JP4041048B2 - Flexible / rigid wiring board and method for manufacturing the same - Google Patents

Description

  The present invention relates to a wiring board having a rigid wiring layer and a flexible wiring layer, and a method for manufacturing the wiring board.

  For example, high-density wiring is required for wiring boards that form electrical circuits as medical devices such as CT scanners and catheters, PC peripherals such as MT heads and PC cards, and mobile phones are becoming shorter, smaller, and thinner. There is a demand for flexibility as well as reduction in size and size. In response to such demands, as shown in an enlarged cross-sectional view of the main part configuration in FIG. 14, a hybrid wiring that integrally combines the flexible wiring layer 1 and the rigid wiring layers 2 and 2 that are difficult to bend. A plate has been developed (see, for example, Patent Document 1).

  Here, the bendable flexible wiring layer 1 has a flexible resin layer, for example, a polyimide resin film 1a having a thickness of about 12 to 50 μm as an insulator layer, and has a required wiring pattern layer 1b on the main surface. Yes. On the other hand, the rigid wiring layers 2 and 2 have a glass epoxy resin system having a thickness of about 60 to 160 μm as an interlayer insulator layer 2a in a partial region of the flexible wiring layer 1, and between the interlayer insulator layers 2a and outside. A configuration is adopted in which required wiring patterns 2b are arranged in multiple layers on the surface.

  The rigid wiring layers 2 and 2 are hard wiring layers that are difficult to bend on the outer surfaces of the layers on which the required electronic components are mounted. The rigid wiring layers 2 and 2 are also formed on the exposed surfaces of the flexible wiring layer 1 and the rigid wiring layers 2 and 2. Is provided with a protective insulator layer 3 such as a solder resist layer. Furthermore, the flexible wiring layer 1 contributes to the connection between the rigid wiring layers 2 and 2, and can be bent so that the position and direction of the rigid wiring layers 2 and 2 can be arbitrarily set.

  In the configuration of the flexible / rigid wiring board, the polyimide resin film 1a and the glass epoxy resin layer 2a constituting the interlayer insulators of the rigid wiring layers 2 and 2 are bonded via a thermosetting adhesive layer. is doing. Further, the connection between the wiring pattern layers 2b and the like has a through hole type or a via type, and these interlayer connection conductors 4 are formed by embedding a conductor or forming a plating film on the inner wall surface of the through hole.

  This type of flexible / rigid wiring board is manufactured as follows. First, a copper foil-bonded sheet is prepared by bonding a copper foil having a thickness of about 12 to 18 μm to the main surface of the polyimide resin film 1a having a thickness of about 12 to 50 μm via an adhesive layer. Next, a predetermined region of the copper foil-bonded sheet is subjected to perforation processing to provide a through hole for interlayer connection, and then the inner wall surface of the through hole is formed into a plated conductor or filled with a conductive composition to form an interlayer connection conductor. 4 is formed. Thereafter, the copper foil on the main surface is subjected to a photo-etching process to form a wiring pattern 1b, thereby forming a flexible wiring layer in which the wiring patterns 1b on the main surface are connected.

  On the other hand, a plurality of copper foil-bonded sheets prepared by bonding a copper foil having a thickness of about 12 to 18 μm to both surfaces of a glass epoxy resin sheet having a thickness of about 60 to 160 μm is prepared. Here, the glass epoxy resin-based sheet forms an interlayer insulator of the rigid wiring layers 2 and 2. Accordingly, the flexible wiring layer has a configuration in which a portion corresponding to the flexible region 1 is cut out or a configuration that can be removed. Next, after drilling a predetermined region of these copper foil-bonded sheets and providing a through hole for interlayer connection, the inner wall surface of the through hole is made into a plated conductor or filled with a conductive composition to connect the interlayer. A conductor 4 is formed. Thereafter, the copper foil is subjected to a photo-etching process to obtain a rigid wiring sheet having an interlayer connection conductor 4 connected to the wiring pattern.

  The flexible wiring layer prepared above and a rigid wiring sheet are aligned and laminated. At this time, a thermosetting adhesive layer is interposed.

  A wiring in which the multilayer rigid wiring layers 2 and 2 are integrated through the flexible wiring layer 1 by subjecting the laminated arrangement to heat and pressure processing and bonding and integrating the flexible wiring layer and the rigid wiring layer. It becomes a board.

