TW201223355A - Flexible circuit board for repeated bending use, and electronic device and cellular phone using same - Google Patents

Abstract

Provided is a flexible circuit board having a high bending-withstanding characteristic in repeated bending use, and which manifests an excellent bending-withstanding characteristic even when used at a sliding section having a narrow gap with just a small bending radius, such as a sliding section of a cellular phone. Also provided is an electronic device with the flexible circuit board mounted on a sliding section thereof. Provided specifically is a flexible circuit board for repeated bending use that comprises a wiring circuit formed to be an arbitrary pattern on a polyimide insulation layer, and that has a circuit protection layer formed upon the wiring circuit. In the flexible circuit board for repeated bending use, the tensile elastic modulus of the polyimide insulation layer at 25 DEG C is in a range of 4-6 GPa, the thickness thereof is in a range of 14-17 μm, the thickness of the wiring circuit is in a range of 7-13 μm, the ratio (tc/tp) between the thickness (tc) of the wiring circuit and the thickness (tp) of the polyimide insulation layer is in a range of 0.4-0.95, and the thickness of the circuit protection layer is in a range of 15-30 μm. Also provided is an electronic device with this flexible circuit board for repeated bending use installed on a sliding section thereof.

Description

201223355 VI. [Technical Field] The present invention relates to a flexible circuit board suitable for use in a reversing buckling application portion of an electronic device such as a mobile phone. [Prior Art] In recent years, the electronic devices that are representative of mobile phones, notebook computers, digital cameras, and game consoles are rapidly becoming smaller, thinner, and lighter. The small space can also accommodate the high-density material of the barrel density of the parts. A flexible circuit board which is thin as material in response to this requirement and which can be folded into a narrow space and which is highly resistant to buckling is gradually being widely used. However, the flexible circuit board for a movable portion such as a folding type mobile phone or a slide type mobile phone, which is highly demanding in terms of high density, is pursuing a material that is softer and more easily bent. When the flexible circuit board of the prior art is more multilayered or has a smaller radius of curvature, the problem of occurrence of disconnection is likely to occur after a long period of use, and it is not always possible to obtain a product having sufficient buckling resistance. Here, in order to achieve higher buckling resistance, the thinning of the flexible circuit board was examined, and as one of the methods, a polyimide-based insulating layer and a metal foil layer of a thinned material were examined. For example, Japanese Patent No. 3 3 5 65 68 (Patent Document 1) proposes a thickness l composed of a polyimine polymer having an initial tensile modulus of elasticity of 400 kg/mm 2 or more (3.92 GPa or more). A flexible copper laminated board formed by directly forming a copper layer having a thickness of one or more sides on a single side or both sides of a polyimide film having a size of ym or less. However, the flexible circuit board made of the -5 - 201223355 flexible copper laminated board shown by the patent document 1 has some high buckling resistance, but the sliding buckling polyimine in the narrow gap in recent years. The rigidity of the film is too low to be the optimum composition. The manufacturing process of the spliced copper laminated board is based on the premise that the poly yttrium is first formed to form a copper layer, so that the operability of the yttrium imide film at the time of manufacture must have a certain degree of initial tensile blast and There is also a limit to the thinning of the polyimide layer. In addition, Japanese Laid-Open Patent Publication No. 2007-273766 (specially, it is proposed to have a tensile modulus of 5 GPa or less and a thickness of 10 to 15 " one or both sides of the imine film, and a tensile modulus of 40 GPa or less is set. a wiring board laminate of a metal foil layer of #m. However, the laminate for a wiring board shown in | has a buckling performance in a gap of 2 mm or more, but has a narrower gap. [Prepared to the present invention] [Patent Document 1] [Patent Document 1] Japanese Patent No. 3356568 (Patent Document 2) Japanese Laid-Open Patent Publication No. Hei 2-7273766 [Problem] As described in the above-mentioned Patent Documents 1 and 2, the idea of the high-buckling circuit board of the prior art is to suppress the degree of application of the copper foil to the extent of the test. , and the literature 2) : m poly 醯, thickness 7 ~ Henry literature 2 dynamic buckling test test can not be flexible stretchable

