JP2017191893A - Printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board including a laminated substrate including a surface conductive layer of electrolytic plated copper and a solder resist layer (SR layer), capable of bringing the surface conductive layer and the SR layer into close contact with each other to suppress delamination.SOLUTION: The printed wiring board includes a laminated substrate 2 and an SR layer 30. The laminated substrate 2 contains a surface conductor layer 26 of electrolytic plated copper on the outermost surface. A bonding layer 50 is interposed between the SR layer 30 and the surface conductor layer 26. The bonding layer 50 is a layer containing copper and nitrogen and having a thickness of 20 to 200 nm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a printed wiring board.

  Conventionally, a surface conductor layer pattern is provided on the surface layer of the laminated base body, the conductor layer is covered with a solder resist layer (insulating protective layer), an opening is formed in a part of the solder resist layer, A printed wiring board in which a part is exposed as a mounting pad for mounting a semiconductor element is known.

  In patent document 1, in the adhesion method of a metal and a resin material, a surface treatment liquid containing an azolesilane compound having a predetermined structure is brought into contact with the surface of a metal such as copper to form a chemical conversion film. It is disclosed to bond a metal and a resin material.

Japanese Patent Laying-Open No. 2015-143395

  Patent Document 1 does not disclose the use of a chemical conversion film composed of a surface treatment liquid containing an azolesilane compound having a predetermined structure for adhesion between a surface conductor layer containing electrolytically plated copper and a solder resist layer. .

  The present inventors have not yet provided a sufficiently satisfactory technique as a technique for bringing a surface conductor layer containing electrolytically plated copper into close contact with a solder resist layer, and thought that the necessity for development is still high.

The present invention includes the following inventions.
The present invention
A laminated base material including at least one conductor layer and an insulating layer, and a solder resist layer laminated on at least one of the surfaces of the laminated base material,
The laminated substrate is a printed wiring board including a surface conductor layer on a surface in contact with the solder resist layer as at least a part of the conductor layer,
The surface conductor layer includes electroplated copper,
A bonding layer is interposed between the surface conductor layer and the solder resist layer,
The bonding layer relates to a printed wiring board which is a layer having a thickness of 20 to 200 nm containing copper and nitrogen.

  According to one embodiment of the printed wiring board of the present invention, the surface conductor layer containing electroplated copper and the solder resist layer can be in close contact with each other through a bonding layer containing copper and nitrogen, and the surface conductor layer and Delamination (haloing) between the solder resist layer is suppressed.

1 is a schematic cross-sectional view of a printed wiring board 1 according to an embodiment of the present invention. It is a schematic sectional drawing (1) for demonstrating the manufacturing process of the printed wiring board 1 which concerns on one Embodiment of this invention. It is a schematic sectional drawing (2) for demonstrating the manufacturing process of the printed wiring board 1 which concerns on one Embodiment of this invention. It is a schematic sectional drawing (3) for demonstrating the manufacturing process of the printed wiring board 1 which concerns on one Embodiment of this invention. It is a schematic sectional drawing (4) for demonstrating the manufacturing process of the printed wiring board 1 which concerns on one Embodiment of this invention. It is a schematic sectional drawing (5) for demonstrating the manufacturing process of the printed wiring board 1 which concerns on one Embodiment of this invention. It is a schematic sectional drawing (6) for demonstrating the manufacturing process of the printed wiring board 1 which concerns on one Embodiment of this invention. It is an enlarged view of the area | region shown by X in the schematic sectional drawing shown in FIG. 1 of the printed wiring board 1 which concerns on one Embodiment of this invention. It is the photograph of the observation image by the transmission electron microscope (TEM) of the junction layer 50 vicinity of the printed wiring board 1 which concerns on one Embodiment of this invention actually manufactured. The analysis result by XPS of the element in each point shown in FIG. 4 is shown.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings.
A printed wiring board 1 according to an embodiment of the present invention is configured as shown in the schematic cross-sectional view of FIG.
The printed wiring board 1 includes one or more laminated conductor layers and insulating layers. Specifically, the printed wiring board 1 includes a core layer 10, a buildup layer 20, and a solder resist layer 30. The printed wiring board 1 is a package board on which a semiconductor element such as an IC chip can be mounted by flip chip connection, and can be mounted on another printed wiring board such as a mother board after the semiconductor element is mounted. The printed wiring board 1 of this embodiment is a multilayer laminated printed wiring board, and has a plate shape or a film shape as a whole. Although not shown, it is natural that the present embodiment can be applied to a coreless printed wiring board that does not include the core layer 10.

