JPH03225994A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To increase a bonding force by a method wherein a metal foil is removed from an insulating organic base material, the uneven shape of the metal foil is transcribed to the surface of the insulating organic base material, a low-temperature plasma treatment is executed to the transcribed face, a catalyst treatment to execute an electroless plating operation is executed and a conductive metal is plated to be in a desired thickness by the electroless plating operation. CONSTITUTION:Not only an ordinary electrolytic copper foil or an ordinary rolled copper foil, but also a desired roughened foil which is obtained, e.g. by plating or by etching the surface of a stainless-steel foil is used as a metal foil. As an insulating organic material, a glass cloth prepreg which is laminated on the metal foil or the metal foil which is coated directly with an insulating resin and is hardened can be used. The bonding force to the electroless plated metal is ensured not only by the physical shape effect by a transcribed and roughened face but also by the chemical bonding strength between a board and the plated metal (including a catalyst) which has been given by a low-temperature plasma treatment. Even when the uneven shape on the transcribed and roughened face is made small, the bonding force between the board and the plated metal is not lowered remarkably.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a printed wiring board by an additive method.

(Prior art) As a method for manufacturing printed wiring boards using the additive method,
Broadly speaking, there is a fully additive method in which wiring of a desired thickness is formed on an insulating substrate by electroless plating, and a method in which a thin base metal layer is formed on an insulating substrate by electroless plating, and plating resist image formation - pattern electroplating → There is a semi-additive method in which wiring is processed by removing a plating resist image and then quick etching.

In manufacturing printed wiring boards by the additive method, the adhesive strength between the insulating substrate and the wiring metal is extremely important for the various characteristics of the wiring board.

Therefore, in the additive method, as a method to ensure adhesive strength, the insulating substrate or the resin layer provided on the insulating substrate is treated physically or chemically to make the surface hydrophilic or rough. This process is essential.

However, most of the roughening solutions that can be used contain oxidizing agents and are highly toxic. Furthermore, the heat resistance of the resin layer (adhesive layer) is low, and there are limits to its application to multilayer printed wiring boards that require high dimensional accuracy and through-hole connection reliability.

Considering the above problems, after laminating copper foil with a copper oxide film on the surface with prepreg etc., the copper foil is etched to simultaneously create the uneven shape of the copper foil and the fine shape of the copper oxide film on the laminated board. A method has been proposed in which a wiring pattern is formed on the transferred surface by an additive method.

(Problems to be solved by the invention) However, even in this method, there are environmental and safety problems because 1) a copper oxide treatment step is required; and 2) copper oxide treatment is usually carried out using a wet method. ■ When forming a resist image on the transfer surface in a post-process, undeveloped resist tends to occur due to the finely roughened shape; ■ In order to form a fine resist image, the unevenness of the roughened transfer surface must be made smaller. If an attempt is made to suppress diffuse reflection on the substrate surface during exposure and development, there are drawbacks such as a significant decrease in the adhesive force between the substrate and the plated metal.

The present invention provides a method for manufacturing printed wiring boards that does not have such problems.

(Means for Solving the Problems) The present invention involves laminating and integrating a metal foil having an uneven surface with an insulating organic base material, and then removing the metal foil from the insulating organic base material by contacting with an etching solution. The uneven shape of the metal foil is transferred to the surface of an insulating organic substrate, the transferred surface is subjected to low-temperature plasma treatment, and a catalyst treatment for electroless plating is applied. This is a method for manufacturing printed wiring boards in which a conductive metal is plated to a desired thickness by plating in the same state or by applying a catalyst treatment for electroless plating, and then using a combination of electroless plating and electroplating.

Metal foils that can be used in the present invention include not only ordinary electrolytic copper foils and rolled copper foils, but also stainless steel foils that have been given a desired roughened shape by plating or etching the surface. be.

The uneven shape is created by forming a copper oxide film, etching a metal foil, or the like.

Examples of insulating organic materials include epoxy, modified polyimide,
It is possible to use a base material such as paper or glass cloth impregnated with a thermosetting resin such as phenol, or a film made of a thermoplastic material such as polyethylene, Teflon, polyether sulfone, or polyetherimide. In addition, substrate materials include not only ordinary copper-clad laminates but also those made by continuously coating and curing a polymer resin on the roughened surface of copper foil (for example, MCF manufactured by Hitachi Chemical Co., Ltd.) 5000-T) etc. can also be applied. As the insulating organic material, a material obtained by laminating a glass cloth prepreg and a metal foil, or a material obtained by directly coating and curing an insulating resin on the metal foil can also be used. In addition to inert gases such as argon, helium, and neon, gases that can be used in low-temperature plasma processing include pure nitrogen, oxygen, air, ammonia, amino type and/or
Alternatively, there are coupling agents that contain imino-type nitrogen in the molecule, diluted with an organic solvent, and then gasified. In order to ensure adhesive strength, it is desirable to perform the treatment under a nitrogen atmosphere.

The catalyst treatment, electroless plating, and electroplating used in the present invention are those generally used in the production of additive printed wiring boards, and palladium, gold, platinum, etc. are used as catalysts. , Copper, nickel, etc. are used as the plating metal.

