JP4793720B2 - Plating method 2-layer circuit substrate manufacturing method - Google Patents

Description

  The present invention relates to a method for producing a plating method two-layer circuit substrate suitable for laminated films and the like used for applications such as flexible printed wiring boards, and a plating apparatus suitable for production of the circuit substrate.

  As electronic devices become smaller, lighter, more functional, more multifunctional, and more densely packed, printed wiring boards are becoming higher due to conductor widths and narrower conductors, multilayers, flexibility, and thinner substrates. The density is rapidly increasing, and it has been developed into a flexible printed circuit (hereinafter sometimes referred to as FPC) substrate.

Conventionally, a flexible printed wiring board having a three-layer structure in which a copper foil as a conductor layer is bonded to a plastic film such as a polyimide film via an adhesive layer is known. The three-layer structure type flexible printed wiring board has a problem that the heat resistance of the adhesive used is inferior to that of the polyimide film, so that the dimensional accuracy after processing decreases, and the thickness of the copper foil used is usually Since the thickness is 10 μm or more, there is a disadvantage that patterning for high-density wiring with a narrow pitch is difficult. Furthermore, when the IC is mounted, the adhesive is melted or thermally decomposed with respect to the IC heated to a high temperature, so that the IC bumps and the leads on the FPC cannot be connected with high accuracy. Therefore, when mounting an IC, it is common to make a hole by punching the IC mounting position by a method such as punching so that no adhesive is interposed under the IC chip.
On the other hand, a two-layer structure in which a metal layer as a conductor layer is formed on a polyimide film by a wet plating method or a dry plating method (for example, a vacuum deposition method, a sputtering method, an ion plating method, etc.) without using an adhesive. A type of flexible printed wiring board is known. Since these plating method two-layer type flexible printed wiring boards (hereinafter, sometimes referred to as plating method two-layer circuit base materials) that do not use an adhesive do not have an adhesive, as described above in IC mounting. It is possible to mount the IC directly on the polyimide film without making a hole in the film surface. Moreover, since the conductive layer for the flexible printed wiring board of the plating method two-layer structure type can be made thinner than 10 μm, the flexibility of the FPC is very good and high-density wiring is possible.

The wet plating method is usually performed by electrolytic plating. When a long plastic film substrate having a conductive layer of about 5000 angstroms attached to a plastic film such as a polyimide film with a thickness of 200 μm or less is electroplated by roll-to-roll, one end of the film substrate Although a method of continuously plating by sequentially holding the electrodes with a power supply chuck has been proposed (see Patent Document 1), there is a drawback that it is inferior to the single wafer processing method in terms of uniformity of plating thickness. On the other hand, the method of supplying electric power to a film base material with the roll provided in the plating tank exterior is proposed (refer patent document 2). However, in this proposal, although the uniformity of plating thickness has been improved, there are problems such as scratching the long plastic film substrate and lowering the surface quality because of the support means such as the rod in the plating tank. was there. In addition, the plating solution adhered to the long plastic film substrate and taken out of the plating solution tank adheres to the roll provided outside the plating solution tank, and the roll is corroded and deteriorated over time. In particular, when the transport roll deteriorates with time, the film base material cannot be transported stably, and the uniformity of the plating thickness may decrease, or the surface quality of the product may decrease due to wrinkles or scratches. In order to improve this point, a plating apparatus with an improved liquid sealing method has been proposed (see Patent Document 3), but even with this, it is not possible to bring the plating solution out of the plating tank. However, when produced for a long time, it was not possible to prevent aging corrosion and deterioration of the roll outside the plating tank.
On the other hand, an example is shown in which plating is performed by repeatedly transporting a long plastic film up and down while being supported in a horizontal direction (see Patent Document 4). FIG. 5 is a side sectional view for explaining the structure of the conventional horizontal conveyance type plating apparatus. The long plastic film substrate 1 having a conductive surface is plated while coming in and out of the plating tank 6 while being in contact with the power supply roll 4 installed horizontally. Conventionally, it is common to configure a plating apparatus by arranging a plurality of such units. As is apparent from FIG. 5, when plating on both surfaces, the anode 2 is formed on the upper processing surface. Exists.
In this system, when plating is performed on both surfaces of the long plastic film substrate 1, the anode 2 (anode) is positioned above the processing surface of the long plastic film substrate 1 because of the structure of the apparatus, so There was a drawback that the slime dropped on the processed surface of the long plastic film substrate 1 to cause surface defects.
In the case of electroplating on both sides of a long plastic film substrate in a plating method two-layer structure type circuit substrate, it is common to supply power by contacting a power supply means on both sides of the long plastic film substrate. there were. However, there is a problem that surface defects such as irregularities are likely to occur in a portion that contacts the power feeding means. When the electrolytic plating is performed on both surfaces of a long plastic film substrate and used as a circuit material, a fine pattern is often formed on one surface and a rough pattern is often formed on the other surface as a ground surface. The fine pattern surface is required to have as little quality as possible with fine irregularities.
Japanese Patent Laid-Open No. 2002-20898 Japanese Patent Laid-Open No. 2003-321796 JP 2003-147582 A Japanese Patent Laid-Open No. 9-235697

