JP6890471B2 - Printing wiring board and manufacturing method of printed wiring board - Google Patents

Description

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

Conventionally, in a printed wiring board that handles high frequencies, the extra part (stub) of the through hole that is not connected to the wiring layer becomes a factor that deteriorates the frequency characteristics, so it is necessary to scrape it off by drilling or the like. It is desired to improve the depth detection accuracy.

When drilling a stub, a conventional printed wiring board has a circuit wiring through which a signal originally flows in order to detect the stop position (depth) of the drill that advances while scraping through holes from one surface (lower surface) of the printed wiring board. Has formed an irrelevant land on the back drill target layer, but its shape and pull-out method are not specified.

Normally, in order to detect the stop position of the drill in the back drill target layer set for each depth of each wiring layer, a test coupon is drawn from the through hole on the same straight line and a circular land is formed at the tip. It is common to place it.

Japanese Unexamined Patent Publication No. 2016-122825

In this way, conventionally, the wiring is drawn longer from the through hole as the starting point for the lower layer, and the land is arranged at a position different from that for the upper layer. Therefore, as the number of stages (types) of the back drill target layer increases, the more There is no choice but to lengthen the lead-out wiring of the lower layer, which increases the wiring area for forming the test coupon.

If the wiring area becomes large, the test coupon cannot be placed near the back drilling portion, and there is a problem that the distance to the test coupon becomes long. Further, if the difference in the distance from the back drilled portion to each land of the test coupon is large, the measurement error increases by that amount, which is disadvantageous in terms of machining accuracy.

The present invention has been made to solve such a problem, and provides a printed wiring board and a method for manufacturing a printed wiring board capable of improving the accuracy of back drilling and reducing the required area of a test coupon. To do.

In the printed wiring board of the present invention, an insulating substrate having a plurality of layers and having circuit wiring formed in the layers and a target layer by a conductor formed in an inner wall of a through hole penetrating the front and back of the insulating substrate are electrically connected. The first through hole for which the interlayer connection is performed and the first section including the first through hole are arranged in the layer adjacent to the first through hole so as not to overlap with other lands in the stacking direction. A line that includes a plurality of lands for detecting the depth of the stub and a plurality of first wirings that connect the plurality of lands and the first through hole, respectively, and connects the centers of the lands as viewed from the stacking direction. The plurality of lands are arranged so that the minutes are square or hexagonal .

The method for manufacturing a printed wiring board of the present invention includes a step of forming circuit wiring in a plurality of layers of an insulating substrate and a first through hole and a first through hole by plating the inner wall of a through hole penetrating the front and back surfaces of the insulating substrate. The step of forming the second through hole and electrically interlayerly connecting the circuit wiring of the target layer through the second through hole and the circuit wiring of the second through hole are not interconnected. In order to detect the depth of the stub which is an unnecessary portion, a plurality of stubs in the first section including the first through hole so as to be adjacent to the first through hole and not overlap with other lands in the stacking direction. A step of arranging the lands so that the line connecting the centers of the lands is a square or a hexagon when viewed from the stacking direction, and a plurality of firsts connecting the plurality of lands and the first through holes, respectively. It has a step of forming a wiring.

According to the present invention, the accuracy of back drilling can be improved and the required area of the test coupon can be reduced.

It is a perspective view which shows the structure of the printed wiring board of one Embodiment. It is a perspective view which looked at the arrangement example of the test coupon of the printed wiring board of FIG. It is a perspective view which looked at the example of the step-like arrangement (straight line arrangement) of the test coupon of the comparative example 1 from above. It is a figure which shows the other example (the configuration example which arranged the test coupon in 9 layers). It is a figure which shows the other example (the configuration example which arranged the test coupon in 12 layers). It is a figure which shows another Example (a configuration example which arranged the test coupon in a hexagonal grid pattern). It is an area comparison table for each number of layers of Comparative Example 1 (straight line arrangement) and the present invention (spiral arrangement).

