JP4832621B2 - Multilayer printed wiring board - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multilayer printed wiring board in which an interlayer resin insulation layer and a conductor layer are alternately laminated, and a buildup layer in which each conductor layer is connected by a via hole is formed on both surfaces of a core substrate. The present invention relates to a multilayer printed wiring board that can be used as a package substrate on which an IC chip is placed, and a method for manufacturing the multilayer printed wiring board.
[0002]
[Prior art]
Conventionally, a build-up multilayer printed wiring board is manufactured by, for example, a method disclosed in JP-A-9-130050.
A roughened layer is formed on the surface of the conductor circuit of the printed wiring board by electroless plating or etching. Thereafter, an interlayer insulating resin is applied, exposed and developed by a roll coater or printing to form a via hole opening for interlayer conduction, and an interlayer resin insulating layer is formed through UV curing and main curing. Further, a catalyst such as palladium is attached to the roughened surface of the interlayer resin insulation layer which has been subjected to a roughening treatment with an acid or an oxidizing agent. Then, a thin electroless plating film is formed, a pattern is formed on the plating film with a dry film, and after thickening by electrolytic plating, the dry film is peeled off with alkali and etched to create a conductor circuit. . By repeating this, a build-up multilayer printed wiring board is obtained.
[0003]
[Problems to be solved by the invention]
Currently, with the increase in frequency of IC chips, multilayer printed wiring boards are also required to have higher transmission speeds. In order to meet such a demand, the present applicant has proposed Japanese Patent Application No. 10-334499. In this configuration, as shown in FIG. 7, a via hole 346 in the lower interlayer resin insulation layer 350 and a via hole 366 in the upper interlayer resin insulation layer 360 are disposed immediately above the through hole 336 to linearize the wiring. This shortens the wiring length and increases the signal transmission speed.
[0004]
However, in the above configuration, it has been found that the via hole 346 of the lower interlayer resin insulation layer 350 and the via hole 366 of the upper interlayer resin insulation layer 360 are peeled off under heat cycle conditions. When the present inventor studied this cause, it was found that the upper via hole 366 was affected by the surface shape of the lower via hole 346 and the connectivity was lowered. Furthermore, since the interlayer resin insulation layers 350 and 360 are not reinforced with a core material such as glass cloth, it is presumed that the interlayer resin insulation layers 350 and 360 are more easily peeled off by a heat cycle than the core substrate including the core material.
[0005]
The present invention has been made in order to solve the above-described problems, and an object of the present invention is to produce a multilayer printed wiring board and a multilayer printed wiring board that can shorten the internal wiring length and are excellent in connection reliability. It is to provide a method.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, in the multilayer printed wiring board according to claim 1, a lower interlayer resin insulation layer , a conductor layer, and an upper interlayer resin insulation layer are sequentially laminated, and each conductor layer is connected by a via hole. In the multilayer printed wiring board in which the built-up layer formed is formed on both surfaces of the core substrate,
A through hole is formed so as to penetrate the core substrate and the lower interlayer resin insulation layer formed on both surfaces of the core substrate;
A conductor film is formed on the inner wall of the through hole, and a filler composed of a resin and an inorganic filler is filled in the through hole. The exposed surface of the filler from the through hole is covered and connected to each other by the conductor film. A pair of conductive layers formed on the lower interlayer resin insulation layer ,
The pair of conductor layers includes an electroless plating film covering an exposed surface from the through hole of the resin filler, and an electrolytic plating film formed on the electroless plating film,
A technical feature is that a via hole connected to the solder is formed immediately above the through hole.
[0011]
In the multilayer printed wiring board according to claim 1 , a through hole is formed so as to penetrate the core substrate and an interlayer resin insulating layer formed on both surfaces of the core substrate, and a via hole is formed immediately above the through hole. . For this reason, the through hole and the via hole are linear, the wiring length is shortened, and the signal transmission speed can be increased. Further, the via hole is directly connected to the via hole connected to the external connection terminal, and the via hole is formed on the conductor layer covering the filler in the through hole flattened by polishing. Therefore, the connection reliability is excellent.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
First, the configuration of the multilayer printed wiring board according to the first embodiment of the present invention will be described with reference to FIG.
