JP6443927B2 - Sensor - Google Patents

Description

  The present invention relates to a printed wiring board, a sensor, and a method for manufacturing a printed wiring board.

  A printed wiring board widely used for electronic parts and the like protects a circuit constituted by a conductive pattern by covering a conductive pattern laminated on one surface side of an insulating base film with a cover coat. . For example, in the case of a flexible printed wiring board, a polyimide film is usually used as a material for the cover coat, and this polyimide film is bonded to one surface of the base film and the conductive pattern via an adhesive layer.

  Since the above adhesive layer generally has low solvent resistance, the base is used in flexible printed wiring boards for automobiles that are in direct contact with or possibly in contact with solvents and flexible printed wiring boards that are used in environments exposed to liquids. It has been studied that a cover coat is directly laminated on one surface of a film and a conductive pattern without using an adhesive layer. For example, in the printed wiring board described in Japanese Patent Application Laid-Open No. 2000-138422, the base film on which the conductive pattern is laminated is composed of a liquid crystal polymer, and is composed of another liquid crystal polymer whose melting point is about 40 ° C. lower than this liquid crystal polymer. The cover coat film is integrated by direct thermocompression bonding to one surface of the base film and the conductive pattern. This eliminates the need for the adhesive layer.

JP 2000-138422 A

  However, in the printed wiring board described in Japanese Patent Application Laid-Open No. 2000-138422, it is difficult to improve the solvent resistance because the base film and the cover coat are not sufficiently integrated. In particular, when applied to a sensor or the like used in a highly permeable solvent such as methanol, there is a problem that the solvent penetrates from the boundary portion between the base film and the cover coat and the cover coat is easily peeled off.

  The present invention has been made based on the above-described circumstances, and a printed wiring board, a sensor, and a printed wiring board capable of suppressing a decrease in solvent resistance while directly laminating a cover coat on one surface of a base film and a conductive pattern. It aims at providing the manufacturing method of.

  A printed wiring board according to an aspect of the present invention made to solve the above problems includes a base film having insulating properties, a conductive pattern laminated on one surface side of the base film, the base film, and the base film. A cover coat directly laminated on one surface of the conductive pattern, wherein the base film and the cover coat are mainly composed of a liquid crystal polymer, and a difference in melting point between the base film and the cover coat is −5 ° C. or more and 5 ° C. The storage elastic modulus at 320 ° C. obtained by measuring with the rheometer of the base film is 0.1 to 10 times the storage elastic modulus at 320 ° C. obtained by measuring with the rheometer of the cover coat. The printed wiring board is as follows.

  The sensor which concerns on another aspect of this invention made | formed in order to solve the said subject is a sensor which has the printed wiring board of the said invention.

  A method for manufacturing a printed wiring board according to still another aspect of the present invention made to solve the above-described problems includes a base film having an insulating property and a laminate including a conductive pattern laminated on one surface side of the base film. And a step of thermocompression bonding a cover coat film directly to one surface of the base film and the conductive pattern of the laminate, wherein the base film and the cover coat film are mainly composed of a liquid crystal polymer. The difference in melting point between the base film and the cover coat film as a component is −5 ° C. or more and 5 ° C. or less, and the storage elastic modulus at 320 ° C. obtained by measuring with the rheometer of the base film is the cover coat. 0.1 to 10 times the storage elastic modulus at 320 ° C. obtained by measuring with a film rheometer It is a manufacturing method of a printed wiring board.

  According to the printed wiring board of the present invention, it is possible to suppress a decrease in solvent resistance while directly laminating a cover coat on one surface of the base film and the conductive pattern. Moreover, according to the sensor of this invention, since it has the printed wiring board of this invention which can suppress a fall of solvent resistance, durability can be improved, for example, when it applies to the use used by being immersed in a solvent. Moreover, according to the method for producing a printed wiring board of the present invention, the printed wiring board of the present invention can be produced easily and reliably.

It is a typical sectional view of a printed wiring board concerning one embodiment of the present invention. It is sectional drawing according to process which shows typically one Embodiment of the manufacturing method of the printed wiring board of this invention. It is sectional drawing according to process which shows typically one Embodiment of the manufacturing method of the printed wiring board of this invention. It is sectional drawing according to process which shows typically one Embodiment of the manufacturing method of the printed wiring board of this invention.

[Description of Embodiment of the Present Invention]
A printed wiring board according to one embodiment of the present invention includes an insulating base film, a conductive pattern laminated on one surface side of the base film, and a direct lamination on one surface of the base film and the conductive pattern. The base film and the cover coat are mainly composed of a liquid crystal polymer, and the difference in melting point between the base film and the cover coat is −5 ° C. or more and 5 ° C. or less. A printed wiring board having a storage elastic modulus at 320 ° C. obtained by measuring with a meter of 0.1 to 10 times the storage elastic modulus at 320 ° C. obtained by measuring with a rheometer of the cover coat.

