JP2004281667A - Method of manufacturing multilayer wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a reliable multilayer wiring board that can be made compact, and can be obtained at a low cost with a high yield. <P>SOLUTION: The method of manufacturing the multilayer wiring board comprises processes of forming projecting conductive bumps 12 for via connection on one principal plane of a conductive metal foil 10; forming a multilayer body 18 consisting of a conductive metal foil 11 and an insulation resin layer 17, both of which are formed with through-holes by laser processing at positions corresponding to the conductive bumps 12 of the conductive metal foil 10; and positioning and stacking the multilayer body 18 on the bump-formed plane of the conductive metal foil 10 via a thermoplastic insulator layer 13, with the metal foil 11 side of the multilayer body 18 facing the bump-formed plane. The method of manufacturing the multilayer wiring board also comprises processes of applying heat and pressure to the laminate in the stacking direction to make top ends of the bumps 12 pass through the thermoplastic insulator layer 13 and the multilayer body 18 to make them integral parts of these layers, and forming into a laminate by removing the insulation resin layer 17 of the multilayer body 18 to expose the conductive metal foil 11 whereon the top ends of the conductive bumps 12 are exposed and forming into a multilayer wiring board with connection terminal bumps by photo-etching the conductive metal foil 11 exposed on the laminate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a highly reliable high-density wiring type multilayer wiring board at low cost.
[0002]
[Prior art]
For example, as electronic devices such as portable telephones and personal computers become shorter and lighter, wiring boards for forming electric circuits are not only required to have higher density wiring and shorter, lighter and thinner, but also to have higher circuit reliability and lower weight. Cost reduction is required. In response to such a demand, a via connection structure in which wiring patterns are arranged in a multilayered manner via an insulating layer, and the wiring patterns are connected by projecting conductive bumps penetrating the interlayer insulating layer. Multilayer wiring boards are known (see Patent Documents 1 and 2).
[0003]
FIG. 3 schematically shows a manufacturing embodiment of this type of multilayer wiring board. That is, first, as shown in FIG. 3A, a copper foil 1a having a thickness of, for example, about 18 μm is prepared, and a conductive composition (for example, a silver paste) is screen-printed on one main surface of the copper foil 1a. Then, a substantially conical (projection-shaped) conductive bump 2 having a bottom diameter of about 100 to 300 μm and a height of about 20 to 50 μm is formed. Next, when the bumps 2 are dried, the bumps 2 are aligned with the bumps 2 and screen-printed with a silver paste again to build up to a required height. Here, the print formation of the conductive bumps 2 is usually repeated a plurality of times, although it depends on the composition of the conductive composition and the size and shape such as the diameter and height of the bumps 2.
[0004]
After the formation of the protruding conductive bumps 2, as shown in FIG. 3B, a thermoplastic insulating layer (for example, a liquid crystal polymer sheet) 3, a copper foil 1b having a thickness of about 18 μm, Pressure forming plates (for example, stainless steel plates) 4 are sequentially arranged and laminated, and heated and pressed in the laminating direction. By this heating and pressing, the tip of the bump 2 penetrated the liquid crystal polymer sheet 3 and abutted and deformed on the copper foil 1b as shown in FIG. A double-sided copper foil-laminated plate or sheet is obtained.
[0005]
Next, a dry film for etching is adhered to the copper foils 1a and 1b surfaces of the double-sided copper foil bonded plate, and the dry film is exposed and developed, masked and etched, and FIG. As shown in d), wiring patterns (1a) and (1b) are formed. Thereafter, a solder resist 5 is provided on the surface formed with the wiring patterns (1a) and (1b) by a screen printing method or the like, and at least one of the required surfaces of the wiring patterns (1a) and (1b) is formed as shown in FIG. As shown in (1), connection terminal bumps 6 for mounting components such as IC sockets are provided.
