JP2007220735A - Method for manufacturing multi-layer printed wiring board including flying tail - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a multilayer printed wiring board for acquiring flexibility of a flying tail, by protecting the flying tail from a solution used in the intermediate steps such as plating step and etching step, etc. in the slit processing method. <P>SOLUTION: The method comprises a step of adhering a bonding material 40 having an aperture 41 and an external layer substrate 30 including a slit 33, so that the slit 33 of the external layer substrate 30 is located at the external side of the aperture 41 of the bonding material 40 provided between both substrates 10, 30 in the substrate laminating step of the internal layer substrate 10 and the external layer substrate 30, and a distance (d) between a side surface 33a as an edge 34a of a part 34 to be removed on the flying tail 2 among both side surfaces 33a, 33b of the slit 33 and the edge 41a of the aperture 41 of the bonding agent becomes 0 mm or more and 0.2 mm or less. An etching resist 20 having resistivity to copper plating solution is formed to a part 14 corresponding to the flying tail 2 of the internal layer substrate 10 before the laminating step, and the etching resist 20 is peeled after the step of exposing the flying tail 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention has a flying tail portion where a circuit is exposed on the inner layer substrate, and slits the outer layer substrate corresponding to the flying tail portion before the step of laminating the inner layer substrate and the outer layer substrate. The present invention relates to a method for manufacturing a multilayer printed wiring board by a slit method in which a portion corresponding to the flying tail portion is removed from an outer layer substrate by a slit.

As a manufacturing method of a multilayer printed wiring board having a flying tail portion, as shown in paragraph 0004 of Patent Document 1, mainly two types of manufacturing methods are known.
(1) A series of such as forming a wiring pattern of a flexible cable portion having a flying tail portion, and further laminating a copper-clad laminated wiring board to produce a multilayer laminate, and then forming a surface layer wiring pattern on the multilayer laminate. After the above processing is performed, the unnecessary conductor layer and insulator layer are removed to expose the flying tail portion.
(2) A method for producing a multilayer laminate by laminating an inner layer FPC and a copper-clad laminate in which unnecessary conductor layers and insulator layers have been cut and removed in advance.

Among these, the method shown in (1) is difficult to apply to a thin multilayer printed wiring board such as a multilayer FPC. This is because the insulator layer to be removed is thin, and it is difficult to control the depth direction by using a generally used V-cut machine or removal processing of unnecessary portions by laser processing. Furthermore, a thin multilayer printed wiring board has a restriction on a substrate fixing method during processing. Therefore, in view of the possibility of application to a thin substrate, it can be said that the method shown in (2) is a more preferable technique.
On the other hand, in the method shown in (2), a series of processes such as surface pattern formation on a copper clad laminated wiring board from which unnecessary conductor layers and insulator layers have been cut and removed, and a multilayer laminate in which an inner layer FPC pattern is exposed. Therefore, it is a complicated process compared with the manufacturing process of a normal multilayer printed wiring board. That is, when performing a series of processing such as surface layer pattern formation, it is necessary to protect the exposed portion (flying tail portion) of the inner layer pattern from the liquid used in the plating step and the etching step.

As a method for protecting the flying tail, (a) a method using a plating resist or an etching resist, (b) a method using a coverlay, (c) a method using a masking tape, (d) a surface copper clad with a slit A method using a laminate is known.
Among these, (a) requires circuit formation for resist formation every time plating or resist is performed, (b) requires a mold for accurately punching the coverlay, and (c) is a tape for each plating or resist. There are various problems such as the need for peeling and manual work in principle, and the slit method of (d) may be able to produce a multilayer printed wiring board having a flying tail portion with the simplest and low cost. It is said.

The process shown in (d) is as follows.
1. An inner layer FPC in which a predetermined wiring pattern is formed so that an opening is provided at a predetermined location and a flying tail portion is exposed in the opening is manufactured.
2. In the single-sided copper-clad laminate, two slits are formed in advance corresponding to the opposite sides of the opening that are located at a predetermined distance from the edge of the opening. To do.
3. The single-sided copper clad laminate is laminated on each of both surfaces of the inner layer FPC via an interlayer adhesive layer in which another opening is provided at a position corresponding to the opening.
4). A required wiring pattern is formed on the conductive layer of each single-sided copper-clad laminate.
5). The single-sided copper-clad laminate is punched at a position including both ends of the two slits, and unnecessary removal pieces are removed to expose the opening of the inner layer FPC including the flying tail portion.