S -6 - 201223355 Force, while improving the buckling resistance by thinning and softening the polyimide film in the laminated board. However, in recent years, the sliding buckling of a narrow gap has not been able to exhibit good buckling performance by such a prior idea, and it is not possible to improve the buckling resistance without optimizing the material composition. The present invention has been made in view of all the problems of the prior art described above, and an object of the invention is to provide a high bending resistance, such as a sliding portion of a mobile phone, which is used for a reverse flexing application, and the like, which is used for a small bending radius. The narrow gap sliding portion can also exhibit an excellent flexion resistance flexible circuit substrate. Further, it is an object of the invention to provide an electronic device having excellent durability against repeated buckling by mounting the flexible circuit board on a sliding portion. [Means for Solving the Problem] In order to solve the above problems, the inventors of the present invention have found that the polyimide film, the wiring circuit, and the circuit provided on the wiring circuit are formed on the flexible circuit board. The protective layer is made of a material having a specific thickness or a range of elastic modulus, and by applying these combinations, the buckling resistance of a narrow gap sliding application of less than 2 mm can also exhibit a specific excellent buckling resistance. this invention. That is, the present invention is a flexible circuit substrate suitable for reverse buckling, which has a wiring circuit formed in an arbitrary pattern on the polyimide insulating layer, and further has a circuit protection layer on the wiring circuit. The polyimine insulating layer has a tensile modulus of 4 to 6 GPa at 25 t: and a thickness of 14 to 17 μm. Further, the thickness of the wiring circuit is 201223355 in the range of 7 to 13 vm. The ratio (tp/tp) of the thick yttrium imide insulating layer of the wiring circuit (tc/tp range, and further, the thickness of the circuit protective layer is 15 to 30. Further, the present invention is characterized by the aforementioned flexible circuit portion Further, the circuit board of the present invention is mounted on a sliding portion as a feature of the invention. [Effects of the Invention] The flexible circuit board of the present invention has a high sliding sliding buckling characteristic of the circuit base gap, so that it can be used as a special type or a sliding type. A flexible portion for use in an electronic device such as a mobile phone. Further, it can be suitably applied to a small-sized way. [Embodiment] Hereinafter, the present invention will be described in detail. The flexible circuit board is formed by forming a wiring circuit on the polyimide, and further on the wiring circuit. In the present invention, the polyimide layer may be composed of only a plurality of layers, and the polyimide layer may be used as a polyimide layer. The elastic modulus must be in the range of 4 to 6 GPa, and the thickness of the polyimide layer having a thickness of 14 to less than 4 GPa is too low, so that the flexural resistance of the flexible circuit substrate is manipulated during the processing of the laminate. It becomes difficult. Further, (tc) and the aforementioned poly) are in the range of 0.4 to 0.95 m. The substrate is mounted on an insulating layer that is bent so that the narrowing required for the flexible telephone board is applied to the folded flexible circuit board, and the circuit layer is provided with a circuit protection layer. The stretch of 1 7 " m at 25 °C. The polyimine insulating layer is lowered, and if it exceeds 6 G Pa, 201223355, the rigidity of the polyimide layer is too high, and the flexural resistance of the flexible circuit substrate is lowered. Similarly, if the thickness of the polyimide layer is less than 14 // m, the rigidity of the polyimide layer is too low, so that the buckling resistance of the flexible circuit substrate is lowered and the operation during processing becomes difficult, exceeding 1 At 7 ym, the rigidity of the polyimide layer is too high, so that the buckling resistance of the flexible circuit substrate is lowered. In particular, when the flexible circuit board of the present invention is used for a sliding flexion portion of a small electronic device, such as a slide portion of a slide type mobile phone, it is particularly required to have excellent buckling resistance. The thickness of the polyimide layer of the polyimide is preferably 16 ± 1.5; c / m, more preferably 16 ± lym, and more preferably more than 15 μm and in the following range. Next, when it is used for the sliding buckling portion as described above, the tensile modulus of the polyimide imide insulating layer is preferably in the range of 4 · 5 to 5 GPa. The tensile modulus of the polyimide layer is controlled to the above range, or may be selected by, for example, a polyimine resin suitable for forming a polyimide layer, or as described below. When the polyimine precursor (also referred to as polylysine) solution is imidized, the heat treatment conditions and the like are adjusted to form an optimum polyimide layer. Further, the tensile modulus of the polyimine resin varies depending on the constituent unit constituting the polyimide. These constituent units are derived from the type of hydrazine or tetracarboxylic acid dihydrate which is a raw material of the polyimide. Decide. In order to obtain a polyimide-imident insulating layer having a tensile modulus of elasticity in the above range, a method of appropriately selecting a raw material component constituting the polyimide, using a single layer of a polyimide having a soft chemical structure, or borrowing may be employed. A well-known method such as a method of adjusting the polyimine layer of a plurality of layers having the same elastic modulus to -9-201223355 as a whole. Further, the term "polyimine" in the present invention means a high molecular weight structure in the molecular structure of quinone imine, polyamidoximine, polyether quinone, polycyclodecane oxime or the like. molecule. The polyimine insulating layer may be coated with a polyimine precursor grease solution on a metal or the like forming a wiring circuit, and subjected to drying and hardening heat treatment to convert the polyimine precursor into a polyfluorene. The solution of the polyimine precursor used herein may be produced by a known method. In a representative method, the tetracarboxylic acid di-anhydride and the hydrazine may be dissolved in an organic solvent. 〇~loo °C Stir for 30 minutes ~ hour to get the reaction. As the organic solvent used for the polymerization, N,N-dimethylformamide, hydrazine, hydrazine-dimethylacetamide, N-methyl-N-propane ketone, dimethyl fluorene, and the like can be obtained. Methyl sulphate, phenol, halogenated phenol, cyclohexanone, dioxin, tetrahydrofuran, diglyme, triglyme, etc. may be used in combination of two or more kinds. The concentration of the polyimine precursor solution is preferably in the range of 500 to 100,000 CP. When it is out of this range, film thickness unevenness and streaking are likely to occur at the time of coating operation by coating. The tetracarboxylic acid dihydrate of the raw material of the polyimine and the hydrazine may be appropriately selected from one or two or more kinds depending on the properties of the polyimide layer of the present invention. That is, in the present invention, it is necessary to make the tensile modulus of the polyimine layer in the range of 4 to 6 GPa, and to select a material suitable for the polyimide layer having such characteristics. Insulation of flexible circuit board In addition to the buckling resistance, the hand-polyamine foil represented by heat resistance and thermal expansion coefficient is added to the 吡 己 吡 24 应 应 应 应 应 吡 吡 吡 吡

