JPH1065348A - Manufacture of multi-layer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a formation time of an inter-layer insulating layer, without causing any defect by inserting a wiring board between a couple of coating rolls while the board stands upright, in the case of forming the inter-layer insulating layer to both sides of the wiring board and applying an inter-layer insulating material to both the sides at the same time. SOLUTION: While a wiring board 4 stands upright, the board 4 is inserted between a couple of coating rolls of a roll coater, and the board is carried from the down side toward the up side to apply an inter-layer insulating material 3 to both sides of the board 4 at the same time. The roll coater used in this case is provided with a doctor bar 2 which allows each roll 1 to make a complete contact with a coated face or to approach the face at a prescribed gap of 0.6mm or below. When each roll 2 is turned, the inter-layer insulating material 3 put in a varnish pool enters the grooves of each roll 1, and when the roll 1 is in contact with the board 4, the material 3 is transferred and applied onto the board. Thus, the forming time of the inter-layer insulating material is reduced, without causing any discrepancy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer printed wiring board, and more particularly to a method for manufacturing an interlayer insulating material layer without causing problems such as warpage of a substrate and mixing of dust into the interlayer insulating material layer. The aim is to reduce the time and further improve the productivity.

[0002]

2. Description of the Related Art In recent years, so-called build-up multilayer printed wiring boards have been receiving attention due to demands for higher density of the multilayer printed wiring boards. This build-up multilayer printed wiring board is manufactured by a method as disclosed in, for example, Japanese Patent Application Laid-Open No. 6-81154. That is, an uncured interlayer insulating material (adhesive for electroless plating) is applied on a core substrate by a roll coater or the like, and dried and cured (exposure, exposure, etc.).
(Development and curing) to form an interlayer insulating material layer having a via hole opening. Next, after roughening the surface of the interlayer insulating material layer, a plating resist is provided on the roughened surface,
Thereafter, electroless plating is performed on the resist non-formed portion to form a conductive circuit pattern including via holes. By repeating such a process a plurality of times, a multilayered build-up multilayer printed wiring board can be obtained.

In such a method of manufacturing a build-up multilayer printed wiring board, if an attempt is made to form wiring layers on both surfaces of a substrate, it is necessary to form an interlayer insulating material layer on both surfaces of the substrate. This interlayer insulating material layer is formed by first applying an uncured interlayer insulating material to one surface of a substrate and drying it, then turning the substrate upside down and applying an uncured interlayer insulating material to the other surface and drying it. Thereafter, the interlayer insulating material applied on both surfaces of the substrate is generally cured to form the insulating material on both surfaces of the substrate.

[0004]

However, in such a conventional method, when forming an interlayer insulating material layer on both surfaces of a substrate, it is necessary to repeat a series of processes of coating and drying twice on both sides. However, it is disadvantageous from the viewpoint of improving the productivity, and shortening the formation time of the interlayer insulating material layer is an important issue.

On the other hand, in the above-mentioned conventional method, a substrate coated with an interlayer insulating material on one side is left uncured (B-stage state) after the interlayer insulating material is dried. The other surface is coated with an interlayer insulating material. For this reason, when the interlayer insulating material layers are formed on both surfaces of the substrate, a problem that dust adheres to the surface on which the interlayer insulating material layers are formed is likely to occur, which causes a failure of the multilayer printed wiring board.

Further, the conventional method has a disadvantage that a substrate coated with only one surface of an interlayer insulating material is warped due to shrinkage of an insulating resin due to evaporation of a solvent when drying the interlayer insulating material. . For this reason, the via hole is likely to be displaced in the formation position, causing a failure of the multilayer printed wiring board.

An object of the present invention is to solve the above-mentioned problems of the prior art, and in particular, in a method for manufacturing a multilayer printed wiring board, the formation time of an interlayer insulating material layer is reduced without any trouble. The idea is to propose a way that you can.

[0008]

Means for Solving the Problems As a result of intensive studies for realizing the above-mentioned object, the inventor has completed a method for making the following contents the gist of the present invention. That is, the present invention, in producing a multilayer printed wiring board, when forming an interlayer insulating material layer on both sides of the wiring board, sandwiched between a pair of coating rolls in a state where the board is vertically standing, A method for manufacturing a multilayer printed wiring board, characterized in that an interlayer insulating material is simultaneously applied to both surfaces.