It is also known that the rigid wiring layers 2 and 2 are configured by the following means. That is, a copper film having a thickness of about 15 μm in which a semi-curable glass epoxy resin layer having a thickness of about 60 to 160 μm is formed on the surface on which the wiring pattern 2 b is formed, and a protruding conductor is provided on a predetermined region surface using a conductive composition as a material. Position and laminate the foil. After that, the laminate is heated and pressurized to be joined and integrated, and a circuit board in which the copper foil is electrically connected by a projecting conductor through which the semi-curable glass epoxy resin layer is inserted is manufactured. Etching is performed to form a wiring pattern. This method is attracting attention as a means suitable for productivity and high-density wiring patterning because the interlayer connection conductor can be easily and finely formed.
JP-A-11-204896 ([0023] to [0033])

  However, the following problems are recognized in the flexible rigid wiring board having the rigid wiring layers 2 and 2 and the flexible wiring layer 1. That is, the polyimide resin film 1a constituting the insulator layer generally has a problem that it has a high dielectric constant and water absorption, and is disadvantageous as a wiring board for high-frequency transmission.

  The present invention has been made in view of the above circumstances, and has a connection reliability high and a flexible / rigid wiring board suitable for high-frequency transmission provided with a rigid wiring layer that does not exhibit warpage or the like, and a method of manufacturing the same. For the purpose of provision.

A flexible rigid wiring board according to an aspect of the present invention includes a flexible insulating layer made of a liquid crystal polymer having a predetermined glass transition temperature, and a first wiring pattern disposed on the surface of the flexible insulating layer or in the layer. A flexible wiring layer comprising:
A rigid insulator layer made of a fiber reinforced thermosetting resin having a glass transition temperature lower than the glass transition temperature of the flexible insulator layer, which is laminated and integrated between both sides of a part of the flexible wiring layer, and the rigid A rigid wiring layer comprising a second wiring pattern disposed on the surface of the insulator layer or in the layer;
A protruding conductor that penetrates the rigid insulator layer and electrically connects the first wiring pattern and the second wiring pattern ;
The rigid insulator layer is characterized in that it gives compressive strain to the flexible insulator layer at room temperature .

  Furthermore, it is preferable that the surface of the second wiring pattern adjacent to the flexible insulator layer is roughened.

  Further, the surface of the flexible wiring layer on which the rigid wiring layer is not laminated is covered with a protective insulator layer, and at least a part of the edge thereof overlaps the adhesive surface between the flexible insulating layer and the rigid wiring layer. In this case, the reliability of the wiring board can be improved.

  Furthermore, when the rigid wiring layer is formed on both surfaces of the flexible wiring layer, the stress strain in the wiring board acts in a direction that cancels out in the layer at a high temperature, and warpage and swelling can be suppressed.

  Furthermore, it is preferable that the rigid insulator layer is an epoxy resin layer containing glass cloth having a wide selection range of the glass transition point of the fiber reinforced thermosetting resin layer.

The manufacturing method according to one aspect of the present invention is a bump in which first wiring patterns are formed on both main surfaces of a flexible insulator layer made of a liquid crystal polymer film having a predetermined glass transition temperature, and penetrates the flexible insulator layer. Forming a flexible wiring layer in which the first wiring patterns are connected with each other with a protruding conductor,
A conductor foil or a second wiring pattern is formed between both principal surfaces or layers of one or more rigid insulator layers made of a fiber reinforced thermosetting resin having a glass transition temperature lower than the glass transition temperature of the flexible insulator layer. Forming a rigid wiring layer formed by connecting the conductor foil or the second wiring patterns with bump-shaped protruding conductors that pass through the rigid insulator layer; and
Forming a conductive bump on one main surface of the rigid wiring layer;
The rigid wiring layer faces the main surface on which the conductive bumps are formed, and the glass transition temperature is lower than the glass transition temperature of the flexible insulator layer so as to be sandwiched between both surfaces of a part of the flexible wiring layer. From the glass transition temperature of the fiber reinforced thermosetting resin layer, laminated at a temperature lower than the glass transition temperature of the flexible insulator layer, sandwiching the adhesive layer of the semi-cured fiber reinforced thermosetting resin of the point temperature Heating and pressurizing at a high temperature, joining the flexible wiring layer and the rigid wiring layer, and connecting the conductive bumps to the first wiring pattern;
And compressive strain is applied to the flexible insulator layer by shrinkage of the rigid insulator layer at room temperature.

  In this method, it is preferable that a rigid wiring layer is formed in a semi-cured state on the rigid insulator layer and cured by the heating and pressurizing together with the adhesive layer.

