JP2007220908A - Manufacturing method of multilayer printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a multilayer printed wiring board whereby its outer connecting terminal can be exposed to the external (be formed) by using no mechanical peeling. <P>SOLUTION: On both the surfaces of an inner-layer wiring base material 10, there are formed respectively in a laminar way an outer-layer wiring base material 20 having an outer-layer insulating layer 22, and an outer-layer conductor layer 24; and an outer-layer wiring base material 21 having an outer-layer insulating layer 23, and outer-layer conductor layer 25 to constitute a multilayer printed wiring board having four conductor layers. The outer-layer insulating layers 22, 23 are opposed to a hard portion As and are not opposed to a flexible portion Af. The outer-layer insulating layers 22, 23 are not laminated on outer connecting terminal 12t and on an outer-terminal coating layer 18. When so exposing to the external finally the outer connecting terminal 12t that the outer connecting terminal 12t and the outer-terminal coating layer 18 are not affected by the outer insulating layers 22, 23; the mechanical peeling of the outer insulating layer 22 becomes unnecessary and the outer insulating layer 22 can be exposed to the external easily and accurately. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a printed wiring board for electronic equipment used for mounting electronic components, and more particularly to a method for manufacturing a multilayer printed wiring board having two or more conductor layer patterns.

  A multilayer printed wiring board having a flexible part and a hard part is commonly called "flex rigid wiring board" or "composite multilayer flexible wiring board", and is likely to be used in many cases as electronic devices become smaller, more precise, and more complex. It has become. Along with this, various problems such as a step difference in the vicinity of the boundary between the flexible part and the hard part, a problem in the surface treatment of the exposed part of the flexible part, and the necessity of simplification of the process have become apparent.

  A multilayer printed wiring board in which external connection terminals are formed of a flexible inner layer wiring base material has been proposed. As described above, the multilayer printed wiring board having the flexible portion and the hard portion has a complicated manufacturing process, difficulty in forming the external connection terminals, and difficulty in processing at the boundary between the flexible portion and the hard portion. Many problems have been pointed out.

  A conventional method for manufacturing a multilayer printed wiring board will be described with reference to FIGS. 10 to 17 are all cross-sectional views, but all hatchings are omitted for easy viewing of the drawings.

  FIG. 10 is a cross-sectional view showing a cross section of an inner layer wiring substrate of a conventional multilayer printed wiring board.

  By configuring the inner wiring substrate 110 with a flexible wiring substrate and configuring the outer wiring substrates 120 and 121 (see FIG. 14) with a hard wiring substrate, the hard portion As and the flexible portion Af are formed. A multilayer printed wiring board 101 having a flex-rigid (composite multilayer printed wiring board) configuration will be described as a conventional example. The multilayer printed wiring board 101 is configured to include an external connection terminal 112t (see FIG. 11) in the flexible portion Af.

  In addition, in addition to the inner layer wiring substrate 110, when the outer layer wiring substrates 120 and 121 are also formed of a flexible wiring substrate, a flexible multilayer printed wiring board can be obtained.

  An inner wiring substrate 110 constituting the inner layer of the multilayer printed wiring board 101 includes an inner insulating layer 111 and inner conductor layers 112 and 113 laminated on both surfaces thereof. In the following description, the multilayer printed wiring board 101 is used even during the process.

  As the inner layer wiring substrate 110, a commercially available double-sided flexible wiring board material is used. The inner insulating layer 111 is made of a flexible insulating resin film, and is generally made of an insulating resin film (FPC material) such as polyimide, polyetherketone, or other liquid crystal polymer.

  The inner conductor layers 112 and 113 are laminated on both sides of the inner insulating layer 111 via an adhesive or without an adhesive. The inner conductor layers 112 and 113 are made of copper foil, but may be made of other metal foil.

  The multilayer printed wiring board 101 includes, in a completed state (see FIG. 17), a rigid hard part As and a flexible flexible part Af formed by being derived from the hard part As. Accordingly, the inner wiring substrate 110 similarly has a hard corresponding portion As and a flexible corresponding portion Af as regions corresponding to the hard portion As and the flexible portion Af when completed (hereinafter, the hard portion As and the completed hard portion As and The flexible portion Af, the hard corresponding portion As and the flexible corresponding portion Af in the process are simply referred to as the hard portion As and the flexible portion Af without distinction.)

  In addition, in the manufacturing process of the multilayer printed wiring board 101, an auxiliary wiring base material that plays a role of holding the hard portion As and the flexible portion Af may be disposed around, but is omitted.

  FIG. 11 is a cross-sectional view showing a cross section of an inner layer wiring base material on which an inner layer circuit pattern of a conventional multilayer printed wiring board is formed.

  By patterning the inner conductor layers 112 and 113, inner circuit patterns 112p and 113p are formed. That is, by applying an etching resist (not shown) to the inner conductor layers 112 and 113 and patterning (etching) the inner conductor layers 112 and 113 by a well-known photolithography technique, the inner circuit patterns 112p and 113p are formed. The external connection terminal 112t is formed.