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a configuration of a printed wiring board according to an embodiment of the present invention.

As shown in FIG. 1, the printed wiring board of this embodiment includes an insulating substrate 10 having a multi-layer structure. The insulating substrate 10 has a plurality of insulating layers such as nine layers, and circuit wiring (not shown) constituting an electrical circuit is formed between the insulating layers. The circuit wiring is also referred to as a wiring pattern, a conductor layer, or the like. In this embodiment, "circuit wiring" is defined as wiring that functions as a device after component mounting, and "wiring" that is simply described is defined as other wiring such as a test coupon.

The insulating substrate 10 is formed with a plurality of wirings 12 as first wirings and wirings 13 as second wirings. The wiring 12 connects the lands R1 to R8 of each layer and the through holes 11 as the first through holes, respectively. The wiring 13 is a wiring that is not connected to the circuit wiring but extends from the through hole 11 to the end of the board along the layer, and is connected to the land R1 to the end of the board when detecting the depth of the stub. This is a wiring for energizing R8. The aggregate of the wiring 12, the lands R1 to R8, and the through hole 11 is a test coupon.

In addition to the through hole 11 as a part of the test coupon, the insulating substrate 10 is formed with at least a second through hole (not shown) as a through hole to be back-drilled. These through holes 11 and the second through holes are formed by plating the inner walls of the through holes penetrating the front and back surfaces of the insulating substrate 10 to form conductors.

The second through hole is for electrically interlayer connection with the circuit wiring of the target layer, and is a through hole for which unnecessary stubs should be removed by back drilling.
On the other hand, the through hole 11 in the test coupon is not a target for removing the stub, and the drill contacts the lands R1 to R12 to print from the drill machine to the lands R1 to R12 in order to detect the stop position. The path of electrical conduction in the wiring board is composed of the wiring 13.

The through-holes to be back-drilled are through-holes in the circuit wiring, and the through-holes 11 in the test coupon are the first through-holes to be distinguished from the through-holes 11 in the test coupon, and the through-holes to be back-drilled. Is called the second through hole. That is, only the second through hole in which the stub adversely affects the electrical characteristics is removed by back drilling.

In the layer on which the circuit wiring is formed, a plurality of lands R1 to R8 for detecting the depth (position) of the stub in advance before stub processing of the second through hole (for test cutting) are formed. .. The layer on which each land R1 to R8 is formed is called a back drill target layer. Lands R1 to R8 are not connected to the circuit wiring of the same layer.

As shown in FIG. 2, the plurality of lands R1 to R8 are arranged in a surface (arranged in each layer so as not to overlap in the stacking direction) in the section A1 as the first section (area) including the through holes 11. The lands R1 to R8 are formed in layers having different stacking directions. Further, the plurality of lands R1 to R8 are formed in a predetermined shape (for example, circular shape) without overlapping each other when viewed through in the stacking direction. The section A1 is an area in which the through holes 11 are arranged in the central portion, and the lands R1 to R8 can be arranged in three vertical rows and three horizontal rows around the through holes 11.

These plurality of lands R1 to R8 are for detecting the depth at which the stub, which is an unnecessary portion of the conductor in which the circuit wiring is not interconnected, is scraped off by drilling or the like in the second through hole. For drilling, for example, an existing back drilling method is used.

The lands R1 to R8 are arranged adjacent to the through holes 11 in a layered order so as not to overlap with other lands in the stacking direction. This is called a "spiral staircase arrangement". In this example, each of the eight lands R1 to R8 is arranged adjacent to the through hole 11 in the section A1 around the one through hole 11. The lands R1 to R8 are arranged so that the line segments 21 connecting the centers of the lands R1 to R8 form a square grid when viewed from the stacking direction.