[0006]
Here, the connection terminal bumps 6 are formed in the following procedure. That is, first, a dry film for etching is stuck on the surface of the solder resist 5, and the dry film is exposed and developed to perform masking. Next, the solder resist 5 is selectively removed by etching to expose and open the wiring pattern (1a) and (1b) surfaces, and the connection terminal bumps 6 are formed on the exposed and opened surfaces by plating. Thereafter, the dry film is peeled and removed, and if necessary, the surfaces of the connection terminal bumps 6 are subjected to gold plating or the like for stabilization, protection, and the like, and are subjected to outer shape processing to produce a product. Alternatively, as shown in FIG. 3F, a multilayer substrate shown in FIG. 3G is formed by laminating the substrates shown in FIGS. 3D and 3E via an insulating layer 3a.
[0007]
In this type of manufacturing method of a multilayer wiring board, when forming the connection terminal bumps 6, an insulating layer in which a through-hole is previously formed in a corresponding position is laminated and integrated so that it protrudes from the insulating layer surface. There is also known means for filling the inside of the through hole with plating or the like (see Patent Document 3).
[0008]
[Patent Document 1]
JP-A-10-79579 (page 4, FIG. 1)
[0009]
[Patent Document 2]
JP-A-11-112149 (page 2, FIG. 1)
[0010]
[Patent Document 3]
JP-A-2001-237511 (page 4, FIG. 1)
[0011]
[Problems to be solved by the invention]
In the via connection type multilayer wiring board, since interlayer connection between the wiring patterns 1a and 1b and the like is performed by pressing and penetrating the conductive bumps 2, high density wiring and simplification of a manufacturing process can be achieved. There are advantages. In other words, in connection between wiring pattern layers, drilling by drilling or the like for each interlayer insulator layer can be omitted, and plating processing in the drilling or filling operation of the conductive composition is not only unnecessary, but also fine. A highly reliable via connection can be achieved. In particular, in the via connection of a fine diameter required for high-density wiring, it is difficult to reliably form a dense and uniform plating layer in a small diameter hole, or a dense conductive layer is formed in a small diameter hole. Problems, such as difficulty in filling the conductive composition, can be easily improved.
[0012]
However, there are concerns about the following problems in terms of mass productivity and reliability. In other words, when the connection terminal bumps 6 are formed by plating on the outer surface side wiring pattern, it is difficult not only to form a dense plating as described above, but also to form the connection terminal bumps 6 having a uniformly controlled height. There is a problem that formation is extremely difficult.
[0013]
Further, when the interval between the connection terminal bumps 6 is set to be small, there is a problem that it is difficult to sufficiently secure electrical insulation between the adjacent connection terminal bumps 6.
[0014]
Here, the difficulty in always forming dense and uniform connection bumps may impair the reliability of the circuit to be formed, and may also cause variations in the height of the connection terminal bumps 6 and the distance between adjacent connection bumps. For example, when an IC device or the like is mounted, there is a concern that an incomplete mounting connection may be formed. Since these inconveniences and concerns relate to the reliability of the wiring board itself or circuit components, it cannot be ignored in improving the quality of applied electronic devices.
[0015]
Also, forming an etching resist on the wiring pattern surface and forming the external connection bumps by plating using the etching resist as a mask complicates the manufacturing process, in other words, increases the number of processing steps and increases costs. Invite. In addition, the complexity of the manufacturing process and the addition of the processing step may cause a reduction in the manufacturing yield, and as a result, the mass productivity is impaired.
[0016]
The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a manufacturing method capable of obtaining a highly reliable multilayer wiring board with high reliability and compactness at low cost and with high yield. And
[0017]
[Means for Solving the Problems]
The present invention provides a step of arranging a protruding conductive bump for via connection on one main surface of a conductive metal foil, and drilling a through hole by laser processing at a position corresponding to the conductive bump of the conductive metal foil. Forming a multilayer body of the conductive metal foil and the insulating resin layer, wherein the metal foil side of the multilayer body is opposed to a bump mounting surface of the conductive metal foil on which the conductive bumps are provided, and the thermoplastic resin is formed. Positioning and laminating via an insulator layer, heating and pressurizing the laminate in the laminating direction, and a step of penetrating and integrating the bump tip with the thermoplastic transfer insulator layer and the multilayer body; Removing the insulating resin layer of the laminated body, exposing the conductive metal foil protruding from the tip end side of the conductive bumps, and photo-etching the exposed conductive metal foil of the laminate. To form a multilayer wiring board with external connection bumps. A method for manufacturing a multilayer wiring board according to claim.
