JP2004204349A - Flexible multilayered wiring board, and electroplating method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plating method where, at the time when filled via plating of filling blind via holes connecting the upper and lower wiring layers in a multilayered wiring board is carried out by an electroplating device performing reel-to-reel continuous treatment, the filled via plating is made possible without requiring a long time for the via filling. <P>SOLUTION: As for the electroplating method, in a continuous electroplating process where blind via holes connecting the upper and lower wiring layers in a flexible multilayered wiring board in which insulating layers and wiring layers are alternately stacked are filled with plating metal, using a reel to reel continuous electroplating device where a cathode power feed part is arranged inside an electroplating liquid, the cathode power feed part is provided with a shield plate for preventing the precipitation of plating, and a plurality of metallic rollers are set in the cathode power feed part for supporting a substrate so as to closely be stuck, the filled via holes are formed in this way. In the plating device, as the conveyance system of the substrate, a vertical conveyance system is adopted. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a flexible multilayer wiring board having a multilayer structure in which insulating layers and wiring layers made of a resin such as polyimide are alternately laminated, and in particular, is used for an interposer for mounting a semiconductor element, and has a small diameter blind. The present invention relates to a flexible multilayer wiring board in which a filled via hole is formed in a via hole using a reel-to-reel continuous electrolytic plating method and an electrolytic plating method thereof.

  In recent years, in a semiconductor element such as a large scale integrated circuit (LSI), the degree of integration of transistors has increased, and the operating speed of the semiconductor device has reached 1 GHz in terms of clock frequency, and the number of input / output terminals has exceeded 1000. Yes.

  In order to mount a semiconductor element on a printed wiring board, interposers such as BGA and CSP have been developed and put into practical use.

  Such a multilayer wiring board is formed by alternately stacking insulating resin layers and conductor wiring layers on a copper-clad substrate or a ceramic substrate (see, for example, Patent Document 1). The insulating layer of the multilayer wiring board manufactured by this method can be formed and thinned by applying a resin such as polyimide. Further, the wiring layer is formed by a plating method, and fine wiring is possible. On the other hand, the via hole connecting the upper and lower wiring layers can be formed by forming a hole by laser processing or the like and plating the inside of the hole.

  Separately from this, a structure in which a polyimide film with copper foil is bonded to a conventional multilayer printed wiring board with an adhesive has also been proposed (for example, see Patent Document 2). Also in this configuration, it is possible to form fine wiring from the thin copper foil, and similarly, high wiring density, thin film, and miniaturization can be achieved. Furthermore, since it is a tape-like film, reel-to-reel processing is possible and, unlike conventional single wafer processing, production efficiency can be improved.

  On the other hand, in a multilayer printed wiring board, a hole for connecting the upper and lower wiring layers is formed by using a laser processing machine using an excimer laser, a YAG third harmonic, or a fourth harmonic to form a small-diameter blind via hole. It has been broken. The holes connecting the upper and lower wiring layers are formed in order with the upper wiring layer and the insulating layer of the organic insulating material by forming a blind via hole with a laser in order to expose the lower wiring layer surface, and then at the bottom of the bottom of the blind via hole The residue of the organic insulating material deposited on the wiring layer is removed, an electroplating seed layer is formed by electroless plating, etc., and this seed layer is used as an electrode to form a constant thickness on the side wall surface and bottom surface inside the blind via hole. Electrolytic plating is deposited to form via holes.

  In this electroplating process in which electrolytic plating deposition of a certain thickness is performed on the side wall surface and bottom of the inside of the blind via hole, in recent years, filled vias that fill the inside of the blind via hole with electroplated metal for the purpose of passing high-speed signals or increasing the degree of freedom of wiring. A stacked via system in which a filled via hole is formed using plating and a filled via hole is formed directly above the filled via hole is actively used. The filled via plating employs a technique in which an electrolytic plating metal is selectively deposited inside the hole by various additives called polymers, brighteners, and levelers (see, for example, Patent Document 3). When this filled via plating is performed on a tape-shaped substrate such as a polyimide film with a copper foil, an electrolytic plating apparatus that performs continuous processing on a reel-to-reel basis is required.

