JP2008166720A - Manufacturing method for multilayer printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of selectively applying electroless nickel and electroless gold plating on a fine pattern on a printed wiring board by efficiently removing inorganic filler material remaining on a front layer of an insulating layer after roughening, and controlling abnormal deposition outside of the pattern. <P>SOLUTION: In a method of manufacturing a multilayer printed wiring board, electroless nickel plating and electroless gold plating are selectively applied on a copper pattern on a printed wiring board by: (a) a step of forming an insulating layer including inorganic filler material on an insulating substrate on which a first circuit layer is formed; (b) a step of forming a via hole on the insulating layer reaching the first circuit layer; (c) a step of roughening the front layer of the insulating layer by an oxidizing solution; (d) a step of immersing the front layer of the insulating layer in an alkaline solution of pH10 or more, the alkaline solution being alkali metal hydroxide or alkaline earth metal hydroxide dissolved in water, and removing remaining inorganic filler material; and (e) a step of applying electroless plating on the front layer of the insulating layer and an inner wall of the via hole, and forming interlayer connection by a second circuit layer and the via hole. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a multilayer printed wiring board.

In recent years, semiconductor package substrate technology for interposers has become important, and the demand for fine patterning, pattern adhesion, and high reliability is particularly important in order to realize small size and multiple functions, since narrow pitch connection technology is essential. The semi-additive construction method is mainly applied to such needs (for example, see Patent Document 1).
JP 2006-165094 A

The manufacturing method of the multilayer printed wiring board by a semi-additive construction method consists of the following processes.
Step a: forming an insulating layer on the insulating substrate on which the first circuit layer is formed.
Step b: a step of forming a via hole in the insulating layer.
Step c: Step of roughening the surface of the insulating layer with an oxidizing solution.
Step d: Step of forming an interlayer connection by the second circuit layer and via hole by electroless plating and electroplating on the insulating layer surface and the inner wall of the via hole.
A two-layer printed wiring board is produced by the above process.

  The second circuit layer of the produced two-layer printed wiring board is regarded as the first circuit layer, and a three-layer multilayer printed wiring board is produced by repeating the steps a to d, and so on. Thus, a multilayer printed wiring board is produced by repeating the steps a to d as many times as necessary.

On the other hand, when printed wiring boards using semi-additive method are used for surface mounting applications that require wire bonding, electroless nickel plating and electroless gold plating treatment should be applied to increase wire bonding connection strength and reliability. The technique to apply is common.
When electroless nickel plating and gold plating are performed on a copper pattern of a printed wiring board, the following surface treatment is generally performed.

  First, cleaning treatment of the printed wiring board on which the copper pattern is formed, followed by palladium catalyst treatment, forming catalyst nuclei only on the copper pattern, and further treating with a few percent hydrochloric acid or sulfuric acid aqueous solution to adhere to the extra portions other than the copper pattern To remove palladium.

  Next, an electroless nickel plating treatment is performed, and only nickel plating is applied on the copper pattern to a thickness of 2 to 5 μm, and then a displacement gold plating treatment is performed on the nickel plating film to provide a catalyst for electroless gold plating. Give activity. Finally, electroless gold plating is performed, and gold plating is applied to a thickness of 0.2 to 1 μm.

  A method of adding a large amount of inorganic filler to the resin in order to reduce the thermal expansion coefficient of the insulating resin as much as possible due to the increasing demand for high connection reliability for the insulating material for the semi-additive method, which has excellent microcircuit formability Has been taken.

  However, by adding a large amount of inorganic filler in the resin, the surface of the insulating layer is roughened with an oxidizing solution, and the inorganic filler cannot be completely removed even after a cleaning process by a conditioner treatment. It is increasing.

  For this reason, as the density of printed wiring boards increases and the demand for fine patterns such that line / space = 30/30 μm or less increases, when processing by electroless nickel plating and electroless gold plating methods, Abnormal precipitation of nickel and gold due to insufficient removal of the palladium catalyst is a major problem.