Here, for the purpose of protecting the flying tail part in the plating process and the etching process, the slit is formed at a position located 0.2 to 1.0 mm outside the edge of the opening as disclosed in Patent Document 2. It is preferable. In other words, in consideration of misalignment or the like when the interlayer adhesive layer and the single-sided copper-clad laminate are bonded (corresponding to 3 in the above process), an interval of 0.2 mm or more is necessary, and less than that At intervals, the flying tail portion is likely to be plated or etched due to liquid intrusion in the plating process or etching process.
JP 2004-172490 A JP 2001-036239 A

  On the other hand, as the amount of the adhesive flowing out increases, the flexibility of the flying tail portion decreases. However, when the gap between the slit and the opening is 0.2 mm or more as described in Patent Document 2, the flow of the adhesive at the boundary between the multilayer portion and the flying tail portion is taken into consideration when misalignment at the time of bonding is considered. It is difficult to suppress the amount (flowing amount) to 0.3 mm or less, desirably 0.2 mm or less. In other words, in the prior art, mechanical error when making an opening to an interlayer adhesive, mechanical error when providing a slit in a single-sided copper-clad laminate, and bonding between an interlayer adhesive layer and a single-sided copper-clad laminate It is necessary to control all misalignment, variation in the flow rate of the adhesive material, etc., and the flow rate of the adhesive material at the boundary between the multilayer part and the flying tail part can be suppressed to 0.3 mm or less, preferably 0.2 mm or less. If not, the flexibility of the flying tail will be significantly reduced.

  The present invention has been made in view of the above circumstances, and when manufacturing a multilayer printed wiring board having a flying tail portion by a slit method, the flying tail portion is used from a liquid used in an intermediate step such as a plating step or an etching step. It is an object of the present invention to provide a method for manufacturing a multilayer printed wiring board that can protect the flying tail portion and can ensure the flexibility of the flying tail portion.

In order to solve the above-described problem, the present invention provides an inner substrate having a flying tail portion from which a circuit is exposed and an outer layer substrate before being laminated, on both sides of a portion to be removed corresponding to the flying tail portion. A slit forming step for making a slit at a position, and a substrate laminating step for laminating the inner layer substrate and the outer layer substrate with the slit through an adhesive having an opening at a position corresponding to a portion to be removed of the outer layer substrate; A method of manufacturing a multilayer printed wiring board comprising: a flying tail portion exposing step of exposing the flying tail portion of the inner layer substrate by removing the portion to be removed from the outer layer substrate by the slit after the substrate laminating step. There,
In the substrate lamination step, the slit of the outer layer substrate is located outside the opening of the adhesive that bonds the inner layer substrate and the outer layer substrate, and the edge of the portion to be removed among the two side surfaces of the slit, A step of bonding the adhesive having the opening and the outer substrate into which the slit is placed so that the distance between the side surface and the edge of the opening of the adhesive becomes 0 mm or more and 0.2 mm or less,
An etching resist forming step of forming an etching resist having resistance to a copper plating solution on a portion corresponding to the flying tail portion of the inner layer substrate before the substrate laminating step, and the etching resist includes the flying tail portion; Provided is a method for producing a multilayer printed wiring board, which is peeled off after an exposure step.

  In the method for producing a multilayer printed wiring board of the present invention, an etching resist having resistance to a copper plating solution is formed where the circuit of the inner layer substrate is exposed and used as a flying tail portion. It remains until the outer layer substrate corresponding to the flying tail is removed, and the etching resist is used as a plating resist in the plating process, and the etching resist is removed last, so the flying tail is etched in the middle process. There is no danger of being plated. In addition, this etching resist prevents the liquid from entering the flying tail, so it is not necessary to make the adhesive openings smaller than necessary, ensuring the flexibility of the flying tail and bending when bent. The stress concentration on the part can be alleviated and a printed wiring board having good bending characteristics can be manufactured.

The present invention will be described below with reference to the drawings based on the best mode.
A multilayer printed wiring board 70 shown in FIG. 5 is a perspective view showing an example of a multilayer printed wiring board that can be manufactured according to the present invention. The multilayer printed wiring board 70 in this example includes an inner layer substrate 71 using a flexible printed circuit board (FPC) and outer layer substrates 72 and 72 laminated on both surfaces of the inner layer substrate 71. It has a flying tail portion 73 constituted by a part and multilayer portions 74 and 75 in which outer layer substrates 72 and 72 are laminated on both surfaces of the inner layer substrate 71 excluding the flying tail portion 73, respectively.

The inner layer substrate 71 has a flying tail portion 73 that can be bent (flexible) and from which a circuit (not shown) of the inner layer substrate 71 is exposed. The flying tail portion 73 can be suitably used as a connection terminal with other components. Moreover, the multilayer parts 74 and 75 can be suitably used as a space for component mounting.
In the present invention, the planar shape and arrangement, the material and the number of layers of the flying tail portion 73 and the multilayer portions 74 and 75 are not particularly limited. Further, the present invention is not limited to the case where the number of flying tail portions 73 is one, and a plurality of flying tail portions 73 may exist on one multilayer printed wiring board 70.

