JP2000289165A - Heat-resistant bonding sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-resistant bonding sheet which shows sufficient mechanical strength and at the same time, outstanding solder heat resistance, adhesion, dimensional stability and low dielectric characteristics. SOLUTION: The base film of the heat-resistant bonding sheet having a thermoplastic polyimide layer formed on at least one of the faces of a heat- resistant base film is treated by plasma discharge in a mixed gas composed mainly of an inert gas. Consequently, the heat-resistant bonding sheet having superb adhesion and solder heat resistance is realized, and can be used especially for a flexible copper-plated laminated sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding sheet having a thermoplastic polyimide layer on at least one surface of a base film and a method for producing the same, and more particularly, to a heat-resistant bonding sheet having excellent heat resistance, adhesiveness and dimensional characteristics. .

[0002]

2. Description of the Related Art In recent years, higher performance and higher functionality of electronic devices have been developed.
The miniaturization is rapidly progressing, and there is an increasing demand for miniaturization and weight reduction of electronic components used in electronic devices. Along with this, the heat resistance, mechanical strength,
Various physical properties such as electrical characteristics are further required, and a higher density, higher function, and higher performance are also required for a semiconductor element packaging method and a wiring board for mounting the same. With regard to flexible printed wiring boards (hereinafter referred to as FPC), fine wire processing, multilayer formation, etc. are performed, and component mounting FPs in which components are mounted directly on the FPC.
C, a double-sided FPC in which a circuit is formed on both sides, a multilayer FPC in which a plurality of FPCs are stacked, and the layers are connected by wiring have appeared.

Generally, an FPC has a structure in which a circuit pattern is formed on a flexible and thin base film, and a surface cover layer is provided. In order to obtain the above-mentioned FPC, an insulating adhesive used as a material thereof is used. And the performance of insulating organic films must be improved. Specifically, it has high heat resistance and mechanical strength, and is excellent in workability, adhesiveness, low hygroscopicity, electrical characteristics, and dimensional stability.

At present, a film made of a polyimide resin having excellent characteristics is widely used as an insulating organic film for FPC. An epoxy resin or an acrylic resin that is excellent in low-temperature workability and workability is used as the insulating adhesive. However, it has been found that these adhesives are not particularly satisfactory in heat resistance. More specifically, when exposed to a temperature of 150 ° C. or more for a long time, these adhesives are deteriorated, which affects various characteristics. Furthermore, when using these adhesives, the adhesive is applied on a base film, dried, and then adhered to a conductor layer (generally, copper foil is used). Have to be heat-treated.

[0005] In particular, with the expanding use of FPCs, there is an urgent need to solve the problem of heat resistance. In order to solve this problem, a two-layer FPC having no adhesive layer and an FPC using a polyimide resin having excellent melt fluidity have been proposed. Regarding the two-layer FPC having no adhesive layer, a method in which a conductor layer is formed directly on an insulating film and a method in which an insulating layer is formed directly on a conductor layer are common. In the method of forming a conductor layer directly on an insulating layer, a method is used in which a thin layer of a conductor is formed by vapor deposition or sputtering, and then a thick layer of the conductor is formed by plating. There are problems that holes are easily generated and it is difficult to obtain a sufficient adhesive force between the insulating layer and the conductor layer.

On the other hand, in a method of forming an insulating layer directly on a conductor layer, a method of casting and drying a solution of a polyimide copolymer or a polyamic acid copolymer on the conductor layer and drying the same is used. In addition, the conductor layer is likely to be corroded by various solvents. Further, when a double-sided plate is manufactured, there is a problem that a complicated process is required such that two single-sided plates are manufactured and then these single-sided plates are adhered to each other.

Further, FPC using a polyimide resin having excellent melt fluidity is disclosed in JP-A-2-138789,
A bonding sheet having a thermoplastic polyimide layer on at least one side of a base film made of a heat-resistant resin proposed in 5-179224 or JP-A-5-112768 is used, but excellent adhesiveness, solder heat resistance, and dimensional stability are used. It was difficult to realize the properties and the like.

[0008]

As described above, the FPC having excellent heat resistance has problems in any form, but in consideration of productivity and characteristics, a base film made of a heat-resistant resin is required. It is considered that a bonding sheet obtained by laminating a thermoplastic polyimide on the substrate is most advantageous. Therefore, the above-mentioned problems relating to this case, that is, adhesiveness, solder heat resistance, dimensional characteristics, further low water absorption, low heat absorption, to provide a heat-resistant bonding sheet used for FPC excellent in low dielectric properties. As a result, the present invention has been achieved.

