| 摘要 |
An exemplary PCB defines a circular first via and includes a first signal layer, a second signal layer, a first reference layer between the first and second signal layer, and a signal transmission line having a first portion on the first signal layer and a second portion on the second signal layer. The first signal layer has a circular first weld pad coaxial with the first via and electrically connected to the first portion, the second layer has a circular second weld pad coaxial with the first via and electrically connected to the second portion. The first weld pad is electrically connected to the second weld pad through the first via, the reference layer defines a first through hole coaxial with the first via, the radius of the first via is R1, the radius of the first through hole is R2, R2=R1+d1, 1.5 mil≦̸d1≦̸4 mil.
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