JP2009123879A - Multilayer wiring board and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer wiring board that improves the durability of electrical conduction between a conductor layer and a conductive paste, and that exhibits high conduction-reliability even under a cold-hot cycling environment. <P>SOLUTION: The multilayer wiring board has an insulating layer 20 with a buit-in via hole 14, a conductive paste 16 that is filled into the via hole 14, a conductor layer 12a that is formed at a position of the via hole 14 at one side of the insulating layer 20 and is electrically connected with the conductive paste 16, and a conductor layer 12b that is formed at a position of the via hole 14 at the other side of the insulating layer 20 and is electrically connected with the conductive paste 16. On the surface in contact with the conductive paste 16 on the conductor layer 12b, provided is a projecting part 50 with a size ensuring to be located within the outer circumferential part of the via hole 14. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

In recent years, electronic devices have become smaller and lighter in addition to higher-frequency and digitized signals, and accordingly, printed wiring boards mounted on electronic devices are also required to have higher densities and multilayers. It has become a thing. In the multilayer wiring board in which the printed wiring board is multilayered, via holes such as IVH (Interstitial Via Hole) are formed in the insulating base material, and the via holes are filled with a conductive paste to obtain conduction between the front and back of the substrate. There are some (see, for example, Patent Document 1).
JP 2003-332747 A

  FIG. 6 is a partial cross-sectional view of an IVH portion in a conventional multilayer wiring board. As shown in FIG. 6, the printed wiring board 100 includes an insulating base material 101 and an adhesive layer 103 that are bonded to each other, and includes an insulating layer 110 in which a via hole 104 is formed at a predetermined location. On the surface of the insulating layer 110 on the insulating base material 101 side, a conductor layer 102 a serving as a circuit pattern is formed at the position of the via hole 104. Further, the inside of the via hole 104 is filled with a conductive paste 105.

  When the printed wiring boards configured as described above are stacked and thermocompression bonded, the conductive paste 105 of each printed wiring board is compressed with high density. As a result, the conductive paste 105 and the conductor layers 102a and 102b are in close contact with each other, and electrical conduction between the front and back of the substrate is obtained. In FIG. 6, a conductor layer 102b disposed below the conductive paste 105 indicates a conductor layer formed on another printed wiring board (not shown) that is laminated.

  The conductive paste 105 used for electrical conduction of the multilayer wiring board as described above is obtained by dispersing a metal filler in a resin binder. The connection strength of the interface between the conductive paste 105 and the conductor layers 102a and 102b is determined by contact between the metal filler sticking into the conductor layers 102a and 102b such as copper foil during thermocompression bonding, and the resin binder and the conductor layers 102a and 102b. Depends on the adhesion strength. If the connection strength here is weak, contact between the metal filler and the copper foil becomes insufficient due to repetitive stresses caused by a cooling and heating cycle in an actual use environment, which may cause a problem in electrical continuity.

  In view of the above-described problems, the present invention improves the durability of electrical conduction between a conductor layer and a conductive paste, and has a highly reliable multilayer wiring board and multilayer wiring board even in a cold cycle environment. It aims at providing the manufacturing method of.

  The first feature of the present invention is that an insulating layer having an interlayer conduction hole therein, a conductive resin composition filled in the interlayer conduction hole, and an interlayer conduction hole are formed on one surface of the insulating layer. A second conductive layer electrically connected to the conductive resin composition and a second conductive layer electrically connected to the conductive resin composition formed on the other surface of the insulating layer at the position of the interlayer conduction hole. The gist of the present invention is a multilayer wiring board having a conductor layer and having a protrusion of a size located within the outer periphery of the interlayer conduction hole on the surface of the second conductor layer in contact with the conductive resin composition.

  According to the multilayer wiring board according to the first feature, it is possible to increase the durability of electrical conduction between the second conductor layer and the conductive resin composition at the interface B shown in FIG. High reliability of conduction can be maintained even in an environment.

