JP2000200950A - Flexible wiring board and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible wiring board and manufacture thereof using a thermoplastic insulation layer and having a conductor foil, such as Cu foil, surely thermally welding to a filmy insulation layer into one body and a solder heat resistance. SOLUTION: A molding material, i.e., a thermoplastic resin compsn. composed of a polyarylketone resin having a crystal melting peak temp. of 260 deg.C or higher 65-35 wt.%, and an amorphous polyetherimide resin 35-65 wt.% is formed into a filmy insulator so as to satisfy the relation (ΔHm-ΔHc)/ΔHmm<=0.5 between the glass transition temp. of 150-230 deg.C measured by the differential scan calorimetry at the temp. rise, the crystal melting heat quantity ΔHm and the crystallizing heat quantity ΔHc generated by the crystallization during temp. rise, and the conductor foil is thermally welded to one or each side of the filmy insulator in the heating and pressing conditions, so as to satisfy the relation (ΔHm-ΔHc)/ΔHmm>=0.7 and then is etched to form a conductive circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a flexible printed circuit board, and more particularly to a flexible printed circuit board having an insulating layer formed of a thermoplastic resin and a method of manufacturing the same.

[0002]

2. Description of the Related Art In order to meet the recent demand for smaller and lighter electronic devices, compared to rigid boards using prepregs in which glass cloth is impregnated with epoxy resin, they are lighter, occupy less space, and have free three-dimensional wiring and wiring. Flexible printed circuit boards (hereinafter, abbreviated as FPC boards) that can simplify the above have been widely used.

As an insulating material of the FPC board, a polyester resin or a polyimide resin is generally used. However, the polyester resin has poor solder heat resistance (about 260 ° C.), and the use of the FPC board using the same is narrow. Is limited to

[0004] FPC boards using a polyimide resin are roughly classified into a three-layer type in which a polyimide film is bonded to a copper foil using an adhesive such as an epoxy resin, and a two-layer type in which no adhesive is used. Problems common to the three-layer type and the two-layer type include poor chemical resistance (weak against a strong base) due to the material properties of polyimide, and a problem in dimensional stability due to high water absorption. Can be Also,
As a problem of the three-layer type, since various properties such as heat resistance, chemical resistance and electric properties are influenced by the properties of the adhesive, there is a problem that the excellent properties inherent in the polyimide resin cannot be fully utilized. .

[0005] One of the two-layer type manufacturing methods is disclosed in Japanese Patent No. 2724026, in which a polyimide solution or a polyamic acid solution which is a precursor of polyimide is directly cast onto a metal foil to form an FPC substrate. It is described that all the insulating layers are made of polyimide. Further, the above publication describes a method of forming an polyimide layer having adhesiveness on one or both sides of a polyimide film, laminating a metal foil on the polyimide layer, and heating and pressing to produce an FPC board in which the insulating layer is entirely made of polyimide. ing.

[0006] As another method of the two-layer type manufacturing method, a thermoplastic polyimide film having a thickness of 300 mm is used.
A method of pressing a copper foil at a temperature of about ° C is known.
Problems of this two-layer type FPC board include a quality problem that a dent is easily formed in a copper foil in an etching process, and a problem of high cost due to a trouble of manufacturing a copper clad board.
Compared with the three-layer type, at present, it has good characteristics as a substrate but is not widely used.

[0007]

Accordingly, an object of the present invention is to solve the above-mentioned problems of the conventional polyimide substrate material and to provide a flexible printed wiring board (FPC board) using a thermoplastic insulating layer having solder heat resistance. )about,
An object of the present invention is to provide an FPC board which is securely bonded and integrated to a conductor foil such as a copper foil by heat fusion at a relatively low temperature.

[0008]

In order to solve the above-mentioned problems, according to the present invention, a crystal melting peak temperature of 260 ° C.
It is composed of 65 to 35% by weight of the above-mentioned polyarylketone resin and 35 to 65% by weight of the amorphous polyetherimide resin, and has a glass transition temperature of 150 to 230 ° C measured when the temperature is raised by differential scanning calorimetry. A film-like insulator made of a thermoplastic resin composition is provided in which the relationship between the heat of crystal melting ΔHm and the heat of crystallization ΔHc generated by crystallization during temperature increase satisfies the relationship represented by the following formula (I). The conductor foil is heat-sealed on one or both sides of the insulator, thereby forming a flexible printed circuit board having a conductive circuit formed on the conductor foil. Formula (I): [(ΔHm−ΔHc) / ΔHm] ≦ 0.5
.

