JPH05129778A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To enable a protective layer of solder to be formed on a foot print part by a method wherein a solder film is formed only on the foot print part of a surface mounting component, a land, and the inner surface of a through- hole. CONSTITUTION:A panel copper plating layer 2 is formed on a copper plated laminated board 1, a first resist pattern 31 is formed covering a region where a circuit is formed, and a copper foil 1b on a region not covered with the first resist pattern 31 is removed through etching. Then, a laminated dry film resist 5 is exposed to light through a positive pattern mask and developed for forming a second resist pattern 51 so as to make the inner surface of a through-hole exposed. Thereafter, an electroplating solder film 6 is formed through electroplating. Therefore, a protective layer of electroplating solder film is formed uniform in thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board having through holes, and more particularly to a method of manufacturing a printed wiring board which is suitable for high density surface mounting.

[0002]

2. Description of the Related Art Conventionally, in a method for manufacturing a surface-mounted printed wiring board, a solder coater method, a heat-resistant preflux method, a nickel-based method, etc., in order to protect a copper film covering the entire surface of the printed wiring board. The gold plating method is known. The solder coater method, after applying a flux to the entire surface of a clean substrate punched in a copper clad laminate,
This laminated plate is passed through solder that has been heated and melted, and excess air is removed and leveled by blowing hot air onto this laminated plate by means such as an air knife, so that the solder is evenly distributed over the entire surface of the copper clad laminated plate. It is a method of coating.
Thus, the solder coater method is a simple means, but since the solder film coated on the surface thereof is leveled by blowing hot air as described above, the shape of the pad of the circuit pattern provided on the substrate and the There is a problem that the thickness of the solder formed on the substrate becomes non-uniform depending on the blowing direction of the hot air, which hinders resist stripping and etching in the next step and formation of the solder resist.
Further, particularly in a board having a circuit pattern in which the size of the pad of the circuit pattern is small and the interval between the pads is narrow, such as a high-density mounting board, the solder between the pads causes a solder bridge or the like that forms a bridging structure. Had a problem.

Further, the heat-resistant preflux method uses a solution in which a rosin-based base is dissolved in an organic solvent or a solution in which a rust preventive having the action of adsorbing copper to form a water-repellent film is dissolved in water. The purpose is to coat the substrate to protect the copper film on the surface of the substrate. However, in a substrate that has been subjected to the heat-resistant preflux method as described above, there is a problem of adhesion failure in soldering in the next step. This is because with the spread of printed wiring boards for surface mounting, recently, in the manufacturing process of printed wiring boards, more and more solders have been soldered more than once. That is, soldering failure occurs in the soldering process. As a cause of such a problem, the ambiguity of the heat resistance effect by the heat-resistant preflux method is regarded as a problem. Further, the heat-resistant pre-flux method has a problem of a limit region for fine pitch of the substrate by cream solder printing in the subsequent step.

In the nickel / gold plating method, the entire surface of the substrate is electroplated or electroless plated to first perform nickel plating and then gold plating to form a protective layer for protecting the copper film on the substrate surface. That is. Therefore, according to this method, an extremely excellent interlayer electrical bonding action between the nickel / gold plating film and the substrate and excellent wettability by the nickel / gold plating film formed on the entire surface of the substrate can be obtained. However, high cost and brittleness of solder joints pose problems.

[0005]

Therefore, the present invention has been made in view of the above circumstances, and a copper film on the surface of a substrate made of a copper clad laminate is used in the manufacturing process of the above-described printed wiring board for surface mounting. A method of manufacturing a printed wiring board that can form a protective film that protects the substrate uniformly and densely, improves its wettability and electrical bonding, and can reliably perform reflow mounting after forming the protective film. The purpose is to provide.

