JPH01137695A - Manufacture of multilayer printed-wiring board - Google Patents

Abstract

PURPOSE:To contrive an increase in density of patterns by a method wherein a specified photopolymer layer is formed on the whole surface of a laminated plate, ultraviolet light is irradiated, and after a development and a post-curing are performed, a part of each land is exposed and a second-layer wiring pattern is formed on the photopolymer layer. CONSTITUTION:Wiring patterns 2 and lands 3 are formed on one side only of a copper-clad laminated plate 1. A specified photopolymer layer 5 having a high glass transition temperature is formed on a substrate 11, on which a conductor pattern 12 is formed. Ultraviolet light is irradiated through a photomask to cure selectively the layer 5 and a developing is performed to form holes 6 for via holes. A plating nucleus 7 is given to the whole surface of the substrate 11 having the layer 5. A resist 8 is patterned. An electroless plating 9 is applied in such a way that the via holes, a second-layer pattern and the lands are formed. Thereby, an increase in the density of the patterns can be contrived.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a multilayer printed wiring board having a fine pattern, particularly a wiring board in which fine via holes can be easily formed and has high thermal reliability. Regarding the manufacturing method.

[Conventional technology]

BACKGROUND ART In recent years, with the miniaturization of electronic devices, higher density and higher multilayer printed wiring boards are required, and various methods for manufacturing multilayer printed wiring boards have been proposed.

Among these, a particularly numerical one is one in which circuits are formed by etching on both sides of copper-clad laminates, which are alternately laminated via prepregs made of glass cloth impregnated with epoxy resin, etc., and then bonded under heat and pressure. It is obtained by drilling the interlayer wires, plating the through holes, and then etching the outer layer pattern of the substrate.

This provides high through-hole connection reliability, but in the case of highly multilayered boards, it is extremely difficult to reduce the through-hole diameter due to the difficulty of drilling small-diameter holes. To solve this shortage, there is a method for manufacturing a multilayer printed board, disclosed in Japanese Patent Application Laid-open No. 58-209195, in which circuits and insulating layers are stacked on a substrate using a photopolymer.

According to this method, fine wiring patterns and holes for via holes can be formed using photopolymer.

[Problem that the invention seeks to solve]

However, the photopolymer layer in the conventional manufacturing method described above has poorer heat resistance than the prepreg that has been used for a long time, so its thermal expansion, especially in the Z direction, increases.
There is a problem that the reliability of the via hole is low.

The present invention has been made to solve the above-mentioned problems, and aims to obtain a multilayer printed wiring board that enables higher density patterns and has highly reliable via holes.

[Means for solving problems]

The method for manufacturing a multilayer printed wiring board according to the present invention includes a step of forming a first layer wiring pattern and a land only on one side of a laminate by a subtractive method or a full additive method, The process of forming a special photopolymer layer on the entire surface, irradiating the photopolymer layer with ultraviolet light through a photomask, then developing and post-curing, and forming holes for via holes in the photopolymer layer using photolithography. and exposing a part of the runt formed on the laminate, forming a second layer wiring pattern and land on the photopolymer layer by a fully additive method, and repeating the above steps. , and further includes the step of forming an upper layer circuit.

In addition, as a photopolymer, conventional methods such as glass and
In order to obtain thermal properties equivalent to those using epoxy prepreg as an interlayer insulation layer, the thermal properties after curing are almost the same as glass-epoxy laminates.High heat resistance, especially equivalent to glass-epoxy laminates. This is characterized by the use of a special material having a glass transition temperature of .

〔Example〕

Hereinafter, the present invention will be explained based on the drawings.

FIG. 1 is a process diagram showing a specific example of the method for manufacturing a multilayer printed wiring board according to the present invention using a sectional view of the printed wiring board.

First, in process A, copper-clad laminates (hereinafter referred to as "laminates")
2 wiring patterns and a land 3 are formed on only one side of the substrate 1 using an etching method.

In addition, instead of performing step A, the wiring pattern 2 and the land 3 may be formed on the laminate 1 by a full additive method in which electroless plating is selectively performed using the plating resist 4 as in step A'. Good too.

Next, in step B, a special photopolymer layer 5 that completely withstands the plating conditions and has high heat resistance, especially high glass transition temperature, is applied to the step A described above.

