JP2009088334A - Printed circuit board manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed circuit board manufacturing method for forming fine wires while securing high connecting reliability. <P>SOLUTION: The both-sided printed circuit board manufacturing method is provided for forming circuits on conductive layers of a both-sided board having the conductive layers on both sides of an insulating layer. It comprises (1) preparing the both-sided plate, (2) forming dissimilar metal patterns having etching property different from the conductive layers on the both-sided board, (3) forming a conduction hole in the both-sided board, (4) applying electrolytic plating treatment to the conduction hole for electric connection between the conductive layers, and (5) using the dissimilar metal patterns as etching resist for applying selective etching to the conductive layers to form the wiring circuits. The multilayer printed circuit board manufacturing method comprises forming conduction holes in the both-sided board or a single-sided board and a printed circuit board, applying electrolytic plating treatment thereto, and then laminating them. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a printed wiring board, and more particularly to a method for manufacturing a printed wiring board that performs electrical connection between layers using through holes and / or non-through holes.

  In recent years, with the miniaturization and multi-functionalization of electronic devices, there is a demand for miniaturization and high density of printed wiring boards used inside the devices. In order to meet such a demand, miniaturization of a wiring circuit formed on the printed wiring board, multilayering of the printed wiring board, and the like are performed.

  When electrical connection between layers is performed in a multilayer printed wiring board, a structure in which inner walls of through holes or non-through holes, which are called through holes or via holes, are covered with a metal electrode layer by electrolytic plating or the like is generally used.

  In this case, since the second metal electrode layer by electrolytic plating or the like is further formed on the metal electrode layer for forming the wiring circuit, the total thickness of the electrode layer forming the wiring circuit increases, and the fine wiring It is disadvantageous to the formation of. In addition, the second metal electrode layer can be formed thin in order to suppress an increase in the total thickness of the electrode layer, but in this case, the thickness of the metal electrode layer provided on the inner wall of the through hole or via hole is also reduced. Therefore, the connection reliability between the layers is lowered, and there is a possibility that it may lead to defects such as disconnection.

  In recent years, through-holes and via-holes that make interlayer connections have become smaller in size as printed wiring boards have become smaller and higher in density, and failures caused by this have spurred a decrease in interlayer connection reliability. ing.

  In contrast to such a current situation, a method called button plating is generally known in which plating is thickened only at an interlayer connection portion to ensure connection reliability.

  A printed wiring board using a button plating method is usually produced by the following steps. That is, first, as shown in FIG. 5A, a double-sided copper clad laminate 53 having a copper foil 52 having a thickness of about 5 μm is prepared on both surfaces of an insulating base material 51 such as polyimide having a thickness of about 25 μm.

  Next, as shown in FIG. 5 (2), a through-hole 54 having a diameter of about 50 μm is formed in the double-sided copper-clad laminate 53 by using a direct laser processing method, and subsequently an interlayer connection is made by electrolytic plating. As the pretreatment, desmear treatment and conductive treatment are performed.

  Then, a photosensitive dry film 55 to be used later as a plating resist is laminated, and then exposed and developed, thereby forming a photosensitive dry film opening 56 in the through hole 54 and its peripheral portion.

  Next, as shown in FIG. 5 (3), a copper plating layer 57 of about 10 μm is formed on the through hole 54 and the opening 56 by using electrolytic copper plating, thereby achieving electrical connection between the layers. At this time, since the electrolytic copper plating process is performed only on the interlayer connection portion, the current density becomes unstable depending on the arrangement of the interlayer connection portion, and it is difficult to reduce the thickness variation of the copper plating layer 57.

  In particular, since current concentrates in isolated interlayer connection portions, the thickness of the copper plating layer 57 needs to be about 15 μm at the maximum. Then, the double-sided copper clad laminated board 53a by which plating was thickened only in the interlayer connection part is obtained by peeling the photosensitive dry film 55.

  Next, as shown in FIG. 5 (4), a photosensitive dry film 58 used as an etching resist is laminated on both sides of the double-sided copper-clad laminate 53a, followed by exposure and development.

  At this time, the thickness of the photosensitive dry film 58 that masks the portion of the copper plating layer 57 having a maximum thickness of about 15 μm is required to be 20 μm or more. For this reason, a thin high-resolution dry film cannot be used, and a thick photosensitive dry film having low resolution performance is used.

