JPH10256736A - Multilayer wiring board and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer wiring board and manufacture thereof, whereby no inferior appearance occurs due to the discoloration of the roughened surface of a Cu conductor circuit which is covered with an insulation resin layer and insulation performance deterioration is little after the moisture absorption. SOLUTION: A metal film 4, dissimilar to Cu is formed on the roughened surface of a Cu conductor circuit 2 with an insulation resin layer 5 covering the metal film 4, which is made of Pd, Sn or Ni and 0.01-2.0μm thick. After roughening the surface of the circuit 2, the metal film 4 is formed and insulation resin layer 5 covering the metal film 4 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer wiring board capable of preventing deterioration such as discoloration of a copper conductor circuit covered with an insulating resin layer and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, multilayer wiring boards used in electronic equipment and electric equipment are constructed by laminating a semi-cured prepreg by impregnating a base material with a resin on a surface of a circuit board for an inner layer on which a copper conductor circuit is formed. It is manufactured by laminating an outer layer substrate or a copper foil on the outside and heating and pressing. In recent years, higher density, smaller size of equipment,
Along with the reduction in thickness, a build-up method in which an insulating resin layer between conductor layers is formed only with a resin component such as an epoxy resin instead of a prepreg containing a base material such as a glass cloth has been studied. The method of forming an insulating resin layer between conductor layers in the build-up method includes a method of applying a resin with a flow coater, a screen printing method, a method of using a resin film,
There is a method of using a resin-attached copper foil which has been preliminarily applied with a resin to a copper foil to be in a semi-cured state.

In the case of a conventional multi-layer system using a prepreg, in order to improve the adhesion between the inner copper conductor circuit and the insulating resin layer, the copper conductor circuit of the inner layer circuit board is called a blackening treatment. Oxidation treatment was the mainstream, but due to environmental issues and demands for simplification of treatment and shortening of treatment time, the surface of the copper conductor circuit was roughened by soft etching or plating instead of blackening treatment. A method to make it is being studied. Also, in the build-up method, the method of roughening the surface of the copper conductor circuit by soft etching or plating may have better adhesion between the copper conductor circuit and the insulating resin layer than the method of blackening treatment. Have been.

[0004] However, when the surface of the copper conductor circuit is roughened by soft etching or plating, the surface of the copper conductor circuit becomes pure unoxidized copper after the roughening. In the meantime, it oxidizes even at room temperature due to moisture absorption,
Discoloration occurs. Also, when forming the insulating resin layer,
Since the high-temperature heating of about 100 to 250 ° C. is performed, the surface of the copper conductor circuit is oxidized by the high-temperature heating, and deterioration such as discoloration proceeds. Deterioration such as discoloration on the surface of the copper conductor circuit may be a cause of poor appearance of the multilayer wiring board as a final product, or may degrade the insulating resin and significantly increase the insulation performance of the multilayer wiring board after the moisture absorption treatment. Therefore, a multilayer wiring board capable of preventing deterioration such as discoloration on the surface of a copper conductor circuit and a method for manufacturing the same are required.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a roughened copper conductor circuit covered with an insulating resin layer. To provide a multilayer wiring board in which deterioration such as discoloration does not occur on the surface, so that appearance defects due to discoloration of the surface of the copper conductor circuit do not occur, and insulation performance after the moisture absorption treatment is less deteriorated; It is to provide a manufacturing method thereof.

[0006]

According to a first aspect of the present invention, there is provided a multilayer wiring board in which a metal film of a metal different from copper is formed on a surface of a copper conductor circuit subjected to a roughening treatment, and the surface of the metal film is further formed. It is a multilayer wiring board on which an insulating resin layer to be coated is formed.

A multilayer wiring board according to a second aspect of the present invention is characterized in that, in the multilayer wiring board according to the first aspect, the metal different from copper is any one of palladium, tin and nickel.

