JP2002353634A - Multi-layer wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simultaneously achieve high density wiring, heat resistance against soldering, and high frequency characteristics. SOLUTION: The multi-layer wiring board 4 comprises a plurality of laminated insulating layers 1 consisting of organic matter. Each insulating layer is provided with a wiring conductor 2 consisting of metal foil on one of the upper and lower surfaces thereof. Wiring conductors 2 disposed on the top and the bottom of the insulating layer 1 are electrically connected by a through conductor 3 formed through the insulating layer 1. The insulating layer 1 comprises a liquid crystal polymer layer 5 on whose upper and lower surfaces there are formed coating layers 6 consisting of organic matter of polyphenylene ether family and organic matter having an elastic modulus smaller than that of above- mentioned matter. The liquid crystal polymer layer 5 is characterized in that it has a thermal expansion coefficient of -20 to 20 ppm/ deg.C and a tensile elastic modulus of >=2 GPa in the layer direction and the coating layer 6 has a tensile elastic modulus of 0.2 to 1.5 GPa in the layer direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer wiring board for use in electronic devices such as various AV devices, home appliances, communication devices, computers, and peripheral devices thereof. The present invention relates to a multilayer wiring board using a polymer layer.

[0002]

2. Description of the Related Art Conventionally, a multilayer wiring board for forming a hybrid integrated circuit in which a predetermined electronic circuit is formed by mounting a large number of active parts such as semiconductor elements and passive parts such as capacitance elements and resistance elements is usually used. It is formed by laminating a large number of wiring boards in which through holes are formed vertically by drilling in an insulating layer formed by impregnating glass cloth with epoxy resin, and a plurality of wiring conductors are formed inside the through holes and on the surface of the insulating layer. ing.

In general, current electronic devices are required to be small, thin, lightweight, high-performance, high-function, high-quality, and high-reliability, as typified by mobile communication devices. Electronic components such as hybrid integrated circuits mounted on
In order to respond to such demands for higher densities, multilayer wiring boards that make up electronic components are also required to have finer wiring conductors and thinner insulating layers.
It is becoming necessary to miniaturize the through holes. For this reason, in recent years, laser processing that can perform finer processing than drill processing has been used in order to make through holes finer.

However, an insulating layer formed by impregnating a glass cloth with an epoxy resin has a limitation in miniaturizing a through-hole because it is difficult to pierce the glass cloth with a laser. There is a problem that it is difficult to form a through-hole having a uniform diameter due to the uneven thickness.

In order to solve such problems, an insulating base material made by impregnating a non-woven fabric made of aramid resin fiber with an epoxy resin or an insulating base material obtained by applying an epoxy-based adhesive to a polyimide film is used as an insulating layer. A multilayer wiring board used has been proposed.

However, an insulating substrate using an aramid nonwoven fabric or a polyimide film has high hygroscopicity. If solder reflow is performed in a state of absorbing moisture, the moisture absorbed by the heat of the solder reflow vaporizes to generate gas, and an insulating interlayer is generated. With the problem of peeling.

In order to solve such problems, use of a liquid crystal polymer as a material for an insulating layer of a multilayer wiring board has been studied. The layer composed of the liquid crystal polymer is composed of rigid molecules and has a structure in which molecules are regularly arranged to some extent, and has a strong intermolecular force.
Shows high heat resistance, high elastic modulus, high dimensional stability, low moisture absorption,
There is no need to use a reinforcing material such as glass cloth, and it has features of being excellent in fine workability. Further, even in a high-frequency region, it has a characteristic that it has a low dielectric constant and a low dielectric loss tangent and has excellent high-frequency characteristics.

[0008] Utilizing the characteristics of such a liquid crystal polymer,
Japanese Patent Application Laid-Open No. 8-97565 discloses a multi-layer printing method in which an adhesive layer containing a second liquid crystal polymer having a melting point lower than that of the first liquid crystal polymer is inserted between circuit layers containing the first liquid crystal polymer. A circuit board has been proposed.
JP-A-2000-269616 proposes a high-frequency circuit board in which a thermoplastic liquid crystal polymer film and a metal foil are bonded using an epoxy-based adhesive.

[0009] However, in the multilayer printed circuit board proposed in Japanese Patent Application Laid-Open No. 8-97565, the liquid crystal polymer molecules are rigid when the circuit layers are bonded by thermocompression bonding by inserting an adhesive layer containing a liquid crystal polymer therebetween. It is difficult to move, and it is not possible to enter the fine recesses on the surface of the circuit layer, as a result, it is not possible to exert a sufficient anchor effect, the adhesion between the circuit layer and the adhesive layer is poor, There is a problem that insulation failure occurs.

The high-frequency circuit board proposed in Japanese Patent Application Laid-Open No. 2000-269616 has a small thickness caused by pressure during lamination since the dielectric constant of an epoxy-based adhesive is significantly different from that of a liquid crystal polymer. Due to the variation, there is a problem that transmission characteristics are degraded in a high frequency region, particularly in a frequency region of 100 MHz or higher.

