KR20050032696A - Biaxial oriented polyethylene naphthalate film - Google Patents

Abstract

The present invention relates to a polyethylene naphthalate film for masking circuit boards having excellent heat resistance, dimensional stability, processing stability, etc., which has excellent mechanical properties and dimensional stability even when used for a long time under high temperature and harsh conditions, and performs laser processing on circuit boards. The present invention also provides a biaxially oriented polyester film which is less deformed and is easy to manufacture a multilayer circuit board. The film has a refractive index of 1.49 to 1.54 in thickness direction, a heat shrinkage of -1 to 1% for 30 minutes at 150 ° C, a heat shrinkage of -2 to 2% for 1 minute at 180 ° C, and a crystallinity of 30% to 60%. It is characterized by.

Description

Biaxial Oriented Polyethylene Naphthalate Film

The present invention relates to a biaxially oriented polyethylene naphthalate film, specifically, excellent mechanical properties and dimensional stability even when used for a long time under high temperature and harsh conditions, easy to manufacture a multilayer circuit board with less deformation even when laser processing or the like Provide one biaxially oriented polyester film.

Saturated linear polyester film, generally represented by polyethylene terephthalate or polyethylene naphthalate film, has excellent mechanical properties, heat resistance, weather resistance, electrical insulation, chemical resistance, etc., so it is suitable for packaging, photography, condenser, electrical insulation, magnetic tape It is widely used in a wide range of fields. In particular, it has excellent heat resistance and dimensional stability at high temperature, so it is flexible printed circuit, flexible flat cable, membrane touch switch, condenser, heat resistant adhesive tape, transformer or motor, etc. Increasingly, industrial films, such as carrier tapes for electrical insulating materials and electronic component processing processes, are increasingly being used.

Until now, research has been conducted by many researchers to provide a polyethylene naphthalate film suitable for the field of electric and electronic, and as a result, a number of proposals have been made.

On the other hand, circuit boards, which are the core materials of electronic components, are getting smaller and smaller, such as the shortening and thinning of electronic devices, especially the development of three-dimensional mounting technologies such as mobile phone PDAs, the expansion of IC cards, and the direct mounting of chips on circuit boards. have.

As a result, the size of the semiconductor chip is also reduced, the circuit board itself on which the semiconductor chip is mounted is also thinned, and a multilayered design is made. For example, a circuit is formed on the surface of a polyimide film with copper foil, and the component is mounted according to the circuit, but it can be made compact by designing in multiple layers. As described above, in the case of a circuit board designed with a plurality of layers, a circuit connection is required between the upper and lower layers. This connection can be easily made by drilling a hole penetrating the inside using a drill or the like and filling the inside of the hole with a conductive material. As such, masking is required so that the circuit board can be filled only with the necessary portions when the circuit board is filled with a conductive material.

In recent years, along with the miniaturization of electronic products, laser drilling is mainly performed to reduce the size of vertical connection holes and to reduce dust generation.

In order to puncture a heat resistant circuit board such as a polyimide film, the laser generates very high heat in the local area, and it is important that there is no deformation around the puncture site. Therefore, although a heat resistant material such as a polyimide film is used as the masking film, it is not preferable in terms of production cost because it is expensive. However, when the film lacking general heat resistance is used, the film shrinks due to heat generated during laser drilling, or molten lumps are formed around the perforation to damage masking adhesion, and thus the conductive material is not needed to fill the conductive material. It may cause fatal losses such as supply.

The technical problem to be achieved by the present invention is to provide a biaxially oriented polyester film with improved heat resistance, dimensional stability, processing stability and the like.

The present invention to achieve the above technical problem,

Biaxial with a thickness direction refractive index of 1.49 to 1.54, thermal shrinkage of -1 to 1% at 150 ° C for 30 minutes, thermal shrinkage of 1 minute at 180 ° C to -2 to 2%, and crystallinity of 30% to 60% An oriented polyethylene naphthalate film is provided.

According to one embodiment of the present invention, the biaxially oriented polyethylene naphthalate film is useful in a circuit board manufacturing process.

Hereinafter, the present invention will be described in detail.

The present invention relates to a polyethylene naphthalate film with improved heat resistance, dimensional stability, processing stability, etc., which is excellent in mechanical properties and dimensional stability even when used for a long time under high temperature and harsh conditions, and is less deformed even when laser processing is performed. The present invention relates to a biaxially oriented polyester film that can easily manufacture a circuit board.

Polyethylene naphthalate used in the present invention is ethylene-2,6-naphthalate as the main repeating unit, it is produced by the following method.

