JP2003101202A - Wiring board and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a wring board which can improve reliability by enhancing tight contact between a core substrate and a protection layer. SOLUTION: In the wiring board, the protection layer 3 including inorganic insulation powder 12 and an organic resin is formed on the surface of the core substrate 1, amount of inorganic insulation powder 12 in the protection layer 3 in the side of the core substrate 1 is larger than that in the side of surface 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board and a method for manufacturing the wiring board, and more particularly, to a wiring board formed by laminating and curing a protective layer formed by using an uncured insulating layer sheet together with a core board at one time. Regarding the manufacturing method.

[0002]

2. Description of the Related Art Conventionally, in a wiring board in which a wiring circuit layer is formed on the surface and / or inside of an insulating substrate formed by laminating a plurality of insulating layers containing an organic resin, when mounting an electronic component or the like. In order to prevent the solder flow, a protective layer containing a photosensitive resin is formed on the surface of the core substrate that is pre-cured and formed.

Such a protective layer is usually printed on the entire surface of the core substrate by screen printing using a photosensitive resin paste having a relatively high viscosity containing a photosensitive resin and an inorganic insulating powder and then using a mask. Exposed to light, developed, and then recured by heating.

[0004]

However, in the above-mentioned conventional wiring board, in order to increase the light transmittance of the printed photosensitive resin paste and to increase the photo-curing degree of the photosensitive resin constituting the protective layer. The amount of inorganic insulating powder in the photosensitive resin paste is adjusted to be small. Therefore, the thermal expansion coefficient of the protective layer is close to the thermal expansion coefficient of the photosensitive resin itself, the thermal expansion coefficient difference between the protective layer and the core substrate is large, cracks and peeling in the protective layer in the temperature cycle test and the like. There is a problem in that it is likely to occur and reliability is reduced.

Further, such a protective layer is formed on the surface of the core substrate once cured, and a protective layer different from the organic resin constituting the core substrate is used. Therefore, even if the re-hardening treatment is performed by heating, there is a problem that the adhesive force between the core substrate and the protective layer is weak and the protective layer is peeled off from the surface of the core substrate.

Therefore, it is an object of the present invention to provide a wiring board which can improve the reliability by improving the adhesion between the core board and the protective layer, and a method for manufacturing the wiring board.

[0007]

A wiring board of the present invention is a wiring board in which a protective layer containing an inorganic insulating powder and an organic resin is formed on the surface of a core substrate, wherein the core in the protective layer is It is characterized in that the amount of the inorganic insulating powder on the substrate side is larger than that on the surface side.

According to this structure, since the inorganic insulating powder contained in the protective layer is dense on the core substrate side and sparse on the opposite surface side, the thermal expansion at the interface between the core substrate and the protective layer. The coefficient difference becomes small, and cracks and peeling do not occur in the protective layer even in a temperature cycle test or the like, and reliability can be improved. On the other hand, since the organic resin has a high concentration on the surface side of the protective layer opposite to the core substrate, the wiring substrate surface can be made flexible and cracks and cracks can be prevented, and at the same time, the water resistance of the wiring substrate can be increased. .

In the above wiring board, the amount of the inorganic insulating powder contained in the entire protective layer is preferably 40% by mass or more. By including a large amount of inorganic insulating powder in the entire protective layer, the thermal expansion coefficient of the protective layer can be reduced,
The difference in coefficient of thermal expansion between the core substrate and the protective layer can be made closer.

In the above wiring board, the thickness of the protective layer is 5 μm.
The above is desirable. By forming the protective layer thick in this way, it is possible to improve the moisture resistance of the wiring board and increase the difference in density of the inorganic insulating powder in the thickness direction of the protective layer.

In the wiring board, the organic resin in the protective layer is preferably the same as the organic resin forming the core board. By using the same component as the organic resin forming the core substrate and the protective layer, a polymer having the same structure is formed at the interface between the core substrate and the protective layer, and the adhesion can be improved.

In the above wiring board, it is desirable that the protective layer is formed on at least a region other than the wiring circuit layer for mounting electronic components on the surface of the core board. By forming a protective layer in such an area, solder flow can be prevented,
By forming the protective layer up to the insulating layer in the area other than the wiring circuit layer, the adhesive force of the protective layer formed on the wiring circuit layer can be reinforced.

