JP2022079841A - Multi-layer printed wiring board and manufacturing method thereof - Google Patents

Abstract

To provide a multi-layer printed wiring board and a manufacturing method thereof that support high-speed transmission and high density of parts by making it possible to remove stubs on the inner wall of a through-hole of a multi-layer printed wiring board while eliminating the expansion of pitch due to stub removal.SOLUTION: A multi-layer printed wiring board made by stacking multiple printed wiring boards with a wiring layer on the surface includes a through hole having a through hole plating layer whose excess portion has been scraped off by etching.SELECTED DRAWING: Figure 1

Description

The present invention relates to a multilayer printed wiring board and a method for manufacturing the same.

In recent years, with the increasing functionality of electronic devices, there has been a demand for high-multilayer printed wiring boards and improved wiring densities.
Recently, the speed of electronic devices has been increasing, and the electric signal flowing in the wiring board transmits more information in a short time, so that the frequency is getting higher and higher. When designing a board that supports high frequencies, it is necessary to consider conductor loss and dielectric loss. For conductor loss, it is effective to make the conductor of the signal line thicker. It is effective to reduce the specific dielectric constant and dielectric loss tangent of the materials arranged around it, but in a high-density wiring board, the conductor width of the signal line that can be handled is limited, so the dielectric loss can be improved. It has become important.

It has become necessary to remove stubs after through-hole plating in order to reduce the reflection of electrical signals even in through-holes. Here, the stub is generally a wiring to which nothing is connected to the tip thereof, and in a through hole for connecting between wiring layers of a multilayer wiring board, a surplus portion that does not contribute to the connection between wiring layers. It means that.
Correspondingly, in the conventional multilayer printed wiring board that requires high-speed transmission of an electric signal, the stub of the through hole may be removed in order to reduce the reflection of the electric signal. In order to remove this stub, a method is known in which a through hole is formed by plating and then back drilled from the through hole entrance on the substrate surface side with a drill having a diameter larger than that of the through hole drill (Patent Documents 1 to 1). 3).

Japanese Unexamined Patent Publication No. 2005-026549 Japanese Unexamined Patent Publication No. 2009-004585 Japanese Unexamined Patent Publication No. 2012-248653

However, in this method, as shown in FIG. 3, the through-hole plating 5 from the entrance (opening) to a predetermined depth is removed electrically with a diameter larger than the diameter of the through hole 6 of the multilayer printed wiring board 100. Since the discontinuous portion 9 that is not connected to the hole is formed, the wiring capacity between the holes is reduced, which hinders high density. Moreover, since the diameter of the drill for removing the stub is larger than the diameter of the drill for forming the through hole for the through hole, it occupies a larger area than the through hole in the plan view. As a result, it is necessary to widen the pitch of the through holes in order to remove the stub, and there is a problem that it is difficult to deal with high-density parts having a narrow pitch.

The present invention eliminates the expansion of the pitch due to the removal of stubs, and by making it possible to remove the stubs on the inner wall of the through hole of the multilayer printed wiring board, it is possible to support high-speed transmission and also to increase the density of parts. It is an object of the present invention to provide a printed wiring board and a method for manufacturing the printed wiring board.

In order to solve the above problems, the present invention provides a multilayer printed wiring board in which a surplus portion of a through-hole plating layer is removed by etching, and a method for manufacturing the same.

That is, the present invention relates to the following.
[1] A multilayer printed wiring board in which a plurality of wiring layers are formed in the thickness direction via an insulating layer, and is characterized by having a through hole having a through hole plating layer from which a surplus portion has been scraped off by etching. Multi-layer printed wiring board.
[2] A method for manufacturing a multilayer printed wiring board in which a plurality of wiring layers are formed in the thickness direction via an insulating layer, wherein a through hole is formed at a predetermined position of the multilayer printed wiring board, and a through hole. Multilayer printed wiring including a step of forming a through-hole plating layer on the inner wall surface of the circuit board, a step of filling the through-hole with a resin, and a step of scraping off an excess portion of the through-hole plating layer by etching. How to make a board.

According to the present invention, by having a structure in which the stubs on the inner wall of the through hole are removed while eliminating the expansion of the pitch due to the removal of the stubs, the multilayer printed wiring can be used for high-speed transmission and high density of parts. A plate and a method for manufacturing the same can be provided.

It is a schematic sectional drawing which shows the structure of one Embodiment of the multilayer printed wiring board of this invention. It is schematic cross-sectional view which shows one Embodiment of the manufacturing process of the multilayer printed wiring board which removes a stub by etching of this invention. It is schematic cross-sectional view which shows an example of the structure of the conventional multilayer printed wiring board which removed the stub by back drilling.

(Multi-layer printed wiring board)
FIG. 1 shows an embodiment (schematic sectional view) of the multilayer printed wiring board 1 of the present invention. The multilayer printed wiring board 1 of the present embodiment has a plurality of wiring layers 2 laminated in the thickness direction via an insulating layer 3, a through hole 6 penetrating the wiring layers 2 in the thickness direction, and the like. A multilayer printed wiring board comprising a through-hole plating 5 arranged on the inner wall of the through hole 6 and electrically connected to the wiring layer 2 and a hole-filling resin 4 filled in the through-hole plating inner wall. The hole plating 5 is a multilayer printed wiring board 1 having a discontinuous portion 9 which is partially scraped off by etching in the thickness direction of the multilayer printed wiring board 1 and is not electrically connected.

