JP5095142B2 - Flexible printed wiring board substrate and manufacturing method thereof - Google Patents

Description

  The present invention relates to a substrate for a flexible printed wiring board and a method for manufacturing the same, and in particular, does not cause curling, twisting, warping, or the like after forming a circuit, and also has bending resistance, heat resistance, dimensional stability, electrical characteristics, and the like. The present invention relates to an excellent flexible printed wiring board substrate and a method for manufacturing the same.

  Conventionally, as a substrate for a flexible printed wiring board, an insulating layer made of a polyimide film and a conductive layer are known to be bonded via an adhesive such as an epoxy resin or an acrylic resin. For example, both surfaces of an insulating layer are known. A double-sided flexible printed circuit board (hereinafter referred to as “double-sided board”) having a five-layer structure in which a conductor layer is laminated with an adhesive such as an epoxy resin or an acrylic resin is known. However, this double-sided plate has a problem that heat resistance, flame retardancy, electrical characteristics and the like are deteriorated because an adhesive layer is present between the conductor layer and the insulating layer. In addition, there has been a problem that the rate of dimensional change is large when the conductor layer is etched or when the substrate is subjected to any heat treatment, which hinders subsequent processes.

  In order to solve such problems, a proposal to solve the above problems by using thermoplastic polyimide having thermocompression bonding as an adhesive layer when bonding the insulating layer made of polyimide film and the conductor layer. (For example, Patent Documents 1 to 6). However, in this configuration, since the thermoplastic polymer is in direct contact with the conductor layer, the rate of dimensional change when the substrate is subjected to any heat treatment increases, and the above problem can be sufficiently solved. It wasn't.

  In addition, in order to maintain the adhesive strength at the interface between the conductor layer and the insulating layer, a certain thickness of the adhesive layer is required. As the insulating layer becomes thinner, the ratio of the adhesive layer to the insulating layer increases, which is described above. Like the double-sided board with a five-layer structure, there is a problem that it is difficult to maintain various substrate characteristics.

JP 2000-103010 A JP 2001-270033 A JP 2001-270034 A JP 2001-270035 A JP 2001-270037 A JP 2001-270039 A

The present invention solves the above problems, can suppress the occurrence of curling, twisting, warping, etc. due to circuit formation or heat treatment, and even when the insulating layer is thin, bending resistance, heat resistance, flame resistance, dimensional stability An object of the present invention is to provide a flexible printed wiring board substrate having a conductor layer on both surfaces excellent in electrical characteristics and the like, and a method for producing the same.

  As a result of intensive studies to solve the above problems, the present inventors formed an insulating layer having a specific configuration directly on the conductor layer without interposing an adhesive layer, and specified the insulating layers to each other. The present inventors have found that the above-mentioned problems can be solved by integrating with an adhesive layer, and have reached the present invention.

That is, the present invention is for a flexible printed wiring board in which a conductor layer is provided on both sides of an insulating layer formed by laminating polyimide films on both sides of an adhesive layer made of a thermoplastic resin having a glass transition point of less than 200 ° C. The thickness of the adhesive layer is not more than 9 % of the thickness of the entire insulating layer, and the dimensional change rate when the conductor layer is entirely etched is within a range of -0.05 to 0.05%. A gist of a substrate for a flexible printed wiring board, characterized in that it is present.

    The gist of the flexible printed wiring board substrate is characterized in that the adhesive strength between the insulating layer and the conductor layer is 1 kN / m or more.

  The flexible film is characterized in that a laminate in which a polyimide film and then an adhesive layer are formed on one side of a conductor layer are arranged so that the adhesive layers face each other and the adhesive layers are bonded together in a heated atmosphere. The gist of the method for manufacturing a printed wiring board substrate is as follows.

  According to the present invention, by specifying the layer configuration of the insulating layer and the thickness of the adhesive layer, both sides suitable for a flexible printed wiring board excellent in bending resistance, heat resistance, flame retardancy, electrical characteristics and dimensional stability. A substrate for a double-sided flexible printed wiring board in which a conductor layer is provided on the substrate is obtained.

