JPH05114784A - Double sided flexible metal plated laminate board - Google Patents

Abstract

PURPOSE:To provide a double sided flexible metal plated laminate board which is excellent in heat resistance, connection reliability when the boards are laminated in multilayer, and mass-productivity and lessened in cost. CONSTITUTION:A metal foil is laminated on both the sides of a polyimide film subjected to an adhesion treatment through the intermediary of an adhesive layer of polyimide adhesive agent whose glass transition point is a temperature of 200-250 deg.C and which is formed as thick as 5-50% of the thickness of the polyimide film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-sided flexible metal-clad laminate excellent in heat resistance, adhesive strength at high temperature, and connection reliability in multiple layers.

[0002]

2. Description of the Related Art Flexible metal-clad laminates are substrates for flexible printed wiring boards, and have been widely used in recent years due to remarkable miniaturization and high density of electronic devices. In order to cope with this high density, the flexible metal-clad laminate is being double-sided, and moreover, more than four layers are also formed by using an interlayer adhesive.

However, since the conventional double-sided flexible metal-clad laminate uses an epoxy or acrylic adhesive and has a glass transition point of about 100 to 150 ° C., the adhesive strength at high temperature and the solder heat resistance are high. It cannot be said that the current requirements are sufficiently satisfied in terms of characteristics such as. Furthermore,
Although a lamination temperature of 170 to 200 ° C is applied when forming multiple layers,
Since this temperature exceeds the glass transition point of conventional adhesives, due to the shrinkage of the adhesives before and after lamination,
There was a problem that the metal circuit was displaced. Further, since the coefficient of thermal expansion in the Z-axis direction is as large as about 5 × 10 ⁻⁴ / ° C. even after lamination, there is a problem that the double-sided flexible metal-clad laminate using a conventional adhesive has poor connection reliability. However, it was not suitable as a material for forming fine lines or a material for increasing the number of layers.

[0004]

In recent years, in the single-sided flexible metal-clad laminate, a two-layer structure without an adhesive has been in widespread use. Also in the double-sided flexible metal-clad laminate, there is a means for forming a double-sided flexible metal-clad laminate by using a single-sided product having a two-layer structure, as shown in JP-A-3-205474, and all the characteristics are good. However, there is a problem that the manufacturing cost is high. The present invention has been made in view of such circumstances, and by using a polyimide-based adhesive having a glass transition point of 200 to 250 ° C as an adhesive used for a double-sided flexible metal-clad laminate, heat resistance and multi-layered It is an object of the present invention to provide a double-sided flexible metal-clad laminate having excellent connection reliability, cost and mass productivity.

[0005]

Means for Solving the Problems The inventors of the present invention have diligently studied alternatives to conventional acrylic and epoxy adhesives, which are the cause of deterioration of properties, and as a result, have found that the glass transition point is 2 or less.
It has been found that the above object can be achieved by using a polyimide-based adhesive having a temperature of 0 to 250 ° C, and the present invention has been completed based on this finding.

That is, the present invention has a glass transition point of 200 to 200 on both surfaces of a polyimide film having both surfaces subjected to adhesive treatment.
Provided is a double-sided flexible metal-clad laminate, which is made of a polyimide adhesive at 250 ° C. and has metal foils laminated via an adhesive layer having a thickness of 5 to 50% of the thickness of the polyimide film. It is a thing.

In the double-sided flexible metal-clad laminate of the present invention, the glass transition point of the adhesive is higher than that of the conventional one, so that the adhesive strength with the metal foil is not significantly reduced even at 200 ° C. and the solder at 350 ° C. No abnormality was observed for 60 seconds or longer even when immersed in the bath.

As the polyimide film used in the present invention, a low thermal expansion polyimide film having a linear thermal expansion coefficient similar to that of the conductor metal is preferably used in order to secure dimensional stability. Examples of such a polyimide film include Upilex S (manufactured by Ube Industries, Ltd.) and Apical NPI (manufactured by Kanegafuchi Chemical Industry Co., Ltd.), but the linear thermal expansion coefficient is 2.5 at 50 to 250 ° C. ×
Those having 10 ⁻⁵ or less are preferably used. If a polyimide film having a coefficient of linear thermal expansion exceeding this is used, the dimensional change rate after circuit processing becomes large, and the connection reliability in the heat cycle test may decrease. A polyimide film having a thickness of 12.5 to 75 μm is preferably used.

Both sides of this polyimide film are subjected to an adhesive treatment. Examples of the adhesion treatment method include mechanical treatment such as brush polishing and sandblast treatment, and chemical treatment such as coupling agent treatment, alkali treatment, corona treatment, and plasma treatment. Of these, oxygen plasma treatment is most preferable from the viewpoint of effects.

