JP2013173888A - Polyimide film, and metal-laminated polyimide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide film of excellent close contact adhesion, and capable of maintaining the close contact adhesion even when exposed to a high-temperature environment for a long period, and a metal-laminated polyimide film using the same.SOLUTION: A polyimide film is obtained by forming a polyamic acid into a film-like gel film, and then by stretching and imidizing the same. The polyimide film has a surface elastic modulus more than 1.04 times or more, preferably within a range of 1.06-1.30 times, with respect to a polyimide imidized without stretching the gel film.

Description

  The present invention relates to a polyimide film that can maintain adhesion even when exposed to a high temperature environment for a long period of time, and a metal laminated polyimide film using the polyimide film.

  For materials used in various devices that support modern society, parts in which different substances are bonded, joined and joined are important. For example, a flexible wiring board used for COF (Chip on film), which is widely used in downsizing of electronic equipment, is a copper clad laminated board (FCCL: Flexible Copper Cladd) in which a copper film is formed on the surface of a base resin film. Laminates) material is used.

  In recent years, with the increasing fineness of flexible wiring boards and semiconductor packages, the requirements for polyimide films used for these have increased. Requirements include having a thermal expansion coefficient comparable to that of a metal as a physical property of a polyimide film, and having an elastic modulus, etc. Among them, excellent pattern formation with excellent adhesion between a base material and a metal. There is a need for a substrate that can.

  Then, in order to improve adhesive force, the polyimide film which made L value 75-85 prescribed | regulated by CIE (International Lighting Commission), for example is proposed (refer patent document 1).

JP 2011-777 A

  However, the polyimide film described in Patent Document 1 includes an insufficient range of adhesion strength at normal temperature and adhesion strength when exposed to a high temperature environment for a long period of time. Not enough.

  The present invention for solving the above problems is a polyimide film that has good adhesion at room temperature and can maintain adhesion even when exposed to a high temperature environment for a long period of time, and a metal laminated polyimide film using the polyimide film It is to provide.

  As a result of diligent research to solve the above-mentioned problems, the inventors of the present invention are polyimide films obtained by forming polyamic acid into a film-like gel film, and then stretching and imidizing the gel film. The present inventors have found that the above problems can be solved by a polyimide film characterized by having a surface elastic modulus of 1.04 times or more with respect to a polyimide film that has been imidized, and have completed the present invention.

  Specifically, the present invention provides the following.

(1) After forming a polyamic acid into a film-like gel film, it is a polyimide film obtained by stretching and imidization,
A polyimide film having a surface elastic modulus of 1.04 times or more with respect to a polyimide film imidized without stretching the gel film.

  (2) The polyimide film according to (1), wherein a surface elastic modulus is in a range of 1.06 times to 1.30 times with respect to a polyimide film imidized without stretching the gel film.

  (3) The polyimide film according to (1) or (2), wherein the polyamic acid is synthesized from a raw material containing an aromatic diamine component and an acid anhydride component.

  (4) The polyimide film as described in (3), wherein the aromatic diamine component is 4,4'-diaminophenyl ether, and the acid anhydride component is pyromellitic dianhydride.

(5) A metal laminated polyimide film in which a metal layer is laminated on the polyimide film according to (1) to (4) without using an adhesive,
A metal-laminated polyimide film comprising a nickel alloy or chromium base metal layer and a copper layer made of copper on the surface of the base metal layer.

  ADVANTAGE OF THE INVENTION According to this invention, the adhesiveness in normal temperature and the polyimide film which can maintain adhesiveness even if it exposes to a high temperature environment for a long period of time, and a metal lamination polyimide film using the same can be provided.

It is a figure which shows the force distance curve of AFM of the polyimide film which concerns on 1st Embodiment of this invention. It is a figure which shows the correlation of the displacement amount and load of the evaluation sample of the polyimide film which concerns on 1st Embodiment of this invention. It is sectional drawing of the metal laminated polyimide film which concerns on 2nd Embodiment of this invention. It is a figure which shows distribution of the elastic modulus of the polar surface of a measurement sample.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and may be implemented with appropriate modifications within the scope of the object of the present invention. it can.

[First Embodiment]
The polyimide film according to the first embodiment of the present invention is a polyimide film obtained by forming and imidizing a polyamic acid into a film-like gel film, and then imidizing without stretching the gel film. It is a polyimide film characterized by having a surface elastic modulus of 1.04 times or more with respect to the polyimide film.

  The method for obtaining the polyimide film according to the first embodiment is not particularly limited, but since a film having stable characteristics can be produced relatively easily, industrially, an aromatic diamine component and an acid anhydride component are combined in an organic solvent. A method of obtaining a polyimide film by forming a gel film of the polyamic acid obtained by synthesizing the gel film and imidizing the gel film is preferable. Hereinafter, about the polyimide film which concerns on 1st Embodiment, the aromatic diamine component used in order to synthesize | combine a polyamic acid, an acid anhydride component, the synthesis method of a polyamic acid, and the manufacturing method of a polyimide film are demonstrated in order.

  When producing a polyimide film by the above-described method, first, an aromatic diamine component and an acid anhydride component are polymerized in an organic solvent to obtain a polyamic acid solution.

