JP2005093517A - Multilayer wiring board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a multilayer wiring board, wherein sharp reduction in the manufacturing cost is realized by planning simplification of manufacturing process and reduction in the environmental load. <P>SOLUTION: A first wiring layer 12 composed of conductive paste is formed on a substrate 11, and a bump electrode 13 composed of the conductive paste is formed on the first wiring layer 12. By using a screen printing version 21, having a mask pattern which shields a region having a predetermined gap 23 from an outer periphery of the bump electrode 13, the bump electrode 13 and the gap 23 are formed, and an insulating resin layer 14, composed of polymer resin, is formed on the first wiring layer 12. The viscosity of polymer resin layer is reduced by heating the insulating resin layer 14, the gap 23 is filled with fluidized polymer resin, and the polymer resin is cured, thereby forming the insulating resin layer 14. A second wiring layer 15 composed of conductive paste is formed on the insulating resin layer 14. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a build-up multilayer wiring board formed by laminating a wiring layer and an insulating resin layer on a substrate and a method for manufacturing the same.

  In recent years, with the progress of miniaturization, thinning, and price reduction of electronic devices typified by mobile phones and personal computers, market needs for miniaturization, high functionality, and low price of wiring boards are increasing. For this reason, a multilayer wiring board has attracted attention.

As a conventional method for manufacturing a multilayer wiring board, there are the following methods. First, a conductor film is formed on a ceramic substrate using a sputtering method. Next, a photoresist film is applied on the substrate on which the conductor film is formed, and an opening through which the conductor film is exposed is formed by a photolithography process at a position where the protruding electrode is formed. Next, a protruding electrode such as nickel (Ni), copper (Cu), or gold (Au) is formed in the opening by a plating process. Then, after the photoresist film is dissolved and removed, a predetermined pattern processing is performed on the conductor film by a photolithography process and an etching process to form a first wiring layer. Next, an insulating resin film, such as a photosensitive polyimide precursor, is applied on the substrate including the first wiring layer so as to be thicker than the protruding electrode, and the protruding electrode is exposed by a photolithography process and an etching process. The insulating resin layer is formed by curing. Next, a second wiring layer connected to the protruding electrode is formed on the insulating resin layer. Thereby, a two-layer wiring board is formed. In the case of further multilayering, these steps are repeated (for example, Patent Document 1).
Japanese Patent Laid-Open No. 06-6034

  In the above conventional method, since a photolithography process or a plating process is used, a high-definition multilayer wiring board can be manufactured. However, such a method has a problem that not only the manufacturing process is complicated and the manufacturing cost is increased, but also environmental measures such as waste liquid treatment caused by a plating process or an etching process are required.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a multilayer wiring board capable of simplifying the manufacturing process and reducing the environmental load, and a method for manufacturing the same, by solving the conventional problems.

  In order to solve the above problems, a multilayer wiring board of the present invention includes a first wiring layer formed on the substrate, a protruding electrode formed on the first wiring layer, and a first wiring layer. An insulating resin layer formed on the substrate and adjacent to the outer peripheral portion of the protruding electrode is formed on the insulating resin layer, and an insulating resin layer formed thinner than the thickness of the region on the first wiring layer And a second wiring layer connected to the protruding electrode.

  With this configuration, it is possible to fabricate a multilayer wiring board with a simple and inexpensive method such as a printing method, and it is possible to reduce variations in contact resistance between the second wiring layer and the protruding electrode, and to achieve high performance multilayer wiring. A substrate can be realized.

  In order to solve the above problems, a method for manufacturing a multilayer wiring board of the present invention includes a step of forming a first wiring layer on a substrate, a step of forming a protruding electrode on the first wiring layer, A step of forming an insulating resin layer on the substrate including the first wiring layer with a predetermined gap from the outer peripheral portion of the protruding electrode; and heating the insulating resin layer to insulate the insulating resin in the gap A method comprising the steps of continuously forming an insulating resin layer to the outer periphery of the protruding electrode by flowing the layer and forming a second wiring layer connected to the protruding electrode on the insulating resin layer Consists of.

