JP2009188154A - Printed circuit board and its production process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed circuit board and its production process that control deformation of an end surface through-hole and peeling of a metallic film at an edge portion and allows favorable productivity by, e.g., doing drilling with two or more boards superimposed. <P>SOLUTION: A printed circuit board 50 is so structured that it includes a board 1, end surface through-holes 40a and 40b prepared in a concave shape to the board end surface, and an insulating layer 17 prepared on one surface side of the board and covering this one surface side of the end surface through-hole. Further, the production process of the printed circuit board includes the steps of drilling a through-hole 4a on the board, forming a through-hole 7a whose through-hole inner surface is covered by metal films 6a and 6b, filling this with a filling material 15, forming insulating layers 17 and 18 on both surfaces of the board that cover the filling material, partially removing one 18 of the insulating layers to expose the filling material and then remove it, and cutting the board such that the through-hole is divided, thus obtaining a printed circuit board 50 having an end surface through-hole 40a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a printed wiring board and a method for manufacturing the same, and more particularly to a printed wiring board having end face through holes and a method for manufacturing the same.

As one form of the printed wiring board, there is one having an end surface through hole (also referred to as a castellation or a side electrode) such as a module substrate (for example, Patent Document 1).
A printed wiring board having an end surface through hole is generally formed by drilling a through hole in a substrate such as a resin substrate that has undergone a predetermined process by drilling or the like, and covering the inner surface of the through hole with a metal film on the substrate surface After the metal film is patterned, it is obtained by dividing the substrate by router processing or the like so that the through hole has a substantially semicylindrical shape. The through hole formed in a substantially semi-cylindrical shape becomes an end face through hole.

  However, when the substrate is divided, a physical load is applied to the edge portion of the formed end surface through hole, so that the end surface through hole may be deformed or the metal film of the edge portion may be peeled off, which is improved. It was desired.

An example of means for solving the above problem is described in Patent Document 2.
According to the description in Patent Document 2, after drilling a hole in a region from one surface side of the substrate to the vicinity of the copper foil on the other surface side, the remaining resin at the bottom of the counterbore hole is further removed. By removing by laser processing until the copper foil on the surface side is exposed, a non-through hole having the exposed copper foil as a bottom surface is formed. Thereby, when the substrate is divided, the physical load applied to the edge portion of the end surface through hole formed by dividing the non-through hole can be reduced by the copper foil of the non-through hole. The deformation of the end face through-hole and the peeling of the metal film at the edge portion can be suppressed.
JP-A-7-183658 JP-A-10-65298

By the way, in the printed wiring board as described in Patent Document 1 and the manufacturing method thereof, when a through hole is drilled in the substrate, usually, in a state where a plurality of substrates are overlapped for the purpose of improving productivity. Drill. Thereby, a through-hole can be drilled in a several resin substrate at once.
However, in the printed wiring board described in Patent Document 2, since the hole serving as the end face through hole is a non-through hole, drilling can be performed in a state where a plurality of substrates are overlapped as described above. Can not. Therefore, since drilling and laser processing must be performed for each substrate, productivity is poor and improvement is desired.

  Therefore, the problem to be solved by the present invention is that the deformation of the end face through-hole and the peeling of the metal film of the edge portion are suppressed, for example, the productivity can be improved such that drilling can be performed in a state where a plurality of substrates are stacked, It is in providing a printed wiring board and its manufacturing method.