In the manufacturing method of one embodiment of the present invention, the first wiring pattern is formed on both main surfaces of the flexible insulator layer made of a liquid crystal polymer film having a predetermined glass transition temperature, and penetrates the flexible insulator layer. Forming a flexible wiring layer in which the first wiring patterns are connected to each other by a bump-shaped protruding conductor;
Forming conductive bumps on the conductive foil or the second wiring pattern;
The conductive foil or the second wiring pattern is directed toward the conductive bump so as to be sandwiched between both surfaces of a part of the flexible wiring layer, and is lower than the glass transition temperature of the flexible insulating layer. The fiber reinforced thermosetting is carried out at a temperature lower than the glass transition temperature of the flexible insulator layer by laminating an adhesive layer as a rigid insulator layer of a semi-cured fiber reinforced thermosetting resin having a glass transition temperature. Heating and pressurizing at a temperature higher than the glass transition temperature of the resin layer; and
And compressive strain is applied to the flexible insulator layer by shrinkage of the rigid insulator layer at room temperature.

  In the manufacturing method, it is preferable that the adhesive layer of the semi-cured fiber reinforced thermosetting resin is formed in a state where the conductive bumps are inserted before heating and pressing.

  The above invention has been made based on the following findings. That is, the present inventors, in a rigid wiring layer formed by laminating different kinds of base materials, causes a decrease in connectivity with a flexible wiring circuit region, warpage in the rigid wiring layer, surface swelling phenomenon, etc. As a result, it was confirmed that it depends on the material, the heating of the laminated body, the setting of the peak temperature of pressurization, and the property of the contact surface (interface) between the wiring pattern and the laminated insulator.

  More specifically, it was found that it is optimal to use a liquid crystal polymer film for the flexible wiring layer and, for example, a glass epoxy resin-based sheet as a fiber reinforced thermosetting resin for the solid wiring layer.

  The flexible rigid wiring board is subjected to two heat treatments, that is, a heating and pressing process when laminating and bonding each insulator layer, and a heating process when the element is mounted on the wiring board and reflowed. In particular, the thermal expansion coefficient of prepreg sheets of thermosetting resins such as glass epoxy (glass cloth impregnated with semi-cured epoxy resin) constituting the rigid insulator layer changes greatly before and after the glass transition temperature. Since the resin is crosslinked and cured with heating, distortion occurs depending on the temperature between the flexible wiring layer to be bonded. That is, in the process of curing, according to the state of the liquid crystal polymer, after curing, it becomes rigid and stress is generated between the flexible wiring layer. On the other hand, the liquid crystal polymer constituting the flexible wiring layer has a high glass transition temperature, and a material having a temperature higher than the reflow temperature at which the solder melts can be selected. Even if the glass transition point of the liquid crystal polymer is higher than the reflow temperature, the liquid crystal polymer becomes slightly softened at the reflow temperature, and the thermal expansion coefficient gradually increases.

  FIG. 7 shows the glass transition point, the reflow temperature region, and the lamination adhesion when an example of glass epoxy (characteristic A) is used for the rigid insulating layer and an example of liquid crystal polymer (characteristic B) is used for the flexible insulating layer. The relationship of pressurization temperature is shown typically. Here, the glass transition point of the glass epoxy is T3 (for example, 140 ° C.), the glass transition point of the liquid crystal polymer is T2 (for example, 292 ° C.), the reflow temperature range is 260 ° C. to 290 ° C., and the pressurization temperature T1 is T1A (T3> T1A). , T1B (T2> T1B> T3).

  In addition, a glass transition point is normally calculated | required by two methods, TMA method and DMA method, by the glass transition temperature measuring method (JIS C6493 attachment figure 1,2,3).

(1) In the TMA method, the test piece is heated from room temperature at a rate of 10 ° C./min, the amount of thermal expansion in the thickness direction is measured with a thermal analyzer, and a tangent line is drawn on the curves before and after the glass transition point. Tg is obtained from the intersection of the tangent lines.

(2) In the DMA method (tensile method), the temperature of a test piece is raised from room temperature at a rate of 2 ° C./min, and the dynamic viscoelasticity and loss tangent of the test piece are measured with a viscoelasticity measuring device. Tg is obtained from the peak temperature.

  The present invention follows the DMA method.

(A) When the pressurization temperature is T1A, the base material itself of both layers is less expanded, so when pressed in this state, the glass epoxy and the liquid crystal polymer expand in the same manner and are harder with less expansion. The pressure is integrated in a state, and even if it is returned to room temperature, it has no internal stress.

(B) When the pressurizing temperature is T1B, the glass epoxy layer itself is greatly expanded, but is pressed and integrated in an expanded soft state. Therefore, the internal stress is relieved at the time of high temperature reflow, but at the normal temperature after the pressure integration, the shape has the internal stress.

  For this reason, in the case of the rigidization by (a), the internal stress at the low temperature is small, but the internal stress at the high temperature (thickness direction) is large, and the occurrence of warpage and swelling is promoted during the reflow. Was confirmed.