Here, when the back drill target layer is 8 layers, the spiral arrangement of the present invention (example of spiral staircase arrangement in FIG. 2) and comparative example 1 (example of linear staircase arrangement in FIG. 3) are compared in terms of area. explain.
As comparison conditions, eight types of depth types (layers), land diameters of lands R1 to R8 are 1 mm, and outer layer land (not shown) diameter of the through hole 11 connecting each layer is 1 mm, and each land is used. It is assumed that the gap B1 from R1 to R8 to the circuit wiring (wiring pattern) needs to be opened by 0.5 mm.

<Placement of test coupon in Comparative Example 1>
As shown in FIG. 3, in the case of Comparative Example 1 (straight line arrangement) in which the lands R1 to R8 are arranged linearly and stepwise when viewed from the wiring end surface when viewed from the stacking direction, the number of layers is eight. When the lands R1 to R8, the through holes 11 connecting the lands R1 to R8, and the gap B1 between the lands R1 to R8 are provided (8 lands + 1 through hole + gap), the lands R1 The distance from the center to the center of the land R8 (distance between the centers) is 7 mm, and the required area is 10 mm × 2 mm = 20 mm ² . In addition to the 8 layers, for example, in the case of 9 layers, the center-to-center distance) is 8 mm, and in the case of 12 layers, the center-to-center distance) is 11 mm.

<Placement of test coupon of the present invention>
On the other hand, in the spiral arrangement of the lands R1 to R8 of the present invention shown in FIG. 2, the vertical width Y1 is the diameter of the three lands R8, R1 and R2 + (gap B1 × 2) = 4 mm, and the horizontal width X1 is also three lands R2. , R3, R4 diameter + (gap B1 × 2) = 4 mm, and the area S0 is Y1 × X1 = 16 mm ² , and the arrangement of lands R1 to R8 of the present invention is better than the arrangement of Comparative Example 1. It can be seen that the required area can be reduced by 4 mm and ^{2 minutes.}

Further, in the present invention, the distance between the lands located at the farthest diagonal, for example, the center-to-center distance H1 between the lands R8 and the lands R4 is 2.8 mm, which is larger than the center-to-center distance of 7 mm in Comparative Example 1. It can be seen that it is less than 1/2.

Hereinafter, a method for manufacturing the printed wiring board of this embodiment will be described.
In the case of this printed wiring board, circuit wiring is formed in a plurality of layers of the insulating substrate 10. Subsequently, a through hole penetrating the front and back surfaces of the insulating substrate 10 is formed, and the inner wall of the formed through hole is plated to form a conductor, and electrical interlayer connection is performed with the circuit wiring of the target layer.

Subsequently, in order to detect the depth of the stub, which is an unnecessary part of the conductor in which the circuit wiring is not interconnected, in the second through hole, the through hole 11 is formed in the first section A including the through hole 11. A plurality of lands R1 to R8 are arranged adjacent to each other so as not to overlap with other lands R1 to R8 in the stacking direction.

Further, a plurality of wirings 12 for connecting the plurality of lands R1 to R8 and the through holes 11 are formed, and a wiring 13 extending from the through holes 11 to the end of the substrate is formed without being connected to the circuit wiring. In this way, a printed wiring board or an intermediate of the printed wiring board on which the wiring 12, the wiring 13, and the lands R1 to R8 are formed is formed.

The "intermediate body" is a state in which a test coupon is produced on the part to be discarded in the outer frame processing of the outer frame of the manufacturing panel when the printed wiring board is manufactured, and the test coupon is placed in the printed wiring board. What is manufactured and finally remains is a "printed wiring board". Hereinafter, the "intermediate body of the printed wiring board" is also referred to as the "printed wiring board".

Subsequently, when back-drilling the printed wiring board for removing stubs, the lands R1 to R8 are energized, and one surface (lower surface) of the insulating substrate 10 is subjected to an unnecessary stub depth. Move the drill to a position in the plane direction of lands R1 to R8 where (position) should be detected, cut the printed wiring board with the drill at that position, and land R1 to stop the tip of the drill by the back drill method. The position in contact with R8 is detected as the depth of the stub.

