JP7210905B2 - Printed wiring board and manufacturing method thereof - Google Patents

Description

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

Conventionally, a printed wiring board having a multilayer structure in which a plurality of wiring substrates are laminated is known. For example, Patent Literatures 1 and 2 listed below disclose configurations in which wirings formed on the main surface of each wiring substrate are connected by conductor posts extending in the thickness direction of the substrate.

WO2011/155162 WO2014/109139

In the printed wiring board according to Patent Document 1, the thickness of the region where the wiring is formed is locally increased. Therefore, when a printed wiring board is constructed by superimposing a plurality of wiring substrates by a technique such as lamination or batch lamination, unevenness is likely to occur on the surface of the printed wiring board, making it difficult to obtain high flatness. . In order to improve the flatness of the printed wiring board, for example, Patent Document 2 above proposes a technique of applying a thermoplastic resin to a part of the main surface region before batch lamination. A task remained.

Accordingly, the inventors have made extensive research on flattening printed wiring boards, and instead of forming wiring on the main surface of the wiring substrate, the inventors have found that by embedding the wiring and conductor posts for interlayer connection in the wiring substrate, the conductor It has been found that an increase in thickness in the region of the post is suppressed, and as a result, the flatness of the wiring substrate can be improved. According to such a configuration, it is possible to improve the flatness and interlayer connection stability of a plurality of printed wiring boards laminated by a method such as batch lamination.

However, resins that make up wiring substrates, especially thermoplastic resins that are often used in parts used in high-frequency regions, generally have low adhesion to conductors such as metals that make up conductor posts and wiring, and resin Since the coefficient of thermal expansion differs greatly between conductors and conductors, the conductor posts on which the wires are stacked may peel off from the wiring substrate, or the insulating resin may peel off from the wires or conductor posts due to temperature changes during manufacturing or driving. can occur.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a printed wiring board in which adhesion of conductor posts to a wiring substrate is improved, and a method for manufacturing the printed wiring board.

A printed wiring board according to one aspect of the present invention includes an insulating resin film having a first main surface and a second main surface; and a wiring embedded in an insulating resin film and extending parallel to the second main surface and exposed from the second main surface, wherein the conductor post is the thickness of the wiring. a wiring portion having the same thickness as the wiring and exposed from the second main surface; and a main body portion integrally formed with the wiring portion and extending from the wiring portion to the first main surface, wherein It has a first portion whose width gradually narrows from the portion toward the first main surface side.

In the above printed wiring board, since the conductor posts including the wiring and the wiring portion of the wiring substrate are embedded in the insulating resin film, an increase in the thickness of the region where the wiring and the wiring portion are formed is suppressed. In addition, since the main body of the conductor post is smoothly connected to the wiring part at the first part, stress is less likely to concentrate at the boundary between the main body and the wiring part, and the conductor post is peeled off from the insulating resin film. situation is suppressed.

According to another aspect of the printed wiring board, the main body portion of the conductor post extends from the first portion toward the first main surface and has a width that gradually widens toward the first main surface. have a part. In this case, the insulating resin film enters the concave portion of the main body composed of the first portion and the second portion, thereby further improving the adhesion between the conductor post and the insulating resin film in the wiring substrate. In addition, a sufficiently large area can be secured for the upper surface of the conductor post on the first main surface. Therefore, when the wiring base including the conductor posts is overlapped with another wiring base on the first main surface side of the wiring base, a sufficiently large bonding area is ensured between the wiring base and the wiring of the other wiring base. and the adhesion between a plurality of wiring substrates is improved.

According to another aspect of the printed wiring board, the end face of the wiring portion of the conductor post exposed from the second main surface is recessed from the second main surface. When a plurality of wiring substrates are laminated through the connecting portion, the connecting portion enters into the portion of the wiring portion recessed from the second main surface, thereby suppressing an increase in thickness due to the connecting portion and further increasing the thickness of the printed wiring board. Flatness can be improved.