According to a third aspect of the present invention, in the multilayer wiring board according to the first or second aspect, the thickness of the metal film different from copper is 0.01 to 2.0 μm. It is characterized by the following.

According to a fourth aspect of the invention, there is provided a method for manufacturing a multilayer wiring board, comprising the steps of roughening a surface of a copper conductor circuit, and forming a metal film of a metal different from copper on the surface of the roughened copper conductor circuit. And then forming an insulating resin layer covering the surface of the metal film.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a multilayer wiring board, comprising the steps of:
The method of roughening the copper conductor circuit is plating.

According to a sixth aspect of the present invention, there is provided a method of manufacturing a multilayer wiring board, comprising the steps of:
The method of roughening the copper conductor circuit is a soft etching process.

According to a seventh aspect of the present invention, in the method of manufacturing a multilayer wiring board according to any one of the fourth to sixth aspects, a metal film of a metal different from copper is formed. The method is characterized by electroless plating.

In the multilayer wiring board according to the first to third aspects of the present invention, a metal film different from copper is formed on the surface of the roughened copper conductor circuit, and the surface of the metal film is coated. Since the insulating resin layer is formed, the surface of the roughened copper conductor circuit hardly undergoes deterioration such as discoloration.

In the method for manufacturing a multilayer wiring board according to the present invention, after roughening the surface of the copper conductor circuit, the surface of the roughened copper conductor circuit is different from copper. Since a multi-layer wiring board is manufactured by forming a metal film of a metal and then forming an insulating resin layer covering the surface of the metal film, deterioration of the surface of the roughened copper conductor circuit is unlikely to occur. It becomes possible to manufacture a multilayer wiring board.

[0015] The soft etching referred to here is:
This indicates partial etching (etching that only removes a metal to be etched to a certain depth), in which the metal to be etched is removed to a certain depth but not all of the metal.

[0016]

Embodiments of the present invention will be described with reference to the drawings. The embodiment shown in the drawings shows a method of manufacturing a multilayer wiring board by a build-up method,
The present invention can be applied to a multilayer wiring board of a batch multilayer system using a prepreg as an adhesive layer and a method of manufacturing the same. FIG.
(A)-(c) is sectional drawing for demonstrating the multilayer wiring board which concerns on this Embodiment, and its manufacturing method. FIG.
As shown in (a), in this embodiment, an inner layer circuit board 1 having a copper conductor circuit 2 on its surface is prepared. The inner layer circuit board 1 can be manufactured by processing a copper-clad laminate in which a prepreg obtained by impregnating a resin such as a glass cloth with a resin and a copper foil are laminated. Examples of the resin include a single product, a modified product, and a mixture such as an epoxy resin, a polyimide resin, a phenol resin, and a PPO resin. The substrate is not particularly limited, but a substrate made of an inorganic material such as glass fiber is preferable because of its excellent heat resistance and hygroscopicity. In addition, a substrate made of organic fibers having excellent heat resistance,
A substrate composed of organic fibers and inorganic fibers having excellent heat resistance can also be used. Furthermore, the circuit board 1 for the inner layer may be an inorganic substrate such as alumina, a substrate such as a flexible substrate such as a polyimide film, which does not use a base material, or a substrate in which a filler or the like is mixed.

The copper conductor circuit 2 can be formed by a subtractive method, an additive method, or the like, and the copper conductor circuit 2 is subjected to a roughening process. This roughening treatment can be performed by a method such as soft etching or plating. In particular, the roughening treatment by soft etching is a desirable method because the liquid management is simple and the treatment speed is high. As an etching system used for soft etching, for example, an oxidation-reduction reaction such as a cupric chloride system, a ferric chloride system, a sulfuric acid-hydrogen peroxide system, a sodium persulfate system, a potassium persulfate system, and an organic acid system is used. Are preferred. On the other hand, in the roughening treatment by plating, for example, bump-like projections are formed on the copper conductor circuit 2 by electroless plating or electroplating to roughen the surface.

