JP3973654B2 - Method for manufacturing printed wiring board - Google Patents

Description

The present invention relates to a method for manufacturing a printed wiring board, and more particularly to a method for manufacturing a so-called through-conductor type multilayer printed wiring board in which wiring layers are connected by through-type conductor wiring portions.

  Conventionally, as a method of manufacturing a multilayer board, a substantially conical conductor bump is press-fitted in the thickness direction of an insulating substrate to achieve electrical continuity between two wiring patterns formed on both surfaces of the insulating substrate. The law is known.

  FIG. 18 is a vertical sectional view schematically showing a manufacturing process of a conventional typical conductor penetration method.

  In this conductor penetration method, first, a printing mask (not shown) in which a plurality of through holes are drilled is superimposed on a conductor plate 100 (FIG. 18A) such as a copper foil, and from above the printing mask. A conductive composition such as silver paste is filled in the through hole while squeezing, and then the printing mask and the conductive plate 100 are peeled to form substantially conical conductive bump groups 102, 102,. (FIG. 18 (b)).

  Next, an insulating substrate prepreg 103 made of a glass fiber impregnated with epoxy resin is laminated on the upper side of the conductor bump groups 102, 102,... (FIG. 18C), and in this state, for example, a roller made of an elastic material When pressed by passing between them, the conductor bump groups 102, 102,... Penetrate through the insulating substrate prepreg 103 and penetrate to the opposite side (upper side in the figure) as shown in FIG.

  Further, a conductor plate 104 such as copper foil is laminated on the insulating substrate prepreg 103 through which the conductor bump groups 102, 102,... Penetrate, and the conductor plate 104 is bonded onto the insulating substrate prepreg 103 when heated under pressure. At the same time, the insulating substrate prepreg 103 is cured to form the multilayer board intermediate body 110 (FIG. 18E). At this time, the leading end side of the conductor bump groups 102, 102,... And the conductor plate 104 are pressed, so that they come into contact with each other and between the conductor plate 100 and the conductor plate 104 via the conductor bump groups 102, 102,. An electrical continuity is formed.

  By performing etching on the conductive plates 100 and 104 on the upper and lower surfaces of the multilayer board intermediate body 110 to perform patterning, the upper and lower surfaces of the insulating substrate 103 as shown in FIG. A multilayer board 111 is obtained in which wiring layers 102 and 105 electrically connected to each other through the conductor bump groups 102, 102,.

  However, in order to pass the conductor bump groups 102, 102,... Through the insulating substrate prepreg 103 in this way, the method of mechanically pressing the insulating substrate prepreg 103 and the conductor plate 100 from the outside of these methods is a roller press. There is a problem of requiring special equipment such as.

  Further, when a multilayer board composed of four wiring layers is manufactured by the above-described method, the conductor board 100 formed with the conductor bump groups 102, 102,... As shown in FIG. In general, a method of forming a multilayer by sandwiching an insulating substrate prepreg 103 between a laminate (not shown) having a wiring layer formed on each side of a single insulating substrate, which is called, and pressing them is generally used. Although this method is used, since the bottom surfaces of the conductor bump groups 102, 102,... Are laminated with the outside facing, the wiring density of the wiring layer formed on the outermost layer side of the multilayer board cannot be increased. There is.

The present invention has been made to solve the above conventional problems. That is, an object of the present invention is to provide a method for manufacturing a printed wiring board with a short process time, which can be manufactured without a large-scale manufacturing facility such as a roller press.

Another object of the present invention is to provide a printed wiring board manufacturing method capable of manufacturing a multilayer board having a high wiring density when the multilayer board is manufactured.

The printed wiring board manufacturing method of the present invention includes a step of forming a substantially conical conductor bump group at a predetermined position on an insulating substrate on which a conductive metal foil or a wiring layer is formed, and a tip side of the conductor bump group. A step of superposing a curable insulating sheet on the surface, a step of projecting the conductive bump group from the insulating sheet, a step of curing the insulating sheet, a surface of the cured insulating sheet, and the conductive bump group A step of polishing and flattening the tip portion of the conductive layer; and a step of forming a wiring pattern by plating on the tip portion of the flattened insulating sheet and conductor bump group .

