JP2008113022A - Substrate with through-hole formed and multilayer printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To propose a technology for directly punching a copper clad laminate with a laser. <P>SOLUTION: A copper foil 132 with a thickness of 12 μm that is applied on both surfaces of a double-sided copper clad laminate 130A is etched with a sulfuric acid/hydrogen peroxide aqueous solution to make the thickness to 5 μm (step (B)). This double-sided copper clad laminate 130A is provided with a hole 116 with a diameter of 150 μm by using a carbon dioxide laser (step (C)). Electroless copper plating is performed in the hole 116 to form a plated through hole 136 (step (D)). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a substrate for forming a through hole using a laser and a multilayer printed wiring board.

In recent years, a build-up multilayer printed wiring board has attracted attention due to the demand for higher density multilayers. This multilayer wiring board is a multilayer wiring board in which conductor circuits and interlayer resin layers are alternately laminated on a core substrate, and the conductor circuits of each layer are connected by via holes. The through hole provided in the core substrate is required to be miniaturized. A through hole having a diameter of less than 100 μm is extremely difficult to drill with a drill, and is drilled into a copper-clad laminate by laser processing.

As a laser beam to be used, a carbon dioxide laser is inexpensive and is optimal for industrial production. However, it was a common technical knowledge that carbonic acid laser light is reflected on the surface of the copper foil and it is impossible to directly form a through-hole in the copper-clad laminate by laser processing. For this reason, Japanese Patent Application Laid-Open No. 61-99596 has proposed a technique in which the copper foil surface of the copper-clad laminate is blackened (oxidized) and irradiated with laser light.
JP-A-61-99596

However, in such a technique, there is a problem that the blackening process is required first and the process becomes long. As a result of intensive studies, the present inventors have found an unexpected fact that an opening can be formed in the copper foil despite the reflection at the surface by making the copper foil thinner.

The present invention has been made in order to solve the above-described problems. The object of the present invention is to form a through hole obtained by such a method together with a technique capable of directly drilling a copper-clad laminate with a laser. It is to propose a substrate and a multilayer printed wiring board.

The substrate for forming a through hole according to the present invention is a substrate in which a through hole is provided in a double-sided copper-clad laminate, and the inner wall is made conductive to form a through hole. Technical features.

In the multilayer printed wiring board of the present invention, the double-sided copper-clad laminate is provided with a through-hole, and the interlayer resin insulation layer and the conductor circuit are provided on at least one surface of the substrate on which the inner wall is made conductive to form a through hole. The multilayer printed wiring board thus formed is characterized in that the through hole is tapered.

As a result of diligent research, the inventors of the present invention cannot pierce a copper foil of 12 μm or more with carbon dioxide laser light, but are not reflected on the surface, but heat conduction is facilitated by increasing the thickness of the copper foil, and the energy of the laser light is reduced. It was found that it was because it propagated as heat. Furthermore, by setting the thickness of the copper foil to less than 12 μm, desirably about 1 to 10 μm, the laser beam energy was prevented from propagating as heat, and the drilling by the laser beam was realized. The copper clad laminate used in the present invention may be a copper clad laminate obtained by attaching a copper foil to a prepreg such as a glass cloth epoxy resin, a glass cloth bismaleimide-triazine resin, or a glass cloth fluororesin.

As for the thickness of copper foil, 1-10 micrometers is desirable. If it is 10 μm or less, it is easy to perforate with laser light, while if it is less than 1 μm, blistering or the like is likely to occur. The thickness of the copper foil is adjusted by etching. Specifically, physical etching such as chemical etching or ion beam etching using an aqueous solution of sulfuric acid-hydrogen peroxide, ammonium persulfate, cupric chloride, or ferric chloride is performed. The thickness of the copper clad laminate is preferably 0.5 to 1.0 mm. This is because if the thickness is too thick, drilling cannot be performed, and if the thickness is too thin, warping is likely to occur. The carbon dioxide laser used in the present invention is preferably a short pulse laser of 20 to 40 mJ, 10 ⁻⁴ to 10 ⁻⁸ seconds. The number of shots is 5 to 100 shots.

