JP2003179350A - Method of manufacturing multilayer printed-wiring board and multilayer printed-wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a multilayer printed-wiring board which is of high density and high reliability by contributing to the miniaturization of a semiconductor package. <P>SOLUTION: In the method of manufacturing the multilayer printed-wiring board, a photosensitive resin coated on a copper foil is laminated on a printed- wiring board, and a circuit formation operation is repeated so as to be multilayered. In the method of manufacturing the multilayer printed-wiring board, circuits in respective layers are electrically bonded by bumps formed of a metal, positions corresponding to the metal bumps formed in a directly lower layer from among resin layers by the photosensitive resin coated on the copper foil are removed in advance, and the metal bumps and resin openings are aligned so as to be laminated. <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, the electrical connection between the electrodes of the semiconductor chip and the terminals of the substrate, which is made of various materials such as plastics and ceramics, which is called a semiconductor package substrate, which has the function of the lead frame of the conventional semiconductor package. As a method, wire bonding method or TA
B (Tape Automated Bonding)
A system, further, 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 a printed wiring board, and a resin-coated copper foil or a copper foil is formed on the bump. A method has been proposed in which prepregs are laminated and pressure-molded to allow the bumps to penetrate through the resin and reach the copper foil to form 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, and it is difficult to cope with a high circuit density.

As a result of various studies, the inventors have used metal bumps for interlayer connection in order to solve the above-mentioned problems, and the bumps do not penetrate the resin at the time of lamination pressure molding and the outermost layer is formed. A multilayer wiring board for a semiconductor package that reaches the copper foil and is capable of coping with high circuit density and having sufficient reliability because the bumps and the outermost copper foil are metal-bonded by the heat applied during the laminated pressure molding. Aiming to provide a manufacturing method of.

[0008]

The present invention is characterized in that (1) a photosensitive resin coated on a copper foil is laminated on a printed wiring board, and circuit formation is repeated to form a multilayer structure. A method for manufacturing a multilayer printed wiring board; (2) a method for manufacturing a multilayer printed wiring board according to item (1), wherein the circuits of each layer are electrically joined by bumps formed of metal; The method for producing a multilayer printed wiring board according to item (2), which is formed by plating, etching, or gold wire bonding, and (4) a layer directly below the photosensitive resin layer coated on the copper foil. The method for producing a multilayer printed wiring board according to item (2) or (3), wherein the positions corresponding to the formed metal bumps are removed in advance, and the metal bumps and the resin openings are aligned and laminated. 5)
When the surface of the copper foil at the bottom of the photosensitive resin coating on the copper foil is tin-plated and at least the tip of the metal bump is gold-plated, the photosensitive resin coated on the copper foil is laminated and molded. The method for producing a multilayer printed wiring board according to the item (4), wherein the copper foil and the metal bump used in the photosensitive resin coated on the copper foil are metal-bonded by solid-phase diffusion by the pressure and heat of 6) The photosensitive resin used for producing the photosensitive resin coated on the copper foil contains a photosensitive component and a thermosetting component, and is irradiated with ultraviolet rays at a predetermined position to give a predetermined amount of energy, whereby a predetermined amount is obtained. It is possible to remove the resin with the developing solution only at the position of, and the thermosetting component is cured by heating after that.
(5) The method for producing a multilayer printed wiring board according to any one of (5), (7) the photosensitive resin has adhesiveness to the immediate underlying layer due to the thermosetting component after irradiation with a predetermined amount of ultraviolet energy, The method for producing a multilayer printed wiring board according to item (6), which is a resin that exhibits fluidity when heated, and (8) the production of a multilayer printed wiring board according to any one of items (1) to (7). A multilayer printed wiring board manufactured by the method.

[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 a photosensitive component,
It is obtained by coating a varnish containing 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 UV energy at a predetermined portion, so that a contrast appears in solubility in a developing solution, and the resin at the predetermined portion is removed.
The photosensitive system in this case 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.

Further, on the printed wiring board which is the base for laminating and press-molding the PIC, metal bumps having a height of 100 to 105% of the thickness of the PIC resin layer are formed at the portions to be vertically joined. It For forming the bumps, any of a method of etching and removing a copper foil having a predetermined thickness, a method of forming by electrolytic plating, and a gold wire bonding method can be applied. In the etching method and the plating method, at least the tip of the bump needs to be covered with gold, and when the gold wire bonding method is applied, it is necessary to crush the tip of the bump by coining to form a flat surface. The resin removal portion of the PIC is formed at a position corresponding to the arrangement of these bumps.