In the present embodiment, the insulating layer supports the wiring layer while ensuring insulation between different wiring layers. It can be formed by using commonly used glass epoxy, glass polyimide, or the like in a multilayer printed wiring board.

The wiring layer is one that conducts electrical conduction through a circuit. A circuit to be a wiring layer can be formed by etching or the like by using a metal foil such as copper foil or a material such as plating which is generally used in a multilayer printed wiring board.

Through-hole plating is arranged on the inner wall of the through hole and electrically connected to the wiring layer. As is generally known, a method of forming using electroless plating for thickening (one-step method), after forming an electroless plating as a base, electroplating is performed using this as a feeding layer. It can be formed by a method (two-step method) or the like.

The hole-filling resin is filled in the inner wall of the through-hole plating to prevent solder from flowing into the through-hole when the component is mounted. As the resin, for example, THP-100DX1 manufactured by Taiyo Ink Mfg. Co., Ltd. is used.

As shown in FIG. 1, the through-hole plating 5 arranged on the inner wall of the through hole 6 has a discontinuous portion 9 which is not electrically connected in a part of the inside of the multilayer printed wiring board 1 in the thickness direction.
The discontinuous portion means a portion where the through-hole plating arranged on the inner wall of the through hole is not electrically connected in a part of the inside of the multilayer printed wiring board in the thickness direction. To form this discontinuity, a photosensitive film is laminated on the front and back surfaces of the multilayer printed wiring board, the parts other than the through hole opening are exposed, then an etching resist is formed by development, and then the inner wall of the through hole is formed. The stub (surplus part) of the This is possible by forming discontinuities that are not connected.

In the present embodiment, back drilling using a drill having a diameter larger than the diameter of the through hole is unnecessary because the stub on the inner wall of the through hole is removed by etching. Therefore, the region where the stub is removed and has a discontinuity is equivalent to the diameter of the through hole in a plan view. Therefore, by eliminating the expansion of the pitch due to the removal of stubs and making it possible to remove through-hole plating in the thickness direction of the multilayer printed wiring board, it is possible to support high-speed transmission and high density of parts. Multilayer printed wiring boards can be provided.

(Manufacturing method of multilayer printed wiring board)
Next, a method for manufacturing a multilayer printed wiring board according to an embodiment of the present invention will be described. As shown in FIG. 2, in the method of manufacturing the multilayer printed wiring board 1 according to the present embodiment, a step of laminating a plurality of wiring layers 2 via an insulating layer 3 and a laminated wiring layer 2 in the thickness direction are used. A step of forming a through hole 6 to penetrate, a step of forming a through hole plating 5 arranged on the inner wall of the through hole 6 and electrically connecting the wiring layer 2, and a step of filling the inner wall of the through hole with a hole-filling resin 4. A step (a), a step of laminating the photosensitive film 7 on the front and back surfaces of the multilayer printed wiring board 1 (b), a step of exposing a portion other than the through hole opening (c), and a step on the through hole opening. It has a step of removing the photosensitive film (d), a step of removing a part of the through-hole plating 5 (e), and a step of peeling off the etching resist 8 (f) (not shown).

According to the method for manufacturing a multi-layer printed wiring board of the present embodiment, the through hole is machined using a drill in the step of forming the through hole, and then the through hole is formed on the inner wall of the through hole by the step of forming the through hole plating. The through-hole plating and the wiring layer are electrically connected to form a connection portion.

Further, the inner wall of the through hole is filled with resin (a), then a photosensitive film is laminated on the surface of the multilayer printed wiring board 1 (b), and then the position of the through hole is circular with the same diameter as the through hole. A portion other than the through-hole opening is exposed using a photomask or the like having a mask (c), then the photosensitive film on the through-hole opening is removed by development to form an etching resist 8 (d), and then the etching resist 8 is formed. A part of the through-hole plating 5 can be removed by etching (e), and then the etching resist 8 can be peeled off (f) to form a discontinuous portion. Also, the area of the opening with the stub removed and having a discontinuity is equivalent to the diameter of the through hole in plan view. Therefore, there is no concern that the density of parts will be increased.

By providing the discontinuous portion, it is possible to suppress the influence of reflection of high frequency signals due to unnecessary through-hole plating. Moreover, since the back drill method using a drill having a diameter larger than the diameter of the through hole is not required, the region of the discontinuous portion is equivalent to the diameter of the through hole. Therefore, it is possible to provide a method for manufacturing a multilayer printed wiring board that can be mounted on both sides and have a high density of parts while supporting high-speed transmission by removing stubs.

1,100 ... Multilayer printed wiring board 2 ... Wiring layer 3 ... Insulation layer 4 ... Hole filling resin 5 ... Through hole plating 6 ... Through hole 7 ... Photosensitive film 8 ... Etching resist 9 ... Discontinuous part

Claims (2)

A multi-layer printed wiring board in which a plurality of wiring layers are formed in the thickness direction via an insulating layer.
A multilayer printed wiring board comprising a through hole having a through hole plating layer from which a surplus portion has been scraped off by etching. A method for manufacturing a multilayer printed wiring board in which a plurality of wiring layers are formed in the thickness direction via an insulating layer.
The process of forming through holes at predetermined positions on the multilayer printed wiring board,
The process of forming a through-hole plating layer on the inner wall surface of the through-hole, and
The process of filling the through hole with resin and
A method for manufacturing a multilayer printed wiring board, which comprises a step of scraping off an excess portion of a through-hole plating layer by etching in this order.

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