JP2007067341A - Method of manufacturing circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a circuit board with which double-sided conductive metal layers are surely conducted in a double-sided circuit board and further, a cross-sectional shape of circuit wiring is not made worse. <P>SOLUTION: In a method of manufacturing a circuit board including a conduction structure formed from a through-hole or a bottomed via-hole, a conductive material 4 is given by forming a conduction hole 3 on a double-sided metal-clad laminate including conductive metal layers 2 on both sides of an insulating base 1, a plating resist film 9 is formed excepting for said conduction hole 3 and a land 5 thereof, the plating resist film 9 is released and removed after conducting the conductive metal layers 2 and forming a circuit wiring pattern 10 by plating, and the circuit wiring pattern 10 is formed by removing the exposed conductive metal layers 2 and electrically separating the circuit wiring pattern 10. The step of forming a plating layer for conduction between the double-coated conductive layers and the step of forming a plating layer for circuit wiring formation are performed separately from each other. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a circuit board, and more particularly, to a method for manufacturing a double-sided circuit board in which high-density circuit wiring is formed by plating.

  In the etching method widely used for forming circuit wiring, since the cross-sectional shape of the wiring becomes a trapezoid, there is a limit to increasing the density. Therefore, conventionally, a wiring forming method by plating suitable for forming a higher density circuit has been used.

  The method for manufacturing the double-sided circuit board is shown in FIGS. 4 (1) to 5 (7). That is, first, as shown in FIG. 4 (1), a double-sided metal-clad laminate having conductive metal layers 22 on both sides of the insulating base material 21 is prepared, and then, as shown in FIG. 4 (2), Conductive holes 23 are formed by through-holes or bottomed via holes in the double-sided metal-clad laminate.

  Next, as shown in FIG. 4 (3), a conductive material 24 is applied to the double-sided metal-clad laminate in which the conduction holes 23 are formed, and then, as shown in FIG. A plating resist film 25 is formed on the conductive metal layers 22 on both sides to which the substance 24 is applied.

  Thereafter, as shown in FIG. 5 (5), the double-sided metal-clad laminate having the plating resist film 25 is electrically connected between the conductive metal layers 22 on both sides by a plating technique, and the circuit wiring is formed. 26 is obtained.

Next, as shown in FIG. 5 (6), the plating resist film 25 is peeled and removed to expose the conductive metal layer. Next, as shown in FIG. 5 (7), by removing the exposed conductive metal layers 22 on both sides and electrically separating the circuit wiring pattern 26 (forming a circuit wiring pattern), double-sided circuit wiring. Manufactures substrates.
JP-A-11-186716 JP 2003-158364 A

  On the other hand, a conductive material is sometimes applied to a double-sided metal-clad laminate having a plating resist film by a plating method in order to establish conduction between the conductive metal layers on both sides. At this time, since the conductive substance remains on the metal layers on both sides, the adhesion strength between the conductive metal layer and the circuit wiring due to plating in the high-density circuit is reduced or peeled off.

  In order to solve these problems, there is a method of performing an etching process for removing the conductive material on the conductive metals on both sides after the conductive material is applied. In this case, even the conductive material on the inner wall of the hole for conduction that should not be removed may be removed, and strict management of the etching amount is required.

  On the other hand, there is a method of applying a conductive substance containing carbon as a component by a method of applying a conductive substance containing carbon as a general component. However, this method is more reliable than the conductive material by direct plating using tin-palladium colloid, in the case of small-diameter through-holes or bottomed via-holes, the reliability of the plating process for conducting between the metal layers on both sides. There is a disadvantage that the property is low.

  Further, as shown in FIG. 6, the arrangement of the conductive holes 23 between the circuit wiring patterns 26 remaining on the conductive metals on both surfaces and the conductive metal layers 22 on both surfaces allows the conductive metal layers 22 on both surfaces to be connected to each other. When the plating thickness on the inner wall of the conductive hole 23 greatly changes, both the inner wall plating thickness of the conductive hole between the conductive metal layers on both sides and the standard of the conductor thickness of the circuit wiring required for component mounting are satisfied. Can be difficult. In that case, a method of providing a resist opening in an unnecessary area on the circuit wiring and avoiding concentration of lines of electric force (commonly called dummy plating) is used.