  In the present invention, an FPC may be used as the outer layer substrates 72 and 72, and a rigid printed circuit (RPC) may be used. A multilayer FPC using FPC as the outer layer substrates 72 and 72 is preferable because the thickness of the entire multilayer printed wiring board can be reduced. A multilayer rigid flex substrate using RPC as the outer layer substrates 72 and 72 is preferable because rigid multilayer portions 74 and 75 are obtained.

  Hereinafter, with reference to FIGS. 1-4, the manufacturing method of the multilayer printed wiring board 1 (refer FIG.1 (f)) which has the flying tail part 2 and the multilayer parts 3 and 4 by this invention is demonstrated illustratively. To do. As for the inner layer substrate 10, first, as shown in FIG. 2A, a double-sided copper-clad laminate in which copper foils 12 and 13 are laminated on both sides of a flexible insulating base material 11 made of an insulator such as polyimide. Prepare the copper foils 12 and 13 to form a circuit.

Further, as shown in FIG. 2B, an etching resist 20 is formed only on the inner substrate 10 where the flying tail portion 2 is to be formed (etching resist forming step).
As this etching resist 20, a resist having resistance to a copper plating solution is used. Thereby, the etching resist 20 can be used as a plating resist.

For the outer layer substrate 30, a single-sided copper-clad laminate 30 (see FIG. 3A) in which a copper foil 32 is laminated on one side of an insulating base 31 made of an insulator such as polyimide is prepared. ), A slit 33 is formed in the outer substrate 30 of the portion 34 to be removed corresponding to the flying tail portion 2 using a mold or the like (slit forming step). The slits 33 are cuts penetrating the outer layer substrate 30 in the thickness direction, and are provided at positions on both sides across a portion corresponding to the flying tail portion. The slit 33 is partially formed so that the portion 34 to be removed and the portion corresponding to the multilayer portions 3 and 4 (hereinafter sometimes referred to as “multilayer portion corresponding portion”) 35 are not separated. . That is, in the outer layer substrate 30 at the stage where the slits 33 are formed, the periphery of the portion 34 to be removed includes a portion separated by the two slits 33, and both ends of the slits 33 and 33, and the other portions of the outer layer substrate 30. There is a part that remains connected to the part.
When a plurality of flying tail portions are present on one multilayer printed wiring board, a portion 34 where the outer substrate 30 is to be removed is set corresponding to each flying tail portion. Then, slits 33 and 33 are formed on both sides of each of the portions 34 to be removed to facilitate the removal of the portions 34 to be removed in the step after the substrate lamination.
Since the slit 33 is a gap (space) between the portion 34 to be removed and the corresponding portion 35 of the multilayer portion, it is on both sides in the width direction of the slit 33 (in FIG. 3B, the left-right direction). There are side surfaces 33a and 33b of the slit 33, respectively. Of these, one side surface 33a is a slit side surface that becomes the edge 34a of the portion 34 to be removed (in FIG. 3B, it is located inward (center side) in the left-right direction with respect to the slits 33, 33) The other side surface 33b is a slit side surface which is an edge 35a of the multilayer portion corresponding portion 35 (in FIG. 3B, it is located outward in the left-right direction with respect to the slits 33 and 33).

For bonding the inner layer substrate 10 and the outer layer substrate 30, an interlayer adhesive 40 (see FIG. 3C) such as an adhesive sheet is prepared, and a portion corresponding to the flying tail portion 2 is punched out using a mold or the like. By removing, as shown in FIG. 3D, an opening 41 is formed (adhesive opening step).
Further, as shown in FIG. 3E, the outer layer substrate 30 in which the two slits 33 and 33 are formed and the interlayer adhesive 40 in which the opening 41 is formed are aligned and bonded (adhesive bonding step). ). Here, when the outer layer substrate 30 and the adhesive 40 are bonded together, the slit 33 of the outer layer substrate 30 is positioned outside the opening 41 of the adhesive 40 for bonding the inner layer substrate 10 and the outer layer substrate 30. The slit 33 is aligned and pasted so that the distance d between the side surface 33a of the slit 34 to be the edge 34a and the edge 41a of the adhesive opening 41 is 0 mm or more and 0.2 mm or less. Match. Here, the distance d is a direction along the surfaces of the outer layer substrate 30 and the adhesive 40 in a state where at least two layers of the outer layer substrate 30 and the adhesive 40 are bonded together (FIGS. 1A and 3E). In the horizontal direction).
In the case where the distance d is 0 mm, the position of the side surface 33a on the side to be the edge 34a of the portion 34 to be removed of the slit 33 and the edge 41a of the adhesive opening 41 is the thickness direction of the substrate ( In this case, the slit 33 itself (space) is located outside the adhesive material opening 41, so that the distance d is 0 mm in the present invention. Even if it is included, it does not contradict the requirement of the present invention that “the slit 33 is located outside the adhesive material opening 41”.
According to the present invention, the adhesive 40 and the outer layer substrate 30 are aligned and bonded as described above, so that the bottom of the slit 33 (the opening below the slit 33 in FIG. 3E) is the adhesive. It is closed at 40. As a result, as shown in FIG. 1A, after the outer layer substrate 30 is laminated with the inner layer substrate 10 (details will be described later), the inner layer substrate 10 and the outer layer substrate 30 in the portion 14 corresponding to the flying tail portion. The gap S is closed. Therefore, it is possible to prevent a chemical solution or the like from entering the gap S through the slit 33.
In order to facilitate this alignment, as shown in FIG. 3, the width b of the opening 41 of the interlayer adhesive 40 is set to the edge of the portion 34 to be removed of the two slits 33, 33 in advance. 34a is smaller than or equal to the distance between the side surfaces 33a on the side (that is, the width of the portion 34 to be removed) a (b ≦ a. More specifically, the difference a−b is in the range of 0 mm to 0.4 mm. It is good to have dimensions. In addition, the space | interval a of the slit 33 and the width | variety b of the opening part 41 shall be set in the mutually corresponding position and direction (in the same cross section).