In the multilayer printed wiring board 10, build-up wiring layers 80 </ b> U and 80 </ b> D are formed on the front surface and the back surface of the core substrate 30. The build-up wiring layers 80U and 80D are formed on the lower interlayer resin insulation layer 50 in which the via hole 46 is formed, the upper interlayer resin insulation layer 60 in which the upper via hole 66 is formed, and the upper interlayer resin insulation layer 60. The solder resist layer 70 is formed. A solder bump (external connection terminal) 76 for connection to an IC chip (not shown) is formed in the upper via hole 66 through the opening 71 of the solder resist 70, and the lower via hole 66. Are connected to conductive connection pins (external connection terminals) 78 for connection to a daughter board (not shown).
[0013]
In the present embodiment, the through hole 36 connecting the build-up wiring layers 80U and 80D is formed so as to penetrate the core substrate 30 and the lower interlayer resin insulation layer 50. The through hole 36 is filled with a resin filler 54, and a lid plating 58 is disposed in the opening. Similarly, the via hole 46 formed in the lower interlayer resin insulation layer 50 is filled with a resin filler 54, and a lid plating 58 is disposed in the opening.
[0014]
In the present embodiment, a through hole 36 is formed so as to penetrate the core substrate 30 and the lower interlayer resin insulation layer 50, and a via hole 66 is formed immediately above the through hole 36. For this reason, the through hole 36 and the via hole 66 are linear, the wiring length is shortened, and the signal transmission speed can be increased. Further, since the through hole 36 and the via hole 66 connected to the external connection terminal (solder bump 76, conductive connection pin 78) are directly connected, the connection reliability is excellent. In particular, in the present embodiment, as will be described later, the filler 54 filled in the through-hole 36 is flattened by polishing, and then a lid plating (conductor layer) 58 covering the filler 54 is disposed thereon. Since the via hole 66 is formed, the surface of the through hole 36 is highly smooth, and the connection reliability between the through hole 36 and the via hole 66 is excellent.
[0015]
Further, in the multilayer printed wiring board of the present embodiment, the same filling resin 54 is filled in the through hole 36 and the lower via hole 46, so that it can be constructed at low cost, and in the through hole and in the via hole. Therefore, the reliability of the multilayer printed wiring board can be improved. Further, as will be described later, the filler 54 filled in the via hole 46 is flattened by polishing, and then a lid plating (conductor layer) 58 covering the filler 54 is provided, and an upper via hole 66 is formed thereon. Since it is formed, the smoothness of the surface of the lower via hole 46 is high, and the connection reliability between the lower via hole 46 and the upper via hole 66 is excellent.
[0016]
Furthermore, as will be described later, in the multilayer printed wiring board of the present embodiment, in the manufacturing process, the desmearing process of the through hole 35 that becomes the through hole 36 and the roughening process of the lower surface interlayer resin insulation layer surface 40 are simultaneously performed by an oxidizing agent. As a result, the number of processes can be reduced and the production can be made inexpensively.
[0017]
Next, a method for manufacturing the multilayer printed wiring board 10 will be described with reference to FIGS.
(1) Starting material is a copper clad laminate 30A in which 18 μm copper foil 32 is laminated on both sides of a substrate 30 made of glass epoxy resin, FR4, FR5, or BT (bismaleimide triazine) resin having a thickness of 0.8 mm. (FIG. 1 (A)). First, the copper-clad laminate is etched into a pattern to form inner layer copper patterns 34 on both sides of the substrate (FIG. 1B).
[0018]
(2) After the substrate 30 on which the inner layer copper pattern 34 and the through hole 36 are formed is washed with water, an etching solution containing a cupric complex and an organic acid is allowed to act on oxygen coexisting conditions such as spraying and bubbling to form a conductor. A roughening layer 38 is provided on the surface of the inner layer copper pattern 34 by a process of dissolving the copper conductor of the circuit to form a void (FIG. 1C).
In addition, the roughening layer may be provided by an oxidation-reduction treatment or an electroless plating alloy. The roughened layer to be formed is preferably in the range of 0.1 to 5 μm. Within this range, the conductor circuit and the interlayer resin insulation layer are unlikely to peel off.
