JP2010138355A - Prepreg sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the flexibility of a prepreg sheet prepared by carrying an epoxy resin composition containing an inorganic filler on a substrate sheet in a semi-cured state. <P>SOLUTION: The prepreg sheet is prepared by carrying the epoxy resin composition containing the inorganic filler on the substrate sheet in a semi-cured state, wherein a fabric cloth is used in the substrate sheet; and a thermal adhesiveness fiber that has a core-in-sheath structure, in which a core portion is formed with polyester resin and a sheath portion is formed with low-melting polyester resin of which the melting point is lower than that of the polyester resin used in the core portion, is used in a thread composing the fabric cloth. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a prepreg sheet in which an epoxy resin composition containing an inorganic filler is supported on a base sheet in a semi-cured state.

Conventionally, a prepreg sheet in which a glass cloth or the like is used as a base sheet and a semi-cured epoxy resin composition is supported on the base sheet is widely used, and a copper foil is laminated on such a prepreg sheet. Laminated sheets are widely used as printed circuit board forming materials in electronic component applications.
Such a prepreg sheet usually does not have sufficient flexibility because the glass cloth itself is formed in a state in which the yarn in which a plurality of glass fibers are bundled is tightly woven into a high bending strength. .
In contrast to this, in order to impart flexibility to the prepreg sheet, it is conceivable to use a base sheet woven with yarn made of soft resin fibers instead of glass cloth.

By the way, it is known that an epoxy resin composition becomes brittle when it is brought into a semi-cured state called a B stage, and cracks and the like are caused by a slight stress.
Therefore, even if the base sheet itself is made flexible, the epoxy resin composition is removed from the base sheet by the stress applied to the prepreg sheet unless it has excellent adhesion between the base sheet and the epoxy resin composition. There is a risk of falling off.
On the other hand, resin fibers excellent in adhesion to the epoxy resin composition have not been sufficiently studied so far, and it is difficult to impart flexibility to the prepreg sheet.

  In recent years, as shown in Patent Document 1 below, attempts have been made to improve the thermal conductivity of a prepreg sheet using an epoxy resin composition containing an inorganic filler, but the inorganic filler is contained. In the epoxy resin composition, embrittlement in the B-stage state is remarkable as compared with the case where no inorganic filler is included, and it is much more difficult to prevent the resin sheet from falling off.

For this reason, in the prepreg sheet having excellent thermal conductivity in which the epoxy resin composition containing the inorganic filler is supported on the base sheet in a semi-cured state, it is particularly difficult to impart flexibility. It has become.
Therefore, it is difficult to ensure flexibility even in a laminated sheet obtained by laminating a prepreg sheet in which an epoxy resin composition containing an inorganic filler is supported on a base sheet in a semi-cured state and a metal foil. It has become.

JP 2008-274046 A

  An object of the present invention is to solve the problems as described above, and the flexibility of a prepreg sheet in which an epoxy resin composition containing an inorganic filler is supported on a base sheet in a semi-cured state. Improvement is an issue.

  As a result of intensive studies on resin fibers excellent in adhesion to the epoxy resin composition, the present inventors have found that the epoxy resin composition has high adhesion to the polyester resin fiber and has a core-sheath structure. The heat-fusible fiber in which the core part is formed of a polyester resin and the sheath part is formed of a low-melting polyester resin having a lower melting point than the polyester resin used for the core part is an epoxy resin composition. The inventors have found that it is easy to make close contact, and have completed the present invention.

  That is, the present invention relating to a prepreg sheet for solving the above problems is a prepreg sheet in which an epoxy resin composition containing an inorganic filler is supported on a base sheet in a semi-cured state, A woven fabric is used for the material sheet, and the yarn constituting the woven fabric has a core-sheath structure, the core is formed of a polyester resin, and has a melting point higher than that of the polyester resin used for the core. The heat-fusible fiber in which the sheath part is formed with the low melting point polyester resin of low is used.