  Moreover, according to the manufacturing method of the board | substrate for flexible printed wiring boards of this invention, the board | substrate for flexible printed wiring boards of this invention is easily realizable.

  Hereinafter, the present invention will be described in detail.

  FIG. 1 is a sectional view showing an example of a flexible printed wiring board substrate of the present invention.

The flexible printed wiring board substrate of the present invention has a configuration in which conductor layers are disposed on both sides of an insulating layer. The insulating layer is a laminated film composed of a polyimide film and an adhesive layer, and is a laminated film in which a polyimide film is disposed on both surfaces of the adhesive layer. The thickness of the adhesive layer in the structure is required to be 9% or less of the total thickness of the insulating layer, it is preferred that the thickness of the adhesive layer to less than 8% of the total thickness of the insulating layer, bending resistance, heat resistance A flexible printed wiring board substrate having excellent flame retardancy, electrical characteristics, and dimensional stability can be obtained.

  In the insulating layer having the above configuration, it is not preferable that the thickness of the adhesive layer exceeds 10% of the thickness of the insulating layer because the heat resistance, electrical characteristics, and dimensional stability tend to be inferior.

  The thickness of the entire insulating layer is not particularly limited, but is preferably 14 μm or less, and more preferably 12 μm or less. If it exceeds 14 μm, for example, it tends to be inferior in bending resistance, and in particular tends to be inferior in repeated bending resistance.

  In addition, the thickness of each polyimide film provided on both surfaces of the adhesive layer is not particularly limited as long as the entire insulating layer is in the above range, but from the viewpoint of preventing curling, twisting, warping, etc. Preferably there is.

  Since the insulating layer has a specific configuration in this way, not only the electrical characteristics and mechanical properties including repeated bending resistance are further enhanced, but also the dimensional stability is further improved. The occurrence of curling, twisting, warping and the like can be further suppressed even when an etching process for the above is performed or various heat treatments are performed in the post-process after the circuit formation. Therefore, the flexible printed wiring board substrate of the present invention can not only satisfactorily mount electronic components and the like, but also realize a high mounting density.

  The dimensional stability can be measured by the method B defined in 2.2.4 of the IPC-TM-650 standard. The substrate for a flexible printed wiring board of the present invention needs to have a dimensional change rate obtained by this measurement (when the conductor layer is entirely etched) in the range of -0.05 to 0.05%.

  Moreover, the adhesive strength between the conductor layer arrange | positioned on both surfaces and an above-described insulating layer can be measured by the method prescribed | regulated to the peeling strength test of the copper foil described, for example in JIS-C6471 standard. . In the flexible printed wiring board substrate of the present invention, it is preferably 1 kN / m or more. When the adhesive strength is less than 1 kN / m, the practicality as a flexible printed wiring board substrate is poor.

  As the adhesive layer for forming the insulating layer, it is necessary to use a resin having a glass transition point of less than 200 ° C., preferably a resin having a glass transition point of 180 ° C. or less, more preferably a glass transition point of 150 ° C. or less. Resin. If the glass transition point is less than 200 ° C., adhesiveness based on thermal fluidity is easily developed at the time of thermocompression bonding, and the adhesive layers can be easily bonded and integrated. On the other hand, if the glass transition point is 200 ° C. or higher, the temperature for pressure bonding in a heated atmosphere during production tends to be high, and the production conditions tend to be more difficult, which is not preferable. In addition, when the temperature at which crimping is increased, the difference in thermal expansion between the layers becomes significant depending on the thermal expansion coefficient specific to the material. In particular, the difference in thermal expansion between the conductor layer and the insulating layer is insulated as residual strain. The rate of inclusion in the layer increases. For this reason, when the temperature for pressure bonding becomes high, the dimensional change caused by the release of residual strain tends to increase when the conductor layer is removed by etching the entire surface. Therefore, in order to suppress the dimensional change rate when the entire surface is etched, it is considered preferable to use an adhesive layer that can be pressure-bonded at a lower temperature.