In the method for manufacturing a wiring board of the present invention, a step of forming a protective layer sheet containing at least an organic resin and having a concentration distribution of inorganic insulating powder in the thickness direction, and containing the inorganic insulating powder and the organic resin Forming an uncured insulating layer sheet using the slurry for forming a wiring circuit layer and / or a via hole conductor on the uncured insulating layer sheet; and the wiring circuit layer and the via hole conductor are formed. A step of forming a core laminated body by laminating a plurality of uncured insulating layer sheets, and laminating and laminating the protective layer sheet so that the high concentration side of the inorganic insulating powder faces the main surface side of the core laminated body. The method is characterized by including a step of forming a body and a step of collectively curing the laminate by heating and pressing.

In this manufacturing method, first, by forming a protective layer sheet having a concentration distribution of the inorganic insulating powder in the thickness direction, a protective layer facing the high concentration side of the inorganic insulating powder can be easily formed on the core substrate side, The difference in thermal expansion coefficient between the substrate and the protective layer can be easily reduced.

Further, since the core laminate and the protective layer sheet are collectively cured, the thermosetting process can be simplified, and the protective layer is formed on the core substrate once cured as in the conventional wiring substrate. The adhesiveness between the protective layer and the core substrate can be easily enhanced as compared with the case of performing the above.

Further, in the above method of manufacturing a wiring board, if the amount of the inorganic insulating powder contained in the entire protective layer is 40% by mass or more, the thermal expansion coefficient of the protective layer can be reduced, and the inorganic insulating powder can be formed in the thickness direction. A protective layer sheet having a powder concentration distribution can be easily formed.

In the above method for manufacturing a wiring board, when the specific gravity of the inorganic insulating powder in the protective layer is SG _P and the specific gravity of the organic resin is SG _R , it is desirable to satisfy the relationship SG _P / SG _R ≧ 2. By using the inorganic insulating powder having such a high specific gravity with respect to the resin, a protective layer sheet having a concentration distribution in the thickness direction can be easily formed.

In the method of manufacturing the wiring board described above, the thickness of the protective layer is preferably 5 μm or more. First, by increasing the thickness of the protective layer, the density difference of the inorganic insulating powder can be easily formed in the thickness direction. Further, by forming the protective layer thick in this way, it is possible to easily form a wiring board having excellent moisture resistance.

In the above-mentioned wiring board manufacturing method, it is desirable that the organic resin in the protective layer is the same as the organic resin forming the core board. By forming the core substrate and the protective layer with the same organic resin, a polymer having the same structure is formed at the interface, the interface between the core substrate and the protective layer can be strengthened, and a wiring substrate with high adhesion can be easily formed. it can.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Structure) FIG. 1 is a schematic sectional view of an example of a wiring board of the present invention.

In the wiring substrate of FIG. 1, protective layers 3 are formed on the front and back surfaces of the core substrate 1. In the core substrate 1, a wiring circuit layer 9 is formed on the surface and / or inside of the insulating substrate 5 formed by stacking a plurality of insulating layers 5a to 5c containing at least an organic resin, and if necessary, these different wirings are formed. Via-hole conductors 11 are formed in the thickness direction of the insulating substrate 5 to connect the circuit layers 9. The protective layer 3 is formed in a region other than where electronic components are mounted.

FIG. 2 is an enlarged view of a main part of the protective layer 3 formed on the surface of the core substrate 1.

As shown in FIG. 2, the protective layer 3 formed on the surface of the core substrate 1 is composed of an organic resin and an inorganic insulating powder 12, and in particular, the amount of the inorganic insulating powder 12 contained in the protective layer 3 is large. The core substrate 1 side is larger than the front surface 15 side.

That is, the inorganic insulating powder 1 contained in the protective layer 3
2 has a concentration distribution in the thickness direction of the protective layer 3, and the core substrate 1
A gradual concentration gradient is formed from the side to the surface 15 side, and the inorganic insulating powder 12 is hardly present near the surface 15.

The protective layer 3 is divided into two in the thickness direction.
The thermal expansion coefficients of the core substrate 1 side and the surface 15 side are
The protective layer 3 is different depending on the amount of the insulating powder 12.
Coefficient of thermal expansion on the side of the core substrate 1 of 18 to 36 × 10^-6/
℃, especially 18-23 × 10 ^-6/ ° C, surface 15
Side thermal expansion coefficient is 43-86 × 10^-6/ ° C, especially 5
3 to 64 x 10^-6/ ° C range is desirable, core substrate 1 side
Expansion coefficient difference between the surface and the surface 15 side is 10-50 × 10^-6/
C, especially 30-46 x 10^-6/ ° C
(A) The peeling between the substrate 1 and the protective layer 3 is suppressed, and the flexibility of the surface 15
It is desirable for the reason that it keeps and prevents chipping.

