JP2919181B2 - Printed circuit board manufacturing method - Google Patents

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 circuit board in which a solder resist is applied on a circuit wiring pattern.

[0002]

2. Description of the Related Art In general, a solder resist is applied to a printed circuit board on which a circuit wiring pattern is formed, except for through-holes and lands for connecting electronic components and a connection region for an external terminal. As is well known, this solder resist is formed as a protective film to insulate and protect circuit wiring patterns when electronic components are mounted on a substrate and connected by soldering. For this reason, it is preferable to use a so-called UV-curable solder resist which is made of, for example, an epoxy-based heat-resistant resin and has photosensitivity for patterning by lithography.

When copper is plated on exposed circuit components using the UV-curable solder resist as a mask during the manufacture of a printed circuit board, electroless copper of a strong alkali having a high temperature of 60 to 70 ° C. and a pH of 10 to 12 is used. Since the plating solution is exposed to severe conditions, if it is immersed in the plating solution for a long time (for example, 10 hours or more), the surface layer is eroded, and a phenomenon of dissolving with time occurs. Therefore, many printed circuit board manufacturers select a process of applying the UV-curable solder resist 5 after forming the electroless copper plating 4 as illustrated in steps (d) to (e) of FIG. , Had avoided this defect.

Recently, a UV-curable solder resist which is resistant to plating solution has been developed, and the above-mentioned problem is being solved. However, a new problem is that the solder resist 5 and the copper of a circuit pattern (line) covering the same are covered. A phenomenon in which the foil surface peeled off in a point-like manner occurred. As a result of various experiments and investigations on the problem of this peeling, the heat treatment when curing the epoxy resin, which is a solder resist component, oxidizes the copper foil surface of the line and inhibits the bonding between the epoxy resin and the copper foil. Was found to be due to the weakening of the adhesive force. Therefore, in order to prevent this oxidation, the resin is cured by heating using a non-oxidizing, for example, nitrogen-filled drying oven.

A method for manufacturing two printed circuit boards having the above-described solder resist coating step will be described more specifically with reference to the process chart of FIG. <Conventional Example 1> (a) Step: A through hole 2 is formed in a copper clad laminate 1 having copper foils 8 stretched on both sides.

Step (b): The catalyst 3 is adsorbed on the entire surface of the substrate.

Step (c): The circuit pattern 8a and the land 8 are etched by using a circuit mask having a predetermined pattern.
b is formed.

Step (d): Electroless copper plating 4 is deposited in through-hole 2 and on circuit pattern 8a and land 8b.

Step (e): A UV-curable solder resist 5 is applied to the entire surface, exposed and developed, and the through-hole 2 is formed.
After the UV-curable solder resist 5 on the lands 4a (8b) is dissolved and removed, it is thermally cured in a drying furnace.

<Second Conventional Example> Steps (a) to (c) are the same as in the first conventional example.

Step (d): A solder resist 5 is applied to the entire surface, exposed and developed to dissolve and remove the solder resist in the through hole 2 and the land, and then thermally cured in a nitrogen-filled drying furnace.

Step (e): Electroless copper plating 4 on the through hole 2 and land portion where the solder resist is dissolved and removed.
Perform

[0013]

As shown in the first conventional example, in the step of performing the electroless copper plating 4 before the application of the UV-curable solder-resist 5, the copper plating solution is coated with a UV-curable solder resist. Since the solder resist 5 is not exposed, the problem of the oxidation of the circuit pattern is solved. However, since the copper plating is performed after the circuit pattern is formed as shown in the step (d), the solder pattern is not exposed.
Copper plating is deposited up to the line portion (circuit pattern) 8a other than the hole 2, and the line portion becomes thick, which becomes an obstacle when forming a high-density, high-fine line pattern. In addition, since the area to be copper-plated is not only the through hole 2 and the land, but also the entire circuit pattern, there is a problem that the consumption of the copper plating solution increases and the material cost increases.

In the case of the second conventional example, since a UV-curable solder-resist having improved resistance to a copper plating solution is used, the copper plating is applied to the UV-curable solder-resist 5.
Can be performed after the formation of the coating, and the problem that the line portion becomes thicker in the plating as in the conventional example 1 is solved. However, the nitrogen-filled drying furnace used to heat and cure the UV-curable solder-resist 5 while preventing oxidation of the copper pattern has special specifications for large printed circuit boards (600 × 600 size). Therefore, there is a problem in that the equipment cost is increased, and there is a problem in mass productivity due to the batch processing.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned conventional problems , and to prevent the oxidation of the surface of the line portion inside the resist during drying of the solder-resist, and to reduce the conditions of the electroless copper plating process. Also, the improved printed circuit board that enables high-density wiring with high reliability without deteriorating the adhesion between the line part and the solder-resist
It is to provide a manufacturing method .

