JP2002266087A - Etchant for copper and method for manufacturing printed circuit board using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an etchant which is capable of suppressing the generation of root remaining of copper foil even in inner layer conductor circuits subjected to rust preventive treatment, such as chromate treatment, abating the shorting defect between the conductor circuits and providing printed circuit boards having excellent circuit formability, and a method for manufacturing the printed circuit boards using this etchant. SOLUTION: The etchant for copper which contains a sulfate exclusive of copper sulfate and/or a hydrogensulate, sulfuric acid and hydrogen peroxide and in which the molar ratio of the sulfate exclusive of the sulfric acid and copper sulfate and/or the hydrogensulfate is >=1 and more particularly the sulfate and the hydrogensulate are ions of a metal baser than sulfuric acid ions and hydrogen.

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, and more particularly to an etching solution suitable for a copper foil which has been subjected to a rust-preventive treatment such as a chromate treatment, and a method for manufacturing a printed wiring board using the same.

[0002]

2. Description of the Related Art In recent years, demands for smaller, lighter, and faster electronic devices have been increasing, and the density of printed wiring boards has been increasing. Conventional printed wiring boards made by etching copper have a limit in miniaturization of wiring due to the influence of side etching, and thus have a limit in increasing the density of a substrate. Therefore, recently, a method of manufacturing a printed wiring board by a semi-additive method using electroplating has attracted attention. This semi-additive method forms a photoresist layer on a copper foil of 5 μm or less as a conductor layer, forms an electroplating circuit after exposure and development, removes the resist, and removes unnecessary conductor layers by etching. This is a method of manufacturing a printed wiring board by forming a circuit.

In the case of forming a circuit by the above-described semi-additive method, when the circuit becomes finer, when the power supply layer is removed by etching, copper residue between conductor circuits is likely to occur, which causes a short circuit failure. .

[0004] This copper residue is remarkably observed in an etching solution containing iron chloride and copper chloride as main components.

Further, the occurrence of short-circuit defects can be reduced by extending the etching time, but in this case, the problem that the conductor circuit is melted tends to occur.

[0006] On the other hand, Japanese Patent Application Laid-Open No. 2000-286531 discloses an invention in which a circuit-forming property is improved by using a chemical reaction-controlled etching solution containing sulfuric acid, hydrogen peroxide and copper ions as main components. Have been.

However, in the process of manufacturing a printed wiring board, in order to improve the adhesion of the insulating resin layer, it is necessary to roughen the conductor circuit of the inner layer and to perform a rust prevention treatment such as a chromate treatment thereon. Many. In this case, it is difficult to dissolve a metal for rust prevention treatment such as chromium with the above-mentioned sulfuric acid-hydrogen peroxide-based etchant, so that the root of the copper foil is generated. When performing a gold plating process, a problem that nickel / gold plating is deposited on a resin is likely to occur.

[0008]

SUMMARY OF THE INVENTION The present invention relates to an inner conductor circuit which has been subjected to rust prevention treatment such as chromate treatment.
Provided is an etching solution that can suppress the generation of root residue of copper foil, thereby reducing short-circuit failure between conductor circuits and providing a printed wiring board excellent in circuit formability, and printed wiring using the etching solution. An object of the present invention is to provide a method for manufacturing a board.

[0009]

The copper etching solution of the present invention contains a sulfate and / or hydrogen sulfate except copper sulfate, sulfuric acid, and hydrogen peroxide, and contains a sulfate other than sulfuric acid and copper sulfate. And / or a molar ratio to hydrogensulfate of 1 or more. In particular,
The sulfate and / or hydrogen sulfate except for the copper sulfate,
This is an etching solution for copper, which is a metal ion that is lower than sulfuric acid and hydrogen. Further, the sulfate except for the copper sulfate,
Those selected from the group consisting of alkali metal sulfates, alkaline earth metal sulfates, iron sulfate, and zinc sulfate are preferable, and the hydrogen sulfate is preferably an alkali metal hydrogen sulfate.