Metal foils are laminated on both sides of the polyimide film of the double-sided flexible metal-clad laminate of the present invention with an adhesive layer interposed therebetween. This adhesive layer has a glass transition temperature of 2
It is made of a polyimide adhesive at a temperature of 00 to 250 ° C.
When the glass transition temperature of the adhesive is less than 200 ° C., the heat resistance and the connection reliability during multilayering of the obtained double-sided flexible metal-clad laminate are lowered, and when it exceeds 250 ° C., the adhesion between the polyimide film and the metal foil is It will be difficult. A copper foil having a thickness of 8 to 105 μm is preferably used as the metal foil.

The polyimide adhesive used in the present invention is obtained by reacting a diamino compound such as 2,2-bis [4- (p-aminophenoxy) phenyl] propane with a tetracarboxylic acid such as benzophenonetetracarboxylic acid. A product obtained by imidizing the obtained polyamic acid, or N, N '-(methylenedi-p-
Examples thereof include those prepared by mixing a bismaleimide compound such as phenylene) bismaleimide and imidizing it.

The thickness of the adhesive layer is 5 to 50% of the thickness of the polyimide film. If the thickness of the adhesive layer exceeds 50% of the thickness of the polyimide film, the connection reliability of the obtained flexible metal-clad laminate will decrease.
It is preferably 5 to 30% of the thickness of the polyimide film. The reason for this is that the coefficient of thermal expansion of the polyimide adhesive in the Z-axis direction is 6.1 × 1 at 50 to 250 ° C.
It is 0 ^-5 / ° C, which is smaller than that of conventional epoxy type and acrylic type by one digit or more, but it is difficult to reduce it to the same level as copper and other metal foils. This is because, when the ratio of occupancy increases, the coefficient of thermal expansion in the Z-axis direction of the entire insulating layer increases, which becomes a problem in terms of dimensional accuracy and connection reliability.

The adhesive layer of the present invention is formed by uniformly applying the polyimide-based adhesive composition on both sides of the adhesive-treated polyimide film, and then, for example, 150 ° C. for 10 minutes, 2
Dry at 00 ° C for 30 minutes. The thickness of each adhesive layer after drying is set to be 5 to 50% of the ratio of the base film to the polyimide film. Further, the polyimide adhesive composition may be evenly applied to the metal foil so as to have the above thickness.

Finally, the polyimide film and the metal foil are thermocompression bonded via an adhesive layer. The temperature at this time needs to be equal to or higher than the glass transition point of the adhesive, and preferably 240 to 2
It is 60 ° C. The pressure is preferably 20 kgf / cm ² or more, but is not particularly limited. There is no particular limitation on the time and the pressure bonding method, and it is determined by observing the actual characteristics. Continuous pressure bonding by roll lamination is also possible, which is very useful.

The double-sided flexible metal-clad laminate obtained as described above has a metal foil peeling strength of 200 ° C.
0.8kgf / cm or more, solder heat resistance is 35
It is 60 seconds or more at 0 ° C., and is excellent in heat resistance, adhesive strength at high temperature, and connection reliability when forming multiple layers.

[0016]

EXAMPLES The present invention will now be described in detail based on examples, but the present invention is not limited thereto. Synthesis Example 1 2,2-bis [4- (p-aminophenoxy) phenyl] propane 4 while flowing 300 ml of dry nitrogen into a reaction vessel made of 601 stainless steel equipped with a thermocouple, a stirrer, a nitrogen inlet, and a condenser 4 20 kg and 42.5 kg of N, N-dimethylacetamide were put and stirred to dissolve BAPP. Use a water jacket to apply this solution 2
While cooling to 0 ° C. or lower, 3.30 kg of benzophenonetetracarboxylic acid was gradually added to carry out a polymerization reaction to obtain a viscous polyamic acid varnish.

For the purpose of improving the coating workability thereafter, the varnish has a rotational viscosity of about 200 poise at 80 ° C.
I cooked at. The amount of polyamic acid formed in this varnish is 7.5 kg (15 wt%). The glass transition temperature of the polyimide obtained from this polyamic acid was 245 ° C.

Next, this polyamic acid varnish was cooled to 40 ° C., and 3.00 kg of N, N ′-(methylenedi-p-phenylene) bismaleimide corresponding to 40 parts by weight with respect to 100 parts by weight of non-volatile polyamic acid was added and dissolved. A polyimide adhesive composition was obtained.

