JP2002237684A - Multilayer printed circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer printed circuit board, capable of preventing occurrences of cracks or the like in the board or an interlayer resin insulating layer, when an optical waveguide to be incorporated in the multilayer printed circuit board, or particularly, when an optical path conversion mirror is formed by using mechanical processing or the like and having superior connection reliability of light signals. SOLUTION: The multilayer printed circuit board comprises a conductor circuit and an interlayer resin insulating layer laminated and formed on both surfaces of a substrate, and the optical waveguide formed on the substrate and the circuit board further comprises an elastic material layer formed between the substrate and the optical waveguide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a multilayer printed wiring board.

[0002]

2. Description of the Related Art In recent years, attention has been focused on optical fibers mainly in the communication field. In particular, in the field of IT (information technology), communication technology using optical fibers is required for maintenance of a high-speed Internet network. Optical fibers have characteristics such as low loss, high bandwidth, small diameter and light weight, no induction, and resource saving. Communication systems using optical fibers having these characteristics require communication using conventional metallic cables. Compared with the system, the number of repeaters can be greatly reduced, construction and maintenance are facilitated, and economical and high reliability of the communication system can be achieved.

In addition, since an optical fiber can simultaneously multiplex not only light of one wavelength but also light of many different wavelengths through one optical fiber, a large-capacity optical fiber can be used for various applications. A transmission path can be realized, and it is possible to support video services and the like.

[0004] In such network communication such as the Internet, optical communication using an optical fiber is used not only for communication on the backbone network but also for communication between the backbone network and terminal equipment (PC, mobile, game, etc.). It has also been proposed to use it for communication between terminal devices. When optical communication is used for communication between the backbone network and the terminal device in this way, an IC that performs information (signal) processing in the terminal device operates with an electric signal. It is necessary to attach a device for converting an optical signal into an electric signal such as an electric-to-optical converter (hereinafter also referred to as an optical / electrical converter). Therefore, in a conventional terminal device, for example, an optical signal transmitted from outside via an optical fiber or the like is transmitted to an optical / electrical converter, or an optical signal transmitted from the optical / electrical converter is transmitted to an optical fiber or the like. An optical waveguide for transmission and a multilayer printed wiring board for transmitting electric signals via solder bumps are separately mounted to perform signal transmission and signal processing.

In such a conventional terminal device, since the optical waveguide and the multilayer printed wiring board are separately mounted, the entire device becomes large, and it is difficult to reduce the size of the terminal device. Therefore, the present inventors have previously proposed a multilayer printed wiring board having an optical waveguide formed inside or on its surface as a multilayer printed wiring board that can contribute to miniaturization of terminal equipment.

[0006]

In an optical waveguide built in such a multilayer printed wiring board, an optical element such as an optical fiber, a light receiving element, and a light emitting element is usually efficiently connected to the optical waveguide. For this reason, an optical path conversion mirror is formed at the end thereof, and such an optical path conversion mirror is formed by, for example, machining with a V-shaped 90 ° diamond saw.

In the optical path conversion mirror formed by such machining or the like, when forming the optical path conversion mirror, a large stress is applied to the substrate and the interlayer resin insulating layer. Cracks sometimes occurred in the interlayer resin insulating layer. Also, a multilayer printed wiring board on which an optical waveguide is formed can be manufactured by attaching a film-shaped optical waveguide on which an optical path conversion mirror is formed, but in this case, when attaching the optical waveguide, As a result, stress is applied to the optical waveguide, and as a result, scratches, cracks, and the like may occur in the attached optical waveguide.

[0008]

Means for Solving the Problems Accordingly, the present inventors have:
As a result of intensive studies to solve the above-described problems, the configuration in which the optical waveguide is formed on the substrate or on the interlayer resin insulating layer via the elastic material layer enables the formation of the optical waveguide, particularly, the formation of the optical path conversion mirror. It has been found that a crack can be prevented from occurring in the substrate and the interlayer resin insulation layer at times, and a multilayer printed wiring board having excellent reliability has been found, and the present invention described below has been completed. In addition, when an optical waveguide on which an optical path conversion mirror is formed in advance is attached during the formation of the optical waveguide, the stress applied to the optical waveguide can be reduced by the elastic material layer, and the optical waveguide is damaged or cracked. And the like can be prevented from occurring.

That is, a multilayer printed wiring board according to a first aspect of the present invention is a multilayer printed wiring board in which a conductive circuit and an interlayer resin insulating layer are laminated on both surfaces of a substrate and an optical waveguide is formed on the substrate. Wherein an elastic material layer is formed between the substrate and the optical waveguide.

A multilayer printed wiring board according to a second aspect of the present invention is a multilayer printed wiring board in which a conductor circuit and an interlayer resin insulation layer are laminated on both sides of a substrate, and an optical waveguide is formed on the outermost interlayer resin insulation layer. A printed wiring board, wherein an elastic material layer is formed between the outermost interlayer resin insulating layer and the optical waveguide.

In the first or second multilayer printed wiring board of the present invention, the elastic material layer has an elastic modulus of 2.5 × 10
The elastic modulus is desirably ³ MPa or less.
More preferably, it is 1.0 to 1.0 × 10 ³ MPa. In the multilayer printed wiring board according to the first or second aspect of the present invention, it is preferable that the elastic material layer is made of a polyolefin resin and / or a polyimide resin.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a multilayer printed wiring board according to the first invention will be described. The multilayer printed wiring board according to the first aspect of the present invention is a multilayer printed wiring board in which a conductor circuit and an interlayer resin insulating layer are laminated on both surfaces of a substrate and an optical waveguide is formed on the substrate. An elastic material layer is formed between the substrate and the optical waveguide.

In the first multilayer printed wiring board of the present invention,
Since the optical waveguide is formed on the substrate via the elastic material layer, the stress applied to the substrate can be reduced when forming the optical waveguide, particularly when forming the optical path conversion mirror on the optical waveguide. It is possible to prevent the occurrence of cracks and the like on the substrate. Therefore, the reliability of the multilayer printed wiring board does not decrease due to cracks or the like generated on the substrate. In addition, when attaching a film-shaped optical waveguide on which an optical path conversion mirror has been formed in advance when forming the optical waveguide, the stress applied to the optical waveguide can be reduced by the elastic material layer, and the Scratches and cracks can be prevented from occurring.

Further, since the multilayer printed wiring board is formed with a conductor circuit and an optical waveguide, both optical signals and electric signals can be transmitted. The built-in wave path can contribute to miniaturization of the optical communication terminal device.

A first aspect of the present invention is a multilayer printed wiring board.
A multilayer printed wiring board with an optical waveguide formed on a board.
An elastic material layer is formed between the substrate and the optical waveguide.
Have been. The elastic material layer has an elastic modulus of 2.5
× 10³MPa (250kgf / mm²Below)
Is desirable, and 1.0 to 1.0 × 10³MPa (0.
1 to 100 kgf / mm²) Is more desirable
No. The elastic modulus is 2.5 × 10 ³When it exceeds MPa, light
When forming a waveguide, especially, forming an optical path conversion mirror on the optical waveguide
The stress applied to the substrate during
This prevents cracks and the like from occurring on the substrate.
In addition to the fact that the optical waveguide
Due to the difference in thermal expansion coefficient from the resin insulating layer,
Optical stress cannot be sufficiently relieved,
This is because a rack may occur. In addition, light conduction
To form a waveguide, attach a film-shaped optical waveguide
In this case, the stress applied to the optical waveguide is sufficiently relaxed.
Damage, cracks, etc. in the optical waveguide
May be. Also, the specific material of the elastic material layer and
A polyolefin resin having an elastic modulus in the above range.
Desirable is resin and / or polyimide resin
New The method of forming the elastic material layer will be described later.
It will be described in detail.

In the multilayer printed wiring board according to the first aspect of the present invention, an optical waveguide is formed on the elastic material layer.
Examples of the optical waveguide include an organic optical waveguide made of a polymer material or the like, an inorganic optical waveguide made of quartz glass, a compound semiconductor, or the like. Among these, an organic optical waveguide is desirable. This is because it has excellent adhesion to the substrate and the interlayer resin insulating layer, and can be easily formed and processed.

The polymer material is not particularly limited as long as it has low absorption in the communication wavelength band.
Thermosetting resin, thermoplastic resin, photosensitive resin, resin in which a part of thermosetting resin is made photosensitive, resin composite of thermosetting resin and thermoplastic resin, photosensitive resin and thermoplastic resin And the like.

More specifically, for example, acrylic resin such as PMMA (polymethyl methacrylate), deuterated PMMA, deuterated fluorinated PMMA, etc., polyimide resin such as fluorinated polyimide, epoxy resin, UV curable epoxy resin, polyolefin Base resins, silicone resins such as deuterated silicone resins, and polymers produced from benzocyclobutene.

In the above optical waveguide, in addition to the above resin component,
For example, particles such as resin particles, inorganic particles, and metal particles may be included. As the resin particles, for example, a thermosetting resin, a thermoplastic resin, a photosensitive resin, a resin in which a part of the thermosetting resin is sensitized, a resin composite of a thermosetting resin and a thermoplastic resin, Examples thereof include those composed of a composite of a photosensitive resin and a thermoplastic resin.

Specifically, for example, thermosetting resins such as epoxy resin, phenol resin, polyimide resin, bismaleimide resin, polyphenylene resin, polyolefin resin, and fluororesin; thermosetting groups of these thermosetting resins (for example, Methacrylic acid, acrylic acid, or the like is reacted with an epoxy group in an epoxy resin to give an acrylic group; phenoxy resin, polyether sulfone (PE
S), polysulfone (PSF), polyphenylene sulfone (PPS), polyphenylene sulfide (PPE)
S), thermoplastic resins such as polyphenyl ether (PPE) and polyetherimide (PI); and photosensitive resins such as acrylic resins. Further, a resin composite of the thermosetting resin and the thermoplastic resin, a resin having the acrylic group, or a resin composite of the photosensitive resin and the thermoplastic resin can also be used. Further, as the resin particles, resin particles made of rubber can be used.

The inorganic particles include, for example, aluminum compounds such as alumina and aluminum hydroxide;
Calcium carbonate, calcium compounds such as calcium hydroxide, potassium compounds such as potassium carbonate, magnesia, dolomite, magnesium compounds such as basic magnesium carbonate, silica, silicon compounds such as zeolite, titanium compounds such as titania and the like. Can be Also,
Silica and titania may be mixed at a certain ratio, melted and homogenized. Further, as the inorganic particles, those made of phosphorus or a phosphorus compound can also be used.

Examples of the metal particles include gold, silver,
Examples thereof include those made of copper, palladium, nickel, platinum, iron, zinc, lead, aluminum, magnesium, calcium, and the like. These resin particles, inorganic particles and metal particles may be used alone or in combination of two or more.

The shape of the particles is not particularly limited.
For example, a spherical shape, an elliptical spherical shape, a crushed shape, a polyhedral shape, and the like can be given. Among these, a spherical shape or an elliptical spherical shape is desirable. This is because spherical or elliptical spherical particles have no corners, and cracks and the like are less likely to occur in the optical waveguide.