S -10- 201223355 Insulation stability must also be excellent. For this reason, the thermal expansion coefficient of at least one layer of the polyimide layer is less than 30xltT6/°C, preferably 16xl0·6~28 xl (T6/ A polyiminoimine layer having a thermal expansion coefficient in the range of ° C (hereinafter referred to as "low thermal expansion polyimine layer") is preferred. When the thermal expansion coefficient of the polyimine layer is outside this range, copper is used. The difference in the coefficient of thermal expansion of the foil becomes large. The dimensional change of the flexible laminated sheet becomes large, which causes curling in the laminated sheet. As the polyimine which forms the polyimide layer, the following may be mentioned. The constituent unit represented by the general formula (1). [Chemical Formula 1]

Here, An in the general formula (1) represents a divalent aromatic hydrazine residue, and Ar2 represents a tetravalent aromatic tetracarboxylic acid residue. The aromatic hydrazine residue ΑΓι is composed of hydrazine (Η 2Ν-ΑΓι-ΝΗ 2 ), and as Ar, the following aromatic hydrazine residue can be exemplified. -11 - 201223355 [Chemical Formula 2]

In addition, the aromatic tetracarboxylic acid residue Ar2 may be a compound represented by an acid anhydride (0(0C)2Ar2(C0)20), and as Ar2, an aromatic acid dihydrate residue represented by the following may be exemplified. base.

S -12- 201223355 [Chemical Formula 3]

The low thermal expansion polyimine layer is preferably a structural unit represented by the general formula (2). [Chemical Formula 4]

In the formula, the ruler 3 is a substituent of any of -(:113, -C2H5, -OCH3, or -OC2H5. Preferably, r3 is preferably -ch3. Further, X and y in the formula represent respective The composition ratio of the constituent units, X is in the range of 0.4 to 0.6, y is preferably in the range of 0.6 to 0.4, and x + y = 1. The ratio of X to y is smaller when X is smaller than -13 - 201223355 0.4. The thermal expansion coefficient of the quinone imine increases, and the dimensional stability required for the insulating layer when the flexible circuit board is used is lowered, and the laminated board on which the circuit board is formed tends to be curled. On the other hand, X is 0.6. When it is larger, the tensile modulus of polyimine is increased, and the buckling resistance of the flexible circuit board tends to be lowered. When the polyimide layer is a plurality of layers, the metal foil forming the wiring circuit is formed. The layer which is connected to each other preferably has a thermal expansion coefficient of 30x1 (a polypyrmine insulating layer having a high thermal expansion coefficient of T6/t or more (hereinafter referred to as "high thermal expansion polyimine layer") as a high thermal expansion polycondensation. The quinone imine layer is preferably composed of a polyimine having a structural unit represented by the general formula (3). [Chemical Formula 5]

In the formula, Ri is at least one group selected from the groups represented by the following structural formulas (4) and (5), and R~2 is selected from the groups represented by the following structural formulas (6) and (7). At least 1 base. Further, in the following structural formula (6), X is any one of -S02-, -CO-, and a linear combination. -14- 201223355 [Chemical Formula 6] Θ-. -〇-°-〇— (4)