  In an electroplating apparatus that performs continuous processing on a reel-to-reel basis, if there is a cathode power feeding part in the plating tank, electrolytic plating is deposited on the cathode power feeding part, resulting in problems such as transportation and damage to the substrate. For this reason, a cathode feeding portion is installed in a portion where there is no electrolytic plating solution outside the plating tank. In the case of continuous electrolytic plating equipment, the length of the plating tank is determined according to the electroplating time and conveyance speed. However, in the case where a cathode feeding part is provided at both ends of one plating tank, the plating tank is long. Depending on the resistance of the base material, the voltage becomes very large with respect to the set current during electrolytic plating, and there are problems such as heat generation of the base material. Is often placed.

These power supply parts are arranged at both ends of the plating tank, exist in the air without being immersed in the electrolytic plating solution, and in order to prevent insufficient power supply due to poor contact between the substrate and the power supply part, Etc. are supplied. However, when filled via plating is performed, filled via plating is not possible due to problems such as water supply in the power feeding portion and loss of additives, substrate oxidation, and metal ion concentration in the blind via hole because the power feeding portion is in the air. There is a problem that it takes longer than a normal electrolytic plating time, that is, via filling is delayed.
JP 4-148590 A JP 2001-53115 A Japanese Patent Laid-Open No. 2001-200386

  The present invention has been made in view of the problems of the related art, and filled via plating for filling blind via holes for connecting upper and lower wiring layers of a multilayer wiring board is performed by an electrolytic plating apparatus that performs continuous processing on a reel-to-reel basis. It is an object of the present invention to provide a plating method that enables filled via plating without taking time for via filling.

  In order to achieve the above-mentioned problems in the present invention, the invention according to claim 1 of the present invention is such that an insulating layer made of an organic insulating material and a wiring layer made of a conductor material are alternately stacked, and upper and lower wiring layers are connected. Electrolysis of a flexible multilayer wiring board characterized in that in a reel-to-reel continuous electrolytic plating process in which a blind via hole of a flexible multilayer wiring board having a blind via hole is made conductive by filling with a plating metal, a cathode feeding portion is in an electrolytic plating solution. It is a plating method.

  The invention according to claim 2 of the present invention is characterized in that a shielding plate is provided at the cathode power feeding portion in order to prevent plating deposition at the cathode power feeding portion. It is.

  The invention according to claim 3 of the present invention is the method for electroplating a flexible multilayer wiring board according to claim 1 or 2, wherein the shielding plate provided in the cathode feeding portion is an insulator. is there.

  The invention according to claim 4 of the present invention is the method for electrolytic plating of a flexible multilayer wiring board according to claim 1 or 2, wherein the shielding plate provided in the cathode feeding portion is a conductor.

  The invention according to claim 5 of the present invention is characterized in that the cathode feeding portion is a metal roller, and a plurality of metal rollers are installed on the cathode feeding portion to support and adhere to the substrate. 5. The method for electrolytic plating of a flexible multilayer wiring board according to any one of 4 above.

  In the invention according to claim 6 of the present invention, the cathode feeding portion is a metal roller, the central portion of the outer periphery of the metal roller is covered with an insulator made of an insulating material, and the metal portions at both ends not covered with the insulator The method of electroplating a flexible multilayer wiring board according to any one of claims 1 to 5, characterized in that power is fed at.

  The invention according to claim 7 of the present invention is the electrolysis of a flexible multilayer wiring board according to any one of claims 1 to 6, characterized in that the conveying method in the reel-to-reel continuous electrolytic plating step is vertical conveyance. It is a plating method.

  The invention according to claim 8 of the present invention has a filled via hole formed by using the electrolytic plating method for a flexible multilayer wiring board according to any one of claims 1 to 7. It is a substrate.

