JPH10200264A - Multilayer printed wiring board and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain reliable continuity by filling and hardening a conductive paste contg. conductive grains and resin matrix as main components into at least one inner layer via-opening and connecting its surface to an outer layer via formed on a dissolved rough surface. SOLUTION: A conductive paste 6 contg. conductive grains and resin matrix as main components is filled into and hardened in inner layer via-openings 5. A protective film 4 is peeled off to remove the paste 6, thereby forming smoothed inner layer vias 7 made of the paste 6. Epoxy resin grains on the surface of an adhesive layer 3 are dissolved away by acid, etc., to rough the adhesive layer surface and the surfaces of the vias 7. A resist 8 is formed on a wiring board contg. a catalyst nuclei and outer layer circuit is formed on another part having no resist. Outer layer vias may be superposed to obtain reliable continuity.

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 and a method of manufacturing the same, and more particularly, to a build-up multilayer printed wiring board capable of connecting conductive via holes provided in a superposed manner with high reliability and a method of manufacturing the same. I do.

[0002]

2. Description of the Related Art A build-up multilayer printed wiring board is a wiring board in which conductive circuits and interlayer insulating layers are alternately built up, and inner and outer conductive circuits are connected and conductive through via holes or the like. It is mainly manufactured by the additive method.

In the additive method, for example, an adhesive for electroless plating is applied to the surface of an insulating substrate such as glass epoxy to form an adhesive layer, and then an opening for forming a via hole is formed in the adhesive layer. This is a method in which a conductor circuit including via holes is formed by providing a roughened surface, forming a plating resist on the roughened surface, and then electroless plating.

According to such a method, the via hole is formed in the opening provided in the adhesive layer by electroless plating, and has a concave shape. Therefore, when a via hole for connecting to a conductor circuit on the outer layer is formed in the adhesive layer on the outer layer directly above the concave via hole,
As shown in FIG. 3, the connection surface between the inner and outer via holes is only the lower end of the side wall of the opening provided in the adhesive layer on the outer layer side. In addition, the lower end of the side wall of the opening needs to be aligned with the land of the inner via hole.
Therefore, it has been a fact that good connection reliability cannot be obtained between the via holes of the inner and outer layers overlapped in such a configuration.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrical connection reliability even when an outer via hole for connecting to a conductor circuit of an outer layer is further formed immediately above the inner via hole. It is an object of the present invention to provide a novel structure of a multilayer printed wiring board having excellent characteristics. Another object of the present invention is to propose a method for advantageously producing a multilayer printed wiring board having the above structure.

[0006]

Means for Solving the Problems The inventor of the present invention has intensively studied for realizing the above-mentioned object, and as a result, has arrived at an invention having the following content as a gist configuration. That is, the present invention provides: (1) a via hole in which an inner conductor circuit and an outer conductor circuit are laminated via an interlayer insulating material layer on a substrate, and inner and outer conductor circuits are provided in the interlayer insulating material layer; In the multilayer printed wiring board electrically connected by the above, at least one inner layer side via hole is formed by filling a conductive paste containing conductive particles and a resin matrix as main components into the via hole opening and hardening the paste. And has a roughened surface formed by dissolving and removing conductive particles or a resin matrix on its surface, and is electrically connected to an outer via hole or an outer conductor circuit formed by being superimposed on the surface. A multilayer printed wiring board characterized by the above.

(2) An inner conductor circuit and an outer conductor circuit are laminated on a substrate via an interlayer insulating layer, and the inner and outer conductor circuits are electrically connected by via holes provided in the interlayer insulating layer. In the method for manufacturing a multilayer printed wiring board, at least one inner-layer-side via hole is irradiated with a laser beam to an interlayer insulating material layer formed on the surface of a substrate having an inner-layer conductor circuit, and an opening reaching the inner-layer conductor is formed. The opening is filled with a conductive paste containing conductive particles and a resin matrix as a main component, cured and formed, and electrically connected to an outer-layer via hole or an outer-layer conductor circuit that is formed by being superimposed immediately thereon. Connecting, forming the outer layer side via hole or the outer layer conductor circuit after roughening the surface of the inner layer side via hole and the interlayer insulating material layer with an acid or an oxidizing agent. This is a method for manufacturing a multilayer printed wiring board.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The multilayer printed wiring board of the present invention
It is characterized in that at least one inner-layer-side via hole is formed by filling a conductive paste containing conductive particles and a resin matrix as main components into an opening for the via hole and curing the paste. According to the method of the present invention for manufacturing such a multilayer printed wiring board, an inner layer side via hole is irradiated with a laser beam onto an interlayer insulating material layer formed on the surface of a substrate having an inner layer conductor circuit to form an opening reaching the inner layer conductor. The opening is filled with a conductive paste containing conductive particles and a resin matrix as main components, and the opening is formed by curing.