A preferred layer structure in which a polyimine layer is formed of a plurality of layers, and a layer of a highly thermally expandable polyimide layer/low heat-expandable polyimide layer is preferably laminated in a stepwise manner. It is a high thermal expansion polyimine layer / low thermal expansion polyimine layer / high thermal expansion polyimine layer. Further, in the case where the polyimine insulating layer is formed of a plurality of layers, a preferred ratio of the low thermal expansion polyimine layer to the high thermal expansion polyimide layer is based on the total thickness, and the low thermal expansion poly is used. The quinone imine layer/high thermal expansion polyimine layer is preferably 1 to 40, more preferably 2 to 30. The wiring circuit of the flexible circuit board of the present invention is formed by forming an arbitrary pattern on the insulating layer of the polyimide. The wiring circuit pattern is usually formed so as to have a line width of about 40 to 1 50 /z m except for a particular limitation. The wiring circuit is formed of a metal which is composed of copper, inscription, stainless steel, iron, silver, palladium, nickel, cobalt, chromium 'molybdenum, tungsten or an alloy of these. Usually, the wiring circuit is often formed of a metal such as a copper box. In this case, the wiring circuit can be formed by patterning these metals from an arbitrary pattern. As a metal mooring, copper box or alloy copper is more suitable for use. In addition, calendered copper foil and electrolytic copper can be used. g 2丨壬_ -15- 201223355 The thickness of the wiring circuit is in the range of 7 to 1 3 // m. If the thickness is less than 7 // m, not only is it cheap and stable, but the rigidity of the flexible circuit board is too low, so processing is difficult. Further, when the thickness is thicker than 13#m, the buckling resistance is remarkable in the present invention. When the thickness of the wiring circuit is tc and the thickness of the insulating layer is tp, the relationship between the wiring circuit and the thickness of the polysilicon is tc/tp. When the range of 0.4 to 0.95 is less than 0.4 in the case of tp, there is a difficulty in the transmission of the wiring circuit, or the occurrence of high buckling, which is more difficult than the high buckling property. The wiring circuit is electrolytically copper-clad, and the thickness of the wiring circuit is 7 to 10 / z m, and the wiring property is preferably in the range of 15 to 40 GPa, and further preferably in the range of 0.4 to 0.7. Further, when the wiring foil is used as a raw material, the thickness of the wiring circuit is 8 to 13; / the tensile modulus of the circuit is 8 to 30 GP a, and the range of preferably tc/tp is 0.5 to 0.9. good. When the wiring circuit is formed of a copper foil, the copper foil exhibiting the former or the tensile modulus can be suitably used as a commercially available product. Here, the tensile modulus of the wiring circuit as described herein can be determined from a metal layer to which a metal laminate is attached by forming a specific pattern by etching. The known cover film or cover coating material of the circuit protective layer of the flexible circuit board of the present invention has a thickness. Wiring circuit When the foil supply is trapped, the operation becomes difficult. Further, the aforementioned polyimine imide insulating layer is necessary. If the capacity of the tc / signal is not 9.5, the circuit of the field circuit of the foil is used to stretch the tc / tp circuit to roll the copper m, and the wiring, and then the copper foil or the thickness range of the copper strip Locally selected to use the circuit as before the circuit in the embodiment can be used commercially as necessary 1 5~3 0