  The inner layer circuit patterns 112p and 113p are formed corresponding to the hard portion As, and the external connection terminal 112t is formed corresponding to the flexible portion Af by the inner layer conductor layer 112 similarly to the inner layer circuit pattern 112p. In the completed multilayer printed wiring board 101, the external connection terminal 112t forms a circuit pattern at the flexible portion Af, and the tip portion is configured as the external connection terminal 112t (see FIG. 17).

  After forming the inner layer circuit patterns 112p and 113p and the external connection terminal 112t, through holes or via holes penetrating between the inner layer circuit patterns 112p and 113p are formed by performing appropriate drilling using a laser or NC drill or the like. After that, an inner through-hole conductor (not shown) or a via-hole conductor (not shown) is appropriately formed by applying plating (for example, gold plating, copper plating, etc.) to the through hole or via hole using a panel plating method. To do. Note that the plating layer is not shown in consideration of the visibility of the drawing.

  FIG. 12 is a cross-sectional view showing a cross-section in a state in which a coating layer that covers an inner layer wiring substrate of a conventional multilayer printed wiring board is formed.

  After forming the inner layer circuit patterns 112p and 113p and the external connection terminal 112t, the adhesive layer 115 and the covering layer 116 in which the opening 112w corresponding to the external connection terminal 112t is formed in advance by windowing with a mold or the like are used as the inner layer conductor layer. 112 (inner layer circuit pattern 112p) is laminated. Note that the thickness of the adhesive layer 115 and the thickness of the coating layer 116 are adjusted to be thin in advance so as to have appropriate thicknesses. Further, a coverlay material in which the coating layer 116 is coated with the adhesive layer 115 may be used.

  FIG. 13 is a cross-sectional view showing a cross-section in a state where an external terminal covering layer covering external connection terminals of a conventional multilayer printed wiring board is aligned.

  The external terminal covering material 117 covering the external connection terminal 112t exposed through the opening 112w and the covering material holding conductor 119 for holding and reinforcing the external terminal covering material 117 are aligned and laminated as the external terminal covering layer.

  The external terminal covering material 117 and the covering material holding conductor 119 are temporarily fixed (applied) after properly aligning the external terminal covering material 117 with the external connection terminal 112t. Since the molded product is mechanically aligned, a tolerance of misalignment of about ± 0.2 mm is required.

  FIG. 14 is a cross-sectional view showing a cross section in a state where an outer layer wiring base material is laminated on an inner layer wiring base material of a conventional multilayer printed wiring board.

  The outer layer wiring substrate 120 and the outer layer wiring substrate 121 are laminated on both surfaces of the inner layer wiring substrate 110. The outer wiring substrate 120 has an outer insulating layer 122 and an outer conductor layer 124, and the outer wiring substrate 121 has an outer insulating layer 123 and an outer conductor layer 125. The outer wiring substrate 120 and the outer wiring substrate 121 are configured as hard wiring substrates.

  That is, the outer conductor layer 124 is laminated on the outer insulating layer 122 as an adhesive to constitute the outer wiring substrate 120, and the outer conductor layer 125 is laminated on the outer insulating layer 123 as an adhesive to form the outer wiring substrate 121. Configure. Therefore, at this stage, a multilayer printed wiring board having four conductor layers is formed.

  The outer insulating layer 122 and the outer conductor layer 124 are arranged so as to cover the entire surface of the inner wiring substrate 110 and cover the covering layer 116 and the covering material holding conductor 119 (external terminal covering material 117).

  In addition, the outer insulating layer 123 and the outer conductor layer 125 are formed in advance so as to face the hard part As and not to the flexible part Af by performing window cutting with a mold or the like. Thereby, the characteristics of the hard part As and the flexible part Af can be reliably maintained.

  As described above, the outer insulating layer 122 as an adhesive is bonded and laminated to the covering material holding conductor 119 (and the external terminal covering material 117) formed corresponding to the external connection terminal 112t.

  After forming outer layer wiring substrate 120 (outer layer insulating layer 122 and outer layer conductor layer 124) and outer layer wiring substrate 121 (outer layer insulating layer 123 and outer layer conductor layer 125), appropriate drilling is performed using a laser or NC drill or the like. To form a through hole or a via hole (not shown) penetrating between the outer layer conductor layer 124 and the inner layer circuit pattern 112p or between the outer layer conductor layer 125 and the inner layer circuit pattern 113p, and thereafter panel plating method A through-hole conductor or a via-hole conductor (not shown) is appropriately formed by plating the through-hole or the via hole using, for example, gold plating or copper plating. Note that the plating layer is not shown in consideration of the visibility of the drawing.

  FIG. 15 is a cross-sectional view showing a cross-section in a state where an outer layer mask pattern for forming an outer layer circuit pattern is formed on an outer layer wiring substrate of a conventional multilayer printed wiring board.

  Outer layer mask patterns 124m and 125m serving as etching resists are formed on the surfaces of the outer conductor layers 124 and 125, respectively, using a well-known photolithography technique.

  The outer insulating layer 122 and the outer conductive layer 124 in the region covering the covering material holding conductor 119 (and the external terminal covering material 117) are coated with the external terminal so that the outer conductive layer 124 is not etched in the next etching step. An outer layer mask pattern 124mt is formed in a region corresponding to the material 117.

