JP2008270593A - Multilayer substrate and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve adhesion of an electric circuit pattern and the resin film of an upper layer in a multilayer substrate constituted by laminating a plurality of resin films on one surface of which an electric circuit pattern is formed. <P>SOLUTION: A plurality of wiring layers 1-4 for which electric circuit patterns 1b-4b whose surface is turned to a shiny surface are formed on one surface of the resin films 1a-4a are prepared, and an organic rust-proof coating 10 is formed only on the surfaces of the respective electric circuit patterns 1b-4b of the plurality of wiring layers 1-4. Then, the plurality of wiring layers 1-4 are stacked, the respective wiring layers 1-4 are heated and thermally pressed, the rust-proof coating 10 formed on the electric circuit patterns 1b-4b is made to disappear by thermal decomposition, and the shiny surfaces of the electric circuit patterns 1b-4b and the other surfaces of the resin films 1a-4a are thermally fused. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a multilayer substrate and a manufacturing method thereof.

  Conventionally, for example, Patent Document 1 proposes a multilayer substrate in which a large number of substrates each provided with an electric circuit pattern are laminated only on one side of a resin film. Specifically, in Patent Document 1, a resin film having an electric circuit pattern formed only on one side is prepared, and a via hole reaching the electric circuit pattern is provided from the side of the resin film on which the electric circuit pattern is not formed. After that, a conductive paste is filled in the via hole. A multilayer substrate that can be manufactured by preparing a plurality of such resin films, stacking each of them, and applying pressure while heating with a vacuum heating press from both the upper and lower surfaces has been proposed.

In such a multilayer substrate, for example, a copper foil is employed as the metal foil used in one layer. The surface of the copper foil is a mirror-finished shiny surface. As a result, the copper foil can be easily etched and an electric circuit pattern can be easily formed. Moreover, a thermoplastic resin is employ | adopted as a resin film. The thermoplastic resin is a resin that is softened by heating. For this reason, a layer can be reliably integrated by pressurizing what laminated each resin film.
Japanese Patent No. 3407737

  However, in the above conventional technique, when the resin films are laminated and integrated by pressing, the surface of the electric circuit pattern is a shiny surface, so the electric circuit pattern and the upper resin film do not adhere to each other. there is a possibility. Thereby, an electric circuit pattern and the upper resin film may peel.

  Generally, when securing adhesion between such an electric circuit pattern and a resin base material (thermosetting resin base material such as epoxy or polyimide), the surface of the electric circuit pattern is roughened to provide an anchor effect. This technique is adopted.

  Therefore, it is conceivable to roughen the surface of the electric circuit pattern also in the above technique so as to obtain an anchor effect with the resin film. Specifically, before the resin films are laminated, the surface of the electric circuit pattern is plated (blackening) or etched to form fine irregularities on the surface of the electric circuit pattern. It is a method to convert.

  However, since the thermoplastic resin, which is a resin film, is softened but not liquefied by heating, the thermoplastic resin does not wrap around the minute recesses on the electric circuit pattern, and the anchor effect cannot be obtained and the adhesion cannot be secured. However, it became clear by examination of inventors. This will be described with reference to FIG.

  FIG. 6 is a cross-sectional view schematically showing the case where the anchor effect is obtained and the case where the anchor effect is not obtained in the case of the thermoplastic resin film and the thermosetting resin substrate. 6A shows a case where a thermosetting resin is used as the resin J1, and FIG. 6B shows a case where the electric circuit pattern J3 and the upper resin films J1 and J2 are obtained when a thermoplastic resin is used as the resin film J2. It is sectional drawing of an interface. In FIG. 6, an electric circuit pattern J3 having a surface with minute irregularities J4 is used.

  First, in the case shown in FIG. 6A, a thermosetting resin is used as the resin base material J1. This thermosetting resin is composed of a low-molecular polymer having a very low viscosity. Therefore, the resin itself is hardened by three-dimensional crosslinking through a heat treatment such as a curing step. When forming a multilayer substrate using such a resin, the resin base material J1 is preliminarily crosslinked in a semi-cured state, and a plurality of resin base materials J1 are formed in a state of being easily handled as a structural material. Laminate and then completely cure under high temperature and high pressure by hot press.

