JP2001089953A - Insulating reinforcing material for multilayer printed circuit board and prepreg and laminate formed from the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulating reinforcing material which has excellent dimensional stability, excellent impact resistance and excellent processability and is useful for multilayer printed circuit boards. SOLUTION: This insulating reinforcing material which has an air permeability of <=50 cm3/cmR2/sec and a thickness of <=150 μm is obtained by applying an opening treatment to a woven fabric comprising melt liquid crystalline copolyester-based fibers. The reinforcing material can be used to produce prepregs and multilayer laminates which are suitable for applying to multilayer printed circuit boards.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reinforcing material for a resin insulating layer used for a multilayer printed wiring board, and more particularly to an insulating reinforcing material made of a molten liquid crystalline polyester fiber woven fabric.

[0002]

2. Description of the Related Art In the advanced information society, which has been increasingly accelerated in recent years, electronic devices such as various computers and measuring devices, communication devices such as satellite broadcasting and mobile radio, audio and visual devices, and other high-tech devices have become increasingly digital. ,
There is a trend toward faster signal processing. Correspondingly, printed wiring boards used in high-tech equipment have been required to have higher performance, and the trend toward miniaturization, weight reduction, and high density has been remarkable. Materials that satisfy high dimensional stability, low dielectric constant, and low dielectric loss tangent are required for printed wiring boards having such high performance, and new technologies for manufacturing printed wiring boards utilizing such materials are required. Is desired.

At present, attention has been paid to the surface mounting technology of IC chips and the manufacturing technology of a multilayer printed wiring board called a build-up method of a printed wiring board (hereinafter abbreviated as a build-up method) in order to meet the demand. ing.
According to this build-up method, after one or both surfaces of a core substrate are coated with an insulating resin or an insulating resin with a copper foil, holes in vias are formed, and a conductive pattern is formed by etching. Then, the above series of the same steps are performed, and this step is repeated as necessary. That is, it is a method that does not rely on the heat and pressure molding by a conventional hot plate press.

[0004]

In the manufacture of printed wiring boards by the above-mentioned build-up method, conventionally, insulating resins used for these coatings have difficulty in workability and dimensional stability due to shrinkage during resin curing. Further, since the thickness of the resin layer to be coated is extremely thin, a problem of cracking due to impact occurs. In order to address these problems, efforts have been made to solve the problems by various methods, such as adding a filler into the resin and reinforcing with a thin glass cloth. In particular, glass fiber reinforcement, which has been generally used as a conventional reinforcement, is a reasonably good material and is almost in a technically mature state, but there is still room for improvement in terms of specific gravity, insulation resistance, laser workability, etc. Is leaving. In order to respond to the demand, for example, a molten liquid crystalline polyester fiber having excellent heat resistance and insulation properties has been attracting attention, and various attempts have been made to use it as a substrate for a printed circuit board in the form of a nonwoven fabric, paper, or the like. (For example, JP-A-10-716784). However, in such a case, methods and products that can satisfy all required performances such as workability, dimensional stability, and impact resistance have not yet been put to practical use.

[0005]

SUMMARY OF THE INVENTION The present invention has been made through experiments and studies to solve the problems of the insulating reinforcing material for a multilayer printed wiring board. As a result, the reinforcing material inserted into the insulating resin layer to be impregnated is obtained. As a material, it has become possible to enhance dimensional stability, impact resistance and workability by finding a woven fabric made of a molten liquid crystalline copolyester fiber having specific air permeability and thickness characteristics. . The insulation reinforcing material is, more generally speaking, a raw woven fabric or a woven fabric after cleaning, woven from warp and weft composed of filament yarn bundles composed of a molten liquid crystalline copolyester fiber, It is a woven fabric that has been subjected to a physical treatment of decreasing air permeability and smoothing.