[0006]

Therefore, in order to solve the above-mentioned problems, according to the present invention, a copper clad laminate having through holes formed by drilling is coated with panel copper plating, and then a circuit is formed on the copper plating. A first resist pattern is provided so as to cover the portion to be covered, the copper clad laminate is then subjected to etching treatment, and then the first resist pattern is removed, followed by electroless copper plating on the entire laminate, and then this A dry film resist is laminated on the copper-clad laminate, and a second resist pattern is formed by exposing and developing the dry-film resist so that the through holes and portions where plating is required to be exposed are exposed. Electroless electroless exposed by performing a solder plating process, removing the second resist pattern, and then performing a short-time etching process. It is a manufacturing method of the printed wiring board substrate, which comprises removing the plating layer.

[0007]

In the method of manufacturing a printed wiring board according to the present invention, since the solder plating film is applied by electroplating only to the footprint portion of the surface mount component and the inner surface of the land and the through hole, the foot having a pitch of 0.5 mm or less is used. It is possible to avoid the occurrence of bridging in the printed area and to form a protective layer with the solder film in the footprint area. Then, as described above, the electric solder plating is performed only on the inner surface of the through hole and the necessary portion, so that the portion where the electric solder plating is performed is narrow and the electric flux lines are easily averaged. Therefore, in the manufacturing method of the present invention, the thickness of the protective layer formed by the electric solder plating film becomes more uniform. Therefore, at the time of mounting, the surface mount parts are inclined,
It is possible to improve yield with less falling.

In the past, when the number of times of mounting was two or more, the heat resistance in the heat-resistant preflux method was regarded as a problem. However, by forming the protective layer of the footprint part with a solder film as in the present invention, It is possible to avoid defective soldering caused by the problem of heat resistance. Therefore, according to the method for manufacturing a printed wiring board according to the present invention, the yield at the time of mounting can be improved even for a surface mounting substrate having a narrow pitch of the footprint.

Further, according to this manufacturing method, after removing unnecessary portions of the copper foil of the copper clad laminate, conduction of the through holes is established by electroless copper plating and electric solder plating. Since only the electroless copper plating layer is formed on the entire laminated plate, the part to be finally removed by etching is only the surface copper foil with a uniform thickness, the panel plating layer and the thin electroless copper plating layer. It will be good. Therefore,
According to the manufacturing method of the present invention, the height of the conductor pattern can be made uniform as compared with the usual pattern plating method. Therefore, according to the manufacturing method of the present invention, a circuit can be formed with an accurate width and a uniform thickness, and a fine circuit can be easily formed.

Further, according to the manufacturing method of the present invention, since the second etching process performed after the conduction in the through hole is performed only for a short time to remove the thin electroless copper plating layer, the inner surface of the through hole is formed. There is no effect on the electric solder plating film formed on the same. Therefore, according to the manufacturing method of the present invention, the etching accuracy is determined only by the substrate copper foil and the panel copper plating layer, and a fine circuit can be formed without obstructing the pattern plated portion.

In addition, in the method of the present invention, electroless copper plating is performed on the entire copper-clad laminate, so that it is not necessary to provide a resist pattern during electroless copper plating. Therefore, in the manufacturing method of the present invention, the resistance of the resist to the electroless copper plating solution does not pose a problem and a precision circuit can be easily formed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The manufacturing method of the present invention will be described below in more detail with reference to the drawings. In this manufacturing method, a drilling process is performed to prepare a first copper clad laminate 1 having through holes 10 as shown in FIG. The first copper-clad laminate 1 shown in the figure has a substrate 1a on which copper foils 1a and 1b are formed on both front and back surfaces. The thickness of the copper foil 1b is selected according to the application of the wiring board. The first copper clad laminate 1 may be subjected to deburring polishing treatment. Various means such as buffing and belt sander can be used for the polishing treatment. Thereafter, the first copper clad laminate 1 is subjected to panel copper plating treatment,
The panel copper plating layer 2 is formed as shown in FIG. For this panel copper plating treatment, a method such as electroless copper plating or electroless copper plating on electroless copper plating is used.
The thickness of the panel plating at this time is selected according to the application of the wiring board.

