JP2024013103A - Core substrate, manufacturing method thereof, and multilayer wiring substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a core substrate capable of suppressing deformation due to shrinkage of prepreg.

SOLUTION: In a core substrate 10, a multilayer wiring board includes a prepreg layer 11K in which first prepregs 11A and second prepregs 11B are alternately laminated and which does not include a conductive layer 17, and a conductive layer 17 laminated on the front and back sides of the prepreg layer 11K, and a warp thread 14 of the first prepreg 11A and the warp thread 14 of the second prepreg 11B are orthogonal to each other, and a plurality of buildup layers are laminated on the front and back sides of the core substrate.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present disclosure relates to a core board, a method for manufacturing the same, and a multilayer wiring board.

As a conventional core substrate, one formed of prepreg is known (for example, Patent Document 1).

JP 2015-88752 (paragraphs [0042] to [0044], Figure 1)

The above-mentioned conventional core substrate has the problem of being deformed due to shrinkage of the prepreg, and there is a need for the development of a technology to suppress this deformation.

The invention of claim 1, which has been made to solve the above problem, is characterized in that first prepregs and second prepregs are alternately laminated, and a prepreg layer that does not include a conductive layer is laminated on the front and back sides of the prepreg layer. The core substrate has a conductive layer in which the warp of the first prepreg and the warp of the second prepreg are perpendicular to each other.

A perspective view of a core substrate according to an embodiment of the present disclosure Exploded perspective view of prepreg layer Schematic diagram of the core board manufacturing process Side sectional view of multilayer wiring board

Hereinafter, a core substrate 10 according to an embodiment of the present disclosure will be described with reference to FIGS. 1 to 4. FIG. 1 shows a cross section of an unused core substrate 10. As shown in FIG. As shown in the figure, this core substrate 10 has a prepreg layer 11K, which is an insulating layer, and conductive layers 17 laminated on both sides of the prepreg layer 11K.

As shown in FIG. 2, the prepreg layer 11K has a structure in which a plurality of first prepregs 11A and a plurality of second prepregs 11B are alternately stacked one by one. These first and second prepregs 11A and 11B are made by impregnating glass cloth 12 with thermosetting resin 13 (eg, epoxy resin, polyimide resin).

The first and second prepregs 11A and 11B have different directions in which the warp 14 included in the glass cloth 12 extends (hereinafter referred to as "warp direction H1") and a direction in which the weft 15 extends (hereinafter referred to as "weft direction H2"). '') also have the same structure, except that they are different from each other. Specifically, the warp direction H1 of the first prepreg 11A and the warp direction H1 of the second prepreg 11B are orthogonal to each other, and the weft direction H2 of the first prepreg 11A and the weft direction of the second prepreg 11B are perpendicular to each other. H2 are also orthogonal to each other. Note that the above-mentioned "orthogonal" does not strictly mean 90 degrees, but also includes substantially orthogonal angles.

As shown in FIG. 1, the warp 14 and the weft 15 described above are made by bundling and flattening a plurality of glass monofilaments 16, and there is no structural difference between the warp 14 and the weft 15. Further, the glass cloth 12 is a so-called plain weave fabric in which the warp threads 14 and the weft threads 15 are woven so as to alternately rise and fall. Here, when the glass cloth 12 is woven, the warp threads 14 are stretched under tension, so that internal stress remains in the glass cloth 12 in the warp direction H1. That is, the first and second prepregs 11A and 11B are in a relationship such that the directions in which internal stresses act are orthogonal to each other, and the magnitudes of these internal stresses are approximately the same.

In this embodiment, the warp 14 and the weft 15 have the same structure, but they may be different. For example, the warp 14 and the weft 15 may have different widths, or the warp 14 and the weft 15 may have different widths. The number and thickness of the monofilaments 16 included may be different. Moreover, although the glass cloth 12 is a plain weave, it is not limited thereto, and may be, for example, a twill weave or a satin weave. Furthermore, although epoxy resin is generally used as the thermosetting resin 13, other materials may be used.

The number of first prepregs 11A and the second prepregs 11B included in the prepreg layer 11K are the same, and the total number of prepregs is, for example, 3 to 20. However, the number of first prepregs 11A and the number of second prepregs 11B may differ by one.

