JP3763666B2 - Method for manufacturing printed wiring board - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method for manufacturing a printed wiring board.
[0002]
[Prior art]
In recent years, with the miniaturization of electronic devices, there has been a demand for miniaturization, high density, light weight, high reliability, and the like of printed wiring boards. Because of these demands, development efforts are also required for manufacturing and processing techniques of printed wiring boards. For example, miniaturization, miniaturization, high reliability, etc. of conductor width, conductor gap, through hole, via hole, etc. are required. Improvement of drilling, improvement of etching solution, improvement of plating solution, improvement of conditions such as temperature, time, speed, etc. have been made by development efforts and improvement efforts to meet these requirements. In these efforts, many laser drilling techniques have been proposed.
[0003]
[Problems to be solved by the invention]
However, in the conventional techniques for drilling by laser and forming via holes, the hole becomes large, the hole has an irregular shape, the reliability of electrical connection at the boundary between the conductor layer and the insulating layer is poor, etc. There's a problem.
[0004]
[Means for Solving the Problems]
The present invention
(1) In a method for manufacturing a printed wiring board in which a conductor layer and an insulating layer are laminated to form a circuit pattern having a via hole, a step of uniformly thinning the conductor layer to form a conductor thin layer having a thickness of 9 to 1 μm; Forming a hole in the conductor thin layer, irradiating a laser on a surface wider than the hole to form a hole for a via hole in the insulating layer, and melting an edge portion of the hole in the conductor thin layer; A method of manufacturing a printed wiring board comprising a step of attaching to a hole, a step of plating by a combination of electroless plating and electrolytic plating , and a step of forming a circuit pattern by a subtractive method ,
(2) The method for producing a printed wiring board according to (1), wherein the adhesion to the hole for the via hole is to adhere to the hole for the via hole in the form of snow avalanche,
(3) The method for producing a printed wiring board according to the above (1) or (2), wherein the via hole has a tapered shape that is dented in the depth direction,
With a hole in the thin conductor layer as a mask, a wide surface can be irradiated with a laser to form a hole in the insulating layer that is almost the same type and the same diameter as the mask hole. It is to provide a printed wiring board.
[0005]
Hereafter, the manufacturing method of the printed wiring board concerning this invention is explained in full detail.
The method of manufacturing a printed wiring board according to the present invention uniformly thins the conductor layer 1 of the substrate on which the conductor layer 1 and the insulating layer 2 are laminated as shown in FIG. Forming a thin conductor layer 3 having a thickness of 9 to 1 μm, forming a hole 4 in the thin conductor layer 3, and irradiating a laser 6 on a surface wider than the hole 4 using the thin conductor layer 3 as a mask. A step of forming a via hole 5 in the insulating layer 2, a step of plating the thin conductor layer 3, the inner wall of the hole 5 and the lower conductor layer to form a via hole 8 and a plated layer 7, and a subtractive method. It consists of the process of forming the circuit pattern 9. Further, a coating film (solder resist or the like) for protecting the surface is formed as necessary. In addition, the manufacturing method of the printed wiring board based on this invention is not limited to one embodiment of FIG.
[0006]
The conductor layer 1 in the method for manufacturing a printed wiring board according to the present invention is not particularly limited. Commonly used metal foils such as copper, stainless steel, nichrome, tungsten, and aluminum are preferable. Preferably, it is a copper foil. More preferably, it is the electrolytic copper foil used in large quantities. Moreover, as for the thickness of metal foil, 10-40 micrometers is preferable. More preferably, it is 10 to 25 μm which is easy to handle and is used in large quantities.
[0007]
The insulating layer 2 in the method for manufacturing a printed wiring board according to the present invention is not particularly limited as long as it is insulative. It may be based on a resin that is generally used, may be a woven fabric, a nonwoven fabric impregnated with the resin, or may be filled with an organic / inorganic filler, Also, a composite of these may be used.
