JP2003229667A - Method of manufacturing multilayered printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a multilayered printed wiring board for semiconductor package that can cope with an increase in density of circuits and has sufficiently high reliability so as to reduce the size of a semiconductor package. <P>SOLUTION: In this method, the muitilayered printed wiring board is manufactured by forming multiple layers by repeating circuit formation, after a photosensitive resin applied to copper foil is laminated upon a printed wiring board and electrically joining the circuits of different layers to each other through metallic bumps. The metallic bumps are formed by performing electroplating by using the copper foil as feeding layers. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a high density printed multilayer wiring board used for semiconductor package applications and the like.

[0002]

2. Description of the Related Art With the recent demand for higher functionality, lightness, thinness, shortness, and miniaturization of electronic equipment, high-density integration and further high-density packaging of electronic parts have been advanced. Semiconductor packages used in these electronic devices have been downsized and have a large number of pins, and mounting substrates for mounting electronic components including the semiconductor packages have also been downsized. Furthermore, in order to enhance the storage property in electronic equipment, a rigid flex substrate, which is made by stacking and integrating a rigid substrate and a flexible substrate and is bendable, has come to be used as a mounting substrate.

As semiconductor packages have become smaller,
In a package using a lead frame as in the past, miniaturization has reached its limit, so recently, a BGA (Ball) has been used as a chip mounted on a circuit board.
Grid Array) and CSP (Chip Sc)
A new package method of area mounting type, such as an all package) has been proposed. In these semiconductor packages, a method for electrically connecting a substrate terminal and a semiconductor chip electrode, which are made of various materials such as plastics and ceramics, which are called semiconductor package substrates having the function of a lead frame of a conventional semiconductor package. As a wire bonding method or TAB
A (Tape Automated Bonding) system, an FC (Flip Chip) system, and the like are known. Recently, BGA and CSP structures using an FC connection method, which is advantageous for miniaturization of semiconductor packages, have been actively proposed. Along with this, substrates used for semiconductor packages are required to have higher density and higher reliability.

[0004]

The laser build-up method, which is most often used in the manufacture of high-density multilayer printed wiring boards (substrates) for semiconductor packages, uses interlayer plating only for via-hole wall plating to connect circuits. It has been pointed out that if the via hole diameter is reduced to increase the density, the reliability is significantly reduced.

Further, bumps formed of conductive paste or plated metal or bumps formed by etching a thick copper foil are provided on the printed wiring board,
A method has been proposed in which a resin-coated copper foil or a copper foil and a prepreg are laminated and pressure-molded thereon, and the bump penetrates through the resin to reach the copper foil for interlayer connection. However, the resin may remain between the bump and the copper foil, and the ratio of the area where the two are actually metal-bonded is extremely low in the contact area between the bump and the copper foil. It has been pointed out that if you do, you will not be able to obtain sufficient reliability.

A method is also proposed in which a hole is preliminarily formed in an insulating resin layer and a conductive paste is embedded in the insulating resin layer, and a copper foil and a copper foil are laminated and pressure-molded on the printed wiring board to form an interlayer connection through the conductive paste. Has been done. But,
The metal bond between the bump and the copper foil is compressed by the thickness of the insulating resin layer during pressure molding, and the conductive paste is compressed and the metal powder contained in the conductive paste locally causes metal bonding. Therefore, it has been pointed out that it is difficult to reduce the diameter of the bump in order to obtain a sufficient conduction resistance, which makes it difficult to cope with a high circuit density.

As a result of various studies, the inventors have used metallic bumps for interlayer connection in order to solve the above-mentioned problems, and printed wirings without bumps penetrating resin during lamination pressure molding. Land formed on the plate,
Further, by providing metal bonding between the bump and the outermost layer copper foil by heat applied during laminated pressure molding, a method for manufacturing a multilayer wiring board for a semiconductor package that can cope with high circuit density and has sufficient reliability is provided. I aimed at that.

[0008]