Further, as for the first and second prepregs 11A and 11B, the diameter of the monofilament 16 is 3 to 10 um, the weaving density of the glass cloth 12 is 40 to 90 fibers/inch, and the first and second prepregs are Prepregs 11A and 11B preferably have a thermal expansion coefficient of 0.1 to 30 ppm/°C and a modulus of elasticity of 8 to 40 GPa. However, the first and second prepregs 11A, 11B and the prepreg layer 11K may have values outside these ranges.

The structure of the core substrate 10 has been described above. This core substrate 10 is manufactured as follows.

(1) As shown in FIG. 3(A), a roll 99 wound with prepreg 98 having a constant width is prepared. For example, the width direction of the prepreg 98 is the weft direction H2.

(2) The prepreg 98 is pulled out from the roll 99, cut into pieces of the same length as its width, and housed in the case 91 as a plurality of square prepreg pieces 90. Further, on the side surface of the case 91, for example, an indication indicating the warp direction H1 or the weft direction H2 is attached.

(3) Two cases 91 containing a plurality of prepreg pieces 90 are prepared as a first case 91 and a second case 91, and the second case 91 is rotated 90 degrees with respect to the first case 91. Then, as shown in FIG. 3(B), the first and second cases 91 are arranged on both sides of a movable base 93 provided in the stacking device 92. From this, the prepreg piece 90 housed in the first case 91 is used as the first prepreg 11A, and the prepreg piece 90 housed in the first case 91 is used as the second prepreg 11B in the laminating apparatus. 92.

(4) The unillustrated robot of the laminating device 92 repeats an operation in which the first and second prepregs 11A and 11B are alternately sucked up one by one from the first and second cases 91 and released onto the movable table 93. The first and second prepregs 11A and 11B are stacked alternately on the movable table 93.

(5) Once a predetermined number of first and second prepregs 11A and 11B are stacked on the movable base 93, the movable base 93 is moved to a hot press machine (not shown), and the plurality of prepregs on the movable base 93 are The first and second prepregs 11A and 11B are heated and pressed. As a result, a prepreg layer 11K is formed.

(6) Copper foil is laminated on both the front and back sides of the prepreg layer 11K and hot pressed. As a result, a conductive layer 17 is formed.

(7) The laminate of the prepreg layer 11K and the conductive layer 17 is trimmed and cut into a predetermined size to form the core substrate 10.

Note that in the above manufacturing method, the first and second prepregs 11A and 11B are cut out from the prepreg 98 on the same roll 99, but they may be cut out from the prepreg 98 on different rolls 99. In addition, in the above-described manufacturing method, two cases 91 containing prepreg pieces 90 having different warp directions H1 were prepared, but one case 91 containing prepreg pieces 90 having the same warp direction H1 was prepared, and these cases 91 were prepared. When stacking the prepreg pieces 90 one by one, the robot may alternately change the orientation of the prepreg pieces 90 by 90 degrees to form the first and second prepregs 11A and 11B. Further, the conductive layer 17 is formed by laminating copper foil on the prepreg layer 11K, but it does not need to be a foil. For example, both sides of the prepreg layer 11K are covered with electroless plating, and electrolytic plating is applied thereon. The conductive layer 17 may be formed by stacking. Moreover, the metal of the conductive layer 17 does not need to be copper as long as it is a conductor.

In the core substrate 10 of this embodiment described above, the prepreg layer 11K, which is an insulating layer, includes the plurality of first and second prepregs 11A and 11B, so that high strength can be achieved. Moreover, since the first and second prepregs are alternately laminated and their warp directions H1 are orthogonal, the internal stress contained in the entire prepreg layer 11K is well balanced, and the deformation of the core substrate 10 is prevented. It can be suppressed. In this way, the core board 10 of the present embodiment has high strength and is suppressed from deformation due to internal stress, so that the shape of the multilayer wiring board 20 including the core board 10 is stabilized as described later, and the multilayer wiring The substrate 20 can be manufactured easily.

