Flexible metal clad laminate and manufacturing method thereof
View Patent ↗A flexible metal clad laminate includes a metal foil, and a multilayered polyimide film including a first polyimide layer having a glass transition temperature of 300° C. or less and disposed on the metal foil, a second polyimide layer disposed on the first polyimide layer and a third polyimide layer disposed on the second polyimide layer. According to the flexible metal clad laminate of the present invention, appearance defects such as blistering generated during curing process in a continuous curing machine using an infrared heat source may be solved, interlayer delamination may be prevented due to a good adhesion strength with a metal layer, and an ACF bonding strength and a dimensional stability may be good. The flexible metal clad laminate may be useful for the manufacturing of a flexible printed circuit boards.
1. A flexible metal clad laminate comprising:
a metal foil; and
a multilayered polyimide film comprising a first polyimide layer having a glass transition temperature of 300° C. or less and disposed on the metal foil, a second polyimide layer disposed on the first polyimide layer and a third polyimide layer disposed on the second polyimide layer,
the multilayered polyimide film satisfying following Equation 1,
C2<C1≦C3 [Equation 1]
in which, C1 represents a coefficient of thermal linear expansion of the first polyimide layer, C2 represents a coefficient of thermal linear expansion of the second polyimide layer, and C3 represents a coefficient of thermal linear expansion of the third polyimide layer.
2. The flexible metal clad laminate of claim 1 , wherein the flexible metal clad laminate satisfies following Equation 2 and Equation 3, and an ACF bonding strength is 0.8 kgf/cm or over,
S MD ≦0.02 [Equation 2]
S TD ≦0.02 [Equation 3]
in Equation 2, S MD represents a standard deviation of a dimensional change in a machine direction (MD) after heating, and in Equation 3, S TD represents a standard deviation of a dimensional change in a transverse direction (TD) after heating.
3. The flexible metal clad laminate of claim 1 , wherein the first polyimide layer has the coefficient of thermal linear expansion of 30 to 50 ppm/K and the glass transition temperature of 200 to 300° C.
4. The flexible metal clad laminate of claim 1 , wherein the second polyimide layer has the coefficient of thermal linear expansion of 1 to 20 ppm/K and the glass transition temperature of 300 to 420° C.
5. The flexible metal clad laminate of claim 1 , wherein the third polyimide layer has the coefficient of thermal linear expansion of 30 to 70 ppm/K.
6. The flexible metal clad laminate of claim 1 , wherein the multilayered polyimide film is imidized by heating with an infrared heat source, the time of heating with an infrared heat source, which is conducted at 300° C. or over, is 40% or over based on a total heating time.
7. A flexible metal clad laminate manufactured by laminating a metal foil on the third polyimide layer included in the multilayered polyimide film in claim 1 .
8. A method of manufacturing a flexible metal clad laminate comprising the steps of:
(a) forming a first polyimide precursor layer having a glass transition temperature of 300° C. or less after complete imidization on a metal film;
(b) forming a second polyimide precursor layer on the first polyimide precursor layer; and
(c) forming a third polyimide precursor layer on the second polyimide precursor layer and then conducting of imidization to form a multilayered polyimide film,
the multilayered polyimide film satisfying following Equation 1,
C2<C1≦C3 [Equation 1]
in which, C1 represents a coefficient of thermal linear expansion of a first polyimide layer obtained through imidization of the first polyimide precursor layer, C2 represents a coefficient of thermal linear expansion of a second polyimide layer obtained through imidization of the second polyimide precursor layer, and C3 represents a coefficient of thermal linear expansion of a third polyimide layer obtained through imidization of the third polyimide precursor layer.
9. The method of manufacturing a flexible metal clad laminate of claim 8 , wherein the imidization in step (c) is conducted by an heating with an infrared heat source,
the time of heating with an infrared heat source, which is conducted at 300° C. or over, is 40% or over based on a total heating time.
10. The method of manufacturing a flexible metal clad laminate of claim 8 , further comprising the step of:
(d) laminating the metal foil on the third polyimide layer included in the multilayered polyimide film in step (c).
11. The method of manufacturing a flexible metal clad laminate of claim 8 , wherein the flexible metal clad laminate satisfies following Equation 2 and Equation 3, and an ACF bonding strength is 0.8 kgf/cm or over,
S MD ≦0.02 [Equation 2]
S TD ≦0.02 [Equation 3]
in Equation 2, S MD represents a standard deviation of a dimensional change in a machine direction (MD) after heating, and in Equation 3, S TD represents a standard deviation of a dimensional change in a transverse direction (TD) after heating.
12. The method of manufacturing a flexible metal clad laminate of claim 8 , wherein the first polyimide layer has the coefficient of thermal linear expansion of 30 to 50 ppm/K and the glass transition temperature of 200 to 300° C.
13. The method of manufacturing a flexible metal clad laminate of claim 8 , wherein the second polyimide layer has the coefficient of thermal linear expansion of 1 to 20 ppm/K and the glass transition temperature of 300 to 420° C.
14. The method of manufacturing a flexible metal clad laminate of claim 8 , wherein the third polyimide layer has the coefficient of thermal linear expansion of 30 to 70 ppm/K.