JPH11126973A - Manufacture of multilayered wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a multilayered wiring board having highly reliable conductive via holes with excellent workability by preforming columnar conductors on a conductor circuit by using conductive high-polymer thick film paste. SOLUTION: After a conductor circuit 2 is formed on a substrate 1, the level difference between the conductor circuit 2 and substrate 1 is eliminated by filling up the spaces of the circuit 2 with an insulating layer 32A. Then columnar conductors 10 are formed on the circuit 2 by using conductive high- polymer thick film paste and the peripheries of the conductors 10 are covered with an insulating layer 32. Thereafter, the head sections of the conductors 10 buried in the insulating layer 32 are exposed by projecting a laser beam upon the layer 32. Finally, a conductor 6 is formed on the entire surface of the insulating layer 32. Therefore, the electrical connectability of via holes can be secured by introducing a process of preforming the via holes as the columnar conductors 10. In addition, the conductors 10 can be manufactured easily by using simple accustomed techniques, such as the printing and thermosetting treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer wiring board, and more particularly, to a so-called build-up multilayer wiring board in which conductive circuits and insulating layers are alternately stacked and electrically connected between layers by via holes. It relates to a manufacturing method.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable progress in high-density wiring technology for electronic component mounting substrates due to demands for higher performance and smaller size of electronic communication devices. In particular, due to the high integration of semiconductor elements, the increase in the number of terminals, and the miniaturization of electronic components, the development of multilayer wiring boards in which wiring circuits are formed in multiple layers for the purpose of increasing the density of printed wiring boards has been rapidly advancing. . Conventionally,
As a multilayer wiring board, for example, a multilayer wiring board in which a plurality of circuit boards on which an inner layer circuit is formed is laminated with a prepreg as an insulating layer, and then heat-pressed and integrated, and the layers are connected to each other by plating through holes to conduct electricity. Was common.

However, in this method of manufacturing a multilayer wiring board, the number of through-holes for interlayer connection increases as the number of layers increases and the density increases, and the area for passing a conductor circuit is reduced. It has become difficult to form circuits and increase the density. As a multilayer wiring board that can solve such problems, a build-up method multilayer wiring board has been developed in which conductive circuits and insulating layers are alternately laminated, and only those parts that require interlayer connection are connected with via holes (blind through holes). Was. High-density circuits are possible with the build-up method multilayer wiring board.

[0004] The manufacturing process of the build-up method multilayer wiring board is as follows.
Generally, it comprises the steps shown in FIG. (1) a step of forming a conductive circuit 2 on a substrate 1; (2) a step of forming an interlayer insulating layer 3 on a conductor 2 of a substrate; (3) an interlayer insulating layer 3
And (4) forming a metal conductor 6 on the interlayer insulating layer on which the via hole 4 has been formed by vapor deposition, plating, or the like.

When a photosensitive resin is used for the interlayer insulating layer in this method, high insulation, high glass transition temperature, high heat resistance, low water absorption, and low dielectric constant required for the insulating layer while imparting photosensitivity are provided. However, it is difficult to design a resin that satisfies low dielectric loss and the like. In addition, it is also difficult to design a resin that retains the property that the unirradiated portion can be removed by development using a solvent or an aqueous alkali solution as a developing solution, while at the same time having chemical resistance such as desmear resistance and plating solution resistance. I have a problem.

On the other hand, when a thermosetting resin is used for the interlayer insulating layer, a via hole is opened by irradiating a laser beam. However, in a heat mode laser, a part of the resin is carbonized.
In the case of the laser remaining in the bottom of the via hole or in the photon mode laser, the inorganic filler or the like in the insulating layer remains as it is, so that the formation of the conductor in the subsequent process is incomplete and the connection reliability has many problems.