  Here, the “main component” is a component having the largest content, for example, a component having a content of 50% by mass or more. The “melting point” is a melting point measured by a differential scanning calorimeter (DSC) in accordance with JIS-K-7121 (2012). The “storage modulus” is a measured value at 320 ° C. measured with a rheometer in accordance with JIS-K-7199 (1999).

  The printed wiring board includes a cover coat that is directly laminated on one surface of the base film and the conductive pattern. In addition, the printed wiring board has a liquid crystal polymer as the main component of both the base film and the cover coat, and the ratio of the melting point of the base film and the cover coat and the ratio of the storage elastic modulus are in the specific range, In the thermocompression bonding process of the cover coat film when manufacturing the printed wiring board, the base film and the cover coat film are melted and integrated. Thereby, the inconvenience resulting from the fall of solvent resistance, such as peeling of the cover coat by the penetration | invasion of the solvent from the boundary part of a base film and a cover coat, for example can be suppressed. Therefore, according to the printed wiring board, it is possible to suppress a decrease in solvent resistance while directly laminating the cover coat on one surface of the base film and the conductive pattern.

  In the printed wiring board, since the cover coat is directly laminated on one surface of the base film and the conductive pattern without using the adhesive layer, inconvenience when using the adhesive layer can be suppressed. Disadvantages when using the adhesive layer include, for example, deterioration of electrical characteristics due to the flame retardant added to the adhesive layer, and dielectric loss of the adhesive layer when applied to electronic equipment used in the high frequency region. The resulting high-frequency characteristics are reduced.

  The melting point of the base film and the cover coat is preferably 300 ° C. or higher. By setting the melting point within the above range, thermal deformation and thermal degradation during solder reflow can be suppressed.

The storage elastic modulus at 320 ° C. obtained by measuring with the rheometer of the base film and the cover coat is preferably 1 × 10 ⁴ Pa or more. By setting the storage elastic modulus in the above range, the liquid crystal polymer can be prevented from flowing out in the thermocompression bonding process of the cover coat film when the printed wiring board is manufactured, and thus the dimensional stability can be improved.

  The difference in tensile strength between the base film and the cover coat is preferably −5 MPa or more and 5 MPa or less. By setting the difference in the tensile strength within the above range, the base film and the cover coat are more firmly integrated, so that it is possible to further suppress a decrease in solvent resistance. In addition, the said "tensile strength" points out the larger one among the tensile breaking strength measured by the method based on ASTMD882-12, and the tensile yield strength.

  The tensile strength of the base film and the cover coat is preferably 100 MPa or more. By making the said tensile strength into the said range, the mechanical strength of a base film and a cover coat can be improved.

  The peel strength between the conductive pattern and the cover coat is preferably 5 N / cm or more. By setting the peel strength within the above range, electrical reliability can be improved. The “peel strength” is a peel strength obtained by a 180 ° direction peel test in accordance with JIS-C-6471 (1995).

  As the liquid crystal polymer, thermoplastic liquid crystal polyester, thermoplastic liquid crystal polyester amide, and combinations thereof are preferable. By using the liquid crystal polymer as the specific polymer, since the base film and the cover coat are more firmly integrated, it is possible to further suppress a decrease in solvent resistance.

  The sensor which concerns on another aspect of this invention is a sensor which has the said printed wiring board.

  Since the sensor has the printed wiring board that can suppress a decrease in solvent resistance, for example, at least a part of a contact portion between the base film and the cover coat in the printed wiring board is in contact with a liquid such as a solvent. When applied to the sensor used in, durability can be improved.

  The method for manufacturing a printed wiring board according to still another aspect of the present invention includes a step of obtaining a laminate including an insulating base film and a conductive pattern laminated on one surface side of the base film, and the laminate. A step of thermocompression bonding a cover coat film directly to one surface of the base film and the conductive pattern, wherein the base film and the cover coat film are mainly composed of a liquid crystal polymer, and the base film and the cover The difference in melting point of the coating film is −5 ° C. or more and 5 ° C. or less, and the storage elastic modulus at 320 ° C. obtained by measuring with the rheometer of the base film is measured with the rheometer of the cover coating film. In the manufacturing method of the printed wiring board which is 0.1 time or more and 10 times or less of the storage elastic modulus in 320 degreeC obtained That.

  In the method for producing the printed wiring board, the main component of both the base film and the cover coat film is a liquid crystal polymer, and the difference between the melting points of the base film and the cover coat film and the ratio of the storage elastic modulus are within the specific range. Therefore, the printed wiring board that can suppress the decrease in solvent resistance can be easily and reliably manufactured.

  The thermocompression bonding is preferably performed under vacuum. When the thermocompression bonding is performed under vacuum, air can be prevented from being sealed between the base film and the cover coat, so that the base film and the cover coat are more firmly integrated. Thereby, the said printed wiring board which can suppress the fall of solvent resistance can be manufactured easily and reliably. In addition, when the thermocompression bonding is performed under vacuum, air can be prevented from being sealed between the conductive pattern and the cover coat, so that the peel strength between the conductive pattern and the cover coat can be improved. Thereby, the said printed wiring board with high electrical reliability can be manufactured easily and reliably. The “vacuum” refers to “a state of a space filled with a gas having a pressure lower than the normal atmospheric pressure” defined in JIS-Z-8126-1 (1999).

