JPH0828575B2 - Manufacturing method of printed wiring board - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method of manufacturing a printed wiring board provided with an electromagnetic wave shield layer. In particular, the present invention is characterized by performing electroless copper plating on a through hole surface and an insulating layer at the same time in a method for manufacturing a printed wiring board having a through hole, which is represented by a part additive process. The present invention relates to a method for manufacturing a printed wiring board provided with an electromagnetic wave shield layer by electrolytic copper plating. The present invention is aimed at clearing interference radio wave regulation values and analog signal protection for all electronic devices including devices including hybrid integrated circuits in which electronic components and optical components are mounted on an insulating substrate, and mixed digital / analog devices. Widely applicable.

BACKGROUND OF THE INVENTION With the recent remarkable spread of digital electronic devices such as personal computers and word processors, electromagnetic waves generated from electronic components and circuit elements used in these devices are sufficiently shielded or shielded. If not, malfunction occurs due to electromagnetic interference between digital devices, and electromagnetic interference occurs in various devices such as navigation devices, radios, televisions, and data communications. In order to prevent the occurrence of such electromagnetic interference, electromagnetic wave shield prevention measures are indispensable.

[Prior Art] As a countermeasure against such electromagnetic wave shielding treatment, there is a method of using a metal package, but a printed wiring board is generally coated with a silver paste or a copper paste after the printed wiring is manufactured.

The outline of this method is shown in FIG. Printed wiring board 1
Is completed by forming the necessary circuit portion with the conductive layer 3, including through-hole plating of the through-hole 2 by a known method. When an electromagnetic wave shield layer made of a conductor is directly formed on the component surface, a short circuit occurs, so that an undercoat layer made of an insulating material is first formed on the printed wiring board 1. This is formed, for example, by printing the first undercoat layer 4 and the second undercoat layer 5. The solder resist 6 is printed on the solder surface. After that, copper or silver paste P was applied onto the second undercoat layer 5, and the overcoat layer 9 was printed to obtain a product.

[Problems to be Solved by the Invention] However, when a silver paste or a copper paste is used, it causes a cost increase, and particularly when a silver paste is used, there is a risk of a short circuit due to migration over time.

As described above, with the recent rapid development of electrodevices, electromagnetic wave shield prevention measures have become an urgent issue. Moreover, it is unacceptable to impose a burden on the manufacturing process for forming the electromagnetic wave shield layer, because it increases the cost of the device.

By the way, as a recent printed wiring board, a type having a through hole is prevalent as shown in FIG. An electroless copper plating film is formed on the wall surface of the through hole by electroless plating for conduction between the component surface and the solder surface. However, implementation of this through-hole plating involves some problems. For example, according to the conventional method of the part-additive process, which consists of forming a through hole, forming a circuit pattern, and plating a through hole portion from a double-sided copper-clad laminate as a starting material, a through-hole is formed in a double-sided copper-clad laminate. Is formed and the catalyst is adhered to the entire surface of the copper-clad laminate and the inner wall of the through hole by immersing it in the catalyst solution, and then the etching resist is applied to the circuit part, at which time the etching solution also penetrates the through hole. Covered to prevent. After that, etching is performed to remove unnecessary portions of the copper foil. After removing the etching resist, through-hole electroless plating was performed after applying a plating-resistant solder resist on portions other than the through-hole portions. However, in this method, after the catalyst is first applied, the plating is carried out after passing through many steps, so that the catalyst is likely to lose its effectiveness and the problem of deposition failure of electroless copper plating is recognized. became. In particular, special consideration was required to prevent the etching solution from entering the through holes. In addition, even in the conventional method of the full additive process in which the conductor circuit portion is formed on the inner wall of the through hole and the circuit portion by electroless copper plating using the adhesive coated substrate as the starting material, the adhesive coated surface and the through hole are formed after the through hole is formed. A catalyst was applied to the inner wall, the non-circuit portion was masked with a resist, and then the conductor circuit portion was formed by electroless copper plating. However, since the masking is performed with the resist after the catalyst is applied, there is a problem that the catalyst existing between the substrate and the resist lowers the resistance between the wirings. As described above, regarding the circuit formation itself on the substrate, there are problems associated with the through-hole electroless plating, and the solution thereof is also demanded.

Therefore, an object of the present invention is to develop a method for manufacturing a printed wiring board with a through hole, which is provided with an electromagnetic wave shield layer at a low cost in a simple process.