Further, it is desirable that the particle size of the particles is shorter than the communication wavelength. If the particle size is longer than the communication wavelength, transmission of an optical signal may be hindered. The specific average particle size of the particles is desirably 0.1 to 20 μm, and particularly desirably 0.5 to 10 μm. As long as the particle diameter is within the above range, two or more kinds of particles having different particle diameters may be contained. In other words, there are cases in which particles having an average particle size of 0.5 to 4 μm and particles having an average particle size of 1 to 10 μm are contained. In the present specification, the particle diameter of a particle refers to the length of the longest part of the particle.

The compounding amount of the particles contained in the optical waveguide is as follows:
It is preferably from 10 to 80% by weight, more preferably from 20 to 70% by weight. If the blending amount of the particles is less than 10% by weight, the effect of blending the particles may not be obtained, and if the blending amount of the particles exceeds 80% by weight, transmission of an optical signal may be hindered. It is. Also,
The shape of the optical waveguide is not particularly limited, but a sheet shape is desirable because the formation is easy.

When particles are contained in the optical waveguide as described above, the coefficient of thermal expansion can be matched between the optical waveguide and the substrate constituting the multilayer printed wiring board, the interlayer resin insulating layer, and the like, and the thermal expansion coefficient can be improved. Cracks, peeling, and the like due to the difference in coefficient are less likely to occur. In addition, the optical waveguide containing particles has an expansion coefficient in a plane direction in contact with a substrate or the like of the optical waveguide,
Because the coefficient of expansion in the direction perpendicular to the substrate etc. is substantially uniform,
There is almost no be lost balance of the TM ₀ mode and the TE ₀ mode of the optical waveguide. Therefore, transmission loss of the optical signal due to these can be suppressed, and the optical signal can be transmitted well.

The thickness of the optical waveguide is 5 to 50 μm.
Is desirable. Further, the width of the optical waveguide is desirably 5 to 50 μm. If the width is less than 5 μm, the formation may not be easy, while if the width exceeds 50 μm,
In some cases, this may impede the degree of freedom in designing the conductor circuit and the like constituting the multilayer printed wiring board.

The ratio between the thickness and the width of the optical waveguide is:
A ratio closer to 1: 1 is desirable. This is because, if the ratio between the thickness and the width deviates from 1: 1, the loss in transmitting an optical signal increases as the ratio deviates. Further, when the optical waveguide is a single-mode optical waveguide having a communication wavelength of 1.55 μm, the thickness and width thereof are more preferably 5 to 15 μm, and the optical waveguide has a communication wavelength of 0.8 μm.
When the optical waveguide is a multi-mode optical waveguide having a thickness of 5 μm, it is more preferable that the thickness and the width thereof be 20 to 80 μm.

Further, it is preferable that a light receiving optical waveguide and a light emitting optical waveguide are formed as the optical waveguide. Note that the light receiving optical waveguide refers to an optical waveguide for transmitting an optical signal sent from the outside via an optical fiber or the like to the light receiving element, and the light emitting optical waveguide is transmitted from the light emitting element. An optical waveguide for transmitting an incoming optical signal to an optical fiber or the like. Further, it is desirable that the light receiving optical waveguide and the light emitting optical waveguide are made of the same material. This is because the matching of the thermal expansion coefficient and the like is easy to measure and the formation is easy.

It is desirable that an optical path conversion mirror is formed on the optical waveguide as described above. This is because the optical path can be changed to a desired angle by forming the optical path conversion mirror. The formation of the optical path conversion mirror can be performed, for example, by cutting one end of the optical waveguide, as described later.

In the multilayer printed wiring board according to the first aspect of the present invention, since an optical waveguide is formed on a part of the surface of the substrate, the optical waveguide and an external optical element (light receiving element, light emitting element, optical It is preferable that an optical path opening for transmitting an optical signal to the optical fiber is formed. Specifically, it is desirable that an opening for an optical path penetrating through the interlayer resin insulating layer laminated on one side of the substrate is formed. In addition, as described later, when a solder resist layer is formed on the outermost layer of the multilayer printed wiring board, an optical path opening that communicates with the solder resist layer on one side and the interlayer resin insulating layer is formed. Is desirable. Also,
In the opening for the optical path, a resin that does not hinder transmission of an optical signal,
For example, it may be filled with the same resin as the resin used for the optical waveguide. By filling the inside of the optical path opening with resin, the optical waveguide formed on the substrate can be protected.

In the above-mentioned multilayer printed wiring board,
It is desirable that the conductor circuits sandwiching the interlayer resin insulation layer be connected by via holes. By connecting the conductor circuits with via holes, the conductor circuits can be wired at a high density, and the degree of freedom in designing the conductor circuits is improved. Further, it is preferable that the conductor circuit is formed by an additive method, as described later in a method of manufacturing a multilayer printed wiring board. This is because the additive method is suitable for forming a fine wiring conductor circuit having an interval of 50 μm or less. The additive method may be a full additive method or a semi-additive method. Further, the conductor circuit may be formed by a build-up method.

In the above-mentioned multilayer printed wiring board, a solder resist layer is formed on the outermost layer, and an opening for mounting an IC chip mounting substrate and various surface mounting electronic components are mounted on the solder resist layer. Is desirably formed. When the above-mentioned opening is formed in the solder resist layer and, if necessary, a surface mounting pad is formed, a solder bump is formed or PGA is formed.
(Pin Grid Array) or BGA (Ball Grid Array) can be provided, so that the multilayer printed wiring board can be electrically connected to an external substrate or the like. Even without forming the solder bumps, BGA and PGA, by connecting the bumps formed on the BGA of the IC chip mounting substrate and the surface mounting type electronic component with the surface mounting pads, A substrate for mounting an IC chip or a surface-mounted electronic component can be mounted on a multilayer printed wiring board.

In the multilayer printed wiring board according to the first aspect of the present invention, an external substrate (IC) on which optical elements such as a light emitting element and a light receiving element are mounted on the side where the optical waveguide is formed.
When the chip mounting substrate is connected via the solder bumps, the multilayer printed wiring board and the external substrate can be reliably arranged at predetermined positions by the self-alignment action of the solder. Therefore, if the mounting position of the optical waveguide in the multilayer printed wiring board of the first invention and the mounting position of the optical element on the external board are accurate, it is possible to transmit an accurate optical signal between the two. it can.

The self-alignment action is an action in which the solder tends to exist in a more stable shape near the center of the opening for forming the solder bump due to its own fluidity during the reflow process. When the solder is repelled by the resist layer and adheres to the metal, it is considered to be caused by a strong surface tension that tends to form a sphere. If this self-alignment effect is used, via the solder bumps, when connecting the multilayer printed wiring board and the external board, even if a positional shift occurs between the two before reflow, At the time of reflow, the external substrate moves, and the external substrate can be mounted at an accurate position on the multilayer printed wiring board.

Hereinafter, an embodiment of the multilayer printed wiring board according to the first aspect of the present invention having the above-described configuration will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing one embodiment of the first multilayer printed wiring board of the present invention.

As shown in FIG. 1, the multilayer printed wiring board 1
In FIG. 00, a conductor circuit 124 and an interlayer resin insulation layer 122 are laminated on both surfaces of a substrate 121, and a through circuit is formed between the conductor circuits sandwiching the substrate 121 and between the conductor circuits sandwiching the interlayer resin insulation layer 122, respectively. It is electrically connected by the hole 129 and the via hole 127, and the solder resist layer 134 is formed on the outermost layer.

On the surface of the substrate 121, an optical waveguide 150 (150a, 150b) is formed via an elastic material layer 152 together with the lowermost conductive circuit 124, and an optical path conversion mirror 151 at the tip of the optical waveguide 150 is formed. (151a,
The opening 138 for the optical path is formed in the portion where 151b) is formed.
(138a, 138b) are formed in the substrate 121 in the vertical direction. The optical path opening 138 is formed by a gap. The optical waveguides 150a, 150
In b, one is a light receiving optical waveguide and the other is a light emitting optical waveguide.

In the multilayer printed wiring board 100 having such a configuration, an optical signal sent from outside via an optical fiber (not shown) or the like is introduced into the optical waveguide 150a, and the optical path conversion mirror 151a and the optical path Opening 138a
Through a light receiving element (not shown). An optical signal sent from a light emitting element (not shown) or the like is transmitted from the optical path opening 138b to the optical conversion mirror 151b.
Is introduced into the optical waveguide 150b through the optical waveguide 150b, is sent to the light receiving element of another IC chip mounting substrate, and is converted into an electric signal,
Alternatively, it is sent out through an optical fiber (not shown) or the like.

When an external board (not shown) such as an IC chip mounting board is connected via the solder bumps 137, the multilayer printed wiring board 100 and the external board may be electrically connected. When the optical element is mounted on the external substrate, the multilayer printed wiring board 1
An optical signal and an electric signal can be transmitted between the external substrate and the external substrate.

The multilayer printed wiring board according to the first aspect of the present invention having the above-described structure has an IC
By appropriately selecting whether or not to form an opening for mounting a chip mounting substrate or a surface mount type electronic component, and to arrange or not to arrange a BGA or PGA, a package substrate, a motherboard, It can be used as a daughter board or the like.

In the multilayer printed wiring board having the optical waveguide having such a configuration, the stress applied to the substrate can be reduced when the optical waveguide is formed, particularly when the optical path conversion mirror is formed on the optical waveguide. Further, when the optical waveguide is formed by attaching an optical waveguide formed in a film shape in advance, stress applied to the optical waveguide at the time of attaching can be reduced. The method of forming the optical waveguide and the method of forming the optical path conversion mirror on the optical waveguide will be described in detail when a method of manufacturing a multilayer printed wiring board is described later.

Next, a method of manufacturing the multilayer printed wiring board according to the first embodiment of the present invention will be described. (1) Using an insulating substrate as a starting material, first, a conductor circuit is formed on the insulating substrate. Examples of the insulating substrate include a glass epoxy substrate, a polyester substrate, a polyimide substrate, a bismaleimide-triazine (BT) resin substrate, a thermosetting polyphenylene ether substrate, a copper-clad laminate, and an RCC substrate. Further, a ceramic substrate such as an aluminum nitride substrate or a silicon substrate may be used. The conductor circuit can be formed, for example, by forming a solid conductor layer on the surface of the insulating substrate by electroless plating or the like and then performing an etching process. Further, it may be formed by performing an etching process on a copper-clad laminate or an RCC substrate.

In place of the method of forming a conductor circuit by performing an etching process, a plating resist is formed on a solid conductor layer, and then an electroplating layer is formed on a portion where no plating resist is formed. The conductor circuit may be formed by using a method of forming a conductor circuit by removing the resist and the conductor layer under the plating resist.

In the case where the connection between the conductor circuits sandwiching the insulating substrate is made by a through hole, for example, a through hole is formed in the insulating substrate using a drill or a laser, and then the electroless plating is performed. Through-holes are formed by performing processing or the like. In addition, the diameter of the said through-hole is 100-300 micrometers normally. When a through hole is formed, it is desirable to fill the through hole with a resin filler.

(2) Next, if necessary, the surface of the conductor circuit is subjected to a roughening process. As the roughening forming process,
For example, a blackening (oxidation) -reduction treatment, an etching treatment using an etching solution containing a cupric complex and an organic acid salt, and the like;
A treatment by u-Ni-P needle-like alloy plating can be exemplified. Here, when the roughened surface is formed, the average roughness of the roughened surface is usually desirably 0.1 to 5 μm, and the adhesion between the conductive circuit and the interlayer resin insulating layer, the electric signal transmission performance of the conductive circuit The thickness is more preferably 2 to 4 μm in consideration of the effect on The roughening process may be performed before filling the through-hole with the resin filler, and a roughened surface may be formed on the wall surface of the through-hole. This is because the adhesion between the through hole and the resin filler is improved.