A dimethyl-2,6-naphthalate and ethylene glycol are used at a molar ratio of 1: 2, and a catalyst containing a metal component such as manganese, potassium, lithium, calcium, magnesium, and zinc is added to undergo a transesterification reaction. Functional derivatives similar to the above dimethyl-2,6-naphthalate include dimethyl-1,2-naphthalate, dimethyl-1,5-naphthalate, dimethyl-1,6-naphthalate, dimethyl-1,7-naphthalate , Dimethyl-1,8-naphthalate, dimethyl-2,3-naphthalate, dimethyl-2,7-naphthalate and the like can be used.

In addition, the diols that may be used in addition to the ethylene glycol are polyethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 2,2-diethyl-1,3-propanediol, 2,2-dimethyl-1, 3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,3-cyclohexanedimethanol, 1,4-cyclodimethanol, and the like .

After the transesterification reaction is finished, the stabilizer and the polycondensation catalyst dispersed in ethylene glycol are added before the condensation polymerization reaction is started. As the stabilizer, a phosphate system such as trimethylene phosphate may be added, and as the catalyst, a catalyst containing a metal component such as titanium, germanium, tin, antimony, zinc, cobalt, manganese, or calcium may be added.

The polycondensation reaction proceeds at a high vacuum condition of 5 to 0.1 Torr at a temperature of 260 ° C. to 300 ° C., and the intrinsic viscosity of the polyethylene naphthalate resin thus produced is preferably 0.5 or more.

For the handleability and processability of the film, it is preferable to contain 0.05 to 0.5% by weight of organic or inorganic fine particles having an average particle diameter of 0.05 to 5 microns. The form of such fine particles is not particularly limited, and amorphous, plate, spherical, etc. can be used. It is preferable to disperse | distribute the said microparticles | fine-particles completely in ethylene glycol before starting a polycondensation reaction, and you may use together a 1 type of wet or dry silica, colloidal silica, calcium carbonate, or 2 or more types selected from these microparticles | fine-particles.

Within the scope of not impairing the effects of the present invention, a mixture of polyethylene naphthalate and other polyesters or a copolymer having ethylene naphthalate as the main structural unit can be used.

In the biaxially stretched polyethylene naphthalate film according to the present invention, polyethylene naphthalate is molded using a conventional melt extrusion method and a die to prepare an unstretched sheet, and the tenter is stretched by a sequential or coaxial method in the longitudinal and transverse directions. It is prepared by heat treatment at.

The longitudinal stretching temperature is preferably in the temperature range of the glass transition temperature (T _g = 123 ℃) to 30 ℃ higher than the glass transition temperature of polyethylene naphthalate, preferably 10 ℃ higher than the glass transition temperature to the glass transition temperature A high temperature range of 20 ° C is suitable. If the longitudinal stretching temperature is lower than the above range, turbidity occurs in the sheet, the fracture becomes more severe, and the heat shrinkage rate is increased. On the other hand, when it is higher than the above range, there is a disadvantage in that the stretching pattern is increased due to the adhesion of the stretching roll, or the orientation is lowered due to the relaxation phenomenon of the oriented polymer chain, and the thickness is uneven.

The longitudinal draw ratio is suitably 3.2 to 4.2 times, preferably 3.7 to 4.0 times. When the longitudinal draw ratio is less than 3.2 times, the orientation of the polymer chains is insufficient, resulting in poor strength, heat resistance and durability of the film. When the longitudinal stretching ratio exceeds 4.2 times, the longitudinal heat shrinkage rate increases and the delamination becomes severe, which is not good.

The transverse stretching temperature is preferably in the range of 10 ° C higher than the glass transition temperature of polyethylene naphthalate to 30 ° C higher than the glass transition temperature. If the transverse stretching temperature is lower than the above range, the fracture is severe, the thermal contraction rate is increased, the bowing is increased, and the transverse physical deviation is increased. If the temperature is higher than the temperature range, the degree of orientation decreases due to the relaxation phenomenon of the polymer chain, and there is a disadvantage in that the thickness in the lateral direction becomes uneven.

The transverse draw ratio is suitably 3.6 to 4.3 times, preferably 3.9 to 4.1 times. When the transverse stretching ratio is less than 3.6 times, the orientation of the polymer chains is insufficient as in the longitudinal stretching, resulting in poor strength, heat resistance and durability of the film. When the transverse draw ratio exceeds 4.3 times, the transverse heat shrinkage rate increases and the fracture becomes severe, which is not good because the process becomes unstable.

The heat treatment temperature is suitably 200 ° C to 250 ° C, preferably 220 ° C to 240 ° C. When the heat treatment temperature is less than 200 ° C., the heat treatment effect is insufficient to increase the thermal shrinkage of the film, and when it exceeds 250 ° C., the crystallinity and thickness variation of the film increase, which is not good.

You may give surface treatments, such as various coating and corona discharge treatment, to a film in the range which does not impair the effect of this invention.