Further, in the invention according to the manufacturing method of the present application, in order to solve the above-mentioned problems, the crystal melting peak temperature 2
65-35% by weight of polyarylketone resin at 60 ° C or higher
A thermoplastic resin composition comprising 35 to 65% by weight of an amorphous polyetherimide resin as a molding material, a glass transition temperature measured by differential scanning calorimetry of 150 to 230 ° C., and crystal melting. The relationship between the amount of heat ΔHm and the amount of heat of crystallization ΔHc generated by crystallization during heating is expressed by the following equation:
(I) molding and processing a film-like insulator so as to satisfy the relationship represented by, the thermoplastic resin composition by laminating a conductor foil on one or both surfaces of the film-like insulator, the following formula (II)
Then, a method is adopted in which the conductive foil is etched to form a conductive circuit after heat-sealing so as to satisfy the relationship shown in FIG. Formula (I): [(ΔHm−ΔHc) / ΔHm] ≦ 0.5 Formula (II): [(ΔHm−ΔHc) / ΔHm] ≧ 0.7.

The flexible printed wiring board of the present invention having the above-described structure has an insulating layer in which a predetermined amount of a crystalline polyarylketone resin and an amorphous polyetherimide resin are mixed. The layer has heat-fusing properties and solder heat resistance due to the excellent properties of both resins, and has the flexibility, mechanical strength, and electrical insulation normally required for FPC boards.

The film-like insulator made of such a thermoplastic resin composition has a glass transition temperature of 150 to 230 ° C.
And the relationship between the heat of crystal melting ΔHm and the heat of crystallization ΔHc generated by crystallization during heating is expressed by the above equation.
Since the relationship represented by (I) is satisfied, the state of progress of crystallization by heating is adjusted to an appropriate range, and for example, it is possible to exhibit heat fusion at a relatively low temperature of less than 250 ° C. it can.

In the method of manufacturing an FPC board according to the present invention, a conductor foil is laminated on one or both sides of a film-like insulator made of the above-mentioned thermoplastic resin composition, and the thermoplastic resin composition has a relationship represented by the above formula (II). Is heat-fused under heat and pressure conditions to satisfy

In the thermoplastic resin composition after heat fusion, the crystallinity of the polyarylketone resin is appropriately advanced.
It becomes an insulating layer that has solder heat resistance that can withstand 260 ° C, and has a large adhesive strength with the conductive foil. Then, the conductive circuit formed by etching the conductive foil is strongly adhered to the insulating layer and peeled off Difficult to do. When a conductor foil whose surface is roughened is used as the conductor foil, the adhesive strength is further increased.

Further, since the film-like insulator and the conductor foil are bonded by heat without interposing an adhesive such as epoxy resin between the layers, various characteristics such as heat resistance, chemical resistance and electric characteristics of the FPC board are obtained. Is not influenced by the properties of the adhesive, and the excellent properties of the insulating layer are fully utilized. Also,
Since there is no step of applying an adhesive or the like in the manufacturing process of the FPC board, the manufacturing method of the FPC board has high manufacturing efficiency.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the structure of a flexible printed wiring board of the present invention and a method of manufacturing the same will be described below with reference to the accompanying drawings.

As shown in FIG. 1 (e), the flexible printed circuit board according to the present invention has a copper foil 2 on both sides of a film-like insulator 1 made of a predetermined thermoplastic resin composition. And a conductive circuit is formed by etching the copper foil 2.

In order to manufacture such a flexible printed wiring board, first, as shown in FIG. 1A, a polyarylketone resin and an amorphous polyetherimide resin are blended and the compound represented by the formula (I) is used. A given crystalline thermoplastic film insulator 1 as shown is prepared. Then, FIG.
As shown in (1), copper foils 2 are stacked on both sides and hot-pressed using a vacuum hot press machine to produce a double-sided copper-clad laminate 5.
Holes 3 for forming through-holes are formed at important points on the double-sided copper-clad plate by laser or drill (FIG. 1 (c)), and copper plating 4 is applied thereto (FIG. 1 (d)). Means for interlayer connection. Next, a conductive circuit is formed by a subtractive method (FIG. 1E).

