1, the common power supply vias size
Power supply via common via10-24, via20-35 and via24-40. Current is relatively large, a pin needs to play a few more vias.
2, size and current power supply via a relational table
1,10mil hole 20mil 20mil line corresponding to the pad over 0.5A current, the hole 20mil. 40mil 40mil pad corresponding to the line over 1A current, 0.5oz
2, via inductance calculation formula is:
L = 5.08h [ln (4h / d) +1]
In fact, the size of the hole on its inductance impact is not great, but added that the length of the impact of bigger, large inductance, the above pressure drop bigger. For the current, and it should be carrying cross-sectional area related to the larger cross-sectional area, the greater the current carrying capacity. The larger the aperture, the larger cross-sectional area, the thicker the copper layer hole wall, the larger cross-sectional area.
3,1, metalized through hole plating thickness of only a few 20 to a few microns, can not withstand high current! Therefore power lines, ground, high current lines through vias have to be here to the other side a few more vias, or through a pass through both sides of the original. 2 feet thick and more devices such as CD-type socket outlet should be as little as possible from the original surface. As a non-conditional can not be added to a device feet vias. Solid easy to destroy hole metallization layer when a plurality of pins inserted at the same time.
4. What is the diameter of the hole should be at least over the width of 1/35, near the Via hole bore traces plus ground effects and principle?
A: pcb board vias, classified according to their role, can be divided into the following categories:
1, the signal vias (via the structural requirements with minimal impact on signal)
2, power supply, ground vias (via holes distributed inductance through the structural requirements of the minimum)
3, thermal vias (via holes through the structural requirements for minimum thermal resistance)
Vias belonging to the above mentioned types of ground vias, in the vicinity of hole traces Via Via holes plus ground effect is to give a signal to provide the shortest return path. Note: The signal vias layer change, that is, an impedance discontinuity, return path signals from the off here, in order to reduce the area of the signal return path surrounded, must play some places around the signal vias vias provide the shortest return path signal to reduce emi radiation signal. This radiation consequent increase so significantly increase the frequency of the signal.