JP5286988B2 - Rigid flexible printed wiring board and manufacturing method thereof - Google Patents

Description

  The present invention relates to a rigid flexible printed wiring board widely used in various electronic devices such as a personal computer, a mobile communication telephone, and a video camera, and a manufacturing method thereof.

  Recently, personal computers, digital cameras, mobile phones, etc. have become widespread as mobile products. Especially, there are strong demands for small size, thinness, light weight, high definition, multi-functionality, etc.・ Low profile and 3D mounting are progressing. As one of methods for easily realizing such a low-profile and three-dimensional mounting of a semiconductor package, a method using a printed wiring board having a cavity is known.

  The form of the rigid flexible printed wiring board which has the conventional cavity below is demonstrated.

  In the rigid flexible printed wiring board in FIG. 13, a flexible substrate 24 having an opening 23 that forms a cavity is mounted on a rigid substrate 22 on which an electronic component 21 is mounted, and the electronic component 21 is mounted on the opening 22. The position is opened, that is, the electronic component 21 is accommodated. The rigid substrate 22 and the flexible substrate 24 are disposed so as to house the electronic component 21 in the opening 23 and are electrically connected by an electrical adhesive member.

As prior art document information related to the application of the present invention, for example, Patent Document 1 is known.
JP 2003-273491 A

  In general, a rigid flexible printed wiring board has a large difference in thermal expansion coefficient between a rigid substrate and a flexible substrate, and thus there is a possibility that distortion occurs due to contraction due to heat. When the openings are provided as shown in FIG. 13, the distortion tends to increase. In particular, when there are a plurality of openings, the distortion is further increased and the rigid substrate and the flexible substrate may be separated.

  The present invention has been made in view of the above problems, and provides a thin rigid flexible printed wiring board capable of connecting multiple pins between substrates and increasing the wiring density in the substrate. is there.

In order to achieve the above object, the present invention provides a rigid substrate having an opening , a flexible substrate having a surface layer wiring and an inner layer via, and a thermosetting resin or thermoplastic resin connecting these substrates . A connection layer made of an insulating material having an opening substantially the same shape as the resin and the opening and not including a film, a through hole formed at a predetermined position of the connection layer, and filling the through hole a paste via made of a conductive paste, a rigid flexible wiring board having a cavity having a side surface surrounding the entire periphery of the bottom surface of the cavity, and characterized by being constituted by the opening of the rigid substrate This configuration makes it possible to connect multiple pins between boards and to increase the wiring density within the board. Furthermore it is possible to realize a thin printed circuit board by one of the substrate and the flexible substrate.

  As described above, the present invention enables multi-pin connection between substrates and increases the wiring density in the substrate, so that the mobile device is small, thin, lightweight, high-definition, multifunctional, etc. Therefore, it is possible to provide a mounting form that can easily realize a small size, a low profile, and a three-dimensional mounting corresponding to the high-functionality and multi-pin semiconductors necessary for realizing the above.

(Embodiment 1)
Embodiment 1 of the present invention will be described below with reference to the drawings.

  FIG. 1 is a perspective view of a rigid flexible printed wiring board according to an embodiment of the present invention. The printed wiring board according to the present embodiment is composed of a rigid board 1, a flexible board 2, and a connection layer 3 having wiring formed on the surface layer and having different shapes, and the rigid board 1 and the flexible board 2 have different shapes. Therefore, as shown in FIG. 1 (A), a recess 4 serving as a cavity is formed. The connection layer 3 desirably has a thickness of 30 to 300 μm. If the thickness is less than 30 μm, the embedding property of the wiring is deteriorated, and if it exceeds 300 μm, it is difficult to reduce the diameter of the via for maintaining the aspect ratio of the via, and connection reliability may be impaired.

  As shown in FIG. 1B, by mounting the mounting component 5 in the recess 4, the total thickness of the mounting body can be reduced.

  Further, as shown in FIG. 1, the multilayer substrate 14 has a complicated structure because the connection substrate 3 and the multilayer substrate 14 having three or more layers are formed on the surface of the flexible substrate 2 where the rigid substrate 1 is not formed. Since a circuit can be formed, a complicated circuit can be formed in the recess 4. In FIG. 1C, the flexible substrate 2 and the multilayer substrate 14 may be interchanged, and the multilayer substrate 14 may be either rigid or flexible.

