JPH1154939A - Wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cool a heat generating electric element and, at the same time, to efficiently radiate the heat generated from the element, by burying a heat transferring layer composed of metal foil in an insulating substrate in the vicinity of the electric element. SOLUTION: A heat transferring member 9 made of a material having high thermal conductivity is buried in the bottom of a cavity 7 housing a heat generating element 6. The member 9 is buried in an insulating layer 2b formed as the bottom of the cavity 7, in an area where neither via-hole conductor 5 nor wiring circuit layer 4 are buried including such a place that the member 9 comes into contact with or faced to the element 6. When a wiring board is constituted in such a structure, the heat generated from the element 6 is diffused and made even throughout the wiring board and, at the same time, the stagnation of the heat in the element 6 can be prevented and the element 6 can be cooled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-power-consumption LSI such as an MPU, a package for storing a semiconductor element on which a power IC element and the like are mounted, and a printed circuit board on which a heating element such as a resistance element is mounted. It is about improvement.

[0002]

2. Description of the Related Art Conventionally, electronic devices have been miniaturized. However, in recent years, with the development of portable information terminals and the spread of so-called mobile computing in which computers are carried and operated, so-called multi-layer wirings of smaller, thinner and higher definition have been developed. Substrates tend to be required.

In a conventional printed wiring board, a copper foil is adhered to the surface of a flat plate containing an organic resin called a prepreg, and then etched to form a fine circuit. Through holes are drilled with a drill, metal is adhered to the inner walls of the holes by plating to form through-hole conductors, and electrical connection between the layers is performed.

However, in this method, since the through-hole conductor penetrates the entire wiring board,
As the number of stacked layers increases, the number of through-holes increases, making it impossible to secure the space required for wiring, and the thinning, miniaturization, and weight reduction of printed circuit boards accompanying the lightness and miniaturization of electronic devices. Can not respond to the current situation.

Therefore, recently, a wiring board has been proposed in which a via hole formed in an insulating layer is filled with metal powder to form a via-hole conductor, and then another insulating layer is laminated to form a multilayer.

[0006] Further, with respect to a conventional printed wiring board,
When mounting semiconductor elements, capacitor elements, resistance elements, etc., these electric elements are mounted on the wiring circuit layer formed on the surface of the wiring board by soldering, etc., and the mounted elements are molded with resin. There is a method of forming a concave portion on the surface of an insulating substrate, housing the element in the concave portion and performing resin molding, or sealing the concave portion hermetically with a lid.

Further, among these electric elements, there are many elements that generate heat during operation, such as power IC elements and resistance elements, and in the case of IC elements, there is a problem that the generated heat causes the IC elements to malfunction. Therefore, how to dissipate the heat of these elements themselves to lower the temperature of the elements themselves has become a major issue.

As a structure for dissipating heat generated from such an element, for example, in a package for housing a semiconductor element, an IC element 52 is mounted on a surface of an insulating substrate 51 as shown in FIG. The IC element 52, a wiring circuit layer 53 formed in the insulating substrate 51, and a connection terminal 55 formed on the bottom surface of the insulating substrate 51 are electrically connected through a through-hole conductor 54. A heat radiator 56 made of metal is directly attached to the IC element 52. FIG. 7 shows that the IC element 59 TAB-connected to the wiring circuit layer 58 formed on the surface of the insulating substrate 57 is housed in the insulating substrate 57, and the connection terminal 60 is attached to the wiring circuit layer 58. ing. A heat radiator 61 is attached to one surface of the insulating substrate 57.

[0009]

However, in the conventional heat dissipation structure as shown in FIGS. 6 and 7, the wiring board itself on which the elements are mounted joins the heat sink to at least one surface of the wiring board. Inevitably, it becomes bulky, and it is difficult to mount it on a small electronic device. In addition, since the heat radiator is attached to one surface of the package, it is difficult to increase the density of the electrical elements and the like and increase the number of elements, and there is a problem that the number of pins of the elements cannot be increased.