As for the diameter of the through-hole formed, 50-150 micrometers is desirable. If it is less than 50 μm, the wall surface cannot be made conductive by plating or the like, and if it exceeds 150 μm, drilling is more advantageous. When the diameter of the through hole exceeds 100 μm, the through hole is tapered. A taper that increases the diameter of the through-hole is formed on the laser beam incident side. Further, when laser light is irradiated from the front surface and the back surface, through-holes having a cross section are formed.

This through hole is made conductive. As a conductive method, electroplating, electroless plating, sputtering, vapor deposition, conductive paste filling, or the like is used. When the conductive paste is filled, it is desirable that the through hole is tapered. This is because it is easy to fill the paste. Even when a through hole is formed by metallizing the inner wall surface by electroplating, electroless plating, sputtering, vapor deposition, or the like, the through hole can be filled with a filler.

Moreover, the metalized through-hole inner wall may be roughened. When the inner wall of the through hole is metallized, the thickness of the copper foil and the metallized layer (for example, electroless plating layer) is preferably 10 to 30 μm. As the filler, various materials such as those composed of bisphenol F-type epoxy resin and inorganic particles such as silica and alumina, and those composed of metal particles and resin can be used.

A conductor circuit is provided on the through hole forming substrate thus formed. The conductor circuit is formed by etching. The surface of the conductor circuit is preferably roughened to improve adhesion. Next, an interlayer resin insulating layer made of an insulating resin is provided.

As the insulating resin, a thermosetting resin, a thermoplastic resin, or a composite resin thereof is used. As the thermosetting resin, an epoxy resin, a phenol resin, a polyimide resin, or the like is used. Moreover, as a thermoplastic resin, as a thermoplastic resin, polyether sulfone (PES), polysulfone (PSF), polyphenylene sulfone (PPS), polyphenylene sulfide (PPES), polyphenyl ether (PPE), polyetherimide (PI) ), Fluororesin and the like can be used.

In the present invention, the interlayer resin insulating layer may be an electroless plating adhesive. For example, a particle that dissolves with an acid or an oxidizing agent is included in a heat-resistant resin that is hardly soluble in an acid or an oxidizing agent, and the surface of the insulating resin layer is roughened by dissolving the particles with an acid or an oxidizing agent can do. Examples of such heat-resistant resin particles include amino resins (melamine resins, urea resins, guanamine resins, etc.), epoxy resins (bisphenol-type epoxy resins cured with an amine curing agent), bismaleimide-triazine resins, etc. Can be used.

In addition, such an electroless plating adhesive may contain, in particular, cured heat-resistant resin particles, inorganic particles, fibrous fillers, and the like as necessary. Such heat-resistant resin particles include (1) heat-resistant resin powder having an average particle diameter of 10 μm or less, (2) agglomerated particles obtained by aggregating heat-resistant resin powder having an average particle diameter of 2 μm or less, and (3) average particle diameter. Is a mixture of a heat-resistant resin powder having an average particle diameter of less than 2 μm and (4) an average particle diameter of 2 μm or less on the surface of the heat-resistant resin powder having an average particle diameter of 2-10 μm (5) heat-resistant resin powder having an average particle diameter of more than 0.8 and less than 2.0 μm and heat-resistant resin having an average particle diameter of 0.1 to 0.8 μm It is desirable to use a mixture with powder and (6) at least one particle selected from the group consisting of heat-resistant resin powder having an average particle diameter of 0.1 to 1.0 μm. This is because these particles form a more complicated roughened surface.

Such an interlayer resin insulation layer can be provided with openings by laser light, exposure, or development.

Next, a catalyst for electroless plating such as a Pd catalyst is applied, the inside of the via hole opening is plated to provide a via hole, and a conductor circuit is provided on the surface of the insulating resin layer. An electroless plating film is formed on the inner wall of the opening and the entire surface of the insulating resin layer, and after providing a plating resist, electroplating is performed to remove the plating resist, and a conductor circuit is formed by etching.