[0018]
That is, a conductive bump for forming a via connection portion is provided to be longer (higher), and a multilayer body of a conductive metal foil for a wiring pattern and an insulating resin layer in which a via connection hole has been formed in advance is used. Multi-layered by laminating and integrating via a thermoplastic insulator, projecting the tip of the conductive bump from the conductive metal foil surface for a wiring pattern, and using the projected portion as a connection terminal bump. This is a method for manufacturing a wiring board.
[0019]
With the adoption of such a manufacturing means, a highly reliable via connection is formed by, for example, projecting bumps having a bottom diameter of 100 μm or less and a height of 10 μm or more. That is, highly reliable mounting connection is possible, and a multilayer wiring board having shaped connection terminal bumps can be obtained at low cost. Furthermore, regardless of the diameter of the conductive bump forming the via connection, the height of the bump can be arbitrarily set / selected to increase the density of the wiring pattern and achieve a highly reliable circuit. A multilayer wiring board with connection terminal bumps having a shape and flatness suitable for the configuration of a highly functional and highly reliable mounting circuit device can be provided with a high yield without requiring complicated steps.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 (a) to 1 (e) and FIG.
[0021]
The multilayer wiring board according to the present invention includes a thermoplastic insulator (for example, a liquid crystal polymer) as an interlayer insulator 13 and wiring patterns 10a and 11a, as shown in an enlarged sectional view in FIG. A configuration is employed in which the conductive bumps 12 penetrating through the interlayer insulator 13 connect the vias between the wiring patterns 10a and 11a. Further, the tip of the conductive bump 12 forming the via connection is configured to penetrate through the wiring pattern 11a and protrude to function as a connection terminal bump. In this configuration, the tip of the conductive bump 12 forming the via connection penetrates through the interlayer insulator 13 and participates in the electrical connection with the wiring pattern 11a. 11a is characterized in that it penetrates and protrudes and is used as a connection terminal such as an IC socket.
[0022]
Here, the wiring patterns 10a and 11a are formed by projecting conductive bumps 12 disposed on the surface of the wiring pattern 10a on the back surface of the corresponding insulating layer 13 so as to penetrate the interlayer insulator 13 and establish a required electrical connection with the wiring pattern 11. Connection is made. That is, if necessary, the tip of the substantially conical or pyramid-shaped conductive bump 12 formed in the shape of a protrusion by coaxially overlapping and printing is electrically connected to the wiring pattern 11a which penetrates the interlayer insulator 3 and faces the same. It is configured to be connected to In the wiring pattern 11a, in a region serving as a connection terminal for mounting and mounting an electronic component, the tip of the conductive bump 12 protrudes from the surface of the wiring pattern 11a. In other words, in the process of pressure lamination and integration of the multilayer wiring board, by simultaneously forming the connection terminal bumps, the manufacturing process is simplified and the cost is reduced, while the adjacent connection terminal bumps are insulated from each other. This arrangement enables a high-density mounting / wiring-type circuit configuration.
[0023]
The conductive bumps 12 can be formed by means of screen printing of a conductive paste or selective plating by printing and patterning a plating resist. The thermoplastic insulator forming the interlayer insulator 3 is, for example, a thermoplastic resin such as a liquid crystal polymer having a thickness of about 25 to 100 μm (for example, a BIAC film having a melting point of 335 ° C.) and a polyether-based resin film. More specifically, examples thereof include multiaxially-aligned liquid crystal polymers and polyether-based polymers represented by, for example, Xidal (trade name, manufactured by Dartco) and Vectra (trade name, manufactured by Clanese). As the liquid crystal polymer, Vectran A type (melting point: 285 ° C.), Vectran C type (melting point: 325 ° C.), BIAC film (melting point: 325 ° C.), and the like are commercially available. Here, the liquid crystal polymer generally has little hygroscopicity, a dielectric constant of about 3.0 (1 MHz), and excellent high-frequency characteristics, and thus exhibits high-speed signal transmission stability.