[Details of the embodiment of the present invention]
Preferred embodiments of the present invention will be described below with reference to the drawings.

<Printed wiring board>
FIG. 1 is a schematic cross-sectional view of a printed wiring board 10 according to an embodiment of the present invention. The printed wiring board 10 includes an insulating base film 1, a conductive pattern 2 laminated on one surface side of the base film 1, and a cover coat directly laminated on one surface of the base film 1 and the conductive pattern 2. 3.

(Base film)
The base film 1 has insulating properties and contains a liquid crystal polymer as a main component. As a minimum of content of the liquid crystal polymer in base film 1, 50 mass% is preferred, 70 mass% is more preferred, and 90 mass% is still more preferred. By making the said content more than the said minimum, the fall of solvent resistance can be suppressed more. In addition, the base film 1 may be comprised only from the liquid crystal polymer, and may contain another polymer, a filler, an additive, etc. Further, the base film 1 may be made porous. Moreover, when applying the printed wiring board 10 to a flexible printed wiring board, as the base film 1, what has flexibility is preferable.

  The liquid crystal polymer is not particularly limited as long as it is a melt-formable liquid crystal polymer. For example, thermoplastic liquid crystal polyester, thermoplastic liquid crystal polyester amide, thermoplastic liquid crystal polyester ether, thermoplastic liquid crystal polyester Examples thereof include carbonate and thermoplastic liquid crystal polyesterimide. Of these, thermoplastic liquid crystal polyester, thermoplastic liquid crystal polyester amide, and combinations thereof are preferred. By making the said liquid crystal polymer into the said specific polymer, since the base film 1 and the covercoat 3 are integrated more firmly, the fall of solvent resistance can be suppressed more.

  Specific examples of the liquid crystal polymer include monomer components such as aromatic or aliphatic dihydroxy compounds, aromatic or aliphatic dicarboxylic acids, aromatic hydroxycarboxylic acids, aromatic diamines, aromatic hydroxyamines, and aromatic aminocarboxylic acids. Examples of the known thermoplastic liquid crystal polymer to be introduced include.

  Of these thermoplastic liquid crystal polymers, a thermoplastic liquid crystal polymer containing a repeating unit derived from p-hydroxybenzoic acid and a thermoplastic liquid crystal polymer containing a repeating unit derived from 6-hydroxy-2-naphthoic acid are preferred, and p-hydroxybenzoic acid is preferred. A thermoplastic liquid crystal polymer containing a repeating unit derived from an acid and a repeating unit derived from 6-hydroxy-2-naphthoic acid is more preferred.

  The base film 1 is obtained, for example, by extruding the thermoplastic liquid crystal polymer described above. As the extrusion molding method, any method can be applied as long as the direction of the rigid rod-like molecule of the thermoplastic liquid crystal polymer can be controlled, but the known T-die method, laminate stretching method, inflation method, etc. are industrially advantageous. . In particular, in the inflation method and the laminate stretching method, stress is applied not only in the mechanical axis direction of the film (hereinafter also referred to as “MD direction”) but also in the direction orthogonal to this (hereinafter also referred to as “TD direction”). The base film 1 in which the dielectric properties and the like are controlled in both the MD direction and the TD direction is obtained.

  In extrusion molding, it is preferable to accompany a stretching process in order to control the orientation. For example, in extrusion molding by the T-die method, the melt sheet extruded from the T-die is stretched simultaneously in both the MD direction and the TD direction of the film. Alternatively, the melt sheet extruded from the T die may be stretched once in the MD direction and then stretched in the TD direction.

  The ratio of the draw ratios in the MD direction and the TD direction (TD direction / MD direction) is, for example, about 0.4 to 2.5.

  Moreover, after performing the extrusion molding, stretching may be performed as necessary. The stretching method itself is not particularly limited, and either biaxial stretching or uniaxial stretching may be adopted, but biaxial stretching is preferred because it is easier to control the degree of molecular orientation. For stretching, a known uniaxial stretching machine, simultaneous biaxial stretching machine, sequential biaxial stretching machine or the like can be used.

  Moreover, after performing the said extrusion molding, it may heat-process as needed and may adjust melting | fusing point of a liquid crystal polymer film. The heat treatment conditions can be appropriately set. For example, the heat treatment may be performed for several hours in the temperature range of −10 ° C. or more and 20 ° C. or less with respect to the melting point of the liquid crystal polymer.

  As a minimum of average thickness of base film 1, 5 micrometers is preferred and 10 micrometers is more preferred. On the other hand, the upper limit of the average thickness of the base film 1 is preferably 300 μm, and more preferably 100 μm. When the average thickness of the base film 1 is less than the above lower limit, the strength of the base film 1 may be reduced. On the other hand, when the average thickness of the base film 1 exceeds the above upper limit, it may be difficult to apply to an electronic device that is required to be thin.