  As a result, the width of the resist gap 58a of the photosensitive dry film 58 is required to be 24 μm or more in view of the resolution performance, and the wiring pitch that can be stably formed is considered in consideration of subsequent etching and etching variations. Increased to 60 μm or more.

  Next, as shown in FIG. 5 (5), a wiring circuit 52a is formed on the copper foil 52 by using an etching method by a normal subtractive method, and the photosensitive dry film 58 is peeled off. Subsequently, a solder resist layer 59 is formed, and surface treatment such as solder plating, nickel plating, or gold plating is performed on the surface of terminals such as component mounting lands and connectors as necessary.

  Through the above steps, a double-sided printed wiring board 53b in which plating is thickened only on the interlayer connection portion is obtained.

  As described above, a printed wiring board using a button plating method in which plating is applied only to the interlayer connection portion can provide high connection reliability, but a thin high-resolution dry film cannot be used in forming a wiring circuit. However, it is difficult to form fine wiring. Furthermore, since there is a large variation in the thickness of the plating applied to the interlayer connection, there is a concern that the flatness of the substrate will be lowered, causing a problem in subsequent component mounting.

  On the other hand, as a method for producing a double-sided printed wiring board having a high-density wiring, in Patent Document 1, after forming a peelable resin layer on the outside of the plating resist and conducting a conductive treatment, A method is described in which a peelable resin layer is peeled off, then interlayer connection is performed by electrolytic plating or the like, and subsequently a wiring circuit is formed.

  However, in such a method, contact between the copper plating formed on the inner wall of the through hole and the wiring pattern is insufficient, and high connection reliability cannot be obtained. In addition, when forming a wiring circuit, a hole in a through hole, a protruding portion of copper plating, and the like become problems, and a thin high-resolution dry film cannot be used. Therefore, the problem cannot be solved.

  Patent Document 2 describes a method of forming copper plating only on one side of a double-sided printed wiring board using a plating resist. Thereby, it is said that a fine wiring circuit can be formed on one side where there is no plating.

  However, in such a method, fine wiring cannot be formed on the surface on which the copper plating is formed, and contact between the copper plating formed on the inner wall of the through hole and the wiring pattern without plating is insufficient. Therefore, high connection reliability cannot be obtained.

  On the other hand, as a method for manufacturing a printed wiring board that achieves both high-density wiring and connection reliability, Patent Document 3 uses a metal foil having a dissimilar metal layer as an etching stopper layer to form fine wiring. A method of laminating using a build-up method later is described.

  However, such a method is disadvantageous in terms of cost because it is difficult to apply to a double-sided printed wiring board and a metal foil having an etching stopper layer needs to be prepared.

  Further, Patent Document 4 describes a method of using, as an etching resist, a dissimilar metal pattern capable of selectively etching only a conductive layer.

However, this method is a method assuming a single-sided printed wiring board, does not mention any interlayer connection structure, and does not solve the problem.
JP 2006-108275 A JP 2006-344921 A JP 2006-253347 A Japanese Patent No. 2787228

  As described above, when electrical connection between layers is performed in a multilayer printed wiring board, a structure in which the inner wall of a through hole or a non-through hole is generally covered with a metal electrode layer by electrolytic plating or the like, which is called a through hole or a via hole Is used. In this case, since the second metal electrode layer by electrolytic plating or the like is further formed on the metal electrode layer for forming the wiring circuit, the total thickness of the electrode layer forming the wiring circuit increases, and the fine wiring It is disadvantageous to the formation of.

  In addition, the second metal electrode layer can be formed thin in order to suppress the increase in the total thickness of the electrode layer, but in this case, the thickness of the metal electrode layer on the inner wall of the through hole or via hole is also reduced. Connection reliability may be reduced, leading to defects such as disconnection. For these reasons, it is desired to form fine wiring while ensuring high connection reliability.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a method for manufacturing a printed wiring board capable of forming a fine wiring at the same time while ensuring high connection reliability.

  In order to achieve the above object, the present application provides the following invention.

According to the first invention,
A method of manufacturing a double-sided printed wiring board, wherein a circuit is formed on the conductive layer of a double-sided board having conductive layers on both sides of an insulating layer,
(1) preparing the double-sided board;
(2) A step of forming a pattern of a dissimilar metal having an etching characteristic different from that of the conductive layer on the double-sided plate,
(3) The process of forming the hole for conduction | electrical_connection in the said double-sided board,
(4) A step of performing electrical connection between the conductor layers by subjecting the hole for conduction to electrolytic plating,
(5) forming a wiring circuit by selectively etching the conductive layer using the pattern of the different metal as an etching resist;
It is characterized by including.