In order to solve the above problems, each invention of the present application has the following means.
1) The substrate (1), the end surface through holes (40a, 40b) provided in a concave shape with respect to the end surface of the substrate, and the insulation provided on one surface side of the substrate and covering the one surface side of the end surface through hole A printed wiring board (50) having a layer (17).
2) In the printed wiring board manufacturing method, a drilling step of drilling through holes (4a, 4b) in the substrate (1), and a metal film covering the inner surface of the through holes on the substrate after the drilling step (6a, 6b) are formed, and the through hole is formed into a through hole (7a, 7b) whose inner surface is covered with the metal film. After the metal film formation process, the through hole is formed in the through hole. A filling step of filling a filler (15), an insulating layer forming step of forming insulating layers (17, 18) covering the filler on both surfaces of the substrate after the filling step, and the insulating layer forming step A filler exposing step of partially removing one of the insulating layers to expose the filler; a filler removing step of removing the exposed filler after the filler exposing step; After the filler removal step, the through hole A step of dividing the substrate so as to be divided, and obtaining a printed wiring board (50) having end face through holes (40a, 40b) formed by dividing the through holes. It is.
3) In the printed wiring board manufacturing method, a drilling step of drilling through holes (64a, 64b) in the substrate (61), and a metal film that covers the inner surface of the through holes on the substrate after the drilling step (66a, 66b) to form through holes (67a, 67b) whose inner surfaces are covered with the metal film, and after the metal film formation process, both surfaces of the substrate are formed. A tenting film and an insulating layer forming step for forming a tenting film (91a, 91b) and an insulating layer (77, 78) covering the through hole, respectively, and after the tenting film and the insulating layer forming step, the substrate The tenting film on one side and the insulating layer are partially removed to open the through hole, and the through hole is separated after the through hole opening step. And dividing the substrate so as to obtain a printed wiring board (100) having end surface through holes (93a, 93b) formed by dividing the through holes. is there.

  According to the present invention, deformation of the end face through hole and peeling of the metal film at the edge portion are suppressed, and for example, it is possible to obtain good productivity that drilling can be performed in a state where a plurality of substrates are stacked.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to FIGS. 1 to 14 according to first and second embodiments which are preferred embodiments.

<First embodiment>
1st Example of the printed wiring board which concerns on this invention, and its manufacturing method is described using FIGS.
FIGS. 1-9 is typical sectional drawing for demonstrating the 1st Example of the printed wiring board which concerns on this invention, and its manufacturing method.
In FIG. 9, (b) is a schematic perspective view when the end face through hole 40b is particularly viewed from the arrow S50 in (a).
Moreover, A1 process-A9 process demonstrated below each show the process of manufacturing the printed wiring board of 1st Example.

[Step A1] (see FIG. 1)
In the double-sided copper-clad plate 1 having the core material 2 and the copper foils 3a and 3b provided on both surfaces of the core material 2, through holes 4a and 4b to be end face through-holes 40a and 40b described later are formed by, for example, drilling or laser Drill by machining.
The core material 2 is, for example, a material mainly composed of an insulating resin such as an epoxy resin or a sheet-shaped reinforcing material such as glass cloth that is cured by impregnating the insulating resin.
In the first embodiment, drilling was performed in a state where a plurality of double-sided copper-clad plates 1 were overlapped, and through holes 4a and 4b were formed in the plurality of double-sided copper-clad plates 1 at a time.

[Step A2] (see FIG. 2)
Copper plating is performed on the double-sided copper-clad plate 1 that has undergone the A1 process to form first copper plating layers 6a and 6b that cover the surfaces of the copper foils 3a and 3b and the inner surfaces of the through holes 4a and 4b.
The first copper plating layers 6a and 6b can be formed, for example, by performing electroless copper plating to form an electroless copper plating layer, and performing electro copper plating using the electroless copper plating layer as a plating conductive layer. .
Here, the through holes 4a and 4b whose inner surfaces are covered with the first copper plating layers 6a and 6b are referred to as through holes 7a and 7b.

[Step A3] (See FIG. 3)
The pattern which consists of the 1st copper plating layer 6a and the copper foil 3a in the one surface side of the core material 2 by partially etching the 1st copper plating layers 6a and 6b and the copper foils 3a and 3b using the photolithographic method The patterned first wiring layer 9 is formed, and the patterned second wiring layer 10 including the first copper plating layer 6b and the copper foil 3b is formed on the other surface side of the core material 2.
The first wiring layer 9 and the second wiring layer 10 are electrically connected through the through holes 7a and 7b.

[Step A4] (see FIG. 4)
Gold plating resists 12a and 12b covering the first wiring layer 9 and the second wiring layer 10 are formed on the double-sided copper-clad plate 1 that has undergone the A3 process, leaving at least the inner surfaces of the through holes 7a and 7b.
The gold plating resists 12a and 12b are resists having corrosion resistance against a gold plating solution, and commercially available products such as a liquid type or a dry film type can be used.
In FIG. 4, the gold plating resist 12a is formed only in the first wiring layer 9 and the vicinity thereof, and the gold plating resist 12b is formed only in the second wiring layer 10 and the vicinity thereof. For example, the gold plating resists 12a and 12b may be formed so as to cover the entire surfaces of both sides of the double-sided copper-clad plate 1 with at least the inner surfaces of the through holes 7a and 7b being left.