The method for manufacturing a printed wiring board of the present invention comprises:
(1) a step of laminating a resin with a copper foil on the upper and lower surfaces of an inner layer plate on which an inner circuit is formed; and (2) providing an interstitial via hole (hereinafter referred to as “IVH”) in the resin with a copper foil, A step of forming a plating layer on the foil and inside the IVH, and (3) a step of forming a resist pattern except for a circuit formation portion on the plating layer,
(4) a step of forming a conductor circuit by electroplating at the circuit formation location; (5) a step of removing the formed resist; (6) a sulfate and / or hydrogen sulfate except copper sulfate; And hydrogen peroxide, and using a copper etchant having a molar ratio of sulfate and / or hydrogen sulfate other than sulfuric acid and copper sulfate of at least 1 to remove copper other than the portion to become a conductor circuit. And removing by etching.

[0011] Further, a method for producing the resin with copper foil, wherein the copper foil surface to be adhered to the resin is subjected to a chromate treatment,
And a method of further performing electroless nickel plating / gold plating on the outermost surface of the conductor circuit.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The etching solution in the present invention is:
The basic composition is sulfuric acid and hydrogen peroxide. Unlike an etchant having a basic composition of sulfuric acid and hydrogen peroxide, an etchant having a basic composition of iron chloride, copper chloride, or the like, it is difficult to form monovalent copper ions, which are hardly soluble, so that a chemical reaction occurs. It is known that it is rate-determining and has excellent uniform etching properties.

The basic idea of the present invention is to improve the solubility of metals other than copper, for example, chromium, by adding sulfate ions to the basic composition. That is,
Chromium is produced in a strong acid atmosphere such as aqua regia, nitric acid, sulfuric acid, etc.
It is believed that it is hexavalently oxidized and takes the form of H ₂ CrO ₄ . In order to dissolve H ₂ CrO ₄ , it is necessary to dissociate protons. However, in a strong acid atmosphere, that is, in the presence of sulfuric acid, protons cannot be dissociated, resulting in poor solubility. On the other hand, chromium is H ₂ CrO ₄ ⇔HCrO in the presence of sulfuric acid.
₄ ^- + H ⁺ of so balancing state, the addition of sulfate ions to the system, the ion becomes proton acceptor sulfate,
The solubility of chromium is improved. Here sulfate ions, it is necessary to merely a proton acceptor, the counterion is a noble ions such as Cu ^++, the ions OH ^- Since it is difficult to form an ion complex with by sulfate ions Less effective.

The sulfate ion can be added as a sulfate salt excluding copper sulfate. For example, calcium sulfate,
It is lithium sulfate, potassium sulfate, iron sulfate, sodium sulfate, magnesium sulfate, zinc sulfate, or beryllium sulfate. As described above, copper sulfate has little effect of sulfate ions and cannot dissolve chromium,
It cannot be used in the present invention. Sulfate ions can add hydrogen sulfate instead of or in combination with the above-mentioned sulfate. Sulfuric acid concentration is 5-300g /
The concentration of L, sulfate and / or hydrogen sulfate is from 1 to 30
It is preferable to adjust 0 g / L and hydrogen peroxide to 5-200 g / L. If the concentration of sulfate and / or hydrogen sulfate is high, the uniform etching property deteriorates. Therefore, it is preferable that the sulfuric acid concentration is higher than the concentration of sulfate and / or hydrogen sulfate as a molar concentration.

This etchant has good circuit formability without impairing the etchability even when a dissimilar metal layer such as chromium, nickel and zinc is formed on the copper foil. Note that a known hydrogen peroxide stabilizer can also be added as an auxiliary agent to the etching solution. Examples of the hydrogen peroxide stabilizer include at least one acid selected from an alkanesulfonic acid group, an alkanolsulfonic acid group, and a hydroxy acid group, and salts thereof.

An embodiment of the etching solution according to the present invention will be described with reference to FIG. First, as shown in FIG. 1A, a wiring substrate having an inner conductor circuit 1 formed on a surface of an insulating substrate 2 is manufactured. The formation of the conductor circuit on the insulating substrate is performed by a subtractive method performed by etching a copper-clad laminate, or a glass epoxy substrate or a polyimide substrate,
There is an additive method in which an adhesive layer for electroless plating is formed on the surface of an insulating substrate such as a ceramic substrate, the surface of the adhesive layer is roughened, and a circuit is formed by copper plating. FIG. 1 (a) shows an example of a double-sided board, but this insulating substrate may be a multilayer board.

Next, the inner conductor circuit 2 on the surface of the insulating substrate 1 is roughened to improve the adhesion to the insulating resin layer 4 formed on the conductor circuit 2. Specifically, there are a method of forming a needle-like electroless plating on the inner conductor circuit 2, a method of oxidizing (blackening) and reducing the inner conductor circuit 2, a method of etching the inner conductor circuit 2, and the like. .