According to the second invention,
A method for producing a multilayer printed wiring board having two or more layers,
(1) A step of preparing a laminate having a conductive layer on both sides or one side of an insulating layer,
(2) forming a dissimilar metal pattern having an etching characteristic different from that of the conductive layer on the conductive layer;
(3) a step of preparing a printed wiring board;
(4) A step of laminating the laminated board on which the pattern of the different metal is formed on the printed wiring board via an interlayer adhesive,
(5) forming a conduction hole in the laminate and the printed wiring board;
(6) A step of performing electrical connection between the conductive layers by subjecting the hole for conduction to electrolytic plating,
(7) forming a wiring circuit by selectively etching the conductive layer using the different metal pattern as an etching resist;
It is characterized by including.

  Due to these features, the present invention has the following effects.

  According to the first invention, due to the above-described features, fine wiring with a pitch of 25 μm can be stably formed on both sides of the printed wiring board while ensuring high connection reliability, and can be miniaturized at high density. A simple double-sided printed wiring board can be manufactured inexpensively and stably.

  Further, according to the second invention, due to the above-described characteristics, fine wiring with a pitch of 35 μm can be stably formed on the surface electrode layer of the multilayer printed wiring board while ensuring high connection reliability. A multilayer printed wiring board that can be reduced in size and density can be manufactured inexpensively and stably.

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

  The printed wiring board which concerns on this invention is related with the manufacturing method of the printed wiring board which performs an electrical connection between layers using a through-hole and / or a non-through-hole.

Embodiment 1

  FIG. 1A, FIG. 1B, and FIG. 2 are conceptual cross-sectional views showing manufacturing steps of the printed wiring board in the first embodiment of the present invention. This printed wiring board is manufactured by the following steps. That is, first, as shown in FIG. 1A (1), a double-sided copper clad laminate 3 in which a copper foil 2 having a thickness of about 5 μm is provided on both sides of an insulating base material 1 made of epoxy, polyimide or the like and having a thickness of about 25 μm is prepared. To do. The thickness of the copper foil 2 used here is preferably 10 μm or less in view of the formation of fine wiring later.

  In addition, the material of the insulating base material 1 is not necessarily limited to epoxy and polyimide, and can be properly used depending on the application. For example, in an application where it is necessary to reduce dielectric loss during high-speed signal transmission, a double-sided copper-clad laminate based on a liquid crystal polymer or the like can be used as a low dielectric loss tangent material. Further, if a rolled copper foil is used for the copper foil 2 and a flexible polyimide or the like is used for the insulating base material 1, it is possible to realize high bending characteristics.

  Next, as shown to FIG. 1A (2), the photosensitive dry film is laminated | stacked on both surfaces of the double-sided copper clad laminated board 3, and then the mask pattern 4 is formed by performing exposure and image development. At this time, since both surfaces of the double-sided copper-clad laminate 3 are flat and there are no holes or the like, a fine mask pattern 4 can be formed by using a thin high-resolution dry film.

  In the first embodiment, by using a high resolution dry film having a thickness of 5 μm, the pattern width of the fine wiring portion 4 a of the mask pattern 4 is 8 μm and the pattern gap is 17 μm (pitch 25 μm). With such a pattern width and pattern gap, a general-purpose exposure machine can be used sufficiently, and an expensive high-precision exposure machine is not necessary.

  Next, as shown in FIG. 1A (3), a nickel layer 5 of about 1 to 3 μm is formed on the opening of the mask pattern 4 by electrolytic nickel plating. Subsequently, the double-sided copper-clad laminate 3a having the nickel layer 5 formed on the surface is obtained by peeling off the mask pattern 4.

  The nickel layer 5 formed here is for use as an etching resist when a fine wiring circuit is formed later. In the first embodiment, the fine wiring portion 5a of the nickel layer 5 has a nickel resist width of 17 μm and a resist gap of 8 μm.

  In addition, since the resist gap formed here is used to form the fine wiring by etching the copper foil 2 later, the thickness of the resist gap to be formed is desirably in the range of 2 μm to 20 μm. The pattern pitch is desirably 60 μm or less.