[0019]
The cupric complex is preferably an azole cupric complex. This cupric complex of azoles acts as an oxidizing agent that oxidizes metallic copper and the like. As azoles, diazole, triazole, and tetrazole are preferable. Among these, imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, and the like are preferable. The addition amount of the cupric complex of azoles is preferably 1 to 15% by weight. It is because it is excellent in solubility and stability.
[0020]
Moreover, in order to dissolve copper oxide, an organic acid is blended with a cupric complex of azoles. Specific examples include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, acrylic acid, crotonic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, maleic acid, benzoic acid, glycolic acid, lactic acid, apple At least one selected from the group consisting of acids and sulfamic acids is preferred. The content of the organic acid is preferably 0.1 to 30% by weight. This is to maintain the solubility of oxidized copper and to ensure dissolution stability.
[0021]
The generated cuprous complex is dissolved by the action of an acid, and combined with oxygen to form a cupric complex, which again contributes to the oxidation of copper.
[0022]
Moreover, in order to assist the dissolution of copper and the oxidizing action of azoles, halogen ions such as fluorine ions, chlorine ions and bromine ions may be added to the etching solution. In the present invention, halogen ions can be supplied by adding hydrochloric acid, sodium chloride or the like. The halogen ion amount is preferably 0.01 to 20% by weight. This is because the adhesion between the formed roughened surface and the interlayer resin insulation layer is excellent.
[0023]
An etching solution is prepared by dissolving a cupric complex of an azole and an organic acid (halogen ion if necessary) in water. Moreover, the roughening surface concerning this invention can be formed using commercially available etching liquid, for example, the product name "MEC etch bond" by a MEC company.
[0024]
(3) A resin film 50α, which is a lower interlayer resin insulation layer, is laminated on the surface of the substrate 30 by vacuum compression laminating at a pressure of 5 kgf / cm ² while raising the temperature to 50 to 150 ° C. (FIG. 1D). ).
The resin film contains a hardly soluble resin, soluble resin particles, a curing agent, and other components. Each will be described below.
[0025]
The resin film used in the production method of the present invention is a resin film in which particles soluble in an acid or an oxidizing agent (hereinafter referred to as soluble particles) are dispersed in a resin that is hardly soluble in an acid or oxidizing agent (hereinafter referred to as a poorly soluble resin). It is.
As used herein, the terms “poorly soluble” and “soluble” refer to those having a relatively fast dissolution rate as “soluble” for convenience when immersed in a solution of the same acid or oxidizing agent for the same time. A relatively slow dissolution rate is referred to as “slightly soluble” for convenience.
[0026]
Examples of the soluble particles include resin particles soluble in an acid or an oxidizing agent (hereinafter, soluble resin particles), inorganic particles soluble in an acid or an oxidizing agent (hereinafter, soluble inorganic particles), and a metal soluble in an acid or an oxidizing agent. Examples thereof include particles (hereinafter, soluble metal particles). These soluble particles may be used alone or in combination of two or more.
[0027]
The shape of the soluble particles is not particularly limited, and examples thereof include spherical shapes and crushed shapes. Moreover, it is desirable that the soluble particles have a uniform shape. This is because a roughened surface having unevenness with uniform roughness can be formed.
[0028]
The average particle size of the soluble particles is preferably 0.1 to 10 μm. If it is the range of this particle size, you may contain the thing of a 2 or more types of different particle size. That is, it contains soluble particles having an average particle diameter of 0.1 to 0.5 μm and soluble particles having an average particle diameter of 1 to 3 μm. Thereby, a more complicated roughened surface can be formed and the adhesiveness with a conductor circuit is excellent. In the present invention, the particle size of the soluble particles is the length of the longest part of the soluble particles.
[0029]
Examples of the soluble resin particles include those made of a thermosetting resin, a thermoplastic resin, and the like, as long as the dissolution rate is higher than that of the hardly soluble resin when immersed in a solution made of an acid or an oxidizing agent. There is no particular limitation.
Specific examples of the soluble resin particles include, for example, an epoxy resin, a phenol resin, a polyimide resin, a polyphenylene resin, a polyolefin resin, a fluorine resin, and the like, and may be composed of one of these resins. And it may consist of a mixture of two or more resins.
