JP2006134927A - Method of forming level difference circuit and its wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a request is toned up which needs a printed circuit board having three dimensional level difference circuit into a loading area in which component elements of the printed circuit board is carried. <P>SOLUTION: A plurality of stages of thickness conductors (level difference circuit) with different thicknesses formed of "a partial solder of different species metals other than a panel copper plating and copper" are superposed partially to the flat identical substrate side in a small area in which the component elements of a wiring board is carried, and a method are provided for forming three-dimensional level difference circuit used as stepped and its wiring board. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a step circuit forming method and a wiring for forming a conductive circuit by panel copper plating and pattern plating for partially plating on the same flat substrate surface when forming a step circuit on a printed wiring board. More particularly, the present invention relates to a printed wiring board for forming a circuit having an operation function and a contact function at a predetermined position of a printed wiring board having a three-dimensional solid circuit, and a stepped circuit forming method thereof.

Conventionally, when a step circuit is formed on a printed wiring board, a flat conductive circuit is formed by setting the thickness of the circuit conductor on the same flat base material surface to be substantially uniform and changing the conductor width. Is.
In the multilayer printed wiring board, the thickness of the circuit conductor in each layer may be changed, but the thickness of the circuit conductor in the same layer is not changed to a three-dimensional solid circuit. For example, there has been no demand for a printed wiring board for forming a stepped circuit in a contact area or an operation area by intentionally changing the thickness of circuit conductors having the same configuration on the same base surface or in the same layer by 5 μm or more.

As a circuit forming method for forming a three-dimensional step circuit, there is a method of forming a step circuit on the surface of a synthetic resin molded product.
As an example, there is a circuit forming method for a synthetic resin molded product disclosed in Japanese Patent Laid-Open No. 8-148809.
In this method, the outer surface of the synthetic resin molded article has a three-dimensional surface shape, and the outer surface of the three-dimensionally molded synthetic resin molded article is subjected to metal coating to form a circuit conductor. The thickness of the circuit conductor on the outer surface of the synthetic resin molded product is such that a conductor is formed on the surface of the synthetic resin molded product in a planar (two-dimensional) manner to form a conductive circuit.
The synthetic resin molded product forming the three-dimensional circuit conductor of the synthetic resin molded product is difficult to be thinned, double-sided, large-sized, and side terminals.
JP-A-8-148809.

The parts having various functions to be mounted on the printed wiring board are diversified, and the demand for a printed wiring board having stepped circuits having different three-dimensional conductor thicknesses has increased.
In order to form stepped circuits having different conductor thicknesses, the same number of copper platings and etchings as the number of stepped circuits are required.

By the way, in order to form a printed wiring board having a step circuit with different three-dimensional conductor thickness by a conventional printed wiring board manufacturing method that is not a special apparatus or a special system, a photosensitive dry film for circuit formation is used, There is a method of repeating the formation of circuits by copper plating and etching step by step from the lower conductor thickness, and stacking and forming three-dimensional step circuits, but the same number of copper plating and etching as the number of step circuits is required, Since there was no photosensitive dry film that could withstand this copper plating and etching (plating mask and etching mask), it was difficult to ensure quality reliability.
In addition, since circuit formation by copper plating and etching is repeatedly performed, the deviation of each step circuit, deformation, poor positional accuracy, conductor thickness variation, and work efficiency are poor.
Further, when plating such as nickel, gold, silver, and rhodium is performed on the copper plating, poor adhesion between the copper plating of each step circuit and the above-described dissimilar metal plating occurs.

In order to solve the above-mentioned problems, the inventions of claim 1 and claim 2 differ in that the printed wiring board on which the component is mounted is made of (different metal plating other than copper + copper) on the same flat and horizontal substrate surface. A printed wiring board is provided in which thick conductors are provided in a plurality of steps.
That is, it is a printed wiring board formed by connecting at least two steps of different thickness conductors made of different metal plating other than copper + copper.
The different thickness conductors that are connected and formed stepwise may be electrically connected or may be an independent circuit depending on the desired purpose.

  According to the first aspect of the present invention, there is provided a plurality of stages in which a single-layer thickness conductor made of at least two kinds of metals is repeatedly stacked on the same flat and horizontal base material surface of a printed wiring board. The wiring board is formed with a thick conductor.

  A second aspect of the present invention is that in the first aspect of the present invention, a plurality of thick conductors are formed by repeatedly stacking at least one stage thick conductor made of at least two kinds of metals (copper + dissimilar metal plating other than copper) higher than the preceding stage. The wiring board is formed so as to be partially overlapped on the thick conductor in the previous stage and connected in a staircase pattern higher than the previous stage.

