JPH11274698A - Manufacturing method of printed wiring board - Google Patents

Abstract

(57) [Problem] To provide a method of manufacturing a printed wiring board capable of manufacturing a solder resist layer of a high-density substrate with high precision at low cost and with a short lead time. A method of manufacturing a printed wiring board including at least an insulating base (31) and a conductor layer (32), comprising: forming a material layer (35) of a solder resist layer on the printed wiring board; Irradiating the solder resist material layer 35 with the laser beam 37 according to the above.

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 printed wiring board for manufacturing a precise printed wiring board at a low cost, and more particularly, to precisely forming a solder resist layer to be formed on the top of the printed wiring board as a protective layer. Manufacturing method.

[0002]

2. Description of the Related Art In accordance with miniaturization and high integration of integrated circuits,
The miniaturization and high integration of printed wiring boards are being promoted, and with the miniaturization of wiring, technologies have been developed from single-sided substrates to double-sided substrates, and further to double-sided multilayer substrates. As for the multilayer substrate, a build-up substrate having a high degree of integration has been used from a through-hole substrate. Although the present invention can be applied to any printed wiring board, a conventional method for manufacturing a printed wiring board will be briefly described using a build-up board as an example.

FIG. 1 is a view showing an example of the structure of a build-up board. A core substrate 11 is a double-sided glass / epoxy substrate or the like, and a metal conductor layer 12 is formed thereon. This metal conductor layer is formed by, for example, bonding a copper foil or plating with copper. The wiring in the conductor layer is formed by photolithography. After applying a photosensitive resin (photoresist) or pasting a dry film resist (DFR) on the substrate on which the metal conductor layer is formed, the circuit pattern of the wiring is exposed and the light-irradiated portion of the resist is cured. Next, development is performed to remove the uncured resist portion, and a photoresist layer corresponding to the circuit pattern of the wiring is obtained. In this state, the substrate is immersed in a solution and etched to remove the exposed portion of the copper foil, and then the remaining resist layer is peeled off to obtain the first conductor layer 12.

[0004] Next, a photosensitive resin that is cured by light such as ultraviolet light is applied to the surface including the conductor layer to form a via hole.
e) Irradiate light for curing except for part 14. This light irradiation is performed, for example, by irradiating curing light through a mask that shields a portion of the via hole 14 from light. When the photosensitive resin irradiated with light is developed with a chemical, the photosensitive resin in the portion of the via hole 14 not irradiated with light is removed, and the conductor layer is exposed. The photosensitive resin that has not been removed becomes the first insulating layer 13. Here, sufficient curing is performed by heating as necessary. Next, the surface of the insulating layer is roughened to 5 μm
Irregularities of about 10 μm to about 10 μm are formed so that the conductor layer bites into the insulating layer to increase the peel strength. Next, electroless plating and electrolytic plating are successively performed to form a second conductive layer. At this time, the inside of the via hole 14 is also plated, and is interlayer-connected to the lower conductor layer. Similarly to the above, the second conductive layer 15 is formed by photolithography and etching.

The above processes are repeated to build up layers. When forming the last conductor layer, as shown in FIG. 1, a hole 18 for a through hole is made, and the last conductor layer 19 is plated. At this time, the conductor layer 19 is also formed on the inner surface of the through hole 18. Similarly, a pattern in the last conductor layer is formed by photolithography and etching. Further, an insulating resin is formed as the solder resist layer 20 to complete the build-up substrate. The solder resist layer 20 is a heat-resistant coating material that protects this portion from soldering during soldering (soldering) work. A solder resist layer is provided on the conductor layer portion for connecting electronic components. Form no holes.

The solder resist layer 20 has been formed mainly by screen printing. The screen printing method is suitable for mass production because it requires only printing and then drying and curing, so productivity is high.However, sufficient alignment accuracy cannot be obtained due to expansion and contraction of the plate during screen printing etc. Limitations on application to high-density (high-resolution) printed wiring boards, which require high alignment accuracy, due to soldering problems such as blurring at pattern edges and bleeding at land areas was there. Therefore, as in the case of the insulating layer, a lithography method of exposing and developing using a photosensitive resin has been used for a high-density printed wiring board. The lithography method has the advantage of high resolution as described above, but requires the steps of coating, exposing, developing, and thermally drying a photosensitive resin, and also requires manufacturing a mask on which a pattern is based. However, there is a problem that the manufacturing process is complicated and the cost is high as compared with the screen printing method.