A method for manufacturing a printed wiring board according to one aspect of the present invention includes an insulating resin film having a first main surface and a second main surface, and an insulating resin film embedded in the insulating resin film and extending from the first main surface to the second main surface. Manufacture of a printed wiring board including at least one wiring substrate having conductor posts penetrating to the surface and wiring embedded in an insulating resin film, extending parallel to a second main surface and exposed from the second main surface a printed wiring board manufacturing method comprising: providing a first mask in a region where the conductor post is to be formed on one surface of the metal plate to be the conductor post and the wiring; A step of etching from one side of the metal plate using a step of forming the body portion of the conductor post, and a step of forming a region where the wiring portion of the conductor post is to be formed and the wiring on one side of the metal plate. providing a second mask in a region to be formed; using the second mask to perform an etching process from one side of the metal plate to form the wiring portion of the conductor post and the wiring; forming an insulating resin film integrally covering conductor posts and wiring provided on one side; and thinning the metal plate from the other side to separate the conductor posts and wiring.

According to the printed wiring board manufacturing method described above, it is possible to obtain a wiring substrate in which conductor posts including wiring and wiring portions are embedded in an insulating resin film, and the wiring and wiring portions are formed in the obtained wiring substrate. An increase in the thickness of the region where the Moreover, in the obtained wiring substrate, since the body portion of the conductor post is smoothly connected to the wiring portion at the first portion, stress is less likely to concentrate at the boundary between the body portion and the wiring portion, and the conductor post is made of insulating resin. The situation of peeling from the film is suppressed.

In the method of manufacturing a printed wiring board according to another aspect, in the step of thinning the metal plate, the metal plate is thinned by etching.

According to another aspect of the method for manufacturing a printed wiring board, in the step of thinning the metal plate, overetching is performed to recede the end surface of the wiring portion of the conductor post from the second main surface. When a plurality of wiring substrates are laminated through the connecting portion, the connecting portion enters into the portion of the wiring portion recessed from the second main surface, thereby suppressing an increase in thickness due to the connecting portion and further increasing the thickness of the printed wiring board. Flatness can be improved.

ADVANTAGE OF THE INVENTION According to this invention, the printed wiring board and its manufacturing method are provided in which the adhesiveness of the conductor post in the wiring substrate is improved.

1 is a schematic cross-sectional view showing a printed wiring board according to one embodiment of the present invention; FIG. FIG. 2 is a schematic cross-sectional view showing the wiring substrate shown in FIG. 1; FIG. 3 is a schematic cross-sectional view showing a conductor post shown in FIG. 2; 3 is a schematic cross-sectional view showing the wiring shown in FIG. 2; FIG. It is the figure which showed each process of the manufacturing method of the printed wiring board shown in FIG. It is the figure which showed each process of the manufacturing method of the printed wiring board shown in FIG. 2 is an enlarged view of a main part of the printed wiring board shown in FIG. 1; FIG. 4A and 4B are schematic cross-sectional views showing conductor posts in different modes; 4A and 4B are schematic cross-sectional views showing conductor posts in different modes; FIG. 4 is a schematic cross-sectional view showing a wiring substrate in a different mode;

Various embodiments are described in detail below with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and overlapping descriptions are omitted.

As shown in FIG. 1, a printed wiring board 1 according to the embodiment has a configuration in which a plurality of wiring substrates 20 are laminated. In this embodiment, a printed wiring board 1 including three layers of wiring substrates 20 will be described.

As shown in FIGS. 1 and 2, the wiring substrate 20 has a thin film shape with a substantially uniform thickness. The wiring substrate 20 includes an insulating resin film 22 , and conductor posts 30 and wires 40 embedded in the insulating resin film 22 .

The insulating resin film 22 is a thin film member having an upper surface 20a (first main surface) and a lower surface 20b (second main surface). The insulating resin film 22 can be made of a thermoplastic resin, and is made of a liquid crystal polymer (LCP) in this embodiment.