FIG. 4 shows an example of a multilayer wiring board 20 including the core board 10. This multilayer wiring board 20 has buildup layers 20F and 20B on both the front and back sides of the core board 10. Each buildup layer 20F, 20B includes a resin layer 22 and a conductive layer 23 that are alternately stacked. An electric circuit is printed on each conductive layer 23, and the electric circuits of adjacent conductive layers 23 with the resin layer 22 in between are connected by a plurality of vias 25.

Further, electric circuits are printed on the conductive layers 17 on both sides of the core substrate 10, and the electric circuits on the conductive layers 17 of the core substrate 10 and the electric circuits on the conductive layers 23 of the buildup layers 20F and 20B are also connected to each other through a plurality of vias. 25. Furthermore, a plurality of through holes 26 are formed in the core substrate 10, and the electrical circuits in the conductive layer 17 of the core substrate 10 are connected to each other by the through holes 26. Further, the outermost surfaces of the buildup layers 20F and 20B are covered with a solder resist layer 27, and pads 23P included in the electrical circuit of the conductive layer 23 of the buildup layers 20F and 20B are exposed within the openings of the solder resist layer 27. There is.

The resin layer 22 included in the buildup layers 20F and 20B is, for example, ABF, and the conductive layer 23 including the electric circuit is formed by plating using a semi-additive method or a subtractive method. Further, the via 25 is formed by laser irradiation, and the through hole 26 is formed by a drill. Then, when the buildup layers 20F and 20B are formed and when the through holes 26 are formed in the core substrate 10, the core substrate 10 is subjected to a load of force and heat. In response to these loads, the core substrate 10 of this embodiment has high strength and is suppressed from deformation due to internal stress as described above, so the stacking of the resin layer 22 and conductive layer 23 of the buildup layers 20F and 20B is This can be easily carried out, and deformation of the completed multilayer wiring board 20 over time can be suppressed.

Note that although specific examples of technologies included in the scope of the claims are disclosed in this specification and drawings, the technologies described in the claims are not limited to these specific examples. This includes various modifications and changes to the example, as well as cases in which a part of the specific example is taken out alone.

10 Core board 11A First prepreg 11B Second prepreg 11K Prepreg layer 14 Warp 15 Weft 16 Monofilament 17 Conductive layer 20 Multilayer wiring board 20F, 20B Buildup layer

Claims (10)

A prepreg layer in which a first prepreg and a second prepreg are alternately laminated and does not include a conductive layer;
A core substrate having a conductive layer laminated on the front and back sides of the prepreg layer,
The warp threads of the first prepreg and the warp threads of the second prepreg are perpendicular to each other. The core substrate according to claim 1, wherein the prepreg layer has a coefficient of thermal expansion of 0.1 to 30 ppm/°C. The core substrate according to claim 1, wherein the prepreg layer has an elastic modulus of 8 to 40 GPa. The core substrate according to claim 1, wherein the monofilaments of the first and second prepregs have a diameter of 3 to 10 um. A multilayer wiring board comprising a plurality of buildup layers laminated on the front and back sides of the core board according to claim 1 or 4. A prepreg layer in which a first prepreg and a second prepreg are alternately laminated and does not include a conductive layer;
A method for manufacturing a core substrate having conductive layers laminated on the front and back sides of the prepreg layer,
a step of forming the prepreg layer by laminating the warp of the first prepreg and the warp of the second prepreg to be perpendicular to each other;
A conductive layer is laminated on the front and back sides of the prepreg layer. 7. The method for manufacturing a core substrate according to claim 6, wherein the first and second prepregs have a coefficient of thermal expansion of 0.1 to 30 ppm/°C. 7. The method for manufacturing a core substrate according to claim 6, wherein the first and second prepregs have an elastic modulus of 8 to 40 GPa. 7. The method for manufacturing a core substrate according to claim 6, wherein the monofilaments of the first and second prepregs have a diameter of 3 to 10 um. A method for manufacturing a core substrate according to claim 6, comprising:
The first and second prepregs have a coefficient of thermal expansion of 0.1 to 30 ppm/°C,
The elastic modulus of the first and second prepregs is 8 to 40 GPa,
The monofilaments of the first and second prepregs have a diameter of 3 to 10 um.

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