In the step of laminating the inner layer substrate 10 and the outer layer substrate 30 (substrate laminating step), the outer layer substrate 30 (see FIG. 3E) in which the interlayer adhesive 40 for bonding the substrates 10 and 30 is bonded together. Two sheets are prepared and, as shown in FIG. 1 (a), sandwiched from both sides in the thickness direction (vertical direction in FIG. 1 (a)) of the inner substrate 10 (see FIG. 2 (b)) provided with the etching resist 20 It is in a state of being laminated and integrated by superposition, heat and pressure.
After the substrate laminating step, the adhesive 40 flows during heating and pressurization, so even when the distance d is 0 mm, the edge 34a of the portion 34 to be removed and the vicinity thereof are removed. The opening edge 41a of the adhesive 40 and the vicinity thereof are in close contact with the portion, and it is possible to prevent entry of a chemical solution or the like into the gap S between the inner layer substrate 10 and the outer layer substrate 30.

As shown in FIG. 1B, the laminate 5 of the inner layer substrate 10 and the outer layer substrate 30 obtained by this substrate lamination step opens a through-through hole 36 in a portion 35 corresponding to the multilayer portion 3, and further plating. A layer 37 is formed to establish interlayer conduction, and a circuit (not shown) of the outer layer substrate 30 is formed. In the plating process and the circuit etching process, as described above, the bottom of the slit 33 is blocked by the adhesive 40, so that the intrusion of the chemical solution or the like into the gap S is prevented. In order to improve the bendability of the flying tail portion 2 after exposure, the side surface 33a on the side that becomes the edge 34a of the portion 34 to be removed and the edge 41a of the adhesive material opening 41 among the side surfaces 33a, 33b of the slit 33 Since the distance d is set to a minimum (0 mm or more and 0.2 mm or less), there is a possibility that a chemical solution or the like may enter the gap S in some cases. In order to cope with this, in the present invention, since the etching resist 20 is formed in the portion 14 corresponding to the flying tail portion 2 of the inner layer substrate 10, even when the chemical solution or the like enters the gap S, the flying resist The tail part 2 can be reliably protected.
Further, with the intention of the distance d being 0 mm or more and 0.2 mm or less, the difference between the width a of the portion 34 to be removed and the width b of the opening 41 of the adhesive 40 (ab, where a ≧ Even when b) is set to 0 mm or more and 0.4 mm or less, a portion where the slit 33 of the outer layer substrate 30 is located inside the opening 41 of the adhesive 40 may occur due to a slight misalignment. In this case, since the bottom of the slit 33 cannot be closed with the adhesive 40 at the location where the slit 33 is located inside the opening 41 of the adhesive 40, a chemical solution or the like from the location enters the gap S between the substrates 10 and 30. According to the method of the present invention, since the etching resist 20 is formed in the portion 14 corresponding to the flying tail portion 2 of the inner layer substrate 10, a chemical solution or the like enters the gap S. Moreover, the flying tail part 2 can be reliably protected.

For the outermost substrate 50, as shown in FIG. 4A, a single-sided copper-clad laminate 50 in which a copper foil 52 is laminated on one side of an insulating base 51 made of an insulator such as polyimide is prepared and bonded. After the interlayer adhesive 60 such as a sheet is bonded, a portion corresponding to the flying tail portion 2 is punched and removed using a mold or the like to form openings 53 and 61 (see FIG. 4B).
In the present invention, the presence or absence of lamination of the outermost substrate 50 is arbitrary.

  The outermost layer substrate 50 (FIG. 4B) in which the interlayer adhesive 60 is bonded from both sides in the thickness direction (vertical direction in FIG. 1B) of the four-layer flexible substrate 5 manufactured up to FIG. 1B. 1) is aligned and bonded as shown in FIG. 1 (c), and then laminated and integrated by heat and pressure.

