JP2014003268A - Wiring board manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a wiring board which is thin and has high density wiring and less warpage.SOLUTION: A wiring board manufacturing method comprises: applying a tensile stress to an insulation layer 1 by copper foils F2, F3 fastened to both principal surfaces of the insulation layer 1, respectively, by performing stretch processing on the copper foils F2, F3 of stretching the copper foils F2, F3 in a direction parallel with the principal surface of the insulation layer 1; subsequently forming a wiring conductor 2 on one principal surface of the insulation layer 1 by etching a copper foil F1 in a predetermined wiring pattern; subsequently laminating a prepreg P2 and the copper foil F3 on the one principal surface of the insulation layer 1 and fastening an insulation layer 3 to the one principal surface of the insulation layer 1 and fastening the copper foil F3 to an outside principal surface of the insulation layer 3 by hardening the prepreg P2; and subsequently removing the copper foils F2, F3 by etching to release the tensile stress applied by the copper foils F2, F3 to the insulation layers 1, 3.

Description

  The present invention relates to a method of manufacturing a wiring board, and more specifically, a first wiring conductor is formed on a first insulating layer formed by curing a first prepreg, and a second prepreg is further formed thereon. The present invention relates to a method for manufacturing a wiring board including a step of forming a second insulating layer by laminating and curing.

  Recently, wiring boards for mounting electronic components such as semiconductor elements are often required to be thin and high-density wiring. As a method of manufacturing a wiring board that meets such requirements, after forming a first wiring conductor made of copper foil on one main surface of a first insulating layer formed by curing a first prepreg, A second prepreg is laminated and cured on the main surface of the first insulating layer to form a second insulating layer, and then the second insulating layer is formed from the other main surface of the first insulating layer. Forming a plurality of first via holes reaching the first wiring conductor and forming a plurality of second via holes reaching the first wiring conductor from the outer main surface of the second insulating layer; A second wiring conductor made of copper plating is formed in the other main surface and the first via hole, and a third wiring conductor made of copper plating is formed in the outer main surface of the second insulating layer and in the second via hole. To form a thin and high-density wiring board. There is a method to.

  However, according to this method, when forming the second insulating layer by laminating and curing the second prepreg on one main surface of the first insulating layer formed by curing the first prepreg, Curing shrinkage occurs in the two insulating layers. As a result, a large warp in which the second insulating layer side becomes concave is generated in the wiring board due to the force of the second insulating layer to cure and shrink.

JP 2003-46249 A

  It is an object of the present invention to provide a method for manufacturing a wiring board with a small warp and a thin and high-density wiring.

The method for manufacturing a wiring board according to the present invention includes laminating a first copper foil on one main surface of a first prepreg and a second copper foil on the other main surface and curing the first prepreg. A first step of fixing the first copper foil to one main surface of the first insulating layer formed by curing the first prepreg and the second copper foil to the other main surface;
By applying a stretching process to the first and second copper foils in a direction parallel to the main surface, the main insulating layer is formed on the first insulating layer by the stretched first and second copper foils. A second step of applying a tensile stress in a direction parallel to the surface;
A third step of forming a first wiring conductor made of the first copper foil on the one main surface by etching the first copper foil into a predetermined wiring pattern;
A second prepreg and a third copper foil are stacked on the outer main surface of the second prepreg on the one main surface on which the first wiring conductor is formed, and the second prepreg is cured. Thus, the second insulating layer formed by curing the second prepreg on the one main surface and the third copper foil fixed on the outer main surface of the second insulating layer are fixed. Process,
Etching and removing the second copper foil fixed to the other main surface of the first insulating layer and the third copper foil fixed to the outer main surface of the second insulating layer, A fifth step of releasing the tensile stress imparted to the first insulating layer by a second copper foil;
A plurality of first via holes reaching the first wiring conductor from the other main surface to the first insulating layer and a plurality of reaching the first wiring conductor from the outer main surface to the second insulating layer. A sixth step of forming a second via hole;
A second wiring conductor made of copper plating is formed in the other main surface of the first insulating layer and in the first via hole, and the outer main surface of the second insulating layer and the second via hole are formed. And a seventh step of forming a third wiring conductor made of copper plating therein.