Then, the drill is moved to the position of the second through hole (not shown) where the stub should be actually removed, and the conductor of the second through hole is scraped by the back drill method based on the detected depth. 2 Remove unnecessary conductor stubs from the through holes.

The example of the manufacturing method shown here is an example, and it is possible to change the manufacturing method in various ways by exchanging each process, adding a new process, or deleting a part of the processes. ..

As described above, according to the printed wiring board of this embodiment, lands R1 to R8 are arranged in the section A including the through hole 11 so as to be adjacent to the through hole 11 and not overlap with other lands in the stacking direction, for example. By arranging the lands R1 to R8 in a spiral staircase around the through hole 11, the distance between the lands R1 to R8 can be shortened, the accuracy of back drilling can be improved, and the lands R1 to R8 can be formed. The required area S0 can be narrowed, and the test coupon can be arranged without sacrificing the area of the printed wiring board originally allocated for the circuit wiring. The spiral staircase is a state in which different layers are three-dimensionally spiral without overlapping in the stacking direction.

More specifically, it has the following effects.
By arranging the lands R1 to R8 on a surface (arranging them in a spiral staircase shape centering on the through hole 11), the lands R1 to R8 can be arranged in a linear manner even if they are stepped as in Comparative Example 1. becomes small area S0 needed to form (the present invention to 20 mm ² of Comparative example 1 is 16 mm ^2), the difference, even in the prior art could not form a test coupon region, forming a test coupon It will be possible to do.

Further, in the section A1 in which the lands R1 to R8 are arranged, the center-to-center distance H1 from the land center of one end located diagonally to the land center of the other end is the present invention with respect to 7 mm of Comparative Example 1. Is 2.8 mm, which is almost half shorter than that of a straight stepped one, so that the detection variation of the depths of lands R1 to R8 actually formed for each layer on the laminated substrate is reduced, and the machining accuracy of back drilling is reduced. Can be improved.

Next, a modified example in which the number and arrangement of lands are changed will be described with reference to FIGS. 4 to 7.
As shown in FIG. 4, for example, when the lands R1 to R9 are arranged in 9 types (9 layers) of 10-layer printed wiring boards, the lands R9 are the width X1 of the section A1 shown in FIG. A2, which is a second section surrounded by the section A1, is provided, and the land R9 is arranged adjacent to the land R8 in the width X2 thereof. The compartment A2 is a compartment in which the compartment A1 is expanded on both sides by the diameter of one land.

According to the dimensional conditions shown in FIG. 2, the area S1 required to form the lands R1 to R9 in this case is 4 mm in the vertical width Y1 and 5 mm in the horizontal width X2, and Y1 × X2 = 20 mm ² .

Further, the distance between the lands located at the farthest diagonal, for example, the distance H2 between the centers of the lands R9 and R4 is 3.6 mm, and in this example as well, the distance between the centers of Comparative Example 1 (straight line arrangement) is 8 mm ( It can be seen that it is sufficiently shorter than (not shown).

As shown in FIG. 5, for example, when the lands R1 to R12 are arranged in 12 types (12 layers) of 13-layer printed wiring boards, the lands R12 may not fit in the vertical width Y1 shown in FIG. The land R12 is arranged adjacent to the land R11 in the vertical width Y2 of the compartment A2. The compartment A2 is wider than the compartment A1 by the diameter of one land on both the vertical and horizontal sides.

According to the dimensional conditions shown in FIG. 2, the area S2 required to form the lands R1 to R12 in this case is 5 mm in the vertical width Y2 and 5 mm in the horizontal width X2, and Y2 × X2 = 25 mm ² .

Further, the distance between the lands located at the farthest diagonal, for example, the distance H3 between the centers of the lands R12 and R6 is 4.2 mm, and in this example as well, the distance between the centers of Comparative Example 1 (straight line arrangement) is 11 mm ( It can be seen that it is sufficiently shorter than (not shown).
That is, according to the modified examples shown in FIGS. 4 and 5, the measurement accuracy for each processing depth of the back drill is improved by shortening the distance between the lands located at the farthest diagonals of the test coupon. As a result, the back drilling accuracy can be improved.

