JPH0453739A - Laminated sheet - Google Patents

Abstract

PURPOSE:To thermally weld a film to a metal foil by bonding the film composed of a high-molecular liquid crystal compound optically forming an anisotropic melting phase within a specific temp. range under pressure. CONSTITUTION:A high-molecular liquid crystal compound pref. has transition temp. to an optically anisotropic melting phase within the temp. range of 200-400 deg.C from the aspect of the heat resistance and flexibility of a film. The film composed of the high-molecular liquid crystal compound is usually bonded to a metal foil by a thermal press bonding method using a hot press or a hot roll. The press bonding temp. of the foil is different according to the structure of the high-molecular crystal compound to be used but set to the range from temp. lower than the transition temp. to a liquid crystal by 80 deg.C to the transition temp. When the press bonding temp. is below temp. lower than the transition temp. to a liquid crystal by 80 deg.C, adhesiveness is insufficient and, when the press bonding temp. exceeds temp. higher than the transition to a liquid crystal, not only the flow of the film at the time of press bonding becomes large and the shape as a laminated sheet is not held but also the capacity of the film is lowered.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a flexible printed wiring board (hereinafter referred to as "flexible printed wiring board").

It relates to a laminate plate used for the development of FPC (abbreviated as FPC) and the like. More specifically, the present invention relates to a laminate having stable performance against temperature changes in the atmosphere in which it is used.

[Conventional technology]

In recent years, demand for FPCs has been increasing due to demands for smaller and lighter equipment in the electronics and electrical industries. This FP
The general structure of C is that after metal foil such as steel foil is laminated on at least one side of a base film, an electric circuit is formed, and a cover film is laminated on top of this circuit. Polyimide films, polyester films, etc. are often used as base films and cover films.
Ct-f! In the case of dipping, polyimide films are used for both the base film and the cover film, and 9FPC is used from the viewpoint of heat resistance.

[Problem to be solved by the invention]

However, when a polyimide film is used as the base film, rubber adhesives, epoxy adhesives, Fe/-y heavy adhesives, acrylic adhesives, etc. are used as adhesives to the metal foil. The heat resistance of these adhesives is not necessarily sufficient, and the adhesive strength decreases at high temperatures, so the heat resistance of FPC is determined by the heat resistance temperature of the adhesive used, and the heat resistance inherent in the polyelectrode film is sufficient. There are many cases where it is not taken advantage of.

Recently, a method has been proposed in which a base film is heat-sealed onto a metal foil, but conventionally used polyimide cannot be used in this method because it does not melt. Polyester is an alternative resin that can be heat-sealed, but its heat resistance is extremely low compared to conventionally used polyimide, and there is a limit to its heat resistance.

Also, apply an organic solvent solution of polyimide precursor on the metal foil12. It is also known to form a polyimide film on a metal foil by drying and then imidizing the film. However, when a polyimide precursor is applied onto a metal foil and then dried, it is heated to carry out the ξ-idization reaction.

There are problems in that the surface is cracked due to the scattering of moisture and the adhesive strength is low, resulting in poor productivity.

The inventors of the present invention have completed the present invention as a result of studying a plastic film that has excellent properties such as heat resistance, water resistance, chemical resistance, and flexibility by being heat-sealed onto metal foil. .

[Means to solve the problem]

The present invention is a laminate made by pressing a film made of a polymeric liquid crystal compound that forms an optically anisotropic melt phase onto a metal foil.

The polymeric liquid crystal compound used in the present invention is any polymeric liquid crystal compound that forms an optically anisotropic melt phase, n
It is a thermotropic liquid crystal compound. As is well known to those skilled in the art, a compound that forms an optically anisotropic molten phase is a compound that transmits polarized light when a sample in a molten state is observed under crossed Nicols under a polarizing microscope equipped with a heating device. It is.

Examples of the A-form side of the polymeric liquid crystal compound used in the present invention include known thermotropic liquid crystal polyesters and polyesteramide compounds derived from the compounds (1) to (4) shown below as VcfPO and their derivatives. However, it goes without saying that in order to form a polymeric liquid crystal, there is an appropriate range of combinations of each raw material compound.

(1) Aromatic or aliphatic dihydroquinated compound HOden
-4 triH (Y is 10-1-12-1-8-, etc.) HO
(CHi) nOH (n is a number from 2 to 12) (2) Aromatic or aliphatic dicarboxylic acid Polymers having the following structural units are listed as the variant side of the polymeric liquid crystal compound obtained from these raw material compounds. be able to.

