JP2727614B2 - Method of manufacturing printed wiring board and method of manufacturing multilayer wiring board - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a printed wiring board particularly suitable for a multilayer wiring board, and more particularly to a method for manufacturing a printed wiring board having a so-called blind through. .

[Summary of the Invention] The present invention closes one opening of a through hole provided in a double-sided copper-clad board by plating technology,
The present invention makes it possible to manufacture a printed wiring board which does not exude resin even when multi-layering is performed and which can realize high density.

[Conventional technology]

Conventionally, in order to achieve a dramatic increase in the density of wiring circuits,
Although a so-called multilayer wiring board has been proposed, the area occupied by the through-holes connecting the layers in the wiring board cannot be ignored when further densification is considered.

For example, in a multilayer wiring board in which three or more wiring layers are stacked, it is necessary to form through holes that penetrate all wiring layers in order to connect between the first layer and the second layer. Even in a wiring layer that does not need to be connected by a through hole, the wiring circuit must be patterned avoiding the through hole. Therefore, the pattern area that can be used in each layer is limited.

Therefore, as a technique for solving the above-described restriction on the pattern area, as shown in FIG.
1) The insulating substrate (104) on which (102) and (103) are formed,
After laminating (105) and (106) to form a multilayer wiring structure, there is a method of drilling holes (107) that penetrate only to the required layers by drilling, that is, penetrate partway instead of penetrating all substrates. It has been implemented.

However, in such a method, it is necessary to control the drill with high precision, and especially when the interlayer is narrow, [when each substrate (104), (105), (106) becomes a thin plate]. Very difficult. In addition, this method can process only one multilayer wiring substrate at a time, which is extremely disadvantageous in terms of productivity.

From such a situation, conventionally, prior to lamination, necessary through-holes are formed in each printed wiring board, and conduction is established between wiring circuits formed on both sides of each board with the through-holes, and then laminated. Techniques for increasing the number of layers are also being studied.

However, when multi-layering is performed after the formation of the through-holes, a new problem that the resin exudes to the outside at the time of laminating arises, and a conduction failure due to the exuded resin becomes a major obstacle.

Therefore, there is an attempt to fill the through holes of each printed wiring board with epoxy resin or the like in advance to prevent the resin from oozing during lamination, but to fill the epoxy resin from one side with the through holes opened. In this case, the resin also exudes to the opposite side, and it is difficult to remove the epoxy resin. On the other hand, if one side of the through hole is masked with a dry film or the like and filled with epoxy resin, the filling is not complete, and it is difficult to remove the dry film due to the heat at the time of curing the epoxy resin. Inconvenience such as becoming occurs.

[Problems to be solved by the invention]

As described above, the technique of forming through holes in each printed wiring board to be laminated, and establishing continuity in each board, and then forming a multilayer is considered promising in increasing the density of the multilayer wiring board. However, the fact is that the exudation of the resin is a major obstacle, and sufficient reliability has not been ensured.

Therefore, the present invention has been proposed in view of such conventional circumstances, and is intended to provide a highly reliable multilayer wiring board that can reliably close through holes and does not exude resin when laminated. It is an object of the present invention to provide a method for manufacturing a printed wiring board which can perform the above.

[Means for solving the problem]

In the method for manufacturing a printed wiring board according to the present invention, a through-hole is formed in a double-sided copper-clad board, and after through-hole plating is performed in the through-hole, at least the through-hole is closed on any one surface of the board. After joining a mask made of metal and performing electroless plating and / or electrolytic plating to form a plating layer that closes the opening on the mask side in the through hole, the mask is peeled off, and the mask is peeled off. A plating layer is formed so as to close one opening of the through hole. Further, the method for manufacturing a multilayer wiring board of the present invention includes forming a through-hole in a double-sided copper-clad board, plating the through-hole in the through-hole, and forming at least the through-hole on any one surface of the board. After joining a mask made of a metal to be closed and applying electroless plating and / or electrolytic plating to form a plating layer for closing the opening on the mask side in the through hole, the mask is peeled off and the through hole is removed. A printed layer is formed by forming a plating layer so as to cover one opening of the through hole, and the printed board is formed such that the opening of the through hole closed by the plating layer is the outermost layer. A plurality of layers are laminated via an adhesive layer.