In the prepreg sheet of the present invention, a woven fabric is used as the base sheet, and the yarn constituting the woven fabric has a core-sheath structure, and the core portion is formed of a polyester resin. Adhesion between the base sheet and the epoxy resin composition because the heat-fusible fiber in which the sheath part is formed of a low-melting-point polyester resin having a lower melting point than the polyester resin used in the part is used Can be improved as compared with the conventional prepreg sheet.
And since this base material sheet is formed with the heat-fusible fiber by which a polyester resin is used, it can form a flexible prepreg sheet compared with a glass cloth.
Therefore, by using an epoxy resin composition containing an inorganic filler, the flexibility can be improved even for a prepreg sheet that has been improved in thermal conductivity.
That is, according to the present invention, the flexibility of a prepreg sheet in which an epoxy resin composition containing an inorganic filler is supported on a base sheet in a semi-cured state can be improved.

Hereinafter, preferred embodiments of the present invention will be described (based on the accompanying drawings).
FIG. 1 is a cross-sectional view showing a prepreg sheet of this embodiment.
Moreover, FIG. 2 is sectional drawing which shows the cross-section of the heat-fusible fiber used for the prepreg sheet of this embodiment.
Furthermore, FIG. 3 is a side view showing an outline of the manufacturing process of the prepreg sheet and the manufacturing process of the laminated sheet performed thereafter.

  As shown in FIG. 1, a prepreg sheet 1 according to this embodiment is supported in a state in which a base sheet 2 is impregnated with a semi-cured epoxy resin composition 3 and is formed into a sheet shape. ing.

  The base sheet 2 is a woven fabric in which yarns 20 made of heat-fusible fibers 20a are used, and the heat-fusible fibers have a core-sheath structure, and the core portion 20a1 is a polyester. The sheath portion 20a2 is formed of a low melting point polyester resin that is formed of resin and has a lower melting point than the polyester resin used for the core portion 20a1.

On this base sheet 2, yarns 20 having a thickness of 50 to 150 μm and formed of the heat-fusible fiber 20 a are plain woven at a weave density of 40 to 80 pieces / inch respectively. A woven fabric is preferably used.
The base sheet 2 preferably has a basis weight of 10 to 50 g / m ² .

  The yarn 20 may be a single yarn made of the heat-fusible fiber, or may be twisted even if a plurality of the heat-fusible fibers are twisted. An “arrangement yarn” may be used, and the heat-fusible fiber 20a constituting the yarn 20 is usually 25 to 300 dTex.

In the present embodiment, the core portion 20a1 is made of a polyester resin such as a polyethylene terephthalate resin, and the sheath portion 20a2 is a low-melting polyester resin having a lower melting point than the polyester resin used for the core portion 20a1. Is used.
Among these, as the material for forming the core portion 20a1, a polyethylene terephthalate resin in which a substantially repeating unit has only a condensed structure of terephthalic acid and ethylene glycol as described below is preferable.

  A polyethylene terephthalate resin not containing a polymerization component other than terephthalic acid and ethylene glycol is preferably used as the material for forming the core 20a1, while the material for forming the sheath 20a2 is isophthalic acid in addition to ethylene glycol and terephthalic acid. It is preferable that it is a low melting-point polyethylene terephthalate resin which contains as a copolymerization component.

In addition, the thread | yarn 20 which comprises the base material sheet 2 does not need to be comprised only with the above heat-fusible fibers 20a, if necessary, natural fibers, such as cotton, wool, silk, polyethylene resin fiber, A synthetic resin fiber such as polypropylene resin fiber, polyamide resin fiber, polyimide resin fiber, or fluororesin fiber, or a yarn in which inorganic fibers such as carbon fiber, glass fiber, rock wool, or metal fiber are mixed with the heat-fusible fiber 20a is used. It may be what was made.
However, from the viewpoint of obtaining a prepreg sheet rich in flexibility, the base sheet 2 is preferably composed only of the heat-fusible fiber 20a.