  An enlarged cross-sectional view of the connection layer 3 in this embodiment is shown in FIG. The connection layer 3 is an insulating material in which an inorganic filler is dispersed in a thermosetting resin. A through hole is formed at a predetermined position of the connection layer 3, and the conductive paste 6 is filled in the through hole. A via 7 is provided.

  In the present invention, the inorganic filler in the connection layer 3 is preferably composed of at least one of silica, alumina, and barium titanate. Moreover, it is preferable that the particle size of the inorganic filler in the connection layer 3 is 1 to 15 μm, and the content of the inorganic filler is 70 to 90% by weight. If the content of the inorganic filler is less than 70%, the amount of the inorganic filler forming the connection layer 3 is less than the amount of the thermosetting resin and is in a rough state, and when the thermosetting resin flows during the press, At the same time, the inorganic filler also flows, and if it exceeds 90%, the resin amount of the connection layer 3 becomes too small, and the embeddability and adhesion of the wiring may be impaired.

  The conductive paste 6 used for the printed wiring board of the present invention is composed of copper, silver, gold, palladium, bismuth, tin, and alloys thereof, and preferably has a particle size of 1 to 20 μm.

  Next, the manufacturing process of the rigid flexible printed wiring board of this Embodiment is demonstrated in detail using FIG.

  First, as shown in FIG. 2A, the PET film 8 is attached to both surfaces of the connection layer 3. Next, as shown in FIG. 2B, the connection layer 3 is cut into the shape of the rigid substrate 1, and a through hole 9 is formed at a position where the rigid substrate 1 and the wiring of the flexible substrate 2 are connected. Next, as shown in FIG. 2C, the through-hole 9 is filled with a conductive paste 6 made of copper or a copper alloy, and a via 7 is formed. Next, as shown in FIG. 2D, in order to bond the connection layer 3 to either the rigid substrate 1 or the flexible substrate 2, the PET film 8 on one surface is peeled off. Here, the PET film on the lower surface is peeled off in order to adhere to the flexible substrate 2 first, but the upper PET film may be peeled off first.

  Next, as shown in FIG. 3A, the connection layer 3 is arranged at a desired position of the flexible substrate 2, and the connection layer 3 is formed on the flexible substrate 2 as shown in FIG. 3B. Temporarily fasten to 10 At the time of this temporary fixing, the wiring 10 is embedded in the connection layer 3. By doing so, the conductive paste 6 is compressed, so that the connectivity with the wiring 10 is improved. Thereafter, as shown in FIG. 3C, the PET film 8 on the surface that has not been peeled first is peeled off.

  Next, as shown in FIG. 4A, the rigid substrate 1 is disposed on the connection layer 3, and as shown in FIG. 4B, it is laminated while being heated and pressurized in the same manner as in the step of FIG. The flexible printed wiring board 15 is completed. The wiring 10 is embedded in the connection layer 3 during this lamination. By doing so, the conductive paste 6 is further compressed, so that the connectivity with the wiring 10 is greatly improved.

  In the present invention, it is preferable to form a solder resist in advance on the surface of the rigid substrate 1 together with the flexible substrate 2 before the connection layer 3 is disposed, and in the surface layer wiring formed on the rigid substrate 1 after the solder resist is formed. More preferably, at least the region in contact with the connection layer 3 is roughened.

  In the present embodiment, the flexible substrate 2 and the connection layer 3 are overlapped, and then the rigid substrate 1 is overlapped. However, the rigid substrate 1 and the connection layer 3 are overlapped first, and then the flexible substrate 2 is overlapped. They can be stacked.

  In general, in the case of a structure having a dent, that is, a recess, dust, base powder, and the like are easily collected in the corner of the recess. In the case of a smooth printed wiring board having no recess, dust and powder were easily removed with a dust-removing adhesive roll, but it was difficult to remove the corner portion of the recess with the adhesive roll.

