Patent ID: 8362365

Claim:
A printed circuit board comprising: a metal substrate; a first insulating layer formed on an upper surface of said metal substrate; first and second wiring traces arranged to be spaced apart from each other on an upper surface of said first insulating layer, wherein said first and second wiring traces are arranged in a direction parallel to the upper surface of said first insulating layer, and said first and second wiring traces constitute a signal line pair that transmits a differential signal; a second insulating layer formed on the upper surface of said first insulating layer to cover both of said first and second wiring traces; and a conductor formed to cover both side surfaces and an upper surface of said second insulating layer, said conductor including: first and second ground traces formed on the upper surface of said first insulating layer to sandwich said first and second wiring traces therebetween, first and second ground walls that extend from said first and second ground traces, respectively, in a direction substantially vertical to the upper surface of said first insulating layer, and a ground cover that extends substantially parallel to the upper surface of said first insulating layer to couple said first ground wall and said second ground wall, wherein one side surface of said first ground trace and one side surface of said first wiring trace are opposite to each other to sandwich part of said second insulating layer therebetween, one side surface of said second ground trace and one side surface of said second wiring trace are opposite to each other to sandwich part of said second insulating layer therebetween, and another side surface of said first wiring trace and another side surface of said second wiring trace are opposite to each other to sandwich part of said second insulating layer therebetween.