JP5439165B2 - Multilayer wiring board and manufacturing method thereof - Google Patents

Description

  The present invention relates to a multilayer wiring board and a method for manufacturing the same.

  In a multilayer wiring board having flexibility, a so-called flexible multilayer wiring board, a resin film (CCL: Copper Clad Laminate) bonded with a copper foil is used as an insulating layer. Conventionally, a plurality of insulating layers in which circuit wiring is formed on a copper foil are laminated with an adhesive layer to form a multilayer, and then panel plating is performed on through holes and via holes formed by drilling or laser processing to obtain interlayer conduction. It is common. Such a method of manufacturing a multilayer wiring board is excellent in productivity. However, there are problems such that mounting parts and other via holes cannot be arranged on the through holes and via holes, and it is difficult to arrange the through holes and via holes at arbitrary positions and layers. Further, since the outermost layer wiring is plated and thickened, it is difficult to form fine wiring.

  In order to overcome the above problems, there is a multilayer wiring board in which an insulating layer on which circuit wiring is formed is bonded by an adhesive layer to be multi-layered, and via holes formed in each insulating layer are filled with a conductive paste to take interlayer conduction. It has been proposed (see Patent Document 1). In this proposal, the via hole used for interlayer conduction is filled with conductive paste, so mounting components and other via holes can be placed directly above the via hole, and the via hole can be placed at any position or layer It is. Further, since the plating step can be omitted, the outermost layer wiring does not become thick, and a fine wiring can be easily formed.

  However, with recent miniaturization and higher functionality of electronic components, the demand for finer wiring on multilayer wiring boards has become more severe. Therefore, it has become difficult to cope with the conventional technology. The wiring of each layer in the conventional multilayer wiring board is formed by a subtractive method for removing unnecessary portions of the CCL copper foil. Although the subtractive method is excellent in mass productivity, it is technically limited to form a wiring having a width of about 30 μm, and it is difficult to miniaturize it to 30 μm or less. On the other hand, in the semi-additive method in which the wiring is formed only on a necessary portion by plating, it is possible to form a fine wiring having a width of 30 μm or less. However, the semi-additive method has a complicated process and has a problem in productivity.

  In response to the above problems, recently, a technique for forming a fine wiring by an ink jet method has attracted attention (see Patent Document 2). In the ink jet method, a fine wiring having a width of several tens of μm or less can be formed. In addition, in the inkjet method, the conductive paste, which is a wiring material, is discharged and applied only to necessary portions, so the number of processes and the wiring material used are reduced compared to the above-described subtractive method and semi-additive method. It is possible. Further, in the formation of the multilayer wiring board, it is possible to further simplify the process by simultaneously drawing the via hole for interlayer connection with the conductive paste in the same manner as the wiring.

Japanese Patent No. 4195619 JP 2006-239899 A

  Usually, in the wiring formation by the inkjet method, a conductive paste (nano paste) containing a metal filler having an average particle diameter of 1 nm to 100 nm is used. In such a nanopaste, metal fillers are bonded only by contacting even at room temperature. For this reason, the metal filler surface is coated with a dispersant and dispersed in an organic solvent to prevent contact between the metal fillers. By heating the applied nanopaste, the dispersant and the organic solvent are volatilized, and the metal filler is sintered at a low temperature.

  Thus, since the nanopaste used in the inkjet method contains a large amount of dispersant and organic solvent, the deposited nanopaste after sintering shrinks to about 10% to 40% before sintering. Resulting in. As a result, it becomes difficult to ensure the reliability of the interlayer connection due to problems such as the shape of the via conductor filling the via hole being non-uniform and the occurrence of voids in the via conductor.

  An object of the present invention is to provide a multilayer wiring board capable of forming fine wiring and capable of highly reliable interlayer connection and a method for manufacturing the same.

  According to the first aspect of the present invention, the first insulating layer, the first wiring layer including the first wiring made of a sintered body of the first conductive paste disposed on one main surface of the first insulating layer; The second insulating layer, the second wiring made of a sintered body of the first conductive paste disposed on one main surface of the second insulating layer, the first insulating layer in contact with one main surface, and the other of the second insulating layer What is the first conductive paste provided on the main surface, penetrating the second insulating layer and the first adhesive layer at a predetermined position, and connecting the first wiring and the second wiring? There is provided a multilayer wiring board including a second wiring layer including a first via conductor made of a sintered body of a different second conductive paste.