Before forming the insulating resin layer on the copper conductor circuit 2 whose surface is roughened, a metal film 4 of a metal different from copper is formed on the copper conductor circuit 2 as shown in FIG. . As a metal different from copper, for example, gold, nickel, tin, palladium, zinc, lead or the like is preferably used from the viewpoint of preventing deterioration such as discoloration due to oxidation of the copper conductor circuit 2. And, from the viewpoint of cost and easiness of film formation, it is more preferable to use any of palladium, tin and nickel. The thickness of the metal film 4 made of a metal different from copper is 0.01 μm or more in terms of adhesion between the inner circuit board 1 and the insulating resin layer and prevention of deterioration such as discoloration due to oxidation of the copper conductor circuit 2. It is preferable that the thickness be more than 2.0 μm, and the effect is not expected to increase even if the thickness exceeds 2.0 μm. Therefore, the thickness is preferably in the range of 0.01 to 2.0 μm.

The method of forming the metal film 4 of a metal different from copper is not particularly limited, but is preferably formed by electroless plating. This is because when the metal film 4 is formed by electroless plating, the inner-layer circuit board 1 is formed.
This is because, even if there is an independent circuit in the copper conductor circuit 2, there is no need to draw out a lead wire for conducting as in the case of electroplating. In recent years, thinning of wiring patterns has been progressing for higher density, and there is often no room to lead out lead wires. Therefore, the usefulness of forming the metal film 4 by electroless plating is increasing.

On the inner layer circuit board 1 in which the metal film 4 of a metal different from copper is formed on the copper conductor circuit 2 in this manner, FIG.
As shown in (c), the insulating resin layer 5 is formed. Examples of the method of forming the insulating resin layer 5 include a method of applying a resin by a flow coater, a screen printing method, a method of using a resin film or a prepreg, and a resin-coated copper foil which has been previously applied to a copper foil to be in a semi-cured state. And the like. Next, as shown in FIG. 1C, a hole 6 for disposing a conductor for connecting the conductor layers to the insulating resin layer 5 is formed,
Next, the hole 6 is filled with a conductor, and then a new copper conductor circuit 3 is formed on the insulating resin layer 5 to obtain a multilayer wiring board. As a method of filling the hole 6 with a conductor, for example, a plating method,
It can be performed by a paste method. As a method for forming a new copper conductor circuit 3, a plating method or a method using a resin-coated copper foil when forming the insulating resin layer 5 is used. An example of the method of formation is given. In order to prevent the surface of the newly formed copper conductor circuit 3 from being deteriorated by oxidation or the like, for example, a method such as applying a resist such as a solder resist may be used, and there is no particular limitation.

In the multilayer wiring board thus obtained, a metal layer of a metal different from copper, such as palladium, is formed on the surface of the inner copper conductor circuit 2 covered with the insulating resin layer 5. The surface of the copper conductor circuit 2 changes over time or is oxidized by heating when the insulating resin layer 5 is formed, and deterioration such as discoloration does not progress. Therefore, there is no appearance defect of the multilayer wiring board caused by the discoloration of the copper conductor circuit 2, and the insulating resin layer 5 is deteriorated in terms of performance, and the insulation performance of the multilayer wiring board after the moisture absorption processing is greatly reduced. No longer occurs.

In the above-described embodiment, an example is shown in which the inner layer circuit board 1 having the copper conductor circuit 2 only on one surface is used, but the inner layer circuit board having the copper conductor circuit 2 on both surfaces is used. The present invention can also be applied to a multilayer wiring board manufactured by forming an insulating resin layer on both surfaces of the above.

[0023]

Next, the present invention will be described based on embodiments.