The present invention relates to a woven fabric woven from a warp and a weft composed of a multifilament yarn bundle of a molten liquid crystalline copolyester fiber, having a thickness of 150 μm or less and a water pressure drop of 1.27 cm. Air permeability at 50
An insulating reinforcing material for a multilayer printed wiring board, comprising a woven fabric of a molten liquid crystalline copolymerized polyester fiber having a density of not more than cm ³ / cm ² / sec. Here, the air permeability is based on a measurement method (a so-called Frazier method) by a JISL 1096.66.27.1A method Frazier type tester, and the cloth per square centimeter area per second when the pressure drop of water is 1.27 cm. Expressed by the amount of air passing through.

According to a preferred embodiment of the present invention, in the woven fabric of the molten liquid crystalline copolymerized polyester fiber, the diameter of each of the monofilaments constituting the warp and the weft is 3 to 25 μm, and the air permeability is reduced and the smoothness is reduced after greige or cleaning. It is characterized by being subjected to an opening treatment, for example, a fiber opening treatment by a jet flow or the like, and has an air permeability of 40 cm ³ / cm ² / sec or less.

[0008] In another embodiment of the present invention, a molten liquid crystalline copolyester fabric having the above-mentioned air permeability and thickness is impregnated with a thermosetting resin mainly composed of an epoxy resin in a semi-cured state. Prepreg.

According to still another embodiment of the present invention, there is provided a printed wiring board for an electronic component, wherein the prepreg is formed as a single layer and laminated in multiple layers.

Hereinafter, the present invention will be described in more detail. The fiber constituting the woven fabric as the insulating reinforcing material of the present invention is composed of a molten liquid crystalline (thermotropic liquid crystal) copolymerized polyester, which is obtained from an aromatic dicarboxylic acid, an aromatic diol, an aromatic hydroxycarboxylic acid, or the like. Which is preferably a compound represented by the formulas (1), (2), (3), (4), (5), (6):
Polymers comprising a combination of repeating structural units exemplified in Chemical formula 7, Chemical formula 8, Chemical formula 9 and / or Chemical formula 10.

[0011]

Embedded image

[0012]

Embedded image

[0013]

Embedded image

[0014]

Embedded image It is. )

[0015]

Embedded image

[0016]

Embedded image

[0017]

Embedded image

[0018]

Embedded image

[0019]

Embedded image

[0020]

Embedded image

The melting point of the polymer is 260-380 ° C., especially 27
The thing of 0-350 ° C is preferred. Here, the melting point is a peak temperature of a main endothermic peak observed by a differential scanning calorimeter. Particularly preferred is a melt-anisotropic aromatic polyester in which the portion composed of the structural units of parahydroxybenzoic acid and 2-hydroxy-6-naphthoic acid represented by Chemical Formula 5 is 80 mol% or more, and particularly to the total amount of both components. Aromatic polyesters having a ratio of the latter component of from 5 to 45 mol% are preferred.

As long as the object of the present invention is not impaired, thermoplastic polymers such as polyethylene terephthalate, polyolefin, polycarbonate, polyarylate, polyamide, polyphenylene sulfide, polyether ether ketone, and fluororesin are used for the molten liquid crystalline polyester polymer. Those obtained by adding a polymer can also be used. Further, titanium oxide, kaolin, silica, barium sulfate, carbon black, pigment, antioxidant, ultraviolet absorber, light stabilizer and the like may be appropriately contained.

The molten liquid crystalline polyester fiber, which is a fiber component of the woven fabric of the present invention, is obtained by melt-spinning the above-mentioned molten liquid crystalline copolyester polymer and then performing a treatment such as solid phase polymerization to increase the degree of polymerization. It is. The spinning method is not particularly limited to the direct spinning method and the sea-island fiber splitting method, and the resulting fiber form is not particularly limited to circular, irregular cross-section fibers, ultrafine fibers, and the like.

The filaments made of the molten liquid crystalline polyester fiber thus obtained are converged into, for example, 10 to 800 filaments to form a multifilament yarn bundle. The diameter of the single filament is adjusted by the subsequent opening or smoothing treatment. In order to obtain a woven fabric having a predetermined air permeability and thickness intended by the present invention, it is essential that the thickness is 3 to 25 μm. If the diameter of the single filament is less than 3 μm, fiber production becomes extremely difficult. On the other hand, if the diameter is more than 25 μm, the flexibility of the single filament itself is impaired, and the fiber opening becomes difficult, so that the object of the present invention cannot be achieved. is there.

