JP2011100755A - Multilayer board and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein it is difficult to bring a plurality of vias closer, via diameters tend to vary, and fine patterning is limited by an influence of cracks, or the like generated on a side face of a hole since laser beams are formed and the hole is used as a via for interlayer connection in a conventional multilayer board. <P>SOLUTION: The multilayer board 11 comprises an insulating layer 13 comprising a core 19 and a first resin 20 impregnated or coated to the core 19, a conductive paste 23 filled into a plurality of holes 29 formed on the insulating layer 13, and wiring 14 subjected to interlayer connection by the conductive paste 23. In the multilayer board 11, the holes 29 are formed by holding the insulating layer 13 containing the first half-cured resin 20 on a support 27 and applying laser beams, thus making vias 12 closely adjacent, reducing variations in the diameters of the vias 12, and miniaturizing and fine-patterning the multilayer board 11. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a multilayer substrate (sometimes referred to as a multilayer printed wiring substrate) used in a mobile phone or various electronic devices, and particularly corresponds to high-density mounting.

  2. Description of the Related Art Conventionally, as electronic devices are becoming lighter, thinner, and smaller, multilayer boards are required to have larger vias and further finer, so that via positions are highly accurate and distances between multiple vias are shortened.

  Next, problems in adjacent vias in the conventional multilayer substrate (adjacent vias mean mutually adjacent vias) will be described with reference to FIG.

  FIG. 24 is a partial cross-sectional view for explaining a problem related to an adjacent via in a conventional multilayer substrate, and is a schematic diagram enlarging a part of a cross section of the conventional multilayer substrate.

  In FIG. 24, a conventional multilayer substrate is formed from a plurality of wirings 1, vias 2 connecting the wirings 1 with each other, and an insulating portion 5 made of a core material 3 and a resin 4 containing them. ing.

  In the side surface of the via 2 in FIG. 24, the crack 6 occurs along the core material 3 or at the interface between the core material 3 and the resin 4. Thus, as shown in FIG. 24, the via 2 in which the crack 6 has occurred has a smaller insulation distance between adjacent vias 2 (for example, a distance indicated by an arrow 7), and therefore insulation between a plurality of adjacent vias 2 is performed. It is difficult to shorten the distance, that is, narrow adjacent.

  Next, the cause of occurrence of the crack 6 as shown in FIG. 24 will be described with reference to FIG.

  FIGS. 25A to 25C are cross-sectional views for explaining a state in which holes are formed in an insulating hard substrate with a laser.

  In FIGS. 25A to 25C, the insulating hard substrate 8 is composed of a core material 3 and a resin 4 impregnated in the core material 3 and cured. As such an insulating hard substrate 8, for example, a glass cloth epoxy resin, a glass non-woven cloth epoxy resin, a glass cloth bismaleide tridiazine resin, an aramid non-woven cloth epoxy resin or the like is known.

  FIG. 25A is a cross-sectional view showing a state in which wiring is formed on one surface of the insulating hard substrate 8 and holes are formed by laser irradiation. In FIG. 25A, an arrow 7a indicates a laser irradiated to the insulating hard substrate 8 (note that a laser device or the like is not shown).

  FIG. 25B is a cross-sectional view showing a state in which the holes 9 are formed in the insulating hard substrate 8. In FIG. 25B, the bottom of the hole 9 is closed with a wiring 1 made of copper foil or the like. The crack 6a in FIG. 25 (B) consists of a crack, a crack, or the like generated on the side surface of the hole 9 or the like. The crack 6a is likely to occur along the core material 3 or at the interface between the core material 3 and the resin 4 due to stress generated by laser irradiation. The crack 6a once generated is not repaired because the resin 4 is already cured.

  An arrow 7b in FIG. 25B indicates the depth (or size and length) of the crack 6a. In addition, since a resin residue remains in the bottom of the hole 9 after laser irradiation, it is desirable to perform a desmear process.

  FIG. 25C is a cross-sectional view showing a state after the desmear process is performed. In FIG. 25C, the crack 6b generated on the side surface of the hole 9 is larger than the crack 6a shown in FIG. 25B (that is, 7c> 7b). This is because the crack 6b has grown (or has become larger or longer) by the desmear treatment, and a part of the resin residue removal liquid that has entered the hole 9 enters the crack 6a and the inner wall of the crack 6a. This is because the resin 4 that forms the is removed.

  For example, Patent Document 1 is known as a method for manufacturing such a multilayer substrate.

  As shown in FIGS. 25B and 25C, once the crack 6a is generated, it does not repair (or disappear) even if it grows as the crack 6b. This is because, in the conventional insulating hard substrate 8, the resin component in the portion where the crack is generated is the cured resin 4 and does not have adhesiveness or self-repairing property.

  The crack 6a may be affected by the diameter of the via 2 (or the hole constituting the via 2) and the variation in diameter. Alternatively, the size, growth, or the like of the crack 6a (or a large crack 6b) may be affected by the processing conditions of the holes constituting the via. And the crack 6a, 6b may become large, so that the diameter variation of a hole is large.

  Next, the variation in diameter of the hole 9 (or the via 2 filled in the hole 9) will be described with reference to FIGS.

  FIG. 26 is a top view illustrating hole diameter variation when through holes are formed by laser in a prepreg when a woven fabric (for example, glass woven fabric) is used.

  In FIG. 26, the prepreg 10 is formed of a core material 3 and a semi-cured insulating resin impregnated in the core material 3 (in FIG. 26, the uncured insulating resin is a cured resin). This is because the uncured insulating resin is laminated and cured to form the cured resin 4).

  In FIG. 26, the core material 3 corresponds to a glass strand formed by bundling a plurality of glass filaments, for example.

  As shown in FIG. 26, since the core material 3 is woven in a mesh shape, depending on the laser irradiation position, a certain amount of energy may be applied to the portion where the core material 3 becomes 0 layer, 1 layer, and 2 layers. When the laser is irradiated, the diameter of the hole is likely to change depending on the thickness of the workpiece (particularly the number of layers of the core material 3). In particular, the size of the hole 9 (in particular, the diameter of the hole on the laser emission side) is affected.

  As shown in FIG. 26, the diameter of the hole is 9c (core material 3 is 2 layers) <9b (core material 3 is 1 layer) <9a (core material 3 is 0 layer). Variation in diameter occurs.

  If the diameters of the holes 9 vary greatly as described above, it means that a larger laser power than necessary is applied, and the surplus laser energy is generated around the holes 9 formed in the prepreg 10 to generate cracks 6. It may be possible to cause damage that triggers.

  That is, the excessive laser power decomposes and removes the semi-cured resin adjacent to the hole 9 in a larger amount than the core material 3 that is difficult to be decomposed by the laser. There is a possibility that the absolute amount of the resin filling this gap (this resin becomes a cured resin 4 after lamination and effect) is insufficient, and this may become a crack 6.

  Needless to say, the influence of the excessive laser power is more likely to occur as the diameter of the via 2 becomes smaller than φ100 μm, and further smaller than φ85 μm.

  27A and 27B are a perspective view and a cross-sectional view of an insulating hard substrate obtained by laminating and curing the prepregs shown in FIG. 26, respectively, and when the diameters of the holes formed in the prepreg vary. This explains that the crack 6 is likely to occur.

  In the insulating hard substrate 8 shown in FIG. 27A, the wiring 1 and the like are not shown.

  FIG. 27B is a cross-sectional view taken along the auxiliary line 40 in FIGS. 24 and 27A.

  In FIG. 27 (B), holes 9a, 9b, 9c are formed in the insulating portion 5 formed by curing the prepreg 10. The holes 9a, 9b, 9c are filled with vias 2a, 2b, 2c made of conductive paste or the like.

  In FIG. 27B, the core 9 (not shown in FIG. 27) is formed in the zero layer portion of the hole 9a as shown in FIG. Further, the hole 9b is formed with the core material 3 in the first layer portion, and the hole 9c is formed with the core material 3 in the second layer portion.

  As shown in FIG. 27B, the diameters of the vias 2a to 2c formed in the holes 9a to 9c are 2c (two layers of the core material 3) <2b (one layer of the core material 3) <2a (the core material 1 is 0). In particular, the diameter of the via on the exit side is likely to vary.

  From FIG. 27B, it can be seen that the cracks 6a to 6c are generated so as to surround the holes 9a to 9c. Note that the cracks 6a to 6c in FIG. 27B correspond to a top view (or a top sectional view) of the crack 6 shown in the sectional view in FIG.

  As shown in FIGS. 26 and 27, when a fine hole is formed adjacent to the prepreg 10, excessive laser power causes variations in the diameter of the via hole 2, and further around the via hole 2. It turns out that the crack 6 is easy to generate.

Japanese Patent No. 34926667

  As shown in FIGS. 24 to 27, in the conventional multilayer substrate, the holes 9 are directly formed by a laser or the like in the insulating hard substrate 8 formed by curing the prepreg 10. Cracks 6 are likely to occur, and once generated, the crack 6 grows greatly by a desmear process or the like, and therefore it is difficult to reduce the distance between the plurality of vias.

  Further, since the diameter of the hole 9 itself is also easily affected by the thickness (or the number of layers) of the core material 3 constituting the prepreg 10, the crack 6 may be further increased, and it is difficult to reduce the distance between the plurality of vias. Met.

  For the purpose of solving such problems, the present applicant has already proposed a technique in which cracks do not occur in the formation of holes in JP-A-8-18238 and the like. In addition, there is a problem that it is difficult to reduce the distance between the plurality of vias.

  Therefore, an object of the present invention is to provide a multilayer substrate that can cope with narrowing of adjacent between a plurality of vias.

  In order to achieve the above object, the multilayer substrate of the present invention comprises an insulating layer formed by impregnating or applying a resin to a core material made of woven fabric or non-woven fabric, and a plurality of layers formed on the insulating layer. A hole, a conductive paste filled in the hole, and a wiring interconnected via the conductive paste, and the hole formed in the insulating layer is a semi-cured resin. The insulating layer is irradiated with the infrared laser light in a state where the insulating layer is interposed between a protective film and is held via an adhesive layer on a support mainly composed of an organic substance having infrared laser photodegradability. Thus, a multilayer substrate having a variation in diameter on the emission side of 5% or less is obtained.

  This configuration reduces the variation in via diameter, and narrows the multiple vias without creating cracks on the side of the via when forming a via hole, making the multilayer board finer and supporting high-density mounting. Increase.