  In the above process, the material used as an etching resist later is not limited to nickel, and any material that functions as an etching resist for the copper foil 2 may be used. For example, solder plating, tin plating, gold plating and the like can be mentioned.

  However, since this etching resist is exposed to a desmear process to be performed later, a polymer material such as a photosensitive dry film is not suitable. In consideration of the corrosion resistance, heat resistance, peelability, etc. at the copper foil interface, it is considered preferable to use nickel.

  Next, as shown in FIG. 1A (4), a direct laser processing method using a UV-YAG laser or the like is used to form a conduction hole having a diameter of about 50 μm for subsequent electrical connection between layers, and laser processing. After performing a desmear process for removing smear generated by the above, followed by a conductive process, a copper plating layer 6 having a thickness of about 10 μm is formed by using an electrolytic copper plating process to achieve electrical connection between the layers. .

  At this time, since the copper plating layer 6 can be uniformly formed on the entire surface of the double-sided copper-clad laminate 3a, the thickness variation of the copper plating layer 6 can be suppressed very small. Further, the unevenness of the nickel layer 5 having a thickness of about 1 to 3 μm is almost leveled by the electrolytic copper plating process, and the surface becomes flat. Through the above steps, a double-sided copper clad laminate 3b having an interlayer connection is obtained.

  Note that the means for forming the hole for conduction is not limited to the UV-YAG laser, and in consideration of the required processing diameter and throughput, processing accuracy, quality, etc., carbon dioxide laser processing and drill processing are performed independently. Or they can be used in combination. In the first embodiment, the through hole is formed through the conduction hole, but the via hole can be formed by forming a non-through hole.

  The thickness of the copper plating layer 6 is determined in consideration of the material and thickness of the insulating base material 1, the diameter of the hole for conduction, the structure of the interlayer connection portion, the required connection reliability, and the like. It is not limited to 10 μm. When higher connection reliability is required, the thickness can be increased. Even when the thickness of the copper plating layer 6 is increased, the thickness of the fine wiring to be formed later is defined by the thickness of the copper foil 2, and there is no disadvantage for the formation of the fine wiring.

  Next, as shown in FIG. 1B (5), a photosensitive dry film 7 is laminated on the double-sided copper-clad laminate 3b, and then exposed and developed, so that a copper plating layer such as an interlayer connection portion or a land is obtained. Mask the part where 6 should be left. As this photosensitive dry film 7, a photosensitive dry film having a thickness of about 20 μm having alkali resistance can be used.

  Next, as shown in FIG. 1B (6), only the copper is selectively etched to form the wiring circuit 2a and the land 6a of the interlayer connection portion, and the photosensitive dry film 7 is peeled off. At this time, the etchant used is low in corrosiveness to nickel, and an etchant that selectively etches copper, such as an alkaline etchant containing ammonia, can be used.

  FIG. 2 is an enlarged view of a fine wiring portion of the wiring circuit 2a. When the wiring circuit 2a is formed, the thickness of the copper foil 2 is as thin as 5 μm, and the etching proceeds from the opening width 8 μm (pitch 25 μm) of the nickel layer 5 used as an etching resist, and the etching proceeds to about 3 μm on one side. Thus, the pattern gap is formed to about 14 μm. If the etching is progressed to this level, there is no possibility of a short circuit or the like even if etching variation is taken into consideration, and the insulation between the wirings can be stably secured.

  Thereby, fine wiring with a pitch of 25 μm (Line / Space = 11 μm / 14 μm, pattern TOP = 7 μm) can be stably formed on both surfaces of the printed wiring board. At this time, since the copper plating layer 6 is not included in the wiring circuit 2a, a high bending characteristic is realized when a rolled copper foil is used for the copper foil 2 and a flexible polyimide is used for the insulating base material 1. can do.

  In addition, when the unevenness corresponding to the thickness (about 10 μm) of the copper plating layer 6 becomes a problem when mounting the components later, the copper plating layer 6 is applied to all lands on which the same component is mounted, such as the lands 8. It is desirable to leave Thereby, the flatness of the part which mounts components is ensured, and the stable mounting process can be constructed | assembled easily.

  Moreover, it is desirable to leave the copper plating layer 6 also about the part which does not become a circuit, such as a product outer peripheral part. Thereby, the electrode layer of the double-sided printed wiring board is thickened, the bending strength of the product is improved, and a stable mounting process can be constructed without causing problems such as warpage in the mounting process such as reflowing later.