  The multilayer wiring board according to the first feature includes a metal layer formed between the conductive resin composition and the first conductor layer, and electrically connected to the conductive resin layer and the first conductor layer. Further, it may be provided.

  According to this multilayer wiring board, durability of electrical conduction between the first conductor layer and the conductive resin composition can be enhanced.

  The second feature of the present invention is that the first conductor layer and the second conductor layer are disposed on both sides of the insulating layer having the interlayer conduction hole therein, and the first conductor layer and the second conductor layer are electrically connected to the interlayer conduction hole. A method of manufacturing a multilayer wiring board in which a wiring board filled with a conductive resin composition to be electrically conductive is laminated, the step of forming a first conductor layer on one surface of the insulating layer; Forming a protrusion having a size located within the outer periphery of the interlayer conduction hole on the surface of the conductor layer opposite to the surface in contact with the insulating layer, and forming a mask layer on the other surface of the insulating layer; A step of forming an interlayer conduction hole having the first conductor layer as a bottom in the insulating layer; a step of filling the interlayer conduction hole with a conductive resin composition; and removing the mask layer to form an insulating layer and a conductive resin composition Thermocompression bonding by laminating multiple wiring boards including the process of exposing the end of the object and the wiring board produced through each process And summarized in that a that process and a method for manufacturing a multilayer wiring board comprising a.

  According to the method for manufacturing a multilayer wiring board according to the second feature, in the laminated multilayer wiring board, the first conductor layer having the protrusion becomes the second conductor layer of another wiring board, and the second conductor layer and the conductive layer are electrically conductive. The durability of electrical conduction between the conductive resin composition and the conductive resin composition can be enhanced, and the conduction reliability can be kept high even in a cold cycle environment.

  The method of manufacturing a multilayer wiring board according to the second feature further includes a step of forming a metal layer on a surface of the first conductor layer on the side of the interlayer conduction hole after the step of forming the interlayer conduction hole, The conductive resin composition may be filled in an interlayer conduction hole having a layer as a bottom.

  According to this method for manufacturing a multilayer wiring board, it is possible to improve the durability of electrical conduction between the first conductor layer and the conductive resin composition at the interface A shown in FIG.

  According to the present invention, there are provided a multi-layer wiring board and a method for manufacturing a multi-layer wiring board having high electric conduction durability between the conductor layer and the conductive paste and having high conduction reliability even in an environment of a thermal cycle. can do.

  Next, embodiments of the present invention will be described with reference to the drawings. In the descriptions of the following aspects, 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 ratios of dimensions and the like are different from actual ones. Accordingly, specific dimensions and the like 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.

(Configuration of multilayer wiring board)
FIG. 1A is a partial cross-sectional view of the multilayer wiring board according to this embodiment, and particularly shows the structure of the IVH portion. A printed wiring board 10 according to the present embodiment includes an insulating base material 11 and an adhesive layer 13 that are bonded to each other, and includes an insulating layer 20 that has a via hole (interlayer conduction hole) 14 at a predetermined location inside. .

  On the surface of the insulating layer 20 on the insulating base material 11 side, a conductor layer 12 a serving as a circuit pattern is formed at the position of the via hole 14. A conductor layer 12b serving as a circuit pattern is formed at the via hole 14 on the surface of the insulating layer 20 on the adhesive layer 13 side. In FIG. 1A, a conductor layer 20b indicates a conductor layer formed on another printed wiring board (not shown) that is laminated. The via hole 14 is filled with the conductive paste 16, and the conductor layer 20a and the conductor layer 20b are electrically connected to the conductive paste 16, respectively, so that the conductor layer 20a and the conductor layer 20b are electrically connected.

  Further, the surface of the conductor layer 20 b that contacts the conductive paste 16 has a protrusion 50 having a size located within the outer periphery of the via hole 14. FIG. 1B is a top view of the multilayer wiring board shown in FIG. In FIG. 1 (b), parts other than the outer shape of the conductor layer 20b and the via hole 14 are omitted. As shown in FIG. 1B, the protrusion 50 provided on the conductor layer 20 b has a circular shape, and the diameter thereof is smaller than the diameter of the via hole 14.