  FIG. 16 is a cross-sectional view showing a cross-section in a state where an outer layer circuit pattern is formed on an outer layer wiring substrate of a conventional multilayer printed wiring board using an outer layer mask pattern.

  The outer layer circuit patterns 124p and 125p are formed by etching (patterning) the outer layer conductor layers 124 and 125 by a known etching technique using the outer layer mask patterns 124m, 124mt, and 125m as a mask.

  Since the outer layer insulating layer 122 and the outer layer conductor layer 124 are left by the outer layer mask pattern 124mt in the region corresponding to the external terminal covering material 117 (external connection terminal 112t) simultaneously with the formation of the outer layer circuit patterns 124p and 125p, The outer insulating layer 122t and the outer conductor pattern 124t remain corresponding to the terminal covering material 117.

  FIG. 17 is a cross-sectional view showing a cross-section in a state in which the external terminal covering material 117 is removed after the outer layer circuit pattern is formed on the outer layer wiring base material of the conventional multilayer printed wiring board.

  The external terminal covering material 117, the covering material holding conductor 119, the outer layer insulating layer 122t, and the outer layer conductor pattern 124t arranged (remaining) corresponding to the external connection terminal 112t are peeled off (trimmed) using the gap formed in the opening 112w as a trigger. Thus, the external connection terminal 112t is exposed.

  In this way, it is possible to expose the external connection terminal 112t. However, as described above, it is difficult to ensure the positional accuracy when laminating (attaching) the external terminal covering material 117. In order to expose the connection terminal 112t, the external terminal covering material 117 arranged corresponding to the region of the external connection terminal 112t is integrally bonded to the covering material holding conductor 119, the outer layer insulating layer 122t, and the outer layer conductor pattern 124t. In the peeling operation in the laminated state, there is a problem that it is difficult to peel off the insulating material (laminated material) at the designed position.

  That is, when the outer insulating layer 122t and the outer conductor pattern 124t are peeled off together with the external terminal covering material 117, the stress is applied to the outer layer circuit pattern 124p that is disposed in the hard portion As and actually used, and the outer layer circuit pattern 124p is peeled off. May be defective.

  In addition, there is a case where an unremoved part is unnecessarily generated and the external connection terminal 112t (or a predetermined inner layer exposed region) is not sufficiently exposed. In addition, when there are a plurality of external connection terminals 112t, it is necessary to perform affixing and peeling work of the external terminal covering material 117 for each external connection terminal 112t. Therefore, as the number of external connection terminals 112t increases, There is a manufacturing difficulty that the working efficiency is poor and the defect ratio becomes high.

A conventional multilayer printed wiring board as shown in FIGS. 10 to 17 is disclosed in, for example, Patent Document 1.
Japanese Patent No. 3354474

  The present invention has been made in view of such a situation, and is a method for producing a multilayer printed wiring board having an external connection terminal formed by laminating an inner layer wiring base material and an outer layer wiring base material and comprising the inner layer wiring base material. The external connection terminal is covered with the external terminal covering layer and the outer conductor layer, so that the external connection terminal is covered without mechanically peeling the external connection terminal by means of mechanical peeling. It is an object of the present invention to provide a method for manufacturing a multilayer printed wiring board that can be exposed (formed).

  The multilayer printed wiring board according to the present invention includes an inner layer wiring substrate having an inner layer insulating layer and an inner layer conductor layer, an outer layer wiring substrate having an outer layer insulating layer and an outer layer conductor layer laminated on the inner layer wiring substrate, and the inner layer. A method of manufacturing a multilayer printed wiring board comprising an external connection terminal constituted by a conductor layer, wherein the external connection terminal covers the external terminal coating layer and the external terminal coating layer when plating the external conductor layer The outer conductor layer is covered with the outer conductor layer.

  With this configuration, it is possible to cover the external connection terminal with the external terminal coating layer and the external conductor layer without going through the external insulation layer, and there is no need to remove the external insulation layer when the external connection terminal is exposed. Therefore, it is possible to prevent the occurrence of defects due to peeling. In addition, since the external terminal covering layer is covered with the outer conductor layer, it is possible to improve the degree of freedom in selecting a material to be applied to the external terminal covering layer.

  In the method for manufacturing a multilayer printed wiring board according to the present invention, the inner layer wiring base material is a flexible wiring base material.

  With this configuration, when the outer layer wiring substrate is composed of a hard wiring substrate, a composite multilayer printed wiring board (flex-rigid multilayer printed wiring board) can be obtained. When it is made of a material, a flexible multilayer printed wiring board can be obtained.

  In the method for manufacturing a multilayer printed wiring board according to the present invention, the external terminal coating layer has an alkali developing property.

  With this configuration, workability when the external terminal covering layer is peeled can be improved, and the external connection terminal can be prevented from being oxidized to be a highly conductive external connection terminal.

  In the method for manufacturing a multilayer printed wiring board according to the present invention, the external terminal coating layer has photosensitive characteristics.

  With this configuration, it is possible to easily form an external terminal coating layer that covers the external connection terminals by applying a photolithography technique.