Next, in the PIC resin removing portion, the bottom of the resin removing portion is coated with electrolytic tin plating using the PIC resin layer as a plating mask. For this reason, the PIC resin layer must withstand the plating solution and the pretreatment solution in the plating process when the exposure and development are completed. In addition, the printed wiring board with bumps is then laminated and pressure-molded. Even after various heat history applied during the plating process, it is necessary to maintain reactivity enough to obtain sufficient adhesive force to the bumped printed wiring board.

Further, the PIC having the bottom of the resin removing portion plated with tin is arranged with the bumps after the resin removing portion is arranged so as to match the position of the metal bump for vertical connection provided on the printed wiring board. One set with a printed wiring board,
It is pressure-molded by a vacuum press together with a flat metal plate. At this time, 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 at the bottom of the resin removal portion and gold at the tip of the bump to form a metal bond over the entire tip of the bump. Express. In addition, since the PIC resin removal portion is formed to have a larger volume than the bump, it is necessary to flow and fill voids existing around the bump with heat applied during pressure molding in a vacuum press.

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

[0014]

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

Example 1 On a roughened surface of an electrolytic copper foil having a thickness of 18 μm, 14.5% of a bifunctional methacrylate monomer, 25% of a phenol novolac resin, and 30 of a crystalline epoxy resin.
%, Spherical silica filler 30%, photoradical generator 0.
A varnish in which 5% of a negative photosensitive resin was dissolved in methyl ethyl ketone (MEK) was cast-coated by a comma coater and dried at 80 ° C. for 7 minutes to obtain a PIC having a resin thickness of 75 μm.

Next, after masking a predetermined portion of the PIC resin layer, the PIC resin layer was exposed to a UV exposure of 200 mJ and developed with a 2.38% tetramethylammonium hydroxide aqueous solution (TMAH) 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, a tin layer having a thickness of 0.5 μm was formed by electrolytic plating on the bottom of the resin-removed portion using the copper foil as a power supply layer.

Next, a copper bump having a diameter of 90 .mu.m, a height of 76 .mu.m and a tip of 2 .mu.m thick was covered with gold was formed by electrolytic plating on a portion of the printed wiring board to be vertically connected. The position of the copper bump is in a mirror image relationship with the PIC resin removal portion.

The printed wiring board with bumps was aligned so that the bumps and the PIC resin removed portion were aligned with each other, then sandwiched between flat SUS plates and laminated and pressure-molded by a vacuum press. 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 of the printed wiring board, a shield plate having metal bumps for vertical connection built in on both surfaces of the printed wiring board was obtained. The shield plate was etched with sulfuric acid until the thickness of the copper foil on both surfaces became 2 μm, and then an appropriate circuit was formed by the semi-additive method, and then a solder resist layer was formed on both surfaces.

A semiconductor element is mounted on the thus obtained multilayer printed wiring board by a die attach film, the printed wiring board and the semiconductor element are joined by gold wire bonding, and then sealed by a mold sealing material. It is a semiconductor package. A reliability test was conducted on this semiconductor package, but no problem was found in its operation as a semiconductor package.

[0021]

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.

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Claims (8)

[Claims] 1. A method for producing a multilayer printed wiring board, comprising: stacking a photosensitive resin coated on a copper foil on a printed wiring board and repeating circuit formation to form a multilayer. 2. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein the circuits of the respective layers are electrically joined by bumps made of metal. 3. The method for manufacturing a multilayer printed wiring board according to claim 2, wherein the metal bumps are formed by plating, etching, or gold wire bonding. 4. A photosensitive resin layer coated on a copper foil is preliminarily removed at a position corresponding to a metal bump formed directly under the resin layer, and the metal bump and the resin opening are aligned and laminated. The method for manufacturing a multilayer printed wiring board according to claim 2 or 3. 5. A photosensitive resin coated on a copper foil, wherein the copper foil surface at the bottom of the opening of the photosensitive resin is tin-plated and at least the tip of the metal bump is gold-plated. The multilayer printed wiring board according to claim 4, wherein the copper foil used in the photosensitive resin coated on the copper foil and the metal bump are metal-bonded by solid-phase diffusion due to pressure and heat during lamination molding. Method 6. A photosensitive resin used for producing a photosensitive resin coated on a copper foil contains a photosensitive component and a thermosetting component, and is irradiated with ultraviolet rays at a predetermined energy amount at a predetermined position. 6. The multilayer print according to any one of claims 1 to 5, wherein the resin can be removed with a developing solution only at a predetermined position, and the thermosetting component is cured by heating thereafter. Wiring board manufacturing method. 7. The photosensitive resin is a resin which has adhesiveness to a layer directly below it by a thermosetting component after being irradiated with a predetermined amount of ultraviolet rays and has fluidity when heated. 7. The method for manufacturing a multilayer printed wiring board according to 6. 8. A multilayer printed wiring board manufactured by the method for manufacturing a multilayer printed wiring board according to claim 1.