  However, this construction method is not applicable to the case where the degree of design freedom of component placement is limited, and furthermore, an opening must be provided due to the nature of the mounted component. Although it is generally known to reduce the current density during plating in order to avoid the concentration of electric field lines, on the other hand, the extension of the plating process time by reducing the current density reduces the productivity. .

  Further, when the plating thickness on the inner wall of the conductive hole 23 between the conductive metal layers 22 on both sides is thin, the plating reliability on the inner wall of the conductive hole 23 is not reduced after the plating resist film is removed. When the thickness of the circuit wiring pattern 26 is thinner than that removed by the electrical separation etching, there is a concern that the conduction failure 27 as shown in FIG. 7 may occur, and therefore, on the inner wall of the conduction hole 23 in each region. The burden of having to fully check the plating thickness is large.

  On the other hand, the thickness of the conductive metal layer 22 must be sufficiently larger than the etching amount in order to prevent the insulating base material 21 from being exposed in the etching process in the process of applying a conductive material as shown in FIG. I must. However, as a result, there is a problem that the cross-sectional shape of the circuit wiring deteriorates.

  The present invention has been made in consideration of the above-described points, and provides a method for manufacturing a circuit board that reliably establishes conduction between double-sided conductive metal layers in a double-sided circuit board and does not deteriorate the cross-sectional shape of circuit wiring. For the purpose.

In order to solve the above problems, in the present invention,
A conductive hole is formed on a double-sided metal-clad laminate having a conductive metal layer on both sides of an insulating base material to provide a conductive material, and a plating resist film is formed except for the conductive hole and its land portion. After conducting conduction between the conductive metal layers and forming a circuit wiring pattern by a plating technique, the plating resist film is peeled and removed, and the exposed conductive metal layer is removed to electrically separate the circuit wiring pattern. In the method of manufacturing a circuit board having a conduction structure with a through-hole or a bottomed via hole, the circuit wiring pattern is formed by:
After applying a conductive substance to the laminate, a double-sided conductive resist film is formed on both sides of the conductive metal layer to which the conductive substance has been applied, except for the conductive hole and its land part,
Plating using the resist film for double-sided conduction and conducting between the conductive metal layers,
Stripping and removing the resist film for double-sided conduction,
The conductive metal layer including the conduction hole and the land portion thereof is thinned by etching,
A resist film for circuit wiring is formed on the conductive metal layer except for a circuit wiring pattern forming portion and a conduction hole and its land portion,
After plating using a circuit wiring resist film to form a circuit wiring pattern, the circuit wiring resist film is peeled off to expose the conductive metal layer,
Forming a circuit wiring pattern by removing the conductive metal layer and electrically separating the circuit wiring pattern;
A method of manufacturing a circuit board,
I will provide a.

  According to the present invention, when removing the conductive material on the conductive metal layers on both sides that are not required when forming the circuit wiring pattern, the conduction between the conductive metal layers is protected by the plating layer, There is no conduction failure between the conductive metal layers on both sides, and strict management of the etching amount is not required, so that productivity is good.

  In addition, since the plating for conduction between the conductive metal layers on both sides and the plating for forming the circuit wiring pattern are performed twice separately, both sides of the circuit wiring pattern required for component mounting are formed. It is not necessary to consider the thickness of the conductive metal layer, and it is possible to prevent a decrease in current density during plating for ensuring the thickness and a decrease in productivity due to this.

  Since plating is performed twice, it is possible to obtain a plating thickness that satisfies the conduction reliability, and after the plating resist film is removed, the occurrence of poor conduction due to etching for separating the circuit wiring pattern. Is resolved. In addition, since the plating thickness is sufficiently secured, the burden of checking the plating thickness is eliminated.

  Furthermore, since the conductive metal layers on both sides are thinned before the circuit wiring pattern is formed by plating, it is possible to prevent the cross-sectional shape of the circuit wiring from being deteriorated.

