JP2008262947A - Wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress an increase in temperature of an electronic component by improving the heat dissipation performance of the surface of the wiring board. <P>SOLUTION: The wiring board 5 provided with an insulating base material 6 and a conductor pattern 7 formed on the insulating base material 6 has a heat dissipation layer 8 for covering one or whole part of the surface where conductor pattern 7 is formed and the heat dissipation layer 8 contains N-type semiconductor particles of 5.0 vol% or more. With this configuration, the wiring board 5 can dissipate heat of the surface of the wiring board 5 as optical energy, and as a result, it can improve the heat dissipation performance of the surface of the wiring board 5 and can suppress an increase in temperature of the electronic component 9. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wiring board such as a single-layer or multilayer circuit board.

  As shown in FIG. 5, the wiring board 1 includes an insulating base 2 and a conductor pattern 3 formed on the insulating base 2. An electronic component 4 such as a semiconductor is mounted on the conductor pattern 3.

  Here, in recent years, these electronic components 4 tend to increase in power consumption and heat generation as performance increases.

For example, Patent Document 1 is known as prior art document information relating to the invention of this application.
JP 2005-252144 A

  In the conventional configuration described above, the mounted electronic component 4 may become hot and break or malfunction.

  This is because the surface temperature of the wiring board 1 rises and the heat of the electronic component 4 cannot be efficiently diffused.

  That is, the heat generated from the electronic component 4 is transmitted to the conductor pattern 3, but the heat radiation property of the conductor pattern 3 is low, while the heat conductivity of the insulating base material 2 is generally low. The temperature gradually rises, and as a result, the electronic component 4 becomes high temperature.

  Accordingly, an object of the present invention is to improve the heat dissipation of the surface of the wiring board and suppress the temperature rise of the electronic component.

  In order to achieve this object, the present invention has a heat radiation layer covering a part or all of the surface on which the conductor pattern is formed, and this heat radiation layer contains 5.0 vol% or more N-type semiconductor particles. To do.

  Thereby, this invention can improve the heat dissipation of the wiring board surface, and can suppress the temperature rise of an electronic component.

  This is presumably because the heat radiation layer released the heat of the wiring board surface as light energy by containing the N-type semiconductor particles.

  That is, the electrons of the N-type semiconductor particles obtain energy by the heat of the electronic component or the wiring board surface, and are excited from the valence band to the conduction band. When the excited electrons fall into a low orbit, they are emitted as light energy.

  As a result, the heat dissipation of the wiring board surface can be improved and the temperature rise of the electronic component can be suppressed.

(Embodiment 1)
As shown in FIG. 1, the wiring board 5 in the present embodiment is a single-sided wiring board provided with an insulating base 6 and a conductor pattern 7 formed on the top surface of the insulating base 6.

  The wiring board 5 has a heat radiation layer 8 that covers the surface on which the conductor pattern 7 is formed. The heat radiation layer 8 is composed of N-type semiconductor particles in the resin composition constituting the heat radiation layer 8. In the above, about 5.0 vol% or more and 40 vol% or less are contained.

  Further, in the present embodiment, an electronic component 9 such as a semiconductor element having high heat generation is soldered on the wiring board 5, and the wiring board is formed from the outer periphery directly below the electronic component 9 and a portion to be soldered. A heat radiation layer 8 is formed over substantially the entire upper surface (element mounting surface) of 5.

  Hereinafter, the material of the wiring board 5 in the present embodiment will be described.

  As the insulating base 6, a prepreg (glass epoxy base) in which an epoxy resin containing about 5 Vol% to 60 Vol% of an inorganic filler such as aluminum oxide was impregnated into a glass cloth was used. The thickness of the insulating base 6 was 0.9 mm.

  As the conductor pattern 7, a copper foil having a thickness of about 0.1 mm is used, and this copper foil is bonded onto the insulating substrate 6. When a copper foil is used, a fine circuit pattern can be easily formed by etching or the like. In particular, copper foil is preferable because it is inexpensive and has high electrical conductivity.

  As the heat radiation layer 8, a material obtained by kneading a titanium oxide (N-type semiconductor particle) powder having an average particle diameter of 1.0 μm to 5.0 vol% or more and 40 vol% or less in an epoxy resin or an acrylic resin or the like is used. It was. In the present embodiment, the thickness of the heat radiation layer 8 is about 50 μm. The average particle size of the N-type semiconductor particles can be appropriately adjusted so that desired emissivity, viscosity, and photosensitivity can be obtained as long as they are in the range of about 0.1 μm to 20 μm.