The method of forming the via-hole conductor by filling the metal powder is effective in reducing the size of the wiring board in that the diameter of the via-hole conductor can be reduced and the via-hole conductor can be arranged at an arbitrary position. However, even if the wiring board is further multi-layered, the elements mounted on the wiring board can be mounted only on the surface of the wiring board, and therefore there is a natural limitation in reducing the size of the wiring board.

Accordingly, the present invention provides a multilayer wiring board on which a heating element such as a semiconductor element or a resistance element is mounted, which can cool the heating element and efficiently dissipate generated heat. The purpose is to do so. Further, the present invention provides a wiring board capable of mounting many elements on the wiring board and dissipating heat generated from those elements without lowering the mounting density of the elements. The purpose is to do so.

[0012]

Means for Solving the Problems The present inventors apply a wiring circuit layer on the surface and / or inside of an insulating substrate containing a thermosetting resin, and form an electric circuit on the surface and / or inside of the insulating substrate. After examining a structure that can reduce the temperature of the heat-generating electric element on the wiring board on which the element is mounted without lowering the mounting density of the electric element, the metal foil was placed inside the insulating substrate near the heat-generating electric element. By burying the heat transfer layer, the heat generated from the electric element can be diffused by the heat transfer layer over the entire wiring substrate and uniformized,
As a result, the inventors have found that the temperature of the element can be reduced, and have reached the present invention.

That is, the wiring board of the present invention comprises an insulating substrate formed by laminating a plurality of insulating layers containing at least a thermosetting resin, and a wiring circuit layer formed on the surface and / or inside the insulating substrate. A multi-layer wiring board having a heat-generating electric element mounted on the surface and / or inside of the insulating substrate, wherein a heat transfer member is buried inside the insulating substrate near the heat-generating electric element. Is what you do. In particular, the heat transfer layer is formed over substantially the entire surface of the wiring board, and an end of the heat transfer layer is exposed or protruded from a side surface of the insulating substrate to increase heat dissipation. The heat-generating electric element is one kind selected from the group consisting of an IC element, a resistance element, a capacitor, an oscillator, and a filter, wherein the heat-generating electric element is mounted and accommodated in a gap provided in the insulating substrate. It is characterized by the following.

According to the wiring board of the present invention, the heat transfer member is
By burying in the insulating substrate near the mounting of the heat-generating electric element (hereinafter referred to as the heat-generating element), the heat generated from the heat-generating element is equalized over the entire wiring board through the heat equalizing layer. As a result, heat stagnation due to the heat generated by the electric element can be eliminated, and the temperature of the heating element can be reduced. Further, by exposing the end portion of the heat equalizing layer from the side surface of the wiring board, heat generated from the heating element can be radiated to the outside of the substrate via the heat equalizing layer.

According to the present invention, by mounting the electric element in the space provided inside the insulating substrate, the electric element can be mounted not only on the surface of the wiring board but also inside the substrate. In addition to being able to mount multiple elements and high density mounting, it is possible to improve the uniformity of the generated heat and the heat dissipation by forming a uniform soaking layer for each of these electric elements. .

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a cutaway perspective view of a main part for explaining a basic structure when applied to a wiring board of a type in which an electric element is mounted on a surface of the wiring board, among wiring boards of the present invention. According to FIG. 1, the wiring board 1 includes a plurality of insulating layers 2a, 2b, 2c and 2 including at least a thermosetting resin.
The wiring circuit layer 4 is formed on the surface and inside of the insulating substrate 3 formed by laminating d, and the insulating substrate 3 further includes a via-hole conductor 5 for connecting the wiring circuit layers between different layers. According to the wiring board of FIG.
A cavity 7 for accommodating the heating element 6 is provided on the surface of the
Are provided, and are electrically connected to the wiring circuit layer 4 formed on the surface of the insulating substrate 3 by wire bonding 8 or the like.

A heat transfer member 9 made of a highly heat-conductive material is embedded in the bottom of the cavity 7 in which the heating element 6 is housed. This heat transfer member 9 is, as shown in FIG.
The via-hole conductor 5 and the wiring circuit layer 4 are provided in the vicinity of the heating element 6 on the surface of the insulating layer 2 b forming the bottom surface of the cavity 7, that is, at the place where the heating element 6 is in contact with or faces the heating element 6. The heat transfer member 9 is buried in an area that is not provided.