[Action]

The present invention is an application of a plating technique in order to cover the through-hole and form a so-called blind through, by applying a non-electrolytic plating and / or electrolytic plating after joining a mask made of a metal closing the through-hole, A plating layer is formed on the wall surface of the through hole and on the inner surface of the mask. When the mask is removed, this plating layer closes the opening on one side of the through hole.

Therefore, unlike the case of filling the through hole by filling with the epoxy resin or the like, the conduction failure due to the exudation of the resin at the time of filling is eliminated, and the through hole is reliably closed. Then, there is no exudation of the resin at the time of lamination when forming a multilayer wiring board.

〔Example〕

Hereinafter, specific embodiments to which the present invention is applied will be described with reference to the drawings.

In this embodiment, to manufacture a printed wiring board having a so-called blind through, first, a double-sided copper-clad board with through-hole plating is manufactured.

That is, as shown in FIG. 1, a double-sided copper-clad board in which copper foils (2) and (3) as conductor layers are bonded to both sides of a base material (1) as a base is prepared, After a through-hole (through hole) (4) is formed, electroless plating (so-called chemical plating) is performed to cover the entire surface of the substrate and the inner wall surface of the through-hole (4) with a first plating layer (for example, copper). Plating layer] (5) is formed. In forming the first plating layer (5), electrolytic plating may be performed in addition to the above-described electroless plating in order to increase the thickness.

Next, as shown in FIG. 2, the substrate is bonded to one surface of the substrate using a metal plate (6) for closing the through hole (4) as a mask. This metal plate (6) has a first plate made of a copper plating layer or the like.
It is preferable to use a metal plate (for example, a stainless steel plate) that does not have good adhesion to the plating layer (5), or a metal plate that has been subjected to a surface treatment that deteriorates the adhesion. It is preferable to be made of a conductive metal material.

Thereafter, electrolytic plating is performed to form a second plating layer (7) as shown in FIG. The second plating layer (7) is formed so as to cover the surface of the first plating layer (5), and since the metal plate (6) is conductive, the metal plate (6) It is also formed continuously on the surface.

Therefore, even if the metal plate (6) is removed as shown in FIG. 4, the portion (7a) formed on the inner surface of the metal plate (6) of the second plating layer (7) remains in the through hole (4). , And the through hole (4) is a blind through with one side closed.

At this stage, the conductor layers (copper foils (2) and (3) and the first plating layer (5) and the second plating layer (7)) on both surfaces of the substrate are etched to form wiring circuits on both surfaces. In order to complete the printed wiring board having a blind through, the conductor layer on the side of the board where the through hole (4) is opened is selectively etched in consideration of multilayering.
First, a printed wiring board (10) having a wiring circuit (8) formed on only one side is provided.

Next, a process of forming a multilayer wiring board using the printed wiring board manufactured as described above will be described.

In order to manufacture a multilayer wiring board using the above-described printed wiring board (10), predetermined wiring circuits (12) and (13) were formed on both sides of a base material (11) as shown in FIG. The printed wiring boards (10) and (11) are laminated on both sides of the printed wiring board (14) with a semi-cured (so-called B stage) prepreg (15) pre-impregnated with resin sandwiched therebetween. At the time of lamination, each printed wiring board (10), (10) has the surface on which the wiring circuit (8) is formed facing inside.

Then, if necessary, through-holes are formed and plated to achieve connection between the layers (especially between the substrates). As shown in FIG. 6, the outermost conductor layer [each printed wiring board (10),
(10) Conductive layer on the side of the substrate on which the through hole (4) is closed] is selectively etched to form a wiring circuit (9), thereby obtaining a multilayer wiring board. In this example, three double-sided printed wiring boards are stacked, and when viewed in terms of the number of wiring layers, a six-layer multilayer wiring board is formed.

