JP2014068047A - Method for manufacturing multilayer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a multilayer printed wiring board provided with a plurality of core substrates by a heat pressurizing process for lamination of one time.SOLUTION: A method for manufacturing a multilayer printed wiring board comprising an insulating layer 3 in an integrated structure comprises the steps of: stacking inside core substrates 1-1 to 1-2 having an inner via hole for conducting inner layer printed wiring on both surfaces; overlapping outside copper foils forming outer layer printed wiring 2 and sandwiching and laminating a prepreg to be an insulating layer 3 between the core substrates; and filling the inner via hole with melted resin from the prepreg by pressurizing a laminate by hot pressing of one time to form a blind via hole 4, and simultaneously bonding to each other and insulating the core substrates 1-1 to 1-2 and the copper foil.

Description

  The present invention relates to a multilayer printed wiring board in which an insulating resin layer and a conductive layer are built up and a method for manufacturing the same. In particular, the present invention relates to a multilayer printed wiring board having a core substrate having a blind via hole as an inner layer and a conductive layer via an insulating layer as an outer layer.

  In a multilayer printed wiring board, printed wiring is provided on both sides of a wiring board, and an inner layer board is formed in which conduction between the double-sided wirings is achieved through inner via holes of the board. Furthermore, at least one of both surfaces is provided with a conductive layer through an insulating layer as an outer layer, and the inner via hole is filled with an insulating material to form a blind via hole, thereby achieving multilayering.

  For example, as a multilayer printed wiring board having a blind via hole according to the prior art, there is a multilayer circuit board in which printed wiring is formed on both surfaces of an insulating layer serving as a substrate and a plurality of the printed wiring boards are laminated. In this multilayer circuit board, an inner via hole is formed in a conductive layer for conduction between adjacent printed wirings, and filling of the inner via hole and lamination processing of a plurality of circuit boards are performed (see Patent Document 1 or Patent Document 2).

  However, in these multilayer printed wiring boards, one core substrate is used as an inner layer substrate and inner via holes for a plurality of conductor circuit layers are formed as blind via holes. That is, it is not intended for a multilayer printed wiring board in which the inner layer is formed of a plurality of core substrates. Moreover, the step of filling the inner via hole connecting adjacent conductor circuit layers with a filler or hole filling resin is a step different from the step of forming the insulating layer between the multilayer printed wirings.

  In addition, when laminating an inner layer circuit board that connects two inner layer wiring patterns with inner via holes and an outer layer circuit board disposed outside the inner layer circuit board, the multilayer circuit board is bonded by using an interlayer lamination adhesive such as a prepreg. There exists a manufacturing method (refer patent document 3).

  However, each of the inner circuit board and the outer circuit board in this multilayer circuit board is composed of an inner wiring pattern or an outer conductive layer and an insulating layer made of an insulating base material. Only prepreg is used. In addition, there is no explanation or suggestion about the connection between the wiring patterns of each of the plurality of core substrates or the inner layer substrates, or the relation between the insulating base material of the insulating layer and the interlayer laminated adhesive for filling the hole.

  Here, a plurality of laminated substrates having printed wiring on the contact surface are formed on one inner layer substrate, and a metal (conduction) layer is provided as an outer layer on both surfaces and the surface of the inner layer substrate via an adhesive (insulating) layer. A method for manufacturing a multilayer printed wiring board is disclosed (for example, see Patent Document 4). In this method, blind (non-through) via holes or blind through holes are formed in the outer layer, and through holes (through holes) penetrating the inner layer and the outer layer are further formed, and metal plating is performed to achieve conduction between printed wirings. Yes.

  That is, in the technique of Patent Document 4, conduction between a plurality of printed wirings is realized using through or non-through holes from both front and back surfaces. However, in this technology, a plurality of internal printed wirings form one core substrate to form an inner layer substrate, and a description is given of blind via holes for conducting conduction between the substrates in the inner layer composed of the plurality of core substrates. Or there is no suggestion.

