JP3379459B2 - Flexible printed circuit board - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible printed board provided with a polyimide insulating layer having anticorrosive properties.

[0002]

2. Description of the Related Art A flexible printed circuit board in which a polyimide insulating layer is directly provided on a metal foil, for example, a copper foil, without an adhesive agent, is used as an aromatic diamine such as paraphenylenediamine and pyromellitic dianhydride. The polyamic acid varnish obtained by addition-polymerizing the aromatic acid dianhydride of 1) in a solvent such as N-methyl-2-pyrrolidone is applied onto a copper foil and dried to obtain a polyamic acid layer (polyimide precursor layer). ), And is heated and imidized at 300 to 350 ° C. to form a polyimide insulating layer.

By the way, since the polyamic acid has a carboxyl group, when the polyamic acid varnish is applied to the copper foil as described above, the surface of the copper foil is corroded and discolored, and further the electrical migration of the flexible printed wiring board is prevented. There is a problem of producing the copper ion that causes the cause.

For this reason, it is a common practice to add an imidazole-based rust preventive agent (for example, ADEKA STAB CDA-1, manufactured by Asahi Denka Co., Ltd.) to the polyamic acid varnish used when manufacturing a flexible printed circuit board.

[0005]

However, the conventionally used rust preventives are difficult to dissolve in the polyamic acid varnish, and further, when heated at a high temperature during imidization, blooming excessively occurs on the polyimide surface, and copper of the polyimide is removed. It causes a problem that the adhesive strength to the foil is lowered. In addition, when imidized, it scatters to form "a little bit", which adheres to the imidization treatment device and the flexible printed circuit board product and causes contamination.

The present invention is intended to solve the above-mentioned problems of the prior art, and does not contain an anticorrosive agent which causes blooming or "slightly" problems during imidization of polyamic acid. Even so, it is an object of the present invention to provide a flexible printed board having a polyimide insulating layer which does not have a problem of electrical migration and exhibits good adhesion strength to a copper foil.

[0007]

Means for Solving the Problems The present inventors have used a specific imidazolyl-diaminoazine as a diamine component of a polyamic acid to introduce an azine structure into the main chain of the polyamic acid and to form an imidazole ring in the side chain. It was found that the above-mentioned object can be achieved by introducing the above, and the present invention has been completed.

That is, the present invention provides a flexible printed circuit board having a polyimide obtained by imidizing a polyamic acid obtained by addition polymerization of diamines and acid dianhydrides as an insulating layer on a metal foil. Is equation (1)

[0009]

[Chemical 5]

(Where A is the formula (1a), (1b) or (1c))

[0011]

[Chemical 6]

Is an imidazolyl group represented by R ¹ is an alkylene group and m is 0 or 1. R ² is an alkyl group, and n is 0, 1 or 2. R ³ and R ⁴ are alkylene groups, and p and q are 0 or 1, respectively. B is a bet triazine residues. ) Imidazolyl represented by - providing a flexible printed circuit board, characterized by containing a diamino birds azines.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

The flexible printed board of the present invention has a structure in which an insulating layer made of polyimide is provided on a metal foil, and the polyimide is obtained by addition polymerization of diamines and acid dianhydride. An imidized polyamic acid is used. Here, the addition polymerization conditions and the imidization conditions can be appropriately set according to the conventionally performed addition polymerization conditions and imidization conditions of the polyamic acid.

[0015] In the present invention, as diamines, imidazolyl represented by at least the formula (1) - diamino DOO
Using the re-azines.

[0016] Here, when m is 0, the alkylene group of R ¹ is not present, and the imidazole ring and preparative triazine residue are directly bonded. When m is 1, examples of the alkylene group for R ¹ include methylene, ethylene, propylene and the like.