  In the method for manufacturing a multilayer printed wiring board according to the present invention, the external terminal coating layer is a photosensitive dry film.

  With this configuration, it is possible to form the external terminal coating layer that coats the external connection terminals with high accuracy and very easily by applying the photolithography technique.

  In the method for producing a multilayer printed wiring board according to the present invention, the external terminal coating layer is formed by exposing and developing the photosensitive dry film.

  With this configuration, it is possible to form the external terminal coating layer that coats the external connection terminals with high accuracy and very easily by applying the photolithography technique.

  In the method for manufacturing a multilayer printed wiring board according to the present invention, the outer insulating layer is removed in a region corresponding to the external connection terminal when being laminated on the inner wiring substrate.

  With this configuration, since the outer insulating layer is not stacked on the external connection terminal, the external connection terminal can be easily and accurately exposed.

  In the method for manufacturing a multilayer printed wiring board according to the present invention, the outer conductor layer covering the external connection terminals is removed when the outer conductor layer is patterned.

  With this configuration, since the outer conductor layer covering the external connection terminal can be removed without using a special process, the process can be simplified. Further, it is possible to avoid the work of peeling off the outer conductor layer, which has been necessary in the past, and it is possible to prevent the occurrence of defects due to the peeling.

  The multilayer printed wiring board manufacturing method according to the present invention is characterized in that the external terminal covering layer is removed after patterning the outer conductor layer.

  With this configuration, since the external connection terminal is kept covered until the patterning of the outer conductor layer is completed, the external connection terminal with good connectivity can be obtained. In addition, the external terminal covering layer can be peeled off simultaneously with the peeling of the outer layer mask pattern used when patterning the outer conductor layer, and the process can be simplified, and there is no defect due to peeling. A clean and highly conductive external connection terminal can be formed.

  According to the method for manufacturing a multilayer printed wiring board according to the present invention, the external connection terminals are covered with the external terminal covering layer and the outer conductor layer, thereby covering and protecting the external connection terminals without going through the outer insulating layer. Therefore, it is possible to expose (form) the external connection terminals without mechanical peeling, and there is no occurrence of defects due to peeling, and a multilayer printed wiring board having a highly conductive external connection terminal is provided. There exists an effect that it can manufacture with sufficient workability.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Embodiment 1>
A method for manufacturing a multilayer printed wiring board according to Embodiment 1 of the present invention (hereinafter sometimes simply referred to as a manufacturing method) will be described with reference to FIGS. 1 to 8 are all cross-sectional views, but all hatching is omitted for the sake of easy viewing.

  FIG. 1 is a cross-sectional view showing a cross section of an inner layer wiring base material of a multilayer printed wiring board in the manufacturing method according to Embodiment 1 of the present invention.

  In the present embodiment, the inner layer wiring base material 10 is formed of a flexible wiring base material, and the outer layer wiring base materials 20 and 21 (see FIG. 5) are formed of a hard wiring base material. A multilayer printed wiring board 1 having a flex-rigid structure (composite multilayer printed wiring board) constituting the As and the flexible portion Af will be described as an example. The multilayer printed wiring board 1 is configured to include an external connection terminal 12t (see FIG. 2) in the flexible portion Af.

  Further, in addition to the inner layer wiring substrate 10, when the outer layer wiring substrates 20 and 21 are also composed of flexible wiring substrates, a flexible multilayer printed wiring board can be obtained.

  The inner wiring substrate 10 constituting the inner layer of the multilayer printed wiring board 1 includes an inner insulating layer 11 and inner conductor layers 12 and 13 laminated on both surfaces thereof. In the following description, the multilayer printed wiring board 1 is used even in the middle of the process.

  As the inner layer wiring substrate 10, a commercially available double-sided flexible wiring board material can be used. The inner insulating layer 11 is made of an insulating resin film having flexibility, and is made of an insulating resin film (FPC material) such as polyimide, polyetherketone, or other liquid crystal polymer.

  The inner conductor layers 12 and 13 are laminated on both sides of the inner insulating layer 11 via an adhesive or without an adhesive. The inner conductor layers 12 and 13 are made of copper foil, but may be made of other metal foils.

  In the present embodiment, the inner-layer wiring substrate 10 is a double-sided flexible wiring board material in which, for example, a 12 to 18 μm copper foil is laminated and bonded to both surfaces of a 25 μm thick polyimide film.

  The multilayer printed wiring board 1 includes, in a completed state (see FIG. 8), a hard portion As having rigidity and a flexible portion Af formed by being derived from the hard portion As and having flexibility. Accordingly, the inner wiring substrate 10 similarly has a hard corresponding portion As and a flexible corresponding portion Af as regions corresponding to the hard portion As and the flexible portion Af when completed (hereinafter, the hard portion As and the completed hard portion As and The flexible portion Af, the hard corresponding portion As and the flexible corresponding portion Af in the process are simply referred to as the hard portion As and the flexible portion Af without distinction.)

  In addition, in the manufacturing process of the multilayer printed wiring board 1, an auxiliary wiring base material that plays a role of holding the hard portion As and the flexible portion Af may be disposed around, but is not shown in the drawing.