Or the substrate 11 on which the conductor pattern 12 is formed at A'
to form. However, since the photopolymer layer is used as an interlayer insulating film, the thickness of the photopolymer layer is 5 to 10 mm after complete curing.
It is desirable that the thickness be 0 μm.

As for the special photopolymer, (a) the reaction ratio of the glycidyl needle type epoxy resin having at least two or more epoxy groups in one molecule and the carboxylic acid containing an ethylenically unsaturated bond is per epoxy group; (b) a linear vinyl polymer having a molecular weight of ~500,000 and a glass transition temperature of 50 to 130°C; (C) a reaction product containing 0.9 or less molecules of carboxylic acid in one molecule; A substance that is liquid at room temperature and contains two or more ethylenically unsaturated bonds, and which contains the above as essential components and has a glass transition temperature of 100 to 16
A temperature of 0°C is used.

In addition, in order to increase the heat resistance after curing, especially the glass transition temperature, cresol novolac type epoxy resin and phenol novolac type epoxy resin are used as glycidyl ether type epoxy resin having at least two or more epoxy groups in one molecule. It is desirable to do so.

Furthermore, examples of carboxylic acids having ethylenically unsaturated bonds include acrylic acid and methacrylic acid.

Linear vinyl polymers with a molecular weight of 10,000 to 500,000 and a glass transition temperature of 50 to 130°C include copolymers of acrylic esters, methacrylic esters, acrylonitrile, etc., and acetalization of polyvinyl alcohol. Examples include polyvinyl formal and polyvinyl butyral obtained by, but are not limited to, stiff ones.

Furthermore, substances that contain two or more ethylenically unsaturated bonds in one molecule and are liquid at room temperature include polyethylene glycol diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, and tris(2 -acryloxy)isocyanurate and the like, but are not limited to these.

Next, in step C, the photopolymer layer 5 is selectively cured by irradiating ultraviolet light through a photomask, and then a development process is performed using an organic solvent to form a hole 6 for a via hole. Thereafter, this photopolymer layer 5 is completely cured by intense ultraviolet light and heat.

Next, in a step, plating nuclei 7 necessary for electroless plating are applied to the entire surface of the substrate 11 having the photopolymer layer 5.

Next, in step E, a plating resist 8 is patterned in a pattern opposite to the wiring pattern and land of the second layer.

Note that as the plating resist 8, the special photopolymer used in step B can be used.

Further, in order to enable high-density wiring, it is preferable that the pattern of the plating resist 8 be formed by a photolithography method rather than a screen printing method.

Next, in step F, electroless plating 9 is performed so that via holes, a second layer wiring pattern, and lands are formed.

By repeating steps B to F described above one after another, a multilayer printed wiring board having a desired number of layers can be manufactured.

Alternatively, instead of performing steps 3 and E, a method is used in which plating nuclei are applied to a desired wiring pattern using a combination of a metal salt and a substance that exhibits or deactivates the ability to reduce metal salts by the action of ultraviolet light. It is also possible.

In addition, examples of substances that exhibit the ability to reduce metal salts by the action of ultraviolet light include anthraquinone derivatives and titanium dioxide, and substances that deactivate the ability to reduce metals by the same action include: I can give you stannous chloride.

Examples of metal salts include palladium chloride, silver chloride, and copper acetate.

In the case of this method, in order to improve the adhesion of the plating core particles, after forming via holes in the photopolymer layer in step C, the above treatment is performed before the plating core is completely cured. It is preferable to allow the photopolymer layer to fully cure after application.

The present invention will be explained below based on examples.

First Example First, a 100 μm wide wiring pattern and a land were formed by photoetching on a 1.0 ml thick glass-epoxy laminate plate covered with a 10 μm thick copper foil on one side.

Next, a photopolymer having the following composition was applied so that the thickness after drying was 50 μm.

(a) Epoxy novolac resin DEN439 (Dow
Chemical company, epoxy equivalent 191) epoxy group 8
A photosensitive material with ethylenically unsaturated bonds introduced by reacting 0% with acrylic acid.
・35 parts (a) A 50/30/20 copolymer of methyl methacrylate, butyl acrylate, and butyl methacrylate, with a molecular weight of 150,000 and a glass transition temperature of 95°C --------15 parts (1) Trimethylolpropane triacrylate
----10 parts (1) Photopolymerization initiator; benzyl dimethyl ketal (Irgacure 651 Gba G
(manufactured by Eigy)...5 parts (e) Solvent; Cellosolve acetate...35 parts Then, after completely volatilizing the solvent, irradiate ultraviolet light of 200 mJ per cII+2 through a negative mask. Then, 1,1,1-trichloroethane was sprayed and developed to complete a hole for a via hole.