  In the present embodiment, glass epoxy is used as the insulating base 6, but various other resins alone, a mixture of a resin and a reinforcing material, ceramic, or the like can also be used.

  Examples of the resin include a phenolic resin, a polyimide resin, an epoxy resin, a silicon resin, and the like, a thermosetting resin, a thermoplastic resin, and a photocurable resin.

  When using an epoxy resin, a phenol resin, or an isocyanate resin, the heat resistance of the insulating substrate 6 can be increased.

  In this embodiment, an inorganic filler made of aluminum oxide and a glass cloth are used as a reinforcing material. However, other fillers made of silica, aluminum nitride, boron nitride, silicon nitride, aluminum hydroxide, etc., and alumina cloth are used. The strength can be improved by using a structure such as carbon fiber or an aramid cross aramid nonwoven fabric.

  Further, in addition to the reinforcing material, a dispersant, a colorant, a coupling agent, or a release agent may be included.

  When the insulating base 6 is ceramic, materials such as alumina, silicon nitride, and aluminum nitride can be used.

  In the present embodiment, the heat radiation layer 8 is made by kneading a titanium oxide powder, which is an N-type semiconductor, with an epoxy resin or an acrylic resin, but other materials described later can also be used.

  Examples of the resin include a phenol resin, a polyimide resin, an epoxy resin, a silicon resin, and the like, a thermosetting resin, a thermoplastic resin, a photocurable resin, and the like.

  The photocurable resin can be formed into a desired pattern by using a photoresist process such as exposure-development or a method such as screen printing.

  Examples of the N-type semiconductor particles include silicon and germanium mixed with arsenic and phosphorus in addition to titanium oxide.

  Further, since the surface area can be increased by reducing the particle size of the N-type semiconductor particles, the average particle size is preferably 20 μm or less. The N-type semiconductor particles are appropriately adjusted so that desired emissivity, viscosity, and photosensitivity are obtained within a range of 20 μm or less. If N-type semiconductor particles having different particle diameters are combined, they can be contained at a high concentration.

  The insulating substrate 6 and the conductor pattern 7 may be formed in multiple layers, and a multilayer substrate such as a build-up substrate in which layers are connected by through holes, plating, conductor paste, or the like may be used. In that case, radiation efficiency can be further improved by forming the heat radiation layer 8 on both surfaces.

  Hereinafter, an example of a method for manufacturing the wiring board 5 in the present embodiment will be described.

  First, the copper foil used as the conductor pattern 7 is laminated | stacked on the whole surface of the above-mentioned unhardened insulating base material 6 (prepreg), and it hardens | cures by heating and pressurizing with a hot press machine.

  Next, a resist is laminated on the copper foil, exposed and developed, and then a conductor pattern 7 is formed by etching.

  Thereafter, the resist on the conductor pattern 7 is removed, and the wiring substrate 5 is covered with a resin composition in which N-type semiconductor particles to be the heat radiation layer 8 are kneaded.

  Next, this resin composition is exposed and developed, and unnecessary portions of the heat radiation layer 8 such as soldered portions are removed. Note that the heat radiation layer 8 may be formed by a method such as printing.

  In this way, the wiring board 5 of the present embodiment can be formed.

  The effect in this Embodiment is demonstrated below.

  In the present embodiment, the heat dissipation of the surface of the wiring substrate 5 (component mounting surface) can be improved, and the temperature rise of the mounted electronic component 9 can be suppressed.

  This is presumably because the heat radiation layer 8 on the wiring board 5 contains N-type semiconductor particles to release the heat on the surface of the wiring board 5 as light energy.

  That is, conventionally, as shown in FIG. 5, the heat generated from the mounted electronic component 4 is diffused by convection through air, radiation (radiation), heat conduction to the wiring board 1, or the like. Among these, the propagation of heat by heat conduction is the most efficient. Therefore, the heat of the electronic component 4 is transferred to the conductor pattern 3 relatively quickly.

  However, the heat radiation of the conductor pattern 3 is low, and on the other hand, the heat conductivity of the insulating base 2 is generally low. Therefore, the surface of the wiring board 1 gradually increases in temperature, and as a result, the electronic component 4 is efficiently radiated. There was a problem that it could not be done and it would become high temperature. The electronic component 4 that has reached a high temperature may malfunction, or may be damaged in the case of a semiconductor element or the like.