Hereinafter, the present invention will be described based on examples and comparative examples.
Example 1
(1) A double-sided copper clad laminate (Matsushita Electric Works R5715) 130A having a thickness of 0.6 mm in which a copper foil 132 having a thickness of 12 μm was attached to the substrate 130 was prepared (see FIG. 1A).
(2) The copper foil 132 was etched with a sulfuric acid-hydrogen peroxide solution to a thickness of 5 μm (see FIG. 1B).
(3) Carbon dioxide laser (Mitsubishi Electric ML605GTL) is used for this double-sided copper clad laminate 130A, and the diameter is 150 μm (upper diameter D1: 160 μm, lower diameter D2) at 10 shots under a pulse condition of 30 mJ, 52 × 10 ⁻⁶ seconds. A hole 116 having a taper of 140 μm was provided (FIG. 1C). Thus, a hole can be made in the substrate 130 by penetrating the 5 μm copper foil 132 with a laser. (3) Electroless copper plating was performed in the hole 116 under the following conditions to form a plated through hole 136 (FIG. 1D).
Electroless plating solution;
EDTA: 150 g / L
Copper sulfate: 20 g / L
HCHO: 30 mL / L
NaOH: 40 g / L
α, α'-bipyridyl: 80 mg / L
PEG: 0.1 g / L electroless plating conditions;
30 minutes at a liquid temperature of 70 ° C

Example 2
(1) A 0.6 mm thick double-sided copper clad laminate (Matsushita Electric Works R5715) 230A in which a 12 μm thick copper foil 232 was attached to a substrate 230 was prepared (FIG. 2A).
(2) The copper foil 232 was etched with a sulfuric acid-hydrogen peroxide solution to a thickness of 9 μm (FIG. 2B).
(3) A carbon dioxide laser (Mitsubishi Electric ML605GTL) is used for this double-sided copper-clad laminate 230A, and a diameter of 150 μm (upper diameter D1: 160 μm, lower diameter D2) at 15 shots under a pulse condition of 30 mJ, 52 × 10 ⁻⁶ seconds. A hole 216 having a taper of 140 μm was provided (FIG. 2C). Thus, a hole can be made in the substrate 130 by penetrating the 9 μm copper foil 132 with a laser.
(4) In the same manner as in Example 1, electroless copper plating was performed to form a plated through hole 236 (FIG. 2C).

Example 3
(1) A 0.6 mm thick double-sided copper clad laminate (Matsushita Electric Works R5715) 330A having a 12 μm thick copper foil 332 attached to a substrate 330 was prepared (FIG. 3A).
(2) The copper foil 332 was etched with a sulfuric acid-hydrogen peroxide solution to a thickness of 5 μm (FIG. 3B).
(3) Using a carbon dioxide laser (Mitsubishi Electric ML605GTL) on this double-sided copper-clad laminate 330A, irradiating it from the front and back with 15 shots under a pulse condition of 30 mJ, 52 × 10 ⁻⁶ seconds, a diameter of 150 μm (maximum diameter) D3: 160 μm Minimum diameter D4: 140 μm taper)) was provided. The cross section of the hole 316 has a sag shape (FIG. 3C).
(4) In the same manner as in Example 1, electroless copper plating was performed to form a plated through hole 336 (FIG. 3D). In Example 4, since the laser is irradiated from the front and back surfaces, a through hole can be formed even if the substrate is thick.

Comparative Example 1
(1) A double-sided copper-clad laminate (Matsushita Electric Works R5715) with a thickness of 0.6 mm to which a 12 μm-thick copper foil was attached was prepared.
(2) Using a carbon dioxide gas laser (Mitsubishi Electric ML605GTL) on this double-sided copper-clad laminate, the laser was irradiated under the conditions of 15 shots under a pulse condition of 30 mJ, 52 × 10 ⁻⁶ seconds, but drilling was not possible. From this example, it was found that if the thickness of the copper foil exceeds 12 μm, a through hole cannot be formed.