  Further, as shown in FIG. 1A, a metal layer 15 is formed between the conductive paste 16 and the conductor layer 12a. The metal layer 15 is electrically connected to the conductive paste 16 and the conductor layer 12a.

  As the insulating base material 11, for example, a flexible resin film such as polyimide or LCP (Liquid Crystal Polymer) can be used.

  As the conductor layers 12a and 12b, for example, conductive members such as copper foil can be used. Moreover, the protrusion part 50 of the conductor layer 12b can be formed by photography.

  As the adhesive layer 13, for example, a thermoplastic resin film such as thermoplastic polyimide, or a thermosetting resin film such as epoxy, polyester, phenol, or acrylic can be used.

  As the metal layer 15, metals such as copper, nickel, tin, solder, zinc, and gold can be used, and these metals are formed on the surface of the conductor layer 12a on the via hole 14 side by metal plating. As a method of metal plating, either electrolytic plating or electroless plating may be used. The thickness of the plating is not particularly limited, but it takes time to increase the thickness of the plating and the cost is high. Further, a masking film may be used to prevent plating from being deposited on the opposite surface of the via hole 14.

  As the conductive paste 16, a polymer-type conductive paste or the like in which a μm-sized metal filler (copper, tin, silver, or the like) is dispersed in a resin binder and mixed with a viscous medium containing a solvent is used. it can. Further, as a method for filling the conductive paste 16 into the via hole 14, for example, a screen printing method, a dispensing method, an ink jet method or the like can be used.

  By laminating a predetermined number of printed wiring boards 10 configured as described above and thermocompression bonding, the conductor layer 12a and the metal layer 15, the metal layer 15 and the conductive paste 16, and the conductive paste 16 and the conductor layer 12b, respectively. Adhering closely, electrical conduction between the front and back of the substrate is obtained.

(Manufacturing method of multilayer wiring board)
Next, a method for manufacturing a multilayer wiring board according to this embodiment will be described with reference to FIGS. FIGS. 2A to 2I and FIGS. 3J to 3L are schematic cross-sectional views showing manufacturing steps of the multilayer wiring board according to this embodiment. In the embodiments described below, materials, processing methods, and the like are merely examples. That is, the present invention includes various embodiments that are not described herein, and the technical scope of the present invention is determined only by the invention specifying matters according to the scope of claims reasonable from the above description. Is.

  First, as shown in FIG. 2 (a), a laminated plate in which a copper foil conductor layer 12 is bonded to the surface of an insulating base material 11 made of polyimide is used as a starting material. As shown in FIG. 2 (b), photolithography is performed. As a result, a circuit pattern is formed so that only necessary portions become wiring. Hereinafter, the conductor layers 12a and 12b are appropriately referred to as the conductor layer 12.

  Next, as shown in FIG. 2C, the protrusion 50 is formed on the surface of the conductor layer 12 opposite to the surface in contact with the insulating base material 11 by photolithography. Here, in consideration of the positional accuracy, it is necessary to form the protrusion 50 so that the outer periphery of the via hole 14 finally falls within the outer periphery of the via hole 14.

  Next, as shown in FIG. 2D, a thermoplastic polyimide resin film to be the adhesive layer 13 is laminated on the back surface of the insulating base material 11. Subsequently, as shown in FIG. 2E, a plastic film that becomes the masking film 18 is laminated on the surface of the adhesive layer 13. The masking film 18 serves to prevent the conductive paste 16 from being applied to the adhesive layer 13 except inside the via hole 14.