(Example 1) A copper conductor circuit was formed by etching using a 0.8 mm thick epoxy resin glass cloth laminate (manufactured by Matsushita Electric Works Co., Ltd., product number R-1700) on which copper foil having a thickness of 18 μm was disposed on one side. Was formed to obtain an inner layer circuit board. The inner layer circuit board was subjected to soft etching with an etching depth of 4 μm using an organic acid-based etchant (manufactured by MEC Co., Ltd., product number CZ-5452) to roughen the surface of the copper conductor circuit. Next, a palladium metal film having a thickness of 0.02 μm was formed on the surface of the roughened copper conductor circuit by an electroless plating method using a trade name system manufactured by Atotech Japan KK. A liquid epoxy resin composition is applied with a flow coater on the surface of the obtained inner layer circuit board on which the copper conductor circuits are arranged, and is applied at 110 ° C. for 30 minutes, then at 150 ° C. for 20 minutes, and further at 170 ° C. It was heated and cured in a drier for 90 minutes, and an insulating resin layer was formed on the entire surface of the inner layer circuit board on which the copper conductor circuits were arranged. The liquid epoxy resin composition was mainly composed of a bisphenol A type epoxy resin, and was made of the same material as the resin composition used for the inner layer circuit board.

Next, a via hole having a diameter of 150 μm was formed by a carbon dioxide laser as a hole for disposing a conductor for connecting the conductor layer to the insulating resin layer. Then, in order to improve the adhesion between the new copper conductor and the insulating resin layer by plating to be formed, the surface of the insulating resin layer including the wall surface of the via hole is coated with a potassium permanganate solution (manufactured by Shipley Co., Ltd.). ), A copper conductor layer filled with via holes and having a thickness of 18 μm on the insulating resin layer was formed by plating. Next, a circuit was formed on the copper conductor layer by etching, and a copper conductor circuit was formed on the surface of the insulating resin layer to obtain a multilayer wiring board.

The multilayer wiring board thus obtained was visually inspected for any external appearance defects such as discoloration and color unevenness of the inner copper conductor circuit covered with the insulating resin layer. As shown, no discoloration or color unevenness was observed. Further, in order to evaluate the deterioration of the insulation performance after the moisture absorption treatment, a test was conducted in which the obtained multilayer wiring board was exposed to steam of 2 atm under conditions of a temperature of 121 ° C. and a humidity of 100%. The processing time until the insulation resistance decreased by 1 × 10 ⁸ ohms or less was measured, and the obtained results are shown in Table 1.

(Example 2) On the surface of a copper conductor circuit roughened by soft etching, a tin metal film having a thickness of 0.1 µm was replaced with a tin metal film having a thickness of 0.1 µm by Shipley Co., Ltd. instead of a palladium metal film. A multilayer wiring board was obtained in the same manner as in Example 1 except that the multilayer wiring board was formed by an electroless plating method using Positive LT-34. The deterioration of the insulation performance was evaluated later, and the obtained results are shown in Table 1.

Example 3 A multilayer wiring board was formed in the same manner as in Example 1 except that a palladium metal film having a thickness of 2 μm was formed on the surface of a copper conductor circuit roughened by soft etching. Then, the multilayer wiring board obtained in the same manner as in Example 1 was evaluated for poor appearance and deterioration of insulation performance after moisture absorption treatment, and the obtained results are shown in Table 1.

Embodiment 4 Instead of roughening the surface of a copper conductor circuit by soft etching, the surface of the copper conductor circuit is subjected to electroless copper plating to form bumps made of copper (having a bump diameter of 2). Except that the multilayer wiring board was obtained in the same manner as in Example 1 except that the multilayer wiring board was formed and roughened. The deterioration of the insulation performance was evaluated, and the obtained results are shown in Table 1.

Comparative Example 1 The surface of a copper conductor circuit roughened by soft etching was not formed on the surface of a metal film such as palladium different from copper, that is, the surface of the copper conductor circuit was merely roughened. , A multilayer wiring board was obtained in the same manner as in Example 1 except that the insulating resin layer was formed on the entire surface of the inner layer circuit board on which the copper conductor circuits were arranged. The multilayer wiring board obtained in the same manner as described above was evaluated for poor appearance and deterioration of insulation performance after the moisture absorption treatment, and the obtained results are shown in Table 1.