  In such a heat treatment stage, the thermosetting resin is again in a very low viscosity state such as water. Therefore, the resin base material J1 which is a thermosetting resin surely wraps around the fine unevenness J4 formed on the surface of the electric circuit pattern J3, particularly the concave portion. Thereby, the adhesive force of the resin film J1 and the electric circuit pattern J3 is improved by the anchor effect.

  On the other hand, in the case shown in FIG. 6B, a thermoplastic resin is used as the resin film J2. This thermoplastic resin does not maintain rigidity by a curing reaction (crosslinking), but maintains rigidity by a binding force due to entanglement between molecules. Therefore, by raising the temperature of the thermoplastic resin, the entanglement between the molecules is loosened and softened by the thermal motion, so that various moldings are possible.

  When the resin film J2 is formed of a thermoplastic resin having such properties to form a multilayer substrate, the resin film J2 is not as soft as a thermosetting resin even when hot pressing is performed under high temperature and pressure. Therefore, as shown in FIG. 6B, the resin film J2 does not wrap around the unevenness J4 of the electric circuit pattern J3, particularly the concave portion. Accordingly, since the resin film J2 and the electric circuit pattern J3 are in contact with each other only at the convex portions of the concavo-convex J4, it becomes point contact and a sufficient adhesion force cannot be ensured.

  In view of the above points, the present invention improves the adhesion between an electric circuit pattern and an upper resin film in a multi-layer substrate configured by laminating a plurality of resin films having an electric circuit pattern formed on one side of the resin film. It is an object of the present invention to provide a multilayer substrate that can be manufactured and a method for manufacturing the same.

  In order to achieve the above object, according to a first feature of the present invention, there is provided a multilayer substrate configured by integrating a plurality of wiring layers (1 to 4), and the plurality of wiring layers. Each of (1-4) is obtained by patterning a resin film (1a-4a) formed of a thermoplastic resin and a metal foil in which at least one surface is a shiny surface into a wiring pattern, An electric circuit pattern (1b-4b) pasted on one surface of the resin film (1a-4a) is provided on the opposite side of the shiny surface, and one of the plurality of wiring layers (1-4) In one wiring layer (1-3) and the upper wiring layer (2-4) of the wiring layer (1-3), the electric circuit pattern (1b-3b) in one wiring layer (1-3) Shiny surface and upper wiring layer (2-4) And the other surface of the lipid film (2a~4a) is heat-sealed.

  This improves the adhesion between the electric circuit patterns (1b to 3b) in one wiring layer (1 to 3) and the other surface of the resin film (2a to 4a) in the upper wiring layer (2 to 4). (See FIG. 5).

  In such a case, the electric circuit patterns (1b to 3b) can be obtained by patterning a metal foil having a shiny surface on both sides into a wiring pattern. Thereby, the adhesive force of the resin film (1a-4a) heat-sealed on both surfaces of the electric circuit pattern (1b-3b) and both surfaces of the said electric circuit pattern (1b-3b) can be improved.

  According to a second aspect of the present invention, in the method for manufacturing a multilayer substrate, a surface opposite to the shiny surface is a resin film (1a to 4a) among metal foils having at least one surface as a shiny surface. A plurality of wiring layers (1 to 4) are prepared in which electric circuit patterns (1b to 4b) are formed by attaching metal foil to a wiring pattern. Next, an anticorrosion film (10) is formed only on the surface of each electric circuit pattern (1b-4b) of the plurality of wiring layers (1-4), and the electric circuit pattern is formed on the plurality of wiring layers (1-4). One surface of the resin film (1a to 3a) provided with (1b to 3b) is opposed to the other surface of the resin film (2a to 4a) not provided with the electric circuit pattern (1b to 4b). Each wiring layer (1 to 4) is overlaid in turn. Subsequently, while heating each of the superimposed wiring layers (1 to 4), the uppermost wiring layer (4) and the lowermost wiring layer (1) are relatively moved so as to approach each other, and pressure is applied. The anticorrosion film (10) formed on the electric circuit patterns (1b to 4b) is thermally decomposed to disappear, and the shiny surface of the electric circuit patterns (1b to 3b) and the other of the resin films (2a to 4a) The surface is heat-sealed.