  After the step of laminating the outermost layer substrate 50, as shown in FIG. 1 (d), holes 54 are made in the surface layer by a laser or the like, a plated layer 55 is formed, and the conductors 52 and 55 on the outermost layer substrate 50 and the outer layer substrate 30 are formed. Conduction with the upper conductors 32 and 37 is established. Further, a circuit (not shown) of the outermost substrate 50 is formed.

After the circuit formation of the outermost layer substrate 50, as shown in FIG. 1 (e), the outer layer substrate 30 is punched out at positions including both ends of the slits 33 and 33, and the outer layer substrate 30 corresponding to the flying tail portion 2 is removed. It removes and the flying tail part 2 is exposed through the opening 41 of the adhesive material 40 (flying tail part exposure process).
After removing the removal piece 34, as shown in FIG. 1F, the etching resist 20 in the portion 14 corresponding to the flying tail portion 2 of the inner layer substrate 10 is peeled off (etching resist peeling step). Further, in order to protect the circuit of the outermost substrate 50, a solder resist (not shown) is formed at a predetermined position.
The multilayer printed wiring board 1 shown in FIG. 1F can be manufactured by the above procedure. In the case of the multilayer printed wiring board 1 manufactured according to the present invention, the slit 33 of the outer layer substrate 30 opens the adhesive 40 that bonds the inner layer substrate 10 and the outer layer substrate 30 when the inner layer substrate 10 and the outer layer substrate 30 are laminated. 41, the edge 41a of the opening 41 of the adhesive 40 is formed in the multilayer portion of the outer layer substrate 30 as shown in FIG. 1 (f) after the portion 34 to be removed is removed. It protrudes from the edge 35a of the corresponding portion 35 onto the flying tail portion 2. The protruding amount c of the protruding portion 42 of the adhesive 40 (that is, the distance from the edge 35a of the corresponding portion 35 of the multilayer portion of the outer substrate 30 to the edge 41a of the opening 41 of the adhesive 40) is the distance d and the slit. This corresponds to the sum of 33 widths.

  The CCL used as the outer layer substrate 30 is not particularly limited, such as those in which an adhesive layer is interposed between the insulating base material and the copper foil, or those in which the insulating base material and the copper foil are directly joined. be able to. Moreover, the double-sided CCL in which the copper foil was provided on both surfaces of the insulating base material can also be used as the outer layer substrate 30. Even when the outer layer is omitted and the inner layer and the two outer layers are laminated, a multilayer printed wiring board of 4 layers (inner layer is double-sided, outer layer is single-sided) or 6 layers (both inner and outer layers are both sides) is manufactured. be able to. That is, the method of the present invention does not limit the number of layers of the multilayer portions 3 and 4 and the flying tail portion 2.

  As described above, in the method for manufacturing a multilayer printed wiring board according to the present embodiment, the etching resist having resistance to the copper plating solution is formed where the circuit of the inner substrate 10 is exposed to form the flying tail portion 2. The etching resist 20 is left until the portion of the outer layer substrate 34 corresponding to the flying tail portion 2 is removed. In the plating process, the etching resist 20 is used as a plating resist. Finally peel. Thereby, there is no possibility that the flying tail part 2 is etched or plated in the middle of the process, and the flying tail part 2 can be protected.

  Furthermore, in the present invention, in the substrate stacking step, the interlayer adhesive 40 that bonds the inner layer substrate 10 and the outer layer substrate 30 is the slit 33 of the outer layer substrate 30 as shown in FIGS. 1 (a) and 3 (e). Is located outside the opening 41 of the interlayer adhesive 40 and the side surface 33a on the side that becomes the edge 34a of the portion 34 to be removed of the slit 33 and the edge 41a of the opening 41 of the adhesive 40 The distance d is in the range of 0 mm to 0.2 mm.

  In order to protect the flying tail portion 2 in the plating process and the etching process, as shown in Patent Document 2, the side surface on the side that becomes the edge 34a of the portion 34 to be removed among the side surfaces 33a and 33b of the slit 33 is shown. When the distance d (see FIG. 3) between the edge 33a and the edge 41a of the opening 41 is 0.2 mm or more, the distance a between the slits 33 and 33 and the width b of the opening 41 of the interlayer adhesive 40 The difference (a−b, where a ≧ b) needs to be 0.4 mm or more, and further considering the possibility of misalignment during bonding, it is desirable that the difference a−b be larger. . However, as described above, when the distance d is large, the outer layer substrate 34 corresponding to the flying tail portion 2 is removed, and the interlayer adhesive 40 protrudes onto the flying tail portion 2 of the multilayer printed wiring board. The protrusion amount c of the portion 42 also increases. Therefore, as shown in FIG. 6B, the projecting portion 42 of the interlayer adhesive material 40 reaches closer to the bent portion of the flying tail portion 2, so that the flexibility of the flying tail portion 2 is significantly reduced. End up.

