JPH0469838B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing double-sided or multilayer conductor circuit boards with through holes.

(Prior Art) Conventionally, as a method for manufacturing a double-sided conductive circuit board with through holes, for example, a metal thin film is formed on the entire surface of a flat conductive base material, a desired resist mask is formed, and this flat conductive substrate is A conductor circuit pattern is formed by an electrolytic plating method using a conductive base material as a cathode, and two such flat conductive base materials are thermocompression bonded via an insulating base material to form a laminate. Through-holes are drilled and through-holes are plated.

In such a method of manufacturing a double-sided conductor circuit board, a so-called high-speed plating method is preferred as the electrolytic plating process for forming conductor circuits, which can form high-quality conductor circuits in a short time. That is, as shown in FIG. 19, after forming a metal thin film 2 on the entire surface of a flat conductive base material 1, a resist mask 3 is formed on the area of this metal thin film 2 excluding the conductor circuit formation area, and then, This flat conductive base material 1
is a cathode, and this cathode and a flat anode (not shown)
are separated by a predetermined distance and an electrolytic solution is supplied between both electrodes at high speed to deposit copper, thereby forming conductor circuits 4, 4'.

(Problems to be Solved by the Invention) However, in such a conductor circuit forming process, if the conductor circuit 4 and the conductor circuit 4' are very far apart, that is, the conductor circuits 4 and 4' are isolated from each other. 19, a so-called edge bead (dog bone) 5 is formed at the boundary between the resist mask 3a and the conductor circuits 4, 4', which corresponds to the blank part between the conductor circuits 4 and 4'. ，
5' occurs intensively. This edge bead 5,
5' is a phenomenon in which plating metal is abnormally deposited at the edges of the circuit due to concentration of electrolytic current at the edges. When this phenomenon occurs, the film thickness and width of the circuit increase significantly from the design values, Air may accumulate in the edge bead portion during transfer and lamination, or the edge bead may penetrate through the insulating base material during transfer, causing shoots and the like. Furthermore, in high-frequency circuit boards, it is required to strictly set the circuit width and insulation spacing in order to ensure good characteristics, so the occurrence of such edge beads causes a problem in that the high-frequency characteristics are significantly impaired. The growth of the edge beads 5, 5' becomes more remarkable as the current density during electrolytic plating increases. t increases from 1.9 to 5 to 6 times.

In order to eliminate this problem, the conductor circuit 4,
A method has been proposed in which a dummy circuit is formed in advance between 4' to suppress the occurrence of edge beads (Japanese Patent Laid-Open No. 123793/1983). In this method,
If the dummy circuit is not to be incorporated into the final target conductor circuit board, it is necessary to remove only the dummy circuit prior to transferring and laminating the conductor circuit. However, since the metal thin film 2 is present, there is a problem in that it is extremely difficult to remove only the dummy circuit.

On the other hand, if a dummy circuit and a conductor circuit are formed without forming the metal thin film 2, it is certainly possible to remove only the dummy circuit, but when the dummy circuit is removed, the surface of the flat conductive substrate is removed between the conductor circuits. is exposed, and during transfer, the insulating material invades the fine pits on the surface of the flat conductive base material, and the flat conductive base material and the insulating material are tightly adhered, making it impossible to transfer. Furthermore, when plating through-holes in independent circuits, a problem arises in that current cannot be applied to the circuits.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide a method for manufacturing a conductive circuit board that suppresses excessive growth of edge beads and has good transferability.

(Means and effects for solving the problem) In order to achieve the above object, according to the present invention, a dummy layer adjacent to an isolated conductor circuit in a conductor circuit forming area and a conductor circuit on the surface of a flat conductive base material is provided. a step of forming a resist mask in an area excluding a circuit forming area; a step of performing electrolytic plating on the flat conductive base material to form a conductor circuit and a dummy circuit on the flat conductive base material; and peeling off the resist mask. a step of forming a metal thin film covering the surface of the flat conductive substrate and the conductor circuit; and a step of forming a metal thin film covering the surface of the flat conductive substrate and the conductor circuit, and placing the two flat conductive substrates on which the conductor circuit has been formed so that the conductor circuit faces each other, a step of laminating them together and press-bonding them together or heat-pressing them to form a laminate;
A step of peeling only the flat conductive base material from this laminate, a step of drilling a through hole in this laminate and then plating the through hole on the inner wall surface of the through hole and both sides of the laminate, and This process consists of a step of etching away the metal thin film that electrically connects the circuits. Further, in the present invention, after forming the conductive circuit and the dummy circuit, at least a portion of the dummy circuit is removed if necessary.

