1. Field of the Invention
The present invention relates generally to substrates for mounting of electronic components. More particularly, the present invention relates to a blind via capture pad structure and method for fabricating the same.
2. Description of the Related Art
In multi-layer substrates, an electrically conductive circular capture pad is formed in a first dielectric layer. The circular capture pad is used to form an electrical connection with an electrically conductive blind via formed through a second dielectric layer mounted to the first dielectric layer.
To compensate for registration errors, the circular capture pad is much larger in diameter than the bottom of the blind via. This guarantees that the bottom of the blind via will be positioned within the diameter of the capture pad insuring electrical connection between the blind via and the circular capture pad.
Laser ablation is used to form the circular capture pad in the first dielectric layer. More particularly, a laser ablation process is used in which a focused laser beam is guided in a helical motion, sometimes called trepanning, to form a circular capture pad opening. The circular capture pad opening is then filled with electrically conductive material to form the circular capture pad.
However, the laser ablation process used to form the circular capture pad opening is relatively slow. More particularly, the laser ablation process requires that a large area of the first dielectric layer be removed to form the circular capture pad opening. Further, moving the focused laser beam in a helical motion is inherently slow.