[Aromatic diamine component]
Specific examples of the aromatic diamine component used for synthesizing the polyamic acid include paraphenylenediamine, metaphenylenediamine, benzidine, paraxylylenediamine, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, 3,3′-dimethyl-4,4′-diaminodiphenylmethane, 1,5-diaminonaphthalene, 3,3′-dimethoxybenzidine, 1, 4-bis (3methyl-5aminophenyl) benzene and amide-forming derivatives thereof are mentioned. Among these aromatic diamine components, it is particularly preferable to use paraphenylenediamine or 4,4′-diaminodiphenyl ether because the polymerization reaction easily proceeds and the resulting polyimide film has excellent flexibility and other physical properties. preferable. Moreover, these aromatic diamine components can be used in combination of two or more.

[Acid anhydride component]
Specific examples of the acid anhydride component include pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 2,3 ′, 3,4′-biphenyltetracarboxylic acid, 3,3 ′. , 4,4′-benzophenonetetracarboxylic acid, 2,3,6,7-naphthalenedicarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) ether, pyridine-2,3,5,6-tetra Examples include acid anhydrides such as carboxylic acids and amide-forming derivatives thereof. Among these acid anhydride components, pyromellitic dianhydride, or 3,3 ′, 4,4 is particularly preferred because the polymerization reaction easily proceeds and the resulting polyimide film is excellent in flexibility and other physical properties. '-Biphenyltetracarboxylic dianhydride is preferred. These acid anhydride components can be used in combination of two or more.

[Method of synthesizing polyamic acid]
The method for synthesizing the polyamic acid is not particularly limited. For example, one of an aromatic amine component or an acid anhydride component is added to an organic solvent, and then the other is added to the organic solvent to obtain an aromatic amine and an acid anhydride. A method of synthesizing them by mixing and polymerizing them so as to be equal is preferred. Moreover, after adding excessively one of an aromatic amine component or an acid anhydride component to a solvent and mixing for a required time, the other can be adjusted and added so that it may become equivalent, and it can also superpose | polymerize.

  Specific examples of the organic solvent used for the synthesis of polyamic acid include, for example, sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide, N, Acetamide solvents such as N-dimethylacetamide and N, N-diethylacetamide, pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone, phenol, o-, m-, or p-cresol , Phenolic solvents such as xylenol, halogenated phenol and catechol, or aprotic polar solvents such as hexamethylphosphoramide and γ-butyrolactone. These organic solvents can be used alone or as a mixture. In addition to the organic solvent, aromatic hydrocarbons such as xylene and toluene may be further used.

  The polyamic acid obtained by the above-described synthesis method is used as a solution-like polyamic acid solution dissolved in a solvent during the production of the polyimide film described later. The polyamic acid solution preferably contains 5 to 40% by weight of solid content. Moreover, the polyamic acid solution may be partially imidized.

[Production method of polyimide film]
Next, the manufacturing method of the polyimide film which concerns on 1st Embodiment of this invention is demonstrated. The method for producing the polyimide film is not particularly limited. For example, (I) a method of obtaining a polyimide film by casting a polyamic acid solution into a film and thermally decyclizing and removing the solvent, and (II) polyamic A method of obtaining a polyimide film by preparing a gel film by mixing a cyclization catalyst and a dehydrating agent into an acid solution, heating and desolvating the gel film, and then imidizing completely is mentioned. Among these, a method for producing a polyimide film using a catalyst (method (II)) is preferable. Hereinafter, a method for producing a polyimide film using a catalyst will be described.

  When producing a polyimide film using a catalyst, the polyamic acid solution has titanium oxide, fine silica, calcium carbonate, calcium phosphate, calcium hydrogen phosphate, polyimide filler, etc. These chemically inert organic fillers and inorganic fillers can be contained. In particular, it is preferable to form fine protrusions by uniformly dispersing silica having a median particle diameter of 1.0 μm or less in the film at a ratio of 0.03 to 0.30% by weight per film resin weight. When the median particle size exceeds 1.0 μm, the surface roughness of the film is impaired. When the addition amount of the orientation filler exceeds 0.30% by weight, a decrease in mechanical strength is observed, and when it is 0.03% by weight or less, a sufficient slidability effect cannot be obtained.

  Specific examples of the cyclization catalyst used in producing the polyimide film include aliphatic tertiary amines such as trimethylamine and triethylenediamine, aromatic tertiary amines such as dimethylaniline, and isoquinoline, pyridine, betapicoline, etc. And at least one amine selected from heterocyclic tertiary amines is preferably used.

  Specific examples of the dehydrating agent used in producing the polyimide film include aliphatic carboxylic acid anhydrides such as acetic anhydride, propionic anhydride and butyric anhydride, and aromatic carboxylic acid anhydrides such as benzoic anhydride. However, acetic anhydride and / or benzoic anhydride are preferred.

  In addition to the cyclization catalyst (imidization catalyst) and the dehydrating agent, the polyamic acid solution may contain a gelation retarder as necessary. Hereinafter, the manufacturing method of a polyimide film is demonstrated in detail.

