JP2015061003A - Rigid flexible multilayer printed wiring board manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of more easily manufacturing a compact size rigid flexible multilayer printed wiring board even when a splitting process is performed in two stages from a surface to from a rear face.SOLUTION: A manufacturing method of a rigid flexible multilayer printed wiring board composed of a rigid part capable of component mounting and a bendable rigid part comprises: a step of forming a rigid printed wiring board; a step of forming a first splitting process part 12 which reaches an intended depth from one surface in a flexible part formation region; a step of arranging an insulation adhesive layer in a region except the flexible part formation region ; a step of laminating a flexible substrate; and a step of forming a second splitting process part which reaches the first splitting process part from the other surface of the rigid printed wiring board. The splitting step of forming the second splitting process part is performed by setting a region which enters the flexible part by a position gap tolerance 22 in each of XY directions from a boundary between the flexible part and the rigid part as a set process range 23.

Description

  The present invention relates to a method for manufacturing a rigid-flex multilayer printed wiring board comprising a rigid part that can be mounted with a component and a flexible part that can be bent, and more particularly, to miniaturization of a rigid-flex multilayer printed wiring board in which a flexible board is disposed in an outer layer. .

  A conventional rigid-flex multilayer printed wiring board Pa is generally configured as shown in the schematic cross-sectional view of FIG.

  That is, a flexible base substrate 15 made of polyimide or the like, a wiring pattern 2 formed on the front and back of the flexible base substrate 15, and a flexible substrate 16a made of a cover lay 18 that protects the wiring pattern 2; An interlayer insulating layer 4 having a penetrating portion 14 in a portion that becomes a flexible portion F after being laminated on the front and back of the flexible substrate 16a; a wiring pattern 2 formed on the interlayer insulating layer 4; the flexible substrate 16a and the interlayer A buried hole 10 for connecting the wiring pattern 2 provided in the insulating layer 4 (hereinafter, “believe hole” is expressed as “BH”); and a flexible portion F after being laminated on the interlayer insulating layer 4 A build-up insulating layer 4d (hereinafter, “build-up insulating layer” is referred to as “BU insulating layer”) having a penetrating portion 14 in the portion; A wiring pattern 2 formed on the U insulating layer 4d; a through hole 10a for connecting the wiring pattern 2 of each layer (hereinafter referred to as "TH"); and a wiring pattern 2 adjacent in the vertical direction is connected Blind via hole 10b (hereinafter referred to as “BVH”); and a solder resist 17 that protects the wiring pattern 2 on the outer layer (“R” in the figure is a “rigid portion”) "And" F "indicate" flexible part ").

  As described above, the rigid-flex multilayer printed wiring board includes the flexible portion F that can be partially bent. Therefore, the rigid-flex multilayer printed wiring board can be used for mobile phone main and sub boards, various module boards, etc. Many have been adopted.

  However, the rigid-flex multilayer printed wiring board as shown in FIG. 8 in which the flexible substrate is disposed at the center has a general reliability up to a specification of a total board thickness of 1.2 mm at the maximum {for example, 1000 cycles of thermal shock Since the through-hole connection reliability by the test (30 minutes at −65 ° C. and 30 minutes at + 125 ° C. as one cycle) has not been secured, for example, the total plate thickness is 1 as in the case of automobile-related equipment. It was not possible to meet the requirements of thicker than 2 mm specifications (for example, 1.6 mm) and more severe through-hole connection reliability (for example, securing 2000 to 3000 cycles by a thermal shock test).

  In more detail, since the stress generated during hot is concentrated in the center layer of the multilayer printed wiring board, the portion that is originally located in the center layer of the through-hole as the plate thickness increases regardless of the presence or absence of the flexible board In such an environment, a flexible substrate with a different linear expansion coefficient is arranged in the center layer, so that cracks are more likely to occur in the portion surrounded by the broken line ○ in FIG. That is why.

  Therefore, a means of solving the above problem by arranging flexible substrates having different linear expansion coefficients in the layer configuration in the outer layer is conceivable. It has already been reported.