Polyethylene naphthalate film, which is preferable in the circuit board manufacturing process provided by the present invention, is a film that is less deformed during use as a masking film in the circuit board manufacturing process, minimizes the deformation and breakage of the circuit board, and is excellent in perforation. , Biaxial orientation with a refractive index of 1.49 to 1.54 in thickness direction, a heat shrinkage of -1 to 1% at 150 ° C for 30 minutes, a heat shrinkage of -2 to 2% for 1 minute at 180 ° C, and a crystallinity of 30 to 60% Refers to polyethylene naphthalate film.

The refractive index of the biaxially oriented film is a numerical value determined through the stretching orientation process. When the refractive index in the thickness direction is smaller than 1.49, the film itself is easily deformed in the laser drilling process of the circuit board. If it is not desirable to occur, and greater than 1.54, mechanical properties such as strength, elongation, cut strength, flexibility, and the like are greatly reduced to increase the likelihood of breaking the film or generating dust due to external impact. The polyethylene naphthalate film which has the said refractive index value can be obtained by adjusting film forming conditions, such as extending | stretching temperature of a longitudinal direction and a lateral direction, a draw ratio, within the scope of invention.

In the present invention, the film's thermal contraction rate is preferably set to -1 to 1.0%, preferably -0.7 to 0.7%, in each of the longitudinal and transverse directions after being left for 30 minutes in a 150 ° C unloaded state. If the thermal shrinkage is greater than 1.0% or less than -1.0%, deformation of the circuit board may occur due to a difference in thermal strain from the circuit board in the laser drilling process.

In addition, the thermal contraction rate at 180 ° C. for 1 minute should be -2 to 2%. This is to prevent the film from momentarily flocking to increase the molten mass when the thermal contraction rate at high temperature is increased. When the molten mass becomes large, the mass is likely to be separated and act as an impurity during the subsequent work of the circuit board, and the molten mass opens a gap between the masking film and the circuit board to infiltrate the conductive material into the corresponding gap when filling the conductive material. This can cause fatal defects in the circuit. In addition, when the heat shrinkage rate is lower than −2% at 180 ° C. for 1 minute, a part where the masking film is separated from the circuit board is likely to occur.

In addition, the crystallinity is preferably 30 to 60%, preferably 35 to 57%. If the crystallization is not made, the film's thermal stability is insufficient, and the film is easily deformed. If the crystallinity is more than 60%, the resistance to impact is insufficient, which is likely to cause breakage or debris in the process. Not preferred.

The present invention also provides a circuit board processing process employing the tape made of the biaxially oriented polyethylene naphthalate film, such a circuit board processing process steps such as etching circuit formation, lamination, masking, punching, conductive material filling When the tape made of the biaxially oriented polyethylene naphthalate film according to the present invention is adopted, the punching state is good in the punching process, so that less foreign matters are generated and less defects occur when filling the conductive material. It can be useful.

Hereinafter, the present invention will be described again with reference to Examples and Comparative Examples.

Various physical properties and properties in Examples and Comparative Examples of the present invention were measured by the following method.

1) Thermal Shrinkage

The film having a length of 200 mm and a width of 10 mm was placed in an air circulating oven at 150 ° C. without a load and heat treated for 30 minutes. The film is taken out of the oven and left at room temperature for 2 hours to measure the change in length. The heat shrinkage rate is determined by the following equation.

[(L _o -L) / L _o ] X 100

(L _o : length before heat treatment, L: length after heat treatment)

In addition, the thermal contraction rate of 1 minute at 180 ℃ is also measured in the same manner except for the heat treatment temperature and time.

2) refractive index

The ABBE refractometer and sodium D-ray (589 nm) were used as a light source, and it measured about the thickness direction of a film.

3) crystallinity

After measuring the specific gravity (d) using a density gradient tube, the crystallinity (X _c ) is calculated by the following equation.

X _c = d _c (dd _a ) / d (d _c -d _a )

Where d _c = 1.407

d _a = 1.325

4) Perforation Evaluation

The masking film was laminated on the circuit board at 150 ° C for 15 minutes at 5kg / cm ² , and processed with CO ₂ gas laser under the condition of output voltage 6000V, pulse width 6.0μsec, energy level 5.0mJ and tit number 4 The shape of the masking film was then observed under a microscope.