In order to solve such a problem, the applicant of the present invention disclosed in Japanese Patent Application No. 2001-53834 a plurality of insulating layers formed by forming a coating layer made of a polyphenylene ether organic material on the upper and lower surfaces of a liquid crystal polymer layer. A laminated multilayer wiring board was proposed.

[0012]

However, a multilayer wiring board comprising a plurality of insulating layers formed by forming a coating layer made of a polyphenylene ether-based organic material on the upper and lower surfaces of a liquid crystal polymer layer has a thermal expansion coefficient of the coating layer. Since the thermal expansion coefficient of the liquid crystal polymer layer is different, cracks tend to occur in the coating layer in a temperature cycle test involving a rapid temperature change. There is also a method of preventing the cracks in the temperature cycle test by filling the coating layer with the inorganic insulating powder at a high density and making the thermal expansion coefficient of the coating layer substantially coincide with the thermal expansion coefficient of the liquid crystal polymer layer.
The adhesion between the coating layer and the wiring conductor is deteriorated, so that the wiring conductor cannot be adhered and formed. In addition, when the insulation layers are bonded to each other, the adhesion between the coating layers forming the insulation layer is deteriorated, and the insulation layer is formed. , And the insulating property is liable to be deteriorated.

The present invention has been devised in view of the above-mentioned problems of the prior art, and has as its object the purpose of having high-density wiring, and being excellent in solder heat resistance, insulation, high-frequency transmission characteristics, and temperature cycle characteristics. To provide a multi-layer wiring board.

[0014]

A multilayer wiring board according to the present invention is formed by laminating a plurality of insulating layers made of an organic material and having a wiring conductor made of a metal foil on at least one of upper and lower surfaces. A multilayer wiring board in which wiring conductors located above and below the insulating layer are electrically connected via through conductors formed in the insulating layer, and the insulating layer is provided on upper and lower surfaces of the liquid crystal polymer layer. The liquid crystal polymer layer has a thermal expansion coefficient of −20 to 20 ppm / ° C. in a layer direction and a tensile elasticity of 2 GPa, which is formed by forming a coating layer made of a polyphenylene ether-based organic substance and an organic substance having a lower elastic modulus. As described above, the coating layer has a tensile elastic modulus in the layer direction of 0.2 to 1.5 GPa.

The multilayer wiring board of the present invention is characterized in that the coating layer contains 5 to 60% by volume of an organic substance having a low elastic modulus.

Further, the multilayer wiring board of the present invention is characterized in that the low elastic modulus organic substance contains 20 to 80% by volume of a stin-based organic substance.

Further, the multilayer wiring board of the present invention is characterized in that the total thickness of the covering layer is 10 to 70% of the thickness of the insulating layer.

According to the multilayer wiring board of the present invention, the insulating layer is formed by forming a coating layer made of a polyphenylene ether-based organic substance and an organic substance having a lower elastic modulus on the surface of the liquid crystal polymer layer. It is possible to form fine through-holes, and as a result, it is possible to obtain a multilayer wiring board having high-density wiring, and the frequency behavior of the dielectric constant of the liquid crystal polymer layer and that of the coating layer are substantially equal. Therefore, even if a slight thickness variation occurs during the lamination, it is possible to obtain excellent high-frequency transmission characteristics without lowering the transmission characteristics in the high-frequency region. The liquid crystal polymer layer has a coefficient of thermal expansion in the layer direction of −20 to 20 ppm / ° C., a tensile modulus of elasticity of 2 GPa or more, and the coating layer has a tensile modulus of 0.2 to 0.2 GPa in the layer direction. Since the thermal expansion coefficient is set to 1.5 GPa, when the coating layer made of a polyphenylene ether-based organic material having a relatively large coefficient of thermal expansion thermally expands and contracts due to a temperature change, the elastic modulus of the coating layer is 0.2 to 1.5 GPa. Due to the low elasticity, the thermal expansion and thermal contraction of the coating layer are restricted by the liquid crystal polymer layer with a low coefficient of thermal expansion and high elasticity,
Thermal expansion and thermal contraction of the coating layer can be reduced. As a result, cracks do not occur in the coating layer even in a temperature cycle test involving a rapid temperature change.
Further, since it is not necessary to fill the coating layer with the inorganic insulating powder at high density, the adhesion between the coating layers can be improved, and the insulating property may be reduced due to peeling between the insulating layers. Absent.

Further, according to the multilayer wiring board of the present invention, in the above configuration, the coating layer contains an organic substance having a lower elastic modulus than the polyphenylene ether-based organic substance in an amount of 5 to 60% by volume. It can easily be in the range of 0.2 to 1.5 GPa.