As shown in FIG. 6, for example, when lands R1 to R6 are arranged in six layers (six layers) of seven-layer printed wiring boards, the lands R1 to R6 are viewed from the stacking direction. A plurality of lands R1 to R6 are arranged so that the line segments connecting the centers form a hexagonal grid (hexagon 22). By arranging in this way, the lands R1 to R6 can be arranged equidistantly from the through holes 11, and the detection variation of the depths of the lands R1 to R6 formed for each layer on the laminated substrate is reduced, and the back drill The processing accuracy of processing can be improved.

The example shown in FIGS. 4 to 6 is an example, and the area comparison between Comparative Example 1 (straight line arrangement) and the present invention (spiral arrangement) when the number of layers of the back drill target layer is 1 to 15 layers is compared. It is shown in FIG.

From FIG. 7, in the case of 11 layers, the area of Comparative Example 1 is 26 mm ² , the area of the present invention (spiral arrangement) is 20 mm ² , and the area difference is 6 mm ² , 15 layers. It can be seen that the area of 1 is 34 mm ² , the area of the present invention (spiral arrangement) is 25 mm ² , the area difference is 9 mm ² , and the area difference increases as the number of layers increases.

Although the embodiment of the present invention has been described, this embodiment is shown as an example, and can be implemented in various other forms, and the components of the present invention are not deviated from the gist of the invention. It can be omitted, replaced, or changed.

10 ... Insulated substrate, 11 ... Through hole, 12, 13 ... Wiring, A1, A2 ... Section, B1 ... Gap, H1, H2, H3 ... Center distance, R1 to R12 ... Land, S0, S1, S2 ... Area, X1, X2 ... width, Y1, Y2 ... height.

Claims (6)

An insulating substrate having a plurality of layers and having circuit wiring formed in the layers,
A first through hole that electrically interconnects the target layer with a conductor formed in the inner wall of the through hole that penetrates the front and back of the insulating substrate.
In the first section including the first through hole, a plurality of lands for detecting the depth of the stub arranged in the layer adjacent to the first through hole so as not to overlap with other lands in the stacking direction. ,
A plurality of first wirings for connecting the plurality of lands and the first through holes are provided .
A printed wiring board characterized in that the plurality of lands are arranged so that a line segment connecting the centers of the lands is square or hexagonal when viewed from the stacking direction. The printed wiring board according to claim 1, wherein the land that does not fit in the first section is arranged in a second section that surrounds the first section. The printed wiring board according to claim 1 or 2, further comprising a second wiring extending from the first through hole to the end of the substrate without being connected to the circuit wiring. The process of forming circuit wiring in multiple layers of an insulating substrate,
The inner wall of the through hole penetrating the front and back surfaces of the insulating substrate is plated to form a first through hole and a second through hole, and the circuit wiring and electrical of the target layer are electrically passed through the second through hole. The process of connecting between layers and
In order to detect the depth of the stub, which is an unnecessary portion where the circuit wiring of the second through hole is not interconnected, the first through hole and the first through hole are formed in the first section including the first through hole. A process of arranging a plurality of lands adjacent to each other so as not to overlap with other lands in the stacking direction so that the line segment connecting the centers of the lands is a square or a hexagon when viewed from the stacking direction.
A method for manufacturing a printed wiring board, which comprises a step of forming a plurality of first wirings for connecting the plurality of lands and the first through holes, respectively. The method for manufacturing a printed wiring board according to claim 4 , further comprising a step of forming a second wiring extending from the first through hole to the end of the substrate without being connected to the circuit wiring. A step of energizing the land, cutting from one surface of the insulating substrate by a back drill method, and detecting the position where the tip of the drill abuts on the land as the depth of the stub.
The method for manufacturing a printed wiring board according to claim 4 or 5 , further comprising a step of removing the stub from the second through hole by a back drill method based on the detected depth.

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