JPH0360182A - Substrate for wiring board - Google Patents

Abstract

PURPOSE:To obtain a substrate for wiring board which can be formed at a low temperature and is excellent in solvent resistance and heat resistance by applying varnish containing a precursor of a specific polyimide resin to metallic foil in a state where the varnish is expanded by flowing and drying the varnish. CONSTITUTION:A polyimide resin 1 expressed by formula I is formed on metallic foil. In order to form the resin 1 on the metallic foil, precursor varnish of the resin 1 is first applied to the metallic toil in a state where the varnish is expanded by flowing and dried. At the time of drying, the metallic foil is heated at a temperature at which the used solvent is removed and the precursor completely changes to imide simultaneously with or after the solvent is removed. When a film of a polyimide type resin is pressed against the metallic foil to adhere to the foil by heating, the film of the resin 1 can be formed on the foil. In this case, the heating temperature must be set at a temperature higher than the softening point of the resin 1 when the polyimide type resin is the polyimide resin 1 and a temperature which is sufficiently high to completely change the precursor to imide when a polyimide type resin is used as the precursor. When the polyimide type resin is a film-like substance, the metallic foil, polyimide type resin, and a supporting body are successively piled up and pressurized in a heated state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a wiring board substrate having excellent solvent resistance and heat resistance.

[Conventional technology]

Printed wiring boards are used to mount electronic components in various devices.
Used for connection. Flexible printed wiring board (
FPC) is made by bonding a polyimide film and metal foil together with an adhesive. Conventionally, resins with low heat resistance such as epoxy resins and acrylic rubber have been used as adhesives, making it impossible to take advantage of the heat resistance of polyimide films and limiting their use at high temperatures. In order to solve this problem, thermoplastic A wiring board substrate has been proposed in which a polyimide film and a metal foil are bonded together using polyimide as an adhesive.

[Problem to be solved by the invention]

JP-A-57-181857, JP-A-57-632
No. 54 and JP-A No. 61-55177 use polyimide as an adhesive, so they have excellent heat resistance;
A bonding temperature higher than that is required. For this reason, it has the disadvantage that it cannot be used to bond materials with low heat resistance.

The polyimide disclosed in JP-A-62-275181 has a low softening point and can be bonded at 230 to 350°C, but this polyimide is soluble in a solvent such as methylene chloride used for wiring formation.

It had a serious drawback as a wiring board substrate: poor solvent resistance.

The present invention provides a wiring board substrate that can be molded at low temperatures and has excellent solvent resistance and heat resistance.

[Means to solve the problem]

The present invention provides a metal foil and general formula (I) or (b)? The present invention relates to a wiring board substrate formed by laminating insulating layers containing a polyimide resin having the repeating unit shown below.

A support body can further be laminated on the wiring board substrate.

The wiring board substrate of the present invention can be produced by casting a varnish containing a precursor of the polyimide resin represented by the general formula (1) on a metal foil and drying it, or by combining the metal foil and the polyimide resin or its precursor. It can be obtained by heat-pressing a film containing the polyimide resin, or by bonding a metal foil and a support using an adhesive containing the polyimide resin or its precursor.

In the wiring board substrate of the present invention, the metal foil may be copper, aluminum, iron, etc., and the support may be polyimide,
Examples include polyimide films such as polyamideimide, polyesterimide, and polyetherimide, aramid films, copper plates, steel plates, aluminum plates, copper-invar copper plates, and ceramic plates.

The above polyimide resin and its precursor will be explained.

The polyimide resin preferably has a softening point of 130 to 1
It is at 80°C. If the softening point is too low, the physical properties of the polyimide resin tend to deteriorate.

Among the precursors of the polyimide resin, polyamic acid has a repeating unit represented by the general formula (U) (wherein R is the same as in the general formula (1)). In addition, other precursors include
Some of the above polyamic acids are partially imidized.

In the present invention, the polyimide resin, the polyamic acid, and the partially imidized polyimide precursor are collectively referred to as a polyimide resin.

The above polyimide resin is 4.4'-[1,4-buenylenebis(1-methylethylidene)]bisaniline (
BAP) and 4.4'-(1,4-phenylenebis(1
4.4
'-(1,3-)unishinbis(1-methylethylidene)]bisaniline (BAP) and 4.4'-(1,3
-) Unishin bis(1-methylethylidene)] bisphenylbistrimellitate dianhydride (BAMBT). in this case,
BAP or BAM which is a diamine and B which is an acid dianhydride
By reacting APBT or BAMBT under appropriate conditions, the degree of imidization can be adjusted as appropriate. For example, in an organic solvent at 100°C or above, especially at 18°C.
At 0°C or higher, use tributylamine or triethylamine as necessary.