[0024]
Further, the conductive bumps 12 constituting the via connection and the like are formed of a mixed system of a conductive metal powder such as gold, silver, copper, nickel, and solder and a binder resin. Here, examples of the binder resin include a polycarbonate resin, a polysulfone resin, a polyester resin, a phenoxy resin, a phenol resin, and a polyimide resin.
[0025]
The conductive metal foil on which the conductive bumps are formed is, for example, a copper foil, an aluminum foil, a nickel foil, or the like. The laminate of the metal foil and the insulating resin layer is formed of, for example, a copper foil having a thickness of about 18 μm and a thermosetting resin layer having a thickness of about 10 μm. Here, the thermosetting resin to be multi-layered has high mechanical strength to mechanically protect the tip of the conductive bump 12 that penetrates and protrudes, and to prevent deformation and damage. Further, it is desired that peeling or dissolution removal can be easily performed finally. Examples of such a thermosetting resin include, for example, films using an epoxy resin, a polyimide resin, a phenol resin, an organic woven fabric or the like as a support. In the drilling of the multilayer body, the hole diameter is selected according to the diameter of the conductive bump to be inserted or the size of the connection terminal bump, and the hole can be drilled. However, laser beam processing is generally used. preferable.
[0026]
Next, a method for manufacturing a multilayer wiring board according to an example will be described with reference to FIGS. 1A to 1E schematically showing an embodiment and a flowchart shown in the figure.
[0027]
First, as shown in FIG. 1 (a), a copper foil 10 having a thickness of about 18 μm is prepared, and a metal mask having a hole of 150 μm in diameter at a predetermined position of, for example, a stainless steel sheet is positioned on one principal surface thereof. Then, the conductive paste is screen-printed to form a conductive bump 12 having a substantially conical cross section. After the conductive bumps 12 are dried, if necessary, a conductive paste is screen-printed repeatedly on the surface on which the conductive bumps 12 are to be formed, thereby building up the conductive bumps 12. Here, the height of the conductive bump 12 may generally be about 1.5 to 2 times the height required for forming a via connection.
[0028]
On the other hand, a copper foil 11 having a thickness of about 18 μm is prepared, and a multi-layer body 18 is prepared by laminating a polyimide resin film 17 having a thickness of about 25 μm on one principal surface thereof. That is, as shown in FIG. 1B, a through hole having a required diameter penetrating in the thickness direction is formed by laser processing at the position where the via connection 12 and the connection terminal 16 are formed.
[0029]
Next, as shown in FIG. 1 (c), the copper foil 10a on which the conductive bumps 2 are formed is placed on the copper foil 10a of the multilayer body 18 via a liquid crystal polymer sheet 13 having a thickness of, for example, about 50 μm. Eleven surfaces are stacked so as to face each other, and a press forming plate (for example, a stainless steel plate) 14 is sequentially stacked, and if necessary, a press forming plate 20 is also arranged at the copper foil position 10 side to heat. Pressing in the laminating direction while pressing. Due to this heating and pressing, the tip of the conductive bump 12 penetrates the liquid crystal polymer sheet 13 and further penetrates the perforated hole of the multilayer body 18, and comes into contact with the surface of the forming plate 14 to be deformed into a flat surface. I do. In other words, as shown in FIG. 1D, the tip of the conductive bump 12, which is higher than the thickness of the liquid crystal polymer sheet 13 and the multilayer body 18, is pressed against the surface of the molding plate 16 and crushed. A copper-clad laminate having a flat surface and the same surface as the polyimide resin film 17 is obtained.