S -16- 201223355 /zm range. When a cover film is used as the circuit protection layer, an adhesive layer made of a thermosetting resin such as an epoxy resin is usually used on one side of the polyimide layer (on the side in contact with the wiring circuit). . Preferred examples of the cover film include a two-layer structure of a thermosetting resin adhesive layer having a thickness of 8 to 17 #m and a polyimide layer having a thickness of 7 to 13/zm, for example, etching. After the copper foil forms a wiring circuit of a specific pattern, the bonding layer is directly connected to the wiring circuit for use. The flexible circuit substrate of the present invention is a wiring circuit having i) a thickness of 14 to 17 gm, a polyimide elastic layer having a tensile modulus of 4 to 6 GPa at 25 ° C, and ii a thickness of 7 to 13 // m, and Iii) A laminate of circuit protection layers having a thickness of I5 to 30//m, and the relationship between the thickness (tc) of the wiring circuit and the thickness (tp) of the polyimide layer of the polyimide layer is in the range of 0.4 to 0.95. By. The flexible circuit board that satisfies all of these conditions is excellent in heat resistance and dimensional stability, and also has excellent results in buckling resistance, so that it can exhibit excellent buckling resistance. Flexible circuit substrate. In other words, it can be applied to an opening and closing operation such as a hinge portion such as a folding type mobile phone or an electronic dictionary, or a slide portion of a slide type mobile phone, an optical pickup portion of a DVD or the like, and the like. A flexible circuit board for reverse buckling purposes such as a sliding motion. In particular, the flexible circuit board of the present invention exhibits a buckling life of 100,000 times or more in a sliding buckling test of a narrow gap of less than 2 mm, and has excellent continuous sliding buckling characteristics, and is therefore suitable for use in a slide type action. The sliding buckling portion of a small electronic machine such as a sliding portion of a telephone. In addition, the high-speed sliding buckling test of an optical pickup head portion of a DVD such as a DVD which is tens of millions of times or more in the case of a gap of more than 2 mm is applied in the same manner. [Examples] Hereinafter, the present invention will be described in more detail by way of examples. Further, the abbreviations used in the examples are as follows. DMAc : Ν,Ν-dimethylacetamide m-TB : 2,2'-dimethyl-4,4'-diaminobiphenyl ODA : 4,4'-diaminodiphenyl ether TPE-R: l,3-bis(4-oxophenoxy)benzene BAPP : 2,2'-bis ( 4.aminophenoxyphenyl)propane PMDA: anhydrous pyromellitic acid BPDA: 3,3',4,4 ,-Diphenyltetracarboxylic acid di-anhydrous copper foil A: Mitsui Metals Mining Co., Ltd. manufactures high-buckling electrolytic copper foil (thickness 9 β m ) Copper foil B: JX Nippon Mining & Metals Co., Ltd. manufactures high buckling calendering Copper foil (thickness 12 A m) Further, the tensile modulus of the polyimide film of the example or the like was evaluated by the following method. Tensile modulus: Toyo Seiki Co., Ltd. (Strograph) R-1 ' was measured under the following conditions (according to IPC-TM-6 50, 2.4.19). Sample size: 12.7mmxl65.lmm Distance between fixtures: 1 0 1 · 7 mms -18- 201223355 Crosshead speed: 50mm / min Elasticity: Calculate the measurement environment in the elastic region with strain less than 1.5%: room temperature (2 3 ° C), humidity (50%) [Synthesis Example 1] N,N-dimethylacetamide (DMAc) was placed in a reaction vessel equipped with a thermocouple and a stirrer to introduce nitrogen gas. In this reaction vessel, 2,2'-1^[4-aminophenoloxyphenyl]propane (8???) was stirred in a vessel while being dissolved. Next, anhydrous pyromellitic acid (PMDA) and 3,3',4,4'-biphenyltetracarboxylic acid di-anhydride (BPDA) were added. The total amount of the monomer input was 12% by weight, and the molar ratio of each anhydrous acid (PMDA: BPDA) was 95:5. Thereafter, stirring was continued for 3 hours to obtain a resin solution of polyamic acid a. The resin solution of this polyimidic acid a had a solution viscosity of 2,000 cps. Further, the polyimide film prepared by the polyamic acid a was measured to have a coefficient of thermal expansion of 54 x 10_6 / K. [Synthesis Example 2] N,N-dimethylacetamide (DMAc) was placed in a reaction vessel equipped with a thermocouple and a stirrer to introduce nitrogen gas. In this reaction vessel, 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB) and 4,4'-diaminodiphenyl ether (OD A ) are stirred in a vessel while allowing Dissolved. These molar ratios (m-TB: ODA) are 5 5 : 45 » followed by the addition of pyromellitic acid dihydrate (PMDA). The total amount of monomer input was I5 wt%. Thereafter, stirring was continued for 3 hours to obtain a resin solution of polyimidate b. The resin of this polyimidic acid b has a solution viscosity of 25,000 cps. Further, the polyimide film prepared by the polyamic acid b was measured to have a thermal expansion coefficient of 19 x 10 _ δ / Κ. [Synthesis Example 3] In a reaction vessel equipped with a thermocouple and a stirrer, nitrogen gas was introduced, and hydrazine, hydrazine-dimethylacetamide was placed. The reaction vessel is such that 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB) and l,3-bis(4-aminophenoxy)benzene (TPE-R) are in a container Stir and dissolve at the same time. These molar ratios (m-TB: TPE-R) are 90:10. Next, anhydrous pyromellitic acid (PMDA) and 3,3',4,4'-biphenyltetracarboxylic acid di-anhydride (BPDA) were added. The total amount of the input of the monomer was 15 wt%, and the molar ratio of each anhydrous acid (PMDA: BPDA) was 80:20. Thereafter, stirring was continued for 3 hours to obtain a resin solution of polyimidate c. The resin solution of this polyimidic acid c had a solution viscosity of 20,000 cps. Further, the coefficient of thermal expansion of the polyimide film prepared by polyamic acid b was 17 x 1 〇 _6 / K. [Example 1] A long-sized copper foil A having a length of 1000 mx and a width of 1080 mm was applied to the prepared polyamine solution a' to be dried (cured to form a thermoplastic high-expansion polycondensation having a film thickness of 2 / zm). The imine) is coated with polylysine b, dried (cured to form a film thickness of 12; low thermal expansion polyimine of ζηη), and further coated with polylysine a to be dried ( After hardening, a thermoplastic high thermal expansion polyimine having a film thickness of 2/m is formed, and the temperature is raised to 340 ° C for 15 minutes or more to carry out the hydrazine imidization reaction to obtain a three-layer structure.