Further, in this method, it is difficult to determine whether or not all the via holes have a desired shape at the stage when the via holes are opened. As an improvement of this method, a method of obtaining an electrical connection by embedding a conductive polymer thick film paste instead of obtaining an electrical connection of a via hole by the above-described means such as vapor deposition and plating has been studied. ing. This is shown in (5) to (7) of FIG. This is after the step of opening the via hole in the conventional process (FIG. 2 (3)).
(5) A step of embedding the conductive polymer thick film paste 5 in the via hole 4 by screen printing or the like and curing the paste to form a conductor, and (6) a step of removing the head of the conductor by mechanical polishing. And (7) forming a conductor 6 over the entire mechanically polished surface.

However, according to this method, the diameter is several
It is necessary to ensure that a paste consisting of metal powder and a resin binder is buried in a via hole with a depth of several tens of microns, which is not more than 00 microns, to ensure high conductivity without bubbles and cracks and connection reliability. It is very difficult, the yield is poor, and practical application is delayed. As a method of solving such a problem of the conventional method of manufacturing a multilayer wiring board by a build-up method, a via-post type build-up wiring board has been proposed. This is a process as shown in FIG.

(1) A step of forming a conductive circuit 2 on a substrate 1, (2) A photosensitive resin 7 (dry film resist, photoresist) is applied and dried on the substrate, and exposed through a predetermined mask. And (3) forming a columnar metal block 9 called a via post in the hole 8 from which the photosensitive resin has been removed by development, by means of electroplating or the like, and (4) photosensitizing. Removing and removing the conductive resin 7,
(5) a step of applying and curing the thermosetting resin 31 over the entire surface of the substrate so as to cover the via posts 9; and (6) performing mechanical polishing to expose the top of the via posts buried in the thermosetting resin 31. (7) a step of forming the metal conductor 6 on the interlayer insulating layer on which the via posts 9 are formed by means such as vapor deposition and plating;

And the like. Since this via post type build-up wiring board makes electrical connection points first,
The feature is that the interlayer connection reliability is very high.
However, the formation of the via posts requires a very large number of steps, which raises the problem that the material cost increases and the yield deteriorates, so that a significant increase in cost is unavoidable.

[0011]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and provides a multilayer wiring board having highly reliable conductive via holes by a method of manufacturing with excellent workability. is there.

[0012]

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted intensive studies on a process for producing a multilayer wiring board, and as a result, a conductive polymer thick film paste was previously used on a conductive circuit. The present inventors have found that the above-mentioned problems can be solved by forming a columnar conductor by using this method, and have completed the present invention. That is, the present invention provides (1) a step of forming a conductor circuit on a substrate, (2) a step of forming a columnar conductor on a conductor of the substrate using a conductive polymer thick film paste,
(3) a step of covering the periphery of the columnar conductor with an insulating layer;
(4) A method of manufacturing a multilayer substrate, comprising: a step of exposing a head of a columnar conductor buried by an insulating layer by laser irradiation; and (5) a step of forming a conductor on a surface.
To provide a multilayer wiring board having high reliability and excellent workability.

Hereinafter, the present invention will be described in detail according to a method for manufacturing a multilayer wiring board according to the present invention (see FIG. 1). In the first step (FIG. 1 (1)) of forming the conductive circuit 2 on the substrate 1, a conventionally known technique can be used. Generally, a glass-epoxy laminate is widely used as the substrate 1, but a paper-phenol laminate, an aramid laminate, a bismaleimide laminate, a polyimide substrate, a metal core substrate, or the like may be used. The conductive circuit 2 is generally obtained by leaving a copper foil bonded to the substrate 1 as a predetermined pattern by applying photolithography technology. Instead of the copper foil, a copper thin film formed by vapor deposition, electroless and / or electrolytic plating, or a conductive metal thin film other than copper may be used. Also, a conductive thick film obtained by printing a conductive paste by a method such as screen printing and curing the conductive paste may be used.

In the present invention, before entering the next second step, as shown in FIG. 1A, a step between the wiring circuit and the base material is filled with an insulating layer 32A in advance and smoothed ( It is also possible to adopt a method of forming a (planarized) structure and proceeding to the second and subsequent steps described below.