  In addition, the overall size reduction of the double-sided printed wiring board is suppressed, which is advantageous for positioning such as later cover formation and component mounting. Is also advantageous. Through the above steps, the double-sided printed wiring board 3c on which fine wiring is formed is obtained.

  Next, as shown in FIG. 1B (7), the nickel layer 5 is peeled off to form a solder resist layer 9, and solder plating, nickel plating, Surface treatment such as tin plating or gold plating is performed alone or in combination.

  At this time, when the nickel layer 5 is peeled off, an etching solution that is low in corrosiveness to copper and that selectively etches only nickel, such as an etching solution containing hydrogen peroxide or nitric acid, can be used. It should be noted that the peeling of the nickel layer 5 is not an indispensable step, and may not be performed as long as it does not lead to a later failure.

  Through the above steps, fine wiring with a pitch of 25 μm (pattern TOP = 7 μm, Line / Space = 11 μm / 14 μm) can be stably formed on both sides of the printed wiring board while ensuring high connection reliability. A double-sided printed wiring board that can be miniaturized with high density can be manufactured inexpensively and stably.

Embodiment 2

  FIG. 3A to FIG. 3C and FIG. 4 are conceptual cross-sectional views showing the manufacturing process of the multilayer printed wiring board in the second embodiment of the present invention. The multilayer printed wiring board according to the second embodiment of the present invention is produced by building up another printed wiring board on one side or both sides of a double-sided printed wiring board serving as a core. This second embodiment can be implemented as long as it is a multilayer printed wiring board using a build-up method.

  First, as shown in FIG. 3A (1), a single-sided copper clad laminate 23 having a copper foil 22 of about 5 μm thickness is prepared on one side of an insulating base material 21 made of epoxy, polyimide, etc. and having a thickness of about 25 μm. . The thickness of the copper foil 22 used here is preferably 15 μm or less in consideration of the formation of fine wiring later.

  Next, as shown to FIG. 3A (2), the photosensitive dry film is laminated | stacked on the side surface of the copper foil 22 of the single-sided copper clad laminated board 23, and then the mask pattern 24 is formed by performing exposure and image development. At this time, since the single-sided copper clad laminate 23 is flat and has no holes or the like, a fine mask pattern 24 can be formed by using a thin high-resolution dry film.

  In the first embodiment, by using a high resolution dry film having a thickness of 5 μm, the pattern width of the fine wiring portion 24a of the mask pattern 24 is 10 μm and the pattern gap is 25 μm (pitch 35 μm). With such a pattern width and pattern gap, a general-purpose exposure machine can be used sufficiently, and an expensive high-precision exposure machine is not necessary.

  Next, as shown in FIG. 3A (3), a nickel layer 25 of about 1 to 3 μm is formed on the opening of the mask pattern 24 by electrolytic nickel plating. The nickel layer formed here is for use as an etching resist when forming a fine wiring circuit later. In the first embodiment, the fine wiring portion 25a of the nickel layer 25 has a nickel resist width of 25 μm and a resist gap of 10 μm.

  Since the copper foil 22 is later etched to form fine wiring from the resist gap formed here, the resist gap to be formed is preferably in the range of 2 to 30 μm, and the resist pattern pitch is 100 μm. The following is desirable. Subsequently, by removing the mask pattern 24, a single-sided copper clad laminate 23a having a nickel layer formed on the surface is obtained.

  In the above process, the material used later as an etching resist is not limited to nickel, and any material that functions as an etching resist for the copper foil 22 may be used. For example, solder plating, tin plating, gold plating and the like can be mentioned.

  However, since this etching resist is exposed to a desmear process to be performed later, a polymer material such as a photosensitive dry film is not suitable. In consideration of the corrosion resistance, heat resistance, peelability, etc. at the copper foil interface, it is considered preferable to use nickel.

  In addition, the copper clad laminated board used here is not limited to a single-sided copper clad laminated board, A double-sided copper clad laminated board may be sufficient. In that case, it is necessary to form a wiring circuit on the surface bonded through the interlayer adhesive before the lamination.

  Next, as shown in FIG. 3A (4), the single-sided copper-clad laminate 23a is aligned with both sides of the double-sided printed wiring board 26 on which the wiring pattern is formed, with an interlayer adhesive 27 interposed therebetween. Laminate with a vacuum press or the like. The double-sided printed wiring board 26 includes a bottomed via hole 30 having wiring patterns 29 having a thickness of about 12 μm on both surfaces of an insulating base material 28 such as polyimide having a thickness of about 25 μm and filled with via fill plating. It is possible to use a double-sided printed wiring board in which interlayer connections are made and the wiring pattern 29 is protected by a general coverlay 30.

