JP2000349427A - Printed wiring board, printed wiring board for surface mounting, and surface-mount wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve insulating property and connection reliability of an insulating resin layer such as an inter-layer insulating resin layer and a solder resist layer by preventing a pinhole from being formed in the insulating resin layer. SOLUTION: The printed wiring board is provided with a conductor circuit 3 and an insulating resin layer 2 on the conductor circuit 3 and also has an opening 1 formed in the insulating resin layer 2 so that the conductor circuit 3 is exposed through the opening 1. The insulating resin layer 2 has a land part 2a around the opening 1 and a peripheral part 2b around the land part 2a, and the peripheral part 2b is taller than the land part 2a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board, a surface-mounted printed wiring board, and a surface-mounted wiring board having excellent insulation and reliability.

[0002]

2. Description of the Related Art A build-up multilayer wiring board is manufactured by a method disclosed in, for example, Japanese Patent Application Laid-Open No. 9-130050.

In such a method, a roughened layer is formed on the surface of a conductor circuit of a printed wiring board by electroless plating or etching, and an interlayer insulating resin is applied by a roll coater or printing, exposed, developed, and subjected to interlayer conduction. Is formed, and an interlayer resin insulation layer is formed through UV curing and main curing.

Further, the interlayer insulating layer is subjected to a roughening treatment with an acid or an oxidizing agent to form a roughened surface, a catalyst such as palladium is applied to the roughened surface, and a thin electroless plating film is formed. A pattern is formed on this plating film with a dry film, and after thickening by electrolytic plating, the dry film is peeled off with an alkali and etched to form a conductor circuit. By repeating this, a build-up multilayer wiring board is obtained.

In forming via holes, a photosensitive resin is applied, dried, and then a translucent thermoplastic resin film (hereinafter referred to as a PET laminator) is attached on the photosensitive resin layer. After mounting, an opening for interlayer conduction is formed by UV curing, the PET laminator is peeled off, and after development and curing (light curing, heat curing), an interlayer insulating layer having via holes formed therein can be formed. . Also,
In the solder resist layer, an opening for a solder pad can be formed in a similar manner.

[0006] After the conductor circuit exposed in the opening,
By forming a roughened layer with chromic acid or the like and forming a metal layer by plating, it is possible to establish a connection with an upper conductive circuit or a solder paste through a via hole.

[0007]

However, the present inventor has found that holes other than via holes and solder pad openings (hereinafter referred to as pinholes) are formed in the insulating resin layer. According to the research of the present inventors,
It has been clarified that the pinhole penetrates the insulating resin layer and significantly lowers the insulation and reliability of the interlayer insulating resin layer and the solder resist layer.

An object of the present invention is to prevent pinholes from being formed in an insulating resin layer such as an interlayer insulating resin layer or a solder resist layer. Another object of the present invention is to provide a printed wiring board having improved insulating properties and connectivity of the insulating resin layer.

[0009]

The present invention comprises a conductor circuit and an insulating resin layer on the conductor circuit, wherein the insulating resin layer has an opening, and the conductor circuit is exposed at the opening. In the printed wiring board, the insulating resin layer has a land portion around the opening and a peripheral portion around the land portion, and the peripheral portion is higher than the land portion. The present invention relates to a wiring board, a printed wiring board for surface mounting using the printed wiring board, and a surface mounting wiring board.

The present inventor has studied the cause of the occurrence of pinholes in the insulating resin layer. As a result, the inventor
It has been found that such pinholes are generated by foreign matter remaining on a mask used for forming via holes and solder pads. The foreign matter may be floating in the air, attached to a mask or substrate, or
Those generated from the exposure apparatus were observed.

When the photosensitive resin is exposed as it is in a state in which such foreign matter remains on a portion of the mask other than the black circle formed in a predetermined size, the photosensitive resin layer hitting the foreign matter portion becomes In the same manner as the exposure through the black circle of the drawn mask, it becomes unexposed, and if the unexposed part is developed, the part is eluted, and holes other than the via hole forming opening are formed in the insulating resin layer. Open and a pinhole is formed.

According to the research of the present inventor, such pinholes are formed on the surface of the insulating resin layer or reach the center of the insulating resin layer, and the insulation and reliability of the insulating resin layer are reduced. It was found that the temperature was significantly reduced.

Further, even if such pinholes are severe, they will penetrate through the interlayer insulating resin layer as an insulating resin layer, and if plated, short-circuits with the underlying circuit, which adversely affects the connectivity. Was.

Further, in the case where the insulating resin layer is a solder resist layer for protecting the circuit, corrosion-resistant metal plating (nickel plating, gold plating, etc.) is applied to the opening to protect the opening from corrosion. If a penetrating pinhole similar to the resin layer is formed, the corrosion-resistant metal plating layer penetrates into the pinhole, and when a solder bump or BGA is formed on the solder resist layer, the pinhole and the pinhole Solder bumps or BGAs were short-circuited via the upper corrosion-resistant metal plating layer and solder paste, or short-circuited between the solder bumps or BGA and the circuit in the solder resist layer.

As a result of intensive studies based on such knowledge, the present inventor has found that when providing an opening in an insulating resin layer, at least two
It has been found that by exposing the photosensitive resin layer using masks in different states and then developing, the pinhole penetrating the insulating resin layer is not formed.

In the present invention, the photosensitive resin layer provided on the conductor circuit is exposed through a pre-exposure mask, and after exposing through the main exposure mask, the photosensitive resin layer is developed.
An opening is formed in the insulating resin layer, and the conductor circuit can be exposed from the opening. The insulating resin layer according to the present invention includes an interlayer insulating resin layer and a solder resist layer.

The pre-exposure mask and the main exposure mask according to the present invention refer to masks in which the positions of foreign substances at the time of exposure differ depending on the relative positional relationship with the photosensitive resin layer. For example, even if one mask is stored under two different states or one mask, by rotating the mask or the like, the mounting state of the first exposure is changed by the second exposure or the like. Is a mask that can be placed in a different mounting state. When exposure is performed using the preliminary exposure mask and the main exposure mask, the unexposed portion of the photosensitive resin layer can be significantly reduced.

