JP2002141628A - Wiring board - Google Patents

Abstract

(57) [Summary] [Problem] Migration by metal ions occurs between through conductors, and the distance between through holes cannot be reduced to 300 μm or less. SOLUTION: A plurality of insulating layers 11a to 1d formed by impregnating a glass fiber base material A with an organic resin, a circuit conductor layer 2 disposed on the surfaces of the insulating layers 1a to 1d and between the layers, and an insulating layer 1a. ~
A resin layer 5 formed on the inner wall of the through hole 3 formed in 1d and covering the end of the glass fiber base material A exposed on the inner wall.
And a through conductor 4 filled in the through hole 3 and electrically connecting the upper and lower circuit conductor layers 2. The resin layer 5 includes the through hole 3. A wiring board 6 having a maximum thickness within a region of ± 40% in the depth direction with a half of the depth as a center. Movement of metal ions between the penetrating conductors 4 can be effectively prevented, and ion migration does not occur.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small and high-density wiring board used for mobile communication devices such as supercomputers, network computers and mobile phones.
In particular, the present invention relates to a wiring board having excellent ion migration resistance.

[0002]

2. Description of the Related Art Conventionally, a wiring board, for example, a wiring board used for a semiconductor element housing package for housing a semiconductor element is made of ceramics such as an aluminum oxide sintered body, and a semiconductor element is mounted on a central portion of an upper surface thereof. And a circuit conductor layer made of a refractory metal powder such as tungsten, molybdenum, or manganese that is led out from the mounting portion of the insulating base to the lower surface. The element is bonded and fixed via an adhesive such as glass, resin, brazing material, etc., and each electrode of the semiconductor element is electrically connected to a circuit conductor layer via an electrical connection means such as a bonding wire, and thereafter, On the upper surface of the insulating substrate, a concave lid made of metal, ceramics, or the like is sealed with glass, resin, brazing material, or the like so as to cover the mounting portion of the insulating substrate. Is bonded through the wood, the semiconductor device as a product by housing the semiconductor element hermetically in the container interior made of an insulating base and the lid.

[0003] In recent years, with the rapid progress of miniaturization and high density of semiconductor elements, it has become necessary to increase the density of circuit conductor layers in wiring boards on which semiconductor elements are mounted.

However, in the conventional wiring board, since the insulating base constituting the wiring board is made of ceramics such as an aluminum oxide sintered body having a relative dielectric constant of about 10, the circuit conductor layers are densified to reduce the spacing therebetween. Then, the electrical coupling between the signal wirings increases, and the crosstalk noise increases. As a result, there is a problem that it is not possible to cope with miniaturization and high density of the semiconductor element.

In order to solve such a problem, recently, instead of ceramics such as an aluminum oxide sintered body having a relative dielectric constant of about 10, for example, a dielectric constant of 3 is used.
A metal foil such as copper, which is a low-resistance metal, is formed on the surface of an insulating layer made of a composite material of a thermosetting resin such as epoxy resin and phenol resin and a woven fabric such as glass fiber and aramid fiber which are relatively small. A so-called printed wiring board on which a circuit conductor layer is formed has been used for various wiring boards, packages for housing semiconductor elements, and the like.

In such a printed wiring board, a circuit conductor layer is formed on the surface thereof, and a copper foil is adhered to the surface of the insulating layer and then etched to form a wiring conductor. It is formed by applying a transfer method of transferring a copper foil, or a plating method of forming a wiring conductor on the surface of an insulating layer by plating.

In addition, this printed wiring board uses an insulating substrate in which a plurality of insulating layers are laminated in accordance with the increase in density thereof, and forms a circuit conductor layer on the surface of each insulating layer. Electrical connection is also performed by the formed through conductor. Such a through conductor is formed by drilling a through hole in a predetermined portion of an insulating layer constituting an insulating substrate with a drill or the like, and then applying a metal such as copper to the inner wall of the through hole by adopting a plating method or a screen. It is formed by embedding a paste made of copper or the like in the through hole by employing a printing method.

However, in the above printed wiring board, a voltage is applied at high temperature and high humidity because the end of the fiber base material such as glass fiber contained in the insulating layer is exposed on the inner wall surface of the through hole. When a high acceleration test is performed, the metal forming the through conductor is ionized and metal ions easily migrate at the interface between the fiber base material and the resin, causing ion migration, and the insulation resistance between the adjacent through conductors is increased. In order to prevent such migration between the penetrating conductors, it is necessary to make the distance between the penetrating conductors as large as 300 μm or more, and it is not possible to increase the density of the wiring board. There was a problem that.