(A)-(C) are sectional drawing of a multilayer substrate in Example 1, a perspective view, and top sectional drawing. Sectional view showing enlarged vias on adjacent multilayer boards (A)-(D) is sectional drawing explaining a mode that several holes are mutually adjacently formed with high precision in the prepreg hold | maintained at this support body by using an insulating hard substrate as a support body. (A), (B) is sectional drawing explaining a mode that a hole is formed in a prepreg by a laser using a resin film as a support body together Typical perspective sectional view showing a state in which a plurality of holes are formed narrowly adjacent to a prepreg held on a support (A)-(C) are sectional drawings explaining a mode that a plurality of holes formed in the narrow adjoining formed in the prepreg are filled with the conductive paste. (A)-(C) is sectional drawing explaining a mode that several metal foil is interlayer-connected through an electrically conductive paste together (A)-(C) is sectional drawing explaining a mode that a multilayer substrate is manufactured by lamination | stacking together (A), (B) is sectional drawing explaining a mode that a support body is hold | maintained on a table through a protection sheet together. (A) and (B) are micrographs of samples in which 10,000 holes of 65 μmφ are formed at a pitch of 180 μm. FIGS. 10A and 10B are plan views showing the micrographs of FIGS. 10A and 10B in schematic drawings. (A) and (B) are micrographs of samples in which 10000 holes of 65 μmφ are formed at a pitch of 150 μm. (A) and (B) are micrographs of samples in which 10,000 holes of 65 μmφ are formed at a pitch of 120 μm. (A) and (B) are micrographs of samples in which 10,000 holes each having a diameter of 85 μm are formed at a pitch of 180 μm. FIG. 14A is a plan view schematically illustrating FIG. (A) and (B) are micrographs of samples in which 10,000 holes of 75 μmφ are formed at a pitch of 180 μm. (A) and (B) are micrographs of samples in which 10,000 holes of 65 μmφ are formed at a pitch of 180 μm. (A) and (B) are micrographs of samples in which 10000 holes each having a diameter of 50 μm are formed at a pitch of 180 μm. Sectional drawing explaining the problem when the prepreg and the protective film provided on the surface of the prepreg are directly fixed on the table and processed by laser Sectional drawing explaining a mode that a hole is formed in a prepreg in the state which hold | maintained the prepreg hollow Cross-sectional perspective view explaining stress generated by hole formation in prepreg or protective film when no support is provided (A) and (B) are respectively a plan view and a cross-sectional view of a core material without fiber opening treatment. (A) to (C) are a plan view and a cross-sectional view of a core material that has been subjected to fiber opening treatment, respectively. Partial cross-sectional view explaining problems with adjacent vias in a conventional multilayer substrate (A)-(C) is sectional drawing explaining a mode that a hole is formed in an insulating hard board | substrate with a laser together Top view explaining hole diameter variation when through holes are formed by laser in prepreg when woven fabric (for example, glass woven fabric) is used (A) and (B) are a perspective view and a sectional view of an insulating hard substrate obtained by laminating and curing the prepregs shown in FIG.

  Embodiment 1 of the present invention will be described below.

  1A to 1C are cross-sectional views of the multilayer substrate in Example 1. FIG. 1A to 1C, 11 is a multilayer substrate, 12 is a via, 13 is an insulating layer, 14 is a wiring, 15 is an electronic component, 16 is an arrow, 17 is a module, and 18 is an auxiliary line.

  In FIG. 1A, a multilayer substrate 11 is formed of a plurality of layers of wirings 14 and vias 12 for interlayer connection between different wirings 14. The plurality of wirings 14 and the plurality of vias 12 are insulated by an insulating layer 13.

  A module 17 is configured by mounting an electronic component 15 such as a semiconductor component or various chip components on the wiring 14 provided on the surface of the multilayer substrate 11 with solder or the like as indicated by an arrow 16.

  FIG. 1B is a perspective view of the multilayer substrate 11, and a cross section taken along the auxiliary line 18 in FIGS. 1A and 1B corresponds to FIG.

  FIG. 1C is a cross-sectional view schematically showing a cross section of the via of the multilayer substrate 11. As shown in FIG. 1C, the variation in the diameter of at least the laser emission side of the plurality of vias 12 incorporated in the multilayer substrate 11 shown in the first embodiment is 5% or less, and accordingly, the multilayer substrate High density and high reliability are possible.

  Note that the laser emission side is the smaller base (or diameter) when the cross section of the via of the multilayer substrate 11 has a trapezoidal shape. The larger trapezoid base (or diameter) is the laser incident side.

  As described above, the diameter of the via 12 (or the hole constituting the via 12) has a relationship of (laser emission side) <(laser incident side).

  In particular, in the present invention, the via 12 is formed by laser irradiation while being held on a support (described later) when the thermosetting resin constituting the insulating layer 13 is in a semi-cured state (so-called B-stage state). Since the hole is filled with the conductive paste, the crack 6 shown in FIGS. 24 and 25 is not generated on the side surface of the via 12. As a result, the interval between the plurality of adjacent vias 12 can be narrowed (hereinafter referred to as “narrow adjacency” or “narrow adjacency”), and the multilayer substrate 11 can be made finer, and further, the module 17 can be mounted at high density.

  Next, shortening (also referred to as narrowing adjacent) of the insulation distance between the plurality of vias 12 will be described with reference to FIG.

  FIG. 2 is an enlarged sectional view showing adjacent via portions of the multilayer substrate.

  In FIG. 2, 19 is a core material, 20 is a first resin, 21 is a conductor, 22 is a second resin, and 23 is a conductive paste.

As the core material 19, for example, inorganic fibers such as glass cloth, glass woven cloth, and glass nonwoven cloth, organic fibers such as aramid woven cloth and aramid nonwoven cloth, or a resin film such as polyimide is used. The first resin 20 is impregnated or coated on the core material 19. When the first resin 20 is in a semi-cured state (so-called B-stage state), a protective film 24 (not shown) is pasted on both surfaces, and then held on the support, and in this state, a CO ₂ laser or the like Is irradiated to form a hole. Thereafter, the hole is filled with the conductive paste 23 and cured to form the insulating layer 13. As the first resin 20, a thermosetting epoxy resin is appropriate in terms of cost, matching with the core material 19, processability by laser, and the like. It is also useful to add various additives that improve the thermal expansion coefficient and reliability to the first resin 20.

  The conductive paste 23 constituting the via 12 is formed of a conductor 21 made of conductive powder such as copper powder and a second resin 22 such as an epoxy resin for fixing the conductor 21. The via 12 is held on a support (not shown) in a state where the first resin 20 in a semi-cured state is protected on both sides by a protective film 24 (not shown). In this state, the conductive paste 23 is filled in the holes formed by laser irradiation.

  In this way, by setting the first resin 20 in a semi-cured state, stress is less likely to occur during laser processing at the interface between the first resin 20 and the core material 19 and crack generation can be suppressed. Narrowing of 12 can be achieved.

  Further, since the first resin 20 in a semi-cured state at the time of laser processing is held on a support (not shown), heat dissipation due to laser processing or deformation of the material due to hole formation is prevented, and The diameter can be reduced and the absolute positional accuracy of the hole position is increased.

  In Example 2, an example of a method for manufacturing the multilayer substrate 11 described in Example 1 will be described with reference to FIGS.

  FIGS. 3A to 3D are cross-sectional views for explaining a state in which a plurality of holes are formed adjacent to each other with high accuracy in a prepreg held by the insulating hard substrate as a supporting body. .

  In FIG. 3, 24 is a protective film and 25 is a prepreg. The prepreg 25 is formed of a core material 19a and a semi-cured first resin 20a, and the surface thereof is protected by a protective film 24 as shown in FIG. 26 is a slightly adhesive layer, 27 is a support, 28 is a crack, and 29 is a hole. As the protective film 24, a PET (polyethylene terephthalate) film or the like is used.

  In FIG. 3, the support body 27 is comprised from the core material 19b and the 1st resin 20b hardened | cured in the state impregnated or apply | coated to the core material 19b. Specifically, as the support 27, the insulating hard substrate (for example, glass cloth epoxy resin, glass nonwoven cloth epoxy resin, glass cloth bismaleidotridiazine resin, aramid) described in FIG. A non-woven epoxy resin or the like cured in a plate shape) can be used.

  As the support 27, a material having infrared laser photodegradability is used. Specifically, by selecting a member mainly composed of an organic substance (that is, an organic substance containing 50% by weight or more, or 50% by volume or more), the decomposability with respect to infrared laser light can be enhanced.

  Thus, by using a hard board | substrate for the support body 27, the prepreg 25 grade | etc., Can be hold | maintained hollow, maintaining the dimensional accuracy.

  By making the first resin 20a included in the prepreg 25 and the first resin 20b included in the support body 27 the same resin system as the support body 27 (for example, unified with an epoxy resin), Mutual matching can be improved.

  Similarly, by making the core material 19a included in the prepreg 25 and the core material 19b included in the support body 27 into the same material system (for example, glass fiber system for glass fiber system, aramid fiber system for aramid fiber system), The matching of can be improved.

  An arrow 16a in FIG. 3A indicates that a protective film 24 is formed on the surface of a prepreg 25 including a core material 19a and a semi-cured first resin 20a impregnated or applied to the core material 19a. In this state, the state of being held on the surface of the support 27 is shown.

  FIG. 3B shows a state in which the prepreg 25 is held by using the slightly adhesive layer 26 provided on the surface of the support 27 over the protective film 24. Note that the prepreg 25 can be held substantially uniformly over the entire surface by providing the surface of the support 27 with the slightly adhesive layer 26 in advance.

  As shown in FIG. 3C, holes 29 are formed in the prepreg 25 for each support 27. Since the first resin 20b constituting the support 27 has been cured, cracks 28 are likely to occur at the interface with the core material 19b. On the other hand, the first resin 20a constituting the prepreg 25 is in a semi-cured state (so-called B-stage state), and in principle, the crack 28 hardly occurs at the interface with the core material 19a. This is because the internal stress is unlikely to occur because it is in a semi-cured state (because it is absorbed even if internal stress is generated), and even if the crack 28 occurs, the first in the semi-cured state. In the process until the resin 20a is heated and cured (for example, in a liquid state with reduced viscosity), the cracks 28 disappear automatically.

  FIG. 3D is a cross-sectional view showing a state where the prepreg 25 is peeled off from the support 27. In FIG. 3D, it is desirable that the adhesive force of the slightly adhesive layer 26 provided on the surface of the support 27 is weaker than the adhesive force between the prepreg 25 and the protective film 24. By doing so, the protective film 24 can be easily peeled from the support 27 in a state where the protective film 24 is fixed to the surface of the prepreg 25, and in this peeling step, the adhesion between the prepreg 25 and the protective film 24 is not affected. .

  The support 27 is not necessarily limited to an insulating hard substrate, and for example, a resin film or the like can be used for the support 27. Even in this case, the rigidity and strength of the support 27 are greater than the rigidity and strength of the prepreg 25. This is because the support 27 is used as a reinforcing material when the holes 29 of the prepreg 25 are formed.

  The case where a resin film is used for the support body 27 is demonstrated using FIG.

  4 (A) and 4 (B) are cross-sectional views for explaining how holes are formed in a prepreg with a laser using a resin film as a support.

In FIG. 4, 30 is a table (sometimes called a stage). The table 30 is a part of a CO ₂ laser device (not shown). When a flexible (or soft) sheet-like material such as a resin film is used as the support 27, the support 27 is held on a table 30 or the like of a CO ₂ laser device as shown in FIG. It is desirable.

Incidentally laser apparatus need not be limited to CO _2, it is useful to use an infrared laser. Infrared lasers (for example, YAG lasers with a fundamental wave of 1.02 μm and CO ₂ lasers) are less expensive and provide higher output than ultraviolet lasers such as excimer lasers and YAG-THG (third YAG wave) lasers. It is. In addition, it is useful to thermally form holes in a prepreg or the like. In particular, an infrared laser is useful because it tends to become thermal energy on the irradiated object.

  A prepreg 25 and a slightly adhesive layer 26 for holding the protective film 24 provided on the surface of the prepreg 25 are formed on the surface of the support 27. The adhesive strength of the slightly adhesive layer 26 is desirably lower than the adhesive strength between the prepreg 25 and the protective film 24. By making the adhesive force between the slightly adhesive layer 26 and the protective film 24 held thereon smaller than the adhesive force between the prepreg 25 and the protective film 24, the prepreg 25 and the like are attached to the support 27. When peeling from the surface, no peeling or the like occurs between the prepreg 25 and the protective film 24. Further, since the peeling force from the table 30 such as the prepreg 25 can be reduced, the effect of preventing the deformation of the prepreg 25 that is easily deformed by forming the plurality of holes 29 can be obtained.

  An arrow 16 a in FIG. 4A shows a state in which the prepreg 25 with the protective film 24 is held on the surface of the table 30 via the support 27 having the slightly adhesive layer 26. Note that it is useful to use a vacuum suction mechanism (not shown) for holding the support 27 and the table 30.