[0007]

In recent years, the density of printed wiring boards has been increasingly increased, and it has become impossible to cope with the formation of a solder resist layer by a screen printing method. For this reason, the lithography method is often used, but there is a problem that the process is complicated and the cost is high as described above.

Further, a mask on which a pattern is based is formed of a film, and pattern data is output from a computer or the like to a film exposure apparatus, and a mask film corresponding to the pattern data is manufactured by the film exposure apparatus. Since the mask film is a film, it expands and contracts due to temperature and humidity, and there is a problem that the positioning accuracy is reduced accordingly.

In recent years, there has been a demand for flexible production of printed wiring boards that can respond to changes in demand, and is required to be able to respond to high-mix low-volume production. However, when using a mask film, it is necessary to prepare the mask film before starting the manufacture of the printed wiring board, and the lead time until the start of the manufacture is long, and there is a problem in terms of flexible production. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a printed wiring board capable of manufacturing a solder resist layer of a high-density substrate with high precision at low cost and with a short lead time. With the goal.

[0011]

In order to achieve the above object, a method for manufacturing a printed wiring board according to the present invention comprises irradiating a laser beam to a material layer of a solder resist layer in accordance with a pattern of the solder resist layer. To form That is, the method for manufacturing a printed wiring board of the present invention includes:
A method for manufacturing a printed wiring board including at least an insulating base and a conductive layer, comprising: forming a material layer of a solder resist layer as a protective layer on the printed wiring board; and forming a laser beam according to a pattern of the solder resist layer. And irradiating the solder resist material layer with the above.

According to the method of manufacturing a printed wiring board of the present invention, the pattern of the solder resist layer is formed by mechanical control of the laser irradiation device, on / off control of the laser beam, and scanning control, so that the alignment accuracy is high. high,
It is applicable to high density printed wiring boards. Furthermore, since the pattern of the solder resist layer by the laser beam irradiation device can be performed by directly giving pattern data to the laser beam irradiation device, it is not necessary to manufacture a mask film, so that it is economical and the lead time is shortened.

A positive or negative photosensitive resin is used as a material for forming a solder resist layer, and pattern irradiation is performed using a laser beam having a wavelength at which the photosensitive resin is exposed, followed by development and drying. However, if a resin such as a photo-curing type or a thermosetting type is used, development is not required and the process is simple. Further, by paying attention to the characteristics of the laser beam as an energy beam, the portion of the solder resist layer irradiated with the laser beam may be melted, evaporated, dissociated, and decomposed. In this case, it is desirable to irradiate a laser beam after curing the material layer of the solder resist layer.

When the solder resist layer is melted / evaporated / dissociated / decomposed by irradiating a laser beam, the upper solder resist layer irradiated with the laser beam is melted / evaporated due to the difference in the material of the solder resist layer and the lower layer. Irradiation conditions such as the number of laser beam energy density shots and irradiation time are set so that dissociation and decomposition occur, but the lower layer is not affected. The part to make a hole in the solder resist layer is
It is a portion for connecting electronic components, and there is generally a conductor layer in a hole portion of the solder resist layer. The solder resist layer irradiated with the laser beam is melted, evaporated, dissociated and decomposed to expose the conductor layer.

Under the above conditions, when a hole is formed in the solder resist layer above the conductor layer, when a hole is formed outside the range of the conductor layer, the above conditions cannot be applied outside the range of the conductor layer. Therefore, it is desirable that the hole be within the range of the conductor layer. If the irradiation conditions of the laser beam are appropriately selected, it is possible to make a hole by irradiating the laser beam to melt, evaporate, dissociate, and decompose only the solder resist layer on the insulating layer. In this case, a solder resist layer and an insulating layer having different light absorption wavelengths are selected, and a laser beam that is easily absorbed by the solder resist layer is used.

The hole formed by melting, evaporating, dissociating and decomposing the solder resist layer has a tapered edge, and has a good condition when the electronic component is soldered. In addition,
There are various types of printed wiring boards such as a single-sided board, a double-sided board, and a multi-layer board. However, since a solder resist layer is formed on the surface, the present invention can be applied to a printed wiring board having any structure. Further, the substrate serving as the base of the printed wiring board may be any substrate such as a flexible substrate and a rigid substrate. Further, the printed wiring board may be formed up to a state before the formation of the solder resist layer by any method such as a subtractive method, an additive method, and a semi-additive method.

