JP3716407B2 - Roughened aromatic polyimide film for FPC and method for producing the same - Google Patents

Description

【００４８】
【表２】

【００４９】
【発明の効果】
本発明のＦＰＣ用粗面化ポリイミドフィルムは、表面が粗面化された芳香族ポリイミドフィルムであって、フィルム表面の平均粗さ（Ra）、最大粗さ（Rmax）、局部山頂の平均間隔（Sm）、ろ波中心線うねり（Wca）、ろ波最大うねり（Wcm）が特定の範囲に制御されているので、接着性が改良される。また、製造方法は比重（ｄ）が７以下の研磨剤を液体に分散し、これを芳香族ポリイミドフィルムの表面に特定の照射速度で照射するものであるので、エッチングなどの水洗工程を経た後でも接着性が改善され、薄いフィルムでもピンホールが生じにくい浅く均一なＦＰＣ用粗面化ポリイミドフィルムを得ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an aromatic polyimide film for FPC having excellent adhesiveness, and more specifically , a roughened polyimide film for FPC that exhibits superior properties in application fields in which a substrate directly bonded to the film surface is thinner than a polyimide film, and It relates to the manufacturing method.
[0002]
[Prior art]
As a method of roughening the surface for the purpose of improving the adhesiveness of the film, there is a method of adding particles to a polymer and forming this into a film, but it is difficult to roughen the surface by itself, and the effect of improving the adhesiveness is small. It was. On the other hand, as a method for improving adhesiveness, there are a method of roughening the surface and an electric treatment. Chemical solution treatment and sand mat are known as methods for roughening the surface. However, the electrical treatment has a drawback that the effect is lost after the washing step and the drying step after the treatment. Since the sand mat is directly irradiated with the abrasive, the stress concentrates on the irradiated portion, so that coarse protrusions are easily formed, and a pinhole is opened particularly in a thin film. In addition, if the processing is performed weakly in order to avoid the occurrence of pinholes, it takes time, processing spots are formed, and the roughening effect is low.
[0003]
In many cases, a polyimide film is laminated with a metal foil via an adhesive or directly laminated with a metal layer. Thereafter, the metal layer is etched to form a circuit. Furthermore, when a semiconductor such as an IC chip is bonded to the exposed portion of the polyimide with an adhesive, the electrical treatment is less effective in improving the adhesion because the washing process and the drying process are performed after the etching process. Therefore, chemical treatment is also known as a method for roughening only the film surface, but its effect is small.
[0004]
[Problems to be solved by the invention]
Polyimide film forms a weak surface layer (WBL: Weak Boundary Layer) by transferring low molecular weight polymers or oligomers derived from degradation products to the surface inside the polymer or through the interface of additive particles. Easy to be. This is considered to be a factor that hinders the adhesion of the polyimide film.
[0005]
The present inventors have found that oligomers are likely to accumulate near the surface layer, and have found that the roughened aromatic polyimide film from which the WBL layer near the surface layer has been removed has improved adhesion.
[0006]
Accordingly, the present invention provides an aromatic polyimide film for FPC having an effectively roughened surface and improved adhesion.
[0007]
Another object of the present invention is to provide a roughened polyimide film for FPC , which has improved adhesiveness even after a washing step such as etching, and is less likely to cause pinholes even with a thin film, and a method for producing the same.
[0008]
Furthermore, the present invention also provides a method for effectively roughening the exposed polyimide film portion without damaging the circuit even if the metal foil circuit is partially present.
[0009]
[Means for Solving the Problems]
The present invention is an aromatic polyimide film having a roughened surface having a thickness of 5 μm or more and 50 μm or less, and the relationship of the film surface roughness is represented by the following formulas (1) to (5): A roughened aromatic polyimide film for FPC .
[0010]
0.2 μm <Ra <1 μm (1)
2Ra <Rmax <5μm (2)
Rmax <Sm <15 μm (3)
0.02μm <Wca <0.2μm (4)
0.2 μm <Wcm <2 μm (5)
Ra ・ ・ ・ arithmetic mean roughness
Rmax: Maximum height
Sm: Average distance between local peaks
Wca ...