  In the present specification, the “average thickness” means the average line between the front-side interface and the back-side interface average line within the measurement length in the cross section cut in the thickness direction of the object. Refers to the distance. Here, the “average line” is an imaginary straight line drawn along the interface, and the total area of the mountains (the total area above the imaginary straight line) divided by the interface and the imaginary straight line and the total of the valleys. It means a line having an equal area (total area below the virtual straight line).

  As a minimum of melting point of base film 1, 300 ° C is preferred, 310 ° C is more preferred, and 320 ° C is still more preferred. Moreover, as an upper limit of melting | fusing point of the base film 1, 360 degreeC is preferable, 350 degreeC is more preferable, and 340 degreeC is further more preferable. By setting the melting point to be equal to or higher than the lower limit, thermal deformation and thermal deterioration during solder reflow can be suppressed. On the other hand, if the melting point exceeds the upper limit, it may be difficult to perform thermocompression bonding with a cover coat film described later.

As a minimum of the storage elastic modulus in 320 degreeC obtained by measuring with the rheometer of the base film 1, 1 * 10 < ⁴ > Pa is preferable and 5 * 10 < ⁴ > Pa is more preferable. Moreover, as an upper limit of the said storage elastic modulus, 1 * 10 < ⁶ > Pa is preferable and 5 * 10 < ⁵ > Pa is more preferable. By setting the storage elastic modulus to be equal to or higher than the above lower limit, the flow-out of the liquid crystal polymer can be suppressed when thermocompression bonding with a cover coat film described later can improve the dimensional stability. On the other hand, when the storage elastic modulus exceeds the upper limit, thermocompression bonding with a cover coat film described later may be difficult.

  The lower limit of the melt viscosity at 320 ° C. measured at a frequency of 1 Hz of the base film 1 is preferably 100 Pa · s, more preferably 120 Pa · s, and even more preferably 150 Pa · s. Further, the upper limit of the melt viscosity is preferably 100,000 Pa · s, more preferably 50,000 Pa · s, and further preferably 10,000 Pa · s. By setting the melt viscosity to be equal to or higher than the above lower limit, it is possible to more effectively suppress the liquid crystal polymer from flowing out when thermocompression bonding with a cover coat film, which will be described later, so that dimensional stability can be further improved. On the other hand, when the said melt viscosity exceeds the said upper limit, there exists a possibility that thermocompression bonding with the film for cover coats mentioned later may become difficult.

  As a minimum of the tensile strength of base film 1, 100 MPa is preferred and 200 MPa is more preferred. Moreover, as an upper limit of the tensile strength of the base film 1, 500 MPa is preferable and 400 MPa is more preferable. By making the said tensile strength more than the said minimum, the mechanical strength of the base film 1 can be improved. On the other hand, when the said tensile strength exceeds the said upper limit, there exists a possibility that manufacturing cost may increase.

  As a minimum of breaking elongation of base film 1, 20% is preferred and 40% is more preferred. Moreover, as an upper limit of the breaking elongation of the base film 1, 80% is preferable and 60% is more preferable. Since the flexibility of a base film can be improved by making the said breaking elongation into the said lower limit or more, the application to a flexible printed wiring board becomes easy, for example. On the other hand, when the breaking elongation exceeds the upper limit, the production cost may increase. The “breaking elongation” is a measured value obtained by a method based on ASTM D882-12.

  As a minimum of the tensile elasticity modulus of base film 1, 500 MPa is preferred and 1000 MPa is more preferred. Moreover, as an upper limit of the tensile elasticity modulus of the base film 1, 5000 MPa is preferable and 4000 MPa is more preferable. The mechanical strength of the base film 1 can be improved by making the said tensile elasticity modulus more than the said minimum. On the other hand, when the tensile modulus exceeds the upper limit, the production cost may increase. The “tensile modulus” is a measured value obtained by a method based on ASTM D882-12.

(Conductive pattern)
The constituent material of the conductive pattern 2 is not particularly limited as long as it is a conductive material. Examples thereof include metals such as copper, aluminum and nickel, and copper is generally used from the viewpoint of cost reduction. The conductive pattern 2 may be plated on the surface.

  The lower limit of the average thickness of the conductive pattern 2 is preferably 2 μm and more preferably 5 μm. On the other hand, the upper limit of the average thickness of the conductive pattern 2 is preferably about 100 μm. When the average thickness of the conductive pattern 2 is less than the above lower limit, the conductivity may be lowered. On the other hand, when the average thickness of the conductive pattern 2 exceeds the above upper limit, it may be difficult to apply to an electronic device that is required to be thin.

  The shape of the conductive pattern 2 is not particularly limited, and examples thereof include a line pattern and a land pattern. For example, when the printed wiring board 10 shown in FIG. 1 is applied to a sensor, the conductive pattern 2 including a pair of wirings 2a as electrodes may be used.