  By this method, since the insulating resin layer is not formed on the upper surface portion of the protruding electrode formed on the first wiring layer, it is not necessary to remove the insulating resin layer by the photolithography process and the etching process. Further, when the protruding electrodes are formed, if the shapes thereof are aligned, the area of the protruding electrodes in contact with the second wiring layer can be made substantially the same. Variation in contact resistance with the electrode can be suppressed to a very small level. Note that the adjacent region portion described above is an insulating resin layer portion formed by flowing in a predetermined gap provided in the outer peripheral portion of the protruding electrode in this manufacturing method.

  Moreover, the manufacturing method of the multilayer wiring board of this invention consists of the method of forming the thickness of an insulating resin layer thinner than the thickness of a protruding electrode. By this method, even when the insulating resin layer is heated and fluidized, the insulating resin layer does not wrap around to the upper surface side of the protruding electrode, and a multilayer wiring board having a smaller contact resistance is manufactured by a simple process. be able to.

  Moreover, the manufacturing method of the multilayer wiring board of this invention consists of a method in which an insulating resin layer is formed by a printing system using a resin paste. By this method, it is easy to form an insulating resin layer on a substrate including the first wiring layer with a predetermined gap from the outer periphery of the protruding electrode, and the manufacturing process is greatly simplified. it can.

  In addition, the method for manufacturing a multilayer wiring board according to the present invention uses a hot melt sheet in which an insulating resin layer is formed with an opening having a predetermined gap from the outer periphery of the protruding electrode. The hot melt sheet is attached to the substrate including the first wiring layer and aligned with the electrode-like electrode.

  By this method, it is only necessary to attach the opening to the substrate after the opening is processed in advance by, for example, punching, so that the process of forming the insulating resin layer can be greatly simplified. Furthermore, since it is in the form of a sheet, variations in thickness are reduced, and even when three or more layers of multilayer wiring are formed, a multilayer wiring board having a relatively flat surface can be obtained. It can be carried out.

  In the method for producing a multilayer wiring board according to the present invention, the resin paste or the hot melt sheet includes at least one of a thermosetting resin and a photocurable resin. By this method, the step of fluidizing and continuously forming the insulating resin layer up to the outer periphery of the protruding electrode can be performed separately from the step of curing the insulating resin layer. The insulating resin layer can be reliably formed in a region other than the upper surface portion. For example, in the case of using a thermosetting resin, the heat for fluidization is after the fluidization to a temperature lower than the temperature at which the network structure is formed above the fluidization temperature (generally called the curing start temperature). Curing of may be set to a temperature at which a network structure is obtained. Note that this step may be performed continuously. In addition, when using a photo-curing resin, fluidization is promoted by heating and an insulating resin layer is continuously formed up to the outer peripheral portion of the protruding electrode, and then cured by irradiation with ultraviolet rays or the like. If necessary, it may be further heat-cured.

  The method for manufacturing a multilayer wiring board according to the present invention includes a method in which the first wiring layer, the second wiring layer, and the protruding electrodes are formed by applying a conductive paste and thermally curing. By this method, all processes including the wiring layer can be formed by, for example, a printing method or a drawing method, so that not only the manufacturing process can be simplified but also the manufacturing equipment cost can be reduced.

  The multilayer wiring board according to the present invention and the method for manufacturing the multilayer wiring substrate are provided by forming a gap portion in the protruding electrode to form an insulating resin layer, and fluidizing the gap portion to continuously form the insulating resin layer. is there.

  As a result, the photolithography process and the etching process are eliminated, or the number of times is reduced, and the plating process is eliminated, so that the manufacturing process can be simplified. In addition, waste liquid treatment of a photolithographic process, an etching process, and a plating process is also reduced, and an environmental load can be reduced.

(Embodiment)
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a cross-sectional view schematically showing a main part of a multilayer wiring board according to an embodiment of the present invention. In the embodiment of the present invention, a multilayer wiring board having a two-layer wiring layer will be described as an example.

