JP3459398B2 - Method of manufacturing multilayer printed circuit board having interlayer connection via hole - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a multilayered circuit board, and more particularly to a circuit board having via holes formed for connecting respective layers. A method for forming the same. 2. Description of the Related Art In order to connect each layer in a multilayered circuit board, holes for connecting the layers, ie, via holes, are provided, the inner walls of the holes are plated, and the circuit patterns provided in each layer are connected to each other. Connecting has been done. In forming via holes, it has become common to use a laser irradiation method capable of high-density processing instead of the conventional drilling method. In order to form via holes in a multilayer printed circuit board that has been subjected to high-density processing, as shown in FIG. 4, a position of an intermediate layer via hole H1 and a position of a first layer via hole H2 are determined. In some cases, the via holes H0 overlap each other, as shown in FIG. The former does not meet the purpose of high density because the area required for forming via holes is large. Therefore, the latter suitable for higher density is becoming more common. [0005] As described above, the method of aligning the via hole H1 connecting the intermediate layers and the via hole H2 of the first layer has become mainstream.
As shown in FIG. 6, it may not be completely concentric due to the design. That is, as shown in FIG. 6, when the via hole H1 of the intermediate layer and the via hole H2 of the first layer are slightly eccentric, the via hole H2 of the outer layer is formed after the formation of the via hole H1 of the inner layer. When a laser beam is irradiated using the circuit pattern of the outer layer to form a portion, the portion inside the circuit pattern of the outer layer and outside the circuit pattern of the inner layer is irradiated with the laser beam, and as an X portion indicated by a broken line, As shown, an abnormally deep through hole may be formed. In this case, if through-hole plating is performed,
In the case of FIG. 6, the via hole becomes conductive up to the sixth layer, which is a problem. The present invention has been made in view of the above points, and has as its object to provide a multilayer printed circuit board which is suitable for high density and has no problem in via holes, and a method of manufacturing the same. . In order to achieve the above object, according to the present invention, at least three circuit boards each having a circuit pattern formed on an insulating layer are laminated to form a multilayer, and a via is provided between the layers. In a method for manufacturing a multilayer printed circuit board connected by holes, a first circuit board is prepared, a second circuit board is fixed on the first circuit board with an adhesive, and a via hole in the second circuit board is provided. the hole portion is removed by the circuit pattern etched to form a via hole formation region, the via hole formation region, laser
The beam irradiation unit, the first to form a hole by removing the insulating layer and the adhesive in the second circuit board to said first circuit board is subjected to through-hole plating the first hole, A third adhesive is applied to the second circuit board with an adhesive.
A circuit pattern for forming a via hole having a smaller diameter than the first hole is formed on the third circuit board, and a laser is formed by using the circuit pattern on the third circuit board. The beam irradiation means
Removing the insulating layer and the adhesive around the hole to form a second hole having a smaller diameter than the first hole, and plating the hole with a through-hole.
A method of manufacturing a multilayer printed circuit board having an interlayer connection via hole. FIG. 1 conceptually shows the structure of an embodiment of the present invention. FIG. 1 shows a vertical sectional view at the top and an overhead view at the bottom. As can be seen from these figures, the circuit board comprises a laminated circuit board having a five-layer structure in which an insulating layer 11, a laminated adhesive 12, an insulating layer 13, a laminated adhesive 14, and an insulating layer 15 are laminated. I have. And the insulating layers 11, 13 and 15
Each upper surface in the diagram of FIG.
1, 22, 24 (only the main parts are shown) are formed. And penetrating all five layers of the laminated circuit board,
Via holes are formed concentrically so that the inner diameter changes in two steps. The via hole has a large diameter on the lower side and a small diameter on the upper side in a two-stage configuration. A large diameter portion connects the lands 21 and the lands 22, and a small diameter portion connects the lands 22 and the lands 24. is there. In order to compose this via hole, lands 21, 22, 24 are concentrically arranged as shown in a bird's-eye view. The outer diameter of land 21 in the innermost layer is φe, the inner diameter is φc, and the middle is φc. The outer diameter of the land 22 is φd, the inner diameter is φc, the outer diameter of the land 24 in the outermost layer is φb, and the inner diameter is φ
a. Then, when comparing the outer diameters and the inner diameters, the diameter on the outer layer side is smaller in each case. In the drawing, φb <φd
Has become . This via hole has an inner land 2
1 and the intermediate land 22 so that the plating layer 23
Is formed, and a plating layer 25 is formed to connect the plating layer 22 and the land 24 of the outer layer. Each of the via holes thus formed, when projected in the vertical direction in the drawing, is in a state in which others are included in the outline of the via hole having the largest diameter. FIGS. 2 and 3 illustrate via vias shown in FIG.
FIG. 4 shows a process for forming a hole, and four processes AD in FIG. 2 and four processes EH in FIG. 3 are a series of processes. Here, the copper foil on each circuit board becomes a circuit pattern after the etching process, and the same reference numerals are given before and after the etching process. First, in FIG. 2, in a first step A, a first circuit board having a land 21 having a size appropriate for forming a bottom surface of a via hole on the upper surface of the insulating layer 11 is prepared. For forming the circuit board, a usual copper-clad laminate material, that is, a glass-epoxy type, polyimide, or the like can be used. The center position of the land 21 is the center position of the via hole. Then, the second circuit board is laminated with the laminating adhesive 12 interposed therebetween so as to cover the upper surface of the first circuit board, and the lands 22 are formed on the copper foil of the second circuit board. In order to form a via hole in the land 22 at a position concentric with the circuit pattern on the first circuit board,