Further, the present inventor has further studied and found that the pre-exposure mask and the main exposure mask are each provided with a black portion drawn in a predetermined size, and the black portion of the pre-exposure mask is the main exposure mask. It has been found that by using a mask larger than the black portion, an insulating resin layer having a land around the opening and a periphery around the land higher than the land is formed.

Based on the above findings, the present inventor has further studied and found that the insulating resin layer is used as an interlayer insulating resin layer, and the interlayer insulating resin layer has a via hole having a step between a land portion and a peripheral portion. When the opening is provided, when the via-hole conductor penetrates into the via-hole opening by plating, it becomes easy for the plating solution to flow from the periphery of the step portion, so that the conductor circuit is exposed to the via-hole opening. It has been found that the adhesion to the via-hole conductor is sufficiently ensured and the electrical connectivity is improved.

Further, the present inventor has proposed a case where a printed wiring board for surface mounting is obtained by using such an insulating resin layer as a solder resist layer and providing a solder bump in an opening having a step between a land portion and a peripheral portion. It was found that the step between the land and the periphery could work as a solder dam.

Further, the present inventor can connect the conductor circuit and the electronic component circuit exposed from the insulating resin layer via a solder layer, so that the solder layer can be formed between the opening, the land portion and the peripheral portion. Elucidating that a surface-mounted wiring board with extremely excellent connection reliability can be obtained without the adjacent molten solder flows being in contact with each other and formed at the steps.
The present invention has been completed.

According to the present invention, since the insulating resin layer is formed by exposing the photosensitive resin layer at least twice, the possibility of foreign matter existing in the same portion of the mask during the exposure is reduced. In addition, it is possible to prevent the photosensitive resin layer from having an unexposed portion originating from the foreign matter remaining on the mask, thereby preventing the formation of pinholes in the insulating resin layer to be formed and preventing the conductor circuit from being exposed. Can be prevented, and the insulation properties and connection reliability of the printed wiring board can be improved.

According to the printed wiring board of the present invention, the land portion and the peripheral portion higher than the land portion around the land portion are formed around the opening of the insulating resin layer. , And via holes are used as at least one of solder bump openings, so that insulation and connection reliability can be ensured by excellent adhesion between via hole conductors and conductor circuits and by preventing contact between adjacent molten solders. Is significantly improved.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the drawings. FIG. 1 is a partial longitudinal sectional view of a printed wiring board according to an example of the present invention. FIG. 2 is a partial longitudinal sectional view of a surface-mounted printed wiring board according to an example of the present invention. FIG. 3 is a partial vertical sectional view of a surface mount wiring board according to an example of the present invention. FIG.
FIG. 4 is a partial plan view showing the flow of solder in the surface mount wiring board of FIG. 3.

In the present invention, the photosensitive resin layer is not developed and opened in the first exposure. In the present invention, an opening is formed in the insulating resin layer by developing the photosensitive resin layer after exposing the photosensitive resin layer at least twice.

In the present invention, the photosensitive resin layer can be exposed using the preliminary exposure mask and the main exposure mask. The pre-exposure mask and the main exposure mask differ in the presence state of the foreign matter on the mask.

In the case of using the pre-exposure mask for the first time and the main exposure mask for the second time, the first pre-exposure mask and the second main exposure mask have different foreign substance existence states. At the time of the second exposure, the portion of the photosensitive resin layer which has not been exposed due to the foreign matter existing on the mask can be exposed at the second exposure, and a pinhole penetrating the insulating resin layer is formed. Disappears.

By doing so, it is possible to prevent the photosensitive resin layer from being unexposed at the time of exposure, thereby preventing the formation of pinholes in the interlayer insulating resin layer and the solder resist layer. Even if a conductor circuit is formed via
Short circuits between circuits can be prevented.

In the present invention, since the photosensitive resin layer is exposed at least twice, the exposure amount can be reduced. In this case, one-time exposure does not sufficiently cure the photosensitive resin layer, but since the photosensitive resin layer is exposed twice, even a portion that has not been exposed by one exposure,
Exposure is performed at least for the second time, and a pinhole cannot penetrate into the insulating resin layer. Therefore, the problem of insulation and reliability of the insulating resin layer caused by the pinhole is eliminated.

Further, according to the present invention, when the via hole of the interlayer insulating resin layer or the solder pad opening of the solder resist layer is opened by exposure and development of the photosensitive resin layer, the resin layer is opened at one time. Without taking, using a mask on which a black circle larger than the desired opening diameter is drawn, the exposure amount is also exposed with an exposure amount smaller than the amount performed at one time, and the surface layer of the photosensitive resin layer other than the opening portion After hardening a little,
Next, using a mask on which a black circle with a desired opening diameter is drawn,
The photosensitive resin layer is exposed.

When the photosensitive resin layer is subsequently developed, an opening as shown in FIG. 1 is formed in the insulating resin layer. The opening 1 is surrounded by an insulating resin layer 2 formed from a photosensitive resin layer. The opening 1 has a conductive circuit 3
Is exposed. The insulating resin layer 2 includes a land portion 2a around the opening 1 and a peripheral portion 2b around the land portion 2a. The peripheral portion 2b is formed higher than the land portion 2a, and a step 4 is formed between the peripheral portion 2b and the land portion 2a. The conductor circuit 3 and the insulating resin layer 2 are provided on a suitable base material 5, for example, a substrate or another insulating resin layer.

The photosensitive resin layer provided in the opening 1 is
In the first and second exposures, due to the black circle drawn on the mask, it is in an unexposed state and is dissolved and removed by development. The peripheral portion 2b has received two exposures, and the land portion 2a has received only one exposure. When the insulating resin layer 2 is formed by developing the photosensitive resin layer, the curing of the land portion 2a is weaker than the curing of the peripheral portion 2b, and the land portion 2a is dissolved and removed more excessively than the peripheral portion 2b, A step 4 is formed.

In the present invention, as shown in FIG. 2, a solder bump 6 is provided on a conductive circuit 3 by using a printed wiring board 1 provided with such an insulating resin layer 2 to form a printed wiring board 7 for surface mounting. Can be manufactured. In the printed wiring board 7 for surface mounting, the step 4 between the land portion 2a and the peripheral portion 2b of the insulating resin layer 2 can function as a solder dam.