[0030]
Moreover, as the soluble resin particles, resin particles made of rubber can be used. Examples of the rubber include polybutadiene rubber, epoxy-modified, urethane-modified, (meth) acrylonitrile-modified various modified polybutadiene rubber, carboxyl group-containing (meth) acrylonitrile-butadiene rubber, and the like. By using these rubbers, the soluble resin particles are easily dissolved in an acid or an oxidizing agent. That is, when soluble resin particles are dissolved using an acid, acids other than strong acids can be dissolved. When soluble resin particles are dissolved using an oxidizing agent, permanganese having a relatively low oxidizing power is used. Even acid salts can be dissolved. Even when chromic acid is used, it can be dissolved at a low concentration. Therefore, no acid or oxidant remains on the resin surface, and as described later, when a catalyst such as palladium chloride is applied after the roughened surface is formed, the catalyst is not applied or the catalyst is oxidized. There is nothing to do.
[0031]
Examples of the soluble inorganic particles include particles composed of at least one selected from the group consisting of aluminum compounds, calcium compounds, potassium compounds, magnesium compounds, and silicon compounds.
[0032]
Examples of the aluminum compound include alumina and aluminum hydroxide. Examples of the calcium compound include calcium carbonate and calcium hydroxide. Examples of the potassium compound include potassium carbonate. Examples of the magnesium compound include magnesia, dolomite, basic magnesium carbonate and the like, and examples of the silicon compound include silica and zeolite. These may be used alone or in combination of two or more.
[0033]
Examples of the soluble metal particles include particles composed of at least one selected from the group consisting of copper, nickel, iron, zinc, lead, gold, silver, aluminum, magnesium, calcium, and silicon. Further, the surface layer of these soluble metal particles may be coated with a resin or the like in order to ensure insulation.
[0034]
When two or more kinds of the soluble particles are used in combination, the combination of the two kinds of soluble particles to be mixed is preferably a combination of resin particles and inorganic particles. Both of them have low electrical conductivity, so that the insulation of the resin film can be ensured, and the thermal expansion can be easily adjusted between the poorly soluble resin, and no crack occurs in the interlayer resin insulation layer made of the resin film. This is because no peeling occurs between the interlayer resin insulation layer and the conductor circuit.
[0035]
The poorly soluble resin is not particularly limited as long as it can maintain the shape of the roughened surface when the roughened surface is formed using an acid or an oxidizing agent in the interlayer resin insulation layer. For example, thermosetting Examples thereof include resins, thermoplastic resins, and composites thereof. Moreover, the photosensitive resin which provided photosensitivity to these resin may be sufficient. By using a photosensitive resin, a via hole opening can be formed in the interlayer resin insulating layer by exposure and development.
Among these, those containing a thermosetting resin are desirable. This is because the shape of the roughened surface can be maintained by the plating solution or various heat treatments.
[0036]
Specific examples of the hardly soluble resin include, for example, an epoxy resin, a phenol resin, a polyimide resin, a polyphenylene resin, a polyolefin resin, and a fluorine resin. These resins may be used alone or in combination of two or more. Furthermore, an epoxy resin having two or more epoxy groups in one molecule is more desirable. Not only can the aforementioned roughened surface be formed, but also has excellent heat resistance, etc., so that stress concentration does not occur in the metal layer even under heat cycle conditions, and peeling of the metal layer is unlikely to occur. Because.
[0037]
Examples of the epoxy resin include a cresol novolac type epoxy resin, a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a phenol novolac type epoxy resin, an alkylphenol novolak type epoxy resin, a biphenol F type epoxy resin, a naphthalene type epoxy resin, Examples thereof include cyclopentadiene type epoxy resins, epoxidized products of condensates of phenols and aromatic aldehydes having a phenolic hydroxyl group, triglycidyl isocyanurate, and alicyclic epoxy resins. These may be used alone or in combination of two or more. Thereby, it will be excellent in heat resistance.
[0038]
In the resin film used in the present invention, it is desirable that the soluble particles are dispersed almost uniformly in the hardly soluble resin. A roughened surface with unevenness of uniform roughness can be formed, and even if a via hole or a through hole is formed in a resin film, the adhesion of the metal layer of the conductor circuit formed thereon can be secured. Because it can. Moreover, you may use the resin film containing a soluble particle only in the surface layer part which forms a roughening surface. As a result, since the portion other than the surface layer portion of the resin film is not exposed to the acid or the oxidizing agent, the insulation between the conductor circuits via the interlayer resin insulation layer is reliably maintained.