When n is 0, the alkyl group of R ² does not exist and a hydrogen atom is bonded to the imidazole ring. as the alkyl group R ² when n is 1, include methyl, ethyl and the like. When n is 2, two R ² groups are bonded to the imidazole ring, and the alkyl group of each R ² is independently methyl,
Ethyl etc. can be mentioned. In some cases, R ² may be directly bonded to the nitrogen atom of the imidazole ring.

[0018] When p is 0, the alkylene group of R ³ is not present, is attached directly to the amino group Gath triazine residue, the alkylene group of R ³ when p is 1, , Methylene, ethylene and the like.

[0019] When q is 0, the alkylene group of R ⁴ is absent, directly bonded to the amino group Gath triazine residue, the alkylene groups R ⁴ when q is 1 , Methylene, ethylene and the like.

[0020] As described above, B is a preparative triazine residue. The diamine having a triazine residue is preferable because it is easy to synthesize and industrially available.

A polyimide obtained by imidizing a polyamic acid obtained by addition polymerization of a diamine of the formula (1) and an acid dianhydride as described above is represented by the following formula (2).

[0022]

[Chemical 7]

(In the formula, A is the formula (1a) as described above,
(1b) or (1c)

[0024]

[Chemical 8]

Is an imidazolyl group represented by: R ¹ ,
R ² , R ³ , R ⁴ , m, n, p, q and B are as described above. D is an acid dianhydride residue. ) Is included in the imide unit.

Since the polyimide containing such an imide unit has an imidazole residue having a rust preventive effect in its side chain, the polymer itself exhibits rust preventive properties. Therefore, if the insulating layer is composed of a polyimide containing such an imide unit, electrical migration can be achieved without using a rust preventive agent that causes the problem of blooming or “slightly” during imidization of polyamic acid. It is possible to provide a flexible printed board having a polyimide insulating layer which does not have the above problem and exhibits good adhesive strength to a copper foil.

The coefficient of thermal expansion of the polyimide used in the present invention may be adjusted to be substantially the same as or slightly higher than the coefficient of linear thermal expansion of the metal foil used, so that the flexible printed circuit board (and the wiring board produced therefrom) can be adjusted. Is preferable from the viewpoint of preventing excessive curling (or curling in which the polyimide side is convex). The thermal expansion coefficient of polyimide can be adjusted by a combination of a diamine and an acid dianhydride as disclosed in JP-A-60-157286.

[0028] imidazolyl the formula (1) of the present invention - polyimide containing a diamino birds azines is imidazolyl - or elongation becomes brittle reduced polyimide contained with the amount of diamino birds azines increases, heat However, the use of other diamines makes it possible to obtain a polyimide having film strength which can be used as a flexible printed circuit board.

The degree of addition of the diamine and the acid dianhydride may be either too much diamine or too much acid dianhydride, but is preferably equimolar.

[0030] imidazolyl the formula (1) - Specific examples of preferred diamino tri A <br/> oxazines include the following compounds p and q are both 0.

2,4-diamino-6- [2- (2-methyl-1-imidazolyl) ethyl] -s-triazine;
2,4-Diamino-6- [2- (2-ethyl-1-imidazolyl) ethyl] -s-triazine; 2,4-diamino-6- [1- (2-undecyl-1-imidazolyl)
Ethyl] -s-triazine; 2,4-diamino-6- [2
-(2-Imidazolyl) ethyl] -s-triazine;
2,4-Diamino-6- [2- (1-imidazolyl) ethyl] -s-triazine; 2,4-diamino-6- (2
-Ethyl-4-imidazolyl) -s-triazine; 2,
4-Diamino-6- [2- (4-methyl-1-imidazolyl) ethyl] -s-triazine; 2,4-diamino-
6- (2-ethyl-5-methyl-4-imidazolyl)-
2,4-diamino-6- (4-ethyl-2-methyl-1-imidazolyl) -s-triazine;
2,4-diamino-6- [3- (2-methyl-1-imidazolyl) propyl] -s-triazine; 2,4-diamino-6- [4- (2-imidazolyl) butyl] -s-triazine; 2,4-diamino-6- [2- (2-methyl-1-imidazolyl) propyl] -s-triazine;
2,4-diamino-6- [1-methyl-2- (2-methyl-1-imidazolyl) ethyl] -s-triazine;
2,4-diamino-6- [2- (2,5-dimethyl-1
-Imidazolyl) ethyl] -s-triazine; 2,4-
Diamino-6- [2- (2,4-dimethyl-1-imidazolyl) ethyl] -s-triazine; or 2,4-diamino-6- [2- (2-ethyl-4-methyl-1-imidazolyl) Ethyl] -s-triazine.