Further, the material of the insulating layer constituting the printed wiring board may be any material. For example, epoxy resin, polyimide resin, polyester resin, phenol resin, polyphenylene ether resin, polyphenylene oxide resin, bismaleimide resin, It is desirable that at least one kind such as a triazine resin be a main component. Further, an insulating resin obtained by impregnating a resin into glass, aramid, paper, porous polytetrafluoroethylene, quartz, or other woven fabric or nonwoven fabric may be used. Resin beads, alumina powder, titanium oxide powder, carbon dioxide Organic or inorganic fillers such as calcium powder may be filled.

Further, any material may be used for the conductor layer constituting the printed wiring board. For example, it is preferable to use a metal foil such as copper, stainless steel, nichrome, tungsten and aluminum or a conductive paste. It is more preferable to use copper. Furthermore, the portion of the conductor on which the hole of the solder resist layer is formed is called a conductor pad, and this shape may be any shape such as a circle, a square, a rectangle, a polygon, a deformed shape, and a teardrop shape. The holes in the resist layer may be of any shape,
Its shape is determined by the shape of the electrodes of the mounted electronic component.

As a light source of a laser irradiation device for outputting a laser beam, a laser having a wavelength of 20 μm to 0.01 μm can be exemplified. Preferably, the laser has a wavelength of 2 μm to 0.1 μm. More preferably, it is a laser of 0.4 μm to 0.1 μm which dissociates and decomposes the material of the solder resist layer, causes less heat damage, and does not require desmear treatment because of no carbonization phenomenon. When selecting the light source, the light source is determined in consideration of the material of the solder resist layer to be used, and also the material of the conductor layer and the insulating layer.

As the material of the solder resist layer, various resins such as a natural curing type, a thermosetting type, and a light curing type can be used. In Examples described later, an alkali development type solder resist manufactured by Taiyo Ink Manufacturing Co., Ltd. PSR-4000 AUS5 "
Although (trade name) was used, other solder resist materials such as epoxy, polyester, phenol, acryl, silicon, and polyurethane can be used.

The solder resist material layer may be formed by any method such as coating (coating), dipping (dipping), and printing, or a film-like material may be attached. Also, the thickness of the solder resist layer is not particularly limited, but is 1 to 100 μm, more preferably 1 to 50 μm in dry thickness.

[0022]

FIG. 2 is a diagram showing a method of manufacturing a printed wiring board according to a first embodiment of the present invention. Here, a manufacturing method using a double-sided board as an example will be described, but the same applies to any printed wiring board. First, a glass epoxy resin plate 31 having an electrolytic copper foil 32 having a thickness of 18 μm stuck on both sides.
0.25m with NC drill on the double-sided printed circuit board 30
Then, a through hole 34 is formed on the surface of the electrolytic copper foil and on the inner wall surface of the through hole 34 by electroless copper plating. Therefore, the electrolytic copper foil 32 on the surface becomes thicker by the amount of plating. Next, after a photosensitive dry film is attached and exposed to ultraviolet (UV) light using a photomask, development, etching of the electrolytic copper foil, and peeling of the dry film are performed to form a circuit pattern. This state is (1) in FIG.

Next, an alkaline development type solder resist “P” manufactured by Taiyo Ink Manufacturing Co., Ltd.
"SR-4000 AUS5" (trade name) was screen-printed almost entirely to a thickness of 30 μm, preliminarily dried at 80 ° C. for 20 minutes, and thermally cured at 150 ° C. for 60 minutes, and then 1000 m
Post-UV exposure with an exposure of J / cm ² . This state is (2) in FIG.

Next, the printed wiring board 30 is positioned and set on a processing table of a carbon dioxide laser device. As shown in FIG. 3, the carbon dioxide laser device places the printed wiring board 30 on a precisely movable stage 42 and moves it in one direction. The laser irradiation device 30 scans the laser beam while converging it on the solder resist layer of the printed wiring board 30. The on / off control of the laser beam is performed, and the portion of the solder resist layer where a hole is to be formed is irradiated with the laser beam. Generally, the laser irradiation device 41 repeatedly scans in one direction at a high speed, and the entire surface of the substrate is scanned by moving the stage 42 on which the printed wiring board 30 is mounted in a direction perpendicular to the scanning direction. By turning on / off the laser beam according to the scanning position of the laser beam according to the irradiation pattern, it is possible to irradiate a desired pattern. The irradiation control unit 43 controls the irradiation of the carbon dioxide laser device. The irradiation control unit 43 reads out the irradiation pattern data created by the CAD system or the like and stored in the irradiation data storage unit 45, and outputs the stage 4 data through the stage control unit 44.
The laser beam is turned on and off in synchronization with the scanning of the laser irradiation device 41 while controlling the movement of the laser beam. The carbon dioxide laser device used in this embodiment has a pulse width of 50 μs,
The frequency is 300 Hz and the beam diameter is 120 μm.