[0039]
In the resin film, the blending amount of the soluble particles dispersed in the hardly soluble resin is preferably 3 to 40% by weight with respect to the resin film. When the blending amount of the soluble particles is less than 3% by weight, a roughened surface having desired irregularities may not be formed. When the blending amount exceeds 40% by weight, the soluble particles are dissolved using an acid or an oxidizing agent. In addition, the resin film is melted to the deep part of the resin film, and the insulation between the conductor circuits through the interlayer resin insulating layer made of the resin film cannot be maintained, which may cause a short circuit.
[0040]
The resin film preferably contains a curing agent, other components and the like in addition to the soluble particles and the hardly soluble resin.
Examples of the curing agent include imidazole curing agents, amine curing agents, guanidine curing agents, epoxy adducts of these curing agents, microcapsules of these curing agents, triphenylphosphine, and tetraphenylphosphorus. And organic phosphine compounds such as nium tetraphenylborate.
[0041]
The content of the curing agent is desirably 0.05 to 10% by weight with respect to the resin film. If it is less than 0.05% by weight, since the resin film is not sufficiently cured, the degree of penetration of the acid and the oxidant into the resin film increases, and the insulating properties of the resin film may be impaired. On the other hand, if it exceeds 10% by weight, an excessive curing agent component may denature the composition of the resin, which may lead to a decrease in reliability.
[0042]
Examples of the other components include fillers such as inorganic compounds or resins that do not affect the formation of the roughened surface. Examples of the inorganic compound include silica, alumina, and dolomite. Examples of the resin include polyimide resin, polyacrylic resin, polyamideimide resin, polyphenylene resin, melanin resin, and olefin resin. By containing these fillers, it is possible to improve the performance of the printed wiring board by matching the thermal expansion coefficient, improving heat resistance, and chemical resistance.
[0043]
Moreover, the said resin film may contain the solvent. Examples of the solvent include ketones such as acetone, methyl ethyl ketone, and cyclohexanone, and aromatic hydrocarbons such as ethyl acetate, butyl acetate, cellosolve acetate, toluene, and xylene. These may be used alone or in combination of two or more.
[0044]
(4) Subsequently, a through-hole 35 for a through hole having a diameter of 300 μm is drilled in the core substrate 30 to which the resin film 50 is attached (FIG. 1E).
[0045]
(5) Then, a via hole opening 52 having a diameter of 80 μm is formed in the resin film 50α by carbonic acid, excimer, YAG, or UV laser (FIG. 2A). Thereafter, the resin film is thermally cured to form the lower interlayer resin insulation layer 50. The via hole may be formed by area processing using a laser or by area processing using a laser with a mask placed thereon. Moreover, a mixed laser (meaning a combination of a carbonic acid laser and an excimer laser) may be used. Both through holes and via holes may be formed by laser.
[0046]
(6) Next, through-holes for through holes formed in the core substrate 30 and the lower interlayer resin insulation layer 50 by using an oxidizing agent made of chromic acid or permanganate (potassium permanganate, sodium permanganate). At the same time as performing the desmear process 35, the surface of the lower interlayer resin insulation layer 50 is roughened (FIG. 2B).
[0047]
In the multilayer printed wiring board of this embodiment, the core substrate 30 is made of any of FR4, FR5, and BT resin, and the lower interlayer resin insulation layer 50 is made of epoxy resin, phenol resin, polyimide resin, polyphenylene resin, polyolefin resin, fluorine resin. Contains at least one of the resins. For this reason, it becomes possible to simultaneously perform the desmear treatment of the through-hole 35 and the roughening treatment of the lower interlayer resin insulation layer 50 with an oxidizing agent made of chromic acid and permanganate, and by reducing the number of steps, Multilayer printed wiring boards can be manufactured at low cost.
[0048]
(7) A palladium catalyst is applied to the surface of the interlayer resin insulation layer 50 whose surface has been roughened, and an electroless copper plating film 42 is formed in an electroless plating aqueous solution (FIG. 2C). Here, the electroless copper plating film is formed, but it is also possible to form a copper or nickel film by sputtering. Further, plasma, UV, or corona treatment may be performed on the surface layer as a dry treatment. This modifies the surface.
