JP2003031625A - Method of processing polyimide resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of processing a polyimide molded body which maintains uniform and higher size accuracy in order to obtain mounting components such as TAB and CSP having higher density, accuracy and reliability. SOLUTION: In this method of processing polyimide resin, a polyimide resin molded body is partly etched. In this method, after the molding of polyimide resin molded body, heat treatment is performed before the etching process. It is preferable that this heat treatment is conducted within the range where the breakdown strength of the polyimide resin molded body after the heat treatment is maintained at 50% or more of the breakdown strength before the heat treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for processing a polyimide resin molded body, and more particularly to improving the processing dimensional accuracy of the polyimide resin molded body.

[0002]

2. Description of the Related Art TAB, CSP, etc., which are known as mounting parts for ICs and LSIs, are made of a so-called copper-polyimide substrate in which a copper film is laminated on the surface of a polyimide resin film formed by molding a polyimide resin. , A copper film is patterned, and a polyimide resin film is etched.

On the other hand, with the recent miniaturization and thinning of portable electronic devices, it is natural that the above TAB, CSP and the like are required to be small and thin, that is, high density.
Extremely high dimensional accuracy is required for processing dimensions.

The above-mentioned etching processing of the polyimide resin film is a method of forming a metal film such as copper or an organic resist as an etching resist on the surface of the polyimide resin film and dissolving and processing the exposed portion of the polyimide resin film with an alkaline solution or the like. Is commonly used.

This method is widely used as a conventional method for manufacturing TAB, CSP and the like. However, as described above, in the case where further densification and extremely high dimensional accuracy with respect to the processing dimensions accompanying this are required, the processing dimensions of the polyimide resin film satisfy the required accuracy in the conventional processing method. There was a problem that I could not.

[0006]

In order to solve the above problems, the present invention provides a method for processing a polyimide resin, which satisfies the extremely high dimensional accuracy required for a polyimide resin film, in the method for processing a polyimide resin described above. The task is to do.

[0007]

In order to solve the above-mentioned problems, the present invention provides a method for processing a polyimide resin by etching a part of a polyimide resin molded body, wherein after the polyimide resin molded body is molded, an etching treatment is performed. In the method for processing a polyimide resin, a heat treatment is performed before the step.

Further, the heat treatment of the polyimide resin molded body before the etching treatment is carried out within a range in which the breaking strength of the polyimide resin molded body after the heat treatment holds 50% or more of the breaking strength before the heat treatment. This is a method of processing a polyimide resin.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have found that when a polyimide resin film is etched by a conventional method, the processing accuracy varies depending on the location of the polyimide resin film, and this variation and the polyimide resin film It was found that there is a correlation in the degree of distortion of the polyimide orientation, and further, by subjecting the polyimide resin film to an appropriate heat treatment, the degree of orientation distortion can be relaxed and the above problems can be solved, leading to the present invention. It was

That is, according to the present invention, in a method for processing a polyimide resin, which is performed by etching a part of the polyimide resin molded body, a heat treatment is performed after the polyimide resin molded body is molded and before the etching treatment. It is something to do. Further, the heat treatment is preferably performed in a range in which the breaking strength of the polyimide resin molded body after the heat treatment is 50% or more of the breaking strength before the heat treatment.

Generally, as a method for molding a polyimide resin film, a polyimide precursor polyamic acid is melted in a polar high-boiling organic solvent such as DMAc (dimethylacetamide) and cast on the surface of a metal support to form a semi-cured state. There is known a method in which a solvent is removed and imide condensation is promoted by performing a predetermined heat treatment while peeling, and finally a film-shaped molded product is obtained.

Further, for the purpose of strengthening the mechanical strength of the polyimide film, the film is subjected to a stretching process together with the above heat treatment, or to adjust the thickness and width of the film for molding as a film. In many cases, the end portion is chucked with a jig or the like and is molded while being supported by applying stress in the width direction.

The orientation of the polyimide polymer in the polyimide resin film obtained by the above treatment is affected by the strength and direction of the stress applied during the film molding, and the orientation should be oriented in the stressed direction. It has been known. For example, when biaxially stretched, the orientation of the polyimide polymer is MD (roll length direction) or T.
D. (Roll width direction) is aligned in the direction in which the biaxial stretching force is combined, and that direction differs depending on the TD position of the film, but in the MD of the polyimide resin film continuously molded under the same conditions, Regardless, the directions tend to be similar.

On the other hand, when the polyimide molded body is etched as described above, for example, the copper film formed on the surface of the polyimide resin film is dissolved and removed into a circular shape by the photolithography technique to remove the polyimide resin in that portion. After exposing, the polyimide resin was etched using a hydrazine monohydrate solution to form a via hole.When the via hole was formed in the center of the film TD, the via hole top and bottom were almost circular, and the shape was distorted. Are not observed.