Further, in the present invention, the surface-mounted printed circuit board 8 as shown in FIG. 3 can be manufactured using the surface-mounted printed circuit board 7. In the surface mount wiring board 8,
The conductor circuit 3 and the electronic component circuit 9 of the printed wiring board 1
The solder bumps are connected via a solder layer 10 made of a solder for melting solder bumps or the like.

As shown in FIG. 2, in the surface-mounted wiring board 8, the solder layer 10
a and a step portion 10b between the peripheral portion 2b. In such a surface mount wiring board 8, the outflow portion 10c formed by flowing out the molten solder or the like stays at the step between the land portion 2a and the peripheral portion 2b and does not flow out. It is possible to prevent a short circuit of the connection part caused by the outflow at the connection part with the electronic component circuit.

Further, in the present invention, when a step between the land portion and the peripheral portion of the insulating resin layer exists in the via hole opening, when the via hole conductor is penetrated into the via hole opening by plating, By facilitating the flow of the plating solution from around the step, the adhesion between the conductor circuit exposed in the via hole opening and the via hole conductor is sufficiently ensured, and the electrical connectivity is improved.

The difference in height between the peripheral portion and the land according to the present invention is preferably 0.01 to 2.00 μm.
If it is less than 0.01 μm, the effect as a dam is offset,
If it exceeds 2.00 μm, it becomes difficult to maintain the shape of the land.

The exposure method according to the present invention and the design of a mask used for exposure will be described. First, the thickness of the insulating resin layer (interlayer insulating resin layer and solder resist layer) according to the present invention is preferably 10 to 60 μm. At this time, the insulating resin layer can be divided into two layers in order to secure insulation. In this case, the insulating property may be improved by reducing the ratio of components such as filler in the lower layer portion.

In the present invention, the exposure is performed a plurality of times.
In this case, in each exposure, a mask in which a small black portion is drawn step by step is used. When the exposure is performed twice, the first exposure is preferably performed using a mask on which a black circle having a size of 105 to 500% with respect to a desired opening diameter is drawn. The size of the black circle is 500%
Is exceeded, the amount of resin remaining at the bottom of the opening increases, so that the resin may not be removed in the second exposure and may remain, and electrical connection within the opening may not be established. The size of the black circle is 1
If it is less than 05%, the step formed between the land and the periphery formed around the opening becomes small, and the advantage of performing the exposure twice is lost.

In the case of exposing twice, each exposure amount is
It is better to lower the exposure amount to 60 to 80% of the exposure amount to be opened at one time. A land is formed more effectively by exposure in this range. For example, if the exposure amount is in this range, even if foreign matter remains on the mask, an opening in a necessary portion can be formed without penetrating the insulating layer and the solder resist layer. .

In each exposure, the exposure time may be changed. In order to perform the exposure twice, the exposure time may be shortened. The exposure amount and exposure time in that case, depending on the thickness of the photosensitive resin layer, the resin used, the material composition of the curing agent, photo-curing material, etc., the size of the opening diameter, the contents, the solvent for development processing, etc. Conditions are different.

When the exposure is performed with the exposure time kept at half the time of one exposure, the aperture diameter having a uniform edge angle can be formed.

The second exposure is performed using a mask on which a black portion having a predetermined size is drawn so that a desired opening diameter can be formed. In the second exposure, since the surface layer of the photosensitive resin layer serving as the interlayer insulating resin layer or the solder resist layer is solidified in the first exposure, foreign matter derived from the resin does not adhere to the mask.

In a printed wiring board in which a predetermined conductor circuit, an interlayer insulating resin layer and the like are provided on both surfaces of the substrate, the back surface is exposed after the exposure of the front surface is completed. Also at this time, the exposure is performed at least twice as in the case of the surface.

In the present invention, after exposure at least twice, D
By developing with an organic solvent such as MTG, an unexposed portion of the opening can be eluted. Thereafter, an interlayer insulating resin layer having an opening or a solder resist layer is formed through light curing and heat curing.

The method of manufacturing a printed wiring board according to the present invention will be described step by step. The following method is mainly based on the semi-additive method, but may use a full-additive method.

First, a wiring board having a conductive circuit formed on the surface of the board is prepared. As the substrate, an adhesive layer for electroless plating is formed on a resin insulating substrate such as a glass epoxy substrate, a polyimide substrate, a bismaleimide-triazine resin substrate, a copper-clad laminate, a ceramic substrate, a metal substrate, and the like. The surface of the agent layer is roughened to a roughened surface, a thin electroless plating is applied to the entire roughened surface, a plating resist is formed, and a thick electrolytic plating is applied to a portion where no plating resist is formed. It is performed by a method of removing a resist, performing an etching treatment, and forming a conductor circuit including an electrolytic plating film and an electroless plating film. The conductor circuit preferably has a copper pattern.

On the substrate on which the conductor circuit is formed, a recess is formed by the conductor circuit or through hole. To fill the recess, apply a resin filler and after drying,
Unnecessary resin filler is ground by grinding to expose the conductor circuit, and then the resin filler is fully cured.

Next, a roughened surface is provided on the exposed conductor circuit. The formed roughened surface is etched, polished,
A roughened surface of copper formed by oxidation treatment or oxidation-reduction treatment or a roughened surface on a roughened layer formed by a plating film is desirable.

The adhesive for electroless plating can also be used as an interlayer insulating resin. Such an adhesive for electroless plating is optimally prepared by dispersing cured heat-resistant resin particles soluble in an acid or an oxidizing agent in an uncured heat-resistant resin hardly soluble in an acid or an oxidizing agent. It is. By treating with an acid or an oxidizing agent, the heat-resistant resin particles are dissolved and removed, and a roughened surface composed of an octopus pot-shaped anchor can be formed on the surface.