  There is a multilayer printed wiring board in which an inner layer is built up with a plurality of core substrates, and blind via holes are formed to connect front and back circuits on the core substrate (see, for example, Patent Document 5). In this wiring board, a base through via hole is provided in the multilayer printed wiring board for further conduction between the plurality of core substrates. Here, the base through via hole is a kind of blind via hole.

  However, when the base through via hole is provided in the multilayer printed wiring board as in Patent Document 5, the inner layer laminating process for forming the blind via hole, and the outer layer printed wiring for forming the base through via hole and mounting the external component are provided. And an outer layer laminating step for forming an outer layer for forming an electrical connection between the inner layer and the inner layer printed wiring outside the inner layer, and at least two laminating steps.

JP-A-11-274730 Japanese Patent Laid-Open No. 11-040949 Japanese Patent Laid-Open No. 2001-077532 JP 02-153594 A JP 2001-257470 A

  In the above-described prior art, as disclosed in Patent Document 5, in particular, an insulating layer is inserted between each of the core substrates and stacked to form a printed wiring as an inner layer, and conduction between the printed wirings of the two core substrates. In order to achieve this, at least two laminating steps are required. That is, an inner layer laminating step and an outer layer laminating step. In the inner layer stacking process, inner via holes for conduction between printed wirings on the core substrate are formed in blind via holes. In the outer layer stacking step, an outer layer is formed by inserting an insulating layer between the outer two conductive layers and the inner printed wiring in order to mount components on the outer side. In this way, at least two lamination steps are required for a total of six printed wiring boards. Under such conditions, further reduction in manufacturing cost is desired.

  In order to solve the above problems, a build-up multilayer printed wiring board according to the manufacturing method of the present invention has a plurality of printed wirings and blind via holes via insulating layers, and has adjacent printed wirings. The insulating layer that adheres while insulating the gap and the insulator filling the inside of the blind via hole form an integrated structure as one insulating layer.

  The blind via hole is in the inner layer and electrically connects the inner layer printed wirings on both surfaces of each core substrate. The insulating layer that adheres and insulates between the insulating material filling the blind via hole and the adjacent printed wiring is formed between the adjacent printed wiring of the inner printed wiring on the plurality of core substrates forming the inner layer and the printed wiring on the outer layer. Adhere while insulating. The integrated structure of these insulating layers and insulators is molded when a semi-cured resin sheet inserted between printed wirings is melted by pressing with a hot press. A prepreg can be used for the semi-cured resin sheet.

  Here, the semi-cured resin sheet refers to a sheet-like molding material impregnated with an uncured resin and made into a semi-cured state. In the present application, the semi-cured resin sheet is a semi-cured thermosetting resin. It shall be defined as an impregnated sheet. Therefore, the semi-cured resin sheet fills the hole portion of the surface to be contacted with the thermosetting resin melted by pressing by the hot press, and adheres to the contact surface to ensure an electrically insulating state at the sheet portion.

  At least one core substrate in the inner layer has the inner layer printed wiring on both surfaces and the blind via hole that electrically connects both surfaces. The core substrate may include one having inner layer printed wiring on at least one of both surfaces.

  The build-up multilayer printed wiring board according to the present invention usually further includes an outer layer printed wiring made of a conductive foil such as a copper foil via an insulating layer outside at least one of the inner layers. This printed wiring board has a micro via hole (Micro Via Hole) for connecting the outer layer printed wiring to the outer inner layer printed wiring and a through hole for selecting and connecting a predetermined printed wiring out of the inner layer / outer layer printed wiring. And a via hole.

  The inner layer printed wiring here is formed on the surface of each of the plurality of core substrates, and usually has a circuit pattern different from each other. The outer layer printed wiring is formed on the front and back surfaces of the printed wiring board, and usually has a circuit pattern different between the front and back surfaces.

  The manufacturing method of this build-up multilayer printed wiring board is characterized by including the following preparatory step, laminating step, and hot pressing step so that the laminate can be molded in a single hot pressing step.

  In the preparation step, at least one core substrate having an inner via hole for connecting the two printed wirings is prepared. In the laminating step, the core substrate and a conductive foil for forming a printed wiring are overlapped on at least one of the core substrate, and a semi-cured resin sheet serving as the insulating layer is sandwiched between the core substrate and the conductive foil. Stack to form a laminate. In the hot pressing step, the laminated body of the core substrate, the conductive foil, and the semi-cured resin sheet is pressed by hot pressing, and the inner via hole is filled with the resin melted from the semi-cured resin sheet, thereby blind via holes. To form. At the same time, the molten resin insulates and adheres between the adjacent core substrate and conductive foil to form the laminate in an integrated structure.

  In other words, the plurality of core substrates constituting the build-up multilayer printed wiring board have printed wiring on both sides or one side, and at least one of them is made conductive by copper plating or the like on both sides. Has an inner via hole. The inner via hole of the core substrate becomes a blind via hole as described above when it is formed in the multilayer printed wiring board by pressing with a hot press.

  The core substrate having at least one inner via hole for conducting the printed wirings on both sides described above is well known as described in, for example, Patent Document 5. The generation of micro via holes in the outer layer is also described in Patent Documents 4 and 5. Furthermore, the above-mentioned patent documents and the like describe that a resin sheet made of a semi-cured resin called a prepreg is used for adhesion and insulation. However, by using a semi-cured resin sheet, the insulating layer can be bonded and formed by a single hot press, and at the same time, the inner via hole of the core substrate can be filled with an insulating material to form an integrated structure. There is no explanation or suggestion about what is done.

  In the present invention, a semi-cured resin sheet is inserted between each of a plurality of core substrates having printed wiring and inner via holes to form an inner layer and a conductive foil for outer printed wiring formed outside thereof. After being stacked on the laminated body, it can be formed into an integrated structure by bonding and insulating the laminated body and filling the inner hole with a single press of a heat press, so an insulating layer is provided in advance between adjacent printed wiring After that, not only the process of bonding them is unnecessary, but also in the case of a multilayer structure, there is an effect that a build-up multilayer printed wiring board can be manufactured with a minimum number of heat pressing processes.

It is explanatory drawing which showed the cross section of the multilayer printed wiring board manufactured by Example 1 of this invention. It is explanatory drawing which showed the cross section of the core board | substrate after the preparatory process applied to Example 1 of this invention. It is explanatory drawing which showed the decomposition | disassembly cross section in the lamination process applied following FIG. 2A by this invention. It is explanatory drawing which showed the cross section of the laminated body integrally molded by the hot press process applied following FIG. 2B by this invention. It is explanatory drawing which showed the cross section after the drilling process applied following FIG. 2C in Example 1 in this invention. It is explanatory drawing which showed the cross section after the plating process applied following Example 2D in Example 1 in this invention. It is explanatory drawing which showed the cross section after the multilayer printed pattern formation process applied following FIG. 2E in Example 1 in this invention. It is explanatory drawing which showed the cross section of the multilayer printed wiring board manufactured by Example 2 in this invention. It is explanatory drawing which showed the cross section in the lamination | stacking state before integration of the multilayer printed wiring board manufactured by Example 3 in this invention.

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

  The core substrate in the present invention has double-sided printed wiring, and there is an inner via hole in which the inner wall is copper-plated for conduction between the printed wirings. The finished multilayer printed wiring board has a blind in which the inner via hole is filled with an insulator. There is a via hole. In the following embodiment, the printed wiring is formed on both surfaces of the core substrate, but the core substrate on only one surface may be included.

  As described above, the present invention is a multilayer printed wiring board in which an inner layer is formed of a plurality of core substrates and a micro via hole is formed in the outer layer, and is particularly effective for a multilayer structure of six layers or more. It is.