  On the other hand, in the present embodiment shown in FIG. 1, the electrons of the N-type semiconductor particles contained in the heat radiation layer 8 on the upper surface of the wiring substrate 5 obtain energy by the heat of the electronic component 9 or the surface of the wiring substrate 5, and the valence electrons Excited from band to conduction band. When the excited electrons fall into a low orbit, they are emitted as light energy having a wavelength corresponding to the band gap.

  As a result, the heat dissipation of the surface of the wiring board 5 can be improved and the temperature rise of the electronic component 9 can be suppressed.

  The reason why the heat radiation of the conductor pattern 7 is generally low is that the conductor pattern 7 is made of a metal that easily reflects incident energy.

  That is, the radiant energy incident on the object surface is divided into whether it is absorbed by the object (absorption rate α), reflected by the surface (reflectance ρ), or transmitted through the object (transmittance τ). If the calculated energy is 1, α + p + τ = 1. Here, since the emissivity and the absorptance are equal, the law of ε = α holds true (Kirchhoff's law), and ε + p + τ = 1 holds from the above equation.

  Therefore, for example, the conductor pattern 7 made of metal does not transmit light, so the transmittance τ is as small as about 0.1, but the reflectance p is as large as about 0.9, and the emissivity is generally small. In addition, many resins have a relatively high emissivity, but it is difficult to obtain sufficient heat dissipation only with existing solder resists. This is because when the thickness is very thin like a solder resist, the transmittance is large and the emissivity tends to be small. Furthermore, the existing solder resist is designed mainly to improve patterning and adhesion, and in order to increase the emissivity, there is a new idea that contains fillers of appropriate materials and particle sizes. This is because it is necessary.

  Moreover, in this Embodiment, sufficient heat dissipation can be obtained, without impairing the ease of exposure as a photosensitive resin, by kneading 5.0 vol% or more of N-type semiconductor particles in the heat radiation layer 8. .

  The reason why the content of the N-type semiconductor particles is set to 40 vol% or less is to ensure electrical insulation between the conductor patterns 7. When the N-type semiconductor particles are subjected to insulation treatment, the content is limited by the viscosity. However, the content can be improved to about 60 vol%. Further, when it is desired to contain more than 60 vol% of N-type semiconductor particles, it is necessary to use a resin having a lower viscosity, or to lower the viscosity with an additive such as a solvent.

  Furthermore, in the present embodiment, the thermal radiation layer 8 contains N-type semiconductor particles having an average particle size of 0.1 μm or more and 20 μm or less, so that the viscosity of the resin composition is increased at a high concentration without excessively increasing the viscosity. Type semiconductor particles can be kneaded, which contributes to improving heat dissipation. If a resin with lower viscosity is used, or if the viscosity can be lowered by an additive such as a solvent, the particle size of the N-type semiconductor particles can be made smaller than 0.1 μm, contributing to heat dissipation. The surface area to be made can be made wider.

  Further, in the present embodiment, since the heat radiation layer 8 contains N-type semiconductor particles, these particles act as a heat conduction filler, and the heat conductivity of the heat radiation layer 8 is higher than that of the resin alone. . Therefore, heat can be easily conducted even inside the heat radiation layer 8, and heat from the heat source is diffused to increase the area, whereby heat can be radiated more efficiently.

  In the present embodiment, the heat radiation layer 8 contains only N-type semiconductor particles, but other heat insulating fillers such as aluminum oxide can also be used in combination. Also in this case, heat is easily conducted inside the heat radiation layer 8, and the heat dissipation on the surface of the wiring board 5 can be further improved.

  Moreover, in this Embodiment, by making the insulating base material 6 contain an inorganic filler, the thermal conductivity of this insulating base material 6 can be improved, and the surface temperature of the wiring board 5 can be lowered.

  The wiring board 5 is not limited to a single layer, and may be a double-sided wiring board or a multilayer wiring board. In any case, if the heat radiation layer 8 is formed on the component mounting surface side of the wiring board 5, the heat dissipation from the surface of the wiring board 5 can be improved. In addition, even if one surface generates heat excessively, it can be quickly radiated by the heat radiation layer 8 on the surface layer, so that the heat capacity conducted to the other surface is reduced and the temperature rise on the other surface is suppressed. it can.