In the method of the present invention, it is preferable that the length of the coating roll is shorter than the width of the substrate.
It is preferable to use an adhesive for electroless plating in which hardened heat-resistant resin particles soluble in an acid or an oxidizing agent are dispersed in an uncured heat-resistant resin hardly soluble in an acid or an oxidizing agent.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method for manufacturing a multilayer printed wiring board according to the present invention is characterized in that, when forming an interlayer insulating material layer on both surfaces of a wiring board, a pair of coating rolls is formed in a state where the board is set upright. It is characterized in that it is sandwiched between rolls and an interlayer insulating material is applied simultaneously on both sides.

According to the method of the present invention, the interlayer insulating material is simultaneously applied to both sides while the substrate is set upright, so that the interlayer insulating material is applied in a shorter time than in the conventional technique in which one side is applied one by one. An insulating material layer can be formed. Further, according to the method of the present invention, the interlayer insulating material applied to the substrate can be simultaneously dried on both sides, so that the insulating resin shrinks due to the evaporation of the solvent occurs on both sides of the substrate at the same time. Absent. Further, according to the method of the present invention, unlike the prior art in which the coating is performed one by one, the substrate does not need to be turned over while the interlayer insulating material is in an uncured state (B-stage state). The problem that the surface does not contact the transporting machine or the like and dust adheres hardly occurs.

As described above, according to the present invention, in manufacturing a multilayer printed wiring board, the formation time of the interlayer insulating material layer can be reduced without any trouble.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a multilayer printed wiring board according to the present invention will be described below. (1) First, an inner layer copper pattern is formed on the surface of the core substrate. The formation of a copper pattern on this substrate is performed by etching a copper-clad laminate, or an adhesive layer for electroless plating is formed on a substrate such as a glass epoxy substrate, a polyimide substrate, a ceramic substrate, and a metal substrate, There is a method in which the surface of the adhesive layer is roughened to a roughened surface, and electroless plating is performed thereon. Note that a through hole is formed in the core substrate, and the wiring layer on the front surface and the back surface can be electrically connected through the through hole.

(2) Next, an interlayer insulating material layer is formed on the substrate on which the inner layer copper pattern has been formed in (1). In particular, in the present invention, when forming an interlayer insulating material layer on both sides of the wiring board, the board is sandwiched between a pair of coating rolls in a state where the board is vertically erected, and the interlayer insulating material is simultaneously applied to both sides. It is characterized by.

As the interlayer insulating material constituting the interlayer insulating material layer, a thermosetting resin such as an epoxy resin, a polyimide resin, a bismaleimide triazine resin, a phenol resin, a photosensitive resin obtained by sensitizing the resin, or a polyether sulfone is used. For example, a thermoplastic resin, a composite of a thermoplastic resin and a thermosetting resin, and a composite of a photosensitive resin and a thermoplastic resin can be used. Each of these interlayer insulating materials is an uncured insulating resin, and is simultaneously applied to both surfaces of the substrate using, for example, a roll coater having a pair of application rolls. This conceptual diagram is shown in FIG.

As shown in FIG. 1, according to the method of the present invention, the wiring board is sandwiched between a pair of coating rolls of a roll coater in a state of being erected vertically, and is conveyed from the lower side to the upper side to be applied to both sides of the substrate. An interlayer insulating material is applied simultaneously. The roll coater used here is provided with a doctor bar that makes complete contact with each roll on the application surface side or that has a certain gap of 0.6 mm or less. The doctor bar also forms a varnish reservoir for storing uncured interlayer insulating material between each roll. On the other hand, the surface of each roll is made of resin such as rubber or urethane, and countless grooves are formed on the surface of the resin in the rotating direction as shown in FIG. For this reason, when the roll rotates, the interlayer insulating material stored in the varnish reservoir enters the groove of the roll, and when the interlayer insulating material contacts the substrate, it is transferred to the substrate side and the interlayer insulating material is applied to the substrate. Is performed.

The substrate is transported as shown in FIG.
The method of transferring from the lower side to the upper side is more preferable than the method of transferring from the upper side to the lower side in that the upper side edges of the substrate can be easily transferred to the drying furnace, which is the next step. is there. The conveying speed is desirably 0.5 to 5 m / min.