  FIG. 2 is a cross-sectional view showing a cross section of the inner layer wiring base material on which the inner layer circuit pattern of the multilayer printed wiring board is formed in the manufacturing method according to the first embodiment of the present invention.

  By patterning the inner conductor layers 12 and 13, inner circuit patterns 12p and 13p are formed. That is, by applying an etching resist (not shown) to the inner conductor layers 12 and 13, and patterning (etching) the inner conductor layers 12 and 13 by a well-known photolithography technique, the inner circuit patterns 12p and 13p are formed. The external connection terminal 12t is formed.

  The inner layer circuit patterns 12p and 13p are formed corresponding to the hard portion As, and the external connection terminal 12t is formed corresponding to the flexible portion Af by the inner layer conductor layer 12 similarly to the inner layer circuit pattern 12p. In the completed multilayer printed wiring board 1, the external connection terminal 12t forms a circuit pattern in the flexible portion Af, and the tip portion is configured as the external connection terminal 12t (see FIG. 8).

  After forming the inner layer circuit patterns 12p and 13p and the external connection terminal 12t, through holes or via holes (not-through) penetrating between the inner layer circuit patterns 12p and 13p are performed by using a laser or an NC drill or the like. After that, an inner through-hole conductor (not shown) or a via-hole conductor is appropriately formed by plating the through-hole or via hole (for example, gold plating or copper plating) using a panel plating method. Note that the plating layer is not shown in consideration of the visibility of the drawing.

  FIG. 3 is a cross-sectional view showing a cross-section in a state in which a coating layer that covers the inner wiring substrate of the multilayer printed wiring board is formed by the manufacturing method according to the first embodiment of the present invention.

  After forming the inner layer circuit patterns 12p and 13p and the external connection terminal 12t, the adhesive layer 15 and the covering layer 16 in which the opening 12w corresponding to the external connection terminal 12t is formed by pre-windowing with a mold or the like are formed as the inner layer conductor layer. 12 (inner layer circuit pattern 12p). Note that the thickness of the adhesive layer 15 and the thickness of the coating layer 16 are previously adjusted to be thin so as to have appropriate thicknesses. Further, a coverlay material in which the coating layer 16 is coated with the adhesive layer 15 may be used.

  FIG. 4 is a cross-sectional view showing a cross section in a state in which an external terminal coating layer that covers the external connection terminals of the multilayer printed wiring board is formed in the manufacturing method according to Embodiment 1 of the present invention.

  The external connection terminal 12t is exposed through the opening 12w formed in the adhesive layer 15 and the coating layer 16. The external terminal coating layer 18 that covers the exposed external connection terminals 12t is formed by applying a general photolithography technique.

  That is, after laminating, for example, a photosensitive dry film on the entire surface of the inner layer wiring substrate 10 or the covering layer 16 on which the inner layer conductor layer 12 (inner layer circuit patterns 12p, 13p, external connection terminals 12t) is formed, By exposing and developing the photosensitive dry film using the exposure mask film, the external terminal coating layer 18 having a predetermined pattern shape can be formed.

  The external terminal coating layer 18 preferably has alkali development characteristics. With this configuration, handling is extremely easy, the external terminal coating layer 18 can be easily formed, and high-sensitivity development is possible. Further, it is possible to prevent the external connection terminal 12t from being oxidized when the external terminal coating layer 18 is peeled off, and it is possible to form the external connection terminal 12t having good conductivity.

  By comprising a photosensitive dry film, the external terminal coating layer 18 can be formed very easily and accurately by applying a general photolithography technique.

  It is also possible to print a photosensitive ink instead of laminating a photosensitive dry film. The effect similar to the lamination of the photosensitive dry film can be obtained by printing the photosensitive ink.

  Further, since the external terminal coating layer 18 has photosensitive characteristics, it can be formed very easily and accurately by applying a photolithography technique.

  Since the external terminal coating layer 18 is formed by applying a photolithography technique, it is possible to ensure the positional accuracy of the region to be coated. For example, in the case of pasting a conventional coating material, a tolerance of misalignment of about ± 0.2 mm is necessary, but the photolithography technique can sufficiently secure a positional accuracy of ± 0.1 mm or less.

  FIG. 5 is a cross-sectional view showing a cross section in a state in which the outer layer wiring base material of the multilayer printed wiring board is laminated on the inner layer wiring base material in the manufacturing method according to the first embodiment of the present invention.

  An outer layer wiring substrate 20 and an outer layer wiring substrate 21 are laminated on both surfaces of the inner layer wiring substrate 10, respectively. The outer wiring substrate 20 includes an outer insulating layer 22 and an outer conductor layer 24, and the outer wiring substrate 21 includes an outer insulating layer 23 and an outer conductor layer 25.

  That is, the outer conductor layer 24 is laminated on the outer insulating layer 22 as an adhesive to constitute the outer wiring substrate 20, and the outer conductor layer 25 is laminated on the outer insulating layer 23 as an adhesive. Configure. Therefore, at this stage, a multilayer printed wiring board having four conductor layers is formed.

