JPS63267514A - Material for flexible printed circuit board - Google Patents

Abstract

PURPOSE:To obtain excellent resistance to flexure fatigue, dimensional stability to heat and electrical resistance, by impregnating specific glass cloth with thermosetting resin. CONSTITUTION:It is necessary that a glass fiber composed of a monofilament whose mean diameter falls within a range of 2.0-4.8mum is used at least for either of warp or weft, in glass cloth. In case where a mean diameter of the monofilament is less than 2.0mum, impregnation properties of resin varnish among the filaments are apt to become insufficient at the time of manufacturing of those prepregs and it becomes difficult to produce stably as a long fiber. On the one hand, in case where the mean diameter of the monofilament exceeds 4.8mum, sufficient resistance to flexure fatigue cannot be afforded. Then it is necessary to make a ratio (warp/weft) of weaving density of the warp of the glass cloth to that of the weft of the glass cloth fall within a range of 0.95-1.35. Although a thermosetting resin composition to be used is selected according to capacity of a circuit board to be required, epoxy resin or polyimide resin is suitable.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a material for a flexible printed wiring board that has excellent bending fatigue resistance, heat-resistant dimensional stability, and electrical insulation.

(Prior Art) In recent years, demand for flexible printed wiring boards has been increasing as electrical and electronic devices have become smaller, lighter, thinner, and more dense. Traditionally, materials for flexible printed wiring boards and their coverlay films are
Polyethylene terephthalate film and polyimide film are mainly used, and glass cloth reinforced epoxy resin sheets and polyester paper are also used.

Although polyester film has excellent mechanical properties, electrical properties, and chemical resistance, it cannot be said to have sufficient heat-resistant dimensional stability. is large, and its uses are severely limited.

In addition, polyimide film has excellent mechanical properties and heat-resistant dimensional stability.

It does not have sufficient water resistance, and requires sufficient moisture control during the coverlay lamination process and soldering process.

Deterioration of electrical properties due to moisture absorption is also a problem.

One of the problems is the high price. Furthermore, the glass cloth reinforced epoxy resin sheet has electrical insulation properties, heat resistance, dimensional stability,
It has excellent chemical resistance, moisture absorption resistance, etc.

The fatal point was that the flexibility required for flexible wiring boards was extremely poor. In other words, the glass fibers constituting the glass cloth used in conventional glass cloth-reinforced flexible printed wiring boards have an average monofilament diameter of 5 μm or more, and while the glass cloth itself is weak against bending, it is also impregnated with epoxy resin or the like.

Even the cured sheet had low flexibility and extremely poor bending fatigue resistance. Furthermore, although aromatic polyamide paper is sometimes used in place of the film, there are many practical problems such as resistance to dimensional changes and curling.

As described above, all conventional flexible printed wiring boards have some problems.

(Problems to be Solved by the Invention) The present invention solves the conventional problems as described above, and its purpose is to maintain the excellent performance of the conventional glass cloth reinforced resin sheet and The object of the present invention is to provide a material for flexible printed wiring boards that has improved bending fatigue resistance, which is the biggest drawback.

(Means for Solving the Problems) In order to solve these problems, the present inventors have made extensive studies and found that the above conventional problems can be solved by using a specific glass cloth. This is what led us to the present invention.

That is, in the present invention, glass fibers made of monofilaments having an average diameter of 2.0 to 4.8 μm are arranged in at least one of the warp and weft, and the ratio of the warp weave density to the weft weave density is 0695 to 1. The gist of the invention is a material for a flexible printed wiring board, which is characterized by impregnating glass cloth No. 35 with a thermosetting resin.

Hereinafter, one aspect of the present invention will be explained in detail.

Firstly, in the flexible printed wiring board material of the present invention, the average diameter of the glass fiber monofilaments constituting the glass cloth is important, and the average diameter is 2.0 to 4.8μ.
It is necessary to use glass fiber made of monofilament in the range of m for at least one of the warp and weft. The average diameter of the monofilament is preferably 2.5~
It is 4.5 μm, more preferably 2.5 to 4.0 μm. If the average diameter of the monofilaments is less than 2.0 μm, the impregnation of resin varnish between the filaments is likely to be insufficient when making prepreg from them, and it is difficult to stably produce long glass fibers. This may be difficult and is not suitable for practical use. On the other hand, when the average diameter of the monofilament exceeds 4.8 μm.