Example 4 Subsequently, a fourth example of manufacturing a multilayer printed wiring board by forming a through hole with a laser will be described with reference to FIGS. First, the structure of the multilayer printed wiring board 10 according to Embodiment 4 of the present invention will be described with reference to FIG. In the multilayer printed wiring board 10, build-up wiring layers 80 </ b> A and 80 </ b> B are formed on the front surface and the back surface of the core substrate 30. The built-up layer 80A includes an interlayer resin insulation layer 50 in which via holes 60 and conductor circuits 58 are formed, and an interlayer resin insulation layer 150 in which via holes 160 and conductor circuits 158 are formed. The build-up wiring layer 80B includes an interlayer resin insulation layer 50 in which the via hole 60 and the conductor circuit 58 are formed, and an interlayer resin insulation layer 150 in which the via hole 160 and the conductor circuit 158 are formed.

On the upper surface side of the multilayer printed wiring board 10, solder bumps 76U for connection to IC chip lands (not shown) are disposed. The solder bump 76U is connected to the through hole 36 via the via hole 160 and the via hole 60. On the other hand, solder bumps 76D for connecting to lands (not shown) of the daughter board are disposed on the lower surface side. The solder bump 76D is connected to the through hole 36 via the via hole 160 and the via hole 60.

Next, a method for manufacturing the multilayer printed wiring board 10 will be described.
Here, first, the A.M. used for the manufacturing method of the multilayer printed wiring board of Example 4 was used. B. Adhesive for electroless plating, Resin filler, C.I. The adjustment of the solder resist composition will be described.

A. Preparation of adhesive for electroless plating (adhesive for upper layer) (1) 35 parts by weight of 25% by weight acrylate of cresol novolac type epoxy resin (Nippon Kayaku: molecular weight 2500), photosensitive monomer (manufactured by Toa Gosei: 3.15 parts by weight of Aronix M315), 0.5 parts by weight of antifoaming agent (S-65 manufactured by Sannopco), and 3.6 parts by weight of N-methylpyrrolidone (NMP) were mixed with stirring.

(2) 12 parts by weight of polyethersulfone (PES), 7.2 parts by weight of epoxy resin particles (manufactured by Sanyo Chemical Co., Ltd .: trade name polymer pole) with an average particle size of 1.0 μm, and 3.09 parts by weight with an average particle size of 0.5 μm After mixing, 30 parts by weight of NMP was further added and stirred and mixed with a bead mill.

(3) 2 parts by weight of imidazole curing agent (Shikoku Kasei: product name 2E4MZ-CN), 2 parts by weight of photoinitiator (Ciba Geigy: Irgacure I-907), photosensitizer (DETX-S, manufactured by Nippon Kayaku) ) 0.2 parts by weight and 1.5 parts by weight of NMP were mixed with stirring.
(4) Mixtures (1) to (3) were mixed to obtain an electroless plating adhesive composition.

B. Adjustment of resin filler (1) Bisphenol F type epoxy monomer (Oilized shell: molecular weight 310, trade name YL983U) 100 parts by weight, SiO ₂ spherical particles with an average particle size of 1.6μm and coated with silane coupling agent on the surface [Manufactured by Admatech: CRS 1101-CE, where the maximum particle size is not more than the thickness (15 μm) of the inner layer copper pattern described later. 170 parts by weight and 1.5 parts by weight of a leveling agent (manufactured by San Nopco: trade name Perenol S4) were kneaded with three rolls, and the viscosity of the mixture was adjusted to 45,000 to 49,000 cps at 23 ± 1 ° C.

(2) 6.5 parts by weight of imidazole curing agent (product name: 2E4MZ-CN, manufactured by Shikoku Kasei)
(3) Mixtures (1) and (2) were mixed to prepare a resin filler.