The epoxy resin composition 3 supported on the base sheet 2 in a semi-cured state contains an epoxy resin and an inorganic filler.
Whether or not the epoxy resin composition is in a semi-cured state can be determined by using a differential scanning calorimeter (DSC) based on whether or not a thermal change due to the curing reaction of the epoxy resin is observed.

Examples of the epoxy resin used in the epoxy resin composition include a bisphenol type and a novolac type. Examples of the bisphenol type include a bisphenol A type epoxy resin and a bisphenol F type epoxy resin, and Examples thereof include those obtained by modifying these with CTBN, and those having an epoxy equivalent of 180 to 2500 g / eq. In addition, this epoxy equivalent can be calculated | required based on JISK7236.
Of these, a bisphenol A type epoxy resin having an epoxy equivalent of any one of 900 to 2500 g / eq, which is not modified such as CTBN modification, is preferable.
Examples of the novolak type include a cresol novolak type epoxy resin and a phenol novolak type epoxy resin. For example, an o-cresol novolak type epoxy resin having any softening point of 70 to 90 ° C. it can. The softening point can be measured by the ring and ball method of JIS K 7234.
These epoxy resins can be contained in the epoxy resin composition alone or in a mixed state.

As the inorganic filler, from the viewpoint of imparting excellent thermal conductivity to the prepreg sheet 1, it is preferable to contain a larger amount of high thermal conductivity.
Examples of such inorganic fillers include boron nitride particles, aluminum nitride particles, silicon nitride particles, gallium nitride particles, aluminum oxide particles, silicon carbide particles, silicon dioxide particles, and diamond particles having a particle size of 10 nm to 100 μm. Can be mentioned.
Among these, boron nitride particles are suitable in that they have a high thermal conductivity while being relatively inexpensive.
The blending ratio of such an inorganic filler is appropriately determined according to the use of the prepreg sheet 1, but peeling occurs with a slight stress in a prepreg sheet in which a glass cloth is used as a base sheet. In view of the fact that the effect of the present invention can be more prominent because it is difficult to carry it, it is preferably blended in the solid content of the epoxy resin composition at a ratio of 40% by volume or more.

In addition, the epoxy resin composition may contain a so-called curing agent or accelerator for curing the epoxy resin.
The curing agent is not particularly limited, and examples thereof include amine curing agents such as diaminodiphenyl sulfone, dicyandiamide, diaminodiphenylmethane, and triethylenetetramine, phenol novolac resins, aralkyl type phenol resins, and dicyclopentadiene modified phenols. Resin, phenolic curing agents such as naphthalene type phenolic resin and bisphenolic phenolic resin, acid anhydrides and the like can be used.
In particular, when the prepreg sheet is strongly required to have electrical insulation, phenol novolac resin, diaminodiphenyl sulfone, and the like are preferable in that it is easy to ensure reliability in electrical characteristics.
The curing accelerator is not particularly limited, but an amine-based curing accelerator such as imidazoles, triphenyl phosphate (TPP), or boron trifluoride monoethylamine is a curing reaction during storage of the prepreg sheet. It is suitable at the point which can suppress progress of this.

  In addition to the above epoxy resin, inorganic filler, curing agent, accelerator, dispersant, tackifier, anti-aging agent, antioxidant, processing aid, stabilizer, antifoaming agent, flame retardant, Rubbers such as thickeners and pigments, and those generally used as plastic compounding chemicals can be appropriately contained in the epoxy resin composition.

  Next, such a prepreg sheet 1 and a method for producing a laminated sheet using the prepreg sheet will be described with reference to FIG.

In the manufacturing method of the prepreg sheet 1 and the laminated sheet in the present embodiment, an epoxy resin varnish in which the epoxy resin composition is liquefied in advance is produced, and then the produced epoxy resin varnish is used as shown in FIG. The prepreg sheet 1 is produced by continuously coating and drying a long belt-like substrate sheet.
As a method for producing this epoxy resin varnish, since the softening point of a bisphenol type epoxy resin or a novolac type epoxy resin is usually 120 ° C. or lower, it is heated to a temperature higher than this softening point (for example, 120 ° C. or higher). The method of obtaining a liquid epoxy resin composition by doing is mentioned.
Moreover, it can replace with such a method and can produce a liquid epoxy resin composition using the organic solvent in which an epoxy resin is soluble.
For example, a liquid epoxy resin composition can be prepared by dispersing an epoxy resin, an inorganic filler, a curing agent, an accelerator, and other compounding agents in an organic solvent such as methyl ethyl ketone.