In such a structure, the heat generated from the heat generating element 6 is diffused by the heat transfer member 9 to the entire wiring board, so that the heat is uniformed, and at the same time, stagnation of the heat in the heat generating element 6 is prevented. Thus, the heating element 6 can be cooled. When the heat transfer member 9 is embedded on the surface of the wiring board,
Since the circuit design on the surface of the wiring board is greatly restricted, it is necessary to bury the wiring board inside the insulating substrate.

It is desirable that the end of the heat transfer member 9 is exposed on the side surface of the wiring board 1 or protrudes from the side surface of the wiring board 1 like the end 10 in FIG.
By exposing or projecting the end of the heat transfer member 9 from the side surface of the wiring board 1 as described above, the heat transmitted from the heat transfer member 9 is transferred to the exposed surface of the heat transfer member 9 or the protrusion of the end 10. Heat can be dissipated from the part 12. In this case, the projecting portion 11 of the heat transfer member 9 can be thermally connected to another heat radiating member (not shown) such as a heat radiating fin to further enhance heat radiation.

The wiring board shown in FIG. 1 is manufactured, for example, by the following method. First, as shown in FIG. 2A, via holes are formed in an uncured or semi-cured soft insulating layer 2a containing a thermosetting resin, and the inside thereof is filled with a conductive paste containing a metal powder. As a result, a via-hole conductor 5a is formed. At the same time, a cavity 7 for accommodating the semiconductor element 6 is formed by punching or the like. Further, the wiring circuit layer 4a is formed on a predetermined portion of the insulating layer 2a. The wiring circuit layer 4a includes: 1) a method of forming a circuit pattern by attaching a metal foil to the surface of the insulating layer and then performing an etching process; 2) a method of forming a resist on the surface of the insulating layer and plating. 3) After attaching a metal foil to the surface of the transfer film and etching the metal foil to form a wiring circuit layer, the wiring circuit layer made of the metal foil can be transferred to the surface of the insulating layer. .

Similarly, for the insulating layer 2b in the soft state shown in FIG. 2B, a via hole conductor 5b and a wiring circuit layer 4b are formed at predetermined locations in the same manner as the insulating layer 2a. Then, the heat transfer member 9 is buried in a portion of the insulating layer 2b where the bottom surface of the cavity 7 is formed. The heat transfer member 9 may be buried by pressing the heat transfer member 9 into the soft insulating layer 2b by force, or when the heat transfer member 9 is thick, the insulating layer 2b may be buried. A concave portion is formed at a location, and the heat transfer member 9 is fitted into the concave portion. The concave portion may be formed by processing the surface of the soft insulating layer 2a 'or by flowing a slurry through a mold. Further, the via-hole conductor 5 and the wiring circuit layer 4 are formed at predetermined locations on the insulating layer 2b ', similarly to the insulating layer 2a.

Further, as shown in FIGS. 2 (c) and 2 (d), the via-hole conductor 5 is applied to the insulating layers 2c and 2d in the soft state, similarly to the insulating layers 2a and 2b.
c, 5d and the wiring circuit layers 4c, 5c are formed.

After the insulating layers 2a, 2b, 2c, and 2d are aligned and laminated and pressed, the multilayer wiring board is manufactured by heating at a temperature sufficient to completely cure the thermosetting resin. Then, the semiconductor element 6 is adhered to the surface of the heat transfer member 9 in the cavity 7 of the substrate, and connected to the wiring circuit layer 4 on the surface of the insulating substrate 3 by wire bonding or the like, thereby mounting the semiconductor element 6 on the surface. 1 can be manufactured. Note that the heating element 6 in the cavity 7 may be sealed with a sealing resin such as an epoxy resin if desired.

FIG. 3 shows a wiring board according to the present invention.
FIG. 9 is a perspective view, partially cut away, for explaining a basic structure when an electric element is applied to a wiring board of a type in which the electric element is mounted inside the wiring board. According to FIG. 3, the wiring board 21 is
Plural insulating layers 22a, 2 containing at least thermosetting resin
A wiring circuit layer 24 is formed on the surface and inside of an insulating substrate 23 formed by laminating 2b, 22c, 22d and 22e, and a via hole conductor 25 for connecting wiring circuit layers between different layers is formed in the insulating substrate 23. Is provided.