Next, a gold plating film 13 is formed on the inner surfaces of the through holes 7a and 7b by performing gold plating on the double-sided copper-clad plate 1 on which the gold plating resists 12a and 12b are formed.
The gold plating film 13 is used to reduce electrical resistance when connecting to other printed wiring boards and electronic components such as connectors, to improve the wettability of solder when soldered, and to be described later. It is formed to prevent oxidation of the surface of the through holes 40a, 40b.

[Step A5] (See FIG. 5)
After removing the gold plating resists 12a and 12b, a liquid or ink-like filler 15 that is soluble in an alkaline solution is filled into the through holes 7a and 7b by using, for example, a screen printing method and then cured.
Next, the excess filler 15 protruding from the through holes 7a and 7b is removed by buffing, for example.

[Step A6] (see FIG. 6)
A first insulating layer 17 that covers one side of the filler 15 and the first wiring layer 9 is formed on one side of the double-sided copper-clad board 1 that has undergone the A5 process, and the other side of the filler 15 and the first side are formed on the other side. A second insulating layer 18 covering the two wiring layers 10 is formed.
The first insulating layer 17 and the second insulating layer 18 are cured after applying an insulating resin such as a liquid or ink-like epoxy resin using a roll coating method, a screen printing method, a curtain coating method, or the like. Obtained by.
As another method for forming the first insulating layer 17 and the second insulating layer 18, a so-called prepreg in a semi-cured state in which an insulating resin is impregnated with a sheet-like reinforcing material such as a glass cloth is laminated. It is also possible to use a method of thermocompression bonding using a method or a lamination press method.

  Next, non-through holes 19 are formed in the first insulating layer 17 and non-through holes 20 are formed in the second insulating layer 18 by laser processing.

Thereafter, copper plating is performed on the double-sided copper-clad plate 1 that has undergone the above steps to form a second copper plating layer 21a that covers the surface of the first insulating layer 17 and the inner surface of the non-through hole 19, and the surface of the second insulating layer 18 And the 2nd copper plating layer 21b which covers the inner surface of the non-through-hole 20 is formed.
The second copper plating layers 21a and 21b can be formed using the same method as the first copper plating layers 6a and 6b described above.
Here, the non-through hole 19 whose inner surface is covered with the second copper plating layer 21 a is referred to as a via 22, and the non-through hole 20 whose inner surface is covered with the second copper plating layer 21 b is referred to as a via 23.

Further, by partially etching the second copper plating layers 21a and 21b using a photolithography method, a patterned third wiring layer 24 made of the second copper plating layer 21a is obtained, and the second A fourth wiring layer 25 which is made of the copper plating layer 21b and patterned so as to expose the second insulating layer 18 in the region filled with the filler 15 is obtained.
The third wiring layer 24 is electrically connected to the first wiring layer 9 through the via 22.
The fourth wiring layer 25 is electrically connected to the second wiring layer 10 through the via 23.
Since the through holes 7a and 7b are filled with the filler 15, the first insulating layer 17 and the third wiring layer 24 can be formed especially on the region where the through holes 7a and 7b are formed.

[Step A7] (See FIG. 7)
The filler 15 is exposed by removing the second insulating layer 18 in the region filled with the filler 15 by laser processing or the like.

[Step A8] (See FIG. 8)
The filler 15 exposed in step A7 is removed by dissolving with an alkaline solution.

[Step A9] (See FIG. 9)
After mounting the predetermined electronic components 30 and 31 on the double-sided copper-clad plate 1 that has undergone the A8 process, the double-sided copper-clad plate 1 is, for example, a mold so that the through holes 7a and 7b are substantially semi-cylindrical. The module substrate 50 which is one form of a printed wiring board is obtained by dividing | segmenting by the outer shape processes, such as used punching and a router process.
The through holes 7a and 7b having a substantially semicylindrical shape become end face through holes (also referred to as castellation or side electrodes) 40a and 40b.