  In addition, the productivity can be improved by sticking the support body 27 to the prepreg 25 whose surface is protected by the protective film 24 and holding the support body 27 on the table 30.

  Next, the prepreg 25 is irradiated with the laser shown in FIG. 4B (infrared laser light is schematically shown by an arrow 16b) to form a hole 29 at a predetermined position. The holes 29 are desirably formed not only on the protective film 24 and the prepreg 25 but also on the support 27 at the same time. By providing the support 27 with the same hole 29 as that formed in the prepreg 25, the upper diameter (laser incident side diameter) and the lower diameter (laser emission side diameter) of the hole 29 formed in the prepreg 25 are provided. The effect of reducing the difference from) can be obtained. In addition, an effect of reducing variation in the diameter of the hole 29 itself can be obtained.

  For the support 27, it is preferable to select a member in which the hole 29 is formed more easily (or with low power or in a short time) than the prepreg 25. As described above, the laser in which the hole 29 is formed in the prepreg 25 immediately forms the hole 29 in the support 27, thereby reducing the reflection of laser from the interface between the support 27 and the protective film 24. And the effect of bringing the hole diameter on the emission side closer to the hole diameter on the irradiation side is also obtained. For this reason, the support 27 is an organic sheet that is more easily flammable (or more easily decomposed by laser) than an inorganic material that is less flammable (or less easily decomposed by laser) than a metal plate or ceramic plate. It is desirable to select a member or a plate material.

  Further, since the prepreg 25 is laser processed while being held on the support 27, even if the prepreg 25 is thinned, the extension and deformation of the prepreg 25 itself are prevented before and after the formation of the hole 29. To do. In addition, the heat generated by the infrared laser light applied to the prepreg 25 is diffused to the prepreg 25 and the support 27 that is entirely bonded to the protective film 24 held by the prepreg 25, thereby preventing the temperature of the prepreg 25 from rising. To do. In addition, when the thickness of the prepreg 25 is 100 μm or less (more preferably 50 μm or less) and is easily deformed, the thickness of the support 27 constituting the support 27 is desirably 50 μm or more (more preferably 100 μm or more). As described above, when the thickness of the prepreg 25 is reduced to 100 μm or less (further 50 μm or less), the deformation of the prepreg 25 can be prevented by setting the thickness of the support 27 to 50 μm or more (further 100 μm or more). It is done. Further, even when the distance between the plurality of holes 29 is narrowly adjacent to about the thickness of the prepreg 25 or about twice the thickness, it is possible to prevent the positional accuracy of the prepreg 25 from being lowered. This is because the prepreg 25 is held almost entirely by the support 27 having a smaller dimensional change than the prepreg 25 even when the plurality of holes 29 are narrowly adjacent.

  FIG. 5 is a schematic perspective sectional view showing a state in which a plurality of holes 29 are formed narrowly adjacent to the prepreg 25 held on the support 27.

  In FIG. 5, a hole 29a indicates a hole where laser irradiation has been completed, and a hole 29b indicates a hole during laser irradiation. As shown in FIG. 5, when the plurality of holes 29a are formed so as to be narrowly adjacent to each other, the core material 19 built in the prepreg 25 is finely cut, so that the strength of the prepreg 25 is reduced, an external force, etc. However, it is difficult to be deformed by being held by the support 27.

  Further, the stress (indicated by the arrow 16) generated in the side surfaces of the holes 29a and 29b formed in the prepreg 25 by laser processing may affect the shapes and positions of the holes 29a and 29b. However, as shown in FIG. 5, since the peripheral portions of the holes 29a and 29b are held by the support 27 through the fine adhesive layer 26, the shape and position of the holes 29a and 29b due to such stress are not affected. .

  Note that it is useful to increase the mechanical strength (or rigidity, dimensional stability, etc.) of the support 27 as compared with the prepreg 25. Thus, even when the thickness of the prepreg 25 is reduced and the plurality of holes 29 are mounted narrowly adjacent to each other, various deformations of the prepreg 25 can be prevented.

  Further, by reducing the thermal expansion coefficient of the support 27 as compared with the prepreg 25, even when the temperature of the workpiece increases during laser processing, the dimensional change can be suppressed.

  Further, by setting the thermal conductivity of the support 27 to 30% or more of the prepreg 25 (preferably 50% or more, more preferably 100% or more), the heat generated in the prepreg 25 is transferred to the table 30 via the support 27. (Or a heat dissipation mechanism attached to the table 30), and thermal deformation can be suppressed. In addition, when the heat conductivity of the support body 27 is less than 30% of the prepreg 25, the heat dissipation effect to the support body 27 may fall.

A CO ₂ laser is useful for forming the holes 29a and 29b. Since the CO ₂ laser is mainly composed of heat, accurate holes 29 can be formed at high speed in the prepreg 25 including the core material 19. In addition, the laser device itself is inexpensive and has excellent productivity.

As shown in FIG. 5, a member having a hole 29 formed by a CO ₂ laser (that is, a protective film 24, a prepreg 25, a slightly adhesive layer 26, a support 27, etc.) has a portion having high thermal conductivity such as a copper foil. Therefore, the generated heat is not diffused far away, but is transmitted from the vicinity of the hole 29 to the support 27 and does not affect the dimensional accuracy of the prepreg 25, the table 30, or the like.

Further, since the workpieces of the holes 29a and 29b by the laser are not provided with the metal portion for reflecting the CO ₂ laser as shown in FIG. 25, the influence on the dimensional accuracy of the hole 29 by the reflected light or the like. Can be reduced.

  In addition, the semi-cured first resin 20 (not shown in FIG. 5) included in the prepreg 25 is in a semi-cured state, so that internal stress itself is not easily generated, and the inside of the first resin 20 and the first resin 20 No cracks occur at the interface between the resin 20 and the core material 19. Even if cracks occur, the first resin 20 is reduced in viscosity (or liquefied) when the first resin 20 changes from a semi-cured state to a cured state in the next heating step. Therefore, even if a crack occurs, it will disappear automatically.

  In addition, since the semi-cured first resin 20 is decomposed by laser in a semi-cured state (that is, before curing), smear itself (smear is a resin residue generated during processing) does not occur. It is not necessary to remove smear with desmear. Further, even when a smear is generated, the first resin 20 is reduced in viscosity (or liquefied) when the first resin 20 is changed from a semi-cured state to a cured state in the next heating step. Disappears automatically.

  Next, how the conductive paste 23 is filled in the holes 29 will be described with reference to FIG.

  6 (A) to 6 (C) are cross-sectional views for explaining a state in which a plurality of holes formed in the narrow adjoining formed in the prepreg are filled with the conductive paste.

  As shown in FIG. 6A, the prepreg 25 with the protective film 24 from which the support 27 has been peeled has a plurality of holes 29 formed narrowly adjacent to each other with high accuracy.

  FIG. 6B is a cross-sectional view illustrating a state in which the hole 29 formed in the prepreg 25 is filled with the conductive paste 23 via the protective film 24. For filling the conductive paste 23, it is useful to use a combination of a squeegee (a kind of rubber spatula), a vacuum suction device (not shown), or the like.

  FIG. 6C is a cross-sectional view illustrating a state after the protective film 24 provided on the surface of the prepreg 25 is removed. An arrow 16 in FIG. 6C indicates that the conductive paste 23 protrudes from the surface of the prepreg 25 by an amount corresponding to the thickness of the protective film 24.

  FIGS. 7A to 7C are cross-sectional views illustrating a state in which a plurality of metal foils are interlayer-connected via a conductive paste. In FIG. 7, 31 is a metal foil, such as a copper foil. By roughening the conductive paste 23 side or the prepreg 25 side of the metal foil 31, the adhesion between the conductive paste 23 and the metal foil 31 or between the prepreg 25 and the metal foil 31 can be enhanced.

  An arrow 16 in FIG. 7A shows a state in which the metal foil 31 is integrated with the conductive paste 23 and the prepreg 25 using a press, a mold, or the like (not shown). As shown in FIG. 7A, the conductive paste 23 is protruded from the surface of the prepreg 25, whereby the press pressure in the conductive paste 23 is increased, and the connectivity between the metal foil 31 and the conductive paste 23 is increased. To increase.

  FIG. 7B is a cross-sectional view showing a state after the metal foil 31 is integrated with the conductive paste 23 and the prepreg 25. The insulating layer 13 in FIG. 7B is obtained by curing the prepreg 25, and the insulating layer 13 does not show the core material 19 and the cured first resin 20 (the core material 19 and the first resin 20 are not shown). ).

  FIG. 7C is a cross-sectional view showing a state in which the metal foil 31 fixed on the surface of the insulating layer 13 is patterned to form the wiring 14. In the patterning, an etching method using a photoresist or the like, that is, a subtract method can be used.

  FIGS. 8A to 8C are cross-sectional views illustrating how the multilayer substrate 11 is manufactured by lamination.

  As shown in FIG. 8A, a prepreg 25 filled with a conductive paste 23 in a hole 29 and a metal foil 31 are set on both surfaces of the sample formed in FIG. (Both not shown) are stacked.

  FIG. 8B is a cross-sectional view illustrating a state after the sample of FIG. 8A is stacked and cured. In FIG. 8B, the prepreg 25 shown in FIG. 8A is cured to form the insulating layer 13.

  FIG. 8C is a cross-sectional view for explaining how the metal foil 31 fixed to the surface layer of the insulating layer 13 is patterned into a wiring pattern to form a wiring 14. Although the multilayer substrate 11 shown in FIG. 8C is a four-layer substrate, a six-layer substrate or an eight-layer substrate can be formed by repeating the steps of FIGS.

  In Example 3, the result of evaluating the insulation between adjacent vias of the multilayer substrate 11 of Example 1 is shown.

(An example of the evaluation result of the multilayer substrate 11 of Example 1)
The following (Table 1) to (Table 6) are examples of the evaluation results of the multilayer substrate 11 in Example 1 prepared by the inventors. In addition, the method of Example 2 can be selected as a manufacturing method.

  The prepreg was tested with commercial products (thicknesses of 40 μm, 60 μm, 100 μm, etc., but similar results were obtained), and the protective film 24 was tested with commercially available PET films (thicknesses 12, 19, and 24 μm). However, similar results were obtained. For the support 27, an insulating hard substrate (cured from a commercially available prepreg) was used.

  The vias 12 in the evaluation multilayer substrate 11 were set to N = 500, and a continuous evaluation pattern was created and evaluated.

  The multilayer substrate 11 for evaluation is formed in the hole 29 formed by laser irradiation while the insulating layer 13 made of the prepreg 25 including the first resin 20 in a semi-cured state is held on the support 27. A predetermined number of sheets filled with the conductive paste 23 are stacked.

  In addition, the insulation evaluation was performed using HAST ((Highly Accelerated temperature and humidity Stress Test, an environmental test method standardized in IEC 68-2-66). In the evaluation of insulating properties, ○ indicates pass, × indicates fail, and Δ indicates that both pass and fail products have occurred.

  The following (Table 1) shows the evaluation results when the via diameter is 90 μm. From Table 1, it can be seen that if the via pitch is 170 μm or more (the insulation distance between the vias 12 is 80 μm or more), insulation is ensured. In addition, when the via pitch was 160 μm (insulation distance between the vias 12 was 70 μm), both a pass product and a reject product were obtained. Therefore, by conducting optimization experiments in the future such as laser conditions and various processing conditions, △ (accepted products and rejected products) is evaluated with a via diameter of 90 μmφ and a via pitch of 160 μm (insulation distance between vias 12 is 70 μm). Both can be improved sufficiently from ○ to ○ (pass).