A gap 27 for accommodating the heating element 26 is provided inside the insulating substrate 23, and the wiring circuit layer 2 formed on the surface of the insulating layer 22 a in the gap 27 is provided.
4a.

According to the wiring board 21 shown in FIG.
A heat transfer member 29 made of metal is buried in the surface of the insulating layer 22c facing the gap portion 27 in which 6 is accommodated. The heat transfer member 29 is formed by the via-hole conductor 25 of the insulating layer 22c.
Buried in a region where the wiring circuit layer 24 is not provided.

In such a structure, the heat generated from the heating element 26 is diffused and uniformized by the heat transfer member 29 over the entire wiring board, and at the same time, the stagnation of the heat in the heating element 26 is prevented. , The heating element 26 can be cooled.

The end 30 of the heat transfer member 29 is exposed on the side surface of the wiring board 21 or the end 30 of FIG.
It is desirable to protrude from the side surface of the wiring board 21 like 0. By exposing or projecting the end of the heat transfer member 29 from the side surface of the wiring board 21 in this manner, the heat transmitted from the heat transfer member 29 is transferred to the exposed surface of the end of the heat transfer member 29 or the end of the heat transfer member 29. The heat can be dissipated from the protrusions 32 of the 30. In this case, the protrusion 32 of the heat transfer member 29
Can be thermally connected to another heat dissipating member (not shown) such as a heat dissipating fin to further enhance heat dissipation.

The wiring board 21 shown in FIG. 3 is manufactured, for example, by the steps shown in FIG. First, FIG.
As shown in (a), via holes are formed in the non-cured or semi-cured soft insulating layer 22a containing a thermosetting resin, if necessary, in the thickness direction, and a conductive paste containing metal powder in the via holes is provided. Is filled while performing screen printing or suction processing to form a via-hole conductor 25a. In addition, a void 35 is formed at a predetermined position of the insulating layer 33.

The wiring circuit layer 24a is formed by: 1) a method of forming a circuit pattern by attaching a metal foil to the surface of the insulating layer and then performing an etching process; and 2) forming a resist on the surface of the insulating layer and forming it by plating. 3) a method of attaching a metal foil to the surface of the transfer film, etching the metal foil to form a circuit pattern, and then transferring the circuit pattern made of the metal foil to the surface of the insulating layer.

Further, as shown in FIG.
Similarly to 2a, a via hole conductor 25b is formed in the soft insulating layer 22a, and a void 27 is formed in a predetermined location. Then, the wiring circuit layer 24b is formed on the surface of the insulating layer 22b, and the heating element 26 is mounted and accommodated in the gap 27 of the insulating layer 22b.

[0032] Mounting of the wiring circuit layer 24b of the heating element 26, as shown in FIG. 4 (b1), ^-5 forming a pre-wiring circuit layer 24A to the surface of the transfer film 33, the wiring circuit layer 24b To the heating element 26, TA
B, mounting by wire bonding or the like. afterwards,
The transfer film 33 on which the wiring circuit layer 24b and the heating element 26 are mounted is laminated on the insulating layer 22b, and only the transfer film 33 is peeled off.
Can be transferred to the insulating layer 22b.

In the above example, basically, the wiring circuit layer 24b on which the heating element 26 is mounted is simultaneously transferred with the heating element 26, but the wiring circuit layer 24b which is not involved in the mounting of the heating element 26 is provided. (Not shown) may be formed simultaneously with the heating element 26 and the wiring circuit layer 24b, or individually by any of the above-described methods 1) to 3). In addition, the heating element 26 housed in the cavity 27 is
It may be sealed with an epoxy resin or the like while being mounted on the wiring circuit layer 24b.

Further, the via-hole conductor 25c is formed on the soft insulating layer 22c in the same manner as described above, and at the same time, the heat transfer member 29 is formed on the insulating layer 22c at a position facing the void 27.
Buried. The embedding of the heat transfer member 29 is performed by a method similar to that described with reference to FIG.