According to the present invention, (1) a photosensitive resin coated on a copper foil is laminated on a printed wiring board and then a circuit is repeatedly formed to form a multilayer structure. In a method for manufacturing a multilayer printed wiring board in which a circuit is electrically joined by bumps formed of metal, a method for manufacturing a multilayer printed wiring board in which metal bumps are formed by electroplating using the copper foil as a power supply layer,
(2) The method for producing a multilayer printed wiring board according to item (1), wherein the photosensitive resin is a negative type photosensitive resin and has adhesiveness even after photocuring, and (3) the metal bump is photosensitive. The method for manufacturing a multilayer printed wiring board according to item (1) or (2), which is formed by filling an opening formed by exposing and developing a resin by electroplating, and (4) the metal bump is copper. The method for manufacturing a multilayer printed wiring board according to any one of (1) to (3), wherein the tip is covered with tin or solder, and (5) the height of the metal bump is equal to the thickness of the photosensitive resin. 95-105%, the manufacturing method of a multilayer printed wiring board according to any one of (1) to (4), (6)
After the metal bumps are formed on the photosensitive resin coated on the copper foil, the metal bumps are aligned so that the land existing on the printed wiring board and the metal bumps are aligned, and then heated and pressed by a vacuum press. It is integrated with a printed wiring board, and the copper foil is processed by a subtractive method or a semi-additive method to form a circuit, which is repeated (1) to (5)
A method for manufacturing a multilayer printed wiring board according to any one of paragraphs,
(7) The multilayer structure according to (6), wherein the tip of the metal bump comes into contact with the land surface on the printed wiring board at the time of integral molding by a vacuum press and is heated under pressure to form a metal bond and be electrically connected. Method for manufacturing printed wiring board, (8)
A multilayer printed wiring board manufactured by the manufacturing method according to any one of items (1) to (7).

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Photosensitive Insulation resin wi coated on the copper foil used in the present invention.
th Copper foil: hereinafter referred to as PIC) is obtained by coating a varnish containing a photosensitive component, a thermosetting component, a filler, a curing agent component, and a solvent on a copper foil and drying it. Next, the resin component is irradiated with energy from a predetermined portion of the UV, so that the solubility of the resin component in the developing solution exhibits a contrast, and the resin of the predetermined portion is removed. The photosensitive system at this time can be applied to any type of negative type and positive type, and an organic solvent or an alkaline aqueous solution is used for development, but it is preferable to develop with an alkaline aqueous solution from the viewpoint of environmental problems.

In the PIC, an opening formed by exposing and developing a portion to be vertically joined is metal-filled by electroplating, preferably 95% to 105% of the thickness of the PIC resin layer. Metal bumps having the following height are formed. Therefore, it is necessary for the PIC resin layer to withstand the plating solution and the pretreatment solution in the plating step when the exposure and development are completed. Furthermore, after this, since PIC in which bumps for vertical bonding are formed in resin is laminated and pressure-molded on the printed wiring board, the printed wiring board with bumps can be printed even after various thermal histories applied during the plating process. It must be reactive enough to provide sufficient adhesion to.

Further, the bumped PIC is arranged such that the bump portion is provided on the printed wiring board and coincides with the position of the land covered with gold, and is then pressure-molded by a vacuum press together with a flat metal plate. To be done. On this occasion,
Heating is performed at the same time to cure the thermosetting component of the PIC resin layer, but this heating causes solid-phase diffusion of tin or solder coating the tip of the bump and gold coating the land to form a metal bond. Are formed on the entire tip of the bump.

The shield plate containing the vertical connection bumps thus obtained has a predetermined circuit formed by the subtractive or semi-additive method, and when more layers are stacked, the above process is repeated to form a multilayer structure. It is possible.

[0013]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

(Example 1) A bifunctional methacrylate monomer (PM20 manufactured by Sanyo Kasei Co., Ltd.) was formed on a roughened surface of an electrolytic copper foil having a thickness of 18 μm.
1) 20% by weight, phenol novolac resin (PR5371 manufactured by Sumitomo Durez) 22% by weight, epoxy resin (EOCN-1020-70 manufactured by Nippon Kayaku) 27% by weight, spherical silica filler (Admatex SE5101) 30.5% by weight, A varnish prepared by dissolving a negative-type photosensitive resin containing 0.5% by weight of a photo-radical generator (Irgacure 651 manufactured by Ciba Specialty Chemicals) in methyl ethyl ketone (MEK) is cast and applied by a comma coater at 80 ° C.
By drying for 7 minutes at a resin thickness of 45 μm PI
I got C.

Next, after masking a predetermined portion of the PIC resin layer, the PIC resin layer was exposed to an exposure amount of 200 mJ by a UV exposure device, and developed with 2.38% TMAH (tetramethylammonium hydroxide aqueous solution) to remove the resin. did. Furthermore, the copper foil on the bottom of the resin removal part is made to have a thickness of 1 μm
After the removal, the copper foil is used as a power supply layer and the resin removed portion is filled with copper by electrolytic plating so that the height is 43 μm in the opening, and then eutectic solder is applied so that the tip has a thickness of 1 μm. It was coated by electrolytic plating.

Next, the bumped PIC is aligned with the bump and a portion of the printed wiring board as a core material that requires vertical connection, and then sandwiched with a flat SUS board and laminated and pressure-molded by a vacuum press. did. At this time, the maximum product temperature reached 185 ° C., and the holding time at 150 ° C. or higher was 45 minutes.