When a conductive paste is used for interlayer connection, as shown in FIG. 2B, holes 3 for forming holes are formed in key portions of the film-like insulator 1 by laser or drill. Is filled with a conductive paste 6 (FIG. 2).
(C)) After drying, the copper foils 2 are overlaid on both sides and hot-pressed using a vacuum hot press machine to obtain a double-sided copper-clad laminate 7.
(FIG. 2D). Next, a conductive circuit is formed by a subtractive method (FIG. 2E).

The polyarylketone resin, which is the first component of the film-like insulator, is a thermoplastic resin having an aromatic nucleus bond, an ether bond and a ketone bond in its structural unit, that is, phenylketone and phenylether. Is a heat-resistant crystalline polymer having a combination structure of

Representative examples of the polyarylketone resin include polyetherketone, polyetheretherketone, and polyetherketoneketone. In the present invention, polyetherketone represented by the following formula 1 is used. It can be used as suitable.

[0021]

Embedded image

The amorphous polyetherimide resin as the second component constituting the film-like insulator is an amorphous thermoplastic resin having an aromatic nucleus bond, an ether bond and an imide bond in its structural unit. In the present invention, a polyetherimide resin represented by the following formula 2 can be applied.

[0023]

Embedded image

The film-like insulator used in the present invention is composed of a composition obtained by blending the above two kinds of heat-resistant resins at a predetermined ratio, that is, a polyarylketone resin 65 having a crystal melting peak temperature of 260 ° C. or higher. 35 to 65% by weight and amorphous polyetherimide resin 35 to 65% by weight
And a glass transition temperature of 150 to 230 ° C. measured when the temperature is raised by differential scanning calorimetry.

The reason for limiting the above mixing ratio is that the polyaryl ketone resin is mixed in a large amount exceeding 65% by weight, or the mixing ratio of the polyetherimide resin is 35% by weight.
If the mixing ratio is small, the crystallization rate of the composition is increased, and the heat-fusibility with the conductive foil is reduced. Also,
When the content of the crystalline polyallyl ether ketone resin is less than 35% by weight or the content of the amorphous polyetherimide resin exceeds 65% by weight, the crystallinity of the composition becomes low, and the crystal melting peak temperature becomes 260 ° C. or more. This is not preferable because the solder heat resistance is reduced.

The thermal characteristics of the film-like insulator, which is an important control factor in the invention of the present application, are expressed by the following formula (I), wherein the relationship between the heat of crystal fusion ΔHm and the heat of crystallization ΔHc generated by crystallization during heating is as follows. That is, the relationship represented by is satisfied. Formula (I): [(ΔHm−ΔHc) / ΔHm] ≦ 0.5 The thermal characteristics are defined by JIS K7121 and JIS K71.
DSC when the temperature is raised by differential scanning calorimetry according to No. 22
Measured values of two transition heats appearing in the curve, heat of crystal fusion ΔH
It is calculated from the value of m (J / g) and the value of the heat of crystallization ΔHc (J / g) by the above equation.

The value of the above formula (I) also depends on the type and molecular weight of the raw material polymer and the compounding ratio of the composition, but greatly affects the conditions for forming and processing the film-shaped insulator. That is, when the film is formed into a film, the raw material polymer is melted and then cooled immediately, whereby the value of the above formula can be reduced. Further, these numerical values can be controlled by adjusting the heat history in each step. The heat history here refers to the temperature of the film-shaped insulator and the time during which the temperature has been reached, and the higher the temperature, the larger the numerical value tends to be.

The relationship represented by the above-mentioned formula (I) is obtained by measuring the FPC plate obtained by heat-sealing a conductor foil on at least one surface of a film-like insulator in the process of manufacturing the FPC board before the heat-sealing step. It is based on.

If the value represented by the above formula (I) exceeds 0.5 before thermal fusion, it becomes difficult to perform thermal fusion at a low temperature of 250 ° C. or lower because the crystallinity is already high. In this case, it is necessary to perform heat fusion with the conductor foil at a high temperature, which is not preferable in terms of manufacturing efficiency.

