JP2002043753A - Manufacturing method of multilayer printed circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer printed circuit board(PCB) made by a build-up process which does not need a desmear processing after drilling holes and has high reliability of connection between layers by via holes. SOLUTION: In this invented build-up multilayer PCB manufacturing, non- through holes between resin interlayer dielectric layer are made by a blasting to form via holes. For the blasting, an air blasting may be applied as well as a wet blasting. If a resin sheet with a coppered foil is used as the resin interlayer dielectric layer, a coppered foil with opening is adopted as a mask for the blasting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a multilayer printed wiring board, and more particularly to a method for manufacturing a high-density multilayer printed wiring board with good productivity at low cost.

[0002]

2. Description of the Related Art With the recent trend toward smaller and higher-density electronic devices, build-up multilayer printed wiring boards incorporating various via hole structures have been developed. Such a wiring board has been conventionally manufactured by using a build-up method as described below.

That is, an insulating resin layer is provided on an inner wiring board serving as a base, and a non-through hole for conduction with an inner circuit is formed in the insulating resin layer by laser irradiation. A method of performing a surface roughening process, further performing an electroless copper plating and an electrolytic copper plating in order, and forming a via that electrically connects the inner and outer conductor layers is performed. In addition, a method in which a resin sheet with copper foil, in which an insulating resin layer and copper foil are integrally bonded, is laminated on an inner wiring board, an opening is formed in the copper foil as a conformal pattern, and then a laser drilling is performed. Have been.

[0004]

In such a method for manufacturing a multilayer printed wiring board, a residue such as carbonized resin is formed at the bottom of a hole (non-through hole) in a step of drilling an insulating resin layer by a laser. Since it remains, it was necessary to remove and clean a residue called desmear treatment as a pretreatment of the plating step. As the desmear treatment, for example, a chemical removal using an oxidizing agent such as a sodium permanganate solution is performed, and a desmear treatment using plasma is used as an auxiliary.

[0005] However, as the via diameter becomes smaller due to the higher density of the printed wiring board, residues may not be completely removed in the desmearing process, and as a result, the connection reliability between the interlayer portions may not be sufficiently obtained. However, there is a problem that the yield of printed wiring boards is deteriorated. Also,
Plasma desmear, which is used as an auxiliary method, has a long processing time, and has caused an increase in cost.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and does not require desmear processing after drilling, has high reliability in connection between layers by vias, and is capable of improving productivity at low cost. An object of the present invention is to provide a method for manufacturing a wiring board.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, by performing piercing of the insulating resin layer by using a blast method, the residual residue in the holes has been obtained. And found that the desmear treatment can be eliminated, thus completing the present invention.

That is, in the method of manufacturing a multilayer printed wiring board according to the present invention, a step of forming an interlayer resin insulating layer on at least one surface of an inner wiring board, and electrically connecting a wiring layer at a predetermined position of the interlayer resin insulating layer. Forming a via to be connected, wherein the step of forming the via includes a step of blasting the interlayer resin insulating layer so as to reach a wiring layer of the inner layer wiring board. Forming a hole; and forming a conductor layer in the non-through hole.

Hereinafter, the present invention will be described in detail.

In the present invention, as the inner wiring board, a glass epoxy substrate, a polyimide substrate, a bismaleimide triazine (BT) substrate, a fluororesin (polytetrafluoroethylene) substrate, a polyphenylene ether (PPE)
A resin board such as a board, or a copper-clad laminated board, a ceramic board, a metal board, or the like of such a resin board may be used as a base board, and a wiring board having a wiring layer (conductor circuit pattern) on at least one surface can be used.

The interlayer resin insulating layer includes a layer made of a thermosetting resin, a thermoplastic resin, or a composite of a thermosetting resin and a thermoplastic resin. In order to form such a resin insulating layer on at least one side of the inner wiring board, a method of applying a resin, a resin sheet formed into a sheet shape as it is, or a copper foil bonded to a resin sheet and integrated with the copper foil Or a method of laminating a resin impregnated sheet in which the resin is impregnated into a glass fiber cloth or the like.

In the present invention, as blasting particles (abrasives), powder particles made of alumina-based, silicon carbide-based, or zinc-based materials and having a particle size of 0.5 to 30 μm can be used. . Further, in the present invention, in addition to the air blast method in which these abrasives are sprayed and processed at high speed using compressed air, a wet blast method in which the abrasives are mixed into a liquid such as water and injected. Can also be used.

In the present invention, a mask (blast mask) formed as described below is used to form a non-through hole having a predetermined diameter at a predetermined position of the interlayer resin insulating layer by blasting. That is, in the method of laminating a resin sheet with a copper foil on the inner wiring board, an opening is formed at a predetermined position of the copper foil by a photo-etching method, and then the interlayer resin insulating layer is blasted using the copper foil as a mask.