(3) Next, an elastic material layer and an optical waveguide are formed in a portion where the conductive circuit is not formed on the substrate. The elastic material layer is formed by, for example, a method of attaching a film-like elastic material which has been cut into a desired size in advance, or a resin composition containing a material resin of the elastic material layer by a roll coater, a curtain coater, or the like. After the application, a method of forming an elastic material layer only at a predetermined position by exposure and development processing can be used. After the resin composition is applied by the above-described method, an elastic material layer may be formed at a predetermined position by performing an etching method, a resist forming method, or the like.

Next, an optical waveguide is formed on the elastic material layer. The optical waveguide can be formed by, for example, a selective polymerization method, a method using reactive ion etching and photolithography, a direct exposure method, a method using injection molding, a photobleaching method, a method combining these, and the like. .

Specifically, for example, first, a resin composition for an optical waveguide to be an under-cladding portion is applied and formed on an elastic material layer by using a spin coater or the like, and this is heated and cured. A resin composition for an optical waveguide to be a core layer is coated and formed on the clad portion, and is cured by heating.
Next, a resist is applied to the surface of the core layer, a resist pattern is formed by photolithography, and the resist pattern is patterned into the shape of the core by RIE (reactive ion etching) or the like. Further, the optical waveguide resin composition can be formed on the under clad portion (including the core portion) by coating and forming a resin composition for an optical waveguide to be an over clad portion, and then heating and curing the resin composition. Here, the coating and film formation of the resin composition for an optical waveguide may be performed by a method using a curtain coater or a roll coater, printing, or the like. In addition,
As the resin composition for an optical waveguide, for example, in addition to the polymer material and particles described above, if necessary, a curing agent,
Those containing a reaction stabilizer, a solvent and the like can be mentioned.

Here, the application of the resin composition for an optical waveguide is performed as follows.
Each may be performed once or may be performed in a plurality of times. Note that which one to select may be appropriately selected in consideration of the thickness of the clad portion and the core portion and the like.

In place of the method of applying an uncured resin composition to form a film, a method of attaching a film (film-shaped optical waveguide) made of a resin composition for an optical waveguide formed in advance is used. Is also good. Specifically, for example, a film-shaped optical waveguide is prepared in advance using a resin composition for an optical waveguide on a base material, a release film, or the like, and is formed by sticking this on an elastic material layer. I do. In this case, an optical path conversion mirror may be formed in advance before attaching the film-shaped optical waveguide on the substrate (on the elastic material layer). The optical path conversion mirror can be formed by a method similar to a method using a diamond saw or the like described later.

Whether the optical path conversion mirror is formed after forming the optical waveguide on the substrate or before attaching the film-shaped optical waveguide on the substrate is determined in consideration of the shape of the optical path conversion mirror and the like. May be selected as appropriate. Specifically, in the multilayer printed wiring board shown in FIG.
Optical path conversion mirror 151 provided at (150a, 150b)
(151a, 151b) has an inclination such that the bottom surface of the optical waveguide 150 is larger than the top surface. The optical path conversion mirror having such a shape can be easily formed by forming the optical waveguide on the substrate (on the elastic material layer) and then performing machining using a diamond saw. Therefore, the optical path conversion mirror having such a shape may be formed after forming the optical waveguide on the substrate (on the elastic material layer).

However, when an optical waveguide having an optical path conversion mirror is formed in the multilayer printed wiring board of the first aspect of the present invention, the shape of the optical path conversion mirror is not limited to the shape shown in FIG. Instead, it may be appropriately selected in consideration of the structure of the multilayer printed wiring board and the like. Therefore, for example, the optical waveguide 1150 (1150) shown in FIG.
a, 1150b), the optical path conversion mirror 11 has a shape such that the upper surface of the optical waveguide 1150 is larger than the bottom surface.
51 (1151a, 1151b) may be formed. FIG. 8 is a cross-sectional view schematically showing another embodiment of the multilayer printed wiring board of the first invention. The multilayer printed wiring board 1000 shown in FIG.
Is different from the multilayer printed wiring board 100 shown in FIG. 1 only in the shape (shape of the optical path conversion mirrors 1151a and 1151b), and the other configuration is the same as that of the multilayer printed wiring board 100.

As shown in FIG. 8, when forming an optical waveguide having an optical path conversion mirror shaped such that the top surface of the optical waveguide is larger than the bottom surface, such an optical path conversion mirror is formed on the substrate (the elastic material layer). It is difficult to form the optical waveguide after forming the optical waveguide. Therefore, the formation of an optical waveguide having such an optical path conversion mirror is performed by attaching a film-shaped optical waveguide on which an optical path conversion mirror has been formed in advance on a substrate (on an elastic material layer). In the production of the multilayer printed wiring board of the first aspect of the present invention, when using the method of attaching a film-shaped optical waveguide in this manner, attaching the film-shaped optical waveguide to an elastic material layer formed on a substrate. Therefore, stress applied to the optical waveguide at the time of attachment can be reduced, and generation of scratches, cracks, and the like can be prevented.

When an optical waveguide is formed using a method of attaching a film on a substrate, a method is used in which a two-layer film in which an elastic material layer and an optical waveguide are stacked in advance is bonded by thermocompression or the like. Thus, the elastic material layer and the optical waveguide may be formed. Also in this case, the stress applied to the optical waveguide can be reduced. The step of forming the optical waveguide includes:
This may be performed before forming a conductive circuit on the substrate.

When an optical path conversion mirror is formed on the optical waveguide, the formation of the optical path conversion mirror may be performed after the optical waveguide is formed on the substrate (on the elastic material layer). The method for forming the optical path conversion mirror is not particularly limited, and a conventionally known formation method can be used. Specifically, machining with a diamond saw having a V-shaped tip of 90 ° or a blade can be used. As described above, when the optical path conversion mirror is formed on the optical waveguide formed on the elastic material layer by the above-described method, the stress applied to the substrate can be reduced, thereby preventing the occurrence of cracks and the like on the substrate. can do.

(4) Next, on the substrate on which the optical waveguide and the conductor circuit are formed, a thermosetting resin, a photosensitive resin, a resin in which part of the thermosetting resin is acrylated, To form an uncured resin layer made of a resin composite containing, or a resin layer made of a thermoplastic resin. The uncured resin layer can be formed by applying the uncured resin with a roll coater, a curtain coater, or the like, or by thermocompression bonding an uncured (semi-cured) resin film. Further, the resin layer made of the thermoplastic resin can be formed by thermocompression bonding a resin molded body molded on a film.

Among these, a method of thermocompression bonding of an uncured (semi-cured) resin film is desirable, and the compression of the resin film can be performed using, for example, a vacuum laminator. The pressure-bonding conditions are not particularly limited, and may be appropriately selected in consideration of the composition of the resin film and the like. Usually, the pressure is 0.25 to 1.0 MPa, the temperature is 40 to 70 ° C,
It is desirable to perform the process under the conditions of a degree of vacuum of 13 to 1300 Pa and a time of about 10 to 120 seconds.

Examples of the thermosetting resin include epoxy resin, phenol resin, polyimide resin, polyester resin, bismaleimide resin, polyolefin resin, polyphenylene ether resin, polyphenylene resin, and fluororesin. Specific examples of the epoxy resin, for example, phenol novolak type, novolak type epoxy resin such as cresol novolak type,
An alicyclic epoxy resin modified with dicyclopentadiene is exemplified.

The photosensitive resin includes, for example, an acrylic resin. Examples of the resin obtained by partially acrylifying the thermosetting resin include those obtained by subjecting the thermosetting group of the thermosetting resin to methacrylic acid or acrylic acid to undergo an acrylation reaction.

Examples of the thermoplastic resin include phenoxy resin, polyether sulfone (PES), polysulfone (PSF), and polyphenylene sulfone (P
PS) polyphenylene sulfide (PPES), polyphenylene ether (PPE) polyetherimide (P
I) and the like.

The resin composite is not particularly limited as long as it contains a thermosetting resin or a photosensitive resin (including a resin obtained by partially acrylizing a thermosetting resin) and a thermoplastic resin. Examples of specific combinations of a thermosetting resin and a thermoplastic resin include, for example, phenol resin / polyethersulfone, polyimide resin / polysulfone,
Epoxy resin / polyether sulfone, epoxy resin / phenoxy resin, and the like. Specific combinations of the photosensitive resin and the thermoplastic resin include, for example, an acrylic resin / phenoxy resin, an epoxy resin in which a part of an epoxy group is acrylated / polyether sulfone, and the like.

The mixing ratio of the thermosetting resin or the photosensitive resin to the thermoplastic resin in the resin composite is as follows: thermosetting resin or photosensitive resin / thermoplastic resin = 95/5 to 5
0/50 is desirable. This is because a high toughness value can be secured without impairing the heat resistance.

The resin layer may be composed of two or more different resin layers. Specifically, for example,
Lower layer is thermosetting resin or photosensitive resin / thermoplastic resin =
For example, the upper layer is formed of a thermosetting resin or a photosensitive resin / thermoplastic resin = 90/10 resin composite, and the like. With such a configuration, it is possible to ensure excellent adhesion to an insulating substrate or the like, and also to ensure ease of formation in forming a via hole opening or the like in a later step.

The resin layer may be formed using a resin composition for forming a roughened surface. The resin composition for forming a roughened surface includes, for example, an acid, an alkali, and the like in an uncured heat-resistant resin matrix that is hardly soluble in a roughening liquid composed of at least one selected from acids, alkalis, and oxidizing agents. And a substance that is soluble in a roughened liquid comprising at least one selected from oxidants. Note that the terms "sparingly soluble" and "soluble" are referred to as "soluble" for convenience when a substance having a relatively high dissolution rate is immersed in the same roughening solution for the same time, and the relative dissolution rate is relatively low. The slower one is called "poorly soluble" for convenience.

The heat resistant resin matrix is preferably a matrix capable of maintaining the shape of the roughened surface when the roughened surface is formed on the interlayer resin insulating layer using the roughening solution. Curable resins, thermoplastic resins, and composites thereof are exemplified. Further, by using a photosensitive resin, an opening for a via hole may be formed in the interlayer resin insulating layer by using exposure and development processes.

Examples of the thermosetting resin include an epoxy resin, a phenol resin, a polyimide resin, a polyolefin resin, a fluororesin and the like. When the thermosetting resin is photosensitized, the thermosetting group is subjected to a (meth) acrylation reaction using methacrylic acid, acrylic acid, or the like.

Examples of the epoxy resin include cresol novolak type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolak type epoxy resin, alkylphenol novolak type epoxy resin, biphenol F type epoxy resin, and naphthalene type epoxy resin. Resin, dicyclopentadiene type epoxy resin, epoxidized product of condensate of phenols and aromatic aldehyde having phenolic hydroxyl group,
Triglycidyl isocyanurate, alicyclic epoxy resin and the like. These may be used alone or in combination of two or more. Thereby, it becomes excellent in heat resistance and the like.