Of these, the following compounds are preferred: 2,4-diamino-6- [2- (2-ethyl-4-
Methyl-1-imidazolyl) ethyl] -s-triazine; 2,4-diamino-6- [2- (2-methyl-1-)
Imidazolyl) ethyl] -s-triazine; or 2,4
-Diamino-6- [1- (2-undecyl-1-imidazolyl) ethyl] -s-triazine.

[0033] In the present invention, imidazolyl the formula (1) - can be used in combination those used as the diamine component of conventional polyamic acids in addition to the diamino birds azines, such as 4,4'-diaminodiphenyl ether, Paraphenylenediamine, 4,4'-diaminobenzanilide, 4,4'-bis (p-aminophenoxy)
Aromatic diamines selected from diphenyl sulfone and 2,2-bis [4- (4-aminophenoxy) phenyl] propane can be preferably used in combination.

Among these aromatic diamines,
When lowering the thermal expansion property of the polyimide, it is preferable to use paraphenylenediamine in combination. Further, in order to increase the thermal expansion property of the polyimide, it is preferable to use 4,4'-diaminodiphenyl ether in combination.

[0035] imidazolyl the formula (1) - the molar ratio of the diamino tri A <br/> oxazines / above aromatic diamines, corrosion protection of polyimide obtained the former is too small is not sufficient, electrical Since migration also tends to occur and the mechanical strength and heat resistance of the polyimide decrease as the number of the former increases, it is preferably 2/98 to 10/90.

In the flexible printed circuit board of the present invention, the acid dianhydride (that corresponds to the acid dianhydride residue of D in the formula (2)) for forming the polyimide as the insulating layer has been conventionally used. What is used as an acid dianhydride of polyamic acid of can be used, for example,
Pyromellitic dianhydride (PMDA), 3,4,3 ',
4'-biphenyltetracarboxylic dianhydride (BPD
A), 3,4,3 ', 4'-benzophenone tetracarboxylic dianhydride (BTDA), or 3,4,3', 4 '
-Diphenylsulfone tetracarboxylic dianhydride (DS
Aromatic acid dianhydrides selected from DA) can be preferably used.

The thickness of the insulating layer made of polyimide as described above is not particularly limited, but is usually 10 to 50 μm.
m.

Various metal foils can be used as the metal foil of the flexible printed circuit board of the present invention.
Preferably, aluminum foil, copper foil, gold foil, etc. can be mentioned. These metal foils may be appropriately subjected to matte treatment, plating treatment, aluminum alcoholate treatment, aluminum chelate treatment, silane coupling agent treatment and the like.

The thickness of the metal foil is not particularly limited, but is usually 5 to 35 μm.

The flexible printed circuit board of the present invention can be manufactured as described below.

[0041] That is, first, imidazolyl the formula (1) - an aromatic diamine to be used in combination as needed and diamino bird azines, solvents (e.g., N- methyl-2-pyrrolidone) dissolved by heating to Further, addition polymerization is carried out for several hours while gradually adding acid dianhydride at 0 to 90 ° C., preferably 5 to 50 ° C. under an inert atmosphere such as nitrogen gas. As a result, a polyamic acid dissolved in a solvent is obtained. The solution-state polyamic acid can be used as it is as a polyamic acid varnish. The type and amount of the solvent used in the varnish, the viscosity of the varnish, the solid content and the like can be appropriately selected.