The thermal properties of the film-like insulator after the heat-sealing with the conductive foil must satisfy the relationship of the following formula (II). Formula (II): [(ΔHm−ΔHc) / ΔHm] ≧ 0.7 Because when the value of the above formula (II) is lower than 0.7, the crystallization of the insulating layer is insufficient, and This is because heat resistance (usually 260 ° C.) cannot be maintained.

The film-like insulator used in the present invention generally has a thickness of 25 to 300 μm, and its production method is, for example, a known film-forming method such as an extrusion casting method using a T-die or a calendering method. What is necessary is just to employ | adopt and it is not necessary to employ | adopt a manufacturing method especially limited. In addition, it is preferable to employ the extrusion casting method using a T-die from the viewpoint of film forming property and stable productivity. The molding temperature of the extrusion casting method is appropriately adjusted depending on the flow characteristics and film forming characteristics of the composition, but is generally from the melting point of the composition to 430 ° C. or less.

The resin composition constituting the film-like insulator used in the present invention may contain other resins and other additives to such an extent that the effects of the present invention are not impaired. , Heat stabilizer, UV absorber, light stabilizer,
Examples include a coloring agent, a lubricant, a flame retardant, and an inorganic filler. Further, the surface of the film-shaped insulator may be subjected to embossing, corona treatment, or the like in order to improve handling properties.

Examples of the conductor foil used in the present invention include metal foils having a thickness of about 8 to 70 μm, such as copper, gold, silver, aluminum, nickel, and tin. Among them, the metal foil to be applied is particularly preferably a copper foil whose surface has been subjected to a chemical conversion treatment such as a black oxidation treatment. The conductor foil is
In order to enhance the bonding effect, it is preferable to use a material whose contact surface (overlapping surface) with the film-shaped insulator is chemically or mechanically roughened in advance. Specific examples of the conductor foil subjected to the surface roughening treatment include a roughened copper foil that has been electrochemically treated when producing an electrolytic copper foil.

When the conductor foil is superimposed on one or both surfaces of the film-shaped insulator and heat-sealed under heating and pressing conditions, for example, a hot pressing method or a heat laminating roll method, a method combining these, or other well-known methods Can be adopted.

[0035]

EXAMPLES AND COMPARATIVE EXAMPLES First, Production Examples 1 to 3 of a film insulator satisfying the conditions of the film insulator of the present invention.
The production methods of Reference Examples 1 and 2 and the physical properties thereof will be described below.

[Production Example 1 of Film Insulator] Polyetheretherketone resin (Victrex: PEE)
K381G) (in the following text or in Tables 1 and 2, P
Abbreviated as EEK. ) 60% by weight and a polyetherimide resin (manufactured by General Electric Company: Ultem-1)
000) (PEI in the following text or in Tables 1 and 2)
Abbreviated. ) 40% by weight was dry blended. This mixed composition was extruded to produce a film insulator having a thickness of 25 μm.

[Production Example 2 of Film Insulator] Production Example 1
, A film-like insulator was produced in the same manner except that the mixing ratio of the mixed composition was 40% by weight of PEEK and 60% by weight of PEI.

[Production Example 3 of Film Insulator] Production Example 1
, A film-like insulator was produced in the same manner except that the mixing ratio of the mixed composition was 30% by weight of PEEK and 70% by weight of PEI.

[Reference Examples 1 and 2 of Film Insulator] In Production Example 1, the mixing ratio of the mixed composition was changed to PEEK100
Each film-shaped insulator was manufactured in the same manner except that the weight% (Reference Example 1) or the PEI 100% by weight (Reference Example 2) was used.

In order to examine the physical properties of the film-like insulator obtained in the above Production Examples and Reference Examples, the following (1) and (2)
The following items were measured or calculated values were calculated from the measured values.
These results are summarized in Table 1.

(1) Glass transition temperature (° C.), crystallization temperature (° C.), crystal melting peak temperature (° C.) Using a 10 mg sample according to JIS K7121 and heating using Perkin Elmer: DSC-7 Speed 1
Each of the above temperatures when the temperature was raised at 0 ° C./min was determined from a thermogram.

(2) (ΔHm−ΔHc) / ΔHm According to JIS K7122, 10 mg of a sample was used, and the heating rate was set to 1 using DSC-7 manufactured by PerkinElmer.
The heat of crystal fusion ΔHm (J / g) and the heat of crystallization ΔHc (J / g) were determined from the thermogram when the temperature was raised at 0 ° C./min, and the value of the above equation was calculated.