Next, as shown in FIG. 1B, an insulating resin with a copper foil 3 is laminated on the wiring board prepared in FIG. 1A. The insulating resin contains an epoxy resin or a polyimide resin as a main component. In addition, an acrylic resin, a polyimide resin, a benzocyclobutene resin, a fluorine resin, a cyanate ester resin, PPE
It may be a resin or the like or a content thereof. The thickness of the resin insulating layer is preferably from 10 to 100 μm, more preferably from 20 to 60 μm. Further, the thickness of the copper foil is preferably from 1 to 5 μm. The roughened surface of the copper foil may be subjected to a rust prevention treatment such as a chromate treatment for improving adhesion.

Next, as shown in FIG.
IVH5 is formed on the resin insulating layer 4 from above. IVH5
It is preferable to use a laser as a method of forming the. The laser that can be used here is C
There are gas lasers such as O ₂ and excimer and solid state lasers such as YAG. Since a large output can be easily obtained, a CO ₂ laser is suitable for processing an IVH having a diameter of 50 μm or more. φ5
In the case of processing a fine IVH of 0 μm or less, a YAG laser having a shorter wavelength and a good condensing property is suitable.

Next, the resin residue inside the IVH is removed using an oxidizing agent such as permanganate, chromate or chromate.

Next, plating catalyst nuclei are provided on the copper foil and inside the IVH. It is preferable to use a colloid of a noble metal or palladium for providing the plating catalyst nucleus. In particular, the use of palladium colloid is more inexpensive and more preferable.

Next, as shown in FIG. 1D, a thin electroless plating layer 6 is formed on the copper foil 3 provided with the plating catalyst nuclei and inside the IVH 5. This electroless plating includes formalin, copper sulfate, sodium hydroxide and ED
CUST2000 containing TA as a main component (trade name, manufactured by Hitachi Chemical Co., Ltd.) or CUS containing formalin, copper sulfate, sodium hydroxide and Rochelle salt as main components
Commercially available electroless copper plating such as T201 (trade name, manufactured by Hitachi Chemical Co., Ltd.) can be used. The thickness of the plating may be any thickness as long as the next electroplating can be performed, and is 0.3 to 1 μm.
About m is enough.

Next, as shown in FIG. 1E, a resist 7 is formed after performing electroless plating. The thickness of the resist is preferably equal to or greater than the thickness of the conductor to be subsequently plated. Examples of the resin usable for the resist include liquid resists such as PMER P-LA900PM (trade name, manufactured by Tokyo Ohka Co., Ltd.) and HW
-425 (Hitachi Chemical Industries, Ltd., trade name), RY-3
025 (Hitachi Chemical Industry Co., Ltd., trade name). No resist is formed on the via hole and on the portion that is to be a conductor circuit.

Next, as shown in FIG. 1 (f), a circuit pattern is formed by electroplating 8. For electroplating,
Copper sulfate electroplating and pyrophosphate electroplating, which are usually used for printed wiring boards, can be used. The plating thickness may be any thickness as long as it can be used as a circuit conductor. 1
１００100 μm, preferably 5-50 μm
More preferably, it is within the range.

Next, the resist is stripped using an alkaline stripping solution, sulfuric acid or a commercially available resist stripping solution.

Next, as shown in FIG. 1 (g), the copper other than the conductor pattern portion is removed using the etching solution according to the present invention, and the circuit formation is completed. Further, as shown in FIG. 1H, electroless nickel plating / gold plating 9 can be performed on the circuit.

[0027]

EXAMPLE 1 As shown in FIG. 1 (a), a glass cloth-based epoxy copper-clad laminate (Hitachi, Ltd.) having a thickness of 0.2 mm in which an 18 μm-thick copper foil was bonded to both sides of an insulating substrate. Using a product name: MCL-E-679 manufactured by Kasei Kogyo Co., Ltd.), the unnecessary portion of the copper foil is removed by etching, a through hole is formed, an inner conductor circuit 1 is formed, and an inner circuit board is produced. did.

The surface of the copper foil of the inner conductor circuit 1 of the inner circuit board was sprayed on the surface of the copper foil using MEC etch BODCZ-8100 (trade name, manufactured by MEC Corporation) at a liquid temperature of 35 ° C. and a spray pressure of 0.15 MPa. Spraying, roughening the copper surface to make irregularities with a roughness of about 3 μm,
Using MEC etch BOND CL-8300 (manufactured by MEC Corporation, trade name), liquid temperature 25 ° C., immersion time 2
The surface of the roughened copper foil was immersed in a condition of 0 second to perform a rustproofing treatment.