[Means for Solving the Problems] In order to solve the above problems, the inventors of the present invention have conducted diligent research, and have concluded that it is optimal to form the electromagnetic wave shield layer by electroless copper plating. . Electroless copper plating does not have the risk of a short circuit with time and has good conductivity. In addition, it is very convenient to solve the conventional problems associated with through-hole electroless plating by performing through-hole plating separately from the circuit formation process and simultaneously forming the electromagnetic wave shield layer. You can do it. Thus
In the process of manufacturing a printed wiring board having through holes, we have succeeded in devising an epoch-making method in which through hole plating and electromagnetic wave shield layer formation are simultaneously performed by electroless copper plating.

[Summary of the Invention] That is, according to the present invention, in a method for manufacturing a printed wiring board having a through hole and having an electromagnetic wave shield layer, a conductive layer having a predetermined pattern is previously formed on a substrate, and the conductive layer of the substrate is provided. By forming an insulating layer in a region to be shielded of the surface, and performing electroless copper plating on the insulating layer at the same time as plating the through holes formed on the substrate, by electroless copper plating Provided is a method for manufacturing a printed wiring board provided with an electromagnetic wave shield layer.

Preferred embodiments include the following: (a) The insulating layer comprises a first undercoat layer and a second undercoat layer containing a roughening substance.

(B) An insulating layer is provided on one surface of the substrate, and a predetermined portion on the other surface is covered with a solder resist.

(C) Prior to the electroless copper plating, a portion not requiring copper plating is coated with a roughening-resistant resist in advance.

(D) After coating the anti-roughening liquid resist, a roughening treatment is performed, then a catalyst is applied, the anti-roughening liquid resist is peeled off, and then electroless copper plating is performed.

(E) An overcoat layer is further provided on the electromagnetic wave shield layer.

[Detailed Description of the Invention] Next, in order to facilitate understanding of the present invention, a specific and detailed description will be given with reference to FIGS. The same elements as those in FIG. 6 are given the same numbers.

First, by a known method, for example, a printed wiring board 1 which is a double-sided copper-clad laminate obtained by laminating copper foils on both sides of an insulating base material.
A through hole 2 is formed by drilling, punching, or the like, and a conductive layer 3 having a predetermined circuit pattern is formed by etching the resist pattern on the printed wiring board 1 with an etching resist and peeling the resist. 11
Is the ground.

At this stage, the electroless copper plating is not applied to the through holes. This makes it possible to form the conductive layer 3 of the circuit pattern completely separately from the through hole plating, simplifying the process and making the entire process efficient.

Next, an undercoat layer is formed as an insulating layer on at least a portion of the component surface where the electromagnetic wave shield is to be applied. The role of the undercoat layer is to prevent a short circuit of the conductive layer when forming the electromagnetic wave shield layer. This may preferably be done by printing and curing the first undercoat layer 4 in the X direction and then the second undercoat layer 5 in the Y direction.

On the other hand, the solder resist layer 6 is printed and cured on the solder surface.

At this time, since a part of the conductive layer 3 is grounded as necessary, the first and second undercoat layers can be omitted as shown by the ground 11.

As the adhesive for applying the first undercoat layer 4 and the solder resist layer 6, a known resist ink having plating solution resistance and good insulating property, such as NKI-100 manufactured by Nippon Mining Co., Ltd. You can use it. The compositions of the first undercoat layer 4 and the solder resist layer 6 may be the same or different, and may be appropriately selected depending on the use and purpose.

On the other hand, the adhesive for applying the second undercoat layer 5 is provided with an electromagnetic wave shield layer formed by electroless copper plating on the subsequent step and thereafter, and therefore, a concentrated sulfuric acid or alkaline permanganate solution or a chromic acid aqueous solution is prepared for it. It is necessary to roughen with a roughening solution such as. Therefore, the above-mentioned resist ink or the like is a substance that is easily roughened by the roughening liquid (roughening substance) such as CaCO ₃ , BaSO ₄ , BaCO ₃ , MgCO ₃ , MnO ₃ , TiO ₂ , ZnO, Zn.
_{(OH) 2, Al 2 O} 3, SiO 2, one or more selection on roughening solution from among such MgO, 1 to 8% relative to the adhesive by weight, should preferably added 3-5% This is preferable from the viewpoint of ensuring the adhesion of the shield layer and the like.