In order to solve such a problem, there has been proposed a method for preventing the ion migration by forming the through holes such that there is no fiber base material connecting the adjacent two when forming the through holes. It has been proposed (Japanese Patent Laid-Open No. 8-139424).
No.).

However, this method has a problem that the through-hole cannot be arranged at an arbitrary position when performing wiring design, and there is a problem that wiring design is restricted.

Therefore, a method has been proposed in which the inner wall of the through hole is covered with a resin to prevent contact between the end of the fiber base material and the through conductor, thereby preventing ion migration (Japanese Patent Laid-Open No. Hei 11 (1999)).
-87869).

[0012]

However, a method of covering the inner wall of the through hole with a resin to prevent the end of the fiber base from contacting with the through conductor and to prevent ion migration is to reduce the diameter of the through hole by a small diameter. The problem is that when the wiring board is made to have a higher density by reducing the connection area, the connection area between the through conductor and the circuit conductor layer is reduced, so that the connection strength between the two is reduced and the connection reliability is reduced. Had.

When the thickness of the resin layer is reduced in order to make the connection area between the through conductor and the circuit conductor layer sufficient, the resin layer can effectively prevent the movement of metal ions between the through conductors. As a result, ion migration is generated, and as a result, there is a problem that it is difficult to arrange the through conductors at a high density of 300 μm or less.

The present invention has been made in view of the above-mentioned problems of the prior art. It is an object of the present invention to reduce the pitch between through conductors to 300 μm or less when performing high-density mounting of a wiring board. Therefore, it is an object of the present invention to provide a highly reliable wiring board which maintains good insulation reliability between through conductors.

[0015]

According to the present invention, there is provided a wiring board comprising: a plurality of insulating layers formed by impregnating a glass fiber base material with an organic resin; and a circuit conductor layer disposed on the surface of the insulating layer and between the layers. A resin layer formed on the inner wall of the through hole formed in the insulating layer and covering the end of the glass fiber base material exposed on the inner wall; and a circuit conductor layer which is filled inside the through hole and located above and below. And a through conductor electrically connecting the through hole, wherein the resin layer has an area of ± 40% in a depth direction around a half of the depth of the through hole. It has a maximum thickness.

According to the wiring board of the present invention, the resin layer formed on the inner wall of the through hole has a maximum thickness within a region of ± 40% in the depth direction centered on a half of the depth of the through hole. Therefore, it is possible to effectively prevent the movement of metal ions between the through conductors without significantly reducing the connection area between the through conductors and the circuit conductor layer. The connection strength between the through conductor and the circuit conductor layer does not decrease.
It can be arranged at a high density of not more than μm.

[0017]

Next, a 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 wiring board according to the present invention, and FIG. 2 is an enlarged sectional view of a main part. In these figures, 1 is an insulating substrate, 2 is a circuit conductor layer, 3 is a through hole, 4 is a through conductor, and 5 is a resin layer, and these mainly constitute a wiring board 6 of the present invention. A is a glass fiber base material.

In this embodiment, the insulating substrate 1 has four insulating layers 1a.
An electronic component (not shown) such as a semiconductor element is adhered and fixed at the center of the upper surface thereof via an adhesive such as a resin.

The insulating layers 1a, 1b, 1c,
1d is formed using a so-called composite organic material in which the glass fiber base material A is impregnated with an organic resin. Such a glass fiber base material A is used as a woven or non-woven fabric as the insulating layers 1a and 1b.
It is contained at a ratio of 30 to 70% by volume with respect to 1c and 1d, and the warpage of the insulating layers 1a, 1b, 1c, and 1d when the organic resin cures and shrinks.
It has a function of suppressing deformation and the like. The organic resin is epoxy resin or PPE (polyphenylene ether resin).
Thermosetting resins generally used for wiring boards, such as phenolic resins, triazine resins, and polyimide resins, are used. In particular, the form of the organic resin raw material is preferably liquid at room temperature.

The insulating layers 1a, 1b, 1c, 1d are made of silicon oxide, aluminum oxide, aluminum nitride, silicon carbide, calcium titanate, titanium oxide, zeolite, barium titanate, strontium titanate in order to increase the strength. -Contains an inorganic filler such as calcium titanate. Such an inorganic filler has an average particle size of 20μ.
It is preferable that the fine particles have an average particle diameter of 7 μm or less.