  According to the method for manufacturing a multilayer wiring board of the present invention, when filled via plating is performed in a reel-to-reel continuous electrolytic plating apparatus, problems such as heat generation of the substrate, delay in via filling, and defects in the plating surface may occur. Filled via plating is possible, and a flexible multilayer wiring board using the plated via plating and an electrolytic plating method thereof can be provided.

  Hereinafter, embodiments of the present invention will be described in detail. 4 (a) to 4 (f) are process diagrams showing, in cross section (enlarging the blind via hole portion), one embodiment of the electrolytic plating method for the flexible multilayer wiring board according to the present invention.

  As shown in FIG. 4A, upper and lower wirings are formed on a flexible multilayer wiring board having a multilayer structure in which insulating layers (102) made of an organic insulating material and wiring layers (101) made of a conductor material are alternately laminated. Blind via holes connecting the layers are formed. In addition, as long as the base material used for a flexible multilayer wiring board can be reel-to-reel processing, various base materials can be used, but the polyimide film with copper foil which uses polyimide for an insulating material and copper foil for a conductor material is more. preferable. The reason why the polyimide film with copper foil is recommended here is that the insulating layer capable of reel-to-reel processing includes liquid crystal polymer, polyimide resin, polyolefin resin, etc., heat resistance, flexibility, smoothness, low water absorption Polyimide resin is recommended as satisfying The conductor layer may be made of metal and has good conductivity. However, copper is generally preferable from the viewpoint of cost and conductivity, and copper foil having good smoothness such as electrolytic copper foil and rolled copper foil is more preferable. preferable.

  As shown in FIG. 4B, laser processing is preferable for the method of forming blind via holes. There are carbon dioxide laser, YAG (fundamental wave, 2nd harmonic, 3rd harmonic, 4th harmonic) laser, excimer laser, etc., but since both conductor layer and insulating layer are processed, both are processed simultaneously. YAG third harmonic, fourth harmonic, and excimer lasers, which are short wavelength lasers of 400 nm or less that can be used, are more preferable. During laser processing, dross (103) is deposited around the blind via hole in the wiring layer (101), and an organic insulating material residue (104) is deposited under the blind via hole.

  Next, as shown in FIG. 4C, the dross (103) due to the conductive material generated when the blind via hole is formed by the laser in the order of the conductive material and the organic insulating material is removed by physical polishing or chemical polishing.

  Next, as shown in FIG. 4D, the substrate of the organic insulating material (104) deposited in the lower layer of the blind via hole is immersed in a liquid such as a mixture of potassium permanganate and sodium hydroxide, Perform desmear processing.

  Next, as shown in FIG. 4E, in order to form an electroplating seed layer on the resin surface, electroless plating or direct plating is performed to form a seed layer (electroless plating layer (105)).

  In FIG. 4F, electrolytic plating is formed on the electroless plating layer (105) to form an electrolytic plating layer (106) (via hole).

  Next, FIGS. 1A to 1B are side sectional views of the reel-to-reel continuous electrolytic plating apparatus of the present invention. FIG. 1A is a schematic top view of an example of an electroplating apparatus, which includes a take-up reel (201) and a take-up reel (205), with the width direction of the flexible multilayer wiring board being vertical. It is a reel-to-reel continuous electrolytic plating apparatus to be conveyed. Electrolytic plating equipment has a long plating tank in one plating tank. Due to the resistance of the base material, the voltage increases with respect to the set current due to the resistance of the base material, causing problems such as heat generation of the base material. A plurality of (203) are provided, and the cathode power feeding portion (202) is arranged between them. In the plating tank, an anode (204) is arranged on one side or both sides through which the substrate (206) passes. The conveyance method may be horizontal conveyance, but in the case of double-sided plating with horizontal conveyance, an anode is present on the lower side and there is a problem in maintainability, so vertical conveyance is preferable.