It is not preferred because it does not have sufficient flexibility and cannot provide sufficient bending fatigue resistance.

Here, the average diameter of the monofilaments constituting the glass fibers is a value measured based on JIS-R-3420, 5, and 6.

In the present invention, the number of monofilaments of the glass fibers used as the warp and weft is usually preferably 50 to 1,600, particularly preferably 100 to 800.

In addition, the number of twists applied to glass fiber is "usually 2.5 Ja
The number of twists is 0.5 to 1.5 times per n, but non-twisted yarns or single-ply yarns may be used.

Next, the ratio (warp/weft) of the weaving density of the warp to the weaving density of the weft of the glass cloth of the present invention (warp/weft) must be 0.95 to 1.35, preferably 1. OO~1.30. Even if the ratio is smaller or larger than this, when a flexible printed wiring board is manufactured, the difference in dimensional change in the longitudinal and latitudinal directions due to heat increases, which is not preferable.

Here, the weaving density of warp or weft means 2 of warp or weft.
This is the number of hits per 5B. The number of warp threads is the number of threads that are threaded along the weaving winding direction of the glass cloth, and the weft thread number is the number of weft threads that are threaded in a direction that is almost perpendicular to the weaving winding direction. It is the number of hits.

In the present invention, the number of glass fibers is usually 1.

The number of warp threads is selected as appropriate from 30 to 70 threads/25 mm, and the number of weft threads is 30 to 70 threads/25 mm. Preferably, the number of warp threads is 40 to 65/25 am,
The number of weft threads is 30 to 60/25 threads.

Since the glass composition of the glass fiber used in the present invention is required to have electrical insulation properties, alkali-free glass is preferable, such as E glass and D glass.

Examples include silica glass and quartz glass, which have a large silica component.

The glass fibers constituting the glass cloth of the present invention can be obtained according to a conventional method for producing glass fibers. That is, a method of melt-spinning a glass raw material with a certain glass composition, a hydrolysis wet spinning method (so-called sol-gel method),
Alternatively, any method may be used, such as spinning a large-count yarn using the method described above and treating it with acid or alkali to make it fine.

but.

Usually, a method is adopted in which melt spinning is performed using a nozzle with a modified nozzle hole diameter, number of holes, and hole arrangement. After applying a sizing agent to the yarn obtained in this way.

It is made into glass cloth through the usual weaving process, namely warping, gluing, and weaving. After that, the glass cloth is degreased, and then a surface treatment agent is applied to the surface of the glass cloth in an amount of about 0.01 to 1% by weight in order to increase the affinity with the resin impregnated into it. The glass cloth used in the present invention. Here, the surface treatment agent 2 is used in the form of a partially hydrolyzed solution of various conventionally known organic silane compounds. As the organic silane compound, for example, epoxysilane, aminosilane, etc. are used. Furthermore, additives such as pigments and activated carbon may be added to the surface treatment agent.

Furthermore, examples of the thermosetting resin composition used in the present invention include epoxy resin, phenol resin, polyester resin, and polyimide resin.

Silicone resins, fluororesins, etc., or modified resins based on these resins, etc. are used. Additionally, these resins also contain hardeners if necessary.

Use with addition of curing accelerator.

Furthermore, if the above single resin alone does not have sufficient flexibility or toughness and is insufficient as an insulating layer for a flexible printed wiring board, it is possible to combine the various resins mentioned above or add various resin components. Good examples of such resin components include -functional and/or polyfunctional vinyl monomers, acrylic monomers, oligomers, polymers, copolymers thereof, rubber-based polymers, and polyethers.

Examples include polyurethane.

Furthermore. In addition to the above resins, lubricants such as silica and talc, flame retardants such as halides, phosphorus compounds, aluminum hydroxide, and antimony trioxide, antioxidants, and ultraviolet absorbers 1 Polymerization inhibitors within the range that does not impair the effects of the present invention stabilizers, mold release agents, and other talc, titanium oxide, and fluoropolymer fine particles.