In the present invention, the adhesive force with the electroless plated metal is not only due to the physical shape effect of the roughened transfer surface, but also due to the chemical bond between the substrate and the plated metal (including the catalyst) provided by low-temperature plasma treatment. Since this is ensured by force, even if the uneven shape of the roughened transfer surface is made smaller, there is no significant decrease in the adhesive force between the substrate and the plated metal as described above. In this case, if reactive ion etching is applied as plasma treatment, it is possible to form fine irregularities in the order of angstroms on the roughened transfer surface with good control, thereby improving the physical shape effect in addition to the chemical bonding of the treated surface. can also be given.

Example 1 A glass cloth-epoxy copper-clad laminate (trade name: MCL E-67) manufactured by Hitachi Chemical Co., Ltd. is prepared, and the copper foil on the surface is removed using an aqueous ammonium persulfate solution. After cleaning and drying the glass epoxy substrate from which the copper foil had been removed, it was subjected to plasma treatment using a PR-501A plasma reactor manufactured by Yamato Scientific Co., Ltd. under the conditions shown below.

Output 150W Gas High purity nitrogen pressure 0.4 Torr Processing time
10 minutes In this case, in addition to the above-mentioned treatments, usable plasma treatments include reactive ion etching and plasma polymerization.

Next, electroless copper plating was performed with the following composition and conditions.

Copper sulfate 10g/I EDTA ・4Na 40g/l pH 12.4 37% formalin 3ml/1 Plating additive Small amount Plating solution temperature 70°C Plating film thickness 10μm Usually, the substrate surface is coated with hydrochloric acid to improve the adsorption of the catalyst to the substrate. Although an etching step with a system solution is required, in the case of the present invention, the substrate surface already has an uneven shape corresponding to the roughened surface of the electrolytic copper foil, and the plasma treatment improves the wettability of the substrate surface. Therefore, an etching process is unnecessary. In addition, it is possible to use a multi-layered substrate using the required number of inner layer substrates and prepreg, or a substrate with drilled holes for through holes.

Next, a desired resist image is formed on the electroless plating layer using a positive liquid resist TF-20 (trade name manufactured by Shipley), electroless plating is applied, and the resist is removed with acetone. A portion of the pattern plating and electroless plating layer was removed with an ammonium sulfate solution. In this case, the line width and space of the wiring is 40 μm
However, by reducing the unevenness of the copper foil,
It is also possible to form ultra-fine interconnections of about 20 μm.

After applying electroless copper plating, the adhesive force to the substrate was measured using a sample in which the total copper thickness was adjusted to 25 μm by electrolytic copper plating. The copper foil was peeled at a width of 10 mm and a peeling speed of 50 mm/min. The measurement result is 1.5
kg/cm, which was good.

Example 2 Direct coat MCF (product name: MC) manufactured by Hitachi Chemical Co., Ltd. was used instead of the copper-clad laminate used in Example 1.
Reactive ion etching treatment was performed using F5000-1) under the conditions shown below as plasma treatment. The device used was a DEM451 reactive ion etching device manufactured by Nikkei Anelva Co., Ltd.
Output: 200 W Gas Ammonia Pressure: 0.1 Torr Processing Time: 10 minutes Next, electroless nickel plating was performed with the following composition and conditions.

Nickel chloride 30g/l Sodium acetate 10g/l Sodium dihydrogen phosphate 10g/l pH5 Plating solution temperature 80°C Plating film thickness 06μm In this case, as in Example 1, the peeling strength after thickening the copper plating was 1.8 kg/cm, which was extremely good.

Following electroless nickel plating, electroless copper plating was applied to a thickness of 1.0 μm, and thereafter a flexible printed wiring board having fine wiring with a line width and space of 40 μm was created using the same semi-additive method as in Example 1. .

(Effects of the Invention) According to the present invention, a printed wiring board with excellent heat resistance and insulation properties and high adhesion of plated metal can be manufactured by an additive method.

Claims (3)

[Claims] 1. A. After a metal foil with an uneven surface is laminated and integrated with an insulating organic base material, the metal foil is removed from the insulating organic base material by contacting with an etching solution, and the uneven shape of the metal foil is replaced with an insulating organic base material. Step of transferring onto the material surface; B. C. performing low temperature plasma treatment on the transfer surface; A method for manufacturing a printed wiring board, comprising the steps of applying a catalyst treatment for electroless plating and plating a conductive metal to a desired thickness by electroless plating. 2. A. After a metal foil with an uneven surface is laminated and integrated with an insulating organic base material, the metal foil is removed from the insulating organic base material by contacting with an etching solution, and the uneven shape of the metal foil is replaced with an insulating organic base material. Step of transferring onto the material surface; B. C. performing low temperature plasma treatment on the transfer surface; A method for manufacturing a printed wiring board, comprising the steps of performing a catalyst treatment for electroless plating, and then plating a conductive metal to a desired thickness by using both electroless plating and electroplating. 3. 3. The method for manufacturing a printed wiring board according to claim 1, wherein the low-temperature plasma treatment is performed in a nitrogen-based gas atmosphere.