If the roughening liquid is contained in the first layer, the undercoat layer of the first layer may be eroded by the roughening liquid, which may cause a short circuit with the lower conductive layer. Is contained, it also affects the electrical characteristics of the circuit, which is not preferable. Therefore, the roughening substance is not contained in the first layer.

Curing is provided, for example, by air oven or far infrared curing.

Next, the roughening resist 7 is applied to the copper plating unnecessary portion of the printed wiring board on which the first and second undercoat layers are formed.
Print.

As the roughening-resistant resist 7, a known acid-resistant alkaline peeling (alkali-soluble) or acid-resistant solvent peeling (organic solvent-soluble) resist ink that is resistant to a roughening liquid and has good peeling property is used. To use. It is also necessary that this resist ink is stable to the catalyst and does not deteriorate the catalytic ability.

Next, the printed wiring board is roughened with a roughening solution such as concentrated sulfuric acid, an alkali permanganate solution, and a chromic acid aqueous solution as described above.

After that, the catalyst 8 is applied using a catalyst solution represented by an aqueous solution containing stannous chloride, palladium chloride and hydrochloric acid, and then the roughening resist 7 is stripped with an alkali or a solvent. The catalyst on the resist 7 is also removed.

Then, using a known electroless copper plating solution, the copper film 9 is simultaneously formed on the inner wall of the through hole and the second undercoat layer.
To form. The thickness of this copper film 9 is usually 10 to 50 μm.
A degree is enough. As the plating solution, it is preferable to use a high-speed thick electroless copper plating solution. Examples of plating solution composition are as follows: Cu ²⁺ 0.005 to 0.1 mol / l EDTA 0.01 to 0.2 mol / l NaOH pH adjusted to 11.0 to 13.5 Additives, surfactants Trace HCHO 0.006 to 0.06 mol / l For example, KC-100 manufactured by Nippon Mining Co., Ltd. is a suitable example.

Thus, the point of the present invention is that the plating of the through hole and the copper film as the electromagnetic wave shield layer are simultaneously formed on the second undercoat layer by electroless plating. As a result, the process of providing through-hole plating by electroless copper plating and the electromagnetic wave shield layer on the printed wiring board can be easily performed at one time without the conventional problems associated with through-hole electroless plating. The process can be greatly simplified.

Finally, if necessary, the overcoat layer 10 is applied to the laminate.
By printing, the printed wiring board provided with the electromagnetic wave shield layer is completed. As this overcoat layer 9, a known solder resist, for example, UVR-150G manufactured by Taiyo Ink Mfg. Co., Ltd. may be used.

As a method for manufacturing a printed wiring board provided with such an electromagnetic wave shield layer, the intended purpose can be achieved without changing the order of the steps described above and by changing the order of some steps. Can be done. The modified examples ~ are shown in the flow sheets of Figs. 3 to 5: As shown in Fig. 3, the formation of the through holes is not performed first but after the roughening resist is printed on the copper plating unnecessary portion and before the roughening treatment. To do. This minimizes the through-hole contamination by the process liquid because the through-hole is formed immediately before copper plating.

As shown in FIG. 4, the printed wiring board is roughened in the flow of FIG. 2 before the roughening resist is printed on the copper plating unnecessary portion.

As shown in FIG. 5, in the flow of FIG. 3, through hole drilling and roughening of the printed wiring board are performed before printing the roughening resistant resist on the copper plating unnecessary portion.

In addition, in FIG. 1, (c) after forming the second undercoat layer or (d) after further coating with a solder resist, these are cured, and then surface roughening by a roughening solution and catalyst application are performed. After that, it is also possible to coat a portion not subjected to copper plating with a resist resisting a plating solution, and then perform electroless copper plating to form a copper plating coating layer on a plating required portion, that is, a through hole portion and an electromagnetic wave shield portion.

 Next, examples will be described.

Example 1 A commercially available copper clad laminate (Cu thickness: 35 μm) was used as a substrate, and after forming a predetermined printed circuit by a known method,
First, the first undercoat layer (thickness: 10-5
0 μm) was printed. As the undercoat ink, resist ink NKI-100 (trade name) manufactured by Nippon Mining Co., Ltd. was used.