Examples of the thermoplastic resin include phenoxy resin, polyether sulfone, polysulfone, polyphenylene sulfone, polyphenylene sulfide, polyphenyl ether, polyether imide and the like. These may be used alone or in combination of two or more.

Examples of the substance soluble in the roughening liquid comprising at least one selected from the above-mentioned acids, alkalis and oxidizing agents include, for example, inorganic particles, resin particles, metal particles, rubber particles, liquid phase resin, liquid phase Rubber and the like are mentioned, and among these, inorganic particles, resin particles and metal particles are desirable. These may be used alone or in combination of two or more.

Examples of the inorganic particles include aluminum compounds such as alumina and aluminum hydroxide, calcium compounds such as calcium carbonate and calcium hydroxide,
Examples include potassium compounds such as potassium carbonate, magnesium compounds such as magnesia, dolomite, basic magnesium carbonate and talc, silicon compounds such as silica and zeolite, and titanium compounds such as titania. These may be used alone or in combination of two or more. The alumina particles can be dissolved and removed with hydrofluoric acid, and the calcium carbonate can be dissolved and removed with hydrochloric acid. Further, sodium-containing silica and dolomite can be dissolved and removed with an alkaline aqueous solution.

Examples of the resin particles include those made of a thermosetting resin, a thermoplastic resin and the like. When immersed in a roughening liquid comprising at least one selected from acids, alkalis and oxidizing agents, There is no particular limitation as long as the dissolution rate is faster than the heat-resistant resin matrix,
Specifically, for example, it is composed of an amino resin (melamine resin, urea resin, guanamine resin, etc.), an epoxy resin, a phenol resin, a phenoxy resin, a polyimide resin, a polyphenylene resin, a polyolefin resin, a fluororesin, a bismaleimide-triazine resin, and the like. Things. These may be used alone or in combination of two or more. It is necessary that the resin particles have been previously cured. If not cured, the resin particles will dissolve in the solvent that dissolves the resin matrix, so they will be uniformly mixed, and it will not be possible to selectively dissolve and remove only the resin particles with an acid or oxidizing agent. is there.

The metal particles include, for example, gold, silver,
Examples include those made of copper, tin, zinc, stainless steel, aluminum, nickel, iron, lead, and the like. These may be used alone or in combination of two or more. The metal particles may have a surface layer coated with a resin or the like in order to ensure insulation.

When two or more soluble substances are used as a mixture, the combination of the two soluble substances to be mixed is preferably a combination of resin particles and inorganic particles. Both have low conductivity, so that the insulation of the interlayer resin insulation layer can be ensured, the thermal expansion can be easily adjusted with the poorly soluble resin, and the interlayer resin made of the resin composition for forming a roughened surface can be easily obtained. This is because no crack occurs in the insulating layer, and no peeling occurs between the interlayer resin insulating layer and the conductor circuit.

Examples of the acid used as the roughening liquid include phosphoric acid, hydrochloric acid, sulfuric acid, nitric acid, and organic acids such as formic acid and acetic acid. Of these, organic acids are preferably used. This is because when the roughening treatment is performed, the metal conductor layer exposed from the via hole is hardly corroded. Examples of the alkali include sodium hydroxide and potassium hydroxide. As the oxidizing agent, it is desirable to use, for example, an aqueous solution of chromic acid, chromic sulfuric acid, or an alkaline permanganate (such as potassium permanganate).

The average particle size of the soluble substance is 10 μm
The following is desirable. Further, coarse particles having a relatively large average particle diameter of 2 μm or less and fine particles having a relatively small average particle diameter may be used in combination. That is, a soluble substance having an average particle diameter of 0.1 to 0.8 μm and a soluble substance having an average particle diameter of 0.8 to 2.0 μm are combined.

As described above, the combination of the coarse particles having a relatively large average particle size and the fine particles having a relatively small average particle size eliminates the dissolution residue of the electroless plating film and reduces the amount of the palladium catalyst under the plating resist. In addition, a shallow and complicated roughened surface can be formed. Further, by forming a complicated roughened surface, a practical peel strength can be maintained even if the unevenness of the roughened surface is small.

(5) Next, when forming an interlayer resin insulating layer using a thermosetting resin or a resin composite as the material, an uncured resin insulating layer is subjected to a curing treatment, and a via hole is formed. An opening is formed to form an interlayer resin insulation layer. In this step, a through-hole may be formed as necessary. The via hole opening is desirably formed by laser processing. When a photosensitive resin is used as the material of the interlayer resin insulating layer, the photosensitive resin may be formed by exposure and development.

When forming an interlayer resin insulation layer using a thermoplastic resin as the material, an opening for a via hole is formed in the resin layer made of the thermoplastic resin to form an interlayer resin insulation layer. In this case, the via hole opening can be formed by performing laser processing. Also,
When a through hole is formed in this step, the through hole may be formed by drilling, laser processing, or the like.

Examples of the laser used for the laser processing include a carbon dioxide gas laser, an ultraviolet laser, an excimer laser, and the like. Of these, excimer lasers and short-pulse carbon dioxide lasers are desirable.

It is desirable to use a hologram type excimer laser among excimer lasers. The hologram method is a method of irradiating a target object with a laser beam through a hologram, a condenser lens, a laser mask, a transfer lens, and the like. By using this method, a large number of apertures can be efficiently formed by a single laser irradiation. Can be formed.

When a carbon dioxide laser is used, the pulse interval is desirably 10 ⁻⁴ to 10 ⁻⁸ seconds. The time for irradiating the laser for forming the opening is preferably 10 to 500 μsec. Also,
By irradiating a laser beam through an optical lens and a mask, a large number of via hole openings can be formed at once. This is because a plurality of portions can be irradiated with laser light having the same intensity and the same irradiation intensity through the optical lens and the mask. After forming the via hole openings in this manner, desmearing may be performed as necessary.

(6) Next, a thin film conductor layer is formed on the surface of the interlayer resin insulation layer including the inner wall of the via hole opening. The thin film conductor layer can be formed by, for example, a method such as electroless plating and sputtering.

Examples of the material of the thin film conductor layer include, for example,
Examples include copper, nickel, tin, zinc, cobalt, thallium, lead and the like. Among these, those made of copper, copper and nickel are desirable from the viewpoint of excellent electrical characteristics, economic efficiency and the like. When the thin film conductor layer is formed by electroless plating, the thickness of the thin film conductor layer is 0.3 to
2.0 μm is desirable, and 0.6 to 1.2 μm is more desirable. Also, when formed by sputtering,
0.1 to 1.0 μm is desirable. When the thin film conductor layer is formed by electroless plating, a catalyst is previously applied to the surface of the interlayer resin insulating layer. As the above catalyst,
For example, palladium chloride and the like can be mentioned.

Before forming the thin film conductor layer, a roughened surface may be formed on the surface of the interlayer resin insulating layer.
By forming the roughened surface, the adhesion between the interlayer resin insulating layer and the thin film conductor layer can be improved.

When the through hole is formed in the step (5), when the thin film conductor layer is formed on the interlayer resin insulating layer, the thin film conductor layer is formed also on the wall surface of the through hole. It may be a through hole.

(7) Next, a plating resist is formed on the substrate having the thin film conductor layer formed on the surface thereof. The plating resist can be formed, for example, by adhering a photosensitive dry film, placing a photomask composed of a glass substrate or the like on which a plating resist pattern is drawn, in close contact, and performing exposure and development processing.

(8) After that, electrolytic plating is performed using the thin film conductor layer as a plating lead to form an electrolytic plating layer in the above-mentioned plating resist non-formed portion. As the above electrolytic plating,
Copper plating is preferred. Further, the thickness of the electrolytic plating layer is preferably 5 to 20 μm. Thereafter, by removing the plating resist and the electroless plating film and the thin film conductor layer under the plating resist, a conductor circuit (including a via hole) can be formed. The removal of the plating resist may be performed using, for example, an alkaline aqueous solution, and the removal of the thin film conductor layer may be performed using a mixed solution of sulfuric acid and hydrogen peroxide, sodium persulfate, ammonium persulfate, ferric chloride, and chloride. It may be performed using an etching solution such as cupric copper. Also, after forming the conductor circuit, if necessary,
The catalyst on the interlayer resin insulating layer may be removed using an acid or an oxidizing agent. This is because a decrease in electrical characteristics can be prevented. Through these steps (6) to (8), a conductor circuit can be formed.

The above methods (6) to (8) are semi-additive methods, but a conductor circuit may be formed by a full-additive method instead of this method. Specifically, after forming an electrolytic plating layer on the entire surface of the thin film conductor layer formed by the same method as in the above (6), an etching resist is formed on a part of the electrolytic plating layer using a dry film. Thereafter, the electrolytic plating layer and the thin film conductor layer under the etching resist non-formed portion may be removed by etching, and the etching resist may be peeled off to form an independent conductor circuit.

Such an additive method has higher etching accuracy than other methods of manufacturing a conductor circuit such as a subtractive method, so that a finer conductor circuit can be formed and the design of the conductor circuit can be freely performed. The degree improves. Note that the conductor circuit may be formed by a build-up method.

When a through hole is formed in the steps (5) and (6), a resin filler may be filled in the through hole. When a resin filler is filled in the through hole, a cover plating layer covering the surface layer of the resin filler layer may be formed by performing electroless plating, if necessary.

(9) Next, when a lid plating layer is formed, the surface of the lid plating layer is subjected to a roughening treatment as required, and further, if necessary, (4) to (8) By repeating the step of (1), an interlayer resin insulating layer and a conductive circuit are laminated on both surfaces thereof. In this step, a through hole may or may not be formed.

(10) Next, if necessary, an outermost solder resist layer is formed. The solder resist layer can be formed using, for example, a solder resist composition comprising a polyphenylene ether resin, a polyolefin resin, a fluororesin, a thermoplastic elastomer, an epoxy resin, a polyimide resin, or the like.

Examples of the solder resist composition other than those described above include, for example, (meth) acrylate of novolak type epoxy resin, imidazole curing agent, bifunctional (meth) acrylate monomer, and molecular weight of 500 to 50.
A paste-like fluid containing a polymer of about 00 (meth) acrylate, a thermosetting resin such as a bisphenol-type epoxy resin, a photosensitive monomer such as a polyvalent acrylic monomer, a glycol ether-based solvent, and the like. It is desirable that the viscosity is adjusted to 1 to 10 Pa · s at 25 ° C. By forming the solder resist layer as the outermost layer, the optical waveguide can be protected from damage, heat, and the like.

(11) Next, an opening for mounting an IC chip mounting substrate and various surface mounting electronic components is formed in the solder resist layer as necessary. Specifically, for example, it can be performed using the same method as the method of forming the via hole opening, that is, exposure and development processing or laser processing. Such an opening may be formed only in one side of the solder resist layer, or may be formed in each of the two sides of the solder resist layer. In addition, when forming a solder resist layer, a resin film having an opening at a desired position is prepared in advance, and the resin film is adhered to form a solder film having an opening for mounting an IC chip mounting substrate or the like. A resist layer may be formed. The opening diameter of the opening for mounting the IC chip mounting substrate is desirably 500 to 1000 μm.

