JP2003086941A - Printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board in which the occurrence of a wrap due to a heat history can be reduced and in which a conductor layer of an outermost layer can be easily formed in a fine pattern. SOLUTION: The printed wiring board is formed by alternatively building up a plurality of insulating resin layers 2a, 2b, etc., and conductor layers 3a, 3b, etc., on the surface of an inner layer circuit substrate 1. The layer 2b of the outermost layer is formed as a layer containing a main body of resin not containing a glass cloth 4 as a base, and the layer 2a of the second layer from the outermost layer is formed as a layer containing the glass cloth 4 as the base.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer printed wiring board used in electronic equipment, electric equipment, computers, communication equipment and the like.

[0002]

2. Description of the Related Art In recent years, electronic parts such as semiconductor chips and chip parts have been made lighter and thinner and smaller, and along with this, in printed wiring boards on which these electronic parts are mounted, the line width and line spacing of conductor circuits are reduced. There is a demand for improvement in manufacturing technology for printed wiring boards having fine patterns with a narrow pitch of 200 μm or less. In particular, there is an increasing demand for fine patterns in lands for mounting and connecting electronic components such as semiconductors.

For the purpose of facilitating the design for such fine patterning of the conductor circuit and reducing the weight, the inner layer circuit board is used as the core material, and the insulating resin layer and the conductor layer are alternately stacked on the surface. A build-up method for forming a multilayer printed wiring board by forming a multilayer structure has been receiving attention.

FIG. 2 shows the production of a multilayer printed wiring board by this build-up method. As shown in FIG. 2 (a), an inner layer circuit board 1 having a conductor layer 11 for the inner layer as a circuit 12a on the surface thereof is formed. First, as shown in FIG. 2B, the insulating resin layer 2a and the conductor layer 3a are provided on the surface of the inner conductor layer 11. Next, as shown in FIG. 2C, a via hole 5 is formed in the insulating resin layer 2a, a plating layer 6 is formed on the inner periphery of the via hole 5, and a circuit forming process is further performed on the conductor layer 3a to form a circuit 12b. Forming and forming via layer 5 in conductor layer 3
Interlayer connection of a and 11 is made.

After processing the circuit 12b on the conductor layer 3a in this manner, the insulating resin layer 2b and the conductor layer 3b are provided on the surface of the conductor layer 3a, and the vias are formed on the insulating resin layer 2b as shown in FIG. 2 (d). The hole 5 is processed, the plating layer 6 is formed on the inner periphery of the via hole 5, and the conductor layer 3b is subjected to a circuit forming process to form a circuit 12c. The via hole 5 connects the conductor layers 3a and 3b to each other. To do. In the example of FIG. 2 (d),
Through holes 13 and through hole plating 14 are provided to connect the inner and outer conductor layers 3a, 3b, 11 to each other. Then, by applying the solder resist 15 to the outermost surface, a multilayer printed wiring board as shown in FIG. 2E can be finished.

[0006]

As described above, a multilayer printed wiring board manufactured by a method of alternately stacking the insulating resin layers 2a and 2b and the conductor layers 3a and 3b on the inner layer circuit board 1 and building up Therefore, the insulating resin layers 2a and 2b are formed by heating and pressing resin films to be laminated, applying a resin to heat and cure, or providing a semi-cured thermosetting resin on one surface of the metal foil. It is generally performed by heat-press molding and laminating the metal foil with resin formed by the above method.

Therefore, the insulating resin layer 2 thus formed
The layers a and 2b are resin-based layers that do not include a reinforcing base material such as glass cloth, and are likely to undergo large dimensional changes due to expansion and contraction due to thermal history. For this reason, when heat history is applied to the printed wiring board, such as when passing through a solder reflow oven to mount the mounted components on the printed wiring board manufactured by the build-up method, the printed wiring board is likely to warp There was a problem that it could hinder the operation.

Therefore, a prepreg prepared by impregnating glass cloth with a thermosetting resin and drying is used, and the insulating resin layers 2a and 2b are formed by heating and pressing the prepreg. In this case, glass cloth can be embedded in the insulating resin layers 2a and 2b as a reinforcing base material.
Since the dimensional changes of a and 2b can be suppressed, it is possible to reduce the occurrence of warpage due to thermal history such as solder reflow.