When printing the undercoat layer of the second layer, as a substance that is easily roughened in the next step to the ink, CaCO ₃ , Al ₂ O ₃ ,
4 kinds of SiO ₂ and MgCO ₃ are selected, and they are weighed in an equal amount so as to be 4% of the ink weight, mixed and crushed, and then added to the ink to prepare a second undercoat layer. Printed. (Thickness: about 10 to 50 μm) Further, the same resist ink as described above was printed on the solder resist layer on the solder surface. To: (a thickness 10~50μm about) electroless copper plating unnecessary portion was coated with a commercially available resist ink acid resistant alkali peeling type, H ₂ SO ₄ -CrO ₃
The system was roughened using a roughening solution, and then a catalyst was applied by a known method. Then, the commercially available resist is peeled off, and plating is performed using an electroless copper plating solution KC-10 (trade name) manufactured by Nippon Mining Co., Ltd., and 10 to 50 μm on the inner wall of the through hole and the second undercoat layer. Of copper was produced.

[Example 2] was performed under the same conditions as described above.

The substrate was roughened as it was, and then a catalyst was applied.
Next, after printing using the plating resistant resist OBZ-4000 (trade name) manufactured by Tokyo Ohka Co., Ltd. on the part where copper plating is not required, electroless copper plating solution KC-10 (manufactured by Nippon Mining Co., Ltd.) (Trade name) was used for plating to simultaneously form a 30 μm copper film on the inner wall of the through hole and the second undercoat layer.

Regarding Examples 1 and 2 described above, a print in which an electromagnetic wave shield layer is provided by further printing an overcoat layer (thickness: 10 to 50 μm) using UVR-150G (trade name) manufactured by Taiyo Ink Mfg. Co., Ltd. The wiring board was obtained.

At this time, the resistivity of the electromagnetic wave shield layer is 1.78 to 1.
It was 82 × 10 ⁻⁶ Ω · cm, and it was found that a material having an electromagnetic wave shielding effect much higher than that when silver paste was applied was obtained.

[Effects of the Invention] As described above, according to the present invention, the formation of an electromagnetic wave shielding layer made of electroless copper plating having an electromagnetic wave shielding effect far higher than that when a silver paste is applied in the manufacturing process of a printed wiring board. It becomes possible to simultaneously perform through-hole plating, and it is possible to manufacture a printed wiring board provided with an electromagnetic wave shield layer at a low cost and with high reliability by a simple process. The conventionally recognized problems such as deactivation of the catalyst do not occur with through-hole plating.

[Brief description of drawings]

1 and 2 show a flow sheet showing an outline of a process sequence of the method of the present invention, FIGS. 3, 4 and 5 show a modified flow sheet thereof, and FIG. 6 shows a prior art flow sheet. 1: Printed wiring board 2: Through hole 3: Conductive layer 4: First layer undercoat layer 5: Second layer undercoat layer 6: Solder resist layer 7: Roughening resist 8: Catalyst 9: Copper film 10: Over Coat layer P: Copper or silver paste 11: Ground

Claims (6)

[Claims] 1. A method of manufacturing a printed wiring board having a through hole and having an electromagnetic wave shielding layer, wherein a conductive layer having a predetermined pattern is previously formed on a substrate, and the surface of the substrate on which the conductive layer is provided is shielded. An insulating layer is formed in a region to be formed, and an electromagnetic shield layer is formed by electroless copper plating, which is characterized by performing electroless copper plating on the insulating layer at the same time as plating the through holes formed in the substrate. Manufacturing method of printed wiring board. 2. The printed wiring board according to claim 1, wherein the insulating layer comprises a first undercoat layer and a second undercoat layer containing a roughening substance. Method. 3. The method of manufacturing a printed wiring board according to claim 1, wherein an insulating layer is provided on one surface of the substrate and a solder resist is coated on a predetermined portion of the other surface. 4. The printed wiring according to any one of claims 1 to 3, characterized in that prior to the electroless copper plating, a portion not requiring copper plating is previously coated with a roughening-resistant resist. Method of manufacturing a plate. 5. A method comprising the steps of: after coating the roughening-resistant resist, performing a roughening treatment, then applying a catalyst, peeling off the roughening-resistant liquid resist, and then performing electroless copper plating. 5. The method for manufacturing a printed wiring board according to claim 4. 6. The method for manufacturing a printed wiring board according to claim 1, further comprising an overcoat layer provided on the electromagnetic wave shield layer.