  On the other hand, when an adhesive layer that can be pressure-bonded at a low temperature is used, various properties as a substrate material such as heat resistance tend to deteriorate. However, in the configuration of the present invention, the thickness of the adhesive layer is less than the thickness of the insulating layer. It has been found that by reducing the thickness to 10% or less, various characteristics including heat resistance are maintained.

Tree fat used in the adhesive layer needs to be a thermoplastic resin. Specific examples of the thermoplastic resin include thermoplastic polyimide, polyamideimide, polyetherimide, polyetheretherketone, polyesters, polyarylates, and fluororesins.

  Although it does not specifically limit as a polyimide film which forms an insulating layer, The film which consists of an aromatic polyimide which is non-thermoplastic whose glass transition point measured with the thermomechanical property analyzer (TMA) is 300 degreeC or more. Preferably used.

The polyimide film is preferably a single layer composed of a single component of the above-mentioned non-thermoplastic polyimide, from the viewpoint of maintaining various characteristics when used as a substrate, but at least the above-mentioned non-heat for the purpose of developing a specific function. A laminated film comprising a plurality of components including a plastic polyimide film may be used.
Examples of the non-thermoplastic aromatic polyimide include those having a structure represented by the following structural formula (1).

Here, R ₁ represents a tetravalent aromatic residue, and R ₂ represents a divalent aromatic residue.

  Examples of the conductor layer include metal foil made of a conductive material such as copper, aluminum, iron, silver, palladium, nickel, chromium, molybdenum, tungsten, or an alloy thereof, and copper foil is most suitable.

  The surface of the conductor layer in contact with the insulating layer may be subjected to chemical or mechanical surface treatment in order to improve the adhesion with the insulating layer. Examples of chemical surface treatment include plating treatment such as nickel plating and copper-zinc alloy plating, treatment with a surface treatment agent such as aluminum alcoholate, aluminum chelate, and silane coupling agent, and other thin coatings with polymers. Of these, surface treatment with a silane coupling agent is preferred. As the silane coupling agent, a silane coupling agent having an amino group can be suitably used. On the other hand, examples of the physical surface treatment include a roughening treatment.

  Although the thickness of a conductor layer is not specifically limited, The thing of 5 micrometers or more and 30 micrometers or less is preferable.

  The substrate for a flexible printed wiring board of the present invention can be easily obtained by pressure-bonding a laminate in which a polyimide film and then an adhesive layer are formed on one side of a conductor layer, with the adhesive layers facing each other and heating in a heated atmosphere. Can be obtained.

    Examples of the method for forming a polyimide film and then an adhesive layer on one surface of the conductor layer include a method in which a polyimide precursor solution is applied on the conductor layer and then dried and thermally cured. Here, the polyimide precursor is the one that becomes the above structural formula (1) after being thermally cured, and any compound can be used as long as it is such a compound.

  After the precursor solution that cures to become a non-thermoplastic polyimide and then the resin solution that constitutes the adhesive layer are sequentially applied onto a conductor layer such as a copper foil, it may be thermally cured together, or the polyimide precursor solution After coating, the resin solution constituting the adhesive layer may be applied to the dried and heat-cured copper foil with polyimide film and dried.

  Industrially, a die coater, a multilayer die coater, a gravure coater, a comma coater, a reverse roll coater, a doctor blade coater, or the like can be used industrially. It can be carried out by a method of heating in a furnace under an inert gas atmosphere while the foil is wound up in a roll shape, a method of providing a heating zone in the production line, or the like.

As a polyimide precursor, the polyamic acid shown by following Structural formula (2) or its alkylester is mentioned, for example. The polyimide precursor solution usually consists of a polyamic acid and a solvent.

Here, R ₃ is a hydrogen atom or an alkyl group.

A solution comprising a polyamic acid is prepared by mixing an aromatic tetracarboxylic dianhydride represented by the following structural formula (3) and an aromatic diamine represented by the following structural formula (4) with a non-aqueous compound such as N, N′-dimethylacetamide. It can be produced by reacting in a protic polar solvent.

Here, R ₁ represents a tetravalent aromatic residue, and R ₂ represents a divalent aromatic residue.