  The following (Table 2) shows the results when the via diameter is 85 μm. From Table 2, it can be seen that if the via pitch is 160 μm or more (the insulation distance between the vias 12 is 75 μm or more), insulation is ensured. When the via pitch was 150 μm (insulation distance between the vias 12 was 65 μm), both acceptable products and rejected products were obtained. Therefore, by conducting optimization experiments such as laser conditions and various processing conditions in the future, the evaluation of insulation with a via diameter of 85 μmφ and a via pitch of 150 μm (insulation distance between vias 12 of 65 μm) is △ (accepted and rejected) From both occurrences) to ○ (pass).

  The following (Table 3) shows the results when the via diameter is 80 μm. From Table 3, it can be seen that if the via pitch is 150 μm or more (the insulation distance between the vias 12 is 70 μm or more), insulation is ensured. When the via pitch was 140 μm (insulation distance between the vias 12 was 60 μm), both acceptable products and rejected products were obtained. Therefore, by conducting optimization experiments such as laser conditions and various processing conditions in the future, the evaluation of insulation with a via diameter of 80 μm and a via pitch of 140 μm (insulation distance between vias 12 of 60 μm) is △ (accepted and rejected) From both occurrences), it can be improved sufficiently from ○ (pass).

  The following (Table 4) shows the results when the via diameter is 75 μm. From Table 4, it can be seen that if the via pitch is 140 μm or more (the insulation distance between the vias 12 is 65 μm or more), the insulation is ensured. When the via pitch was 130 μm (insulation distance between the vias 12 was 55 μm), both acceptable products and rejected products were obtained. Therefore, by conducting optimization experiments such as laser conditions and various processing conditions in the future, the evaluation of insulation with a via diameter of 75 μm and a via pitch of 130 μm (insulation distance between vias of 55 μm) is △ Both occurrences) can be sufficiently improved from ○ (pass).

  The following (Table 5) shows the results when the via diameter is 70 μm. From Table 5, it can be seen that if the via pitch is 130 μm or more (insulation distance between the vias 12 is 60 μm or more), insulation is ensured. Further, when the via pitch was 120 μm (insulation distance between the vias 12 was 50 μm), both acceptable products and rejected products were obtained. Therefore, by conducting optimization experiments such as laser conditions and various processing conditions in the future, the evaluation of insulation with a via diameter of 70 μmφ and a via pitch of 120 μm (insulation distance between vias of 50 μm) is △ (accepted and rejected) Both occurrences) can be sufficiently improved from ○ (pass).

  The following (Table 6) shows the results when the via diameter is 65 μm. From Table 6, it can be seen that if the via pitch is 120 μm or more (the insulation distance between the vias 12 is 55 μm or more), insulation is ensured. When the via pitch was 110 μm (insulation distance between the vias 12 was 45 μm), both acceptable products and rejected products were obtained. Therefore, by conducting optimization experiments such as laser conditions and various processing conditions in the future, the evaluation of insulation with a via diameter of 65 μm and a via pitch of 110 μm (insulation distance between vias 12 of 45 μm) is △ (accepted and rejected) From both occurrences) to ○ (pass).

  From the results of the above (Table 1) to (Table 6), it was found that the multilayer substrate 11 in Example 1 of the present invention can reduce the insulation distance between the vias 12 as the via diameter is reduced. This is because the via diameter is small (that is, the facing area of the opposing electrodes is small with the insulator sandwiched in the middle), and the increase in insulation is due to the material causing the degradation of insulation. , It was not attributed to the process (for example, the step of forming holes in the prepreg).

  The inventors made similar prototypes for the conventional multilayer substrates shown in FIGS. 24 and 25 as comparative examples, and performed insulation evaluation. The result is shown as a comparative example.

(Comparative example: Evaluation results for a conventional multilayer substrate)
The following (Table 7) and (Table 8) are examples of results obtained by creating a prototype and evaluating the insulation between adjacent vias 12 formed in a conventional multilayer substrate.

  First, a conventional multilayer substrate was prepared. As a conventional multilayer substrate, as shown in FIGS. 24 and 25, several conventional commercial prepregs (thickness 40 μm to 150 μm) were thermally cured to form an insulating hard substrate. Then, 500 holes 9 of 60 μmφ and 100 μmφ were formed on this insulating hard substrate at a pitch of 160 μm to 240 μm, respectively, using the carbon dioxide laser device in the same manner as described above (Table 1). Thereafter, the through-holes were filled with the conductive paste 23, a multilayer substrate having the same evaluation pattern as in (Table 1) was created, and the insulation between adjacent vias was evaluated using this multilayer substrate. The insulation was evaluated using HAST ((Highly Accelerated Temperature and Humidity Stress Test, an environmental test method standardized by IEC 68-2-66), but the same result was obtained with THB. In the evaluation of insulation, ○ indicates pass and × indicates fail.

  The following (Table 7) is an example of evaluation results with a via diameter of 100 μm in a conventional multilayer substrate.

  The following (Table 8) is an example of evaluation results with a via diameter of 60 μm in a conventional multilayer substrate.

  As a result of the inventors filling the samples of (Table 7) and (Table 8) with a resin and evaluating the cross section with an optical microscope or SEM (scanning microscope), the inventor compared the conventional multilayer substrate with the above-mentioned comparative product. It was confirmed that the crack 6 shown in FIGS. 24 and 25 was generated. From this result, it was found that in the conventional multilayer substrate, the presence of the crack 6 on the side surface of the via is a major factor in the deterioration of the insulating property.

  Further, from the results of (Table 7) and (Table 8), the insulation distance between the plurality of vias is 130 μm or more regardless of the via diameter (that is, regardless of the facing area of the electrodes facing each other with the insulator sandwiched in the middle). It turns out that it is necessary. From this result, in the conventional multilayer substrate, it is expected that the cause of the insulation deterioration is caused by the process (for example, the hole forming step) rather than the material.

  As described above, the multilayer substrate 11 described in the first embodiment and (Table 1) to (Table 6) includes the core material 19 and the first resin 20 impregnated or applied to the core material 19. A multilayer substrate 11 comprising an insulating layer 13, a conductive paste 23 individually filled in a plurality of holes 29 formed in the insulating layer 13, and a wiring 14 that is interlayer-connected by the conductive paste 23. The hole 29 is formed by holding the insulating layer 13 containing the first resin 20 in a semi-cured state on a support 27 and irradiating with a laser. A plurality of vias 12 can be narrowly adjacent from the paste 23, and the multilayer substrate 11 can be further miniaturized and made into a fine pattern.

  In Example 4, an example of the result of evaluating the variation in via diameter is shown using (Table 9).

  (Table 9) shows an example of the results of evaluation of commercially available prepregs having different thicknesses of 40 μmt to 80 μmt. This is because a difference in the number of fibers is provided in the core material using either a woven fabric or a non-woven fabric in order to provide a difference in the number of fibers in the thickness direction. And an example of the result of having evaluated the variation of the diameter of the hole diameter by the side of a laser beam emission at the time of producing a hole with a different diameter (45 micrometers-85 micrometers φ) at the time of forming a through-hole by n = 1000 is shown. In Table 9, the invention is a case where the support 27 is used, and a comparative product is a case where the support 27 is not used. The variation is defined as 3σ (sometimes referred to as 3σ / average value). This is 68.26% within the range of 1σ (that is, average value ± 1σ) and 95.44% within the range of 2σ (that is, average value ± 2σ) in the normal distribution. This is because the range of 3σ (that is, the average value ± 3σ) is 99.73%.

  In Table 9, the case where 3σ (that is, the average value ± 3σ) is within a range of ± 5% or less of the diameter is indicated by ◯. A case where the diameter is within ± 5% of the diameter and within ± 10% is indicated by Δ. Moreover, the case where it is larger than +/- 10% of a diameter and the case where formation of a hole was difficult are shown by x.

  From Table 9, it can be seen that in the case of the invention product, the variation in diameter on the exit side can be reduced by the thickness of the prepreg, and further the variation can be kept to 5% or less. This is presumably because, in the case of the invention, excess energy of the laser added to the prepreg 25 is absorbed by the support 27. In the case of the invention product, as shown in FIG. 23 described later, the presence of the support 27 absorbs the difference in the presence or absence of the core material and the presence or absence of the overlap included in the prepreg 25 (not shown in FIG. 23). It is thought that variation was achieved.

  On the other hand, in the case of a comparative product (that is, when the support 27 or the like is not used), it is considered that excessive energy of the laser applied to the prepreg 25 or heat generation of the processed member caused variations in the diameter of the hole on the emission side. It is done. In the case of the comparative product, it is considered that the difference in the amount of fibers contained in the woven fabric and the non-woven fabric described in FIG.

  Note that (Table 9) shows variations in the diameter of the exit side of the via 12, but the via 12 having a large variation has the holes 9a to 9c or the vias 2a to 2c as shown in FIG. Needless to say, there is a possibility that the cracks 6a to 6c formed around the substrate grow larger.

  In addition, when the laser power larger than necessary is applied at the time of forming the hole 29 for forming the via 12, the diameter of the hole 29 tends to be larger than the original design value. The excess laser energy is higher than the design value in the hole 29 (for example, in the prepreg 25 including the core material 19a and the first resin 20a shown in FIGS. 3C and 3D, the laser decomposability is high. As the first resin 20a is significantly reduced, the first resin 20a filling the gaps of the core material 19a around the hole 29 is reduced), as shown in FIG. 24 and FIG. 27B described above. There is a possibility that a problem corresponding to the crack 6 may occur.

  In Example 5, a device for attaching the prepreg 25 and the support body 27 holding the protective film 24 provided on the surface of the prepreg 25 to the table 30 will be described with reference to FIG.

  For example, when the support body 27 is held on the table 30, it is useful to perform vacuum suction for ease of attachment and removal, but a vacuum hole provided in the table 30 (or a metal sintered body for vacuum suction or the like). May appear on the surface of the support 27, or the adsorption force may vary. In such a case, it is useful to select a sheet having air permeability such as paper as a protective sheet used in FIG. 9 described later.

  In the present invention, the holes 29 are also formed in the support 27 by the laser penetrating the prepreg 25. This is to prevent the laser penetrating the prepreg 25 from being reflected on the surface of the support 27 and being re-irradiated to the prepreg 25.

  As described above, the support 27 used in the present invention has a structure, configuration, and material system (especially preferably organic) in which the holes 29 are easily formed by the laser penetrating the prepreg 25. 27, reflection of infrared laser light from the surface is reduced, and the effect of reducing variation in the dimensional accuracy of the holes of the prepreg 25 (for example, the hole diameter on the incident side and the emission side) is exhibited. Therefore, in some cases, the laser penetrating the support 27 may reach the table 30 and cause damage.

  In such a case, as shown in FIG. 9, it is useful to provide a protective sheet 32 between the support 27 and the table 30 so that the laser does not reach the table 30 directly.

  FIGS. 9A and 9B are cross-sectional views for explaining a state in which the support 27 is held on the table 30 via the protective sheet 32. In FIG. 9, 32 is a protective sheet. The protective sheet 32 is preferably paper or a heat resistant film.

  The protective sheet 32 desirably has heat resistance or an appropriate thickness (10 μm or more). When the thickness of the protective sheet 32 is 10 μm or less, wrinkles are likely to occur when the protective sheet 32 is attached to the surface of the table 30.

  Further, by providing the protective sheet 32 with appropriate air permeability, the prepreg 25 and the protective film 24 provided on the surface of the prepreg 25 can be easily vacuum-adsorbed to the table 30 via the protective sheet 32.

  Further, by providing the surface of the protective sheet 32 with appropriate adhesiveness, the prepreg 25, the prepreg 25, or the table 30 can be easily held. In addition, moderate adhesiveness is a grade which the protective film 24 provided in the surface of the prepreg 25 and the prepreg 25 at the time of laser processing does not peel (further, the interface of the prepreg 25 and the protective film 24 does not peel). If the adhesive strength of the protective sheet 32 is too high, peeling may occur at the interface between the prepreg 25 and the protective film 24 when the prepreg 25 is peeled off together with the support 27 after laser processing. That is, it is desirable that the adhesive strength of the protective sheet 32 be weaker than the adhesive strength at the interface between the prepreg 25 and the protective film 24.