[0009] Thereby, the inner layer side via hole is
It is electrically surface-connected to a via hole or a conductor circuit on the outer layer formed immediately above via a surface corresponding to the size of the via hole opening. As a result, the electrical connection reliability is excellent even if the outer layer via hole for connecting to the conductor circuit or the outer layer conductor circuit is formed directly above the inner layer via hole.

In the method of the present invention, the outer layer conductor circuit or the outer layer via hole which is formed to be superimposed on the inner layer side via hole is formed by forming the inner layer side via hole and the surface of the interlayer insulating material layer. Another feature is that it is formed after roughening with an acid or an oxidizing agent.

As a result, the surfaces of the inner via hole and the interlayer insulating material layer are roughened, and the anchor effect provides good adhesion to a conductor circuit or an outer via hole formed to be superimposed directly on the inner via hole. Connected.

In the present invention, the conductive paste is a paste containing conductive particles and a resin matrix as main components, and at least one of the conductive particles and the resin matrix is made of an acid or an oxidizing agent. It is composed of something that can be dissolved and removed. Here, silver, copper, Ni, and Au can be used as the conductive particles that can be dissolved and removed with an acid or an oxidizing agent, and epoxy resin, polyphenylene ether (PPE) can be used as a resin matrix that can be dissolved and removed with an acid or an oxidizing agent. ), Polysulfone (PS), polyethylene terephthalate (PET), and polyimide (PI).

Next, a method for manufacturing a multilayer printed wiring board according to the present invention will be described with reference to one manufacturing process shown in FIG. (1) First, a wiring board having an inner copper pattern 2 formed on the surface of a core board 1 is manufactured (see FIG. 1A). The copper pattern 2 is formed on the core substrate 1 by etching a copper-clad laminate, or by applying an adhesive layer for electroless plating to a substrate such as a glass epoxy substrate, a polyimide substrate, a ceramic substrate, or a metal substrate. There is a method of forming and roughening the surface of the adhesive layer to form a roughened surface, and performing electroless plating on the roughened surface. It should be noted that a through hole is formed in the core substrate 1, and the wiring layer on the front surface and the back surface can be electrically connected through the through hole.

(2) Next, an interlayer insulating material is applied on the wiring board manufactured in the above (1) using an application device such as a roll coater, and then dried, and then dried at 150 ° C. × 3.
By thermal curing under the condition of time, the interlayer insulating layer 3 is formed (see FIG. 1 (b)). Incidentally, in the case of a photosensitive resin, the interlayer insulating layer 3 is formed by heat curing after exposure curing.

Here, it is desirable to use an adhesive for electroless plating as the interlayer insulating material. The most suitable adhesive for electroless plating is one in which heat-resistant resin particles soluble in a cured acid or oxidizing agent are dispersed in an uncured heat-resistant resin hardly soluble in an acid or oxidizing agent. is there. This is because by dissolving and removing the heat-resistant resin particles soluble in the acid or the oxidizing agent, an octopus-shaped anchor can be formed on the surface of the adhesive layer, and the adhesion to the conductor circuit can be improved.

In the above-mentioned adhesive for electroless plating, the heat-resistant resin particles particularly subjected to the curing treatment include a heat-resistant resin powder having an average particle size of 10 μm or less, and an average particle size of 2 μm.
Aggregated particles obtained by aggregating the following heat-resistant resin powder, a heat-resistant powder resin powder having an average particle size of 10 μm or less and an average particle size of 2 μm
m and a mixture with a heat-resistant resin powder having a mean particle size of 2 or less.
It is desirable to use at least one selected from pseudo particles obtained by adhering at least one of a heat-resistant resin powder or an inorganic powder having an average particle diameter of 2 μm or less to the surface of a 10 μm heat-resistant resin powder. . This is because they can form more complex anchors.

(3) A protective film 4 is bonded on the interlayer insulating agent layer 3 formed in the above (2) by thermocompression as required (see FIG. 1 (c)). Here, as the protective film 4, polyimide (PI), polyethylene terephthalate (PET), polybutylene terephthalate (PBT),
A film such as polyphenylene sulfide (PPS) can be used.