  In particular, when a large amount of the inorganic filler exposed on the surface of the insulating layer remains in the step of (d) roughening the surface layer of the insulating layer with an oxidizing treatment liquid by a semi-additive method, the surface of the inorganic filler or the resin / inorganic filler The palladium catalyst adhered to the interface, and the palladium catalyst was not sufficiently removed even by treatment with several percent of hydrochloric acid or sulfuric acid aqueous solution, which was a major cause of out-of-pattern precipitation.

  In the present invention, electroless nickel and electroless gold plating are selectively applied on a fine pattern of a printed wiring board by efficiently removing the inorganic filler remaining on the surface layer of the insulating layer after roughening. The present invention provides a method for suppressing abnormal precipitation outside the pattern.

  In the method of forming a fine circuit pattern by a semi-additive method and performing electroless nickel plating and electroless gold plating, the present inventors have a large amount of inorganic filler remaining on the surface layer of the insulating layer after roughening. It was also found that the palladium catalyst could not be sufficiently removed even by the palladium catalyst application and washing steps, and deposited out of the pattern, causing a short circuit failure.

  The present invention includes (a) forming an insulating layer containing an inorganic filler on an insulating substrate on which a first circuit layer is formed, and (b) forming a via hole reaching the first circuit layer in the insulating layer. (C) a step of roughening the surface of the insulating layer with an oxidizing solution, (d) an alkali having a pH of 10 or more obtained by dissolving an alkali metal hydroxide or an alkaline earth metal hydroxide in water. After removing the remaining inorganic filler by immersing in the solution, and (e) forming the interlayer connection by the second circuit layer and the via hole by electroless plating on the surface of the insulating layer and the inner wall of the via hole. The present invention also relates to a method for manufacturing a multilayer printed wiring board, wherein electroless nickel plating and electroless gold plating are selectively performed only on a copper pattern of the printed wiring board.

  According to the present invention, in the method for producing a multilayer printed wiring board having a fine circuit pattern by a semi-additive construction method, by removing the inorganic filler remaining in the roughening step of the surface of the insulating layer by washing with an alkaline solution of PH10 or more, It is possible to selectively remove the inorganic filler, and it is possible to produce a multilayer printed wiring board excellent in insulation reliability without abnormal precipitation in the method of performing electroless nickel plating and gold plating.

Hereinafter, the best mode for carrying out the invention will be described in detail.
First, the manufacturing method of the multilayer printed wiring board of this invention is equipped with the process of forming the insulating layer containing an inorganic filler on the insulating substrate in which (a) 1st circuit was formed.
The insulating substrate on which the first circuit is formed is not particularly limited as long as it can be used as a substrate for a printed wiring board. For example, what formed the circuit pattern in the glass cloth board | substrate epoxy resin laminated board can be used.

  In order to increase the adhesive strength between the first circuit and the insulating layer containing the inorganic filler, the conductor surface of the first circuit is oxidized to form irregularities, or these irregularities are further formed by sodium borohydride, dimethylaminoborane, etc. It is preferable to reduce using an alkaline reducing agent.

  The insulating layer containing the inorganic filler preferably has a plating solution resistance, a heat resistance and an insulating property, and preferably has a roughening property for forming irregularities on the resin surface layer with an oxidizing solution. What added the inorganic filler to the resin currently used for the adhesive film which does not contain a material, or an adhesive film with a copper foil can be used.