S -20- 201223355 Polyimide insulation layer (thickness 16/zm) single-sided copper laminated board. Next, the polyimide layer of the single-sided copper-clad laminate is made of the other copper foil A of the same size as described above at a set temperature of 3 85 ° C on the surface of the roll, and the line pressure between the rolls is 150 kN/cm. And continuous thermocompression bonding was carried out under the condition of a time of 3 seconds to produce a double-sided copper laminated board. Further, the tensile modulus of the polyimine insulating layer (25 ° C) is obtained by etching away the copper foil on both sides of the double-sided copper-clad laminate produced under the same conditions as above to obtain a polyimide film. The tensile modulus of elasticity was measured using this polyimide layer. The result 'is 5. OGP a. On the other hand, the tensile modulus of the copper foil serving as the wiring layer was 2 3.0 G Pa. Next, a specific mask is covered on one side of the double-sided copper-clad laminate obtained as described above, and etched using a ferric chloride/copper chloride-based solution to have a line width of 1 3 0 vm and a width of 1 8 0 // m forms a wiring pattern (the opposite side copper foil is completely etched away). Next, on the wiring pattern formed on one side, the cover film C formed by the thickness of the polyimide insulating layer (tensile modulus: 4.1 GPa) and the epoxy resin adhesive layer having a thickness of 15/zm is heated. The test piece 1 of the circuit board for sliding test was obtained by crimping and pressing. The reverse sliding test of the slide test test substrate sample 1 is a test for sliding buckling using one of the buckling modes of a mobile phone, etc., and the buckling radius, the sliding cycle speed, and the sliding stroke can be individually set and can be individually The resistance of the circuit rises to determine the test machine at the end of the test. As shown in FIG. 1, the flexure portion is provided by the gap length 6 defined by the two plates 7 for the circuit board sample, and the one side is fixed by the fixing portion 4, and the opposite side is also fixed by the fixing portion 5, as shown in FIG. As shown in (a-2) and (a-2), the stroke of the portion corresponding to the reciprocating motion is repeated by repeating the reciprocating motion of the plate on the side of the fixed portion 4 of the -21 - 201223355 as shown in the figure. The area of the circuit substrate is subjected to repeated sliding buckling. As for the test conditions, as shown in Fig. 1 and Fig. 2, the circuit protection layer (cover film) 1 is inside, the gap length is 1.5 mm (even if the buckling radius is 0.75 mm), and the sliding cycle speed is 15 rpm, the sliding stroke In the case of 38.0 mm, the number of times of sliding at the time when the initial resistance 配线 of the wiring circuit of the circuit board sample rises by 1% is taken as the buckling life. When the test of the circuit substrate sample 1 was carried out by this method, the buckling life was 308,300 times. The layer constitution and test results of the circuit substrate sample 1 are shown in Table 1. [Table 1] Copper foil polyimine insulation coating film buckling life Europe] Copper foil type tensile modulus [GPa] Tensile modulus [GPa] Thickness [/inn] Example 1 A 23.0 5.0 16 C 308.300 2 B 12.0 5.0 16 C 193,200 3 A 23.0 5.0 16 E 382,500 Comparative Example 1 A 23.0 5.0 25 C 10,000 2 A 23.0 7.5 20 C 16?7〇〇3 B 12.0 5.0 25 C 29,200 4 B 12.0 7.5 20 C 16,700 5 A 23.0 5.0 16 D 1,100 6 B 12.0 5.0 16 D 2,600 [Example 2] A double-sided copper-clad laminate was obtained in the same manner as in Example 1 except that the copper foil B was used. With respect to the double-sided copper-clad laminate according to the second embodiment, the tensile modulus of the polyimide film and the copper foil of the wiring -22-201223355 circuit were measured in the same manner as in the first embodiment (2 5 t When they are 5 · OGPa and 1 2 .OGPa. Then, the circuit board sample 2' obtained by the same procedure as in the first embodiment of the circuit board was evaluated in the same sliding test conditions as in the first embodiment, and the buckling life was 1,93,200 times. The results are shown in Table 1. [Example 3] The same procedure as in Example 1 was carried out except that a cover film E formed of a polyethylene polyimide insulating layer (tensile modulus: 4.1 GPa) and an epoxy resin adhesive layer having a thickness of 15/zm was used. The condition of the circuit board sample 3 for sliding test was obtained. Next, when evaluated in the same sliding test conditions as in Example 1, the buckling life was 382,500 times. The results are shown in Table 1. [Comparative Example 1] Polyacrylic acid a was applied to copper foil A in the same manner as in Example 1 (hardening to form a thermoplastic high-expansion polyimine having a film thickness of 2.5 /zm), polylysine b (forming a low thermal expansion polyimine having a film thickness of 20 # m after hardening) and poly-proline acid a (forming a thermoplastic high-expansion polyimine having a film thickness of 2.5 μm after curing), and drying it, The yttrium was imidized to obtain a single-sided copper-clad laminate having a polylayered imide insulating layer (thickness 25; zm) composed of a three-layer structure. Then, the polyimide film of the single-sided copper-clad laminate was continuously thermocompression-bonded to the copper foil A in the same manner as in Example 1 to obtain a double-sided copper-clad laminate according to Comparative Example 1. With respect to the double-sided copper-clad laminate according to Comparative Example 1, the tensile modulus (25°) of the polyimide foil insulating layer and the copper foil -23-201223355 which is the wiring layer was measured in the same manner as in the first embodiment. C) is '5.0 GPa and 23.0 GPa, respectively. Then, the circuit board sample 4 obtained by the same circuit board fabrication step as in Example 1 was evaluated for the same buckling test conditions as in Example 1, and the buckling life was 1 〇. The results are shown in Table 1. [Comparative Example 2] Polyacrylic acid a (curing to form a thermoplastic high-expansion polyimine having a film thickness of 2 / m) and polyamine was applied to the copper foil A in the same manner as in Example 1. Acid c (forming a low thermal expansion polyimine having a film thickness of 16 # m after hardening) and polyglycolic acid a (forming a thermoplastic high-expansion polyimine having a thickness of 2/zm after curing) and drying it The yttrium is aminated to obtain a single-sided copper-clad laminate having a polymethylene imide insulating layer (thickness 20 #m) composed of a three-layer structure. Then, the polyimide film of the single-sided copper-clad laminate was continuously thermocompression-bonded to the copper foil A in the same manner as in Example 1 to obtain a double-sided copper-clad laminate according to Comparative Example 2. In the double-sided copper-clad laminate according to Comparative Example 2, when the polyimide elastic layer was measured and the tensile modulus (25 ° C) of the copper foil serving as the wiring layer was measured in the same manner as in Example 1, They are 7.5GPa and 23.0GPa respectively. Then, the circuit board sample 5 obtained by the same circuit board manufacturing step as in the first embodiment was evaluated in the same sliding test conditions as in the first example, and the buckling life was 1,6,700 times. The results are shown in Table 1. [Comparative Example 3] Polyacrylic acid was sequentially applied to copper foil B in the same manner as in Example 1.