  The wiring patterns on both surfaces of the multilayer board intermediate may be connected by an interlayer connection.

  In the present invention, each outermost layer wiring pattern may be formed with a metal layer on the inner wall surface of the through-hole by drilling a through-hole penetrating the whole.

  In the present invention, by using a method of applying a pressure reduction to the space between the insulating substrate and the insulating sheet as a method of penetrating the conductor bumps through the insulating sheet, large equipment such as a press machine is not required. Multilayer boards can be manufactured.

In addition, since the conductor bumps are formed on the patterned wiring layer, there are few connection mistakes between the conductor bumps and the wiring pattern, a precise wiring pattern can be formed, and the degree of integration can be improved.

  Moreover, a highly integrated multi-layer board can be formed by combining the method of forming conductor bumps on the wiring layer and the method of interlayer connection by through-hole plating.

  Furthermore, a multilayer board having a higher degree of integration can be formed by using a core material in which conductor bumps are inserted in a central insulating substrate as a method of interlayer connection.

  In the printed wiring board of the present invention, a conductor bump connecting the wiring pattern of the multilayer board intermediate body and the outermost layer wiring pattern is formed of a conductive composition or conductive paste containing conductive metal powder, and Since the tip side is flattened by polishing and connected to the outermost wiring pattern side, there are few connection mistakes between the conductor bumps and the wiring pattern, a precise wiring pattern can be formed, and the degree of integration is improved. Can do.

  Moreover, a highly integrated multi-layer board can be formed by combining the method of forming conductor bumps on the wiring layer and the method of interlayer connection by through-hole plating.

  Furthermore, a multilayer board having a higher degree of integration can be formed by using a core material in which conductor bumps are inserted in a central insulating substrate as a method of interlayer connection.

(First embodiment)
Hereinafter, a method for manufacturing a printed wiring board according to an embodiment of the present invention will be described.

  FIG. 1 is a flowchart showing the flow of each process of the method for manufacturing a printed wiring board according to the present embodiment, and FIGS. 2 to 10 are vertical sectional views schematically showing each process of the method.

  In order to manufacture the printed wiring board according to the present embodiment, a conductive plate 2 such as a copper foil is laminated on the insulating substrate 1, or the conductive plate 2 is previously laminated on the insulating substrate 1 as shown in FIG. A so-called copper-clad laminate is prepared. Then, the conductor plate 2 is patterned by, for example, etching (step 1) to form wiring layers 3, 3,..., That is, a wiring circuit as shown in FIG. Next, in correspondence with the wiring layers 3, 3,..., Substantially conical conductor bump groups 4, 4,... Made of a conductive composition such as silver paste are formed using, for example, a printing technique (FIG. 4). / Step 2).

  Next, a sheet made of a curable resin such as an epoxy resin is prepared as an insulating sheet. Specifically, a three-layer dry film (carrier film + insulating layer + cover film) mainly composed of a photosensitive epoxy resin, for example, a Dupont VIALUX81 series (registered trademark) was prepared, and the cover film was peeled off. In this state, as shown in FIG. 5, the insulating sheet 5 is set so as to overlap the insulating layer on the tip side of the conductor bump groups 4, 4,... Formed on the conductor plate 1.

  By using a dry film type insulating material having such a three-layer structure as the insulating sheet, handling becomes easy, and there is no need to separately prepare auxiliary materials such as a release sheet for bump penetration.

  Next, the conductive bump groups 4, 4,... Are penetrated through the insulating sheet 5, and as a method for that, a reduced pressure is applied to the space formed between the insulating substrate 1 and the insulating sheet 5. Thus, the insulating sheet 5 and the insulating substrate 1 are brought into close contact with each other, and the conductor bump groups 4, 4,... Are penetrated through the insulating sheet (step 4).