Further, a blast mask can be formed by using a resist made of a photosensitive resin. That is, a photosensitive resist layer is formed on an interlayer resin insulating layer formed by thermocompression bonding of an insulating resin sheet, and this resist layer is subjected to photoetching to form a resin mask having an opening at a predetermined position. After formation, blasting can be performed.

The conditions for the blasting process vary depending on the type and thickness of the interlayer resin insulating layer, the diameter of the non-through hole to be formed, and the like.
/ Cm 2, the scanning speed of the blast nozzle is desirably 0.5 to 5 m / min.

In the present invention, in manufacturing a multilayer printed wiring board by a build-up method, a non-through hole for forming a via hole is formed by blasting, so that a laser drilling machine is not required and a hole is not required. Desmear treatment after dawn is not required, and connection reliability between via layers is high, and low cost and high productivity are achieved.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to these examples.

In the first embodiment of the present invention, as shown in FIG. 1, an inner wiring board 3 having an inner copper foil circuit 2 on both surfaces of an insulator (inner insulator) 1 is formed. That is, on a copper foil on both sides of a double-sided copper-clad laminate, a commercially available photosensitive dry film is adhered, and after an exposure and development process, an etching resist pattern is formed. Dissolve and remove the foil with an etchant, peel off the etching resist,
An inner copper foil circuit 2 is formed. Here, as the etching solution for the copper foil, a known etching solution such as an aqueous solution of ferric chloride, an aqueous solution of cupric chloride, or an aqueous solution of sulfuric acid and hydrogen peroxide can be used. Further, the surface of the inner layer copper foil circuit 2 is subjected to a surface roughening treatment in order to improve the adhesion with an interlayer resin insulating layer described later. Examples of the surface roughening treatment include a blackening treatment and a chemical treatment based on sulfuric acid and hydrogen peroxide.

Next, as shown in FIG. 2, a resin sheet 6 with a copper foil on which an insulating resin layer 4 and a copper foil 5 are adhered is laminated on both surfaces of the inner layer wiring board 3 and is laminated by heating and pressing. Integrate.

Next, as shown in FIG. 3, predetermined positions (via formation positions) of the copper foil 5 on both sides of the resin sheet 6 with a copper foil.
Then, an opening 7 having a predetermined diameter is formed as a mask hole. The opening (mask hole) 7 is formed by attaching a commercially available photosensitive dry film on the copper foil 5, forming an etching resist having an opening at a via formation position through exposure and development steps, and then forming a resist opening. The copper foil is dissolved and removed with an etchant such as a ferric chloride solution, and the etching resist is peeled off.

Next, as shown in FIG. 4, blasting is performed on the copper foil 5 having the opening 7 by an air blast device, and as shown in FIG. A non-through hole 8 that is exposed is formed. The conditions of the air blast are, for example, alumina particles having a particle size of 5 to 10 μm as the abrasive 9, an injection pressure of 2 kg / cm 2, and a scanning speed of the blast nozzle of 1.5 m / min.

Next, using a commercially available electroless copper plating solution,
After electroless copper plating is performed on the inner surface of the non-through hole 8 and on the outer layer copper foil 5, electrolytic copper plating is further performed for thickening to form a copper plating layer 10 (see FIG. 6). In the drawing, reference numeral 10a indicates the via thus formed.

Next, a photosensitive dry film is stuck on the copper plating layer 10 and an etching resist pattern is formed through exposure and development steps. Then, the exposed portions of the outer copper foil 5 and the copper plating layer 10 are exposed to a known material. By dissolving / removing with an etchant and further removing the etching resist, an outer conductive circuit pattern 11 is formed as shown in FIG. Thus, a multilayer printed wiring board is obtained. Further, by repeating the steps of laminating the resin sheet 6 with the copper foil shown in FIG. 2 and the step of forming the conductor circuit pattern 11 shown in FIG. 7, a multilayer printed wiring board having a further multilayer structure can be obtained.

In the first embodiment configured as described above, since the non-through hole 8 for forming the via is formed by air blast, a laser drilling machine is not required and the hole is not formed in the hole. Since no residue remains, desmearing after drilling is not required, and the connection reliability between layers is high. Therefore, a build-up multilayer printed wiring board can be efficiently obtained at low cost. Further, in this embodiment, since the interlayer resin insulating layer is formed using the resin sheet 6 with the copper foil in which the insulating resin layer 4 and the copper foil 5 are adhered and integrated, the insulating resin layer 4 and the copper foil 5 are insulated. It is possible to obtain a multilayer printed wiring board having a high adhesive strength to a resin layer and a low peeling between layers.

Next, a second embodiment of the present invention will be described.