As a second step (FIG. 1 (2)), the conductor 2
On top of this, a columnar conductor 1 is formed using a conductive polymer thick film paste.
0 is formed. The conductive polymer thick film paste is obtained by dispersing conductive particles in a polymer (resin) binder.
After forming a film with a predetermined size in a predetermined place by printing,
This is cured to form a conductor. Generally, screen printing or metal mask printing is used as the printing means. Here, as the conductive particles, gold,
Any material such as silver, copper, nickel, carbon, and graphite can be used, but copper powder, silver powder, or silver-plated copper powder is generally used in consideration of conductivity, stability, cost, and the like.

Further, epoxy resin as a binder,
Various thermosetting resins such as a phenol resin, a melamine resin, and a thermosetting acrylic resin are used alone or in combination. Further, in consideration of the solubility of the resin and the printing workability, these thermosetting resins can be used after being diluted with an organic solvent, a plasticizer, or the like. As described above, a method of embedding a via hole with a conductive polymer thick film paste has been considered as one of the conventional methods for manufacturing a multilayer wiring board. It is an undetermined condition that the molecular thick film paste 5 is solvent-free. This is because heat treatment (for example,
Heating of the interlayer insulation layer, soldering during component mounting, heating in pressure cooker test, heat resistance test, heat cycle test, etc.), foaming and blistering occur due to volatilization of the remaining solvent and connection This is because the reliability is impaired.

On the other hand, the conductive polymer thick film paste 10 used in the method of the present invention does not have this limitation. This is because, as is apparent from FIG. 1 (2), in the present invention, the conductive polymer thick film paste is printed in a columnar shape and thermoset, but the columnar body 10 is in an open state, This is because gas diffusion of the solvent is extremely easy and can be surely performed at the time of curing. As a result, a phenol resin, a melamine resin, a curable acrylic resin, or the like, which is relatively difficult to eliminate the solvent, can be used as the conductive polymer thick film paste resin of the present invention.

Further, even when an epoxy resin is used, not only bisphenol A or bisphenol F type liquid resin but also solid resin novolak epoxy or various polyfunctional epoxy resins can be dissolved in a solvent and used as a binder. As a result, a highly reliable columnar conductor 10 can be formed. In addition, even if the solvent is not used, a certain degree of shrinkage of the thermosetting resin is inevitable during curing.Therefore, when the via holes are filled with the conductive polymer thick film paste, voids are generated or internal stress is generated. According to the present invention, the columnar body can be freely contracted in the X and Y directions and the Z direction even though there is a possibility that the columnar body will remain. Can be In this step, it is also a major feature of the present invention that it is easy to visually inspect or check with a checker whether or not the predetermined conductive columnar conductor 10 having a predetermined size and a predetermined size is completed. In addition, compared to the prior art shown in FIG. 2 in which columnar conductors are formed by electrolytic copper plating by electroforming, the method of the present invention is a very simple process of printing and thermosetting, so that the product yield is low. It has a feature that it is expensive and can significantly reduce the cost.

As a third step, the periphery of the columnar conductor 10 is covered with an insulating layer 32. Here, for the insulating layer 32, a photocurable or / and thermosetting resin composition is used.
The material design of the insulating layer 32 is easier than that of the insulating layer 32 used as an interlayer insulating layer in a conventional build-up method of manufacturing a multilayer wiring board. That is, when the photosensitive resin is used as the insulating layer 32 in the present invention, the entire surface of the insulating layer 32 is irradiated with light and cured, so that the insulating layer 32 has high insulating properties and high glass transition temperature required while having photosensitivity. It is only necessary to design a resin that satisfies high heat resistance, low water absorption, low dielectric constant, low dielectric loss, etc., and since a development process is unnecessary, it is easy to combine desmear resistance, plating solution resistance, etc. .

The photosensitive resin used in the present invention contains a photosensitive resin, a photopolymerization catalyst and a filler, and is diluted with a photosensitive monomer or an organic solvent, if necessary, to form a paste. , Spray coating, curtain coating, centrifugal coating and the like. After the application, it is dried if necessary and cured by light irradiation. At the B stage by the photoreaction, the mechanical polishing of the next process is performed at this stage, and then the photocuring or the thermosetting is further performed to form the insulating layer 32
Can be improved in various physical properties.