A portion from which the copper foil has been removed is formed. [0018] In the second step B, from the upper side of the second circuit board via a land 22, removal of the resin component by laser <br/> Bimu irradiation is anisotropic processing means is performed. As the laser, any laser capable of sublimating a resin component such as an excimer laser or a CO2 laser may be used. The laser beam is applied to remove the insulating layer 13 and the laminating adhesive 12 of the second circuit board, exposing the upper surface of the land 21 on the first circuit board. The anisotropic treatment means means for removing a substance in the vertical direction in the drawing, but does not act at all in the horizontal direction in the drawing, and acts in both the vertical and horizontal directions at that point. This is different from etching or the like which can be called isotropic processing means. In the third step C, the land 21 and the land 2
Then, a plating layer 23 is formed so as to connect to the plating layer 2. The plating may be based on ordinary through-hole plating. This forms a first via hole. In a fourth step D, a third circuit board having an insulating layer 15 and a copper foil 24 is laminated with a laminating adhesive 14 therebetween so as to cover the plating layer 23. Thereby, the process shifts to the process E in FIG. In the fifth step E shown in FIG. 3, the first to third circuit boards are stacked in the fourth step D. That is, a second circuit board including the insulating layer 13 and the land 22 is laminated via the laminating adhesive 12 on the first circuit board including the insulating layer 11 and the land 21, and the land 21 and the land 22 are formed by the plating layer 23. Are connected to each other, and a third circuit board composed of the insulating layer 15 and the copper foil 24 is laminated thereon with the laminating adhesive 14 interposed therebetween. In a sixth step F, lands 24 for forming via holes by processing the copper foil by etching.
To form This is the same state as in the first step A.
The lands 24 are for forming the second via holes. Since the second via holes are smaller in diameter than the first via holes, the circuit patterns are also formed in such a manner. . Next, in a seventh step G, a laser beam is irradiated to remove the insulating layer 15 and the laminated adhesive 14 according to the circuit pattern. This is the same state as in the second step. As a result, the insulating layer 15 and the laminating adhesive 14 which are not covered with the lands 24 and are higher than the plating layer 23 are all removed, and a two-stage via hole is formed. In this state, the land 2
Then, a plating layer 25 including via holes is formed from above 4. As a result, the lands 21 and 21 are formed by the plating layer 25.
2, 24 are all connected. That is, the land 21 and the land 22 are connected by the plating layer 23,
The plating layer 25 and the land 24 are connected by the plating layer 25, and as a result, the three lands 21, 22, and 24 are connected. Subsequent to the above steps, a general printed circuit board manufacturing process is applied to manufacture a multilayer printed circuit board. In the case of an eccentric via hole, if the entire outer layer via hole is inside the inner wall of the innermost via hole, it can be formed as a stepped via hole even if it is not concentric. . However, in consideration of the displacement in the process operation, it is actually necessary to take a certain margin. (Application Example) In the above embodiment, a via hole having a two-stage structure is illustrated. However, the present invention is also applicable to a configuration in which four or more circuit boards are stacked and interconnected by three or more via holes. Can be applied. In the above embodiment, an adhesive is used for lamination, but this may be replaced with an equivalent such as a prepreg. Further, in order to remove the residue before the plating treatment, it is more preferable to immerse in a permanganic acid solution. As described above, according to the present invention, when forming via holes for interlayer connection in a multilayer printed circuit board, a laser via using a circuit pattern of an outer layer circuit board.
Since the unnecessary material is removed by the beam irradiation means and covered with the plating layer, an inclusive via hole in which the outer layer via hole is arranged within the range of the inner layer via hole is formed. As a result, it is possible to provide a printed circuit board that does not impair the conduction reliability while supporting high density.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing a configuration of a circuit board according to the present invention. FIG. 2 is an explanatory diagram showing a first half of a process according to one embodiment of the present invention. FIG. 3 is an explanatory view showing the latter half of the process of the embodiment shown in FIG. 2; FIG. 4 shows an example of the structure of a conventional via hole.
Explanatory drawing when changing the position of a via hole. FIG. 5 shows an example of the structure of a conventional via hole.
Explanatory drawing of the same diameter overlapping type via hole. FIG. 6 is an explanatory view showing a problem at the time of manufacturing a conventional via hole. [Description of Signs] 11, 13, 15 Insulating layers 12, 14 Laminating adhesive 21, 22, 24 Land 23, 25 Plating layer

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-9-232760 (JP, A) JP-A-9-293970 (JP, A) JP-A 2002-9443 (JP, A) JP-A 2001-156450 ( JP, A) JP-A-2001-308529 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05K 3/46 H05K 3/40 H05K 3/42

Claims (1)

(57) Claims 1. A multilayer printed circuit board in which at least three circuit boards each having a circuit pattern formed on an insulating layer are laminated to form a multilayer, and the layers are connected by via holes. in the method, the first circuit board is prepared, by an adhesive to the first circuit board to fix the second circuit board, removing the via hole section in the second circuit board by the circuit pattern etching Forming a via hole forming region, and irradiating the via hole forming region with an insulating layer and an adhesive in the second circuit board up to the first circuit board by a laser beam irradiating means. Is removed to form a first hole, the first hole is plated with a through hole, and a third circuit board is fixed to the second circuit board with an adhesive. Group The first form small circuit patterns for via holes formed in diameter than the hole, les utilize a circuit pattern in said third circuit board
Removing the insulating layer and the adhesive around the via hole by a laser beam irradiating means to form a second hole having a smaller diameter than the first hole, and plating the hole with a through hole. A method for manufacturing a multilayer printed circuit board having an interlayer connection via hole.