  The material of the masking film 18 is not particularly limited, and plastic films such as polyethylene terephthalate, polyethylene naphthalate, polyfinylene sulfite, polyimide, polypropylene, polyethylene, epoxy resin, silicone resin, phenol resin, and melamine resin can be used. it can. For the lamination of the masking film 18, a roll laminator, a parallel plate press or the like can be used. These methods may be performed in a vacuum.

  Next, as shown in FIG. 2 (f), a carbon dioxide laser is irradiated from a predetermined position on the masking film 18 to form a via hole 14 having the conductor layer 12 as a bottom. In addition to the carbon dioxide laser, for example, a laser such as a UV-TAG laser or an excimer laser can be used to form the via hole 14.

  Further, after the via hole 14 is formed, in order to improve the connection reliability between the conductor layer 12 and the conductive paste 16, a desmear treatment for removing smear (organic contaminants) remaining in the via hole 14 as necessary. May be implemented. Furthermore, in order to remove copper oxide, the inside may be washed with an aqueous solution such as hydrochloric acid or sulfuric acid.

  Next, as shown in FIG. 2G, copper to be the metal layer 15 is formed on the surface of the conductor layer 12 on the via hole 14 side by electrolytic plating. Subsequently, as shown in FIG. 2H, a copper paste to be a conductive paste 16 is filled into the via hole 14 having the metal layer 15 as a bottom by a screen printing method. Further, as shown in FIG. 2 (i), the masking film 18 is removed to expose the adhesive layer 13 and the protrusions 16 a of the conductive paste 16.

  A printed wiring board for one sheet is completed through the above steps (a) to (i). This is produced as much as necessary.

  Next, as shown in FIG. 3 (j), a plurality of printed wiring boards 10 produced in the same process as described above, and a lowermost layer in which a conductor layer 12 serving as a circuit pattern is formed on an insulating base material 11. The printed wiring board 30 is aligned and stacked. The alignment is performed using, for example, a method based on image recognition or a method such as passing a pin through a hole (not shown) provided in each printed wiring board 10. Further, as shown in FIG. 3 (k), the plurality of laminated printed wiring boards 10 are thermocompression bonded by a not-shown press. As a result, the adhesive layer 13 of each printed wiring board 10 and the corresponding insulating base material 11 are bonded to each other to complete a multilayered wiring board 40.

  In addition, by thermocompression bonding, the protruding portion 16a of the conductive paste 16 is pressed against the conductive layer 12b (circuit pattern) of the printed wiring board and is crushed to fill the via hole 14 with high density. At the same time, the conductive paste 16 and the conductor layer 12 are brought into close contact with each other, whereby electrical connection between the front and back of the substrate is obtained.

  Then, as shown in FIG. 3L, a cover lay (film) or a solder resist serving as an insulating protective film 19 is formed so as to cover the surface of the printed wiring board 10 as the uppermost layer.

(Function and effect)
In the multilayer wiring board according to the present embodiment, the printed wiring board disposed in each layer has a protrusion 50 having a size located within the outer periphery of the via hole 14 on the surface of the conductor layer 12b that contacts the conductive paste 16. By providing such a protrusion 50, the connection strength at the interface between the conductor layer 12b and the conductive paste 16 is increased, and the durability of electrical conduction between the conductor layer 12b and the conductive paste 16 is increased. Can do. Further, when a crack occurs at the interface between the conductor layer 12 b and the conductive paste 16, the progress of the crack can be stopped by the protrusion 50. Therefore, according to the multilayer wiring board according to the present embodiment, high conduction reliability can be maintained even under a harsh environment such as a thermal cycle.

  In addition, as shown in FIG. 4, when the outer periphery of the protrusion 50 is located outside the outer periphery of the via hole 14, cracks progress from the interface between the conductor layer 12 b and the conductive paste 16 in the region C located outside. End up. For this reason, in the multilayer wiring board according to the present embodiment, it is important that the outer periphery of the protrusion 50 is located within the outer periphery of the via hole 14.

  According to the multilayer wiring board having the configuration having the protrusion 50 described above, the connection strength at the interface B shown in FIG. 6 described as the conventional configuration can be increased.