  In addition, as a hard wiring base material used for the outer layer wiring base material 21 which does not oppose the external connection terminal 12t of an inner layer, the single-sided wiring board material which laminated | stacked the insulating layer and the conductor layer, for example, single-sided FPC material, single-sided hard board material, etc. It is possible to apply. The outer conductor layer 24 and the outer conductor layer 25 are made of, for example, copper foil.

  In the present embodiment, the outer layer wiring substrate 20 and the outer layer wiring substrate 21 are configured as hard wiring substrates, but are not limited thereto. As another embodiment, a flexible wiring substrate can be used. In this case, a flexible multilayer printed wiring board is obtained.

  Further, the outer insulating layer 22 and the outer insulating layer 23 are formed in advance so as to face the hard part As and not to the flexible part Af by performing a window cutting process in advance with a mold or the like. That is, the outer insulating layer 22 and the outer insulating layer 23 are not stacked on the external connection terminal 12 t and the external terminal covering layer 18. Therefore, the external connection terminal 12t and the external terminal coating layer 18 are not affected by the outer layer insulation layer 22 and the outer layer insulation layer 23, and the mechanical properties of the outer layer insulation layer 22 are finally exposed when the external connection terminal 12t is finally exposed. Peeling is not required, and exposure can be performed easily and accurately.

  Further, since the outer layer conductor layer 24 and the outer layer conductor layer 25 are formed so as to face the inner layer wiring substrate 10, the outer layer conductor layer 24 covers the external connection terminal 12t and the external terminal coating layer 18. It becomes. That is, the external connection terminals 12t are double-covered by the external terminal covering layer 18 and the outer conductor layer 24.

  In this figure, for the sake of easy understanding, a space is shown between the external terminal covering layer 18 and the outer conductor layer 24, but actually, the outer wiring substrate 20 (the outer insulating layer 22 and the outer layer). The conductor layer 24) and the outer layer wiring substrate 21 (the outer layer insulating layer 23 and the outer layer conductor layer 25) are pressure-heated and thermocompression bonded to the inner layer wiring substrate 10, so that the external terminal covering layer 18 and the outer layer The conductor layer 24 is in close contact with each other.

  Therefore, as described above, since the external terminal covering layer 18 is covered with the outer conductor layer 24 without the outer insulating layer 22, the external terminal covering layer 18 is exposed (see FIGS. 7 and 8). Since the outer insulating layer 22 does not need to be mechanically peeled off, the occurrence of defects due to peeling, which is a problem in the prior art, is completely eliminated.

  After forming outer layer wiring substrate 20 (outer layer insulating layer 22 and outer layer conductor layer 24) and outer layer wiring substrate 21 (outer layer insulating layer 23 and outer layer conductor layer 25), appropriate drilling is performed using a laser or an NC drill or the like. To form a through hole or via hole (not shown) penetrating between the outer layer conductor layer 24 and the inner layer circuit pattern 12p or between the outer layer conductor layer 25 and the inner layer circuit pattern 13p, and then panel plating method. A through-hole conductor or a via-hole conductor (not shown) is appropriately formed by plating the through-hole or the via hole using, for example, gold plating or copper plating. Note that the plating layer is not shown in consideration of the visibility of the drawing.

  Therefore, since the outer conductor layer 24 and the outer conductor layer 25 are plated with the external connection terminal 12t covered with the double layer of the outer terminal covering layer 18 and the outer conductor layer 24, the external connection terminal 12t is reliably protected. It becomes possible to do.

  Further, as described above, the external terminal covering layer 18 that directly covers the external connection terminal 12t is in a state in which the outer conductor layer 24 (copper foil) is substantially in close contact with the surface (a state in which it is directly in contact with and covered). Therefore, it is possible to prevent the influence of the chemical used in the plating process.

  For example, it is possible to eliminate the influence of a permanganic acid solution for performing a desmear process for removing smear formed at the time of opening a through hole or an alkaline solution used in a chemical copper plating process.

  Therefore, since the external terminal covering layer 18 is directly covered and protected by the outer conductor layer 24, the degree of freedom of material selection limited by the resistance to chemicals used in the plating process is improved. Is possible.

  FIG. 6 is a cross-sectional view showing a cross section in a state in which an outer layer mask pattern for forming an outer layer circuit pattern is formed on the outer layer wiring substrate of the multilayer printed wiring board in the manufacturing method according to the first embodiment of the present invention. .

  Outer mask patterns 24m and 25m, which are etching resists, are formed on the surfaces of the outer conductor layers 24 and 25, respectively, using a well-known photolithography technique.

  The outer layer conductor layer 24 in the region covering the external terminal coating layer 18 is patterned so that the outer layer mask pattern 24m does not exist in the region corresponding to the external terminal coating layer 18 so as to be etched in the next etching step. Is done.

  FIG. 7 is a cross-sectional view showing a cross-section in a state in which an outer layer circuit pattern is formed on the outer layer wiring substrate of the multilayer printed wiring board using the outer layer mask pattern in the manufacturing method according to Embodiment 1 of the present invention.