Therefore, in the present invention, in the step of laminating the inner layer substrate 10 and the outer layer substrate 30, the slit 33 of the outer layer substrate 30 is positioned outside the opening 41 of the adhesive 40 that bonds the inner layer substrate 10 and the outer layer substrate 30, and The distance d between the side surface 33a, which is the end edge 34a of the portion 34 to be removed, of each of the two side surfaces 33a, 33b of the slit 33 and the end edge 41a of the opening 41 of the adhesive 40 is 0 mm or more and 0.2 mm or less. Paste together so that Thereby, as shown in FIG. 1 (f) and FIG. 6 (a), the protruding amount (residual amount) c of the protruding portion 42 of the interlayer adhesive 40 on the flying tail portion 2 can be suppressed to be small. A multilayer printed wiring board having the flying tail portion 2 having excellent characteristics can be manufactured.
6A and 6B show the boundary between the flying tail portion 2 and the multilayer portions 3 and 4 in a state where the flying tail portion 2 of the multilayer printed wiring board is bent in a 180 ° direction with a predetermined bending radius. It is the elements on larger scale which expanded and showed the part vicinity.

  When laminating the inner layer substrate 10, the interlayer adhesive 40, and the outer layer substrate 30, the order of bonding these three layers is not particularly limited, but as shown in FIG. 3 (e), the outer layer substrate in which the slits 33 are formed. 30 and the interlayer adhesive 40 on which the opening 41 is formed are aligned and bonded together, and then the edge of the portion 34 to be removed of the slit 33 is performed when the interlayer adhesive 40 and the inner substrate 10 are bonded together. The distance d between the side surface 33a on the side to be 34a and the end edge 41a of the opening 41 can be easily controlled, which is preferable.

  In the present invention, an etching resist 20 having resistance to the copper plating solution is formed where the circuit of the inner layer substrate 10 is exposed to form the flying tail portion 2, and the liquid enters the flying tail portion 2. Therefore, it is not necessary to make the opening 41 of the interlayer adhesive 40 for bonding the inner layer substrate 10 and the outer layer substrate 30 smaller than necessary. For this reason, the flexibility of the flying tail portion 2 can be ensured, stress concentration on the bent portion can be relaxed when the flying tail portion 2 is bent, and a printed wiring board having good bending characteristics can be manufactured.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely with an Example and a comparative example, this invention is not limited only to these Examples.

(Multilayer printed wiring board according to the embodiment)
In the example, a double-layer FPC was used as the inner layer substrate by the method shown in FIGS. 1 to 4, and a six-layer flexible printed wiring board in which two single-sided FPCs were laminated on both surfaces was produced.
The slit was formed at a location located 0.05 to 0.2 mm outside from the edge of the opening of the interlayer adhesive. As shown in Table 1, the distance d between the side surface serving as the edge of the portion to be removed and the edge of the opening of the interlayer adhesive is 0.05 mm in (1), 2) was 0.1 mm, (3) was 0.2 mm, and the number of samples was 200.
The multilayer printed wiring board produced in these examples has one flying tail portion per sample.

<Board configuration>
Substrate size: 350 mm × 400 mm.
Inner layer FPC: TLF-W-521 18/25/18 (manufactured by Kyocera Chemical Co., Ltd., double-sided copper foil 18 μm thickness, substrate: polyimide 25 μm thickness).
Outer layer FPC: TLF-521 18/25 (manufactured by Kyocera Chemical Co., Ltd., single-sided copper foil 18 μm thickness, substrate: polyimide 25 μm thickness).
Adhesive sheet: TFA-880 CA35 (manufactured by Kyocera Chemical Co., Ltd., adhesive layer 35 μm thick).
Etching resist: AQ-3058 (manufactured by Asahi Kasei Corporation, resin 30 mm thick).

<Substrate manufacturing procedure>
1. An inner layer FPC circuit is formed.
2. An etching resist is formed only in a portion that becomes a flying tail portion of the inner layer FPC.
3. A notch (slit) is made at a position corresponding to two sides of the flying tail portion of the outer layer FPC with a mold or the like.
4). The part corresponding to the flying tail part of the adhesive sheet is punched out with a mold or the like.
5). After aligning and bonding the outer layer FPC and the adhesive sheet, both sides of the inner layer FPC are laminated by heat and pressure so as to be sandwiched by the outer layer FPC.
6). Open through-holes and conduct interlayer conduction by plating.
7). The outer layer circuit is formed.
8). The outermost layer FPC and the adhesive sheet are bonded together, and a portion corresponding to the flying tail portion of the outermost layer FPC and the adhesive sheet is punched out with a mold or the like.
9. The outermost layer FPC is aligned and pasted from both sides of the four-layer flexible substrate formed up to 7 and then laminated by heat and pressure.
10. A hole is made in the surface layer with a laser or the like, and conduction is obtained by plating.
11. The outermost layer circuit is formed.
12 A portion (slit portion) corresponding to the flying tail portion of the outer layer FPC is removed.
13. Strip the etching resist on the flying tail.
14 A solder resist is formed at a predetermined position.