◎ Maintaining circular shape with good drilling

○ Slightly elliptical, with less than 10 micron molten protrusions perforated

△ Oval with oval shape and less than 50 micron melt projections

X Perforation is carbonized and shattered

<Example 1>

Dimethyl-2,6-naphthalate and ethylene glycol were added in a 1: 2 molar ratio, and 0.05% by weight of manganese acetate tetrahydrate was added to complete the transesterification reaction with methanol being distilled out. 0.1 wt% and 0.2 wt% of wet silica having an average particle diameter of 3 microns and colloidal silica having 0.1 micron, respectively, were added to the reaction mixture as inert fine particles, 0.05 wt% of trimethylene phosphate as a stabilizer and 0.04 wt% of a polycondensation catalyst. After addition of the antimony trioxide, polycondensation reaction was performed and the polyethylene naphthalate resin was obtained. After drying the resin at 180 ° C. for 6 hours, melt extruding at 290 ° C. to obtain an unstretched sheet, stretching the unstretched sheet 3.8 times longitudinally at 135 ° C., and stretching 4.1 times transversely at 145 ° C., Heat treatment at 230 ° C. for 20 seconds yielded a biaxially oriented polyethylene naphthalate film having a thickness of 25 microns. The thickness direction refractive index at this time was 1.511, 150 degreeC, the thermal contraction rate in 0.5 minute, the thermal contraction rate in 0.5 degreeC, 180 degreeC, and 1 minute was 1.2%, and the crystallinity was 44.2%. The film thus obtained was subjected to a silicone release adhesive coating and used as a masking film on a polyimide circuit board. As a result of evaluating the perforation of the circuit board, the perforation state was very good.

<Examples 2 to 4>

Within the scope of the present invention, Example 1 was changed except that a film having a different refractive index, thermal shrinkage, and crystallinity was prepared by changing the stretching ratio in the longitudinal or transverse direction, or changing the stretching temperature or the heat setting temperature in the longitudinal or transverse direction. It carried out similarly to the obtained stretched film. The results of evaluating the physical properties of the film thus obtained are shown in Table 1 below. The film was used as a masking film on the circuit board to measure the puncture, and as a result, all the physical properties were excellent.

<Comparative Examples 1 to 3>

The film of Comparative Example 1 was obtained in the same manner as in Example 1 except that the heat treatment conditions were performed at 250 ° C. for 30 seconds. The film of Comparative Example 2 was obtained in the same manner as in Example 1 except that the film was stretched 4.2 times in the longitudinal direction and 4.6 times in the transverse direction. The film of Comparative Example 3 was obtained in the same manner as in Example 1 except that 3.0-fold stretching in the longitudinal direction and 4.0-fold stretching in the transverse direction and heat treatment conditions were performed at 220 ° C. for 10 seconds.

The results of evaluating the physical properties of the film thus obtained are shown in Table 1 below. In Comparative Example 1, although the film was satisfactory without deformation, a phenomenon in which the film collapsed during the process of removing the masking film appeared, which is very high. In the case of Comparative Examples 2 to 3, the puncture property was poor.

<Comparative Example 4>

Using a 25 micron PET film on the market, the release adhesive coating was carried out in the same manner as in Example 1 and used as a circuit board masking film.

Comparative Example 5

As a result of using a release adhesive coating in the same manner as in Example 1 using a commercially available 25 micron PP film as a circuit board masking protective film, the shrinkage of the film was very large and unsuitable.

division Refractive index Heat shrinkage Crystallinity Perforation Comprehensive Evaluation 150 ℃ * 30 minutes 180 ℃ * 1 minute Example 1 PEN Film * 1.511 0.5% 1.2% 44.3% ◎ ◎ Example 2 PEN Film 1.500 0.9% 1.8% 36.9% ◎ ◎ Example 3 PEN Film 1.495 0.9% 1.5% 47.4% ◎ ◎ Example 4 PEN Film 1.531 0.4% 0.6% 52.3% ◎ ◎ Comparative Example 1 PEN Film 1.542 0.4% 0.7% 58.0% ◎ X Comparative Example 2 PEN Film 1.520 1.2% 2.2% 44.8% △ X Comparative Example 3 PEN Film 1.520 0.9% 3.2% 25% △ X Comparative Example 4 PET film - 2.5% 3.7% - X X Comparative Example 5 PP film - - - - X x

* PEN Film: Polyethylene Naphthalate Film

PET Film: Polyethylene Terephthalate Film

PP film: polypropylene film

The biaxially stretched polyethylene naphthalate film according to the present invention is a film having improved heat resistance and dimensional stability, and has excellent mechanical properties and dimensional stability even when used for a long time under high temperature and harsh conditions, and has low deformation and puncture resistance when used as a masking film of a circuit board. It is excellent in that it is useful for the manufacturing process of high quality precision circuit board.

Claims (2)

The thickness direction refractive index is 1.49 to 1.54, the heat shrinkage rate at 150 ° C for 30 minutes is -1 to 1%, the heat shrinkage rate at 180 ° C for 1 minute is -2 to 2%, and the crystallinity is 30% to 60%. A biaxially oriented polyethylene naphthalate film, characterized by the above-mentioned. The biaxially oriented polyethylene naphthalate film according to claim 1, which is for a circuit board manufacturing process.