  In the case of the rigidification according to (b), the internal stress (thickness direction) is present at a low temperature, but conversely, the internal stress at a high temperature of reflow (250 ° C. or higher) is reduced, and warping during reflow is reduced. It was confirmed that the occurrence of blistering was suppressed or prevented. That is, at the reflow temperature, since the flexible insulating layer of the liquid crystal polymer is in a slightly softened state with respect to the cured rigid insulating layer, the thermal expansion of the rigid insulating layer is absorbed and the occurrence of distortion due to the expansion difference is reduced. In the normal temperature state after reflow, the rigid insulator layer contracts greatly and gives a compressive strain to the flexible insulator layer. This strain is not in the direction of expanding the rigid wiring layer, and the deformation of the wiring board is suppressed.

  FIG. 8 (a) illustrates the state of normal temperature and strain at the time of reflow in the case of (a). There is no distortion at normal temperature, and distortion occurs at the time of reflow, particularly, as shown by the arrow S in the figure. It is shown that. On the other hand, FIG. 8B illustrates the state of strain at normal temperature and reflow in the case of (b) described above. Stress strain occurs as indicated by an arrow toward the inside of the layer at normal temperature. It indicates that it has not occurred. R indicates a rigid wiring layer and F indicates a flexible wiring layer.

  From the above phenomena and properties, the glass transition temperature T3 of the fiber reinforced thermosetting resin constituting the rigid wiring layer is made lower than the glass transition temperature T2 of the liquid crystal polymer, and the lamination pressure of the wiring board (press peak temperature). ) By setting T2 to a relationship of T2> T1> T3, a rigid wiring layer free from warping or swelling can be easily formed.

  In addition, in the construction of the above rigid wiring layer, measures such as joint integrity based on the difference in thermal expansion coefficient between the liquid crystal polymer film and the glass epoxy resin sheet, and connection reliability between the flexible wiring layer and the rigid wiring layer should be taken. Is preferred. As a countermeasure, the formation of a protective insulator layer (solder resist) on the flexible wiring layer is regarded as important. On the other hand, the interface between the glass epoxy resin sheets to be laminated, in particular, the interface between the glass epoxy resin sheet and the wiring pattern surface, that is, the mutual contact surface is roughened in advance, When integrated, it was confirmed that the required connection reliability could be easily secured.

  According to the present invention, a flexible wiring layer that can be bent and a rigid wiring layer that is suitable for mounting electronic components, and suitable for high-frequency signal transmission, have excellent structural stability, and have a highly reliable function. Thus, it is possible to provide a wiring board suitable for the circuit configuration of small electronic devices.

  In addition, according to the manufacturing method of the present invention, a flexible / rigid wiring board suitable for high-frequency signal transmission, excellent in structural stability, highly reliable, and suitable for circuit configurations of small electronic devices. Can be mass-produced with good yield.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 6 and FIGS. 11 to 13.

  FIG. 1 is an enlarged perspective view showing a main part of a flexible / rigid wiring board 10 according to the present embodiment, and FIG. 2 is an enlarged sectional view taken along the line AA. That is, a part of the flexible / rigid wiring board 10 of the present embodiment is a flexible wiring layer (having a flexible function) 11, and a partial region 11 a of the flexible wiring layer 11 is a rigid wiring layer 12, 12. The flexible wiring layer to be formed is sandwiched as a core base material. An element group 10A of semiconductor layers and passive elements is mounted on the surface of the rigid wiring layer 12. Here, as shown in FIG. 2, the flexible wiring layer 11 is a liquid crystal polymer insulating layer 13 having a thickness of about 25 to 50 μm, and wiring patterns 14 formed by etching copper foil are disposed on both main surfaces thereof. . The wiring pattern 14 includes a wiring pattern 14 a that electrically connects the rigid wiring layers 12 and 12, and a wiring pattern 14 b that is a core of the rigid wiring layer 12.

  The rigid wiring layer 12 partially laminated and integrated with a part of the flexible wiring layer 11 has a thickness of about 400 to 500 μm, for example, a glass epoxy resin layer as a rigid insulator layer 16, and a required wiring pattern. The layer 17 is configured to be formed on the surface or in the layer. Here, the rigid insulator layer 16 is a material whose glass transition temperature is lower than the glass transition temperature of the liquid crystal polymer forming the flexible insulator layer 13. The rigid insulator layer is a fiber reinforced resin layer obtained by impregnating a fiber reinforced thermosetting resin, that is, a cloth (cloth) such as glass, with a semi-curable (including uncured) thermosetting resin. Glass epoxy is known as a prepreg because glass fiber is impregnated with an epoxy resin to form a sheet. The thickness of the flexible wiring layer 11 of the flexible / rigid wiring board 10 of the present embodiment is, for example, 100 μm, and the thickness of the rigid wiring layer 12 is, for example, 450 μm.

