a thermosetting resin such as an uncured epoxy resin between the insulating plates 4 and 7. At the same time, it is bonded via the bonding layer 9 by thermosetting. The wiring conductor layer 5 attached to the upper surface of the insulating plate 4
Is formed of a metal such as copper foil, and is formed in a plurality of band-shaped patterns from the vicinity of the opening of the through hole 4a to the outer peripheral portion. The wiring conductor layer 5 functions as a part of a conductive path for electrically connecting each electrode of the semiconductor element 3 to an external electric circuit, and each electrode of the semiconductor element 3 is bonded to a portion near the through hole 4a. The connection is made via a wire 13, and the outer periphery thereof is connected to the through conductor 11. The ground or power supply conductor layer 6 adhered to the lower surface of the insulating plate 4 is made of metal such as copper foil.
Is formed on substantially the entire lower surface of the substrate. The ground or power supply conductor layer 6 has a function of supplying a ground or power supply potential to the semiconductor element 3 and adjusting the characteristic impedance of the wiring conductor layer 5 to a predetermined value, and is electrically connected to the through conductor 11. ing. The wiring conductor layer 5 and the ground or power supply conductor layer 6 are formed by attaching copper foil to the upper and lower surfaces of an uncured sheet for the insulating plate 4 and curing the sheet. It is formed by etching a copper foil adhered to a sheet into a predetermined pattern by a photolithography technique. The external connection conductor 8 attached to the upper surface of the insulating plate 7 functions as a connection conductor with an external electric circuit, and is formed so as to be electrically connected to the through conductor 11. An external connection member 14 made of a solder ball or the like is attached to the external connection conductor 8. The external connection conductor 8 is connected to the wiring conductor layer 5 or the ground or power supply conductor layer 6.
A copper foil is adhered to the upper surface of an uncured sheet for the insulating plate 7 in the same manner as described above, and after the sheet is cured, the copper foil adhered to the sheet is subjected to photolithography technology. To form a predetermined pattern. The wiring conductor layer 5 and the external connection conductor 8
Usually has a thickness of about 5 to 50 μm. The thickness is preferably 5 μm or more from the viewpoint of transmitting a high-speed signal, and is preferably 50 μm or less in order to process the wiring conductor layer 5 and the external connection conductor 8 with high dimensional accuracy. On the exposed surfaces of the wiring conductor layer 5 and the external connection conductor 8, a nickel plating layer having a thickness of about 1 to 10 μm and a gold plating layer having a thickness of about 0.1 to 3 μm are usually electroless. They are sequentially deposited by plating or electrolytic plating. Thereby, oxidation corrosion of the wiring conductor layer 5 and the external connection conductor 8 can be effectively prevented, and the wiring conductor layer 5 and the bonding wire 1
3 and the electrical connection between the external connection conductor 8 and the external connection member 14 can be improved. The through conductor 11 attached to the inner wall of the through hole 10 functions as a connection conductor for electrically connecting the wiring conductor layer 5 or the ground or power supply conductor layer 6 to the external connection conductor 8, and 1 is formed by applying a copper plating layer having a thickness of about 4 to 50 μm to the inner wall of a large number of through holes 10 drilled from the upper surface to the lower surface by using an electroless plating method or an electrolytic plating method. If the thickness of the through conductor 11 is less than 4 μm, it tends to be difficult to electrically connect the wiring conductor layer 5 or the ground or power supply conductor layer 6 to the external connection conductor 8 satisfactorily. If it exceeds, it takes a long time to form the through conductor 11 having such a thickness, and the efficiency of manufacturing the wiring board 1 tends to be extremely low. Further, an insulating layer 12 made of a thermosetting resin such as an epoxy resin is provided on the lower surface of the wiring board 1 on which the ground or power supply conductor layer 6 is adhered. It is partially formed so as to be exposed in a frame shape. The insulating layer 12 is provided on the heat insulating plate 2
Function as a bonding base member for firmly bonding the heat sink to the grounding or power supply conductor layer 6 and the insulating layer 12 so that the heat radiating plate 2 is made of an epoxy resin or the like containing a conductive filler made of a metal powder such as copper or silver. The insulating substrate 1 and the radiator plate 2 are joined by being joined via the conductive adhesive layer 15 made of a curable resin, and the ground or power supply conductor layer 6 and the radiator plate 2 are electrically connected. ing. The insulating layer 12 may contain about 5 to 50% by mass of an inorganic filler made of an inorganic insulating powder such as silica. By including such an inorganic filler, the thermal expansion coefficient of the insulating layer 12 can be adjusted and the insulating layer 12
Can be improved in heat resistance and the like. Such an insulating layer 12 is formed by partially applying a thermosetting resin paste such as an uncured epoxy resin to the lower surface of the wiring board 1 and then thermosetting the paste. On the other hand, a conductive adhesive layer 1
The heat radiating plate 2 joined through the joint 5 is made of copper and joined so as to close the through hole 4a. This heat sink 2
Functions not only as a support for supporting the semiconductor element 3 but also as a heat radiating member for satisfactorily radiating the heat generated during operation of the semiconductor element 3 to the outside. It has a mounting portion 2a for mounting. The semiconductor element 3 is bonded and fixed to the mounting portion 2a via a conductive adhesive such as an epoxy resin containing a conductive filler made of a metal powder such as copper or silver. Further, in the present invention, the heat radiating plate 2 made of copper has a large number of fine protrusions 2a formed by stacking a plurality of copper crystals on the upper surface thereof, as shown in an electron micrograph in FIG. ing. And that is important. The fine projections 2a have, for example, a particle size of 0.5.