  A method for industrially producing a polyimide film from a polyamic acid solution to which a cyclization catalyst or the like has been added is not particularly limited. For example, a polyamic acid solution to which a cyclization catalyst, a dehydrating agent, and optional components are added is known T A method in which a gel film having a self-supporting property is formed by casting it on a support from a die with a slit, such as a die, and forming it into a film shape. Is preferred. Here, when a polyimide film obtained by stretching a gel film to obtain an imidized polyimide film (hereinafter also simply referred to as a stretched polyimide film) is heated while stretching the gel film to remove the solvent, and then heat treated at a high temperature. Complete imidization. On the other hand, when obtaining a polyimide film imidized without stretching the gel film (hereinafter, also simply referred to as an unstretched polyimide film), the gel film is heated to remove the solvent, and then heat treated at a high temperature to imidize. To complete.

  More specifically, first, the polyamic acid solution is formed into a film shape through a slit-shaped die, cast on a heated support, and undergoes a thermal ring closure reaction on the support, thereby having self-supporting properties. It becomes a gel film and is peeled from the support. In addition, a well-known metal rotation drum, a metal belt, etc. can be used with a support body. The temperature of the support is controlled by radiant heat such as a liquid or gas heating medium or an electric heater.

  Subsequently, the obtained gel film is heated to 30 to 200 ° C. by receiving heat from the support and / or receiving heat from a heat source such as an electric heater, and causes a ring-closing reaction to dry volatile components such as the liberated organic solvent. Due to this, it has self-supporting properties and is peeled off from the support.

  The gel film peeled off from the support is conveyed by a roll and stretched. The film is stretched in the transport direction, that is, in the machine direction (referred to as MD direction) while the transport speed is regulated by a roll. In stretching in the MD direction, the gel film is sandwiched between a metal roll and a nip roll whose surface is covered with rubber, and the conveyance speed is regulated. Thereafter, the gel film is stretched in the width direction (TD direction) with a known tender device such as a tender roll. Generally, the suitable draw ratio to MD direction and TD direction is 1.01-2.00 times, and the temperature of the gel film in the case of extending | stretching has preferable 10 to 140 degreeC, 50 to 100 ° C. is more preferable. Moreover, when making it want to make the thermal expansion coefficient of TD direction higher than MD direction, it can select by making the draw ratio of TD direction higher than MD direction. At the time of one stretching in the MD direction and the TD direction, the other direction may shrink, so it is necessary to pay attention to the regulation of the conveyance speed with the roll conveyance speed and the nip roll, the utilization of a tender device, and the like.

  The desirable total stretching ratio of the gel film is preferably 1.01 to 2.00 times, and more preferably 1.01 to 1.5 times. If the total stretching ratio is in the range of 1.01 to 2.00 times, a stretched polyimide film having a surface elastic modulus described later of 1.04 times or more with respect to the unstretched polyimide film can be obtained. And if the surface elasticity modulus of a stretched polyimide film is 1.04 times or more with respect to an unstretched polyimide film, when forming the metal laminated polyimide film mentioned later, the adhesiveness of a polyimide film and a base metal layer will be improved. can do. Here, when 10% is stretched in an arbitrary direction, the stretch amount, that is, the stretch scalar, is the stretched 10% length, and the stretch ratio is the ratio of the length before and after stretching. 10 times. If stretching is performed in both the MD direction and the TD direction, the total stretching amount is the scalar amount of the combined vector of the stretching vectors in both directions.

  Moreover, although the thickness of a polyimide film can be adjusted by adjusting a conveyance speed and an extending | stretching rate, as a thickness of the polyimide film for metal lamination polyimide films, 10 micrometers-100 micrometers are preferable. If it is thinner than this, it is difficult to produce a metal laminated polyimide film, and if it is thicker than this, the flexibility of the metal laminated polyimide film is impaired.

  The stretched gel film is continuously heated and dried, and then heat-treated with hot air and / or an electric heater at a temperature of 250 ° C. to 500 ° C. for 15 seconds to 20 minutes. Become.

  The imidization of the gel film also proceeds by heating during stretching, but the temperature and stretching speed during stretching and the heat treatment conditions after stretching are appropriately selected, and the surface elasticity of the polyimide film is unstretched. What is necessary is just to make it 1.04 times or more with respect to the polyimide film of this, More preferably, it should just be 1.04 times-1.3 times. In addition, when the surface elastic modulus of a polyimide film exceeds 1.3 times with respect to an unstretched polyimide film, it will be easy to lose a softness | flexibility.

  In addition, the following method is preferable for producing a small amount as an experiment with respect to the method for industrially producing the polyimide film according to the present invention.

  When producing a small amount of the polyimide film according to the present invention, first, a polyamic acid solution is cast on a support such as a plate glass or a metal plate and heated to obtain a gel film. The obtained gel film is peeled off from the support and adjusted to a substantially rectangular shape. The end of one side of each of the four sides of the gel film arranged in a substantially rectangular shape is fixed, and the solvent is removed by drying at a predetermined temperature while stretching by stretching the end facing the fixed end. Then, it imidizes at the temperature of 250 to 500 degreeC, and obtains a polyimide fill. As described above, when a small amount of polyimide film is produced, the amount of production can be achieved by appropriately adjusting the time, temperature, temperature rising rate, stretching rate at the time of stretching, etc. according to industrial production conditions in drying and heat treatment. The influence of can be suppressed. Moreover, by manufacturing in this way, even when manufacturing a small amount as an experiment, industrial manufacturing conditions can be estimated roughly.