  When the pressing temperature (press peak temperature) at the time of lamination is about 170 to 250 ° C., a liquid crystal polymer (for example, glass transition temperature 292 ° C.) and a glass epoxy resin layer (for example, glass transition temperature 140 to 220 ° C.) And combine. Furthermore, since the combination of materials with respect to the press peak temperature exhibits good reflow characteristics at the press peak temperature, the joint between the flexible wiring layer 11 and the rigid wiring layers 12 and 12 also exhibits a good interface structure.

  Here, as the liquid crystal polymer, for example, multiaxially oriented thermoplastics such as Bexter (trade name, manufactured by Kuraray Co., Ltd., glass transition point 292 ° C.), and Biac (trade name, manufactured by Japan Gore-Tex Co., Ltd., glass transition point 310 ° C.). It is a polymer and has a glass transition point of 270 ° C to 320 ° C.

  On the other hand, the fiber reinforced thermosetting resin sheet is an epoxy resin sheet containing glass cloth such as glass epoxy (FR4) and (FR5), BT resin, glass resin, and other commercially available epoxy resins and polyimide resins. A composition having a glass transition point of 140 ° C. to 220 ° C. is suitable.

  In addition, in the selective combination of the above glass epoxy resin layers, it is considered that the glass transition point temperature (Тg value) is higher from the viewpoint of heat resistance. It was confirmed that the heat resistance when a rigid wiring circuit was formed was better as the temperature was slightly lower and the coefficient of thermal expansion α2 after the glass transition temperature was exceeded was closer to the coefficient of thermal expansion of the liquid crystal polymer.

  Further, the wiring patterns 14b of the flexible wiring layer are connected by the protruding conductors 18. In addition, the wiring patterns 16 of the rigid wiring layer that is a multilayer wiring are connected by a protruding conductor 19 that is an interlayer connection conductor. Connection of the flexible wiring layer to the wiring pattern 17 of the rigid wiring layer 12 is made by a protruding conductor 19a penetrating the solid insulating layer 16B serving as an adhesive layer.

  The laminated interface between the wiring pattern 17 and the insulator layer 16 is roughened (not shown) and bonded. Here, the protruding conductors 18 and 19 serving as interlayer connection conductors are made of, for example, a conductive metal such as gold, silver, copper, or solder, or a mixed system of the conductive metal powder and a binder resin. The binder resin is a polycarbonate resin, a polysulfone resin, a polyester resin, a phenoxy resin, a phenol resin, a polyimide resin, or the like. Furthermore, each surface of the flexible wiring layer 11 and the rigid wiring layers 12 and 12 is provided with a protective insulator layer 20 such as an ultraviolet curable solder resist.

  Next, a method for manufacturing a flexible / rigid wiring board having the above structure will be described with reference to FIGS. As shown in FIG. 3, the manufacturing process 30 of the flexible wiring layer 11 and the manufacturing process 40 of the rigid wiring layer 12 are prepared and prepared in separate processes, followed by a process 50 of stacking, heating and pressing, and integrating.

First, the flexible wiring layer 11 which becomes a base material base is manufactured. 4 (a) to 4 (c) are cross-sectional views illustrating the manufacturing process of the flexible wiring layer. As shown in FIG. 4 (a), a liquid crystal polymer sheet having a thickness of 25 to 50 μm (glass transition temperature 292). 13A), and a copper foil 14A with an adhesive having a thickness of 12 to 18 μm provided with a projecting (conical) conductive bump 18 on one main surface side is simply bonded to the other main surface side. The copper foil 14B with the agent is laminated and disposed. Thereafter, a backing plate such as a stainless steel plate is disposed on both copper foils 14A and 14B of the laminate, and heated and pressurized at a heating temperature of about 290 to 320 ° C. and a pressure of about 30 to 80 kg / cm ² .

  Both surfaces of the copper foils 14A and 14B on both sides as shown in FIG. 4 (b) are electrically connected by bump-shaped conductors 18 penetrating the liquid crystal polymer sheet 13A as an interlayer insulator by this heating and pressurization. A copper foil pasting board is produced.

  Next, the copper foils 14 </ b> A and 14 </ b> B on both sides are subjected to a photo-etching process to form a wiring pattern 14, thereby producing a flexible wiring layer 11 as shown in FIG. The region surface having the property is covered with a protective insulator layer 20 such as a solder resist. The protruding conductor 18 is disposed for connection between the wiring patterns 14b and 14b on both sides of the region where the wiring layer is disposed.