[0049]
(8) After washing the substrate on which the electroless copper plating film 42 is formed, a plating resist 43 having a predetermined pattern is formed (FIG. 2D).
(9) Then, the substrate is immersed in an electrolytic plating solution, and a current is passed through the electroless copper plating film 42 to form the electrolytic copper plating film 44 (FIG. 2E).
[0050]
(10) The plating resist 43 is peeled and removed with KOH, and the electroless copper plating film 42 under the plating resist is peeled off by light etching, whereby a via hole 46 made of the electroless copper plating film 42 and the electrolytic copper plating film 44 and A through hole 36 is formed (FIG. 3A).
[0051]
(11) A roughened layer (alloy made of Cu—Ni—P) 47 is formed in the via hole 46 and the through hole 36 by electroless plating (FIG. 3B). Instead of this electroless copper plating, the roughened layer is formed by etching (eg, etching is performed by spraying or dipping with a liquid containing a cupric complex and an organic acid salt) or by oxidation-reduction treatment. It is also possible to form
[0052]
(12) The resin filler 54 is filled into the through hole 36 and the via hole 46, and dried in a drying furnace at a temperature of 100 ° C. for 20 minutes (FIG. 3C). In this embodiment, since the same filler is filled in the through hole 36 and the via hole 46 at the same time, the manufacturing process can be reduced.
Here, as a resin filler, the following raw material composition can be used.
[Resin composition (1)]
Bisphenol F-type epoxy monomer (Oilized Shell, molecular weight 310, YL983U) 100 parts by weight, SiO2 spherical particles (manufactured by Admatech, CRS 1101-CE, with an average particle size of 1.6 μm, coated with a silane coupling agent on the surface) The maximum particle size is not more than the thickness (15 μm) of the inner layer copper pattern, which will be described later) 170 parts by weight and 1.5 parts by weight of a leveling agent (manufactured by Sannopco, Perenol S4) Obtained by adjusting to 360,000 to 49,000 cps at ± 1 ° C.
[Curing agent composition (2)]
6.5 parts by weight of imidazole curing agent (Shikoku Chemicals, 2E4MZ-CN).
[0053]
(13) One surface of the substrate 30 after the processing of (12) is polished so as to smooth the surface of the resin filler 54 protruding from the opening of the via hole 46 and the through hole 36, and then scratches caused by polishing Perform buffing to remove. Such a series of polishing is similarly performed on the other surface of the substrate (FIG. 3D).
Next, the resin filler 54 was cured by heat treatment at 100 ° C. for 1 hour and 150 ° C. for 1 hour.
The resin constituting the resin filler means an epoxy resin, a phenol resin, a fluorine resin, a triazine resin, a polyolefin resin, a polyphenylene ether resin, etc., and may be a thermosetting resin, a thermoplastic resin, or a composite of each, The resin may contain an inorganic filler such as silica or alumina and the coefficient of thermal expansion is adjusted. Moreover, you may use the paste which mainly has conductive metal fillers, such as conductive resin, gold | metal | money, silver, and copper. Furthermore, each composite may be used.
[0054]
(14) A palladium catalyst is applied to the surface of the interlayer resin insulation layer 50, and an electroless copper plating film 56 is formed in an electroless plating aqueous solution (FIG. 4A). Although the electroless copper plating film is formed here, it is also possible to form a copper or nickel film by sputtering.
[0055]
(15) After forming a predetermined pattern of plating resist (not shown), the electrolytic copper plating film 57 is formed, and then the plating resist is peeled and removed, and the electroless copper plating film 56 under the plating resist is light etched. By peeling off, the lid plating 58 composed of the electroless copper plating film 56 and the electrolytic copper plating film 57 is formed in the openings of the via hole 46 and the through hole 36 (FIG. 4B).
[0056]
(16) A roughened layer (Cu—Ni—P) 59 is formed by electroless plating on the lid plating 58 at the opening of the via hole 46 and the through hole 36 (FIG. 4C). Instead of this electroless copper plating, a roughened layer can be formed by etching or oxidation-reduction treatment.