A rubber component that can be decomposed or dissolved in an oxidizing solution for obtaining roughening in a resin composition in which a curing agent, a flame retardant, a curing accelerator, etc. are added to an epoxy resin as an insulating layer containing an inorganic filler. However, the present invention is not limited to these.
Examples of the epoxy resin include bisphenol A type, bisphenol F type, biphenyl type, novolac type, polyfunctional phenol type, naphthalene type, alicyclic and alcohol type glycidyl ethers and halides thereof, glycidyl amine type and glycidyl type. An ester type etc. are mentioned, 1 type or 2 types can be mixed and used.
Examples of the curing agent include various phenol resins, acid anhydrides, amines, hydragits, and the like. In view of heat resistance and insulation, novolac type phenol resin is preferable.
Examples of flame retardants include halogen-containing resins such as hexabromobenzene, brominated polycarbonate, brominated epoxy resins and brominated phenol resins, phosphate ester flame retardants, phosphorus-containing resins, red phosphorus, antimony trioxide, nitrogen-containing resins, Examples include inorganic fillers such as aluminum hydroxide and magnesium hydroxide.
Examples of the curing accelerator include various imidazoles and BF ₃ amine complexes which are latent thermosetting agents.
Examples of the rubber component include NBR, polybutadiene rubber, epoxy-modified polybutadiene rubber, and carboxylic acid-modified acrylonitrile butadiene rubber particles. The carboxylic acid-modified acrylonitrile butadiene rubber particles are, for example, made into particles by copolymerizing acrylonitrile, butadiene and carboxylic acid and partially cross-linking at the stage of copolymerization. These may be used alone or in combination of two or more.
Examples of the filler include inorganic fillers. Examples of the inorganic filler include silica, fused silica, talc, alumina, aluminum hydroxide, barium sulfate, calcium hydroxide, aerosil, and calcium carbonate, and these may be used alone or in combination. From the viewpoint of flame retardancy and low thermal expansion, aluminum hydroxide and silica are preferably used alone or in combination. These inorganic fillers may be subjected to a coupling treatment for the purpose of improving dispersibility, or may be dispersed by a known kneading method such as a kneader, a ball mill, a bead mill, or a three roll.
When the insulating layer containing the inorganic filler of the present invention is formed as a resin varnish, the insulating resin composition is diluted with a solvent. Solvents include methyl ethyl ketone, xylene, toluene, acetone, ethylene glycol monoethyl ether, cyclohexanone, ethyl ethoxypropionate, N, N-dimethylformamide, N, N-dimethylacetamide, propylene glycol monomethyl ether, ethyl ethoxypropionate And propylene glycol monomethyl ether acetate. These solvents may be used alone or in a mixed system. The ratio of the solvent to the insulating resin composition may be the ratio used in the past, and the amount of use is adjusted according to the equipment for forming the coating film of the resin varnish.

Insulating layer with inorganic filler is applied as a resin varnish by roll coal, curtain coating, etc., laminated by using a sheeted insulating resin composition, pressure laminated press sandwiched between end plates It may be formed by any method.
Next, the method of the present invention includes a step (b) of forming a via hole in the insulating layer.
As a method for forming a via hole, a carbon dioxide laser, a YAG laser, an excimer laser, or the like can be mainly used.

  Next, the method of the present invention includes the step (c) of roughening the surface of the insulating layer with an oxidizing solution. A roughened surface is formed by swelling and dissolving the surface of the insulating layer with an oxidizing solution. An example of the swelling liquid is a sodium hydroxide solution of diethylene glycol butyl ether. As a roughening liquid, a well-known oxidizing roughening liquid can be used, For example, alkaline permanganic acid aqueous solution, chromic acid-sulfuric acid, chromic acid-sulfuric acid-sodium fluoride etc. mixtures are mentioned. Examples of the alkaline permanganate aqueous solution include potassium hydroxide or sodium hydroxide solution of sodium permanganate. The swelling treatment is preferably performed at 60 to 90 ° C. for 5 to 30 minutes, and the roughening treatment is preferably performed at 60 to 90 ° C. for 5 to 30 minutes. After the roughening treatment, the insulating surface is neutralized.

Next, the method of the present invention includes a step (d) of removing the inorganic filler remaining in the surface layer of the insulating layer. In order to remove the inorganic filler, the surface of the insulating layer is immersed in an alkaline solution.
Examples of the alkaline solution include an aqueous solution of an alkali metal hydroxide and an aqueous solution of an alkaline earth metal hydroxide. Examples of the alkali metal hydroxide include sodium hydroxide and potassium hydroxide. Examples of the alkaline earth metal hydroxide include magnesium hydroxide and calcium hydroxide. Among these, a sodium hydroxide aqueous solution is preferable. From the viewpoint of removing only the inorganic filler, the alkaline solution preferably has a pH of 9 or more, more preferably 10 to 13. When the pH is 9 or more, the inorganic filler can be removed in a short time. The treatment with the alkaline solution is preferably performed at 20 to 90 ° C. for 2 to 30 minutes. Thereafter, the surface of the insulating layer is washed with water.

