JP2000022330A - Multilayer interconnection board and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer interconnection board free of inferiority of close adhesion between insulating layers, in a wiring board possessing a wiring circuit layer comprising of a large area of metallic foil such as a ground layer, etc., and its manufacturing method. SOLUTION: A wiring layer (a) of one unit is manufactured by roughening the exposed face of a wiring circuit layer 15 after transcribing the wiring circuit layer 15 of a metallic foil whose surface is roughened while burying the wiring circuit layer 15 in the surface of an insulating sheet 11 by adding pressure to the surface of the insulating sheet 11 containing at least organic resin in soft condition from a transcription sheet 14. It and wiring layers (b) and (c) manufactured likewise are stacked and pressure-bonded and then, they are heated thereby being hardened en block, thus a multilayer wiring board is made into such structure that a plurality of insulating layers where wiring circuit layers consisting of metallic foils are buried in the surfaces are stacked is made. Hereby, a multilayer interconnection board where the top and bottom of the wiring circuit layer arranged between the insulating layers out of the wiring circuit layers are roughened and processed into surface roughness (Ra) of 0.1-5 μm is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer wiring board in which an insulating substrate used for, for example, a motherboard of a large computer called a main frame or a substrate for mounting a semiconductor element contains an organic resin, and a method of manufacturing the same. .

[0002]

2. Description of the Related Art Hitherto, a multilayer printed wiring board has been used for manufacturing a motherboard and the like, and a motherboard of a large computer called a mainframe has a board provided with at least 20 wiring circuit layers.

[0003] Conventional multilayer printed wiring boards generally include:
After laminating a semi-cured insulating sheet on the surface of the fully cured insulating substrate as a base, heating and curing the insulating sheet, a wiring circuit layer is formed on the surface, and a semi-cured insulating sheet is further formed on the surface. It is formed into a multilayer by repeating lamination, heat curing, and formation of a wiring circuit layer.

According to this conventional multilayer printed wiring board, a wiring circuit layer is formed by etching or plating of a metal foil. At this time, the thermosetting resin used in the insulating substrate is a circuit board. It had to be completely cured when the layer was formed. This is because the etching liquid or the plating liquid penetrates into the uncured insulating substrate to cause migration or discoloration.

Therefore, in the conventional method, as the number of laminations increases, it is necessary to repeat the lamination hardening process many times before completion, resulting in a remarkably low productivity. Further, since the thermosetting resin shrinks at the time of curing, it shrinks each time the curing process is performed, so that deformation such as warpage and dimensional variation are likely to occur.

[0006] In order to solve the drawbacks in the conventional manufacturing method, the present applicant firstly applied a wiring circuit layer made of metal foil from a transfer sheet to a conventional soft or semi-cured insulating sheet. A method of manufacturing a multilayer wiring board, which is formed by transferring a plurality of insulating sheets, laminating and pressing the plurality of insulating sheets, and heat-curing all at once. This method simplifies the process, and press-transfers a wiring circuit layer made of a metal foil onto a soft insulating sheet, so that the wiring circuit layer is buried on the surface of the insulating sheet. It has many advantages, such as not occurring.

[0007]

In the above simultaneous curing method, the bonding between the insulating sheets is performed by the adhesiveness of the insulating sheet itself in a soft state. However, in circuit design, a ground layer or a shield layer is used as a measure against noise. When forming a large area circuit pattern by transferring from a transfer sheet, a copper foil surface of the transfer sheet usually has a large area. Because of the roughening treatment, there is no problem in transferability, but since the exposed surface of the wiring circuit layer made of the metal foil after transfer is usually formed of a smooth surface, the insulating sheet laminated on this surface is There is a problem that the adhesion strength of the resin is extremely reduced and lamination failure occurs.

In such a case, it is usually conceivable to use a metal foil which has been roughened on both sides as the metal foil to be bonded to the transfer sheet. In addition, an adhesive such as a glue of an adhesive tape remains on the unevenness of the metal foil on the transfer sheet side, resulting in a transfer failure, discoloration, and peeling of the metal foil.

Accordingly, an object of the present invention is to provide a multilayer wiring board having no adhesion failure between insulating layers even in a wiring board having a wiring circuit layer made of a metal foil having a large area such as a ground layer, and a method of manufacturing the same. It is assumed that.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the above-mentioned problems, and as a result, first, a wiring circuit layer made of a metal foil whose surface has been roughened is formed on an insulating sheet such as an uncured prepreg. After pressure transfer, the roughened surface of the transferred metal foil is found to be able to improve the adhesion between the internal wiring circuit layer and the insulating layer, and the present invention has been achieved.