Pigments, dyes, inorganic and organic fillers such as calcium carbide, etc. can be added.

The thermosetting resin composition is appropriately selected depending on the required performance of the flexible printed wiring board, and epoxy resins and polyimide resins are preferred, but other resins may be used as necessary. Further, the characteristics of the above resins vary depending on their type, but taking epoxy resin as an example, the molecular weight is 300 to 4000. Epoxy equivalent weight 13
A bisphenol type epoxy resin having a molecular weight of 0 to 5500 is suitable, and if necessary, a novolac type epoxy resin, an alicyclic epoxy resin, a brominated epoxy resin, a polyglycol type epoxy resin, etc. are used alone or in combination. Further, as the curing agent for the epoxy resin, dicyandiamide is preferred, but other accelerators may also be used.

The material for a flexible printed wiring board of the present invention is made into a flexible printed wiring board by using this as a base material and forming a conductive pattern on at least one side thereof. As a method for forming conductive patterns.

Conventional methods such as additive methods and subtractive methods are employed. In the case of subtractive law.

A sheet in which a base material and metal foil are laminated is manufactured in advance.

In this case, the metal foil and the base material may be laminated via an adhesive, or the base material with an adhesive may be laminated without using an adhesive.

Furthermore, the flexible printed wiring board material of the present invention can also be used for a coverlay of a flexible printed wiring board. Furthermore, the flexible printed wiring board material of the present invention also includes materials for flat cables, integrated circuit chip carrier tapes, and the like.

The flexible printed wiring board material of the present invention is:

It may be used only for the substrate of the above-mentioned flexible printed wiring board, it may be used only for the coverlay, or it may be used for both the substrate and the coverlay.

The above-mentioned material for a flexible printed wiring board of the present invention can be obtained in the following manner. That is, basically, a so-called prepreg is obtained by impregnating a glass cloth with a solution of a thermosetting resin composition, followed by drying, removing the solvent, and curing. However, when attaching metal foil without using an adhesive, heat and pressure are applied to attach the prepreg while it still has thermal adhesive properties.

Thereafter, the resin is cured to produce a flexible printed wiring board material with desired performance. Alternatively, instead of impregnating a glass cloth with a solution of the resin composition, a solid resin sheet may be formed from the resin composition in advance, and the glass cloth may be sandwiched between the resin sheets and heated and pressurized. Alternatively, the glass cloth may be impregnated with the resin composition.

The glass cloth is impregnated with the resin composition using a normal impregnating machine 9, such as a horizontal or vertical impregnating machine.

Impregnate once or multiple times. Alternatively, the solution of the resin composition may be coated on one side of the glass cloth and then coated on the opposite side. For drying after impregnation or coating, a drying temperature appropriate for each resin component constituting the resin composition is adopted. Furthermore, if the glass cloth is sticky after drying, it should be treated in an appropriate process.

A release sheet may be attached to both sides of the glass cloth.

As the release sheet, 1, ordinary cellulose paper or film coated with a release agent, polypropylene film, polyvinyl alcohol film, etc. are used.

(for production) The flexible printed wiring board material of the present invention is as follows.

As mentioned above, it is made by impregnating thermosetting resin into a glass cloth woven from glass fibers with a narrow average monofilament diameter within a specific range, so the flexibility of the thin glass fibers is reflected. Excellent in

Therefore, a flexible printed wiring board having excellent bending fatigue resistance can be obtained. Moreover,
Since the base material is monofilament glass cloth with a small average diameter, the impregnation of thermosetting resin between the monofilaments is good, and it has excellent heat-resistant dimensional stability, electrical properties such as electrical insulation, and adhesion to metals. It is also excellent in sex.

(Example) Next, the present invention will be explained in detail based on examples.

In the following examples, the properties were measured and evaluated as follows.