  The problem to be solved in the present invention is to minimize the surface defects generated in the plating process as described above when producing a plating method two-layer circuit substrate having metal layers formed on both sides.

  An object of the present invention is to provide a method for producing a plating method two-layer circuit substrate with few surface defects such as protrusions and dents on the plating surface and a plating apparatus suitable for producing the circuit substrate.

  Means for solving the above problems are as follows.

The plating method two-layer circuit substrate manufacturing method of the present invention includes a plating solution tank for containing a plating solution, and the plating solution tank while transporting the plastic film substrate in the longitudinal direction with its width direction directed up and down. A metal plating layer is formed on both surfaces of the plastic film substrate using an electroplating apparatus having a conveying means for immersing in an inner plating solution and a power supply means electrically contacting the conductive surface of the plastic film substrate. In the manufacturing method of the circuit substrate to be formed,
The conductive metal layers provided on both surfaces of the plastic film substrate are electrically connected to each other, and an anode (anode) that causes electrolysis with the plastic film substrate is provided inside the plating solution tank. The power supply rolls installed on both sides of the plastic film and used as power supply means (cathode) are installed only on one side of the plastic film substrate, and are electrolyzed on both sides by supplying power from the power supply roll to the plastic film substrate. the plating facilities,
Both a drive roll used as a conveying means and a power supply roll used as a power supply means are provided outside the plating bath, and the power supply roll has substantially no driving force and follows the plastic film substrate being conveyed. It is a manufacturing method of the plating method two-layer circuit base material characterized by rotating by .

  According to the preferable aspect of the manufacturing method of the plating method 2 layer circuit base material of this invention, the said drive roll and electric power feeding roll exist in the same surface side of the plastic film base material plated.

  According to a preferred aspect of the method for producing a plating method two-layer circuit substrate of the present invention, the plating solution is a copper sulfate plating solution, and the portion of the power supply roll in contact with at least the conductive surface of the plastic film substrate. The material is copper.

  According to a preferred embodiment of the plating method two-layer circuit substrate manufacturing method of the present invention, the Vickers hardness of the material of at least the portion of the drive roll that contacts the plastic film substrate is higher than that of the metal plated on the plastic film. The material of the drive roller at least in contact with the plastic film substrate is Vickers hardness (Hv) of 150 or more.

  In the present invention, the plastic film substrate is suitably used for a long plastic film substrate. The long length is usually used for a film substrate having a width of 5 m or less and a length of 10 m or more.

  According to the present invention, preferably, the conductive metal layers provided on both sides of the long plastic film base are electrically connected to each other, and the power feeding means is from only one side of the long plastic film base. By supplying power, electrolytic plating can be performed on both sides of the long plastic film substrate.

  According to the present invention, when a metal such as copper is adhered to both sides of a long plastic film substrate, an insulating film with a metal layer and a circuit substrate having few surface defects such as protrusions and depressions on the plating surface can be obtained.