  Specific examples of the aromatic tetracarboxylic dianhydride represented by the structural formula (3) include pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 3,3 ′, 4,4 ′. -Benzophenone tetracarboxylic acid, 3,3 ', 4,4'-diphenylsulfone tetracarboxylic acid, 2,3,3', 4'-diphenyl ether tetracarboxylic acid, 2,3,3 ', 4'-benzophenone tetracarboxylic acid Acid, 2,3,6,7-naphthalenetetracarboxylic acid, 1,4,5,7-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, 3,3 ', 4,4' -Diphenylmethanetetracarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) propane, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane, 3,4, , 10-tetracarboxyperylene, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] propane, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] hexafluoropropane And the dianhydrides. These aromatic tetracarboxylic dianhydrides can be used in combination of two or more. In the present invention, pyromellitic acid, dianhydride of 3,3 ′, 4,4′-biphenyltetracarboxylic acid or a mixture thereof is particularly preferable.

  Specific examples of the aromatic diamine represented by the structural formula (4) include p-phenylene diamine, m-phenylene diamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane. 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 1,2-bis (anilino) ethane, diaminodiphenylsulfone, diaminobenz Anilide, diaminobenzoate, diaminodiphenyl sulfide, 2,2-bis (p-aminophenyl) propane, 2,2-bis (p-aminophenyl) hexafluoropropane, 1,5-diaminonaphthalene, diaminotoluene, diaminobenzotrifluor Ride, 1,4-bis (p- Minophenoxy) benzene, 4,4′-bis (p-aminophenoxy) biphenyl, diaminoanthraquinone, 4,4′-bis (3-aminophenoxyphenyl) diphenyl sulfone, 1,3-bis (anilino) hexafluoropropane, Examples thereof include 1,4-bis (anilino) octafluorobutane, 1,5-bis (anilino) decafluoropentane, 1,7-bis (anilino) tetradecafluoroheptane and the like. These aromatic diamines can be used in combination of two or more. In the present invention, p-phenylenediamine, 4,4′-diaminodiphenyl ether or a mixture thereof is particularly preferable.

  In the present invention, an amine, diamine, dicarboxylic acid, tricarboxylic acid, or tetracarboxylic acid derivative having a polymerizable unsaturated bond may be added to the polyimide precursor solution to form a crosslinked structure during thermal curing. . Specifically, maleic acid, nadic acid, tetrahydrophthalic acid, ethynylaniline and the like can be used.

  In addition, there is no particular problem even if the polyimide precursor is partially imidized due to synthesis conditions, drying conditions, and other reasons of the polyimide precursor.

  Moreover, you may mix other heat resistant resins, such as a polyimide resin and a polyamide-imide resin, which are soluble in a solvent, in the solution of these polyimide precursors. Furthermore, in order to improve adhesiveness (adhesiveness) and film properties, a silane coupling agent and various surfactants can be added in minute amounts.

  The laminated body in which the polyimide film and then the adhesive layer are formed on one side of the conductor layer thus obtained are arranged with the adhesive layers facing each other, and the adhesive layers are bonded and integrated in a heated atmosphere. Examples of the method include a batch type vacuum press, a continuous roll press, a belt press, and the like.

The heating temperature is not particularly limited, but is preferably lower than the decomposition point temperature of the resin constituting the adhesive layer and exceeding the glass transition point of the resin constituting the adhesive layer. Usually, it is in the range of 150 to 250 ° C. Although the pressure-bonding force is not particularly limited, it may be usually in the range of 10 to 1000 N / cm ² . When the pressure is less than 10 N / cm ² , it is not preferable because the adhesion between the adhesive layers tends to be insufficient or the pressure is not uniformly pressed. When the pressure exceeds 1000 N / cm ² , for example, the conductor layer is strong. It is not preferable because the material tends to be destroyed by the applied pressure.

  EXAMPLES Next, although this invention is demonstrated concretely based on an Example, this invention is not limited only to these Examples. In the following examples and comparative examples, methods for measuring various physical properties and raw materials are as follows.