That is, the multilayer wiring board of the present invention has a structure in which at least an organic resin is contained, and a plurality of insulating layers each having a surface in which a wiring circuit layer made of a metal foil is embedded are laminated. There is provided at least one wiring circuit layer disposed and having a surface roughness (Ra) of 0.1 to 5 μm on the upper surface and the lower surface in contact with the insulating layer, and the upper and lower surfaces are rough. As the integrated wiring circuit layer, a ground layer, a shield layer, or the like is optimal.

Further, a method of manufacturing a multilayer wiring board according to the present invention is intended to manufacture a multilayer wiring board having at least an insulating layer containing an organic resin, and a wiring circuit layer disposed on and inside the insulating layer. (A) The surface roughness (Ra) of the exposed surface of the transfer sheet surface is 0.1 to 5 μm.
forming a wiring circuit layer made of a metal foil of m.
(B) laminating the exposed surface of the wiring circuit layer on the surface of the transfer sheet while applying pressure to at least the surface of a soft insulating sheet containing an organic resin; embedding the wiring circuit layer on the surface of the insulating sheet; Removing the transfer sheet and transferring the wiring circuit layer to the insulating sheet surface,
(C) The exposed surface of the transferred wiring circuit layer has a surface roughness (R
a) a step of performing a roughening treatment to 0.1 to 5 μm;
(A) through (c), a step of laminating and pressing a plurality of insulating sheets having a wiring circuit layer formed on the surface thereof, and a step of collectively heating and curing.

In the above manufacturing method, the exposed surface of the wiring circuit layer in the steps (a) and (c) is roughened by an etching treatment with an acid.
A step (b ') of pressurizing and heating an insulating sheet having a wiring circuit layer embedded on its surface to densify the insulating sheet, between the step (b) and the step (c); It is desirable that the densification in ') is performed by applying pressure and heating at a temperature of 100 to 200 ° C. while applying a pressure of 5 kg / cm ² or more.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram for explaining the structure of a multilayer wiring board according to the present invention. The multilayer wiring board of the present invention has a plurality of insulating layers 1a to 1 at least containing an organic resin.
The laminated body 1d is used as an insulating substrate 1, and a wiring circuit layer 2 made of metal foil is formed between the surface and the insulating layer.
Then, a via hole conductor 3 for connecting the wiring circuit layers 2 is formed at an arbitrary position of the insulating layer between the wiring circuit layers 2 if desired.

According to the present invention, the wiring circuit layer disposed between the insulating layers has a surface roughness (Ra) of 0.1 to 5 μm, particularly 0.2 μm, on the upper surface and the lower surface in contact with the insulating layer.
There is at least one wiring circuit layer having a thickness of 4 μm or more.
It is desirable that all the wiring circuit layers disposed between the insulating layers have been subjected to the above-described roughening treatment of the upper and lower surfaces. It is desirable to apply at least to a large wiring circuit layer. If the surface roughness is smaller than 0.1 μm, the adhesion to the insulating layer is low, and lamination failure or adhesion failure occurs. If the surface roughness exceeds 5 μm, disconnection or the like is likely to occur in the wiring circuit layer.

Further, according to the multilayer wiring board of the present invention, as shown in FIG.
Since it is buried in the surface of 1d to 1d, there is no gap or the like due to the thickness of the wiring circuit layer 2 itself, and it has excellent adhesion between insulating layers and extremely excellent smoothness. . It is effective for the cross section of the wiring circuit layer 2 to have an inverted trapezoidal shape as shown in FIG. 2 in terms of the adhesion to the insulating layer and the embedding property, and in particular, the formation angle θ in the inverted trapezoidal shape.
Is preferably 30 to 80 °.

According to the method for manufacturing a multilayer wiring board of the present invention, as shown in the process diagram of FIG. 3, first, as shown in FIG. 3A, an uncured or semi-cured soft insulating sheet 1 is formed.
For 1, via holes 12 are formed by laser processing, micro drilling, or the like, and the via holes 12 are filled with a conductive paste containing a metal powder to form via hole conductors 13.

On the other hand, as shown in FIG. 3B, a wiring circuit layer 15 made of a metal foil is formed on the surface of the transfer sheet 14. The wiring circuit layer 15 is formed by adhering a metal foil to the surface of the transfer sheet 14 with an adhesive, applying a resist on the surface of the metal foil in a circuit pattern, and performing an etching process and a resist removal. . At this time,
The exposed surface 15a of the wiring circuit layer 15 made of metal foil needs to be roughened by etching or the like to a surface roughness (Ra) of 0.1 to 5 μm, especially about 0.2 to 4 μm. If the surface roughness at this time is smaller than 0.1 μm, poor adhesion occurs at the time of transfer to an insulating sheet to be described later or at the time of lamination of a multilayer wiring board, and lamination failure occurs.