Next, a first resist pattern 31 is formed on the second copper-clad laminate 1A so as to cover a portion where a circuit is formed. To form the first resist pattern, first, as shown in FIG. 3, the resist 3 is thermally laminated on the entire front and back utilization surfaces of the second copper clad laminate 1A. As the resist 3, various materials such as a dry film resist, a liquid photoresist, and an electrodeposition resist can be used. Next, the laminated resist 3 is exposed and developed to form a first resist pattern 31 so as to cover a portion where a circuit is formed, as shown in FIG.

After the first resist pattern 31 is formed in this way, an etching process is performed, and as shown in FIG. 5, a portion of the copper foil 1b not covered with the first resist pattern 31.
To remove. As the etching liquid, a copper chloride-based, iron chloride-based, ammonia-based, or the like can be used. Next, after removing the first resist pattern 31 and making the fifth copper-clad laminate 1D in the state shown in FIG. 6, electroless copper plating is performed on the entire sixth copper-clad laminate 1E, as shown in FIG. The entire surface is covered with the electroless copper plating layer 4 as described above. It is desirable that the plating layer 4 be formed as thin as possible, for example, to have a thickness of about 1.0 to 3.0 μm, as long as it does not hinder the continuity of electroplating to be performed subsequently.

Next, a dry film resist 5 is thermally laminated to this as shown in FIG. Since unevenness exists on the surface of the eighth copper clad laminate 1G at this stage,
It is desirable to carry out the treatment using a vacuum laminator. The dry film resist 5 used at this time is thicker than the electric solder plating film 6 formed in the next step in order to prevent the electric solder plating film 6 formed in the next step from projecting over the resist. The thickness of 50 μm or more is used. Above all, when a dry film resist having a thickness of 80 μm or 100 μm is used, there is an advantage that the burying property in the resist substrate can be improved.

Next, the laminated dry film resist is exposed and developed through a positive pattern mask to form a second resist pattern 51 so that the inner surface of the through hole 10 is exposed as shown in FIG. At this time, the second resist pattern 51 is formed so that the land portion, the photo print portion of the surface-mounted component, and the like, which will be described later, need to be subjected to the electric solder plating treatment. After that, an electric solder plating process is performed on the ninth copper clad laminate 1H to form an electric solder plating film 6. Then, the second resist pattern 51 is removed to obtain the state shown in FIG. As the resist stripping solution, one corresponding to the dry film resist is used. For example, 1 to 5% by weight of sodium hydroxide or potassium hydroxide is used for an alkali developing type dry film resist. Further, methylene chloride is used for the organic solvent type dry film resist.

Then, this eleventh copper-clad laminate 1J is subjected to a short-time etching treatment to remove the electroless copper-plated layer 4 which is exposed without being covered with the electric solder plating film 6. For this etching, an ammonia-based, sulfuric acid / hydrogen peroxide-based etching liquid or the like can be preferably used. When this etching process is completed, the printed wiring board 1K shown in FIG. 12 is obtained. Further, the printed wiring board 1K manufactured by the manufacturing method of the present invention may be subjected to solder fusing depending on the purpose of use.

(Embodiment 1) Next, a method for manufacturing a printed wiring board according to the present invention will be described in more detail with reference to embodiments.
As shown in Fig. 1, 18 μm thick copper foils 1b, 1b on both sides
A through hole 10 was formed by drilling a hole in a predetermined position of a 2.2-mm-thick 6-layer copper-clad laminate in which b was laminated. After that, deburring polishing and a smear treatment in the through hole 10 with permanganate were performed. Thereafter, as shown in FIG. 2, panel plating was performed by applying thin electroless copper plating 0.5 μm and copper sulfate electroplating 35 μm on the surface of the first copper clad laminate 1. This electroless copper electroplating treatment was carried out through a cleaner conditioner, microetching, sulfuric acid treatment, catalyst adhesion, acceleration process and the like. Further, the copper sulfate plating was carried out successively from the electroless copper plating, and the current density was 2.5 A / dm ² . Then, the surface of the second copper clad laminate 1A was buffed. For the buff, HD-SF (manufactured by Sumitomo 3M) was used in duplicate. The processing conditions are buff rotation speed 2200 rpm and oscillation 5
The speed was 00 rpm and the passing speed was 2 m / min. Next, this product was washed with water, removed of water with an air knife, and then dried.