Here, in order to cope with the fine patterning of the circuit, it is desirable that the surface conductor layer 3b is formed by plating by an additive method or a semi-additive method. When forming the conductor layer 3b on the outermost insulating resin layer 2b by plating, in order to form the conductor layer 3b with a high adhesion strength and a fine pattern, the outermost insulating resin layer 2b is roughened to have a flat surface. It must be a face. However, when the glass cloth is embedded in the outermost insulating resin layer 2b as described above, the weave of the glass cloth appears on the surface of the insulating resin layer 2b, and the surface of the insulating resin layer 2b becomes uneven. However, there is a problem that it is difficult to form the conductor layer 3b having a fine pattern by plating.

The present invention has been made in view of the above points, and it is possible to reduce the occurrence of warpage due to thermal history, and it is easy to form the outermost conductor layer in a fine pattern. The purpose is to provide a plate.

[0011]

In a printed wiring board according to claim 1 of the present invention, a plurality of insulating resin layers 2a, 2b ... And conductor layers 3a, 3b. In the printed wiring board formed by building up, the outermost insulating resin layer 2b is formed as a resin-based layer that does not contain the glass cloth 4 as a base material, and is the second layer from the outermost layer. Insulating resin layer 2a
Is formed as a layer containing the glass cloth 4 as a base material.

The invention of claim 2 is characterized in that in claim 1, the conductor layer 3b is formed by plating on the surface of the outermost insulating resin layer 2b.

According to a third aspect of the present invention, in the first or second aspect, the insulating resin layer 2a second from the outermost layer and the conductor layer 3a provided on the surface of the insulating resin layer 2a are prepregs having the glass cloth 4 as a base material. It is characterized in that it is formed by stacking a metal foil and heating and pressing.

The invention according to claim 4 is based on any one of claims 1 to 3, wherein the connection between the conductor layers 3a and 3b is:
It is characterized in that it is performed by the plating layer 6 in the via hole 5 formed in the insulating resin layers 2a and 2b.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

In the present invention, an arbitrary one can be used as the inner layer circuit board 1, and a double-sided metal-clad laminate is processed to form the inner conductor layer 1 on both sides of the laminate 16.
Those provided with 1 can be used. For example, one or more prepregs obtained by impregnating a base material such as a glass cloth with a thermosetting resin such as an epoxy resin and drying the prepregs are stacked, and a metal foil such as a copper foil is stacked on both sides of the prepreg and heated. A double-sided metal-clad laminate is produced by pressure forming,
The inner layer circuit board 1 as shown in FIG. 1A can be manufactured by forming the circuit 12a on the metal foils on both sides by a tenting method using a dry film and providing the inner conductor layer 11. . In this inner layer circuit board 1, the surface of the inner conductor layer 11 is subjected to an oxidation treatment using an oxidant (which is referred to as a blackening treatment or a black oxidation treatment) in advance to roughen the surface, and the insulating resin to be described later. It is preferable to increase the adhesion to the layer 2a.

Then, the insulating resin layer 2a and the conductor layer 3a are built up on both surfaces of the inner layer circuit board 1. A glass cloth 4 is embedded as a base material in the insulating resin layer 2a as shown in FIG. 1 (b). When the insulating resin layer 2a containing the glass cloth 4 and the conductor layer 3a are built up and provided, for example, a thermosetting resin such as an epoxy resin is impregnated into a base material such as a glass cloth and dried. The prepreg and a metal foil such as a copper foil which are stacked in this order on the surface of the inner layer circuit board 1 can be heated and pressed to form a glass. Cross 4
It is possible to form the insulating resin layer 2a in which is embedded and to form the conductor layer 3a with a metal foil.