The conductor post 30 is made of a conductive material, and is made of Cu in this embodiment. The conductor post 30 extends along the thickness direction of the wiring base 20 and penetrates the wiring base 20, and as shown in FIG. I have. The height of the conductor post 30 (the length in the thickness direction of the wiring substrate 20) is approximately 30 to 100 μm, and is 50 μm as an example.

The wiring portion 32 is a plate-shaped thin piece portion extending parallel to the lower surface 20 b of the insulating resin film 22 . The wiring portion 32 has a substantially uniform thickness t1. A thickness t1 of the wiring portion 32 is, for example, 10 μm. The lower surface of the wiring portion 32 constitutes the lower surface 30b of the conductor post 30, and the lower surface 30b of the conductor post 30 is parallel to and flush with the lower surface 20b of the wiring substrate 20. As shown in FIG. The upper surface 32 a of the wiring portion 32 extends parallel to the lower surface 30 b of the conductor post 30 and the lower surface 20 b of the wiring base 20 . A side surface 32b of the wiring portion 32 is a curved surface that is curved inwardly. In this embodiment, the angle θ1 between the upper surface 32a and the side surface 32b is less than 90° (that is, an acute angle).

The body portion 34 is a columnar portion extending upward from the wiring portion 32 to the upper surface 20a. In the present embodiment, the body portion 34 has a circular cross-sectional shape perpendicular to its extending direction (that is, the thickness direction of the wiring substrate 20).

The body portion 34 has a lower portion (first portion) 35 whose width gradually narrows upward and an upper portion (second portion) whose width gradually expands upward. ) 36.

The lower portion 35 has a maximum width W1 at its lower end and the upper portion 36 has a maximum width W2 at its upper end. In this embodiment, the maximum width W1 of the lower portion 35 is longer than the maximum width W2 of the upper portion 36 (W1>W2). The body portion 34 has a minimum width W3 at a switching position P where the lower portion 35 is switched to the upper portion 36 (W1>W2>W3). A side surface 34a of the body portion 34 in the lower portion 35 is a curved surface, and is continuously connected to the upper surface 32a of the wiring portion 32 at its lower end. The side surface 34a of the body portion 34 in the upper portion 36 is also a curved surface, and its lower end is continuously connected to the side surface 34a of the body portion 34 in the lower portion 35 .

The upper surface of the upper portion 36 constitutes the upper surface 30 a of the conductor post 30 . The upper surface 30a of the conductor post 30 is parallel to and flush with the upper surface 20a of the wiring substrate 20. As shown in FIG.

The wiring 40 is made of the same conductive material as the conductor post 30, and is made of Cu in the board of this embodiment. The wiring 40 has a substantially rectangular cross-section, as shown in FIG. The wiring 40 is formed on the lower surface 20b side of the wiring substrate 20 and is not formed on the upper surface 20a side. The wiring 40 extends parallel to the bottom surface 20b of the insulating resin film 22 and is exposed on the bottom surface 20b. The wiring 40 has a substantially uniform thickness t2. The thickness t2 of the wiring 40 is the same as the thickness t1 of the wiring portion 32 of the conductor post 30, and is 10 μm as an example. The wiring 40 forms part of the circuit of the wiring substrate 20 on the lower surface 20b side.

The lower surface 40b of the wiring 40 is parallel to and flush with the lower surface 20b of the wiring substrate 20 . The upper surface 40 a of the wiring 40 extends parallel to the lower surface 40 b of the wiring 40 and the lower surface 20 b of the wiring substrate 20 . A side surface 40c of the wiring 40 is a curved surface that is curved inwardly. In this embodiment, the angle θ2 between the upper surface 40a and the side surface 40c is less than 90° (that is, an acute angle).

Next, a method for manufacturing the printed wiring board 1 described above will be described with reference to FIGS.