C. Preparation of solder resist 46.67g of photosensitizing oligomer (molecular weight 4000) obtained by acrylating 50% of epoxy group of 60% cresol novolak type epoxy resin (manufactured by Nippon Kayaku) dissolved in DMDG was dissolved in methyl ethyl ketone. 80% by weight of bisphenol A type epoxy resin (Oka Chemical Shell, Epicoat 1001) 15.0 g, imidazole curing agent (Shikoku Chemicals, 2E4MZ-CN) 1.6 g, polyvalent acrylic monomer (Nippon Kayaku) R604) 3 g, 1.5 g polyvalent acrylic monomer (Kyoeisha Chemical Co., DPE6A), 0.71 g dispersion antifoam (Sannopco, S-65) are mixed, and the photoinitiator is mixed with this mixture. 2 g of benzophenone (manufactured by Kanto Chemical Co., Inc.) and 0.2 g of Michler ketone (manufactured by Kanto Chemical Co., Ltd.) as a photosensitizer were added, and the viscosity was adjusted to 2.0 Pa · s at 25 ° C. A rudder resist composition was obtained.

Manufacture of printed wiring boards
(1) A copper-clad laminate 30A in which a 12 μm copper foil 32 is laminated on both surfaces of a substrate 30 made of glass epoxy resin having a thickness of 0.6 mm was used as a starting material (FIG. 4A). This was etched to adjust the thickness to 5 μm (FIG. 4B).

(2) Using a carbon dioxide laser (Mitsubishi Electric ML605GTL) to irradiate the copper clad laminate 30A with a laser of 15 shots under a pulse condition of 30 mJ, 52 × 10 ⁻⁶ seconds, a diameter of 100 μm (upper diameter) D1: 110 μm, lower diameter D2: with a taper of 90 μm) was provided (FIG. 4C). Next, electroless plating and electrolytic plating are performed (FIG. 4D), and the copper foil is further etched into a pattern according to a conventional method, whereby an inner layer copper pattern (lower conductor circuit) 34 having a thickness of 15 μm is formed on both surfaces of the substrate. And the through-hole 36 was formed (FIG.4 (E)).

Next, a roughened surface 38 was provided on the surface of the inner layer copper pattern 34, the land 36A surface and the inner wall of the through hole 36, respectively, and a wiring board was manufactured (FIG. 4F). The roughened surface 38 is obtained by washing the substrate 30 with water and drying it, and spraying an etching solution on both surfaces of the substrate by spraying to etch the surface of the inner layer copper pattern 34, the surface of the land 36a of the through hole 36, and the inner wall. Formed by. The etching solution used was a mixture of 10 parts by weight of imidazole copper (II) complex, 7 parts by weight of glycolic acid, 5 parts by weight of potassium chloride, and 78 parts by weight of ion-exchanged water.

(3) Next, the resin layer 40 was provided between the inner layer copper patterns 34 of the wiring board and in the through holes 36 (FIG. 5G). The resin layer 40 is prepared by applying the resin filler B prepared in advance onto both sides of the wiring board with a roll coater, filling the space between the inner layer copper patterns and the through holes, and then at 100 ° C. for 1 hour and at 120 ° C. for 3 hours. It was cured by heating for 1 hour at 150 ° C. and 7 hours at 180 ° C., respectively.

(4) One side of the substrate 30 obtained by the treatment in (3) was subjected to belt sander polishing. In this polishing, a # 600 belt polishing paper (manufactured by Sankyo Rikagaku) was used so that the resin filler 40 did not remain on the roughened surface 38 of the inner layer copper pattern 34 or the land 36a surface of the through hole 36 (FIG. 5 ( H)). Next, buffing was performed to remove scratches caused by this belt sander polishing. Such a series of polishing was similarly performed on the other surface of the substrate.

In the obtained wiring board 30, the resin layer 40 is provided between the inner layer copper patterns 34, and the resin layer 40 is provided in the through hole 36. The roughened surface 38 of the inner layer copper pattern 34 and the roughened surface of the land 36a surface of the through hole 36 are removed, and both surfaces of the substrate are smoothed with a resin filler. The resin layer 40 is in close contact with the roughened surface 387 on the side surface of the inner layer copper pattern 34 or the roughened surface 38 on the side surface of the land portion 36a of the through hole 36, and the resin layer is in close contact with the roughened surface of the inner wall of the through hole. Yes.