  Furthermore, by using the support body 27 and the protective sheet 32 in combination, an effect of increasing the dimensional stability of the prepreg 25 can be obtained. That is, not only the support 27 but also the protective sheet 32 is used in combination, so that even if the thickness of the prepreg 25 is extremely thin (for example, 50 μm or less), handling becomes easy. As a result, even when the ultra-thin prepreg 25 has a reduced strength due to the formation of a large number of holes 29, these members can be removed without peeling the ultra-thin prepreg 25 having a reduced strength from the support 27 and the protective sheet 32. By handling in a state of being held on top, deformation against external force can be prevented. As described above, not only the protective film 24 but also the support 27 (for example, a hard plate or a film) bonded to the protective film 24 through the slightly adhesive layer 26 with respect to the prepreg 25 whose strength has been reduced, and This is because dimensional changes are prevented by handling the protective sheet 32 in combination.

  An arrow 16a in FIG. 9A shows a state where the sheet-like protective sheet 32 is set on the table 30 and the support 27 is vacuum-sucked (not shown) thereon.

  In order to hold the prepreg 25 on the support 27 or to hold the protective film 24 formed on the surface of the prepreg 25 on the support 27, a slightly adhesive layer 26 provided on the surface of the support 27 is used. Useful. In FIG. 9, vacuum suction holes and sintered metal provided on the surface of the table 30 are not shown.

  FIG. 9B shows a state in which holes 29 are formed in both the prepreg 25 and the support 27. As shown in FIG. 9B, it is desirable to form holes 29 in the support body 27 as well. By doing so, the accuracy of the holes 29 formed in the prepreg 25 (incidence side, exit side hole diameter, hole position, etc.) can be improved. Further, it is desirable that the slightly adhesive layer 26 has an adhesive force sufficient to prevent the prepreg 25 and the protective film 24 from being peeled from the surface when the holes 29 are formed by laser.

  In addition, although the hole 29 may be formed in the protective sheet 32, the member which is not easily decomposed by a laser (for example, a member having a high glass transition temperature, heat measured by Tg) than the member used for the support 27 in the protective sheet 32. By actively selecting a member having a high decomposition temperature, such as a heat-resistant film or paper, it is possible to prevent damage to the table 30 caused by the laser penetrating the protective sheet 32.

  The support 27 is preferably disposable. By doing so, since the support 27 is always present immediately below the position where the hole 29 is desired to be formed by the laser, the processing accuracy of the hole 29 can be improved. In addition, by selecting a member having high durability against the laser to be used as the protective sheet 32, it becomes possible to reuse it multiple times.

  In Example 6, an example of actually experimenting to narrow the pitch of the plurality of holes 29 using a commercially available prepreg using a sample photograph made by the inventors will be described with reference to FIGS. .

  10, 12 to 14, and FIGS. 16 to 18, holes 29 are formed in the commercially available prepreg 25 in which the protective film 24 is formed on both sides as shown in FIG. 5 and the like. It is a microscope picture of the sample which shows a back state.

Note that Hitachi Chemical (GEA-679FG) was selected as the commercially available prepreg, and a commercially available CO ₂ laser device was used as the laser.

  FIGS. 10 and 12 to 13 are examples of micrographs of samples prepared by forming 10,000 holes 29 each having a diameter of 65 μm adjacent to each other.

  In FIG. 10, reference numeral 33 denotes an edge, which is formed in a slightly raised state so as to surround the peripheral edge of the hole 29 formed in the prepreg 25 (not visible in the back of the protective film 24 in the photograph). .

FIGS. 10A and 10B are micrographs of a sample in which 10,000 holes 29 each having a diameter of 65 μm are formed at a pitch of 180 μm. FIG. 10A is a photomicrograph of the CO ₂ laser incident side hole (before peeling of the protective film 24), and FIG. 10B is a micrograph of the CO ₂ laser emitting side hole (before peeling of the protective film 24). . From FIG. 10, it can be seen that the holes 29 of 65 μmφ are regularly and accurately formed with a pitch of 180 μm. Further, this sample was filled with resin, and the cross section was also observed using a microscope or SEM. However, no crack 28 was observed at the interface between the core material 19 and the semi-cured first resin 20. This is considered because the first resin 20 is in a semi-cured state, so that internal stress is hardly generated due to distortion caused by laser processing.

  Note that when the edge 33 in FIG. 10A is compared with the edge 33 in FIG. 10B, it can be seen that the thickness of the edge 33 in FIG. 10B is smaller. This is presumably because the protective film 24 on the laser emission side (which uses the same protective film 24 on both the incident side and the emission side) is held on the support 27 via the fine adhesive layer 26.

  FIGS. 11A and 11B are plan views showing the micrographs of FIGS. 10A and 10B in schematic drawings. As shown in FIGS. 11A and 11B, it can be seen that the holes 29 of 65 μmφ are regularly and accurately formed at a pitch of 180 μm. Further, the edge 33 shown in FIG. 11B is smaller than the edge 33 formed on the incident side shown in FIG. 11A and is not conspicuous, and is held by the support 27 via the slightly adhesive layer 26. It is thought that it is because.

FIGS. 12A and 12B are micrographs of a sample in which 10,000 holes 29 each having a diameter of 65 μm are formed at a pitch of 150 μm. Figure 12 (A) is a CO ₂ laser (before peeling of the protective film 24) entrance side of the holes, and FIG. 12 (B) is located in the photomicrograph of the exit side of the hole of the CO ₂ laser (before peeling of the protective film 24) . From FIG. 12, it can be seen that the holes 29 of 65 μmφ are regularly and accurately formed with a pitch of 150 μm. The cross section of this sample was also observed using a microscope or SEM, but no cracks 28 were found at the interface between the core material 19 and the semi-cured first resin 20. This is considered to be because the first resin 20 is in a semi-cured state, and therefore easily absorbs distortion caused by laser processing.

FIGS. 13A and 13B are micrographs of samples in which 10,000 holes 29 each having a diameter of 65 μm are formed at a pitch of 120 μm. 13A is a photomicrograph of the CO ₂ laser incident side hole (before peeling of the protective film 24), and FIG. 13B is a photomicrograph of the CO ₂ laser emitting side hole (before peeling of the protective film 24). . From FIG. 13, it can be seen that the holes 29 of 65 μmφ are regularly and accurately formed with a pitch of 120 μm. The cross section of this sample was also observed using a microscope or SEM, but no cracks 28 were found at the interface between the core material 19 and the semi-cured first resin 20. This is considered to be because the first resin 20 is in a semi-cured state, and therefore easily absorbs distortion caused by laser processing.

In FIGS. 10 to 13, the thickness of the ring-shaped bulge of the protective film 24 surrounding the hole 29 (the edge 33 that seems to be affected by the CO ₂ laser) is smaller on the exit side than on the entrance side. This is because the protective film 24 provided on the emission side is held on the support 27 via the fine adhesive layer 26, so that the heat from the CO ₂ laser and the deformation (or expansion and contraction) of the protective film 24 after processing are suppressed. It is thought that it was because of.

  In Example 7, an example of a result of an experiment for reducing the diameter of the hole 29 using a commercially available prepreg will be described using a photograph of a sample prototyped by the inventors.

  FIGS. 14 and 16 to 18 are examples of micrographs of samples in which the hole diameter is changed from 85 μmφ to 50 μmφ in a state where the pitch is fixed at 180 μm.

FIGS. 14A and 14B are micrographs of a sample in which 10,000 holes 29 each having a diameter of 85 μm are formed at a pitch of 180 μm. 14A is a photomicrograph showing an enlarged portion of the hole 29, and FIG. 14B is a photomicrograph showing a state in which a plurality of 85 μmφ holes 29 are formed adjacent to each other with a pitch of 180 μm. FIGS. 14A and 14B are photomicrographs of a hole on the emission side of the CO ₂ laser (before removal of the protective film 24). From FIG. 14, it can be seen that the holes 29 of φ85 μm are regularly and accurately formed with a pitch of 180 μm. The cross section of this sample was also observed using a microscope or SEM, but no cracks 28 were found at the interface between the core material 19 and the semi-cured first resin 20. This is considered to be because the first resin 20 is in a semi-cured state, and therefore easily absorbs distortion caused by laser processing.

  FIG. 15 is a plan view schematically illustrating FIG. In FIG. 15, the hole diameter (85 μmφ) is measured and expressed on the inner side of the edge 33, but it may be evaluated at an optimum portion according to the use and purpose of the edge 33.

FIGS. 16A and 16B are micrographs of a sample in which 10,000 holes 29 each having a diameter of 75 μm are formed at a pitch of 180 μm. FIG. 16A is an enlarged micrograph of a 75 μmφ hole 29 portion, and FIG. 16B is a microphotograph showing a plurality of 75 μmφ hole 29 formed adjacent to each other at a pitch of 180 μm. FIGS. 16A and 16B are photomicrographs of the CO ₂ laser emission side hole (before the protective film 24 is peeled off). From FIG. 16, it can be seen that the holes 29 of 75 μmφ are regularly and accurately formed with a pitch of 180 μm. The cross section of this sample was also observed using a microscope or SEM, but no cracks 28 were found at the interface between the core material 19 and the semi-cured first resin 20. This is considered to be because the first resin 20 is in a semi-cured state, and therefore easily absorbs distortion caused by laser processing.

FIGS. 17A and 17B are micrographs of a sample in which 10,000 holes 29 each having a diameter of 65 μm are formed at a pitch of 180 μm. FIG. 17A is a photomicrograph showing an enlargement of the 65 μmφ hole 29 portion, and FIG. 17B is a photomicrograph showing a state in which a plurality of 65 μmφ holes 29 are adjacently formed at a pitch of 180 μm. FIGS. 17A and 17B are photomicrographs of the CO ₂ laser emission side hole (before the protective film 24 is peeled off). From FIG. 17, it can be seen that the holes 29 of 65 μmφ are regularly and accurately formed with a pitch of 180 μm. The cross section of this sample was also observed using a microscope or SEM, but no cracks 28 were found at the interface between the core material 19 and the semi-cured first resin 20. This is considered to be because the first resin 20 is in a semi-cured state, and therefore easily absorbs distortion caused by laser processing.

FIGS. 18A and 18B are micrographs of a sample in which 10,000 holes 29 each having a diameter of 50 μm are formed at a pitch of 180 μm. 18A is an enlarged micrograph of a 50 μmφ hole 29 portion, and FIG. 18B is a microphotograph showing a plurality of 50 μmφ hole 29 formed adjacent to each other at a pitch of 180 μm. 18A and 18B are photomicrographs of the hole on the emission side of the CO ₂ laser (before the protective film 24 is peeled off). From FIG. 18, it can be seen that the holes 29 of 50 μmφ are regularly and accurately formed with a pitch of 180 μm. The cross section of this sample was also observed using a microscope or SEM, but no cracks 28 were found at the interface between the core material 19 and the semi-cured first resin 20. This is considered to be because the first resin 20 is in a semi-cured state, and therefore easily absorbs distortion caused by laser processing.

In the photograph of FIG. 18B, the actual hole size is smaller than the set value of the CO ₂ laser device (the optical system and aperture are set so that a 50 μmφ hole is formed). (The actual measurement value was 47.6 μmφ). 18B, there is a variation in the diameter of the plurality of holes 29. This can be solved by optimizing the laser conditions and the like.