In order to manufacture the printed wiring board 1, it is necessary to manufacture the wiring substrate 20. FIG. When manufacturing the wiring substrate 20, first, as shown in FIG. 5A, one sheet of metal plate 50 (Cu plate in this embodiment) to be the conductor posts 30 and the wirings 40 is prepared. Then, a first mask 51 is formed on the upper surface 50a of the metal plate 50 in a region where the main body portion 34 of the conductor post 30 is formed and a region where a frame 56, which will be described later, is formed.

Next, as shown in FIG. 5B, using a first mask 51, the metal plate 50 is etched for the first time from the upper surface 50a side. By the first etching process, the protrusion 52 and the frame 56 that will become the main body 34 of the conductor post 30 are formed in the region where the first mask 51 is formed. Further, the upper surface 50a sinks in areas other than the area where the first mask 51 is formed.

Then, as shown in FIG. 5(c), after removing the first mask 51, on the upper surface 50a of the metal plate 50, a first film is formed on the region where the wiring portion 32 of the conductor post 30 and the wiring 40 are formed. 2 mask 53 is formed. The second mask 53 has an opening 53a in a region other than the region where the wiring portion 32 of the conductor post 30 and the wiring 40 are formed, and the upper surface 50a of the metal plate 50 is exposed through the opening 53a.

Next, as shown in FIG. 5D, using a second mask 53, the metal plate 50 is etched for the second time from the upper surface 50a side. By the second etching process, the metal plate 50 in the regions corresponding to the openings 53a of the second mask 53 is selectively removed, and holes 54 are formed in the removed portions.

Then, as shown in FIG. 6A, the second mask 53 is removed. Thereby, the upper surface 50a of the metal plate 50 is exposed. At this time, on the upper surface 50 a of the metal plate 50 , a protruding portion 55 that protrudes from the bottom surface of the hole portion 54 is formed in a region other than the region where the hole portion 54 is formed. After removing the second mask 53, a layer (a Cr layer, a Ti layer, etc.) for preventing the oxidation of Cu can be formed on the upper surface 50a of the metal plate 50, particularly on the top surfaces of the protrusions 52. FIG.

Further, as shown in FIG. 6(b), resin powder 60 to be the insulating resin film 22 is supplied into the frame 56 on the upper surface 50a to cover the entire upper surface 50a with the resin powder 60. As shown in FIG. At this time, the projections 52 and the protuberances 55 formed on the upper surface 50 a are also covered with the resin powder 60 . Then, using the heat plate 62, the metal plate 50 is hot-pressed from the upper surface 50a side, and then cooled.

As a result, as shown in FIG. 6C, the upper surface 50a of the metal plate 50 is covered with the insulating resin film 22 described above. At this time, the upper surface 52 a of the protrusion 52 is exposed from the insulating resin film 22 . After hot pressing, if a resin film is formed on the upper surface 52a of the projection 52, a polishing process such as CMP, grindstone polishing, or fly-cutting is performed in order to expose the upper surface 52a of the projection 52 from the insulating resin film 22. may be performed. In the process of forming the insulating resin film 22, the frame 56 prevents the material of the insulating resin film 22 from flowing out of the region and prevents excessive pressing that may cause the film to become thinner than the desired thickness. Therefore, it is useful for controlling the thickness of the insulating resin film 22 . When the frame 56 is formed by the above-described procedure, the height position of the upper surface 52a of the protrusion 52 and the height position of the upper surface of the frame 56 are likely to match. It is even more useful.

Finally, the metal plate 50 is thinned from the lower surface 50b side to obtain the wiring substrate 20 shown in FIG. Specifically, the metal plate 50 is thinned from the lower surface 50b side to a position reaching the hole 54 (position D indicated by the dashed dotted line in FIG. 6C). As a result, the adjacent protuberances 55 are separated and insulated at the hole 54 . In this embodiment, the metal plate 50 is thinned by etching.

The printed wiring board 1 described above is obtained by collectively laminating a plurality of wiring substrates 20 produced as described above by hot pressing in a state of being superimposed. When stacking the wiring substrates 20 , a connecting conductor layer made of Au, Sn, Ag, solder, or the like may be formed on one or both of the upper surface 30 a and the lower surface 30 b of the conductor post 30 .