Further, the thermal expansion coefficient of the core substrate 1 constituting the wiring board of the present invention is 10 to 25 × 10 ⁻⁶ / ° C. In order to improve the mounting reliability of the semiconductor element or the like, the heat of the entire wiring board is increased. It is desirable because it suppresses the expansion coefficient.

The difference in thermal expansion coefficient between the core substrate 1 and the protective layer 3 on the core substrate side is 0 to 18 × 10 ^-6 / ° C., and particularly,
It is more preferably 0 to 5 × 10 ^-6 / ° C.

The thickness of the protective layer 3 is preferably 5 μm or more, and in particular, the reason is that the exposure resolution of the wiring circuit layer 9 formed on the surface of the core substrate 1 is increased and the moisture resistance of the wiring substrate is improved. Therefore, the thickness of the protective layer 3 is preferably 15 to 40 μm.

The amount of the inorganic insulating powder 12 contained in the entire protective layer 3 is preferably 40% by mass or more, and in particular, the difference in thermal expansion coefficient between the protective layer 3 and the core substrate 1 is reduced. In order to suppress the presence of the inorganic insulating powder 12 near the surface while forming the concentration gradient of the inorganic insulating powder 12 in the protective layer 3, the content thereof is 45 to 85% by mass, particularly 55 to 70% by mass. Is desirable.

Further, the inorganic insulating powder 12 present in the protective layer 3 is 60 to 85% by mass on the side of the core substrate 1 from the central portion in the thickness direction of the protective layer 3, and 20 on the opposite surface side.
It is desirable to be distributed at a ratio of ˜60% by mass, which allows the thermal expansion coefficient of the protective layer 3 to be close to the thermal expansion coefficient of the core substrate 1, and peeling between the protective layer 3 and the core substrate 1 can be prevented. At the same time, since the amount of the inorganic insulating powder 12 on the surface 15 side of the protective layer 3 is small, the flexibility of the surface 15 of the protective layer 3 is increased and cracks and cracks can be prevented.

Further, the inorganic insulating powder 1 constituting the protective layer 3
The average particle size of 2 is at least 1/50 of the thickness of the protective layer 3.
The following is desirable, and in particular, the inorganic insulating powder 12 in the protective layer 3
It is desirable that the average particle diameter is 1/130 to 1/80 of the thickness of the protective layer 3 in order to improve the dispersibility of the protective layer 3 and to form a concentration gradient in the thickness direction. The shape of the inorganic insulating powder 12 may be any of spherical and polygonal powders, and the dispersibility of the inorganic insulating powder 12 in the slurry and the fluidity at the time of stacking by pressurizing and heating. In terms of, it is desirable that the shape is spherical.

On the other hand, the insulating layers 5a-
Like the protective layer 3, 5c is also composed of an organic resin and inorganic insulating powder 13, but the inorganic insulating powder 13 contained in the insulating layers 5a to 5c has a substantially uniform concentration distribution in the thickness direction.

The amount of the inorganic insulating powder 13 contained in the insulating layers 5a to 5c is preferably 40% by mass or more, and in particular, the difference in the thermal expansion coefficient between the insulating layers 5a to 5c is made small and the mechanical strength is reduced. , The inorganic insulating powder 13 contained in the insulating layers 5a to 5c for the purpose of increasing the Young's modulus.
The amount of is preferably 45 to 65% by mass.

The thickness of the insulating layers 5a-5c is 70 μm.
The above is preferable, and in particular, in order to adjust the capacitance of the insulating layers 5a to 5c and achieve impedance matching,
The thickness of the insulating layers 5a-5c is preferably 80-130 μm.

The average particle size of the inorganic insulating powder 13 constituting the insulating layers 5a-5c is at least the insulating layers 5a-5c.
1/30 or less of the thickness of the insulating layer 5a
In order to enhance the dispersed state of the inorganic insulating powder 13 in 5c, the average particle diameter is 1 / th of the thickness of the insulating layers 5a-5c.
It is preferably 70 to 1/40. The shape of the inorganic insulating powder 13 may be any of spherical and polygonal powders, and the dispersibility of the inorganic insulating powder 13 in the slurry and the fluidity at the time of stacking by pressurizing and heating. In terms of, it is desirable that the shape is spherical.