Next, this polyamic acid varnish is coated on a metal foil using a comma coater or the like and dried to form a polyamic acid layer as a polyimide precursor layer. In this drying, the residual volatile amount in the polyamic acid layer (content of “undried solvent and water generated by imidization”) is 50 in order to prevent foaming during the imidization in the subsequent step. % Or less is preferable.

The obtained polyamic acid layer is heated at 300 to 350 ° C. in an inert atmosphere (for example, nitrogen atmosphere) to be imidized to form an insulating layer made of polyimide. Thereby, a flexible printed board is obtained.

In the thus obtained flexible printed circuit board, corrosion or discoloration occurs on the surface of the metal foil such as copper foil (polyimide forming surface) even if the rust preventive agent is not added to the polyamic acid varnish. Absent. Also, when a flexible printed board is used as a wiring board, electrical migration due to copper ions does not occur. Further, the rust preventive agent does not bloom on the surface of the polyimide, and “slightly” does not occur during imidization, and the adhesive strength between the copper foil and the polyimide layer becomes good.

[0045]

The present invention will be specifically described below.

Examples 1-9 and Comparative Examples 1-2 2,4-diamino-6- [2- (2-ethyl-4-methyl-1-imidazolyl) ethyl] was added to a 5 liter reaction kettle equipped with a jacket. -S-triazine (2E4MZ T ,
11.6 g (0.05 mol) of Shikoku Kasei) and 81.1 g of paraphenylenediamine (PDA, Daishin Kasei)
(0.75 mol) and 40.0 g (0.2 W) of 4,4'-diaminodiphenyl ether (DPE, Wakayama Seika)
0 mol) with a solvent N-methyl-2 under a nitrogen gas atmosphere.
-Pyrrolidone (NMP, manufactured by Mitsubishi Chemical) was dissolved in about 3 kg and kept at 50 ° C. After that, 3, 4, 3 ', 4'-
A reaction was performed for 3 hours while gradually adding 294.2 g (1.0 mol) of biphenyltetracarboxylic dianhydride (BPDA, manufactured by Mitsubishi Chemical). This gives a solids content of about 14
%, A polyamic acid varnish containing the polyamic acid of Example 1 having a viscosity of 15 Pa · S (25 ° C.) was obtained. This varnish is coated on a copper foil and dried at a temperature as low as possible, 100 ° C. or lower, at which imidization does not occur and a thickness of about 5
A μm polyamic acid film was obtained. The infrared absorption spectrum of this film was measured by the surface reflection method (ATR method). As a result, 1710 cm ^-1 (COOH), 1
660 cm ^-1 (CONH), 2900-3200 cm ^-1
Characteristic absorption of polyamic acid broad in (COOH, NH ₂ ) was detected.

The same operations as in Example 1 were repeated according to the blending composition shown in Table 1 to give Examples 2 to 9 and Comparative Example 1.
~ 2 polyamic acid varnish was obtained.

The compounds used in Table 1 are as follows.

(Acid dianhydride) BPDA: 3,4,3 ', 4'-biphenyltetracarboxylic dianhydride PMDA: Pyromellitic dianhydride (diamines) 2E4MZ T : 2,4-diamino-6 -[2- (2-
Ethyl-4-methyl-1-imidazolyl) ethyl] -s
-Triazine 2MZ: 2,4-diamino-6- [2- (2-methyl-1-imidazolyl) ethyl] -s-triazine C11Z: 2,4-diamino-6- [2- (2-undecyl-1- Imidazolyl) ethyl] -s-triazine PDA: paraphenylenediamine DPA: 4,4′-diaminodiphenyl ether

[0050]