Wcm ··· Maximum waviness of filtering wave Further, an abrasive having a specific gravity (d) of 7 or less is dispersed in a liquid, and this is irradiated onto the surface of the aromatic polyimide film at an irradiation speed of 30 to 100 m / s. This is a method for producing the roughened aromatic polyimide film.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The polyimide film with improved adhesion according to the present invention has a roughened surface, and the relationship between the surface roughness is expressed by the following formulas (1) to (5).
[0012]
0.2 μm <Ra <1 μm (1)
2Ra <Rmax <5μm (2)
Rmax <Sm <15 μm (3)
0.02μm <Wca <0.2μm (4)
0.2 μm <Wcm <2 μm (5)
Ra ・ ・ ・ arithmetic mean roughness
Rmax: Maximum height
Sm: Average distance between local peaks
Wca ...
Wcm ... The biggest wave of waves
Ra, Rmax and Sm are values obtained from the roughness curve. Ra is an arithmetic average roughness, and is an average value of the height difference between the average line and the roughness curve. Rmax is the maximum height and is the distance between the highest peak and the deepest valley bottom of the roughness curve. Sm is the average value of the interval from the change point to the next change point, with the change point being the point from the peak to the valley.
[0013]
Wca and Wcm are curves obtained from a waviness curve. Wca is called a filtered centerline swell, and is an arithmetic average value of the absolute value of the deviation between the centerline and the filtered centerline swell curve. Wcm is called the maximum wave swell and is the distance between the highest peak and the deepest valley bottom of the swell curve.
[0014]
When Ra is 0.2 μm or less, WBL cannot be sufficiently removed, and the effect of improving adhesion is small. If Ra is 1 μm or more, the effect of adhesion is sufficient, but there is a problem that coarse protrusions increase. Preferably it is more than 0.3 μm, more preferably more than 0.4 μm. Moreover, it is preferably less than 0.8 μm.
[0015]
In addition, when Rmax is 5 μm or more, it is impossible to achieve the uniform roughening intended in the present application. Moreover, the problem that a pinhole arises in a thin film arises. The minimum value is about twice Ra.
[0016]
When Sm is 15 μm or more, the precise roughening intended in the present application cannot be realized. The minimum value is about Rmax. Preferably it is less than 12 μm.
[0017]
When Wca is 0.02 μm or less, WBL cannot be removed sufficiently, and the effect of improving adhesion is small. When Wca is 0.2 μm or more, the effect of adhesion is sufficient, but there is a problem that coarse protrusions increase. The minimum value is about 0.02 μm. Preferably it is over 0.03 μm, more preferably over 0.4 μm.
[0018]
In addition, when Wcm is 2 μm or more, the shallow and uniform roughening intended in the present application cannot be realized. Moreover, the problem that a pinhole arises in a thin film arises. The minimum value is about 0.2 μm. Preferably it is less than 1 μm.
[0019]
As a preferred surface roughening method, an abrasive having a specific gravity (d) of 7 or less is dispersed in a liquid and is irradiated (sprayed on the film surface) to roughen the surface, and the specific gravity of the abrasive is 0.8-7. Is preferred.
[0020]
When the specific gravity exceeds 7, it is difficult to disperse in the liquid, and therefore, processing spots may occur.
[0021]
The abrasive is dispersed in a liquid, and it is preferable to use a non-explosive liquid as the liquid. Water or alcohol is also preferred in terms of price and ease of handling. It is also preferable to add an abrasive dispersing agent or a rust inhibitor such as a surfactant to these liquids.
[0022]
The viscosity of the liquid is preferably in the range of 0.5 to 2 (mPa · s), and the boiling point is preferably 150 ° C. or lower.
The size of the abrasive is preferably a maximum diameter of 0.1 μm to 100 μm, and the shape can be used from spherical to polygonal.
[0023]
The liquid in which the abrasive is dispersed is irradiated with a compressed gas. The gas is preferably air or nitrogen. An irradiation speed of 30 m / s to 100 m / s is preferable. The treatment speed is preferably 10 mm / s to 1000 m / s, more preferably 50 mm / s to 500 m / s. The higher the processing speed, the better the work efficiency, but if it is too fast, processing spots will occur. The treatment pressure is preferably 0.12 to 0.3 (MPa).