(Embodiment 2)
The difference between the present embodiment and the first embodiment is that, as shown in FIG. 2, the conductor pattern 7 is formed of a thick copper plate, and is embedded on the insulating base 6 so that the surface thereof is exposed. The point is that the heat radiation layer 8 selectively covers the conductor pattern 7. In the present embodiment, the heat sink 10 is disposed on the lower surface of the conductor pattern 7.

  Below, the composition of the member of this Embodiment, etc. are demonstrated.

  The material of the heat radiation layer 8 is the same as that in the first embodiment. In the present embodiment, the content can be set to 40 vol% or more regardless of whether or not the N-type semiconductor particles are insulated.

  As the conductor pattern 7, a tough pitch copper plate having a thickness of 0.1 mm to 2.0 mm was used.

Moreover, as the insulating substrate 6, a thermosetting resin such as an epoxy resin, a phenol resin, or a cyanate resin is filled with 70 to 95% by weight of a filler made of Al ₂ O ₃ , MgO, SiO ₂ , BN, or AlN. Using. The filler particle size was in the range of 0.1 to 100 μm for high concentration filling, and a combination of a large average particle size and a small one was used. If the filler is filled at a high concentration in this way, the thermal conductivity of the insulating base 6 can be improved to 2.0 W / m · K or more.

  In addition, the thickness of the insulating base 6 was set to 0.6 mm or more in order to enhance the withstand voltage.

  As the heat radiating plate 10, an aluminum plate having a thickness of about 0.5 to 3.0 mm was used.

  The manufacturing method in the present embodiment will be described below.

  First, wiring is patterned on a tough pitch copper plate to be the conductor pattern 7 by a press or the like. In this way, a thick metal plate can form wiring by punching or etching, and if the thickness is large, the conductor resistance is low and can cope with a large current.

  Next, a filler-filled resin mass to be the insulating substrate 6 is placed on the conductor pattern 7 and stretched. At this time, the conductor pattern 7 is embedded so that the upper surface (component mounting surface) is exposed on the upper surface of the insulating substrate 6. Further, the heat radiating plate 10 is disposed on the insulating base 6, and the insulating base 6 is formed so as to be sandwiched between the conductor pattern 7 and the heat radiating plate 10.

  Thereafter, the resin component of the insulating base 6 is polymerized and cured at about 200 ° C.

  Finally, the heat radiation layer 8 is formed by screen printing. At this time, the heat radiation layer 8 is formed along the conductor pattern 7.

  The effect in this Embodiment is demonstrated below.

  In the present embodiment, a plate-like conductor pattern 7 having a large thickness (0.1 mm to 2.0 mm) is used as the conductor pattern 7, and the heat radiation layer 8 is formed on the conductor pattern 7. The heat dissipation of the surface of the wiring board 5 can be improved well.

  That is, in this embodiment, since the conductive pattern 7 having excellent thermal conductivity (heat conductivity of about 400 W / m · K) is thickened, the thermal resistance is further reduced, and the conductive pattern 7 further increases the heat of the electronic component 9. The conductor pattern 7 can be efficiently diffused and the thermal energy can be radiated as light energy on the conductor pattern 7.

  As a result, the heat dissipation on the surface of the wiring board 5 can be improved.

  In the present embodiment, the heat radiation layer 8 is not formed on the surface of the insulating base 6 having low thermal conductivity, and the heat radiation layer 8 may be selectively formed on the conductor pattern 7 having a higher temperature. , Leading to cost reduction.

  Further, since it is selectively formed on the conductor pattern 7, N-type semiconductor particles can be contained up to about 60 vol% without considering the electrical insulation, and the heat dissipation is improved.

  In the present embodiment, since the conductor pattern 7 is embedded in the insulating base 6, the surface of the wiring board 5 is substantially flush. Thus, when the unevenness | corrugation of the wiring board 5 surface is small, the heat radiation layer 8 can be easily formed by screen printing.

  In this embodiment, the screen printing method is used when forming the heat radiation layer 8, but electrodeposition coating or the like may be used. In this case, as in the present embodiment, when the conductor pattern 7 is made of a single plate and is entirely conductive, it can be applied at a time, which contributes to an improvement in productivity.

  In the case of electrodeposition coating, the content of N-type semiconductor particles can be improved to about 95 vol%, which contributes to improvement in heat dissipation.