The surface 15b of the wiring circuit layer 15 on the transfer sheet side preferably has a surface roughness (Ra) of 0.5 μm or less. This is because if the surface roughness is more than 0.5 μm, an adhesive or the like tends to adhere to the wiring circuit layer side when transferring a wiring circuit layer described later, resulting in poor transfer, discoloration, Problems such as peeling of the film are likely to occur.

The wiring circuit layer 15 formed on the surface of the transfer sheet 14 preferably has a trapezoidal cross section. This is because at the time of transfer to a soft insulating sheet to be described later, the embedding property into the insulating sheet and the adhesion to the insulating sheet can be improved. In addition,
From such a viewpoint, the trapezoidal formation angle (corresponding to θ in FIG. 2) of the cross section of the wiring circuit layer is desirably 30 to 80 °.

Next, as shown in FIG. 3C, the transfer sheet 14 on which the wiring circuit layer 15 having a roughened surface is formed is replaced with the soft insulating sheet 1 on which the via-hole conductor 13 is formed.
After being aligned and pressure-laminated on the surface of the substrate 1, the transfer sheet 14 is peeled off, and the wiring circuit layer 15 is transferred to the insulating sheet 11, thereby forming one unit of the wiring layer a.

At this time, since the insulating sheet 11 is in a soft state, the wiring circuit layer 15 is buried in the surface of the insulating sheet 11 and substantially covers the surface of the insulating sheet 11 and the wiring circuit layer 1.
The layers 5 are laminated under pressure so that the surfaces 5 are flush with each other. The pressure lamination conditions at this time were as follows: a pressure of 20 kg / cm ² or more;
A temperature of 60-140 ° C is suitable.

According to the present invention, when one unit of the wiring layer a is laminated to form a multilayer structure, the insulating sheet 11 having a wiring circuit layer serving as an internal wiring layer in the multilayer wiring structure is shown in FIG. As shown in d), the exposed surface 15a of the wiring circuit layer 15 is roughened by performing an etching process.

This roughening treatment can be performed by a chemical treatment using an acid such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid, formic acid, etc. In particular, an acid solution is sprayed on the exposed surface of the wiring circuit layer 15. It is desirable.

The surface roughness (Ra) of the exposed surface 15a of the wiring circuit layer 15 by such processing is responsible for the adhesion between the insulating sheets, and particularly, the surface roughness (Ra) is 0.1 to 5
Roughening treatment is performed so as to be μm. When the surface roughness of the exposed surface 15a of the wiring circuit layer 15 is less than 0.5 μm, the adhesion between the wiring circuit layer 15 and another insulating sheet becomes insufficient,
If it exceeds 5 μm, disconnection or the like is likely to occur in some of the wiring circuit layers, and the yield of the substrate is reduced when a fine pattern is formed. The surface roughness is optimally between 0.2 and 4 μm.

Further, according to the present invention, before performing the above-described roughening treatment, the insulating sheet 11 having the wiring circuit layer 15 embedded in the surface thereof is provided.
Is preferably densified to a porosity of 3% or less. This is to prevent the etchant from entering the uncured or semi-cured insulating sheet 11 due to the above-described roughening process and causing unevenness in color. Such densification treatment is 5 kg / c
While applying a pressure of at least m ^{2, the} heating is performed under pressure at a temperature of 100 to 200 ° C. At this time, the heating does not completely cure the thermosetting resin in the insulating sheet. It is applied to such an extent that the adhesiveness is maintained. If it is completely cured by the heat treatment at this time,
This is because the adhesion between the insulating sheets is reduced in the subsequent lamination processing.

Then, one unit of the wiring layer a manufactured as described above and one unit of the wiring layers b and c manufactured in the same manner are laminated and pressed as shown in FIG. The multilayer wiring board of the present invention can be manufactured by heating to a temperature at which the thermosetting resin in the inside is completely cured and by being simultaneously cured.

In the above manufacturing method, the process of forming and laminating via holes in the insulating sheet and the process of forming the wiring circuit layer can be performed in parallel, so that the manufacturing time in the wiring board can be greatly reduced. it can.

In this embodiment, in order to seal both ends of the via-hole conductor with a wiring circuit layer made of metal foil, the thickness of the wiring circuit layers 2 and 15 is appropriately 5 to 40 μm.