(Cover coat)
The cover coat 3 is directly laminated on one surface of the base film 1 and the conductive pattern 2. The cover coat 3 is mainly composed of a liquid crystal polymer. As a minimum of content of the liquid crystal polymer in cover coat 3, 50 mass% is preferred, 70 mass% is more preferred, and 90 mass% is still more preferred. By making the said content more than the said minimum, the fall of solvent resistance can be suppressed more. In addition, the cover coat 3 may be comprised only from the liquid crystal polymer, and may contain another polymer, a filler, an additive, etc. The cover coat 3 may be made porous. When the printed wiring board 10 is applied to a flexible printed wiring board, the cover coat 3 is preferably flexible.

  Preferred types of liquid crystal polymers contained in the cover coat 3, preferred methods for producing a cover coat film as a material for the cover coat 3, and the average thickness, melting point, storage elastic modulus, melt viscosity, tensile strength, and breakage of the cover coat 3 About the preferable range of elongation and a tensile elasticity modulus, it is the same as that of the base film 1 mentioned above.

(Relationship between base film and cover coat)
The difference in melting point between the base film 1 and the cover coat 3 is −5 ° C. or more and 5 ° C. or less. Further, the storage elastic modulus at 320 ° C. obtained by measuring with the rheometer of the base film 1 is 0.1 to 10 times the storage elastic modulus at 320 ° C. obtained by measuring with the rheometer of the cover coat 3. is there. Accordingly, since the base film and the cover coat film are melted and integrated in the thermocompression bonding process of the cover coat film when the printed wiring board 10 is manufactured, for example, from the boundary portion between the base film 1 and the cover coat 3. Inconvenience due to a decrease in solvent resistance such as peeling of the cover coat 3 due to permeation of the solvent can be suppressed.

  From the viewpoint of further suppressing the decrease in solvent resistance, the difference between the melting points of the base film 1 and the cover coat 3 is preferably −3 ° C. or higher and 3 ° C. or lower, more preferably −1 ° C. or higher and 1 ° C. or lower. More preferably, it is 0. “Substantially 0” means a value obtained by rounding off the first decimal place of the measured value of the melting point of the base film 1 and a value obtained by rounding off the first decimal place of the measured value of the melting point of the cover coat 3. Means the same value. The same applies to “melt viscosity”, “tensile strength”, “breaking elongation”, and “tensile modulus” described later.

  From the viewpoint of further suppressing the decrease in solvent resistance, the storage elastic modulus at 320 ° C. obtained by measuring with the rheometer of the base film 1 is the storage elastic modulus at 320 ° C. obtained by measuring with the rheometer of the cover coat 3. It is preferably 0.5 times or more and 5 times or less, more preferably 1 time. “Substantially 1 time” means that the value obtained by rounding off the first decimal place of the calculated value obtained by dividing the storage elastic modulus of the base film 1 by the storage elastic modulus of the cover coat 3 is 1. To do.

  From the viewpoint of further suppressing the decrease in solvent resistance, the difference in melt viscosity between the base film 1 and the cover coat 3 is preferably -3 Pa · s or more and 3 Pa · s or less, more preferably -1 Pa · s or more and 1 Pa · s or less. Preferably, it is substantially 0.

  From the viewpoint of further suppressing the decrease in solvent resistance, the difference in tensile strength between the base film 1 and the cover coat 3 is preferably -5 MPa or more and 5 MPa or less, more preferably -3 MPa or more and 3 MPa or less, and -1 MPa or more and 1 MPa or less. More preferably, it is particularly preferably substantially zero.

  From the viewpoint of further suppressing the decrease in solvent resistance, the difference in breaking elongation between the base film 1 and the cover coat 3 is preferably −5% to 5%, more preferably −3% to 3%, − It is more preferably 1% or more and 1% or less, and particularly preferably substantially 0.

  From the viewpoint of further suppressing the decrease in solvent resistance, the difference in tensile elastic modulus between the base film 1 and the cover coat 3 is preferably −100 MPa to 100 MPa, more preferably −10 MPa to 10 MPa, and substantially zero. More preferably it is.

(Peel strength between conductive pattern and cover coat)
The lower limit of the peel strength between the conductive pattern 2 and the cover coat 3 is preferably 5 N / cm, more preferably 7 N / cm, and even more preferably 10 N / cm. Electrical reliability can be improved by making the said peeling strength into the said minimum or more. On the other hand, the upper limit of the peel strength is not particularly limited, but is, for example, about 20 N / cm. The peel strength can be controlled by, for example, thermocompression bonding conditions (temperature, pressure bonding time, pressure, degree of vacuum, etc.) in the thermocompression bonding process of the cover coat film described later.

<Sensor>
The sensor according to an embodiment of the present invention includes a printed wiring board 10. Since the sensor includes the printed wiring board 10 that can suppress a decrease in solvent resistance, for example, at least a part of the contact portion between the base film 1 and the cover coat 3 in the printed wiring board 10 is in contact with a liquid such as a solvent. When applied to the sensor used in, durability can be improved.