  In the present embodiment, the printed wiring board 1 has a vertically symmetrical structure with the central axis CL of the core insulating layer 11 in between. For this reason, in the following description, only one side from the central axis CL will be described. In the present embodiment, the printed wiring board 1 has a vertically symmetrical structure with the central axis CL in between. However, the printed wiring board 1 may have an asymmetrical structure according to the target circuit configuration, and the structure is not limited. Absent.

  The core layer 10 includes a core insulating layer 11 and a first conductor layer 12 formed on each of both main surfaces of the core insulating layer 11. The core layer 10 is provided with a filled through hole 13 that conducts between the first conductor layers 12 formed on both main surfaces of the core insulating layer 11.

  The buildup layer 20 is laminated on both surfaces of the core layer 10. Each buildup layer 20 is formed by laminating one or more conductor layers and one or more insulating layers. Specifically, the following structures can be exemplified.

  The first insulating layer 21 covers the first conductor layer 12 of the core layer 10. A second conductor layer 23 is formed on the surface of the first insulating layer 21 on the side where the first conductor layer 12 is not disposed. A first conductor via 22 that penetrates the first insulating layer 21 and electrically connects the first conductor layer 12 and the second conductor layer 23 is formed inside the first insulating layer 21. The second conductor layer 23 is further covered with a second insulating layer 24.

  A surface conductor layer (third conductor layer) 26 is formed on the surface of the second insulating layer 24 on the side where the second conductor layer 23 is not disposed. Inside the second insulating layer 24, a second conductor via 25 that penetrates the second insulating layer 24 and electrically connects the second conductor layer 23 and the surface conductor layer 26 is formed.

  The surface conductor layer 26 is a conductor layer located on the outermost layer of the conductor layers, and includes at least a plurality of conductor pads 27 connected to a board mounting component (not shown). A wiring pattern may be included. Since the surface conductor layer 26 has a pattern including a plurality of conductor pads 27, it can be referred to as a “pad conductor layer”. The build-up layer 20 may include a further insulating layer and / or a conductor layer, and the conductor layer may be connected by a further conductor via.

  The solder resist layer 30 is the outermost layer of the printed wiring board 1 and is provided so as to cover the surface conductor layer 26 of the buildup layer 20. The solder resist layer 30 is an insulating layer located in the outermost layer among the insulating layers included in the printed wiring board 1. A plurality of openings 31 are provided in the solder resist layer 30. In each opening 31, it is located so that the conductor pad 27 of the surface conductor layer 26 may be exposed.

  The conductor pad 27 is arranged so as to bite into the edge of the opening 31 (specifically, the vicinity 31a of the laminated base material of the opening 31). The conductor pads 27 arranged in this way are referred to as SMD (Solder Mask Defined) pads. On the other hand, although not shown, the conductor pads arranged in the opening 31 so that a gap is formed between the conductor pad and the edge of the opening 31 (specifically, the portion 31a near the laminated base material of the opening 31). This is referred to as NSMD (Non Solder Mask Defined) pad. In this specification, when it is necessary to distinguish between an SMD pad and an NSMD pad, the conductor pad 27 may be expressed as an SMD pad 27, the opening 31 may be expressed as an SMD opening 31, and the like.