<Surface elastic modulus>
The polyimide film according to the first embodiment of the present invention is characterized in that the stretched polyimide film has a surface elastic modulus of 1.04 times or more that of the unstretched polyimide film. Hereinafter, the surface elastic modulus of the polyimide film will be described.

  As will be described later, the surface elastic modulus of the polyimide film is measured by measuring the extreme surface layer of the polyimide film with an atomic force microscope. When the surface elastic modulus of the stretched polyimide film is less than 1.04 times that of the unstretched polyimide film, unreacted polyamic acid remains due to insufficient imidization in the extreme surface layer of the polyimide film. Probability is high. Since such a polyimide film is not properly oriented in polyimide, a desired surface elastic modulus cannot be obtained, indicating that the surface state is not sufficient for improving the adhesion of a metal-laminated polyimide film described later.

  Usually, the stretched polyimide film has a higher surface elastic modulus than the unstretched polyimide film, and the surface elastic modulus of the unstretched polyimide film is low. For this reason, the surface elastic modulus of the stretched polyimide film is not less than 1.04 times that of the unstretched polyimide film.

  For example, a polyimide film obtained by the above production method from a polyamic acid synthesized from a raw material containing 4,4′-diaminophenyl ether as an aromatic diamine component and pyromellitic dianhydride as an acid anhydride is fully stretched. The maximum value of the surface elastic modulus appears at a rate of 1.1 to 1.5 times, and even if the stretching rate is higher than this, the maximum value of the surface elastic modulus does not exceed the surface elasticity of the stretched polyimide film The rate does not exceed 1.10 times the unstretched polyimide film. Further, for example, in the polyimide film obtained by the above production method from polyamic acid obtained using 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride as the acid anhydride, the surface elasticity of the stretched polyimide film is Although the ratio exceeds 1.1 times that of the unstretched polyimide film, it is difficult to obtain good flexibility of the polyimide film, and therefore does not exceed 1.30 times. When the total stretching ratio exceeds 2.00 times, the polyimide film may be wrinkled or may be easily broken and become a weak film.

  Furthermore, the surface elastic modulus of the stretched polyimide film is preferably in the range of 1.06 to 1.30 times that of the unstretched polyimide film. At this time, the total stretch ratio of the gel film is 1.01 to 1.5. The range is preferably doubled, and more preferably 1.01 to 1.4 times.

  The total stretch ratio in a polyimide film obtained from a polyamic acid synthesized from a raw material containing 4,4′-diaminophenyl ether as an aromatic diamine component and pyromellitic dianhydride as an acid anhydride is expressed as the surface elastic modulus. From the adhesion, 1.1 times to 1.5 times is particularly desirable, and further desirably 1.1 times to 1.3 times, and the surface elasticity is high and the adhesion to the base metal layer is further improved. An effect appears in both the strength after heating with loading and the room temperature (initial) strength.

  Hereinafter, a method for measuring the surface elastic modulus of the polyimide film according to the present invention will be described. The surface modulus of elasticity of the polyimide film can be measured with an atomic force microscope (hereinafter sometimes referred to as AFM).

<Measurement method of surface elastic modulus>
The AFM is a microscope that evaluates the surface shape using a displacement induced in a cantilever that holds a probe by a force acting between a sample surface and the probe. Specifically, the AFM detects an interaction force acting between a cantilever having a sharp probe at the tip and a sample. The cantilever warps when the probe contacts the sample. The amount of warpage of the cantilever is a load applied to the measurement sample from Hooke's law. The AFM includes optical means for detecting the amount of warpage of the cantilever, and a piezo element for detecting the relative distance relationship between the measurement sample and the cantilever in the direction in which the probe is pushed, and the signal detected by the piezo element is measured. Convert to the amount of displacement. The optical means for detecting the amount of warp irradiates the cantilever with a laser beam, and detects the reflection angle of the laser that changes due to the warp of the cantilever by the change in the detection position of the reflected laser beam. The amount of displacement of the measurement sample varies depending on the device used, but the displacement of the sample can also be determined by moving the measurement sample with a piezo element with respect to a fixed probe. This can also be known by controlling the movement with a piezo element.

  AFM is generally used for observing uneven images on the surface of a substance. As a special method of use, a probe is used in the range of sample displacement (elastic displacement) in which the sample is elastically deformed without plastic deformation. There is also a method of obtaining the physical property of the elastic modulus of the extreme surface, not the surface shape, by pressing and determining the elastic modulus from the amount of deformation of the sample. Furthermore, the displacement of the measurement sample (detachment displacement) when the probe pushed into the measurement sample is released from the measurement sample while reducing the load, and the measurement sample is elastic by pushing the probe into the measurement sample. It is also possible to know whether it has been deformed or plastically deformed.

  That is, in the polyimide film according to the first embodiment of the present invention, the surface elastic modulus is measured by pressing the probe into the measurement sample within a range of elastic deformation and calculating the load calculated from the amount of warpage of the cantilever (indentation load). Then, the elastic modulus can be measured from the displacement amount (indentation displacement amount) of the measurement sample detected by the piezo element and the curvature radius of the tip of the probe.