Next, as shown in FIG. 3, an alkali development type dry film resist 3 was laminated on this product. The resist 3 used was Dialon FRA305 (manufactured by Mitsubishi Rayon) having a thickness of 50 μm. When laminating the resist 3, a preheater for a dry film and a laminator were used. At this time, the temperature of the third copper clad laminate 1B was 60 ° C. after preheating and 60 ° C. immediately after lamination. Then, after the third copper clad laminate 1B on which the dry film resist 3 was laminated was left for 30 minutes to return to room temperature, a negative pattern mask was overlaid and exposure was performed using a dry film exposure device.
The exposure amount was equivalent to 17 steps remaining with a dialon step tablet (manufactured by Mitsubishi Rayon Co., Ltd.). Then, after peeling off the polyester film on the dry film resist,
It was developed for 60 seconds by a spray type horizontal developing machine containing a developing solution of a 0.9 wt% sodium carbonate aqueous solution (30 ° C.). After development, it was thoroughly washed with the attached washing tank. The treated fourth copper-clad laminate 1C was in the state shown in FIG.

Next, the fourth copper clad laminate 1C is immersed in a copper chloride-based etching solution to etch the copper foil 1b, and then the copper foil 1b is etched as shown in FIG.
The state shown in FIG. After that, the resist pattern 31 was peeled off in a peeling tank containing a 5% by weight aqueous sodium hydroxide solution at 40 ° C. Then, it was washed with water, pickled, washed with water, drained and dried to obtain the state shown in FIG. Then, electroless copper plating was performed on the entire sixth copper clad laminate 1E to form an electroless copper plating layer 4 having a thickness of 2 μm as shown in FIG. This electroless copper plating process is the Meltex 9048 electroless copper plating process (McDamit)
, A cleaner conditioner, a micro etch, a sulfuric acid treatment, a catalyst adhesion, an acceleration process and the like. Then, using a vacuum laminator, resist 5 (Dialon FRA063-50μ
m; made by Mitsubishi Rayon) was laminated as shown in FIG. The temperature of the eighth copper-clad laminate 1G was 60 ° C. after the preheater and 60 ° C. immediately after lamination.

Next, the laminated resist 5 is exposed using a positive pattern mask and developed for 60 seconds to expose only the through holes 10, lands and footprints of surface mount components as shown in FIG. The second resist pattern 51 was formed. At this time, the exposure amount of the dialon step doublet was equivalent to 11 steps remaining. Then, after pretreatment such as degreasing and micro-etching, tin borofluoride / lead plating is performed to obtain 8 μm as shown in FIG.
A solder plating film (tin / lead plating film) 6 having a thickness of 1 was formed.

Then, this is immersed in a 5% by weight aqueous sodium hydroxide solution at 40 ° C. to form a second resist pattern 5.
1 was peeled off to obtain the state shown in FIG. Then, the material after this is etched by an ammonia etching type etchant A process (Meltex),
The exposed electroless copper plating layer 4 was removed to complete the printed wiring board 1K shown in FIG. Thereafter, this printed wiring board 1K was subjected to solder fusing, and then a solder mask was formed. As the solder mask, a dry film solder mask (Dialon SRA103-75 μm; manufactured by Mitsubishi Rayon) was used.