[0016]

The pudding according to the present invention described above.
The board has a copper-clad laminate on which component connection portions including through holes and lands, conductor circuits (line portions), and external connection terminals are arranged. A printed circuit board formed by coating at least the conductor circuit with a solder resist, except that the conductor circuit coated with the solder resist has a complex structure formed with copper of 0.5 to 3.0 μm. Characterized by forming
Have .

The film having a complex structure with copper may be any film which can prevent oxidation of copper and does not deteriorate the bond with the solder-resist. For example, an imidazole compound such as an alkylimidazole may be used. A complex-structured film reacted on the surface is preferred. Since the thickness of the film is important, it is not sufficient to simply treat it with a complexing agent that forms a complex salt with copper without forming a film,
You cannot achieve your goals.

The effect of the thickness of the film on the adhesion of the solder-resist will be described in detail with reference to FIG. 4. It is preferable that the film having a complex structure with copper as shown is too thin or too thick. I understand that there is no. As described above, the thickness is preferably 0.5 to 3 μm, more preferably 1.0 to 3 μm.
2.5 μm. If the thickness exceeds 3.0 μm, the tendency of peeling between the resist and the film gradually increases,
If the thickness is smaller than μm, the film is formed coarsely.
It turned out that peeling occurred between the resist and the line, which had a bad influence on the adhesion. The peeling width on the vertical axis in this figure is a value obtained by measuring the degree of peeling by visually inspecting the printed circuit board coated with the solder resist.
When the resist is peeled off from the wiring, the portion is observed as a white line along the pattern shape of the wiring circuit, and the width is measured. No white spots or lines are observed when they are in close contact.

The solder resist is preferably a UV-curable solder resist. However, the solder resist is not limited to this. Good) and any insulating material that can be patterned as a resist can be used. However, as described later in the section of the manufacturing method, it is necessary to use a solder resist having a plating resistance that does not dissolve in an electroless copper plating solution (generally a strong alkali). The reason is that electroless copper plating generally has a low deposition rate (for example, 1 to 4 μm).
m / h) and when several tens of μm of sulfol plating is required, it must be immersed in a high pH and high temperature environment for a long time.

A conductor such as electroless Ni plating or electroless copper plating may be formed in the through hole as a base for electroless copper plating.

The object of the present invention is to provide a copper-clad laminate with (a)
For example, a step of drilling a through hole with a drill or a punch, (b) a step of applying a catalyst to at least the inside of the through hole, and (c) a land and an external connection terminal using a predetermined resist mask pattern. Conductor circuit (line part)
Forming a pattern by etching; and (d)
A step of applying a film-forming complex-forming agent to the substrate surface and reacting with the copper on the lands and the conductor circuit surface to form a complex structure film having a thickness of 0.5 to 3 μm; and (e) a plating solution resistant solder A step of applying a resist over the entire surface, selectively removing the solder resist on the through-holes, lands and external connection terminals, and thermally curing; (f) a region where the solder resist has been removed ( After dissolving and removing the complex structure film on the through-hole, land portion and external connection terminal) as a pretreatment,
This is achieved by a method of manufacturing a printed circuit board having a step of performing electroless copper plating (first manufacturing method).

As a preferable manufacturing method, when the plating resist-resistant solder resist is a photosensitive UV-curable solder resist, the through hole, the land portion and the external connection terminal are masked. U through the mask
Exposure to V and photo-curing of the parts other than the masking part. Thereafter, the unexposed portion may be dissolved and removed with a developing solution of an organic solvent, and the UV-curable solder-resist may be heat-cured in a drying furnace and subjected to electroless copper plating.

As a method of applying the complexing agent to the substrate surface, various coating methods are used.
It can be applied by silk screen, spray, roller method or the like.

As the complex forming agent for forming a film in the step (d), one having an action as a rust preventive for preventing oxidation of copper and a good binding property with a solder resist is used. An imidazole compound such as
Nitrogen-containing organic compounds having unpaired electrons, such as benzotriazole and benzothiazole, are preferred. As for the reaction conditions for forming the complex structure film, a complex forming agent for film formation is applied and the reaction is carried out at room temperature to 60 ° C. The film thickness can be easily adjusted by controlling the time during which the substrate is brought into contact with the solution. The longer the time, the thicker the film.