On the other hand, when a thermosetting resin is used for the interlayer insulating layer 32, there is little restriction on the type of resin and the choice of filler, and many thermosetting resins and functional fillers are selected for the interlayer insulating film. Can be used. The thermosetting resin used in the present invention includes epoxy resin, phenol resin, xylene resin, melamine resin, urea resin, benzoguanamine resin, bismaleimide resin, polyamide resin, polyimide resin, thermosetting polyphenylene ether resin, thermosetting acrylic Various thermosetting resins such as resins are used alone or in combination. If necessary, a filler or a curing catalyst is added. These are diluted with an organic solvent and applied as a paste.

The coating method includes screen printing, dip coating, spray coating, curtain coating, centrifugal coating and the like. After the application, the coating is dried and cured as needed. The curing reaction can be controlled to achieve the B stage. At this stage, mechanical polishing in the next step is performed, and then thermal curing is further performed to improve various physical properties of the insulating layer 32.

The fourth step (FIG. 1D) is a step of exposing the head of the columnar conductor 10 buried by the insulating layer by laser irradiation. As a laser irradiator, YAG
Both a heat mode such as a laser and a carbon dioxide laser and a photon mode such as an excimer laser can be used. As described above, also in the conventional example (FIG. 2), when a thermosetting resin is used for the insulating layer, a via hole is opened by irradiating a laser beam. However, it was pointed out that, in the case of photon mode laser, inorganic fillers etc. in the insulating layer remained as they were, resulting in incomplete conductor formation in the subsequent process and many problems in connection reliability. In the present invention, the laser processing depth is extremely shallow, about one-tenth or less of the conventional depth, so that the processing time is short even in the heat mode, so that carbonization is small, and the remaining fillers are cleaned even in the photon mode. There is no problem because it can be removed very easily.

The fifth step is a step of forming the conductor 6 on the entire surface. This step is the same as the step performed in the conventional method. That is, in general, etching is performed using permanganate, which is used as a desmear treatment in a through hole, and then electroless copper plating is performed, followed by electrolytic copper plating to form a conductive layer 6 on the entire surface of the substrate. I do. By repeating the steps (1) to (5), the multilayer wiring board of the present invention is manufactured.

The method for manufacturing a multilayer wiring board according to the present invention has the following features. 1) Via-holes are previously formed in conductive pillars (pillar conductors)
By introducing the step of forming the via hole, the electrical connectivity of the via hole can be reliably ensured. 2) The columnar conductor can be easily manufactured in a short time by a simple and familiar technique such as printing and thermosetting. 3) As the columnar conductor, a conductive polymer thick film paste (PTF, Polymer) generally used widely is used.
Thick Film) can be used. This conductive PT
The F paste does not necessarily need to be a solventless type. 4) At the stage when the columnar conductor is formed, it can be easily inspected whether the conductor is as designed. 5) Various materials can be applied as an interlayer insulating layer material that supports the columnar conductor and functions as an electrical insulator, as compared with the conventional method. 6) A dry film or a resist ink can be used for forming an insulating layer. The resist ink does not necessarily need to be solventless. 7) Various types of commercially available irradiation apparatuses can be used as they are for the laser irradiation processing, and the processing time is extremely short, so that the running cost can be kept low.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a multilayer wiring board according to the present invention is shown in the following examples. It goes without saying that the present invention is not limited to these examples. Further, the unit symbol “part” indicating the ratio in the examples indicates part by weight.