The rigid-flex multilayer printed wiring board Pb shown in FIG. 9 is an example.
That is, an insulating substrate 1 made of a glass epoxy substrate, a wiring pattern 2 formed on the front and back of the insulating substrate 1, an interlayer insulating layer 4 laminated on the front and back of the insulating substrate 1 having the wiring pattern 2, A wiring pattern 2 a formed on the interlayer insulating layer 4, a BH 10 connecting the wiring patterns 2, 2 a, and a core substrate 11 made of a hole-filling resin 9 filling the hole of the BH 10; From the flexible laminated BU insulating layer 4a and the BU insulating layer 4b laminated on the front and back; the flexible base substrate 15 laminated on the flexible laminated BU insulating layer 4a and the wiring pattern 2b formed thereon A flexible substrate 16; a wiring pattern 2b formed on the BU insulating layer 4b; a TH 10a connecting between the wiring patterns of each layer; and a wiring pattern adjacent in the vertical direction. BVH 10b that connects between the wirings 2a and 2b; a solder resist 17 that protects the wiring pattern 2b on the outer layer; and a wiring pattern 2b that is formed in the flexible portion F formation region of the wiring pattern 2b on the outer layer Each of the flexible printed circuit boards 21 laminated on the surface opposite to the surface on which the flexible substrate 16 of the flexible laminated BU insulating layer 4a and the flexible laminated BU insulating layer 4a is laminated; It is the structure provided with the hollow part 14 formed in the part corresponded to the part F.

  However, in the rigid-flex multilayer printed wiring board Pb having the above-described configuration, although it is possible to solve the problem of securing the connection reliability of TH10a with respect to the condition where the plate thickness is 1.6 mm or more, It had such a problem.

  That is, in order to obtain the rigid-flex multilayer printed wiring board Pb in which the flexible substrate 16 is arranged on the outer layer, in order to make the flexible portion F bendable, the portion corresponding to the flexible portion F of the rigid printed wiring board 21 is divided. Conventionally, as this division processing, the cut-out portion 14 is formed in accordance with the dimension of the flexible portion F, and at that time, the flexible substrate 16 is not damaged. Therefore, before laminating the metal foil-clad flexible substrate 16b (flexible substrate in which the metal foil 5 such as copper foil is laminated on the flexible base substrate 15 such as polyimide), the metal foil-clad flexible substrate 16b is laminated. Slitting to the desired depth of the rigid printed wiring board 21 by slitting from the laminated surface side of 7 (see FIG. 10 (a)), and then the back surface after the metal foil-clad flexible substrate 16b is laminated, the outer layer circuit is formed, and the solder resist is formed (that is, after the final step). The remaining slit processing (slit processing for the slit processing planned portion 27a) is performed in two steps from the side (see FIG. 10B).

  For this reason, depending on the imposition position of the worksheet (the substrate to be flowed to the production line, which is a plurality of pieces of rigid flex multilayer printed wiring boards), it occurs when slitting from the back side. There is a problem that the insulation reliability and conduction reliability of the wiring pattern 2 located in the vicinity of the misaligned machining misalignment portion 28 cannot be ensured due to the misalignment of the machining position (the portion surrounded by the broken line ○ in FIG. 10B). (Reference numeral 27b shown in FIG. 10 (a) is a "substrate support" that serves as a support when a circuit is formed on the metal foil-clad flexible substrate 16b).

  Conventionally, this problem has been dealt with by setting the dimensions of the rigid-flex multilayer printed wiring board to the dimensions (upsizing) that take into account the machining position deviation tolerance. Since the demand for “miniaturization”, which is increasing in demand, cannot be met, a new countermeasure has been desired.

  By the way, the cause of such processing position misalignment includes a plurality of manufacturing processes such as a lamination process, circuit formation, or solder resist formation between the slit process performed first and the slit process performed later. (That is, it is considered that the expansion and contraction of the substrate that occurs during this time is the cause), and this effect is prominent when the number of impositions of the worksheet is increased.

JP 2009-290193 A

  The present invention does not require the dimensions of the rigid-flex multilayer printed wiring board to be a dimension that takes into account the processing position deviation tolerance, even when dividing the rigid printed wiring board into two stages from the front and back surfaces. An object of the present invention is to provide a method for producing a rigid-flex multilayer printed wiring board.

  The present invention forms a rigid printed wiring board having at least a rigid insulating layer and a wiring pattern in a manufacturing method of a rigid flex multilayer printed wiring board comprising a rigid part capable of mounting components and a flexible part capable of bending. A step of forming a first divided processing portion that reaches a desired depth from one surface of the rigid printed wiring board in a flexible portion forming region of the rigid printed wiring board; and the first divided processing portion A step of disposing the insulating adhesive layer on one surface of the rigid printed wiring board on which the flexible portion is formed, excluding the flexible portion forming region portion, a step of laminating a flexible substrate via the insulating adhesive layer, Forming a second divided processing portion that reaches the first divided processing portion from the other surface of the rigid printed wiring board. In addition, the division processing for forming the second division processing portion is performed by setting a region that enters the flexible portion side by the machining position deviation tolerance in the XY direction from the boundary portion between the flexible portion and the rigid portion. The above-described problems are solved by a method for manufacturing a rigid-flex multilayer printed wiring board.

  If the manufacturing method of the rigid-flex multilayer printed wiring board which arrange | positioned the flexible substrate in the outer layer is made into the structure of this invention, the division | segmentation process which forms a 2nd division | segmentation process part will be outside the area | region of a flexible part (namely, area | region of the rigid part R). No need to set the rigid flex multilayer printed wiring board to a size that takes into account the processing position deviation tolerance. As a result, it is easier to make a rigid flex multilayer printed wiring board smaller than before. Can get to.

The schematic cross-section manufacturing process figure for demonstrating the manufacturing method of this invention rigid-flex multilayer printed wiring board. FIG. 2 is a schematic cross-sectional manufacturing process diagram following FIG. 1. FIG. 3 is a schematic cross-sectional manufacturing process diagram following FIG. 2. The schematic sectional drawing for demonstrating the setting process range in the 2nd division | segmentation process of this invention. The schematic sectional drawing for demonstrating utilizing the protrusion part of a rigid printed wiring board as a wiring pattern formation area. The schematic sectional drawing for demonstrating using the protrusion part of the rigid printed wiring board which protrudes in a flexible part as a bumper which guards the bending vertex of a flexible substrate when it folds with a flexible substrate inside. It is a schematic sectional drawing for demonstrating the structure in the case of making the slit formed along the outline of a flexible part unnecessary, (a) provided the dam which prevents the resin of an insulating adhesive layer from flowing into a flexible part. The schematic plan view in the case, (b) is a schematic cross-sectional view in the case of using an insulating adhesive layer having a small resin flow. The schematic sectional drawing of the conventional rigid flex multilayer printed wiring board by which a flexible substrate is arrange | positioned in an intermediate | middle layer. The schematic sectional drawing of the conventional rigid flex multilayer printed wiring board which has arrange | positioned the flexible substrate to the outer layer. It is a schematic sectional view for explaining a processing position shift state that occurs when a hollow part is formed by slit processing. (A) forms a slit from the laminated surface side of the flexible substrate before laminating the flexible substrate. (B) shows a state in which a processing position shift has occurred when slit processing is performed from the back side.

  An embodiment of the present invention will be described with reference to schematic sectional process diagrams shown in FIGS. The “interlayer insulation layer”, “BU insulation layer” and “flexible laminate insulation layer” appearing in the text are actually semi-cured “insulation adhesive layers (for example, glass fiber and other reinforcing substrates). Prepreg impregnated with a thermosetting resin such as an epoxy resin, etc.) ”is indicated by being cured and laminated with a heating / pressing press. For convenience of explanation, the heating / pressing press process is described. The description is omitted from the beginning, in the form of “lamination of an interlayer insulating layer, a BU insulating layer, and a BU insulating layer for flexible lamination”.

  First, as shown to Fig.1 (a), the double-sided printed wiring board 3 is obtained by forming the wiring pattern 2 in the front and back of the insulating substrates 1, such as a glass epoxy board | substrate.

  Here, as a means for forming the wiring pattern 2, a subtractive method in which a metal foil (for example, “copper foil”) is formed by etching, an additive method in which plating (for example, “copper plating”) is deposited, or the like is used. Can be formed.