In the step (f) of applying the electroless copper plating, the film formed on the copper foil and having a complex structure with copper must be easily dissolvable by the pretreatment of the copper plating. If this remains, it causes copper plating quality such as void defects to deteriorate. As the dissolution treatment solution, a 2 to 3% by weight solution of an inorganic acid such as hydrochloric acid, sulfuric acid or nitric acid, or a peroxide such as sodium persulfate is used.

Further, the above object is also achieved by the following second manufacturing method. That is, after a through hole is formed on a copper-clad laminate by, for example, a drill or a punch, a catalyst is adsorbed on the entire surface of the substrate, and electroless Ni plating is performed for 0.5 to
Precipitate 1.0 μm. Further, the substrate surface is polished to
After the i-plating is removed (Ni plating is left only in the through-hole), exposure is performed by a UV exposing machine using a mask in which a portion other than a conductor circuit (line portion) including lands and external connection terminals is masked by an electrodeposition type UV resist. I do. further,
A circuit pattern is drawn by development, and a land and a conductor circuit pattern are formed by etching.

In the subsequent steps, a complex-forming agent for forming a film is applied to the substrate surface in step (d) in the above-described first manufacturing method, and is reacted with copper on the lands and the surface of the conductor circuit to achieve a thickness of 0.1 mm. Following the step of forming a complex structure film of 5 to 3 μm,
Hereinafter, the same steps are performed. In this method, Ni plating is performed as a base for copper plating of through holes, and a base conductor is formed as a measure against electrolytic corrosion during copper plating. Conductive metal may be formed. Note that the thickness of the electroless Ni plating is preferably 0.5 μm or more. Further, the thickness is preferably 0.5 to 1.0 μm. 0.5μ
If the thickness is less than m, the plating will be coarse, so that the electrodehole type UV resist cannot completely coat the inside of the through-hole.
Therefore, the portion where the catalyst is exposed is dissolved and removed by the etching solution, which causes a sulfur void. In addition, since the Ni plating solution is expensive, it is not necessary to increase the thickness by 0.5 to 1.0 from the viewpoint of cost reduction by prolonging the service life without increasing the thickness unnecessarily.
μm is preferred.

Furthermore, the above object is also achieved by the following third manufacturing method. That is, after the step of applying a catalyst into at least the through hole in the step (b) of the first manufacturing method, the electroless copper plating is performed by 2.5 times.
A step of forming a layer having a thickness of about 10.0 μm is added. Thereby, the first copper plating is formed in advance at least in the through hole. Thereafter, the same steps as those in the first manufacturing method are performed. According to this manufacturing method, the inside of the through hole is the first and the second.
Double copper plating of [copper plating in step (f) in the first manufacturing method] is performed.

In this case, the first electroless copper plating film thickness is
2.5 μm or more is preferred. In addition, preferably 3.0 to 3.0
10.0 μm. When the film thickness is smaller than 2.5 μm, the copper plating is completely dissolved by a soft etching solution (a surface cleaning treatment before the second copper plating) which is a pretreatment of the second electroless copper plating. A part of the catalyst may also be dropped off, and a sulfol void may be locally generated.

[0030]

[Function] Conductive circuit pattern coated with solder resist
The film that forms a complex structure with copper provided as a surface treatment film on the solder has a thickness of 0.5 to 3.0 μm as shown in FIG. 4 and sufficiently prevents the peeling of the solder-resist. To facilitate the formation of a solder resist having good adhesion. As a result, oxidation of the surface of the line copper foil inside the resist can be prevented, so that the solder resist and the surface of the line copper foil do not peel off under electroless copper plating conditions, realizing a highly reliable printed circuit board. can do.

[0031]

Embodiments of the present invention will be described below with reference to the drawings. <Embodiment 1> FIG. 1 is a process diagram for explaining an example of a method for manufacturing a printed circuit board according to the present invention. The contents will be described in order according to steps (a) to (f) shown in the drawings. (A) Step: Copper-clad laminate 1 having copper foils 8 bonded on both sides
Then, a through hole 2 is formed by drilling with a drill or a punch. Step (b): The substrate 1 is immersed in a colloid solution containing palladium and tin, and the catalyst 3 is adsorbed and applied to the entire surface of the substrate.

Step (c): A conductive circuit pattern 8a is formed. As a pattern forming method, first, after the surface of the substrate is adjusted with a brush, a UV-curable dry film is thermocompressed,
A mask having a mask other than the circuit pattern (line portion) 8a including the lands and the external connection terminals is brought into close contact with both surfaces, and the high-pressure exposure apparatus using an ultra-high pressure mercury lamp is used for 40 to 40 masks.
Printing is performed with an exposure amount of 800 mj / cm ² . Thereafter, the unexposed portion is dissolved and removed with an alkaline developer, a mask pattern of a dry film is formed, and the exposed copper foil is dissolved with an alkaline etchant. Then, unnecessary UV-curable dry films are removed with a stripping solution containing NaOH.