[1] Measuring method (1) Adhesive strength (kN / m): The adhesive strength between the insulating layer and the conductor layer was measured using a Tensilon tester (manufactured by Intesco, precision universal material testing machine 2020). In the measurement, a test piece was prepared according to the method described in the section of JIS-C6471 copper peel strength test, and the substrate was subjected to Method A (90 ° direction peel).

(2) Solder heat resistance: A test piece obtained by cutting a produced substrate into a 40 mm square was used. The test piece was left to stand in an atmosphere of 23 ° C. and 60 ± 5% RH for 48 hours for humidity control. The test piece was floated and taken out for 5 minutes in a solder bath heated and melted at 300 ° C. in a conditioned atmosphere. After the test, it was confirmed visually that there was no abnormality such as swelling. No abnormality was indicated as ○, and abnormality such as swelling was observed as ×.

(3) Dimensional change rate (%): A test in which holes having a hole diameter of 1 mm were formed in the four corners of a substrate cut out to a width of 270 mm and a length of 290 mm according to the method described in IPC-TM-650, item 2.2.4. Created a piece. Then, according to Method B, the dimensional change rate during etching was obtained. The value was calculated by averaging the dimensional change rate obtained from the measured values at 6 points between the holes.

(4) Folding strength: an index of repeated bending resistance. According to the method described in JIS C-5016, the bending strength of the bent surface is measured at a radius of curvature of 0.4 mm. It was evaluated as follows.

○: 800 times or more Δ: 600 to 799 times ×: 1 to 599 times

(5) Glass transition point (Tg): Using a fully dried film having a thickness of about 10 μm as a sample, using a thermomechanical property analyzer (TMA, TMA2940 manufactured by TA Instruments), a constant speed of 5 ° C./min. The temperature was raised from 20 ° C. in nitrogen in a 30 mN tension mode, and the dimensional change with respect to the initial length of about 12.5 mm (at 20 ° C.) was measured. Tg was the temperature at the inflection point of the temperature-dimension change plot line.

[2] Production Example of Non-thermoplastic Polyimide Precursor Solution In order to form an insulating layer, a non-thermoplastic polyimide precursor solution was synthesized. The terms used in the following description are as follows.
(Reaction component)
BPDA: 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride ODA: 4,4′-oxydianiline PDA: p-phenylenediamine (solvent)
DMAc: N, N-dimethylacetamide NMP: N-methyl-2-pyrrolidone

(Synthesis example)
In a three-necked flask, under a nitrogen gas stream, 30.03 g (0.15 mol) of ODA, 91.92 g (0.85 mol) of PDA, 2330 g of DMAc and 999 g of NMP were collected, and this flask was placed in ice water, and the contents were placed for 30 minutes. Stir. Next, 294.22 g (1.00 mol) of BPDA was added, and the mixture was stirred in a hot water bath at 40 ° C. for 1 hour to obtain a uniform solution composed of polyamic acid . This is referred to as a polyimide precursor solution “P-1”.

[3] Production Example of Thermoplastic Polyimide Precursor Solution A thermoplastic polyimide precursor solution was synthesized in order to form an adhesive layer. The terms used in the following description are as follows.
(Reaction component)
ODPA: 3,3 ′, 4,4′-diphenyl ether tetracarboxylic dianhydride HMDA: hexamethylenediamine (solvent)
NMP: N-methyl-2-pyrrolidone

(Production example)
Under a nitrogen gas stream, 18.36 g (0.158 mol) of HMDA and 420 g of NMP were collected in a three-necked flask, the flask was placed in ice water, and the contents were stirred for 30 minutes. Next, 49.04 g (0.158 mol) of ODPA was added, and the mixture was stirred in a hot water bath at 40 ° C. for 1 hour to obtain a uniform solution composed of polyamic acid . This is designated as polyimide precursor solution “P-2”.