Then, irradiate with strong ultraviolet light of 3J per cm2,
A photopolymer layer having a glass transition temperature of 120°C was formed by heating at 150°C for 60 minutes.

Palladium metal particles were applied as plating nuclei onto the photopolymer layer using a method similar to that used as a normal electroless plating pretreatment process.

On top of this, apply full-speed photopolymer to a thickness of 30 μm after drying.
The second layer land and wiring pattern were formed using the same method, and cured using ultraviolet light and heat.

Finally, electroless plating was performed on this substrate for 20 hours to form a second plate.
A thick layer and via holes were formed.

Thereafter, the above-described method was repeated to obtain a multilayer wiring board with four layers on one side.

The conductivity reliability of the via holes in the first wiring board was sufficient even after thermal shocks such as solder float and heat cycle tests were applied.

Second Example First, after the surface of a 1.0 m+n thick glass-epoxy laminate was roughened using chromic acid, palladium particles were applied to the entire surface as plating nuclei.

Next, the photopolymer used in the first example was applied to a dry thickness of 30 μm, and after drying, ultraviolet light was irradiated through a photomask, developed, and cured to form the desired conductor pattern. A plating resist layer with a reverse pattern was formed. This substrate was immersed in an electroless copper plating solution for 20 hours to form a first layer wiring pattern and land.

Thereafter, the same photopolymer was applied as an interlayer insulating layer to a thickness of 50 μm after drying, and via holes and a -L layer were formed in the same manner as in the first example. A multilayer printed wiring board was obtained.

The reliability of the via holes in the wiring board against thermal shock was equivalent to that of a conventional product using prepreg as an interlayer insulating layer.

Third Example First, a photopolymer having the following composition was used,
A multilayer printed wiring board with six layers on one side was obtained in the same manner as in the second example. Note that the glass transition temperature of the photopolymer after curing is 130°C.

(Power) Talesol novolac type epoxy resin ESCN1
Photosensitive material in which 60% of the epoxy groups of 95XL (manufactured by Sumitomo Chemical Co., Ltd., equivalent weight 195) were reacted with methacrylic acid to introduce ethylenic double bonds -----
--50 parts (g) Resin obtained by reacting polyvinyl alcohol with an average degree of polymerization of 2400 with butyraldehyde (molecular diameter approx. 300,000, glass transition temperature 90°C)...5 parts (g) Pentaerythritol tri Acrylate -----
-5 parts (k) Photopolymerization initiator: 2-methyl [4-(methylthio)
Phenyl-2-morpholino-1-propanone (TR
GACURE907, manufactured by Giba Geigy)
・---3 parts (C) R Color agent: Phthalocyanine green 2 parts (S) Solvent: Toluene 35 parts 4th example First, a 10 μm copper foil was Wires and lands with a width of 100 μm were formed on a glass-epoxy laminate with a thickness of 1.0 mm and covered on one side using a photoetching method.

Next, a photopolymer having the composition of Example 3 was applied so that the thickness after drying was 50 μm.

After that, after completely volatilizing the solvent from the photopolymer layer, it was irradiated with ultraviolet light of 300 mJ/cm2 through a negative mask, and then developed by spraying 1,1°1-trichloroethane to form a via hole. A hole was formed.

Next, after immersing the laminate in an aqueous solution of stannous chloride, the water is evaporated, and then ultraviolet light is applied through a mask film that irradiates the second layer wiring and lands in the opposite pattern. irradiated with light. Next, the laminate was immersed in an aqueous palladium chloride solution and washed with water to deposit palladium particles in the pattern of the second layer wiring and lands. Electroless copper plating was performed using this as a plating core to form a second thick layer and via holes.

Thereafter, the above-described method was repeated to obtain a multilayer printed wiring board with six layers on one side. The reliability of the via holes in the wiring board was good even after being subjected to thermal shock.

First Comparative Example Using a photopolymer having the following composition and a glass transition temperature of 50° C. after curing, a four-layer printed wiring board was obtained in the same manner as in the first example.