S -24- 201223355 a (thermoplastic high-expansion polyimine with a film thickness of 2.5 vm after hardening), poly-proline b (low thermal expansion polyimine with a film thickness of 20 m after hardening), and poly Proline acid a (hardened to form a thermoplastic high-expansion polyimine with a film thickness of 2.5 vm), dried, and imidized to obtain a polyimine insulating layer composed of a three-layer structure (thickness 25 # m) Single-sided copper laminated board. Then, the polyimide film of the single-sided copper-clad laminate was continuously thermocompression-bonded to the copper foil B in the same manner as in Example 1 to obtain a double-sided copper-clad laminate according to Comparative Example 3. In the double-sided copper-clad laminate according to Comparative Example 3, when the polyimide elastic layer was measured and the tensile modulus (25 ° C) of the copper foil serving as the wiring layer was measured in the same manner as in Example 1, They are 5.0GPa and 12.0GPa respectively. Then, the circuit board sample 6 obtained by the same circuit board fabrication step as in Example 1 was evaluated for the same buckling test condition as in Example 1, and the buckling life was 29,200 times. The results are shown in Table 1. [Comparative Example 4] Polyacrylic acid a (curing to form a thermoplastic high-expansion polyimine having a film thickness of 2 // m after curing) and polyamine were applied to copper foil B in the same manner as in Example 1. Acid c (forming a low thermal expansion polyimine having a film thickness of 16 / zm after hardening) and polyglycolic acid a (a thermoplastic high-expansion polyimide having a thickness of 2 vm after curing) is dried A unilateral copper-clad laminate having a polymethylene imide insulating layer (thickness 20 "m) composed of a three-layer structure is obtained by imidization. Next, the polyimide film of the single-sided copper-clad laminate was continuously thermocompression-bonded to the copper foil B in the same manner as in Example 1 to obtain a double-sided copper laminate according to Comparative Example 4 -25-201223355. board. In the double-sided copper-clad laminate according to Comparative Example 4, when the polyimide elastic layer was measured and the tensile modulus (25 ° C) of the copper foil serving as the wiring layer was measured in the same manner as in Example 1, They are 7.5 GPa and 12.0 GPa, respectively. Then, the circuit board sample 7 obtained by the same circuit board fabrication step as in the first embodiment was evaluated for the flexural life of 16,700 times under the same sliding test conditions as in the first embodiment. The results are shown in Table 1. [Comparative Example 5] The same procedure as in Example 1 was carried out except that the cover film D was used instead of the halogen-free cover film C. That is, after the double-sided copper-clad laminate obtained in Example 1 was formed into a wiring pattern on one side in the same manner, a polyimide layer having a thickness of 2 5 vm (tensile modulus: 4.1 GPa) was used. The cover film D formed of the epoxy resin bonding layer having a thickness of 30 #m was covered by thermocompression bonding to obtain a circuit board sample 8 for sliding test. When the circuit board sample 8 was evaluated under the same sliding test conditions as in Example 1, the buckling life was 1,100 times. The results are not shown in Table 1. [Comparative Example 6] The same procedure as in Example 2 was carried out except that the halogen-free cover film D was used instead of the halogen-free cover film C. That is, after the double-sided copper-clad laminate obtained in Example 2 was formed into a wiring pattern on one side in the same manner, a polyimide layer having a thickness of 25 μm was stretched (tensile modulus: 4.1 GPa). The halogen-free cover film D formed with the epoxy resin bonding layer having a thickness of 30 μm is punched by thermocompression bonding.