In the method for manufacturing the printed wiring board 1 described above, the side surface 34a of the main body portion 34 of the conductor post 30 is formed in the first etching process shown in FIG. 5(b). Since the first etching process is isotropic etching, the side surface 34a of the main body 34 becomes a curved surface. Moreover, since the height of the body portion 34 of the conductor post 30 is relatively high, the body portion 34 has a constricted shape. In other words, the body portion 34 has a shape in which the width of the upper portion 36 gradually narrows downward to reach the minimum width W3 at the switching position P, and the width of the lower portion 35 gradually widens downward.

As described above, in the wiring substrate 20 of the printed wiring board 1 , the conductor post 30 including the wiring portion 32 and the wiring 40 are embedded in the insulating resin film 22 . Therefore, the thickness of the wiring substrate 20 does not increase in the region where the wiring portion 32 is formed. Also, the thickness of the wiring substrate 20 does not increase in the region where the wiring 40 is formed. Therefore, by forming printed wiring board 1 by laminating a plurality of wiring substrates 20, printed wiring board 1 having high flatness can be obtained.

Moreover, in the wiring substrate 20 of the printed wiring board 1, as shown in FIG. 7, the body portion 34 of the conductor post 30 is smoothly connected to the wiring portion 32 at the lower portion 35 thereof. In other words, the boundary between the main body portion 34 and the wiring portion 32 is not formed with a corner portion or a stepped portion where stress tends to concentrate. Therefore, even if temperature changes occur during manufacturing or driving of the printed wiring board 1 , stress is less likely to concentrate at the boundary between the main body portion 34 and the wiring portion 32 , and the conductor post 30 is separated from the insulating resin film 22 . The situation is effectively contained.

Since the wiring portion 32 and the main body portion 34 of the conductor post 30 are integrally formed, the wiring portion and the main body portion are formed separately, and an interface exists between the wiring portion and the main body portion. Defects such as cracks along the interface are less likely to occur than in the case of a structure that does not.

Further, as shown in FIG. 7, in the wiring substrate 20 of the printed wiring board 1, the main body portion 34 of the conductor post 30 is smoothly connected to the upper conductor post 30 at the upper portion 36 thereof. In other words, corners and steps where stress tends to concentrate are not formed at the boundaries with the conductor posts 30 positioned above. Therefore, even if temperature changes occur during manufacturing or driving of the printed wiring board 1 , stress is less likely to concentrate at the boundary between the conductor posts 30 , effectively preventing the conductor posts 30 from peeling off from the insulating resin film 22 . is constrained to

Furthermore, since the main body portion 34 of the conductor post 30 has the lower portion 35 and the upper portion 36 whose width increases as the distance from the switching position P increases, the lower portion 35 and the upper portion 36 are arranged on the sides of the main body portion 34 . A recess is defined. In the wiring substrate 20, the resin material of the insulating resin film 22 enters the concave portion of the side portion of the main body portion 34 in the step of hot pressing shown in FIG. It is sandwiched from both sides by the resin material. As a result, the adhesion of the conductor posts 30 to the wiring substrate 20 is further improved.

In addition, since the main body portion 34 of the conductor post 30 extends from the lower portion 35 toward the upper surface 20a and has the upper portion 36 whose width gradually increases toward the upper surface 20a, the conductor post 30 is A sufficiently large area can be secured for the upper surface 30a of the . Therefore, when the wiring substrate 20 including the conductor posts 30 is overlapped with another wiring substrate 20 on the upper surface 20a side of the wiring substrate 20, there is sufficient space between the wires 40 and the conductor posts 30 of the other wiring substrate 20. A large bonding area can be secured between the wiring substrates 20, and high adhesion is realized between the plurality of wiring substrates 20. As shown in FIG.