  The polyimide precursor solutions “P-1” and “P-2” were applied on a clean glass substrate by a bar coater so that the thickness of the heat-cured film was 10 μm, and dried at 130 ° C. for 10 minutes. Next, the temperature was raised from 100 ° C. to 360 ° C. in a nitrogen atmosphere over 2 hours, and then heat-treated at 360 ° C. for 2 hours. After the polyimide precursor was thermoset and imidized, the polyimide film was peeled off from the glass substrate. Obtained.

  As a result of measuring the film obtained from the polyimide precursor solution “P-1” by TMA, Tg of this polyimide film was not observed at a temperature of 400 ° C. or lower.

  Moreover, as a result of measuring the film obtained from polyimide precursor solution "P-2" by TMA, Tg of this polyimide film was 125 degreeC.

Reference example 1
The polyimide precursor solution “P-1” was applied to the roughened surface of the electrolytic copper foil having a thickness of 9 μm by a bar coater so that the thickness of the film after thermosetting was 6.3 μm, and dried at 130 ° C. for 10 minutes. . Next, in order to form an adhesive layer, the polyimide precursor solution “P-2” was applied to the coated surface by a bar coater so that the thickness of the heat-cured film became 0.7 μm, and dried at 130 ° C. for 10 minutes. After fixing to a metal frame and raising the temperature from 100 ° C. to 350 ° C. in a nitrogen atmosphere over 2 hours, heat treatment is performed at 350 ° C. for 5 minutes, the polyimide precursor is thermoset and imidized, and a copper foil / non-thermoplastic polyimide film / The laminated film which consists of three layers of a thermoplastic polyimide film was obtained.

Next, the two laminated films were superposed so that the thermoplastic polyimide films face each other, and heated under pressure at a pressure of 300 N / cm ² and a temperature of 200 ° C. for 30 minutes. Thereafter, the pressure was kept down to 70 ° C., and the resultant was thermocompression-bonded and integrated.

  The obtained conductor layer (copper foil) / polyimide film (non-thermoplastic polyimide) / adhesive layer (thermoplastic polyimide) / polyimide film (non-thermoplastic polyimide) / conductor layer (copper foil) has a five-layer structure. The thickness of each conductor layer was 9 μm, the total thickness of the insulating layer was 14 μm, the thickness of the adhesive layer among the insulating layers was 1.4 μm, and the total thickness was 32 μm. Table 1 shows the physical properties measured for this flexible printed wiring board substrate.

Example 2
The thickness of the film after thermosetting the polyimide precursor solution “P-1” is 5.5 μm so that the thickness of the film after thermosetting the polyimide precursor solution “P-2” is 0.5 μm. The thickness of the conductor layer is 9 μm each, the total thickness of the insulating layer is 12 μm, and the thickness of the adhesive layer (thermoplastic polyimide) of the insulating layer is 1 μm, as in Reference Example 1 except that A flexible printed wiring board substrate having a thickness of 30 μm was obtained. Table 1 shows the physical properties measured for the obtained flexible printed wiring board substrate.

Example 3
An NMP solution containing 8% by weight of polyvinylidene fluoride (abbreviation: PVDF, SOLEF1010 manufactured by Solvay Solexis, Tg = 178 ° C.) was prepared, and this was used as a resin solution for the adhesive layer. A polyimide film having a thickness of 5.5 μm was formed on the roughened surface of the 9 μm thick electrolytic copper foil using the polyimide precursor solution “P-1” by the method described in Reference Example 1. Next, the PVDF solution was applied by a bar coater so that the thickness after drying was 0.5 μm, and dried at 180 ° C. for 10 minutes. Next, the two laminated films were overlapped so that the PVDF layers face each other, and heated under pressure at a pressure of 300 N / cm ² and a temperature of 185 ° C. for 30 minutes. Thereafter, the pressure was kept down to 70 ° C., and the resultant was thermocompression-bonded and integrated.

  The obtained five-layer substrate has a conductor layer thickness of 9 μm, an insulating layer thickness of 12 μm, an adhesive layer (PVDF resin) thickness of 1 μm of the insulating layer, and an overall thickness of 30 μm. there were. Table 1 shows the physical properties measured for the obtained flexible printed wiring board substrate.