  Therefore, in order to prevent dust and powder from entering the recess 4, powder scattering to the recess 4 of the rigid substrate 1, the flexible substrate 2 and the connection layer 3, adhesion of dust and the like to the recess 4, and thereby In order to prevent mounting defects, as shown in FIG. 5, a permanent resist 11 in the form of a dry film having a thickness of 5 to 30 μm is pasted to cover the walls of the rigid substrate 1, the flexible substrate 2 and the connection layer 3. However, it is more preferable as the rigid flexible printed wiring board of the present invention. As a result, it is possible to prevent the powder and dust from adhering to the corner portions of the recess 4 in particular. When the thickness of the permanent resist 11 is less than 5 μm, pinholes are likely to be generated, resulting in insufficient coating. When the thickness exceeds 30 μm, the followability to the substrate may be deteriorated.

  The thermal expansion coefficient of the connection layer 3 of the present invention is desirably lower than the thermal expansion coefficient of the rigid substrate 1 and the flexible substrate 2, that is, 65 ppm / ° C. or lower, or lower than the thermal expansion coefficient of the printed wiring board.

  When it exceeds 65 ppm / ° C. or higher than the thermal expansion coefficient of the rigid substrate 1 and the flexible substrate 2, warping or deformation of the rigid flexible printed wiring board may easily occur due to the deformation of the connection layer 3.

  The glass transition point (DMA method Dynamic Mechanical Analysis dynamic viscoelasticity measurement method) of the connection layer 3 is preferably 185 ° C. or higher or higher by 10 ° C. or more than the rigid substrate 1 and the flexible substrate 2. If the temperature is less than 185 ° C. or the difference is less than 10 ° C., the waviness of the substrate may become a complicated shape or become irreversible in a process requiring a high temperature such as reflow.

  Moreover, the connection layer 3 uses the structure which does not contain core materials, such as a woven fabric, a nonwoven fabric, and a film. When the core material is included, it is difficult to embed the wiring pattern formed on the surfaces of the rigid substrate 1 and the flexible substrate 2 as described above.

  The minimum melt viscosity of the connection layer 3 is suitably 1000 to 100,000 Pa · s as shown in the melt viscosity curve of FIG. If the pressure is less than 1000 Pa · s, the resin flow becomes large and may flow into the recess 4. If the pressure exceeds 100000 Pa · s, poor adhesion to the printed wiring board or poor embedding in the wiring 10 occurs. There is a fear.

  The connection layer 3 may contain a colorant. In this case, mountability and light reflectivity are improved.

  Moreover, in order to suppress the resin flow of the connection layer 3, that is, it is necessary to prevent the resin from flowing into the recess 4, it is desirable that the connection layer 3 contains an elastomer for suppressing the resin flow. .

  In the present embodiment, the recess 4 is formed on the rigid substrate 1, but may be formed on the flexible substrate 2, or may be formed on both the rigid substrate 1 and the flexible substrate 2. Moreover, the recessed part 4 may be formed in multiple places.

  The rigid substrate 1 and the flexible substrate 2 are not particularly limited as long as they are resin substrates such as through-hole wiring boards and all-layer IVH structure ALIVH wiring boards, and even double-sided boards are multilayer boards. The number of layers is not limited even in a multilayer substrate.

(Embodiment 2)
Embodiment 2 of the present invention will be described below with reference to the drawings. In addition, about what has the same structure as Embodiment 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  FIG. 7A is a perspective view of a rigid flexible printed wiring board according to Embodiment 2 of the present invention. The rigid flexible printed wiring board of the present embodiment has the same configuration as the three-dimensional printed wiring board of the first embodiment. A feature of the second embodiment is that the connection layer 3 is an insulating layer made of a thermoplastic resin, and has a via filled with a conductive paste in the insulating layer. The connection layer 3 desirably has a thickness of 30 to 300 μm. 7B and 7C are cross-sectional views. The basic configuration is the same as that of the first embodiment.

  Next, the manufacturing process of the rigid flexible printed wiring board of this Embodiment is demonstrated in detail using FIG.