By reacting in the presence of a catalyst such as triphenyl phosphite, almost completely imidized polyimide resins can be produced (the catalyst is used in an amount of 0 to 15% by weight based on the total amount of reaction components). It is preferred to use, especially 0.01
~15% by weight) in an organic solvent, 1
If the reaction is carried out at a temperature of 00°C or lower, especially 50°C or lower, a polyamic acid which is a precursor of the polyimide resin and is hardly imidized can be produced. Furthermore, it is also possible to produce a pre-waste polyimide resin in which imidization has partially progressed.

The foreleg body of the polyamic acid or partially imidized polyimide is further heated at 100°C or higher, particularly at 120°C.
Imidize by heating above, or use an acid anhydride such as acetic anhydride, propionic anhydride, benzoic anhydride, a ring-closing agent such as a carbodiimide such as dicyclohexylcarbodiimide, and optionally pyridine.

A method of chemically closing the ring (imidization) by adding a ring-closing catalyst such as isoquinoline, tolumethylamine, aminopyridine, imidazole, etc. (The ring-closing agent and the ring-closing catalyst are each in the range of 1 to 8 mol per 1 mol of acid anhydride. polyimide resins can be produced by using

As the organic solvent, N-methyl-pyrrolidone (NM
P), N, N'-dimethylacetamide, N, N'-
Dimethylformamide (DMF), dimethyl sulfoxide, sulfolane, hexamethyl phosphoric triamide, 1.
Aprotic polar solvents such as 3-dimethyl-2-imidazolitone, phenol, cresol, xylenol, P-
Examples include phenolic solvents such as chlorophenol.

These solvents include benzene, toluene, and xylene.

Methyl ethyl ketone, acetone, tetrahydrofuran,
Dioxane, monoglyme, diclyme.

A mixture of solvents such as methyl cellosolve, cellosolve acetate, methanol, ethanol, isopropanol, methylene chloride, chloroform, trichlene, and tetrachloroethane can be used.

When producing the above-mentioned polyimide and its pre-cleaved polyamic acid, solid phase reaction, melt reaction at 300° C. or lower, etc. can be used depending on the case.

The above polyimide resin is a diamine, BAP or BA.
BA which is a diisocyanate and acid dianhydride corresponding to M
It can be manufactured in one step using PBT or BAMBT. At this time, it is sufficient that the reaction temperature is at least room temperature, especially at least 60°C.

In the present invention, the acid dianhydride and its reaction partner are preferably used in approximately equimolar amounts, but an excess of either one of them is allowed up to 10 mol%, particularly preferably up to 5 mol%.

In the above, the acid dianhydride may be used in the form of an acid derivative such as its diester.

The polyimide resin used in the present invention also includes N, N'
-(4,4'-(1,4-phenylenebis(l-methylethylidene))bisaniline]bistrimeritimide (hereinafter referred to as "imidodicarboxylic acid IJ") and 4.4
' -(1,4-phenylenebis(1-methylethylidene))] React with bisphenol or N, N' -
(4,4'-(1゜3-phenylenebis(1-methylethylidene)]bisaniline)bistrimeritimide (hereinafter referred to as "imidodicarboxylic acid ■") and 4,4'
[1,3-phenylenebis(neemethylethylidene)]
It can also be produced by reacting bisphenol. In this case, ■ heat polycondensation reaction of the imidodicarboxylic acid ■ or ■ and the above bisphenol or direct polycondensation reaction using a condensing agent such as phosphite or tosyl chloride, ■ the above imidodicarboxylic acid ■ or ■
A low-temperature polymerization reaction between diacid chloridone and the above-mentioned bisphenol can be used.

Methods (1) and (2) may be carried out in the same manner as the usual polyester polycondensation method. Regarding direct polycondensation, see Mitsuru Ueda, Kobunshi 35 (2) 128 (1986), Higashifukuji 1 Journal of Japan Adhesive Association, 24 (12) 504 (1988).
, Takashi Takazawa et al., Polymerρreprints
Japan, 1 Sat. (6) 1345 (1985).

In addition, the polyimide resin in the present invention can be produced as a polyamic acid by reacting trimellitic anhydride, BAP or RAM, and the above-mentioned bisphenol in the same container using a condensing agent such as tosyl chloride. It can be obtained as a polyimide by a thermal ring-closing method or a chemical ring-closing method. For methods like this.