  In the invention of claim 3, when the step circuit is formed on the printed wiring board, the first stage made of two kinds of metals on the same flat base material surface (panel copper plating + partial pattern plating with different metal other than copper). A step of forming a thick conductor of the first layer, a step of forming a second step of thick conductor consisting of covering the first stage thick conductor (panel copper plating + partial pattern plating with a different metal other than copper), and the second A step of forming a third-stage thick conductor comprising covering the step-thick conductor (panel copper plating + partial pattern plating with a different metal other than copper), and partial pattern plating of a predetermined shape of the different metal other than copper. It is a circuit formation method for forming at least a plurality of stages of thick conductors made of (copper + different kinds of metal plating other than copper) by an etching step as an etching mask.

  In addition, in partial pattern plating for forming a desired thickness conductor, a circuit in which pattern plating formed partially of a different metal other than copper including any one of nickel, gold, silver, and rhodium is used as an etching mask It is also a forming method. In other words, the dissimilar metal other than copper is required to be a dissimilar metal film having performance suitable for the action of the etchant and the contact function, operation function selection, operation state selection, component mounting, and the like.

Further, according to the present invention, a plurality of thick conductors obtained by repeatedly stacking and stacking one stage of thick conductors made of at least two different metals (copper + dissimilar metal plating) are independent of each other. Or may be partially overlapping and touching.
Further, in this circuit formation, the dissimilar metal plating can be, for example, two kinds of dissimilar metal plating as (nickel + gold).

  For example, when forming a step circuit on a printed wiring board, a step of forming a first thickness conductor by pattern plating of a predetermined shape with a different metal other than panel copper plating + copper on the same flat and horizontal base material surface; Panel copper plating connected to the first thickness conductor + a step of forming a second thickness conductor by pattern plating of a predetermined shape using a different metal other than copper, and panel copper plating connected to the second thickness conductor + A step of forming a third thickness conductor by pattern plating of a predetermined shape using a different metal other than copper, and an etching step using the pattern plating film of a different metal other than the first to third copper as an etching mask. The desired three-stage (type) of thick conductor is formed on the same base material surface.

Further, the number of stages can be increased by repeatedly stacking (panel copper plating + pattern plating with different metal other than copper having a predetermined shape) while shifting the position. Furthermore, a plurality of step circuits can be three-dimensionally formed on one side and both sides of the substrate surface of the wiring board.
The printed wiring board of the present application is provided with through conduction holes (plating through holes) and non-through conduction holes that directly connect the double-sided outer layer conductors, and a three-dimensional step circuit can be formed only on the component mounting surface side.
The printed wiring board may be formed with step circuits on one side and both sides of the outer layer surface of the multilayer wiring board having the inner layer circuit.

According to the first aspect of the present invention, a wiring board in which at least two or more thickness conductors having different steps are stacked on each other on the same flat base material (copper and different metal plating other than copper) is stacked. It is possible to form a three-dimensional three-dimensional circuit to be applied to a high-quality, thin, small, and high-density contact portion and operation portion without deformation, poor positional accuracy, and conductor thickness variation. In addition, in the conventional synthetic resin molded product, it was impossible to reduce the thickness to 0.5 mm or less, but the wiring board of the present invention can be as thin as 0.05 mm, and printed wiring manufactured with high work efficiency. The board can be supplied to electronic component manufacturers and equipment manufacturers.
Since the dissimilar metal plating is used as a resist mask for etching without using a photosensitive dry film to withstand (copper plating and etching) of the present invention (copper plating mask and etching mask), etching of thick copper plating is possible. Can withstand quality and ensure quality reliability.

According to the invention of claim 2, in addition to the effect of claim 1, the thickness of each component (copper plating + different metal plating) can be freely set, and the number of stages can be formed by freely connecting a plurality of stages. Can be widely supplied according to the demands of electronic parts manufacturers and equipment manufacturers.
Also, since different types of metal plating other than copper are used as etching masks, in addition to contact and operation functions, different metal plating can be used for component mounting performance (wire bonding, bump connection, surface connection, discrete components). A highly reliable printed wiring board that can be formed on demand can be supplied at low cost.