In the above-mentioned adhesive for electroless plating, particularly as the heat-resistant resin particles subjected to the curing treatment, a heat-resistant resin powder having an average particle diameter of 10 μm or less, an average particle diameter of 2 μm
Aggregated particles obtained by aggregating the following heat-resistant resin powder, a heat-resistant powder resin powder having an average particle size of 2 to 10 μm and an average particle size of 2 μm
m and a mixture with a heat-resistant resin powder having a mean particle size of 2 or less.
Pseudo particles obtained by adhering at least one of a heat-resistant resin powder or an inorganic powder having an average particle diameter of 2 μm or less to the surface of a 10 μm heat-resistant resin powder, and an average particle diameter of 0.1 to
0.8μm heat resistant resin powder and average particle size 0.8μ
m, and a mixture with a heat-resistant resin powder of less than 2 μm,
It is desirable to use a heat-resistant resin powder having an average particle size of 0.1 to 1.0 μm. This is because they can form more complex anchors.

The heat-resistant resin hardly soluble in an acid or an oxidizing agent is a “resin composite composed of a thermosetting resin and a thermoplastic resin” or a “resin composite composed of a photosensitive resin and a thermoplastic resin”. It is desirable. This is because the former has high heat resistance, and the latter can form a via hole opening by photolithography.

As the thermosetting resin, epoxy resin, phenol resin, polyimide resin and the like can be used.
In the case of photosensitization, methacrylic acid, acrylic acid or the like is reacted with a thermosetting group for acrylation. Particularly, acrylate of epoxy resin is most suitable.

As the epoxy resin, novolak type epoxy resins such as phenol novolak type and cresol novolak type, and alicyclic epoxy resins modified with dicyclopentadiene can be used.

As the thermoplastic resin, polyether sulfone (PES), polysulfone (PSF), polyphenylene sulfone (PPS), polyphenylene sulfide (PPES), polyphenyl ether (PP
E), polyetherimide (PI) and the like can be used.

The mixing ratio of the thermosetting resin (photosensitive resin) and the thermoplastic resin is preferably thermosetting resin (photosensitive resin) / thermoplastic resin = 95/5 to 50/50. High toughness value can be secured without impairing heat resistance.

The mixing ratio of the heat-resistant resin particles is 5 to 50% by weight, preferably 10 to 40% by weight, based on the solid content of the heat-resistant resin matrix.

The heat-resistant particles are preferably amino resins (melamine resins, urea resins, guanamine resins), epoxy resins and the like.

The adhesive may be composed of two layers having different compositions.

Next, while the interlayer insulating resin layer is cured,
An opening for forming a via hole is provided in the interlayer resin layer.

In the present invention, the interlayer insulating resin layer is subjected to an opening and a curing treatment. In this case, a photosensitive resin is used as a resin matrix of the adhesive for electroless plating, or the adhesive for electroless plating is exposed and developed by sensitizing the adhesive for electroless plating by appropriate means. Can be drilled.

In the present invention, the exposure is performed at least twice at this time. In the first exposure and development processing, a photomask (preferably a glass substrate) on which a circular pattern for forming a via hole is drawn with a size of 105 to 500% with respect to a desired opening diameter is drawn. After the pattern side is placed in close contact with the photosensitive interlayer resin insulating layer, exposure can be performed.

The exposure amount is 60 to 60 when formed once.
An exposure of 80% can be used. When opening at once, when it 100 mJ / cm ² must, when the divided exposure of the two is 60~80mJ / cm ^2. Next is the second exposure and development process. A photomask on which a black circle having a desired size corresponding to the opening diameter for forming a via hole is drawn in close contact with the photomask in the same manner as in the first time, and after performing exposure, development processing and curing can be performed. .

Next, the surface of the interlayer resin insulating layer (adhesive layer for electroless plating) provided with openings for forming via holes is roughened. In particular, the surface of the adhesive layer is roughened by dissolving and removing the heat-resistant resin particles present on the surface of the adhesive layer for electroless plating with an acid or an oxidizing agent. At this time, a roughened surface is formed on the interlayer insulating resin layer.

For the acid treatment, phosphoric acid, hydrochloric acid, sulfuric acid, or an organic acid such as formic acid or acetic acid can be used.
In particular, it is desirable to use an organic acid. This is because it is difficult to corrode the metal conductor layer exposed from the via hole when the roughening treatment is performed.

For the oxidation treatment, it is desirable to use chromic acid or permanganate (such as potassium permanganate).

The roughened surface has a maximum roughness Rmax of 0.1 to
20 μm is preferred. If the thickness is too large, the rough surface itself is likely to be damaged and peeled off, and if the thickness is too small, the adhesion is reduced. In particular,
In the semi-additive method, the thickness is preferably 0.1 to 5 μm. This is because the electroless plating film can be removed while ensuring adhesion.

Next, a thin electroless plating film is formed on the entire surface of the interlayer insulating resin provided with the roughened catalyst nuclei. This electroless plating film is preferably formed by electroless copper plating, and has a thickness of 1 to 5 μm, more preferably 2 to 3 μm. As the electroless copper plating solution, those having a liquid composition employed in a usual manner can be used. For example, copper sulfate: 29 g / l, sodium carbonate: 25 g / l, EDTA: 140 g / l, sodium hydroxide : 40g / l, 37% formaldehyde: 150m
1 (pH = 11.5).

Next, a photosensitive resin film (dry film) is laminated on the electroless plating film thus formed, and a photomask (glass substrate is formed) on which a plating resist pattern is drawn is formed on the photosensitive resin film. Good)
Are placed in close contact with each other, exposed, and developed to form a non-conductive portion on which a plating resist pattern is provided.

Next, an electrolytic plating film is formed on a portion other than the non-conductor portion on the electroless copper plating film to provide a conductor circuit and a conductor portion serving as a via hole. As the electrolytic plating, it is desirable to use electrolytic copper plating, the thickness of which is 10 to 20 μm.
m is good.

Next, after removing the plating resist of the non-conductive circuit portion, the mixture is further treated with a mixed solution of sulfuric acid and hydrogen peroxide or an etching solution such as sodium persulfate, ammonium persulfate, ferric chloride and cupric chloride. To remove the electroless plating film,
Independent conductor circuits and via holes are obtained, which are composed of two layers, an electroless plating film and an electrolytic plating film. The palladium catalyst nuclei on the roughened surface exposed to the non-conductive portion are dissolved and removed with chromic acid, sulfuric acid and hydrogen peroxide.

Next, a roughened surface is formed on the surface conductor circuit. The formed roughened surface is etched, polished,
It is desirable that the surface be a roughened surface of copper formed by an oxidation treatment or a redox treatment or a roughened surface of a roughened layer formed by a plating film.