  According to the method for manufacturing a wiring board of the present invention, in the second step, the first and second copper foils fixed to both main surfaces of the first insulating layer are parallel to the main surface of the first insulating layer. By applying a stretching process that stretches in any direction, a tensile stress is applied to the first insulating layer in the direction along the main surface by the stretched first and second copper foils. After that, in the fourth step, when the second prepreg and the third copper foil are laminated on one main surface of the first insulating layer and the second prepreg is cured, the second insulation is obtained. Due to the hardening shrinkage of the layer, the second insulating layer is pulled by the first insulating layer and the third copper foil in the direction along the main surface. Thereafter, in the fifth step, when the second and third copper foils are removed by etching, the tensile stress applied to the first insulating layer and the second insulating layer is released, and the first and second insulating layers are released. The layers try to shrink together. As a result, the warping force is canceled by the contraction of the first and second insulating layers, and the occurrence of warping is reduced. Therefore, it is possible to provide a wiring board with small warpage.

1A to 1C are schematic cross-sectional views for each step for explaining an example of an embodiment of a method for manufacturing a wiring board according to the present invention. 2D to 2G are schematic cross-sectional views for each process for explaining an example of the embodiment of the method for manufacturing a wiring board according to the present invention. 3 (h) to 3 (k) are schematic cross-sectional views for each process for explaining an example of the embodiment of the method for manufacturing a wiring board according to the present invention. FIG. 4 is a schematic cross-sectional view for explaining an example of another embodiment of the method for manufacturing a wiring board of the present invention.

  Next, an example of an embodiment of the method for manufacturing a wiring board according to the present invention will be described with reference to FIGS.

  First, as shown in FIG. 1A, a first prepreg P1, a first copper foil F1, and a second copper foil F2 are prepared. The first prepreg P1 is formed, for example, by impregnating a glass cloth with a thermosetting resin such as an epoxy resin or a bismaleimide triazine resin and semi-curing it. The dimensions of the first prepreg P1 are, for example, a thickness of 40 μm, a length of 500 mm, and a width of 600 mm. Moreover, the 1st copper foil F1 and the 2nd copper foil F2 consist of electrolytic copper foil. The dimensions of the first copper foil F1 and the second copper foil F2 are, for example, 18 μm in thickness, and the vertical and horizontal dimensions are substantially the same as those of the first prepreg P1.

  Next, as shown in FIG. 1B, the first copper foil F1 is laminated on one main surface of the first prepreg P1, and the second copper foil F2 on the other main surface is laminated. By thermally curing the prepreg P1, the first copper foil F1 is fixed to one main surface of the first insulating layer 1 formed by curing the first prepreg P1, and the second copper is fixed to the other main surface. The foil F2 is fixed. For example, a vacuum press apparatus is used for lamination, and an oven is used for thermosetting. In addition, you may use a commercially available double-sided copper-clad board instead of performing the process demonstrated by Fig.1 (a), (b) by itself.

  Next, as shown in FIG. 1C, the first copper foil F <b> 1 and the second copper foil F <b> 2 are subjected to a stretching process that extends in a direction parallel to the main surface of the insulating layer 1. For such a stretching process, for example, a belt sander S is used. By this stretching process, a tensile stress T1 in a direction parallel to the main surface is applied to the first insulating layer 1. In addition, not only a belt sander but other apparatuses, such as a roll sander and a rolling roll, can also be used for an extending | stretching process. In the case of using a belt sander, it is preferable to use a polishing belt having a count of about # 320 to # 1000 and perform stretching on both copper foils F1 and F2. When the count of the polishing belt is less than # 320, deep polishing marks remain on the surfaces of the copper foils F1 and F2, and it is difficult to form fine wiring due to the influence. Moreover, when the count of the polishing belt exceeds # 1000, the force for stretching the copper foils F1 and F2 becomes weak, and it becomes difficult to apply sufficient stretching.