(Function) When forming an isolated conductor circuit, specifically, a conductor circuit in which there is no adjacent conductor circuit on at least one side of the conductor circuit with a required interval,
By simultaneously forming dummy circuits adjacent to these conductor circuits, excessive growth of edge beads can be suppressed, resulting in a significant increase in circuit size, air pockets that occur in edge bead areas during transfer lamination, and edge bead damage to insulating substrates. This prevents the occurrence of shoots, etc. caused by penetrating through. Furthermore, by performing the metal thin film forming step as a post-process, only the dummy circuit can be easily removed, and the transferability of the conductor circuit can also be maintained well. Furthermore, even if the circuit forming the through hole is an independent circuit, the presence of the metal thin film maintains good electrical conductivity.

(Example) Hereinafter, an example of the method of the present invention will be described based on FIGS. 1 to 15.

First, the flat conductive substrate 11 used in the method of the present invention is preferably one that has chemical resistance and electrical corrosion resistance against chemicals used in the plating process, and is preferably made of a stainless steel plate (for example, a hardened plate). (preferably treated SUS630), nickel plate, titanium or titanium alloy plate,
Copper or copper alloy plates are used. It is preferable to perform a pretreatment step to remove dirt and oxide film from the surface of the flat conductive substrate 2 and to give the surface a desired roughness (FIG. 1a). The surface roughness of the flat conductive base material 2 affects the adhesion strength and pinhole formation of the copper thin film 15 formed on the flat conductive base material 11 in a subsequent process, and also affects the surface roughness of the copper thin film 15. give. This surface roughness is desirably set so as to provide adhesion that allows easy peeling in the step of peeling off the flat conductive base material 11 (FIG. 1h), which will be described later.

Specifically, the surface roughening treatment of the flat conductive base material 11 is carried out by a chemical method, or by chemically cleaning the surface of the flat conductive base material 11 and then mechanically roughening it by wet sandblasting (liquid honing) or the like. A method such as surfaceization is used.

Conductor circuit 1 on the surface of this flat conductive base material 11
A resist mask 12 is formed by photoresist method, printing method, etc. on the surface excluding the portion where 3, 13' and dummy circuit 13'' are to be formed (FIG. 1b,
Figure 2). As the resist agent, one that has excellent adhesion to the flat conductive base material 11 is selected. Specifically, a resist layer is formed by laminating a photosensitive resist film or by coating and drying a liquid photosensitive resist, and then exposing and drying the resist layer.
A resist mask 12 with a desired pattern is formed by development.
form. Note that when the linear density of the conductor circuit is low, the resist mask 12 may be formed by, for example, a screen printing method.

Next, the flat conductive base material 11 on which the resist mask 12 has been formed as described above is used as a cathode, and this is connected to the anode 14 at a predetermined distance (for example, 3 to 30 mm,
Preferably, the conductor circuits 13, 13' and the dummy circuit 13'' are electroformed in copper by high-speed plating, facing each other with a distance of 11 to 15 mm (Fig. 1c, 3).
figure). The electrolytic solution for this high-speed plating has a metal copper concentration of 0.20 to 2.0 mol/, preferably 0.35 to 2.0 mol/
A copper sulfate plating solution containing 0.98 mol/, and a sulfuric acid concentration of 50 to 220 g/ is sufficient.
Add 1.5 ml of CUPPORAPID Hs (trade name). Ordinary plating solutions such as copper pyrophosphate solution may also be used. Also, current density 0.15~4A/
cm ² , liquid contact speed to electrode 2.6 to 20 m/sec,
The electrolytic solution temperature is set at 45 to 70°C, preferably 60 to 65°C. If the plating liquid temperature is less than 45° C., the moving speed of copper ions decreases, making it easier to form a polarized layer on the electrode surface, resulting in a decreased plating deposition rate. On the other hand, when the liquid temperature exceeds 70°C, the amount of evaporation of the plating liquid increases, making the concentration unstable, and equipment restrictions are imposed due to the high liquid temperature.

In this electroforming process, conductor circuits 13', 1
3' are separated by a distance that exceeds the allowable edge bead height ratio t'/t (for example, 2 mm or more), dummy circuits 13'' and 13'' are formed between them. This suppresses the growth of edge beads in the conductor circuit 1 in the transfer process described later.
There is an advantage that the occurrence of shoots etc. between 3' and 13' is prevented. That is, in this step, the ratio t'/t between the thickness t at the center of the conductive circuits 13, 13' described above and the height t' of the edge bead from the surface of the flat conductive base material is suppressed to a range of 1.0 to 1.8. be able to.
Note that the formation position, number, distance from the conductor circuit 13', etc. of the dummy circuit 13'' are different from the conductor circuits 13', 1.
It is preferable to set the distance appropriately depending on the distance between 3' and the like.