[0024]
The processing pressure of the conventional sandblasting process is 0.4 to 0.6 (MPa), and it is easy to apply a high pressure, and since it is not dispersed in the liquid, it is easy to apply the processing pressure locally, and it is easy to make a pinhole as described above. .
[0025]
The specific gravity (d) of the abrasive and the content w (% by weight) of the abrasive contained in the liquid are preferably represented by the following formula (3).
[0026]
20lnd <w <20ln (d) +50 (3)
(However, ln is a logarithm with the base number being e, and d is the specific gravity of the abrasive.)
Preferably, 20lnd + 10 <w <20ln (d) +40.
[0027]
By adjusting the content of the abrasive to this range, it is possible to prevent the processing spots and obtain a polyimide film having a large roughening effect.
[0028]
In the present invention, since the abrasive used is always covered with a liquid, it does not pierce like a sand mat. Since it is always poured out by high-pressure liquid, the surface is clean and there are few foreign substances. Moreover, since it is dispersed in the liquid, the irradiation stress is reduced by one and shallow and uniform rough surface processing can be performed. Further, a fine abrasive can be used, and thus a uniform surface treatment can be performed. Moreover, since the improvement of the adhesiveness by a shape can be anticipated, there is little change with time.
[0029]
In addition, since the polyimide film to be surface-treated uses a liquid, it is preferable that some residual solvent is included. The content is 0.001% or more and 1% or less.
[0030]
In particular, when gold, copper, aluminum or the like is used for the metal foil circuit, inorganic particles having a Mohs hardness of 6 or less are preferable as the abrasive. More preferably, it is 5 or less, and most preferably 3 or more and 4 or less inorganic particles. An example of a material having a Mohs hardness in the range of 3 to 4 is calcium carbonate.
[0031]
Below, the roughening method of the roughening polyimide film concerning this invention is demonstrated. The polyimide film here has a thickness of 5 μm or more and 50 μm or less, more preferably 25 μm or less, and most preferably 15 μm or less.
[0032]
The molecular structure of the polyimide film preferably includes a flexible portion in the acid or diamine component. The reason is not clear, but it is presumed that the soft part derived from the bending component is easily roughened by being specifically treated. Accordingly, a polyimide film composed of three or more components having a bending component and a linear component is particularly preferable.
[0033]
In order to improve the handleability at the time of film formation, the film may be formed by adding particles in advance, but preferred particles when added are inorganic particles having an average primary particle size of 0.01 μm to 5 μm Is preferably used. Examples of the inorganic particles include SiO2, CaHPO4, Ti02, Ca2P2O7, etc., but group IIa alkaline earth metal orthophosphate is particularly preferable. By adding it in advance in the film, fine protrusions are generated on the surface, the surface state can be controlled, and in particular, the film running and handling properties before and during the roughening treatment can be improved. . The addition amount is 10 wt% or less. If it exceeds 10 wt%, the film may be easily broken during film formation, and the handleability may be adversely affected. The lower limit of the addition amount can be made as small as possible so that the effect of improving the running property can be exhibited, but is about 10 ppm or more.
[0034]
The thickness of the polyimide film base layer is sufficient if it can be surface-treated, but is preferably 250 μm or less. In the roughening method, a liquid in which an abrasive is dispersed with compressed gas is fed into the die and irradiated onto the polyimide film surface. The target surface roughness is controlled by the distance from the die, the irradiation angle, and the number of irradiations.
[0035]
Moreover, it is also possible to perform a well-known process after the above processes. As post-treatment, for example, electrical treatment or adhesion-imparting agent can be applied.
[0036]
The polyimide film with improved adhesiveness according to the present invention is suitable as an FPC base film, a cover film thereof, or a stiffener film (backing).
[0037]
【Example】
In the following examples, all parts and percentages are by weight unless otherwise specified.