  A method for producing a plating method two-layer circuit substrate of the present invention and a plating apparatus suitable for producing the plating method two-layer circuit substrate will be described with reference to the drawings.

  In the method for producing a plating method two-layer circuit substrate of the present invention, a plating apparatus as shown in FIG. 1 is used. FIG. 1 is a perspective cross-sectional view for illustrating the structure of a plating solution tank and a power supply unit of a plating apparatus of the present invention.

  In FIG. 1, a plating solution tank 6 in the power supply unit 7 is a part that accommodates a plating solution. A pair of side walls facing the plating solution tank 6 are provided with slits through which a long plastic film substrate 1 described later can enter and exit. The plating solution tank 6 is usually provided with an anode 2 as an electrode immersed in the plating solution. The anode 2 can be installed on one side or both sides according to the surface of the long plastic film substrate 1 to be plated. In the present invention, the anode 2 needs to be installed on both sides in order to provide the metal layers on both sides of the long plastic film substrate 1. The conveying means immerses the long plastic film substrate 1 in the plating solution in the plating solution tank 6 while conveying the long plastic film substrate 1 to be plated in the longitudinal direction with the width direction facing up and down. Means. In the plating apparatus shown in FIG. 1, the driving roll 3 corresponds to a conveying means, and rotates with a driving force, so that the long plastic film substrate 1 and the auxiliary roll 5 facing the plated circuit substrate are opposed to each other. And conveyed in the direction indicated by the arrow MD (hereinafter sometimes referred to as the conveyance direction MD). Further, if necessary, an auxiliary roll 5 is additionally installed in the vicinity of the drive roll 3 or the power supply roll 4, and an appropriate holding angle is provided between the long plastic film substrate 1 and the drive roll 3 or the power supply roll 4. May be allowed.

  The drive roll 3 is preferably made of a material having corrosion resistance to the plating solution because it prevents the roll material from deteriorating due to contact with the plating solution. In the present invention, “having corrosion resistance” means that there is no weight change or discoloration for 6 months in the immersion test using a plating solution. When the roll deteriorates due to the plating solution, the roll surface roughness and roll diameter change, and the long plastic film substrate 1 cannot be stably conveyed. Therefore, it is particularly preferable that the driving roll 3 is disposed outside the plating solution tank 6 to avoid contact with the plating solution.

  Further, it is desirable that the drive roll 3 has a Vickers hardness higher than that of the metal plated on the long plastic film substrate 1. In the case of copper sulfate plating, since the Vickers hardness of copper is about 46, the material of the drive roll 3 should be higher than this, preferably 100 or more, and more preferably 150 or more. Higher hardness is better, but it is not preferable that brittleness develops, so about 1500 is considered the upper limit.

  If the material of the surface of the driving roll 3 is lower than the metal to be plated, the surface of the driving roll 3 is scratched by the metal plated on the long plastic film substrate 1, and the long plastic film substrate 1 or circuit is damaged. The substrate is not preferable because it may cause meandering and wrinkling.

  The power supply electrode is an electrode that is in electrical contact with the long plastic film substrate 1 and supplies power so that a portion of the long plastic film substrate 1 to be plated serves as a cathode for the anode 2 described above. In the apparatus illustrated in FIG. 1, the power supply roll 4 corresponds to a power supply electrode. In the present invention, the power supply roll 4 is in contact with only one surface of the long plastic film substrate 1 (that is, power is supplied from only one surface) and is positioned on the same side as the drive roll 3. Is desirable.

Furthermore, the feed roll 4 is preferably made of a material having a specific electric resistance of 30 × 10 ⁻⁶ Ω / cm or less. If a material having a specific electric resistance exceeding 30 × 10 ⁻⁶ Ω / cm is used as the power supply roll 4, heat generation when energized increases, which may cause problems in continuous processing. Furthermore, when the plating solution is a copper sulfate solution, the roll material is preferably copper.

  Similarly to the drive roll 3, the auxiliary roll 5 is also preferably made of a material having corrosion resistance to the plating solution, in order to prevent the roll material from being deteriorated by contact with the plating solution.