However, at the TD position, the circle becomes an elliptical shape toward the end and the degree of deformation thereof becomes remarkable, and the direction of the major axis of the ellipse is almost the same regardless of the position in the MD of the polyimide resin film. It turned out to face the same direction.

From the above findings, a correlation was observed between the orientation of the polyimide polymer and the etching anisotropy. Therefore, the present inventors, in order to improve the dimensional accuracy when etching the polyimide molded body, a phenomenon in which the orientation of the polyimide polymer is biased in a certain direction depending on the site of the molded body, that is,
It is thought that the method of relaxing the strain is effective, and as a method therefor, before carrying out the etching process, as a result of diligent research focusing on the heat treatment of the polyimide molded body, the above-mentioned object can be achieved by applying a predetermined heat treatment. I found that I could achieve it.

The heat treatment carried out in the present invention is influenced by the structure of the polyimide polymer, the thickness of the molded body, the heat treatment conditions required during molding, the magnitude of the stress applied during molding, etc., and therefore is generally limited. Instead, an appropriate heat treatment condition range may be obtained in advance from the viewpoint of dimensional accuracy after etching, but in general, it is better to perform heat treatment at high temperature for a long time.
The dimensional accuracy of the etching process performed thereafter tends to be improved.

However, when the above heat treatment is carried out at a temperature far exceeding the glass transition point of polyimide or for a very long time, the mechanical characteristics of the polyimide molded body are changed, and the expected characteristics are not obtained. There is a problem that it cannot be obtained sufficiently.

Therefore, in the present invention, it is preferable that the heat load applied to the substrate by the heat treatment is in a range in which the breaking strength of the polyimide resin molded body after the heat treatment is 50% or more of the breaking strength before the heat treatment. Was found together. This is, for example, Kapton (Toray DuPont), NP
For a polyimide film such as I (manufactured by Kanegafuchi Chemical Co., Ltd.), it is equivalent to performing heat treatment at about 300 to 500 ° C. for about 10 minutes to 2 hours.

The present invention is not particularly limited to the polyimide etching method, and as described above, when performing dissolution processing using hydrazine or an alkaline solution, or when performing laser processing such as carbon dioxide gas laser or excimer laser, etc. It has a wide range of effects and can be applied.

[0021]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 Kapton EN molded into a polyimide film having a thickness of 50 μm and a width of 1048 mm was used, and this was heat-treated at 400 ° C. for 30 minutes in a nitrogen atmosphere. The breaking strength of the polyimide film before heat treatment was 340 MPa (measured by JIS C-2318), the breaking strength after heat treatment was 300 MPa, and the retention rate of breaking strength was 88%.

After that, a copper film having a thickness of 1 μm is formed on both surfaces of the film by a plating method, and the copper surface has a thickness of 20 μm.
After forming a resist layer of μm and patterning the resist layer by photolithography so that the lead width in the narrowest part is 20 μm and the lead interval is 20 μm on one surface, this is used as a plating resist on the exposed copper surface. Leads were formed by electroplating.

After that, the plating resist layer is removed, and the other surface on which the leads are formed is patterned into a circle with a diameter of 200 μm by the same photolithography technique.
Using this as an etching resist, the exposed copper plating film was removed by etching, and the copper plating film having a thickness of 1 μm exposed between the leads was removed by etching. afterwards,
On the other surface on which the leads were formed, a circularly exposed polyimide portion having a diameter of 200 μm was dissolved by etching.
The etching processing conditions were as follows: hydrazine monohydrate concentration: 800 ml / liter, anhydrous ethylenediamine concentration: 200 ml / liter.
The temperature was 50 ° C. and the time was 5 minutes.

As a result of observing with a microscope, the via hole formed in the polyimide film obtained by the above treatment, the diameter of the via hole top was 210 μm.
It was confirmed that m and the bottom of the via hole were etched into a circular shape with a diameter of 110 μm.
It was found that the shape and size of the polyimide resin hardly changed depending on the positions of the MD and TD of the film, and the polyimide resin was uniformly and accurately etched over the entire surface of the film.

(Example 2) A copper lead was formed on one surface of a polyimide film and a via hole was formed from the opposite surface according to the same procedure as in Example 1 except that the heat treatment applied to the polyimide film was 500 ° C for 10 minutes. Formed. The polyimide film after heat treatment had a breaking strength retention rate of 55%.