The organic resin and the inorganic filler were mixed at a ratio of 85: 1.
By appropriately blending at a volume ratio of 5 to 15:85, it is possible to form a through hole 3 having a stable hole diameter particularly when forming a through hole 3 using a laser described later.

For example, when the organic resin is an epoxy resin, the insulating layers 1a, 1b, 1c, 1d are made of an epoxy resin such as a bisphenol A type epoxy resin, a novolak type epoxy resin, a glycidyl ester type epoxy resin, or the like. A mixture obtained by adding an inorganic filler such as silicon oxide, a solvent, a plasticizer, a dispersant, and the like is kneaded to obtain a liquid varnish, and the liquid varnish is impregnated into the glass fiber base material A to obtain a precursor sheet, 60 to 100 of these precursor sheets
It is formed by drying at a temperature of ° C for 30 minutes to 24 hours. The thickness of the insulating layers 1a, 1b, 1c, 1d can be freely set, but the thickness is preferably 50 μm or more from the viewpoint of insulation, and 200 μm or less from the viewpoint of thinning the wiring board 6. .

The insulating layers 1a, 1b, 1c and 1d are made of glass, for example, in order to make the hole diameter and shape uniform when forming the through holes 3 in the insulating layers 1a, 1b, 1c and 1d by laser. Fiber base material A
Can be formed by impregnating an organic resin into the glass fiber base material A having a uniform density by reducing the gap between the glass fibers.

The surfaces of the insulating layers 1a, 1b, 1c, 1d
A circuit conductor layer 2 made of a metal foil such as copper or gold is adhered and formed.

The circuit conductor layer 2 has a function of electrically connecting electronic components such as semiconductor elements mounted on the wiring board 6 to wiring conductors (not shown) of an external electric circuit. By adopting a transfer method of transferring a copper foil formed in the shape of the above, a plating method of forming the circuit conductor layer 2 by plating, and the like, the insulating film is formed on the surfaces of the insulating layers 1a, 1b, 1c, and 1d.

The circuit conductor layer 2 has a thickness of 1 to 40.
μm, and preferably 1 μm or more from the viewpoint of transmitting high-speed electrical signals. In order to make the circuit conductor layer 2 difficult to peel off from the insulating layers 1a, 1b, 1c, 1d, 40 μm is required. It is preferable to set the following.

Further, in the insulating layers 1a, 1b, 1c, 1d, through holes 3 having a diameter of about 50 to 300 μm are formed. The through hole 3 is formed by a mechanical method such as a drill, a carbon dioxide gas laser, or a YA.
It is formed by using a conventionally known laser such as a G laser or an excimer laser. Preferably, fine processing can be performed independently of the material of the insulating layers 1a, 1b, 1c, and 1d, and the diameter of the through hole 3 can be reduced to 50%.
It is preferable to use a carbon dioxide laser that can be formed freely in the range of up to 300 μm and has a high processing speed.

A resin layer 5 is formed on the inner wall of the through hole 3 so as to cover the end of the glass fiber substrate A exposed on the inner wall of the through hole 3.

In the wiring board 6 of the present invention, the resin layer 5
± 40% centered on half the depth of through hole 3
It is important to have the maximum thickness in the region of the above.

In the wiring board 6 of the present invention, the resin layer 5 formed on the inner wall of the through-hole 3 has a maximum thickness within a range of ± 40% around a half of the depth of the through-hole 3. As a result, the resin layer 5 formed on the inner wall of the through-hole 3 has a maximum thickness within a range of ± 40% in the depth direction around a half of the depth of the through-hole 3. As a result, the movement of metal ions between the through conductors 4 can be effectively prevented without greatly reducing the connection area between the through conductor 4 and the circuit conductor layer 2, and as a result, ion migration occurs or penetration occurs. The connection strength between the conductor 4 and the circuit conductor layer 2 is not reduced, and the distance between the through conductors 4 is 300 μm.
It can be arranged with high density as follows.

The maximum thickness of the resin layer 5 formed on the inner wall of the through hole 3 is desirably in the range of 5 to 20 μm, and if it is less than 5 μm, the resin layer 5 can effectively prevent the movement of metal ions between the through conductors 4. When the diameter exceeds 20 μm, the diameter of the through-hole 3 is reduced to about 100 μm or less in recent years, and the gap in the through-hole 3 is narrowed and the through-conductor 4
When forming the via, poor filling is likely to occur, and the resistance value of the through conductor 4 tends to increase and disconnection tends to occur. Therefore, the maximum thickness of the resin layer 5 is preferably in the range of 5 to 20 μm.