  Examples of the solvent include alcohol solvents such as methanol and ethanol, hydrocarbon solvents such as gasoline, ether solvents such as diethyl ether, ketone solvents such as acetone, amide solvents such as acetamide, and esters such as ethyl acetate. And solvents based on these solvents. Among these, methanol is a solvent that has extremely high permeability at high temperatures. However, according to the sensor, since the printed wiring board 10 that can suppress a decrease in solvent resistance is included, a sensor that is used in contact with methanol. Durability can be improved even when applied to. In addition, solid content may be melt | dissolved or disperse | distributed to the solvent used as a measuring object.

  Examples of the sensor that is used in contact with the liquid include a sensor that measures physical properties such as the viscosity, temperature, and concentration of the liquid, the amount of liquid, and the flow rate.

<Method for manufacturing printed wiring board>
Next, an embodiment of a method for producing a printed wiring board according to the present invention will be described with reference to FIGS. 2A to 2C, the same components as those in FIG. 1 described above are denoted by the same reference numerals. Further, the description overlapping with the printed wiring board 10 described above is omitted.

  The method for manufacturing a printed wiring board according to the present embodiment includes a step of obtaining a laminate 5 including an insulating base film 1 and a conductive pattern 2 laminated on one surface side of the base film 1 (hereinafter, “step 1”). And a step of thermocompression bonding the cover coat film 30 directly to one surface of the base film 1 and the conductive pattern 2 of the laminate 5 (hereinafter also referred to as “step 2”). And the cover coat film 30 is mainly composed of a liquid crystal polymer, and the difference in melting point between the base film 1 and the cover coat film 30 is −5 ° C. or more and 5 ° C. or less. The storage elastic modulus at 320 ° C. is 0.1 times or more the storage elastic modulus at 320 ° C. obtained by measuring with the rheometer of the cover coat film 30 1 Times is less than or equal to. According to the method for manufacturing a printed wiring board according to the present embodiment, a printed wiring board capable of suppressing the above-described decrease in solvent resistance can be easily and reliably manufactured. Hereinafter, each step will be described.

(Process 1)
Step 1 is a step of obtaining the laminate 5 shown in FIG. 2A. The method for obtaining the laminate 5 is not particularly limited. For example, a conductive film 2 including a pair of wirings 2a is formed by laminating a metal film on one side of the base film 1, masking the metal film, and etching. It is possible to adopt a method of forming As a method for laminating the metal film, for example, a method of thermocompression bonding the base film 1 and a metal foil or the like, a method of bonding the base film 1 and the metal foil or the like with an adhesive, and vapor deposition by depositing a metal on the base film 1 Examples include a method of laminating films. Moreover, you may form the conductive pattern 2 with the ink containing a conductive paste and metal microparticles. In this case, the conductive pattern 2 having various pattern shapes can be formed by a printing technique. In addition, the process 1 may be a process of obtaining the laminated body 5 formed in advance.

(Process 2)
Step 2 is a step in which the cover coat film 30 is directly thermocompression bonded to one surface of the base film 1 and the conductive pattern 2 of the laminate 5 using the press machine 100 (see FIG. 2B). The cover coat film 30 is mainly composed of a liquid crystal polymer, has a melting point difference of −5 ° C. or more and 5 ° C. or less from the base film 1, and has a storage elastic modulus ratio of 0.1 to 10 times the base film 1. Although it is not limited as long as it is twice or less, for example, the same film as the base film 1 may be used.

  The thermocompression bonding conditions may be determined according to the type of liquid crystal polymer constituting the base film 1 and the cover coat film 30. For example, the temperature is 270 ° C. or higher and 350 ° C. or lower, and the pressure bonding time is 10 minutes or longer and 180 minutes. Hereinafter, the pressure may be in the range of 0.1 MPa to 10 MPa. By the thermocompression bonding, the above-described printed wiring board 10 in which the cover coat 3 is directly laminated on one surface of the base film 1 and the conductive pattern 2 is obtained (FIG. 2C).

  In step 2, the thermocompression bonding is preferably performed under vacuum. When the thermocompression bonding is performed under vacuum, air can be prevented from being sealed between the base film 1 and the cover coat 3, so that the base film 1 and the cover coat 3 are more firmly integrated. Thereby, the printed wiring board 10 which can suppress the fall of solvent resistance can be manufactured easily and reliably. Further, when the thermocompression bonding is performed under vacuum, it is possible to suppress air from being sealed between the conductive pattern 2 and the cover coat 3, thereby improving the peel strength between the conductive pattern 2 and the cover coat 3. be able to. Thereby, the printed wiring board 10 with high electrical reliability can be manufactured easily and reliably.

  When the thermocompression bonding is performed under vacuum, the upper limit of the degree of vacuum is preferably 100 mmHg, and more preferably 10 mmHg. By setting the degree of vacuum to the above upper limit or less, it is possible to more effectively suppress air from being sealed between the base film 1 and the cover coat 3 and between the conductive pattern 2 and the cover coat 3. On the other hand, the lower limit of the degree of vacuum is not particularly limited, but is, for example, about 0.1 mmHg.