Solder bumps S are provided on the conductor pads 27 in each opening 31.
A portion of the printed wiring board 1 excluding the solder resist layer 30, that is, a portion including the core layer 10 and the buildup layers 20 arranged on both surfaces of the core layer 10 is referred to as a laminated base material 2. Furthermore, a portion of the laminated base material 2 excluding the surface conductor layer 26 which is the outermost layer is referred to as a laminated body 3. The laminated body 3 includes a laminated conductor layer and an insulating layer. The multilayer base material 2 includes a multilayer body 3 and a conductor layer (surface conductor layer 26) including one or more pads 27 disposed on at least one of the main surfaces of the multilayer body 3. Of the insulating layers included in the printed wiring board 1, the insulating layers (first insulating layer 21 and second insulating layer 24) included in the stacked body 3 are “interlayer insulating layers”, and the solder resist layer 30 is “protective insulating layer”. It may be called.

  Each interlayer insulating layer can be formed of an insulating composition such as a thermosetting resin composition or a photosensitive resin composition. These insulating compositions may contain an inorganic filler, and the content thereof is, for example, 30 to 80% by mass.

  As shown in FIG. 1, each conductor layer (the first conductor layer 12, the second conductor layer 23, the surface conductor layer 26, the filled through hole 13, the first conductor via 22, and the second conductor via 25) includes a plurality of conductors. It may be formed by stacking layers. For example, as shown in FIG. 2A to FIG. 2F, the second conductor layer 23 can be configured by a laminated structure of a second seed layer 23a and a second electrolytic plating layer 23b. 2B to 2F, the surface conductor layer 26 can be configured by a laminated structure of a third seed layer 26a and a third electrolytic plating layer 26b. Although not indicated, the first conductor layer 12 can be similarly configured by a laminated structure of a first seed layer and a first electrolytic plating layer. Further, the seed layer included in the filled through hole 13 can be integrated with the first seed layer. Similarly, the seed layer included in the first conductor via 22 may be integral with the second seed layer 23a, and the seed layer included in the second conductor via 25 may be integral with the third seed layer 26a. Each seed layer is a layer serving as a base for forming an electrolytic plating layer on the surfaces of the interlayer insulating layers 21 and 24 and the core insulating layer 11, and more specifically, an electroless plating layer, a metal formed by sputtering. Layer etc. An example of the conductor constituting each conductor layer is copper. In particular, the third electroplating layer 26b of the surface conductor layer (third conductor layer) 26 is preferably an electroplated copper layer.

  The solder resist layer 30 is a layer made of an insulating resin composition. The composition of the insulating resin composition constituting the solder resist layer 30 is not particularly limited. For example, the solder resist layer 30 can be an insulating resin composition layer formed by photocuring a photosensitive resin composition containing at least a photosensitive resin and a photopolymerization initiator.

  Here, the photosensitive resin is also called a photosensitive polymer or a photopolymer. The photosensitive resin is a polymer compound whose physical properties change as a result of a photochemical reaction, and is typically a polymer compound that is cured by light irradiation in the presence of a photopolymerization initiator. A typical example of the photosensitive resin is a polymer compound having a radical polymerizable double bond. The photosensitive resin is, for example, a polymer compound containing a (meth) acryloyl group in a side chain derived from at least one selected from acrylic acid and methacrylic acid (expressed as “(meth) acrylic acid”), Specifically, the photosensitive resin which (meth) acrylate-ized the said thermosetting group of the thermosetting resin which has a thermosetting group is mentioned. As said thermosetting resin which has a thermosetting group, the epoxy resin which has an epoxy group which is a thermosetting group can be illustrated. Examples of the epoxy resin include novolak type epoxy resins such as phenol novolak type and alkylphenol novolak type (cresol novolak type), alicyclic epoxy resins and the like, and novolak type epoxy resins are particularly preferable. As the (meth) acrylate of the epoxy resin, those having both thermosetting property and photosensitivity in which two or more epoxy groups remain in one molecule are preferable. Two or more photosensitive resins may be used in combination.

  The photopolymerization initiator is a compound that can absorb light energy and supply radically active species, and typical examples thereof include aromatic ketones. Examples of aromatic ketone photopolymerization initiators include alkylphenone derivatives and benzophenone derivatives. Two or more photopolymerization initiators may be used in combination.