(12) Next, the conductor circuit portion exposed by forming the opening for mounting the IC chip mounting substrate or the like is replaced with nickel, palladium, gold, silver, platinum, or the like, if necessary. Cover with a corrosion resistant metal to form a surface mounting pad. Of these, nickel-gold,
It is desirable to form the coating layer with a metal such as nickel-silver, nickel-palladium, and nickel-palladium-gold. The coating layer can be formed, for example, by plating, vapor deposition, electrodeposition, or the like. Among these, it is preferable to form the coating layer by plating because of excellent uniformity of the coating layer.

(13) Next, an optical path opening penetrating the solder resist layer and the interlayer resin insulating layer is formed on one surface of the substrate. The optical path opening is formed by, for example, laser processing. Examples of the laser used in the laser processing include those similar to the laser used in forming the via hole opening. In this case, it is desirable to use a laser having a wavelength at which the optical waveguide has no absorption as the laser. This is because the surface of the optical waveguide is less likely to be damaged when the optical path opening is formed. The formation position of the optical path opening is not particularly limited as long as it can transmit an optical signal from the optical waveguide or a signal to the optical waveguide, and may be appropriately selected in consideration of the design of the conductor circuit and the like. I just need.

The opening diameter of the optical path opening is 100 to 50.
0 μm is desirable. The shape is not particularly limited,
For example, a columnar shape, an elliptical columnar shape, a square columnar shape, a polygonal columnar shape, and the like can be given. The formation of the optical path opening may be performed after the formation of the solder resist layer as described above, but in some cases, after the formation of the interlayer resin insulating layer, the optical path opening is formed once, and the solder resist layer is formed. After the formation, an opening communicating with the optical path opening provided in the interlayer resin insulating layer may be formed again to be used as the optical path opening. This is because, depending on the thickness of the interlayer resin insulating layer or the solder resist layer, it may be difficult to form the optical path opening by a single laser process. When the opening is formed in two steps, the opening formed in the solder resist layer may be formed by exposure and development.

(14) Next, if necessary, a solder paste (for example, Sn / Ag =) is applied to the surface mounting pad via a mask having an opening formed in a portion corresponding to the surface mounting pad. After filling 96.5 / 3.5), reflow is performed to form solder bumps. In the solder resist layer on the side opposite to the surface on which the optical waveguide is formed, if necessary, pins may be provided on the external substrate connection surface using a conductive adhesive or the like, or solder balls may be formed. PGA (Pin Grid Array) and BGA (Ball
Grid Array). The pin is not particularly limited, but is preferably a T-shaped pin. Examples of the material include Kovar and 42 alloy.

In this case, after filling the solder paste and before reflowing, a substrate for mounting an IC chip or other surface-mounted electronic components is mounted, and then soldering is performed by reflowing. Good. In this case, the order of mounting (soldering) the IC chip mounting substrate and the surface mounting type electronic component is not particularly limited, but it is preferable to mount the IC chip mounting board having a large number of connection terminals later.

In this step, solder bumps, PGA,
The BGA need not be formed. BGA of IC chip mounting board and bumps formed on surface mounted electronic components,
By connecting the surface mounting pad, an IC chip mounting substrate or a surface mounting type electronic component can be mounted on the multilayer printed wiring board. Through such steps, the multilayer printed wiring board of the first present invention can be manufactured.

Next, the multilayer printed wiring board according to the second embodiment of the present invention will be described. A multilayer printed wiring board according to a second aspect of the present invention is a multilayer printed wiring board in which a conductor circuit and an interlayer resin insulating layer are laminated on both surfaces of a substrate, and an optical waveguide is formed on an outermost interlayer resin insulating layer. Wherein an elastic material layer is formed between the outermost interlayer resin insulating layer and the optical waveguide.

In the second multilayer printed wiring board of the present invention,
Since the optical waveguide is formed on the outermost interlayer resin insulating layer via the elastic material layer, the stress applied to the interlayer resin insulating layer during the formation of the optical waveguide, particularly when forming the optical path conversion mirror in the optical waveguide, is reduced. The stress can be alleviated, and cracks and the like caused by the stress can be prevented from being generated on the substrate. Therefore, the reliability of the multilayer printed wiring board does not decrease due to cracks or the like generated in the interlayer resin insulating layer. In addition, when attaching a film-shaped optical waveguide on which an optical path conversion mirror has been formed in advance when forming the optical waveguide, the stress applied to the optical waveguide can be reduced by the elastic material layer, and the Scratches and cracks can be prevented from occurring.

Further, since a conductor circuit and an optical waveguide are formed on the multilayer printed wiring board, both optical signals and electric signals can be transmitted. The built-in wave path can contribute to miniaturization of the optical communication terminal device.

A multilayer printed wiring board according to a second aspect of the present invention is a multilayer printed wiring board having an optical waveguide formed on an outermost interlayer resin insulating layer, wherein the optical waveguide is formed between the interlayer resin insulating layer and the optical waveguide. , An elastic material layer is formed. The elastic material layer preferably has an elastic modulus of 2.5 × 10 ³ MPa or less, like the elastic material layer of the multilayer printed wiring board according to the first aspect of the present invention. It is more preferable that the pressure is × 10 ³ MPa. The elastic modulus is 2.5 × 10 ³
When the pressure exceeds MPa, the stress applied to the interlayer resin insulating layer during the formation of the optical waveguide cannot be sufficiently reduced, and in addition to the occurrence of cracks or the like in the interlayer resin insulating layer, it may not be possible to prevent it. This is because stress applied to the optical waveguide cannot be sufficiently reduced due to a difference in thermal expansion coefficient between the optical waveguide and the interlayer resin insulating layer or the solder resist layer, and cracks may occur in the optical waveguide. . Further, when the optical waveguide is formed by attaching a film-shaped optical waveguide, the stress applied to the optical waveguide cannot be sufficiently reduced, and the optical waveguide may be damaged or cracked. is there. Further, as a specific material of the elastic material layer, a material made of a polyolefin resin and / or a polyimide resin having an elastic modulus in the above range is desirable.

The multilayer printed wiring board of the second invention differs from the multilayer printed wiring board of the first invention in that the optical waveguide and the elastic material layer are formed on the outermost interlayer resin insulation layer. However, the members and materials constituting the multilayer printed wiring board such as the above-mentioned elastic material layer, optical waveguide and interlayer resin insulating layer are the same as those used for the multilayer printed wiring board of the first present invention. Is mentioned. Therefore, the description of the members constituting the multilayer printed wiring board according to the second aspect of the present invention will be omitted.

Next, an example of a second embodiment of the multilayer printed wiring board of the present invention will be described with reference to the drawings. FIG. 2 is a sectional view schematically showing one embodiment of the multilayer printed wiring board according to the second invention.

As shown in FIG. 2, the multilayer printed wiring board 2
In FIG. 00, a conductor circuit 224 and an interlayer resin insulation layer 222 are laminated on both surfaces of a substrate 221, and a through circuit is formed between the conductor circuits sandwiching the substrate 221 and between the conductor circuits sandwiching the interlayer resin insulation layer 222. It is electrically connected by the hole 229 and the via hole 227, and a solder resist layer 234 is formed on the outermost layer.

The optical waveguide 250 (250) is formed on the outermost interlayer resin insulation layer 222a via the elastic material layer 252.
a, 250b) are formed, and the optical path opening mirror 251 (251a, 251b) is formed at the end of the optical waveguide 250 at the optical path opening 238 (238a, 23).
8b) is formed in the direction perpendicular to the substrate 221. The optical path opening 238 is formed by a gap. One of the optical waveguides 250a and 250b is a light receiving optical waveguide, and the other is a light emitting optical waveguide.

In the multilayer printed wiring board 200 having such a configuration, an optical signal sent from the outside via an optical fiber (not shown) or the like is introduced into the optical waveguide 250a, and the optical path conversion mirror 251a and the optical path conversion mirror 251a. Opening 238a
Through a light receiving element (not shown). An optical signal sent from a light emitting element (not shown) or the like is transmitted from the optical path opening 238b to the optical conversion mirror 251b.
Is introduced into the optical waveguide 250b through the optical waveguide 250b, is sent to the light receiving element of another IC chip mounting substrate, and is converted into an electric signal,
Alternatively, it is sent out through an optical fiber (not shown) or the like.

When an external substrate (not shown) such as an IC chip mounting substrate is connected via the solder bumps 237, the multilayer printed wiring board 200 and the external substrate can be electrically connected. Further, when an optical element is mounted on this external substrate, the multilayer printed wiring board 20
An optical signal and an electric signal can be transmitted between 0 and the external board. The multilayer printed wiring board according to the second aspect of the present invention having such a configuration also has a solder resist layer in which an opening for mounting an IC chip mounting substrate or the like is formed or not. By appropriately selecting whether or not to dispose, it can be used as a package substrate, a motherboard, a daughter board, or the like.

Also, in the multilayer printed wiring board according to the second aspect of the present invention, when an optical path conversion mirror is formed in the optical waveguide, the shape of the optical path conversion mirror is such that the bottom surface of the optical waveguide as shown in FIG. The shape is not limited to a shape that is larger than the top surface, and may be a shape that the top surface of the optical waveguide is larger than the bottom surface.

In the multilayer printed wiring board having the optical waveguide having such a configuration, the stress applied to the interlayer resin insulating layer can be reduced when forming the optical waveguide, particularly when forming the optical path conversion mirror on the optical waveguide. . Further, when the optical waveguide is formed by attaching an optical waveguide formed in a film shape in advance, stress applied to the optical waveguide at the time of attaching can be reduced.

Next, a method for manufacturing the multilayer printed wiring board according to the second aspect of the present invention will be described. Note that, as described above, the multilayer printed wiring board according to the second aspect of the present invention differs from the multilayer printed wiring board according to the first aspect in the formation positions of the elastic material layer and the optical waveguide. Therefore, the method of manufacturing the multilayer printed wiring board of the second invention is different from the method of manufacturing the multilayer printed wiring board of the first invention only in the step of forming the elastic material layer and the optical waveguide. It can be carried out in the same manner as in the first method for producing a multilayer printed wiring board of the present invention. Here, the manufacturing process of the elastic material layer and the optical waveguide will be mainly described, and the entire manufacturing process will be briefly described.

(1) First, an insulating substrate is used as a starting material,
(3) of the method for producing a multilayer printed wiring board of the first invention
Step, ie, steps (1) to (9) of the first method for manufacturing a multilayer printed wiring board of the present invention, except that the step of forming the elastic material layer and the optical waveguide on the substrate is not performed To form a multilayer wiring board.

(2) Next, an elastic material layer and an optical waveguide are formed on the outermost interlayer resin insulating layer at the portion where no conductor circuit is formed.
The formation of the elastic material layer, for example, a method of attaching a film-like elastic material that has been cut into a desired size in advance,
After applying a resin composition containing the material resin of the elastic material layer using a roll coater, a curtain coater, or the like, the method can be performed using a method of forming the elastic material layer only at a predetermined position by exposure and development processing. . After the resin composition is applied by the above-described method, an elastic material layer may be formed at a predetermined position by performing an etching method, a resist forming method, or the like.

Next, an optical waveguide is formed on the elastic material layer. The optical waveguide can be formed by, for example, a selective polymerization method, a method using reactive ion etching and photolithography, a direct exposure method, a method using injection molding, a photobleaching method, a method combining these, and the like. .