When the resin layer 5 has a maximum thickness outside a range of ± 40% around a half of the depth of the through hole 3, the connection area between the through conductor 4 and the circuit conductor layer 2 is increased. Becomes small, and as a result, the connection strength between the two tends to decrease, and the connection reliability tends to decrease. In addition, it is difficult for the resin layer 5 to effectively prevent the movement of metal ions between the through conductors 4. Tend to be. Therefore, it is preferable that the resin layer 5 has a maximum thickness in a range of ± 40% around a half of the depth of the through hole 3.

The resin layer 5 is manufactured by the following method.

First, through holes 3 are formed at predetermined positions of the insulating layers 1a, 1b, 1c, 1d by using, for example, a drill or the like, and then the through conductors 3 on the front and back surfaces of the insulating layers 1a, 1b, 1c, 1d are formed. The other areas are masked, and then the insulating layers 1a, 1b, 1c, 1d are immersed in a liquid resin bath to fill the through holes 3 with resin.

The resin may contain a filler such as an inorganic filler such as silicon oxide or aluminum oxide in order to improve migration resistance. In addition, the through-holes 3 are formed beforehand on the front and back surfaces of the insulating layers 1a, 1b, 1c, and 1d, and then are formed.
-Positioning for masking 1c and 1d is not required, and the manufacturing process can be simplified.

Next, the insulating layer 1a is added to the resin filled in the through hole 3.
Irradiating carbon dioxide laser from both sides of 1b, 1c, 1d to remove unnecessary resin and form resin layer 5 Generally, when forming a through hole using a laser processing method,
The shape of the hole is such that the diameter of the hole on the laser incident side is slightly larger than the diameter of the hole on the emission side, and the taper shape is controlled by adjusting the processing conditions such as the laser pulse energy, pulse length, and focal length. And the insulating layers 1a, 1b, 1c, 1d are processed from the front and back surfaces so that the resin layer 5 is formed within a region of ± 40% in the depth direction around a half of the depth of the through hole 3. Can be processed so as to have a maximum thickness.

Further, by performing laser processing from the front side of the insulating layers 1a, 1b, 1c and 1d in a state where a metal plate such as copper is adhered to the back surface of the insulating layers 1a, 1b, 1c and 1d, It is possible to make the hole diameter on the back side of the insulating layers 1a, 1b, 1c, 1d larger than the hole diameter at the center of the through-hole by the laser light reflected by the through-hole.
± 40% in the depth direction centered on one half of the depth
May be formed so that the resin layer 5 has the maximum thickness in the region of FIG. Further, by using a machining method such as a drill from the front and back sides of the insulating layers 1a, 1b, 1c, 1d, the depth of the through hole 3 is reduced by two times.
The resin layer 5 may be formed so as to have a maximum thickness within a region of ± 40% in the depth direction with a half of the center as the center.

In the through hole 3 in which the resin layer 5 is formed on the inner wall, a through conductor 4 formed by filling a conductive paste formed by bonding a metal powder such as copper with an organic material such as a thermosetting resin is filled. It is formed by employing a conventionally known screen printing method, press-fitting method, or the like.

The conductor paste serving as the penetrating conductor 4 is made of a metal powder mainly composed of one or a mixture of two or more metal materials such as copper, silver, aluminum, and gold. It is formed by bonding with an organic material such as resin, and from the viewpoint of a low resistance value, a metal powder mainly composed of copper or a mixture containing copper or a metal selected from the above coated with another metal. It is preferable to form using. Further, in order to further reduce the resistance of the through conductor 4, a powder of a low melting point metal such as solder or tin is used. Further, for the purpose of adjusting the resistance value, a high-resistance metal such as a Ni—Cr alloy or a metal powder obtained by alloying the high-resistance metal and the low-resistance metal is also used.

The content of the metal powder contained in the through conductor 4 is preferably not less than 70% by weight in order to secure conductivity, and the metal powder contained in the through conductor 4 is thermoset. The content is preferably 95% or less in order to bond strongly with a thermoplastic resin or a thermoplastic resin. Therefore, the through conductor 4
Is preferably in the range of 70 to 95% by weight.