Hereinafter, the manufacturing process of the wiring board of the present invention will be described with reference to FIGS.
First, the first half manufacturing process of the wiring board according to the first embodiment of the present invention will be described with reference to FIG.
FIG. 3A shows a copper-clad laminate 2 (with a base material thickness of 0.1 mm) in which copper foils 3a (9 μm, 18 μm, and 35 μm) are attached to both surfaces.
Although it is possible to form the patterned copper plating conductor (3) on both sides of the insulating base material by additive plating using an insulating base material coated with an emulsion adhesive, the processing cost becomes high.
In FIG. 3B, a predetermined portion of the copper-clad laminate 2 is drilled by an NC drilling machine or a laser machine to form a through hole 4a.

Next, as shown in FIG. 3 (c), panel copper plating (plating thickness 15 μm) is applied to the entire inner surface of the through hole 4a formed at a predetermined location and the entire surface of the copper foil 3a on both sides of the copper clad laminate 2. A through-conduction hole 4 (plating through hole) is formed by forming one panel copper plating conductor (3b).
Thereafter, as shown in FIG. 3 (d), a dry film is laminated on both sides of the copper clad laminate 2, and a pattern film mask of a predetermined pattern (image) is overlaid and exposed and developed to form a predetermined shape for dissimilar metal plating. A plating mask 6 is formed.
Next, as shown in FIG. 3 (e), the first panel copper-plated conductor (3b) formed on the copper-clad laminate 2 is subjected to pattern plating with a different metal other than copper, and a plating mask at a predetermined position. In addition to 6, a first dissimilar metal plating conductor (5a) having a predetermined shape is partially formed.

Then, after forming the first dissimilar metal plating conductor (5a) as shown in FIG. 3 (f), the dry film as the plating mask 6 is peeled off.
That is, in this example, the first dissimilar metal plating conductor (5a) having a predetermined shape was formed at a predetermined location on the through conduction hole 4 and the upper surface (in this example, a partial gold plating with a thickness of 0.5 μm by electrolytic gold plating). The first dissimilar metal plating conductor (5a) may be formed on both sides.
The first thick conductor made of (copper foil + panel copper plating + partial pattern plating with a different metal other than copper) is formed on the same flat base material surface in the steps so far. Therefore, in this example, the conductor thickness of the first thick conductor is about 30 μm to 35 μm.

The latter half of the manufacturing process of the wiring board according to the first embodiment of the present invention will be described based on FIG.
FIG. 4G shows the [first copper conductor 3a + first panel copper-plated conductor (3b) + first dissimilar metal-plated conductor (5a) other than copper] as the first thickness conductor 7 as described above. After the plating process is performed, panel copper plating is performed on the entire surface of the through conduction hole 4 and the second panel copper plating conductor (3c). The thickness of the second panel electrolytic copper plating was 20 μm.
Next, as shown in FIG. 4 (h), a dry film is laminated on top of the second panel copper plating conductor (3c) of the copper clad laminate 2 in the same manner as in FIG. Then, a second plating mask 6 having a predetermined shape for the next dissimilar metal plating is formed.

Thereafter, as shown in FIG. 4 (i), a portion of the second panel copper-plated conductor (3c) formed on the copper-clad laminate 2 is partially applied to a portion other than where the second plating mask 6 is formed. Then, pattern plating with a dissimilar metal (in this example, electrolytic gold plating with a thickness of 0.5 μm) is performed to form a second dissimilar metal plating conductor (5b) having a predetermined shape in addition to the plating mask 6.
Then, after forming a second dissimilar metal plating conductor (5b) as shown in FIG. 4 (j), the dry film as the plating mask 6 is peeled off.
Accordingly, the thickness of the base conductor of the second thickness conductor 8 of the flat portion made of [copper foil 3a + first panel copper plating conductor (3b) + second panel copper plating conductor (3c) + dissimilar metal plating conductor (5b)]. Was about 50 μm to 55 μm.

Thereafter, as shown in FIG. 4 (k), a first dissimilar metal plating conductor (5a) and a second dissimilar metal plating conductor (5b) partially formed in a predetermined shape at a predetermined portion of the copper clad laminate 2 Is used as an etching mask, and unnecessary copper plating and copper foil are removed by a single etching process to form a predetermined shape (metal copper + metal plating other than copper) (first thickness conductor 7 and second metal plating). Two steps (two types) of thickness conductors having different thickness conductors 8) can be formed adjacent to or connected in a staircase pattern.
If this dissimilar metal plating is 0.3 μm or more in thickness, it can withstand etching that dissolves and removes thick metal copper (eg, copper thickness of 50 μm or more) that is unstable and unbearable with a film mask, and can ensure quality reliability. Become.
In addition, after forming two or more types of thick conductors in a stepped manner by etching, the side surfaces (thickness side surfaces) of the step conductors and the exposed portions of the copper metal on the end surfaces of the through-conduction holes 4 are covered with different metal plating. Therefore, a third dissimilar metal plating may be performed.