  The outer layer circuit patterns 24p and 25p are formed by etching (patterning) the outer layer conductor layers 24 and 25 by a known etching technique using the outer layer mask patterns 24m and 25m as a mask.

  Since the outer layer conductor layer 24 in the region corresponding to the external terminal covering layer 18 (external connection terminal 12t) is removed by etching (patterning) simultaneously with the formation of the outer layer circuit patterns 24p and 25p, the external terminal covering layer 18 is exposed. It becomes a state. Since the external connection terminal 12t is covered with the external terminal coating layer 18, the external connection terminal 12t is not affected when the outer conductor layer 24 is patterned.

  That is, the outer layer conductor layers 24 and 25 covering the external connection terminal 12t can be simultaneously removed in the normal outer layer circuit pattern 24p and 25p forming process without using a special process, thereby simplifying the process. It becomes possible to do. Further, since it is not necessary to mechanically peel off, the influence on the external connection terminal 12t and the external terminal coating layer 18 can be removed.

  FIG. 8 is a cross-sectional view showing a cross section in a state where the outer layer mask pattern is removed after the outer layer circuit pattern is formed on the outer layer wiring base material of the multilayer printed wiring board in the manufacturing method according to the first embodiment of the present invention. .

  The outer layer mask patterns 24m and 25m are removed using a known etching resist stripping technique. At this time, the external terminal covering layer 18 having the same configuration as the outer layer mask patterns 24m and 25m is also peeled off at the same time. Accordingly, since the external connection terminals 12t can be exposed simultaneously in the process of forming the outer layer circuit patterns 24p and 25p, it is possible to form the external connection terminals 12t that are extremely clean and have good conductivity and connectivity.

  That is, the external connection terminal 12t is exposed (formed) in a peeling process in which the external terminal covering layer 18 is peeled off simultaneously when the outer layer mask patterns 24m and 25m used for forming the outer layer circuit patterns 24p and 25p are peeled off. .

  Therefore, since the mechanically strong stress required for the peeling work in the prior art is not applied, it is possible to form the external connection terminal 12t very easily and accurately and with a high yield. Become. In addition, since a special process for peeling the external terminal coating layer 18 is not required, it is possible to simplify the production process and improve the production efficiency and workability.

  In the prior art, the outer layer wiring base material is peeled off, and each multilayer printed wiring board is processed one by one. However, according to the present embodiment, a production work unit in which a number of multilayer printed wiring boards 1 are connected. Therefore, it is possible to perform processing (photolithographic processing), and it is possible to greatly improve the work efficiency.

  Also, in the conventional technique of peeling off the outer layer wiring substrate, the multilayer printed wiring boards were processed one by one, so the pasting deviation accuracy was ± 0.2 mm, but photolithography technology should be applied. As a result, the positional accuracy can be improved to a level of ± 0.1 mm or less, and the design freedom can be expanded and the yield can be improved.

<Embodiment 2>
A method for manufacturing a multilayer printed wiring board according to Embodiment 2 of the present invention (hereinafter sometimes simply referred to as a manufacturing method) will be described with reference to FIG. In the present embodiment, a configuration of a multilayer printed wiring board in which the number of conductor layers is further increased and the number of conductor layers is six will be described. In this embodiment as well, a composite (flex rigid) multilayer printed wiring board provided with a hard part and a flexible part is provided.

  FIG. 9 is a cross-sectional view showing a cross section of a multilayer printed wiring board in the manufacturing method according to Embodiment 2 of the present invention. Although FIG. 9 is a cross-sectional view, all hatching is omitted in consideration of easy viewing of the drawing.

  In the multilayer printed wiring board 2 according to the present embodiment, two inner layer wiring base materials 10 are used, and the inner layer wiring base materials 10s and 10r are respectively used. Since the inner layer wiring base materials 10s and 10r can be formed in the same manner as the inner layer wiring base material 10 shown in the first embodiment, detailed description thereof is omitted. The inner layer wiring substrates 10s and 10r are bonded to each other by the inner layer adhesive layer 10b. In addition, external connection terminals 12ts and 12tr are formed on the inner wiring bases 10s and 10r, respectively, and can be formed in the same manner as the external connection terminals 12t shown in the first embodiment.

  Covering layers 16s and 16r are laminated on the inner layer wiring bases 10s and 10r via adhesive layers 15s and 15r, respectively, and are formed in the same manner as the adhesive layer 15 and covering layer 16 described in the first embodiment. Is possible. For example, a coverlay material in which the coating layer 16s is coated with the adhesive layer 15s may be used.

  Further, the outer layer wiring substrate 20 having the outer layer insulating layer 22 and the outer layer circuit pattern 24p is laminated and formed on the covering layer 16s as in the first embodiment, and the covering layer 16r is formed on the covering layer 16r. As shown in FIG. 1, an outer wiring substrate 21 having an outer insulating layer 23 and an outer circuit pattern 25p is laminated and formed.

  As described above, the multilayer printed wiring board 2 having six or more conductor layers can be formed by a process similar to the process shown in the first embodiment. Also according to the present embodiment, it is possible to achieve the same effects as those of the first embodiment.