In addition, in FIG. 3, the epoxy resin varnish 3r produced using the organic solvent is applied to the base material sheet 2s continuously drawn out from the base material sheet roll 2r in which the belt-like base material sheet 2s is wound in a roll shape. A mode that it coats continuously with the spray coater 4 is shown.
In this embodiment, after this coating, the base sheet 2s is introduced into the drying furnace 5 in a state where the epoxy resin varnish 3r is supported, and is heated and dried to produce a strip-shaped prepreg sheet 1, The belt-shaped prepreg sheet 1s is wound into a roll shape to form a prepreg sheet roll 1r.

  In addition, when the space | interval of the thread | yarn which comprises the base material sheet 2s is large open and it is difficult to make the base material sheet 2 impregnate the epoxy resin varnish 3r by such coating and to carry it, for example, a base material The sheet is supported by a release-treated film from the lower surface side, and the film is introduced into the drying furnace 5 while being heated and dried while maintaining the state in which the epoxy resin varnish 3r is supported on the base sheet 2s by the film. You can do it.

The strip-shaped prepreg sheet 1s thus obtained is, for example, drawn out from the prepreg sheet roll 1r by a predetermined length as shown in FIG. The laminated prepreg sheet 1 and the metal foil M are superposed on each other and heat-pressed under a temperature condition that does not completely cure the epoxy resin composition with a hot press 8 to produce a laminated sheet L that can be thermally bonded. Can do.
What is necessary is just to select the metal foil at this time suitably according to a use, and if it is for printed circuit boards, 5-300 micrometer-thick electrolytic copper foil, rolled copper foil, electrolytic aluminum foil, rolled aluminum foil, nickel plating copper foil And aluminum / copper bilayer clad foil.

Further, such a laminated sheet is bonded to a copper plate, an aluminum plate, a SUS plate, or the like, and a metal foil is etched to form a circuit, thereby being used as a metal base circuit board.
Furthermore, it is also possible to produce a laminated sheet in which metal foils are laminated on both sides and to make a multilayer circuit board material.

The prepreg sheet and laminated sheet according to the present embodiment can be suitably used not only for printed circuit board applications but also for applications that require thermal conductivity and electrical insulation.
For example, the prepreg sheet is interposed between a heat generating member such as a power module and a heat radiating member such as a heat radiating fin, and the power module and the heat radiating fin are pressed close to each other and the epoxy resin composition is cured. While heating up to the reaction temperature, one surface side is thermally bonded to the power module, and the other surface side is thermally bonded to the radiation fin, and can be used as a thermally conductive adhesive sheet.

Normally, when a prepreg sheet is produced using a plain woven fabric as a base sheet, pressure is concentrated at the portion where the yarns are overlapped during pressing and misalignment occurs, and the pressure is not uniform. As a result, the adhesive force tends to vary.
On the other hand, the prepreg sheet of the present embodiment uses a polyester resin having a melting point lower than that of the core part in the sheath part. The misalignment of the yarn can be suppressed and the adhesive force can be made uniform.

Furthermore, the prepreg sheet and laminated sheet in the present embodiment are rich in flexibility because the yarn constituting the base sheet is formed of heat-fusible fibers using a polyester resin, and should be handled with care. I don't need it.
For example, handling with a roll-to-roll as shown in FIG. 3 is possible, and improvement in work efficiency can be expected not only during manufacturing but also during processing.
Also, in the accommodation form by roll winding, the bending radius can be reduced, so that it is not necessary to use a thick core material to prevent the epoxy resin composition from peeling, and the accommodation space can be reduced compared to the conventional case. Can be planned.