Further, according to the multilayer wiring board of the present invention,
In the above configuration, since the low elastic modulus organic substance contains 20 to 80% by volume of the styrene organic substance, the styrene organic substance has a low dielectric constant and a low dielectric loss tangent, and thus has a low dielectric constant and a low dielectric loss tangent.
A multilayer wiring board having excellent transmission characteristics even at a high frequency of MHz or higher can be obtained.

Further, according to the multilayer wiring board of the present invention, in the above configuration, the total of the thickness of the covering layer is reduced by the thickness of the insulating layer.
Since the content is set to 10 to 70%, a multilayer wiring board having good adhesion to the wiring conductor, high heat resistance, low moisture absorption, and high dimensional stability can be obtained.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a multilayer wiring board according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an example of an embodiment of a hybrid integrated circuit in which a semiconductor element is mounted on a multilayer wiring board of the present invention. FIG. 2 is a cross-sectional view of the multilayer wiring board shown in FIG. 3 is an enlarged sectional view of a main part of FIG. In these figures, reference numeral 1 denotes an insulating layer, 2 denotes a wiring conductor, and 3 denotes a through conductor, and these mainly constitute a multilayer wiring board 4 of the present invention. In this example, a multi-layer wiring board 4 formed by laminating four insulating layers 1 is shown.

The insulating layer 1 is composed of a liquid crystal polymer layer 5 and a coating layer 6 made of a polyphenylene ether-based organic substance and an organic substance having a lower elastic modulus than the liquid crystal polymer layer 5 on the surface thereof. 4 has a function as a support for the electronic components 7 and the wiring conductors 2 mounted on the electronic component 7.

Here, the liquid crystal polymer refers to a polymer having a liquid crystal state or an optically birefringent property when melted, and generally a lyotropic liquid crystal polymer which exhibits liquid crystallinity in a solution state or a thermotropic liquid crystalline polymer which exhibits liquid crystallinity when melted. It includes a liquid crystal polymer or a liquid crystal polymer of all types 1, 2, and 3 classified by heat distortion temperature. The polyphenylene ether-based organic material is a polyphenylene ether resin or a resin in which various functional groups are bonded to polyphenylene ether, or a derivative or a derivative thereof.
It means a polymer.

In the multilayer wiring board 4 of the present invention, the liquid crystal polymer layer 5 has a thermal expansion coefficient in the layer direction of −20 to -20 from the viewpoint of temperature cycle reliability, solder heat resistance and workability.
20 ppm / ° C and a tensile modulus of 2 GPa
As described above, the melting point is preferably 200 to 400 ° C. The liquid crystal polymer layer 5 has a thermal expansion coefficient of −20 ppm / ° C.
If it is less than 20 ° C., the difference in the thermal expansion coefficient between the liquid crystal polymer layer 5 and the coating layer 6 tends to increase, and the coating layer 6 tends to crack, and if it exceeds 20 ppm / ° C., the insulating layer 1 and the wiring conductor 2 has a large thermal expansion coefficient, and the coating layer 6 tends to crack in the vicinity of the wiring conductor 2. If the tensile modulus is less than 2 GPa, the bending strength of the insulating layer 1 tends to be small, and the multilayer wiring board 4 tends to be warped. Therefore, the liquid crystal polymer layer 5
It is preferable that the thermal expansion coefficient in the layer direction is −20 to 20 ppm / ° C., and the tensile elastic modulus is preferably 2 GPa or more. In particular, from the viewpoint of connection reliability when the electronic component 7 is mounted, the thermal expansion coefficient -10 to 10 ppm / ° C, melting point 250
Those having a temperature of ~ 350 ° C are preferred.

The liquid crystal polymer layer 5 includes a light stabilizer such as an antioxidant for improving thermal stability and an ultraviolet absorber for improving light resistance, as long as the physical properties of the layer are not impaired. Halogen or phosphoric acid flame retardants to improve flame retardancy, antimony compounds and zinc borate
Flame retardant aids such as barium metaborate and zirconium oxide,
Lubricants such as higher fatty acids, higher fatty acid esters, higher fatty acid metal salts, fluorocarbon surfactants and the like for improving lubricity, aluminum oxide for adjusting thermal expansion coefficient and / or improving mechanical strength, Silicon oxide, titanium oxide, barium oxide, strontium oxide
Zirconium oxide, calcium oxide, zeolite, silicon nitride, aluminum nitride, silicon carbide, potassium titanate, barium titanate, strontium titanate, calcium titanate, aluminum borate, barium stannate.
A filler such as barium zirconate and strontium zirconate may be contained.

The particle shape of the above-mentioned filler and the like includes a substantially spherical shape, a needle shape, a flake shape and the like, and a substantially spherical shape is preferable from the viewpoint of the filling property. Further, the particle size is usually 0.1 to 15 μm
And smaller than the thickness of the liquid crystal polymer layer 5.