Specifically, for example, first, a resin composition for an optical waveguide to be an under-cladding portion is applied and formed on an elastic material layer by using a spin coater or the like, and is heat-cured. A resin composition for an optical waveguide to be a core layer is coated and formed on the clad portion, and is cured by heating.
Next, a resist is applied to the surface of the core layer, a resist pattern is formed by photolithography, and the resist pattern is patterned into the shape of the core by RIE (reactive ion etching) or the like. Furthermore, an optical waveguide resin composition can be formed on the under clad portion (including the core portion) by coating and forming a resin composition for an optical waveguide to be an over clad portion, and then heating and curing the resin composition. Here, the application and film formation of the resin composition for an optical waveguide may be performed by a method using a curtain coater or a roll coater, printing, or the like. In addition,
Examples of the resin composition for an optical waveguide include those similar to those used in the first method for producing a multilayer printed wiring board of the present invention.

Here, the application of the resin composition for an optical waveguide is performed as follows.
Each may be performed once or may be performed in a plurality of times. Note that which one to select may be appropriately selected in consideration of the thickness of the clad portion and the core portion and the like.

Instead of applying the uncured resin composition to form a film, a method of attaching a film (film-shaped optical waveguide) made of a resin composition for an optical waveguide formed in advance is used. Is also good. Specifically, for example, by preparing a film-shaped optical waveguide in advance using the resin composition for an optical waveguide on a base material or a release film, and by pasting this on the elastic material layer Form. in this case,
Before attaching the film-shaped optical waveguide on the substrate (on the elastic material layer), an optical path conversion mirror may be formed in advance. Whether the formation of the optical path conversion mirror is performed after forming the optical waveguide on the substrate or before attaching the film-shaped optical waveguide on the substrate may be appropriately selected in consideration of the shape of the optical path conversion mirror and the like. Good. The optical path conversion mirror can be formed by a method similar to a method using a diamond saw or the like described later. Further, the step of forming the optical waveguide may be performed before forming the conductive circuit on the interlayer resin insulating layer.

Further, the elastic material layer and the optical waveguide may be formed by using a method of pasting a two-layer film in which the elastic material layer and the optical waveguide are previously laminated on the substrate by thermocompression bonding or the like. Good.

When an optical path conversion mirror is formed on the optical waveguide, the optical path conversion mirror may be formed after the optical waveguide is formed on the substrate (on the elastic material layer). The method for forming the optical path conversion mirror is not particularly limited, and a conventionally known formation method can be used. Specifically, machining with a diamond saw having a V-shaped tip of 90 ° or a blade can be used. As described above, when the optical path conversion mirror is formed on the optical waveguide formed on the elastic material layer by the above-described method, the stress applied to the interlayer resin insulating layer can be reduced. Can be prevented from occurring.

(3) Next, in the same manner as in the steps (10) to (12) of the method for manufacturing a multilayer printed wiring board according to the first aspect of the present invention, the interlayer in which the optical waveguide is formed via the elastic material layer. A solder resist layer having an opening for mounting an IC chip mounting substrate or the like is formed on the resin insulating layer, and further, a surface mounting pad is formed. The opening may be formed only on one side of the solder resist layer, or may be formed on both sides of the solder resist layer.

(4) Next, an optical path opening is formed in one side of the solder resist layer. The optical path opening is formed by, for example, laser processing. Examples of the laser used in the laser processing include those similar to the laser used in forming the via hole opening. In this case, it is desirable to use a laser having a wavelength at which the optical waveguide has no absorption as the laser. This is because the surface of the optical waveguide is less likely to be damaged when the optical path opening is formed. The formation position of the optical path opening is not particularly limited as long as it can transmit an optical signal from the optical waveguide or a signal to the optical waveguide, and may be appropriately selected in consideration of the design of the conductor circuit and the like. I just need.

The diameter of the optical path opening is 100 to 50.
0 μm is desirable. The shape is not particularly limited,
For example, a columnar shape, an elliptical columnar shape, a square columnar shape, a polygonal columnar shape, and the like can be given.

The optical path opening formed in the multilayer printed wiring board according to the second aspect of the present invention is an opening that penetrates only one side of the solder resist layer. Therefore, in the production of the multilayer printed wiring board according to the second aspect of the present invention, when forming the opening for the optical path, instead of the method using the laser processing described above, the IC is formed by the exposure and development processing in the step (3). When forming an opening for mounting a chip mounting substrate, etc.,
At the same time, the optical path opening may be formed by exposure and development processing. This is because the number of steps can be reduced, and the possibility of damaging the optical waveguide is reduced as compared with the laser processing.

(5) Next, solder bumps, PGAs, and BGAs are formed in the same manner as in the step (14) of the first method for manufacturing a multilayer printed wiring board according to the present invention.

Also, in the case of manufacturing the multilayer printed wiring board of the second aspect of the present invention, in this step, after the solder paste is filled and before reflow, an IC chip mounting substrate or other surface mounting type After mounting the electronic components,
The soldering may be performed by reflow.

In this step, solder bumps, PGA,
The BGA need not be formed. BGA of IC chip mounting board and bumps formed on surface mounted electronic components,
By connecting the surface mounting pad, an IC chip mounting substrate or a surface mounting type electronic component can be mounted on the multilayer printed wiring board. Through such steps, the multilayer printed wiring board of the second present invention can be manufactured.

In this specification, when forming an optical waveguide, particularly when forming an optical path conversion mirror in the optical waveguide,
Cracks and the like caused by stress on the substrate and the outermost interlayer resin insulation layer are unlikely to occur in the substrate and the interlayer resin insulation layer, and the difference in thermal expansion coefficient between the optical waveguide and the substrate or the interlayer resin insulation layer Since the stress applied to the optical waveguide can be reduced, cracks and the like due to this stress are less likely to occur in the optical waveguide, and further, the stress applied to the optical waveguide is reduced even when a film-shaped optical waveguide is attached. As a multilayer printed wiring board that can prevent scratches and cracks due to this stress from being generated in the optical waveguide, the optical waveguide has an elastic material layer on the substrate or on the outermost interlayer resin insulation layer. Although the multilayer printed wiring board formed via the above has been described, the optical waveguide is located at a position different from that of the multilayer printed wiring board, that is, via an elastic material layer between interlayer resin insulating layers or the like. You can also obtain the same effect as described above in made multilayer printed wiring board.

[0131]

The present invention will be described in more detail below. Example 1 A. Preparation of Resin Film for Interlayer Resin Insulation Layer Bisphenol A type epoxy resin (Epoxy equivalent 46
9. Yuka Shell Epoxy Epicoat 1001) 30
Parts by weight, 40 parts by weight of a cresol novolak type epoxy resin (epoxy equivalent: 215, Epicron N-673 manufactured by Dainippon Ink and Chemicals, Inc.) Light KA-705
2) 30 parts by weight were dissolved by heating in 20 parts by weight of ethyl diglycol acetate and 20 parts by weight of solvent naphtha while stirring, and epoxidized polybutadiene rubber (Denalex R-45EPT manufactured by Nagase Kasei Kogyo Co., Ltd.) was added thereto.
15 parts by weight, 1.5 parts by weight of a crushed product of 2-phenyl-4,5-bis (hydroxymethyl) imidazole, 2 parts by weight of finely divided silica, and 0.5 part by weight of a silicon-based antifoaming agent are added, and an epoxy resin composition is added. Was prepared. The resulting epoxy resin composition is applied on a 38 μm-thick PET film using a roll coater so that the thickness after drying becomes 50 μm, and then dried at 80 to 120 ° C. for 10 minutes to form an interlayer resin. A resin film for an insulating layer was produced.

B. Preparation of Resin Composition for Filling Through Holes 100 parts by weight of a bisphenol F type epoxy monomer (manufactured by Yuka Shell Co., Ltd., molecular weight: 310, YL983U), the average particle size of which surface is coated with a silane coupling agent is 1.6 μm, S whose maximum particle diameter is 15 μm or less
iO ₂ spherical particles (CRS 1101- manufactured by Adtech Co., Ltd.)
CE) 170 parts by weight and 1.5 parts by weight of a leveling agent (Perenol S4 manufactured by San Nopco Co.) are placed in a container, and the mixture is stirred and mixed to have a viscosity of 45-4 at 23 ± 1 ° C.
A resin filler of 9 Pa · s was prepared. In addition, as a curing agent, an imidazole curing agent (2E4MZ- manufactured by Shikoku Chemicals Co., Ltd.)
6.5 parts by weight (CN).

C. Production of multilayer printed wiring board (1) Glass epoxy resin or BT with a thickness of 0.8 mm
A starting material was a copper-clad laminate in which an 18 μm copper foil 28 was laminated on both sides of an insulating substrate 21 made of (bismaleimide triazine) resin (see FIG. 3A). First, the copper clad laminate was drilled, subjected to an electroless plating treatment, and etched in a pattern to form conductor circuits 24 and through holes 29 on both surfaces of the substrate 21.

(2) Through-hole 29 and conductor circuit 2
The substrate on which the substrate 4 was formed was washed with water, acid-degreased, and then soft-etched. Then, an etching solution was sprayed on both surfaces of the substrate by spraying, and then sent by a transport roll to form a conductive circuit 24 including the through-hole 29. A roughened surface (not shown) was formed on the surface. As an etching solution, an etching solution (Mec etch bond, manufactured by Mec Co.) consisting of 10 parts by weight of imidazole copper (II) complex, 7 parts by weight of glycolic acid, and 5 parts by weight of potassium chloride was used.

(3) Next, a laminate of a dry film made of a polyolefin resin, which has been cut into a desired size in advance, is laminated on a predetermined position (a portion where a conductive circuit is not formed) on the substrate to obtain an elastic modulus. An elastic material layer 52 having a thickness of 10 MPa and a thickness of 25 μm was formed.

(4) Next, on the elastic material layer 52 formed in the above step (3), a film-shaped organic optical waveguide made of PMMA (Microparts, width 25 μm, thickness 2)
5 μm) 50 was attached so that the side surface of one end of the optical waveguide and the side surface of the substrate 21 were aligned. The bonding of the organic optical waveguide was performed by applying an adhesive made of a thermosetting resin to the surface of the organic optical waveguide on the substrate side, and after pressing, curing at 60 ° C. for 1 hour. In this embodiment, 6
Although curing was performed under the condition of 0 ° C./1 hour, step curing may be performed in some cases. This is because stress is not easily generated by the organic optical waveguide at the time of sticking.

Further, one end of the optical waveguide 50 has a V
A 45 ° optical path conversion mirror 51 was formed using a 90 ° diamond saw (see FIG. 3B).

(5) Next, after preparing the resin filler described in the above B, within 24 hours after the preparation by the following method, the inside of the through-hole 29 and one side of the substrate 21 where the conductive circuit is not formed, A layer of a resin filler 30 'was formed on the non-wave path forming portion and the outer edge of the conductor circuit 24 (FIG. 3).
(C)). That is, first, the resin filler was pushed into the through holes using a squeegee, and then dried at 100 ° C. for 20 minutes. Next, a mask having an opening corresponding to the portion where the conductor circuit is not formed (including the portion where the optical waveguide is not formed) is placed on the substrate, and the squeegee is used to remove resin to the portion where the conductor circuit is not formed. Fill with filler, 100 ℃, 2
By drying under the condition of 0 minutes, a layer of the resin filler 30 'was formed. Next, a layer of the resin filler 30 'was similarly formed on the other surface of the conductor circuit non-formation portion (including the optical waveguide non-formation portion) and the outer edge of the conductor circuit.