  On the other hand, the manufacturing process of the rigid wiring layer 12 will be described with reference to FIGS. A semi-cured (including uncured) glass epoxy resin layer (glass transition temperature 140 ° C.) 16A having a thickness of 60 to 160 μm is prepared. A copper foil 17A having a thickness of 12 to 18 μm provided with a protruding (conical) conductive bump 19 on one main surface side of the glass epoxy resin layer 16A is disposed, and is passed between heated rolls. A copper foil tension layer in which the tip of the bump 19 penetrates the glass epoxy resin layer 16A is formed.

Thereafter, a copper foil 17B having a thickness of 12 to 18 μm is disposed on the end surface of the conductive bump 19 of the glass epoxy resin layer 16A, a stainless steel plate is disposed on both sides, and a heating temperature of 170 to 190 ° C. Heating and pressurizing at a pressure of about 30 to 80 kg / cm ² . By this heating and pressing, a double-sided copper foil-laminated plate in which both-sided copper foils 17A and 17B are electrically connected by protruding conductive bumps 19 having the interlayer insulating sheet 16A inserted therethrough as shown in FIG. 5 (b). Is made. The double-sided copper foil-clad plate may be manufactured by sequentially laminating and arranging the copper foil 17A provided with the conductor bumps 19, the glass epoxy resin layer 16A, and the copper foil 17B, and heating and pressurizing them all at once. Good.

  Next, a layer unit 12A of the rigid wiring layer 12 as shown in FIG. 5C is manufactured by subjecting one of the copper foils 17A and 17B on both sides to a photo-etching process to form a wiring pattern 17. Further, the surface of the wiring pattern 17 of the manufactured rigid wiring layer is roughened.

  After that, as shown in FIG. 5D, a protruding conductive bump 19 a is provided on the required wiring pattern 17 surface of the wiring pattern 17. In the rigid wiring layer manufacturing process, the flexible wiring layer 11 is processed so that the flexible region (region between ff) can be punched (cut out) or separated (slit) and peeled off in advance. It is necessary to keep. The protruding conductor 19a is for electrical connection to the wiring pattern 14b of the flexible wiring layer 11.

  Next, a flexible / rigid wiring board is manufactured with reference to FIGS. That is, the rigid wiring layer unit 12A is formed on the flexible wiring layer 11 manufactured as described above, and the flexible wiring layer 11 is used as a core as shown in FIG. 6A, and a semi-cured adhesive layer 16B is formed on both sides thereof. The glass epoxy resin layer having a thickness of 60 to 160 μm is positioned and laminated in a sandwich manner through a prepreg. Here, the adhesive layer 16 </ b> B is punched in advance corresponding to the flexible region ff of the flexible wiring layer 11.

Thereafter, a backing plate is disposed on both the copper foils 17A and 17B of the laminate, and heated and pressurized at a heating temperature of about 170 to 190 ° C. and a pressure of about 30 to 80 kg / cm ² . As shown in FIG. 6B, the flexible wiring layer 11 and the solid wiring layer 12 are laminated and bonded by heating and pressing, and the wiring pattern 14b of the flexible wiring layer and the wiring pattern 17 of the solid wiring layer are formed by the protruding conductor 19a. Are connected to each other, and a double-sided copper foil-laminated plate in which both sides of the solid wiring layer 12 are covered with copper foils 17A and 17B can be obtained. The edge of the protective insulator layer 20 on the flexible wiring layer is bitten into the rigid insulator layer. If the glass epoxy resin layer 13 has been punched, a dummy piece (resin piece) is fitted and incorporated in the opening (notch) region so that the glass epoxy resin layer 13 has an integrated and flat surface. Heating and pressing may be performed, and the flexible region may be secured by removing the dummy piece after joining.

  Next, the copper foils 17A and 17B on both sides (surface) are subjected to a photo-etching process to form a wiring pattern 17, whereby the rigid wiring layers 12 and 12 and the flexible wiring layer 11 as shown in FIG. A wiring board provided integrally is obtained, and a protective insulating layer 20 (see FIG. 2) such as a solder resist is provided on the exterior surface of the rigid wiring layers 12 and 12. In the final process of the flexible / rigid wiring board, an outer shape process and a characteristic test are performed to obtain a flexible / rigid wiring board whose main part is shown in cross section in FIG.

  In the method for manufacturing a wiring board according to the present embodiment, the conical protruding conductors 18, 19, 19a are formed on the copper foils 14a, 17A, 17B by the following means, for example. That is, on one main surface side of the copper foil, for example, a metal mask having a hole having a diameter of about 0.1 to 0.15 mm is positioned and arranged at a predetermined position of a stainless steel sheet, and a conductive paste such as a silver paste is printed. .