(ri) A photosensitive material in which an ethylenic double bond is introduced into the epoxidized novolac resin used in the first example.
...35 parts (h) Average degree of polymerization 20
Resin obtained by the reaction of 0.0 polyvinyl alcohol and butyraldehyde (molecular weight 30,000, glass transition humidity 40°C) 35 parts (
T) Photopolymerization initiator: 7:1 mixture of benzophenone and Michler's ketone...5 parts (T) Solvent: Methyl ethyl ketone...25 parts
When floated in a solder bath at 60°C, 30% of the via hole
%, cracks were formed and conductivity was no longer possible, or the resistance value increased.

Second Comparative Example Using a photopolymer having the following composition and having a glass transition temperature of 40° C. after curing, a four-layer printed wiring board was obtained in the same manner as in the second example.

(su) 1/1/1 copolymer of methyl methacrylate, butyne methacrylate, methacrylic acid (molecule!1t50,00
0. Glass transition temperature 40℃)・Transition-・・40 parts (d) Diethylene glycol diacrylate・・・・
・25 parts (nu) Photopolymerization initiator: 2-ethylanthraquinone
°------5 parts (ne) Solvent, Triclean...30 parts and 16 parts for the surface board.
When a heat cycle test was performed in which the sample was left at 5° C. for 15 minutes and at 125° C. for 15 minutes, half of the via holes developed cracks at the 50th cycle, resulting in poor conductivity.

This result shows that when the glass transition temperature of the photopolymer layer after curing is out of the range defined in the present invention, the desired characteristics cannot be obtained.

(Effects of the Invention) As explained above, according to the present invention, first, the first layer wiring pattern and land are formed only on one side of the laminate by a subtractive method, etc., and a special photo is applied to the entire surface of the laminate. A polymer layer is formed, irradiated with ultraviolet light through a photomask, developed and post-cured, and a hole for a via hole is formed by a photolithography method to expose a part of the land. A manufacturing method is provided in which a second layer wiring pattern and a land are formed on a photopolymer layer by a fully additive method, and these steps are repeated to further form an upper layer circuit, and the photopolymer includes:
Since we decided to use a glass/epoxy laminate and a special material with a glass transition temperature such as ρ1, we created a multilayer print that not only has highly reliable small-diameter via holes but also allows for high-density conductor patterns. This has the effect that a wiring board can be obtained.

[Brief explanation of the drawing]

FIG. 1 shows the method for manufacturing a multilayer printed wiring board of the present invention.
It is a process diagram of a specific example showing the circuit formation process up to the second layer using a cross section of the substrate. 1.... Copper-clad laminate 2 --- Wiring 3 --- Land 4 --- Plating resist 5 --- Photopolymer layer 6 --- ... Hole for via hole 7 ... Plating core 8 ... Plating resist 9 ... Electroless plating

Claims (2)

[Claims] (1) In the manufacturing process of multilayer printed wiring boards, (A)
A step of forming a first layer wiring pattern and a land on only one side of the copper-clad laminate by a subtractive method of etching or a full additive method of electroless plating on the laminate. (B) A special photopolymer layer with high heat resistance, especially high glass transition temperature, which can withstand electroless copper plating conditions after being completely cured, is applied to the entire surface of the laminate with wiring patterns and lands formed on one side. The process of forming. (C) The above photopolymer layer is irradiated with ultraviolet light through a photomask, then developed and post-cured to form holes for via holes in the photopolymer layer using photolithography, and formed on the laminate. The process of exposing a part of the land that has been removed. (D) A step of forming a second layer wiring pattern and lands on the photopolymer layer formed and cured in step (C) by a full additive method using the photopolymer as a plating resist. (E) A method for manufacturing a multilayer printed wiring board, comprising the step of forming an upper layer circuit by repeating steps (B) to (D). (2) withstands electroless copper plating conditions after being fully cured;
As a special photopolymer with high heat resistance, especially high glass transition temperature, (a) Reaction ratio of glycidyl ether type epoxy resin having at least two or more epoxy groups in one molecule and carboxylic acid having ethylenically unsaturated bond. (b) A linear vinyl having a molecular weight of 10,000 to 500,000 and a glass transition temperature of 50 to 130°C. Polymer (c) A substance that is liquid at room temperature and contains two or more ethylenically unsaturated bonds in one molecule.It contains the above as essential components and has a glass transition temperature of 100 to 160°C after being completely cured. 2. A method for manufacturing a multilayer printed wiring board according to claim 1, characterized in that connection reliability of via holes is improved by using a method characterized in that: