JP2005268505A - Multilayer wiring board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid a resin base from being brought into a state likely to be exfoliated by relaxing stress exerted on an interlayer part of a mother board printed wiring board and an island-shaped circuit-equipped resin base when inflecting the mother board printed wiring board. <P>SOLUTION: A cutout 14 is provided at a portion located around the sticking portion (partial multilayered portion 20) of the single-sided wiring circuit-equipped resin base 21 of the mother board printed wiring board 11, and the cutout A is made to be more easily inflected than the other portion B. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a multilayer wiring board and a manufacturing method thereof, and more particularly to a printed wiring board partially having a multilayer portion and a manufacturing method thereof.

  In recent years, electronic devices have become smaller and lighter in addition to high-frequency signals, digitization, and the like, and accordingly, printed wiring boards mounted on electronic devices are also required to be small and have high density mounting. As a printed wiring board that meets these requirements, there is a rigid flex printed wiring board that is excellent in high-speed signal transmission and high flexibility in installation in equipment (for example, Patent Document 1).

  However, in the case of such a rigid flex board, since the outer shape of the rigid portion and the flex portion are simultaneously punched (processed by outer shape processing), an extra multilayered region exists in the rigid portion in the manufacturing process. The material cost is wasted, contrary to resource saving and waste saving. In addition, restrictions are placed on the position of the multilayer region, and the degree of freedom of wiring is impaired.

  In order to overcome this problem, the same applicant as the present applicant bonded a plurality of resin base materials with a single-sided wiring circuit on the motherboard printed wiring board in advance. An electrically connected partial multilayer wiring board, and further on the motherboard printed wiring board, an outer shape smaller than the outer shape of the motherboard printed wiring board, and an island-like one side having no outer shape matching the motherboard printed wiring board A partial multilayer wiring board is proposed in which a plurality of resin substrates with wiring circuits are bonded together and are electrically connected by inner via holes (Japanese Patent Application No. 2003-11635).

  However, when a flexible motherboard printed wiring board is bent in order to mount the partial multilayer wiring board on an electronic device, the island-shaped resin with circuit attached to the mother board printed wiring board and the motherboard printed wiring board Stress concentrates on the interlayer between the base material and the resin base material is easily peeled off from the end face.

As a result, if it is used repeatedly, it may cause the island-shaped resin substrate with circuit to peel off from the mother board printed wiring board, and it is likely to become a starting point of destruction by the thermal shock test, thereby impairing reliability. become.
Japanese Patent Laid-Open No. 2002-158445

  The problem to be solved by the present invention is that when the motherboard printed wiring board is bent, the stress applied to the interlayer portion between the mother board printed wiring board and the island-shaped resin substrate with circuit is relieved, and the resin substrate peels off. It is to avoid being placed in an easy state, to ensure high reliability and durability, and to take advantage of the good flexibility that is characteristic of FPC (flexible printed circuit board) and rigid flex circuit boards.

  In the multilayer wiring board according to the present invention, a resin base material with a single-sided wiring circuit that has been subjected to external processing is arranged on a mother board printed wiring board made of a flexible material, and the resin base material is placed on the wiring layer of the motherboard printed wiring board. In the multi-layered wiring board that is bonded, the peripheral part of the resin base material with a single-sided wiring circuit in the motherboard printed wiring board is more easily bent than the part other than the peripheral part of the bonding. .

  In the multilayer wiring board according to the present invention, a notch, a hole or a groove is formed in a peripheral portion of the resin base material with a single-sided wiring circuit, and the surface is orthogonal to the plate surface of the wiring board. Since the cross-sectional area of the board is small, the peripheral portion of the printed circuit board with the single-sided wiring circuit in the motherboard printed wiring board is more easily bent than the portion other than the peripheral portion of the bonding. Yes.

  In the multilayer wiring board according to the present invention, preferably, a plurality of notches, holes, or grooves are provided in a direction crossing the peripheral portion of the bonding.

  In the multilayer wiring board according to the present invention, the insulating layer of the mother board printed wiring board is preferably made of a flexible resin selected from polyimide, liquid crystal polymer, polyethylene terephthalate, and polyethylene naphthalate.

  In the method for manufacturing a multilayer wiring board according to the present invention, a resin base material with a single-sided wiring circuit that has been subjected to external processing is arranged on a mother board printed wiring board, and the resin base material is pasted on the wiring layer of the mother board printed wiring board. In the method of manufacturing a multilayer wiring board, the mother board in a portion located around the bonding portion of the resin base material with a single-sided wiring circuit by the same processing method as the outer shape processing method of the mother board printed wiring board A notch or a hole is formed in the printed wiring board.

  According to this invention, since the portion located around the bonding portion of the resin base material with a single-sided wiring circuit in the mother board printed wiring board is more easily bent than the portion other than the bonding peripheral portion, the motherboard. Even if the printed wiring board is bent, a large bending stress is not generated around the bonded portion of the resin base material with a single-sided wiring circuit.

  As a result, the stress concentration at the interlayer between the mother board printed wiring board and the resin substrate with an island-like circuit attached on the mother board printed wiring board is alleviated, and the resin substrate is easily peeled off. Thus, high reliability and durability can be ensured, and the flexibility that is a characteristic of a flexible printed circuit board or a rigid flex circuit board can be utilized.

  One embodiment of a multilayer wiring board (flexible multilayer wiring board) according to the present invention will be described with reference to FIGS. 1 (a), (b) and (c).

  The flexible multilayer wiring board 10 of this embodiment has a flexible motherboard printed wiring board 11 that forms a base substrate. The motherboard printed wiring board 11 has an insulating layer 12 made of a flexible material and a wiring layer 13 made of copper foil or the like, and is flexible so that the whole can be bent.

  The insulating layer 12 of the motherboard printed wiring board 11 can be made of a flexible resin selected from polyimide (PI), liquid crystal polymer (LCP), polyethylene terephthalate (PET), and polyethylene naphthalate (PEN).

  On the side of the wiring layer 13 of the mother board printed wiring board 11, a plurality of resin base materials 21 with a single-sided wiring circuit that have been subjected to external processing are bonded in a laminated state. The laminated portion of the resin base material 21 is referred to as a partial multilayer portion 20.

  The resin base material 21 with a single-sided wiring circuit has an insulating layer 22 made of polyimide or the like, a wiring layer 23 made of copper foil or the like, and an interlayer adhesive layer 24, and is formed with an interlayer conducting portion 25 having an IVH structure for interlayer conduction. ing.

  Rectangular cutouts 14 are formed on both side edges of the mother board printed wiring board 11 in the bonding portion of the resin base material 21 with a single-sided wiring circuit, that is, the portion located around the partial multilayered portion 20. The notches 14 are provided on both side edges 12a and 12b of the insulating layer 12 of the mother board printed wiring board 11 along a direction (straight line) X that crosses the peripheral portion A to be bonded while avoiding the conductor pattern of the wiring layer 13. It has been. A direction (straight line) X across the bonding peripheral portion A is a direction (FIG. 1) orthogonal to the longitudinal direction (vertical direction in FIG. 1A) of the parallel side edges 12a and 12b of the insulating layer 12. (A) in the left-right direction).

  As a result, the cross-sectional area (hereinafter referred to as the cross-sectional area) of the plane orthogonal to the board surface of the wiring board 11 across the peripheral part A of the partial multilayered portion 20 of the motherboard printed wiring board 11 is changed to the other part B. (In the case where the planar shape of the wiring board 11 is a simple rectangle as shown in FIG. 1A), the peripheral portion A of the partial multilayered portion 20 of the motherboard printed wiring board 11 is a straight line. It is easier to bend along the X than the other part B.

  As described above, the peripheral portion A of the partial multilayered portion 20 of the motherboard printed wiring board 11 is more easily bent than the other portions B along the straight line X that crosses the wiring board 11 left and right. As indicated by phantom lines in (b), even if the mother board printed wiring board 11 is bent, a large bending stress does not occur around the bonded portion of the resin base material 21 with a single-sided wiring circuit.

  As a result, the stress concentration in the interlayer portion C between the mother board printed wiring board 11 and the island-shaped single-sided wiring circuit-attached resin substrate 21 affixed on the motherboard printed wiring board 11 is alleviated, and the resin substrate 21 becomes It is avoided that the mother board printed wiring board 11 is easily peeled off.

  As a result, it is compatible with taking advantage of the flexibility that is a characteristic of the flexible multilayer wiring board 10 and ensuring high reliability and durability.

  The cutout portion 14 provided in the mother board printed wiring board 11 is, of course, set in the arrangement position and size so as not to concentrate stress on the interlayer part C as much as possible within the range not impairing the freedom of wiring of the mother board printed wiring board 11. .

  The shape of the notch 14 is not limited to a rectangle, but may be a triangle as shown in FIG.

  Further, the peripheral portion A of the partial multilayered portion 20 of the mother board printed wiring board 11 is more easily bent than the other portions B so that the peripheral portion A of the partial multilayered portion 20 of the motherboard printed wiring board 11 is easily bent. Making the cross-sectional area smaller than the other part B is not limited to the notch part 14, and as shown in FIGS. 2B and 2C, the through-hole 15 having a round shape, an oval shape, or the like, This can also be done by drilling in the insulating layer 12 of the motherboard printed wiring board 11.

Unlike the through-holes of the multilayer substrate, a plurality of through-holes 15 are provided at a predetermined pitch along the direction (straight line) X across the bonding peripheral portion A, avoiding the conductor pattern of the wiring layer 13. The cutouts 14 and the through holes 15 can be formed by press punching, laser processing, plasma etching, or the like.

  Further, as shown in FIG. 2 (d), a thin portion 16 that constitutes a flexible hinge is formed on the insulating layer 12 of the motherboard printed wiring board 11 in the peripheral portion A of the partial multilayered portion 20. The peripheral portion A of the partial multilayered portion 20 of the mother board printed wiring board 11 is formed by another half-etching or the like along the direction (straight line) crossing the peripheral portion A of the bonding, avoiding the conductive pattern of It may be easier to bend compared to the portion B. Since the thin portion 16 is provided in the insulating layer 12 of the motherboard printed wiring board 11, it does not affect the degree of freedom of wiring of the mother printed wiring board 11.

  In addition, as shown in FIG. 3, when the planar shape of the partial multilayered portion 20 is rectangular, the partial multilayer such as an opening (hole) 17 surrounding the peripheral portion A of the partial multilayered portion 20 is formed. It may be formed in parallel with each side of the conversion unit 20. That is, the opening 17 parallel to each side of the partial multilayer portion 20 may be formed around the bonded portion.

  Next, one embodiment of a method for manufacturing a multilayer wiring board according to the embodiment shown in FIG. 1 will be described with reference to FIGS.

  As shown in FIG. 4A, a polyimide base material 100 with a single-sided copper foil having a copper foil layer 102 on one side of a polyimide film (insulating layer) 101 is used as a starting material. As shown, a conductive circuit (wiring layer) 103 was formed by etching the copper foil layer 102 by a subtractive method, and a printed circuit board (circuit formed resin base material) 104 with a circuit formed thereon was obtained.

  The printed circuit board 104 on which the circuit has been formed can also be obtained by an additive method or a semi-additive method using a polyimide base material having no copper foil as a starting material.

  Next, as shown in FIG. 4C, an interlayer adhesive layer 105 is formed on the surface of the printed circuit board 104 on which the circuit has been formed on the side opposite to the conductor circuit 103 by bonding.

  As the adhesive constituting the interlayer adhesive layer 105, the interlayer adhesive layer 105 used was a thermoplastic polyimide provided with a thermosetting function. Of course, this is based on a thermosetting resin typified by epoxy or the like. Or a thermoplastic resin such as thermoplastic polyimide may be used.

  However, the configuration of the printed circuit board 104 with the interlayer adhesive layer formed on the circuit is asymmetrical on the front and back sides, and it is preferable that the warp that causes a problem in a later process does not occur in the state where the interlayer adhesive layer 105 is formed. . For this reason, the adhesive constituting the interlayer adhesive layer 105 preferably has a glass transition temperature of 110 ° C. or lower and a room temperature elastic modulus of 1300 MPa or lower.

  Next, as shown in FIG. 4 (d), a through-hole (inner via hole) 106 penetrating the interlayer adhesive layer 105 and the polyimide film 101 is drilled by UV / YAG laser, and soft etching by plasma irradiation is performed. Desmear is performed by applying. The through hole 106 is filled with a silver paste to form an IVH structure interlayer conductive portion 107. Thereby, one printed circuit board (base material) 108 with a single-sided wiring circuit with an interlayer conductive portion is completed.

  The drilling laser can be processed at a higher speed at present by using a carbon dioxide laser, an excimer laser or the like in addition to the UV / YAG laser. Further, as a desmear method, wet desmear using a permanganate is also very common. As the conductive paste filled in the IVH, various metal pastes such as a copper paste, a carbon paste, and a nickel paste can be used in addition to the silver paste.

  Subsequently, the outer shape was processed by a die press as shown by a dotted line La in FIG. 4E, and the outer base was processed as shown in FIG. A plurality of materials 110 were obtained.

  Next, as shown in FIG. 5 (g), conductor circuits 152 and 153 made of copper foil have been formed on both front and back surfaces of the polyimide film 151 forming the insulating layer, and an opening 156 is formed in the portion to be laminated. A motherboard wiring board 150 having insulating protection cover layers 154 and 155 formed on the surface was prepared.

  Then, a plurality of single-sided wiring circuit-attached resin base materials 110 each having an outer shape processed were superimposed on the motherboard wiring board 150 after being aligned with each other.

  For alignment, a pin alignment method may be used, but a space for drilling a pin hole is required, which is not preferable. Moreover, since the base material 110 has room temperature adhesiveness, alignment by the pin alignment method is difficult. Therefore, alignment by image recognition was performed.

  After that, heating and pressurization are performed by a vacuum heat press machine under a vacuum degree of 1 kPa or less, and the main adhesion by the interlayer adhesive layer 105 is performed. As shown in FIG. The multilayer circuit board 160 in which the conductor circuit 103 between the base materials 110, the conductor circuit 103 of the base material 110, and the conductor circuit 152 of the motherboard wiring board 150 are conductively connected is obtained.

  Next, as shown in FIG. 5I, a solder resist 157 was applied to the gap between the opening 156 and the laminated base material 110 by a printing method, and this was cured.

  Next, the multilayer wiring board 160 is subjected to outer shape processing along the outer shape processing line indicated by the dotted line Lb in FIG. 5I by punching with a press die. At the time of this outer shape processing, as shown in FIG. 5 (j), a notch opening 158 is formed around the multilayered portion simultaneously with the outer shape processing by punching with the same press die as the outer shape processing. 160 was completed.

  The outer shape processing and the formation of the notch opening 158 can be simultaneously formed by laser processing and plasma etching, in addition to punching by a press die.

(A)-(c) is sectional drawing which shows typically one Embodiment of the multilayer wiring board by this invention. (A)-(d) is sectional drawing which shows typically other embodiment of the multilayer wiring board by this invention, respectively. It is sectional drawing which shows typically other embodiment of the multilayer wiring board by this invention. (A)-(f) is process drawing which shows the process of the manufacturing method of the multilayer wiring board by this embodiment. (G)-(j) is process drawing which shows the process of the manufacturing method of the multilayer wiring board by this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Multilayer wiring board 11 Mother board printed wiring board 12 Insulating layer 13 Wiring layer 14 Notch part 15 Hole 16 Thin part 20 Partial multilayer part 21 Resin base material with single-sided wiring circuit 100 Polyimide base material 101 with single-sided copper foil Polyimide film 102 Copper foil Layer 103 Conductor circuit 104 Circuit-formed printed circuit board 105 Interlayer adhesive layer 106 Through hole 107 Interlayer conduction part 108 Printed circuit board with single-sided wiring circuit 110 Resin substrate 150 with single-sided wiring circuit Motherboard wiring board 151 Polyimide films 152 and 153 Conductor circuit 154 155 Cover layer 156 Opening 157 Solder resist 158 Notch opening 160 Multilayer wiring board

Claims (5)

A multilayer wiring board in which a resin base material with a single-sided wiring circuit that has been preliminarily processed is arranged on a mother board printed wiring board made of a flexible material, and the resin base material is bonded onto a wiring layer of the motherboard printed wiring board In
A multilayer wiring board in which a bonding peripheral portion of the resin substrate with a single-sided wiring circuit in the motherboard printed wiring board is more easily bent than portions other than the bonding peripheral portion.   Notches, holes, or grooves are formed in the peripheral portion of the resin substrate with the single-sided wiring circuit, and the cross-sectional area of the surface orthogonal to the board surface of the wiring board is reduced across the peripheral portion of the bonding. 2. The multilayer according to claim 1, wherein a bonding peripheral portion of the resin base material with a single-sided wiring circuit in the motherboard printed wiring board is more easily bent than a portion other than the bonding peripheral portion. Wiring board.   The multilayer wiring board according to claim 2, wherein a plurality of cutouts, holes, or grooves are provided along a direction crossing the pasted peripheral portion.   The multilayer wiring board according to any one of claims 1 to 3, wherein the insulating layer of the mother board printed wiring board is made of a flexible resin selected from polyimide, liquid crystal polymer, polyethylene terephthalate, and polyethylene naphthalate. In a method for manufacturing a multilayer wiring board, wherein a resin base material with a single-sided wiring circuit that has been subjected to external shape processing is disposed on a motherboard printed wiring board, and the resin base material is bonded onto a wiring layer of the motherboard printed wiring board ,
A method of manufacturing a multilayer wiring board in which a notch or a hole is formed in the motherboard printed wiring board in the peripheral portion of the bonding of the resin base material with the single-sided wiring circuit by the same processing method as the outer shape processing method of the motherboard printed wiring board .

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