  Next, after roughening the surface of the wiring pattern 2 (for example, a soft etching process mainly composed of formic acid or an amine complexing agent), the interlayer insulating layer 4 and copper are formed on the front and back of the double-sided printed wiring board 3. A metal foil 5 such as a foil is sequentially laminated (or a metal foil with resin 6 in which an interlayer insulating layer 4 is previously laminated on one surface of the metal foil 5 is laminated so that the interlayer insulating layer 4 is in contact with the double-sided printed wiring board 3. Thus, the substrate of FIG. 1B in which the interlayer insulating layer 4 and the metal foil 5 are laminated on the front and back of the double-sided printed wiring board 3 is obtained.

  Next, the through-hole 7 is drilled at a desired position by drilling or the like, and then the through-hole 7 is cleaned by performing a desmear treatment such as a sodium permanganate solution or a potassium permanganate solution (see FIG. 1 (c)).

  Next, by sequentially performing an electroless plating process (for example, “electroless copper plating process”) and an electrolytic plating process (for example, “electrolytic copper plating process”), the plating 8 is deposited on the entire surface of the substrate including the through holes 7. Next, the through-hole 7 in which the plating 8 is formed is filled with a hole-filling resin 9 to obtain the substrate shown in FIG.

  Next, by forming a circuit by the subtractive method, a four-layer core substrate 11 on which the wiring pattern 2a including the dummy pattern 25 and the BH 10 connecting the wiring patterns 2 and 2a of each layer are formed is obtained (FIG. 1). (See (e)).

Here, although the example which provides the dummy pattern 25 in the flexible part F formation area part in the core board | substrate 11 was shown, the said dummy pattern 25 does not necessarily need to provide.
However, when forming a circuit on the metal foil-clad flexible substrate 16b to be laminated later, the gap between the metal foil-clad flexible substrate 16b and the core substrate 11 is reduced (that is, the flexure in the flexible portion F is suppressed). In forming a good wiring pattern, the dummy pattern 25 is preferably formed.

  Next, the first divided processing portion 12 that reaches the desired depth from one surface A (the first divided processing side surface) of the core substrate 11 is within the flexible portion F forming region region of the core substrate 11. At the same time, a slit 13 reaching from the one surface A to a desired depth is formed along the contour of the flexible portion F formation region (see FIG. 2 (f1). Incidentally, FIG. 2 (f2) It is a principal part enlarged plan view when "first divided processing part 12" and "slit 13" are viewed from above.

  Here, the “first divided processing portion 12” and the “slit 13” can be formed by router processing, for example.

  In the present embodiment, an example is shown in which the slit 13 is provided as a means for escaping the resin flowing out from the flexible laminated BU insulating layer 4a to be laminated later (that is, means for securing the flexible portion F). For example, as shown in FIG. 7A, a dam 26 for preventing the inflow of resin is provided by screen printing or the like, or as shown in FIG. This can also be dealt with by providing a material with a small amount of resin flow during lamination (for example, “low flow prepreg 4c”).

  Next, after roughening the surface of the wiring pattern 2 a (including the dummy pattern 25) formed on the outer layer of the core substrate 11, the first buildup layer C is applied to one surface A of the core substrate 11, and the other The second buildup layer D is laminated on the surface B (the second divided processing surface to be performed later) (see FIG. 2G).

  Here, the first build-up layer C laminated on one surface A of the core substrate 11 corresponds to the flexible laminated BU insulating layer 4a {that is, the flexible portion F forming region portion ("bent portion 14" in the figure). ), And a flexible substrate 16b (flexible substrate composed of the flexible base substrate 15 and the metal foil 5) laminated via the flexible laminated BU insulating layer 4a. And the second buildup layer D laminated on the other surface B of the core substrate 11 includes a BU insulating layer 4b and a metal foil 5 (or metal foil) laminated via the BU insulating layer 4b. 5 is a resin-coated metal foil 6a in which a BU insulating layer 4b is laminated in advance on one side. If possible, in order to suppress warping of the final rigid-flex multilayer printed wiring board, The thickness of the first buildup layer C and the second buildup layer D, preferably set to substantially the same thickness.

  Further, the BU insulating layer 4a and the BU insulating layer 4b for flexible lamination are not particularly limited, but it is possible to use a prepreg in which a glass woven fabric or a glass nonwoven fabric is impregnated with an epoxy resin to fill the wiring pattern 2a with a resin. It is preferable to perform the process well or to suppress warping and twisting.

  Next, a through hole 7a and a non-through hole 7b are drilled by drilling, laser processing or the like in a portion where a via hole (TH or BVH) for interlayer connection is formed, and then the inside of the through hole 7a and the non-through hole 7b is formed. Cleaning by desmear treatment (see FIG. 2 (h)), and then performing electroless plating treatment (for example, “electroless copper plating treatment”) and electrolytic plating treatment (for example, “electrolytic copper plating treatment”) in order, Plating 8 is deposited on the entire surface including the inside of the hole (see FIG. 2 (i)).

  Next, the circuit pattern of the outer layer is formed by the subtractive method to form the wiring patterns 2b, TH10a, and BVH10b (see FIG. 3J), and then the solder resist 17 that protects the wiring pattern 2b and the wiring pattern A cover lay 18 that protects the wiring pattern 2b formed in the flexible portion F formation region portion of 2b is formed (see FIG. 3 (k)).

  Here, in order to perform the second division processing satisfactorily in the solder resist 17 (that is, to prevent the solder resist 17 from being cracked by the second division processing), at least the second division processing is performed. It is preferable to provide a solder resist removal portion 17a so as to avoid the planned processing portion 19a.

  Further, as the coverlay 18 that protects the wiring pattern 2b formed in the flexible portion F formation region, a flexible film having an adhesive layer, a flexible insulating adhesive layer that has flexibility even after curing (so-called so-called) "Bonding sheet") and a flexible solder resist, etc. are mentioned, but any of them may be selected.

  Next, as shown in FIG. 4, the second division processing is performed by setting an area that enters the flexible portion F side by a machining position deviation tolerance of 22 in the XY direction from the boundary between the flexible portion F and the rigid portion R as a set processing range 23. By performing (for example, router processing), the rigid-flex multilayer printed wiring board P of FIG. 3 (l) in which the second divided processing portion 19 reaching the first divided processing portion 12 is formed is obtained.

  The remarkable point of the present invention is that the divided portion 20 (first divided processing portion) is formed on the rigid printed wiring board 21 laminated on the surface opposite to the surface on which the flexible substrate 16 of the flexible laminated BU insulating layer 4a is laminated. 12 and the second divided processed portion 19), at least the second divided processing from the back side performed so as to reach the first divided processed portion 12 is performed between the flexible portion F and the rigid portion R. This is a point where an area that enters the flexible part F side by the machining position deviation tolerance in the XY direction from the boundary portion is set as the set machining range (see FIGS. 3 (l) and 4).

As a result, there is no concern that the second division processing for forming the second division processing portion 19 extends outside the area of the flexible portion F, that is, inside the rigid portion R. Therefore, the size of the rigid flex multilayer printed wiring board P is divided. It is not necessary to set the size in consideration of machining position deviation tolerance.
Therefore, the rigid flex multilayer printed wiring board P can be made smaller than before.

In describing the present invention, the second divided processing unit 19 has been described using an example in which the second divided processing unit 19 is formed smaller than the first divided processing unit 12. However, the second divided processing unit 19 reaches the first divided processing unit 12. In addition, if it is formed within the region of the flexible portion F, it can be formed larger than the first divided processing portion 12.
In this case, there is an advantage that misalignment between the first divided processing unit 12 and the second divided processing unit 19 is less likely to occur.

  Incidentally, as shown in the present embodiment, when the second divided processing portion 19 is formed to be smaller than the first divided processing portion 12, a rigid projecting into the flexible portion F as shown in FIG. Since the protruding portion 24 of the printed wiring board 21 can be used as a wiring pattern forming area, the rigid-flex multilayer printed wiring board P can be further downsized (in the figure, an example in which the wiring pattern 2b is formed only on the outer layer of the protruding portion 24) However, if the number of layers of the rigid printed wiring board 21 is larger than that of the present embodiment, a wiring pattern can also be formed on the inner layer located in the region of the protrusion 24).