  In the multilayer wiring board according to the present embodiment, the printed wiring board disposed in each layer has a metal layer 15 formed on the surface of the conductor layer 12a on the via hole 14 side, and the via hole 14 having the metal layer 15 as a bottom. The inside is filled with the conductive paste 16. As a result, as shown in the partially enlarged view of FIG. 5, the interface between the conductor layer 12a and the metal layer 15 is brought into close contact by metal bonding, so that the stresses F1 and F2 are considered to be most concentrated. The connection strength of the connection portion 17 of the insulating base material 11 / metal layer 15 is higher than the connection strength of the conventional structure without the metal layer 15 (see FIG. 6). For this reason, even when a repeated stress is applied due to the thermal cycle, cracks are unlikely to occur at the interface between the conductor layer 12 a and the conductive paste 16, and the electrical continuity between the conductor layer 12 a and the conductive paste 16 is durable. Can be increased. Therefore, according to the multilayer wiring board according to the present embodiment, high conduction reliability can be maintained even under a harsh environment such as a thermal cycle.

  According to the multilayer wiring board having the metal layer 15 described above, the connection strength at the interface A shown in FIG. 6 described as the conventional configuration can be increased.

(Other embodiments)
Although the present invention has been described according to the above-described embodiments, 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.

  For example, in the multilayer wiring board shown in FIG. 1, it has been described that the conductor layer 12 b disposed on the adhesive layer 13 side has the protrusion 50, but the conductor layer 12 a disposed on the insulating base material 11 side is also the protrusion 50. You may make it the structure which has.

  Further, in the multilayer wiring board shown in FIG. 1, the shape of the protrusion 50 has been described as a circular shape, but the protrusion 50 only needs to have an outer shape smaller than the outer shape of the via hole 14, and the shape is not limited to a circle, but an elliptical shape. It may be a shape or a polygonal shape.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, 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.

  Hereinafter, the substrate for a wiring board according to the present invention will be specifically described with reference to examples, but the present invention is not limited to those shown in the following examples, and the gist thereof is not changed. In the range, it can implement by changing suitably.

Example 1
The multilayer wiring board according to Example 1 was manufactured according to the manufacturing method described in the above embodiment. In the manufacturing process shown in FIG. 2C, the outer periphery of the protrusion 50 is formed so as to be within the outer periphery of the via hole 14, and the difference between the outer periphery of the via hole 14 and the outer periphery of the protrusion 50 is 50 μm.

(Comparative Example 1)
The multilayer wiring board according to Comparative Example 1 was manufactured by the same process as that of Example 1 except that the process of forming the protrusions 50 shown in FIG.

(Comparative Example 2)
The multilayer wiring board according to Comparative Example 2 is the same as Example 1 except that the formation process of the protrusions 50 shown in FIG. 2C and the formation process of the metal layer 15 shown in FIG. It was produced by the same process.

(Evaluation)
As a pretreatment when carrying out the thermal cycle test, the multilayer wiring boards according to Example 1, Comparative Example 1 and Comparative Example 2 were subjected to 30 ° C. and 85% R.D. H. After 24 hours, a heat history of 260 ° C. peak was given three times in a reflow furnace. Then, the -25 degreeC / 125 degreeC cooling-heat cycle test was implemented 5000 cycles and 6000 cycles. And after the test, the presence or absence of electrical disconnection in each multilayer wiring board was confirmed with a tester. Here, when there was a disconnection, cross-sectional observation was performed and the disconnection location was specified. The evaluation results of Example 1, Comparative Example 1 and Comparative Example 2 are shown in Table 1.