[0009]

SUMMARY OF THE INVENTION A heat-resistant bonding sheet and a method of manufacturing the same according to the present invention are characterized in that a base film made of a heat-resistant resin has a thermoplastic polyimide layer on at least one surface. The film is characterized by being subjected to a plasma discharge treatment in a mixed gas mainly composed of an inert gas.

[0010] In the bonding sheet, the thermoplastic polyimide resin layer has a general formula (Formula 11)

[0011]

Embedded image (In the formula, k is an integer of 1 or more, m and n are each an integer of 0 or more, where m + n is 1 or more. A and B are tetravalent organic groups, and X and Y are divalent organic groups. )).

Further, A and B in the above general formula (Formula 11) are represented by the following formulas (Formula 12) to (Formula 20)

[0013]

Embedded image

[0014]

Embedded image

[0015]

Embedded image

[0016]

Embedded image

[0017]

Embedded image

[0018]

Embedded image

[0019]

Embedded image

[0020]

Embedded image

[0021]

Embedded image And at least two kinds selected from the group of tetravalent organic groups shown in (1). Further, in the general formula (Chemical Formula 1), X,
Y is represented by the following formulas

[0022]

Embedded image

[0023]

Embedded image

[0024]

Embedded image

[0025]

Embedded image

[0026]

Embedded image

[0027]

Embedded image

[0028]

Embedded image

[0029]

Embedded image

[0030]

Embedded image

[0031]

Embedded image

[0032]

Embedded image

[0033]

Embedded image

[0034]

Embedded image

[0035]

Embedded image

[0036]

Embedded image

[0037]

Embedded image

[0038]

Embedded image

[0039]

Embedded image

[0040]

Embedded image At least one selected from the group of divalent organic groups shown in the above.

Further, the base film made of the heat-resistant resin is a non-thermoplastic polyimide film or a thermoplastic polyimide film having a glass transition temperature of 350 ° C. or more.

[0042]

Embodiments of the present invention will be described below. First, a method for preparing a polyamic acid copolymer solution used as a thermoplastic polyimide layer in the present invention will be described.

The polyamic acid copolymer can be obtained by reacting an acid dianhydride with a diamine in an organic solvent. In the present invention, first, a general reaction is carried out in an atmosphere of an inert gas such as argon or nitrogen. Formula (Formula 40)

[0044]

Embedded image (In the formula, C represents a tetravalent organic group.) At least one acid dianhydride is dissolved or diffused in an organic solvent. The solution has the general formula (Formula 41)

[0045]

Embedded image (In the formula, X represents a divalent organic group.) At least one kind of diamine is added in a solid state or an organic solvent solution state. Furthermore, a mixture of one or more acid dianhydrides represented by the above general formula (Chemical Formula 11) is added in a solid state or an organic solvent solution, and a polyamic acid solution as a polyimide precursor is added. Get. In this reaction, contrary to the above addition procedure, a diamine solution may be prepared first, and a solid acid dianhydride or an organic solvent solution of acid dianhydride may be added to the solution. The reaction temperature at this time is preferably from -10C to 0C. The reaction time is 30 minutes to 3 hours. By this reaction, an adhesive of a polyamic acid solution which is a precursor of the thermoplastic polyimide is prepared.

Examples of the organic solvent used in the synthesis reaction of the polyamic acid include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide, and N, N-dimethylformamide. Acetamide solvents such as N-dimethylacetamide and N, N-diethylacetamide can be mentioned. These may be used alone or in combination of two or more. Further, a mixed solvent composed of these polar solvents and a non-solvent of polyamic acid can also be used. Examples of the non-solvent for the polyamic acid include acetone, methanol, ethanol, isopropanol, benzene, and methyl cellosolve.

The molecular weight of the polyamic acid copolymer and the polyimide copolymer is not particularly limited, but in order to maintain the strength as a heat-resistant adhesive, the number average molecular weight is 50,000 or more, and It is preferably at least 80,000, particularly preferably at least 100,000. The molecular weight of the polyamic acid copolymer (solution) as an adhesive can be measured by GPC (gel permeation chromatography).

Next, in order to obtain a polyimide from the polyamic acid solution as a precursor, a method of thermally or chemically dehydrating a ring-closing (imidization) method may be used. Specifically, in the method of thermally dehydrating ring closure (imidization), a solution of the above polyamic acid is coated on a base film made of a heat-resistant resin to form a film, and the organic solvent is evaporated and dried to be self-supported. Get a body membrane. Furthermore, the evaporation of the organic solvent is 1
It is preferable to carry out at a temperature of 50 ° C. or less for about 5 minutes to 90 minutes. Next, it is heated and dried to imidize it. The heating temperature at the time of imidization is preferably in the range of 150 ° C to 350 ° C. Particularly, the final heat treatment is preferably performed at 300 ° C. or higher. More preferably, the temperature is 300 to 350 ° C. The heating time varies depending on the thickness and the maximum temperature, but is generally preferably in the range of 10 seconds to 10 minutes after the maximum temperature is reached.