In this embodiment, as shown in FIG. 8, a thermoplastic or thermosetting resin sheet 12 is laminated on both surfaces of the inner wiring board 3 by heating and pressing to form an interlayer resin insulating layer. I do. Next, a photosensitive resist layer is formed on the resin sheet 12 by, for example, pasting a photosensitive dry film, and the resist layer is subjected to photoetching (exposure and development) to form openings 7 in predetermined positions. Is formed. Then, as shown in FIG. 9, blasting is performed using the resin resist layer 13 as a mask to form the non-through holes 8 in the resin sheet 12.

Next, as shown in FIG.
An electroless copper plating and an electrolytic copper plating are sequentially performed on the inner surface of the resin sheet 12 and the resin sheet 12 to form a copper plating layer 10.
Thereafter, a photosensitive dry film is stuck on the copper plating layer 10, and an exposure and development process is performed to form an etching resist pattern. Then, the exposed portion of the copper plating layer 10 is removed by etching, as shown in FIG. The outer conductor circuit pattern 11 is formed.

In the second embodiment constructed as described above, as in the first embodiment, a laser drilling machine is not required, and the desmear after drilling for via formation is performed. No processing is required, the reliability of via connection between layers is high, and the productivity is low and the cost is high. In addition, since the conductor circuit pattern 11 of the outer layer is formed by electroless plating and electrolytic plating, and the conductor layer does not become too thick, it is possible to form a via hole having a small diameter (for example, a diameter of 100 μm or less) with high productivity. There is an advantage that you can.

[0029]

As is apparent from the above description, according to the present invention, in drilling a non-through hole for a via, a laser drilling machine is not required, and desmearing after drilling is unnecessary. In addition, a build-up multilayer printed wiring board having high connection reliability between layers can be obtained with a smaller number of steps than in the related art. Therefore, in manufacturing a multilayer printed wiring board, it is possible to reduce costs and improve productivity.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a step of forming an inner-layer wiring board in a first embodiment of the method of manufacturing a multilayer printed wiring board according to the present invention.

FIG. 2 is a cross-sectional view illustrating a step of laminating a resin sheet with a copper foil in the first embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a step of forming an opening (mask hole) in a copper foil in the first embodiment of the present invention.

FIG. 4 is a cross-sectional view for explaining a blast processing step in the first embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a state in which a non-through hole is formed in the insulating resin layer by blasting in the first embodiment of the present invention.

FIG. 6 is a cross-sectional view illustrating a step of forming a copper plating layer in the first embodiment of the present invention.

FIG. 7 is a cross-sectional view of the multilayer printed wiring board obtained in the first embodiment of the present invention.

FIG. 8 is a sectional view for explaining a resin sheet laminating step in the second embodiment of the present invention.

FIG. 9 is a cross-sectional view illustrating a blast processing step using a resin resist layer as a mask in the second embodiment of the present invention.

FIG. 10 is a cross-sectional view for explaining a step of forming a copper plating layer in the second embodiment of the present invention.

FIG. 11 is a sectional view of a multilayer printed wiring board obtained in a second embodiment of the present invention.

[Explanation of symbols]

 2 ... inner layer copper foil circuit 3 ... inner layer wiring board 5 ... copper foil 6 ... resin sheet with copper foil 7 ... opening (mask hole) 8 ... non-through hole 9 ... Abrasive 10 Copper plating layer 10a Via 11 Outer conductor pattern 12 Resin sheet 13 Resin resist layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E317 AA24 BB01 BB11 CC31 CD27 CD32 GG16 5E346 AA43 CC32 DD12 DD25 DD48 EE06 GG15 GG22 GG23 HH33

Claims (5)

[Claims] 1. A multilayer comprising: a step of forming an interlayer resin insulation layer on at least one surface of an inner wiring board; and a step of forming a via for electrically connecting a wiring layer at a predetermined position of the interlayer resin insulation layer. In the method for manufacturing a printed wiring board, the step of forming the via includes a step of forming a non-through hole reaching the wiring layer of the inner wiring board by blasting the interlayer resin insulating layer; Forming a conductor layer. 2. The method according to claim 1, further comprising: laminating a composite sheet having an insulating resin layer and a copper foil attached to at least one side of the inner wiring board to form the interlayer resin insulating layer and form the non-through hole. 2. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein in the step, after forming an opening at a predetermined position of the copper foil, the blasting is performed using the copper foil as a mask. 3. A resin resist having the interlayer resin insulating layer formed by laminating an insulating resin sheet on at least one surface of the inner wiring board, and having an opening at a predetermined position in the non-through hole forming step. 2. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein after forming a layer on the insulating resin sheet, blasting is performed using the resin resist layer as a mask. 4. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein said blasting is air blasting. 5. The method according to claim 1, wherein the blasting is wet blasting.