[0043]

[Table 1]

Example 1 Thickness 25 obtained in Production Example 1
Electrochemically roughened electrolytic copper foil having a thickness of 12 μm is superposed on both surfaces of a film-shaped insulator of μm, and 760 mmHg in a vacuum atmosphere, a press temperature of 220 ° C., a press pressure of 30 kg / cm ² , and a press time Heat bonding was performed for 20 minutes to produce a double-sided copper-clad laminate.

The film-like insulator of the double-sided copper-clad laminate was subjected to the measurement test of (2) (ΔHm−ΔHc) / ΔHm in the same manner as described above.

The adhesive strength of the obtained double-sided copper-clad laminate was examined by the method (3) described later, and the results are shown in Table 2.

Next, a circuit pattern was formed on the obtained double-sided copper-clad laminate by a subtractive method, and an FPC board having a conductive circuit formed by etching was manufactured.

The solder heat resistance of the obtained FPC board was examined by the following test method (4), and the results are shown in Table 2.

The presence or absence of delamination of the obtained FPC board was examined by the following method (5). The results are also shown in Table 2.

(3) Adhesive strength The peel strength of the copper foil of the FPC blank was measured in accordance with the normal peel strength of JIS C6481, and the average value was shown in kgf / 10 cm.

(4) Solder heat resistance According to the normal solder heat resistance of JIS C6481,
After the test piece was floated on a solder bath at 60 ° C. for 10 seconds while the copper foil side of the FPC plate was in contact with the solder bath, the test piece was taken out of the bath, allowed to cool to room temperature, and visually inspected for swelling or peeling. , The quality was evaluated.

(5) The FPC board is embedded in epoxy resin, a sample for cross-section observation is prepared by a precision cutting machine, and the cut surface is observed by a scanning electron microscope (SEM). Of the conductive circuit was evaluated for the presence or absence of delamination.

[0053]

[Table 2]

Example 2 In Example 1, the production temperature was changed to 240 ° C. and the press time was changed to 30 minutes in the production of the double-sided copper-clad laminate using Production Example 2 as the film-like insulator. Except for the above, an FPC board was produced in the same manner as in Example 1, and the evaluations of Tests (3) to (5) are also shown in Table 2.

[Comparative Example 1] An FPC board was prepared in the same manner as in Example 2 except that the pressing temperature was changed to 230 ° C and the pressing time was changed to 10 minutes when producing a double-sided copper-clad laminate. Table 2 shows the results of the tests (3) to (5).

[Comparative Example 2] In Example 1, the production temperature was changed to 240 ° C. and the press time was changed to 20 minutes when producing the double-sided copper-clad laminate using Production Example 3 as the film-like insulator. Except for the above, an FPC board was produced in the same manner as in Example 1, and the evaluations of Tests (3) to (5) are also shown in Table 2.

As is clear from the results in Table 2, the adhesive strength of the double-sided copper-clad laminate of Example 1 was 1.5 kgf / 10
cm, and the results of the solder heat resistance test showed that no swelling or peeling was observed on the substrate, and no delamination was observed by SEM observation on the FPC substrate after forming the conductive circuit.

The adhesive strength of the double-sided copper-clad laminate of Example 2 was also a good value of 1.3 kgf / 10 cm, the result of the solder heat resistance test was good, and the FPC board after forming the conductive circuit by etching. No delamination was observed at all by SEM observation.

On the other hand, in the SEM observation of the FPC board of Comparative Example 1, although the adhesion between the layers was good because of the adhesion between the layers, the solder heat resistance was poor due to swelling and peeling observed on the board. It was a result.

In the FPC board of Comparative Example 2, the adhesive strength of the double-sided copper-clad laminate was a poor value of 0.2 kgf / 10 cm, and the copper foil of the circuit portion was peeled off after the formation of the conductive circuit by etching.

[0061]

As described above, in the flexible printed wiring board of the present invention, a predetermined amount of a predetermined amount of a polyarylketone resin and a predetermined amount of an amorphous polyetherimide resin are blended, and a predetermined thermal characteristic is determined. A film-like insulator made of a thermoplastic resin composition that satisfies the above conditions is used as an insulating layer, and a conductive foil having a conductive circuit formed thereon is provided thereon, so that the flexibility and mechanical strength normally required for this type of substrate are provided. And has sufficient solder heat resistance, and the conductor foil such as copper foil and the insulating layer are laminated and integrated by relatively low-temperature heat fusion,
There is an advantage of having excellent adhesive strength.