  Note that the material of the insulating base material 28 is not limited to polyimide, and can be properly used depending on the application. In addition, the interlayer connection structure of the double-sided printed wiring board is not limited to the bottomed via hole filled with via fill plating. A double-sided printed wiring board having a structure can be used.

  Moreover, a single-sided printed wiring board can be used instead of the double-sided printed wiring board. As the interlayer adhesive 27, for example, an adhesive such as acrylic or epoxy having a thickness of 30 μm can be used. The multilayer base material 31 that has been built up is obtained through the above steps.

  Next, as shown in FIG. 3B (5), a diameter 100 to 100 for performing electrical connection between layers at a predetermined position of the multilayer base material 31 using a direct laser processing method such as a UV-YAG laser later. A conductive hole having a thickness of about 150 μm is formed, a desmear process for removing smear generated by the laser process is performed, followed by a conductive process, and then a copper plating layer 32 having a thickness of about 30 μm using an electrolytic copper plating process. Is deposited to form a via hole 33, and electrical connection between layers is achieved.

  At this time, since the copper plating layer 32 can be uniformly formed on the entire surface of the multilayer base material 31, variation in the thickness of the copper plating layer 32 can be suppressed to a very small level. Further, the unevenness of the nickel layer 25 having a thickness of about 1 to 3 μm is substantially leveled by the electrolytic copper plating process, and the surface becomes flat. Through the above steps, the multilayer base material 31a having an interlayer connection is obtained.

  The formation of the conduction hole is not limited to the UV-YAG laser, and in consideration of the required processing diameter and throughput, processing accuracy, quality, etc., carbon dioxide laser processing, drill processing, etc. are performed alone or Can be used in combination. In the second embodiment, a non-penetrating conduction hole is formed and a via hole is formed. However, a through hole can be formed and a through hole can be formed.

  The thickness of the copper plating layer 32 is determined in consideration of the material and thickness of each layer, the diameter of the hole for conduction, the structure of the interlayer connection portion, the required connection reliability, and the like. It is not limited. When higher connection reliability is required, the thickness can be increased. Even when the thickness of the copper plating layer 32 is increased, the thickness of the fine wiring to be formed later is defined by the thickness of the copper foil 22 and is not disadvantageous for the formation of the fine wiring.

  Next, as shown in FIG. 3B (6), a photosensitive dry film 41 is laminated on both surfaces of the multilayer base material 31a, and then exposed and developed to form a copper plating layer 32 such as an interlayer connection portion or a land. Mask the parts that need to be left. As the photosensitive dry film 41, an alkali-resistant photosensitive dry film having a thickness of about 20 μm can be used.

  Subsequently, as shown in FIG. 3C (7), only the copper is selectively etched to form the wiring circuit 22a and the land 32a of the interlayer connection portion, and the photosensitive dry film 41 is peeled off. At this time, the etchant used is low in corrosiveness to nickel, and an etchant that selectively etches copper, such as an alkaline etchant containing ammonia, can be used.

  Here, FIG. 4 is an enlarged view of a fine wiring portion of the wiring circuit 22a. When the wiring circuit 22a is formed, the thickness of the copper foil 22 is as thin as 5 μm, and etching proceeds from a fine opening width of 10 μm (opening pitch 35 μm) of the nickel layer 25 used as an etching resist. By proceeding the etching to about 5 μm, the pattern gap is formed to about 19 μm. If the etching is progressed to this level, there is no possibility of a short circuit or the like even if etching variation is taken into consideration, and the insulation between the wirings can be stably secured.

  Usually, when a wiring circuit is formed on the surface electrode layer of a multilayer printed wiring board in the case of performing a build-up method, there are the following problems in addition to the total thickness of the electrode layer.

  The multilayer printed wiring board has larger irregularities on the surface of the wiring board than the double-sided printed wiring board due to the presence or absence of an inner electrode layer and the presence of a flexible cable portion. For this reason, the photosensitive dry film to be used must be thick and have a low resolution. Further, the unevenness of the surface becomes an error with respect to the clearance during exposure, and the resolution of the exposure itself is lowered.