Next, a solder resist layer can be formed on the conductor circuit. The thickness of the solder resist layer is preferably 5 to 40 μm. If the thickness is too small, the opening for forming a solder bump does not function. If the thickness is too large, the opening is difficult, and the solder bumps come into contact with the solder body and cause cracks in the solder body.

As the solder resist layer, various resins can be used. For example, bisphenol A epoxy resin, acrylate of bisphenol A epoxy resin,
A novolak epoxy resin or a resin obtained by curing an acrylate of a novolak epoxy resin with an amine curing agent or an imidazole curing agent can be used.

In particular, when an opening is formed in the solder resist layer to form a solder bump, a solder bump made of "novolak epoxy resin or acrylate of novolak epoxy resin" and containing "imidazole hardener" as a hardener is used. preferable.

The solder resist layer having such a structure is
There is an advantage that migration of lead (phenomenon in which lead ions diffuse in the solder resist layer) is small. Moreover, this solder resist layer is a resin layer obtained by curing an acrylate of a novolak type epoxy resin with an imidazole curing agent, has excellent heat resistance and alkali resistance, does not deteriorate even at a temperature at which solder is melted (around 200 ° C.), and does not deteriorate. It is not decomposed by a strongly basic plating solution such as plating or gold plating.

However, since such a solder resist layer is made of a resin having a rigid skeleton, peeling is likely to occur. Therefore, the roughened surface on the conductor circuit is advantageous because such peeling can be prevented.

Here, as the acrylate of the novolak type epoxy resin, an epoxy resin obtained by reacting glycidyl ether of phenol novolak or cresol novolak with acrylic acid, methacrylic acid or the like can be used.

The above imidazole curing agent is desirably liquid at 25 ° C. This is because a liquid can be uniformly mixed.

As such a liquid imidazole curing agent, 1-benzyl-2-methylimidazole (product name: 1B2MZ
), 1-cyanoethyl-2-ethyl-4-methylimidazole (product name: 2E4MZ-CN), and 4-methyl-2-ethylimidazole (product name: 2E4MZ).

The addition amount of the imidazole curing agent is desirably 1 to 10% by weight based on the total solid content of the solder resist composition. The reason for this is that if the added amount is within this range, uniform mixing is easy.

The composition before curing of the solder resist is as follows:
It is desirable to use a glycol ether-based solvent as the solvent.

A solder resist layer using such a composition does not generate free oxygen and does not oxidize the copper pad surface. It is also less harmful to the human body.

As such a glycol ether-based solvent, one having the following structural formula, particularly preferably at least one selected from diethylene glycol dimethyl ether (DMDG) and triethylene glycol dimethyl ether (DMTG) is used. This is because these solvents can completely dissolve benzophenone and Michler's ketone as reaction initiators by heating at about 30 to 50 ° C. CH ₃ O— (CH _{2 CH 2} O) _n -C
H ₃ (N = 1-5) The amount of the glycol ether solvent is preferably 10-40% by weight based on the total weight of the solder resist composition.

The solder resist composition as described above may further include various antifoaming agents and leveling agents, thermosetting resins for improving heat resistance and base resistance and imparting flexibility.
A photosensitive monomer or the like can be added to improve the resolution.

For example, as the leveling agent, one made of a polymer of an acrylate ester is preferable. The initiator is preferably Irgacure I907 manufactured by Ciba Geigy, and the photosensitizer is preferably DETX-S manufactured by Nippon Kayaku.

Further, a dye or a pigment may be added to the solder resist composition. This is because the wiring pattern can be hidden. It is desirable to use phthalocyanine green as this dye.

As the thermosetting resin as an additional component, a bisphenol-type epoxy resin can be used. This bisphenol type epoxy resin includes a bisphenol A type epoxy resin and a bisphenol F type epoxy resin, and when importance is attached to base resistance, the former is required to reduce viscosity (when importance is attached to coating properties). The latter is better.

As the photosensitive monomer as an additional component, a polyacrylic monomer can be used.
This is because the polyvalent acrylic monomer can improve the resolution. For example, Nippon Kayaku's DPE-6A
Polyacrylic monomers such as R-604 manufactured by Kyoeisha Chemical Co., Ltd. are desirable.

These solder resist compositions may be used at a temperature of 25 ° C. in a range of 0.5 to 10 Pa · s, more preferably, 1 to 10 Pa · s.
-10 Pa · s is preferred. This is because the viscosity is easy to apply with a roll coater. After forming the solder resist resin layer, an opening for a solder pad is formed.

In the present invention, the opening is formed by at least two exposure processes. The first exposure and development process
For the desired opening diameter required for opening the solder pad, 1
A photomask (preferably a glass substrate) on which a black circle pattern having a size of from 0.05 to 500% is drawn is placed on the photosensitive solder resist resin layer with the circle pattern side in close contact, and then exposed. Can be.

The amount of exposure is 60 to 60 when formed once.
It can be performed with an exposure of 80%. 100% when opening one time
When the exposure amount of mJ / cm ² is that it is necessary, when the divided exposure to 2 times, a 60~80mJ / cm ^2.

Next, in the second exposure and development process, a photomask in which a black portion of a desired size required for the opening of the solder pad is drawn is brought into close contact with the photomask in the same manner as in the first exposure, and the exposure is performed. Developing and curing the solder resist resin layer.

After the formation of the solder resist layer, a nickel plating layer is formed in the opening by electroless plating. As an example of the composition of the nickel plating solution, nickel sulfate 4.5 g /
l, sodium hypophosphite 25 g / l, sodium citrate 40 g / l, boric acid 12 g / l, thiourea 0.1 g
/ L (pH = 11). With the degreasing solution, the opening of the solder resist layer, the surface is washed, and a catalyst such as palladium is applied to the conductor portion exposed in the opening, and after activation,
It can be immersed in a plating solution to form a nickel plating layer.

The thickness of the nickel plating layer is 0.5 to 20.
In particular, a thickness of 3 to 10 μm is desirable. 0.5μ
If it is less than m, it is difficult to make a connection between the solder bump and the nickel plating layer, and if it exceeds 20 μm, the solder bump formed in the opening cannot be completely accommodated and peels off.