  Moreover, FIG.1 (b) is an enlarged top view detail drawing of a plating tank (203), and the nozzle (207) for performing a jet flow is also installed in a plating tank. In the reel-to-reel electroplating apparatus, the film thickness variation in the conveyance direction is averaged by conveyance, but the film thickness variation occurs in the width direction. In particular, since current lines are concentrated at both ends of the substrate, shielding plates (208) are installed on the upper and lower sides of the substrate to prevent the concentration of current lines on the upper and lower portions of the substrate, thereby causing variations in the width direction. To control.

  Next, a plurality of cathode power feeding portions (202), such as two metal rollers (301) as shown in FIG. 2 (a) and three as shown in FIG. 2 (b), are installed using metal rollers. Suppose that the substrate is nipped and the substrate is brought into close contact with the metal roller, thereby preventing power feeding failure and substrate wobbling.

  FIG. 3 is a top view of the plating tank (203), (a) is a conventional one, and (b) is a plating tank of the present invention. Conventionally, the cathode feeding portion (202) has been installed in an air portion that is not immersed in the electrolytic plating solution as shown in FIG. 3 (a). It is not preferable for via filling to leave in the air during electroplating. In the present invention, installation is performed in an electrolytic plating solution as shown in FIG. If the cathode power feeding portion is installed in the electrolytic plating solution as it is, electrolytic plating will be deposited on the cathode power feeding portion, so that the cathode power feeding portion is installed so as to be covered with the shielding plate (209).

  In addition, since this shielding plate is installed in order to prevent electrolytic plating deposition on the cathode feeding portion, it may be an insulator that shields the current line from the anode, or a conductor that is to be electroplated as a dummy substrate. It doesn't matter.

  Moreover, about the metal roller 301 used for this cathode electric power feeding part, even when a shielding plate is installed in a cathode electric power feeding part, there exists a possibility that a plating metal may precipitate. When the plating is deposited on the metal roller, the tape-like substrate causes defects such as a dent due to the deposited plating metal, a protrusion due to the transfer of the plating metal, and subsequent plating deposition abnormality. In order to prevent the above-described defects from occurring, the product portion in the center of the metal roller is wrapped with an insulating material 603 as shown in FIGS. 6A and 6B, and plating is deposited on the center product portion. Do not do it. In this case, the power supply is performed by the conductive portions 602 of the metal roller in contact with both end portions of the tape-like base material.

  Note that when an insulating material is wound around the metal roller 301 at the center of the outer periphery, if it is wound around a flat metal roller, a step occurs at the boundary portion, and a defect such as a fold occurs in the substrate. Step processing is performed, and an insulating material is wound so that the metal portion and the insulating portion are substantially flat.

  As described above, by covering the power supply roller at the central product portion with the insulating material, it is possible to reliably supply power at both ends of the substrate without causing defects in the cathode power supply portion in the plating solution.

  Regarding the electrolytic plating conditions, the transport speed, the cathode current density, and the like that can secure a sufficient electrolytic plating time for filling with respect to the length of the plating tank are used as parameters. The flexible multilayer wiring board formed by such an electrolytic plating method can be filled with blind via holes in an appropriate electrolytic plating time as shown in FIG.

  Hereinafter, the present invention will be described by way of specific examples. In addition, this invention is not limited to the Example mentioned later at all.

  Example 1 will be described with reference to FIGS. A polyimide tape 102 with a double-sided copper foil 101 (Neolex Cu / PI / Cu = 9 μm / 30 μm / 9 μm manufactured by Mitsui Chemicals) was used for the substrate 1. Reference is made to FIG.

  In order to process the blind via hole on the substrate 1, a blind via hole (2) was processed using an ultraviolet laser having a wavelength of 355 nm. The processed blind via hole diameter was 30 μm.

  When the processed blind via hole was observed with an optical microscope, it was confirmed that dross due to via processing was generated at the opening end of the blind via hole. Therefore, physical polishing was performed to remove the dross portion. Thereafter, in order to remove the resin residue deposited on the bottom of the blind via hole, potassium permanganate and sodium hydroxide were dissolved in ion exchange water at a weight ratio of 3 to 2, and heated to about 50 ° C. The substrate was immersed in this mixed solution, and the resin residue was removed.