In the obtained multilayer wiring board, prepreg (15)
Resin is the through hole (4) of each printed wiring board (10), (10)
Although they penetrate, they do not seep outside because the through holes (4) are closed by the second plating layer (7). Further, interlayer connection in each of the printed wiring boards (10) and (10) is achieved by a first plating layer (5) and a second plating layer (7) formed in the through hole (4), The number of through-holes penetrating all the substrates can be reduced, which is advantageous in achieving high density.

Although the specific embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications can be made without departing from the gist of the present invention.

Further, as shown in FIG. 7, a metal plate (6) as a mask is bonded with a soluble adhesive (20), and a portion exposed in the through hole (4) as shown in FIG. The adhesive (20a) may be removed with a solvent, water, acid, alkali or the like, and then the second plating layer (7) may be formed.

With any of these methods, the same effect as in the previous embodiment can be expected, and a plating layer that blocks one opening of the through hole (4) is formed.

〔The invention's effect〕

As is clear from the above description, in the present invention, the through hole is closed by plating to form a blind through, so that the inconvenience due to resin filling or the like is eliminated, the through hole is reliably closed, and the conduction is prevented. It is possible to manufacture a highly reliable printed wiring board free from defects and the like.

Therefore, in the present invention, the printed wiring board is laminated with a plurality of layers via the adhesive layer so that the opening of the through hole closed by the plating layer becomes the outermost layer, so that the resin does not exude to the outside. Thus, it is possible to provide a high-density and high-reliability multilayer wiring board.

[Brief description of the drawings]

1 to 6 are schematic cross-sectional views of a main part showing a manufacturing process in an embodiment to which the present invention is applied in the order of steps. FIG. 1 is a through-hole plating process, FIG. 3 shows an electrolytic plating step, and FIG. 4 shows a metal plate removing and etching step. FIG. 5 is a schematic cross-sectional view of an essential part showing a laminated state in a disassembled state, and FIG. 7 and 8 are schematic cross-sectional views of main parts showing another example of a mask bonding process. FIG. 7 is a bonding process of a metal plate using an adhesive, and FIG. 8 is a diagram of an adhesive exposed in a through hole. Each of the removing steps will be described. FIG. 9 is a schematic sectional view of a main part showing a conventional example of interlayer connection in a multilayer wiring board. DESCRIPTION OF SYMBOLS 1 ... Base material 2, 3 ... Copper foil 4 ... Through-hole (through-hole) 5 ... 1st plating layer 6 ... Metal plate (mask) 7 ... 2nd plating layer

Claims (2)

(57) [Claims] 1. A method of forming a through-hole in a double-sided copper-clad substrate, plating the through-hole in the through-hole, and applying a mask made of a metal for closing at least the through-hole on one of the surfaces of the substrate. After joining and forming a plating layer that closes the opening on the mask side in the through hole by performing electroless plating and / or electrolytic plating, the mask is peeled off, and one of the through holes is placed in the through hole. A method for manufacturing a printed wiring board, comprising forming a plating layer that closes the opening of the printed wiring board. " 2. After forming a through-hole in a double-sided copper-clad substrate, plating the through-hole in the through-hole, and masking at least one of the surfaces of the substrate with a mask made of a metal for closing the through-hole. After joining and forming a plating layer that closes the opening on the mask side in the through hole by performing electroless plating and / or electrolytic plating, the mask is peeled off, and one of the through holes is placed in the through hole. A printed wiring board is formed by forming a plating layer that covers the opening of the printed wiring board, and a plurality of the printed boards are laminated via an adhesive layer such that the opening of the through hole closed by the plating layer is the outermost layer. A method for manufacturing a multilayer wiring board. "