<Measurement of force distance curve>
The AFM can measure not only the height unevenness information and evaluate the surface shape but also the information of a force distance curve in which the displacement of the piezo element is plotted on the x axis and the amount of warpage of the cantilever is plotted on the y axis. . The force applied to the cantilever can be obtained from this force distance curve.

  The following procedure is used to obtain the force distance curve. First, a standard sample that is less elastically deformed than the cantilever is set in the AFM, and the cantilever is calibrated. The cantilever is pressed against the standard sample to bend the cantilever, and the relationship between the amount of warpage of the cantilever and the amount of displacement of the piezo element is measured.

  Next, the measurement sample is set in the AFM and pressed in the same manner as the calibration of the standard sample, and the force distance curve of the measurement sample is measured. Elasticity measurement by this AFM can be evaluated as long as it is a device capable of measuring a normal contact-mode. However, since mechanical properties such as elastic modulus have a large variation in measurement, evaluation is not performed at one point but at multiple points. It is desirable. In particular, it is desirable that the unevenness information on the surface of the measurement sample and force distance curves at multiple points can be measured simultaneously. Examples of such a device include scanning probe microscopes Nanoscope and Dimension manufactured by Veeco Instruments, and if the force volume mode of the measuring device is used, the surface unevenness information of the measurement sample and a multi-point force distance curve are included. Can be measured simultaneously. The obtained elastic modulus at multiple points can be obtained by performing a statistical analysis. Note that the AFM other than the scanning probe microscope Nanoscope manufactured by Veeco Instruments can also measure the force distance curve, so that the elastic modulus of the extreme surface at the measurement point can be known.

  When selecting the cantilever and the probe, be aware that even if the probe is pushed in within the range that gives elastic deformation to the measurement sample, the cantilever and the probe are not broken by the force generated between the measurement sample and the sample. . The selection of the cantilever and the probe may be made based on the pressure at the point where the probe contacts the measurement sample and the predicted elastic modulus of the pole surface of the measurement sample. When the cantilever probe is pushed into the measurement sample and the cantilever is plastically deformed, the cantilever is deformed and broken instead of the sample being deformed, and the elastic modulus of the cantilever instead of the measurement sample is measured. Because it will be.

  If the measurement sample is an engineering plastic such as polyamide or polyimide, it is much harder than commonly known polymer materials, so the silicon probe used in the polymer sample will break the probe itself. End up. Further, even if a hard DLC (Diamond like Carbon) probe is used, destruction of the probe is inevitable. When selecting a probe or a cantilever, selection should be made with attention to toughness and brittleness. If the measurement sample is engineering plastic, it is desirable to select a diamond probe, and the cantilever is preferably made of a material such as stainless steel. A cantilever and a probe may be appropriately selected depending on the measurement sample.

  Since the above measurement is analyzed using Hertz's elastic contact theory, it cannot be applied to a sample having an adhesion force. Therefore, when it is desired to evaluate a sample having a strong adhesion force using Hertz's elastic contact theory, a cantilever having a spring constant high enough to ignore the influence of the adhesion force must be selected. Generally, a commercially available cantilever has a spring constant of about 0.01 to 300 N / m, and it is necessary to select a cantilever having a spring constant suitable for a sample to be measured.

  Generally, when evaluating a material that undergoes plastic deformation, if the probe is pushed too far, plastic deformation occurs. However, in the engineering plastic such as the polyimide film according to the first embodiment of the present invention, when the surface elastic modulus is measured, it is necessary to adjust the pushing amount so that only the elastic deformation is caused without plastic deformation.

  In the method of measuring the elastic modulus of the extreme surface using engineering plastic as the measurement sample, the elastic modulus of engineering plastic is high, so it is not possible to measure accurately with a general silicon probe, and it is necessary to measure with a diamond probe. is there. In this combination, it is desirable to adjust the amount of warpage of the cantilever that is elastically deformed without plastic deformation by 0.1 to 3 nm. If the amount of warpage of the cantilever exceeds 3 nm, the measurement sample may be plastically deformed, which may make it impossible to measure the elastic modulus of the extreme surface of the measurement sample.

  On the other hand, when a resin film such as a polyimide film according to the first embodiment of the invention is used as a measurement sample, it is desirable to suppress the amount of displacement of the sample by pushing the probe within 10 nm.

  The amount of warpage of the cantilever is affected not only by the material of the cantilever but also by the shape of the tip of the probe. The radius of the tip of a commercially available probe is 10 to 100 nm. Also, the probe wears during measurement. The shape of a probe worn with a new probe must be controlled within a certain range. If the tip of the probe is sharp, the sample surface deforms with a small force. If the tip is blunt, the sample surface does not deform unless a greater force is applied. If a large force is applied to the cantilever, a large force is applied to the measurement sample, which may cause plastic deformation. Therefore, in order to keep the amount of warpage of the cantilever in the range of 0.1 nm to 3 nm and to suppress the displacement amount (pushing depth) applied to the measurement sample by the cantilever to within 10 nm, the probe needs to evaluate the tip. . The shape of the tip of the probe may be selected as appropriate so that the warp of the cantilever and the amount of displacement given to the measurement sample by the cantilever can be managed. Further, knowing the curvature of the probe is necessary to calculate the elastic modulus. Thus, the radius of curvature of the tip of the probe is important in the elastic modulus evaluation by AFM.

