JPH02218774A - flexible wiring board - Google Patents

Abstract

PURPOSE:To obtain the subject wiring board excellent in heat resistance, free from curling and having an excellent workability in circuit work by forming a polyamide-imide resin layer composed of a specified aromatic diisocyanate, etc., and a trimellitic anhydride on a metallic foil. CONSTITUTION:The objective wiring board produced by forming a polyamide- imide resin layer represented by formula I (R<1> and R<2> are H, halogen, alkyl or alkoxy) composed of a diisocyanate component consisting of an aromatic diisocyanate (preferably compound of formula II) and another aromatic diisocyanate (e.g. diphenylmethane-4,4'-diisocyanate) and trimellitic anhydride (derivative) directly or through an adhesives layer on a metallic foil.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flexible wiring board in which a polyamide-imide resin layer is closely formed on a metal foil surface either directly or via an adhesive layer.

[Conventional technology and problems]

Flexible wiring boards improve the flexibility of electronic circuits,
It is often used in electronic equipment because it is small, lightweight, and simple.

This flexible wiring board is made by laminating metal foil and polyimide film using an adhesive. However, since the heat resistance of the adhesive layer is significantly inferior to that of polyimide film, flexible wiring boards manufactured by this method do not take advantage of the heat resistance peculiar to polyimide film, and have a problem of poor heat resistance.

Therefore, in order to solve the above problem, a polyimide resin layer or a polyamide-imide resin layer is formed by directly coating and casting a polyimide precursor solution or a polyamide-imide solution on a metal foil and heat-treating it, thereby manufacturing a flexible wiring board. Methods are being considered.

However, flexible wiring boards obtained by directly forming a polyimide resin layer or a polyamide-imide resin layer on metal foil do not have a polyimide resin layer or a polyamide-imide resin layer.
A phenomenon called curling occurs in which the flexible wiring board is warped with the polyamide-imide resin layer on the inside.

Such curls pose a very serious problem in handling during processing.

Structure of the Invention [Means for Solving the Problems] In order to solve the above problems, the present inventors focused on aromatic diisocyanate, which is a raw material for the amide-imide resin layer, and as a result of intensive studies, the structural formula Aromatic diisocyanate represented by formula (1) and OCN N
C0 (R1 and R2 represent hydrogen, halogen, alkyl group, and alkoxy group.) A polyamide-imide resin layer consisting of a diincyanate component consisting of another aromatic diisocyanate and trimellitic acid anhydride or a derivative thereof is placed on a metal foil. We have invented a flexible wiring board with less curl by forming it directly or through an adhesive layer.

The present invention will be explained in detail below.

Examples of the aromatic diisocyanate represented by the structural formula (1) used in the present invention include diphenyl-4,47-diincyanate diphenyl-3,37-diincyanate diphenyl-3,4'-diisocyanate 3.37- cyclodiphenyl-4,4
'-diisocyanate 2.2'-dichlorodiphenyl-
4,4'-diisocyanate 3.3'-dibromodiphenyl-4,4'-diincyanate 2.27-dibromodiphenyl-4,47-diincyanate 3.37-dimethyldiphenyl-4,47-diisocyanate 2 .2
7-dimethyldiphenyl-4,47-diisocyanate 2.37-dimethyldiphenyl-4.4'-diisocyanate 3.3'-diethyldiphenyl-4,47-diisocyanate 2.2'-diethyldiphenyl-4, 47
-diincyanate 2.3'-diethyldiphenyl-4
,47-diisocyanate 3.3'-dimethoxydiphenyl-4,4'-diisocyanate 2.2'-dimethoxydiphenyl-4,47-diincyanate 2.3'-
Dimethoxydiphenyl-4,4'-diincyanate 3
．． 37-jethoxydiphenyl-4,4'-diisocyanate 2.2'-jethoxydiphenyl-4,4'-diincyanate 2.3'-jethoxydiphenyl-4,
Examples include 4'-diisocyanate, but 8.8'
-Dimethyldiphenyl-4,4'-diisocyanate is most preferred from the viewpoint of adhesion to the metal foil or insulating layer, ease of material availability, and the like.

In the present invention, other aromatic diisocyanates used include: diphenylmethane-4,47-diincyanate diphenylmethane-3.37-diincyanate diphenylmethane-3.47-diincyanate diphenyl ether 4.47 - Dicyanate benzophenone-4,
4'-Diincyanate diphenyl sulfone-4,47
-diincyanate 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-xylylene diisocyanate, P-xylylene diisocyanate, and the like.

These may be used alone or in combination.

Among these diincyanates, diphenylmethane
4,47-diisocyanate, diphenyl ether-4
,47-diisocyanate is preferred.