  On the other hand, in the formation of the wiring circuit of the multilayer printed wiring board according to the present invention, a fine etching resist can be accurately formed by the nickel layer 25 before the build-up process. For this reason, in the formation of the etching resist, the unevenness of the surface of the multilayer printed wiring board is not a problem. Thereby, fine wiring with a pitch of 35 μm (Line / Space = 16 μm / 19 μm, pattern TOP = 11 μm) can be stably formed on the surface electrode layers on both surfaces of the multilayer printed wiring board.

  At this time, if the diameter of the via hole 33 is 100 μm, a land 32a having a diameter of about 220 μm can be formed on the via hole in consideration of an exposure shift of about 25 μm on one side and a laser processing shift of about 35 μm. The nickel pattern land connected to the via hole 33 may be formed to have a diameter of 270 μm in consideration of exposure deviation of only 25 μm per side.

  By forming such fine wiring on the surface electrode layer, for example, when a CSP having a connection pin with a pitch of 0.4 mm is mounted, the land diameter is 270 μm, so the gap between lands is 130 μm. Three fine wirings with a pitch of 35 μm can be formed between connecting pins with a pitch of 4 mm.

  As a result, even when a component having a large number of connection pins with a narrow pitch, which has been required in recent years, is mounted, there is a margin in the routing of the wiring, which leads to downsizing and higher density of the entire printed wiring board. .

  Note that when a component such as CSP is mounted on the via hole 33 later, unevenness corresponding to the thickness (about 30 μm) of the copper plating layer 32 may be a problem. In such a case, it is desirable to leave the copper plating layer 32 on all lands on which the same component is mounted, such as the lands 42. Thereby, the flatness of the part which mounts components is ensured, and the stable mounting process can be constructed | assembled easily.

  Moreover, it is desirable to leave the copper plating layer 32 also about the part which does not become a circuit, such as a product outer peripheral part. As a result, the surface electrode layer of the multilayer printed wiring board becomes thick and the bending strength of the product is improved, and a stable mounting process can be established without problems such as warping in the subsequent mounting process such as reflow. In addition, it reduces the overall shrinkage of the multilayer printed wiring board, which is advantageous in the subsequent alignment of solder resist formation and component mounting, and further reduces the consumption of unnecessary etching solution, thereby reducing costs. Is also advantageous. Through the above steps, the multilayer printed wiring board 31b on which fine wiring is formed is obtained.

  Then, as shown in FIG. 3C (8), the nickel layer 25 is peeled off, a solder resist layer 43 is formed, and solder plating, nickel plating, tin, etc. are applied to the terminal surfaces of component mounting lands and connectors as necessary. Surface treatment such as plating and gold plating is performed alone or in combination.

  At this time, when the nickel layer 25 is peeled off, an etching solution that is low in corrosiveness to copper and that selectively etches only nickel, such as an etching solution containing hydrogen peroxide or nitric acid, can be used. Note that the nickel layer 25 is not an indispensable process, and may not be performed as long as it does not lead to later defects.

  Through the above steps, fine wiring with a pitch of 35 μm (pattern TOP = 11 μm, Line / Space = 16 μm / 19 μm) is stably provided on the surface electrode layers on both sides of the multilayer printed wiring board while ensuring high connection reliability. A multilayer printed wiring board that can be formed and can be miniaturized at a high density can be manufactured inexpensively and stably.

The conceptual sectional view of the manufacturing method of the printed wiring board by a first embodiment of the present invention. The conceptual sectional view of the manufacturing method of the printed wiring board by a first embodiment of the present invention. The enlarged view of the part wiring part of the wiring circuit 2a in FIG. 1B. The conceptual sectional drawing of the manufacturing method of the multilayer printed wiring board by 2nd embodiment of this invention. The conceptual sectional drawing of the manufacturing method of the multilayer printed wiring board by 2nd embodiment of this invention. The conceptual sectional drawing of the manufacturing method of the multilayer printed wiring board by 2nd embodiment of this invention. The enlarged view of the fine wiring part of the wiring circuit 22a in FIG. 3C. The conceptual sectional drawing of the manufacturing method of the printed wiring board by the conventional button plating method.