(5) Further, the exposed inner layer copper pattern 34 and the upper surface of the land 36a of the through hole 36 were roughened by the etching process (2) to form a roughened surface 42 having a depth of 3 μm (FIG. 5 (I)).

The roughened surface 42 was subjected to tin substitution plating to provide a Sn layer (not shown) having a thickness of 0.3 μm. In the displacement plating, the roughened surface was subjected to a Cu—Sn substitution reaction under the conditions of tin borofluoride 0.1 mol / L, thiourea 1.0 mol / L, temperature 50 ° C., pH = 1.2.

(6) The electroless plating adhesive (A) was applied to both surfaces of the obtained wiring board 30 using a roll coater. This adhesive was allowed to stand for 20 minutes in a horizontal state and then dried at 60 ° C. for 30 minutes to form an adhesive layer 50 having a thickness of 35 μm (FIG. 5J).

(7) Both surfaces of the obtained wiring board 30 were exposed to 500 mJ / cm ² with an ultrahigh pressure mercury lamp and heated at 150 ° C. for 5 hours.

(8) The obtained substrate 30 was immersed in chromic acid for 1 minute, and the epoxy resin particles present on the surface of the adhesive layer 50 were dissolved and removed. By this treatment, a roughened surface was formed on the surface of the adhesive layer 50. Thereafter, the obtained substrate 30 was immersed in a neutralization solution (manufactured by Shipley Co., Ltd.) and washed with water (FIG. 5 (K)).

(9) Next, electroless copper plating 44 having a thickness of 0.6 μm was applied to the entire surface of the substrate 30 (FIG. 6L).

(10) An etching resist (not shown) is provided and etched with a sulfuric acid-hydrogen peroxide solution to provide an opening 44a of φ50 μm in the via hole forming portion of the electroless copper plating 44 (FIG. 6 (M)). .

(11) Using the electroless copper plating 44 as a conformal mask, the adhesive layer 50 under the opening 44a is removed by a short pulse (10 ⁻⁴ second) laser beam (Mitsubishi Electric ML605GTL) to open a via hole. 48 was provided (FIG. 6 (N)).

Further, by applying a palladium catalyst (manufactured by Atotech) to the surface of the wiring board 30, catalyst nuclei were attached to the surface of the electroless plating film 44 and the roughened surface of the via hole opening 48.

(12) The obtained substrate 30 was immersed in an electroless copper plating bath under the following conditions to form an electroless copper plating film 52 having a thickness of 1.6 μm on the entire substrate 30 (FIG. 6 (O)).
Electroless plating solution;
EDTA: 150 g / L
Copper sulfate: 20 g / L
HCHO: 30 mL / L
NaOH: 40 g / L
α, α'-bipyridyl: 80 mg / L
PEG: 0.1 g / L
Electroless plating conditions;
30 minutes at a liquid temperature of 70 ° C

(13) Next, a commercially available photosensitive dry film (not shown) was attached to the electroless copper plating film 52, and a mask film (not shown) on which a pattern was printed was placed. The substrate 30 was exposed at 100 mJ / cm ² and then developed with 0.8% sodium carbonate to provide a plating resist 54 having a thickness of 15 μm (FIG. 6 (P)).

(14) Next, electrolytic copper plating was performed on the obtained substrate under the following conditions to form an electrolytic copper plating film 56 having a thickness of 15 μm (FIG. 6 (Q)).
Electrolytic plating solution;
Sulfuric acid: 180 g / L
Copper sulfate: 80 g / L
Additive: 1 mL / L (additive is manufactured by Atotech Japan: trade name Kaparaside GL)
Electrolytic plating conditions;
Current density: 1 A / dm ²
Time: 30 minutes Temperature: Room temperature

(15) After removing the plating resist 54 with 5% KOH, etching is performed with a mixed solution of sulfuric acid and hydrogen peroxide to dissolve and remove the electroless plating film 52 under the plating resist, and the copper foil 32, the electroless plating 44, A conductor circuit 58 having a thickness of 18 μm (10 μm to 30 μm) composed of the electroless copper plating film 52 and the electrolytic copper plating film 56 and 60 via holes were obtained (FIG. 6R). Here, the fine pitch and the connection reliability are made compatible by setting the thickness to 10 μm to 30 μm.