Next, as shown in FIG. 1B, an insulating adhesive with copper foil 3 (manufactured by Hitachi Chemical Co., Ltd., trade name: MCF-7000LX, copper foil is Mitsui Mining & Smelting Co., Ltd.) (Manufactured by Mitsui Microsyn Co., Ltd., thickness: 3 μm) was heated and pressed at 170 ° C. and 3 MPa for 60 minutes to form an insulation layer 4 having a thickness of 40 μm.

Next, as shown in FIG.
A non-through hole (IVH) 5 having a diameter of 80 μm was provided from above using a carbon dioxide impact laser drilling machine (trade name: L-500, manufactured by Sumitomo Heavy Industries, Ltd.), and 65 g / L of potassium permanganate. It was immersed in a mixed aqueous solution of 40 g / L of sodium hydroxide at a liquid temperature of 70 ° C. for 20 minutes to remove smear. Then, a palladium colloid solution (manufactured by Hitachi Chemical Co., Ltd., trade name: HS-202B) was added to the palladium colloid solution.
After immersion at 5 ° C. for 15 minutes to apply a plating catalyst, electroless copper plating was performed, and a thickness of 0.1 mm as shown in FIG.
An electroless copper plating layer 6 of 3 μm was formed. The electroless copper plating was performed under the conditions of a liquid temperature of 25 ° C. and 30 minutes using CUST-201 (trade name, manufactured by Hitachi Chemical Co., Ltd.).

Next, as shown in FIG. 1E, a resist is laminated on the surface of the electroless plating layer 6, and is exposed to ultraviolet rays through a photomask masking a portion to be subjected to electrolytic copper plating, developed and plated. A resist 7 was formed. The resist used was RY-3025 (trade name, manufactured by Hitachi Chemical Co., Ltd.) which is a dry film photoresist.

Next, as shown in FIG. 1 (f), electrolytic copper plating was performed using a copper sulfate bath under the conditions of a liquid temperature of 25 ° C. and a current density of 1.0 A / dm ² to obtain a 20 μm thick electrolytic copper plating. A copper plating layer 8 was formed. At this time, the ratio of circuit conductor width / circuit conductor interval (L / S) was 35/25 μm.

Next, as shown in FIG. 1 (g), the dry film was removed by dipping in a resist stripper. As the resist stripping solution, HTO manufactured by Nichigo Morton Co., Ltd. was used. Thereafter, using an etching solution having the composition shown in Example 1 of Table 1, copper other than the conductor pattern portion was removed by etching. When etching, put the substrate on one side
After cutting into small pieces of dm ^2, placed in a 1-liter beaker,
After heating to 40 ° C., etching was performed while stirring the etching solution with a magnetic stirrer.

Finally, as shown in FIG. 1 (h), an electroless nickel plating / electroless gold plating layer 9 was formed on the conductor circuit 8 to produce a printed wiring board. Table 2 shows the conditions of the electroless plating.

[0035]

[Table 1]

[0036]

[Table 2]

Examples 2 to 10 A printed wiring board was produced in the same manner as in Example 1 except that the etching solutions shown in Examples 2 to 10 in Table 1 were used.

Comparative Examples 1 to 3 Printed wiring boards were prepared in the same manner as in Example 1 except that the etching solutions shown in Comparative Examples 1 to 3 in Table 1 were used.

With respect to Examples 1 to 10 and Comparative Examples 1 to 3 thus produced, the residual etching between circuits of the printed wiring board, nickel plating / gold plating deposition between circuits, and wiring variation σ were evaluated. Table 3 shows the results together with the etching rate and the etching time of the etching solution.

As shown in FIG. 2, the etching residue between the circuits and the nickel plating / gold plating deposition between the circuits occur in such a manner that the bottom of the circuit is cut off. Therefore,
The difference between the interval (St) between the top surface of the circuit conductor and the interval (Sb) between the bottom surface is taken, and 1/2 of this difference is defined as the width of the hem, and the width of the hem is 5 μm.
In the case where the distance was not less than m, it was determined that the etching residue between the circuits and the nickel plating / gold plating deposition between the circuits were present. The wiring variation σ was arbitrarily measured at 20 points of the circuit conductor width (L) 35 μm on the upper surface. Here, the circuit conductor width (L) on the upper surface, the interval (St) between the upper surface of the circuit conductor and the interval (S
Regarding b), 20 points were arbitrarily selected, a photograph was taken from above the substrate using an optical microscope, and image processing was performed.