In the method of the present invention, it is preferable that the length of the coating roll is shorter than the width of the substrate. The reason for this is that, as shown in FIG. 3, gripping portions without interlayer insulating material can be provided on both side edges of the substrate. When the grip portion is provided, handling can be performed by holding the grip portion, and a transport jig can be fixed to the grip portion and transported. As a result, at the time of handling or transporting, the hand of the worker or the transporting machine / equipment does not come into contact with the interlayer insulating material layer, and no dust or the like adheres to the interlayer insulating material layer. The roll length is 1 to 3 from the width of the substrate.
It is desirable to be shorter by cm. As a result, both sides of the substrate
This is because a grip portion having a thickness of 0.5 to 1.5 cm without an interlayer insulating material can be provided.

In the method of the present invention, since the interlayer insulating material is simultaneously applied to both surfaces of the substrate as described above, the drying process of the interlayer insulating material by the drying furnace is also performed on both surfaces simultaneously. As a result, the shrinkage of the insulating resin accompanying the volatilization of the solvent occurs simultaneously on both surfaces of the substrate, so that the substrate does not warp. Therefore, it is possible to prevent the via hole formed in the interlayer insulating material layer from being displaced and the conductor pattern from being displaced.

In the method of the present invention, it is desirable to use an adhesive for electroless plating as the interlayer insulating material. As the adhesive for electroless plating, an adhesive obtained 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 is optimal. . This is because by roughening and removing the heat-resistant resin particles soluble in an acid or an oxidizing agent, an octopus-shaped anchor can be formed on the surface and the adhesion to the conductor circuit can be improved.

In the above-mentioned adhesive for electroless plating, the heat-resistant resin which is hardly soluble in an acid or an oxidizing agent is preferably a sensitized thermosetting resin or a composite of a sensitized thermosetting resin and a thermoplastic resin. . Exposure by photosensitization,
This is because via holes can be easily formed by development. In addition, by forming a composite with a thermoplastic resin, the toughness can be improved, and the peel strength of the conductor circuit can be improved,
This is because the occurrence of cracks in the via holes due to the heat cycle can be prevented. Specifically, epoxy acrylate obtained by reacting an epoxy resin with acrylic acid, methacrylic acid, or the like, or a composite of epoxy acrylate and polyether sulfone is preferable. The epoxy acrylate is preferably one in which 20 to 80% of all epoxy groups have reacted with acrylic acid or methacrylic acid.

In the above-mentioned adhesive for electroless plating, the heat-resistant resin particles include a heat-resistant resin powder having an average particle diameter of 10 μm or less and a heat-resistant resin powder having an average particle diameter of 2 μm or less. Agglomerated particles having a size of 2 to 10 μm, a mixture of a heat-resistant resin powder having an average particle size of 10 μm or less and a heat-resistant resin powder having an average particle size of 2 μm or less, and a heat-resistant resin powder having an average particle size of 2 to 10 μm It is desirable to select from pseudo particles obtained by adhering at least one of a heat-resistant resin powder and an inorganic powder having an average particle diameter of 2 μm or less on the surface. These are because they can form complex anchors. As the resin of the heat-resistant resin particles, epoxy resin, amino resin (melamine resin, urea resin, guanamine resin) and the like are preferable. Particularly, the solubility of an epoxy resin in an acid or an oxidizing agent can be arbitrarily changed by changing the type of the oligomer, the type of the curing agent, and the crosslinking density. For example, a bisphenol A-type epoxy resin oligomer cured with an amine-based curing agent is easily dissolved in an oxidizing agent. However, the novolak epoxy resin oligomer cured with an imidazole-based curing agent is hardly dissolved in the oxidizing agent.

In the method of the present invention, the interlayer insulating material layer does not need to be formed by one application, but may be formed by applying a plurality of times. In this case, first, an uncured resin insulating material is applied according to the method of the present invention, and after drying, an adhesive for electroless plating is further applied according to the method of the present invention to form a two-layered interlayer insulating material layer. It can be.

(3) After drying the interlayer insulating material layer formed in the above (2), the photosensitive resin is exposed and developed, and the thermosetting resin is thermally cured. An opening for a via hole is provided by laser processing.