  For the purpose of the drive roll 3, the power supply roll 4, and the auxiliary roll 5, at least the portion that contacts the long plastic film substrate 1 may be the above material, and the material of the portion that does not contact the long plastic film substrate 1 is Not specified.

  Further, if the drive roll 3, the power supply roll 4 and the auxiliary roll 5 arranged outside the plating solution tank 6 can be washed away with water or the like, it is possible to prevent deterioration due to adhesion of the plating solution, which is a more preferable embodiment.

  The plating apparatus can increase the number of plating baths according to the thickness of the target conductive layer and the speed of the long plastic film substrate 1 to be conveyed. At that time, the long plastic film substrate 1 and the circuit substrate can be stably conveyed by configuring the power supply unit 7 having the conveyance / power supply rolls on both sides of the plating bath as one unit.

  Using such a plating apparatus, the long plastic film substrate 1 can be plated by filling the plating solution tank 6 with the plating solution and passing a current between the anode 2 and the power feeding electrode.

  FIG. 2 is a schematic cross-sectional view for illustrating the long plastic film substrate 1 used in the present invention. In FIG. 2, a long plastic film substrate 1 used in the present invention is composed of an insulating film 8 and a conductive layer 9. For the insulating film 8, a known resin material typified by polyimide resin or polyester resin can be used, and additives, lubricants, plasticizers and the like may be added as necessary. The conductive layer 9 may be a metal such as copper, gold, silver, nickel and chromium, or an alloy or a laminate thereof, and may be formed on the insulating film 8 by a method such as a sputtering method, a vacuum evaporation method, or an electroless plating method. However, a sputtering method is preferably used in that the adhesion between the insulating film 8 and the metal layer 10 described later can be increased.

  In the present invention, it is necessary that the conductive layer 9 is electrically connected on both sides of the long plastic film substrate 1. In the case of FIG. 2, the entire insulating film 8 is covered with the conductive layer 9, but both surfaces may be connected using staples or the like near the end.

  The thickness of the insulating film 8 in the present invention is preferably 10 μm or more from the viewpoint of transportability, and the upper limit of the concept of the insulating film 8 is 200 μm at most. In addition, the lower limit of the thickness of the conductive layer 9 provided on the insulating film 8 is not particularly limited as long as the electric resistance value becomes 1Ω or less during the plating process. The upper limit for good productivity and good productivity is 5000 angstroms. The long plastic film substrate 1 used in the present invention needs to be provided with metal conductive layers 9 on both sides, and the metal conductive layers 9 on both sides must be electrically connected. Thus, both sides can be plated by power feeding from one side.

  The long plastic film substrate 1 is preferably subjected to pretreatment such as acid treatment, degreasing treatment, and water washing treatment before introducing the plating bath.

  FIG. 3 is a schematic cross-sectional view for illustrating the plating method two-layer circuit substrate obtained by the plating method two-layer circuit substrate manufacturing method of the present invention. In FIG. 3, a conductive layer 9 (in the example of FIG. 3, a lower nickel chrome layer and a sputtered copper layer thereon) is formed on both surfaces of the insulating film 8 by a dry plating method such as sputtering or vacuum deposition. In the present invention, it is necessary that the metal layers 10 on both sides are electrically connected. In FIG. 3, the side surfaces of the insulating film 8 are dry-plated, so that both surfaces are electrically connected. Yes.

  After performing plating treatment with the current applied adjusted to the desired thickness in the plating bath, post-processing steps such as washing bath, rust prevention treatment, and drying to remove the plating solution were performed as necessary. Thereafter, the intended plating method two-layer type circuit material (substrate) can be obtained.

  FIG. 4 is a plan view for illustrating the structure of the plating apparatus of the present invention. In FIG. 4, after the long plastic film 1 set in the unwinding device 15 is unwound and subjected to treatment such as water washing and degreasing in the pretreatment tank 11, a plurality of power supply units 7 illustrated in FIG. Plating is performed in the arranged plating apparatus, and the film is wound around the winding apparatus 16 through the cleaning tank 12, the antirust treatment tank 13, and the drying chamber 14. Rectifiers 1 a, 1 b to 8 a, 8 b are disposed between the anode 2 and the power supply roll 4 in the plating solution layer 6.