  As a specific method, for example, the outer peripheral edges of the insulating substrate 1 and the sheet 5 are sealed to form a sealed space between the insulating substrate 1 and the sheet 5, and the sealed space is connected to a vacuum pump. Examples include a method of connecting a vacuum pipe and operating a vacuum pump.

  Next, although the insulating sheet is cured, there is a method in which the insulating sheet is separately cured by a vacuum press apparatus, an oven, or the like. However, it is preferable to cure the conductive bump group through the insulating sheet as described below.

  When the conductor bump groups 4, 4,... On the wiring are passed through the insulating sheet 5, the insulating sheet 5 is simultaneously cured by heating or irradiating ultraviolet rays.

By performing penetration and curing at the same time, the time (process time) required for manufacturing can be shortened. In particular, the process time can be further shortened by using both ultraviolet irradiation and curing by heating. Further, the insulating sheet 5 is plasticized by irradiation with heat or ultraviolet rays, and the conductive bump groups 4, 4,. From that viewpoint, it is preferable to use the insulating sheet 5 having a low glass transition temperature. A preferable glass transition temperature is 60 to 70 ° C.

  Here, the preferable range of the glass transition temperature of the insulating sheet is set as the above range. If the glass transition temperature of the insulating sheet is lower than the above range, it is difficult to ensure stability as a film. In addition, the resin flows too much at the time of laminating, which causes adverse effects such as variations in the thickness of the insulating layer.On the other hand, if the glass transition temperature of the insulating sheet exceeds the above range, the bump itself softens and the insulating sheet becomes This is because it is impossible to penetrate, and it is necessary to cope with the equipment for raising the temperature, or the process time is lost.

  The insulating sheet 5 preferably has a thickness of 50 to 75 μm.

  Here, the preferable range of the thickness of the insulating sheet is defined as the above range. If the thickness of the insulating sheet is less than the above range, the insulating layer is insufficient in thickness, and insulation reliability between layers can be secured. This is because it becomes difficult. On the other hand, if the thickness of the insulating sheet exceeds the above range, bump penetration becomes difficult.

  As described above, for example, when a reduced pressure is applied, the insulating sheet 5 is pressed by the atmospheric pressure and sucked to the insulating substrate 1 side. At this time, the conductor bump groups 4, 4,. As shown in FIG. 6, the insulating sheet 5 comes into close contact with the insulating substrate 1 and at the same time, the conductor bump groups 4, 4,... Penetrate the insulating sheet 5, and the leading end reaches the carrier film. Like. In addition, since the curing by heating or ultraviolet irradiation occurs at the same time when the reduced pressure is applied, the insulating sheet 5 is cured in a state of being in close contact with the insulating substrate 1.

  Through the above steps, the conductor bump groups 4, 4,... Are formed only on one surface of the insulating substrate 1 and the insulating sheet 5 is laminated. When the same is laminated on the opposite side of the insulating substrate 1 as well. 1 returns to Step 1 from Step 5 in FIG. 1, and performs the steps from Step 1 to Step 4 also on the opposite side of the insulating substrate 1 to peel off the carrier film, so that the insulation as shown in FIG. A multilayer board intermediate 20 in which conductive bump groups 4, 4,..., 8, 8, .. and insulating sheets 5 and 6 are laminated on the upper and lower surfaces of the conductive substrate 1 is obtained.

  Next, in order to perform interlayer connection for the multilayer board intermediate body 20, surface polishing is performed (step 6), and the end portions of the conductor bump groups 4, 4,... And 8, 8,. As a result, the multilayer plate intermediate 21 having a flat surface as shown in FIG. 8 is obtained.

  At this time, since the conductive bump is formed of a conductive composition (silver paste), polishing is easy, and the polishing conditions for the insulating sheet and the conductive composition (silver paste) can be almost the same. Easy to flatten.

  Moreover, although the above-mentioned description demonstrated the example which a conductor bump penetrates an insulating sheet, even when the front-end | tip of a conductor bump does not penetrate an insulating sheet, it can produce by the process similar to the above. That is, by polishing the insulating sheet, it is possible to expose the tip of the conductor bump and at the same time planarize.