According to the multilayer wiring board of the present invention, a through hole can be formed by using a drill, and a metal plating layer can be formed on the inner wall of the hole. In this case, in the multilayer wiring board of the present invention, since there is substantially no gap between the insulating layer or the wiring circuit layer and the insulating layer due to lamination failure or the like, the plating solution may enter the board during the plating process. As a result, it is possible to suppress the occurrence of migration and discoloration.

The insulating layer in the multilayer wiring board of the present invention is made of an insulating material containing at least an organic resin.
Specifically, as the organic resin, for example, a resin such as PPE (polyphenylene ether), BT resin (bismaleimide triazine), an epoxy resin, a polyimide resin, a fluororesin, and a phenol resin is desirable. It is desirable that the resin is a thermosetting resin having a temperature of not lower than ° C. In addition, a filler component can be compounded in the organic resin in order to increase the strength of the entire substrate. As the filler, SiO ₂ , Al ₂ O
₃ , ZrO ₂ , TiO ₂ , AlN, SiC, BaTiO
₃ , inorganic fillers such as SrTiO ₃ , zeolite and CaTiO ₃ are preferably used. Further, a nonwoven fabric or a woven fabric made of glass or aramid resin may be used by impregnating the above resin. When compounding with the filler component as described above, the organic resin and the filler have a volume ratio of 30:70 to
It is desirable to composite at a ratio of 70:30.

Further, the wiring circuit layer is desirably made of at least one alloy selected from the group consisting of copper, aluminum, gold and silver, or two or more alloys.
Copper or an alloy containing copper is most desirable. In some cases, a high-resistance metal such as a Ni—Cr alloy may be mixed or alloyed to adjust the resistance of the circuit.

Further, as the conductor paste to be filled in the via hole, a paste obtained by adding a resin component such as epoxy or cellulose to the metal powder for forming the wiring circuit layer and kneading with a solvent such as butyl acetate is used. You.
It is desirable that the conductive paste be solvent-free from the beginning after drying the solvent after filling into the via holes. Further, in order to reduce the resistance of the via-hole conductor, the metal powder may contain a low melting point metal such as solder or tin.

[0034]

EXAMPLE A via hole having a diameter of 0.1 mm was formed with a carbon dioxide laser on a prepreg (A) impregnated with 50% by volume of a PPE resin and a glass cloth woven with E glass at a ratio of 50% by volume. Was filled with a copper paste containing a copper powder plated with silver to form a via-hole conductor.

On the other hand, polyethylene terephthalate (PE)
T) An adhesive is applied to the surface of a transfer sheet made of a resin to impart tackiness, and a copper foil having a thickness of 12 μm, a surface roughness of a shiny surface of 0.1 μm, and a surface roughness of a matte surface of 0.8 μm is formed on a PET surface. And the copper foil were adhered so as to face each other. Thereafter, a photoresist was applied and subjected to exposure and development, and then immersed in a ferric chloride solution to remove non-pattern portions by etching to form a wiring circuit layer. The fabricated wiring circuit layer is 50% of the area of the prepreg for convenience.
Is a ground layer pattern having a surface roughness (Ra) of 0.8 μm on the surface of the wiring circuit layer made of a square-shaped conductor layer having an area of 0.8 μm.

Next, after the transfer sheet having the copper foil wiring circuit layer formed thereon is positioned and brought into close contact with the prepreg (A), the transfer sheet is applied with a pressure of 50 kg / cm ² for 120 to 120 kg / cm ^2.
The transfer sheet was peeled off by heating to 130 ° C., and a wiring circuit layer made of copper was formed to form one wiring layer. The transferred wiring circuit layer was embedded in the surface of the insulating sheet, and it was confirmed that the surface of the wiring circuit layer and the surface of the insulating sheet were flush with each other.

Next, the prepreg on which the wiring circuit layer was transferred was pressurized and heated at 150 ° C. and a pressure of 10 kg / cm ² for 5 minutes to perform semi-curing of the prepreg. The porosity of the prepreg after this treatment was measured by Archimedes' method and found to be 2%.

Then, a 10% by weight formic acid solution is sprayed onto the transfer surface of the densified prepreg to transfer the wiring circuit layer, and the surface is etched to reduce the surface roughness (Ra) of the processed wiring circuit layer surface. One unit of 0.5 μm was formed as a wiring layer.

In the same manner as described above, 12 unit wiring layers were formed. These wiring layers are aligned and laminated, and 2
It was heated at 200 ° C. for 1 hour while applying a pressure of 0 kg / cm ² , and was completely cured at once to produce a multilayer wiring board.