(Multilayer printed wiring board according to Comparative Example 1)
As shown in FIG. 7, as Comparative Example 1, all the examples of the material configuration, the substrate manufacturing process, etc., except that the etching resist forming step (2.) and the peeling step (13) are not performed. A 6-layer flexible printed wiring board similar to the above was prepared. Fig.7 (a) shows the 4 layer board | substrate obtained by the lamination process (5.), FIG.7 (b) shows the 6-layer flexible printed wiring board.
As in the example, the slit was formed at a location located 0.05 to 0.2 mm outside from the edge of the opening of the interlayer adhesive. As shown in Table 1, the distance d between the side surface serving as the edge of the portion to be removed of the slit and the edge of the opening of the interlayer adhesive is 0.05 mm in (4) and 0.1 mm in (5). In (6), the thickness was 0.2 mm, and the number of samples was 200.

(Multilayer printed wiring board according to Comparative Example 2)
As shown in FIG. 8, as Comparative Example 2, the etching resist forming process (2.) and the peeling process (13.) of the flying tail portion are performed, and the material configuration, the substrate manufacturing process, and the like are the same as in the example. A six-layer flexible printed wiring board was produced. FIG. 8A shows a four-layer substrate obtained in the laminating step (5.), and FIG. 8B shows a six-layer flexible printed wiring board.
However, in Comparative Example 2, unlike the example, in order to prevent liquid from entering the flying tail portion, the slit is formed at a position located 0.3 to 0.5 mm outside from the edge of the opening of the interlayer adhesive. did. As shown in Table 1, the distance d between the side surface serving as the edge of the portion to be removed of the slit and the edge of the opening of the interlayer adhesive is 0.3 mm in (7) and 0.4 mm in (8). , (9), 0.5 mm, and the number of samples was 200, respectively.

(Evaluation result 1)
After the completion of the 6-layer flexible printed wiring board produced according to the examples and comparative examples of the present invention, an appearance inspection of the flying tail portion was performed. As a result, as shown in Table 1, the multilayer printed wiring board produced by Example [(1), (2), (3)] and Comparative Example 2 [(7), (8), (9)] While no abnormality was observed, the multilayer printed wiring board produced in Comparative Example 1 [(4), (5), (6)] had a discoloration on the circuit surface due to partial etching. there were.
In the example and the comparative example 2, as shown in FIGS. 1 and 8, the inner layer substrate of the portion 14 corresponding to the flying tail portion 2 by the outer layer substrate 30 in which the slit 33 is blocked by the etching resist 20 or the interlayer adhesive 40. In contrast, in Comparative Example 1, the slit 33 was too close to the opening 41 of the interlayer adhesive 40 as shown in FIG. This is probably because the liquid easily penetrated.
From this evaluation result, when an etching resist is formed in the flying tail (Example, Comparative Example 2), or when a slit is formed outside the adhesive material opening by 0.3 mm or more (Comparative Example 2), the flying tail is formed in the flying tail. It has been found that a multilayer printed wiring board can be produced without liquid intrusion.

(Evaluation result 2)
After completion of the 6-layer flexible printed wiring board produced according to the examples and comparative examples of the present invention, a 180 ° bend as shown in JIS C 5016 using a flying tail portion that obtained a good appearance in the evaluation result 1 A test (bending resistance test) was performed, and a continuity test was performed after bending 100,000 times. As a result, as shown in Table 1, the multilayer printed wiring board produced by Example [(1), (2), (3)] and Comparative Example 1 [(4), (5), (6)] was disconnected. On the other hand, in the multilayer printed wiring board produced by Comparative Example 2 [(7), (8), (9)], some circuit failures occurred. In Comparative Example 2, as shown in FIGS. 6B and 8B, the protruding portion 42 of the interlayer adhesive 40 on the flying tail portion 2 reaches the vicinity of the bent portion of the flying tail portion 2. Therefore, it is considered that the stress is concentrated in the narrow region of the bent portion, and the circuit failure occurs.
From this evaluation result, it was found that a multilayer printed wiring board having a flying tail portion having excellent bending characteristics can be manufactured under the condition that the difference in width between the adhesive material opening and the slit is small (Example and Comparative Example 1).

  The multilayer printed wiring board manufactured according to the present invention can be used for various electric devices, electronic devices and the like.