  Next, when drilling is performed in this multilayer board intermediate body 21 by a method such as drilling or laser beam irradiation to form a through hole for interlayer connection (step 7), the through hole 13 as shown in FIG. A perforated multilayer board intermediate 22 is obtained. When the metal layers 10, 12, and 14 are formed on the multilayer board intermediate 22 by, for example, electroless plating (step 8), the multilayer board 23 as shown in FIG. 10 is obtained.

  In this multilayer board 23, the conductor bump groups 4, 4,... And the conductor bump groups 8, 8,... Have a structure in which the tip side is arranged outward, so that the wiring formed on the outermost layer of the multilayer board 23 The intervals between the patterns 10, 10,... And the wiring patterns 12, 12,. Therefore, the wiring density of the wiring pattern can be improved, and as a result, the degree of integration can be improved.

  Further, since the conductor bump groups 4, 4,... Are directly formed on the wiring layer 3, the electrical connection between them is reliably formed.

  Moreover, since the wiring layer 10 is formed on the multilayer board intermediate body 22 by plating, the electrical connection between them is reliably formed.

  Furthermore, as described above, in this embodiment, since the conductor bumps are formed on the patterned wiring layer, there are few connection mistakes between the conductor bumps and the wiring patterns, and a precise wiring pattern can be formed. The degree can be improved.

  Moreover, a highly integrated multi-layer board can be formed by combining the method of forming conductor bumps on the wiring layer and the method of interlayer connection by through-hole plating.

  Furthermore, a multilayer board having a higher degree of integration can be formed by using a core material in which conductor bumps are inserted in a central insulating substrate as a method of interlayer connection.

  In addition, by using a technique that applies pressure reduction to the space between the insulating substrate and the insulating sheet as a technique for penetrating the conductor bumps through the insulating sheet, a multilayer board can be used without requiring large facilities such as a press machine. Can be manufactured.

  In addition, this invention is not limited to the content of the said embodiment.

For example, in this embodiment, the insulating substrate used for penetrating the conductor bumps includes a glass cloth, a mat, an organic synthetic fiber cloth, a mat, or a synthetic resin sheet reinforced with a reinforcing material such as paper. It is done. Here, as synthetic resins, for example, polycarbonate resins, polysulfone resins, thermoplastic polyimide resins, polytetrafluoroethylene hexafluoropropylene resins, polyether ether ketone resin and other thermoplastic resins, epoxy resins, bismaleimide triazine resins, Examples thereof include thermosetting resins such as polyimide resins, phenol resins, polyester resins, and melamine resins, and rubbers such as butadiene rubber, butyl rubber, natural rubber, neoprene rubber, and silicone rubber.

  When forming the substantially conical conductor bumps with a conductive composition, for example, a substantially conical conductor bump group having a high aspect ratio can be formed by a printing method using a relatively thick metal mask.

In the present invention, as a means for forming a substantially conical conductor bump group with a conductive metal, for example, a tip of a gold or copper ball is pressed against a predetermined position of a supporting base surface such as a copper foil and then pulled away. A substantially conical conductor (element) group with sharp points can be formed. It is also possible to form a substantially conical conductor bump group by previously injecting molten metal into a plate in which a recess corresponding to the shape of a substantially conical conductor is formed. As another means, a thick photosensitive resist is applied on the surface of the support film and exposed from the support film side to form a depression group having a trapezoidal recess with a sharp tip, and then the support film is removed. Then, a metal film may be applied to the support film removal surface, and copper, gold, silver, solder, or the like may be plated to form a small, substantially conical conductor bump group at a predetermined position.

  In the present invention, examples of the substrate that supports the substantially conical conductor bump group include a releasable film or a metal foil, and the support substrate may be a single sheet. The shape thereof is not particularly limited.

(Second Embodiment)
Hereinafter, a second embodiment according to the present embodiment will be described. Note that, in the present embodiment, the description overlapping with the first embodiment is omitted.

  11 to 17 are vertical sectional views schematically showing each step of the printed wiring board manufacturing method according to this embodiment.