  First, since the connection layer 3 in the present embodiment does not have adhesiveness, the adhesive layer 12 made of a thermosetting resin having a thickness of 1 to 10 μm is formed as a temporary fixing means for attaching the cover film 13. In addition, since a pinhole will generate | occur | produce when thickness is less than 1 micrometer, when it exceeds 10 micrometers, there exists a possibility that the cover film 13 may not be peeled in a post process. After forming the adhesive layer 12, cover films 13 are attached to both surfaces of the connection layer 3. This state is shown in FIG. Note that the adhesive layer 12 may be attached to the connection layer described in Embodiment 1, that is, an insulating layer in which an inorganic filler is dispersed in a thermosetting resin.

  The adhesive layer 12 preferably has no tackiness at room temperature in order to improve laminating properties. Next, as shown in FIG. 8B, the connection layer 3 is cut into the shape of the rigid substrate 1, and the through hole 9 is formed at a position where the rigid substrate 1 and the wiring of the flexible substrate 2 are connected. Next, as shown in FIG. 8C, the through-hole 9 is filled with a conductive paste 6 made of copper or a copper alloy, and a via 7 is formed. Next, as shown in FIG. 8D, in order to bond the connection layer 3 to the rigid substrate 1 and the flexible substrate 2, the cover films 13 on both sides are peeled off.

  Next, as shown in FIG. 9 (A), the connection layer 3 is placed while being aligned with desired positions of the rigid substrate 1 and the flexible substrate 2, and the connection layer 3 is connected as shown in FIG. 9 (B). The layer 3 is overlapped so as to be sandwiched between the rigid substrate 1 and the flexible substrate 2 and laminated while being heated and pressed to complete the rigid flexible printed wiring board 15. The wiring 10 is embedded in the connection layer 3 during this lamination. By doing so, the conductive paste 6 is further compressed, so that the connectivity with the wiring 10 is greatly improved. In this embodiment, the stacking method of FIGS. 3 to 4 of Embodiment 1 may be used.

  Also in the first embodiment, the adhesive layer 12 may be formed before the PET film 8 is formed on the connection layer 3. In this case, the effect of preventing the material of the connection layer 3 from being crushed can be obtained.

  As in the first embodiment, as shown in FIG. 10, a thickness of 5 to 30 μm is used to prevent dust and the like from adhering to the rigid substrate 1, the flexible substrate 2, and the recess 4 and mounting defects. It is more preferable as the rigid flexible printed wiring board of the present invention to apply the dry film-like permanent resist 11 and coat the wall surfaces of the rigid substrate 1, the flexible substrate 2, and the connection layer 3. As a result, it is possible to prevent dust and the like from adhering to the corners of the recess 4. When the thickness of the permanent resist 11 is less than 5 μm, pinholes are likely to be generated, resulting in insufficient coating. When the thickness exceeds 30 μm, the followability to the substrate may be deteriorated.

  As the thermoplastic resin of the connection layer 3 in the present embodiment, PPS (polyphenylene sulfide), PEEK (polyether ether ketone), PES (polyether sulfone), thermoplastic polyimide, or the like is used.

  The thermal expansion coefficient of the connection layer 3 of the present invention is desirably lower than the thermal expansion coefficient of the rigid substrate 1 and the flexible substrate 2, that is, 65 ppm / ° C. or lower, or lower than the thermal expansion coefficient of the printed wiring board.

  Further, the glass transition point (DMA method) of the connection layer 3 is desirably 185 ° C. or higher, or higher by 10 ° C. or more than the rigid substrate 1 and the flexible substrate 2.

  Moreover, the connection layer 3 uses the structure which does not contain core materials, such as a woven fabric, a nonwoven fabric, and a film. When the core material is included, it is difficult to embed the wiring patterns formed on the upper and lower printed wiring board surfaces as described above.

  As in the first embodiment, the minimum melt viscosity of the connection layer 3 is suitably 1000 to 100,000 Pa · s as shown in the melt viscosity curve of FIG.

  In the present embodiment, the recess 4 is formed on the rigid substrate 1, but may be formed on the flexible substrate 2, or may be formed on both the rigid substrate 1 and the flexible substrate 2. Moreover, the recessed part 4 may be formed in multiple places.

  The rigid substrate 1 and the flexible substrate 2 are not particularly limited as long as they are resin substrates such as through-hole wiring boards and all-layer IVH structure ALIVH wiring boards, and even double-sided boards are multilayer boards. The number of layers is not limited even in a multilayer substrate.