In the present invention, the molar ratio of the aromatic diisocyanate represented by formula (1) and other aromatic diisocyanate is as follows:
80:70 to 90:10 is preferred. This is the formula (1
) If the content of aromatic diincyanate is less than 30%, the flexible wiring board will curl with the polyamide-imide resin layer inside, and if it is more than 90%, the flexibility of the polyamide-imide resin will deteriorate. This is because the elongation and strength of the polyamide-imide resin layer become insufficient.

The method for producing the polyamide-imide paint according to the present invention is not particularly limited. For example, approximately stoichiometric amounts of trimellitic anhydride or its derivatives and a diisocyanate component are mixed in an organic polar solvent at a temperature in the range of 0 to 180°C. This is carried out by reacting for 1 to 24 hours to form a polyamide-imide paint.

Examples of the organic polar solvent include N-methyl-2-pyrrolidone, N,N'-dimethylformamide, N,N'-dimethylacetamide, and the like, and these can be used alone or in combination.

The polyamide-imide coating material obtained as described above is coated and cast on a metal foil directly or via an adhesive layer, and then heat-treated to form a polyamide-imide resin layer.

The metal foil includes copper, aluminum, iron, gold, silver,
Examples include Pd, Ni, Cr + Mo, and alloys thereof. When copper foil is used, it is preferable to use electrolytic copper foil, rolled copper foil, or a surface-treated version of these in order to strengthen the adhesion between the polyamide-imide resin and the metal foil.

The adhesive layer is preferably one that firmly adheres to the metal foil, and most preferably a polyamide-imide resin layer whose structural formula is represented by formula (2).

As a coating method, known means such as knife caulk, reverse coater tip caulk, flow caulk, etc. can be used.

Hereinafter, the present invention will be explained in more detail based on Examples.

[Example 1] Synthesis of polyamide-imide paint> A flask equipped with a thermometer, cooling tube, calcium chloride, stirrer, and Ng inlet was heated at 150 m1 per minute! While flowing N2 of
(abbreviated as I) and 22.1 g of diphenylmethane-4,
After putting 4'-diisocyanate (hereinafter abbreviated as MDI) into a flask, 800 g of N-methyl-2-pyrrolidone was added and reacted at 80°C for 3 hours.
Raise the temperature at a rate of °C/hr, stop heating at 170 °C, keep warm, and type B viscosity at 30 °C is 2000 to 3000 cps.
Heating was terminated when the temperature reached 20%, and a polyamide-imide paint with a concentration of 20% was obtained. Apply this polyamide-imide paint to a thickness of 3
Cast coating on 5 μm electrolytic copper foil using a doctor knife at 100°C for 30 minutes.

Heating was performed at 200°C for 30 minutes and at 280°C for 30 minutes to form a polyamide-imide resin with a thickness of 25 μm to obtain a flexible wiring board.

[Example 2] A flexible wiring board was obtained in the same manner as in Example 1 except that the molar ratio of the diisocyanate components ODI/MDI in Example 1 was changed to 7/3.

[Example 3] A flexible wiring board was obtained in the same manner as in Example 1 except that the molar ratio of the diisocyanate components ODI/MDI in Example 1 was changed to 4/6.

[Comparative Example 1] A flexible wiring board was obtained in the same manner as in Example 1 except that the molar ratio of the diisocyanate components ODI/MDI in Example 1 was changed to 1070.

[Comparative Example 2] A flexible wiring board was obtained in the same manner as in Example 1 except that the molar ratio of diincyanate component ODI/MDI in Example 1 was changed to 278.

[Example 4] Among the diincyanate components of Example 1, MDI was changed to diphenyl ether-4,47-diisocyanate (hereinafter abbreviated as EDI), and the molar ratio of TODI/EDI was set to 9/1. A flexible wiring board was obtained in the same manner as above.

[Example 5] A flexible wiring board was obtained in the same manner as in Example 1 except that the molar ratio of diincyanate component ODI/EDI in Example 5 was changed to 7/3.

[Example 6] A flexible wiring board was obtained in the same manner as in Example 1 except that the molar ratio of diincyanate components ODI/EDI in Example 5 was changed to 4/6.

[Comparative Example 3] A flexible wiring board was obtained in the same manner as in Example 1 except that the molar ratio of the diisocyanate components ODI/EDI in Example 5 was changed to 2/8.

[Example 7] A flask equipped with a thermometer, cooling tube, calcium chloride, stirrer, and N2 inlet was heated at 150 nl per minute! After introducing 108.6 g of TMA and 141.4 g of MDI into a flask while flowing N2, 1000 g of N-methyl-2-pyrrolidone was added and reacted at 80'C for 3 hours, and further heated at 20°C. Raise the temperature to 170'C at a rate of C/hr.
Stop heating and keep warm until the B type viscosity at 30℃ is 2000~30.
Heating was terminated when the temperature reached 00 cps, and a polyamide-imide paint represented by formula (2) with a concentration of 20% was obtained.