14 and 16 to 18 are photographs of the emission side of the CO ₂ laser, and ring-shaped swelling of the protective film 24 surrounding the hole 29 (thickness of the edge 33 considered to be affected by the CO ₂ laser). Is smaller than the incident side (not shown). This is because the protective film 24 provided on the emission side is held on the support 27 via the fine adhesive layer 26, so that the heat from the CO ₂ laser and the deformation (or expansion and contraction) of the protective film 24 after processing are suppressed. It seems that it was because of

  In Example 8, with respect to a commercially available prepreg (50 cm square), the results of investigating the dimensional change of the prepreg when 30 million holes 29 of 30 μmφ to 70 μmφ were formed adjacent to each other at a pitch of 100 μm are shown in Table 10 Will be described.

  In (Table 10), “within ○ standard” indicates that the interlayer alignment accuracy (or matching accuracy) is within the standard when the multilayer substrate 11 is formed using the prepreg used.

  (Table 10) shows that, in the prototype prepreg, the dimensional change of the prepreg is ◎ (the dimensional change is extremely small even with the formation of the holes, although the large number of holes 29 are formed. It can be seen that no change was detected. This is presumably because the prepreg 25 was held uniformly (or adsorbed or adhered) over the entire surface by the slightly adhesive layer 26 formed on the surface of the support 27.

  As a result, the prepreg 25 and the protective film 24 provided on the surface of the prepreg 25 are held by the support 27 having a small dimensional change, so that the prepreg 25 having a large size exceeding 50 cm square can be further obtained. It can be seen that even if the thickness of the hole is 50 μm or less, the hole 29 with high pitch and absolute accuracy can be processed.

  Further, since the prepreg 25 and the protective film 24 provided on the surface of the prepreg 25 are held on the table 30 via the support 27, the table 30 is not damaged (for example, generation of scratches due to laser irradiation). It was. It was also useful to lay a protective sheet 32 between the support 27 and the table 30.

  Hereinafter, as a comparative example of (Table 10), the result of performing the same experiment without using the support 27 is shown.

(Comparative example)
FIG. 19 is a cross-sectional view illustrating a problem when the prepreg 25 and the protective film 24 provided on the surface of the prepreg 25 are directly held on the table 30 and laser processed. In FIG. 19, 34 is a damaged part and 35 is a peeling part.

  As shown in FIG. 19, when the prepreg 25 and the protective film 24 provided on the surface of the prepreg 25 are directly held on the table 30 and laser processed, a large number of holes 29 are formed adjacent to the prepreg 25. However, the variation in absolute dimensions was expected to be small.

  However, the inventors' experiments have shown that the shape and dimensions of the holes 29 formed in the prepreg 25 are affected by the reflected laser light from the surface of the table 30 as shown in FIG. Moreover, the infrared laser beam (for example, the arrow 16a shows an infrared laser beam) which passed the prepreg 25 reached the surface of the table 30, and the damaged part 34 was formed.

  Further, the protection provided on the surface of the prepreg 25 or prepreg 25 from the table 30 by the infrared laser beam reflected on the surface of the table 30 or the internal stress generated in the protective film 24 or prepreg 25 due to the formation of the holes 29. The film 24 may be peeled off to form a peeled portion 35. Thus, when the peeling part 35 generate | occur | produces, since the prepreg 25 is extended and deform | transformed, there existed a possibility of affecting the position accuracy of the hole 29. FIG.

  These results are shown in (Table 11).

  In Table 11, “within the standard” indicates that the interlayer alignment accuracy (or matching accuracy) is within the standard when a multilayer substrate is produced using the prepreg used. In addition, ◎ to × varied greatly depending on the location, up to ◎ (the absolute dimension is accurate and cannot be measured) and x (the absolute dimension changed and became out of specification).

  As shown in FIG. 19, this was considered to be caused by the prepreg 25 being partially peeled off due to the influence of reflected light (arrow 16b) from the table 30 and the like.

  From the above (Table 11), it is effective that the support 27 used in the present invention reduces reflection with respect to infrared laser light (in other words, the reflection is reduced by positively forming holes). It turned out that. Further, from Table 10, it can be seen that there is a possibility that the table 30 (whether metal or ceramic) may be damaged (or damaged part 34) due to laser irradiation even if there is a slight difference.

  In the ninth embodiment, an example of damage prevention for the table 30 will be described.

  From the results of (Table 11), when the prepreg 25 or the protective film 24 provided on the surface of the prepreg 25 is held on the table 30, the prepreg 25 is hollowed in response to the occurrence of the damaged portion 34 in the table 30. The result of the experiment for the case of holding the above will be described.

FIG. 20 is a cross-sectional view for explaining how the holes 29 are formed in the prepreg 25 in a state where the prepreg 25 is held hollow. In FIG. 20, the prepreg 25 is separated from the table 30 by a distance indicated by an arrow 16c. An arrow 16b indicates a state in which tension is applied in order to reduce the slack of the prepreg 25 (or deformation due to its own weight). As shown by the arrow 16b, the prepreg 25 and the protective film 24 provided on the surface of the prepreg 25 are fixed to a frame (not shown) or the like, and a certain tension (for example, the arrow 16b) is applied, whereby the prepreg 25 Can reduce slack. An arrow 16a indicates an infrared laser beam such as CO ₂ or YAG emitted from a CO ₂ laser device (not shown).

  As shown in FIG. 20, when the prepreg 25 is handled in a hollow state, its productivity can be improved, but the prepreg 25 is deformed, and the diameter of the hole 29 due to the influence of the slight deflection of the prepreg 25 on the laser focal depth. There is a possibility that the prepreg 25 may be deformed by the variation shown in FIG.

  For comparison, a commercially available adhesive tape was applied on the protective sheet 32 fixed to the prepreg 25 while taking care not to bite air using a roller, and an experiment as shown in FIG. 20 was performed. I did it.

  However, although the dimensional accuracy and the absolute position accuracy of the sample hole 29 thus obtained were evaluated, results such as (Table 1) to (Table 6) and (Table 9) were not obtained. The cause seems to be that it was separated from the table 30 as shown in FIG. 20 and was in a hollow state as indicated by an arrow 16c.

  Moreover, although the commercially available adhesive tape was affixed on the surface of the protective film 24 fixed to the prepreg 25, and it hold | maintained on the table 30 as shown in FIG. 19, formation of the hole 29 was tried, (Table 1)- Results such as (Table 6) and (Table 9) were not obtained. This seems to be due to the influence of the internal stress of the adhesive tape, the strength of the force, the dimensional stability of the adhesive tape itself, the laser processability, the tensile strength, and the like.

  As described above, the support 27 has a mechanical strength (that is, a higher modulus of elasticity or Young's modulus or flexural modulus than that of the prepreg sheet) that cannot be dealt with by simply diverting a commercially available adhesive tape, Dimensional stability (coefficient of thermal expansion lower than that of prepreg, or higher modulus of elasticity than prepreg), and necessary adhesive strength at the time of processing. After processing, it can be peeled off so as not to affect the adhesion between the prepreg and the protective sheet. It is desirable to have a slight adhesive property.

  FIG. 21 is a perspective cross-sectional view for explaining the stress generated by hole formation in the prepreg 25 and the protective film 24 when the support 27 is not provided. In FIG. 21, since the prepreg 25 and the protective film 24 provided on the surface of the prepreg 25 are not held by the support 27, a hole 29 is formed, and variously depending on the internal stress (for example, the arrow 16). It was found that it stretches and deforms in any direction.

  As described above, the insulating layer 13 composed of the core material 19 and the first resin 20 impregnated or applied to the core material 19 and the plurality of holes 29 formed in the insulating layer 13 are filled. The multilayer substrate 11 is composed of the conductive paste 23 and the interconnect 14 connected with the conductive paste 23, and the hole 29 is formed in the semi-cured state (that is, the B stage state). A multilayer substrate 11 formed by laser irradiation in a state in which the insulating layer 13 including the resin 20 is held on a support 27 having a thickness of 5 mm or less made of an organic material having infrared laser photodegradability; As a result, the multiple vias 12 can be narrowly adjacent, and the multilayer substrate 11 can be reduced in size, the module 17 can be reduced in size, and the density can be increased.

The organic substance having infrared laser photodegradability is decomposed by infrared laser light, but decomposition by heat is more preferable than decomposition by ablation. This is because decomposition by ablation is slow. In order to thermally decompose by laser light, an organic substance having a decomposability by a laser in the infrared region (preferably a wavelength of 0.7 μm or more, more preferably 1.0 μm or more) is desirable. Organic substances are more easily decomposed by laser than inorganic substances. In addition, it is known that the peak wavelength of infrared rays emitted by a substance near room temperature (for example, 20 ° C.) is about 1 μm to about 20 μm (for example, black body radiation). Therefore, in order to form the holes 29 with the infrared laser light in the prepreg 25 and the support 27 near room temperature, the wavelength of the infrared laser light is desirably about 1 μm or more and about 10 μm. This is because, in principle, the peak of infrared rays emitted from an object matches the wavelength of infrared rays (that is, laser light) that the object absorbs at that temperature. Therefore, it is desirable to select an infrared laser beam having a wavelength of 1 μm to 20 μm (preferably a wavelength of 10 μm ± 3 μm, and more preferably a wavelength of 10 μm ± 2 μm). By selecting a laser in such a wavelength region (for example, a YAG laser or a CO ₂ laser), the infrared laser photodegradability of the support 27 can be improved, and the thermal influence in the vicinity of the hole 29 formed by the infrared laser light (for example, Edge 33, interface peeling between the protective sheet 32 and the support 27, or interface peeling between the protective film 24 and the prepreg 25, etc.) are prevented.

  The thickness of the support 27 is desirably 5 mm or less. If it exceeds 5 mm, the cost may be affected. The thickness of the support 27 is preferably 10 μm or more (more preferably 20 μm or more). When the thickness of the support 27 is 10 μm or less, handling is difficult, and there is a possibility that it may be affected by wrinkles and dust.

  A slightly adhesive layer 26 may be formed on the surface of a commercially available resin film (for example, a resin film such as a PET film, a PEN film, a PP film, a PE film, or a polyester film), and this may be used as the support 27. In this case, the thickness of the support 27 is desirably 50 μm or more and 300 μm or less (preferably 60 μm or more and 250 μm or less). A resin film having a thickness of less than 50 μm is weak and has low handling properties in a large format exceeding 30 cm square. If it exceeds 300 μm, it is expensive. The thickness of the support can be measured according to JIS Z0237.

  The adhesive force of the slightly adhesive layer 26 to the film is desirably 50 mN / 25 mm or more (or 50 fg / 25 mm or more). If it is less than 50 mN / 25 mm, the tackiness may be too low. The adhesive strength is evaluated by a general method (for example, a method in which a film is reciprocated once with a 2 kg rubber roller referring to JIS Z0237 and left for 20 minutes, and then the film is peeled off in a 180 degree direction at a pulling speed of 300 mm / min). That's fine. For such applications, acrylic pressure-sensitive adhesives are useful in terms of their variety and laser degradability. The thickness of the slightly adhesive layer 26 is preferably 1 μm or more and 100 μm or less. If it exceeds 100 μm, there is a possibility of deformation during processing. On the other hand, when the thickness is less than 1 μm, it is easily affected by coating unevenness and the like, which may affect the uniformity of the adhesive force.

  As the resin contained in the prepreg 25, it is also useful to use BT resin (BT resin is a trade name of Mitsubishi Gas Chemical Co., Ltd. and is a thermosetting resin made of bismaleimide triazine resin) in addition to epoxy. . Both the epoxy resin and the BT resin are excellent in workability by a carbon dioxide laser.