In FIG. 9, as an example, the electronic component 30 is shown as an IC chip, and the electronic component 31 is shown as a chip component such as a chip resistor or a chip capacitor.
The electronic component 30 (IC chip) is electrically connected to the third wiring layer 23 via a gold wire 32 and is molded with a sealing resin 33.
The electronic component 31 is electrically connected to the third wiring layer 23 via the solder 35.
These electronic components 30 and 31 are not limited to IC chips and chip components, and the mounting method of these electronic components is not limited.

  According to the printed wiring board and the manufacturing method thereof described above, when the double-sided copper-clad board 1 is divided, the physical load applied to the edge portions of the end face through-holes 40a and 40b formed by the division is determined as through holes 7a, Since it can be reduced by the first insulating layer 17 covering 7b, deformation of the end surface through holes 40a and 40b and peeling of the first copper plating layers 6a and 6b and the gold plating film 13 at the edge portion can be suppressed.

  Moreover, according to the printed wiring board and the manufacturing method thereof described above, the through holes 4a and 4b to be the end face through holes 40a and 40b can be formed in the plurality of double-sided copper-clad boards 1 at a time, so that high productivity is achieved. Is obtained.

<Second embodiment>
Next, a second embodiment of the printed wiring board and the manufacturing method thereof according to the present invention will be described with reference to FIGS.
FIGS. 10-14 is typical sectional drawing for demonstrating the 2nd Example of the printed wiring board which concerns on this invention, and its manufacturing method.
14B is a schematic perspective view when the end face through hole 93b is particularly viewed from the arrow S100 in FIG.

Further, processes B1 to B5 described below show processes for manufacturing the printed wiring board of the second embodiment.

[Step B1] (see FIG. 10)
About the double-sided copper-clad board 61 which has the copper foil 63a, 63b provided in both surfaces of the core material 62 and this core material 62, the process similar to the A1 process-A4 process of 1st Example is performed, and the core material 62 of A patterned first wiring layer 69 composed of a first copper plating layer 66a and a copper foil 63a is formed on one surface side, and a patterned second wiring composed of a first copper plating layer 66b and a copper foil 63b is formed on the other surface side. The wiring layer 70 is formed, and through holes 67a and 67b in which inner surfaces of the through holes 64a and 64b are covered with the first copper plating layers 66a and 66b and the gold plating film 73 are formed.
The first wiring layer 69 and the second wiring layer 70 are electrically connected via through holes 67a and 67b.
Then, the gold plating resist (not shown) used when forming the gold plating film 73 is removed.

The core material 62 is made of, for example, an insulating resin such as an epoxy resin as a main component, or a sheet-like reinforcing material such as a glass cloth impregnated with an insulating resin and cured.
The through holes 64a and 64b are formed by, for example, drilling or laser processing.
In the second embodiment, as in the first embodiment, drilling is performed in a state where a plurality of double-sided copper-clad plates 61 are overlapped, so that the through holes 64a and 64b are once formed in the plurality of double-sided copper-clad plates 61. Formed.
The first copper plating layers 66a and 66b can be formed, for example, by performing electroless copper plating to form an electroless copper plating layer, and performing electro copper plating using the electroless copper plating layer as a plating conductive layer. .

[Step B2] (see FIG. 11)
Photosensitive dry films 90a and 90b are respectively bonded to both surfaces of the double-sided copper-clad plate 61 that has undergone the B1 process (laminate).
Next, the dry films 90a and 90b are removed using the photolithography method, leaving the through holes 67a and 67b and the region in the vicinity thereof, thereby tenting films 91a and 91b covering both sides of the through holes 67a and 67b. Form.

[Step B3] (see FIG. 12)
The same process as the A6 process of the first embodiment is performed, and the first insulating layer 77, the via 82, and the third wiring layer 84 are sequentially formed on one surface side of the double-sided copper-clad plate 61 that has undergone the B2 process. A second insulating layer 78, a via 83, and a fourth wiring layer 85 are sequentially formed on the surface side.
The third wiring layer 84 is electrically connected to the first wiring layer 69 through the via 82.
The fourth wiring layer 85 is electrically connected to the second wiring layer 70 through the via 83. The fourth wiring layer 85 is formed so that the second insulating layer 78 in the region where the tenting film 91b is formed is exposed.
Since the through holes 67a and 67b are particularly covered with the tenting film 91a, the first insulating layer 77 and the third wiring layer 84 can be formed on the region where the through holes 67a and 67b are formed. .