In the method of chemically dehydrating and ring-closing (imidizing), a dehydrating agent having a stoichiometric amount or more and a tertiary amine as a catalyst are added to the above polyamic acid solution, and thermal dehydration is performed in the same manner. Upon treatment, a desired polyimide film can be obtained in a shorter time than when thermally dehydrating.

The tertiary amine used as a catalyst includes pyridine, α-picoline, β-picoline and γ-picoline.
Picoline, trimethylamine, triethylamine, isoquinoline and the like are preferred.

Next, a copper foil is laminated on one or both sides of the bonding sheet thus obtained and thermocompression-bonded to obtain a copper-clad laminate.

The base film referred to in the present invention is FPC
Any film may be used as long as it can be used as a base film, but a polyimide film having excellent heat resistance is particularly preferably used. Specifically, as the polyimide film used as the base film, for example, a polyimide film having no adhesive property such as “Apical (registered trademark; manufactured by Kaneka Chemical Co., Ltd.)” can be used. It may be a polyimide film.

Next, the plasma discharge processing will be described.

The gas type, gas pressure, and processing density of the plasma processing are not particularly limited.
It is preferable to carry out under a pressure in the range of 0 to 1330000 Pa. Gases that can be used to form the plasma gas include, for example, inert gases such as helium, argon, krypton, xenon, neon, radon, nitrogen, and oxygen,
Examples include air, carbon monoxide, carbon dioxide, carbon tetrachloride, chloroform, hydrogen, ammonia, carbon tetrafluoride, trichlorofluoroethane, and trifluoromethane. Further, a known fluorinated gas or a mixed gas of the above gases may be used. Preferred combinations of gas mixtures are argon / oxygen, argon / ammonia, argon / helium /
Oxygen, argon / carbon dioxide, argon / nitrogen / carbon dioxide, argon / helium / nitrogen, argon / helium / nitrogen / carbon dioxide, argon / helium, argon /
Helium / acetone, helium / acetone, helium /
Air, argon / helium / silane. The processing density is preferably in the range of 100 to 10000 w · min / m ² . More preferably, 300 to 7000 w · min /
A range of m ² is preferred. If the value is out of the above range, desired effects cannot be obtained.

Although the embodiment of the heat-resistant bonding sheet according to the present invention has been described above, the present invention is not limited to this, and the present invention is based on the knowledge of those skilled in the art without departing from the scope of the present invention. , Various improvements,
The present invention can be implemented in a form in which changes and modifications are made. The present invention will be described more specifically with reference to the above examples, but the present invention is not limited to these examples.

[0056]

EXAMPLES Example 1 The whole system was cooled with ice water and placed in a 2000 ml three-neck separable flask purged with nitrogen.
Take 3.2 g of 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride (hereinafter referred to as BTDA) and 287 g of dimethylformamide (hereinafter referred to as DMF) and stir using a stirrer. To sufficiently dissolve. Subsequently, 43.1 g of 2,2′-bis [4- (4-aminophenoxy) phenyl] propane (hereinafter referred to as BAPP) was added to 20 parts of the mixture.
The reaction was carried out using g of DMF. After stirring for 15 minutes, 76.0 g of 3,3 ', 4,4'-ethylene glycol dibenzoate tetracarboxylic dianhydride (hereinafter referred to as TMEG) was added using 150 g of DMF. After stirring for 15 minutes, 80.0 g of BAPP was charged using 150 g of DMF and reacted. After stirring for 30 minutes, an additional 4.1
A solution prepared by dissolving TMEG in 47.2 g of DMF was gradually added while paying attention to the viscosity of the solution in the flask, and then left for 1 hour with stirring. Thereafter, 106 g of DMF was charged and stirred to obtain a polyamic acid solution.