As a result of observing with a microscope the via hole portion formed in the polyimide film obtained by the above treatment, the diameter of the via hole top portion was 210 μm.
It was confirmed that m and the bottom of the via hole were etched into a circular shape with a diameter of 110 μm.
Its shape and dimensions hardly change depending on the film MD and TD positions, and it is uniform over the entire surface of the film.
It was also found that the polyimide resin was accurately etched.

(Example 3) A copper lead was formed on one side of a polyimide film and a via hole was formed on the opposite side in the same procedure as in Example 1 except that the heat treatment applied to the polyimide film was 300 ° C for 2 hours. Formed. In addition,
The breaking strength retention of the polyimide film after heat treatment is 94.
%Met.

As a result of observing the via hole portion formed in the polyimide film obtained by the above treatment with a microscope, the diameter of the via hole top portion was 210 μm.
It was confirmed that m and the bottom of the via hole were etched into a circular shape with a diameter of 110 μm.
Its shape and dimensions hardly change depending on the film MD and TD positions, and it is uniform over the entire surface of the film.
It was also found that the polyimide resin was accurately etched.

Example 4 A copper lead was formed on one surface of a polyimide film according to the same procedure as in Example 1 except that NPI molded to a thickness of 50 μm and a width of 1028 mm was used as the polyimide film, and the opposite surface was formed. A via hole was formed from. The polyimide film after heat treatment had a breaking strength retention rate of 83%.

As a result of observing the via hole portion formed in the polyimide film obtained by the above treatment with a microscope, the diameter of the via hole top portion was 210 μm.
It was confirmed that the bottom of the m and via holes were etched into a circular shape with a diameter of 130 μm.
Its shape and dimensions hardly change depending on the film MD and TD positions, and it is uniform over the entire surface of the film.
It was also found that the polyimide resin was accurately etched.

(Embodiment 5) The polyimide etching processing in Embodiment 1 was performed by using a carbon dioxide gas laser to remove the exposed polyimide portion at a processing energy of 100 J / cm ² and a shot number of 2, except that a via hole was formed. Followed a similar procedure.

As a result of observing the via hole portion formed in the polyimide film obtained by the above treatment with a microscope, the diameter of the via hole top portion was 200 μm.
It was confirmed that the bottom of the via hole was etched into a circular shape with a diameter of 180 μm.
Its shape and dimensions hardly change depending on the film MD and TD positions, and it is uniform over the entire surface of the film.
It was also found that the polyimide resin was accurately etched.

Comparative Example 1 A copper lead was formed on one surface of the polyimide film and a via hole was formed on the opposite surface thereof in the same procedure as in Example 1 except that the heat treatment was not performed on the polyimide film.

As a result of observing the via hole portion formed in the polyimide film obtained by the above treatment with a microscope, the via hole top portion in the TD central portion of the polyimide film had a diameter of 210 μm and the via hole bottom portion had a diameter of 130 μm. It was confirmed that it was etched into a circular shape. On the other hand, at the same MD position, the via hole top and bottom shapes become elliptical as they reach the TD end, and 4 from the TD center.
At 80mm position, via hole top is 40 against MD
The elliptical shape having a major axis of 230 μm in the direction of degree and a minor axis of 200 μm so as to be orthogonal to the major axis, and the via hole bottom portion being 130 μm in the direction of 40 degrees with respect to MD, and being orthogonal to the major axis. It was found to be processed into an elliptical shape having a short axis of 100 μm.

This does not mean that the polyimide is uniformly and accurately etched over the entire surface of the film, and lacks reliability when used as a mounting component such as TAB and CSP.

(Comparative Example 2) A copper lead was formed on one surface of a polyimide film and a via hole was formed on the opposite surface in the same procedure as in Example 1 except that the heat treatment applied to the polyimide film was 600 ° C. for 10 minutes. Formed. The polyimide film after heat treatment has a breaking strength retention rate of 48%, which is unreliable when used as a material for mounting components such as TAB and CSP.

[0038]

EFFECTS OF THE INVENTION According to the present invention, it is possible to perform processing which is extremely uniform and maintains high dimensional accuracy over the entire area of the polyimide molded body, which has been difficult in the past, resulting in high density / high accuracy / high reliability TAB and CSP. It is possible to obtain mounted parts such as.

Claims (2)

[Claims] 1. A method of processing a polyimide resin, which comprises etching a part of a polyimide resin molding, wherein the polyimide resin molding is heat-treated before the etching treatment. Resin processing method. 2. The method for processing a polyimide resin according to claim 1, wherein the heat treatment is performed within a range in which the breaking strength of the polyimide resin molded body after the heat treatment holds 50% or more of the breaking strength before the heat treatment. .