[0008]
The processing method which forms the conductor thin layer 3 in the manufacturing method of the printed wiring board which concerns on this invention is not specifically limited. There are mechanical polishing / grinding and etching methods that are generally used. The method for thinning the copper foil is preferably processing by an etching method using an alkali type, cupric chloride type, ferric chloride type, sulfuric acid / hydrogen peroxide type, sulfite type, or the like. Particularly preferred is processing by etching of sulfuric acid / hydrogen peroxide system, which is easy to control etching, has a small surface roughness, and is uniformly etched. Moreover, the thickness of the conductor thin layer 3 is 9-1 micrometer. Preferably, it is 7-1 micrometer. More preferably, it is 5-2 micrometers. By thinning in this way, an accurate and sharp hole 4 can be formed in a later process, and a tapered hole 5 can be formed by slightly melting by laser processing. The step of forming the conductor thin layer 3 may be performed before the step of plating. Preferably, the conductor thin layer has a low heat conduction and the conductor thin layer slightly melts in the vicinity of the hole. Therefore, it is before the laser irradiation, and more preferably before the formation of the hole, because an accurate hole can be formed by the thin conductor layer in the step of forming the hole.
[0009]
The method of forming the hole 4 in the thin conductor layer 3 in the method for manufacturing a printed wiring board according to the present invention, and the shape of the hole 4 are not particularly limited. For example, a method using a drill or a method using etching. Preferably, the etching method can form a large number of the holes 4 at a time. Examples of the shape of the hole include a circle, a triangle, a quadrangle, a polygon, and a teardrop type.
[0010]
The method for forming the hole 5 for the via hole 8 in the method for manufacturing a printed wiring board according to the present invention is a method using a laser, which irradiates a surface wider than the hole 4, and does not limit the type of laser. Absent. The irradiation method is to irradiate a laser with a surface wider than the hole 4, and may irradiate a wide surface spot-like laser, or scan a small laser spot on a wide surface. The thin conductor layer 3 serves as a mask for the laser 6 and the resin layer 2 in the hole 4 is removed to form the hole 5. The resin layer is removed by the laser irradiation to form a hole, and the edge of the hole of the thin conductor layer is slightly melted and widened, and the hole 5 becomes tapered.
[0011]
The plating method in the method for manufacturing a printed wiring board according to the present invention is not particularly limited. A plating layer 7 is laminated on the inner wall surface of the hole 5, the conductor thin layer 3, and the inner conductor layer by a combination of electroless plating and electrolytic plating that is generally performed.
[0012]
The method for forming the circuit pattern 9 in the method for manufacturing a printed wiring board according to the present invention is formed by a subtractive method and does not particularly limit the steps, materials, and the like of the subtractive method.
[0013]
The via hole of the printed wiring board manufactured by the method for manufacturing a printed wiring board according to the present invention has a tapered hole, and there is no plating swelling at the edge of the hole in the thin conductor layer, and the plating thickness is uniform. Connection reliability is high. Further, the conductor line width and the gap can be narrowed to etch the plating layer having a large etching factor formed by electrolytic plating, and the wiring density is improved, so that the entire printed wiring board can be miniaturized.
[0014]
【Example】
Examples of the method for producing a printed wiring board according to the present invention will be described below. In addition, the manufacturing method of the printed wiring board based on this invention is not restricted to a following example.
[0015]
Example 1
Example 1 will be described with reference to FIG. On the epoxy resin substrate on which the inner layer circuit pattern is formed, an electrolytic copper foil 1 (conductor layer 1) having a thickness of 18 μm and an exfoliating film with an epoxy resin (insulating layer) of about 50 μm attached as an insulating resin layer are stacked. Then, they were laminated in a vacuum chamber (pressure 25 kg, temperature 180 degrees, time 120 minutes) (FIG. 1 (a)). The peeling film is peeled off, and then the electrolytic copper foil 1 of the laminated substrate is uniformly etched over the entire surface using a sulfuric acid / hydrogen peroxide-based etching solution as an etching solution. 3 (thin conductor layer 3) was formed (FIG. 1B).