It should be noted that the shear rate is determined by the viscosity of the conductive paste.
Under the measurement conditions of 100 s ⁻¹ , the range is preferably 20 to 1000 Pa · s. Conductor paste viscosity is 100s ^-1
If the measurement condition is less than 20 Pa · s, the penetration hole 3
When the conductive paste is filled into the through hole, it becomes easy to cause dripping, bleeding, etc. around the through-hole 3, and when it exceeds 1000 Pa · s, the fluidity of the conductive paste decreases, and the through-hole 3 is filled with the conductive paste. Tends to be difficult. Therefore, the viscosity of the conductive paste is preferably in the range of 20 to 1000 Pa · s under the measurement condition where the shear rate is 100 s ⁻¹ . The viscosity of the conductive paste can be appropriately adjusted by adding an organic binder or a solvent.

The metal powder has an average particle size of 0.1-1.
Preferably in the range of 5μm, the average particle size is 0.1μm
If it is less than 3, the viscosity of the conductive paste increases, and it tends to be difficult to fill the through-hole 3 with the conductive paste satisfactorily. If it exceeds 15 μm, it is difficult to uniformly disperse the metal powder in the organic material. It tends to be. Therefore, the average particle size of the metal powder contained in the conductor paste is 0.1 to 15 μm.
It is preferably in the range of m.

Next, the through-hole 3 is filled with a conductive paste by using, for example, a screen printing method to form a through-conductor 4. Then, the transfer sheet is previously placed at a predetermined position of the insulating layers 1a, 1b, 1c and 1d. A metal foil such as a copper foil formed in the shape of the circuit conductor layer 2 is overlaid on the substrate and pressed, so that the circuit conductor layer 2 is formed on the surfaces of the insulating layers 1a, 1b, 1c and 1d, and the through conductor is formed. 4 is electrically connected. When the through conductor 4 is formed, projecting portions are formed on the surfaces of the insulating layers 1a, 1b, 1c, and 1d with a conductive paste, and the conductive paste is applied to the connection between the through conductor 4 and the circuit conductor layer 2. The connection strength between the through conductor 4 and the circuit conductor layer 2 can be further increased by forming the interlayer connection portion wider than the area of the through hole 3 by pushing out.

Further, a plurality of insulating layers 1a, 1b, 1c, 1d each having a required circuit conductor layer 2 formed on the surface thereof are superposed,
30 minutes at a temperature of 60 to 200 ° C while applying a pressure of 4 to 6 MPa
By heating for 24 hours, the wiring board 6 of the present invention is manufactured.

Thus, according to the wiring board 6 of the present invention, the movement of metal ions between the penetrating conductors 4 can be effectively prevented without greatly reducing the connection area between the penetrating conductor 4 and the circuit conductor layer 2, and as a result, In addition, there is no occurrence of ion migration or a decrease in the connection strength between the through conductor 4 and the circuit conductor layer 2, and the wiring board 6 can be arranged at a high density of 300 μm or less between the through conductors 4. can do.

The wiring board 6 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. For example, one layer
Three or five or more insulating layers are laminated to form an insulating substrate 1
May be formed. Further, the outermost layer of the insulating substrate 1 may be formed of an inorganic filler-containing resin in order to improve the moisture resistance of the insulating substrate 1. Alternatively, the through conductor 4 may be formed by metal plating.

[0048]

EXAMPLES In order to evaluate the characteristics of the wiring board of the present invention,
The following samples were prepared and evaluated. (Example) First, a glass woven fabric was impregnated with a liquid varnish obtained by mixing a thermosetting polyphenylene ether (PPE) resin and toluene, and dried to prepare a plurality of prepregs each serving as an insulating layer having a thickness of 100 µm. The prepreg is P
The PE resin was 50% by volume and the glass woven fabric was 50% by volume.

The prepreg was subjected to carbon dioxide gas laser irradiation for 150 hours.
A plurality of through holes having a hole diameter of 100 μm were formed at intervals of μm, and thereafter, a resin layer was formed on the inner wall surface of the through hole. At this time, the resin layer had a maximum thickness within a range of ± 40% around a half of the depth of the through hole and a maximum thickness of 10 μm. Next, screen-printing a conductor paste prepared by adding triallyl isocyanate to a mixture in which solder powder and silver-plated copper powder each having an average particle size of 5 μm were mixed in a weight of 50% by weight in the through holes. The through conductor was filled by using the method.