  In the multilayer wiring board according to the embodiment of the present invention, as shown in FIG. 1, a first wiring layer 12 is formed on a substrate 11, and a second wiring layer 15 is formed on the first wiring layer 12. A protruding electrode 13 is formed at a location where electrical connection is made. The insulating resin layer 14 is formed on the entire surface of the substrate 11 including on the first wiring layer 12. The insulating resin layer 14 is formed so that the thickness of the adjacent region portion 14a adjacent to the outer peripheral portion of the protruding electrode 13 is smaller than the thickness of the region portion on the first wiring layer 12 that is out of the adjacent region portion 14a. ing.

  Further, the thickness of the region on the first wiring layer 12 that is out of the adjacent region 14 a is formed to be thinner than the protruding electrode 13. That is, the thickness (h2) of the insulating resin layer 14 is formed thinner than the thickness (h1) of the protruding electrode 13. Such a thickness structure can be easily obtained by a manufacturing method described later. Note that the thickness of the insulating resin layer 14 is such that the insulating resin layer 14 does not cover the upper surface portion 13 a of the protruding electrode 13 when the insulating resin layer 14 flows to the outer peripheral portion of the protruding electrode 13. It is.

  Further, a second wiring layer 15 connected to the protruding electrode 13 is formed on the insulating resin layer 14 to constitute the multilayer wiring board according to the embodiment of the present invention.

  Moreover, as the substrate 11, a heat-resistant substrate such as an epoxy resin containing glass fiber or a ceramic plate, a polyester resin such as polyethylene terephthalate (PET) or a polyethylene terephthalate copolymer (PETG), acrylonitrile butadiene styrene resin (ABS resin), Any film or sheet made of polycarbonate or polyimide may be used as long as it is used for a normal circuit board. In particular, a film-like or sheet-like substrate can be made as thin as 50 μm to 400 μm, and thus is preferable in that it is effective for thinning a multilayer wiring substrate.

  The first wiring layer 12, the second wiring layer 15, and the protruding electrode 13 are made of a single substance such as gold (Au), silver (Ag), copper (Cu), nickel (Ni), palladium (Pd), or the like. Screen printing, stencil printing, drawing printing, etc. using conductive paste obtained by dispersing and mixing conductive particles, such as an alloy of palladium (Pd) and silver (Ag), refined to 0.1 μm to 20 μm in a binder If this printing method is used, it can be formed easily and at low cost. In particular, a conductive paste using a thermosetting resin or a photocurable resin as a binder is preferable in that the adhesive strength is high and the strength of the wiring layer and the protruding electrode itself can be increased. In addition, when it is necessary to make the electrical resistance of a wiring layer still smaller, it is good to use the silver nano paste which made the particle size of silver (Ag) particles 100 nm or less. Further, when it is necessary to make the electric resistance of the protruding electrode 13 lower than that of the conductive paste, the protruding electrode 13 may be a metal electrode made of a metal such as copper (Cu).

  The resin material used for the insulating resin layer is a thermosetting resin such as unsaturated polyester resin, epoxy resin, acrylic resin, polyimide resin or photocurable resin, or olefin resin, polycarbonate, polyethylene terephthalate, polyurethane resin. A thermoplastic resin such as That is, any resin may be used as long as it is excellent in electrical insulation and flows with reduced viscosity by heating.

  Next, the manufacturing method of the multilayer wiring board in embodiment of this invention is demonstrated.

  FIG. 2 is a process cross-sectional view of the main part for explaining the method for manufacturing a multilayer wiring board in the embodiment of the present invention. In addition, the same code | symbol is attached | subjected about the same element as FIG.

  First, as shown in FIG. 2A, a conductive paste containing a thermosetting binder is used to form a conductive paste on the substrate 11 by a normal printing method such as screen printing, drawing printing, or stencil printing. A wiring pattern is formed. After forming this wiring pattern, the first wiring layer 12 is formed by heating and curing.