Furthermore, by setting the current density and the speed of contact with the electrodes to the above-described predetermined conditions, the conductor circuits 13, 13' and the dummy circuit 13 are deposited on the flat conductive substrate 11 at a deposition rate of 25 to 100 μm per minute. Moreover, the deposited copper particles can be made extremely fine, and the conductor circuits 13, 13'
The elongation rate reaches 16-25% without loss of tensile strength. This elongation rate is 1.5 to 2 times or more than the elongation rate of a conductor circuit formed by a normal plating method (a value equivalent to or higher than that of rolled annealed copper foil), and an extremely soft copper film can be produced. Since it has performance equivalent to that of rolled annealed copper foil, it is particularly effective in flexible substrates that require high bendability.

In the copper electroforming process, the conductor circuits 13, 13' and the dummy circuit 13'' have the required thickness (for example, 2 μm).
300 μm), the supply of electricity and plating solution is stopped, and after washing with water, the process proceeds to the step of removing the resist mask 12 (FIG. 1d, FIG. 4). For example, a solution such as caustic soda is used to peel off and remove the resist mask 12.
The resist mask 12 is dissolved and removed by dipping for a second, washed with water, and dried.

After that, the dummy circuit 13'' that will not be finally incorporated into the conductor circuit board is removed (Fig. 1e, Fig. 5).Specifically, the dummy circuit 13'' to be removed is removed.
A method of physically, that is, mechanically removing only 3″;
Then, a method is used in which the conductor circuits 13, 13' are removed by chemical etching while being protected with a resist mask or the like. Furthermore, this dummy circuit 1
3'' removal process may be performed prior to the resist mask 12 removal process, and the dummy circuit 1
It is not necessarily necessary to remove all of 3'', but only the portion that would cause trouble if left on the circuit board may be removed, and the other portions may be left.

Next, a metal thin film 15 is formed on the entire surface of the flat conductive base material 11 on which only the conductor circuits 13 and 13' are formed in this manner. Copper, nickel, zinc, etc. are used as the metal, and the film is formed to have a thickness of 0.5 to 5 μm. As a method for forming the thin film, any of dry methods such as vacuum evaporation, sputtering, and CVD, and wet methods such as electrolytic plating and electroless plating can be used. Among them, the high-speed plating method is excellent in terms of workability. To explain the process of forming a copper thin film by the high-speed plating method, the flat conductive base material 11 is used as a cathode, and this is used as an anode 14 as shown in FIG. at a predetermined distance of 3 to 30
The copper thin film 15 is electrolytically deposited on the flat conductive base material 11 and the conductor circuits 13, 13' by high-speed plating with a distance of mm apart from each other (FIG. 1F and FIG. 6).

In this case, the high-speed plating conditions are 45 to 70℃.
The plating solution is placed in a turbulent state on the cathode surface, that is,
The cathode electrode is rotated so that the distance between the electrodes is 3 to 30 mm and the speed of contact with the electrode is 2.6 to 20.0 m/sec, or the electrolyte is forcibly supplied between the fixed electrodes. At this time, for example, copper sulfate plating solution, copper pyrophosphate solution, etc. are used as the plating solution, and a current with a cathode current density of 0.15 to 4.0 A/cm ² is applied, so that the deposition rate of the thin metal layer is 25 to 100 μm/cm 2 . It is desirable to set it so that it is min.

The copper thin film 15 subjected to high-speed electrolytic plating is applied to the flat conductive base material 11 having the required surface roughness as described above.
Since the copper thin film 15 is electrolytically laminated, the copper thin film 15 is in close contact with the flat conductive base material 11 with an appropriate adhesion force, and the transfer lamination in the next step can be carried out smoothly.

Next, two flat conductive base materials 11 obtained in this way are prepared, and these flat conductive base materials 1 are
The conductive circuits 13, 13' and the copper thin film 15 formed on the insulating base material 1 together with the flat conductive base material 15 are
6, and heat and press them together using a hot press (FIG. 1g, FIG. 7).
The insulating base material 16 may be either an organic material or an inorganic material, and for example, materials such as glass, epoxy resin, phenol resin, polyimide resin, polyester resin, and aramide resin can be used. can. Alternatively, a material insulated by coating the surface of a conductive material such as iron or aluminum with enamel and performing an alumite treatment to oxidize the aluminum surface may be used. Generally, a glass cloth or the like is impregnated with epoxy resin, and the conductor circuits 13, 13' and a part of the copper thin film 15 are immersed in the semi-cured prepreg (B stage) (the state shown in FIG. 8). It is heated and pressurized to bond it.