  Embodiment 1 of the present invention will be described below with reference to FIGS.

Embodiment 1

  FIG. 1 shows each step in Embodiment 1 of the present invention.

  First, as shown in FIG. 1 (1), a double-sided metal-clad laminate in which a copper foil having a thickness of 4 μm is provided as a conductive metal layer 2 on both sides of an insulating base material 1 such as a polyimide film is prepared. Next, as shown in FIG. 1 (2), this double-sided metal-clad laminate is irradiated with a UV-YAG laser to form conduction holes 3 as through-holes.

  Next, as shown in FIG. 1 (3), the conductive material 4 is applied to the double-sided metal-clad laminate having the conduction holes 3 formed by conductron treatment or the like. Subsequently, as shown in FIG. 1 (4), a photosensitive dry film resist (not shown) is laminated on the conductive metal layers 2 to which the conductive material 4 is applied, and pattern exposure and development are performed. Process. Thereby, the resist film 6 for both-side conduction is formed except for the conduction hole 3 and its land portion 5.

  Next, as shown in FIG. 2 (5), conductive plating 7 between the conductive metal layers 2 on both sides is formed on the double-sided metal-clad laminate having the double-sided conductive resist film 6 by copper sulfate plating. To do. In the present invention, a conductive treatment of direct plating using a tin-palladium colloid can be used for imparting the conductive substance.

  Next, as shown in FIG. 2 (6), the double-sided conductive resist film 6 is peeled and removed. Subsequently, as shown in FIG. 2 (7), after removing the double-sided conductive resist film 6, the conductive metal layer 2 on both sides including the conductive hole 3 and its land portion 5 is mixed with a sodium persulfate-based mixture. Etching treatment of 3 μm is performed with the liquid, and the thickness is reduced to 1 μm.

  Here, as the etching after the removal of the resist film for double-sided conduction, unnecessary conductive materials on the conductive metal layers on both sides excluding the conduction hole and its land part can be removed, and after the etching, an insulating base material is obtained. It is preferable that the conductive metal layers on both sides have a thickness of 0.5 μm or more and 2.5 μm or less. The thickness of the inner wall plating of the conduction hole for conduction between the conductive metal layers on both sides is preferably at least twice the etching amount after the removal of the resist film 6 for both-side conduction.

  Thereafter, as shown in FIG. 2 (8), a photosensitive dry film resist (not shown) is laminated on the thinned conductive metal layer 2 on both sides, and pattern exposure and development are performed. Then, a circuit wiring resist film 9 is formed except for the circuit wiring pattern forming portion 8 and the conduction hole 3 and its land portion 5.

  Next, as shown in FIG. 3 (9), a circuit wiring pattern 10 is formed by a copper sulfate plating method. Next, as shown in FIG. 3 (10), the circuit wiring resist film 9 is peeled and removed to expose the conductive metal layer 2.

  Finally, as shown in FIG. 3 (11), the exposed conductive metal layers 2 on both sides are removed by etching to electrically isolate the circuit wiring pattern 10 to form a substrate having the circuit wiring pattern. .

  This will be described more specifically with reference to the first embodiment.

  First, “Espanex” (thickness 25 μm) manufactured by Nippon Steel Chemical Co., Ltd. as a double-sided non-adhesive copper-clad laminate with copper foil on both sides of the polyimide film is prepared, and the thickness of the conductive metal layers on both sides is Half-etching is performed so that the thickness becomes 4 μm.

  Next, a through hole with an opening diameter of 50 μm was formed by a UV-YAG laser. Next, a conductive substance is applied by conductron treatment.

  Subsequently, a photosensitive dry film having a thickness of 20 μm is laminated, and pattern exposure and development are performed to form a double-sided conductive resist film excluding the conductive holes and the land portions thereof. Then, plating with a thickness of 8 μm or more and 12 μm or less is obtained as conduction between the conductive metal layers on both sides by copper sulfate plating treatment.