Further, the insulating layer 22d and the insulating layer 22e in the soft state are applied to the wiring circuit layer 2 in the same manner as described above.
4d and 24e and via-hole conductors 25d and 25e are formed.

Then, the insulating layers 22a, 22b, 22c, 22d, and 22e in the respective soft states produced as described above.
Are aligned and laminated and pressure-bonded, the insulating layers 22a to 22a-2
By heating to a temperature sufficient to cure the thermosetting resin in 2e and performing complete curing at once, the heating element 26 as shown in FIG.
A wiring board in which the heat transfer member 29 is embedded in the insulating substrate 22 in the vicinity of 26 can be manufactured. Further, other electronic components can be mounted on the surface of the wiring board.

Further, according to the present invention, it is possible to manufacture a multilayer wiring board of any form based on the above-described mounting structure of the heating element in the void formed in the insulating substrate and the method of embedding the heat transfer member. According to the lamination technique of the insulating layer having the voids described in FIGS. 3 and 4 and the insulating layer in which the heat transfer member is embedded, for example, as shown in FIG. In the above, the gaps 37 and 38 for accommodating the heating elements such as the IC element 35 and the resistance element 36 are provided.
Are formed in the same plane or in different layers, and the plurality of heating elements can be mounted and housed. Then, the heat transfer members 39, 40, 41 are provided for the respective heating elements 35, 36.
, The generated heat can be uniformed over the entire substrate with respect to the individual heating elements, and the heat transfer member 3
By projecting 9, 40, and 41 from the side of the substrate, the heat dissipation can be further enhanced. As a result, it is possible to obtain a multilayer wiring board capable of cooling the heating elements while realizing high-density mounting and miniaturization of elements on the wiring board. According to the embodiment of FIG. 5, electronic components can be mounted on the surface of the substrate.

In the present invention, as the heat transfer member embedded in the substrate, a metal or ceramic having excellent heat conductivity can be used favorably. As the metal, copper, aluminum or an alloy thereof is suitable. Aluminum nitride for ceramics,
Silicon carbide is preferably used, but copper and aluminum are most suitable from the viewpoint of workability. The thickness of this heat transfer member is 50
μm or more, preferably 100 μm or more. Even if the thickness of the heat transfer member is less than 50 μm, the heat uniformity and heat dissipation can be improved, but handling as the heat transfer member becomes difficult, and there is a difficulty in manufacturing. The upper limit of the thickness is not particularly limited, but is preferably 1 mm or less, and more preferably 0.5 mm or less for use in small and lightweight equipment. Optimally thickness 0.1-0.3
mm. A thicker one is suitable for a power amplifier, and one having a thickness of about 0.5 to 5 mm can be used, and most preferably 0.5 to 2 mm.

The heat transfer member can also serve as a wiring layer such as a ground (ground) if necessary. in this case,
The via-hole conductor may be formed so as to be directly connected to the heat transfer member.

In this case, by removing contamination such as an oxide film and oils and fats on the surface of the heat transfer member in advance by etching or the like, the contact resistance with the via-hole conductor is increased, thereby preventing heat generation from the connection portion. Can be.

In the manufacturing method described with reference to FIGS. 2 and 4, the insulating layer containing the thermosetting resin used is formed by kneading a thermosetting organic resin or a composition such as a thermosetting organic resin and a filler. The mixture is sufficiently mixed by means such as a mill or a three-roll mill and formed into a sheet by a rolling method, an extrusion method, an injection method, a doctor blade method, or the like. Then, the thermosetting resin is semi-cured by heat treatment if desired. For semi-curing, the resin is heated to a temperature slightly lower than a temperature sufficient to completely cure the resin.

Then, via holes are formed in the insulating layer.
A well-known method such as drilling, punching, sandblasting, or processing by irradiation with a carbon dioxide gas laser, a YAG laser, an excimer laser, or the like is used to form the gap.