  Next, as shown in FIG. 2 (B), the same conductive paste as above is used to form protrusions on the first wiring layer 12 where electrical connection with the second wiring layer 15 described later is required. The electrode pattern is printed. In this case, since it is necessary to relatively increase the thickness to increase the ratio of thickness to width, that is, the aspect ratio, the viscosity of the conductive paste is increased, printing by a drawing method or printing is performed a plurality of times. Thereafter, the protruding electrode 13 is formed by heat curing.

  Next, as shown in FIG. 2C, a printing plate having a shielding area 24 that shields an area including a predetermined gap from the outer periphery of the protruding electrode 13 is prepared. When the protruding electrode 13 is formed by the screen printing method or the stencil printing method, the screen printing plate 21 or the shielding region portion 24 of the stencil printing plate 21 and the protruding electrode 13 are aligned. Thereafter, printing is performed on the first wiring layer 12 and the surface of the substrate 11 by using a resin paste obtained by pasting an insulating resin material for printing. By this printing, the insulating resin layer 14 is not formed from the outer peripheral portion of the protruding electrode 13 to the predetermined gap portion 23 as shown in FIG. It is formed.

  In addition, when a resin containing at least one of a thermosetting resin and a photocurable resin is used as the insulating resin layer 14, a step of heating and reducing the viscosity to increase fluidity and filling the gap portion 23; Since the curing step can be divided as necessary, the range of production conditions is widened, which is preferable. For example, when a thermosetting resin is used, the heating for fluidization may be performed at a temperature equal to or higher than the fluidization temperature and lower than a temperature at which a network structure is formed (generally, a temperature called a drop start temperature). As the viscosity at this time, it is necessary to select an optimum value according to the dimension of the gap portion 23 to be set, and it is desirable that the viscosity be 6 Pa · s or more and 10 Pa · s or less. Curing after fluidization may be performed at a temperature at which a network structure is obtained. Note that this step may be performed continuously. In the case of using a photo-curing resin, if fluidization is promoted by heating and the insulating resin layer 14 is continuously formed up to the outer peripheral portion of the protruding electrode 13, it is cured by irradiation with ultraviolet rays or the like. Good.

  Next, as shown in FIG. 2D, the insulating resin layer 14 is heated to lower the viscosity, and the insulating resin layer 14 flows into the gap 23 and continues to the outer periphery of the protruding electrode 13. A typical layer is formed. At this time, the gap 23 is filled with the flowing insulating resin layer 14 to form the adjacent region portion 14a. The thickness of the adjacent region portion 14a is the first of the positions outside the adjacent region portion 14a. It becomes thinner than the thickness of the insulating resin layer 14 on one wiring layer 12. This is because the insulating resin layer 14 flowing into the gap portion 23 is limited to the peripheral portion of the protruding electrode 13, and the insulating resin layer 14 at a position greatly deviated from this hardly flows.

  Further, since the insulating resin layer 14 is formed thinner than the thickness of the protruding electrode 13, the insulating resin layer 14 is formed on the upper surface portion 13a of the protruding electrode 13 even if the insulating resin layer 14 is fluidized. It can be surely prevented from going around. Therefore, the contact area between the protruding electrode 13 and the second wiring layer 15 does not vary, and variation in contact resistance can be greatly suppressed. The size of the gap 23 is determined by optimization in advance according to the size of the protruding electrode 13, the printing accuracy of screen printing, and the viscosity of the insulating resin layer 14 during heating. After the insulating resin layer 14 is continuously formed up to the outer peripheral portion of the protruding electrode 13, if the insulating resin layer 14 is further cured by heating or ultraviolet irradiation as necessary, the final cured state is obtained. The insulating resin layer 14 is obtained.

  Next, as shown in FIG. 2E, a conductive paste is printed on the insulating resin layer 14 by, for example, a screen printing method to form the second wiring layer 15. At this time, since the protruding electrode 13 contacts not only the second wiring layer 15 and the upper surface portion 13a but also a part of the outer peripheral portion, the contact resistance can be reliably reduced. As a result, a multilayer wiring board in which the first wiring layer 12 and the second wiring layer 15 are conducted through the protruding electrodes 13 is obtained.