In this transfer process, the conductor circuits 13, 13'
The copper thin film 15 is laminated together with the thick flat conductive base material 11 on the insulating base material 16 and bonded by heat and pressure, so that the conductor circuits 13 and 13' are transferred while being held on the flat conductive base material 11. This ensures dimensional stability. Moreover, the flat conductive base material 11
Since it also serves as a transfer jig during transfer, no special jig is required.Furthermore, since the conductor circuits 13, 13' and the copper thin film 15 are bonded with strong adhesive force, the conductor circuits 13, 13' can be transferred easily. Move at different times (so-called
Because it has good dimensional stability and does not cause swing (swing), it can be applied to high-density circuits with fine conductor circuit patterns (for example, pattern widths of several μm to several tens of μm can be realized).

Next, after waiting for the insulating base material 16 to harden by heating, the flat conductive base material 11 is peeled off from the conductor circuits 13, 13' and the copper thin film 15 transferred to the insulating base material 16 (Fig. 1 h, 8 figure). At this time, due to the adhesion between the flat conductive base material 11 and the copper thin film 15, the copper thin film 1
5 and the conductor circuits 13, 13', and furthermore, the adhesion between the copper thin film 15 and the insulating base 16 is greater than the adhesion between the flat conductive base 11 and the copper thin film 15. Since the plate-shaped conductive base material 11 is separated at the interface with the conductive circuits 13, 13' and the copper thin film 15, the copper thin film 15 and the conductive circuits 13, 13' are integrated on the insulating base material 16 side. Closely attached to.

Next, through holes 17 are formed to connect the conductor circuits 13, 13 laminated on both sides of the insulating base material 16 (FIG. 1i, FIG. 9). This through-hole forming step can be performed using a conventional method such as cutting using a drill or the like. Thereafter, in preparation for through-hole plating to be described later, a thin copper layer 18 is formed by chemical copper plating on the entire surface of the laminate including the inner wall surface 17a of the through-hole 17 (FIG. 10).

Next, a resist is applied to the inner wall surface 1a of the through hole 17 on the thin copper layer 18, the peripheral edge of the opening of the through hole 17, that is, the land portion, and if necessary, the area excluding the connector portion and other portions where it is not desirable to form a flash circuit. A mask 19 is formed (FIG. 1j, FIG. 11). This step can be carried out in the same manner as described in the step of FIG. 1d above.

Thereafter, through-hole plating is applied to the areas where the resist mask 19 is not formed, for example, by copper electrolytic plating using a copper pyrophosphate bath or a copper sulfate bath (bright copper sulfate plating solution). After forming layer 20 (first
(K, FIG. 12), and the resist mask 19 is peeled off (FIG. 1L, FIG. 13). In the present invention, the chemical copper plating process and the through-hole process by electrolytic plating described above are collectively referred to as the through-hole plating process. In this through-hole plating process, even if the conductor circuit 13 in which the through-hole 17 is formed is an independent circuit, the insulating base material 1
Since the thin copper film 15 is formed over the entire surface of the electrode 6, it has the advantage of extremely high conductivity.

Note that the through-hole plating process is not limited to the processes shown in FIGS. 10 to 12,
For example, it can also be implemented through the procedures shown in FIGS. 16 to 18. That is, through hole 17
A resist mask 19' is formed on the surface of the insulating base material 16 on which a resist mask 19' is formed, excluding areas where it is not desirable to form a flash circuit, such as the land portion and, if necessary, a connector portion, etc. (FIG. 16). Next, a thin copper layer 18' is formed by chemical copper plating (FIG. 17).
Subsequently, a through-hole plating layer 20' is formed by electrolytic plating (FIG. 18). Thereafter, the resist mask 19' is removed and the copper thin film 15 is etched in the same manner as above. (Figure 14). According to this through-hole plating process, it is possible to perform electroless plating and through-hole plating in succession, so there is an advantage that workability is improved. However, in the above process, since electroless plating, that is, chemical copper plating is performed after the resist mask 19' is formed, the resist material must contain, for example, catalyst poison and an alkaline non-alkaline material to prevent electroless plating. It is desirable to select an alkali-resistant material so that it will not be attacked by the electrolytic plating solution. If an alkali-resistant resist material cannot be used due to various restrictions, electroless plating may be performed using acid plating such as acid nickel plating.