Further, the invention relating to the method for manufacturing a flexible printed wiring board is a method for efficiently manufacturing a flexible printed wiring board having the above-mentioned advantages because steps such as application of an adhesive are omitted.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a manufacturing process of a flexible printed wiring board.

FIG. 2 is a schematic view showing a manufacturing process of a flexible printed wiring board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Film-shaped insulator 2 Copper foil 3 Hole 4 Copper plating 5, 7 Double-sided copper-clad laminate 6 Conductive paste

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05K 3/00 H05K 3/00 R 3/38 3/38 B // B29K 73:00 79:00 B29L 9 : 00 31:34 (72) Inventor Jun Takagi 5-8, Mitsuya-cho, Nagahama-shi, Shiga Prefecture Mitsubishi Plastics Co., Ltd. Inside Nagahama Plant (72) Inventor Koichiro Taniguchi 5-8, Mitsuya-cho, Nagahama-shi, Shiga Prefecture Mitsubishi Plastics, Inc. Inside the Nagahama Plant (72) Inventor Shingo Kuwamura 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Corporation (72) Inventor Kaoru Nomoto 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture F-term ( Reference) 4F100 AB01B AB01C AB33B AB33C AK01A AK49A AK49J AK54A AK54J AK56A AK56K AL01A AR00A BA03 BA08 BA26 DD07B DD07C EA031 EC032 EH152 EJ152 GB43 JA04A JA12A JA20A JB16 JG04JG01JG04B J03 JK17 YY00A 4F211 AA32 AA40 AD03 AD28 AE03 AG01 AG03 AH36 AP05 TA13 TC02 TN07 TQ04 5E343 AA16 AA18 AA33 BB24 BB67 DD54 DD76 GG02

Claims (6)

[Claims] 1. A method comprising 65 to 35% by weight of a polyarylketone resin having a crystal melting peak temperature of 260 ° C. or higher and 35 to 65% by weight of an amorphous polyetherimide resin, which is measured when heated by differential scanning calorimetry. The glass transition temperature is 150 to 230 ° C., and the relationship between the heat of crystal fusion ΔHm and the heat of crystallization ΔHc generated by crystallization during temperature rise is as follows:
(I) A film-like insulator made of a thermoplastic resin composition satisfying the relationship shown in (I) is provided, and a conductor foil is heat-sealed on one or both sides of the film-like insulator, and a conductive circuit is formed on the conductor foil. A flexible printed wiring board formed by: Formula (I): [(ΔHm−ΔHc) / ΔHm] ≦ 0.5 2. The flexible printed circuit board according to claim 1, wherein the conductive foil is a surface-roughened conductive foil. 3. The flexible printed circuit board according to claim 1, wherein the polyarylketone resin is a polyetheretherketone resin. 4. A thermoplastic resin composition comprising 65 to 35% by weight of a polyarylketone resin having a crystal melting peak temperature of 260 ° C. or higher and 35 to 65% by weight of an amorphous polyetherimide resin as a molding material. The glass transition temperature measured when the temperature is raised by scanning calorimetry is 150 to 230.
C., a film-shaped insulator is formed and processed such that the relationship between the heat of crystal melting ΔHm and the heat of crystallization ΔHc generated by crystallization during temperature rise satisfies the relationship represented by the following formula (I). After one or both surfaces of the insulator is laminated with a conductive foil and the thermoplastic resin composition is heat-sealed so as to satisfy the relationship represented by the following formula (II), the conductive circuit is etched to form a conductive circuit. A method for manufacturing a flexible printed wiring board, comprising: Formula (I): [(ΔHm−ΔHc) / ΔHm] ≦ 0.5 Formula (II): [(ΔHm−ΔHc) / ΔHm] ≧ 0.7 5. The method for manufacturing a flexible printed wiring board according to claim 4, wherein the conductive foil to be overlapped on one or both surfaces of the film-shaped insulator is a conductive foil having a roughened surface. 6. The method according to claim 4, wherein the polyaryl ketone resin is a polyether ether ketone resin.