  Next, the method of the present invention includes the step of (e) electroless plating the surface of the insulating layer and the inner wall of the via hole to form an interlayer connection by the second circuit layer and the via hole. A copper plating layer is formed on the surface of the insulating layer. After a predetermined alkali or acidic conditioner treatment as a pretreatment for electroless plating, plated copper is deposited on the insulating layer surface and the inner wall of the via hole by electroless plating. The thickness of the plated copper is preferably about 0.3 to 1.0 μm.

Next, the method of the present invention selectively performs electroless nickel plating and electroless gold plating only on the copper pattern of the printed wiring board.
A plating resist layer is formed on the surface of the electroless plating layer, electroplating is thickened and the resist layer is removed, and finally the remaining electroless plating layer is microetched to form a circuit. Commercially available products can be applied to the electroless nickel plating and electroless gold plating of the outermost layer pattern.
Furthermore, a multilayer printed wiring board having the required number of layers can be obtained by using the present substrate as an inner layer substrate and repeating the above steps.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, in this invention, it does not restrict | limit to these Examples.

(Example 1)
The following materials were blended and mixed to obtain a resin composition for an insulating resin adhesive sheet.
-Bisphenol A type epoxy resin (Nippon Kayaku Co., Ltd., trade name: EPICLON153) ... 100 parts by weight-Carboxylic acid modified acrylonitrile butadiene rubber (JSR Corporation, trade name: PNR-1H) ... 5 parts by weight-Thermosetting Agent phenol novolac resin (manufactured by Hitachi Chemical Co., Ltd., trade name: HP-85) ... 10 parts by weight
-Flame retardant phosphoric acid ester (trade name: PX-200, manufactured by Sanko Chemical Co., Ltd.) 30 parts by weight-Inorganic filler spherical silica (trade name: SC2050, manufactured by Admatechs Co., Ltd.) ... 70 parts by weight-Diluting solvent : Low boiling point solvent methyl ethyl ketone ... 100 parts by weight

  Subsequently, the resin composition was applied to a carrier film (PET: 38 μm) and dried at 110 ° C. to obtain an insulating resin adhesive sheet. The coating conditions were adjusted so that the adhesive sheet had a film thickness of 40 μm and a volatile content of 5.0%.

  Glass cloth base epoxy resin double-sided copper-clad laminate (made by Hitachi Chemical Co., Ltd., trade name: MCL) having a 35 μm thick double-sided roughened copper foil on both sides using the adhesive sheet obtained above -E-679) was laminated at 110 ° C. for 60 seconds, and then heat-cured at 170 ° C. for 60 minutes to produce an insulating resin substrate having an insulating resin as the outermost layer. Via holes were formed at predetermined locations on the insulating resin substrate by a carbon dioxide laser.

Next, in order to chemically roughen the insulating resin layer, an aqueous solution of diethylene glycol monobutyl ether: 200 ml / L, NaOH: 5 g / L is prepared as a swelling liquid, heated to 70 ° C. and immersed for 5 minutes, Then, an aqueous solution of KMnO ₄ : 60 g / L and NaOH: 40 g / L was prepared as a roughening solution, heated to 80 ° C., soaked for 10 minutes, and neutralized to roughen the resin layer surface. Thereafter, the inorganic filler remaining on the surface of the insulating layer was removed by immersing in an aqueous solution (pH = 10) of NaOH: 0.5 g / L heated to 60 ° C. for 5 minutes and washing with water.

  Next, immersed in a conditioner (manufactured by Hitachi Chemical Co., Ltd., trade name: CLC-601) at 60 ° C. for 5 minutes, rinsed with hot water at 60 ° C., rinsed with water at room temperature (the same applies hereinafter), for electroless plating Immersion in a catalyst solution (manufactured by Hitachi Chemical Co., Ltd., trade name: HS-202B) at room temperature for 10 minutes, washing with water at room temperature, activation treatment solution of palladium (trade name: ADP-401, manufactured by Hitachi Chemical Co., Ltd.) ) And then washed with water in this order at room temperature for 5 minutes.