Next, copper thin film 15 and conductor circuits 13, 13'
The conductor circuit board is completed by etching the surface (Fig. 1m, Fig. 14). At this time, the through-hole plating layer 20 may be protected, for example, by a tenting method using a dry film, if necessary. This etching step can be performed, for example, by wet etching. Through this process, the conductor circuits 13, 1 on both sides of the laminate
The insulating base material 16 is exposed in each region sandwiched between the regions 3'.

Furthermore, after the above steps are completed, if desired, solder resist printing may be performed on both sides of the conductive circuit board to form a solder resist layer 21 (FIG. 1n, FIG. 15).

In the above embodiment, two conductor circuits 13, which are separated by a predetermined distance or more, are used as isolated conductor circuits.
Although we have described a conductor circuit board having a
Isolated conductor circuits are not limited to these, but include terminals provided separately from the circuit part on the board, or an outer frame similarly separated from the circuit part, etc.
It is extremely effective to apply the manufacturing process of the present invention to any device that has a conductor portion on at least one side of which there is no conductor portion after a required interval.

In the above embodiment, a case was described in which the metal thin film was formed of the same type of metal as the conductor circuit, that is, a copper thin film, but if a metal of a different type than the conductor circuit is used as the metal thin film, the metal thin film shown in FIG. In the etching process, there is an advantage that workability is improved by using an etchant that selectively etches only the metal thin film.

(Effects of the Invention) As explained above, according to the present invention, a resist mask is applied to the conductor circuit formation area on the surface of a flat conductive base material and the area of the conductor circuit excluding the dummy circuit formation area adjacent to the isolated conductor circuit. forming a conductor circuit and a dummy circuit on the flat conductive base material by electrolytically plating the flat conductive base material; peeling off the resist mask; A step of forming a metal thin film covering the surface and the conductor circuit, and two flat conductive base materials on which the conductor circuit is formed, the conductor circuits facing each other, laminated with an insulating base material in between, and crimped together. or a step of heat-pressing to form a laminate, and a step of peeling only the flat conductive base material from this laminate;
After drilling through holes in this laminate, through-hole plating is performed on the inner wall surfaces of the through holes and both surfaces of the laminate, and a step of etching away the metal thin film that electrically connects the conductor circuits. This structure suppresses excessive growth of edge beads during the formation of conductor circuits, prevents deviations from circuit design values such as circuit film thickness and circuit width, and prevents deterioration of high frequency characteristics in the case of high frequency circuits. It has the effect of preventing Furthermore, it has various advantages such as being able to maintain good transferability and electrical conductivity in the through-hole plating process.

[Brief explanation of drawings]

FIG. 1 is a process flowchart showing the manufacturing procedure of the method for manufacturing a conductive circuit board according to the present invention, FIGS. 2 to 15 are cross-sectional configuration diagrams of the conductive circuit board in each process shown in FIG. 18 are cross-sectional configuration diagrams of a conductor circuit board showing other embodiments of the through-hole plating process in FIG. FIG. 5, 5'... Edge bead, 11... Flat conductive base material, 12, 19... Resist mask, 13, 13'
...Conductor circuit, 13''...Dummy circuit, 15...Metal thin film, 16...Insulating base material, 17...Through hole, 2
0,20'...Through hole plating layer.

Claims (1)

[Scope of Claims] 1. A step of forming a resist mask in the conductor circuit formation region and the conductor circuit on the surface of the flat conductive base material, except for the dummy circuit formation region adjacent to the isolated conductor circuit, and A step of electrolytically plating a conductive base material to form a conductor circuit and a dummy circuit on the conductive base material, a step of peeling off the resist mask, and a step of forming a metal thin film covering the surface of the conductive base material and the conductor circuit. and a step of forming a laminate by placing two flat conductive substrates on which conductor circuits are formed so that the conductor circuits face each other, laminating them with an insulating substrate interposed therebetween, and press-bonding or heat-pressing them together; A step of peeling only the flat conductive base material from the laminate;
After drilling through holes in this laminate, through-hole plating is performed on the inner wall surfaces of the through holes and both surfaces of the laminate, and a step of etching away the metal thin film that electrically connects the conductor circuits. A method for manufacturing a conductor circuit board, characterized by comprising the steps of: 2. The method of manufacturing a conductor circuit board according to claim 1, further comprising the step of removing at least a portion of the dummy circuit after forming the conductor circuit and the dummy circuit.