[0030]
Next, the polyimide resin film 17 of the copper-clad laminate is peeled or dissolved and removed, and a so-called dry film is laminated on the exposed surfaces of the copper foils 10a and 11a. Then, the dry film is exposed and developed to form an etching mask, and the copper foils 10 and 11 are selectively removed by etching, as shown in FIG. , 11 are formed into wiring patterns 10a, 11a, and a wiring board having a structure in which the distal end of the conductive bump 12 penetrates and protrudes from the wiring pattern 11a surface is obtained.
[0031]
Thereafter, a solder resist layer is printed and formed on the surfaces of the wiring patterns 10a and 11a, in other words, on the entire area from which the multilayer body 17 has been removed, by exposing the protruding tips of the conductive bumps. A conventional plating process on the connection terminal bumps, for example, gold plating, is performed on the leading end surface of the conductive bumps. After the insulation protection of the wiring board surface and the provision of the stability of the connection terminal bumps are performed in this way, the product is manufactured by performing the external processing, which is a conventional means.
[0032]
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the invention. For example, the number of wiring patterns may be a three-layer type or a multi-layer type of four or more layers. Also, as an interlayer insulator, a combination of a liquid crystal polymer and a thermoplastic resin, and the thickness and material of each layer of the multi-layer body may also be used. It can be appropriately selected depending on the situation.
[0033]
【The invention's effect】
According to the present invention, a highly reliable via connection is formed by the projecting bumps, and a multilayer wiring board having connection terminal bumps capable of highly reliable mounting connection can be obtained at low cost. That is, irrespective of the diameter of the conductive bump forming the via connection, the height of the bump can be arbitrarily set and selected, so that a high-density wiring pattern and a highly reliable circuit can be achieved. In addition, the configuration of a highly functional and highly reliable mounting circuit device can be achieved without the need for complicated steps (while simplifying the steps) and by providing fine connection terminal bumps that can easily ensure insulation and mutual separation. A multi-layer wiring board suitable for a high yield can be provided. In other words, it is possible to provide a high-density wiring or a high-functionality and highly reliable mounting multilayer wiring board in mass production with high yield while achieving a reduction in length and size.
[Brief description of the drawings]
1A to 1E are cross-sectional views schematically showing an embodiment of a method for manufacturing a multilayer wiring board according to an example.
FIG. 2 is a flowchart showing an outline of a manufacturing procedure of the multilayer wiring board according to the embodiment.
3A to 3G are cross-sectional views schematically showing an embodiment of a conventional method for manufacturing a multilayer wiring board.
[Explanation of symbols]
10, 11: conductive metal foil (copper foil)
10a, 11a: Wiring pattern 12: Conductive bump 13: Thermoplastic insulator 14: Pressed forming plate 15: Solder resist layer 16: Pressed forming plate 17: Insulating resin layer 18: Multilayer 19: Penetration Hole

Claims (3)

Arranging a protruding conductive bump for via connection on one main surface of the conductive metal foil,
A step of forming a multilayer body of a conductive metal foil and an insulating resin layer in which a through hole is formed by laser processing at a position corresponding to the conductive bump of the conductive metal foil,
A step of positioning and laminating via a thermoplastic insulator layer the metal foil side of the multilayer body facing the bump mounting surface of the conductive metal foil provided with the conductive bumps,
A step of heating and pressurizing the laminate in the laminating direction to bump the tip portion, and inserting and integrating the thermoplastic transfer insulating layer and the multilayer body.
Removing the insulating resin layer of the integrated multilayer body, a step of forming a laminated plate in which the conductive metal foil protruding the tip side of the conductive bump is exposed,
A step of photoetching the conductive metal foil of the exposed laminate to form a wiring board with bumps for external connection,
A method for manufacturing a multilayer wiring board, comprising: 2. The method for manufacturing a multilayer wiring board according to claim 1, wherein the conductive bumps for via connection are provided by screen printing of the conductive composition. 3. The method according to claim 1, wherein the thermoplastic insulator is a liquid crystal polymer film.

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