(4) After roughening the surface of the interlayer insulating material layer provided with the opening for via hole in (3) with an acid or an oxidizing agent, a catalyst nucleus is provided. Here, examples of the acid that can be used for the above-mentioned roughening treatment include phosphoric acid, hydrochloric acid, sulfuric acid, and organic acids such as formic acid and acetic acid, and organic acids are particularly desirable. This is because when the roughening treatment is performed, the metal conductor layer exposed from the via hole is hardly corroded. On the other hand, as the oxidizing agent, chromic acid and permanganate (such as potassium permanganate) are desirable. In particular, in the case of dissolving and removing the amino resin, it is preferable to perform a roughening treatment alternately with an acid and an oxidizing agent. In addition, it is desirable to use a noble metal ion or a noble metal colloid for providing the catalyst nucleus. Generally, palladium chloride or a palladium colloid is used.
Note that it is desirable to perform a heat treatment to fix the catalyst core. Palladium is preferred as such a catalyst core.

(5) After providing the catalyst nucleus in the above (4), a plating resist is formed. As this plating resist,
A commercially available product may be used, or a composition comprising an epoxy acrylate and an imidazole curing agent obtained by reacting an epoxy resin with acrylic acid or methacrylic acid, or a composition comprising an epoxy acrylate, polyether sulfone and an imidazole curing agent may be used. . Here, the ratio of epoxy acrylate to polyether sulfone is 50 / 50-
About 80/20 is desirable. If the amount of epoxy acrylate is too large, the flexibility is reduced, and if the amount is too small, photosensitivity, base resistance,
This is because the acid resistance and antioxidant properties are reduced. The epoxy acrylate is preferably one in which 20 to 80% of all epoxy groups have reacted with acrylic acid or methacrylic acid. If the acrylate ratio is too high, the hydrophilicity due to the OH group increases and the hygroscopicity increases, and if the acrylate ratio is too low, the resolution decreases. As the epoxy resin as the basic skeleton resin, a novolak type epoxy resin is desirable. This is because the crosslinking density is high, the water absorption of the cured product can be adjusted to 0.1% or less, and the base resistance is excellent. Novolak type epoxy resins include cresol novolak type and phenol novolak type.

(6) Primary plating is applied to the portion where the plating resist has not been formed in the process (5). At this time, not only a copper pattern but also a via hole is formed. The primary plating is desirably an alloy plating using at least two or more metal ions selected from copper, nickel, cobalt and phosphorus. This is because these alloys have high strength and can improve the peel strength. In the electroless plating solution for the primary plating, it is necessary to use at least two kinds of metal ions selected from copper, nickel and cobalt. The reason for this is that these alloys have high strength and peel strength. This is because it can be improved. In the electroless plating solution for the primary plating, it is desirable to use a hydroxycarboxylic acid as a complexing agent that forms a stable complex with copper, nickel, and cobalt ions under basic conditions. In the electroless plating solution for the primary plating, reducing agents for reducing metal ions to metal elements include aldehydes, hypophosphites (called phosphinates),
At least one selected from borohydride salts and hydrazine
Desirably a seed. This is because these reducing agents are water-soluble and have excellent reducing power. In particular, hypophosphite is desirable in terms of depositing nickel. In the electroless plating solution for the primary plating, at least one selected from sodium hydroxide, potassium hydroxide, and calcium hydroxide is used as a pH adjuster for adjusting under basic conditions.
It is desirable to use some basic compounds. This is because under basic conditions, hydroxycarboxylic acid forms a complex with nickel ions and the like. As the hydroxycarboxylic acid, citric acid, malic acid, tartaric acid and the like are desirable. This is because these easily form a complex with nickel, cobalt, and copper. The concentration of the hydroxy carboxyl is
Desirably, it is 0.1 to 0.8M. If the amount is less than 0.1 M, a sufficient complex cannot be formed, resulting in abnormal precipitation or decomposition of the liquid. On the other hand, when the concentration exceeds 0.8 M, the precipitation rate becomes slow,
This is because problems such as increased generation of hydrogen occur. The electroless plating solution for the primary plating desirably contains bipyridyl. The reason for this is that bipyridyl can suppress the generation of metal oxides in the plating bath and the generation of nodules. Note that copper ions, nickel ions, and cobalt ions are supplied by dissolving copper, nickel, and cobalt compounds such as copper sulfate, nickel sulfate, cobalt sulfate, copper chloride, nickel chloride, and cobalt chloride.