Therefore, in this manufacturing method, the solder plating film 6 is applied only by the electroplating method to the footprint portion of the surface mount component and the land and the through hole 10, so that the footprint portion having a pitch of 0.5 mm or less is formed. It is possible to avoid generation of a bridge and to form a protective layer by the solder plating film 6 in the footprint portion. Also,
As described above, since the electric solder plating is performed only on the inner surface of the through hole and the necessary portion by the electric tin / lead plating, the portion where the electric solder plating is performed is small and the lines of electric force are easily averaged. Therefore, in the manufacturing method of the present invention, the thickness of the protective layer formed by the electric solder plating film 6 becomes more uniform. Therefore, at the time of mounting, the surface mount component is less likely to tilt or fall, and the yield can be improved.

In the past, when the number of times of mounting was two or more, the heat resistance in the heat-resistant preflux method was considered to be a problem. However, as in the present invention, the protective layer of the footprint portion is formed by the solder plating film 6. Thus, defective soldering due to the heat resistance problem can be avoided. Therefore, according to the method for manufacturing a printed wiring board according to the present invention, the yield at the time of mounting can be improved even for a surface mounting substrate having a narrow pitch of the footprint.

Further, in this manufacturing method, after removing unnecessary portions of the copper foil of the copper-clad laminate, conduction of the through holes is established by electroless copper plating and electric solder plating. Since only the electroless copper plating layer 4 is formed on the entire stretched laminated plate 1J, the portions to be finally removed by etching are the surface copper foil having a uniform thickness, the panel plating layer, and the thin electroless copper plating layer 4. Only good. Therefore, according to the manufacturing method of the present invention, the height of the conductor pattern can be made uniform as compared with the pattern plating method. Therefore, according to the manufacturing method of the present invention, a circuit can be formed with an accurate width and a uniform thickness, and a fine circuit can be easily formed.

Further, in the manufacturing method of the present invention, since the second etching process performed after the conduction in the through hole 10 is conducted is short enough to remove the thin electroless copper plating layer 4, The electric solder plating film 6 formed on the inner surface of the through hole 10 is not affected at all. Therefore, according to the manufacturing method of the present invention, the etching accuracy is determined only by the substrate copper foil and the panel copper plating layer, and a fine circuit can be formed without obstructing the pattern plating portion.

In addition, according to the method of the present invention, the copper clad laminate 1F
Since the electroless copper plating layer 4 is formed on the entire surface, there is no need to provide a resist pattern during the electroless plating process. Therefore, in the manufacturing method of the present invention, the resistance of the resist to the electroless copper plating solution does not pose a problem, and the precision circuit can be easily formed.

[0028]

As described above, according to the method for manufacturing a printed wiring board of the present invention, the solder plating film is applied by the electroplating method only to the footprint portion of the surface mount component, the land and the through hole. It is possible to avoid the occurrence of bridges in the footprint portion having a pitch of 0.5 mm or less and to form the protective layer by the solder film in the footprint portion. Then, as described above, the electric solder plating is performed only on the inner surface of the through hole and the necessary portion, so that the portion where the electric solder plating is performed is narrow and the electric flux lines are easily averaged. Therefore, in the manufacturing method of the present invention, the thickness of the protective layer formed by the electric solder plating film becomes more uniform. Therefore, at the time of mounting, the surface-mounted component is less likely to tilt or fall, and the yield can be improved.

Conventionally, when the number of times of mounting is two or more, the heat resistance of the heat-resistant preflux method was regarded as a problem.
By forming the protective layer of the footprint part with the solder film as in the present invention, it is possible to avoid the soldering failure due to the heat resistance problem. Therefore, according to the method for manufacturing a printed wiring board according to the present invention, the yield at the time of mounting can be improved even for a surface mounting substrate having a narrow pitch of the footprint.

Further, in this manufacturing method, after the unnecessary portion of the copper foil of the copper clad laminate is removed, conduction of the through hole is established by electroless copper plating and electric solder plating. Since only the electroless copper plating layer is formed on the entire laminated plate, only the surface copper foil with uniform thickness, the panel copper plating layer and the thin electroless copper plating layer need to be removed by etching. .. Therefore, according to the manufacturing method of the present invention, the height of the conductor pattern can be made uniform as compared with the pattern plating method. Therefore, according to the manufacturing method of the present invention, a circuit can be formed with an accurate width and a uniform thickness, and a fine circuit can be easily formed.