As with the conductor post 30, the wiring 40 has a recess defined by a side surface 40c that is curved inwardly. Therefore, the wiring 40 is sandwiched from both sides by the resin material of the insulating resin film 22, and the adhesion of the wiring 40 to the wiring substrate 20 is improved.

The conductor post 30 is not limited to the shape described above, and may have the shape shown in FIGS. 8 and 9, for example. Both the conductor post 30A shown in FIG. 8 and conductor post 30B shown in FIG. are the same as the conductor posts 30 described above.

The conductor post 30A shown in FIG. 8 is designed such that the maximum width W1 of the lower portion 35 and the maximum width W2 of the upper portion 36 are the same (W1=W2). different from 30. Even the wiring substrate 20 having such a conductor post 30A has the same or equivalent effect as the wiring substrate 20 having the conductor post 30 described above.

In the conductor post 30B shown in FIG. 9, the body portion 34B is composed only of a portion 35 (first portion) whose width gradually narrows upward from the wiring portion 32 . That is, the main body portion 34B does not have a switching position P, and the main body portion 34B has a minimum width W2 at its upper end. Even the wiring substrate 20 having such a conductor post 30B has the same or equivalent effect as the wiring substrate 20 having the conductor post 30 described above.

The wiring substrate 20 is also not limited to the shape described above, and may have the shape shown in FIG. 10, for example. The wiring substrate 20A shown in FIG. 10 is different from the lower surface 30b of the conductor post 30 exposed from the lower surface 20b of the insulating resin film 22 (that is, the lower end surface of the wiring portion 32). It is different from the wiring substrate 20 . The structure of the wiring substrate 20A is obtained by, for example, performing overetching in the step of thinning the metal plate 50 shown in FIG. 6(c). When the lower surface 30b of the conductor post 30 is recessed from the lower surface 20b of the insulating resin film 22, when laminating a plurality of wiring substrates 20 via the connecting portion 10 formed on the lower surface 30b of the conductor post 30, The connecting portion 10 enters into the portion of the wiring portion 32 that is receded from the lower surface 20b. As a result, an increase in the thickness of the region where the connecting portion 10 is formed is suppressed, and the flatness of the printed wiring board 1 is further improved. The connecting portion 10 can be made of solder, conductive paste, or the like, for example.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made. For example, the number of wiring substrates constituting the printed wiring board is not limited to three layers, and the number can be increased or decreased as appropriate.

DESCRIPTION OF SYMBOLS 1... Printed wiring board 10... Connection part 20, 20A... Wiring base 30, 30A, 30B... Conductor post 32... Wiring part 34... Main body part 35... Lower part 36... Upper part 40... Wiring, 50... Metal plate.

Claims (3)

An insulating resin film having a first main surface and a second main surface, a conductor post embedded in the insulating resin film and penetrating from the first main surface to the second main surface, and the insulating resin film. A printed wiring board manufacturing method for manufacturing a printed wiring board including at least one wiring substrate having wiring embedded in a second main surface and extending parallel to the second main surface and exposed from the second main surface. hand,
providing a first mask in a region where the conductor post is to be formed on one surface of the metal plate to be the conductor post and the wiring;
a step of performing an etching process from one side of the metal plate using the first mask to form a body portion of the conductor post;
providing a second mask on one surface of the metal plate in a region where the wiring portion of the conductor post is to be formed and in a region where the wiring is to be formed;
a step of performing an etching process from one surface side of the metal plate using the second mask to form the wiring portion of the conductor post and the wiring;
forming an insulating resin film integrally covering the conductor post and the wiring provided on one surface of the metal plate;
and thinning the metal plate from the other surface side to separate the conductor post and the wiring. 2. The method of manufacturing a printed wiring board according to claim 1 , wherein in the step of thinning the metal plate, the metal plate is thinned by etching. 3. The method of manufacturing a printed wiring board according to claim 2 , wherein in the step of thinning the metal plate, overetching is performed to retreat an end surface of the wiring portion of the conductor post from the second main surface.

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