After the insulating resin layer 2a and the conductor layer 3a are built up in this way, as shown in FIG. 1C, the insulating resin layer 2a is laser-processed to form a via hole 5 and the via hole 5. A plating layer 6 is formed on the inner circumference by electroless plating of copper, etc., and the conductor layer 3a is printed by a tenting method using a dry film or the like to form a circuit 12b, and the via hole 5 is used to form the conductor layer 3a. And the inner conductor layer 11 are connected to each other. Circuit 12 on conductor layer 3a
After the formation of b, it is preferable that the surface of the conductor layer 3a is subjected to blackening treatment to roughen the surface so as to enhance the adhesion with the insulating resin layer 2b described later.

Next, the insulating resin layer 2b is built up on the surfaces of the insulating resin layer 2a and the conductor layer 3a formed as described above. This insulating resin layer 2b does not contain a base material such as glass cloth as shown in FIG. 1 (d).
It is formed as a layer mainly composed of resin. When the insulating resin layer 2b containing no such base material is built up and provided, for example, a thermosetting resin such as an epoxy resin formed into a film in a semi-cured state is used, and the semi-cured resin film is used as a conductor. It can be carried out by superposing it on the surface of the layer 3a and applying heat and pressure, and the insulating resin layer 2b can be formed by the cured resin of the semi-cured resin film.

After forming the insulating resin layer 2b as described above, the conductor layer 3b is provided on the surface of the insulating resin layer 2b. This conductor layer 3b is for forming the outermost circuit 12c, and is an additive method of forming a circuit by electrolessly plating a metal such as copper, or a semi-additive method of forming a circuit by combining electroless plating and electrolytic plating. With the construction method,
The conductor layer 3b is provided on the surface of the insulating resin layer 2b. Since the insulating resin layer 2b does not include a base material such as glass cloth, the surface of the insulating resin layer 2b is a flat rough surface without large unevenness, and the conductor layer 3b is adhered in a fine pattern by plating. It can be formed high. At this time, prior to forming the conductor layer 3b, the insulating resin layer 2b is laser-processed to form the via hole 5, and after the formation of the conductor layer 3b, electroless plating of copper is performed on the inner periphery of the via hole 5. Plating layer 6
Is formed, and the via holes 5 are used to connect the conductor layers 3a and 3b to each other as shown in FIG. 1 (d). Further, in the embodiment shown in FIG. 1D, the through hole 1 penetrating therethrough is used.
3 is provided, and the conductor layers 3a, 3b and 11 are connected to each other by the through hole plating 14 formed on the inner periphery of the through hole 13 by electroless plating of copper or the like.

Then, by applying a solder resist 15 to the portions of the surfaces of the insulating resin layer 2b and the conductor layer 3b formed as described above, which are not to be soldered, as shown in FIG.
The multilayer printed wiring board as shown in (e) can be finished. In the printed wiring board thus manufactured by the build-up method, the insulating resin layer 2a,
The outermost insulating resin layer 2b of 2b does not include a base material such as glass cloth and is a layer suitable for an additive method or a semi-additive method.
A glass cloth 4 is embedded as a base material in the glass cloth 4. The dimensional change of the insulating resin layer 2a can be suppressed by the reinforcing effect of the glass cloth 4, and the insulating resin layer 2a containing the glass cloth 4 is suppressed. Thus, it is possible to suppress the dimensional change of the entire printed wiring board. Therefore, even if thermal history such as solder reflow acts on the printed wiring board, it is possible to reduce the occurrence of warpage of the printed wiring board.

In the embodiment of FIG. 1, two layers of insulating resin layers 2a and 2b are provided on both surfaces of the inner layer circuit board 1, and the outer layer insulating resin layer 2b includes a base material such as glass cloth. The innermost insulating resin layer 2a was formed as a layer in which the glass cloth 4 was embedded as a base material, but the outermost layer was a resin-based layer containing no base material such as glass cloth. The second layer from the outer layer is glass cloth 4
The number of insulating resin layers is not limited as long as it is formed as a layer embedded as a base material. For example, the number of layers may be three or more on each side, and an inner copper circuit board may be used. It may be built up on only one side.

[0023]

EXAMPLES Next, the present invention will be specifically described with reference to examples.