  According to the second aspect of the present invention, the first conductive paste is selectively applied to one main surface of the first insulating layer to form the first wiring, and the one main surface of the second insulating layer is formed. A step of selectively applying the first conductive paste to form a second wiring; a step of forming a first adhesive layer on the other main surface of the second insulating layer; and a step of forming the first adhesive layer at a predetermined position. Forming a via hole penetrating the first adhesive layer and the second insulating layer so that a part of the second wiring is exposed from one side, and printing a second conductive paste different from the first conductive paste in the via hole Filling and forming a via conductor connected to the second wiring, and overlaying one surface of the first adhesive layer on one main surface of the first insulating layer, and via conductor at a predetermined position of the first wiring And the first adhesive layer and the first insulating layer are bonded by heating while pressing the first adhesive layer against the first insulating layer. Method for manufacturing a multilayer wiring board comprising the steps of a via conductor is heated while being pressed to the first wiring for connecting the via conductor in the first wiring are provided at the same time.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide a multilayer wiring board which can form fine wiring and can perform highly reliable interlayer connection, and its manufacturing method.

It is sectional drawing which shows an example of the multilayer wiring board which concerns on embodiment of this invention. It is process sectional drawing (the 1) which shows an example of the manufacturing method of the multilayer wiring board which concerns on embodiment of this invention. It is process sectional drawing (the 2) which shows an example of the manufacturing method of the multilayer wiring board which concerns on embodiment of this invention. It is process sectional drawing (the 3) which shows an example of the manufacturing method of the multilayer wiring board which concerns on embodiment of this invention. It is process sectional drawing (the 4) which shows an example of the manufacturing method of the multilayer wiring board which concerns on embodiment of this invention. It is process sectional drawing (the 5) which shows an example of the manufacturing method of the multilayer wiring board which concerns on embodiment of this invention. It is process sectional drawing (the 6) which shows an example of the manufacturing method of the multilayer wiring board which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  The following embodiments of the present invention exemplify apparatuses and methods for embodying the technical idea of the present invention. The technical idea of the present invention is based on the material and shape of component parts. The structure, arrangement, etc. are not specified below. The technical idea of the present invention can be variously modified within the technical scope described in the claims.

  The multilayer wiring board according to the embodiment of the present invention includes a first wiring layer 2, a second wiring layer 4, a third wiring layer 6, and a fourth wiring layer 8, as shown in FIG. The first wiring layer 2 includes a first insulating layer 12 and a first wiring 32 disposed on one main surface of the first insulating layer 12. The second wiring layer 4 is in contact with one main surface of the second insulating layer 14, the second wiring 34 arranged on one main surface of the second insulating layer 14, and the first main surface of the first insulating layer 12. And a first via conductor 44 provided through the second insulating layer 14 and the first adhesive layer 24 at a predetermined position.

  The third wiring layer 6 is in contact with one main surface of the third insulating layer 16, the third wiring 36 disposed on one main surface of the third insulating layer 16, and the second main surface of the second insulating layer 14. And a second via conductor 46 provided through the third insulating layer 16 and the second adhesive layer 26 at a predetermined position. The fourth wiring layer 8 is in contact with one main surface of the fourth insulating layer 18, the fourth wiring 38 disposed on one main surface of the fourth insulating layer 18, and the third insulating layer 16. And a third via conductor 48 provided through the fourth insulating layer 18 and the third adhesive layer 28 at a predetermined position.

  The first to fourth wirings 32, 34, 36, and 38 are sintered bodies of the first conductive paste. The first to third via conductors 44, 46, and 48 are sintered bodies of a second conductive paste different from the first conductive paste. The first via conductor 44 connects the first wiring 32 and the second wiring 34. The second via conductor 46 connects the second wiring 34 and the third wiring 36. The third via conductor 48 connects the third wiring 36 and the fourth wiring 38.

  As the first to fourth insulating layers 12, 14, 16, and 18, resin films having a thickness of 12 μm to 50 μm such as polyimide and liquid crystal polymer are used. In particular, a liquid crystal polymer is preferable as an insulating layer for a high-frequency circuit or a high-speed circuit because it has a low water absorption rate and a low dielectric constant and dielectric loss. As the first to third adhesive layers 24, 26, and 28, epoxy or acrylic thermosetting resin films, thermoplastic adhesives such as thermoplastic polyimide, or varnish-like resins are used.

  As the first conductive paste, a conductive paste (nano paste) containing a silver filler having an average particle diameter of 1 nm to 100 nm is used. The filler contained in the first conductive paste is not limited to silver, and low resistance metals such as gold, copper, tin, and nickel may be used. As the second conductive paste, a conductive paste containing low-resistance metal particles and low-melting-point metal particles and mixed with a binder mainly composed of an epoxy resin is used. The low resistance metal particles are at least one kind of metal particles selected from nickel, silver, and copper. The low melting point metal particles are at least one metal particle selected from tin, bismuth, indium, and lead.

  The manufacturing method of the multilayer wiring board which concerns on embodiment is demonstrated with reference to FIGS. For convenience of explanation, the third wiring layer 6 is mainly illustrated, but the other wiring layers are manufactured in the same process or a similar process.

