JP2001191467A - Heat-resistant bonding sheet and copper clad laminated sheet comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-resistant bonding sheet having sufficient mechanical strength and excellent in solder heat resistance, adhesiveness, dimensional stability and low dielectric characteristics and a copper clad laminated sheet using this bonding sheet. SOLUTION: In a heat-resistant bonding sheet obtained by coating at least the single surface of a base film comprising a heat-resistant resin with a polyamic acid being a precursor of a thermoplastic polyimide resin and subsequently adjusting the imidation ratio of the polyamic acid to 10-90%, the high adhesiveness of the base film and the thermoplastic polyimide interface can be especially realized. This bonding sheet is also excellent in heat resistance and solder heat resistance and can be especially used for a flexible copper clad 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 side of a base film and a copper-clad laminate comprising the same, and more particularly, to a heat resistance excellent in heat resistance, adhesion and dimensional characteristics. The present invention relates to a bonding sheet and a copper-clad laminate comprising the same.

[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.

[0007] FPCs using a polyimide resin having excellent melt fluidity are disclosed in Japanese Patent Application Laid-Open Nos.
No. 179224 or a bonding sheet having a thermoplastic polyimide layer on at least one surface of a base film made of a heat-resistant resin proposed in JP-A-5112768,
It has been difficult to achieve excellent adhesion, dimensional stability, solder heat resistance, 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 method of bonding a copper foil and 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, dimensional characteristics, solder heat resistance, 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]

The present invention provides a bonding sheet having a thermoplastic resin layer formed on at least one surface of a heat-resistant base film, wherein the thermoplastic resin layer has an imidization ratio of 10% to 90%. It contains a heat-resistant bonding sheet made of a thermoplastic polyimide resin and a copper-clad laminate made of the same. After application, it can be produced by adjusting the imidation ratio to 10% to 90%.

In the bonding sheet, the precursor of the thermoplastic polyimide resin is represented by the general formula (1):

[0011]

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(Where k is an integer of 1 or more, and m and n are m
+ N is an integer of 0 or more, each of which is 1 or more.
A and B each represent a tetravalent organic group, and X and Y each represent a divalent organic group. ). Further, A and B in the general formula (1) represent the following group (I)

[0013]

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It is at least one kind of tetravalent organic group selected from the group consisting of: Further, X and Y in the general formula (1) represent the following group (II)

[0015]

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At least one divalent organic group selected from the group consisting of:

Furthermore, 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.

[0018]

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. For example, at first, at least in an inert gas atmosphere such as argon or nitrogen, A kind of acid dianhydride is dissolved or diffused in an organic solvent. At least one diamine compound is added to this solution in a solid state or an organic solvent solution state. Further, a mixture of one or more acid dianhydrides is added in a solid state or an organic solvent solution to obtain a polyamic acid solution which is a precursor of polyimide. 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, a polyamic acid solution which is a precursor of the thermoplastic polyimide is prepared.

Examples of the organic solvent used for 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 dimethyl Acetamide solvents such as acetamide 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, the base film will be described.
Apical A is already on the market for base film
H, NPI and HP (in each case, Kaneka Corporation) are preferably used. In addition, polyimides obtained from various combinations of acid dianhydrides and diamines can be used according to required characteristics.

After applying a polyamic acid solution, which is a precursor of the above-mentioned thermoplastic polyimide, to the base film,
The imidization reaction is allowed to proceed, and the imidization rate is increased from 10% to 90%.
%, Preferably 20% to 90%, more preferably 30%
By adjusting it to 85%, a bonding sheet having a desired configuration can be obtained. If the imidation ratio is less than 10%, swelling occurs during solder immersion, and voids such as foaming tend to occur during bonding of the copper foil. On the other hand, when the imidization ratio is larger than 90%, the adhesive strength is reduced.