  The photosensitive resin composition may further contain other components. Examples of other components that can be contained in the photosensitive resin composition include photosensitizers, thermosetting resins, epoxy resin curing agents, and inorganic fillers.

  The photosensitizer can be appropriately selected according to the wavelength of light to be irradiated, the photopolymerization initiator, and the like. Examples of the photosensitizer include Michler's ketone and thioxanthone photosensitizer. Two or more photosensitizers may be used in combination.

  Specific examples of the thermosetting resin include epoxy resin, phenol resin, polyimide resin, polyester resin, bismaleimide resin, polyolefin resin, polyphenylene ether resin, and the like. Two or more thermosetting resins may be used in combination.

  As the epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolak type, alkylphenol novolak type (cresol novolak type, etc.) novolak type epoxy resin, alicyclic epoxy resin, biphenyl type epoxy resin, naphthalene type Examples thereof include epoxy resins, dicyclopentadiene type epoxy resins, epoxidized products of condensates of phenols and aromatic aldehydes having a phenolic hydroxyl group, and triglycidyl isocyanurate. Two or more epoxy resins may be used in combination.

  The epoxy resin curing agent is used in combination when an epoxy resin is used as the thermosetting resin. The epoxy resin curing agent is involved in the formation of crosslinks between epoxy groups. Examples of the epoxy resin curing agent include an imidazole curing agent, an amine curing agent, an acid anhydride curing agent, a phenol curing agent, and a polymercaptan curing agent, and an imidazole curing agent is particularly preferable. Two or more epoxy resin curing agents may be used in combination.

Examples of the inorganic filler include silica, barium sulfate, and talc.
The photosensitive resin composition may be used in the form of a fluid (liquid or paste) containing an appropriate solvent. Although it does not specifically limit as said solvent, For example, they are glycol ethers. Examples of glycol ethers include diethylene glycol dimethyl ether and triethylene glycol dimethyl ether. Two or more kinds of solvents may be used in combination.

As the photosensitive resin composition, one prepared separately as a photosensitive dry film may be used.
The photosensitive resin composition may be prepared independently, may be a commercially available composition for forming a solder resist, or may be a modification of a commercially available composition for forming a solder resist. There may be.

  Furthermore, solder bumps S are installed on the conductor pads 27 surrounded by the openings 31. In this case, before the solder bump S is installed, a surface treatment layer (not shown) for preventing oxidation may be provided on the surface of the conductor pad 27. By providing the surface treatment layer on the surface of the conductor pad 27, it is possible to prevent the conductor pad 27 from being oxidized before the solder bump is formed, and to improve the riding of the solder on the conductor pad 27. Examples of the surface treatment layer include plating films such as nickel-gold plating, nickel-palladium-gold plating, and tin plating, and OSP (organic solderability preservative) films (preflux films).

  In the printed wiring board 1 of the present embodiment, the bonding layer 50 is interposed between the surface conductor layer 26 including the third electrolytic plating layer 26 b and the solder resist layer 30. The bonding layer 50 is considered to play a role of bonding the surface conductor layer 26 and the solder resist layer 30.

Hereinafter, characteristics of the bonding layer 50 will be described.
FIG. 3 shows a schematic diagram in which the region X in FIG. 1 is enlarged. The region X is a portion where the surface conductor layer 26 (conductor pad 27), the solder bump S, the bonding layer 50, and the solder resist layer 30 are close to each other.
In the present embodiment, the thickness T of the bonding layer 50 is preferably 20 to 200 nm. When the thickness T is in this range, it is preferable in view of the function of the bonding layer 50 that firmly bonds the surface conductor layer 26 (conductor pad 27) and the solder resist layer 30.