  The inorganic fiber such as glass or the organic fiber such as aramid used for the core material 19 is desirably subjected to fiber opening processing. The term “opening” means that the filaments constituting the fiber are scattered and dispersed or spread almost uniformly in the width direction. By using the opened core material 19 for the core material 19, the prepreg 25 can be thinned and the drilling accuracy by the laser can be increased. This is because the density difference in the plane direction of the bundle of fibers constituting the core material 19 can be reduced by the fiber opening process. By spreading the fiber bundle in the plane direction by the fiber opening process, the core material 19 by laser energy is used. The decomposition energy can be reduced, and the variation can be reduced. In addition, it can be judged from the distribution state of the core material 19 in the cross section of a product about the presence or absence of a fiber opening process.

  Next, the influence of the core material 19 on the diameter of the hole 29 will be described with reference to FIGS.

  22A and 22B are a plan view and a cross-sectional view, respectively, of the core material 19 made of glass fiber or the like (or glass strand or the like). In FIG. 22, 36 is a fiber part, and the fiber part 36 is a bundle of, for example, about 70 inorganic fibers such as glass fibers or organic fibers such as aramid. Reference numeral 37 denotes a basket hole portion, which corresponds to an opening portion in which the fiber portion 36 is woven in the XY directions. 22 indicates the size of the basket hole portion 37 (for example, the length of one side of the square basket hole portion 37).

  As shown in FIG. 22 (B), the core material 19 that has not been subjected to the fiber opening process has a plurality of fibers (for example, about 70) in a lump, so that the thickness of the core material 19 itself is also large (for example, , The thickness of the fiber constituting the fiber portion 36) and the size of the basket hole portion 37 (for example, the length of one side of the basket hole portion 37 is equal to the thickness of the fiber constituting the fiber portion 36). 5 times more).

  FIGS. 23A to 23C are a top view and a cross-sectional view showing the results of experiments performed on the core material that has been subjected to the fiber opening process.

  23 (B) and 23 (C) are cross-sectional views showing a prepreg 25 using the core material 19 that has been subjected to different opening processes. FIG. 23B shows a state in which two fiber portions 36 form layers (or two strands each) in the X direction Y direction, and FIG. 23C shows 1 in both the X direction Y direction of the fiber portion 36. It shows how a book (or one strand at a time) forms a layer.

  In FIGS. 23B and 23C, the semi-cured resin impregnated in the core material 19 is not shown. As shown by the arrow 16, the size of the basket hole portion 37 in the core material 19 can be reduced by performing the fiber opening process.

  Further, by performing the fiber opening process, the prepreg 25 having a reduced basket hole portion 37 is fixed on the support 27 via the slightly adhesive layer 26 as shown in FIGS. Needless to say, even if the diameter is 85 microns or less, the holes 29 and the vias 12 having small diameter variations (further less than 5% variation) can be formed with high accuracy.

  23A to 23C, the support 27 and the slightly adhesive layer 26 that fix the prepreg 25 are not shown. The hole 29a corresponds to the portion without the core material 19 (φ layer), the hole 29b corresponds to the one-layer portion of the core material 19, and the hole 29c corresponds to the two-layer portion of the core material 19.

  As shown in FIGS. 23A to 23C, in a state where the prepreg 25 is fixed to the support 27 (not shown) via the slightly adhesive layer 26) (not shown), the holes 29a, By forming 29b and 29c, the variation in diameter on the exit side of these holes 9a to 9b can be made 5% or less, further 3% or less, and substantially the same. This is because the infrared laser beam applied to the prepreg 25 and the amount of heat generated by the irradiation are absorbed by the support 27, and accordingly, the holes 29a, 29b, 29c are changed depending on the presence or absence of the core material 19 and the thickness. As a matter of course, it is possible to suppress the occurrence of the crack 6 shown in FIG. 24, FIG. 25, and FIG. 27 and the crack 28 shown in FIG. There is no.

  According to experiments by the inventors, when the variation in diameter on the emission side of the prepreg 25 is 5% or less, in the multilayer substrate 11 in which the conductive paste 23 is filled in this prepreg, the variation in via diameter is 7%. It turns out that it becomes the following.

  That is, in the case of the multilayer substrate 11 in which the prepreg 25 is laminated and cured, it seems that it is difficult to confirm that the variation in diameter on the emission side in the prepreg 25 is 5% or less. By observing, that is, the diameter of the via 12 in the portion that enters the inner side (or the core material 19 side) by about 10 μm in the thickness direction from the laser emission side (practically in the range of 10 μm to 30 μm is sufficient). By measuring the variation, or by measuring the variation in the diameter of the hole 29 (or the via 12 made of the conductive paste 23 filled in the hole 29) formed in the laser emission surface of the core member 19, the prepreg state It can be seen whether the diameter variation was 5% or less.

  That is, according to the experiments by the inventors, a double-sided substrate was prepared using a base material having a prepreg state emission-side diameter variation of 5% or less, and about 10 μm in the thickness direction from the laser emission side (practically 10 μm to 30 μm). The diameter of the via 12 in the portion that is inside (or the core material 19 side) only within the range, or the hole 29 (or the hole 29 filled in the laser emission surface side of the core material 19) is filled. When the diameter of the via 12) made of the conductive paste 23 was measured, the variation was 7% or less.

  In addition, when a plurality of types of vias 12 having different diameters are provided, if the diameter variation of the most frequent (or most or the smallest diameter) via is 7% or less, the prepreg state is almost certainly obtained. The variation in the diameter of the hole 29 is 5% or less. In the case of the multilayer substrate 11 in which a plurality of types of vias 12 having different diameters are provided in one prepreg 25 and a plurality of the vias 12 are laminated and cured, it may be difficult to evaluate the variation in diameter. As described above, it is useful to measure via diameters by frequency or by rank of diameters.

  In the case of the multilayer substrate 11 in which a plurality of prepregs 25 are laminated, it is sufficient to measure the variation in the diameter of the via 12 in one (or any one layer) prepreg 25. In some cases, the holes 29 are formed in the individual prepregs 25 using different laser devices. If a portion consisting of one (or one layer) prepreg 25 is evaluated and the variation is 7% or less, it can be said that the variation in the diameter of the prepreg state is almost certainly 5% or less.

  In addition, the evaluation of the variation is within an area of 3 mm square or less in an arbitrary portion of the multilayer substrate 11 (more preferably within an area of 5 mm square or less, more preferably 10 mm square or less), and the number of vias 12 is n = 10 or more. (Desirably 20 pieces, more desirably 50 pieces, or even 100 pieces) is sufficient. This is because it is difficult to accurately measure the diameter of the via 12 over a wide area. In addition, even when there are a plurality of arbitrary portions, it is sufficient if the variation in any one portion is evaluated.

The pitch of the plurality of holes 29 is set to 40 μm or more and 180 μm or less, so that the multilayer substrate 11 can be reduced in size, the module 17 can be reduced in size, and the density can be increased. When the hole pitch is less than 40 μm, when a CO ₂ laser (wavelength 10.2 μm) is used, theoretically necessary processing accuracy may not be obtained, and mechanical limitations may be considered. Further, when the hole pitch exceeds 180 μm, necessary processing may be performed without using the support 27.

The shortest distance between the adjacent vias 12 made of the conductive paste 23 is 20 μm or more and 120 μm or less, so that the multilayer substrate 11 can be miniaturized, the module 17 can be miniaturized, and the density can be increased. When the shortest distance between the plurality of vias 12 is less than 20 μm, when a CO ₂ laser (wavelength 10.2 μm) is used, necessary mechanical restrictions may be imposed in addition to wavelength restrictions. If the shortest distance between the vias 12 exceeds 120 μm, necessary processing may be performed without using the support 27.

The diameter of the hole 29 is 90 μm or less and 20 μm or more, and the difference in diameter between the incident side and the emission side of the hole 29 is 1 μm or more and 20 μm or less, thereby reducing the size of the multilayer substrate 11 and the module 17. It can cope with densification. When the diameter of the hole 29 exceeds 90 μm, necessary processing may be performed without using the support 27. In addition, when the diameter of the hole 29 is less than 20 μm, when a CO ₂ laser (wavelength: 10.2 μm) is used, there is a possibility of being subjected to mechanical restrictions in addition to wavelength restrictions.

Even with a CO ₂ laser, it is useful to use a short wavelength side such as 9.4 μm. By using the short wavelength side of the CO ₂ laser, it is possible to cope with finer processing. Moreover, since it is not ablation but thermal processing, the prepreg can be drilled with the core material at high speed.

The diameter of the hole 29 is 0.5 to 5.0 times the thickness of the insulating layer 13 filled with the conductive paste 23, thereby reducing the size of the multilayer substrate 11, the size of the module 17, and the high density. It can respond to conversion. If the diameter of the hole 29 is less than 0.5 times the thickness of the insulating layer 13, it may be difficult to form the hole 29 at high speed with a CO ₂ laser. Further, if the diameter of the hole 29 exceeds 5.0 times the thickness of the insulating layer, it may affect the miniaturization of the multilayer substrate 11, the miniaturization of the module 17, and the high density.

The laser is in a form using carbon dioxide (CO ₂ ), and the core material 19 is one of resin films such as glass fiber, glass woven fabric, glass nonwoven fabric, organic fiber, organic woven fabric, organic nonwoven fabric, or polyimide film. By increasing the number of layers, it is possible to reduce the cost of the multilayer substrate 11 and increase the strength when the insulating layer 13 is thinned or when the multilayer substrate 11 itself is thinned (for example, improved bending strength). Is possible.

In particular, the hole 29 can be formed at high speed by combining a CO ₂ laser with a galvanometer mirror or the like in the laser device. Further, even when glass fiber, glass woven fabric, glass nonwoven fabric, organic fiber, organic woven fabric, organic nonwoven fabric, resin film, or the like is used for the core material 19, the formation of holes by laser becomes easy. This is because the formation mechanism of the CO ₂ holes 29 is due to thermal decomposition.

  For example, a commercially available short wavelength laser (for example, 532 nm which is half of YAG, 355 nm which is one third, or excimer laser) or the like is accompanied by ablation, and the processing speed of the hole 29 is low, and the multilayer It may be unsuitable for forming the holes 29 in the substrate 11.

On the other hand, since the CO ₂ laser and YAG laser mainly perform thermal processing, even if the prepreg 25 having the core material 19 or the first resin 20 is in a semi-cured state, the high speed of the holes 29 is high. Excellent workability or productivity.

A protection step of providing a protective film 24 on the surface of a prepreg 25 made of the core material 19 and a semi-cured first resin 20 impregnated or applied to the core material 19, and the protective film 24 provided therein In the state where the prepreg 25 is held on the support 27, a hole forming step of forming holes 29 in both the prepreg 25 and the support 27 with an infrared laser beam such as a CO ₂ laser, and the prepreg 25, From the peeling step of peeling from the support 27 together with the protective film 24, the filling step of filling the holes 29 with the conductive paste 23 via the protective film 24, and the prepreg 25 obtained in the filling step, A peeling step of peeling the protective film 24, a step of laminating the metal foil 31 on the peeling surface of the prepreg 25 obtained in the peeling step, A multilayer substrate that can be reduced in size and increased in density by a method for manufacturing the multilayer substrate 11 in which the curing step of curing the prepreg 25 and the step of patterning the metal foil 31 to form the wiring 14 are repeated at least once each. 11 can be provided stably.

  An adhesive layer (for example, a slight adhesion layer 26) is provided on the surface of the support 27, and the adhesive force of the adhesive layer is weaker than the adhesive force between the prepreg 25 and the protective film 24. Thus, peeling at the interface between the prepreg 25 and the protective film 24 can be prevented, and highly accurate hole processing can be performed.

  As described above, the core material 19 is woven fabric (woven fabric such as glass fiber or resin fiber) or non-woven fabric (nonwoven fabric of glass fiber or resin fiber. The non-woven fabric includes paper formed from glass or resin). It is useful to use. Further, the resin impregnated or applied to the core material 19 (for example, the first resin 20) is in a semi-cured state, and the insulating layer 13 in which the resin is in a semi-cured state is sandwiched between the protective films 24, It is useful to hold the support 27 and form the holes 29 with an infrared laser.