(17) The upper interlayer resin insulation layer 60 is formed by repeating the steps (3) to (11) described above, and the electroless copper plating film 62 and the electrolytic copper plating film are formed on the upper interlayer resin insulation layer 60. A via hole 66 made of 64 is formed (FIG. 4D).
(18) Subsequently, solder resist and solder bumps are formed. The raw material composition of the solder resist consists of the following.
46.67g of photosensitizing oligomer (molecular weight 4000) obtained by acrylating 50% of epoxy group of 60% by weight of cresol novolak type epoxy resin (manufactured by Nippon Kayaku) dissolved in DMDG, 80% by weight dissolved in methyl ethyl ketone 15.0 g of bisphenol A type epoxy resin (manufactured by Yuka Shell, Epicoat 1001), 1.6 g of imidazole curing agent (manufactured by Shikoku Kasei Co., Ltd., 2E4MZ-CN), polyvalent acrylic monomer (Nippon Kayaku Co., Ltd., R604) 3 g, 1.5 g of a polyacrylic monomer (Kyoeisha Chemical Co., DPE6A) and 0.71 g of a dispersion antifoam (Sanopco Co., S-65) were mixed, and benzophenone (photoinitiator) was added to this mixture. 2 g of Kanto Chemical Co., Ltd.) and 0.2 g of Michler's ketone (manufactured by Kanto Chemical Co., Ltd.) as a photosensitizer were added to adjust the viscosity to 2.0 Pa · s at 25 ° C. Get.
As the solder resist layer, various resins can be used, for example, bisphenol A type epoxy resin, bisphenol A type epoxy resin acrylate, novolac type epoxy resin, novolak type epoxy resin acrylate, amine-based curing agent, imidazole curing agent, etc. Resin cured with can be used.
In particular, when forming solder bumps by providing openings in the solder resist layer, it is preferable that the solder resist layer is made of “novolak type epoxy resin or acrylate of novolak type epoxy resin” and contains “imidazole curing agent” as a curing agent.
The solder resist composition 70α is applied to both surfaces of the multilayer printed wiring board obtained in the above (17) with a thickness of 20 μm (FIG. 5A).
[0057]
(19) Next, after drying at 70 ° C. for 20 minutes and at 80 ° C. for 30 minutes, a 5 mm thick photomask film on which a circular pattern (mask pattern) was drawn was placed in close contact, and 1000 mJ Expose with UV light of / cm ² and develop with DMTG. Further, the solder resist layer 70 (thickness 20 μm) having an opening 71 (opening diameter 200 μm) is heat-treated at 80 ° C. for 1 hour, 100 ° C. for 1 hour, 120 ° C. for 1 hour, and 150 ° C. for 3 hours. ) Is formed (FIG. 5B).
[0058]
(20) After that, the plating post 242 exposed from the multilayer printed wiring board opening 71 was replaced with nickel chloride 2.3 × 10 ⁻¹ mol / l, sodium hypophosphite 2.8 × 10 ⁻¹ mol / l, sodium citrate 1.6 × 10 A nickel plating layer 72 having a thickness of 5 μm is formed in the opening 71 by dipping in an electroless nickel plating solution having a pH = 4.5 consisting of ⁻¹ mol / l for 20 minutes. Further, potassium gold cyanide 7.6 × 10 ⁻³ mol / l, ammonium chloride 1.9 × 10 ⁻¹ mol / l, sodium citrate 1.2 × 10 ⁻¹ mol / l, sodium hypophosphite 1.7 × 10 ⁻¹ mol / l A gold plating layer 74 having a thickness of 0.03 μm is formed on the nickel plating layer 72 by immersing in an electroless gold plating solution consisting of 7.5 minutes at 80 ° C. (FIG. 5C).
In the above-described example, the intermediate layer is formed of nickel and the noble metal layer is formed of gold. However, in addition to nickel, there are cases where the layer is formed of palladium, titanium, or the like. Further, two or more noble metal layers may be formed. As the surface treatment, dry treatment, plasma, UV, or corona treatment may be performed. Thereby, the filling property of the underfill is improved.
[0059]
(23) Then, solder paste is printed in the opening 71 of the solder resist layer 70 and reflowed at 200 ° C. to form solder bumps (solder bodies) 76 in the via holes 66 on the upper surface. The conductive connection pin 78 is attached to the via hole 66 through the solder 77 (see FIG. 6). A BGA may be formed instead of the conductive connection pin.