It is sectional drawing which shows the cross section of the inner-layer wiring base material of the multilayer printed wiring board by the manufacturing method which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the cross section of the inner-layer wiring base material in which the inner-layer circuit pattern of the multilayer printed wiring board in the manufacturing method which concerns on Embodiment 1 of this invention was formed. It is sectional drawing which shows the cross section of the state in which the coating layer which coat | covers the inner-layer wiring base material of the multilayer printed wiring board by the manufacturing method which concerns on Embodiment 1 of this invention was formed. It is sectional drawing which shows the cross section of the state in which the external terminal coating layer which coat | covers the external connection terminal of the multilayer printed wiring board by the manufacturing method which concerns on Embodiment 1 of this invention was formed. It is sectional drawing which shows the cross section of the state which laminated | stacked the outer layer wiring base material of the multilayer printed wiring board on the inner layer wiring base material with the manufacturing method which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the cross section of the state which formed the outer layer mask pattern for forming an outer layer circuit pattern in the outer layer wiring base material of the multilayer printed wiring board by the manufacturing method which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the cross section of the state which formed the outer layer circuit pattern in the outer layer wiring base material of the multilayer printed wiring board by the manufacturing method which concerns on Embodiment 1 of this invention using the outer layer mask pattern. It is sectional drawing which shows the cross section of the state which removed the outer layer mask pattern, after forming an outer layer circuit pattern in the outer layer wiring base material of the multilayer printed wiring board by the manufacturing method which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the cross section of the multilayer printed wiring board by the manufacturing method which concerns on Embodiment 2 of this invention. It is sectional drawing which shows the cross section of the inner-layer wiring base material of the conventional multilayer printed wiring board. It is sectional drawing which shows the cross section of the inner-layer wiring base material in which the inner-layer circuit pattern of the conventional multilayer printed wiring board was formed. It is sectional drawing which shows the cross section of the state in which the coating layer which coat | covers the inner-layer wiring base material of the conventional multilayer printed wiring board was formed. It is sectional drawing which shows the cross section of the state in which the external terminal coating layer which coat | covers the external connection terminal of the conventional multilayer printed wiring board was formed. It is sectional drawing which shows the cross section of the state which laminated | stacked the outer layer wiring base material on the inner layer wiring base material of the conventional multilayer printed wiring board. It is sectional drawing which shows the cross section of the state which formed the outer layer mask pattern for forming an outer layer circuit pattern in the outer layer wiring base material of the conventional multilayer printed wiring board. It is sectional drawing which shows the cross section of the state which formed the outer layer circuit pattern using the outer layer mask pattern in the outer layer wiring base material of the conventional multilayer printed wiring board. It is sectional drawing which shows the cross section of the state which removed the external terminal coating | covering material 117, after forming an outer layer circuit pattern in the outer layer wiring base material of the conventional multilayer printed wiring board.

Explanation of symbols

1, 2 Multilayer printed wiring board 10, 10s, 10r Inner layer wiring substrate 10b Inner layer adhesive layer 11 Inner layer insulating layer 12, 13 Inner layer conductor layer 12p, 13p Inner layer circuit pattern 12t, 12ts, 12tr External connection terminal 12w Opening 15, 15s , 15r Adhesive layer 16, 16s, 16r Coating layer 18 External terminal coating layer 20, 21 Outer wiring substrate 22, 23 Outer insulating layer 24, 25 Outer conductor layer 24p, 25p Outer circuit pattern 24m, 25m Outer mask pattern As Hard Part Af Flexible part

Claims (9)

An inner-layer wiring substrate having an inner-layer insulating layer and an inner-layer conductor layer, an outer-layer wiring substrate laminated on the inner-layer wiring substrate and having an outer-layer insulating layer and an outer-layer conductor layer, and an external connection terminal constituted by the inner-layer conductor layer; A method for producing a multilayer printed wiring board comprising:
The method for producing a multilayer printed wiring board, wherein when the outer conductor layer is plated, the external connection terminals are covered with an outer terminal covering layer and the outer conductor layer covering the outer terminal covering layer.   The method for manufacturing a multilayer printed wiring board according to claim 1, wherein the inner wiring substrate is a flexible wiring substrate.   The method of manufacturing a multilayer printed wiring board according to claim 1, wherein the external terminal coating layer has alkali development characteristics.   The method of manufacturing a multilayer printed wiring board according to claim 3, wherein the external terminal coating layer has photosensitive characteristics.   The method for manufacturing a multilayer printed wiring board according to claim 4, wherein the external terminal coating layer is a photosensitive dry film.   6. The method of manufacturing a multilayer printed wiring board according to claim 5, wherein the external terminal coating layer is formed by exposing and developing the photosensitive dry film.   7. The multilayer according to claim 1, wherein the outer insulating layer is removed in a region corresponding to the external connection terminal when the outer insulating layer is laminated on the inner wiring substrate. A method for manufacturing a printed wiring board.   8. The multilayer printed wiring board according to claim 1, wherein when patterning the outer layer conductor layer, the outer layer conductor layer covering the external connection terminal is removed. Manufacturing method.   9. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein the external terminal covering layer is removed after patterning the outer conductor layer.

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