(Material) As the organic resin used for the protective layer 3 constituting the wiring board of the present invention, a thermosetting resin is preferably used. The thermosetting resin is at least one selected from the group consisting of epoxy resin, polyimide resin, phenol resin, thermosetting polyphenylene ether resin, polyimide amide resin, and bismaleimide triazine resin.
Seed. Particularly, a thermosetting polyphenylene ether resin is desirable because it has a high glass transition temperature and excellent heat resistance. Furthermore, it is desirable that the organic resin used for the protective layer 3 has the same component as that of the organic resin used for the insulating layers 5a to 5c because the adhesiveness between the core substrate 1 and the protective layer 3 is enhanced.

On the other hand, the inorganic insulating powder 1 constituting the protective layer 3
2 is at least one selected from the group of fused silica, aluminum oxide, aluminum nitride, silicon carbide, barium titanate, strontium titanate, calcium titanate, titanium oxide, and zeolite. In particular, spherical fused silica is preferably used because of its low expansion.

On the other hand, the insulating layers 5a to 5c are also the protective layers 3
Like the above, it contains a thermosetting resin having excellent heat resistance. Examples of the thermosetting resin include at least one selected from the group consisting of epoxy resin, polyimide resin, phenol resin, thermosetting polyphenylene ether resin, and polyimide amide resin.

The insulating layers 5a-5c include at least one inorganic insulating powder 13 selected from the group of fused silica, aluminum oxide, aluminum nitride, silicon carbide, zeolite and potassium titanate whiskers, and / or glass. It is desirable to include at least one filler component selected from the group of woven and non-woven fabrics such as fibers and aramid fibers.

Since the strength of the insulating substrate 5 can be increased by dispersing the inorganic insulating powder 13 in the thermosetting resin, it is possible to prevent chipping, cracking, cracking or the like due to the collision of the wiring substrates. You can

The wiring circuit layer 9 is made of at least one metal selected from the group consisting of copper, silver and gold.
It can be formed by printing a conductor paste in which an organic resin such as an epoxy resin is mixed with these metal powders, or a metal foil. The via-hole conductor 11 is formed by filling the through-hole with a paste of the same metal as described above.

When the content of the metal powder in the conductor paste is less than 70% by mass, the conductivity of the wiring circuit layer 9 and the via-hole conductor 11 tends to deteriorate, and when it exceeds 95% by mass, the metal powder is contained. It tends to be difficult to firmly bond with an organic resin. Therefore, the content of the metal powder in the paste forming the wiring circuit layer 9 and the via-hole conductor 11 is preferably in the range of 70 to 95 mass%.

The exposed surface of the wiring circuit layer 9 is made of at least one metal selected from the group consisting of Ni and Au, which is excellent in corrosion resistance and has a good conductivity, and is plated by a plating method in an amount of 1.0.
By applying a thickness of up to 20 μm, the oxidative corrosion of the wiring circuit layer 9 can be effectively prevented. Therefore, it is usually desirable to form a plating layer of the above metal with a thickness of 1.0 to 20 μm on the exposed surface of the wiring circuit layer 9.

The protective layer 3 constituting the wiring board of the present invention is formed so as to cover the peripheral portion of the wiring circuit layer 9 on which electronic components are mounted. By thus forming the protective layer 3 so as to cover a part of the wiring circuit layer 9, the insulating layers 5a to
It is possible to reinforce the close contact between the wiring layer 5c and the wiring circuit layer 9 and to prevent the solder flow to the extra wiring circuit layer 9 which is not used for mounting in the wiring circuit layer 9.

(Manufacturing Method) Next, a method for manufacturing the above-described wiring board of the present invention will be described with reference to FIGS.

First, as shown in FIG. 3A, an uncured insulating layer sheet 17 made of a composite of a thermosetting resin made of an organic resin and an inorganic insulating powder 13 is used as an insulating layer sheet.
Prepare a to 17c. In addition, in this manufacturing method, uncured refers to the insulating layer sheets 17a to 17c that are only molded but not subjected to any heat treatment, and the semi-cured state means that the thermosetting resin is completely cured. It is a state prepared by heating to a temperature lower than a sufficient temperature.