[advantage]
In the printed wiring board, the main components of both the base film and the cover coat are liquid crystal polymers, and the difference in melting point between the base film and the cover coat and the ratio of the storage elastic modulus are in the specific range. The base film and the cover coat film are melted and integrated in the thermocompression bonding process of the cover coat film when the plate is manufactured. Thereby, for example, it is possible to suppress inconvenience due to a decrease in solvent resistance such as peeling of the cover coat due to permeation of the solvent from the boundary portion between the base film and the cover coat. At the same time, the minute air and moisture remaining between the base film and the conductive pattern are removed, and the adhesion of the conductive pattern can be improved and the occurrence of peeling and swelling due to solvent penetration can be suppressed.

  Since the sensor has the printed wiring board that can suppress a decrease in solvent resistance, for example, at least a part of a contact portion between the base film and the cover coat in the printed wiring board is in contact with a liquid such as a solvent. When applied to the sensor used in, durability can be improved.

  In the method for producing the printed wiring board, the main component of both the base film and the cover coat film is a liquid crystal polymer, and the difference between the melting points of the base film and the cover coat film and the ratio of the storage elastic modulus are within the specific range. Therefore, the printed wiring board that can suppress the decrease in solvent resistance can be easily and reliably manufactured.

[Other Embodiments]
The disclosed embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is not limited to the configuration of the embodiment described above, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims. The

  For example, the printed wiring board may be a printed wiring board (single-sided board) in which a conductive pattern is laminated on one side of the base film as in the embodiment shown in FIG. It may be a printed wiring board (double-sided board) on which patterns are laminated.

  In the case of the double-sided board, it may be a printed wiring board in which a cover coat is directly laminated on one side of the base film, or may be a printed wiring board in which a cover coat is directly laminated on both sides of the base film, It may be a printed wiring board in which a cover coat is directly laminated on one side of the base film and a cover coat is laminated on the other side of the base film via an adhesive layer.

  Moreover, when a cover coat is laminated | stacked on both surfaces of a base film, the difference of melting | fusing point with a base film and ratio of storage elastic modulus do not need to be made into the said specific range about one cover coat.

  Moreover, the said printed wiring board should just be laminated | stacked directly on at least one part of one surface of a base film, and at least one part of one surface of a conductive pattern. Therefore, there may be a region where the cover coat is not laminated on a part of one surface of the base film and the conductive pattern.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

<Method for measuring physical properties of liquid crystal polymer film>
The measuring method of the physical property of the liquid crystal polymer film used by the Example and the comparative example is shown below.

(Melting point)
The melting point was defined as an endothermic peak value that appeared when the temperature was raised at a rate of 10 ° C./min by a differential scanning calorimeter (DSC) in accordance with JIS-K-7121 (2012).

(Storage modulus)
The storage elastic modulus is based on JIS-K-7199 (1999), using a viscoelastic rheometer (“Capillograph 1D PMD-C” manufactured by Toyo Seiki Seisakusho Co., Ltd.), with a heating rate of 3 ° C./min, a frequency of 1 Hz, The measured value at 320 ° C. was measured under the conditions of strain 0.1% and normal stress 5N.

(Tensile strength)
The tensile strength was the larger value of the tensile rupture strength and tensile yield strength measured by a method according to ASTM D882-12.

(Elongation at break and tensile modulus)
The elongation at break and tensile modulus were both measured values obtained by a method based on ASTM D882-12.

<Test Example 1>
A laminate in which a copper wiring pattern having an average width of 5 mm and an average thickness of 25 μm is formed on one surface of a liquid crystal polymer film A having an average thickness of 100 μm and having the physical properties shown in Table 1 below is prepared. A cover coat film provided with an opening of 10 mm × 10 mm was directly thermocompression bonded to one surface of the polymer film A and the copper wiring pattern to obtain a printed wiring board of Test Example 1. As the cover coat film, a liquid crystal polymer film A, which is the same material as the base film of the laminate, was used. The thermocompression bonding conditions were a temperature of 305 ° C., a pressure bonding time of 30 minutes, a pressure of 1 MPa, and a degree of vacuum of 10 mmHg.

<Test Example 2>
In the above test example 1, except that the liquid crystal polymer film B having an average thickness of 100 μm having the physical properties shown in Table 1 below was used instead of the liquid crystal polymer film A, and the thermocompression bonding temperature was changed to 300 ° C. The printed wiring board of Test Example 2 was obtained by the procedure of Test Example 1.

<Test Example 3>
In the above Test Example 1, except that the liquid crystal polymer film B having the physical properties shown in Table 1 below was used in place of the liquid crystal polymer film A and having an average thickness of 100 μm, and the thermocompression bonding temperature was changed to 290 ° C. The printed wiring board of Test Example 3 was obtained by the procedure of Test Example 1.