Further, the surface of the liquid crystal polymer layer 5 is subjected to a method such as buff polishing, blast polishing, brush polishing, plasma treatment, corona treatment, ultraviolet treatment, chemical treatment, etc. in order to enhance the adhesion to the coating layer 6. Using center line surface roughness Ra
Is preferably roughened to a value of 0.05 to 5 μm. The center line surface roughness Ra is preferably 0.05 μm or more from the viewpoint of preventing separation of the liquid crystal polymer layer 5 and the coating layer 6 during solder reflow. When the coating layer 6 is formed on the surface, From the viewpoint of preventing air entrapment, the thickness is preferably 5 μm or less.

Next, the covering layer 6 is formed by forming the wiring conductor 2 on the insulating layer 1.
Has the function of an adhesive when forming and adhering, and also functions as an adhesive when the insulating layers 1 are laminated. Such a coating layer 6 is made of a polyphenylene ether-based organic material and an organic material having a lower elastic modulus than the above, and preferably has a tensile elastic modulus in the layer direction of 0.2 to 1.5 GPa.
This is also important.

According to the multilayer wiring board 4 of the present invention, the insulating layer 1 is formed by forming a coating layer 6 made of a polyphenylene ether-based organic substance and an organic substance having a lower elastic modulus on the surface of the liquid crystal polymer layer 5. Therefore, it is possible to form fine through holes, and as a result, it is possible to obtain a multilayer wiring board 4 having high-density wiring,
Since the frequency behavior of the dielectric constant of the liquid crystal polymer layer 5 and that of the coating layer 6 are almost equal, even if a slight thickness variation occurs during lamination, the high frequency transmission characteristics are not deteriorated in the high frequency region. It can be.

The polyphenylene ether-based organic substance is contained in the coating layer 6 in an amount of 20 to 80% by volume, and a polyphenylene ether resin or a derivative thereof, or a polymer alloy thereof is used. In particular, it is preferable to contain a thermosetting polyphenylene ether such as an allyl-modified polyphenylene ether from the viewpoint of heat cycle reliability and positional accuracy during lamination. If the content of the polyphenylene ether-based organic substance is less than 20% by volume, the kneadability tends to decrease. If the content exceeds 80% by volume, the coating layer 6 is formed on the surface of the liquid crystal polymer layer 5 when the coating layer 6 is formed. The thickness variation of the layer 6 tends to increase. Therefore, the content of the polyphenylene ether-based organic substance is preferably in the range of 20 to 80% by volume.

According to the multilayer wiring board 4 of the present invention,
Since the tensile elastic modulus in the layer direction of the coating layer 6 is set to 0.2 to 1.5 GPa, when the coating layer 6 containing a polyphenylene ether-based organic substance having a relatively large thermal expansion coefficient undergoes thermal expansion and thermal contraction due to temperature change, The elastic modulus of the coating layer 6 is 0.2 to
Due to the low elasticity of 1.5 GPa, thermal expansion of the coating layer 6
The thermal contraction is restrained by the liquid crystal polymer layer 5 having a small coefficient of thermal expansion and a high elastic modulus, so that the thermal expansion and thermal contraction of the coating layer 6 can be reduced. As a result, cracks do not occur in the coating layer 6 even in a temperature cycle test involving a rapid temperature change. In addition, since it is not necessary to fill the coating layer 6 with the inorganic insulating powder at a high density, the adhesion between the coating layers 6 can be improved, and
There is no possibility that insulation is deteriorated due to peeling between them.

The coating layer 6 has a tensile modulus of 0.2 GP.
If it is less than a, the rigidity of the multilayer wiring board 4 will be small, and the multilayer wiring board 4 will be warped and the wiring conductor layer 2 tends to be disconnected. If the pressure exceeds 1.5 GPa, it tends to be difficult for the liquid crystal polymer layer 5 to restrain the coating layer 6 at a high temperature. As a result, the liquid crystal polymer layer 5 is stretched to increase the thermal expansion of the multilayer wiring board 4. And the connection with the electronic component 7 tends to be broken. Therefore, the coating layer 6 has a tensile elasticity of 0.2 to 1.5 G.
Pa, preferably 0.7 to 1.2 GPa.

The coating layer 6 contains 5 to 60% by volume of an organic substance having a lower elastic modulus than that of the polyphenylene ether-based organic substance, and this is important.

According to the multilayer wiring board 4 of the present invention, the coating layer 6 contains 5 to 60% by volume of an organic substance having a lower elastic modulus than that of the polyphenylene ether-based organic substance.
Can easily be in the range of 0.2 to 1.5 GPa. When the content of the organic substance having a lower elastic modulus than that of the polyphenylene ether-based organic substance is less than 5% by volume, the effect of lowering the tensile elasticity of the coating layer 6 tends to be not exhibited, and more than 60% by volume. In addition, the tensile elastic modulus of the coating layer 6 becomes too low, and the multilayer wiring board 4 becomes soft and warps, and as a result, the wiring conductor layer 2 tends to be disconnected. Therefore, the content of the organic substance having a lower elastic modulus than the polyphenylene ether-based organic substance of the coating
It is preferred that the volume percentage is, optimally, 20 to 40 volume%.