As shown in FIG. 2C, a portion of the solder resist layer where a hole is to be formed is irradiated with a laser beam 37 using the carbon dioxide laser device of FIG. The portion of the solder resist layer irradiated with the laser beam is melted and evaporated to form a hole 36. Here, 0.
A rectangular hole of 30 × 0.15 mm and a circular hole of 0.12 mm in diameter for a solder bump were formed. Since the carbide remains in the state where the holes are formed, desmear treatment is performed to clean the surface.

Next, the symbols of the electronic components to be mounted on the remaining solder resist are printed by silk to complete the printed wiring board. In the method of manufacturing a printed wiring board according to the first embodiment described above, since the holes (pads) of the solder resist layer can be directly drawn, the manufacturing process is simplified, and the laser beam is accurately irradiated. Is good. Further, the pads of the solder resist layer have a tapered shape in which the upper portion is slightly open, so that the solder can easily be put on and cut off, and troubles when mounting electronic components can be reduced.

Here, the melting and evaporating action at the laser beam irradiation part will be discussed with reference to FIG. As shown in FIG. 4A, it is assumed that a metal conductor layer 32 is formed on a substrate 31, and a solder resist material layer 35 is formed over the entire surface of the substrate 31. The solder resist material layer 35 is formed by drying, natural curing, heat curing,
It is cured by light curing. A hole 36 is formed by irradiating the laser beam 37 on the metal conductor layer 32. The irradiated laser beam 37 is absorbed by the solder resist material layer 35 and a part reaches the metal conductor layer 32 and is absorbed and reflected. The temperatures of the solder resist material layer 35 and the metal conductor layer 32 that have absorbed the laser beam 37 rise sharply.
Since the solder resist material layer 35 is on the upper layer, it absorbs the laser beam 37 more, has a lower thermal conductivity than the metal conductor layer 32, and does not diffuse heat to the surroundings. Further, the heat of the metal conductor layer 32 propagates through the metal conductor layer and diffuses to other portions.
Therefore, the temperature of the solder resist material layer 35 becomes higher than that of the metal conductor layer 32. Further, since the melting temperature of the solder resist material layer 35 is lower than that of the metal conductor layer 32, the solder resist material layer 35 melts and evaporates, but the metal conductor layer 32 remains as it is.

In the first embodiment, a carbon dioxide laser is used as a laser light source. In the second embodiment, an ultraviolet (UV) laser is used. The difference from the first embodiment is that the solder resist used is a thermosetting type S manufactured by Taiyo Ink Manufacturing Co., Ltd.
-22], which is formed by curing at 30 ° C. for 20 minutes at 140 ° C., and then irradiating an ultraviolet laser having a wavelength of 355 nm to form a pattern. When a UV laser is used, desmearing is not required.

[0029]

As described above, according to the present invention,
A solder resist layer on a high-density substrate that requires high resolution and precise alignment accuracy can be manufactured at low cost and with a short lead time.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a structure of a printed wiring board according to a conventional build-up method.

FIG. 2 is a diagram illustrating a manufacturing process of the printed wiring board according to the first embodiment of the present invention.

FIG. 3 is a block diagram of a carbon dioxide laser device used in the first embodiment.

FIG. 4 is a view for explaining an exposure action when a hole is formed in a solder resist layer on a conductor layer.

[Explanation of symbols]

 Reference Signs List 30 printed wiring board 31 substrate (insulating base, core) 32 conductor layer 33 through-hole conductor layer 34 through hole 35 solder resist layer 36 hole (pad) 41 laser irradiation device 42 stage

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masami Uema 176-120, Kasagi, Iwabuchi, Ogawa, Sukagawa-shi, Fukushima

Claims (3)

[Claims] 1. A method for manufacturing a printed wiring board comprising at least an insulating base and a conductive layer, comprising: forming a material layer of a solder resist layer on the printed wiring board; Irradiating the solder resist material layer with a laser beam according to the following. 2. The method for manufacturing a printed wiring board according to claim 1, wherein the material layer of the solder resist layer is cured, and then the material layer of the solder resist layer is irradiated with the laser beam. Is a method for manufacturing a printed wiring board that melts, evaporates, dissociates, and / or decomposes. 3. The method for manufacturing a printed wiring board according to claim 1, wherein the pattern of the solder resist layer is a hole on the conductor layer, and the hole is located within a range of the conductor layer. A method of manufacturing a printed wiring board.