  As a result of examining the evaluation method of the shape of the tip of the AFM probe, that is, the curvature (radius), the influence of the scanning speed and resolution in the measurement of the concavo-convex image on the calculated value of the curvature radius was confirmed. The radius of the tip of the probe is an important factor in calculating the elastic modulus and cannot be ignored, so it must be accurately evaluated. The shape of the tip of the probe includes a method of directly observing with a SEM, a method of calculating backward from a concavo-convex image of a sample for probe shape evaluation manufactured by Aurora Nano Device.

  In other words, the method of measuring the curvature of the probe is to measure a concavo-convex image of a sample having the following shape with a high resolution of 2 nm / pixel or less using a probe whose radius of curvature is to be known. The radius is calculated.

  Specifically, there are 5 or more recesses between the projections at regular intervals from 1 to 100 nm or at random, and one projection is a sample having a shape with a height of 10 to 1000 nm. Using a sample having a hardness equal to or higher than the elastic modulus of silicon, an uneven image by AFM is measured.

  At this time, the measurement resolution needs to be high resolution measurement of 2 nm / pixel or less, and the accuracy of the curvature radius obtained becomes higher as this value is reduced. Moreover, the noise in the measurement needs to be 11 nm or less. Furthermore, the obtained concavo-convex image needs to include 5 or more concavo-convex portions in the vertical and horizontal directions. Furthermore, in the case of a sample having a sharp concavo-convex with the curvature radius of the concavo-convex tip being several tens of nanometers or less, if the scanning speed is increased, a correct concavo-convex image cannot be measured.

  The curvature radius of the tip of the probe is calculated from the concavo-convex image obtained in this way by the method of Villarrubia in Non-Patent Document 1. Since it is difficult to calculate the radius of curvature by this method by hand, analysis by computer programming is effective. An example of analysis software in which such a program is incorporated is SPIP made by Image Metrology.

<Analysis of force distance curve>
To calculate the elastic modulus of the pole surface by AFM, use the piezo element displacement-cantilever warpage curve obtained by force distance curve measurement, multiply the cantilever warpage by the spring constant, and deform the measured sample. -Obtain a load curve. When the measurement sample is measured by the AFM, the surface of the measurement sample is deformed by the load of the cantilever (probe). The load applied to the sample is determined by the spring constant of the cantilever and the amount of warpage, but the displacement detected by the piezo element is the sum of the amount of warpage of the cantilever and the amount of deformation of the measurement sample. By subtracting the piezo element displacement at the time of calibration from the piezo element displacement at the time of measuring the evaluation material, the displacement of the measurement sample can be calculated.

  The displacement amount-load curve of the measurement sample can be considered by a spherical model of Hertz's elastic contact theory of the following formula 1.

Here, F is a load, δ is a sample deformation amount, and K ₀ is a fitting parameter. For the load F, the hook law of the following formula 2 is established.

Here, k and x are a spring constant and a warp amount of the cantilever, respectively. The above K ₀ can be expressed by the following Equation 3 according to the Hertz theory.

  From the above Equation 3, the elastic modulus E is obtained. Here, ν is the Poisson's ratio of the sample, R is the radius of the tip of the probe, and the radius of the tip of the commercially available probe is about 10 to 100 nm. The Poisson's ratio is about 0.3 to 0.5 for a polymer material, and is so small that it is almost negligible because it is squared. On the other hand, the radius of the tip of the probe is an important factor in calculating the elastic modulus and cannot be ignored, so it must be evaluated accurately.

  The relationship between the force distance curve and the displacement weighting curve of the measurement sample will be described with reference to FIGS. A force distance curve of the AFM is shown in FIG. 1, and a displacement-load curve of the measurement sample is shown in FIG. The zero point (denoted as ZERO in FIG. 1) of the horizontal axis (displacement amount of the measurement sample: deformation) of the measurement sample displacement amount-load curve in FIG. 2 is the vertical axis direction (probe warpage amount: deformation) in FIG. ) Corresponds to the amount of piezo displacement whose value started to increase rapidly. When the displacement amount of the piezo element increases in the force distance curve of FIG. 1, the amount of warpage of the cantilever increases, and the displacement amount-load curve of the measurement sample of FIG. 2 corresponds to the force distance curve of FIG. As the value increases, the load increases.

  With reference to FIG. 2, the displacement amount-load curve of the measurement sample is analyzed. In the displacement-load curve of the measurement sample shown in FIG. 2, when the probe is pushed into the measurement sample by increasing the load (indentation load) (indentation process), the load from the pushed probe is reduced (detachment load) from the measurement sample. Both curves in the case of detachment (detachment process) are substantially the same curve, and there is almost no difference in the relationship between the displacement of the measurement sample and the load. This means that the measurement sample is elastically deformed. Even if the probe is pushed into the measurement sample, it is not plastically deformed, so the curves are substantially the same.