As the organic substance having an elastic modulus lower than that of the polyphenylene ether-based organic substance, a resin or rubber-like elastic body having an elastic modulus of 1 GPa or less is used. For example, natural rubber, polybutadiene / polyisoprene / polyisobutylene / neoprene are used. -Polysulfide rubber-Thiokol rubber-Acrylic rubber-Urethane rubber-Silicone rubber-Ebichlorohydrin rubber-Styrene-butadiene block copolymer (SBR)-Hydrogenated styrene-butadiene block copolymer (SEB / SEBC)-Styrene-butadiene- Styrene block copolymer (SBS) / hydrogenated styrene-butadiene-styrene block copolymer (S
EBS) · Styrene-isoprene block copolymer (S
IR) hydrogenated styrene-isoprene block copolymer (SEP) styrene-isoprene-styrene block copolymer (SIS) hydrogenated styrene-isoprene-styrene block copolymer (SEPS) ethylene propylene rubber (EPR) -Ethylene propylene diene rubber (EPDM)-Butadiene-acrylonitrile-styrene-core-shell rubber (ABS)-Methyl methacrylate-butadiene-styrene-core-shell rubber (MBS)
・ Methyl methacrylate-butyl acrylate-styrene-core-shell rubber (MAS) ・ Octyl acrylate-butadiene-styrene-core-shell rubber (MABS)
Core-shell type particle-like elastic bodies such as alkyl acrylate-butadiene-acrylonitrile-styrene core-shell rubber (ABS), butadiene-styrene-core-shell rubber (SBR), and siloxane-containing core-shell rubber such as methyl methacrylate-butyl acrylate siloxane; or Modified rubbers and the like are used.

These organic substances having a low elastic modulus may be modified by a modifier having a polar group such as maleic anhydride or epoxy. Furthermore, these organic substances having a low elastic modulus may be used alone or in combination of two or more.

Further, in the multilayer wiring board 4 of the present invention, it is preferable that the low elastic modulus organic substance contains 20 to 80% by volume of a styrene organic substance. Multilayer wiring board 4 of the present invention
According to this, since the styrene-based organic substance has a low dielectric constant and a low dielectric loss tangent, the multilayer wiring board 4 having excellent transmission characteristics even at a high frequency of 100 MHz or more can be obtained.

The low elastic modulus organic material containing such a styrene-based organic material is an organic material having styrene as a monomer unit in the molecular structure, and particularly, SBR or SBR.
EB / SEBC / SBS / SEBS / SIR / SEP /
SIS and SEPS, or organic substances having a low elastic modulus modified from these are used.

If the content of the styrene-based organic substance is less than 20% by volume, the dielectric constant and the dielectric loss tangent of the organic substance having a low elastic modulus become large, and the transmission characteristics in a high-frequency region of 100 MHz or more deteriorate. When the content exceeds 80% by volume, the modulus of elasticity of the organic material having a low modulus of elasticity increases, so that it tends to be difficult to set the tensile modulus of the coating layer 6 in a desired range. Therefore, the content of styrenic organic matter is 20
~ 80% by volume is preferred.

The coating layer 6 has two or more functional groups capable of performing a polymerization reaction from the viewpoint of improving the adhesiveness with the liquid crystal polymer layer 5 and the adhesiveness with the wiring conductor 2 and the through conductor 3. It is preferable to contain an additive such as a polyfunctional monomer or a polyfunctional polymer. For example, it is preferable to contain triallyl cyanurate, triallyl isocyanurate, and a polymer thereof.

Further, when the insulating layer 1 is laminated and pressed, the fluidity of the covering layer 6 is suppressed, and from the viewpoint of preventing the displacement of the through conductor 3 and the thickness variation of the covering layer 6 described below, The coating layer 6 preferably contains 10% by volume or more of inorganic insulating powder as a filler. Further, from the viewpoint of preventing peeling at the time of solder reflow at the bonding interface with the liquid crystal polymer layer 5 and the bonding interface with the wiring conductor 2, the content of the filler is preferably set to 70% by volume or less. Therefore, it is preferable that the coating layer 6 contains 10 to 70% by volume of the filler.

The thickness of the insulating layer 1 is preferably from 10 to 200 μm from the viewpoint of securing insulation reliability, and the total thickness of the coating layer 6 improves the adhesion to the wiring conductor 2. From the viewpoint of making the thickness of the insulating layer 1 10
% Is preferable. Furthermore, from the viewpoint of ensuring high heat resistance, low moisture absorption and high dimensional stability, 70%
It is preferable to set the following. Therefore, the total thickness of the coating layer 6 is preferably set to 10 to 70% of the thickness of the insulating layer 1.