(4) Next, the substrate having undergone the steps (1) to (3) is subjected to laser processing for irradiating a laser beam to form a via hole penetrating the adhesive layer 3 and the protective film 4. Perforation 5 is made (see FIG. 1 (d)). here,
As a laser beam used for laser processing, a CO ₂ gas laser or an excimer laser can be used.

Before the adhesive layer 3 is heat-cured in the above (2) and (3) and the protective film 4 is bonded, the adhesive layer 3 made of a photosensitive resin is exposed and developed to form a via hole. There is a method of perforating the forming opening 5. However, this method is not an efficient method but disadvantageous in that it is difficult to form a hole in the protective film 4 in accordance with the via hole forming opening 5.

(5) To remove the resin residue remaining on the conductive circuit surface at the bottom of the via hole forming opening 5, for example,
Desmear treatment is performed by immersing in a potassium permanganate solution or a mixed solution of chromic acid and sulfuric acid (see FIG. 1 (e)). Also,
Plasma treatment such as O ₂ plasma may be performed.

(6) Next, a conductive paste 6 containing conductive particles and a resin matrix as main components is filled in the via hole forming opening 5 and hardened (see FIG. 1 (f)). Here, as a method for filling the opening 5 with the conductive paste 6, there are a printing method, a dispensing method, and an inkjet method. As the conductive particles, plate-like silver or copper of 20 to 30 μm,
Preferably, gold or Ni is used. As the resin matrix, epoxy resin or polyphenylene ether (P
It is desirable to use PE), polysulfone (PS), polyethylene terephthalate (PET), and polyimide (PI). The conductive paste has a viscosity of 1 to 200 Pa · s at the time of printing and a specific resistance of 1.0 after filling and curing.
It is desirable to use a material having a resistivity of × 10 ⁻³ Ω · cm or less.

(7) Next, by peeling off the protective film 4, the conductive paste 6 printed on the portion other than the inside of the opening 5 is removed, and further polished if necessary, so that the surface of the adhesive layer 3 is removed.
An inner via hole 7 made of a conductive paste 6 smoothed so as to be flush with the surface of the substrate is formed (FIG. 1).
(g)). In this step, if the protective film 4 is not to be bonded in the step (3), the conductive paste 6 printed outside the opening 5 is removed by polishing, and the surface is flush with the surface of the adhesive layer 3. Via holes 7 made of a conductive paste 6 smoothed upward are formed.

(8) Next, the surface of the adhesive layer 3 is roughened by dissolving and removing the epoxy resin particles present on the surface of the adhesive layer 3 with an acid or an oxidizing agent. The surface of the via hole 7 is roughened by dissolving and removing the conductive particles or resin matrix present on the surface of the via hole 7 with an acid or an oxidizing agent (see FIG. 1 (h)). Here, examples of the acid include phosphoric acid, hydrochloric acid, sulfuric acid, and organic acids such as formic acid and acetic acid, and it is particularly preferable to use an organic acid. On the other hand, it is desirable to use chromic acid and permanganate (such as potassium permanganate) as the oxidizing agent.

(9) Next, a catalyst nucleus is applied to the wiring substrate having the surface of the adhesive layer 3 and the surface of the via hole 7 roughened. It is desirable to use a noble metal ion or a noble metal colloid for providing the catalyst nucleus, and generally, palladium chloride or a palladium colloid is used. Note that it is desirable to perform a heat treatment to fix the catalyst core. Palladium is preferred as such a catalyst core.

(10) Next, a plating resist 8 is formed on the wiring substrate provided with the catalyst nucleus. As the plating resist composition, it is particularly desirable to use a composition comprising an acrylate of a cresol novolak or a phenol novolak type epoxy resin and an imidazole curing agent, but other commercially available products can also be used.

(11) Next, electroless plating is applied to the portion where the plating resist is not formed, and the outer conductor circuit 9 including the pad is formed to manufacture a printed wiring board (see FIG. 1 (i)). Here, it is desirable to use copper plating as the electroless plating.

(12) Further, by repeating the above steps (2) to (11), a desired multilayer printed wiring board is manufactured (see FIG. 1 (j)).