[Table 1] Diamine molar ratio Example dianhydride (a) (b) (c ) (a) / (b) / (c) 1 BPDA 2E4MZ T PDA DPE 5/75/20 2 BPDA 2E4MZ T PDA DPE 7.5 / 75 / 17.5 3 BPDA 2E4MZ T PDA DPE 10/75/15 4 BPDA 2E4MZ T PDA DPE 2/78/20 5 BPDA 2MZ PDA DPE 5/75/20 6 BPDA C11Z PDA DPE 5/75/20 7 BPDA 2E4MZ T DPE − 5 / 95 / − 8 BPDA 2E4MZ T PDA DPE 12.5 / 75 / 12.5 9 PMDA 2E4MZ T PDA DPE 5/75/20 Comparative Example 1 BPDA − PDA DPE − / 80/20 2 PMDA − − DPE − / − / 100

Next, the polyamic acid varnishes of Examples 1 to 9 and Comparative Examples 1 and 2 were applied to a copper foil soft-etched with 2% hydrochloric acid (Mitsui Kinzoku SQ-VLP 12 μm electrolytic foil) and dried. A 10 μm thick polyamic acid layer was formed. The obtained laminated body was placed in an atmosphere of 40 ° C. and 90%, and whether or not the surface of the copper foil was discolored was visually observed. The results (rust prevention effect) are shown in Table 2.

Next, a flexible printed board was manufactured using the above polyamic acid varnish and copper foil. Polyamic acid varnish is applied to copper foil and dried to form a 25 μm thick polyamic acid layer, which is heated at 350 ° C. in a nitrogen atmosphere.
It was imidized by heating for 15 minutes.

With respect to the obtained flexible printed circuit board, a copper foil was patterned into a parallel circuit having a conductor interval of 0.1 mm to prepare a wiring board. Then, with a DC voltage of 50 V applied between the adjacent conductor patterns, 85 ° C./90
It was left for 7 days in an atmosphere of% Rh. After standing, the resistance value between adjacent conductors was measured, and the occurrence of electrical migration was measured. In this case, if the resistance value was 10 ⁷ Ω or more, it was determined to be acceptable.

Regarding the polyimide layer of the flexible printed board, JIS C6471 (width 1.59 mm,
The peel strength (kg / cm) was measured as the adhesive strength at 23 ° C. and 260 ° C. according to (90 degree peeling). The obtained results are shown in Table 2.

[0055]

[Table 2] Rust prevention effect Electric adhesive strength (kg / cm)Example (discoloration) Simulation 23 ℃ 260 ℃ 1 None Pass 1.80 1.55 2 None Passed 1.62 1.50 3 None Pass 1.67 0.90 4 None Pass 1.48 1.05 5 None Pass 2.06 1.68 6 None Passed 1.34 1.00 7 None Pass 2.18 1.55 8 None Pass 1.45 0.75 9 None Pass 1.75 1.30 Comparative example 1 Immediate discoloration Fail (short) 1.05 0.63 2 Immediate discoloration Fail (short) 1.25 0.20

From the results shown in Table 2, the flexible printed circuit board of the present invention having a polyimide insulating layer using a specific imidazolyl-diaminoazine as a diamine component has an excellent rust preventive effect without using a separate rust preventive agent. You can see that it has. Further, it can be seen that no electric migration occurs and the adhesive strength between the polyimide insulating layer and the copper foil is good.

On the other hand, the flexible printed boards of Comparative Examples 1 and 2 which did not use a specific imidazolyl-diaminoazine as a diamine component had no rust preventive effect and no electric migration, and the adhesive strength between the polyimide insulating layer and the copper foil. Was also insufficient.

[0058]

According to the present invention, there is no problem of electrical migration, and copper is not contained even if it does not contain a rust preventive agent that causes blooming or "slightly" problem during imidization of polyamic acid. Provided is a flexible printed circuit board having a polyimide insulating layer that exhibits good adhesive strength to a foil.