(Example 1) 1) Copper paste (abbreviated as PTF-C-1) 90 parts of 10% silver-coated copper powder, 7 parts of epoxy resin (manufactured by Yuka Shell, Epicoat 806L), epoxy diluent (Asahi Denka) Glycidol ED502), 2.5 parts of an epoxy curing agent (manufactured by Ajinomoto, Amicure PN23) and 0.5 part of a dispersant (manufactured by Toho Chemical Co., Ltd., dispersant PN160), and then kneaded using a three-roll mill. Viscosity 700PS
(Poise) copper paste was obtained. 2) Next, a copper paste PTF-C-1 is screen-printed at a predetermined position on a wiring of a printed wiring board obtained by photo-etching the surface of a copper-clad laminate (copper foil thickness 18 μm) by an ordinary method. Was printed. For screen printing,
Using a screen printing machine, a screen plate of 350 mesh stainless steel and an emulsion thickness of 20 μm was printed twice to produce a columnar body having a diameter of 150 μm. The printed wiring board on which the copper paste column was printed was dried at 80 ° C. for 30 minutes, and then heat-cured at 150 ° C. for 30 minutes to obtain a columnar conductor (about 45 μm high on a copper foil).

3) Insulating paste (abbreviated as PTF-I-1) 75 parts of a 50% acrylate of cresol novolak epoxy resin, 5 parts of dipentaerythritol hexaacrylate, epoxy resin (manufactured by Yuka Shell, Epicoat 100)
7) 20 parts, photopolymerization initiator (Circa Geigy, Irgacure 651) 5 parts, thermosetting catalyst (Shikoku Chemicals, 2P4)
MHZ) 5 parts, Silica (Crystalite, Tatsumori) 40
After mixing 20 parts of butyl cellosolve acetate,
The mixture was kneaded with three rolls to adjust the viscosity to 400 ps. 4) The entire surface of the printed circuit board on which the columnar conductor is formed,
The insulating paste PTF-I-1 was printed twice using a screen printing plate having a thickness of 20 mesh and an emulsion thickness of 20 μm, and was printed at 70 ° C.
For 30 minutes to form an insulating layer having a dry film thickness of about 50 μm (on the copper foil). 5) Next, after performing 500 mJ / cm ² whole surface exposure with a high pressure mercury lamp, heat treatment was performed at 100 ° C. for 1 hour.

6) High peak short pulse carbon dioxide laser (wavelength 10.6 μm, peak output 5 kW, pulse width 40)
Irradiation was performed for 20 shots at μs, an energy density per pulse of 0.2 J, and a pulse frequency of 20 Hz) to expose the head of the columnar conductor, which was a cured copper paste PTF-C-1. 7) The surface of the printed wiring board having the columnar conductor exposed in this way is roughened by chromate treatment according to a conventional method, and then subjected to neutralization treatment, water washing, chemical copper plating treatment, and electrolytic copper plating. After uniformly forming a 20 μm conductor, annealing was performed at 150 ° C. for 2 hours. The heat treatment of the insulating layer proceeds by this annealing treatment. 8) Next, the conductor was etched by photoetching in a conventional manner to form a circuit.

Example 2 1) A copper-clad laminate (copper foil having a thickness of 18 μm) was screen-printed at a predetermined position on a wiring of a printed wiring board obtained by photoetching the surface of the printed wiring board by a conventional method. Paste PT
FC-1 was printed. For screen printing, use a metal mask (stainless steel plate thickness: 50 μm), diameter 150
A μm column was produced. The printed wiring board on which the copper paste column was printed was dried at 80 ° C. for 30 minutes, and then heat-cured at 150 ° C. for 60 minutes to obtain a columnar conductor (about 45 μm in height).

2) Insulating paste (abbreviated as PTF-I-2) Cresol novolak epoxy resin (manufactured by Dainippon Ink.
N-680 solid content 70% butyl cellosolve solution) 30
Part, epoxy resin (made by Yuka Shell, Epicoat 100
1. 20 parts of a 70% butyl cellosolve solution in solid content), 10 parts of an epoxy resin (manufactured by Yuka Shell, Epicoat 828),
5 parts of thermosetting catalyst (manufactured by Nippon Kayaku, Kayahard AS), 20 parts of silica (crystallite, Tatsumori), 10 parts of calcium carbonate, 5 parts of talc, butyl cellosolve acetate 2
After mixing 0 parts, kneading with 3 rolls and viscosity of 300ps
Was adjusted. 3) The entire surface of the printed circuit board on which the columnar conductors are formed,
The insulating paste PTF-I-2 was printed twice using a 00 mesh tetron plate and a screen printing plate having an emulsion thickness of 15 μm, dried at 80 ° C. for 30 minutes, and then heat-treated at 150 ° C. for 30 minutes to obtain a dry film thickness of about An insulating layer of 47 μm (on copper foil) was formed.