  Thereby, without oxidizing the surface of the electric circuit pattern (1b to 3b), the electric circuit pattern (1b to 3b) in one wiring layer (1 to 3) and the resin film in the upper wiring layer (2 to 4) The other surface of (2a-4a) can be bonded together, and the electric circuit patterns (1b-3b) in one wiring layer (1-3) and the resin film (2a in the upper wiring layer (2-4)) -4a) can be improved in adhesion with the other surface (see FIG. 5).

  Further, as the metal foil, one having both surfaces that are shiny surfaces can be used. Thereby, the adhesive force of the resin film (1a-4a) heat-sealed on both surfaces of the electric circuit pattern (1b-3b) and both surfaces of the said electric circuit pattern (1b-3b) can be improved.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. The multilayer substrate shown in the present embodiment is applied to, for example, PALAP (registered trademark).

  FIG. 1 is a schematic cross-sectional view of a multilayer substrate according to an embodiment of the present invention. As shown in this figure, the multilayer substrate 100 is configured by overlapping a plurality of wiring layers 1 to 4 constituting the multilayer substrate 100. In the present embodiment, for example, a multilayer substrate 100 including four wiring layers 1 to 4 is shown. Each of the wiring layers 1 to 4 includes resin films 1a to 4a and electric circuit patterns 1b to 4b formed on one surface of the resin films 1a to 4a.

  The resin films 1a to 4a are insulating base materials and form the base of the wiring layers 1 to 4. These resin films 1a to 4a are made of a thermoplastic resin. As the thermoplastic resin, a liquid crystal polymer (LCP), a mixed resin of polyetheretherketone (PEEK) and polyetherimide (PEI), or the like is adopted. Is done. Further, as the resin films 1a to 4a, thermoplastic resins composed of 65% to 35% by weight of polyetheretherketone resin and 35% to 65% by weight of polyetherimide resin can be employed. The thickness of such resin films 1a to 4a is, for example, 50 μm to 100 μm.

  The electric circuit patterns 1b to 4b are provided on one surface of the resin films 1a to 4a, and are formed by patterning a metal foil into a wiring pattern by etching or the like. Moreover, the surface on the opposite side to the surface joined to resin film 1a-4a among the electric circuit patterns 1b-4b is a smooth smooth surface, ie, a shiny surface (glossy surface). That is, the surface of the electric circuit pattern is not roughened. As a metal foil used for forming such electric circuit patterns 1b to 4b, for example, a copper foil, an aluminum foil, a nickel foil, a brass foil or the like is employed. Moreover, the thickness of metal foil is 9 micrometers-35 micrometers, for example.

  In each of the wiring layers 1 to 4, electrical circuit patterns 1b to 4b of wiring patterns necessary for the wiring layers 1 to 4 are formed, and a plurality of wiring layers 1 to 4 are laminated as shown in FIG. Thus, the multilayer substrate 100 is configured. In each of the wiring layers 1 to 4, via holes (not shown) are provided in the resin films 1a to 4a, and the electric circuit patterns 1b to 4b of the wiring layers 1 to 4 are in an electrically connected state.

  In the multilayer substrate 100, for example, in the lowermost wiring layer 1 and the upper wiring layer 2 of the wiring layer 1, the lowermost wiring layer 1 and the upper wiring layer 2 of the wiring layer 1 are in a high temperature state. It is in close contact with each other and is integrated. Thus, the electric circuit pattern 1b is sandwiched between one surface of the resin film 1a and the other surface of the resin film 2a.