Explanation of symbols

1 Insulating base material having a thickness of about 25 μm 2 Copper foil 2 a having a thickness of about 5 μm Wiring circuit 3 Double-sided copper-clad laminate 3 a Double-sided copper-clad laminate 3 b with a nickel layer formed on the surface Double-sided copper-clad laminate with interlayer connection Plate 3c Double-sided copper-clad laminate 4 with fine wiring formed Mask pattern 4a Mask pattern fine wiring portion 5 Nickel layer 5a Nickel layer fine wiring portion 6 Copper plating layer 6a Land 7 Photosensitive dry film 8 Land 9 Solder resist 21 Insulating base material 22 having a thickness of about 25 μm Copper foil 22a having a thickness of about 5 μm Wiring circuit 23 Single-sided copper-clad laminate 23a Single-sided copper-clad laminate 24 having a nickel layer formed on the surface Mask pattern 24a Fine wiring portion 25 of the mask pattern Nickel layer 25a Fine wiring part 26 of nickel layer Double-sided printed wiring board 27 Interlayer adhesive sheet 28 Thickness of about 25 μm Base material 29 Wiring pattern 30 Via hole 31 Multilayer base material 31a built up Multilayer base material 31b with interlayer connection Multilayer printed wiring board 32 with fine wiring formed Copper plating layer 32a Land 33 Via hole 41 Photosensitive dry film 42 Land 43 Solder resist 51 Insulation base material 52 having a thickness of about 25 μm 52 Copper foil 53 having a thickness of about 5 μm Double-sided copper-clad laminate 53a Double-sided copper-clad laminate 53b Double-sided printed wiring board 54 Through hole 55 Photosensitive dry film 56 Photosensitive dry film Opening 57 copper plating layer 58 photosensitive dry film 58a photosensitive dry film resist gap 59 solder resist

Claims (6)

A method of manufacturing a double-sided printed wiring board, wherein a circuit is formed on the conductive layer of a double-sided board having conductive layers on both sides of an insulating layer,
(1) preparing the double-sided board;
(2) A step of forming a pattern of a dissimilar metal having an etching characteristic different from that of the conductive layer on the double-sided plate,
(3) The process of forming the hole for conduction | electrical_connection in the said double-sided board,
(4) A step of performing electrical connection between the conductor layers by subjecting the hole for conduction to electrolytic plating,
(5) forming a wiring circuit by selectively etching the conductive layer using the pattern of the different metal as an etching resist;
The manufacturing method of the double-sided printed wiring board characterized by including. It is a manufacturing method of the double-sided printed wiring board according to claim 1,
Form a mask pattern on both sides of the double-sided plate using a photosensitive resin material,
Forming a pattern of the dissimilar metal on a portion that is not masked by the photosensitive resin material using a plating process;
The manufacturing method of the double-sided printed wiring board characterized by peeling the said photosensitive resin material. In the manufacturing method of the double-sided printed wiring board of Claim 2,
Forming a layer of the dissimilar metal on the surface of the double-sided plate;
Forming a mask pattern on the surface of the layer of the dissimilar metal using the photosensitive resin material;
Selectively etching the layer of dissimilar metal to form a pattern;
The manufacturing method of the double-sided printed wiring board characterized by peeling the said photosensitive resin material. A method for producing a multilayer printed wiring board having two or more layers,
(1) A step of preparing a laminate having a conductive layer on both sides or one side of an insulating layer,
(2) forming a dissimilar metal pattern having an etching characteristic different from that of the conductive layer on the conductive layer;
(3) a step of preparing a printed wiring board;
(4) A step of laminating the laminated board on which the pattern of the different metal is formed on the printed wiring board via an interlayer adhesive,
(5) forming a conduction hole in the laminate and the printed wiring board;
(6) A step of performing electrical connection between the conductive layers by subjecting the hole for conduction to electrolytic plating,
(7) forming a wiring circuit by selectively etching the conductive layer using the different metal pattern as an etching resist;
A method for producing a multilayer printed wiring board, comprising: In the manufacturing method of the multilayer printed wiring board of Claim 4,
Forming a mask pattern on the conductive layer of the laminate,
Forming a pattern of the dissimilar metal by plating on a portion not masked by the photosensitive resin material;
A method for producing a multilayer printed board, comprising peeling off the photosensitive resin material. In the manufacturing method of the multilayer printed wiring board of Claim 4,
Forming the dissimilar metal layer on the conductive layer of the laminate;
Form a mask pattern on the surface of the layer of the dissimilar metal using a photosensitive resin material,
Selectively etching the layer of dissimilar metal to form a pattern;
The manufacturing method of the multilayer printed wiring board characterized by peeling the said photosensitive resin material.

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