After forming the nickel plating layer, a gold plating layer is formed by gold plating. The thickness is preferably 0.03 μm.

After applying the metal layer to the opening, a solder paste is provided by printing to form a solder bump in the opening. Thereafter, the solder bumps are fixed in the openings by passing through nitrogen reflow at a temperature of 250 ° C.

[0098]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail with reference to the drawings based on examples and comparative examples. Example 1 A. Raw material composition for preparation of adhesive for electroless plating (adhesive for upper layer) [Resin composition] 25% acrylate of cresol novolak type epoxy resin (Nippon Kayaku, molecular weight 2500) at a concentration of 80% by weight DMDG 35 parts by weight of a resin solution dissolved in water, photosensitive monomer (Aronix M315, manufactured by Toagosei Co., Ltd.) 3.15
Parts by weight, 0.5 parts by weight of an antifoaming agent (manufactured by San Nopco, S-65)
3.6 parts by weight of NMP were obtained by stirring and mixing.

[Resin composition] 12 parts by weight of polyether sulfone (PES), epoxy resin particles (manufactured by Sanyo Chemical Co., Ltd.)
After mixing 7.2 parts by weight of an average particle diameter of 1.0 μm and 3.09 parts by weight of an average particle diameter of 0.5 μm,
Further, 30 parts by weight of NMP was added and the mixture was stirred and mixed by a bead mill.

[Curing Agent Composition] 2 parts by weight of imidazole curing agent (2E4MZ-CN, manufactured by Shikoku Chemicals), 2 parts by weight of photoinitiator (Irgacure I-907, manufactured by Ciba Geigy), photosensitizer (manufactured by Nippon Kayaku) , DETX-S) 0.2 parts by weight and NMP 1.5 parts by weight.

B. Raw material composition for preparing interlayer resin insulation agent (adhesive for lower layer) [Resin composition] Dissolved in DMDG at a concentration of 80% by weight of 25% acrylate of cresol novolak type epoxy resin (Nippon Kayaku, molecular weight 2500) 35 parts by weight of a resin solution, 4 parts by weight of a photosensitive monomer (manufactured by Toagosei Co., Aronix M315), 0.5 parts by weight of an antifoaming agent (manufactured by San Nopco, S-65), NM
P 3.6 parts by weight were obtained by stirring and mixing.

[Resin Composition] 12 parts by weight of polyether sulfone (PES), epoxy resin particles (manufactured by Sanyo Chemical Industries, Ltd.)
After mixing 14.49 parts by weight of a polymer pole having an average particle size of 0.5 μm, 30 parts by weight of NMP was further added, and the mixture was stirred and mixed with a bead mill.

[Curing agent composition] 2 parts by weight of imidazole curing agent (2E4MZ-CN, manufactured by Shikoku Chemicals), 2 parts by weight of photoinitiator (Irgacure I-907, manufactured by Ciba Geigy), photosensitizer (manufactured by Nippon Kayaku) , DETX-S) 0.2 parts by weight and NMP 1.5 parts by weight with stirring.

C. Raw material composition for resin filler preparation [Resin composition] 100 parts by weight of bisphenol F type epoxy monomer (manufactured by Yuka Shell, molecular weight 310, YL983U), having an average particle diameter of 1.6 μm coated with a silane coupling agent on the surface Si0 ₂ Spherical particles (Admatech, CRS 1
101-CE, where the maximum particle size is 170 parts by weight of a later-described inner layer copper pattern thickness (15 μm or less) and 1.5 parts by weight of a leveling agent (manufactured by San Nopco, Perenol S4) by stirring and mixing. The viscosity of the mixture is 23 ±
It was obtained by adjusting to 45,000 to 49,000 cps at 1 ° C.

[Curing agent composition] 6.5 parts by weight of imidazole curing agent (2E4MZ-CN, manufactured by Shikoku Chemicals).

D. Production of Printed Wiring Board (1) A copper-clad laminate in which 18 μm copper foil was laminated on both sides of a substrate made of glass epoxy resin or BT (bismaleimide triazine) resin having a thickness of 1 mm was used as a starting material. First, the copper-clad laminate was drilled, subjected to an electroless plating treatment, and etched in a pattern to form an inner copper pattern and through holes on both surfaces of the substrate.

(2) The substrate on which the inner layer copper pattern and the through hole were formed was washed with water and dried, and then used as an oxidation bath (blackening bath) as NaOH (10 g / l) and NaClO _2. (40g /
l), Na ₃ PO ₄ (6 g / l), NaOH (10
g / l), NaBH ₄ (6 g / l), a roughened surface was provided on the surface of the inner layer copper pattern and the through-hole by the oxidation-reduction treatment.

(3) The raw material composition for preparing the resin filler C was mixed and kneaded to obtain a resin filler. (4) The resin filler obtained in (3) was applied and filled between conductor circuits or through holes within 24 hours after preparation.

The coating method was a printing method using a squeegee. For the first printing application, the inside of the through hole was mainly filled and dried in a drying oven at a temperature of 100 ° C. for 20 minutes.

In the second printing application, the recesses mainly formed in the formation of the conductor circuits were filled and filled between the conductor circuits and in the through holes, and then dried under the aforementioned drying conditions.

(5) One surface of the substrate after the treatment of (4) is subjected to belt sanding using # 600 belt abrasive paper (manufactured by Sankyo Rikagaku Co., Ltd.) to form the surface of the inner layer copper pattern and the land surface of the through hole. Was polished so that no resin filler remained, and then buffed to remove scratches caused by the belt sander polishing. Such a series of polishing was similarly performed on the other surface of the substrate.

Next, heat treatment was performed at 100 ° C. for 1 hour and at 150 ° C. for 1 hour to cure the resin filler.

In this manner, the surface layer of the resin filler filled in the through holes and the roughened layer on the upper surface of the inner conductor circuit are removed, the both surfaces of the substrate are smoothed, and the resin filler and the side surface of the inner conductor circuit are removed. Were firmly adhered through the roughened surface, and a wiring board in which the inner wall surface of the through hole and the resin filler were firmly adhered through the roughened surface was obtained. That is, by this process,
The surface of the resin filler and the surface of the inner layer copper pattern are flush with each other.