[0041]

[Table 3]

The printed wiring boards prepared in Examples 1 to 10 had no etching residue between circuits and no Au plating deposition, had little wiring variation, and had good circuit formability. on the other hand,
The printed wiring board produced in Comparative Example 1 had a sulfuric acid / sulfate molar ratio of less than 1, and the etching solution was poor in uniform etching properties, so wiring variation was large. The printed wiring boards prepared in Comparative Examples 2 and 3 are etching solutions containing no sulfate or copper sulfate according to the present invention, and the etching residue between circuits and Au plating are affected by the effect of chromate-treated chromium. Precipitation occurred.

[0043]

As described above, by using the etching solution according to the present invention, the influence of chromium used in the smear treatment can be removed, and as a result, short-circuit defects between conductor circuits are reduced, and circuit formability is reduced. A good printed wiring board can be manufactured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating one embodiment of a method for manufacturing a printed wiring board according to the present invention.

FIG. 2 is a cross-sectional view illustrating a circuit conductor width (L) and a circuit conductor interval (S).

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 insulating substrate 2 inner layer conductor circuit 3 insulating resin layer 4 copper foil 5 IVH 6 electroless copper plating layer 7 resist 8 electroplating layer 9 electroless nickel plating / gold plating layer

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor: Toyoki Ito 1500, Oji Ogawa, Shimodate City, Ibaraki Prefecture Inside Hitachi Chemical Co., Ltd. (72) Inventor Shoji Nakaso 1500 Ogawa, Shimodate, Ibaraki Pref.Hitachi Kasei Kogyo Co., Ltd.F-term (reference) 4K057 WA10 WB04 WE03 WE25 WG01 WN01 5E339 AC01 BC02 BE17 DD03 5E343 AA07 AA15 AA16 AA17 AA18 AA19 BB23 BB24 BB44 BB67 CC34 CC46 CC50 CC73 DD76 EE54 ER16 ER18 GG13 5E346 AA43 CC08 CC09 CC10 CC14 CC32 CC37 CC38 CC54 CC58 DD12 DD24 EE33 FF07 FF14 GG15 HH07

Claims (7)

[Claims] 1. A sulfate and / or hydrogen sulfate salt excluding copper sulfate, sulfuric acid, and hydrogen peroxide, wherein the molar ratio of sulfuric acid to sulfate and / or hydrogen sulfate salt other than copper sulfate is 1
A copper etching solution characterized by the above. 2. The copper etching solution according to claim 1, wherein the sulfate and / or hydrogen sulfate other than copper sulfate is a salt of sulfate ions and ions of a metal that is lower than hydrogen. 3. The sulfate other than the copper sulfate is a sulfate selected from the group consisting of alkali metal sulfates, alkaline earth metal sulfates, iron sulfate, and zinc sulfate.
Or a copper etching solution according to 2. 4. The copper etching solution according to claim 1, wherein the hydrogen sulfate except copper sulfate is an alkali metal hydrogen sulfate. 5. A step of laminating a resin with a copper foil on the upper and lower sides of an inner layer board on which an inner layer circuit is formed, and (2) providing an interstitial via hole (IVH) in the resin with a copper foil; A step of forming a plating layer on the copper foil and inside the IVH; (3) a step of forming a resist except for a circuit formation location on the plating layer; (4)
Forming a conductive circuit by electroplating at the circuit formation location, (5) stripping the formed resist, (6) sulfate and / or hydrogen sulfate except copper sulfate, and sulfuric acid. Using a copper etchant containing hydrogen oxide and having a molar ratio of sulfuric acid other than sulfuric acid and copper sulfate and / or hydrogensulfate of 1 or more, copper other than a portion to be a conductor circuit is etched away. And a process for producing a printed wiring board. 6. The method for manufacturing a printed wiring board according to claim 5, wherein the copper foil surface of the resin with copper foil adhered to the resin is subjected to a chromate treatment. 7. The method for manufacturing a printed wiring board according to claim 5, wherein the outermost surface of the conductive circuit is further subjected to electroless nickel plating / electroless gold plating.