The cross section of the obtained multilayer wiring board was observed. As a result, the adhesion between the wiring circuit layer and the prepreg was good, and there was no lamination failure. In addition, migration, discoloration, cracks, and the like due to the etching solution did not occur in the prepreg. Near the formation of the via-hole conductor, the wiring circuit layer and the via-hole conductor were in a good connection state. As a result of conducting a continuity test between the respective wirings, no disconnection of the wiring was observed.

Further, a through hole having a diameter of 200 μm is formed in the multilayer wiring board using a drill,
A copper plating layer having a thickness of 30 μm was formed therein by a plating method, but no intrusion of the plating solution into the substrate was observed at all, and it was a good one without migration or discoloration.

Further, for comparison, as a result of performing laminating pressure bonding and batch hardening processing without performing the above-described roughening processing after the transfer of the wiring circuit layer to the prepreg, the ground circuit layer forming surface was formed. It was confirmed that poor adhesion between the metal foil and the insulating layer had occurred.

[0043]

As described above in detail, according to the present invention, by forming a wiring circuit on an insulating layer by transferring from a transfer sheet, the laminating step and the curing step can be performed collectively. The manufacturing process of the wiring board can be greatly simplified, and a multilayer wiring board having good adhesion can be produced by performing a predetermined roughening treatment on a wiring circuit layer having a large area such as a ground layer. can do.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a multilayer wiring board according to the present invention.

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

FIG. 3 is a process diagram illustrating a method for manufacturing a multilayer wiring board according to the present invention.

[Explanation of symbols]

 1a to 1d Insulating layer 1 Insulating substrate 2 Wiring circuit layer 3 Via hole conductor 11 Insulating sheet 12 Via hole 13 Via hole conductor 14 Transfer sheet 15 Wiring circuit layer a to c Wiring layer

Continuation of the front page F term (reference) 5E338 AA03 AA16 BB02 BB12 BB25 BB63 CC01 CC05 CC06 CD23 EE27 EE32 5E343 AA02 AA12 BB02 BB24 BB66 CC33 DD56 DD62 EE52 ER33 ER39 GG04 5E346 AA11 AA11 BB03 DD08 EE02 EE06 EE07 EE14 FF18 FF35 FF36 GG01 GG15 GG27 GG28 HH11 HH32

Claims (6)

[Claims] 1. A structure in which a plurality of insulating layers each containing at least an organic resin and having a wiring circuit layer made of a metal foil embedded in a surface thereof are laminated, the insulating layers being disposed between the insulating layers and contacting the insulating layers. A multilayer wiring board comprising at least one wiring circuit layer having a surface roughness (Ra) of 0.1 to 5 μm on the upper and lower surfaces. 2. The multilayer wiring board according to claim 1, wherein the wiring circuit layer whose upper and lower surfaces are roughened is a ground layer or a shield layer. 3. An insulating layer containing at least an organic resin,
In the method for manufacturing a multilayer wiring board having a surface of the insulating layer and a wiring circuit layer disposed therein, (a) the surface of the transfer sheet has a surface roughness (Ra) of 0.1 to 5 μm.
Forming a wiring circuit layer made of metal foil,
(B) laminating the exposed surface of the wiring circuit layer on the surface of the transfer sheet while applying pressure to at least the surface of a soft insulating sheet containing an organic resin; embedding the wiring circuit layer on the surface of the insulating sheet; Removing the transfer sheet and transferring the wiring circuit layer to the insulating sheet surface,
(C) The exposed surface of the transferred wiring circuit layer has a surface roughness (R
a) a step of performing a roughening treatment to 0.1 to 5 μm;
(C) a step of laminating and pressing a plurality of insulating sheets on each of which a wiring circuit layer is formed on the surface by the steps (a) to (c), followed by heating and curing at once. Method. 4. The method according to claim 3, wherein the exposed surface of the wiring circuit layer in the steps (a) and (c) is roughened by an etching treatment with an acid. 5. The method according to claim 1, wherein said step (b) and said step (c)
5. The method for manufacturing a multilayer wiring board according to claim 3, further comprising: (b ') a step of applying pressure and heating to densify the insulating sheet having a wiring circuit layer embedded on a surface thereof. 6. The method according to claim 1, wherein the densification in the step (b ′) is 5 k
g / cm ² or more while applying a pressure of 100 to 200
The method for producing a multilayer wiring board according to claim 5, wherein the method is performed by heating under pressure at a temperature of ° C.