(6) The printed wiring board on which the conductive circuit is formed is degreased with alkali and soft-etched.
After treatment with a catalyst solution composed of palladium chloride and an organic acid to give a Pd catalyst and activate the catalyst, copper sulfate 3.9 × 10 ⁻² mol / l, nickel sulfate 3.8 × 1
0 ⁻³ mol / l, sodium citrate 7.8 × 10 ⁻³
Mol / l, sodium hypophosphite 2.3 × 10 ⁻¹ mol / l, surfactant (Surfir 46, manufactured by Nissin Chemical Industry Co., Ltd.)
5) Immersion in an electroless plating solution consisting of 1.1 × 10 ⁻⁴ mol / l, pH = 9, and one minute after immersion, vertical and horizontal vibrations were performed once every 4 seconds to obtain a conductor circuit. Further, a coating layer of a needle-shaped alloy made of Cu-Ni-P and a roughened surface were provided on the surface of the land of the through hole.

Further, tin borofluoride 0.1 mol / l,
A Cu—Sn substitution reaction was performed under the conditions of thiourea 1.0 mol / l, temperature 35 ° C., and pH = 1.2, and a 0.3 μm thick Sn layer was provided on the surface of the roughened layer.

(7) The raw material composition for preparing the interlayer resin insulating agent B was stirred and mixed, and the viscosity was adjusted to 1.5 Pa · s to obtain an interlayer resin insulating agent (for lower layer).

Next, the raw material composition for preparing the adhesive for electroless plating of A was mixed by stirring, and the viscosity was adjusted to 7 Pa · s to obtain an adhesive solution for electroless plating (for the upper layer).

(8) The interlayer resin insulating material (for lower layer) having a viscosity of 1.5 Pa · s obtained in the above (7) was applied to both surfaces of the substrate of the above (6) by a roll coater within 24 hours after preparation. In a horizontal position
Leave for 20 minutes, then dry at 60 ° C for 30 minutes (pre-bake)
Then, apply the photosensitive adhesive solution (for upper layer) having a viscosity of 7 Pa · s obtained in the above (7) within 24 hours after preparation, leave it in a horizontal state for 20 minutes, For 30 minutes (prebaking) to form an adhesive layer having a thickness of 35 μm.

(9) A photomask film on which a black circle having a diameter of 120 μm is printed is brought into close contact with both surfaces of the substrate on which the adhesive layer has been formed in the above (8), and is subjected to 75 mJ / cm ² by an ultra-high pressure mercury lamp.
, And then a photomask film on which a black circle of 85 μmφ was printed was brought into close contact with the photomask film, and the second exposure was performed at 75 mJ / cm ² using an ultra-high pressure mercury lamp. This is DMTG
The substrate was exposed to light at 3,000 mJ / cm ² by an ultra-high pressure mercury lamp, and the substrate was exposed to light at 100 ° C. for 1 hour for 120 hours.
After heating for 1 hour at 150 ° C and then for 3 hours at 150 ° C, the thickness with an 85 μmφ opening (via hole forming opening) with excellent dimensional accuracy equivalent to a photomask film as shown in Fig. 1 An interlayer resin insulation layer (two-layer structure) having a thickness of 35 μm was formed. Between the land and the periphery,
A step having a height of 0.05 μm was formed. Note that the tin plating layer was partially exposed in the opening serving as the via hole.

(10) The substrate having the openings formed is treated with chromic acid.
The surface of the interlayer resin insulating layer is roughened by immersing for 19 minutes to dissolve and remove the epoxy resin particles present on the surface of the interlayer resin insulating layer, and then immersed in a neutralizing solution (manufactured by Shipley) and then washed with water did.

Further, by applying a palladium catalyst (manufactured by Atotech) to the surface of the substrate which has been subjected to the surface roughening treatment (roughening depth: 6 μm), the surface of the interlayer resin insulating layer and the inner wall surface of the via hole opening are formed. The catalyst core was attached.

(11) The substrate was immersed in an aqueous electroless copper plating solution having the following composition to form a 0.6-1.2 μm
An electroless copper plating film was formed. [Electroless plating aqueous solution] EDTA 0.08 mol / l Copper sulfate 0.03 mol / l HCHO 0.05 mol / l NaOH 0.05 mol / l α, α'-bipyridyl 80 mg / l PEG 0.10 g / l [Electroless plating conditions] 65 ° C 20 minutes at liquid temperature

(12) A commercially available photosensitive dry film is stuck on the electroless copper plating film formed in the above (11), a mask is placed, exposure is performed at 100 mJ / cm ² , and development is performed with 0.8% sodium carbonate. After processing, a plating resist having a thickness of 15 μm was provided.

(13) Next, electrolytic copper plating was applied to the non-resist-formed portion under the following conditions to form a 15 μm thick electrolytic copper plating film. [Electrolytic plating aqueous solution] Sulfuric acid 2.24 mol / l Copper sulfate 0.26 mol / l Additive (Atotech Japan, Capparaside HL) 19.5 ml / l [Electroplating conditions] Current density 1 A / dm ² hours 65 minutes Temperature 22 ± 2 ° C.

(16) By repeating the above steps (7) to (15), a conductor circuit of a further upper layer was formed, and a multilayer wiring board was obtained. However, Sn substitution was not performed on the roughened surface of the surface layer.

(17) On the other hand, 60% by weight dissolved in DMDG
Cresol novolak epoxy resin (Nippon Kayaku)
46.67 g of a photosensitizing oligomer (molecular weight 4000) obtained by acrylizing 50% of the epoxy groups of epoxy resin, 15.0 g of an 80 wt% bisphenol A type epoxy resin (made by Yuka Shell, Epicoat 1001) dissolved in methyl ethyl ketone, imidazole curing 1.6 g of an agent (2E4MZ-CN, manufactured by Shikoku Chemicals Co., Ltd.) and a polyacrylic monomer (R604, manufactured by Nippon Kayaku, a photosensitive monomer)
3 g), 1.5 g of polyvalent acrylic monomer (Kyoeisha Chemical, DPE6A), and a dispersion defoaming agent (San Nopco,
S-65) of 0.71 g, and 2 g of benzophenone (Kanto Chemical) as a photoinitiator was added to the mixture.
0.2 of Michler's ketone (Kanto Chemical) as photosensitizer
g was added to obtain a solder resist composition whose viscosity was adjusted to 2.0 Pa · s at 25 ° C. The viscosity was measured using a B-type viscometer (Tokyo Keiki, DVL-B type) at 60 rpm and the rotor No.
In the case of 4, 6 rpm, the rotor No. 3 was used.