The first insulating layer 77 and the second insulating layer 78 are coated with an insulating resin such as a liquid or ink-like epoxy resin using a roll coating method, a screen printing method, a curtain coating method, or the like, and then cured. Obtained by.
As another method for forming the first insulating layer 77 and the second insulating layer 78, a so-called prepreg in a semi-cured state in which an insulating resin is impregnated into a sheet-like reinforcing material such as a glass cloth is used. A method of thermocompression bonding using a lamination press method can also be used.

[Step B4] (see FIG. 13)
By removing the tenting film 91b and the second insulating layer 78 in the region where the tenting film 91b is formed by laser processing or the like, one end side (the lower side in FIG. 13) of the through holes 67a and 67b is opened. To do.

[Step B5] (see FIG. 14)
After mounting predetermined electronic components 80 and 81 on the double-sided copper-clad plate 61 that has undergone the B4 step, the double-sided copper-clad plate 61 is, for example, a mold so that the through holes 67a and 67b are substantially semi-cylindrical. The module substrate 100 which is one form of a printed wiring board is obtained by dividing | segmenting by outer shape processing, such as used punching and router processing.
The through holes 67a and 67b having a substantially semicylindrical shape become end surface through holes (also referred to as castellation or side electrodes) 93a and 93b.

In FIG. 14, as an example, the electronic component 80 is shown as an IC chip, and the electronic component 81 is shown as a chip component such as a chip resistor or a chip capacitor.
The electronic component 80 (IC chip) is electrically connected to the third wiring layer 84 via a gold wire 94 and is molded with a sealing resin 95.
The electronic component 81 is electrically connected to the third wiring layer 84 via the solder 96.
These electronic components 80 and 81 are not limited to IC chips and chip components, and the mounting method of these electronic components is not limited.

  According to the printed wiring board and the manufacturing method thereof described above, when the double-sided copper-clad plate 61 is divided, the physical load applied to the edge portions of the end surface through-holes 93a and 93b formed by the division is determined as through holes 67a, Since it can be reduced by the first insulating layer 77 and the tenting film 91a covering 67b, it is possible to suppress the deformation of the end surface through holes 93a and 93b and the peeling of the first copper plating layers 66a and 66b and the gold plating film 73 at the edge portions. it can.

  Moreover, according to the printed wiring board and the manufacturing method thereof described above, the through holes 64a and 64b to be the end face through holes 93a and 93b can be formed in the plurality of double-sided copper-clad boards 61 at a time, so that high productivity is achieved. Is obtained.

  The embodiment of the present invention is not limited to the configuration and procedure described above, and it goes without saying that modifications may be made without departing from the scope of the present invention.

  For example, in the first and second embodiments, the copper plating layers 6a, 6b, and 6b are used as metal films covering the inner surfaces of the through holes 4a, 4b, 64a, and 64b to be the end surface through holes 40a, 40b, 93a, and 93b. Although 66a and 66b were formed, it is not limited to this.

  In the first embodiment and the second embodiment, the electronic component is mounted on the double-sided copper clad plate that has undergone a predetermined process, and then the double-sided copper clad plate is cut. However, the present invention is not limited to this. Alternatively, the electronic component may be mounted after cutting the double-sided copper-clad plate.

  In the first embodiment, the insulating layers are formed on both sides of the double-sided copper clad plate in which the through hole is filled with the filler. However, the present invention is not limited to this. An insulating layer may be formed so as to cover the filler only on the side, and the filler may be removed from the other side with the other side of the filler exposed.

  In the second embodiment, the tenting film and the insulating layer are formed on both sides of the double-sided copper-clad plate in which the filler is filled in the through hole. However, the present invention is not limited to this. A tenting film and an insulating layer may be formed on only one side of the copper-clad plate so as to cover the through hole, and the next step may be performed with the other side of the through hole exposed.

  In the first and second embodiments, the double-sided copper-clad plate is used. However, the present invention is not limited to this, and instead of the double-sided copper-clad plate, for example, insulating layers and wiring layers are alternately laminated. In addition, so-called shield plates in which copper foils are bonded to both surfaces may be used.