  As shown in Table 1, in the multilayer wiring board according to Example 1 in which the protrusions 50 and the metal layer 15 are formed, disconnection does not occur even under the environment of the 6000 cycle cooling cycle, and it is as severe as the cooling cycle. Even in a difficult environment, it was possible to maintain high conduction reliability. On the other hand, in the multilayer wiring board according to Comparative Example 1 in which the protrusions 50 were not formed, disconnection occurred at the interface B shown in FIG. 6 under a 6000 cycle cooling / heating cycle environment. Further, in the multilayer wiring board according to Comparative Example 2 in which the metal layer 15 was not formed, disconnection occurred at the interface A shown in FIG. 6 in a thermal cycle environment of 5000 cycles and 6000 cycles.

  Therefore, by forming the protrusion 50 on the conductor layer 12, the connection strength at the interface between the conductor layer 12b and the conductive paste 16 is increased, and the electrical continuity between the conductor layer 12b and the conductive paste 16 is improved. It was found that the sex can be improved. Further, by forming the metal layer 15, the connection strength at the interface between the conductor layer 12a and the conductive paste 16 is increased, and the durability of electrical conduction between the conductor layer 12a and the conductive paste 16 is increased. I found out that

(A) is sectional drawing which shows the structure of the multilayer wiring board concerning embodiment, (b) is a top view of (a). It is process drawing which shows the manufacturing method of the multilayer wiring board which concerns on embodiment (the 1). It is process drawing which shows the manufacturing method of the multilayer wiring board which concerns on embodiment (the 2). It is a figure for demonstrating the effect | action and effect of the multilayer wiring board which concern on embodiment (the 1). It is a figure for demonstrating the effect | action and effect of the multilayer wiring board which concern on embodiment (the 2). It is sectional drawing which shows the structure of the conventional multilayer wiring board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Printed wiring board 11 ... Insulation base material 12a, 12b ... Conductor layer 13 ... Adhesive material layer 14 ... Via hole (interlayer conduction hole)
15 ... Metal layer 16 ... Conductive paste (conductive resin composition)
17 ... Connection part 18 ... Masking film 19 ... Protective film 20 ... Insulating layer 30 ... Printed wiring board (for the bottom layer)
40 ... Multilayer wiring board 50 ... Protrusions

Claims (4)

An insulating layer having an interlayer conduction hole therein;
A conductive resin composition filled in the interlayer conduction holes;
A first conductor layer formed on one side of the insulating layer at the position of the interlayer conduction hole and electrically connected to the conductive resin composition;
A second conductor layer formed on the other surface of the insulating layer at the position of the interlayer conduction hole and electrically connected to the conductive resin composition;
A multilayer wiring board having a protrusion having a size located within an outer periphery of the interlayer conduction hole on a surface of the second conductor layer in contact with the conductive resin composition.   The method further comprises a metal layer formed between the conductive resin composition and the first conductor layer, and electrically connected to the conductive resin layer organism and the first conductor layer. 2. The multilayer wiring board according to 1. Conductivity that electrically arranges the first conductor layer and the second conductor layer in the interlayer conduction hole by arranging the first conductor layer and the second conductor layer on both sides of the insulating layer having the interlayer conduction hole therein. A method for producing a multilayer wiring board obtained by laminating wiring boards filled with a resin composition,
Forming the first conductor layer on one surface of the insulating layer;
Forming a protrusion having a size located within the outer periphery of the interlayer conduction hole on the surface of the first conductor layer opposite to the surface in contact with the insulating layer;
Forming a mask layer on the other surface of the insulating layer;
Forming the interlayer conduction hole having the first conductor layer as a bottom in the insulating layer;
Filling the interlayer conductive holes with the conductive resin composition;
Removing the mask layer to expose the insulating layer and the end of the conductive resin composition;
And a step of laminating a plurality of wiring boards including the wiring board produced through each of the above steps and thermocompression bonding. After the step of forming the interlayer conduction hole, further comprising the step of forming a metal layer on the surface of the first conductor layer on the interlayer conduction hole side,
The method for producing a multilayer wiring board according to claim 3, wherein the conductive resin composition is filled in the interlayer conduction hole having the metal layer as a bottom.

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