(1) Peeling resistance strength of copper foil (g/dragon) In accordance with JIS-C-6481, one end of the copper foil was peeled off from the copper foil-clad laminate of a sample of 9 width 1 (h + m), and the The copper foil was then pulled in the direction of the other end using an autograph at a tensile speed of 50 m/min to measure the peel strength at 180@ peel.

(2) Surface resistance (ohm) Based on JIS-C-6481, temperature 20°C, relative humidity 65%.

When processing for 90 hours (in Table 2, A
), and in addition to the above treatment, the temperature was 40°C.

Measurements are made for the case of further treatment at a relative humidity of 90% and a treatment time of 96 hours (denoted as B in Table 2).

(3) Solder resistance In accordance with JIS-C-6481, the sample is immersed in a solder bath at 260° C. for 30 seconds, and then the presence or absence of “blister” or the like is visually determined.

(4) Bending fatigue resistance A copper foil pattern with a width of 21 mm is made in the center of a substrate with a width of 15 fins in a direction perpendicular to the width direction, and measured in accordance with JIS-P-8115. When measuring, a load of 500g was applied.

While applying electricity to the copper foil pattern, the diameter of the bent part of the board is 1
The board is bent in such a manner that the number of times the board is bent in such a manner that the number of times the board is bent in one energization period is determined in the longitudinal direction and in the latitudinal direction.

Examples 1-3. Comparative example 1. Using warp and weft yarns made of 2E glass fibers shown in Table 1, five types of glass fabrics having the same woven fabric properties shown in Table 1 were manufactured. The glass fibers constituting the warp and weft were coated with aminosilane as a surface treatment agent. In addition, the number of twists of the warp yarns is i, o times/2.54.
cm (Z), the number of twists of the weft is 0.7 times/2.54c
m(Z) was used. Furthermore, the glass cloth F in Table 1
For hl, 3.4, the average monofilament diameter and number of monofilaments are different, but the weight and thickness of the glass cloth are at the same level.Similarly, for glass cloth 2.5, the average monofilament diameter and number of monofilaments are different. Others.

The weight and thickness of the glass cloth were made to be at the same level.

Each of the above glass cloths is impregnated with a face of an epoxy resin composition having the following composition so that the resin content is 45% by weight,
A prepreg was prepared by heating and drying at a temperature of 150°C for 8 minutes so that the gelation time of the resin was 120 to 150 seconds at 170°C.

Brominated bisphenol A type epoxy resin (Epicor 5045, manufactured by Yuka Shell Co., Ltd.) 100 parts by weight Novolac type epoxy resin (Epicor 1, manufactured by Yuka Shell Co., Ltd.)
54) 30 parts by weight dicyandiamide (curing agent) 4 parts by weight 2-ethyl-methyl-4-imidazole (curing accelerator)
065 parts by weight Methyl cellosolve (solvent) Thickness 35 parts on both sides of the prepreg obtained as above
Copper foil of μm thickness is laminated and press pressure is 14 kg/cJ.

Lamination and adhesion were carried out at a curing temperature of 170° C. and a curing time of 100 minutes to obtain a laminate in which both sides of a single layer of prepreg were coated with copper.

Table 2 shows the results of evaluating the mechanical properties of the obtained laminate using the method described above.

Table 2 As is clear from Table 2, the substrates made of glass double oxides 1 to 3 (Examples 1 to 3) that satisfy the requirements for the flexible printed wiring board material of the present invention have glass double oxides 4.5 (comparative examples 1 to 3).
9 surface resistance (electrical insulation resistance) compared to that according to 2)
It can be seen that the copper foil peel strength and bending fatigue resistance are excellent.

(Effects of the Invention) Since the flexible printed wiring board material of the present invention has the above-described structure, it has excellent bending fatigue resistance, and
A flexible printed wiring board having excellent heat-resistant dimensional stability, electrical properties, and adhesion to metals is provided.

Claims (1)

[Claims] (1) Glass fibers made of monofilaments with an average diameter of 2.0 to 4.8 μm are arranged in at least one of the warp and weft, and the ratio of the weave density of the warp to the weave density of the weft is 0.
．． A material for a flexible printed wiring board, characterized by impregnating a thermosetting resin into a glass cloth having a diameter of 95 to 1.35.