In the above embodiment, a method of manufacturing a multilayer printed wiring board in which all via holes are formed of a conductive paste containing conductive particles and a resin matrix as main components has been described. In the method of the present invention, in addition, a multilayer printed wiring board in which only the inner-layer-side via holes are formed of a conductive paste, a multilayer in which only the inner-layer-side via holes having the outer-layer-side via holes superimposed thereon are formed of a conductive paste only. A printed wiring board or the like can be manufactured. That is, in the method of the present invention, at least one inner via hole is formed by irradiating a laser beam to the interlayer insulating material layer formed on the surface of the substrate having the inner conductor circuit to form a hole reaching the inner conductor. Filled with conductive paste containing conductive particles and resin matrix as the main component, cured and formed,
An outer layer conductor circuit or an outer layer side via hole is formed immediately above it so as to overlap.

The multilayer printed wiring board of the present invention manufactured as described above has, for example, the following embodiments as the structure of the inner-layer side via hole portion made of the conductive paste. . There is a multilayer printed wiring board having a structure that is not electrically connected to an outer conductor circuit formed above the inner via hole but is directly electrically connected to the outer via hole. Among them, the outer via hole has a structure made of a conductive paste (see FIG. 2A) and the outer via hole has a structure made of a conventionally known electroless plating layer (see FIG. 2B). There is. . There is a multilayer printed wiring board having a structure in which a part of an outer-layer conductor circuit formed directly above the inner-layer via hole is used as a conductor pad and is electrically connected to the outer-layer via hole via the conductor pad. Of these, the outer-layer-side via hole has a structure made of conductive paste (FIG. 2).
(see FIG. 2 (c)) and those having a structure in which the outer via hole is formed of a conventionally known electroless plating layer (see FIG. 2 (d)).

It should be noted that the multilayer printed wiring board of the present invention can be used for various processings generally performed on printed wiring boards.
For example, formation of a solder resist layer on the surface, nickel / gold plating or soldering on the surface wiring pattern, drilling, cavity processing, through-hole plating, or the like can be performed. Further, the multilayer printed wiring board of the present invention is used for mounting electronic components such as IC packages, bare chips, and chip components.

[0031]

As described above, according to the present invention, electrical connection reliability can be obtained even when an outer layer via hole for connecting to an outer layer conductor circuit is further formed immediately above the inner layer via hole. It is possible to provide a multilayer printed wiring board having excellent properties. As a result, the outer-layer via hole can be freely formed on the inner-layer via hole, so that a higher-density wiring is possible.

[Brief description of the drawings]

FIG. 1 is a view showing one manufacturing process of a multilayer printed wiring board according to the present invention.

FIG. 2 is a partial cross-sectional view showing an embodiment of an inner layer via hole portion made of a conductive paste in the multilayer printed wiring board of the present invention.

FIG. 3 is a partial cross-sectional view showing a connection state of multi-stage via holes provided to be overlapped in a conventional multilayer printed wiring board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Inner layer copper pattern 3 Interlayer insulating material layer (adhesive layer) 4 Protective film 5 Via hole opening 6 Conductive paste 7 Inner layer side via hole 8 Plating resist 9 Outer layer conductor circuit (outer layer copper pattern) 10 Outer layer side via hole

Claims (2)

[Claims] An inner conductor circuit and an outer conductor circuit are laminated on a substrate via an interlayer insulating material layer, and the inner and outer conductor circuits are electrically connected by via holes provided in the interlayer insulating material layer. In the connected multilayer printed wiring board, at least one inner layer side via hole is formed by filling a via hole opening with a conductive paste containing conductive particles and a resin matrix as main components, and curing the paste. The surface has a roughened surface formed by dissolving and removing conductive particles or a resin matrix, and is electrically connected to an outer layer side via hole or outer layer conductor circuit formed by being superimposed directly on the surface. Multi-layer printed wiring board. 2. An inner conductor circuit and an outer conductor circuit are laminated on a substrate via an interlayer insulating layer, and the inner and outer conductor circuits are electrically connected by via holes provided in the interlayer insulating layer. A method of manufacturing a multilayer printed wiring board comprising: irradiating at least one inner layer side via hole with a laser beam to an interlayer insulating material layer formed on a surface of a substrate having an inner layer conductor circuit to form an opening reaching the inner layer conductor. This opening is filled with a conductive paste containing conductive particles and a resin matrix as the main components, cured and formed, and is electrically connected to an outer layer via hole or an outer layer conductor circuit which is formed by being superimposed on the conductive paste. Forming the outer-layer-side via hole or the outer-layer conductor circuit after roughening the surface of the inner-layer via hole and the surface of the interlayer insulating material layer with an acid or an oxidizing agent; Method for manufacturing a multilayer printed wiring board characterized.