By repeating the same steps on the other surface, a shield plate having metal bumps for vertical connection built in on both surfaces of the printed wiring board was obtained. This shield plate was etched with hydro sulfuric acid until the copper foil thickness on both sides became 2 μm, and then a predetermined circuit was formed by the semi-additive method, and then a solder resist layer was formed on both sides.

In the multilayer printed wiring board thus obtained, the semiconductor element was mounted by the die attach film, and the printed wiring board and the semiconductor element were joined by gold wire bonding. Next, it was encapsulated with a mold encapsulant, incorporated into a semiconductor package, and subjected to a reliability test, but no problem was found in the operation as a semiconductor package.

(Example 2) 19% by weight of a bifunctional methacrylate monomer (Actylene 420 manufactured by ACROS CHEMICALS), 22% by weight of phenol novolac resin (VR9305 manufactured by Mitsui Chemicals), and epoxy resin (Japan Kayaku NC-7300) 24% by weight, spherical silica filler (Admatex SE5101) 34.5
A varnish prepared by dissolving a negative photosensitive resin containing 0.5% by weight of a photo-radical generator (IRGACURE 651 manufactured by Ciba Specialty Chemicals) in MEK is cast by a comma coater and dried at 80 ° C for 7 minutes. By doing so, a PIC having a resin thickness of 50 μm was obtained.

Next, after masking a predetermined portion of the PIC resin layer, the PIC resin layer was exposed by a UV exposure machine so that the exposure amount was 200 mJ, and developed by 2.38% TMAH to remove the resin. Further, after removing the copper foil at the bottom of the resin-removed portion with a thickness of 1 μm with a hydrosulfuric acid aqueous solution, the copper foil was used as a power supply layer
After filling the resin-removed portion with copper so that the opening has a height of 51 μm by electrolytic plating, the tip has a thickness of 0.8 μm.
The tin was coated by electrolytic plating so that the thickness was m.

Next, the PIC with bumps is aligned with a printed wiring board which has been pre-plated with gold at the portions where vertical connection with the bumps is required, then sandwiched between flat SUS boards and laminated and pressed by a vacuum press. Molded. At this time, the maximum product temperature reached 178 ° C., and the holding time at 150 ° C. or higher was 49 minutes.

By repeating the same process on the other surface, a shield plate having metal bumps for vertical connection built in on both surfaces of the printed wiring board was obtained. A predetermined circuit was formed on this shield plate by the subtractive method.

Further, on both sides of the four-layer printed wiring board,
PICs with bumps were laminated by repeating the above process, the outermost copper foil was formed into a circuit by a subtractive method, and a solder resist layer was further provided to obtain a 6-layer printed wiring board vertically joined by metal bumps.

In the multilayer printed wiring board thus obtained, a semiconductor element was bonded to one surface via solder balls, and then an underfill resin was injected between the semiconductor element and the printed wiring board. Next, it was encapsulated with a mold encapsulant, incorporated into a semiconductor package, and subjected to a reliability test, but no problem was found in the operation as a semiconductor package.

[0025]

According to the present invention, it is possible to further improve the wiring density of the high-density multilayer printed wiring board for a semiconductor package, which contributes to downsizing of the semiconductor package.

Claims (8)

[Claims] 1. A multilayer structure is formed by repeatedly forming a circuit after laminating a photosensitive resin coated on a copper foil on a printed wiring board, and each layer circuit is electrically formed by a bump formed of metal. A method of manufacturing a multilayer printed wiring board, wherein the metal bump is formed by electroplating using the copper foil as a power supply layer in the method of manufacturing a multilayer printed wiring board. 2. The photosensitive resin is a negative type photosensitive resin,
The method for manufacturing a multilayer printed wiring board according to claim 1, which has adhesiveness even after photocuring. 3. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein the metal bump is formed by filling an opening formed by exposing and developing a photosensitive resin with electroplating. 4. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein the metal bump is made of copper and its tip is covered with tin or solder. 5. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein the height of the metal bump is 95 to 105% of the thickness of the photosensitive resin. 6. A metal bump is formed on a photosensitive resin coated on a copper foil, and then a land existing on a printed wiring board is aligned with a position of the metal bump, and then a vacuum is formed. 6. The production of a multilayer printed wiring board according to claim 1, wherein heating and pressurizing with a press is integrated with the printed wiring board, and the copper foil is processed by a subtractive method or a semi-additive method to form a circuit. Method. 7. The multi-layer according to claim 6, wherein the tip of the metal bump is brought into contact with the land surface on the printed wiring board during integral molding by a vacuum press and is heated under pressure to form a metal bond and be electrically connected. Method for manufacturing printed wiring board 8. A multilayer printed wiring board manufactured by the manufacturing method according to claim 1.