  In this embodiment, instead of the insulating substrate 1 shown in FIG. 2, a core material 50 connected between layers by conductor bump groups 39, 39,... As shown in FIG.

  After the conductor plates 32a and 32b on the upper and lower surfaces of the core material 50 are patterned to form the wiring layers 33 and 37 on both sides (FIG. 12), the conductor bump groups 34 and 34 and the wiring layers 33 and 37 are formed on the wiring layers 33 and 37, respectively. ... and conductive bump groups 38, 38, ... are respectively formed (Fig. 13), and insulating sheets 35, 36 are respectively set thereon (Fig. 14), and between the core material 50 and the insulating sheets 35, 36. After the space is sealed, a reduced pressure is applied to the space so that the conductor bump groups 34, 34,... And the conductor bump groups 38, 38,. Was cured (FIG. 15). .. And then the tips of the conductor bump groups 34, 34,... And the conductor bump groups 38, 38,... Protruding on the insulating sheets 35, 36 are removed (FIG. 16). , 34,... And conductor bump groups 38, 38,.

  According to this embodiment, since the core material 50 connected between the layers by the conductor bump groups 39, 39,... Is used, it is not necessary to form a through hole. Therefore, it is not necessary to secure a space for drilling through holes, and the wiring density can be further increased, so that a specific effect that the degree of integration can be further improved is obtained.

It is a flowchart of the printed wiring board manufacturing method which concerns on the 1st Embodiment of this invention. It is the vertical sectional view showing each process of the printed wiring board manufacturing method concerning a 1st embodiment of the present invention. It is the vertical sectional view showing each process of the printed wiring board manufacturing method concerning a 1st embodiment of the present invention. It is the vertical sectional view showing each process of the printed wiring board manufacturing method concerning a 1st embodiment of the present invention. It is the vertical sectional view showing each process of the printed wiring board manufacturing method concerning a 1st embodiment of the present invention. It is the vertical sectional view showing each process of the printed wiring board manufacturing method concerning a 1st embodiment of the present invention. It is the vertical sectional view showing each process of the printed wiring board manufacturing method concerning a 1st embodiment of the present invention. It is the vertical sectional view showing each process of the printed wiring board manufacturing method concerning a 1st embodiment of the present invention. It is the vertical sectional view showing each process of the printed wiring board manufacturing method concerning a 1st embodiment of the present invention. It is the vertical sectional view showing each process of the printed wiring board manufacturing method concerning a 1st embodiment of the present invention. It is the vertical sectional view showing each process of a printed wiring board manufacturing method concerning a 2nd embodiment of the present invention. It is the vertical sectional view showing each process of a printed wiring board manufacturing method concerning a 2nd embodiment of the present invention. It is the vertical sectional view showing each process of a printed wiring board manufacturing method concerning a 2nd embodiment of the present invention. It is the vertical sectional view showing each process of a printed wiring board manufacturing method concerning a 2nd embodiment of the present invention. It is the vertical sectional view showing each process of a printed wiring board manufacturing method concerning a 2nd embodiment of the present invention. It is the vertical sectional view showing each process of a printed wiring board manufacturing method concerning a 2nd embodiment of the present invention. It is the vertical sectional view showing each process of a printed wiring board manufacturing method concerning a 2nd embodiment of the present invention. It is the vertical sectional view which showed the manufacturing process of the printed wiring board manufacturing method by the conventional conductor penetration method.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Insulating substrate, 2 ... Conductor board, 3 ... 1st wiring layer, 4 ... Conductor bump, 5 ... Insulating sheet, 10 ... 2nd wiring layer.

Claims (1)

Forming a substantially conical conductor bump group at a predetermined position on the insulating substrate on which the conductive metal foil or the wiring layer is formed;
A step of stacking a curable insulating sheet on the tip side of the conductor bump group;
Projecting the conductor bump group from the insulating sheet;
Curing the insulating sheet;
Polishing and flattening the surface of the cured insulating sheet and the tip of the conductor bump group;
And a step of forming a wiring pattern by plating on the flattened insulating sheet and the tip of the conductor bump group.

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