  Next, as shown in FIG. 2 (d), the first copper foil F1 is etched into a predetermined wiring pattern using a known subtractive method, so that the first main surface of the insulating layer 1 has a first surface. The wiring conductor 2 is formed. The first wiring conductor 2 includes a plurality of lands for connecting to a second wiring conductor 6 and a third wiring conductor to be described later via a first via hole 4 and a second via hole 5 to be described later. Yes. The diameter of the land is 150 μm.

  Next, as shown in FIG. 2E, a second prepreg P2 and a third copper foil F3 are prepared. The second prepreg P2 is made of substantially the same material and the same dimensions as the first prepreg P1. The third copper foil F3 is made of substantially the same material and the same size as the first and second copper foils F1 and F2. In addition, instead of preparing the second prepreg P2 and the third copper foil F3 separately, the one-side copper foil with the third copper foil F3 laminated in advance on one main surface of the second prepreg P2 is attached. A prepreg may be used.

  Next, as shown in FIG. 2 (f), the second prepreg P2 and the third copper foil F3 are formed on one main surface of the first insulating layer 1 on which the first wiring conductor 2 is formed. The insulating layer 3 formed by curing the second prepreg P2 is fixed to one main surface of the insulating layer 1 by laminating the layers one after another and thermosetting the second prepreg P2. The third copper foil F3 is fixed to the main surface. At this time, since the insulating layer 3 undergoes curing shrinkage when the second prepreg P2 is thermally cured, the first insulating layer 1 and the third copper foil F3 are parallel to the main surface of the second insulating three layer. A tensile stress T2 in a specific direction is applied. For example, a vacuum press apparatus is used for lamination, and an oven is used for thermosetting.

  Next, as shown in FIG. 2G, the second copper foil F2 and the third copper foil F3 are removed by etching. As a result, the tensile stress T1 applied by the second copper foil F2 and the tensile stress T2 applied by the third copper foil F3 are released. As a result, since both the first insulating layer 1 and the second insulating layer 3 try to contract, the warping force is canceled and the occurrence of warping is reduced. Therefore, according to the present invention, it is possible to provide a wiring board with small warpage. When the second and third copper foils F2 and F3 are removed by etching, the second and third copper foils F2 and F3 are formed in a frame shape on the outer periphery of the first and second insulating layers 1 and 3. It is preferable to leave it in The copper foils F2 and F3 remaining in such a frame shape can reinforce the mechanical strength in the laminate of the first insulating layer 1 and the second insulating layer 3, and the second and second described later. When the third wiring conductors 6 and 7 are formed, these remaining copper foils F2 and F3 can be used as connection electrodes connected to the power supply terminals of the electroplating apparatus that supplies electric charges for electroplating. . It should be noted that the outer peripheral portion where the copper foils F2 and F3 are left is a discarding area that cannot be a wiring board, and is cut out after the wiring board is formed.

  Next, as shown in FIG. 3 (h), a plurality of first via holes 4 reaching the first wiring conductor 2 from the other principal surface are formed in the first insulating layer 1, and the second insulation is formed. A plurality of second via holes 5 reaching the first wiring conductor 2 from the outer principal surface thereof are formed in the layer 3. The via holes 4 and 5 are formed by laser processing. The via holes 4 and 5 have a diameter of 50 μm at the bottom and 70 μm at the opening. After the via holes 4 and 5 are formed, desmear processing is performed.

  Next, as shown in FIG. 3I, a second wiring conductor 6 made of copper plating is formed in the other main surface of the first insulating layer 1 and in the first via hole 4, and the second insulation is formed. A third wiring conductor 7 made of copper plating is formed in the outer main surface of the layer 3 and in the second via hole 5. These wiring conductors 6 and 7 are formed by adopting a known semi-additive method. By adopting the semi-additive method, the wiring conductors 6 and 7 having fine and high-density wiring can be formed.