(Example 1) As the inner layer circuit board 1, a double-sided copper-clad laminated board ("R1766" manufactured by Matsushita Electric Works, Ltd .: board thickness 0.
The conductor layer 11 for the inner layer was blackened using a copper foil having a thickness of 4 mm and a copper foil thickness of 18 μm, which was subjected to a circuit forming process by a tenting method (see FIG. 1A).

A glass cloth base prepreg (“R166” manufactured by Matsushita Electric Works, Ltd.) is formed on both surfaces of the inner layer circuit board 1.
1 ": a thickness of 0.06 mm) and a copper foil having a thickness of 18 μm are laminated in this order, under a reduced pressure atmosphere of 10 kPa, 170 ° C., and 2.
The insulating resin layer 2a having the glass cloth 4 embedded therein and the conductor layer 3a were laminated by vacuum press molding under conditions of 5 MPa and 100 minutes (see FIG. 1B). Then, carbon dioxide gas laser processing is performed on the insulating resin layer 2a to form the via holes 5.
Then, electroless copper plating was performed to form a plating layer 6 in the via hole 5, and the conductor layer 3a was subjected to circuit forming processing by a tenting method (see FIG. 1C).

Next, after the conductor layer 3a is blackened, a semi-cured film of epoxy resin is laid on the conductor layer 3a, and a vacuum laminator is used under a reduced pressure atmosphere of 10 kPa at 110 ° C.
By pressing at 1.0 MPa for 2 minutes,
The insulating resin layer 2b having a thickness of 60 μm was laminated. Then, a through hole 13 is formed by drilling, a carbon dioxide gas laser is processed on the insulating resin layer 2b to form a via hole 5, and electroless copper plating is performed to form a through hole plating 14 in the through hole 13. A plating layer 6 was provided in each via hole 5, and a conductor layer 3b was formed on the surface of the insulating resin layer 2b. Next, the conductor layer 3b was subjected to a circuit forming process by a tenting method (see FIG. 1D).

After that, a desired printed wiring board was obtained by printing a solder resist 15 on predetermined portions of the conductor layer 3b and the insulating resin layer 2b (see FIG. 1 (e)).

Comparative Example 1 A resin-coated metal foil (“R0880” manufactured by Matsushita Electric Works, Ltd .: copper foil thickness 18 μm, resin thickness 60 μm) prepared by coating a semi-cured epoxy resin on one surface of a copper foil. Using this same metal foil with resin on both sides of the same inner layer circuit board 1 as in Example 1 on the resin side, 175 ° C.
The insulating resin layer 2a and the conductor layer 3a were laminated by vacuum press molding under the conditions of 3.0 MPa and 100 minutes (see FIG. 2B). Then, carbon dioxide gas laser processing is performed on the insulating resin layer 2a to form via holes 5, electroless copper plating is performed to provide a plating layer 6 in the via holes 5, and circuit formation processing is performed on the conductor layer 3a by a tenting method. (See FIG. 2 (c)).

Next, after the conductor layer 3a is blackened, a semi-cured film of epoxy resin is laid on the conductor layer 3a, and a vacuum laminator is used in a reduced pressure atmosphere of 10 kPa at 110 ° C.
By pressing at 1.0 MPa for 2 minutes,
The insulating resin layer 2b having a thickness of 60 μm was laminated. Then, a through hole 13 is formed by drilling, a carbon dioxide gas laser is processed on the insulating resin layer 2b to form a via hole 5, and electroless copper plating is performed to form a through hole plating 14 in the through hole 13. A plating layer 6 was provided in each via hole 5, and a conductor layer 3b was formed on the surface of the insulating resin layer 2b. Next, the conductor layer 3b was subjected to a circuit forming process by a tenting method (see FIG. 2D).

After that, a desired printed wiring board was obtained by printing a solder resist 15 on predetermined portions of the conductor layer 3b and the insulating resin layer 2b (see FIG. 2 (e)).

The printed wiring boards obtained in the above Example 1 and Comparative Example 1 were cut into 100 × 100 mm, and this was cut into 240
After passing through the solder reflow oven under conditions of 10 ° C for 10 seconds, place this printed wiring board on a horizontal surface plate and measure the lifted dimension of the largest lifted portion at the four corners of the printed wiring board as the amount of warpage. did. Table 1 shows the results of performing this test on seven printed wiring boards.