  In the production of the flexible / rigid wiring board, when the number of wiring patterns 17 of the rigid wiring layers 12 and 12 is increased, a plurality of rigid wiring layer units 12A may be stacked as shown in FIG.

  Further, as shown in FIG. 10, only one rigid wiring layer unit 12A may be arranged on both main surfaces of the flexible wiring layer. In this case, the copper foil 17A or the wiring pattern 17 printed with the protruding conductor 19a is laminated and integrated on the flexible wiring layer 11 via the adhesive layer 16B.

  In addition, by forming the same number of rigid wiring layer units on both surfaces of the flexible wiring layer as described above, the strain generated in the layer thickness direction is balanced and effective in preventing warping of the wiring board. The number of layers can be selected depending on the application.

Table 1 shows the evaluation of Examples 1, 2, and 3. Here, the glass transition point: Tg, the thermal expansion coefficient (less than Tg): α1, the thermal expansion coefficient (Tg or more): α2, the pressurizing temperature during lamination: ° C, the reflow temperature: 260-290 ° C. As the flexible wiring layer 11, a liquid crystal polymer having a glass transition point of 292 ° C. and a thermal expansion coefficient α1 of 40 to 70 in the layer thickness direction at a temperature equal to or lower than the glass transition point was used. In the table, ○ indicates good and × indicates poor.

  11 to 13 show the characteristics of the present embodiment in comparison with the characteristics of the flexible wiring layer of the liquid crystal polymer.

Measurement of characteristic impedance (Fig. 11)
The measurement was performed by observing the waveform by the ТDR method. A high-frequency probe was connected to a test point at one end of the sample to be measured for transmission characteristics, and measurement was performed at a measurement frequency band of 10 GHz. As a result of this measurement, the characteristic A of the present embodiment and the characteristic B of the liquid crystal polymer wiring board are almost the same, and in the present embodiment, no defect is observed in the interlayer connection portion other than the contact portion of the probe (due to mismatching). High-quality transmission in the high-speed frequency band is possible.

Insertion loss (Figure 12)
The loss up to 8 GHz was measured with a scalar network analyzer. In both cases of the embodiment A and the liquid crystal polymer substrate B, it can be said that transmission is possible up to 7 GHz, assuming that the level at which transmission is possible is -6 dBm. In other words, even if it has a multi-layer rigid wiring layer as in this embodiment, it has the same characteristics as a flexible board without a rigid layer, and transmission in the high frequency band is possible even when viewed from the results of insertion loss measurement It was confirmed.

Through waveform (Figure 13)
To see the effect on the actual waveform, we measured the input / output waveform of the through waveform. The input side has a rising waveform with a slew rate of 45 ps. When the waveform on the output side is confirmed, there is no significant difference between the characteristics of the embodiment A and the liquid crystal polymer substrate B. That is, in the high-speed transmission region, it was confirmed that the same excellent characteristics as the liquid crystal polymer substrate were exhibited.

  The present invention is not limited to the above-described embodiment, and can include various modifications without departing from the spirit of the invention. For example, a combination of another liquid crystal polymer having a different glass transition temperature and a glass epoxy resin system can be appropriately selected depending on the application.

The perspective view of one embodiment of the present invention. FIG. 2 is a partially enlarged cross-sectional view taken along line AA in FIG. 1. The schematic diagram explaining the process of the manufacturing method of one Embodiment of this invention. (A), (b), (c) is sectional drawing explaining the manufacturing process of the flexible wiring board of one Embodiment of this invention. (A), (b), (c), (d) is sectional drawing explaining the manufacturing process of the rigid wiring board of one Embodiment of this invention. (A), (b), (c) is sectional drawing explaining the manufacturing process of the flexible rigid type | mold wiring board of one Embodiment of this invention. The curve figure explaining the effect | action of this invention. (A), (b) is the schematic explaining the distortion of the wiring board by this invention, and the wiring board of a comparative example. Sectional drawing explaining other embodiment of this invention. The cross-sectional schematic diagram explaining other embodiment of this invention. The curve figure which compares and shows the characteristic impedance of embodiment of this invention and a flexible wiring board. The curve figure which compares and shows the transmission characteristic of embodiment of this invention and a flexible wiring board. The curve figure which compares and shows the through waveform of embodiment of this invention and a flexible wiring board. The partial expanded sectional view of the conventional wiring board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10: Flexible rigid wiring board 11: Flexible wiring layer 12: Rigid wiring layer 12A: Rigid wiring layer unit 13: Flexible insulator layer 14 (14a, 14b): Wiring pattern 14A, 14B: Copper foil 16: Rigid insulator layer 16A: Rigid insulator layer (semi-curing)
16B: adhesive layer (semi-curing)
17: Wiring pattern 17A, 17B: Copper foil 18, 19, 19a: Protruding conductor 20: Protective insulator layer