(Embodiment 3)
Embodiment 3 of the present invention will be described below with reference to the drawings. In addition, about the structure similar to Embodiment 1, 2, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  FIG. 11 is a cross-sectional view of a rigid flexible printed wiring board according to Embodiment 3 of the present invention. As shown in FIG. 11, the third embodiment is characterized in that a rigid substrate 1a having an opening from above, a connection layer 3a having an opening of a moving shape that matches the opening of the rigid substrate 1a, and a flexible substrate 2 Further, another connection layer 3b and another rigid substrate 1b are laminated in this order. A recess 4 serving as a cavity is formed by the openings of the rigid substrate 1a and the connection layer 3a. By taking such a configuration, a complicated circuit can be formed in the recess 4.

  Next, the manufacturing method of the rigid flexible printed wiring board in this Embodiment is demonstrated using FIG. First, a rigid substrate 1a having wiring (not shown) formed on the surface layer is prepared, and an opening is formed. A connection layer 3a is prepared, an opening having a substantially same shape as the opening of the rigid substrate 1a is formed, and a via (not shown) is formed as in the first and second embodiments. Next, a flexible substrate 2 with wiring on the surface layer, another connection layer 3b, another rigid substrate 1b with wiring on the surface layer (FIG. 12A), and a rigid substrate 1a, connection layer are prepared. 3a, the flexible substrate 2, the connection layer 3b, and the rigid substrate 1b are stacked while being aligned in this order. Thereby, the rigid flexible printed wiring board 15 is completed (FIG. 12B).

  In the present embodiment, the insulating material used for the connection layer 3 is one in which an inorganic filler as in the first embodiment is dispersed in a thermosetting resin, or a thermoplastic resin as in the second embodiment. Either may be sufficient.

  Further, by using the rigid substrate 1b as a multilayer substrate, a more complicated circuit can be formed. A plurality of the recesses 4 may be formed.

  In the present embodiment, the rigid substrate 1 may be replaced with a flexible substrate and the flexible substrate 2 may be replaced with a rigid substrate, or two or more flexible substrates 2 may be stacked via the connection layer 3. The configuration is not limited to that shown in FIG.

  As in the first and second embodiments, in order to prevent the adhesion of dust and the like to the rigid substrate 1, the flexible substrate 2, and the recess 4 and the mounting defects caused thereby, a dry film-like shape having a thickness of 5 to 30 μm is used. It is more preferable for the rigid flexible printed wiring board of the present invention to attach the permanent resist 11 and cover the walls of the rigid substrate 1, the flexible substrate 2, and the connection layer 3.

  The thermal expansion coefficient of the connection layer 3 of the present invention is desirably lower than the thermal expansion coefficient of the rigid substrate 1 and the flexible substrate 2, that is, 65 ppm / ° C. or lower, or lower than the thermal expansion coefficient of the printed wiring board.

  Further, the glass transition point (DMA method) of the connection layer 3 is desirably 185 ° C. or higher, or higher by 10 ° C. or more than the rigid substrate 1 and the flexible substrate 2.

  Moreover, the connection layer 3 uses the structure which does not contain core materials, such as a woven fabric, a nonwoven fabric, and a film.

  As in the first embodiment, the minimum melt viscosity of the connection layer 3 is suitably 1000 to 100,000 Pa · s as shown in the melt viscosity curve of FIG.

  The rigid substrate 1 and the flexible substrate 2 are not particularly limited as long as they are resin substrates such as through-hole wiring boards and all-layer IVH structure ALIVH wiring boards, and even double-sided boards are multilayer boards. The number of layers is not limited even in a multilayer substrate.

  Since the rigid flexible printed wiring board according to the present invention can be formed with a thin total board thickness as a mounting body after component mounting, such as a personal computer, a digital camera, a mobile phone, etc., small, thin, lightweight, high definition, multi-function It can be used as a package substrate for coping with downsizing and the like, and can be applied to applications related to these mounting substrates as one of the methods for easily realizing a low profile and three-dimensional mounting of a semiconductor package.