  In the case of further multilayering, since the same process can be performed by repeating the above steps, the description is omitted.

  Specific examples of the multilayer wiring board of the present invention will be described below.

  In this example, a sheet made of polyethylene terephthalate (PET) having a thickness of 100 μm was used as the substrate 11.

  The first wiring layer 12 formed on the substrate 11 used a screen printing method. The screen plate has a mesh wire diameter of 25 μm and a photosensitive emulsion layer thickness of 10 μm. As the conductive paste, the conductive particles consisted of mixed particles of spherical silver (Ag) and scaly silver (Ag), and the binder was a thermosetting epoxy resin. The blending ratio was 25 parts by weight of the binder with respect to 75 parts by weight of the conductive particles. After a wiring pattern having electrode pads having a diameter of 0.6 mm is printed on the substrate 11 by the screen printing method, the substrate 11 is placed in a hot air circulation furnace set at 130 ° C. and heated for 10 minutes, The first wiring layer 12 having a film thickness of 20 μm to 30 μm was formed on the substrate 11 by curing.

  Thereafter, the protruding electrode 13 is formed under the following conditions. In the formation of the protruding electrode 13, a stencil printing method was used. As the conductive paste, the same paste as that used when forming the first wiring layer 12 was used. As a stencil plate in the stencil printing method, an opening having a diameter of 0.3 mm, that is, an opening corresponding to the outer shape of the protruding electrode 13 was provided, and the thickness of the plate was 80 μm. After the conductive paste is printed on the electrode pads of the first wiring layer 12, the substrate 11 is placed in a hot air circulating furnace set at 130 ° C. and heated for 10 minutes to cure the conductive paste and to have a height of approximately about the electrode pads. A protruding electrode 13 of 80 μm was formed.

  Next, the insulating resin layer 14 was formed with a predetermined gap from the outer peripheral portion of the protruding electrode 13, and the method was as follows. The same method as the screen printing method in which the first wiring layer 12 was formed was used. As the resin paste, an ultraviolet curing and thermosetting epoxy resin was used, and its viscosity was 30 Pa · s to 50 Pa · s (25 ° C.). The screen plate had an opening diameter of 0.5 mm so that a gap 23 of 0.1 mm from the outer periphery of the protruding electrode 13 was provided. In addition, although the optimal magnitude | size of this gap | interval part 23 changes with the viscosity of the resin paste to be used, the range of 0.05 mm-0.2 mm is favorable in general. Using this screen plate, a resin paste was printed on the entire surface of the substrate 11 including the first wiring layer 12 to a thickness of 25 μm to 30 μm.

  Then, the whole board | substrate 11 was hold | maintained for 1 minute-5 minutes in the hot air circulating furnace set to 50 to 60 degreeC. As a result, the viscosity of the resin paste decreased to about 10 Pa · s, and it became easy to flow. With this resin paste, the resin paste flowed into the gap 23, and the adjacent region portion 14 a was formed.

  In addition, in order to improve the wettability with the resin on the side surface of the protruding electrode 13, application of a resin modifying substance such as a silane coupling agent or the surface smoothness of the side surface may be reduced.

After the insulating resin layer 14 is continuously formed up to the outer peripheral portion of the protruding electrode 13 in this way, ultraviolet rays (50 mJ / cm ² ) are irradiated, and the substrate 11 is further placed in a hot air circulating furnace set at 150 ° C. The insulating resin layer 14 cured by heating for 30 minutes was formed. As a result, the insulating resin layer 14 in a state of flowing to the protruding electrode 13 was obtained. However, since the thickness at this time is 25 μm to 30 μm, this process was performed once again to obtain a thickness of 50 μm to 60 μm as a whole. Even after this step, the insulating resin layer 14 did not adhere to the upper surface portion 13a of the protruding electrode 13.

  Next, the second wiring layer 15 was formed on the insulating resin layer 14 under the same conditions as the method for forming the first wiring layer 12.