The thermosetting resin forming the insulating layer is not particularly limited as long as it is a thermosetting resin having electrical properties, heat resistance and mechanical strength as an insulating material. , Aramid resin, phenolic resin,
Epoxy resins, imide resins, fluororesins, phenylene ether resins, bismaleide triazine resins, urea resins, melamine resins, silicone resins, urethane resins, unsaturated polyester resins, allyl resins and the like can be used alone or in combination.

In addition, a filler can be compounded with an organic resin in the insulating layer in order to increase the strength of the entire insulating substrate or wiring substrate. As the filler to be combined with the organic resin, SiO ₂ , Al ₂ O ₃ ,
ZrO ₂ , TiO ₂ , AlN, SiC, BaTiO ₃ ,
Inorganic fillers such as SrTiO ₃ , zeolite, CaTiO ₃ and aluminum borate are preferably used. Further, a nonwoven fabric or a woven fabric made of glass or aramid resin may be used by impregnating the above resin. The organic resin and the filler are preferably compounded in a volume ratio of 15:85 to 50:50.

The insulating layer forming the gap for accommodating these heating elements is formed of the above-described various materials because the gap can be easily processed by punching or laser.
Most preferably, it is a mixture of an epoxy resin, an imide resin, a phenylene ether resin and a silica or aramid nonwoven fabric.

On the other hand, the metal paste filled in the via-hole conductor includes metal powder having an average particle size of 0.5 to 50 μm, such as copper powder, silver powder, silver-coated copper powder, and copper-silver alloy.
If the average particle size of the metal powder is smaller than 0.5 μm, the contact resistance between the metal powders increases and the resistance of the through-hole conductor tends to increase. If the average particle size exceeds 50 μm, it is difficult to reduce the resistance of the through-hole conductor. Tend to be.

The conductive paste is prepared by adding and mixing the above-mentioned organic resin for binding and the solvent to the above-mentioned metal powder. The solvent to be added to the paste may be any solvent that can dissolve the binding organic resin to be used. For example, isopropyl alcohol, terpineol, 2-octanol, butyl carbitol acetate and the like are used.

As the organic resin for binding in the above-mentioned conductor paste, cellulose and the like are used in addition to the above-mentioned organic resins constituting the various insulating sheets. This organic resin is
The metal powders are bonded in a state where they are in contact with each other, and the metal powders are bonded to the insulating sheet. This organic resin, in the metal paste,
It is desirable that the content is 0.1 to 40% by volume, particularly 0.3 to 30% by volume. This means that the amount of resin is 0.1.
If the amount is less than 1% by volume, it is difficult to firmly bond the metal powders to each other, and it is difficult to firmly bond the low-resistance metal to the insulating layer. This makes it difficult to bring the powders into sufficient contact with each other and increases the resistance of the through-hole conductor.

As the wiring circuit layer, copper, aluminum,
It is desirable to be made of at least one kind or two or more kinds of alloys selected from the group of gold and silver, and particularly, copper or an alloy containing copper is most desirable. In some cases, a high-resistance metal such as a Ni—Cr alloy may be mixed or alloyed as the conductor composition for adjusting the resistance of the circuit.
Further, in order to reduce the resistance of the wiring layer, a metal having a lower melting point than the low-resistance metal, for example, a low-melting metal such as solder or tin is used in an amount of 2 to 20% by weight in the metal component in the conductor composition. May be included.

In order to increase the adhesion strength between the wiring circuit layer and the insulating layer or between the heat transfer member and the insulating layer, the surface of the insulating layer or the surface of the wiring circuit layer or the heat transfer member must be 0.1 μm thick.
As described above, in particular, 0.3 μm to 3 μm, most preferably 0.3 μm to 1 μm.
It is desirable to roughen the surface to 5 μm. In order to seal both ends of the via-hole conductor with a wiring circuit layer made of metal foil, the thickness of the wiring circuit layer is appropriately 5 to 40 μm.

As described above, according to the present invention, the stagnation of heat by the heating element mounted on the surface or in the gap inside the insulating substrate can be achieved without deteriorating the mountability of various elements on the surface of the wiring board. As a result, it is possible to dissipate the heat through the heat transfer member, thereby cooling the heat-generating element and preventing malfunction such as element malfunction. Can be prevented.