It is typical sectional drawing for demonstrating the 1st Example of the printed wiring board which concerns on this invention, and its manufacturing method. It is typical sectional drawing for demonstrating the 1st Example of the printed wiring board which concerns on this invention, and its manufacturing method. It is typical sectional drawing for demonstrating the 1st Example of the printed wiring board which concerns on this invention, and its manufacturing method. It is typical sectional drawing for demonstrating the 1st Example of the printed wiring board which concerns on this invention, and its manufacturing method. It is typical sectional drawing for demonstrating the 1st Example of the printed wiring board which concerns on this invention, and its manufacturing method. It is typical sectional drawing for demonstrating the 1st Example of the printed wiring board which concerns on this invention, and its manufacturing method. It is typical sectional drawing for demonstrating the 1st Example of the printed wiring board which concerns on this invention, and its manufacturing method. It is typical sectional drawing for demonstrating the 1st Example of the printed wiring board which concerns on this invention, and its manufacturing method. It is typical sectional drawing for demonstrating the 1st Example of the printed wiring board which concerns on this invention, and its manufacturing method. It is typical sectional drawing for demonstrating the 2nd Example of the printed wiring board which concerns on this invention, and its manufacturing method. It is typical sectional drawing for demonstrating the 2nd Example of the printed wiring board which concerns on this invention, and its manufacturing method. It is typical sectional drawing for demonstrating the 2nd Example of the printed wiring board which concerns on this invention, and its manufacturing method. It is typical sectional drawing for demonstrating the 2nd Example of the printed wiring board which concerns on this invention, and its manufacturing method. It is typical sectional drawing for demonstrating the 2nd Example of the printed wiring board which concerns on this invention, and its manufacturing method.

Explanation of symbols

1_double-sided copper-clad plate, 2,62_core material, 3a, 3b, 63a, 63b_copper foil, 4a, 4b, 64a, 64b_through hole, 6a, 6b, 21a, 21b, 66a, 66b_copper plating layer, 7a, 7b 67a, 67b_through hole, 9, 10, 24, 25, 69, 70, 84, 85_ wiring layer, 12_ gold plating resist, 13, 73_ gold plating film, 15_ filler, 17, 18, 77, 78_ insulating layer 19, 20_ non-through hole, 22, 23, 82, 83_ via, 30, 31, 80, 81_ electronic component, 32, 94_ gold wire, 33, 95_ sealing resin, 35, 96_ solder, 40a, 40b, 93a 93b_end face through hole, 50,100_module substrate, 90a, 90b_dry film, 91a, 91b_tenting film

Claims (3)

A substrate,
An end face through hole provided in a concave shape with respect to the end face of the substrate;
An insulating layer provided on one side of the substrate and covering the one side of the end face through hole;
A printed wiring board having: In the method for manufacturing a printed wiring board,
A drilling step of drilling a through hole in the substrate;
After the drilling step, forming a metal film covering the inner surface of the through hole on the substrate, and forming the through hole into a through hole whose inner surface is covered with the metal film; and
A filling step of filling the through hole with a filler after the metal film forming step;
After the filling step, an insulating layer forming step of forming insulating layers covering the filler on both surfaces of the substrate,
After the insulating layer forming step, a filler exposing step of partially removing one of the insulating layers to expose the filler;
After the filler exposure step, a filler removal step of removing the exposed filler,
After the filler removing step, the substrate is divided so that the through hole is divided, and a dividing step of obtaining a printed wiring board having an end surface through hole formed by dividing the through hole;
The manufacturing method of the printed wiring board which has this. In the method for manufacturing a printed wiring board,
A drilling step of drilling a through hole in the substrate;
After the drilling step, forming a metal film covering the inner surface of the through hole on the substrate, and forming the through hole into a through hole whose inner surface is covered with the metal film; and
After the metal film forming step, a tenting film and insulating layer forming step for forming a tenting film and an insulating layer covering the through holes on both surfaces of the substrate, respectively,
After the tenting film and insulating layer forming step, the tenting film and the insulating layer on one side of the substrate are partially removed to open the through hole; and
After the through hole opening step, the substrate is divided so that the through hole is divided, and a dividing step of obtaining a printed wiring board having an end surface through hole formed by dividing the through hole;
The manufacturing method of the printed wiring board which has this.

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