(18) The solder resist composition was applied to both sides of the multilayer printed wiring board obtained in the above (16) in a thickness of 20 μm. Next, after performing a drying process at 70 ° C. for 20 minutes and at 70 ° C. for 30 minutes, a 5 mm-thick photomask film on which a circular pattern (mask pattern) having a diameter of 300 μm is drawn is placed in close contact with the substrate, and 100 mJ / Cm ² UV-light, a 200 μm-diameter circular pattern (mask pattern) on which a 5 mm-thick photomask film is drawn in close contact, and a ^second exposure with 100 mJ / cm ² UV-light , And then subjected to DMTG development processing.

Further, at 80 ° C. for 1 hour and at 100 ° C. for 1 hour,
1 hour at 120 ° C. and 3 hours at 150 ° C. to open a solder pad portion (including a via hole and its land portion) as shown in FIG.
μm) A solder resist layer (thickness: 20 μm) was formed.
A step having a height of 0.05 μm was formed between the land and the periphery.

(19) Then, nickel chloride 2.3 × 10^-1Mole
/ L, sodium hypophosphite 2.8 × 10 ^-1Mol / l, que
Sodium phosphate 1.6 × 10^-1PH consisting of mol / l =
Immerse in the electroless nickel plating solution of 4.5 for 20 minutes,
A nickel plating layer having a thickness of 5 μm was formed in the opening. Sa
In addition, the substrate is placed on potassium potassium cyanide 7.6 × 10^-3Mole
/ L, ammonium chloride 1.9 × 10^-1Mol / l, citric acid
Sodium 1.2 × 10^-1Mol / l, sodium hypophosphite
1.7 × 10^-1Mol / l of electroless gold plating solution of 80 ° C
Immerse for 7.5 minutes under the conditions
A 0.03 μm gold plating layer was formed.

(20) Then, a solder paste was printed on the opening of the solder resist layer and reflowed at 200 ° C. to form a solder bump (solder body), thereby producing a printed wiring board for surface mounting. .

(Comparative Example 1) This is almost the same as the example, except that
100mJ / c when forming via holes in interlayer insulating resin layer
an exposure amount of m ^2, were exposed once, even when forming the opening portion of the solder pads on the solder resist layer with an exposure dose of 150 mJ / cm ^2, were exposed once.

As described above, in the printed wiring boards manufactured in Example 1 and Comparative Example 1, the pinhole occurrence rate, the penetration pinhole occurrence rate, and the reliability other than the openings of the interlayer insulating resin layer and the solder resist layer. A comparison was made on a total of four results of the continuity test depending on the presence or absence of the sex test. Table 1 shows the results
Shown in

As shown in Table 1, in the case of performing the exposure twice in the example, there was no formation of pinholes and through-holes, and no particular problem occurred in the reliability test.

[0134]

[Table 1]

[0135]

According to the present invention, by exposing the photosensitive resin layer at least twice, the possibility of the presence of foreign matter in the same portion of the mask is reduced, and the photosensitive resin layer remains on the mask. It is possible to prevent the occurrence of an unexposed portion originating from the foreign material, thereby preventing the formation of pinholes in the insulating resin layer, preventing a short circuit between conductor circuits, and providing excellent insulation and connection reliability. A printed wiring board, a printed wiring board for surface mounting, and a surface mounting wiring board can be obtained.

Further, according to the printed wiring board of the present invention,
Around the opening of the insulating resin layer, a land portion and a peripheral portion around the land portion, which is higher than the land portion, are formed, and such an opening is at least one of a via hole opening and a solder bump opening. Because it is used as one side, excellent adhesion between via-hole conductor and conductor circuit,
The prevention of contact between the adjacent molten solders significantly improves insulation properties and connection reliability.

[Brief description of the drawings]

FIG. 1 is a partial longitudinal sectional view of a printed wiring board according to an example of the present invention.

FIG. 2 is a partial vertical cross-sectional view of a printed wiring board for surface mounting according to an example of the present invention.

FIG. 3 is a partial vertical sectional view of a surface mount wiring board according to an example of the present invention;

FIG. 4 is a partial plan view showing a flow of solder in the surface mount wiring board of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Opening 2 Insulating resin layer 2a Land part 2b Peripheral part 3 Conductor circuit 4 Step 5 Base material 6 Solder bump 7 Surface mount printed wiring board 8 Surface mount wiring board 9 Electronic component circuit 10 Solder layer 10a Opening portion 10b Step portion 10c Outflow section

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kota Noda 1-1, Ibigawa-cho, Ibi-gun, Gifu, Japan F-term in the Ogaki-Kita Plant (reference) 5E319 AA03 AC13 AC17 BB05 CD29 GG05 5E346 AA12 AA43 CC08 CC09 CC32 DD03 DD12 DD23 DD32 EE39 FF19 GG15 HH08

Claims (4)

[Claims] 1. A printed wiring board, comprising: a conductive circuit; and an insulating resin layer on the conductive circuit, wherein the insulating resin layer has an opening, and the conductive circuit is exposed at the opening. The printed wiring board, wherein the insulating resin layer includes a land portion around the opening and a peripheral portion around the land portion, and the peripheral portion is higher than the land portion. 2. A height difference between the peripheral portion and the land portion is 0.01 to 2.00 μm.
The printed wiring board according to claim 1. 3. A printed wiring board for surface mounting, wherein a solder bump is provided on the conductive circuit of the printed wiring board according to claim 1, wherein a step between the land portion and the peripheral portion is: A printed wiring board for surface mounting, which can function as a solder dam. 4. The surface-mounted wiring board according to claim 1, wherein the conductor circuit and the electronic component circuit of the printed wiring board are connected via a solder layer. And is formed at a step portion between the land portion and the peripheral portion,
Surface mount wiring board.