In the present embodiment, the case where the prepreg sheet is configured as described above and manufactured as described above is exemplified, but the present invention is not limited to the above example.
For example, it is possible to further provide a process for improving the adhesion between the base sheet and the epoxy resin composition.

This will be described more specifically. In the prepreg sheet according to the present embodiment, the yarn constituting the base sheet is formed of heat-fusible fibers using a polyester resin.
Usually, polyethylene terephthalate resin has a melting point of 250 ° C. or higher, and other polyester resins are similarly heated to a melting temperature of epoxy resin or a drying temperature for volatilizing an organic solvent (for example, 100 to 160 ° C.). It has a higher melting point.
Therefore, for example, even when an epoxy resin varnish is produced by a method using an organic solvent and dried at a temperature of 100 to 160 ° C., the epoxy resin varnish is obtained by thermally melting the epoxy resin at a heating temperature of about 100 to 160 ° C. Even when manufactured, there is a sufficiently low possibility of causing a problem in supporting the substrate sheet.

Further, the heat-fusible fiber constituting the base sheet has a core-sheath structure, and the sheath 20a2 is composed of a low-melting polyester resin having a lower melting point than the polyester resin used for the core 20a1. Therefore, the adhesiveness of a base material sheet and an epoxy resin composition can be improved using this difference in melting point.
That is, the contact temperature between the epoxy resin composition and the heat-fusible fiber by contact with the heat-melted epoxy resin varnish or heat when the epoxy resin varnish using the organic solvent is heated and dried on the base sheet, The adhesion between the epoxy resin composition and the heat-fusible fiber can be improved in the vicinity of the melting point of the low-melting polyester resin constituting the sheath 20a2 or higher than the melting point.

  For example, in a fiber that does not have a core-sheath structure and is made of the same resin up to the inside, the inside of the fiber softens when heated to the melting point temperature of the resin constituting the fiber for the purpose of improving adhesion. Therefore, the fiber will be cut, but the base sheet according to the present embodiment is made of the heat-fusible fiber and the epoxy resin composition by adjusting the temperature conditions in the process while suppressing such a fear. Adhesion can be improved.

In other words, the melting point of the low melting point polyester resin constituting the sheath part 20a2 is made sufficiently low than that of the polyethylene terephthalate resin while the core part 20a1 is made of a general polyethylene terephthalate resin having a melting point of 250 ° C. or higher. By setting the temperature to 160 ° C. or lower, even when general conditions are set, the adhesion of the epoxy resin composition to the substrate sheet can be made excellent.
That is, since the melting of the epoxy resin and the drying for volatilizing the organic solvent are usually performed in a temperature range of 100 to 160 ° C., a melting point of 160 ° C. or less (preferably as a resin for constituting the sheath portion 20a2). Can improve the adhesiveness between the base sheet and the epoxy resin composition by adopting a material having a melting point of 140 ° C. or lower.
In addition, about melting | fusing point of this resin, it can obtain | require by measuring a melting peak value by the thermal analysis with the temperature increase rate of 10 degrees C / min using DSC.

  Moreover, in addition to the method for improving the adhesion between the base material sheet and the epoxy resin composition by selecting the material of the core portion 20a1 and the sheath portion 20a2, for example, hot pressing is performed on the prepreg sheet once produced. Therefore, the adhesion can be further improved.

For example, the prepreg sheet is hot-pressed at a temperature not lower than the melting point of the low-melting polyester resin constituting the sheath portion 20a2 and not higher than the melting point of the polyester resin constituting the core portion 20a1, and the base sheet and the epoxy resin composition It is possible to improve the adhesion to objects.
At that time, the degree of curing of the epoxy resin composition (B stage state) can be adjusted at the same time, and the quality of the prepreg sheet can be made uniform.