Next, polyethylene terephthalate (PE)
T) An adhesive is applied to the surface of a transfer sheet made of a resin, and a copper foil having a thickness of 12 μm and an average surface roughness of 0.8 μm is adhered. Then, a photoresist is applied and exposed and developed. Was immersed in ferric chloride and etched to form a circuit conductor layer. Further, the transfer sheet on which the circuit conductor layer is formed is attached to the insulating layer so that the through conductor and the circuit conductor layer are electrically connected, and the circuit conductor layer is transferred onto the surface of the insulating layer. Was peeled off to obtain an insulating layer having a circuit conductor layer. After laminating four insulating layers each having a circuit conductor layer produced in the same manner, the laminate was heated at a temperature of 200 ° C. for 1 hour while applying a pressure of 5 MPa and completely cured to prepare a wiring board for evaluation. (Comparative Example) As a comparative example, a prepreg having a thickness of 100 μm and a hole diameter of 100 μm was prepared in the same manner as the wiring board of the example.
And a resin layer having a thickness of about 5 μm was formed on the inner wall surface of the through hole. The distance between adjacent through conductors was 150 μm as in the case of the wiring board of the embodiment.
And Other conditions and processes were the same as those of the wiring board of the example, to prepare a wiring board A for comparison. Furthermore,
A comparative wiring board B in which a resin layer having a thickness of about 20 μm was formed on the inner wall surface of the through hole was prepared.

Reliability Tests 100 samples of the samples for evaluation and the samples of the comparative example were prepared, and the resistance value of the through conductor was measured. Then, a reliability test was performed. The reliability test items are high acceleration test (HAST) and temperature cycle test (T
In CT), HAST measures the insulation resistance and evaluates an object with a resistance value of 10 × 10 ⁶ Ω or less as having poor insulation and causing migration, and TCT evaluates the appearance such as electrical continuity and peeling. went.

In the HAST, using a high-acceleration tester, a sample for reliability evaluation was subjected to a voltage of 5.5 V for 300 hours in an atmosphere at a temperature of 130 ° C. and a relative humidity of 85% to confirm insulation properties. The TCT was performed using a gas phase cold test gas, and the sample for reliability evaluation was left in a gas phase at a temperature of −55 ° C. and 125 ° C. for 30 minutes each, and this was performed as one cycle under the conditions of 2000 cycles. Table 1 shows the evaluation results.

[0053]

[Table 1]

The wiring board of the example had no migration and the disconnection rate after TCT was 0.0%, confirming that the wiring board had good reliability. On the other hand, the wiring board A of the comparative example had an initial resistance value that was lower by about 10% as compared with the wiring board of the example, but migration was low.
It was confirmed that the wiring board had a low reliability of 65.0%. Although no migration occurred in the wiring board B, it was confirmed that the disconnection rate after TCT was 25.0%, which was a large and low reliability wiring board. The connection area between the through conductor of the wiring board B and the circuit conductor layer was about 55% as compared with that of the wiring board of the example.

[0055]

According to the wiring board of the present invention, the resin layer formed on the inner wall of the through-hole is placed within a region of ± 40% in the depth direction around a half of the depth of the through-hole. Having the maximum thickness makes it possible to effectively prevent the migration of metal ions between the through conductors without significantly reducing the connection area between the through conductors and the circuit conductor layer. The connection strength between the through conductor and the circuit conductor layer does not decrease, and the space between the through conductors is set to 30
It can be arranged at a high density of 0 μm or less.

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view of a main part showing an example of an embodiment of the present invention.

[Explanation of symbols]

 1 Insulating substrate 1a ・ 1b ・ 1c ・ 1d ・ ・ ・ ・ ・ ・ ・ ・ ・ Insulating layer 2 ・ ・ ・ ・ ・ ・.... Circuit conductor layer 3 ... Through hole 4 ... Through conductor 5 ... ······ Resin layer 6 ······· Wiring board A ····· Glass fiber base material

Claims (2)

[Claims] 1. A plurality of insulating layers formed by impregnating a glass fiber base material with an organic resin, a circuit conductor layer disposed on the surface and between layers of the insulating layer, and a through hole formed in the insulating layer. A resin layer formed on an inner wall of the glass fiber substrate and covering an end portion of the glass fiber base material exposed on the inner wall; and a through-hole filled in the through-hole and electrically connecting the circuit conductor layers located above and below. A wiring board comprising a conductor, wherein the resin layer has a maximum thickness in a range of ± 40% in a depth direction around a half of a depth of the through hole. A wiring board characterized by the above. 2. The wiring board according to claim 1, wherein the maximum thickness of the resin layer is 5 to 20 μm.