[0016]
Next, a photoresist dry film is closely laminated on the electrolytic copper foil thin layer 3, exposed and developed using a photomask film, and the electrolytic copper foil thin layer 3 is etched to form a plurality of holes. 4 (multiple types of circular holes having a diameter of 80 to 200 μm) were formed (photo etching method) (FIG. 1C). The remaining photoresist dry film was peeled off.
[0017]
Next, the substrate on which the hole 4 is formed is positioned and set in the carbon dioxide laser device, and a carbon dioxide laser having a beam diameter of about 280 μm is irradiated to a surface wider than the hole 4 (pulse width 50 μsec) to reach the lower conductor layer. A hole 5 was formed (FIG. 1 (d)). When the surface was observed, the electrolytic copper foil thin layer 3 at the edge of the hole 4 was slightly melted and adhered to the hole 5 so as to collapse into a snow, and the hole 5 was tapered so as to dent in the depth direction. there were. Subsequently, general smear treatment was performed.
[0018]
Next, copper is deposited on the inner wall of the hole 5, the electrolytic copper foil thin layer 3 and the inner conductor layer using an electroless plating solution, and further, the inner wall of the hole 5 and the electrolytic copper foil thin layer are formed by electrolytic plating. A plating layer 7 having a deposition thickness of about 15 μm is formed on the conductor layer 3 and the inner layer to form a via hole 8, and a circuit pattern 9 comprising the electrolytic copper foil thin layer 3 and the plating layer 7 is formed by a subtractive method. A printed wiring board was manufactured (FIG. 1 (e)).
[0019]
The printed wiring board manufactured in this way does not have a large hole diameter immediately below the hole, the hole does not become irregular, the hole is tapered, and the reliability of electrical connection is improved by forming a via hole. did. Further, since the plating layer 7 is formed by electrolytic plating, the etching factor is large, the side etching width of the circuit pattern is small, the conductor line width and the gap can be narrowed, and the wiring density can be improved.
[0020]
【The invention's effect】
The method for producing a printed wiring board according to the present invention forms a hole by forming a hole in a thin conductor layer having a thickness of 9 to 1 μm that is uniformly thinned, and irradiates a laser on a surface wider than the hole, A via hole is formed by plating, and a circuit pattern is formed by a subtractive method. The printed wiring board manufactured by the manufacturing method of the present invention does not have a large via hole, does not have an irregular shape, has a tapered shape, and has high reliability of electrical connection due to the formation of the via hole. Moreover, since the etching factor of the plating layer is large, a high-density circuit pattern can be formed.
[0021]
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a process showing an embodiment of a method for producing a printed wiring board according to the present invention. (A) is sectional drawing by which the conductor layer was laminated | stacked on the insulating layer. (B) is sectional drawing which formed the conductor thin layer by thinning this conductor layer. (C) is the figure which formed the hole in this conductor thin layer. (D) is sectional drawing which forms a hole by irradiating a laser to this hole. (E) is a cross-sectional view in which a via hole is formed by plating and a circuit pattern is further formed.
[0022]
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Conductor layer 2 Insulating layer 3 Conductor thin layer 4 Hole 5 Hole 6 Laser 7 Plating layer 8 Via hole 9 Circuit pattern

Claims (3)

In a method of manufacturing a printed wiring board in which a conductor layer and an insulating layer are laminated to form a circuit pattern having via holes, a step of uniformly thinning the conductor layer to form a conductor thin layer having a thickness of 9 to 1 μm, Forming a hole in the layer, irradiating a surface wider than the hole with a laser to form a hole for the via hole in the insulating layer, and melting the edge of the hole in the thin conductor layer to adhere to the hole for the via hole A printed wiring board manufacturing method comprising: a step of performing plating, a step of plating by a combination of electroless plating and electrolytic plating , and a step of forming a circuit pattern by a subtractive method. The method for producing a printed wiring board according to claim 1, wherein the adhesion to the hole for the via hole is to adhere to the hole for the via hole in such a manner that it snows. The method for manufacturing a printed wiring board according to claim 1, wherein the via hole has a tapered shape that is dented in the depth direction.

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