The insulating layer 1 has, for example, a particle size of 0.1.
A paste obtained by adding a thermosetting polyphenylene ether resin and an organic substance, a solvent, a plasticizer, a dispersant, etc. having a lower modulus of elasticity to an inorganic insulating powder such as silicon oxide having a thickness of about 15 μm is placed above and below the liquid crystal polymer layer 5. The surface of the liquid crystal polymer layer 5 is formed by forming the coating layer 6 on the surface by using a conventionally known sheet forming method such as a doctor blade method, or by immersing the liquid crystal polymer layer 5 in the above-mentioned paste and vertically lifting the same. After forming the coating layer 6, it is manufactured by heating and drying at a temperature of 60 to 100 ° C. for 5 minutes to 3 hours.

Next, the wiring conductor 2 is formed on the insulating layer 1 on at least one of the upper and lower surfaces. The wiring conductor 2 has a thickness of 2 to 30 μm and is made of a highly conductive metal foil such as copper or gold.
Is electrically connected to an external electric circuit (not shown).

In order to prevent the occurrence of voids around the wiring conductor 2 when a plurality of the insulating layers 1 are stacked, such a wiring conductor 2 is formed on the coating layer 6 at least on the surface of the wiring conductor 2. It is preferable that the surface of the coating layer 6 is buried so as to be flat. Further, when the porosity of the coating layer 6 in the dry state is set to 3 to 40% by volume when the wiring conductor 2 is embedded in the coating layer 6, the coating layer 6 around the wiring conductor 2 may be formed.
The resin can be flattened without causing resin swelling, and the air trapped between the wiring conductor 2 and the coating layer 6 can be easily discharged to prevent air bubbles from being trapped. When the porosity in the dry state exceeds 40% by volume,
After the plurality of laminated insulating layers 1 are pressurized and heated and hardened, pores remain in the coating layer 6, and the pores may absorb moisture in the air and the insulating property may be reduced.
It is preferable to set the porosity in the dry state to a range of 3 to 40% by volume.

The porosity of the coating layer 6 in the dry state can be adjusted by appropriately controlling the drying conditions such as the drying temperature and the heating rate when the coating layer 6 is applied on the surface of the liquid crystal polymer layer 5 and dried. By doing so, the porosity can be set to a desired value.

It is preferable that the thickness of the coating layer 6 located between the wiring conductor 2 and the liquid crystal polymer layer 5 is 3 to 35 μm. Assuming that the thickness of the coating layer 6 located between the wiring conductor 2 and the liquid crystal polymer layer 5 is 3 to 35 μm,
By bringing the wiring conductor 2 and the liquid crystal polymer layer 5 having a low dielectric loss tangent closer to each other, the dielectric loss tangent around the wiring conductor 2 can be reduced, and as a result, the transmission characteristics in the high frequency region, particularly in the frequency region of 100 MHz or more, are further improved. Can be done. If the thickness of the coating layer 6 is less than 3 μm, the stress generated by the thermal expansion and contraction of the wiring conductor 2 cannot be effectively relieved by the coating layer 6, and cracks are formed from the corners of the wiring conductor 2. Tend to occur,
If it exceeds 35 μm, the effect of lowering the dielectric loss tangent around the wiring conductor 2 tends to decrease. Therefore, the wiring conductor 2
The thickness of the coating layer 6 located between the
It is preferable that the thickness be in the range of about 35 μm.

Further, the wiring conductor 2 provided on the insulating layer 1
Has a trapezoidal shape in which the length of the base on the insulating layer 1 side is shorter than the length of the opposing base, and the angle between the base and the side on the insulating layer 1 side is 95 to 150 °. It is preferable that The cross-sectional shape in the width direction of the wiring conductor 2 disposed on the insulating layer 1 is trapezoidal in which the length of the base on the side of the insulating layer 1 is shorter than the length of the opposite base, and the width of the base on the side of the insulating layer 1 is reduced. By setting the angle between the side and the side at 95 to 150 °, when the wiring conductor 2 is embedded in the coating layer 6, the wiring conductor 2
Can be easily embedded in the coating layer 6. In addition, from the viewpoint of burying without entrapping air bubbles, it is preferable that the angle between the bottom side and the side of the insulating layer 1 is 95 ° or more, and from the viewpoint of miniaturizing the wiring conductor 2, it is 15 °.
Preferably, it is 0 ° or less.

The thickness x (μm) of the coating layer 6 located between the short base of the wiring conductor 2 and the liquid crystal polymer layer 5 between the insulating layers 1 is set between the upper and lower liquid crystal polymer layers 5. Is T (μm), and the thickness of the wiring conductor 2 is t (μm).
m), 3 μm ≦ 0.5T−t ≦ x ≦ 0.5T ≦ 35
μm (8 μm ≦ T ≦ 70 μm, 1 μm ≦ t ≦ 32 μm
m) is preferred.