The filament yarn bundle is used for the warp and the weft, and the weaving density is, for example, 45 to 70 yarns / 25 mm.
Is woven into a suitable structure such as plain weave, twill weave and satin weave, but plain weave is particularly preferred. The obtained cloth is left as it is or after being subjected to cleaning for removing the sizing agent, and then subjected to a filament opening treatment, for example, by receiving a pressure wave (jet stream) or a vibration wave of a fluid such as water or air, or a calender. By the treatment or the like, the air permeability finally measured by the Frazier tester measurement method is 50c.
m ³ / cm ² / sec or less, more preferably 40 cm ³
/ Cm ² / sec or less. Further, it is indispensable that the thickness of the woven fabric is 150 μm or less as an insulation reinforcing material in a high-performance printed wiring board. The woven fabric having the air permeability and the thickness in such ranges is provided for use as an insulating reinforcing material for the intended multilayer printed wiring board of the present invention.

The reason why it is an essential requirement for the present invention that the woven fabric as the insulating reinforcing material has an air permeability and a thickness below the above upper limits is as follows. In other words, such a property means that when viewed from a microscopic viewpoint, the gap between the warp and the weft threads is in a state in which most of the gaps between the warp and the weft threads are uniformly filled with the opened filaments. Not only can the surface of the woven fabric be smoothed, but also the resin content when used as an insulating reinforcing material can be made uniform. When a printed wiring board is used, the dimensional stability of the printed wiring board caused by internal stress can be improved by relaxing internal stress generated during weaving and removing distortion. The dimensional stability can be improved by reducing the unevenness of the volume ratio of the woven fabric (substrate) per unit volume of the substrate.

The thermosetting resin composition mainly composed of an epoxy resin used in the prepreg of the present invention comprises a resin, a curing agent,
It is composed of a solvent and the like. Examples of the resin include, in addition to the epoxy resin, a BT resin having a bismaleimide and a triazine component, a polyimide resin, a fluoropolymer resin, and a resin derived from monomers of cyanate, dicyanate, and benzodicyclobutane, and the like. Or can be used in combination. A brominated flame-retardant epoxy resin-based resin may also be used. For example, dicyandiamide is used as a curing agent, and dimethylformamide (DM
F), methyl ethyl ketone (MEK), acetone, methyl cellosolve and the like.

The thermosetting resin mainly composed of the epoxy resin is
A prepreg is obtained by impregnating a molten liquid crystalline polyester fiber woven fabric having the above-mentioned air permeability and thickness characteristics to a semi-cured state, in which case there is a single filament in the gap between the warp and the weft of the woven fabric. Therefore, a thermosetting resin can be interposed. However, if the air permeability is 50
When the density is not less than cm ³ / cm ² / sec, the density of single filaments in the gap formed by the warp and the weft becomes low, and it becomes difficult for the thermosetting resin to intervene. It is. Since the dimensional stabilization rate of the laminate is related to the volume ratio of the woven fabric (base material) per unit laminate volume, it is preferable for the dimensional stability that the variation in the resin content be small.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be more specifically described below with reference to examples and comparative examples.

[0030]

EXAMPLES Examples 1 to 3 and Comparative Examples 1 and 2 Plain woven fabrics are woven from a molten liquid crystalline polyester fiber having a monofilament diameter within the range of the present invention shown in Table 1 and subjected to jet water jet treatment or not. After making a reinforcing material, impregnated with the following thermosetting resin composition, and dry-heat-treated at 150 ° C. for 5 minutes to obtain a resin content of 60% by weight.
Was prepared. Further, this prepreg was produced. Four prepregs were laminated, and the pressure was 4 ° C. at 170 ° C.
Pressure molding was performed at 0 kg / cm ² for 60 minutes to produce a printed wiring board. Formulation of thermosetting resin composition Epicoat 5045 (manufactured by Yuka Shell) 80 parts by weight Epicoat 154 (manufactured by Yuka Shell) 20 parts by weight Dicyandiamide 3.2 parts by weight Benzyldimethylamine 0.18 parts by weight Dimethylformamide 20 parts by weight Methyl cellosolve 20 parts by weight Methyl ethyl ketone 25 parts by weight In a comparative example, a woven fabric was prepared, prepreg and printed in the same manner as in the present invention, under the conditions lacking either the monofilament diameter range or the opening treatment conditions of the present invention. A wiring board was manufactured. The air permeability, thickness, and smoothness of each of the woven fabrics according to the examples of the present invention and the comparative examples were measured, and the state of the prepreg, the dimensional stability of the laminate, and the like were also measured. The results are also shown in Table 1.