[0031]

[Table 1]

From the results shown in Table 1, it can be seen from Examples 1 to 4 that the appearance failure due to the discoloration of the surface of the copper conductor circuit in the inner layer did not occur, and that after the moisture absorption treatment, as compared with Comparative Example 1, It was confirmed that a multilayer wiring board with a small degree of deterioration of the insulation performance was obtained.

[0033]

In the multilayer wiring board according to the first to third aspects of the present invention, a metal film different from copper is formed on the surface of the roughened copper conductor circuit, and the surface of the metal film is further formed. Since the insulating resin layer to be coated is formed, deterioration such as discoloration is unlikely to occur on the surface of the roughened copper conductor circuit. Therefore, the multilayer wiring board according to the first to third aspects of the present invention does not cause appearance defects due to discoloration of the surface of the copper conductor circuit in the inner layer, and has a small degree of deterioration of insulation performance after moisture absorption processing. This has a useful effect.

In the method for manufacturing a multilayer wiring board of the invention according to claims 4 to 7, after roughening the surface of the copper conductor circuit, the surface of the roughened copper conductor circuit is different from copper. A metal film of a metal is formed, and then an insulating resin layer covering the surface of the metal film is formed to manufacture a multilayer wiring board. Therefore, according to the method for manufacturing a multilayer wiring board of the invention according to claims 4 to 7, the appearance defect due to the discoloration of the surface of the copper conductor circuit in the inner layer does not occur, and the insulation after the moisture absorption processing is performed. It is possible to manufacture a multilayer wiring board with a small degree of performance deterioration.

[Brief description of the drawings]

FIGS. 1A to 1C are cross-sectional views illustrating a manufacturing process according to an embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 inner layer circuit board 2 copper conductor circuit 3 copper conductor circuit 4 metal film 5 insulating resin layer 6 hole

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shoichi Fujimori 1048 Kadoma Kadoma, Kadoma City, Osaka Pref. (72) Inventor Kiyoaki Ihara 1048 Kazuma Kadoma, Kadoma-shi, Osaka Prefecture Inside Matsushita Electric Works, Ltd. (72) Inventor Shuji Maeda 1048 Kadoma Kadoma, Kadoma-shi, Osaka Prefecture Inside Matsushita Electric Works, Ltd. (72) Inventor Satoru Ogawa 1048 Okadoma Kadoma, Kadoma City, Osaka Prefecture (72) Yoshihiro Nakagawa, Inventor Yoshihiro Nakagawa 1048 Okadoma Kadoma, Kadoma City, Osaka Prefecture (72) Inventor Masayuki Ishihara 1048 Okadoma Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Works, Ltd.

Claims (7)

[Claims] 1. A multilayer wiring board comprising: a metal film of a metal different from copper formed on a surface of a roughened copper conductor circuit; and an insulating resin layer covering the surface of the metal film. 2. The multilayer wiring board according to claim 1, wherein the metal different from copper is one of palladium, tin and nickel. 3. The metal film of a metal different from copper has a thickness of 0.
3. The multilayer wiring board according to claim 1, wherein the thickness is from 0.01 to 2.0 [mu] m. 4. After roughening the surface of the copper conductor circuit, a metal film of a metal different from copper is formed on the surface of the roughened copper conductor circuit, and then an insulating film covering the surface of the metal film is formed. A method for manufacturing a multilayer wiring board, comprising forming a resin layer. 5. The method for manufacturing a multilayer wiring board according to claim 4, wherein the method of roughening the copper conductor circuit is plating. 6. The method for manufacturing a multilayer wiring board according to claim 4, wherein the method of roughening the copper conductor circuit is a soft etching process. 7. The method for manufacturing a multilayer wiring board according to claim 4, wherein the method for forming a metal film of a metal different from copper is electroless plating.