  The plating method two-layer circuit base material obtained by the present invention is not only used for a COF (chip on flex) circuit board in which an IC is directly mounted on a film base material, but also a small size such as an IC card, an IC tag antenna circuit, and a mobile phone. It is suitably used for various FPC applications such as thin-film circuit components for electronic devices, electromagnetic shielding materials for flat panel displays, and external conductors for coaxial cables. The circuit pattern formation method is not particularly limited, such as a subtractive method or a semi-additive method.

  Hereinafter, although the manufacturing method of the plating method two-layer circuit base material of this invention is demonstrated as an example, this invention is not limited to these Examples.

(1) Production of long plastic film base material “Kapton” (registered trademark) EN (polyimide film manufactured by Toray DuPont, thickness 38 μm, width 520 mm, length 1500 m) was used as an insulating film. A nickel / chromium layer having a thickness of 300 angstroms was provided on both surfaces of the insulating film by sputtering, and a copper layer having a thickness of 1500 angstroms was further formed thereon to produce a long plastic film substrate with a conductive layer. Adhesive tape is wound around the cooling roll of the sputtering device, both ends of the long plastic film are slightly lifted from the roll surface, and both sides of the long plastic film are electrically connected by adhering sputter metal to the edge part. It was.

(2) Selection of roll material In order to select a roll material, the immersion test by the copper sulfate plating solution was done using the metal test piece (Thickness 1mm, size 80mm x 80mm). Test pieces of the materials shown in Table 1 were immersed at a temperature of 25 ° C. for a maximum of 6 months, and weight change and discoloration during that period were evaluated. As a result, it was found that the SUS-based material or the tungsten-based thermal spraying treatment was a material having no change in weight and discoloration for 6 months and having corrosion resistance to the plating solution.

(3) Evaluation of surface quality The surface of a copper film of a polyimide film with a copper film (50 mm × 500 mm) was observed with a stereomicroscope (× 40), and surface defects having a size of 30 μm or more were counted. Further, these defects were measured with a laser microscope (VK8500 manufactured by Keyence Corporation) to determine whether the defects were protrusions or depressions. The copper layer of the uneven part detected here is removed by etching, and defects due to the uneven part of the polyimide surface are omitted and not counted.

Example 1
Using a circular tube made of SUS316 having an outer diameter of 80 mm and a wall thickness of 5 mm, a roll having a length of 600 mm was produced as a drive roll 3 and an auxiliary roll 5. Moreover, the feed roll 4 was similarly produced using the copper pipe of the same dimension specification. Using these rolls, a power supply unit 7 was produced and arranged before and after the plating bath 6 as shown in FIG. 8 units were made continuous, and before and after that, a plating apparatus (circuit base material manufacturing apparatus) shown in FIG. 4 in which an unwinding device 15 and a winding device 16, a pretreatment tank 11 and a posttreatment tank were installed was produced. .

  Using this plating apparatus, copper was used for the anode (anode), a copper sulfate plating solution was used for the electrolytic solution, and electrolytic copper plating with a thickness of 4 μm was performed on both surfaces of the long plastic film substrate. . The conveyance speed of the long plastic film substrate is 0.8 m / min, and the composition and electrolysis conditions of the copper electrolyte are as shown in Tables 2 and 3.

  Table 4 shows the results of evaluating the surface quality of the obtained plating method two-layer type circuit substrate (FIG. 3) in accordance with the above method. In the evaluation, the side in contact with the auxiliary roll in FIG. 4 was defined as A surface, and the surface in contact with the power supply roll and the drive roll was defined as B surface.

(Example 2)
A polyimide film-coated polyimide film was produced in the same manner as in Example 1 except that the spray roll in Table 1 was used as the drive roll. As a result, the surface quality was excellent as shown in Table 4, and the quality could be maintained even after 6 months of production.