  When the probe is pushed down to the plastic deformation region, the pushing process and the releasing process do not have substantially the same curve. In such a case, the surface elastic modulus (the elastic modulus of the extreme surface layer) is not measured, but the elastic modulus of the sample as a bulk is measured. For example, the base metal layer of the metal laminated polyimide film and the polyimide film Adhesion cannot be predicted accurately.

  Various adhesives and the like can be used as a method of fixing the measurement sample to the AFM sample stage. For example, you may fix using a carbon paste. However, care must be taken not to contaminate the sample.

  The polyimide film which concerns on 1st Embodiment demonstrated above has favorable adhesiveness, and can maintain adhesiveness even if exposed to a high temperature environment for a long period of time. Moreover, in the measurement method of the above-mentioned surface elasticity modulus, about the metal lamination polyimide film which formed the metal film in the polyimide film which concerns on 1st Embodiment of this invention, the adhesiveness of a polyimide film and a metal layer can be evaluated. it can.

[Second Embodiment]
The metal laminated polyimide film according to the second embodiment of the present invention is a metal laminated polyimide film in which a metal layer is laminated on the polyimide film of the first embodiment without using an adhesive. The present invention relates to a metal-laminated polyimide film characterized by forming a base metal layer and a copper layer made of copper on the surface of the base metal layer. Hereinafter, the metal laminated polyimide film according to the second embodiment of the present invention will be described.

(Metal laminated polyimide film)
As shown in the cross-sectional view of FIG. 3, the metal laminated polyimide film is formed by laminating a base metal layer 3 such as a nickel-chromium alloy, a copper thin film layer 4 and a copper electrolytic plating layer 5 on the surface of the polyimide film 2. The laminated body of the copper thin film layer 4 and the copper electrolytic plating layer is referred to as a copper layer 6. The copper layer may be formed of only the copper thin film layer 4. Moreover, you may form the copper electrolytic plating layer 5 together with an electroless-plating method.

(Production method of metal laminated polyimide film)
As a method for producing a metal laminated polyimide film, first, a base metal layer 3 such as nickel, a nickel-based alloy or chromium is formed on the surface of the polyimide film 2 by a sputtering method. The thickness of the base metal layer 3 is not particularly limited, but is generally 5 to 50 nm. Known nickel alloys such as nickel-chromium alloy, nickel-chromium-molybdenum alloy, nickel-vanadium-molybdenum alloy can be used as the nickel-based alloy that can be used for the base metal layer. However, the metal used for the base metal layer needs to pay attention to the insulating property of the flexible wiring board and the etching property by the subtractive method. Subsequently, in order to give good conductivity to the surface of the base metal layer 3, the copper thin film layer 4 is subsequently formed by a sputtering method of a dry plating method. The thickness of the copper thin film layer 4 formed by this process is 50 to 1000 nm, and is generally 50 to 500 nm in terms of productivity.

  Furthermore, a copper layer made of a copper electrolytic plating layer 5 is further provided on the surface of the metal thin film layer made of a laminate of the base metal layer 3 and the copper thin film layer 4, that is, on the surface of the copper thin film layer 4. The copper electroplating layer 5 has a desired film thickness by an electrolytic plating method which is a kind of wet plating method, or a combination of an electroless plating method and an electrolytic plating method which are a kind of wet plating method. The film thickness of the copper electroplating layer 5 formed on the surface of the metal thin film layer is generally 5 to 18 μm, for example, when a circuit pattern is formed by a known subtractive method.

  When the copper layer 5 is formed by using both the electroless plating method and the electrolytic plating method, copper is formed on the surface of the metal thin film layer 6 by electroless plating, and then formed by electroless plating. It is preferable to perform electrolytic plating on the surface.

  In the metal laminated polyimide film according to the second embodiment described above, since the polyimide film according to the first embodiment is used, the metal and the polyimide film can be satisfactorily adhered, and even when exposed to a high temperature environment for a long time, The adhesion between the metal and the polyimide film can be maintained.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention does not receive a restriction | limiting at all in these description.

[Example 1]
In a 1000 mL separable flask, 250 g of dimethylacetamide was added, and 13.29 g (0.066 mol) of 4,4′-diaminodiphenyl ether and 14.48 g (0.066 mol) of pyromellitic dianhydride were added thereto. The mixture was reacted for 1 hour at room temperature and normal pressure and stirred to obtain a polyamic acid solution.

  After cooling this polyamic acid solution to minus 5 ° C., 15 parts by weight of acetic anhydride as a dehydrating agent and 15 parts by weight of pyridine as a cyclization catalyst are mixed with 100 parts by weight of the polyamic acid solution to obtain a mixed solution. It was.

  The obtained mixed solution was cast on a plate glass of a support and heated at 90 ° C. for 30 minutes to obtain a gel film. The gel film was peeled off from the plate glass, adjusted to a substantially rectangular shape, fixed to a stretching jig, and dried at 200 ° C. for 1 hour while being stretched 1.2 times to remove the solvent. The stretching jig is fixed to one side of the short side of a substantially rectangular frame, and a fixing bracket for fixing one side of the gel film arranged in a substantially rectangular shape, and is opposed to the short side provided with the fixing bracket while being substantially parallel to each other. And the extending | stretching fixing metal fitting which can be slid to a long side direction is provided. The stretch fixture may be fixed at one side of the gel film and at a slide position in the long side direction of the frame.