  As shown in FIG. 2, an insulating layer (third insulating layer) 16 made of a polyimide film is prepared. As shown in FIG. 3, a nano paste (first conductive paste) containing a silver filler having an average particle diameter of 1 nm to 100 nm is selectively applied to the surface (one main surface) of the insulating layer 16 by an inkjet method. Then, a wiring (third wiring) 36 is formed.

  As shown in FIG. 4, an epoxy thermosetting resin film is attached to the back surface (other main surface) of the insulating layer 16 by thermocompression bonding to form an adhesive layer (second adhesive layer) 26. For thermocompression bonding, a vacuum laminator is used, and in a reduced pressure atmosphere, the temperature is not higher than the curing temperature of the thermosetting resin film, for example, about 100 ° C. to 140 ° C., and pressed and bonded at a pressure of about 0.25 MPa. .

As shown in FIG. 5, a via hole 50 that penetrates the adhesive layer 26 and the insulating layer 16 is exposed to ultraviolet rays (UV) laser so that a part of the wiring 36 is exposed from one side of the adhesive layer 26 at a predetermined position. Open. The diameter of the via hole 50 is, for example, about 100 μm. After plasma desmear treatment using a mixed gas of carbon tetrafluoride (CF ₄ ) and oxygen (O ₂ ), the conductive paste (second conductive paste) is filled into the via hole 50 by a printing method such as screen printing. Thus, a via conductor (second via conductor) 46 is formed. The conductive paste is a paste that includes low-resistance metal particles and low-melting-point metal particles and is mixed with a binder component mainly composed of an epoxy resin.

The opening of the via hole 50 is not limited to the UV laser, and for example, a carbon dioxide laser, an excimer laser, or the like may be used. Alternatively, the via hole 50 may be opened by drilling or chemical etching. The gas used for the plasma desmear process is not limited to a mixed gas of CF ₄ and O ₂ , and an inert gas such as argon (Ar) may be used. Alternatively, wet desmear treatment using a chemical solution may be used instead of dry treatment.

  As shown in FIG. 6, the first wiring layer 2, the second wiring layer 4, and the fourth wiring layer 8 are manufactured by the above-described manufacturing method of the third wiring layer 6. In the first wiring layer 2, it is not necessary to form an adhesive layer and a via conductor. A first adhesive layer 24 is laminated on the surface of the first insulating layer 12, a second adhesive layer 26 is laminated on the surface of the second insulating layer 14, and a third adhesive layer 28 is laminated on the surface of the third insulating layer 16, respectively. Temporary fixing is performed by heating at a temperature lower than the curing temperature of the first to third adhesive layers 24, 26, and 28 and the first and second conductive pastes. At this time, the first via conductor 44 contacts the predetermined first wiring 32, the second via conductor 46 contacts the predetermined second wiring 34, and the third via conductor 48 contacts the predetermined third wiring 36. In addition, alignment marks (not shown) formed on each of the first to fourth wiring layers 2, 4, 6, and 8 are used.

  As shown in FIG. 7, the first to fourth wiring layers 2, 4, 6, and 8 stacked by temporary fastening are heated to 150 ° C. to 200 ° C. and about 1 kPa or less using a vacuum curing press device. A multilayer wiring board is manufactured by heat-compression in a reduced pressure atmosphere. During the thermocompression bonding, the first to third adhesive layers 24, 26, and 28 are thermally cured, and the first to third via conductors 44, 46, and 48 and the first to fourth wirings 32, 34, and 36 are cured. , 38 are thermally cured to form a sintered body. At the same time, the contacted first to third via conductors 44, 46, 48 and the first to third wirings 32, 34, 36 are alloyed. In this way, the multilayer wiring board shown in FIG. 1 is manufactured.

  In the multilayer wiring board according to the embodiment, the first to fourth wirings 32, 34, 36, and 38 of the first to fourth wiring layers 2, 4, 6, and 8 are directly drawn on necessary portions by the ink jet method. To be formed. Therefore, it is possible to form fine wiring of 30 μm or less, which was difficult with the conventional subtractive method.

  In the conventional subtractive method, a photolithography process such as resist coating, exposure, development, etching, resist stripping, or the like is required. As described above, according to the ink jet method, the wiring forming process and time can be significantly reduced and shortened as compared with the subtractive method.

  Further, in the subtractive method and the semi-additive method, resources used for photolithography such as a photomask, a resist, a developing solution, an etching solution, and a resist stripping solution are necessary for wiring formation. In particular, resist, developer, etchant, resist stripper, etc. are discarded after processing. Furthermore, in the subtractive method, unnecessary copper foil on the insulating layer is removed by etching, and as a result, part of the raw material is wasted. On the other hand, the inkjet method does not require the above-described photolithography resources. Further, since the wiring pattern is formed by direct drawing, waste of raw materials can be reduced. As a result, the manufacturing cost can be reduced.