  Then, in order to form the electroplating seed layer 3, a normal electroless copper plating process was performed.

Electrolytic copper plating was performed with the reel-to-reel continuous electrolytic plating apparatus of the vertical conveyance of the present invention. The length of the plating tank is 3 m, and feed rollers are installed at both ends of the plating tank. Three plating tanks were used. Two cathode power supply portions in which the central portion of the metal roller was covered with a Teflon (registered trademark) heat-shrinkable tube were installed, and an S-shaped nip was performed. The power supply roller was covered with a vinyl chloride shielding plate, and the power supply roller was immersed in the electrolytic plating solution. In the plating tank, anodes were placed on both sides of the substrate, and phosphorus-containing copper balls were placed in a titanium case. In addition, a nozzle for jet flow was installed between the anodes, and a shielding plate for controlling film thickness variation was installed on the upper and lower portions of the substrate with a PVC plate. The composition of the electrolytic plating solution was 200 g / L for copper sulfate pentahydrate, 50 g / L for sulfuric acid, 50 mg / L for chlorine, and 25 ml / L for plating additives. In order to set the electroplating current density and electroplating time to 1 A / dm ² , which allows filled via plating by single wafer processing, and 30 minutes, the conveyance speed was set to 0.3 m / min. Filled via plating (4) was performed on the seed layer (3). Reference is made to FIG.

  When the surface of the conductor layer after plating was observed, no defects such as dents and protrusions were observed on the product surface at the center of the base material.

  Next, in order to form a wiring pattern on both sides, a dry film resist for wiring formation was heated and pressed with a laminator to form a laminated resist layer.

  Next, using a photomask having a predetermined pattern, exposure was performed with parallel light using an ultrahigh pressure mercury lamp as a light source, and development was performed with a 1% by weight aqueous sodium carbonate solution to obtain a desired resist shape.

  Copper was etched by ferric chloride having a specific gravity of 1.50. Thereafter, the resist was stripped with a 3% by weight aqueous sodium hydroxide solution to obtain a circuit pattern (5). Reference is made to FIG.

  Thereafter, polyimide with a single-sided copper foil (Mitsui Chemicals product name Neofrex) was pasted on both sides with a roll laminator via an adhesive, and then filled via holes were similarly formed to form circuits. Reference is made to FIG.

  Next, a pattern is formed on the outer layer portion with a solder resist to form a solder layer (7). Next, nickel gold plating treatment was performed on the opening to form a nickel gold terminal (6) to obtain a flexible multilayer wiring board. Reference is made to FIG.

Thereafter, the cross-section of the substrate was observed, and copper filling defects were investigated in 1250 filled via holes. However, there were 0 defective portions in which via filling was not completed.
<Comparative Example 1>
As Comparative Example 1, the electroplating was performed in the same manner by placing a feeding roller in the air without immersing the electroplating solution in the cathode feeding portion of the electroplating apparatus of Example 1 above. Thereafter, cross-sectional observation of the substrate was performed, but filling was not completed in all filled via holes, and dents remained in the via portions.
<Comparative Example 2>
As Comparative Example 2, the plating tank of the electroplating apparatus was set to 9 m, and cathode feeding rollers were installed at both ends thereof, and electrolytic plating was performed with one plating tank. The cathode feeding roller was installed in the air without being immersed in the electrolytic plating solution. The conveyance speed was 0.3 m / min and the current density was 1 A / dm ² . As a result, since a long plating tank of 9 m was fed, it was confirmed that the voltage increased to a maximum of around 5 V with respect to the set current due to the resistance of the substrate, and the surface temperature of the substrate increased to about 70 ° C. . Therefore, it was determined that it was impossible to feed power to the long plating tank of 9 m only at both ends.
<Comparative Example 3>
As Comparative Example 3, electrolytic plating was performed without covering the outer peripheral central portion of the cathode feeding roller of the electrolytic plating apparatus of Example 1 with an insulating material. Thereafter, when the surface of the conductor layer after plating was observed, dents and protrusions of about 5 to 30 μm were observed. In addition, although this base material was performed to circuit formation, the chip | tip of the circuit and the disconnection had generate | occur | produced by the influence of a dent and a protrusion.