It is typical sectional drawing which shows an example of the manufacturing method of the multilayer printed wiring board of this invention in order of a process, (a) laminated | stacked the inner layer board | substrate and the outer layer board | substrate, (b) formed the interlayer through-hole further (C) is a further laminate of the outermost layer substrate, (d) is a perforated hole in the outermost layer substrate, and (e) is a portion where the outer layer substrate corresponding to the flying tail portion is removed. (F) shows the etching resist removed from the flying tail. FIG. 2 is a schematic cross-sectional view showing an example of a processing procedure of an inner layer substrate used in the method for manufacturing the multilayer printed wiring board shown in FIG. 1 in order of steps, where (a) shows the inner layer substrate and (b) shows etching in the flying tail portion. A resist is formed. It is typical sectional drawing which shows an example of the process sequence of the outer layer board | substrate used with the manufacturing method of the multilayer printed wiring board shown in FIG. 1 in order of a process, (a) shows an outer layer board | substrate, (b) shows a slit in an outer layer board | substrate. Shows what was formed. (C) shows an adhesive, and (d) shows an adhesive formed with an opening. (E) shows what stuck the outer layer board | substrate which formed the slit, and the adhesive material which formed opening. FIG. 1 is a schematic cross-sectional view illustrating an example of a processing procedure of an outermost layer substrate used in the manufacturing method of the multilayer printed wiring board illustrated in FIG. 1, in which (a) illustrates a laminate of an outermost layer substrate and an adhesive; (B) shows a further punched opening. It is a perspective view which shows roughly an example of the multilayer printed wiring board which has a flexible part. It is explanatory drawing explaining the mode of a bending of a flying tail part, Comprising: (a) is a case where the protrusion amount on the flying tail part of an adhesive material is small, (b) is the flying material part on a flying tail part. It is a figure which shows the case where protrusion amount is large. It is typical sectional drawing which shows the outline of the manufacturing method of the multilayer printed wiring board which concerns on the comparative example 1, Comprising: (a) shows the 4 layer board | substrate obtained by the lamination process of the inner layer board | substrate and the outer layer board | substrate, (b) The multilayer printed wiring board which laminated | stacked the outermost layer and exposed the flying tail part is shown. It is typical sectional drawing which shows the outline of the manufacturing method of the multilayer printed wiring board concerning the comparative example 2, Comprising: (a) shows the 4 layer board | substrate obtained by the lamination process of the inner layer board | substrate and the outer layer board | substrate, (b) is The multilayer printed wiring board which laminated | stacked the outermost layer and exposed the flying tail part is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Multilayer printed wiring board, 2 ... Flying tail part, 10 ... Inner layer board, 14 ... The part applicable to the flying tail part of an inner layer board | substrate, 20 ... Etching resist, 30 ... Outer layer board | substrate, 33 ... Slit, 33a ... Slit 2 Of the two side surfaces, the side surface serving as the edge of the portion to be removed, 33b... The side surface serving as the edge of the corresponding portion of the multilayer portion of the two side surfaces of the slit, 34... Corresponding to the flying tail portion of the outer layer substrate Part (part to be removed), 34a ... edge of the part to be removed, 35 ... part corresponding to the multilayer part of the outer layer substrate (multilayer part corresponding part), 35a ... edge of the multilayer part corresponding part, 40 ... inner layer substrate Adhesive (interlayer adhesive) for adhering the outer substrate to the outer layer substrate, 41... Adhesive opening (adhesive opening), 41 a ... Edge of the adhesive opening, 42 ... Adhesive on the flying tail Protrusion 70 ... multilayer printed wiring board, 71 ... inner layer board, 72 ... outer substrate, 73 ... flying tail section.

Claims (1)

A slit forming step of slitting the outer layer substrate before being laminated with the inner layer substrate having the flying tail portion where the circuit is exposed, with a portion to be removed corresponding to the flying tail portion interposed therebetween,
A substrate laminating step of laminating the inner layer substrate and the outer layer substrate having the slits through an adhesive having an opening at a position corresponding to a portion to be removed of the outer layer substrate;
A method of manufacturing a multilayer printed wiring board comprising: a flying tail portion exposing step of exposing the flying tail portion of the inner layer substrate by removing the portion to be removed from the outer layer substrate by the slit after the substrate laminating step. And
In the substrate lamination step, the slit of the outer layer substrate is located outside the opening of the adhesive that bonds the inner layer substrate and the outer layer substrate, and the edge of the portion to be removed among the two side surfaces of the slit, A step of bonding the adhesive having the opening and the outer substrate into which the slit is placed so that the distance between the side surface and the edge of the opening of the adhesive becomes 0 mm or more and 0.2 mm or less,
An etching resist forming step of forming an etching resist having resistance to a copper plating solution on a portion corresponding to the flying tail portion of the inner layer substrate before the substrate laminating step, and the etching resist includes the flying tail portion; A method for producing a multilayer printed wiring board, comprising peeling after an exposure step.

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