  In addition, a well-known subtractive method, an additive method, or a drill method is used for manufacturing the core substrate described in the following examples, and a well-known conformal method or direct method is used for the drilling process of the micro via hole. A laser such as a method may be used. Moreover, although copper foil is used as an embodiment, the copper foil may be made of another material as long as electrical connection can be obtained as a conductive foil. These methods, materials, etc. are not particularly limited as long as the functions shown in the claims or the functions shown in the following description are satisfied.

  A build-up multilayer printed wiring board according to Example 1 will be described with reference to FIGS. 1 and 2A-2F.

  The build-up multilayer printed wiring board according to the present invention shown in FIG. 1 includes core substrates 1-1 and 1-2, outer layer printed wiring 2, insulating layer 3, blind via hole 4, micro via hole 5, and through via hole. 6 and an outer layer plating circuit 7, and has a six-layer structure printed wiring.

  The two core substrates 1-1 and 1-2 are electrically isolated by the insulating layer 3, and each of the core substrates 1-1 and 1-2 has printed wirings with different patterns on the front and back surfaces. Applicable. The printed wirings on both sides of the core substrates 1-1 and 1-2 are electrically connected by the conductive plating layer of the blind via hole 4. The printed wirings of the core substrates 1-1 and 1-2 can be electrically connected by through via holes 6 at predetermined positions. In the outer layer printed wiring 2, a copper foil is used as a conductive foil in the outer layer, and a printed wiring pattern is formed using a photolithography technique.

  The insulating layer 3 is a characteristic part in the present invention, and a multilayer printed wiring is integrated in the entire laminate, and the formation method thereof will be described later by a manufacturing method. The blind via hole 4 is in a predetermined position on the inner layer, and the inside is filled with an insulator when forming the insulating layer, and the printed wiring of the core substrate laminated on the inner layer is electrically connected by the conductive plating layer on the inner wall of the blind via hole 4 Has been.

  The micro via hole 5 is an outer layer that occupies the outer side of the inner layer, and electrically connects the outer layer printed wiring 2 and the outermost printed wiring of the core substrates 1-1 and 1-2 by a conductive plating layer and is used for mounting external components. At this time, the terminals of the parts are embedded and bonded to each other for electrical connection. The through via hole 6 penetrates the multilayer printed wiring board and is provided at a position where the inner layer / outer layer printed wiring can be selected and electrically connected by the conductive plating layer on the inner wall. The outer layer plating circuit 7 forms an outer layer on the outer side of the inner layer by a well-known technique, and then forms a conductive layer on the outer wall surfaces of the front and back surfaces including the inner walls of the micro via hole 5 and the through via hole 6. These constructions can be performed by known techniques described in the above-mentioned patent documents.

  FIG. 2A is an explanatory view showing a cross section of the core substrate after the preparation step applied to the first embodiment of the present invention.

  The core substrates 1-1 and 1-2 shown in FIG. 2A are manufactured by a well-known technique.

  For example, first, each of the core substrates 1-1 and 1-2 has a hole using a drill method on a double-sided copper-clad laminate such as an epoxy insulating resin reinforced with glass fiber, and a through hole is formed. Yes. This through hole then becomes an inner via hole 20 that connects both sides of the copper clad by a plating operation such as panel copper electroplating or pattern copper electroplating. Furthermore, a plating layer is also formed on the copper-clad laminate, and a conductive pattern of the inner layer printed wiring 40 is formed on the surface of the copper-clad laminate by exposure, development, and etching processing operations.

  Next, FIG. 2B is an explanatory view showing an exploded cross-section in the stacking process applied subsequent to FIG. 2A in the present invention.

  As shown in FIG. 2B, copper foils 2-1 and 2-2 serving as conductive layers are stacked on top and bottom of the two stacked core substrates 1-1 and 1-2, and the core substrates 1-1 and 1- 2 and copper foils 2-1 and 2-2 are sandwiched between semi-cured prepregs 3-1, 3-2 and 3-3 made of epoxy resin or the like as a semi-cured resin sheet. As a result, as shown in the figure, the copper foil 2-1, the prepreg 3-1, the core substrate 1-1, the prepreg 3-2, the core substrate 1-2, the prepreg 3-3, and the copper foil 2-2 Stacked in order, a single laminate is formed.