Hozumi Tanaka at al,, Pro
ceedings/AbstractSof Th1
rd International Conference
ce on Polyimide p, 64 (19
88).

The polyimide resin is used in powder form.

It can be in any form such as a solution (in the case of a precursor) or a film. When used in the form of a solution, the polyimide resin (precursor) is dissolved in a suitable organic solvent selected from among the above-mentioned organic solvents. As for the form of use, it is preferably in the form of a film for ease of handling.

To create a film-like adhesive, the polyimide resin is dissolved in an appropriate organic solvent such as those mentioned above (varnish) and then placed on a drum, a steel belt, a glass plate, and the resin. It can be created by casting on a support such as a film and heating to remove most of the solvent, and then the created film can be peeled off to form a self-supporting film. can. In this case, the polyimide resin is a polyamic acid or a partially imidized precursor, and there is a method of further heating it, and a method of immersing the film in a solution in which the above-mentioned ring-closing agent and, if necessary, a ring-closing catalyst are dissolved. etc., these can be made into polyimide resins. Furthermore, when the polyimide resin is a polyimide resin, it can be made into a film by melting and forming the polyimide resin into a film.

Furthermore, polyimide resins are used in the form of impregnated woven or nonwoven fabrics made of glass fibers, carbon fibers, aramid fibers, etc. (prepreg).
But that's fine. These are made by impregnating the woven or nonwoven fabric with the varnish described above and drying it. In this case as well, the polyimide resin is a polyamic acid or a partially imidized polyimide precursor, but as in the case of the self-supporting film described above, the polyimide resin can be used.

In the present invention, as the polyimide resin.

It is preferable to use polyimide resin because there is less risk of void generation.

The polyimide resin may be mixed with ceramics such as alumina, silica, glass, metal powder, short fibers such as whisker carbon fibers, glass fibers, aramid fibers, fluororesin particles, pigments, and the like. Further, a coupling agent such as silane or titanium may be mixed in order to further improve adhesiveness.

In order to laminate the polyimide resin on the metal foil, a precursor varnish of the polyimide resin is cast onto the metal foil and dried. At this time, simultaneously with or after removing the solvent, the precursor is heated to a temperature at which it is completely imidized. It can also be obtained by heat-pressing a metal foil and a film (prepreg) of the polyimide resin.

In this case, if the polyimide resin is a polyimide resin, the heating temperature is higher than the softening point of the polyimide resin, and if the polyimide resin is a precursor thereof,
The temperature is high enough to complete imidization.

The metal foil and the support can be bonded as follows.

When the polyimide resin is in the form of a film (including prepreg), the metal foil, the polyimide resin, and the support are sequentially laminated and heated and pressurized.

When the polyimide resin (precursor) is a varnish, the varnish is cast onto a metal foil or a support, the solvent is dried and removed, and then the varnish is laminated with the support or metal foil and heated and pressed. Further, in this case, complete imidization may be carried out when or after drying and removing the solvent.

In these cases, if the polyimide resin is a polyimide resin, the heating temperature during bonding is set to be above the softening point of the polyimide resin, and if the polyimide resin is the precursor, The temperature is high enough to complete the process.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

The present invention is not limited to these ranges.

Example 1 34.4 g of BAP was placed in a four-loaf flask equipped with a stirrer, a thermometer, a calcium chloride tube, and a nitrogen gas introduction tube.

After 415 g of N,N-dimethylformamide was added and dissolved, 69.4 g of BAPBT was added little by little at a temperature below 5°C. A polyamic acid varnish was obtained by reacting at 10° C. or lower for 3 hours.

The varnish was cast onto a glass plate using an applicator, and then dried at 80°C for 30 minutes. After peeling the film from the glass plate, dry it at 150°C for 2 hours to reach a softening point of 165.
Adhesive film made of polyimide resin (thickness 25μ
m) was obtained.

This adhesive film was sandwiched between a 25 μm thick single-sided roughened copper foil and a 50 μm thick polyimide film, and heated at 250°C.
It was heated and pressurized at 30 kgf/J for 15 minutes. J4S-C-6
, 481, the 90' copper foil peel strength was measured to be 2.1 kgf/am at room temperature and 1,3 at 150°C.
kg f/cs. Furthermore, when this copper-clad substrate was immersed in methylene chloride, there was no change in appearance.

Example 2 An adhesive film (thickness: 30 μm) made of a polyimide resin having a softening point of 150° C. was obtained in the same manner as in Example 1, except that 34.4 g of RAM and 69.4 g of RAMBT were used.