  The bonding layer 50 includes copper and nitrogen. FIG. 4 is a photograph of an observation image obtained by a transmission electron microscope (TEM) of a cross section of a printed wiring board 1 in which a surface conductor layer 26 made of electrolytically plated copper, a bonding layer 50, and a solder resist layer 30 are laminated. Indicates. The lower right gap in FIG. 4 corresponds to the opening 31 of the solder resist layer 30. A portion of the surface conductor layer 26 facing the opening 31 is provided with a surface treatment layer containing nickel. No solder bump is provided in the opening 31. In FIG. 4, the scale bar indicates 50 nm. The elemental composition at each point shown in FIG. 4 was evaluated using X-ray photoelectron spectroscopy (XPS) in which the photoelectron energy generated upon irradiation with X-rays was measured to analyze the element structure. Let the surface of the surface conductor layer 26 be a point e.

  The result of XPS is shown in FIG. The numerical value on the horizontal axis indicates the mass ratio of each element. Although carbon is included in addition to the elements shown in FIG. 5, the relative amount of carbon is not shown in FIG. Nitrogen (N) and copper (Cu) exist at each point from point f to point i. The point i is about 115 nm away from the point e on the surface of the surface conductor layer 26 made of electrolytically plated copper. The nickel (Ni) contained in the point f is considered to be derived from the surface treatment layer provided in the portion facing the opening 31 of the surface conductor layer 26. The points j and k are separated from the point e by about 145 nm and about 210 nm, respectively, and at these points, nitrogen (N) and copper (Cu) are almost not included. A portion of about 120 nm (including points f, g, h, and i) laminated on the surface conductor layer 26 made of electrolytically plated copper corresponds to the bonding layer 50, and the upper portion corresponds to the solder resist layer 30.

  The bonding layer 50 is interposed at the interface between the surface conductor layer 26 (conductor pad 27) and the solder resist layer 30, and has a function of bonding the two. In particular, if the bonding pad 50 does not exist when the conductor pad 27 is an SMD pad as shown in FIGS. 1 and 3, the conductor pad 27 (surface conductor) is introduced when the solder bump S is introduced into the opening 31. It is considered that the interface between the layer 26) and the solder resist layer 30 riding on the layer 26) is easily peeled off from the vicinity of the laminated base material 31a of the opening 31. On the other hand, according to the present embodiment, the conductor pad 27 that is an SMD pad and the solder resist layer 30 that rides on the conductor pad 27 are joined via the joining layer 50, so that the conductor pad 27 and the solder resist layer 30 are peeled off. Is unlikely to occur.

  The bonding layer 50 preferably has a liquid composition containing an azole compound having two or more nitrogen atoms in one aromatic ring and a liquid medium in contact with the surface of the surface conductor layer 26 containing electrolytically plated copper, It is formed by drying. The drying is preferably performed under oxidizing conditions, for example, in an air atmosphere, at a relatively high temperature, for example, 20 to 130 ° C, more preferably 45 to 100 ° C. By drying under this condition, it is considered that copper on the surface of the surface conductor layer 26 is oxidized to copper (II) ions and diffuses into the coating containing the azole compound. The azole compound is considered to coordinate to a copper (II) ion by an unshared electron pair on a nitrogen atom, and a plurality of nitrogen atoms can be coordinated to one copper (II) ion. Moreover, the azole compound has two or more nitrogen atoms in one ring, and it is considered that each nitrogen atom can coordinate to a copper (II) ion. For this reason, in the film containing the azole compound, it is considered that the diffused copper (II) ions and the azole compound are alternately bonded to form a polymer. The bonding layer 50 which is such a coating has affinity for both the surface conductor layer 26 containing electrolytic plated copper and the solder resist layer 30 containing resin, and the surface conductor layer 26 and the solder resist layer. 30 can be joined.

  An azole compound having two or more nitrogen atoms in one aromatic ring may have an azole ring having two or more nitrogen atoms in one aromatic ring, and may have a substituent on the ring. . Examples of the azole compound include a diazole compound in which the azole ring part is diazole (1,2-diazole or 1,3-diazole), and the azole ring part is triazole (1,2,3-triazole or 1,2 , 4-triazole), a tetrazole compound in which the azole ring portion is 1H-tetrazole, and the like.