This dissimilar metal plating other than copper performs partial pattern plating to form a desired thickness conductor, so that a metal containing any one of nickel, gold, silver, and rhodium is good, and the dissimilar metal plating is made into a predetermined pattern. It is also a circuit formation method using the formed pattern plating as an etching mask.
Two-level (two types) or more thick conductors with different steps are three-dimensionally formed on only one side of the wiring board, and the other side (back side) is mainly composed of signal circuits and wiring circuits with no steps similar to normal wiring boards. A planar circuit may be formed.

4 (j), the second dissimilar metal plating conductor shown in FIG. 4 (j) is formed, and the dry film as the second dissimilar metal plating mask 6 is peeled off. g), a step of forming a plating mask for dissimilar metal plating shown in FIG. 4 (h), a step of forming a dissimilar metal plating conductor shown in FIG. 4 (i), and FIG. 4 (j). After the process of peeling the dry film as the plating mask shown is repeated and the base conductor of the third thickness conductor 9 is formed, unnecessary metal copper (copper plating and copper foil) shown in FIG. The third thick conductor 9 may be formed by processing. (Drawing is omitted)
Furthermore, the fourth thickness conductor, the fifth thickness conductor and a plurality of thickness conductors having different thicknesses can be formed in a staircase pattern or a staggered pattern by sequentially repeating the steps of FIGS. 4 (g) to 4 (j). It is.

FIG. 1 is an enlarged cross-sectional view of a part of a wiring board having two steps (two types) of thick conductors according to the first embodiment of the present invention.
Through-conduction by forming panel first copper plating conductor (3b) by applying panel copper plating (plating thickness 15μm) to both sides of double-sided copper clad laminate 2 of substrate thickness 0.1mm and copper foil 3a (18μm) Hole 4 (plating through hole) is formed.

The outer layer conductors on both sides made of the first panel copper plating conductors (3b) on both sides of the wiring board are first hole plating conductors on the inner wall of the through-conduction hole 4 (plating through hole). The panel copper plating conductor (3b) and the first dissimilar metal plating conductor (5a), and the second panel copper plating conductor (3c) and the second dissimilar metal plating conductor (5b) are electrically connected. .
However, in the second panel copper plating step shown in FIG. 4 (g), the dry film is used as the second panel copper plating mask, and the through-conduction holes 4 (through holes) and the back surface of the wiring board are masked with copper plating. The second panel copper plating may not be formed by coating.

  The printed wiring board 1 according to the first embodiment of the present invention includes a first thickness conductor 7 composed of [copper foil 3a + first copper plating conductor (3b) + first dissimilar metal plating conductor 5a], Second made of [copper foil 3a + first copper-plated conductor (3b) + second copper-plated conductor (3c) + second dissimilar metal-plated conductor 5b] adjacent to or connected to one thickness conductor 7 The wiring board 1 has a thickness conductor different from that of the thickness conductor 8 provided on the upper surface of the wiring board 1 in two steps.

The second thickness conductor 8 is [copper foil 3a + first copper plating conductor (3b) + first dissimilar metal plating conductor 5a + second copper plating conductor (3c) + second dissimilar metal plating conductor 5b]. It may be configured in a sand-etched state. (No drawing display)
Therefore, two or more kinds of conductors with different thicknesses in the (copper plating + different metal plating other than copper) configuration are concentrated in the area (area) where the component elements are mounted, arranged in a staircase pattern, and the contacts on this area This is a wiring board 1 serving as a base on which functional parts that perform functions, operation functions, display functions, and the like are mounted.

  In other words, the wiring board 1 is formed by forming at least two stepped thickness conductors having different thicknesses in the vicinity of or connected in two steps, and the through-conduction hole 4 is disposed in the area of the first thickness conductor 7. The example which formed is shown. The second thickness conductor 8 is formed close to the first thickness conductor 7, but this portion is electrically connected by a combination request with a functional component for causing a contact function, an operation function, a display function, and the like. However, the second thick conductor 8 may be partially overlapped with the first thick conductor 7, or the first thick conductor 7 and the second thick conductor 8 may be concentric and eccentric. It can also be arranged in a shape.