  Electrical measurement of the multilayer wiring board obtained as described above was performed. The measurement was evaluated based on the electrical resistance between the first wiring layer 12 and the second wiring layer 15, that is, the absolute value of the electrical resistance via the protruding electrode 13 and its variation. As a result, it was confirmed that the resistance value was in the range of 5 mΩ to 10 mΩ, and the variation was very small and a multilayer wiring board with good reproducibility was obtained.

  The multilayer wiring board according to the present invention is not limited to the configuration shown in FIG. 1, but can be applied to a multilayer wiring board in which wirings are laminated in three or more layers.

  Another method for forming the insulating resin layer 14 may be a method using a hot melt sheet in which a resin such as polyolefin resin, synthetic rubber, polyester resin, or polyurethane resin is formed into a sheet. That is, a hot melt sheet in which an opening having a predetermined gap from the outer peripheral portion of the protruding electrode 13 is formed in a position corresponding to the protruding electrode 13 in advance is pasted on the first wiring layer 12. May be. Since this method can form the insulating resin layer 14 with a uniform thickness, it is suitable for a method of manufacturing a multilayer wiring having three or more layers that requires the dimensional accuracy of the insulating resin layer 14.

  The present invention can be used in a general electronic device including a device using a multilayer wiring board, for example, a mobile device such as a mobile phone, a notebook computer, a camera-integrated VTR, and the industrial applicability is very wide. large.

Sectional drawing which shows the principal part which showed the multilayer wiring board in embodiment of this invention typically 5A is a process cross-sectional view of a main part for explaining a method for manufacturing a multilayer wiring board in an embodiment of the present invention. FIG. 5A is a first wiring layer forming process diagram, FIG. Resin layer forming process diagram (D) Adjacent region forming process diagram (E) Second wiring layer forming process diagram

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Board | substrate 12 1st wiring layer 13 Projecting electrode 13a Upper surface part 14 Insulating resin layer 14a Adjacent area | region 15 2nd wiring layer 21 Screen printing plate (stencil printing plate)
23 Gap 24 Shielding area h1 Thickness of protruding electrode h2 Thickness of insulating resin layer

Claims (8)

A first wiring layer formed on the substrate;
A protruding electrode formed on the first wiring layer;
An insulating property formed on the substrate including the first wiring layer and formed so that the thickness of the adjacent region adjacent to the outer peripheral portion of the protruding electrode is thinner than the thickness of the region on the first wiring layer A resin layer;
A multilayer wiring board comprising: a second wiring layer formed on the insulating resin layer and connected to the protruding electrode. Forming a first wiring layer on the substrate;
Forming a protruding electrode on the first wiring layer;
Forming an insulating resin layer on the substrate including the first wiring layer with a predetermined gap from the outer periphery of the protruding electrode;
Heating the insulating resin layer to flow the insulating resin layer in the gap to continuously form the insulating resin layer up to the outer periphery of the protruding electrode;
Forming a second wiring layer connected to the protruding electrode on the insulating resin layer. 3. The method of manufacturing a multilayer wiring board according to claim 2, wherein the insulating resin layer is formed thinner than the protruding electrode. 4. The method for manufacturing a multilayer wiring board according to claim 2, wherein the insulating resin layer is formed by a printing method using a resin paste. The insulating resin layer is formed by aligning the opening and the protruding electrode using a hot melt sheet in which an opening having a shape having a predetermined gap is formed from the outer periphery of the protruding electrode. 4. The method for manufacturing a multilayer wiring board according to claim 2, wherein the hot melt sheet is attached to the substrate including the first wiring layer. The method for manufacturing a multilayer wiring board according to claim 4, wherein the resin paste contains at least one of a thermosetting resin and a photocurable resin. The method for manufacturing a multilayer wiring board according to claim 5, wherein the hot melt sheet contains at least one of a thermosetting resin and a photocurable resin. 4. The multilayer wiring board according to claim 2, wherein the first wiring layer, the second wiring layer, and the protruding electrode are formed by applying a conductive paste and thermally curing. 5. Manufacturing method.

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