As a liquid medium used for the preparation of the liquid composition containing the azole compound, water or an organic solvent can be used.
As the water, pure water such as ion-exchanged water or distilled water can be used.
Examples of the organic solvent include methanol, ethanol, propanol and the like.
A mixture of two or more of the liquid media can also be used.

  In the present embodiment, the concentration of the azole compound in the liquid composition is preferably 0.001 to 10% by mass, and more preferably 0.01 to 5% by mass. When the concentration of the azole compound is within this range, the bonding effect between the surface conductor layer 26 and the solder resist layer 30 is considered to be sufficient and economical.

There is no restriction | limiting in particular as a method of making the said liquid composition contact the surface of the surface conductor layer 26, Means, such as immersion, application | coating, and spraying, can be used.
The time (treatment time) for bringing the liquid composition into contact with the surface of the surface conductor layer 26 is not particularly limited, but may be 1 second to 10 minutes, and more preferably 5 seconds to 3 minutes. When the treatment time is within the above range, it is easy to form a film of the liquid composition having a sufficient thickness on the surface of the surface conductor layer 26. The temperature of the liquid composition at the time of bringing the liquid composition into contact with the surface of the surface conductor layer 26 is preferably 5 to 50 ° C., but can be set as appropriate in relation to the processing time. .

After contacting the liquid composition and the surface of the surface conductor layer 26, the liquid composition may be washed with water and dried, or may be dried without washing with water. The drying temperature is as described above.
The water used for washing is preferably pure water such as ion-exchanged water or distilled water, but the washing method and time are not particularly limited, and may be washed for an appropriate time by means such as immersion or spraying.

  Before bringing the liquid composition into contact with the surface of the surface conductor layer 26, the surface is subjected to at least one pretreatment selected from the group consisting of pickling treatment, roughening treatment, heat treatment, rust prevention treatment or chemical conversion treatment. May be performed.

  The pickling treatment is performed to remove oil and fat components adhering to the surface of the surface conductor layer 26 and to remove the oxide film on the copper surface. For this pickling treatment, solutions such as hydrochloric acid solution, sulfuric acid solution, nitric acid solution, sulfuric acid-hydrogen peroxide solution, organic acid solution, inorganic acid-organic solvent solution, organic acid-organic solvent solution, etc. Can be used.

  The roughening treatment is performed in order to enhance the adhesion between copper and the resin due to the anchor effect. A rough surface is provided on the surface of the copper, and the adhesion between the copper and the resin material can be enhanced. In this roughening treatment, methods such as microetching, electrolytic plating, electroless plating, oxidation (black oxide, brown oxide), oxidation / reduction, brush polishing, jet scrub, etc. may be employed. it can.

In the microetching method, for example, organic acid / cupric ion type, sulfuric acid / hydrogen peroxide type, persulfate type, copper chloride type or iron chloride type etchants can be used.
In the electrolytic plating method described above, unevenness is formed on the copper surface by precipitating fine copper particles on the copper surface.

  The heat-resistant treatment is selected from nickel, nickel-phosphorus, zinc, zinc-nickel, copper-zinc, copper-nickel, copper-nickel-cobalt, or nickel-cobalt on the surface of the surface conductor layer 26 containing electrolytically plated copper. A treatment for forming at least one kind of coating film. This coating can be formed by employing a known method by electrolytic plating, but is not limited to electroplating, and any other means such as vapor deposition may be used.

  The rust prevention treatment is performed to prevent the surface of the surface conductor layer 26 containing electrolytic plating copper from being oxidized and corroded. On the surface of the copper, a plated coating of zinc or a zinc alloy composition, electrolytic A method of forming a chromate plating film can be employed.

  In the chemical conversion treatment, a method of forming a passive film of tin on the surface of the surface conductor layer 26 containing electrolytically plated copper or a method of forming a passive film of copper oxide can be employed.