Further, according to the manufacturing method of the present invention, the second etching process performed after the conduction in the through hole is performed only for a short time to remove the thin electroless copper plating layer. There is no effect on the electric solder plating film formed on the same. Therefore, according to the manufacturing method of the present invention, the etching accuracy is determined only by the substrate copper foil and the panel copper plating layer, and a fine circuit can be formed without obstructing the pattern plating portion.

In addition, according to the method of the present invention, since electroless copper plating is performed on the entire copper clad laminate, there is no need to provide a resist pattern during electroless plating. Therefore, in the manufacturing method of the present invention, the resistance of the resist to the electroless copper plating solution does not pose a problem, and the precision circuit can be easily formed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a first copper clad laminate provided with a prepared through hole in an initial preparation step showing a manufacturing process of a printed wiring diagram of the present invention.

FIG. 2 is a cross-sectional view of a second copper-clad laminate with panel copper plating formed after the step shown in FIG.

FIG. 3 is a cross-sectional view of a third copper-clad laminate in a state where resist is thermally laminated on both front and back surfaces after the process shown in FIG.

FIG. 4 is a cross-sectional view of the fourth copper-clad laminate with the first resist pattern formed so as to cover the portion where the circuit is to be formed after the step shown in FIG.

FIG. 5 is a cross-sectional view of the fifth copper clad laminate in a state where after the step shown in FIG. 4, etching treatment is performed to remove the copper foil in the portion not covered with the first resist pattern.

FIG. 6 is a cross-sectional view of the sixth copper-clad laminate with the first resist pattern removed after the step shown in FIG.

7 is a cross-sectional view of the seventh copper-clad laminate with the entire surface covered with an electroless copper plating layer after the step shown in FIG.

FIG. 8 is a cross-sectional view of an eighth copper clad laminate in which a dry film resist has been thermally laminated on both front and back surfaces after the step shown in FIG.

9 is a cross-sectional view of a ninth copper clad laminate in which a second resist pattern has been formed so as to expose a portion that needs to be subjected to solder plating after the step shown in FIG.

FIG. 10 is a cross-sectional view of a tenth copper clad laminate with an electric solder plating film formed outside the inner surface of the through hole and the portion where the second resist pattern is formed after the step shown in FIG. 9;

FIG. 11 is a cross-sectional view of the eleventh copper-clad laminate with the second resist pattern removed after the step shown in FIG.

FIG. 12 is a twelfth copper-clad laminate in which the exposed portion of the electroless copper plating that is not covered with the electric solder plating film is removed after the step shown in FIG. 11, that is, the completed printed wiring board. It is sectional drawing of a board.

[Explanation of symbols]

 1 Copper Clad Laminate 1a Substrate 1b Copper Foil 2 Panel Copper Plating Layer 3 Resist 4 Electroless Copper Plating Layer 5 Dry Film Resist 6 Electric Solder Plating Film 10 Through Hole 31 First Resist Pattern 51 Second Resist Pattern

Claims (1)

[Claims] 1. A copper clad laminate having through holes formed by drilling is coated with panel copper plating, and then a first resist pattern is provided on the copper plating so as to cover a portion where a circuit is formed. After etching the copper-clad laminate, then removing the first resist pattern, electroless copper plating is performed on the entire laminate, then dry film resist is laminated on the copper-clad laminate,
This is exposed and developed to form a second resist pattern so as to expose the through hole and a portion that needs to be plated, and then this is subjected to an electric solder plating treatment, after which the second resist pattern is removed. Then, the exposed electroless copper plating layer is removed by performing an etching process for a short period of time, and then the exposed electroless copper plating layer is removed.