[0032]

[Table 1]

As shown in Table 1, in Comparative Example 1 in which neither of the two insulating resin layers 2a and 2b contained a substrate such as glass cloth, a large amount of warpage occurred.
In the example 1 in which the glass cloth 4 is embedded in the insulating resin layer 2a as the base material among the insulating resin layers 2a and 2b of the layers, it is confirmed that the warpage is significantly reduced.

[0034]

As described above, the printed wiring board according to claim 1 of the present invention is formed by alternately building up a plurality of insulating resin layers and conductor layers on the surface of the inner layer circuit board. In the printed wiring board, the outermost insulating resin layer is formed as a resin-based layer that does not contain glass cloth as a base material, and the second insulating resin layer from the outermost layer contains glass cloth as a base material. Since it is formed as a layer to be formed, the dimensional change can be suppressed by the reinforcing action of the second insulating resin layer from the outermost layer containing glass cloth as the base material, and the occurrence of warpage due to thermal history can be reduced. In addition, the outermost insulating resin layer does not contain glass cloth as a base material so that no unevenness is generated on the surface, and the outermost conductor layer is formed in a fine pattern. It is intended that is facilitated.

According to the second aspect of the present invention, since the conductor layer is formed on the surface of the outermost insulating resin layer by plating, unevenness does not occur on the surface of the outermost insulating resin layer as described above. Thus, the outermost conductor layer can be formed in a fine pattern by plating.

According to a third aspect of the present invention, the insulating resin layer second from the outermost layer and the conductor layer provided on the surface of the insulating resin layer are formed by superposing a prepreg having a glass cloth as a base material and a metal foil and heating and pressing. Since it is formed by carrying out, it is possible to simultaneously form an insulating resin layer and a conductor layer,
The number of steps can be reduced.

According to the invention of claim 4, the connection between the conductor layers is made by the plating layer in the via hole formed in the insulating resin layer, so that the connection between the conductor layers is made with high reliability. Is something that can be done.

[Brief description of drawings]

FIG. 1 shows an example of an embodiment of the present invention,
(A)-(e) is sectional drawing, respectively.

FIG. 2 is a view showing an example of the related art, and (a) to (e)
Are sectional views, respectively.

[Explanation of symbols]

1 Inner layer circuit board 2 Insulating resin layer 3 conductor layers 4 glass cloth 5 via holes 6 plating layer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shinya Nishimoto             1048, Kadoma, Kadoma-shi, Osaka Matsushita Electric Works Co., Ltd.             Inside the company F-term (reference) 4F100 AB01A AB17A AG00C AK01B                       AK53 AK53B BA10A BA10C                       DG11C DH00C DH01 EH71A                       EJ172 EJ422 JG01A JG04B                       JG04C                 5E346 AA05 AA06 AA12 AA15 AA22                       AA32 AA43 AA51 CC02 CC04                       CC08 CC32 DD02 DD12 DD22                       DD32 DD33 EE06 EE07 EE09                       EE13 FF01 FF04 FF07 FF15                       FF45 GG15 GG17 GG22 GG28                       HH11 HH26

Claims (4)

[Claims] 1. In a printed wiring board formed by alternately building up a plurality of insulating resin layers and conductor layers on the surface of an inner circuit board, the outermost insulating resin layer is made of glass cloth. A printed wiring board, characterized in that it is formed as a resin-based layer not containing as a material, and that the second insulating resin layer from the outermost layer is formed as a layer containing glass cloth as a base material. 2. The printed wiring board according to claim 1, wherein a conductor layer is formed on the surface of the outermost insulating resin layer by plating. 3. The second insulating resin layer from the outermost layer and the conductor layer provided on the surface of the insulating resin layer are formed by stacking a prepreg having a glass cloth as a base material and a metal foil and performing heat-press molding. Claim 1 or 2 characterized in that
The printed wiring board described in. 4. The printed wiring board according to claim 1, wherein the connection between the conductor layers is made by a plating layer in a via hole formed in the insulating resin layer. .