  Before bringing the liquid composition into contact with the surface of the surface conductor layer 26, an aqueous solution containing copper ions may be brought into contact with the surface. The aqueous solution containing copper ions has a function of making the thickness of the bonding layer 50 formed on the surface of the surface conductor layer 26 uniform. The copper ion source is not particularly limited as long as it is a copper salt that dissolves in water, and examples thereof include copper salts such as copper sulfate, copper nitrate, copper chloride, copper formate, and copper acetate. In order to solubilize the copper salt in water, ammonia or hydrochloric acid may be added.

  After the liquid composition is brought into contact with the surface of the surface conductor layer 26, an acidic aqueous solution or an alkaline aqueous solution may be brought into contact with the surface. This acidic aqueous solution or alkaline aqueous solution also has a function of making the thickness of the bonding layer 50 formed on the surface of the surface conductor layer 26 uniform, similarly to the aqueous solution containing copper ions. The acidic aqueous solution or alkaline aqueous solution is not particularly limited, and examples of the acidic aqueous solution include an aqueous solution containing a mineral acid such as sulfuric acid, nitric acid, and hydrochloric acid, and an organic acid such as formic acid, acetic acid, lactic acid, glycolic acid, and amino acid. it can. Examples of the alkaline aqueous solution include aqueous solutions containing alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and amines such as ammonia, ethanolamine and monopropanolamine.

<Method for manufacturing printed wiring board>
Next, an example of the manufacturing method of the printed wiring board 1 of this embodiment is demonstrated with reference to FIG.
(1. Preparation process (FIGS. 2A to 2C))
In this embodiment, the laminated base material 2 shown in FIG. 2C can be used as a starting material. The details of the laminated substrate 2 are as described above with reference to FIG. The method for forming the laminated substrate 2 is not particularly limited.

In the laminated base material 2 shown in FIG. 2C, the method for forming the second conductor via 25 and the surface conductor layer 26 is not particularly limited, but an example thereof will be described with reference to FIGS. 2A and 2B.
FIG. 2A shows the vicinity of the surface layer of the intermediate product completed up to the second insulating layer 24 in the printed wiring board 1 of the present embodiment shown in FIG. A via hole (hole) 60 is formed in the second insulating layer 24. The method for forming the intermediate product is not particularly limited.

  Next, as shown in FIG. 2B, in the intermediate product, the surface of the second insulating layer 24 and the surface of the second electrolytic plating layer 23b exposed in the via hole (hole) 60 are electrolessly plated or sputtered. A third seed layer 26a is formed.

  Next, as shown in FIG. 2C, the second conductor via 25 and the third electrolytic plating layer 26b are formed. Specifically, although not shown, a resist is applied on the third seed layer 26a to form a resist layer having a predetermined pattern. Subsequently, a third electrolytic plating layer 26b made of copper is formed on a portion not covered with the resist layer, and the resist layer is removed and the third seed layer 26a exposed by the removal is removed by an etching process. Thus, the second conductor via 25 is formed in the via hole 60, and the surface conductor layer (third conductor layer) composed of the third seed layer 26a and the third electrolytic plating layer 26b is formed on the surface of the second insulating layer 24. 26 can be formed (see FIG. 2C).

(2. Joining layer forming step (FIG. 2D))
Next, as shown in FIG. 2D, the bonding layer 50 is formed on the surface of the surface conductor layer 26.
The method of forming the bonding layer 50 is as described above. Preferably, the liquid composition containing the azole compound and the liquid medium is brought into contact with the surface of the surface conductor layer 26 containing electrolytic plated copper and dried. Thus, the bonding layer 50 is formed. A more specific aspect of the method for forming the bonding layer 50 is as described above.

(3. Solder resist precursor layer forming step (FIG. 2E))
Next, as shown to FIG. 2E, the soldering resist precursor which consists of a resin composition which can form the soldering resist layer 30 by hardening | curing to the surface 2a in which the surface conductor layer 26 in the laminated base material 2 is formed. A solder resist precursor layer forming step for forming the layer 40 is performed.

The solder resist precursor layer 40 is shown as a single layer, but may be a layer in which a plurality of layers are laminated.
Examples of the resin composition that can form the solder resist layer 30 include the above-described photosensitive resin composition containing a photosensitive resin and a photopolymerization initiator.