(1rimo0C-C)-Co-)(-OCJ(gcHto
Shimo α? ()0-3-copolymer ooc HOOC (CHz), C0OH (n Fi integer from 2 to 12) (81 aromatic hydroxycarboxylic acid (4) aromatic dianne or aromatic hydroxylamine t take aromatic aminocarboxylic acid -E-06X copolymer (e) (-0-O-CO-) (-OC-Q-CO-)
%-0%0-3-mo0-Q-X-O-0 copolymer (X is 10-7-4, -8-, etc.) These polymeric liquid crystal compounds improve the heat resistance of the film. In terms of processability, it is preferable to have a transition temperature to an optically anisotropic molten phase in the range of 200 to 400" C1, particularly 250 to 350 °C. Also, it is a range that does not impair the physical properties of the film. A lubricant, an antioxidant, a filler, etc. may also be added.

In the present invention, the thermal expansion coefficient of the film made of the above polymeric liquid crystal compound is 1. OX 10-'(1/'C)
The following is preferably 1-<, more preferably Fh, o
xxo-'(l/"C) or less. This means that when the film is heat-sealed to a metal foil, especially a steel foil, if the thermal expansion coefficients of the copper and film are different, curling will occur when the film is returned to room temperature. Furthermore, when the laminate of the present invention is used as an FPC, a similar problem occurs when the laminate is immersed in a solder bath when mounting components on the FPC.

Further, the heat shrinkage rate of the film made of the above polymeric liquid crystal compound is preferably 2% or less, particularly 0.5% or less at 250°C. This is because the temperature of the solder bath is usually 250 to 260.
1. For example, when the FPC is immersed in a solder bath, if the heat shrinkage rate of the film is large, the FPC is likely to wrinkle.

However, in the case where the laminate of the present invention is used in the manufacturing of FPCs or the like, or when the film is not heated, it is not necessary to satisfy the above-mentioned ranges of thermal expansion coefficient and thermal contraction rate. .

Films made of polymeric liquid crystal compounds are produced using the T-die method.

It is molded by a known film forming method such as an inflation method or a combination of these methods.

The polymeric liquid crystal compound used in the present invention is:

Once melted and cooled, normal biaxial stretching becomes difficult. Kg simultaneously in both directions (hereinafter referred to as TD force direction)
Stretching is preferable in order to improve mechanical properties in both the MD direction and the TD force direction. The stretching ratio in the MD direction is 1.0 or more.

#49 is in the range of 1.25 to 15%) TD force direction stretch ratio is 1.0 or more, # is in the range of 1.5 to 20,
and the stretching ratio in the TD force direction is 1.2 of the stretching ratio in the MD direction.
It is preferable that it is in the range of ~2.4 times. Films can be formed under these conditions not only in the 5-MD direction.

A film having excellent properties also in the TD force direction can be obtained. Such films can be easily formed by the inflation method. The film thickness used is 5
00P or less, preferably in the range of 0.00f to 500/#, more preferably in the range of 1 to 250 μm.

The metal foil used in the present invention is selected from metals used for electrical connections, preferably gold.

It is made of silver, steel, nickel, aluminum, and more preferably steel. Copper foil is rolled using the rolling method.

Any material produced by electrolysis can be used, but those produced by electrolysis are preferred because of their large surface roughness. The thickness of metal foil is 0.001
-500 μm, preferably 1-500 μm, more preferably 5-500 μm.

Adhesion between a film made of a polymeric liquid crystal compound and a metal foil is usually performed by a thermocompression bonding method using a hot press, a hot roller, or the like. The compression temperature varies depending on the structure of the liquid crystal polymer compound used, but is preferably in the range from 80° C. lower than the transition temperature to liquid crystal to 20° C. higher than the transition temperature to liquid crystal. If the pressure bonding temperature is less than 8°C (lower than the transition temperature to liquid crystal), the adhesion will be insufficient.

If the temperature exceeds the temperature 20° C. higher than the transition temperature to liquid crystal, the film may not flow as thickly during pressure bonding, the form of the laminate may not be maintained, or the performance of the film may deteriorate.

FPC can be mentioned as a main use of the laminate of the present invention. FPC is a gold laminate obtained according to the present invention! R
A circuit is formed by etching the foil into a lunar pattern, and if the electrical circuit is multi-layered, through-hole processing is performed, and a cover film is laminated on top of this circuit using a heat-resistant adhesive. It is then formed into a predetermined shape by drilling and punching. The cover film may be a film made of the polymeric liquid crystal compound used in the present invention, or may be another film. When using a polyimide film or other film as a cover film, if the cover film is located at the outermost layer of the FPC and absorbs moisture through contact with the outside air, the water vapor permeability coefficient may decrease. 3. Of/100
in''-24hr-mLJ! or less is preferably used.