S -26- 201223355 Covered, a sample 9 of the circuit board for sliding test was obtained. When the circuit board sample 9 was evaluated under the same sliding test conditions as in Example 1, the flexural life was 260 times. The results are shown in Table 1. From the results of the back sliding test obtained in the above Examples and Comparative Examples (Table 1), it is understood that the tensile modulus of the polyimide layer is 4 to 6 GPa > and the thickness is in the range of 14 to 17 /zm. A copper-clad laminate having a copper wiring circuit having a thickness of 7 to 13/m, and a flexible circuit substrate having a halogen-free cover film having a thickness of 15 to 30/zm, exhibits a good buckling life in a sliding test. Therefore, it can be suitably used as a flexible circuit substrate suitable for reverse buckling applications of various electronic devices including mobile phones. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an explanatory view of a reverse sliding test of an embodiment. Fig. 2 is a cross-sectional view showing the X-X cross section of the test circuit substrate sample of the reverse sliding test shown in Fig. 1. [Description of main component symbols] 1 : Circuit protection layer 1 a : Polyimine layer of circuit protection layer lb: Bonding layer of circuit protection layer 2 : Wiring circuit 3 : Polyimide insulating layer 4 : Fixing portion 5 : Fixed -27- 201223355 6 : Gap length 7 : board

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Claims (1)

201223355 VII. Patent application scope: 1. A flexible circuit substrate suitable for reverse buckling, which has a wiring circuit formed in an arbitrary pattern on the polyimide layer and further provides circuit protection on the wiring circuit. The layer is characterized in that: the polyimine insulating layer has a tensile modulus of 4 to 6 GPa at 25 t and a thickness of 14 to 17/zm, and the thickness of the wiring circuit is 7 to 13/zm. The range (tc/tp) of the thickness (tc) of the wiring circuit and the thickness (tp) of the polyimide layer is in the range of 0.4 to 0.95, and further, the thickness of the circuit protection layer is 15 to 30#. The range of m. 2. The flexible circuit substrate suitable for the reverse buckling application according to the first aspect of the patent application, wherein the wiring circuit is formed by an electrolytic copper foil having a thickness of 7 ΙΟ/zm, and the tensile modulus of the electrolytic copper foil is In the range of 15 to 40 GPa, the aforementioned ratio t(tc/tp) is in the range of 0.4 to 0.7. 3. The flexible circuit substrate suitable for the reverse buckling application according to the first aspect of the patent application, wherein the wiring circuit is formed by a rolled copper foil having a thickness of 8 to 13 #m, and the tensile modulus of the rolled copper foil is The range of 8 to 30 GP a, the aforementioned ratio t (tc/tp) is in the range of 0.5 to 0.9. 4. The flexible circuit substrate suitable for reverse buckling use according to any one of claims 1 to 3, wherein the circuit protection layer is formed of a coverless film (coverUy film), the halogen-free cover film, The bonding layer made of a thermosetting resin having a thickness of 8 to 17 #.m and two layers of a polyimide layer having a thickness of 7 to 13 μm are directly bonded to the bonding layer in the wiring circuit. 5. An electronic device characterized in that the sliding portion is provided with a flexible -29-201223355 circuit board suitable for reverse buckling as described in any one of claims 1 to 4. A mobile phone characterized in that the slidable portion is provided with a flexible circuit substrate suitable for reverse buckling as described in any one of claims 1 to 4. S -30-