Specifically, for example, as the inorganic insulating powder 13, fused silica powder, potassium titanate whiskers, and the like, and a thermosetting resin such as a polyphenylene ether resin that binds the inorganic insulating powder 13 as a thermosetting resin and a crosslinking agent thereof are used. It is obtained by forming a slurry containing a volatile resin into a sheet using a sheet forming method such as a doctor blade method. The thickness of the uncured insulating layer sheets 17a to 17c is
The thickness is set to 80 to 150 μm, and is appropriately changed in consideration of the capacitance and impedance matching of the wiring board. Further, the insulating layer sheets 17a to 17c have a temperature of about 50 to 150 ° C. immediately after molding.
It is also possible to facilitate handling by heating at a temperature of 1 to 60 minutes to bring the material into a semi-cured state.

Next, as shown in FIG. 3 (b), through holes 18 are formed in predetermined positions of the uncured insulating layer sheets 17a to 17c by the well-known punching method and laser method, respectively.
And the through hole 18 is filled with a conductor paste containing metal powder and an organic resin to form the via-hole conductor 11.

After that, as shown in FIG. 3C, the wiring circuit layer 9 is formed on each surface of the insulating layer sheets 17a to 17c on which the via-hole conductor 11 is formed. This wiring circuit layer 9
Can be formed in a predetermined circuit shape by screen printing using the same conductor paste as that used for filling the via-hole conductor 11. When the conductor paste is used for printing, the via hole conductor 11 and the wiring circuit layer 9 can be formed at the same time. After forming the via-hole conductor 11 and the wiring circuit layer 9 with the conductor paste, the temperature of about 50 to 150 ° C.
It is desirable to heat for 60 minutes to semi-cure.

The wiring circuit layer 9 can also be formed of a metal foil. In the case of forming with a metal foil, after adhering the metal foil to the surfaces of the insulating layer sheets 17a to 17c, for example, a photosensitive resist is used to form a circuit by performing an etching process after exposure and development, or a predetermined pattern. It can also be formed by forming a circuit shape using a metal foil on the transfer film and then transferring it to the surfaces of the insulating layer sheets 17a to 17c. According to this transfer method, the insulating layer sheet 1
This is effective in that the formation of 7a to 17c and the formation of the wiring circuit layer 9 can be performed in parallel. In this case, the wiring circuit layer 9 is made of a metal foil having a surface roughness of 0.1 to 5 μm and a thickness of 9 to 18 μm, and is formed on a resin film of polyethylene terephthalate (PET), for example. Copper is preferably used as the metal foil having low resistance.

The metal paste to be the via-hole conductor 11 and the wiring circuit layer 9 has, for example, an average particle size of 0.1 to 20 μm.
m of copper or a metal powder obtained by coating the surface of copper powder with silver, a thermosetting resin such as a bisphenol A type epoxy resin, a novolac type epoxy resin, a glycidyl ester type epoxy resin, an amine type curing agent, an imidazole type curing agent. It is manufactured by adding and mixing a curing agent such as an acid anhydride curing agent.

Further, a low melting point metal powder made of tin-lead solder or the like is mixed in this conductor paste, the low melting point metal powder is melted at the time of curing treatment, and the metal powder is bonded by the molten low melting point metal. As a result, the resistance of the wiring circuit layer 9 and the via-hole conductor 11 can be reduced.

Next, the protective layer sheet 19 comprises an inorganic insulating powder 12 having an average particle size of 0.1 to 20 μm, a thermosetting polyphenylene ether resin and its cross-linking agent, a bisphenol A type epoxy resin, a bisphenol F type epoxy resin. At least one thermosetting resin selected from the group consisting of a novolac type epoxy resin and a glycidyl ester type epoxy resin, and an amine type curing agent, an imidazole type curing agent,
At least one curing agent selected from the group of acid anhydride-based curing agents is mixed to prepare a slurry, and then a thickness of 5 to 10 is obtained by a sheet forming method such as a doctor blade or a die coater.
It is made into a sheet of 0 μm.

The concentration of the inorganic insulating powder 12 contained in the protective layer sheet 19 can be changed by adding a solvent to the slurry, and the distribution state of the inorganic insulating powder 12 in the thickness direction inside the protective layer sheet 19 can be changed. It is controlled by adjusting the slurry viscosity according to the amount of solvent and the amount of organic resin.