Claims (9)

A flexible wiring layer comprising a flexible insulating layer made of a liquid crystal polymer having a predetermined glass transition temperature and a first wiring pattern disposed in the surface of the flexible insulating layer or in the layer;
A rigid insulator layer made of a fiber reinforced thermosetting resin having a glass transition temperature lower than the glass transition temperature of the flexible insulator layer, which is laminated and integrated between both sides of a part of the flexible wiring layer, and the rigid A rigid wiring layer comprising a second wiring pattern disposed on the surface of the insulator layer or in the layer;
A protruding conductor that penetrates the rigid insulator layer and electrically connects the first wiring pattern and the second wiring pattern;
And the rigid insulator layer applies compressive strain to the flexible insulator layer at room temperature.   2. The flexible rigid wiring board according to claim 1, wherein a surface of the second wiring pattern adjacent to the flexible insulating layer is roughened. 3.   A surface of the flexible wiring layer on which the rigid wiring layer is not laminated is covered with a protective insulating layer, and at least a part of an edge thereof overlaps an adhesive surface between the flexible insulating layer and the rigid wiring layer. The flexible rigid wiring board according to claim 1.   4. The flexible rigid wiring board according to claim 1, wherein the rigid wiring layer is formed on both surfaces of the flexible wiring layer.   The flexible / rigid wiring board according to claim 1, wherein the fiber reinforced thermosetting resin layer is an epoxy resin layer containing glass cloth. A first wiring pattern is formed on both principal surfaces of a flexible insulator layer made of a liquid crystal polymer film having a predetermined glass transition temperature, and the bump-like projecting conductor penetrates the flexible insulator layer. Forming a flexible wiring layer in which the wiring patterns are connected to each other;
A conductor foil or a second wiring pattern is formed between both principal surfaces or layers of one or more rigid insulator layers made of a fiber reinforced thermosetting resin having a glass transition temperature lower than the glass transition temperature of the flexible insulator layer. Forming a rigid wiring layer formed by connecting the conductor foil or the second wiring patterns with bump-shaped protruding conductors that pass through the rigid insulator layer; and
Forming a conductive bump on one main surface of the rigid wiring layer;
The rigid wiring layer faces the main surface on which the conductive bumps are formed, and the glass transition temperature is lower than the glass transition temperature of the flexible insulator layer so as to be sandwiched between both surfaces of a part of the flexible wiring layer. From the glass transition temperature of the fiber reinforced thermosetting resin layer, laminated at a temperature lower than the glass transition temperature of the flexible insulator layer, sandwiching the adhesive layer of the semi-cured fiber reinforced thermosetting resin of the point temperature Heating and pressurizing at a high temperature, joining the flexible wiring layer and the rigid wiring layer, and connecting the conductive bumps to the first wiring pattern;
And a compressive strain is applied to the flexible insulator layer by shrinkage of the rigid insulator layer at room temperature.   The method of manufacturing a flexible / rigid wiring board according to claim 6, wherein a rigid wiring layer is formed in a semi-cured state of the rigid insulator layer, and is cured by the heating and pressing together with the adhesive layer. A first wiring pattern is formed on both main surfaces of the flexible insulator layer made of a liquid crystal polymer film having a predetermined glass transition temperature, and the bump-like projecting conductors penetrate the flexible insulator layer. Forming a flexible wiring layer in which wiring patterns are connected to each other;
Forming conductive bumps on the conductive foil or the second wiring pattern;
The conductive foil or the second wiring pattern is directed toward the conductive bump so as to be sandwiched between both surfaces of a part of the flexible wiring layer, and is lower than the glass transition temperature of the flexible insulating layer. The fiber reinforced thermosetting is carried out at a temperature lower than the glass transition temperature of the flexible insulator layer by laminating an adhesive layer as a rigid insulator layer of a semi-cured fiber reinforced thermosetting resin having a glass transition temperature. Heating and pressurizing at a temperature higher than the glass transition temperature of the resin layer; and
And a compressive strain is applied to the flexible insulator layer by shrinkage of the rigid insulator layer at room temperature. The flexible rigid wiring board according to claim 6 or 8, wherein the adhesive layer of the semi-cured fiber-reinforced thermosetting resin is formed in a state where the conductive bumps are inserted before heating and pressing. Manufacturing method.

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