[0052]

【Example】

Example 1 A via hole having a diameter of 0.1 mm was formed with a carbon dioxide laser on a prepreg impregnated with 50% by volume of an imide resin in a nonwoven fabric of an aramid resin, and the hole was filled with a copper paste containing copper powder plated with silver. To form a via-hole conductor. Further, a cavity for installing a power IC element as a heating element by a laser was formed to form an insulating layer b.

Next, a varnish-state resin and powder were mixed so as to have a ratio of 50% by volume of imide resin and 50% by volume of silica powder, and a via hole having a diameter of 0.1 mm was punched into an insulating layer formed by a doctor blade method. The holes are filled with a copper paste containing copper powder plated with silver to form via-hole conductors, and an insulating layer a and an insulating layer c are formed.
Was prepared.

On the other hand, polyethylene terephthalate (PE)
T) An adhesive was applied to the surface of a transfer sheet made of a resin to make it sticky, and a portion was cut off for TAB connection. Thereafter, a copper foil having a thickness of 12 μm and a surface roughness of 0.8 μm was bonded to one surface. Thereafter, a photoresist (dry film) was applied and exposed and developed, and then immersed in a ferric chloride solution to remove non-pattern portions by etching to form a wiring circuit layer. Note that the manufactured wiring circuit layer is a fine pattern having a line width of 20 μm and an interval between wirings of 20 μm. Then, this wiring circuit layer was transferred to the surface of the insulating layer b.

Further, a wiring circuit layer was similarly formed on the insulating layers a and c by transfer.

Then, a concave portion is formed on the surface of the insulating layer b where the via hole conductor and the wiring circuit layer are not formed, and silicon carbide having a thickness of 0.1 mm (thermal conductivity of 200 W / m 2) is formed in the concave portion. -A heat transfer member made of K) was fitted.

After that, the insulating layer a, the insulating layer b, and the insulating layer c are laminated and pressure-bonded in this order, and then pressure-bonded with a pressure of 50 kg / cm ² , and heated at 200 ° C. for 1 hour to be completely cured to obtain a multilayer wiring board. Produced. Then, the power IC element is adhered to the surface of the heat transfer member exposed in the cavity with a heat conductive adhesive, and the power IC element is connected to the wiring circuit layer on the surface of the insulating layer A by wire bonding. -A wiring board on which an IC element was mounted was manufactured. For comparison, a wiring board on which a power IC element was mounted was manufactured in exactly the same manner except that the heat transfer member was not embedded.

In each of the obtained wiring boards, a power IC
As a result of measuring the temperature of the IC element itself after operating the element for 10 hours, the temperature of the IC element during operation could be lowered by 12 ° C. by embedding the heat transfer member according to the present invention.

Further, as a result of observing the place where the heat transfer member was formed, no problem was found. The wiring circuit layer and the via-hole conductor were in a good connection state. As a result of conducting a continuity test between the wirings, no disconnection of the wiring was observed. Even if a special cooling fan was not used, various elements and electronic components were confirmed to perform predetermined operations.

Example 2 A copper paste containing copper powder in which a via hole having a diameter of 0.1 mm was formed in a prepreg impregnated with 50% by volume of an imide resin in a nonwoven fabric of an aramid resin with a carbon dioxide gas laser and silver was plated in the hole. Was filled to form a via-hole conductor. Further, a gap for installing a power IC element as a heating element was formed by a laser to form an insulating layer A.

On the other hand, polyethylene terephthalate (PE)
T) An adhesive was applied to the surface of a transfer sheet made of a resin to make it sticky, and a portion was cut off for TAB connection. Thereafter, a copper foil having a thickness of 12 μm and a surface roughness of 0.8 μm was bonded to one surface. Thereafter, a photoresist (dry film) was applied and exposed and developed, and then immersed in a ferric chloride solution to remove non-pattern portions by etching to form a wiring circuit layer. Note that the manufactured wiring circuit layer is a fine pattern having a line width of 20 μm and an interval between wirings of 20 μm. Thereafter, a power IC element was TAB-connected to this wiring circuit layer and sealed with epoxy resin.