That is, the slurry viscosity is 0.5 to 4 Pa · s, especially 1 because the inorganic insulating powder 12 in the protective layer 3 has a distribution of the inorganic insulating powder 12 in the thickness direction.
~ 1.8 Pa · s is desirable. The slurry viscosity is a value measured with an RS100 rheometer manufactured by Haake Co., Ltd., using a cone having an angle of 1 ° and a diameter of 10 mmφ at a shear rate of 200 s ^-1 . The slurry viscosity is limited to this range because when the slurry viscosity is lower than 0.5 Pa · s, the dispersion of the inorganic insulating powder 12 in the slurry becomes poor and pinholes and cracks are likely to occur in the formed sheet, which is the reverse. In addition, when the slurry viscosity is higher than 4 Pa · s, a molded sheet having a uniform film thickness cannot be formed.

That is, since the distribution state of the inorganic insulating powder 12 in the protective layer sheet 19 is formed by the sedimentation of the inorganic insulating powder 12 when forming the protective layer sheet 19, for example, a spherical inorganic insulating powder is used. If 12 is the closest packed,
The maximum filling rate is about 70% by volume, and by increasing the sedimentation rate, the inorganic insulating powder 12 does not exist on the side opposite to the surface of the protective layer sheet 19 which is closest packed, and only the organic resin is used. A structured part is formed.

Further, the inorganic insulating powder 12 in the protective layer 3
When the specific gravity of is SG _P and the specific gravity of the organic resin is SG _R , S
It is desirable that G _P / SG _R ≧ 2 because the density difference of the inorganic insulating powder 12 can be further formed, and the insulating layer 5a
.About.5c and the reason why the specific gravity of the wiring board using them is small, the range of the specific gravity ratio is 4 ≧ SG _P / SG _R ≧ 2.
Is more preferable.

The protective layer sheet 19 is also semi-cured at a temperature of about 50 to 150 ° C. like the insulating layer sheets 17a to 17c.
The opening 2 is formed at a predetermined place by using a punching method or a laser method.
0 is formed.

Next, as shown in FIG. 3 (d), a plurality of insulating layer sheets 17a to 17c on which the wiring circuit layer 9 and the via-hole conductor 11 are formed are laminated to form a core laminated body 17, and the core is formed. The protective layer sheets 19 are laminated on the upper and lower surfaces of the laminated body 17 so that the surface side having a large amount of the inorganic insulating powder 12 is adhered to the core laminated body 17 side, and this is then thermoset contained in each sheet. About 10 seconds to 24 at a temperature at which the functional resin is completely cured, for example, a temperature of 150 to 300 ° C.
The wiring board of the present invention can be manufactured by completely curing them by heating for collective curing for a time.

In the example shown in FIG. 3, three insulating layer sheets 1 are used.
Although the wiring board is manufactured by laminating 7a to 17c, the number of layers of the insulating layer sheets 17a to 17c may be four or more, or may be one. (Operation) As described above, in the wiring board of the present invention and the manufacturing method thereof, by forming the protective layer 3 formed on the surface of the core substrate 1 on the core substrate 1 side so that the amount of the inorganic insulating powder 12 is large, The difference in coefficient of thermal expansion at the interface between the substrate 1 and the protective layer 3 becomes small, and cracks and peeling do not occur in the protective layer 3 even in a temperature cycle test or the like, and reliability can be improved.

Further, the wiring board is made of the insulating layer sheets 17a ...
17c and the protective layer sheet 19 are formed by collective curing using the same organic resin, and therefore, compared with the protective layer 3 formed on the surface of the core substrate 1 that is previously cured, the insulating layer that constitutes the core substrate 1 The adhesiveness between 5a to 5c and the protective layer 3 can be enhanced.

Further, as compared with the protective layer 3 formed by using a photosensitive resin, the inorganic insulating powder 1 contained in the protective layer 3
Since the amount of 2 can be made high, the difference in thermal expansion coefficient between the core substrate 1 and the protective layer 3 can be easily reduced.

Furthermore, since the organic resin has a high concentration on the surface 15 side of the protective layer 3 opposite to the core substrate 1, the surface of the wiring board can be made flexible and cracks and cracks can be prevented, and at the same time the water resistance of the wiring board can be prevented. You can improve your sex.