  In the embodiment, the first to third via conductors 44, 46 and 48 are formed by filling a via hole with a conductive paste by a printing method. Since the printing method is used, a plating process is not necessary as compared with the conventional build-up method. As a result, the manufacturing time can be shortened. Further, as the second conductive paste used for the interlayer connection, a composition that is alloyed at about the curing temperature of the thermosetting resin used for the first to third adhesive layers 24, 26, and 28 is applied. Metal particles contained in the conductive paste, and metal particles contained in the first and second conductive pastes can be diffused and bonded to each other. Therefore, the reliability of the interlayer connection equivalent to the interlayer connection using bulk metal or plated metal can be ensured.

(Other embodiments)
Although the embodiments of the present invention have been described as described above, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art. Accordingly, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

  The present invention can be applied to a multilayer wiring board and a manufacturing method thereof.

DESCRIPTION OF SYMBOLS 2 ... 1st wiring layer 4 ... 2nd wiring layer 6 ... 3rd wiring layer 8 ... 4th wiring layer 12 ... 1st insulating layer 14 ... 2nd insulating layer 16 ... 3rd insulating layer 18 ... 4th insulating layer 24 ... 1st adhesive layer 26 ... 2nd adhesive layer 28 ... 3rd adhesive layer 32 ... 1st wiring 34 ... 2nd wiring 36 ... 3rd wiring 38 ... 4th wiring 44 ... 1st via conductor 46 ... 2nd via conductor 48 ... Third via conductor 50 ... via hole

Claims (6)

A first insulating layer, a first wiring layer including a first wiring made of a sintered body of a first conductive paste disposed on one main surface of the first insulating layer;
A second insulating layer; a second wiring made of a sintered body of the first conductive paste disposed on one main surface of the second insulating layer; and the second insulating layer in contact with the one main surface of the first insulating layer. A first adhesive layer provided on the other main surface of the layer, provided through the second insulating layer and the first adhesive layer at a predetermined position, and connecting the first wiring and the second wiring. A second wiring layer including a first via conductor made of a sintered body of a second conductive paste different from the first conductive paste ,
The first and second wirings are formed by directly drawing the first conductive paste by an inkjet method,
The multilayer conductive board according to claim 2, wherein the second conductive paste is alloyed at a temperature at which the first adhesive layer is bonded to the first insulating layer and cured .   The first conductive paste includes a metal filler having an average particle diameter of 1 nm to 100 nm including at least one selected from gold, silver, copper, tin, and nickel. The multilayer wiring board as described.   The second conductive paste includes at least one metal particle selected from nickel, silver, and copper, and at least one metal particle selected from tin, bismuth, indium, and lead. The multilayer wiring board according to claim 1, wherein the multilayer wiring board is a conductive paste containing a binder mainly composed of an epoxy resin.   The multilayer wiring board according to claim 1, wherein the first and second insulating layers are made of a polyimide resin or a liquid crystal polymer having a thickness of 12 μm to 50 μm.   A third insulating layer; a third wiring made of a sintered body of the first conductive paste disposed on one main surface of the third insulating layer; and the third insulating layer in contact with one main surface of the second insulating layer. A second adhesive layer provided on the other principal surface of the layer, provided through the third insulating layer and the second adhesive layer at a predetermined position, and connecting the second wiring and the third wiring. The multilayer wiring board according to claim 1, further comprising a third wiring layer including a second via conductor made of a sintered body of the second conductive paste. Selectively applying a first conductive paste on one main surface of the first insulating layer to form a first wiring;
Selectively applying the first conductive paste on one main surface of the second insulating layer to form a second wiring;
Forming a first adhesive layer on the other main surface of the second insulating layer;
Forming a via hole penetrating the first adhesive layer and the second insulating layer so that a part of the second wiring is exposed from one surface side of the first adhesive layer at a predetermined position;
Printing and filling a second conductive paste different from the first conductive paste into the via hole to form a via conductor connected to the second wiring;
Superimposing one surface of the first adhesive layer on one main surface of the first insulating layer and bringing the via conductor into contact with a predetermined position of the first wiring;
The first adhesive layer is heated while being pressed against the first insulating layer to bond the first adhesive layer and the first insulating layer, and at the same time, the via conductor is heated while being pressed against the first wiring. and a step of connecting the via conductor in the first wiring seen including,
The first and second wirings are formed by directly drawing the first conductive paste by an inkjet method,
The method for producing a multilayer wiring board, wherein the second conductive paste is alloyed at a temperature at which the first adhesive layer adheres to the first insulating layer and cures .

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