A power IC is provided on the surface of the insulating layer A.
The transfer sheet on which the elements were mounted was positioned and pressure-bonded by lamination. Only the transfer sheet was peeled off, and the power IC element was transferred to the insulating layer A together with the wiring circuit layer.

Next, a varnish-state resin and powder were mixed so as to have a ratio of 50% by volume of imide resin and 50% by volume of silica powder, and a via hole having a diameter of 0.1 mm was punched into an insulating layer formed by a doctor blade method. Then, the holes were filled with a copper paste containing copper powder plated with silver to form via-hole conductors, whereby insulating layers B and C were formed. Then, a heat transfer member made of copper having a thickness of 0.1 mm was buried in the portion of the insulating layer B facing the void portion of the insulating layer A by pressing. Further, an insulating layer B and an insulating layer C
The wiring circuit layer was transcribed to the necessary part.

Thereafter, the heat transfer member of the insulating layer A having the power IC element housed in the gap, the insulating layer C thereon, and the insulating layer B therebelow is arranged so as to face the gap. The layers were laminated and pressed at a pressure of 50 kg / cm ² at 200 ° C.
For 1 hour to complete the curing, thereby producing a multilayer wiring board incorporating a power IC element. Also, for comparison,
Except that the heat transfer member is not embedded, the power I
A multilayer wiring board incorporating a C element was manufactured. In addition, a thermocouple was embedded in the insulating layer so as to be in contact with the IC element for evaluation of heat dissipation.

As a result of measuring the temperature of the IC element itself after operating the power IC element for 10 hours with respect to this substrate, the heat transfer member according to the present invention was embedded, as compared with the case where it was not embedded. The temperature of the IC element during operation is 15
° C could be lowered.

[0066]

As described in detail above, according to the present invention,
By embedding the heat transfer member in the insulating substrate of the wiring board on which the heating element is mounted, the heat generated from the heating element does not stagnate without impairing the mountability of the element on the surface of the board. It is possible to equalize the heat and further radiate the heat, thereby preventing malfunction due to abnormal heating of the heating element. In addition, even in a wiring board having a plurality of built-in heating elements, by burying a heat transfer member in an insulating substrate near each of the built-in heating elements, it is possible to increase the number of elements of the board and increase the mounting density. A heat dissipation structure that can be provided can be provided.

[Brief description of the drawings]

FIG. 1 is a cutaway perspective view of an essential part for explaining an embodiment of a multilayer wiring board of the present invention.

FIG. 2 is a process chart for manufacturing the multilayer wiring board of FIG. 1;

FIG. 3 is a cutaway cross-sectional view of an essential part for explaining another embodiment of the multilayer wiring board of the present invention.

FIG. 4 is a process chart for manufacturing the multilayer wiring board of FIG. 3;

FIG. 5 is a schematic sectional view for explaining still another embodiment of the multilayer wiring board of the present invention.

FIG. 6 is a schematic cross-sectional view for explaining a conventional wiring board.

FIG. 7 is a schematic cross-sectional view for explaining another conventional wiring board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wiring board 2a-2d Wiring layer 3 Insulating board 4 Wiring circuit layer 5 Via hole conductor 6 Heating element 7 Cavity 8 Wire-bonding 9 Heat transfer member 10 End part

Claims (4)

[Claims] 1. An insulating substrate comprising: an insulating substrate formed by laminating a plurality of insulating layers containing at least a thermosetting resin; and a wiring circuit layer formed on a surface and / or inside the insulating substrate. A multi-layer wiring board having a heat-generating electric element mounted on the surface and / or inside thereof, wherein a heat transfer member having high thermal conductivity is embedded in the insulating substrate near the heat-generating electric element. substrate. 2. The wiring board according to claim 1, wherein an end of said heat transfer member is exposed or protrudes from a side surface of said insulating substrate. 3. The wiring board according to claim 1, wherein the electric element is mounted and housed in a gap provided inside the insulating substrate. 4. The wiring board according to claim 1, wherein the heat-generating electric element is one selected from the group consisting of an IC element, a resistance element, a capacitor, an oscillator, and a filter.