  For each of the obtained printed wiring boards, the following items were evaluated. The results are shown in Table 2. The physical property values of the base film and the cover coat shown in Table 2 are all the physical property values of the liquid crystal polymer film that is a constituent material.

<Dimensional stability>
The minimum value of the length of one side of the opening of the cover coat of each printed wiring board was measured, and the case where the minimum value was 9.4 mm or more was evaluated as “A”, and the case where it was less than 9.4 mm was evaluated as “B”. In the case of A, since the flow-out of the liquid crystal polymer can be suppressed, it can be evaluated that the dimensional stability is excellent.

<Solvent resistance>
After immersing each printed wiring board in a methanol aqueous solution (60 ° C.) having a concentration of 15% by mass for a predetermined time and drying, the peel strength between the base film and the cover coat of each printed wiring board is measured, and solvent resistance It was used as an index. It can be evaluated that the solvent resistance is better as the peel strength is higher. The predetermined time was 250 hours, 500 hours, and 1000 hours. The peel strength was defined as a peel strength obtained by a 180 ° direction peel test in accordance with JIS-C-6471 (1995). As a reference, the peel strength was also measured for each printed wiring board not immersed in the methanol aqueous solution.

<Peel strength between copper wiring pattern and cover coat>
The peel strength between the copper wiring pattern and the cover coat was defined as the peel strength obtained by a 180 ° direction peel test in accordance with JIS-C-6471 (1995). In addition, each printed wiring board which is not immersed in the said methanol aqueous solution was used for the measurement.

  As shown in Table 2, the solvent resistance of Test Example 1 in which the difference between the melting points of the base film and the cover coat and the ratio of the storage elastic modulus was within the specific range showed a good value even after 1000 hours. . The evaluation of dimensional stability was also good. On the other hand, the solvent resistance of Test Example 2 in which the difference between the melting points of the base film and the cover coat and the ratio of the storage elastic modulus was outside the above specified range decreased to a value less than half that of Test Example 1 after 1000 hours. Moreover, evaluation of dimensional stability was also inferior. Test Example 3 in which the thermocompression bonding temperature was lower than Test Example 2 was good in evaluating the dimensional stability, but the solvent resistance was remarkably inferior to Test Example 1 including unimmersed cases. It was. From this result, according to the printed wiring board of this invention, it turns out that a solvent-resistant fall can be suppressed, laminating | stacking a cover coat directly on one side of a base film and a conductive pattern. In addition, about the peeling strength, all the test examples showed the favorable value of 5 N / cm or more.

  According to the printed wiring board of the present invention, it is possible to suppress a decrease in solvent resistance while directly laminating a cover coat on one surface of the base film and the conductive pattern. Moreover, according to the sensor of this invention, since it has the printed wiring board of this invention which can suppress a fall of solvent resistance, durability can be improved, for example, when it applies to the use used by being immersed in a solvent. Moreover, according to the method for producing a printed wiring board of the present invention, the printed wiring board of the present invention can be produced easily and reliably.

1 Base Film 2 Conductive Pattern 2a Wiring 3 Cover Coat 5 Laminate 10 Printed Wiring Board 30 Cover Coat Film 100 Press

Claims (10)

An insulating base film;
A conductive pattern laminated on one side of the base film;
A cover coat directly laminated on one surface of the base film and the conductive pattern,
The base film and the cover coat are mainly composed of a liquid crystal polymer,
The difference between the melting points of the base film and the cover coat is −5 ° C. or more and 5 ° C. or less,
The storage elastic modulus at 320 ° C obtained by measuring with the rheometer of the base film is 0.1 to 10 times the storage elastic modulus at 320 ° C obtained by measuring with the rheometer of the cover coat,
The sensor which has a printed wiring board whose storage elastic modulus in 320 degreeC obtained by measuring with the rheometer of the said base film and the said cover coat is 1 * 10 < ⁴ > Pa or more and 1 * 10 < ⁶ > Pa or less. The sensor according to claim 1, wherein the base film and the cover coat have a melting point of 300 ° C. or higher. The sensor according to claim 1 or 2, wherein a difference in tensile strength between the base film and the cover coat is -5 MPa or more and 5 MPa or less. The sensor according to claim 3, wherein the base film and the cover coat have a tensile strength of 100 MPa or more. The sensor according to any one of claims 1 to 4, wherein a peel strength between the conductive pattern and the cover coat is 5 N / cm or more. The sensor according to any one of claims 1 to 5, wherein the liquid crystal polymer is a thermoplastic liquid crystal polyester, a thermoplastic liquid crystal polyester amide, or a combination thereof. The sensor according to any one of claims 1 to 6, wherein at least a part of a contact portion between the base film and the cover coat on the printed wiring board is in contact with a liquid. The sensor according to claim 7, wherein the liquid is a solvent. The sensor according to claim 8, wherein the solvent is an alcohol solvent, a hydrocarbon solvent, an ether solvent, a ketone solvent, an amide solvent, an ester solvent, or a mixture of these solvents. The sensor according to claim 9, wherein the alcohol solvent is methanol.

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