The distance between the liquid crystal polymer layers 6 is T (μm),
When the thickness of the wiring conductor 2 is t (μm), the thickness x (μm) of the coating layer 6 between the short base of the wiring conductor 2 and the liquid crystal polymer layer 5 is 3 μm ≦ 0.5T−t ≦ x ≦ 0.5T ≦ 35μ
m, the difference between the distance between the short bottom of the wiring conductor 2 and the liquid crystal polymer layer 5 and the distance between the long bottom of the wiring conductor 2 and the adjacent liquid crystal polymer layer 5 is represented by t (μ).
m), the dispersion of the dielectric loss tangent around the wiring conductor 2 can be reduced, and as a result, a decrease in transmission characteristics can be prevented. Therefore, the thickness x (μm) of the covering layer 6 located between the trapezoidal upper bottom surface of the wiring conductor 2 and the liquid crystal polymer layer 5 is defined as T (μm), the distance between the liquid crystal polymer layers 6 is defined as T (μm). Assuming that the thickness of No. 2 is t (μm), it is preferable that the range of 3 μm ≦ 0.5T−t ≦ x ≦ 0.5T ≦ 35 μm is satisfied.

Such a wiring conductor 2 is formed by forming a pattern on a precursor sheet to be the insulating layer 1 by a subtractive method using a known photoresist, for example, by applying a metal foil made of copper by a transfer method or the like. It is formed by doing. First, a metal foil transfer film is prepared by bonding a metal foil made of copper on a film serving as a support with an adhesive, and then the metal foil on the film is subjected to a subtractive method using a known photoresist. Is used to etch in a pattern. At this time, the side surface on the front surface side of the pattern is more likely to be etched because it has a longer time in contact with the etching solution than the side surface on the film side, and the cross-sectional shape in the width direction of the pattern can be trapezoidal. The trapezoidal shape can be formed by adjusting the concentration of the etching solution and the etching time so that the angle between the short bottom and the side is 95 to 150.
° trapezoidal shape. Then, this metal foil transfer film is laminated on a precursor sheet to be the insulating layer 1,
After hot pressing at a temperature of 100 to 200 ° C. and a pressure of 0.5 to 10 MPa for 10 minutes to 1 hour, the film serving as the support is peeled off and the metal foil is transferred to the surface of the precursor sheet serving as the insulating layer 1. As a result, the short base of the trapezoid is
Can be formed.

The thickness x (μm) of the coating layer 6 between the liquid crystal polymer layer 5 and the base having the shorter length of the wiring conductor 2.
Can be set in the range of 3 to 35 μm by adjusting the pressure of the hot press during the transfer of the metal foil. The surface of the wiring conductor 2 is preferably roughened by a process such as buffing, blasting, brushing, or chemical treatment in order to enhance the adhesion to the coating layer 6.

The insulating layer 1 has a diameter of 20 to 150 μm.
The through conductor 3 is formed to a degree. The through conductor 3 has a function of electrically connecting the wiring conductors 2 positioned above and below the insulating layer 1, and after forming a through hole by drilling the insulating layer 1 with a laser, Copper /
It is formed by embedding a conductive paste made of silver, gold, solder or the like by a conventionally known screen printing method.

According to the multilayer wiring board 4 of the present invention, the insulating layer 1 has the coating layer 6 made of a polyphenylene ether-based organic material and an organic material having a lower elastic modulus than the liquid crystal polymer layer 5 on the upper and lower surfaces. From the liquid crystal polymer layer 5
Has high heat resistance, high elastic modulus, high dimensional stability, and low hygroscopicity, making it possible to form the insulating layer 1 without using a reinforcing material such as glass cloth. As a result, laser drilling This facilitates fine and uniform through holes.

In such a multilayer wiring board 4, a through conductor 3 is formed at a desired position on a precursor sheet serving as an insulating layer 1 manufactured by the method described above, and then a patterned metal foil of, for example, copper is formed. , Temperature is 100 ~ 200 ℃ and pressure is 0.5 ~ 10
Transfer by hot pressing under the condition of MPa for 10 minutes to 1 hour,
These are laminated and finally the temperature is 150-300 ° C and the pressure is 0.
It is manufactured by hot-pressing under conditions of 5 to 10 MPa for 30 minutes to 24 hours to completely cure.

Thus, according to the multilayer wiring board 4 of the present invention, the insulating layer 1 is formed by forming the coating layer 6 made of a polyphenylene ether organic substance and an organic substance having a lower elastic modulus than the liquid crystal polymer layer 5 on the surface of the liquid crystal polymer layer 5. The liquid crystal polymer layer 5 has a coefficient of thermal expansion in the layer direction of -20 to 20 pp.
m / ° C., the tensile modulus is 2 GPa or more, and the coating layer 6 has a tensile modulus in the layer direction of 0.2 to 1.5 GP.
As a result, the multilayer wiring board 4 having high-density wiring and having excellent solder heat resistance, insulation properties, high-frequency transmission characteristics, and temperature cycle properties can be obtained.

The multilayer wiring board 4 of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention. Manufactured the multilayer wiring board 4 by laminating the four insulating layers 1;
The multilayer wiring board 4 may be manufactured by laminating more than one insulating layer 1. Further, on the upper and lower surfaces of the multilayer wiring board 4 of the present invention,
One, two, or three or more build-up layers or solder resist layers composed of an insulating layer mainly containing an organic resin may be formed.