Example 1 A pressure of 0.1 torr was applied to both sides of a 25 μm polyimide film (trade name UPILEX-S manufactured by Ube Industries, Ltd.).
Oxygen plasma treatment was performed under the conditions of an applied power of 15 kW and a treatment time of 5 seconds, and the polyimide adhesive composition synthesized in Synthesis Example 1 was applied on both sides so that the thickness after drying was 10 μm, and 150 ° C. It was dried under the conditions of / 10 minutes and 200 ° C./30 minutes. 0.3% by weight of residual volatiles in the adhesive
was.

Next, the adhesive surface of the above-mentioned polyimide film and a copper foil of 35 μm (manufactured by Nippon Mining Co., Ltd., trade name BH
The polyimide film and the copper foil are overlapped with the roughened surface of Y) facing each other, and the temperature is 250 ° C./30 minutes, 40 kgf / cm.
Pressing was performed under the laminating conditions of ² to obtain a double-sided flexible copper-clad laminate. Peel strength with metal foil is 1.2k at room temperature
gf / cm, 1.2 kgf / cm even at 200 ° C.,
No decrease in adhesive strength at high temperature was observed, and at 350 ° C, 3
No abnormality was found in the solder bath test for one minute.

Example 2 The polyimide adhesive composition synthesized in Synthesis Example 1 was dried on the roughened surface of a 35 μm copper foil (trade name: BHY, manufactured by Nippon Mining Co., Ltd.) to have a thickness of 10 μm after drying. And apply 15
It was dried under the conditions of 0 ° C./10 minutes and 200 ° C./30 minutes. The residual volatile content in the adhesive was 0.3% by weight.

Next, an oxygen plasma treatment surface and adhesive composition of both sides of a 25 μm polyimide film (Ube Industries Co., Ltd., trade name UPILEX-S) whose both surfaces were subjected to oxygen plasma treatment under the same conditions as in Example 1. The polyimide coating and copper foil are overlapped with the coated surfaces facing each other, 250 ° C / 30
Min, 40 kgf / cm ² was pressed under a lamination condition to obtain a double-sided flexible copper clad laminate. Peel strength with metal foil is 1.3kgf / cm at room temperature, 1.2 at 200 ℃
It was kgf / cm, and no abnormality was found in the solder bath test at 350 ° C. for 3 minutes.

Comparative Example 1 An epoxy / NBR adhesive (Hitachi Kasei Polymer Ltd., trade name H-2766 glass transition temperature 60 ° C.) was used as the adhesive composition, and the drying conditions were 120 ° C./10 minutes and lamination. A double-sided flexible metal-clad laminate was obtained in the same manner as in Example 1 except that the conditions were 170 ° C./60 minutes. The peel strength from the metal foil was 1.5 kgf / cm at room temperature, but at 200 ° C., the metal foil peeled off. Also,
The metal foil was peeled off even in the solder bath test at 350 ° C.

Comparative Example 2 A double-sided flexible metal-clad laminate was obtained in the same manner as in Example 1, except that the adhesive coating thickness was 30 μm. No abnormalities were found in the peeling strength and the solder bath test,
The dimensional change rate was as large as -0.15%, which caused a problem during multilayer lamination. Further, the coefficient of thermal expansion in the Z-axis direction is 8.0 ×
Large at 10 ^-5 / ° C. During thermal cycle test (-65 ° C / 30
Min ← → 125 ° C./30 minutes), a crack was generated.

[0025]

According to the present invention, it is possible to provide a double-sided flexible metal-clad laminate which is extremely excellent in peel strength at high temperature and solder heat resistance. As a result, it has become possible to manufacture a flexible printed wiring board that has high connection reliability even after being multilayered, has low cost, and has excellent characteristics.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Nagao 1150 Gotomiya, Shimodate City, Ibaraki Prefecture Goseimiya Plant, Hitachi Chemical Co., Ltd. (72) Keito Ochi 1150 Gozomiya, Shimodate City, Ibaraki Prefecture Hitachi Chemical Co., Ltd. Goshomiya Plant (72) Inventor Yasushi Kato 1150 Gozamiya, Shimodate City, Ibaraki Prefecture Hitachi Chemical Co., Ltd. Goshomiya Plant

Claims (2)

[Claims] 1. An adhesive comprising a polyimide-based adhesive having a glass transition point of 200 to 250 ° C. and a thickness of 5 to 50% of the thickness of the polyimide film, on both sides of a polyimide film having both surfaces subjected to an adhesion treatment. A double-sided flexible metal-clad laminate characterized by laminating metal foils via layers. 2. The double-sided flexible metal-clad laminate according to claim 1, wherein the adhesion treatment of the polyimide film is plasma treatment.