4) A KrF excimer laser (wavelength 2)
48 nm, energy density 1.3 J / cm ² , frequency 1
00 Hz) for 10 shots. As a result, the head of the columnar conductor, which was a cured product of the copper paste PTF-C-1, was exposed. 5) After the surface of the printed wiring board having the columnar conductor exposed in this way is ultrasonically cleaned with isopropyl alcohol, the surface is ground by chromate treatment according to a conventional method.
Neutralization treatment, water washing, chemical copper plating treatment, and electrolytic copper plating were performed to uniformly form a 20 μm conductor, and then annealing treatment was performed at 150 ° C. for 2 hours.

(Example 3) P as a conductive metal paste
A printed wiring board was produced in the same manner as in Example 1 except that PTF-C-2 was used instead of TF-C-1 and PTF-I-2 was used as the insulating paste. The silver paste (PTF-C-2) used in this example was prepared as follows. 70 parts of silver powder, epoxy resin (made by Yuka Shell, Epicoat 1
007) was mixed with 7.5 parts of a butyl cellosolve solution having a solid content of 60%, and 15 parts of a methylated melamine resin (manufactured by Sanwa Chemical Co., Ltd., mixed solution of 70% butyl cellosolve / isopropyl alcohol) was mixed with a volatile solvent. After removal, the mixture was kneaded using three rolls and diluted with butyl carbitol to obtain a copper paste having a viscosity of 500 PS.

(Embodiment 4) According to the present invention, the connection reliability of a blind through-hole in which a columnar conductor was previously formed on a conductor circuit by using a conductive polymer thick film paste was evaluated by MIL-ST.
D-202F Thermal Shock Test Method 107G, C
As a result of evaluation at condition C (−65 ° C. to + 200 ° C.), each of the samples produced in Examples 1 to 3 was 1
As a result of the test up to 00 cycles, no disconnection occurred.

[0035]

As described above, according to the method of the present invention, a highly reliable build-up multilayer wiring board can be manufactured at a low cost, which greatly contributes industrially.

[Brief description of the drawings]

FIG. 1 shows a method for manufacturing a multilayer wiring board of the present invention.

FIG. 2 shows a conventional method for manufacturing a multilayer wiring board.

FIG. 3 shows a conventional method for manufacturing an improved multilayer wiring board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base material 2 Conductive circuit 3 Interlayer insulating layer 4 Via hole 5 Conductive polymer thick film 6 Metal conductor 7 Photosensitive resin 8 Hole 9 Via post 10 Columnar conductor 31 Insulating layer 32 Insulating layer 32A Insulating layer

Claims (4)

[Claims] 1. A method of manufacturing a multilayer wiring board in which a conductive circuit and an insulating layer are laminated in a multi-layer, and a circuit between the circuits is provided by a via hole, (1) a step of forming a conductive circuit on a substrate; 2) a step of forming a columnar conductor on the conductor of the substrate using a conductive polymer thick film paste; (3) a step of coating the periphery of the columnar conductor with an insulating layer; and (4) a step of burying the columnar conductor. A method of manufacturing a multilayer substrate, comprising: a step of exposing a head of a columnar conductor by laser irradiation; and (5) a step of forming a conductor on a surface. 2. The method according to claim 1, wherein the conductive polymer thick film paste contains a conductive metal powder and a thermosetting resin as essential components. 3. The method according to claim 1, wherein the conductive polymer thick film paste is formed into a column shape by printing, and is thermally cured to form a columnar conductor. 4. The method according to claim 1, wherein the insulating layer is a photocurable and / or thermosetting resin composition.