This adhesive film was sandwiched between a 35-μm-thick single-sided roughened copper foil and a 1-inch-thick aluminum plate.

A copper-clad substrate was obtained by heating and pressing at 200° C. and 50 kgf/aJ for 30 minutes. The #I foil peel strength of this board is 2 at room temperature.
, 2 kg f/tym, 1,4 at 150 °C
kgf/aa. Furthermore, when this copper-clad substrate was immersed in methylene chloride, there was no change in appearance.

Comparative Example 1 Using equimolar moles of metaphenylenediamine and 2,2-bis(p-trimellitoxyphenyl)propanihydride, a 5-thickness polyimide resin was prepared in the same manner as in the example above.
A 0 μm adhesive film was prepared, and this film was used in the same manner as in Example 2 at 250°C, 50 kgf/cd,
A copper-clad substrate was obtained by heating and pressing for 30 minutes. The copper foil peeling strength of this board was 1.8 kgf/aJ at room temperature. Furthermore, when this copper-clad substrate was immersed in methylene chloride, the adhesive layer dissolved.

Comparative Example 2 3.3'-diaminobenzophenone and 3,3'4.4'
- Apply equimolar amounts of benzophenone tetracarboxylic dianhydride externally, and use the same method as in Example 1 to prepare a polyimide resin 2.
A 5 μm adhesive film was produced. Using this film, the same procedure as in Example 2 was carried out at 250°C and 30 kgf/cd.
When heated and pressurized for 30 minutes, no adhesion occurred. 30
The copper foil peeling strength of the copper-clad board obtained by heating and pressurizing at 0°C and 30 kgf/aJ for 30 minutes is 0.2 kg at room temperature.
The f/am was extremely low.

Example 3 The polyamic acid varnish of Example 1 was applied to an aluminum plate with a thickness of 1 mm, and then dried at 100°C for 30 minutes and in a vacuum dryer at 150°C for 1 hour to form an adhesive made of polyimide resin with a thickness of 30 μm. A coating layer was formed. Layer a single-sided roughened copper foil with a thickness of 35 μm on the adhesive layer and heat at 200°C and 50 kgf.
/aJ, was heated and pressed for 30 minutes to obtain a copper-clad substrate. The copper foil peeling strength of this board is 2.0) cg f /
am, 1.2 kg f/ai at 150°C. Furthermore, when this copper-clad substrate was immersed in methylene chloride, there was no change in appearance.

Example 4 A polyamic acid varnish was obtained in the same manner as in Example 1 except that 34.2 g of RAM and 69.4 g of BAMBT were used.

This varnish was applied to the roughened side of a single-sided roughened steel foil having a thickness of 35 μm, and then dried at 80° C. for 30 minutes and at 150° C. for 2 hours to form an adhesive layer made of polyimide resin with a thickness of 25 μm. After this adhesive layer am and a polyimide film with a thickness of 25 μm were laminated.

A copper-clad substrate was obtained by heating and pressing at 230° C. and 30 kgf/country for 1 hour. The copper foil peel strength of this board is 2 at room temperature.
, 3 kg f/am, 1,4 kg at 150 °C
f/Cal, and there was no change in appearance even when immersed in methylene chloride.

Note that the adhesive films obtained in Example 1 and Example 2 (
A portion of the polyimide resin) was sampled and the following physical properties were measured.

Resin obtained in Example 1: (1) Thermal decomposition temperature 431°C (2) Main absorption in IR spectrum (KBr method) 1785 am-” (imide group) 1730C11-1 (ester group) 2970.2880 cm-” ( Methyl group) Resin obtained in Example 2: (1) Thermal decomposition temperature 418°C (2) Main absorption in IR spectrum (KBr method) 179'Oex-'' (imide group) 1730aa-'' (x stell group) 2980.2880 value -1 (methyl group) From the above, the resin obtained in Example 1 has the general formula CI) in which R is the formula (
The resin obtained in Example 2 is a polyimide resin having a repeating unit represented by formula (a), and the resin obtained in Example 2 is a polyimide resin having a repeating unit in which R is represented by formula (b) in general formula (I). It was resin.

〔Effect of the invention〕

Claims (2)

[Claims] 1. Metal foil and general formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, in the formula, R is formula (a) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ Or formula (b) ▲Mathematical formula, A wiring board substrate made by laminating insulating layers containing polyimide resin having a repeating unit represented by the chemical formula, table, etc. 2. 2. The wiring board substrate according to claim 1, which is formed by sequentially laminating a metal foil, an insulating layer containing the polyimide resin according to claim 1, and a support.