(6) The surface of the conductor circuit 24 or the through hole 29 is polished on one side of the substrate after the processing of the above (5) by belt sanding using # 600 belt abrasive paper (manufactured by Sankyo Rikagaku Co., Ltd.). Polishing was performed so that the resin filler 30 'did not remain on the land surface, and then buffing was performed to remove the scratches caused by the belt sander polishing. Such a series of polishing was similarly performed on the other surface of the substrate. Then, at 100 ° C for 1 hour, at 120 ° C for 3 hours,
Heat treatment was performed at 50 ° C. for 1 hour and at 180 ° C. for 7 hours to form the resin filler layer 30.

As described above, the surface layer of the resin filler 30 formed in the through-hole 29 and the portion where the conductor circuit is not formed and the surface of the conductor circuit 24 are flattened, and the resin filler 30 and the side surface of the conductor circuit 24 are separated. An insulating substrate in which the inner wall surface of the through-hole 29 and the resin filler 30 were firmly adhered through the roughened surface was obtained (FIG. 3).
(D)). By this step, the surface of the resin filler layer 30 and the surface of the conductor circuit 24 become flush with each other.

(7) After the above substrate is washed with water and acid degreased,
Soft etching was performed, and then an etching solution was sprayed on both surfaces of the substrate by spraying to etch the surface of the conductor circuit 24 and the land surface of the through hole 29, thereby forming a roughened surface on the entire surface of the conductor circuit 24. . As an etching solution, an etching solution (Mec etch bond, manufactured by Mec Co.) containing 10 parts by weight of imidazole copper (II) complex, 7 parts by weight of glycolic acid, and 5 parts by weight of potassium chloride was used.

(8) Next, a resin film for an interlayer resin insulating layer slightly larger than the substrate prepared in the above A was placed on the substrate, and the pressure was 0.4 MPa, the temperature was 80 ° C., and the pressure bonding time was 10 seconds. After temporary compression bonding and cutting, an interlayer resin insulating layer 22 was formed by bonding using a vacuum laminator by the following method (see FIG. 3E). That is, the resin film for an interlayer resin insulation layer was fully press-bonded on a substrate under the conditions of a degree of vacuum of 65 Pa, a pressure of 0.4 MPa, a temperature of 80 ° C., and a time of 60 seconds, and then was thermally cured at 170 ° C. for 30 minutes.

(9) Next, a CO ₂ gas laser having a wavelength of 10.4 μm is used to form a beam having a beam diameter of 4.10 μm through a mask having a through hole having a thickness of 1.2 mm formed on the interlayer resin insulating layer 22.
Under the conditions of 0 mm, top hat mode, pulse width of 8.0 μsec, through-hole diameter of the mask of 1.0 mm, and one shot, a via-hole opening 26 of 80 μm in diameter was formed in the interlayer resin insulating layer 22 (FIG. a)).

(10) The substrate on which the via hole opening 26 was formed was immersed in a solution containing 60 g / l of permanganic acid at 80 ° C. for 10 minutes to remove the epoxy resin particles present on the surface of the interlayer resin insulating layer 22. By dissolving and removing, a roughened surface (not shown) was formed on the surface including the inner wall surface of the via hole opening 26. Next, the substrate after the above treatment was immersed in a neutralizing solution (manufactured by Shipley) and then washed with water. Further, by applying a palladium catalyst to the surface of the substrate subjected to the surface roughening treatment (roughening depth: 3 μm), catalyst nuclei are added to the surface of the interlayer resin insulating layer 22 (including the inner wall surface of the via hole opening 26). (Not shown). That is,
The substrate was immersed in a catalyst solution containing palladium chloride (PdCl ₂ ) and stannous chloride (SnCl ₂ ) to deposit a palladium metal, thereby providing a catalyst.

(11) Next, the substrate is immersed in an electroless copper plating aqueous solution having the following composition, and the surface of the interlayer resin insulating layer 22 (including the inner wall surface of the opening 26 for via hole) has a thickness of 0.1 mm. 6-3.0 μm thin conductor layer (electroless copper plating film)
32 were formed (see FIG. 4B). [Electroless plating aqueous solution] NiSO ₄ 0.003 mol / l tartaric acid 0.200 mol / l copper sulfate 0.030 mol / l HCHO 0.050 mol / l NaOH 0.100 mol / l α, α'-bipyridyl 100 mg / l Polyethylene glycol (PEG) 0.10 g / l [Electroless plating conditions] 40 minutes at a liquid temperature of 30 ° C

(12) Next, a commercially available photosensitive dry film is attached to the substrate on which the electroless copper plating film 32 has been formed, a mask is placed, and exposure is performed at 100 mJ / cm ² .
By performing development processing with a 0.8% aqueous sodium carbonate solution, a plating resist 23 having a thickness of 20 μm was provided (FIG. 4).
(C)).

(13) Then, the substrate was washed with water at 50 ° C., degreased, washed with water at 25 ° C., further washed with sulfuric acid, and then subjected to electrolytic plating under the following conditions. In the forming part, a 20 μm thick electrolytic copper plating film 33
Was formed (see FIG. 4D). [Electroplating solution] Sulfuric acid 2.24 mol / l Copper sulfate 0.26 mol / l Additive 19.5 ml / l (Atotech Japan, Capparaside GL) [Electroplating conditions] Current density 1 A / dm ² hours 65 minutes Temperature 22 ± 2 ℃

(14) Further, the plating resist 23 is
% NaOH, the plating resist 23
The lower electroless copper plating film is dissolved and removed by etching with a mixed solution of sulfuric acid and hydrogen peroxide, and the electroless copper plating film 32 is removed.
A conductive circuit 25 (including a via hole 27) having a thickness of 18 μm and a copper plating film 33 was formed (FIG. 5).
(A)).

(15) Next, by repeating the above steps (7) to (14), an upper interlayer resin insulating layer and a conductor circuit were formed by lamination (FIGS. 5B to 6B). reference). Further, the outermost conductor circuit 25 (via hole 27) is formed by using the same method as that used in the step (7).
) To form a roughened surface (not shown) to obtain a multilayer wiring board.

(16) Next, a cresol novolak type epoxy resin (manufactured by Nippon Kayaku Co., Ltd.) dissolved in diethylene glycol dimethyl ether (DMDG) so as to have a concentration of 60% by weight was used. Oligomer for imparting properties (molecular weight: 4000) 46.6
7 parts by weight, 80% by weight dissolved in methyl ethyl ketone
Of bisphenol A type epoxy resin (manufactured by Yuka Shell Co., Ltd.
Trade name: Epicoat 1001) 15.0 parts by weight, imidazole hardener (manufactured by Shikoku Chemicals, trade name: 2E4MZ-C)
N) 1.6 parts by weight, bifunctional acrylic monomer as photosensitive monomer (trade name: R604, manufactured by Nippon Kayaku Co., Ltd.) 3.0
Parts by weight, also polyvalent acrylic monomer (manufactured by Kyoei Chemical Co.,
A trade name: 1.5 parts by weight of DPE6A) and 0.71 parts by weight of a dispersion defoaming agent (manufactured by San Nopco, S-65) are placed in a container, stirred and mixed to prepare a mixed composition, and the mixed composition is prepared. Of benzophenone (manufactured by Kanto Chemical Co., Ltd.) as a photopolymerization initiator and 0.2 part by weight of Michler's ketone (manufactured by Kanto Chemical Co., Ltd.) as a photosensitizer at 25 ° C. A solder resist composition adjusted to 2.0 Pa · s was obtained. The viscosity was measured with a B-type viscometer (DVL-B type, manufactured by Tokyo Keiki Co., Ltd.) for 60 min ^{- 1} (r
pm), the rotor No. 4, 6 min ^-1 (rp
m), the rotor No. According to 3. In addition, as the solder resist composition, a commercially available solder resist composition can be used.

(17) Next, the above-mentioned solder resist composition is applied to both surfaces of the multilayer wiring board, and the coating is performed at 70 ° C. for 20 minutes.
A drying treatment was performed at 70 ° C. for 30 minutes to form a layer of the solder resist composition.

(18) Next, a photomask having a thickness of 5 mm on which an opening pattern for mounting an IC chip mounting substrate and other openings for mounting surface mounting components having an arbitrary shape is drawn. Exposure to 1000 mJ / cm ² ultraviolet light while being in close contact with the solder resist composition layer,
Development was performed with a DMTG solution to form an opening having an opening diameter of 600 μm. Further, a heat treatment is performed at 80 ° C. for 1 hour, at 100 ° C. for 1 hour, at 120 ° C. for 1 hour, and at 150 ° C. for 3 hours to cure the layer of the solder resist composition. Was formed with a solder resist layer 34 having an opening 39 for mounting.

(19) Next, the solder resist layer 34 is
The formed substrate is coated with nickel chloride (2.3 × 10^-1mo
1 / l), sodium hypophosphite (2.8 × 10^-1m
ol / l), sodium citrate (1.6 × 10^-1m
ol / l) and pH = 4.5 electroless nickel plating
Immersed in the solution for 20 minutes, and a 5 μm thick nickel
A plating layer was formed. In addition, the substrate is
Potassium (7.6 × 10 ^-3mol / l), ammonium chloride
Num (1.9 × 10^-1mol / l), sodium citrate
Li (1.2 × 10^-1mol / l), sodium hypophosphite
Thorium (1.7 × 10^-1mol / l)
Immerse in a gold plating solution at 80 ° C for 7.5 minutes,
A 0.03μm thick gold plating layer is formed on the Kel plating layer.
The pad 36 for surface mounting was formed. (See FIG. 7 (a)
See).

(20) Next, a mask having a through-hole formed at a position facing the optical waveguide 50 is placed on one side (the optical waveguide forming side) of the substrate on which the solder resist layer is formed, and the carbon dioxide laser is used. An opening having a diameter of 400 μm penetrating the solder resist layer 34 and the interlayer resin insulating layer 22 on one side was formed, and the wall surface of the opening was subjected to desmear treatment to form an opening 38 for an optical path (see FIG. 7B).

(21) Next, the solder paste (Sn / Ag = 96.
5 / 3.5) was printed and reflowed at 250 ° C. to form solder bumps in the openings 39 to obtain a multilayer printed wiring board (see FIG. 1).

(Example 2) In step (4) of Example 1, first, one end of a film-shaped organic optical waveguide made of PMMA (manufactured by Microparts, width 25 μm, thickness 25 μm) was attached to one end. A 45 ° optical path conversion mirror is formed using a V-shaped 90 ° diamond saw, and then the optical waveguide on which the optical path conversion mirror is formed is placed in the first embodiment so that the side surface of one end thereof and the side surface of the substrate are aligned. A multilayer printed wiring board was manufactured in the same manner as in Example 1 except that the layers were attached under the same conditions as in step (4). Note that the optical waveguide was attached in such a direction that its top surface was larger than its bottom surface (see FIG. 8).

(Example 3) (1) A multilayer wiring board was fabricated in the same manner as in the steps (1) to (15) except that the steps (3) and (4) were not performed. Obtained. (2) Next, a film made of a polyimide resin that has been cut into a desired size in advance is attached to a predetermined position (a portion where a conductive circuit is not formed) on the outermost interlayer resin insulating layer, thereby obtaining an elastic modulus. 2.45 × 10 ³ MPa, thickness 50 μm
Was formed.