Next, this polyamic acid solution was applied on both sides of a plasma-treated base film 12.5NPI (manufactured by Kaneka Chemical Co., Ltd.) so that the final thickness would be 6.5 μm on one side, and at 100 ° C. After heating for 6 minutes,
Heating was performed at 00 ° C. and 300 ° C. for 6 minutes each to obtain a bonding sheet. The plasma treatment was performed under the conditions shown in Table 1.
An 18 μm-thick rolled copper foil is laminated on the adhesive layer surface (one or both surfaces) of the obtained bonding sheet, and 25 μm
Arrange the thick polyimide film as a release film,
Lamination was performed with a double belt press (DBP) to obtain a copper-clad laminate. Laminating temperature 280 ° C, pressure 70k
gf / cm and the lamination time was about 5 minutes. The obtained copper-clad laminate was measured for adhesive strength (N / cm) according to JIS C6481 and solder heat resistance according to JIS6471. Table 1 shows the results. Solder heat resistance is 300 ° C after normal condition adjustment (20 ° C, 60% RH, 24 hours)
・ Immerse for 1 minute and absorb moisture (40 ° C, 90% RH, 96
After a period of time, the test was carried out under two conditions of immersion at 280 ° C. for 10 seconds, and a judgment was made based on whether or not a defect in appearance occurred.

[0058]

[Table 1] (Example 2) After producing a 17HP (manufactured by Kanebuchi Chemical Co., Ltd.)-Based bonding sheet subjected to plasma treatment under the conditions shown in Table 2 in the same manner as in Example 1, a copper-clad laminate was prepared using DBP. It was fabricated and its characteristics were evaluated. Table 2 shows the results.

[0059]

[Table 2] (Example 3) A 17HP (manufactured by Kanebuchi Chemical Co., Ltd.)-Based bonding sheet subjected to plasma treatment under the conditions shown in Table 3 in the same manner as in Example 1 was manufactured, and a copper-clad laminate was formed using DBP. It was fabricated and its characteristics were evaluated. Table 3 shows the results.

[0060]

[Table 3] Example 4 A bonding sheet based on 17HP (manufactured by Kanebuchi Chemical Co., Ltd.) subjected to plasma treatment under the conditions shown in Table 4 in the same manner as in Example 1 was prepared, and a copper-clad laminate was formed using DBP. It was fabricated and its characteristics were evaluated. Table 4 shows the results.

[0061]

[Table 4] (Comparative Examples 1 and 2) Using a base film not subjected to plasma treatment, a bonding sheet was prepared in the same manner as in Example 1, and a copper-clad laminate was prepared using DBP to evaluate characteristics. Table 5 shows the results.

[0062]

[Table 5]

[0063]

As described above, the bonding sheet according to the present invention is particularly excellent in solder heat resistance and peel strength with copper foil, and is suitable for FPC and rigid-flex substrate materials, COL and LOC.
It is suitable for use in new high-density packaging materials such as packages and MCMs, and other uses are not particularly limited.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05K 1/03 670 H05K 1/03 670Z // C08J 5/18 CFG C08J 5/18 CFG C08L 79:08 F Term (Reference) 4F071 AA60 AG16 AH13 BC01 BC02 4F073 AA01 BA31 BB01 CA01 CA62 CA64 CA65 CA67 4F100 AB17 AK01A AK49A AK49B AK49C BA02 BA03 BA04 BA06 BA10B BA10C EH462 EJ422 EJ60A EJ86A04 J04B05J04B05J04A05 QB15 QB26 QB31 RA34 RA35 SA06 SA43 SA44 SA71 TA22 UA121 UA122 UA131 UA132 UA141 UA151 UA152 UA662 UA672 UB011 UB012 UB021 UB022 UB052 UB062 UB121 VA122 UB132 VA2A 03A1

Claims (4)

[Claims] 1. A bonding sheet having a thermoplastic polyimide layer on at least one surface of a base film made of a heat-resistant resin, wherein the base film has been subjected to a plasma discharge treatment in a mixed gas mainly containing an inert gas. A heat-resistant bonding sheet characterized by the following. 2. A thermoplastic polyimide layer whose precursor is represented by the general formula (1): ## STR1 ## (In the formula, k is an integer of 1 or more, m and n are each an integer of 0 or more, where m + n is 1 or more. A and B are tetravalent organic groups, and X and Y are divalent organic groups. The heat-resistant bonding sheet according to claim 1, comprising a polyimide represented by the following formula: 3. A and B in the general formula (Chem. 1) are represented by the following formulas (Chem. 2) to (Chem. 10). Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image The heat-resistant bonding sheet according to claim 2, wherein the heat-resistant bonding sheet is at least two kinds selected from the group of tetravalent organic groups shown in the following. 4. The heat-resistant bonding sheet according to claim 1, wherein the heat-resistant resin base film is a non-thermoplastic polyimide film or a thermoplastic polyimide film having a glass transition temperature of 350 ° C. or higher. .