  Specifically, the shiny surface of the electric circuit pattern 1b of the lowermost wiring layer 1 and the other surface of the resin film 2a of the wiring layer 2 are bonded to the outermost molecule of the electric circuit pattern 1b and the resin film 2a by heat fusion. It is in a state of binding to the molecule. Further, one surface of the resin film 1a of the lowermost wiring layer 1 and the other surface of the resin film 2a of the wiring layer 2 are in a state where the thermoplastic resins are softened and bonded to each other.

  The wiring layer 2 and the wiring layer 3, and the wiring layer 3 and the wiring layer 4 are also integrated in the same manner as described above, so that the multilayer substrate 100 shown in FIG. 1 is configured. The above is the overall configuration of the multilayer substrate 100 according to the present embodiment.

  Next, a method for manufacturing the multilayer substrate 100 shown in FIG. 1 will be described. FIG. 2 is a schematic view showing a manufacturing process of the multilayer substrate 100. FIG. 3 is an enlarged cross-sectional view of the interface between the shiny surfaces of the electric circuit patterns 1b to 4b and the other surfaces of the resin films 1a to 4a when the wiring layers 1 to 4 are stacked.

  First, each wiring layer 1-4 is prepared. Specifically, resin films 1a to 4a made of a thermoplastic resin and a copper foil as a metal foil having at least one surface as a shiny surface are prepared. The opposite surface is opposed to one surface of the resin films 1a to 4a, and the copper foil and the resin films 1a to 4a are thermocompression bonded. And what laminated | stacked copper foil on resin film 1a-4a is cut | disconnected in multiple to a fixed size, and a copper foil is patterned to a desired wiring pattern by an etching process. In this way, a plurality of wiring layers 1 to 4 provided with the electric circuit patterns 1b to 4b with the shiny surfaces exposed on one surface of the resin films 1a to 4a are prepared.

  In each of the wiring layers 1 to 4, a via hole (not shown) that penetrates one surface and the other surface of the resin films 1 a to 4 a is provided, and wiring is formed in the via hole.

  Next, in order to prevent oxidation that inhibits adhesion on the shiny surfaces of the electric circuit patterns 1b to 4b, the surface of the electric circuit patterns 1b to 4b exposed from one surface of the resin films 1a to 4a is subjected to rust prevention treatment. The antirust treatment is a so-called antioxidation treatment. By performing this anti-oxidation treatment, the shiny surfaces of the electric circuit patterns 1b to 4b are prevented from being oxidized to form irregularities. In the present embodiment, when the rust preventive treatment is performed on the electric circuit patterns 1b to 4b, the organic rust preventive film 10 is formed only on the surfaces of the electric circuit patterns 1b to 4b.

  Such a rust preventive film 10 has a heat resistance enough to thermally decompose in the following steps so as not to hinder the adhesion between the originally required resin films 1a to 4a and the electric circuit patterns 1b to 4b. A film is preferred. As the rust preventive coating 10, for example, a benzotriazole type is employed.

  Specifically, for example, when the electric circuit patterns 1b to 4b are formed of copper foil, a benzotriazole-based chemical that reacts only with copper is dissolved in water, and the water is put on the wiring layers 1 to 4 in a shower shape. Thus, the rust preventive film 10 is formed only on the electric circuit patterns 1b to 4b formed of copper.

  Thereafter, the wiring layers 1 to 4 are laminated and integrated. Specifically, as shown in FIG. 2, in the plurality of wiring layers 1 to 4, one surface of the resin films 1 a to 4 a provided with the electric circuit patterns 1 b to 4 b is the electric circuit patterns 1 b to 4 b. The wiring layers 1 to 4 are sequentially overlapped so as to face the other surfaces of the resin films 1a to 4a that are not provided.

  Subsequently, the uppermost wiring layer 4 and the lowermost wiring layer 1 of the stacked wiring layers 1 to 4 are relatively moved so as to approach each other. That is, the stacked wiring layers 1 to 4 are sandwiched between the hot plates 20 and hot pressed. In this case, the wiring layers 1 to 4 are heated to a high temperature of 320 ° C., for example, and one of the hot plates 20 is relatively moved to the other side, and a high pressure of 5 MPa, for example, is applied for 1 hour, for example.