(3) Next, on the elastic material layer formed in the above step (2), a film-shaped organic optical waveguide made of PMMA (Microparts: 50 μm wide, 50 μm thick)
m) was attached so that the side surface of one end of the optical waveguide was aligned with the side surface of the substrate. The bonding of the organic optical waveguide was performed under the same conditions as in step (4) of Example 1. Further, a 45 ° optical path conversion mirror was formed at one end of the optical waveguide using a diamond saw having a V-shaped end of 90 °.

(4) Next, a solder resist composition was prepared in the same manner as in step (16) of Example 1, and this solder resist composition was treated under the same conditions as in step (17) of Example 1. , A solder resist composition was applied to both sides of the multilayer wiring board to form a layer of the solder resist composition.

(5) Next, on one side of the substrate, a 5 mm-thick photomask on which a pattern of an opening for mounting an IC chip mounting substrate and the like and an opening for an optical path is drawn is formed on the layer of the solder resist composition. 1000mJ / cm
Exposure with ultraviolet light of No. ² and development processing with DMTG solution, IC
Opening and opening diameter 400 for mounting chip mounting substrate
An opening for an optical path of μm was formed. The opening for mounting the IC chip mounting substrate was formed with a diameter of 600 μm and a pitch of 1.27 mm. The other surface was exposed and developed under the same conditions using a mask on which only patterns of openings for mounting various surface-mounted electronic components were drawn to form openings. Further, at 80 ° C. for 1 hour,
An opening and an optical path for mounting a substrate for mounting an IC chip and the like are cured by performing a heat treatment under the conditions of 00 ° C. for 1 hour, 120 ° C. for 1 hour, and 150 ° C. for 3 hours. And a solder resist layer having an opening for use.

(6) Next, surface mounting pads 36 are formed in the same manner as in the step (19) of the first embodiment, and further, solder bumps are formed in the same manner as in the step (21) of the first embodiment. Then, a multilayer printed wiring board was obtained (see FIG. 2).

(Example 4) In the step (3) of Example 3, first, one end of a film-shaped organic optical waveguide made of PMMA (manufactured by Microparts, width 50 μm, thickness 50 μm) was attached to one end. A 45 ° optical path conversion mirror is formed using a V-shaped 90 ° diamond saw, and then the optical waveguide on which the optical path conversion mirror is formed is placed in the first embodiment so that the side surface of one end thereof and the side surface of the substrate are aligned. A multilayer printed wiring board was manufactured in the same manner as in Example 3 except that the bonding was performed under the same conditions as in the step (4). Note that the optical waveguide was attached in such a direction that its upper surface was larger than its bottom surface.

Comparative Example 1 A multilayer printed wiring board was manufactured in the same manner as in Example 1, except that the step (4), that is, the step of forming the elastic material layer was not performed.

Comparative Example 2 A multilayer printed wiring board was manufactured in the same manner as in Example 3, except that the step (2), ie, the step of forming the elastic material layer, was not performed.

The multilayer printed wiring boards obtained in Examples 1 to 4 and Comparative Examples 1 and 2 were evaluated according to the following evaluation method. (1) Observation of the shape of the optical waveguide and the substrate or interlayer resin insulating layer below the optical waveguide , (2) optical signal detection and (3) continuity test.

[0166]Evaluation method  (1) Observation of shape The obtained multilayer printed wiring board is bladed so as to pass through the optical waveguide.
It was cut with an object and the cross section was observed.

(2) Detection of Optical Signal First, on the side of the obtained multilayer printed wiring board on which the optical waveguide is formed, an I / O device on which a light receiving element and a light emitting element are mounted is mounted.
The C-chip mounting substrate was connected via solder bumps such that the light receiving element and the light emitting element were respectively disposed at positions facing the optical path opening. Next, an optical fiber is attached to the exposed surface of the optical waveguide facing the light emitting element from the side of the multilayer printed wiring board, and the detector is attached to the exposed surface of the optical waveguide facing the light receiving element from the side of the multilayer printed wiring board. Then, an optical signal was sent through an optical fiber, operated by an IC chip, and then detected by a detector.

(3) Continuity test In the same manner as in the detection of the optical signal, the multi-layer printed wiring board is
The substrate for mounting the C chip was connected, and then a continuity test was performed. The continuity state was evaluated from the results displayed on the monitor.

As a result of the above evaluation, in the multilayer printed wiring board of Example 1, two types of optical waveguides, a light receiving optical waveguide and a light emitting optical waveguide, were formed at predetermined positions. No crack occurred in the underlying substrate. In the multilayer printed wiring board according to the third embodiment, two types of optical waveguides, a light receiving optical waveguide and a light emitting optical waveguide, are formed at predetermined positions, and the optical waveguide and an interlayer resin existing below the optical waveguide are formed. No crack occurred in the insulating layer. Further, in the multilayer printed wiring boards of Examples 2 and 4, no crack was generated in the optical waveguide.

Further, in the multilayer printed wiring boards of Examples 1 to 4, a desired optical signal can be detected when an IC chip mounting substrate is connected and an optical signal is transmitted. It has been clarified that the multilayer printed wiring board has a sufficient optical signal transmission capability. Example 1
In the multilayer printed wiring boards of Nos. 1 to 4, I through a solder bump
In the continuity test when the C-chip mounting board was connected, there was no problem with the continuity of the electric signal, and together with the optical signal,
It has become clear that electric signals can also be transmitted.

On the other hand, in the multilayer printed wiring boards of Comparative Examples 1 and 2, two types of optical waveguides, that is, a light receiving optical waveguide and a light emitting optical waveguide, were formed at predetermined positions. Cracks were observed in a part of the substrate or the interlayer resin insulation layer existing in the above. Comparative Example 1
In the multilayer printed wiring boards of (2) and (3), when an IC chip mounting substrate is connected and an optical signal is transmitted, the connection loss in the optical waveguide is larger than that of the multilayer printed wiring board of the embodiment, and some of the optical signals that cannot be detected Existed. In the continuity test, no particular problem was found.

[0172]

Since the first multilayer printed wiring board has the above-described structure, the stress applied to the substrate when forming the optical waveguide, particularly when forming the optical path conversion mirror in the optical waveguide, can be reduced. In addition to being able to prevent cracks and the like caused by this stress from occurring in the substrate, it is also possible to alleviate the stress applied to the optical waveguide due to the difference in the coefficient of thermal expansion between the optical waveguide and the substrate or the interlayer resin insulation layer. It is possible to prevent cracks and the like caused by this stress from occurring in the optical waveguide. Therefore, the reliability of the multilayer printed wiring board does not decrease due to cracks or the like generated on the substrate.

Further, in the case where a film-shaped optical waveguide on which an optical path conversion mirror has been formed is pasted during the formation of the optical waveguide, the stress applied to the optical waveguide can be reduced by the elastic material layer. It is possible to prevent scratches and cracks from being generated in the wave path. Further, since the conductor circuit and the optical waveguide are formed on the multilayer printed wiring board, both the optical signal and the electric signal can be transmitted, and the optical waveguide is built in the multilayer printed wiring board. Therefore, it is possible to contribute to downsizing of the optical communication terminal device.

Since the second multilayer printed wiring board has the above-described structure, the stress applied to the interlayer resin insulating layer can be reduced when forming the optical waveguide, particularly when forming the optical path conversion mirror on the optical waveguide. In addition to being able to prevent cracks and the like caused by this stress from being generated in the interlayer resin insulating layer, the cracks and the like are applied to the optical waveguide due to the difference in thermal expansion coefficient between the optical waveguide and the interlayer resin insulating layer or the solder resist layer. The stress can be reduced, and cracks and the like caused by the stress can be prevented from occurring in the optical waveguide. Therefore, the reliability of the multilayer printed wiring board does not decrease due to cracks or the like generated in the interlayer resin insulating layer.

Further, when a film-shaped optical waveguide on which an optical path conversion mirror is formed is pasted at the time of forming the optical waveguide, the stress applied to the optical waveguide can be reduced by the elastic material layer. It is possible to prevent scratches and cracks from being generated in the wave path. Further, since the conductor circuit and the optical waveguide are formed on the multilayer printed wiring board, both the optical signal and the electric signal can be transmitted, and the optical waveguide is built in the multilayer printed wiring board. Therefore, it is possible to contribute to downsizing of the optical communication terminal device.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing one embodiment of a multilayer printed wiring board of the first invention.

FIG. 2 is a sectional view schematically showing one embodiment of the multilayer printed wiring board according to the second invention.

FIGS. 3A to 3E are cross-sectional views schematically showing a part of a process of manufacturing the multilayer printed wiring board of the first invention.

FIGS. 4A to 4D are cross-sectional views schematically showing a part of a process of manufacturing the multilayer printed wiring board according to the first embodiment of the present invention.

FIGS. 5A to 5C are cross-sectional views schematically showing a part of a process of manufacturing the multilayer printed wiring board according to the first embodiment of the present invention.

FIGS. 6A and 6B are cross-sectional views schematically showing a part of a step of manufacturing the multilayer printed wiring board of the first invention.

FIGS. 7A and 7B are cross-sectional views schematically showing a part of a process of manufacturing the multilayer printed wiring board of the first present invention.

FIG. 8 is a sectional view schematically showing another embodiment of the multilayer printed wiring board of the first invention.

[Explanation of symbols]

 100, 200 multilayer printed wiring board 21, 121, 221 substrate 22, 122, 222 interlayer resin insulation layer 24, 124, 224 conductor circuit 25, 125, 225 conductor circuit 27, 127, 227 via hole 29, 129, 229 through hole 38, 138, 238 Optical path opening 34, 134, 234 Solder resist layer 36, 136, 236 Solder pad 37, 137, 237 Solder bump 50, 150, 250, 1150 Optical waveguide

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H047 KA04 KB08 KB09 LA09 MA05 MA07 PA01 PA02 PA15 PA21 PA22 PA24 PA28 QA01 QA05 QA07 TA05 5E338 AA03 AA16 BB63 BB75 CC01 CC10 EE22 EE28 5E346 AA06 AA11 CC01 CC01 EE22 BB DD02 DD03 DD22 EE31 EE38 FF04 FF45 GG28 GG40 HH22 HH33

Claims (5)

[Claims] 1. A multilayer printed wiring board in which a conductive circuit and an interlayer resin insulating layer are formed on both surfaces of a substrate and an optical waveguide is formed on the substrate, wherein the substrate and the optical waveguide are A multilayer printed wiring board, wherein an elastic material layer is formed therebetween. 2. A multilayer printed wiring board in which a conductor circuit and an interlayer resin insulation layer are laminated on both surfaces of a substrate, and an optical waveguide is formed on an outermost interlayer resin insulation layer, wherein the outermost layer is A multilayer printed wiring board, wherein an elastic material layer is formed between the interlayer resin insulating layer and the optical waveguide. 3. The elastic material layer has an elastic modulus of 2.5 × 10.
The multilayer printed wiring board according to claim 1 or 2, wherein the pressure is ³ MPa or less. 4. The elastic modulus is 1.0 to 1.0 × 10 ^3.
The multilayer printed wiring board according to claim 3, which is in MPa. 5. The multilayer printed wiring board according to claim 1, wherein the elastic material layer is made of a polyolefin resin and / or a polyimide resin.