  Next, it was immersed in an electroless copper plating solution (manufactured by Hitachi Chemical Co., Ltd., trade name: CUST201) at room temperature for 15 minutes, washed with water, and dried at 80 ° C. for 10 minutes. Thereafter, baking, development, and etching are performed by a pattern forming method by forming a plating resist layer to produce a line / space = 20/20, 30/30, 40/40 μm comb circuit pattern, and electrolytic plating is used to form a 20 μm thick thickness. A copper plating layer was formed, and a conductor circuit was formed by removing the resist layer and etching removing the electroless copper plating layer, and finally heated at 180 ° C. for 60 minutes for annealing.

  This printed wiring board is subjected to a predetermined treatment, then treated with a palladium catalyst Melplate activator (Meltex, trade name: 350) for 10 minutes at 30 ° C., further washed with water, and electroless nickel plating solution (Hitachi). It was processed at 85 ° C. for 12 minutes with Kasei Kogyo Co., Ltd. (trade name: NIPS-100) to obtain a 3 μm nickel coating.

  Next, it was washed with water and treated with a displacement gold plating solution (manufactured by Hitachi Chemical Co., Ltd., trade name: HGS-100) at 80 ° C. for 10 minutes. Finally, it was washed with water and treated with an electroless gold plating solution (manufactured by Hitachi Chemical Co., Ltd., trade name: HGS-5000) at 85 ° C. for 5 minutes to obtain a gold film having a thickness of 0.5 μm.

(Example 2)
Ca (OH) ₂ : (1 g / L) Through the same steps as in Example 1, except that the step of removing the inorganic filler remaining on the insulating layer surface layer was performed with an alkaline solution (60 ° C., 5 minutes) of pH 13 A multilayer printed wiring board was produced.

(Comparative Example 1)
A multilayer printed wiring board was produced through the same steps as in Example 1 except that the step of removing the inorganic filler remaining on the surface of the insulating layer with an alkaline solution was omitted.

(Comparative Example 2)
NaHCO ₃ : (10 g / L) A multilayer print through the same steps as in Example 1 except that the inorganic filler remaining on the surface of the insulating layer was removed with a weak alkaline solution (60 ° C., 5 minutes) at pH 8 A wiring board was produced.

  About the multilayer printed wiring board produced above, the presence or absence of abnormal deposition of electroless nickel plating and gold plating and the accelerated test of insulation reliability of line / space = 20/20, 30/30, 40/40 μm were performed.

The insulation reliability is measured by laminating and drying the insulating resin adhesive sheet prepared in the above example on the insulating substrate having the comb-shaped circuit pattern previously prepared, and then setting the test pattern at 130 ° C. and 85% RH. Shows 10 ⁸ Ω or more when placed in a thermostat adjusted to an unsaturated atmosphere, taken out for a predetermined time while applying a DC voltage of 5 V, and measured by applying 50 V for 1 minute at room temperature of the inner comb circuit pattern The time was defined as the insulation reliability time.

  As shown in Table 1, it is clear that the multilayer printed wiring boards produced in Examples 1 and 2 are free from plating and have excellent insulation reliability.

Claims (1)

  (A) forming an insulating layer containing an inorganic filler on the insulating substrate on which the first circuit layer is formed; (b) forming a via hole reaching the first circuit layer in the insulating layer; c) a step of roughening the surface of the insulating layer with an oxidizing solution, (d) immersing the surface layer of the insulating layer in an alkali solution having a pH of 10 or more in which an alkali metal hydroxide or an alkaline earth metal hydroxide is dissolved in water. A step of removing the remaining inorganic filler, and (e) a step of forming an interlayer connection by the second circuit layer and the via hole by electroless plating on the surface of the insulating layer and the inner wall of the via hole. A method for producing a multilayer printed wiring board, wherein electroless nickel and electroless gold plating are selectively performed only on a copper pattern of the wiring board.