  Next, FIG. 2C illustrates a manufacturing process that is a feature of the present invention. That is, FIG. 2C is an explanatory view showing a cross section of the laminate integrally molded by the heat pressing step applied subsequent to FIG. 2B in the present invention.

  As shown in FIG. 2C, when the laminate is pressed from above and below the plurality of layers shown in FIG. 2B with a hot press for lamination, the laminate is molded into a build-up multilayer printed wiring board with a single lamination press and completed. . That is, the pressing in the hot press melts the heat-effect resin impregnated in the prepregs 3-1, 3-2, and 3-3, fills the molten resin from both openings of the inner via hole 20, and the prepreg 3. −1, 3-2, and 3-3 are both insulating adhesives.

  As a result, the prepregs 3-1, 3-2, and 3-3 in FIG. 2 and the copper foil 2-2 are bonded and insulated to form an integrated multilayer printed wiring board. Accordingly, the inner via hole 20 having copper plating on the inner surface in FIG. 2A is formed in the blind via hole 4 filled with the insulating layer 3. This hot pressing step can be performed, for example, by thermosetting the whole after thermocompression bonding with a roll laminator.

  Next, FIG. 2D is an explanatory view showing a cross section after a drilling step applied subsequent to FIG. 2C in Embodiment 1 of the present invention.

  2D, in order to form the micro via hole 5 of FIG. 1, the copper foils 2-1 and 2-2 at the position where the micro hole (non-through hole) 50 is formed in FIG. After removing by etching, a hole is drilled until a predetermined inner layer printed wiring 40 is exposed by a laser method. Further, in order to form the through via hole 6 shown in FIG. 1, a through hole 60 is formed by drilling a multilayer printed wiring board by a drilling method. Another known construction technique can be applied to this step. The order of the two drilling steps may be reversed or simultaneous construction.

  Next, FIG. 2E is an explanatory view showing a cross section after the plating step applied subsequent to FIG. 2D in Example 1 of the present invention.

  In FIG. 2E, the outer plating layer 70 is formed on the surface of the conductive material by performing copper plating on the entire inner surface of the multilayer printed wiring board shown in FIG. The For the plating operation, a panel plating method or a pattern plating method can be used. By this step, the micro via hole 5 and the through via hole 6 having a conductive material on the inner wall surface are formed. The through via hole 6 at a predetermined position can interconnect a predetermined inner layer printed wiring. That is, the through via hole 6 is formed at a position where a predetermined inner layer printed wiring can be interconnected.

  Next, FIG. 2F is an explanatory view showing a cross section after the multilayer print pattern forming step applied subsequent to FIG. 2E in Example 1 of the present invention, and is the same as FIG.

  In FIG. 2F, the outer layer conductive layer in the outer layer printed wiring 2 is removed by removing the outer layer plating layer 70 and the copper foils 2-1 and 2-2 shown in FIG. 2E until the insulating layer 3 is exposed by exposure, development, and etching. A pattern 8 is formed.

  As shown in FIG. 2C described above, in the present invention, the inner layer and the outer layer can be laminated in a single hot pressing step, and the insulator filled in the space of the inner layer portion is a laminated hot press. In the pressing, the outer layer copper foil does not blow out, so the step of removing the insulating layer by polishing and flattening is unnecessary.

  A build-up multilayer printed wiring board according to Example 2 will be described with reference to FIG.

  FIG. 3 is an explanatory view showing a cross section of a multilayer printed wiring board manufactured according to Example 2 of the present invention.

  The build-up multilayer printed wiring board according to the present invention shown in FIG. 3 includes a core substrate 1-1, 1-2, 1-3, a conductive foil for the outer printed wiring 2, and an insulating layer 3 in one laminating press. Thus, a single laminate is completed. The difference from Example 1 is that the core substrate 1-3 is added, and the thickness of the insulating layer 3 is increased correspondingly.