  Next, the resist film for double-sided conductive plating is peeled and removed with caustic soda. Next, the conductive metal layers on both sides including the conduction hole and the land portion thereof are thinned to a thickness of 1 μm by an etching process of 3 μm with a sodium persulfate mixed solution. By this treatment, the conductive material is removed.

  Subsequently, by laminating a photosensitive dry film type resist and performing pattern exposure and development processing, a circuit wiring resist film is formed except for the circuit wiring pattern forming portion, the conduction hole and the land portion thereof.

  Thereafter, a circuit wiring pattern having a conductor thickness of 9 μm or more and 10 μm or less is obtained by a copper sulfate plating method. By this treatment, the conductive plating thickness of the conductive metal layers on both sides can be set to 15 μm or more and 20 μm or less. Next, the circuit wiring resist film is peeled and removed with caustic soda to expose the conductive metal layer.

  Finally, the exposed conductive metal layers on both sides are removed by etching with a mixed solution of sodium persulfate to electrically separate the circuit wiring patterns to obtain a circuit wiring board having a high-density circuit wiring pattern. .

Process sectional drawing which shows one Embodiment of this invention. Process sectional drawing following FIG. Process sectional drawing following FIG. Sectional drawing which shows the conventional manufacturing method. Process sectional drawing following FIG. Sectional drawing of the circuit board by the conventional manufacturing method. Sectional drawing of the circuit board by the conventional manufacturing method. Sectional drawing of the circuit board by the conventional manufacturing method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulation base material 2 Conductive metal layer 3 Conductive hole 4 Conductive substance 5 Conductive hole land part 6 Double-sided conductive resist film 7 Conductive plating 8 Circuit wiring pattern forming part 9 Circuit wiring resist film 10 Circuit wiring pattern 21 Insulating base material 22 Conductive metal layer 23 Conductive hole 24 Conductive substance 25 Plating resist film 26 Circuit wiring pattern 27 Conduction failure due to etching

Claims (4)

A conductive hole is formed on a double-sided metal-clad laminate having a conductive metal layer on both sides of an insulating base material to provide a conductive material, and a plating resist film is formed except for the conductive hole and its land portion. After conducting conduction between the conductive metal layers and forming a circuit wiring pattern by a plating technique, the plating resist film is peeled and removed, and the exposed conductive metal layer is removed to electrically separate the circuit wiring pattern. In the method of manufacturing a circuit board having a conduction structure with a through-hole or a bottomed via hole, the circuit wiring pattern is formed by:
After applying a conductive substance to the laminate, a double-sided conductive resist film is formed on both sides of the conductive metal layer to which the conductive substance has been applied, except for the conductive hole and its land part,
Applying plating using the resist film for double-sided conduction to take conduction between the conductive metal layers,
Stripping and removing the resist film for double-sided conduction,
The conductive metal layer including the conduction hole and the land portion thereof is thinned by etching,
A resist film for circuit wiring is formed on the conductive metal layer except for a circuit wiring pattern forming portion and a conduction hole and its land portion,
After plating using a circuit wiring resist film to form a circuit wiring pattern, the circuit wiring resist film is peeled off to expose the conductive metal layer,
Forming a circuit wiring pattern by removing the conductive metal layer and electrically separating the circuit wiring pattern;
A method of manufacturing a circuit board. In the manufacturing method of the circuit board of Claim 1,
Etching after removing the resist film for double-sided conduction can remove unnecessary conductive material on the conductive metal layers on both sides except for the conduction hole and its land, and after etching, the conductive metal on both sides of the insulating base material A method for producing a circuit board, characterized in that the layer has a thickness of 0.5 μm or more and 2.5 μm or less. In the manufacturing method of the circuit board of Claim 1,
The thickness of the inner wall plating of the conductive hole for conductive metal interlayer conduction on both sides by the plating method on the double-sided metal-clad laminate is at least twice the etching amount according to claim 2. Production method. In the manufacturing method of the circuit board of Claim 1,
A conductive material layer formed by applying a conductive material to a double-sided metal-clad laminate in which a hole for conduction is formed is a direct plating using a tin-palladium colloid. Production method.

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