It is formed by stacking a plurality of copper crystals of about 1 to about 1 μm, the height is about 2 to 3 μm, and the number per unit length on the heat sink 2 is 200 to 500 pieces / mm.
It is about. Thus, in the wiring board of the present invention,
Since a large number of fine protrusions 2a formed by stacking a plurality of copper crystals are formed on the upper surface of the heat radiating plate 2 made of copper, these fine protrusions 2a
The heat sink 2 and the conductive adhesive layer 15 are bonded very firmly. Therefore, the wiring board 1 and the radiator plate 2 are securely and firmly joined via the conductive adhesive layer 15, and the semiconductor element 3 mounted on the radiator plate 2 can operate normally and stably for a long period of time. When the height of the micro projections 2a is less than 2 μm or the number per unit length on the heat radiating plate 2 is less than 200 / mm, the heat radiating plate 2 and the bonding layer 1
5 tends to be difficult to join firmly,
If the height exceeds 3 μm or the number per unit length on the heat sink 2 exceeds 500 / mm, it tends to be difficult to efficiently form such minute projections 2a. Therefore, the minute protrusions 2a have a height of 2 to 3 μm and a number per unit length on the heat sink 2 of 200 μm.
The range of -500 / mm is preferred. The fine projections 2a are formed, for example, by using electrolytic copper as the heat sink 2 and depositing a large number of copper crystal lump thereon by electrolytic plating using a pulse current near the limit current density. Is done. The conductive adhesive layer 15 for joining the insulating substrate 1 and the heat radiating plate 2 is made of, for example, a thermosetting resin such as an uncured epoxy resin and a conductive filler made of a metal powder such as copper or silver. A conductive resin paste made of a mixture is printed and applied to the lower surface of the wiring board 1 by using a screen printing method, and a heat sink 2 is brought into contact with the paste and thermally cured while applying pressure from above and below. It is formed so as to be joined to the heat sink 2. Thus, according to the wiring board with a radiator plate of the present invention, the semiconductor element 3 is bonded and fixed to the mounting portion 2a of the radiator plate 2 via the conductive adhesive, and each electrode of the semiconductor element 3 is connected to the wiring conductor. The semiconductor device 3 is electrically connected to the semiconductor device 3 via a bonding wire 13, and the semiconductor element 3 is sealed by filling the through holes 4a and 7a with a sealing resin (not shown). In such a wiring board with a heat sink, a solder resist layer 16 covering the outer peripheral portion of the external connection conductor 8 may be provided on the wiring board 1 if necessary. Such a solder resist layer 16 is made of a thermosetting resin such as an epoxy resin containing an insulating filler such as silica, and is used when attaching the external connection member 14 such as a solder ball on the external connection conductor 8. It functions as a dam for preventing unnecessary external spreading of the external connection member 14. The solder resist layer 16 is formed by applying an uncured photosensitive thermosetting resin paste to the upper surface of the insulating plate 7 on which the external connection conductors 8 are formed by using a screen printing method, and using a conventionally known photo resist. After etching into a predetermined pattern by lithography, it can be formed by thermosetting. The present invention is not limited to the above-described embodiment, and various changes can be made without departing from the gist of the present invention. For example, in the above-described embodiment, the wiring board 1 to which the two insulating plates 5 and 7 are bonded is described.
However, a wiring board formed by integrally forming a wiring conductor layer and an external connection conductor on the upper surface of one insulating plate and forming a ground or power supply conductor layer on the lower surface, Using a wiring board formed by laminating the above insulating plates. According to the wiring board with a heat sink of the present invention,
Since the upper surface of the heat sink has a large number of fine protrusions formed by stacking a plurality of copper crystals, these fine protrusions cut into the conductive adhesive layer, and the heat sink and the conductive adhesive layer Very strong mechanical and electrical bonding. Accordingly, it is possible to provide a wiring board with a radiator plate, which allows a semiconductor element mounted on the radiator plate to operate normally and stably for a long period of time.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing an example of an embodiment of a wiring board with a heat sink according to the present invention. FIG. 2 is an electron micrograph of the upper surface of a heat sink in the wiring board with a heat sink of the present invention. FIG. 3 is a cross-sectional view of a conventional wiring board with a heat sink. [Description of Signs] 1... Insulating substrate 2... Heat radiating plate 2a... Microprojections 3... Semiconductor element 4a. ······ Wiring conductor layer 6 ····· Ground or power supply conductor layer 12 ····· Insulating layer 15 ····· Conductive adhesive layer

Claims (1)

Claims: 1. An insulating substrate having a through hole for accommodating a semiconductor element in a central portion, and a plurality of wirings attached from an upper surface around the through hole to an outer peripheral portion of the insulating substrate. A conductor layer, a ground or power supply conductor layer adhered to substantially the entire lower surface of the insulating substrate, and a lower surface of the ground or power supply conductor layer so as to expose a part of the ground or power supply conductor layer. An insulating layer made of a cured thermosetting resin, and a conductive adhesive made of a conductive filler and a thermosetting resin on a lower surface of the insulating layer and an exposed portion of the grounding or power supply conductor layer so as to cover the through hole. A heat sink with a heat sink, comprising: a heat sink made of copper joined through layers; wherein the heat sink has a large number of minute crystals formed by stacking a plurality of copper crystals on an upper surface thereof. Characterized by having projections Hot plate with a wiring board.