Example 4
An NMP solution containing 8% by weight of a resin (abbreviation: P3001, Tg = 175 ° C.) obtained by melt-kneading a polycarbonate resin and a polyarylate resin (U-100 manufactured by Unitika) at a weight ratio of 1: 1 was prepared. A resin solution for the adhesive layer was obtained. A polyimide film having a thickness of 5.5 μm was formed on the roughened surface of the 9 μm thick electrolytic copper foil using the polyimide precursor solution “P-1” by the method described in Reference Example 1. Next, the P3001 solution was applied by a bar coater so that the thickness after drying was 0.5 μm, and dried at 180 ° C. for 30 minutes. Next, the two laminated films were superposed so that the P3001 layers face each other, and heated under pressure at a pressure of 300 N / cm ² and a temperature of 220 ° C. for 30 minutes. Thereafter, the pressure was kept down to 70 ° C., and the resultant was thermocompression-bonded and integrated.

  The obtained five-layered substrate has a conductor layer thickness of 9 μm, an insulating layer thickness of 12 μm, an insulating layer adhesive layer (P3001 resin) thickness of 1 μm, and an overall thickness of 30 μm. there were. Table 1 shows the physical properties measured for the obtained flexible printed wiring board substrate.

Comparative Example 1
In the same manner as in Example 2 except that the polyimide precursor solution “P-2” was applied so that the thickness of the film after thermosetting was 1 μm, the thickness of the conductor layer was 9 μm and the total thickness of the insulating layer was A flexible printed wiring board substrate having a thickness of 13 μm, an adhesive layer (thermoplastic polyimide) of 2 μm among the insulating layers, and an overall thickness of 31 μm was obtained. Table 1 shows the physical properties measured for the obtained flexible printed wiring board substrate.

Comparative Example 2
The polyimide precursor solution “P-1” was applied by a bar coater so that the thickness of the film after thermosetting was 10 μm, and dried at 130 ° C. for 10 minutes. Next, the thickness of the conductor layer was 9 μm each in the same manner as in Reference Example 1 except that the polyimide precursor solution “P-2” was applied to the coated surface by a bar coater so that the thickness of the film after thermosetting was 2 μm. A flexible printed wiring board substrate was obtained in which the total thickness of the insulating layer was 24 μm, the thickness of the adhesive layer (thermoplastic polyimide) of the insulating layer was 4 μm, and the total thickness was 42 μm. Table 1 shows the physical properties measured for the obtained flexible printed wiring board substrate.

Examples 2 to 4 all satisfy the requirements of the present invention, and a substrate that can be an excellent flexible printed wiring board was obtained.

  In Comparative Examples 1 and 2, the thickness ratio of the adhesive layer (thermoplastic polyimide) in the insulating layer is large and does not satisfy the requirements of the present invention, and the dimensional change rate when the conductor layer is entirely etched satisfies the requirements of the present invention. It was not satisfied, and other characteristics were inferior.

  In Comparative Example 2, the thickness of the entire insulating layer was large, and the bending resistance was inferior.

It is sectional drawing which shows an example of the board | substrate for flexible printed wiring boards of this invention.

Explanation of symbols

1: Conductor layer 2: Insulating layer 3: Polyimide film 4: Adhesive layer

Claims (3)

A substrate for a flexible printed wiring board in which a conductor layer is provided on both sides of an insulating layer formed by laminating polyimide films on both sides of an adhesive layer made of a thermoplastic resin having a glass transition point of less than 200 ° C., The thickness of the adhesive layer is 9 % or less of the total thickness of the insulating layer, and the dimensional change rate when the entire conductor layer is etched is in the range of -0.05 to 0.05%. Flexible printed wiring board substrate. The flexible printed wiring board substrate according to claim 1, wherein the adhesive strength between the insulating layer and the conductor layer is 1 kN / m or more. The laminated body in which the polyimide film and then the adhesive layer are formed on one side of the conductor layer are arranged so that the adhesive layers are opposed to each other, and the adhesive layers are bonded and integrated in a heated atmosphere. The manufacturing method of the board | substrate for flexible printed wiring boards of 2.