(Comparative Example 1)
In FIG. 4, a polyimide film with a double-sided copper film was prepared in the same manner as in Example 1 except that the auxiliary roll 5 was entirely replaced with a copper power supply roll and the electrodes were connected and power was supplied from both sides.

(Comparative Example 2)
In FIG. 4, a polyimide film with a double-sided copper film was prepared in the same manner as in Example 1 except that the drive roll was a copper roll and power was supplied from the drive.

(Comparative Example 3)
A double-sided copper film is formed in the same manner as in Example 1 except that a horizontal transfer type plating solution tank 6 as shown in FIG. 5 is incorporated in place of the vertical plating solution tank, using the same plating apparatus as in FIG. An attached polyimide film was prepared. In FIG. 5, SUS316 is used for the power supply roll 4, and is driven by a motor.

  Table 4 shows the evaluation results of Examples 1-2 and Comparative Examples 1-3.

  Those within the scope of the present invention had excellent surface quality as shown in Table 4 and were able to maintain the quality even after 6 months of production.

FIG. 1 is a perspective sectional view for illustrating the structure of a plating solution tank and a power supply unit of a plating apparatus according to the present invention. FIG. 2 is a schematic cross-sectional view for illustrating the long plastic film substrate used in the present invention. FIG. 3 is a schematic cross-sectional view for illustrating the plating method two-layer circuit substrate obtained by the plating method two-layer circuit substrate manufacturing method of the present invention. FIG. 4 is a plan view for illustrating the structure of the plating apparatus of the present invention. FIG. 5 is a side sectional view for explaining the structure of a conventional horizontal conveyance type plating apparatus used in Comparative Example 3.

Explanation of symbols

-Long plastic film substrate-Anode-Drive roll-Feed roll-Auxiliary roll-Plating bath-Feed unit-Insulating film-Conductive layer Metal layer 11. Pretreatment tank 12. Washing tank 13. Anti-rust treatment tank 14. Drying chamber 15. Unwinding device 16. Winding device 1a, 1b, ~ 8a, 8b. rectifier

Claims (5)

A plating solution tank for containing the plating solution, a conveying means for immersing the plastic film substrate in the plating solution in the plating solution tank while conveying the plastic film substrate in the longitudinal direction with the width direction thereof being up and down, and the plastic In the method of manufacturing a circuit base material, a metal plating layer is formed on both surfaces of the plastic film base material using an electroplating apparatus having a power feeding means electrically contacting the conductive surface of the film base material.
The conductive metal layers provided on both surfaces of the plastic film substrate are electrically connected to each other, and an anode (anode) that causes electrolysis with the plastic film substrate is provided inside the plating solution tank. The power supply rolls installed on both sides of the plastic film and used as power supply means (cathode) are installed only on one side of the plastic film substrate, and are electrolyzed on both sides by supplying power from the power supply roll to the plastic film substrate. the plating facilities,
Both a drive roll used as a conveying means and a power supply roll used as a power supply means are provided outside the plating bath, and the power supply roll has substantially no driving force and follows the plastic film substrate being conveyed. A method for producing a two-layer circuit base material by plating, characterized by being rotated by the following method. The method for producing a plating method two-layer circuit substrate according to claim 1 , wherein the driving roll and the power supply roll are on the same surface side of the long plastic film substrate to be plated. The plating method according to claim 1 or 2 , wherein the plating solution is a copper sulfate plating solution, and the material of the portion of the power supply roll that contacts at least the conductive surface of the plastic film substrate is copper. A method of manufacturing the material. The plating method according to any one of claims 1 to 3 , wherein a Vickers hardness of a material of at least a portion of the driving roll that contacts the long plastic film base is higher than a metal plated on the plastic film. A method for producing a two-layer circuit substrate. Plating two layers circuit group according to any one of claims 1 to 4, at least the material of the part in contact with the lengthwise plastic film substrate of the drive rolls is equal to or is a Vickers hardness (Hv) 0.99 or more A method of manufacturing the material.

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