[0064]

[Example] Thermosetting polyphenylene as an organic resin
Mixed resin of ter resin and triallyl isocyanurate
35% by mass of spherical molten Si having an average particle size of about 3 μm
O ₂To 65% by weight of the mixture as a solvent.
Addition of ene to further accelerate the curing of the organic resin
The slurry prepared by adding and mixing the catalyst is applied to the die coater method.
By molding to produce an insulating layer sheet with a thickness of 100 μm
It was And for this insulating layer sheet, carbon dioxide laser
A through hole with a diameter of 100 μm using
Copper powder with silver plated in the holes and epoxy as binder
Form a via-hole conductor by filling it with a conductor paste containing resin.
I made it.

On the other hand, polyethylene terephthalate (PE
T) resin film surface, surface roughness (Ra) 0.4μ
An electrolytic copper foil having a thickness of m and a thickness of 12 μm was adhered via an acrylic adhesive. Then, after applying a photosensitive resist on the surface of the copper foil and exposing it through a glass mask to form a circuit pattern, a solution of ferric chloride is sprayed onto the non-patterned portion at a speed of 35 μm / min. It was removed by etching to form a mirror image wiring circuit layer.

Then, the resin film on which the wiring circuit layer is formed is aligned and laminated on the surface of the insulating layer sheet on which the via-hole conductor is formed, and the pressure is 30 kg / cm ² for 30 minutes.
After pressing for 2 seconds, only the resin film and the adhesive layer were peeled off to transfer the wiring circuit layer to the insulating layer sheet. The wiring circuit layer transferred to the insulating layer sheet was completely embedded in the surface of the insulating layer sheet, and it was confirmed that the surface of the insulating layer sheet and the surface of the wiring circuit layer were substantially flush with each other. .

As the protective layer sheet, a thermosetting resin made of thermosetting polyphenylene ether, which is the same as the organic resin used for the insulating layer sheet, is used as an inorganic insulating powder having a spherical shape with an average particle size of 0.5 μm. Molten SiO ₂ powder was mixed, toluene was added to this mixture as a solvent, and a catalyst for promoting the curing of the organic resin was further added and mixed to prepare a slurry. Next, this slurry was used to form a sheet by a die coater method to produce a protective layer sheet having a thickness of about 30 μm. The amount of the inorganic insulating powder and the slurry viscosity at this time are shown in Table 1. The amounts of the inorganic insulating powder on the core substrate side and the surface side of the protective layer are the respective contents when the protective layer is divided into two parts at the central portion in the thickness direction. Next, on this protective layer sheet, an opening for exposing the wiring circuit layer formed on the core substrate was formed in a predetermined region of the protective layer by using a carbon dioxide laser.

Next, five layers of insulating layer sheets having wiring circuit layers and via-hole conductors are laminated to form a core laminated body, and one protective layer sheet is laminated on each of the uppermost surface and the lowermost surface. A laminate was formed. At this time, a predetermined wiring circuit layer formed on the surface of the core laminate was exposed from the opening of the protective layer sheet.

Finally, this laminated body was collectively cured at a temperature of 200 ° C. and a pressure of 3 MPa for a processing time of 2 hours to produce a wiring board. The coefficient of thermal expansion of the core substrate manufactured here was 18 × 10 ⁻⁶ / ° C.

Next, with respect to the produced wiring board, -55
The temperature cycle of up to 125 ° C. was repeated up to 2000 cycles, and the interface between the core substrate and the protective layer at 1750 cycles and 2000 cycles was observed. In addition, a pressure cooker (PCT) test (121
(° C, 0.2 MPa) for 300 hours to evaluate the water resistance of the surface of the protective layer, and those showing a change in color tone or swelling were regarded as defective products (no change ○, color tone change Δ, color tone change + swelling ×).
The number of samples was 20 in each test.

[0071]

[Table 1]

As is clear from Table 1, the amount of inorganic insulating powder is different between the core substrate side and the surface side of the protective layer, and the difference in the coefficient of thermal expansion between the core substrate and the core substrate side of the protective layer is 0-18.
Sample No. 10 × 10 ⁻⁶ / ° C. In Nos. 1 to 6, in the reliability test, delamination and cracks in the protective layer were not observed until 1750 cycles. In particular, the viscosity of the slurry forming the protective layer is set to 1 to 1.8 Pa · s, and the thermal expansion coefficient difference between the core substrate and the core substrate side of the protective layer is 0 to 5 × 10 ⁻⁶ /
Sample No. In Nos. 1, 3, and 4, delamination and cracking of the protective layer were not observed until 2000 cycles. In addition, in these samples (1, 3, 4), the PCT test 30
No change in color tone or swelling was observed even at 0 hours.