  Next, as shown in FIG. 3J, a solder resist layer 8 is formed on the other main surface of the first insulating layer 1 and the outer main surface of the second insulating layer 3. The solder resist layer 8 is formed by applying a photosensitive resin paste made of, for example, an acryl-modified epoxy resin on the other main surface of the first insulating layer 1 and the outer main surface of the second insulating layer 3, and well-known photolithography. The film is formed by exposing and developing into a predetermined pattern using a technique and then thermally curing.

  Finally, as shown in FIG. 3 (k), a wiring board 10 having a thin and high-density wiring is manufactured by cutting out a region to be the wiring board 10 using a cutting device such as a dicing machine or a router. Is done.

In addition, this invention is not limited to an example of above-mentioned embodiment, A various change is possible if it is a range which does not deviate from the summary of this invention. For example, in the example of the above-described embodiment, the belt sander S is used when the first copper foil F1 and the second copper foil F2 are subjected to a drawing process that extends in a direction parallel to the main surface of the insulating layer 1. However, a wet blast method may be used instead. By using the wet blast method, the first and second copper foils F1 and F2 can be more uniformly stretched in all directions parallel to the main surface of the insulating layer 1. A uniform tensile stress T3 is applied to the insulating layer 1. Such a drawing process by the wet blast method is performed in place of the process described with reference to FIG. 1C after the process described with reference to FIGS. 1A and 1B is performed. . Specifically, as shown in FIG. 4, the nozzles N for wet blasting are arranged at positions above and below the first and second copper foils F1 and F2. And the jet J of the abrasive | polishing material which mixed the fine powder in the water | moisture content is sprayed from a nozzle, and it is parallel to the main surface of the 1st insulating layer 1 in the 1st copper foil F1 and the 2nd copper foil F2. Add a stretching process to stretch in the direction. As the fine powder, aluminum oxide, silicon oxide, iron oxide, titanium oxide, or the like is used. After the process by the wet blasting method is completed, the processes described based on FIG. 2 and FIG. 3 described above may be performed sequentially.

DESCRIPTION OF SYMBOLS 1 1st insulating layer 2 1st wiring conductor 3 2nd insulating layer 4 1st via hole 5 2nd via hole 6 2nd wiring conductor 7 3rd wiring conductor P1 1st prepreg P2 2nd prepreg F1 1st copper foil F2 2nd copper foil F3 3rd copper foil

Claims (2)

By laminating the first copper foil on one main surface of the first prepreg and the second copper foil on the other main surface and curing the first prepreg, the first prepreg is cured. Fixing the first copper foil to one main surface of the first insulating layer and the second copper foil to the other main surface;
By applying a stretching process to the first and second copper foils in a direction parallel to the main surface, the main insulating layer is formed on the first insulating layer by the stretched first and second copper foils. Applying a tensile stress in a direction parallel to the surface;
Forming the first wiring conductor made of the first copper foil on the one main surface by etching the first copper foil into a predetermined wiring pattern;
A second prepreg and a third copper foil are stacked on the outer main surface of the second prepreg on the one main surface on which the first wiring conductor is formed, and the second prepreg is cured. A second insulating layer formed by curing the second prepreg on the one main surface, and fixing the third copper foil on the outer main surface of the second insulating layer;
Etching and removing the second copper foil fixed to the other main surface of the first insulating layer and the third copper foil fixed to the outer main surface of the second insulating layer, Releasing the tensile stress applied to the first insulating layer by a second copper foil;
A plurality of first via holes reaching the first wiring conductor from the other main surface to the first insulating layer and a plurality of reaching the first wiring conductor from the outer main surface to the second insulating layer. Forming a second via hole;
A second wiring conductor made of copper plating is formed in the other main surface of the first insulating layer and in the first via hole, and the outer main surface of the second insulating layer and the second via hole are formed. And a step of forming a third wiring conductor made of copper plating therein.   The method of manufacturing a wiring board according to claim 1, wherein the stretching process is performed using a wet blast method.

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