The perspective view and sectional drawing which show an example of the rigid flexible printed wiring board in Embodiment 1 of this invention Sectional drawing which shows the manufacturing process of the rigid flexible printed wiring board in Embodiment 1 of this invention Sectional drawing which shows the manufacturing process of the rigid flexible printed wiring board in Embodiment 1 of this invention Sectional drawing which shows the manufacturing process of the rigid flexible printed wiring board in Embodiment 1 of this invention Sectional drawing which shows an example of the rigid flexible printed wiring board in Embodiment 1 of this invention The figure which shows the melt viscosity of the connection layer of the rigid flexible printed wiring board in Embodiment 1, 2 of this invention The perspective view and sectional drawing which show an example of the rigid flexible printed wiring board in Embodiment 2 of this invention Sectional drawing which shows the manufacturing process of the rigid flexible printed wiring board in Embodiment 2 of this invention. Sectional drawing which shows the manufacturing process of the rigid flexible printed wiring board in Embodiment 2 of this invention. Sectional drawing which shows an example of the rigid flexible printed wiring board in Embodiment 2 of this invention Sectional drawing which shows an example of the rigid flexible printed wiring board in Embodiment 3 of this invention Sectional drawing which shows the manufacturing process of the rigid flexible printed wiring board in Embodiment 3 of this invention. A perspective view showing a conventional printed wiring board

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rigid board 2 Flexible board 3 Connection layer 4 Recessed part 5 Mounting component 6 Conductive paste 7 Via 8 PET film 9 Through-hole 10 Wiring 11 Permanent resist 12 Glue layer 13 Cover film 15 Rigid flexible printed wiring board

Claims (10)

A rigid substrate having an opening , a flexible substrate having a surface layer wiring and an inner layer via, and a thermosetting resin or thermoplastic resin connecting these substrates and an opening having a shape substantially the same as the opening. has a section, a film having a connecting layer made of an insulating material which does not include a through hole formed at a predetermined position of the connecting layer, and the paste via consisting of conductive paste filled in the through hole, the A rigid flexible printed wiring board having a cavity, wherein a side surface surrounding the entire circumference of the bottom surface of the cavity is constituted by the opening of the rigid substrate . The rigid flexible printed wiring board according to claim 1, wherein the connection layer is formed by dispersing an inorganic filler in a thermosetting resin or a thermoplastic resin . The rigid flexible printed wiring board according to claim 1, wherein an inner wall surface of the cavity is covered with an insulating film. The rigid flexible printed wiring board according to claim 1, wherein the insulating coating contains an antistatic agent. The rigid flexible printed wiring board according to claim 1, wherein the connection layer contains a colorant. A thermosetting or thermoplastic resin for bonding the rigid and flexible substrates on which wiring is formed on the surface layer between these substrates, to prepare the connection layer film made of an insulating material free, rigid A step of cutting the rigid substrate and the connection layer into a desired shape to form a flexible portion and a flexible portion; a step of forming a through hole at a predetermined position of the connection layer; and a conductive paste in the through hole Filling the flexible substrate, the rigid substrate, and the connection layer while aligning them, and laminating the flexible substrate, the connection layer, and the rigid substrate while heating and pressing at least a method of manufacturing a rigid flexible printed wiring board having a cavity, characterized by comprising, a bottom surface of the cavity Side surrounding the periphery method for manufacturing a rigid flexible printed wiring board, characterized in that it is constituted by the opening of the rigid substrate. Before preparing a connecting layer having a rigid substrate with wiring formed on the surface layer, a flexible substrate, and an insulating material containing a resin for connecting between these substrates, a solder resist is formed on the surface of the flexible substrate in advance. The manufacturing method of the rigid flexible printed wiring board of Claim 6 provided with the process to do. The manufacturing method of the rigid flexible printed wiring board of Claim 6 provided with the process of forming a soldering resist beforehand on the surface of a rigid board | substrate. Before the step of stacking the connection layer and the rigid substrate and the flexible substrate of claim 6 comprising the step of roughening the region in contact with at least the connecting layer in advance the surface layer formed on the flexible board wiring Manufacturing method of rigid flexible printed wiring board. 7. The method according to claim 6 , further comprising a step of roughening at least a region in contact with the connection layer in the surface layer wiring formed in advance on the rigid substrate before the step of laminating the flexible substrate, the connection layer, and the rigid substrate. Manufacturing method of rigid flexible printed wiring board.

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