  Further, as described above, when the flexible substrate 16 is bent so that the second divided processing portion 19 is smaller than the first divided processing portion 12, the bending vertex 16c of the flexible substrate 16 is bent. However, if it is formed with dimensions that do not protrude beyond the rigid portion R (that is, corresponding to the protruding portion 24 in FIG. 6) located on both sides of the flexible portion F, the wiring pattern forming area of the protruding portion 24 can be further increased. In addition, the projection 24 can be used as a bumper for guarding the flexible substrate 16. In addition, the rigid flex multilayer printed wiring board can be further miniaturized.

  In addition, as an example of the rigid-flex multilayer printed wiring board used in explaining the present invention, a structure in which a flexible laminated BU insulating layer and a flexible substrate are sequentially laminated on one surface of a rigid-printed wiring board having a build-up structure However, the configuration of the present invention is not limited to this. For example, a conventional multilayer print in which a plurality of double-sided printed wiring boards are laminated via an insulating adhesive layer such as a prepreg as a rigid printed wiring board. Of course, it can be used for other configurations as long as it does not depart from the present invention, such as a wiring board or a double-sided structure of a flexible substrate.

  In addition, as described above, the rigid-flex multilayer printed wiring board obtained by the manufacturing method of the present invention was developed targeting products that have a plate thickness of 1.6 mm or more and require severe through-hole connection reliability. Of course, in this regard as well, the product is not limited to the above-mentioned conditions. For example, even when the plate thickness is about 0.8 mm, like a product used in an automobile interior or an industrial robot, Needless to say, it can also be used for products with strict requirements for through-hole connection reliability.

1: Insulating substrate 2, 2a, 2b: Wiring pattern 3: Double-sided printed wiring board 4: Interlayer insulating layer 4a: BU (build-up) insulating layer 4b, 4c, 4d for flexible lamination: BU (build-up) insulating layer 5 : Metal foil 6, 6a: Metal foil 7 with resin, 7a: Through hole 7b: Non-through hole 8: Plating 9: Filling resin 10: BH (Belede hole)
10a: TH (through hole)
10b: BVH (blind via hole)
11: Core substrate 12: First division processing portion 13: Slit 14: Bored portion 15: Flexible base substrate 16, 16a: Flexible substrate 16b: Metal foil-clad flexible substrate 16c: Bending vertex 17: Solder resist 17a: Solder Resist removal portion 18: Cover lay 19: Second division processing portion 19a: Second division processing scheduled portion 20: Division portion 21: Rigid printed wiring board 22: Processing position deviation tolerance 23: Set processing range 24: Projection portion 25: Dummy Pattern 26: Dam 27: Slit 27a: Slit processing planned portion 27b: Substrate support 28: Processing shift portion P, Pa, Pb: Rigid flex multilayer printed wiring board R: Rigid portion F: Flexible portion A: First division processing Side B: Second split processing side C: First buildup layer D: Second buildup layer

Claims (3)

  In a manufacturing method of a rigid-flex multilayer printed wiring board comprising a rigid part capable of mounting a component and a flexible part capable of bending, a step of forming a rigid printed wiring board having a rigid insulating layer and a wiring pattern, and the rigid printing A step of forming a first divided processing portion that reaches a desired depth from one surface of the wiring board in a flexible portion forming region of the rigid printed wiring board, and a rigid print in which the first divided processing portion is formed A step of disposing an insulating adhesive layer on one surface of the wiring board excluding the flexible portion forming region, a step of laminating a flexible substrate via the insulating adhesive layer, and the other of the rigid printed wiring board Forming a second divided processed portion that reaches the first divided processed portion from the surface of the second portion, and the second divided portion. Rigid flex multi-layer printed wiring characterized in that the division processing that forms the processing portion is performed as a set processing range by entering the flexible portion side from the boundary between the flexible portion and the rigid portion by the processing position deviation tolerance in the XY direction. A manufacturing method of a board.   2. The method of manufacturing a rigid flex multilayer printed wiring board according to claim 1, wherein the size of the second divided processed portion is smaller than the size of the first divided processed portion.   When the size of the second divided processing portion formed smaller than the first divided processing portion is bent so that the flexible substrate is on the inner side, the bending vertices of the flexible substrate are located on both sides of the flexible portion. 3. The method of manufacturing a rigid-flex multilayer printed wiring board according to claim 2, wherein the rigid-flex printed wiring board is formed so as not to protrude beyond the rigid printed wiring board.