Flexible printed circuit board

A printed circuit board comprising:

• a first insulating layer;
• first, second, third, fourth, fifth, sixth, seventh and eighth connection terminals formed on one surface of said first insulating layer;
• a first conductor line formed between said first connection terminal and said second connection terminal;
• a second conductor line formed between said third connection terminal and said fourth connection terminal;
• a third conductor line formed between said fifth connection terminal and said sixth connection terminal;
• and
• a fourth conductor line formed between said seventh connection terminal and said eighth connection terminal, wherein:
• said first and second conductor lines constitute a first transmission line pair,
• said third and fourth conductor lines constitute a second transmission line pair,
• a thickness of said first insulating layer is not less than 4 μm and not more than 50 μm,
• a distance between said first and second conductor lines and a distance between said third and fourth conductor lines is not less than 10 μm and not more than 30 μm,
• a thickness of each of said first, second, third and fourth conductor lines is not less than 8 μm and not more than 20 μm,
• a ratio of the thickness of each of said first, second, third and fourth conductor lines to the distance between said first and second conductor lines and the distance between said third and fourth conductor lines is 0.8 or more,
• each of said first, second, third and fourth conductor lines has a constant width, and
• portions of said first insulating layer overlapping said first, second, third and fourth conductor lines have a constant thickness.