Metal clad laminate, preparation method thereof, and method for preparing flexible circuit board by using the same

A metal clad laminate, comprising:

• a first metal foil;
• a first polyimide layer directly disposed on the first metal foil;
• a second metal foil;
• and
• a second polyimide layer directly disposed on the second metal foil;
• wherein the first polyimide layer is in contact with the second polyimide layer,
• wherein the first polyimide layer and the second polyimide layer each have a coefficient of thermal expansion ranging from 15 to 25 ppm/° C., and
• wherein the first polyimide layer and the second polyimide layer each comprises in its composition a polymeric unit derived from a diamine monomer, wherein the diamine monomer comprises a diaminosiloxane monomer, an alkylene diamine monomer or a combination thereof and wherein the total amount of the diaminosiloxane monomer and the alkylene diamine monomer is in the range from 2 to 10 mol %, based on the total moles of the diamine monomer, and
• wherein a peeling strength between the first polyimide layer and the second polyimide layer is greater than 3 and less than 84 gf/cm.