FIG. 2 is a cross-sectional view of a wiring board having three-stage thick conductors according to Example 2 of the present invention.
First, as shown in FIG. 2, the through-conduction hole 4 is arranged and formed in the area of the first thickness conductor 7 of the first embodiment of the present invention shown in FIG. 1, and the second thickness conductor 8 has the first thickness. Thickness conductors that are formed close to the conductor 7 and have different steps are formed close to two steps.

  A step of forming a third-stage thick conductor consisting of covering the second-stage thick conductor (panel copper plating + partial pattern plating with a different metal other than copper); and in addition to this, [copper foil 3a + first copper plating The third thick conductor 9 composed of the conductor (3b) + second copper-plated conductor (3c) + third copper-plated conductor (3d) + third dissimilar metal-plated conductor 5c] This is a wiring board 1 in which thick conductors having different steps on the surface are formed close to or connected in three steps.

Further, the third thickness conductor 9 has a second thickness composed of [copper foil 3a + first copper plating conductor (3b) + second copper plating conductor (3c) + second dissimilar metal plating conductor 5b]. A panel copper plating is formed by overlapping the third copper plating conductor (3d) in addition to the upper surface of the conductor 8, and then the third dissimilar metal plating conductor 5c is partially overlapped with the above portion [ Copper foil 3a + first copper plating conductor (3b) + second copper plating conductor (3c) + second dissimilar metal plating conductor 5b + third copper plating conductor (3d) + third dissimilar metal plating conductor 5c] Are connected to each other, and the entire copper-clad laminate 2 is etched at a time to partially form the second thickness conductor 8 and the third thickness conductor 9 in the same pattern area in plan view. Steps that are connected in a staircase pattern without any overlapping insulation gaps A step structure having steps is possible.
A three-dimensional structure in which complicated steps with different conductor thicknesses are freely (randomly) arranged on the XY plane in the same kind of component element mounting area in plan view is possible.

  Further, the first thickness conductor 7 and the second thickness conductor 8 may be brought into contact with each other in the same component element mounting area to form a stepped portion connected in a staircase pattern. It is also possible to form a step portion consisting of three steps in which the second thickness conductor 8 and the third thickness conductor 9 are connected to all the thickness conductors having different thicknesses and connected in a staircase pattern. That is, an inclined stepped recess can be formed. (No drawing display)

This dissimilar metal plating includes any one of nickel, gold, silver and rhodium as a partial pattern plating to form a desired thickness conductor, or if necessary, Ni plating-gold plating (Au), Ni plating- An additional plating process such as silver plating (Ag) can also be performed.
In addition to the contact function and operation function, various steps and connection lands (surfaces) can be selected to meet the required performance of mounted components (wire bonding, bump connection, surface connection, discrete component connection, etc.). An attached land, a wire-bonden ground, a bump connection land, etc.) can also be provided.

It is sectional drawing of the wiring board which has a 2 step | paragraph thick conductor of Example 1 of this invention. It is sectional drawing of the wiring board which has a 3 step | paragraph thick conductor of Example 2 of this invention. It is sectional drawing explaining the manufacturing process of the first half of the wiring board of this invention Example 1. FIG. It is sectional drawing explaining the manufacturing process of the second half of the wiring board of this invention Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Wiring board, 2 ... Copper clad laminated board, 3 ... Copper plating conductor, 4 ... Through-conduction hole, 5 ... Dissimilar metal plating conductor, 6 ... Plating mask, 7 ... 1st thickness conductor,
8: Second thickness conductor, 9: Third thickness conductor.

Claims (3)

  The fact that multiple thickness conductors were formed by repeatedly layering at least one thickness conductor consisting of at least two kinds of metals (copper + different metal plating other than copper) on the same flat and horizontal substrate surface of the wiring board. A characteristic wiring board.   2. The wiring board according to claim 1, wherein a plurality of thick conductors are overlapped repeatedly and partially overlapped to form a stepped shape.   When forming a step circuit on a wiring board, a step of forming a first-stage thick conductor made of two kinds of metals by (panel copper plating + partial pattern plating with different metal other than copper) on the same flat base material surface; A step of forming a second-stage thick conductor comprising covering the first-stage thickness conductor (panel copper plating + partial pattern plating with a different metal other than copper), and a predetermined shape of the different metal other than copper A circuit forming method, comprising: forming a plurality of thickness conductors made of (copper + dissimilar metal plating other than copper) in an etching step using partial pattern plating as an etching mask.

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