[Measurement and evaluation]
The surface roughness was measured with a scanning laser microscope (Model 1LM15, manufactured by Lasertec Corporation). He-Ne laser (wavelength: 632.8 nm, CW: 0.1 mW), microscope magnification 200 times, measurement length 0.6 mm, cut-off value 0.025 mm for creating roughness curve from cross-section curve, filtered waviness curve from cross-section curve A cut-off value of 0.25 μm for creation, a cut-off value of 0.8 μm for creating a filtered center line waviness curve from a filtered waviness curve, and a value obtained by averaging five measurements.
[0038]
The definition of Ra and Rmax (also described as Ry) is, for example, as shown in Jiro Nara “Surface Roughness Evaluation Method” (General Technology Center, 1983).
Prepare a box with polished glass on a pinhole fluorescent lamp, place a film on the polished glass, observe the point that shines brightly with the naked eye, and use that point as a pinhole.
The surface of the film having a residual particle area of 100 cm ² is observed with an optical microscope, and the number of remaining abrasive particles is observed.
[0039]
0 ・ ・ ・ ○
1-2 ... △
3 or more ... ×
Adhesion strength (1) Using the sample after the initial surface treatment, the treated film and copper foil (electrolytic copper foil manufactured by Mitsui Mining & Smelting Co., Ltd.) using an acrylic adhesive ("Pyralax" manufactured by DuPont) “3EC” (35 μm thickness) was laminated, and a curing reaction of the adhesive was performed at 185 ° C. for 1 hour to prepare a film / adhesive / copper foil laminate (hereinafter referred to as FC laminate). A sample with a width of 10 mm and a length of 30 cm was cut out from the obtained FC laminate, and a tensile test of 90-degree peeling was performed at a peel test speed of 50 mm / min using a tensile tester (Tensilon Universal Testing Machine UTA-300KN manufactured by A & D). went. The average of 5 times was taken.
(2) After water treatment The surface-treated sample was immersed in water for 1 day and then dried in an oven at 110 degrees. Except using the sample, it carried out according to the evaluation method of the above-mentioned initial adhesion strength.
Test specimens with the same composition and crystal structure as the particles added to the Mohs hardness film are scratched together with the standard mineral for Mohs hardness measurement, and the hardness number is measured to the unit of 0.1 depending on whether or not scratches are made. To do.
Sample preparation Sample A
In a 500 cc glass flask, 150 ml of DMAc (dimethylacetamide) is placed, PDA (phenylenediamine) is fed into DMAc and dissolved, followed by 44′ODA (4,4′-oxydianiline) and PMDA (pyrrole). Meltic acid dianhydride) is sequentially supplied and stirred at room temperature for about 1 hour. Finally, a solution with a polyamic acid concentration of 20% by weight was prepared, in which the tetracarboxylic dianhydride component and the diamine component consisted of components having the composition shown in Table 1 at about 100 mol% stoichiometry.
[0040]
A mixed solution was prepared by mixing 30 g of this polyamic acid solution with 12.7 ml of DMAc, 3.6 ml of acetic anhydride and 3.6 ml of β-picoline, and this mixed solution was cast on a glass plate. Was heated for about 4 minutes on a hot plate heated to form a self-supporting polyamic acid-polyimide gel film, which was peeled from the glass plate.
[0041]
This gel film is fixed to a metal fixed frame having a large number of pins, heated for 30 minutes while being heated from 250 ° C. to 330 ° C., and then heated at 400 ° C. for about 5 minutes. Various thickness polyimide films Got.
[0042]
Sample B
Using the composition shown in Table 1, a polyimide film was obtained according to the preparation method of Sample A.
[0043]
Sample C
A polyimide film was obtained according to the preparation method of Sample A using only 44′ODA without using PDA as the diamine.
Examples 1-6
Using the MICRO-SURFACE-ETCHER apparatus manufactured by MACOHO Co., Ltd., the surface treatment of the film obtained above was performed.