The primary plating film formed by such an electroless plating solution has excellent followability to the roughened surface of the adhesive layer for electroless plating, and traces the form of the roughened surface as it is. Therefore, the primary plating film has an anchor like the roughened surface. Therefore, the adhesion of the secondary plating film formed on the primary plating film is secured by the anchor. Therefore, in order to control the peel strength, the primary plating film is desirably a plating film having a high strength to be deposited by the electroless plating solution as described above, while the secondary plating film has a high electric conductivity and a high deposition rate. Therefore, a plating film deposited with a simple copper plating solution is more desirable than composite plating.

(7) Secondary plating is performed on the primary plating film formed in (6) to form a conductor circuit including a via hole composed of the primary plating film and the secondary plating film. The plating film formed by the secondary plating is preferably a copper plating film. The electroless plating solution for the above-mentioned secondary plating has a copper ion concentration of 0.005 in an electroless plating solution comprising copper ions, trialkanolamine, a reducing agent and a pH adjuster.
~ 0.015mol / l, concentration of pH adjuster is 0.25 ~ 0.35mol
/ L, and it is preferable to use an electroless plating solution having a reducing agent concentration of 0.01 to 0.04 mol / l. This is because the plating solution has a stable bath and generates little nodules and the like. In the above electroless plating solution for secondary plating,
Desirably, the concentration of trialkanolamine is 0.1-0.8M. This is because the plating precipitation reaction most easily proceeds in this range. The trialkanolamine is desirably at least one selected from triethanolamine, triisopanolamine, trimethanolamine, and tripropanolamine. Because it is water-soluble. In the above electroless plating solution for secondary plating, the reducing agent is desirably at least one selected from aldehyde, hypophosphite, borohydride, and hydrazine. This is because it is water-soluble and has a reducing power under basic conditions. The pH adjuster is desirably at least one selected from sodium hydroxide, potassium hydroxide, and calcium hydroxide.

(8) In the surface layer of the multilayer printed wiring board thus obtained, the surface of the interlayer insulating layer is roughened, a plating resist is formed on the roughened surface, and a conductive circuit is formed on the non-formed surface of the plating resist. Is provided in an exposed state. Therefore, the exposed conductor circuit is protected by covering with a solder resist having an opening in a portion where a solder layer is to be formed.

(9) Then, nickel-gold plating is applied to a portion (pad portion) of the solder resist opening where the solder layer is to be formed, and the solder layer is formed on this portion by a solder transfer method or a screen printing method. Form. In the solder transfer method, a solder pattern is formed on a film,
In this method, the solder pattern is heated and reflowed while being in contact with the pad to transfer the solder to the pad. In addition,
The solder layer may be a solder bump.

(10) Finally, the grip provided on the wiring board is cut and removed. In the case of mass production, a plurality of product pieces are cut out from a substrate of one work size by processing with a dicing machine or the like. In this processing, the grip portion can be cut and removed.

[0033]

As described above, according to the present invention, it is possible to reduce the time required for forming an interlayer insulating layer without causing problems such as warpage of a substrate and mixing of dust into the interlayer insulating layer. The productivity of the wiring board can be further improved.

[Brief description of the drawings]

FIG. 1 is a view showing a method of forming an interlayer insulating material layer in a manufacturing method of the present invention.

FIG. 2 is a view showing the surface structure of a coating roll used in the production method of the present invention.

FIG. 3 is a diagram showing a state in which grip portions without interlayer insulating material are provided on both side edges of the substrate.

[Explanation of symbols]

 Reference Signs List 1 roll 2 doctor bar 3 interlayer insulating material 4 wiring board 5 gripper

Claims (3)

[Claims] In manufacturing a multilayer printed wiring board, when forming an interlayer insulating material layer on both sides of a wiring board, the board is sandwiched between a pair of coating rolls in a state where the board is set upright. A method for manufacturing a multilayer printed wiring board, characterized in that an insulating material is simultaneously applied to both surfaces. 2. The method according to claim 1, wherein the length of the coating roll is shorter than the width of the substrate. 3. An electroless plating method in which, as the interlayer insulating material, hardened heat-resistant resin particles soluble in an acid or an oxidizing agent are dispersed in an uncured heat-resistant resin hardly soluble in an acid or an oxidizing agent. The method according to claim 1, wherein an adhesive is used.