[0031]

[Table 1] However, in Table 1, methods for measuring various properties are based on the following methods. Air permeability: conforms to the JIS L 1096.66.27.1A method. Flatness: conforms to JIS B0601 “Method for measuring surface roughness”. In addition, SEF-IA manufactured by Kosaka Laboratory Co., Ltd. was used as a universal shape measuring device. For evaluation criteria, see 15
μm was set as a reference, and evaluated on four scales: very good 、, good 、, normal △, and bad x. State of prepreg: Judgment was made based on the presence or absence of voids in the state in which the prepreg was prepared by resin impregnation and semi-curing (no voids, little voids, many voids x). Dimensional stability: based on JIS C 6486. The evaluation criteria are based on 30 ppm both vertically and horizontally. (Very good ◎, good ○, normal △, bad × 4 levels)

As described above, the reinforcing material of the present invention is woven from a yarn having a monofilament diameter of 3 to 25 μm, is subjected to a smoothing treatment, and has an air permeability of 40 cm ³ / cm ² / sec or less. It can be seen that a laminated material for a multilayer printed wiring board can be obtained.

[0033]

According to the present invention, not only excellent workability can be obtained by using a molten liquid crystalline polyester fiber woven fabric as an insulation reinforcing material for a multilayer printed wiring board,
Since an insulating material for a multilayer printed wiring board having excellent dimensional stability and impact resistance in a plane can be obtained, it is possible to sufficiently cope with such a multilayered board, light weight, and compactness by a build-up method. In addition, the production of this reinforcing material does not require any new equipment, and can be carried out with the existing production equipment, so that there is no need for unnecessary investment, the workability is easy, and the productivity is improved. be able to.

Claims (7)

[Claims] 1. A woven fabric woven from a warp and a weft composed of a multifilament yarn bundle of a molten liquid crystalline copolyester fiber, having a thickness of 150 μm or less and a water pressure drop of 1.27 cm. Air permeability is 50cm ³
An insulating reinforcing material for a multilayer printed wiring board, comprising a molten liquid crystalline copolymerized polyester fiber woven fabric having a density of not more than / cm ² / sec or less. 2. The insulation reinforcing material for a multilayer printed wiring board according to claim 1, wherein the air permeability is 40 cm ³ / cm ² / sec or less. 3. The insulation reinforcing material for a multilayer printed wiring board according to claim 1, wherein a single filament diameter of each yarn of the molten liquid crystalline copolyester fiber woven fabric is 3 to 25 μm. 4. The molten crystalline copolyester fiber woven fabric is a woven fabric obtained by reducing air permeability and smoothing after greige or cleaning.
4. The insulation reinforcing material for a multilayer printed wiring board according to any one of items 3 to 3. 5. The multilayer print according to claim 1, wherein the molten liquid crystalline copolyester fiber woven fabric is a woven fabric obtained by subjecting a filament to a fiber opening treatment by jet flow after greige or cleaning. Insulation reinforcement for wiring boards. 6. A prepreg obtained by impregnating a thermosetting resin containing an epoxy resin as a main component in a semi-cured state with the insulating reinforcing material comprising the molten liquid crystalline copolyester fiber woven fabric according to claim 1. 7. A printed wiring board for electronic parts, wherein each layer is formed from a multilayer laminate comprising the prepreg according to claim 6.