Further, the surface of the adhesive layer 50 for electroless plating between the conductor circuits 58 was etched by 1 μm at 70 ° C. for 3 minutes in 80 g / L chromic acid, and the palladium catalyst on the surface was removed.

(16) The same treatment as in (5) was performed to form a roughened surface 62 made of Cu—Ni—P on the surface of the conductor circuit 58 and the via hole 60, and further Sn substitution was performed on the surface (FIG. 7). (See (S)).

(17) By repeating the steps (6) to (16), an upper interlayer resin insulation layer 160, a via hole 160, and a conductor circuit 158 are formed. Further, a roughened layer 162 is formed on the surfaces of the via hole 160 and the conductor circuit 158, thereby completing a multilayer printed wiring board (FIG. 6 (T)). In the step of forming the upper conductor circuit, Sn substitution was not performed.

(18) Then, solder bumps are formed on the multilayer printed wiring board described above. On the both surfaces of the substrate 30 obtained in (17) above, C.I. The solder resist composition described in 1 is applied at a thickness of 45 μm. Next, after drying at 70 ° C. for 20 minutes and at 70 ° C. for 30 minutes, a photomask film (not shown) having a thickness of 5 mm on which a circular pattern (mask pattern) is drawn is placed in close contact. , Exposed to 1000 mJ / cm ² of UV light and developed with DMTG. Further, heat treatment was performed at 80 ° C. for 1 hour, 100 ° C. for 1 hour, 120 ° C. for 1 hour, and 150 ° C. for 3 hours, and the solder pad part (including the via hole and its land part) was opened (opened). A solder resist layer (thickness 20 μm) 70 having a diameter (200 μm) 71 is formed (FIG. 8 (U)).

(19) Next, pH = 4.5 consisting of nickel chloride 2.31 × 10 ⁻¹ mol / l, sodium hypophosphite 2.8 × 10 ⁻¹ mol / l, sodium citrate 1.85 × 10 ⁻¹ mol / l The substrate 30 was immersed in the electroless nickel plating solution for 20 minutes to form a nickel plating layer 72 having a thickness of 5 μm in the opening 71. Further, the substrate was made of potassium gold cyanide 4.1 × 10 ⁻² mol / l, ammonium chloride 1.87 × 10 ⁻¹ mol / l, sodium citrate 1.16 × 10 ⁻¹ mol / l, sodium hypophosphite 1.7 × 10 ^-1 mol / l in an electroless gold plating solution at 80 ° C. for 7 minutes and 20 seconds to form a 0.03 μm thick gold plating layer 74 on the nickel plating layer. Solder pads 75 are formed on the conductor circuit 158 (FIG. 8 (V)).

(22) Then, solder bumps (solder bodies) 76U and 76D are formed by printing solder paste on the opening 71 of the solder resist layer 70 and reflowing at 200 ° C., and the multilayer printed wiring board 10 is formed. (See FIG. 8 (W)).

(Example 5)
Although it is the same as that of Example 4, the through-hole formation board | substrate 330 which has the penetration type through-hole 336 obtained in Example 3 was used as a core board | substrate.

(Example 6)
FIG. 10 shows a configuration of a multilayer printed wiring board according to the sixth embodiment. In this printed wiring board, the diameter D of the through hole 16 of the through hole 36 is formed to be 100 to 200 μm by a laser. In this example, the through hole 16 is not tapered. In the multilayer printed wiring board 10, the via hole 60 is formed immediately above the through hole 36 by forming the via hole 60 so as to close the through hole 16 of the through hole 36 formed in the core substrate 30. . For this reason, the wiring length in the multilayer printed wiring board is minimized, and it is possible to cope with the increase in the speed of the IC chip.