Next, as a method for obtaining a polyimide from these polyamic acids, a method of thermally or chemically dehydrating a ring closure (imidization) may be used. Specifically, in the method of thermally dehydrating ring closure (imidization), it is preferable to carry out at a temperature of 150 ° C. or less for about 5 minutes to 90 minutes in order to evaporate the organic solvent. Subsequently, this is dried by heating 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 cyclizing (imidizing), a dehydrating agent having a stoichiometric amount or more and a tertiary amine as a catalyst are added to the polyamic acid solution, and the method is performed in the same manner as in the case of thermally dehydrating. Upon treatment, a desired polyimide film can be obtained in a shorter time than when thermally dehydrating.

As the tertiary amine used as a catalyst, pyridine, α-picoline, β-picoline, γ-picoline, trimethylamine, triethylamine, isoquinoline and the like are preferable.

The imidization is carried out by the above-mentioned method. In order to adjust the imidation ratio to 10 to 90%, it is necessary to appropriately set processing conditions such as temperature and time. The imidation ratio is calculated from the following equation using infrared absorption spectroscopy. (A / B) × 100 / (C / D) Formula In the formula 1, A, B, C, and D represent the following. A: absorption peak height of the object 1780 cm ^-1 B: absorption peak height of 1500 cm ^-1 of the object C: absorption peak height D of the chemical imidization of polyimide of 1780 cm ^-1: chemical imidization of polyimide 1500 cm ^- Absorption peak height of ¹ * Chemically imidized polyimide; target thermoplastic polyimide by chemical curing method at 120 ° C, 150 ° C, 200 ° C,
A polyimide subjected to an imidization reaction at 300 ° C. and 350 ° C. for 3 minutes each (this state is defined as an imidation ratio of 100%).

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.

The copper-clad laminate of the present invention can be obtained by arranging a copper foil on at least one side of the heat-resistant bonding sheet by a press method or a laminating method.

[0030]

EXAMPLES Example 1 The whole system was cooled with ice water and placed in a 2000 ml three-neck separable flask purged with nitrogen.
26.1 g of 2,2'bis [4- (4-aminophenoxy) phenyl] propane (hereinafter referred to as BAPP) was 716.2 g.
Of dimethylformamide (hereinafter referred to as DMF) and stirred for 15 minutes. Subsequently, 33.8 g of 3,3′4,4′benzophenonetetracarboxylic dianhydride (hereinafter referred to as “BTDA”) was added using 20 g of DMF. Then, 7
6.0 g of 3,3'4,4'-ethylene glycol dibenzoate tetracarboxylic dianhydride (hereinafter referred to as TMEG) was added thereto using 20 g of DMF, and the mixture was stirred for 30 minutes. After stirring for 30 minutes, a solution prepared by dissolving 4.1 g of TMEG in 36.9 g of DMF was gradually added while paying attention to the viscosity of the solution in the flask.
A 23% polyamic acid solution was obtained.

The obtained polyamic acid is applied to both sides of a polyimide film (Apical 12.5 NPI; manufactured by Kaneka Chemical Industry Co., Ltd.) so that the final thickness of one side of the thermoplastic polyimide layer is 6 μm. 120
The resultant was heated at 300 ° C. and 300 ° C. for 2 minutes each to obtain a bonding sheet having an imidization ratio of 50%. A rolled copper foil having a thickness of 18 μm is laminated on the thermoplastic polyimide surface of the obtained bonding sheet, and a polyimide film having a thickness of 25 μm is disposed thereon as a release film. A double belt press (DBP)
To obtain a copper-clad laminate. Laminating temperature is 280 ° C, pressure is 70kgf / cm, laminating time is about 5
Minutes. JIS C6
481, adhesive strength (kgf / cm), and solder heat resistance according to JIS6471. Table 1 shows the results.
Solder heat resistance after normal condition adjustment (20 ° C, 60% RH, 24
After adjusting the time, soak for 1 minute at 300 ° C) and after absorbing moisture (40
C., 90% RH for 96 hours, and immersion for 10 seconds at 280.degree. C.). Table 1 shows the results.