On the other hand, the difference in the coefficient of thermal expansion between the core substrate and the core substrate side of the protective layer is 20 × 10 ⁻⁶ / ° C., and the amount of the inorganic insulating powder is made uniform in the thickness direction of the protective layer and the core substrate side. Sample No. in which the difference in thermal expansion coefficient from the surface side was 0. 7 in 1
Delamination and cracks in the protective layer were seen at 750 cycles. In addition, a color tone change and swelling were observed in the protective layer after 300 hours of the PCT test.

[0074]

As described above in detail, according to the present invention, by forming the inorganic insulating powder contained in the protective layer so that the core substrate side is larger than the surface side, the core substrate and the protective layer are not formed. The difference in coefficient of thermal expansion becomes small, and cracks and peeling do not occur in the protective layer even in a temperature cycle test or the like, and reliability can be improved.

Further, since the wiring board is formed by collective curing using the same organic resin for the insulating layer sheet and the protective layer sheet, as compared with the protective layer formed on the surface of the core substrate which is previously cured, The adhesion with the core substrate can be improved.

Further, since the amount of the inorganic insulating powder contained in the protective layer can be made higher than that of the protective layer formed by using the photosensitive resin, the difference in the coefficient of thermal expansion between the core substrate and the protective layer. Can be easily reduced.

Furthermore, since the organic resin has a high concentration on the surface side of the protective layer opposite to the core substrate, the surface of the wiring substrate can be made flexible and cracks and cracks can be prevented, and at the same time the water resistance of the wiring substrate can be improved. be able to.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of a wiring board of the present invention.

FIG. 2 is an enlarged view of a main part of a protective layer formed on a core substrate that constitutes the wiring substrate of the present invention.

FIG. 3 is a process drawing for manufacturing the wiring board of the present invention.

[Explanation of symbols]

1 --- Core substrate 3 ... Protective layer 5a-5c ... Insulating layer 7 ... Insulating substrate 9 ・ ・ ・ ・ ・ ・ Wiring circuit layer 12, 13 ... Inorganic insulating powder 15 ・ ・ ・ ・ Surface 17 --- Core laminate 17a to 17c ... Insulating layer sheet 19 ... Protective layer sheet 20 ... Opening

Claims (10)

[Claims] 1. A wiring board having a protective layer containing an inorganic insulating powder and an organic resin formed on the surface of a core substrate, wherein the amount of the inorganic insulating powder on the core substrate side in the protective layer is greater than that on the surface side. Wiring board characterized by many. 2. The amount of inorganic insulating powder contained in the entire protective layer is 4
The wiring board according to claim 1, which is 0 mass% or more. 3. The wiring board according to claim 1, wherein the protective layer has a thickness of 5 μm or more. 4. The wiring board according to claim 1, wherein the organic resin in the protective layer is the same as the organic resin forming the core board. 5. The wiring board according to claim 1, wherein the protective layer is formed on at least a region other than the wiring circuit layer for mounting electronic components on the surface of the core substrate. 6. A step of forming a protective layer sheet containing at least an organic resin and having a concentration distribution of inorganic insulating powder in the thickness direction, and an uncured insulating layer sheet containing the inorganic insulating powder and the organic resin. A step of forming a wiring circuit layer and / or a via-hole conductor in the step of forming a core laminate by stacking a plurality of the uncured insulating layer sheets having the wiring circuit layer and / or the via-hole conductor formed thereon, A step of forming a laminate by laminating the protective layer sheet so that a high concentration side of the inorganic insulating powder faces the main surface side of the core laminate, and a step of collectively curing the laminate by heating and pressing, A method of manufacturing a wiring board including. 7. The amount of inorganic insulating powder contained in the entire protective layer is 4
It is 0 mass% or more, The manufacturing method of the wiring board of Claim 6 characterized by the above-mentioned. 8. The specific gravity of the inorganic insulating powder in the protective layer is SG
_Supposing that _P and the specific gravity of the organic resin are SG _R , SG _P / SG _R ≧
The relationship of 2 is satisfied, and claim 6 or 7 characterized by the above-mentioned.
The method for manufacturing a wiring board according to. 9. The method for manufacturing a wiring board according to claim 6, wherein the protective layer has a thickness of 5 μm or more. 10. The method for manufacturing a wiring board according to claim 6, wherein the organic resin in the protective layer is the same as the organic resin forming the core board.