  Further, in the present embodiment, the heat conductivity of the insulating base material 6 is improved to 2 W / m · K or more, and the heat radiating plate 10 is formed on the lower surface of the insulating base material 6 so that the heat radiation layer 8 radiates heat. The heat that could not be exhausted can be released by the heat radiating plate 10 through the insulating base 6, and the temperature rise on the surface of the wiring board 5 can be further effectively suppressed.

  Note that, in the wiring board 5 having a relatively good thermal conductivity as in the present embodiment, as shown in FIG. The overall heat dissipation can be improved.

  In order to improve heat dissipation, it is effective to enlarge the heat dissipation area, so it is also effective to form irregularities in the heat radiation layers 8 and 11.

  In the present embodiment, the conductor pattern 7 is embedded in the insulating base material 6. However, the conductor pattern 7 may be attached to the insulating base material 6 with an adhesive or the like. The conductor pattern 7 may not form a circuit and may be a simple heat diffusion conductor.

  Other configurations and effects are the same as those in the first embodiment, and are omitted.

(Embodiment 3)
As shown in FIG. 4, the difference between the present embodiment and the first embodiment is that the surface of the wiring board 5 on which the conductor pattern 7 is formed is covered with a resin layer 12 (solder resist). The heat radiation layer 8 further covers the upper surface of the layer 12.

  That is, in the present embodiment, the resin layer 12 (solder resist) is formed between the upper surface of the wiring board 5 and the heat radiation layer 8.

  The resin layer 12 and the heat radiation layer 8 cover substantially the entire area of the component mounting surface except for the portion immediately below the electronic component 9 and the soldered portion of the electronic component 9.

  With the above configuration, the heat radiation layer 8 can be formed over substantially the entire upper surface of the wiring board 5 while maintaining electrical insulation between the conductor patterns 7, and even when the conductor pattern 7 is very fine, it is easy. Can be formed.

  Further, since a resin layer that is an insulator is formed below the heat radiation layer 8, the content of the N-type semiconductor particles kneaded in the heat radiation layer 8 can be 40 vol% or more, and the surface of the wiring board 5 The heat dissipation can be further improved.

  When the content of the N-type semiconductor particles is increased, it is desirable that the heat radiation layer 8 be formed slightly inward from the resin layer 12 in order to improve the electrical insulation of the conductor pattern 7.

  Other configurations and effects are the same as those in the first embodiment, and are omitted.

  The present invention can release heat of an electronic component mounted on a wiring board as light energy, so that it is very useful for mounting a semiconductor element or the like whose operation efficiency is reduced or damaged by heat. It is.

Cross-sectional view of wiring board in the present embodiment Cross-sectional view of wiring board in the present embodiment Cross-sectional view of wiring board in the present embodiment Cross-sectional view of wiring board in the present embodiment Cross-sectional view of a conventional wiring board

Explanation of symbols

DESCRIPTION OF SYMBOLS 5 Wiring board 6 Insulation base material 7 Conductor pattern 8 Thermal radiation layer 9 Electronic component 10 Heat sink 11 Thermal radiation layer 12 Resin layer

Claims (7)

An insulating substrate;
In a wiring board provided with a conductor pattern formed on this insulating base material,
This wiring board
A heat radiation layer covering a part or all of the surface on which the conductor pattern is formed;
This heat radiation layer
A wiring substrate containing 5.0 vol% or more N-type semiconductor particles. An insulating substrate;
In a wiring board provided with a conductor pattern formed on this insulating base material,
This wiring board
A resin layer covering a part or all of the surface on which the conductor pattern is formed;
A heat radiation layer covering the resin layer,
This heat radiation layer
A wiring substrate containing 5.0 vol% or more N-type semiconductor particles. The thermal radiation layer is
The wiring board according to claim 1, wherein the wiring board is selectively formed on a surface of the wiring pattern. The thermal radiation layer is
The wiring board according to claim 1, comprising 5.0 vol% or more and 40 vol% or less of N-type semiconductor particles. The thermal radiation layer is
The wiring board according to claim 2 or 3, comprising 5.0 vol% or more and 95 vol% or less of N-type semiconductor particles. The conductor pattern is
The wiring board according to claim 1, wherein the wiring board is embedded on the insulating base so that the surface thereof is exposed. The average particle size of the N-type semiconductor particles is
The wiring board according to claim 1, wherein the wiring board is 0.1 μm or more and 20 μm or less.

Images