Step (d): A film 6 for forming a complex structure with the copper foil is formed on the copper foil pattern. As a method of forming a film having a complex structure, a film-forming complex forming agent is sprayed on the entire surface of the substrate,
It was applied and formed into a film at normal temperature. A commercially available alkylimidazole-based compound was used as a complex-forming agent for forming a film. The relationship between the film thickness and the film formation time is as shown in FIG.
By jetting for about 15 minutes, 1.5 μm was formed.

Step (e): A UV-curable solder-resist 5 is applied over the entire surface and preliminarily dried. And, sulfo-
The substrate 2, the land portion 8b, and the external electrode connection terminal (not shown) are brought into close contact with the substrate using a mask having a mask, and irradiated with a high vacuum exposure machine at 80 to 800 mj / cm ^{2 to} illuminate the area exposed from the mask. Let it cure. Further, the unexposed portion is dissolved and removed using 1,1,1-trichloroethane as a developing solution, and the solution is placed in a normal drying oven to form a 140 to 140.degree.
The UV-curable solder resist 5 is thermally cured at 160 ° C.

Step (f): Using a soft etching solution containing soda persulfate to dissolve and remove the film 6 forming a complex structure with copper on the exposed conductor, and then electroless copper plating 4
Perform

<Embodiment 2> An electroless Ni plating step is added between the steps (b) and (c) of the embodiment 1,
The substrate is immersed in a plating solution to make Ni plating 0.5-1.
Deposit 0 μm. After plating, polished the substrate surface,
The Ni plating on the copper foil 8 was removed, and the Ni plating was left only in the through holes 2. Then, instead of the UV-curable dry film in the step (c) of Example 1, the substrate is coated with an electrodeposition type UV resist, and the circuit pattern (line portion) 8a including the lands and external connection terminals is masked except for the circuit pattern (line portion) 8a. The exposed mask is brought into close contact with both surfaces, and is exposed by a high vacuum exposure machine using an ultra-high pressure mercury lamp. Further, a circuit pattern is drawn by development to form a mask. The circuit pattern 8a is formed by selectively etching the copper foil 8 using this mask. The subsequent steps are described in Example 1.
(D) to (f). FIG. 3 shows a cross-sectional view of a principal part of the printed circuit board thus obtained. As shown, the inside of the through hole 2 has a two-layer structure of a Ni plating 7 and a copper plating 4 as a base film.

<Embodiment 3> This embodiment is a modification of the embodiment 2 in which copper plating is applied instead of the Ni plating 7 as the base plating in the through hole 2 shown in FIG. Therefore, the inside of the through hole 2 is the first copper plating (corresponding to the Ni plating 7) formed as a base film.
And a second copper plating 4 (the same as the copper plating 4 of Examples 1 and 2).

More specifically, this embodiment will be described specifically. An electroless copper plating step as a first copper plating step is added between the steps (b) and (c) of the first embodiment. The substrate is immersed in a plating solution to form a copper plating of 3.0.
１10.0 μm. Subsequent steps were performed according to the steps (c) to (f) of Example 1.

<Embodiment 4> Steps (a) to (d) of the embodiment 1 are carried out in the same manner, and as the step (e), the UV-curable solder-resist 5 used in the embodiment 1 is used instead of thermosetting. A mold solder resist is applied over the entire surface using a silk screen plate in which the through hole 2, the land portion 8b and the external electrode connection terminals (not shown) are masked, and then the substrate is placed in a normal drying furnace. Then, the thermosetting solder resist is cured at 140 to 160 ° C. Next, the step (f) was performed in the same manner as in Example 1. That is, using a soft etching solution containing soda persulfate to dissolve and remove the film 6 forming a complex structure with copper on the exposed conductor, electroless copper plating 4 was performed.

[0040]

As described above, the intended object has been achieved by the present invention. That is, since the printed circuit board can prevent oxidation of the resist and the surface of the line copper foil which occur during drying after the application of the solder-resist, the resist and the surface of the line copper foil are peeled even under electroless copper plating conditions. Does not occur. Therefore, it is not necessary to change the conventional process only by adding a process, so that the conductive circuit pattern can be thinned. That is, a higher density printed circuit board can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a process of manufacturing a printed circuit board according to an embodiment of the present invention.

FIG. 2 is a process schematic diagram showing a conventional printed circuit board manufacturing process.

FIG. 3 is a sectional view of a main part of a printed circuit board according to another embodiment of the present invention.