  At this time, for example, one surface of the resin film 1a of the wiring layer 1 provided with the electric circuit pattern 1b and the electric circuit pattern 1b are connected to the electric circuit pattern 2b of the resin film 2a of the upper wiring layer 2 of the wiring layer 1. Are arranged so that the other surface opposite to the one surface on which the is provided is opposed to each other, and they are moved relative to each other and pressed against each other. The same applies to the wiring layer 2 and the wiring layer 3, and the wiring layer 3 and the wiring layer 4.

  And the anticorrosion film | membrane 10 formed in the surface of the electric circuit patterns 1b-4b is thermally decomposed by pressing the other surface of the resin films 1a-4a which became high temperature, and oxidation of the electric circuit patterns 1b-4b The role of prevention ends and disappears from the surface of the electric circuit patterns 1b to 4b.

  Moreover, as FIG. 3 shows, when the other surface of resin film 2a-4a is pressed on the surface of electric circuit pattern 1b-3b, the other surface of electric circuit pattern 1b-3b and resin film 2a-4a The heat fusion reaction occurs at the contact interface. The thermal fusion reaction is an adhesion principle caused by high temperature and high pressure. According to this, the molecule | numerator of the surface of the electric circuit patterns 1b-3b and the molecule | numerator of the other surface of resin film 2a-4a couple | bond together, and the other surface of the electric circuit patterns 1b-3b and resin film 2a-4a Can be obtained. In this case, since the surfaces of the electric circuit patterns 1b to 3b are shiny surfaces, the contact areas of the resin films 2a to 4a that are in contact with the shiny surfaces can be ensured, and as a result, the adhesion can be improved. . In this way, the multilayer substrate 100 shown in FIG. 1 is completed.

  The inventors evaluated the peeling strength of the multilayer substrate 100 manufactured as described above. FIG. 4 is a diagram showing a test method for peeling evaluation. Copper foil was adopted as the metal foil constituting the electric circuit patterns 1b to 4b.

  Then, as shown in FIG. 4, for example, in a multilayer substrate composed of two wiring layers, the surface of the upper wiring layer 5 on which the electric circuit pattern is formed is fixed, and the lower wiring layer 6 is connected to the upper layer. The copper foil peel strength was measured when the lower wiring layer 6 was pulled from the upper wiring layer 5 by pulling in the normal direction of the lower surface of the wiring layer 5. For comparison, the peel strength was also measured in the same manner for the copper foil constituting the electric circuit pattern subjected to the roughening treatment on both sides. The result is shown in FIG. The horizontal axis shown in FIG. 5 indicates the number for identifying the sample.

  As shown in FIG. 5, when the surface of the metal foil constituting the electric circuit patterns 1 b to 4 b attached to the resin films 1 a to 4 a is a shiny surface (in the case of no shiny surface roughening treatment), The peel strength may be larger than when the surface of the metal foil constituting the electric circuit patterns 1b to 4b attached to the resin films 1a to 4a is subjected to a roughening treatment (with a shiny surface roughening treatment). Recognize. That is, if the surface of the electric circuit patterns 1b to 4b is a shiny surface, it can be said that the adhesion with the upper resin films 1a to 4a can be improved.

  As described above, in the present embodiment, in each of the wiring layers 1 to 4 constituting the multilayer substrate 100, the surfaces of the electric circuit patterns 1b to 4b provided on one surface of the resin films 1a to 4a are shiny surfaces. It is a feature. Thereby, the adhesive force of the lower-layer electric circuit patterns 1b to 3b and the upper-layer resin films 2a to 4a can be improved.

  In this case, it is preferable that both surfaces of the electric circuit patterns 1b to 4b are shiny surfaces. Thereby, the adhesive force of both surfaces of the electric circuit patterns 1b to 4b and the lower and upper resin films 1a to 4a can be improved.