(Example 2) Polyamic acid was applied to a base film in the same manner as in Example 1,
Each of #C was heated for 2 minutes to obtain a bonding sheet having an imidization ratio of 60%. Subsequent production of CCL and measurement of physical properties were performed in the same manner as in Example 1. Table 1 shows the results.

Example 3 The whole system was cooled with ice water, and 82.2 g of BAPP was charged into a 2000-ml three-neck separable flask purged with nitrogen using 650.0 g of DMF.
Stir for 5 minutes. Subsequently, 21.3 g of BTDA was introduced using 40 g of DMF. Subsequently, 71.5 g of 2,2′-bis (hydroxyphenyl) propanedibenzoatetetracarboxylic dianhydride (hereinafter referred to as ESDA) was added using 20 g of DMF, and the mixture was stirred for 30 minutes. After stirring for 30 minutes,
Further, a solution prepared by dissolving 5.8 g of ESDA in 52.2 g of DMF was gradually added while paying attention to the viscosity of the solution in the flask, and then left under stirring for 1 hour to obtain a polyamic acid solution of SC23%. . Using the obtained polyamic acid solution, a bonding sheet was produced in the same manner as in Example 1. Preparation of CCL and measurement of physical properties were performed in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 1 Polyamic acid was applied to a base film in the same manner as in Example 1,
Each #C was heated for 2 minutes to obtain a bonding sheet having an imidization ratio of 8%. Subsequent production of CCL and measurement of physical properties were performed in the same manner as in Example 1. Table 1 shows the results.

(Comparative Example 2) A polyamic acid was applied to a base film in the same manner as in Example 1,
By heating for 4 minutes each at #C and 350 # C, a bonding sheet having an imidization ratio of 95% was obtained. Subsequent production of CCL and measurement of physical properties were performed in the same manner as in Example 1. Table 1 shows the results.

[0036]

[Table 1]

[0037]

As described above, the bonding sheet according to the present invention is particularly excellent in heat resistance, the peel strength at the interface between the base film and the thermoplastic polyimide and between the thermoplastic polyimide and the copper foil, and the dimensional characteristics. It is suitable for new high-density packaging materials such as flex board materials, COF and LOC packages, and MCM, and other uses are not particularly limited.

 ──────────────────────────────────────────────────の Continuing on the front page F term (reference) 4F071 AA60 AA60X AA76X AA86 AA86X AB07 AF39 AF45 AH13 BA02 BB02 BC01 BC02 4F100 AB17C AK01A AK01B AK46B AK49A AK49B BA03 BA07 BA10A BA10C EH46B16J04 J05 J04 J05 J06 J04 J05 J05 J05 J05

Claims (6)

[Claims] 1. A bonding sheet having a thermoplastic resin layer formed on at least one surface of a heat-resistant base film, wherein the thermoplastic resin layer has an imidization ratio of 10% to 90%.
% Heat-resistant bonding sheet made of thermoplastic polyimide resin. 2. The heat-resistant base film according to claim 1, which is obtained by applying a polyamic acid, which is a precursor of a thermoplastic polyimide resin, to at least one surface of the heat-resistant base film, and then adjusting the imidation ratio to 10% to 90%. Heat resistant bonding sheet. 3. The precursor of a thermoplastic polyimide resin has the following general formula (1): (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 2, which is represented by the following formula: 4. A and B in the general formula (1) according to claim 3 are represented by the following group (I): The heat-resistant bonding sheet according to claim 3, wherein the heat-resistant bonding sheet is at least one kind of tetravalent organic group selected from the group consisting of: 5. The heat-resistant bonding film according to claim 1, wherein the heat-resistant base film is a non-thermoplastic polyimide film or a thermoplastic polyimide film having a glass transition temperature of 350 ° C. or higher. Sheet. 6. A copper-clad laminate wherein a copper foil is disposed on at least one surface of the heat-resistant bonding sheet according to claim 1.