FIG. 4 is a characteristic curve diagram of an example of the present invention, in which the effect of the thickness of a film having a complex structure with copper on the peel width between a solder resist and the surface of a line copper foil is measured.

FIG. 5 is a characteristic curve showing the relationship between the thickness of a film having a complex structure with copper and the film formation time, which is also one example of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Copper-clad laminate, 2 ... Through-hole, 3 ... Catalyst, 4 ... Electroless copper plating, 5 ... UV curing solder resist,
6: film having a complex structure with copper, 7: electroless Ni plating, 8: copper foil, 8a: circuit pattern,
8b (4a): Land.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuo Hamaoka 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Pref. Hitachi, Ltd. Information Communication Division (56) References 59-228788 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05K 3/28

Claims (11)

(57) [Claims] 1. A step of forming a hole in a copper-clad laminate by forming a through hole; (b) a step of applying a catalyst to at least the inside of the through hole; and (c) using a predetermined resist mask pattern. Forming a land and a conductive circuit pattern including the external connection terminal by etching,
(D) A film-forming complex-forming agent is applied to the substrate surface, and is reacted with copper on the land and the conductor circuit surface to have a thickness of 0.5 to 3 μm.
And (e) applying a plating solution resistant solder-resist over the entire surface to selectively remove the through-hole, the land portion, and the solder-resist on the external connection terminals. A thermal curing step; and (f) a step of dissolving and removing the complex structure film as a pretreatment in a region from which the solder resist has been selectively removed, and then performing electroless copper plating. Manufacturing method. 2. The method according to claim 1, wherein said plating resist solder resist is a photosensitive UV-curable solder resist.
UV exposure is performed through a mask in which the holes, lands and external connection terminals are masked, and the portions other than the masked portions are photo-cured, the unexposed portions are dissolved and removed with a developing solution, and the UV-curable solder resist is heat-cured 2. The method for manufacturing a printed circuit board according to claim 1, wherein the method comprises a step of performing electroless copper plating. 3. An unpaired electron having a rust-preventing effect of preventing oxidation of copper and a binding property with a solder resist as a complex-forming agent for forming a film in the step (d), and which forms a complex with copper. 2. A film forming step of using a nitrogen-containing organic compound having the formula ( 1 ) and adjusting the film thickness of the complex structure film by controlling the time for which the substrate is brought into contact with the film forming complex forming agent solution.
The method for manufacturing a printed circuit board according to the above. Wherein said film forming complexing agent imidazole compounds, benzotriazole, one something <br/> Re one of claims 1 to 3 comprising constituted by either the nitrogen-containing organic compounds of benzothiazole The method for manufacturing a printed circuit board according to the above. 5. The method according to claim 4, wherein said imidazole compound is an alkylbenzeneimidazole compound. 6. The treatment liquid for dissolving and removing the complex structure film with copper formed on the copper foil in the step of applying the electroless copper plating in the step (f) is diluted with an inorganic strong acid or a peroxide. printed circuit board manufacturing method according to any one of claims 1 to 5 comprising as a solution. 7. The inorganic strong acid is selected from hydrochloric acid, sulfuric acid and nitric acid, and the peroxide is sodium sulfate.
7. The method for producing a printed circuit board according to claim 6, wherein the solution is a diluted solution of weight%. 8. Between the steps (b) and (c), electroless Ni plating is deposited in a thickness of 0.5 to 1.0 μm, and the surface of the substrate is polished to remove the Ni plating from the substrate surface. ,
Adding step left only in the through hole, the final step method of manufacturing the printed board according to claim 1, wherein by forming a double plating film consisting of Ni plating and copper plating in the through holes in. 9. In the step (c), the resist mask pattern is exposed by a UV exposing machine using a mask masked by an electrodeposition type UV resist except for a conductor circuit including lands and external connection terminals, and the circuit is developed by development. drawing a pattern, this copper foil was etched as a mask, a land and a manufacturing method of the printed board according to claim 1 or 8, wherein comprising a step of forming a conductor circuit pattern. 10. The method according to claim 10, wherein the steps (b) and (c) are performed between
A step of forming an electroless copper plating of 2.5 to 10.0 μm is added, whereby at least a first copper plating is formed in advance in at least the through hole, and the above steps (c) to (f) are performed; method of manufacturing a printed circuit board according to claim 1, wherein in the through holes by forming a double copper plating. 11. The above step (d), as a method for applying the film forming complexing agent on the substrate surface, dipping, silk screening, spraying, according to claim 1, wherein comprising selecting one of methods of rollers Manufacturing method of printed circuit board.