  Furthermore, in this embodiment, there are three core substrates in the inner layer, but even if it is more than that, it can be manufactured in one hot pressing step.

  A method for manufacturing a build-up multilayer printed wiring board according to Example 3 will be described with reference to FIG.

  FIG. 4 is an explanatory view showing a cross section in a laminated state before integration of a multilayer printed wiring board manufactured according to Example 3 of the present invention.

  FIG. 4 corresponds to the structure shown in FIG. 2B in the manufacturing process of the first embodiment, and instead of the copper foil and the insulating layer as the outermost layer for forming the micro via hole, a well-known copper foil with resin is used. 9-1 and 9-2 are used. The laminated body is pressed by a hot press with a well-known technique to form an insulating film between the inner layer and the copper foil on the outermost surface to form the integrated structure shown in FIG. 2C. be able to. Therefore, the entire laminate can be molded into a multilayer printed wiring board by a single pressing process.

  In the present invention, when laminating a plurality of core substrates having inner via holes as inner layers, a conductive foil such as a copper foil is stacked on the outermost layer, and a semi-cured resin sheet such as a prepreg is used as an insulating adhesive between the layers. Since a multilayer printed wiring board having blind via holes is manufactured in a single hot press process, a flat electrical circuit such as printed wiring is laminated and a product having a multilayer structure including blind via holes is manufactured. It can be used to reduce costs.

1-1, 1-2, 1-3 Core substrate 2 Outer layer printed wiring 2-1, 2-2 Copper foil (conducting foil)
3, 3-1, 3-2, 3-3 prepreg (semi-cured resin sheet)
4 Blind via hole 5 Micro via hole 6 Through via hole 7 Outer plating circuit 8 Outer layer conduction pattern 9-1, 9-2 Resin copper foil 20 Inner via hole 40 Inner layer printed wiring 50 Micro hole 60 Through hole 70 Outer plating layer

Claims (4)

A build including a core substrate on which a printed wiring is formed, an insulating layer provided on the surface of the core substrate, a plurality of printed wirings via the core substrate, and blind via holes connecting the two printed wirings A method for manufacturing an up-layer printed wiring board,
Preparing at least two core substrates having an inner via hole connecting the two printed wirings; and
A conductive foil for forming printed wiring is sandwiched between the uppermost core substrate and the lowermost core substrate, and a semi-cured resin sheet serving as the insulating layer is sandwiched between them, and A lamination step in which a semi-cured resin sheet serving as the insulating layer is sandwiched between the core substrates and stacked to form a laminate;
By pressing the laminated body once by hot pressing, the inner via hole is filled with a resin melted from the semi-cured resin sheet to form a blind via hole and between the core substrates adjacent to each other by the molten resin, And heat-pressing step to bond and insulate between the core substrate adjacent to the conductive foil to form an integrated structure;
As a subsequent step of the heat pressing step, a step of forming a micro via hole in the conductive foil by a predetermined patterning process and then drilling by a laser method until a predetermined inner layer printed wiring is exposed, and a predetermined penetration Forming a through hole at the via hole position by a drilling method, plating the surface after the drilling, forming the micro via hole and the through via hole, and forming an outer layer printed wiring by a predetermined patterning process And a process of
The manufacturing method of the buildup multilayer printed wiring board characterized by including this.   2. The method for manufacturing a build-up multilayer printed wiring board according to claim 1, wherein the conductive foil is a copper foil, and the semi-cured resin sheet is a prepreg.   2. The preparation process according to claim 1, wherein the preparing step includes preparing a plurality of double-sided conductive foil-clad laminates on the core substrate, and then drilling holes at respective predetermined positions to form inner via holes. A process for producing a build-up multilayer printed wiring board, comprising the step of plating the entire surface of the substrate and forming a first printed wiring by a predetermined patterning process.   4. The method of manufacturing a build-up multilayer printed wiring board according to claim 3, wherein the predetermined patterning process is performed by a photolithographic technique of exposure, development, and etching.

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