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) C08G 73/00-73/26 CAPLUS (STN) REGISTRY (STN)

Claims (6)

(57) [Claims] 1. A flexible printed circuit board comprising a polyimide obtained by imidizing a polyamic acid obtained by addition polymerization of a diamine and an acid dianhydride as an insulating layer on a metal foil, wherein the diamine has the formula (1) ) [Chemical 1] (In the formula, A is the formula (1a), (1b) or (1c) Is an imidazolyl group represented by. R ¹ is an alkylene group and m is 0 or 1. R ² is an alkyl group, and n is 0, 1 or 2. R ³ and R ⁴ are alkylene groups, and p and q are 0 or 1, respectively. B is a triazine residue. A flexible printed circuit board, characterized by containing a diamino tri azines - imidazolyl represented by). 2. A polyimide is represented by the following formula (2): (In the formula, A is the formula (1a), (1b) or (1c) Is an imidazolyl group represented by. R ¹ is an alkylene group and m is 0 or 1. R ² is an alkyl group, and n is 0, 1 or 2. R ³ and R ⁴ are alkylene groups, and p and q are 0 or 1, respectively. B is an azine residue, a diazine residue or a triazine residue. D
Is an acid dianhydride residue. ] The flexible printed circuit board of Claim 1 containing the imide unit shown by these. Imidazolyl wherein formula (1) - diamino tri <br/> azines is, 2,4-diamino-6- [2- (2-methyl-1-imidazolyl) ethyl] -s-triazine; 2 , 4-Diamino-6- [2- (2-ethyl-1-imidazolyl) ethyl] -s-triazine; 2,4-diamino-6- [1- (2-undecyl-1-
Imidazolyl) ethyl] -s-triazine; 2,4-diamino-6- [2- (2-imidazolyl) ethyl] -s-triazine; 2,4-diamino-6- [2- (1-imidazolyl) ethyl] -S-triazine; 2,4-diamino-6- (2-ethyl-4-imidazolyl) -s-triazine; 2,4-diamino-6- [2- (4-methyl-1-imidazolyl) ethyl]- s-triazine; 2,4-diamino-6- (2-ethyl-5-methyl-4)
-Imidazolyl) -s-triazine; 2,4-diamino-6- (4-ethyl-2-methyl-1)
-Imidazolyl) -s-triazine; 2,4-diamino-6- [3- (2-methyl-1-imidazolyl) propyl] -s-triazine; 2,4-diamino-6- [4- (2-imidazolyl) ) Butyl] -s-triazine; 2,4-diamino-6- [2- (2-methyl-1-imidazolyl) propyl] -s-triazine; 2,4-diamino-6- [1-methyl-2- (2-Methyl-1-imidazolyl) ethyl] -s-triazine; 2,4-diamino-6- [2- (2,5-dimethyl-1)
-Imidazolyl) ethyl] -s-triazine; 2,4-diamino-6- [2- (2,4-dimethyl-1)
-Imidazolyl) ethyl] -s-triazine; or 2,
4-diamino-6- [2- (2-ethyl-4-methyl-
The flexible printed board according to claim 1, which is 1-imidazolyl) ethyl] -s-triazine. 4. The diamines further include 4,4′-diaminodiphenyl ether, paraphenylenediamine, 4,
4'-diaminobenzanilide, 4,4'-bis (p-
The flexible printed circuit board according to claim 1, further comprising an aromatic diamine selected from aminophenoxy) diphenyl sulfone and 2,2-bis [4- (4-aminophenoxy) phenyl] propane. 5. imidazolyl - diamino tri azines /
The flexible printed circuit board according to claim 4, wherein the molar ratio of the aromatic diamine is 2/98 to 10/90. 6. The acid dianhydride is pyromellitic dianhydride, 3,4,3 ′, 4′-biphenyltetracarboxylic dianhydride, 3,4,3 ′, 4′-benzophenonetetracarboxylic acid. The flexible printed board according to claim 1, which is a dianhydride or an aromatic acid dianhydride selected from 3,4,3 ', 4'-diphenylsulfone tetracarboxylic acid dianhydride.