[0060]
(Comparative example)
As a comparative example, a multilayer printed wiring board was obtained by filling the lower via hole side with copper plating while having the same configuration as the multilayer printed wiring board of the present embodiment shown in FIG. The result of evaluating the multilayer printed wiring board of this embodiment and the multilayer printed wiring board of the comparative example is shown in FIG.
[0061]
The electrical tangency was checked for continuity with a checker. The case where there was a short circuit or disconnection was determined as NG, and the case where there was no short circuit was determined as OK. In addition, peeling and swelling were performed after a heat cycle test (-65 ° C / 3 minutes + 130 ° C / 3 minutes as one cycle and repeated 1000 cycles), and the cross-section was cut between layers with a microscope (× 100 to 400). The resin insulation layer and via hole were visually inspected for peeling and swelling.
[0062]
In the comparative example, a depression that was not completely filled by plating was formed on the surface of the lower via hole, and the connectivity with the upper via hole was lowered. For this reason, a portion that is not electrically connected between the via holes may occur.
In addition, after the heat cycle test, it was confirmed that the interlayer resin insulation layer was peeled and swollen due to peeling between the via holes. In the multilayer printed wiring board of this embodiment, the above-described connectivity was satisfactory, and neither peeling nor swelling was confirmed.
[Brief description of the drawings]
FIG. 1 is a manufacturing process diagram of a multilayer printed wiring board according to a first embodiment of the present invention.
FIG. 2 is a manufacturing process diagram of the multilayer printed wiring board according to the first embodiment of the present invention.
FIG. 3 is a manufacturing process diagram of the multilayer printed wiring board according to the first embodiment of the present invention.
FIG. 4 is a manufacturing process diagram of the multilayer printed wiring board according to the first embodiment of the present invention.
FIG. 5 is a manufacturing process diagram of the multilayer printed wiring board according to the first embodiment of the present invention.
FIG. 6 is a cross-sectional view of the multilayer printed wiring board according to the first embodiment of the present invention.
FIG. 7 is a cross-sectional view of a multilayer printed wiring board according to the prior art.
FIG. 8 is a chart showing evaluation results of the first embodiment and a comparative example.
[Explanation of symbols]
30 Core substrate 32 Copper foil 34 Conductor circuit 35 Through hole 36 Through hole 38 Roughening layer 42 Electroless copper plating film 43 Resist 44 Electrolytic copper plating film 46 Via hole 47 Roughening layer 48 Conductor circuit 50 Lower interlayer resin insulation layer 52 Opening 54 Filling resin 56 Electroless copper plating film 57 Electroless copper plating film 58 Lid plating 59 Roughening layer 60 Upper interlayer resin insulation layer 62 Electroless copper plating film 64 Electrolytic copper plating film 66 Via hole 70 Solder resist 71 Opening 72 Nickel Plating layer 74 Gold plating layer 76 Solder bump 77 Solder 78 Conductive connection pins 80U, 80D Build-up wiring layer

Claims (3)

A multilayer print in which a build-up layer in which a lower interlayer resin insulation layer , a conductor layer, and an upper interlayer resin insulation layer are sequentially laminated and each conductor layer is connected by a via hole is formed on both surfaces of the core substrate In the wiring board,
A through hole is formed so as to penetrate the core substrate and the lower interlayer resin insulation layer formed on both surfaces of the core substrate;
A conductor film is formed on the inner wall of the through hole, and a filler composed of a resin and an inorganic filler is filled in the through hole. The exposed surface of the filler from the through hole is covered and connected to each other by the conductor film. A pair of conductive layers formed on the lower interlayer resin insulation layer ,
The pair of conductor layers includes an electroless plating film covering an exposed surface from the through hole of the resin filler, and an electrolytic plating film formed on the electroless plating film,
A multilayer printed wiring board, wherein a via hole connected to solder is formed immediately above the through hole.   The multilayer printed wiring board according to claim 1, wherein the solder is provided in a via hole.   3. The multilayer printed wiring board according to claim 1, wherein a via hole immediately above the through hole is formed in the outermost interlayer resin insulation layer and on the pair of conductor layers. .

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