(Other embodiments)
In the above embodiment, for example, the multilayer substrate 100 is composed of four wiring layers 1 to 4, but the multilayer substrate can be composed of ten or twenty wiring layers.

  When preparing the wiring layers 1 to 4, a metal foil having at least one surface as a shiny surface is pressure-bonded to one surface of the resin films 1a to 4a, but both surfaces are as shiny surfaces. A metal foil can be prepared and the metal foil can be thermocompression bonded to the resin films 1a to 4a.

  The conditions (320 ° C., 5 MPa, 1 hour) for integrating the wiring layers 1 to 4 shown in the above embodiment are examples, and the wiring layers 1 to 4 can be pressed according to other conditions.

1 is a schematic cross-sectional view of a multilayer substrate according to an embodiment of the present invention. It is the schematic which showed the manufacturing process of the multilayer substrate shown by FIG. It is sectional drawing to which the interface of the shiny surface of an electric circuit pattern at the time of laminating | stacking each wiring layer and the other surface of a resin film was expanded. It is the figure which showed the test method of peeling evaluation. It is the figure which showed the evaluation result of peeling strength. It is a figure for demonstrating a subject, (a) when a thermosetting resin is employ | adopted as a resin film, (b) is an electric circuit pattern in the case where a thermoplastic resin is employ | adopted as a resin film, and the upper layer resin film FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1-4 ... Wiring layer, 1a-4a ... Resin film, 1b-4b ... Electric circuit pattern, 10 ... Rust prevention film.

Claims (4)

A multilayer substrate configured by laminating and integrating a plurality of wiring layers (1 to 4),
Each of the plurality of wiring layers (1 to 4)
A resin film (1a-4a) formed of a thermoplastic resin;
A metal foil having at least one surface as a shiny surface is patterned into a wiring pattern, and the surface opposite to the shiny surface is attached to one surface of the resin films (1a to 4a). Electric circuit patterns (1b to 4b)
Among the plurality of wiring layers (1 to 4), one wiring layer (1 to 3) and the upper wiring layer (2 to 4) of the wiring layer (1 to 3) include the one wiring layer ( 1-3), the shiny surface of the electric circuit pattern (1b-3b) and the other surface of the resin film (2a-4a) in the upper wiring layer (2-4) are heat-sealed. Multi-layer board. 2. The multilayer board according to claim 1, wherein the electric circuit patterns (1 b to 3 b) are obtained by patterning a metal foil having a shiny surface on both sides into a wiring pattern. A method for manufacturing a multilayer substrate comprising a plurality of wiring layers (1 to 4) laminated and integrated,
Of the metal foil whose at least one surface is a shiny surface, the surface opposite to the shiny surface is attached to one surface of the resin film (1a to 4a), and the metal foil is patterned into a wiring pattern. A step of preparing the plurality of wiring layers (1 to 4) on which the electric circuit patterns (1b to 4b) are formed;
Forming a rust preventive film (10) only on the surface of each electric circuit pattern (1b-4b) of the plurality of wiring layers (1-4);
In the plurality of wiring layers (1 to 4), one surface of the resin films (1a to 3a) provided with the electric circuit patterns (1b to 3b) is provided with the electric circuit patterns (1b to 4b). A step of sequentially superimposing the respective wiring layers (1 to 4) so as to face the other surface of the resin films (2a to 4a) that are not formed;
Each of the superimposed wiring layers (1 to 4) is heated and relatively moved so that the uppermost wiring layer (4) and the lowermost wiring layer (1) come closer to each other, and pressure is applied. The rust preventive film (10) formed on the circuit pattern (1b to 4b) is thermally decomposed to disappear, and the shiny surface of the electric circuit pattern (1b to 3b) and the resin film (2a to 4a) And a step of heat-sealing the other surface. 4. The method for manufacturing a multilayer substrate according to claim 3, wherein in the step of preparing the plurality of wiring layers (1 to 4), a metal foil having a shiny surface on both sides is used.

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