In the solder resist precursor layer forming step, as shown in FIG. 2E, a solder resist precursor layer 40 made of the resin composition is formed on the surface 2 a of the laminated base material 2. At this time, the resin composition is made into a fluid containing a solvent as described above, the fluid is applied to the laminated substrate 2 to form a coating film, and then the solvent is removed from the coating film by volatilization ( That is, the solder resist precursor layer 40 can be formed by drying. Further, the solder resist precursor layer forming step may be a step of laminating the solder resist precursor layer 40 made of the resin composition separately prepared as a dry film on the laminated base material 2.
In the present embodiment, the thickness of the solder resist precursor layer 40 is not particularly limited, but is generally 10 to 70 μm.

(4. Exposure process)
Subsequently, the following exposure process is performed. A preferred embodiment of the exposure step is a step in which the region other than the region corresponding to the opening 31 of the solder resist precursor layer 40 formed by the solder resist precursor layer forming step is irradiated and cured. Typically, the exposure process can be performed by irradiating the solder resist precursor layer 40 with light in a state where a light shielding mask that selectively shields a region corresponding to the opening 31 is disposed on the surface of the solder resist precursor layer 40. It is.

  Conditions such as the wavelength of light irradiated in the exposure step, light illuminance, and irradiation time can be appropriately determined according to the resin composition constituting the solder resist precursor layer 40. In general, the irradiated light is ultraviolet light.

(5. Development process (FIG. 2F))
A development process is performed after the exposure process. The development process is a process of forming the solder resist layer 30 in which the openings 31 are formed by developing with a developer after the exposure process (see FIG. 2F).

  As the developer, a solvent in which an uncured portion of the solder resist precursor layer 40 is soluble and a photocured portion of the solder resist precursor layer 40 is insoluble can be used. Examples of such a solvent include the same solvents as used when forming the fluid.

  In the case where the solder resist layer 30 obtained in the development step can be further photocured, it is preferable that after the development step, a photocuring completion step is performed in which light irradiation is further performed to complete the photocuring.

  Moreover, when the soldering resist layer 30 obtained by the image development process contains a thermosetting resin, it is preferable after the image development process that the thermosetting process of thermosetting the soldering resist layer 30 is performed.

(6. Solder bump formation process)
Further, a solder bump forming process is performed in which a solder bump S is placed on the conductor pad 27 in the opening 31. Further, in the present embodiment, before the solder bump S is installed, it is preferable to remove a portion of the bonding layer 50 exposed in the opening 31 by etching. In the present embodiment, a solder bump forming step is further performed after providing a surface treatment layer (not shown) for preventing oxidation on the surface of the conductor pad 27 exposed by removing the portion of the bonding layer 50. Preferably it is done. Specific examples of the surface treatment layer are as described above.

1: printed wiring board, 2: laminated base material, 12, 23, 26: conductor layer, 11, 21, 24: insulating layer, 26: surface conductor layer, 27: conductor pad (SMD pad), 30: solder resist layer , 31: opening (SMD opening), 50: bonding layer, S: solder bump

Claims (2)

A laminated base material including at least one conductor layer and an insulating layer, and a solder resist layer laminated on at least one of the surfaces of the laminated base material,
The laminated substrate is a printed wiring board including a surface conductor layer on a surface in contact with the solder resist layer as at least a part of the conductor layer,
The surface conductor layer includes electroplated copper,
A bonding layer is interposed between the surface conductor layer and the solder resist layer,
The bonding layer is a layer having a thickness of 20 to 200 nm containing copper and nitrogen. The printed wiring board according to claim 1,
The surface conductor layer has a pattern including a conductor pad;
An opening is provided in the solder resist layer,
The conductor pad is located in the opening;
The conductor pad is an SMD (Solder Mask Defined) pad arranged so as to bite into the lower part of the edge of the opening of the solder resist layer,
Solder bumps are provided on the conductor pads in the openings.

Images