  From the above results, it is difficult to feed a long plating tank only at both ends, so it is necessary to install a cathode feeding roller in the middle, and the cathode feeding roller installed in the middle is not installed in the air, By installing in the liquid and covering the product central part of the cathode power supply roller with an insulator, filling can be performed without defects on the product surface.

It is a top view which shows the reel to reel continuous electroplating apparatus of this invention, (a) is a general view, (b) is the elements on larger scale. It is a top view which shows the cathode electric power feeding part of this invention, (a), (b) is an example. (A)-(b) is a figure which shows the shielding board of the cathode electric power feeding part of this invention. (A)-(f) is a figure which shows the manufacturing process of the multilayer wiring board of this invention. (A)-(f) is a figure which shows the manufacturing process of the flexible multilayer wiring board of one Example of the multilayer wiring board of this invention. It is a figure which shows the cathode electric power feeding roller of this invention, (a) is sectional drawing, (b) is a top view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Board | substrate 2 ... Blind via hole 3 ... Seed layer 4 ... Filled via plating 5 ... Circuit pattern 6 ... Nickel gold terminal 7 ... Solder layer 101 ... Conductive layer 102 ... Insulating layer 103 ... Dross 104 ... Organic insulating material residue 105 ... Electroless plating Layer 106 ... Electrolytic plating layer 201 ... Unwinding reel 202 ... Cathode feeding portion 203 ... Plating tank 204 ... Anode 205 ... Winding reel 206 ... Substrate 207 ... Jet nozzle 208 ... Film thickness control shielding plate 209 ... Cathode feeding portion shielding Plate 210 ... Electrolytic plating solution 301 ... Metal roller 602 ... Conductive material 603 ... Insulating material

Claims (8)

  Reel-to-reel, in which insulating layers made of an organic insulating material and wiring layers made of a conductive material are alternately laminated, and the blind via holes of a flexible multilayer wiring board having blind via holes connecting upper and lower wiring layers are made conductive by filling them with plating metal An electrolytic plating method for a flexible multilayer wiring board, characterized in that, in the continuous electrolytic plating step, the cathode feeding portion is in an electrolytic plating solution.   2. The method of electrolytic plating of a flexible multilayer wiring board according to claim 1, wherein a shielding plate is provided at the cathode power feeding portion in order to prevent plating deposition at the cathode power feeding portion.   3. The method for electrolytic plating of a flexible multilayer wiring board according to claim 1, wherein the shielding plate provided in the cathode power feeding portion is an insulator.   3. The method for electrolytic plating of a flexible multilayer wiring board according to claim 1, wherein the shielding plate provided in the cathode power feeding portion is a conductor.   5. The flexible multilayer wiring according to claim 1, wherein the cathode feeding portion is a metal roller, and a plurality of metal rollers are installed on the cathode feeding portion to support and adhere to the substrate. Electrolytic plating method for substrates.   The cathode feeding part is a metal roller, the central part of the outer periphery of the metal roller is covered with an insulator made of an insulating material, and feeding is performed with the metal parts at both ends not covered with the insulator. The electrolytic plating method for a flexible multilayer wiring board according to any one of 1 to 5 above.   The method for electrolytic plating of a flexible multilayer wiring board according to any one of claims 1 to 6, wherein the conveying method in the reel-to-reel continuous electrolytic plating step is vertical conveyance.   A flexible multilayer wiring board comprising filled via holes formed by using the electrolytic plating method for a flexible multilayer wiring board according to any one of claims 1 to 7.

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