The application of the laminate of the present invention is not limited to Queen FPC. Furthermore, the laminate of the present invention basically has a two-layer structure of a film made of a polymeric liquid crystal compound and a metal foil, but may also have a three-layer structure of metal foil/film/metal foil, metal foil/film/metal foil/film. /It also includes multilayer structures such as metal foil.

〔Example〕

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to these Examples in any way.

In addition, the physical property values in the examples were measured by the following method.

(1) Transition temperature to optically anisotropic molten phase (liquid crystal) Using a differential scanning calorimeter (Mettler T) I-3000), the sample was heated at a rate of 20°C/min. It depends on the position of the endothermic peak when thermal behavior is observed.

a) Coefficient of thermal expansion Calculated from dimensional changes in the range of 80 to 150°C when the film was heated to 150°C and gradually cooled. The amount of dimensional change was measured using a thermal mechanical analyzer (TMA).

(8) Heat shrinkage rate Mark a certain length in the MD and TD directions of the film, leave it in a TABAI high-temperature hot air dryer set at 250°C for 30 minutes without tension, and then measure the length before and after heat treatment. The honeymoon was measured, and the heat shrinkage rate was calculated using the following formula.

(4) Peel strength 2. After hot-pressing the Otx width film and copper foil.

Peel strength was measured by the T-peel method.

(6) Heat cycle test Peel strength after immersing the laminate in a methanol-dry ice solution at -42°C for 5 minutes and then leaving it in a hot air dryer at 200°C for 5 minutes, repeated 20 times. was measured.

(6) Solder resistance properties When the laminate was immersed in a KIO solder bath at 260° C. for seconds, blisters, peeling, etc. were visually observed.

Example 1 Polymer liquid crystal compound A (Vectra, manufactured by Hoechst Seven Needs Co., Ltd.) having the repeating unit described below was heated to 280 ml using a single-screw extruder.
The mixture was heated and kneaded at ~300°C and melt-extruded through an inflation die to obtain a film with a thickness of 100P and a good appearance.

This electrolytic steel foil having a thickness of 35 μm was heat-pressed at 230° C. and 290″C to obtain a laminate.

The physical properties of the film and laminate were measured, and the results are shown in Table 1.

Example 2 Polymer liquid crystal compound B having a repeating unit described below was heated and kneaded at 300 to 320°C using a single screw extruder.

By melt extrusion using an inflation die, a film having a thickness of 100 Jm and having a good appearance was obtained. Jin's film and 35μ
Electrolytic steel having a thickness of m was heat-pressed at 240° C. and 300″C to obtain a laminate.

The physical properties of the film and laminate were measured, and the results are shown in Table 1.

Example 3 Polymer liquid crystal compound C having a repeating unit as described below was heated and kneaded at 210° C. using a single screw extruder, and melt extruded through a T-die to obtain a 100 μm thick film with good appearance. This film and 35 μm thick electrolytic steel were heated at 260°C and 290°C.
A laminate was obtained by heat-pressing at ℃.

The physical properties of the film and laminate were measured, and the results are shown in Table 1.

Example 4 A laminate was obtained by pressing in the same manner as in Example 1, except that the laminate structure was copper foil/film/copper foil instead of film/steel foil, and hot-press bonded with electrolytic steel foil at 230°C.

Each physical property of the laminate was measured and the results are shown in Table IK.

Comparative Example 1 In the same manner as in Example 1, except that a polyimide film (Kneepilon, manufactured by Ube Industries, Ltd., thickness 100 μm) was used in place of the film made of polymeric liquid crystal compound, electrolytic copper foil was heated at 300°C and 350°C. A laminate was obtained by heat-pressing at ℃.

Measure the physical properties of films and laminates and report the results! ! 1
Shown below.

Blank space below [Effects of the Invention] The laminate of the present invention does not use adhesives, so it can be easily manufactured, and it also has excellent heat resistance, chemical resistance, and flexibility, so it does not generate heat. Suitable for electronic materials that are exposed to high temperatures, such as those that use harsh elements.

Patent applicant RiRashi Co., Ltd.

Claims (1)

[Claims] A laminate made by pressing a film made of a polymeric liquid crystal compound that forms an optically anisotropic molten phase onto a metal foil.