Thus, a prepreg sheet excellent in flexibility can be obtained while the epoxy resin composition containing an inorganic filler is supported in a semi-cured state.
Although not described in detail here, conventionally known technical matters in the prepreg sheet can also be adopted in the present invention.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

Example 1
An epoxy resin composition containing 60% by volume of aluminum oxide particles has a core-sheath structure, the core is formed of a polyester resin, and has a lower melting point than the polyester resin used in the core Thickness 130 μm × width 20 mm × length 50 mm supported in a semi-cured state on a base sheet (weight per unit 20 g / m ² ) using a heat-fusible fiber having a sheath part formed of a polyester resin A prepreg sheet having a shape was prepared and used as the prepreg sheet of Example 1.

(Comparative Example 1)
A prepreg sheet having a thickness of 130 μm, a width of 20 mm, and a length of 50 mm was produced without using the base material sheet, and used as a prepreg sheet of Comparative Example 1.

(Comparative Example 2)
A prepreg as in Example 1 except that a base sheet having the same structure as the base sheet used in Example 1 was used except that polyester fibers not having a core-sheath structure were used. A sheet was prepared and used as a prepreg sheet of Comparative Example 1.

(Evaluation 1: Bending test)
Each state when the prepreg sheet of Example 1 and the prepreg sheet of Comparative Example 1 were bent so as to be bent at an angle of 90 degrees at the intermediate portion in the length direction was observed.
As a result, the prepreg sheet of Comparative Example 1 was completely broken, whereas the prepreg sheet of Example 1 was broken as in Comparative Example 1 to the extent that some cracks were observed in the bent portion. I couldn't see how it reached.

(Evaluation 2: Adhesive strength test)
A prepreg sheet of Example 1 was sandwiched between an electrolytic copper foil having a thickness of 35 μm and an aluminum plate having a thickness of 2 mm, and heat bonding was performed by a hot press to prepare a test piece for peeling off the copper foil.
Moreover, the test piece for copper foil peeling was similarly produced using the prepreg sheet of the comparative example 2.
About each of these test pieces, the 90 degree | times peeling test of the copper foil was implemented according to JISC6481.
The measurement was performed in two ways: in the initial state and after performing a solder heat resistance test in which the test piece was floated in a 260 ° C. solder bath for 2 minutes.
As a result, the minimum value and the maximum value of the peel strength in each measurement were as shown in Table 1 below.

As can be seen from Table 1, the substrate sheet used in the prepreg sheet of the present invention shows excellent adhesion to the epoxy resin composition.
It can also be seen that there is little variation in adhesion.
From the above, it can be seen that according to the present invention, it is possible to provide a flexible prepreg sheet and laminated sheet.

Sectional drawing of the prepreg sheet | seat in one Embodiment. Sectional drawing showing the heat-fusible fiber used for the prepreg sheet | seat of the embodiment. The side view which shows the schematic manufacturing process of the prepreg sheet | seat and laminated sheet of one Embodiment.

Explanation of symbols

  1: Prepreg sheet, 2: Base sheet, 3: Epoxy resin composition, 20: Yarn, 20a: Heat-fusible fiber, 20a1: Core part, 20a2: Sheath part, L: Laminated sheet, M: Metal foil

Claims (4)

An epoxy resin composition containing an inorganic filler is a prepreg sheet carried on a base sheet in a semi-cured state,
A woven fabric is used for the base sheet, and the yarn constituting the woven fabric has a core-sheath structure, the core portion is formed of a polyester resin, and the polyester resin used for the core portion is used. A prepreg sheet characterized by using a heat-fusible fiber having a sheath part formed of a low-melting polyester resin having a low melting point.   The prepreg sheet according to claim 1, wherein the proportion of the inorganic filler in the solid content of the epoxy resin composition is 40% by volume or more.   The prepreg sheet according to claim 1 or 2, wherein the heat-fusible fiber has a core portion formed of a polyethylene terephthalate resin and a sheath portion formed of a low melting point polyethylene terephthalate resin containing isophthalic acid as a copolymerization component.   The base material sheet is a woven fabric in which a yarn having a thickness of 50 to 150 µm is woven at a woven density of 40 to 80 yarns / inch. The prepreg sheet according to item.

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