This polyamide-imide paint was cast onto an electrolytic copper foil with a thickness of 35 μm using a doctor knife, and
minutes, heat at 180℃ for io minutes, thickness 5. The formula of c+m (2
) was formed.

Furthermore, the polyamide-imide paint synthesized in Example 2 was similarly cast using a doctor knife, heated at 100°C for 30 minutes, 200°C for 30 minutes, and 280°C x 30 minutes to form a film with a thickness of 20 μm. A flexible wiring board with polyamide-imide resin was obtained.

[Example 8] The polyamide-imide paint synthesized in Example 2 used in Example 7 was replaced with the polyamide-imide paint synthesized in Example 3, and a flexible wiring board was obtained in the same manner as in Example 7. Ta.

[Example 9] The polyamide-imide paint synthesized in Example 2 used in Example 7 was replaced with the polyamide-imide paint synthesized in Example 5, and a flexible wiring board was manufactured in the same manner as in Example 7. Obtained.

[Comparative Example 4] A commercially available 25 μm polyimide film was laminated with a 35 μm electrolytic copper foil using an adhesive to obtain a flexible wiring board.

Table 1 shows the results of characteristic evaluation of the flexible wiring boards obtained from the above Examples and Comparative Examples using the following measurement method.

Radius of curvature: amount of strain δ (cm) after a flexible substrate measuring 5 cm in length and width is placed on a glass plate with the polyimide resin layer facing the glass side as shown in FIG.

Measure a(an) and calculate the radius of curvature from the following formula: Find P(an) and evaluate the degree of curl. I valued it.

Rough tensile speed 50an/min Measured at

Film elongation rate: Samples with a width of 5 pans and a chuck distance of 20 mm were prepared, and measured using an O-Toge Ruff at a tensile speed of 50 mm/min.

Heat aging property: After being left at 200° C. for 240 hours in a constant temperature bath, the adhesive strength with copper foil was measured.

Bending resistance: Measured in accordance with JIS P-8115 under the conditions of bending radius of the bending surface of 0.4 n+m + restraining weight of 0.5 kg.

Soldering heat resistance: Based on JIS C-6481, 30
The time required for delamination, blistering, and voids to occur was measured at 0°C.

Adhesive strength with copper foil: In accordance with JIS C-6481, a sample with a width of 10a+m was peeled off at 180 degrees and a radius of curvature of 1oa was determined as a characteristic value of an autog flexible wiring board.
n or more, preferably 20an or more, adhesive strength with copper foil 1.0
kg/am or more, film elongation 10% or more, oil bending resistance 20
0 times or more, soldering heat resistance, peeling at 300°C for 60 seconds, no blistering, heat aging, 50% or more of adhesive strength with initial copper foil, and 0.
86) If it is above Cg/an, no practical problem will occur.

As shown in Table 1, compared to the flexible wiring board of Comparative Example 4 in which an adhesive layer is present between the polyamide-imide resin layer and the copper foil, the 7 lexiple wiring board without an adhesive layer has It can be seen that it has excellent soldering heat resistance and heat aging resistance.

From Examples 1 to 6 and Comparative Examples 1 to 3, as the proportion of TODI increases, the curl becomes smaller and the adhesive strength, film elongation rate, bending resistance, and heat aging resistance become worse. Therefore, T.O.
The molar ratio of DI and MDI or EDI is 80:70-9
It can be seen that in the range of 0:10, a flexible wiring board that satisfies all of the above characteristics can be obtained.

Furthermore, in Examples 7 to 9, no problem occurred even if the polyamide-imide resin was formed through the insulating layer, and the adhesive strength was improved by using a resin that firmly adheres to the metal foil as the insulating layer. can be greatly improved.

Effects of the Invention As described above, since the flexible wiring board of the present invention does not have an adhesive layer between the polyamide-imide resin layer and the metal foil, it has excellent heat resistance among various properties and is suitable for use under high temperature conditions. Effective.

Furthermore, since almost no curling occurs, it has the advantage of excellent workability during circuit processing.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a method for measuring the radius of curvature. (1) Metal foil (2) Polyimide resin layer (3) Glass plate figure

Claims (3)

[Claims] (1) Aromatic diisocyanate whose structural formula is represented by formula (1) ▲ There are numerical formulas, chemical formulas, tables, etc. ▼... (1) (R_1 and R_2 represent hydrogen, halogen, alkyl group, and alkoxy group. ) A flexible wiring characterized in that a polyamide-imide resin layer consisting of a diisocyanate component consisting of another aromatic diisocyanate and trimellitic acid anhydride or a derivative thereof is formed on a metal foil directly or via an adhesive layer. substrate. (2) The molar ratio of aromatic diisocyanate represented by formula (1) to other aromatic diisocyanate is 30:70 to 9
The flexible wiring board according to claim 1, wherein the ratio is 0:10. (3) The flexible wiring board according to claim 1, wherein the aromatic diisocyanate represented by formula (1) has a formula, a chemical formula, a table, etc.