  Further, the dead space is eliminated by making the region immediately above the through hole 36 function as an inner layer pad. In addition, since it is not necessary to wire an inner layer pad for connecting the through hole 36 to the via hole 60, the shape of the land 36a of the through hole 36 can be a perfect circle. As a result, the arrangement density of the through holes 36 provided in the multilayer core substrate 30 is improved. In the present embodiment, if 20% to 50% of the bottom surface of the via hole 60 is in contact with the land 36a of the through hole 36, sufficient electrical connection can be achieved.

As described above, in the present invention, since a copper-clad laminate can be directly punched with a carbon dioxide laser, a fine through hole can be formed at low cost.

1A, FIG. 1B, FIG. 1C, and FIG. 1D are manufacturing process diagrams of a through-hole forming substrate according to Example 1 of the present invention. 2 (A), 2 (B), 2 (C), and 2 (D) are manufacturing process diagrams of the through hole forming substrate according to Example 2 of the present invention. 3 (A), 3 (B), 3 (C), and 3 (D) are manufacturing process diagrams of the through hole forming substrate according to Example 3 of the present invention. 4 (A), 4 (B), 4 (C), 4 (D), 4 (E), and 4 (F) show a multilayer printed wiring board according to Example 4 of the present invention. FIG. 5 (G), FIG. 5 (H), FIG. 5 (I), FIG. 5 (J), and FIG. 5 (K) are manufacturing process diagrams of the multilayer printed wiring board according to Example 4 of the present invention. 6 (L), FIG. 6 (M), FIG. 6 (N), FIG. 6 (O), and FIG. 6 (P) are manufacturing process diagrams of the multilayer printed wiring board according to Example 4 of the present invention. 7 (Q), FIG. 7 (R), FIG. 7 (S), and FIG. 7 (T) are manufacturing process diagrams of the multilayer printed wiring board according to Example 4 of the present invention. 8 (U), FIG. 8 (V), and FIG. 8 (W) are manufacturing process diagrams of the multilayer printed wiring board according to Example 4 of the present invention. It is sectional drawing of the multilayer printed wiring board which concerns on Example 4 of this invention. It is sectional drawing of the multilayer printed wiring board which concerns on Example 6 of this invention.

Explanation of symbols

16 Through-hole 30 Core substrate 34 Conductor circuit 36 Through hole 48 Opening 50 Interlayer resin insulation layer 52 Electroless plating layer 56 Electrolytic plating layer 58 Conductor circuit 60 Via hole 80A, 80B Build-up wiring layer 150 Interlayer resin insulation layer 158 Conductor circuit

Claims (8)

A substrate in which a through hole is formed in a double-sided copper-clad laminate, and the through hole is formed by conducting the through hole, wherein the through hole is tapered. The through hole forming substrate according to claim 1, wherein the taper is formed so that a diameter of the through hole increases in one direction of the substrate. The through hole forming substrate according to claim 9, wherein the taper is formed so that a cross section of the through hole is a stagnation type. In a multilayer wiring board in which a through-hole is provided in a double-sided copper-clad laminate, the interlayer resin insulating layer and a conductor circuit are formed on at least one surface of a substrate in which the through-hole is made conductive and a through-hole is formed, A multilayer printed wiring board, wherein the through hole is tapered. 5. The multilayer printed wiring board according to claim 4, wherein a thickness obtained by adding a thickness of the copper foil of the double-sided copper clad laminate and a thickness of the plating layer formed on the copper foil is 10 to 30 μm. The multilayer printed wiring board according to claim 4, wherein the taper is formed so that a diameter of the through hole increases toward one direction of the substrate. The multilayer printed wiring board according to claim 4, wherein the taper is formed so that a cross-section of the through hole is a stagnation type. The multilayer printed wiring board according to claim 4, wherein the through hole is filled with a filler.

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