[0060]

According to the multilayer wiring board of the present invention, the insulating layer is formed by forming a coating layer made of a polyphenylene ether-based organic substance and an organic substance having a lower elastic modulus than this on the surface of the liquid crystal polymer layer. Therefore, it is possible to form fine through holes, and as a result, it is possible to obtain a multilayer wiring board having high-density wiring, and the frequency behavior of the dielectric constant of the liquid crystal polymer layer and the coating layer is substantially reduced. Since they are equal to each other, even if a slight thickness variation occurs during lamination, it is possible to obtain excellent high-frequency transmission characteristics without lowering the transmission characteristics in the high-frequency region.
The liquid crystal polymer layer has a coefficient of thermal expansion in the layer direction of −20 to 20 ppm / ° C., a tensile modulus of elasticity of 2 GPa or more, and the coating layer has a tensile modulus of 0.2 to 0.2 GPa in the layer direction. Since it is assumed to be 1.5 GPa, when the coating layer made of a polyphenylene ether-based organic material having a relatively large coefficient of thermal expansion thermally expands and contracts due to temperature change, the elastic modulus of the coating layer is 0.2 to 1.5 GPa. Due to the low elasticity, the thermal expansion and thermal contraction of the coating layer are restrained by the liquid crystal polymer layer having a low thermal expansion coefficient and a high elastic modulus, and the thermal expansion and thermal contraction of the coating layer can be reduced. . As a result, cracks do not occur in the coating layer even in a temperature cycle test involving a rapid temperature change. Further, since it is not necessary to fill the coating layer with the inorganic insulating powder at high density, the adhesion between the coating layers can be improved, and the insulating property may be reduced due to peeling between the insulating layers. Absent.

Further, according to the multilayer wiring board of the present invention, since the coating layer contains 5 to 60% by volume of an organic substance having a lower elastic modulus than that of the polyphenylene ether-based organic substance, the elastic modulus of the coating layer can be easily reduced to 0.2 to 60%. It can be in the range of 1.5 GPa.

Further, according to the multilayer wiring board of the present invention,
Since the low elastic modulus organic material contains 20 to 80% by volume of the styrene organic material, the styrene organic material has a low dielectric constant
By having a low dielectric loss tangent, a multilayer wiring board having excellent transmission characteristics even at a high frequency of 100 MHz or more can be obtained.

According to the multilayer wiring board of the present invention, since the total thickness of the covering layer is 10 to 70% of the thickness of the insulating layer, the adhesion to the wiring conductor is good, and the heat resistance and the heat resistance are low. It is possible to obtain a multi-layer wiring board having hygroscopicity and high dimensional stability.

[Brief description of the drawings]

FIG. 1 is an example of an embodiment of a hybrid integrated circuit in which a semiconductor element is mounted on a multilayer wiring board of the present invention.

FIG. 2 is an enlarged sectional view of a main part of the multilayer wiring board of the present invention.

[Explanation of symbols]

 1. Insulating layer 2. Wiring conductor 3. Through conductor 4. .... Multilayer wiring board 5 ... Liquid crystal polymer layer 6 ... Coating layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J002 AC01X AC03X AC06X AC08X AC09X AC11X BB15X BB18X BG04X BN11X BN13X BN15X BN16X BP01X CH04X CH07W CK02X CN02X CP03X GQ01 5E346 AA12 A32 AA32 AA12 AA12 AA12 AA12 AA12 AA12 CC EE13 EE18 FF01 GG15 GG28 HH11 HH16 HH18 HH26

Claims (4)

[Claims] 1. An insulating material comprising a plurality of insulating layers made of an organic material and having a wiring conductor made of a metal foil disposed on at least one of upper and lower surfaces, and located above and below the insulating layer. A multilayer wiring board in which the wiring conductors are electrically connected to each other via a through conductor formed in the insulating layer, wherein the insulating layer has a polyphenylene ether-based organic substance on upper and lower surfaces of a liquid crystal polymer layer and a lower conductive material. The liquid crystal polymer layer has a thermal expansion coefficient in a layer direction of -20 to 20 ppm.
/ ° C, the tensile elastic modulus is 2 GPa or more, and the coating layer has a tensile elastic modulus in a layer direction of 0.2 to 0.2 GPa.
A multilayer wiring board having a pressure of 1.5 GPa. 2. The multilayer wiring board according to claim 1, wherein the coating layer contains the organic material having a low elastic modulus in an amount of 5 to 60% by volume. 3. The multilayer wiring board according to claim 1, wherein the organic material having a low elastic modulus contains 20 to 80% by volume of a styrene-based organic material. 4. The multilayer wiring board according to claim 1, wherein the total thickness of said coating layer is 10 to 70% of the thickness of said insulating layer.