[0044]
The treatment conditions were 800 mesh alumina (hardness 9), 2000 mesh alumina, 800 mesh spherical silica (hardness 6) and 800 mesh calcium carbonate (hardness 4) as abrasives, ion-exchanged water and ethanol as the liquid, and mouth opening The shape of the part was 250 mm × 2 mm, the air pressure was 1.5 kgf / cm 2, the treatment speed was 10 mm / s, the irradiation distance was 50 mm, the irradiation angle was 90 degrees, and the treatment was performed once. Thereafter, it was washed with water and dried by air blow.
[0045]
Other conditions and results are shown in Table 2.
Comparative Examples 1-3
As in Comparative Example 1, the liquid was not used and only the abrasive was irradiated on the surface. The processing conditions are: the shape of the mouthpiece opening 250 mm × 2 mm, air pressure 4.5 kgf / cm ² , processing speed 10 mm / s, irradiation distance 50 mm, irradiation angle 90 degrees, number of treatments once, 800 mesh alumina as abrasive. Used, then washed with water and dried by air blow. The results are shown in Table 2.
Comparative Example 4
Corona discharge treatment was performed on both sides under the condition of 200 W / m ² / min. The results are shown in Table 2.
[0046]
As shown in Comparative Example 1 and Comparative Example 2, in the sandblasting method that is not dispersed in a liquid, residual particles are generated and the surface roughness is not within the scope of the present application, so that the adhesion strength is not sufficient. In Comparative Examples 1 and 3, pinholes occurred in the thin film. Moreover, it turns out that the adhesive strength after water treatment falls only by electrical treatment without roughening treatment.
[0047]
[Table 1]

[0048]
[Table 2]

[0049]
【The invention's effect】
The roughened polyimide film for FPC of the present invention is an aromatic polyimide film having a roughened surface, and the average roughness (Ra), maximum roughness (Rmax) of the film surface, and the average distance between local peaks ( Sm), filtered centerline waviness (Wca), and filtered maximum waviness (Wcm) are controlled within specific ranges, thereby improving adhesion. In addition, since the manufacturing method is to disperse an abrasive having a specific gravity (d) of 7 or less in a liquid and irradiate the surface of the aromatic polyimide film at a specific irradiation rate, after passing through a washing step such as etching. However, the adhesiveness is improved, and a shallow and uniform roughened polyimide film for FPC can be obtained which is less likely to cause pinholes even with a thin film.

Claims (6)

Surface is 5μm or more roughened thickness, a following aromatic polyimide film 50 [mu] m, for FPC, wherein the relationship between the film surface roughness is represented by the following (1) to (5) Roughened aromatic polyimide film.
0.2 μm <Ra <1 μm (1)
2Ra <Rmax <5μm (2)
Rmax <Sm <15 μm (3)
0.02μm <Wca <0.2μm (4)
0.2 μm <Wcm <2 μm (5)
Ra ・ ・ ・ arithmetic mean roughness
Rmax: Maximum height
Sm: Average distance between local peaks
Wca ...
Wcm ... The biggest wave of waves Ra, Sm is a (1-a) type | formula and a (3-a) type | formula, The roughening aromatic polyimide film for FPCs of Claim 1 characterized by the above-mentioned.
0.4 μm <Ra <0.8 μm (1-a)
Sm <12 μm (3-a) Wca and Wcm are (4-a) type and (5-a) type | formula, The roughening aromatic polyimide film for FPCs of Claim 1 or 2 characterized by the above-mentioned.
0.04 μm <Wca <0.2 μm (4-a)
0.2 μm <Wcm <1 μm (5-a) 4. An abrasive having a specific gravity (d) of 7 or less is dispersed in a liquid, and this is irradiated onto the surface of the aromatic polyimide film at an irradiation rate of 30 to 100 m / s. A method for producing a roughened aromatic polyimide film for FPC . 5. The roughened aromatic for FPC according to claim 4, wherein the liquid is water or alcohol, and the content w (% by weight) of the abrasive contained in the liquid is represented by the following formula (6): A method for producing a polyimide film.
20lnd <w <20ln (d) +50 (6)
(However, ln is a logarithm with the base number being e, and d is the specific gravity of the abrasive.) The method for producing a roughened aromatic polyimide film for FPC according to claim 4 or 5, wherein the abrasive is inorganic particles having a Mohs hardness in the range of 1 to 4.