  The gel film that had been dried to remove the solvent was heated at 400 ° C. for 1 hour to terminate thermal imidization, and a polyimide film having a thickness of about 40 μm was obtained.

  A 10 nm-thick base metal layer made of a nickel-chromium alloy containing 20 wt% chromium having a thickness of 10 nm is formed on the surface of the obtained polyimide film, and a copper thin film having a thickness of 100 nm is formed on the surface of the base metal layer by sputtering. did. After the sputtering film formation, copper electroplating was performed on the surface of the copper thin film in a copper sulfate solution having a pH of 1 or less to form a copper film having a thickness of 8 μm to obtain a metal laminated polyimide film.

  A test piece was prepared on the obtained metal laminated polyimide film by a measuring method based on IPC-TM-650 and NUMBER 2.4.9, and the peel strength after heating at room temperature was measured. The conditions for measuring the peel strength after heating were that the sample was heated to 150 ° C. for 168 hours and then cooled to room temperature. The peel strength was measured by the subtractive method so that the peel angle was 90 ° and the lead width of the test piece was 1 mm. The results are shown in Table 1. At room temperature, the peel strength was 550 N / m or more as acceptable and less than 550 N / m as unacceptable. In addition, after heating, 350 N / m or more was accepted and less than 350 N / m was rejected. The peel strength after heating is more preferably 400 N / m or more, and even more preferably 500 N / m or more.

  Moreover, the surface elastic modulus of the polyimide film which was not formed into a film was measured by AFM. Measurement was performed in the Force Volume mode using NanoScope V manufactured by Veeco Instruments, a probe scanning microscope, for the AFM. A diamond probe (spring constant: 236 N / m) manufactured by Veeco was used as the probe. The measurement screen was 5 × 5 μm, the number of measurement points was 64 points per side, and the total number of points on all screens was 4096 points. The Poisson's ratio at the time of calculation was assumed to be 0.3. The amount of warpage of the cantilever was measured at 1 nm, and the indentation depth was 5 nm at most.

  FIG. 1 shows the result of the force distance curve of Example 1, and FIG. 2 shows the correlation between the displacement and the load of Example 1 and Comparative Example 1 (unstretched polyimide film) described later. The surface elastic modulus is calculated from the displacement amount and the load from Formula 3, and the ratio of the surface elastic modulus when the elastic modulus of Comparative Example 1 (unstretched polyimide film) is set to 1 is shown in Table 1, and Examples and Comparative Examples The distribution of elastic modulus is shown in FIG.

[Example 2]
A polyimide film and a metal laminated polyimide film were produced in the same manner as in Example 1 except that the stretching ratio was 1.5 times. The adhesion force and surface elastic modulus were measured, and the results are shown in Table 1.

[Example 3]
A polyimide film and a metal laminated polyimide film were produced in the same manner as in Example 1 except that the stretching ratio was 1.8 times. The adhesion force and surface elastic modulus were measured, and the results are shown in Table 1.

[Comparative Example 1]
A polyimide film and a metal-laminated polyimide film were produced in the same manner as in Example 1 except that stretching was not performed. The adhesion force and surface elastic modulus were measured, and the results are shown in Table 1.

  According to Table 1, the polyimide films of Examples 1 to 3 that were imidized by stretching a gel film had a surface elastic modulus of 1.04 relative to the polyimide film of Comparative Example 1 that was imidized without stretching the gel film. Since it was more than twice, it turned out that not only the adhesiveness with the metal film in room temperature but the adhesiveness with the metal film after a heating is also favorable.

  Furthermore, in the polyimide film of Example 1 and Example 2 whose surface elastic modulus is in the range of 1.06 times to 1.30 times with respect to the polyimide film imidized without stretching the gel film, the metal film at room temperature It was found that the adhesion with the metal film and the adhesion with the metal film after heating were better.

  On the other hand, it was found that the polyimide film of Comparative Example 1 obtained by imidizing without stretching the gel film had poor adhesion with the metal film at room temperature and after heating.

2 Polyimide film 3 Underlying metal layer 4 Copper thin film layer 5 Copper electrolytic plating layer

Claims (5)

After forming polyamic acid into a film-like gel film, it is a polyimide film obtained by stretching and imidization,
A polyimide film having a surface elastic modulus of 1.04 times or more with respect to a polyimide film imidized without stretching the gel film.   The polyimide film according to claim 1, wherein a surface elastic modulus is in a range of 1.06 times to 1.30 times with respect to a polyimide film imidized without stretching the gel film.   The polyimide film according to claim 1 or 2, wherein the polyamic acid is synthesized from a raw material containing an aromatic diamine component and an acid anhydride component.   The polyimide film according to claim 3, wherein the aromatic diamine component is 4,4′-diaminophenyl ether, and the acid anhydride component is pyromellitic dianhydride. A metal laminated polyimide film in which a metal layer is laminated without an adhesive on the polyimide film according to claim 1,
A metal-laminated polyimide film comprising a nickel alloy or chromium base metal layer and a copper layer made of copper on the surface of the base metal layer.

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