Further, it is useful to use an infrared laser (further, a YAG laser or a CO ₂ laser) for forming the holes 29.

  As described above, the insulating layer 13 formed by impregnating or applying the first resin 20 to the core material 19 made of either woven fabric or non-woven fabric, and the plurality of holes formed in the insulating layer 13 29, the conductive paste 23 filled in the hole 29, and the wiring 14 connected between the layers via the conductive paste 23, and the hole 29 formed in the insulating layer 13 has a half The insulating layer 13 containing the first resin 20 in a cured state is sandwiched between protective films 24, and a slightly adhesive layer 26 that becomes an adhesive layer on a support 27 mainly composed of an organic material having infrared laser photodegradability. In this state, the insulating layer 13 (or prepreg 25) is irradiated with the infrared laser light while being held in a gap, and a variation in diameter on the emission side is formed to be 5% or less. And multilayer It is possible to further narrow the adjacent of the plate 11.

  An insulating layer 13 formed by impregnating or applying a resin (for example, the first resin 20) to a core material 19 made of either woven fabric or non-woven fabric, and a plurality of holes 29 formed in the insulating layer 13; The conductive paste 23 filled in the hole 29 and the wiring 14 connected between the layers via the conductive paste 23 are provided. The hole formed in the insulating layer 13 is semi-cured. The insulating layer 13 (or prepreg 25) containing the resin (for example, the first resin 20) is sandwiched between protective films 24, and on a support 27 mainly composed of an organic material having infrared laser photodegradability. By irradiating the insulating layer 13 (or prepreg 25) with the infrared laser light while being held through an adhesive layer (for example, the slightly adhesive layer 26), the variation in the diameter on the emission side is reduced to 5% or less. Has been the pitch of the holes 29, by a multi-layer substrate 11 is 40μm or more 180μm or less, it is possible to further narrow the adjacent of the multilayer substrate 11.

  An insulating layer 13 formed by impregnating or applying a resin (for example, the first resin 20) to a core material 19 made of either woven fabric or non-woven fabric, and a plurality of holes 29 formed in the insulating layer 13; The conductive paste 23 filled in the hole 29 and the wiring 14 connected between the layers via the conductive paste 23 are provided. The hole formed in the insulating layer 13 is semi-cured. The insulating layer 13 (or prepreg 25) containing the resin (for example, the first resin 20) is sandwiched between protective films 25, and on a support 27 mainly composed of an organic material having infrared laser photodegradability. It is formed by irradiating the infrared laser light to the insulating layer 13 (or prepreg 25) while being held via an adhesive layer (for example, a slightly adhesive layer 26), and is the shortest of the holes 29 Away, by a multilayer substrate is 20μm or more 120μm or less, it is possible to further narrow the adjacent of the multilayer substrate 11.

  Further, an insulating layer 13 formed by impregnating or applying a resin (for example, the first resin 20) to a core material 19 made of either woven fabric or non-woven fabric, and a plurality of holes formed in the insulating layer 13 29, a conductive paste 23 filled in the hole 29, and a wiring 14 connected between the layers via the conductive paste 23. The hole formed in the insulating layer 13 is semi-cured. The insulating layer 13 (or prepreg 25) containing the resin in a state (for example, the first resin 20) is sandwiched between protective films 24, and a support 27 mainly composed of an organic material having infrared laser photodegradability. By irradiating the insulating layer 13 (or prepreg 25) with the infrared laser light while being held via an adhesive layer (for example, a slightly adhesive layer 26), the variation in diameter on the emission side is 5% or less. The diameter of the holes 29 is 0.5 to 5.0 times the thickness of the insulating layer filled with the conductive paste. Narrowing becomes possible.

  The thickness of the support 27 is not less than the thickness of the insulating layer 13 (or prepreg 25) and not more than 5 mm. The support 27 is irradiated with infrared laser light together with the insulating layer 13 (or prepreg 25) and the protective film 24. By forming the hole 29 by this, the multilayer substrate 11 can be further narrowed.

  The insulating layer 13 (that is, the prepreg 25) in which the resin impregnated or applied to the core material 19 (for example, the first resin 20) is semi-cured is sandwiched between the protective films 24. The electrical connection stability between the conductive paste 23 and the wiring 14 can be improved.

  The laser is an infrared laser and uses carbon dioxide gas, and the core material 19 is one or more of one or more layers of glass fiber, glass woven fabric, glass nonwoven fabric, organic fiber, organic woven fabric, and organic nonwoven fabric. As a result, it is possible to increase the strength and cost of the multilayer substrate 11.

  Further, a protection step of providing a protective film 24 on the surface of a prepreg 25 having a core material 19 made of either woven fabric or nonwoven fabric and a semi-cured resin (for example, a semi-cured first resin 20), A holding step of holding the prepreg 25 with the protective film 24 on a support 27 mainly composed of an organic substance having infrared laser photodegradability via a fine adhesive layer 26 serving as an adhesive layer; In the state where the prepreg 25 is held on the support 27, a hole forming step of forming holes in both the prepreg 25 and the support 27 with an infrared laser, and the prepreg 25 together with the protective film 24, A peeling step of peeling from the support 27, a filling step of filling the holes 29 with the conductive paste 23 via the protective film 24, and the filling From the prepreg 25 obtained in the process, a peeling process for peeling the protective film 24, a laminating process for laminating the metal foil 31 on the peeling surface of the prepreg 25 obtained in the peeling process, and the prepreg 25 are cured. A method of manufacturing the multilayer substrate 11 in which the curing step and the wiring step of patterning the metal foil 31 to form the wiring 14 are repeated at least once each, and the variation in diameter on the emission side of the prepreg 25 is 5%. By using the following multilayer substrate manufacturing method, the multilayer substrate 11 can be stably produced.

  The protective film 24 held on the support 27 is an adhesive layer (for example, the slightly adhesive layer 26) of the support 27 itself or an adhesive layer (for example, the slightly adhesive layer 26) formed on the support 27. ) Or an adhesive sheet provided on the support 27 (for example, a sheet-like or double-sided tape-like micro-adhesive layer 26) is held by any one or more adhesive forces, and the adhesive force is By making the adhesive strength between the prepreg 25 and the protective film 24 weaker, the multilayer substrate 11 can be stably produced.

  The support 27 in which the holes 29 are formed is used a plurality of times while being held on the table 30 of the infrared laser device, so that the manufacturing cost of the multilayer substrate 11 can be suppressed.

  If it is difficult to distinguish between the exit side and the entrance side, it is desirable to select the exit side that has a larger diameter. This is because the insulation resistance between adjacent vias with larger diameters may be important.

  According to the multilayer substrate and the method of manufacturing the same according to the present invention, the plurality of vias can be brought close to each other at a short distance, not only further narrowing of the plurality of vias in the multilayer substrate but also further reduction of the diameter of the via hole, Variations in via diameters can be reduced, and it is possible to cope with further increases in density, accuracy, and weight of multilayer substrates, and reductions in the size and thickness of various electronic devices.

DESCRIPTION OF SYMBOLS 11 Multilayer substrate 12 Via 13 Insulating layer 14 Wiring 15 Electronic component 16 Arrow 17 Module 18 Auxiliary line 19 Core material 20 First resin 21 Conductor 22 Second resin 23 Conductive paste 24 Protective film 25 Prepreg 26 Slightly adhesive layer 27 Support Body 28 Crack 29 Hole 30 Table 31 Metal foil 32 Protective sheet 33 Edge 34 Damaged part 35 Peeling part 36 Fiber part 37 Basket hole part

Claims (9)

An insulating layer formed by impregnating or applying a resin to a core material made of either woven or non-woven fabric, a plurality of holes formed in the insulating layer, and a conductive paste filled in the holes; The hole formed in the insulating layer, the insulating layer containing the semi-cured resin is sandwiched between protective films, and an infrared ray Irradiation of the infrared laser light to the insulating layer in a state of being held via an adhesive layer on a support mainly composed of an organic substance having laser photodegradability, the variation in diameter on the emission side is formed to 5% or less. Multilayer board. An insulating layer formed by impregnating or applying a resin to a core material made of either woven or non-woven fabric, a plurality of holes formed in the insulating layer, and a conductive paste filled in the holes; The hole formed in the insulating layer, the insulating layer containing the semi-cured resin is sandwiched between protective films, and an infrared ray Irradiation of the infrared laser light to the insulating layer in a state of being held via an adhesive layer on a support mainly composed of an organic substance having laser photodegradability, the variation in diameter on the emission side is formed to 5% or less. A multilayer substrate in which the pitch of the holes is 40 μm or more and 180 μm or less. An insulating layer formed by impregnating or applying a resin to a core material made of either woven or non-woven fabric, a plurality of holes formed in the insulating layer, and a conductive paste filled in the holes; The hole formed in the insulating layer, the insulating layer containing the semi-cured resin is sandwiched between protective films, and an infrared ray Irradiation of the infrared laser light to the insulating layer in a state of being held via an adhesive layer on a support mainly composed of an organic substance having laser photodegradability, the variation in diameter on the emission side is formed to 5% or less. A multilayer substrate in which the shortest distance between the holes is 20 μm or more and 120 μm or less. An insulating layer formed by impregnating or applying a resin to a core material made of either woven or non-woven fabric, a plurality of holes formed in the insulating layer, and a conductive paste filled in the holes; The hole formed in the insulating layer, the insulating layer containing the semi-cured resin is sandwiched between protective films, and an infrared ray Irradiation of the infrared laser light to the insulating layer in a state of being held via an adhesive layer on a support mainly composed of an organic substance having laser photodegradability, the variation in diameter on the emission side is formed to 5% or less. The multilayer substrate has a diameter of 0.5 to 5.0 times the thickness of the insulating layer filled with the conductive paste. The thickness of the support is not less than the thickness of the insulating layer and not more than 5 mm, and the support is formed with a hole when irradiated with infrared laser light together with the insulating layer and the protective film. Any one multilayer board. The laser is a form using carbon dioxide gas, and the core material is one or more of glass fiber, glass woven fabric, glass nonwoven fabric, organic fiber, organic woven fabric, and organic nonwoven fabric. The multilayer substrate according to one. A protection step of providing a protective film on the surface of the prepreg having a core material made of either woven fabric or nonwoven fabric and a semi-cured resin;
Holding the prepreg with the protective film on a support mainly composed of an organic substance having infrared laser photodegradability via an adhesive layer; and
In the state where the prepreg with a protective film is held on the support, a hole forming step of forming holes in both the prepreg and the support with an infrared laser;
A peeling step of peeling the prepreg together with the protective film from the support, and a filling step of filling the hole with a conductive paste via the protective film;
From the prepreg obtained in the filling step, a peeling step for peeling the protective film,
A lamination step of laminating a metal foil on the peeling surface of the prepreg obtained in the peeling step;
A curing step of curing the prepreg;
A wiring step of patterning the metal foil to form a wiring;
Is a method for producing a multilayer substrate that is repeated at least once each,
The manufacturing method of the multilayer substrate whose variation of the diameter at the output side of the prepreg is 5% or less. The protective film held on the support is
The pressure-sensitive adhesive layer of the support itself, the pressure-sensitive adhesive layer formed on the support, or the pressure-sensitive adhesive sheet provided on the support is held by any one or more adhesive forces,
And the said adhesive force is a manufacturing method of the multilayer substrate of Claim 7 weaker than the adhesive force between a prepreg and the said protective film. 8. The method of manufacturing a multilayer substrate according to claim 7, wherein the support in which the hole is formed is used a plurality of times while being held on an infrared laser table.

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