Hi. We’re confused on the calculations on the “Conductors on Adjacent Layers” tab of the “PCB Conductor Spacing and Voltage Calculator”. IPC-2221 Section 6.3 states that Table 6-1 is to be used for “layer-to-layer conductive spaces (z-axis)” which provides different numbers (B1) than your adjacent layer calculator. Question: what specification or standard is used for the adjacent layer calculator? The IPC specification appears not to factor in the material breakdown strength. Thank you so much! - Kevin
Hi Kevin,
Calculations for the conductor spacing voltage calculator tool for the same layer (in the first tab of the tool) are derived from the IPC-2221B Table 6-1. the numbers calculated in this tool are derived numbers based on the table and give a more realistic steady increase in voltage and spacing whereas in the IPC table, the change is sudden from one voltage range to another. The tool also lets you calculate up to any value.
IPC states that you can use the same table for the z-axis, but for the practical scenario, those values are too high, and Z direction height is governed by the PCB dielectric material used between the two layers. For most of the PCB materials, IPC stated minimum electrical strength is 750 V/mil. It’s more than 1000 V/mil for many materials.
This material’s electrical strength and the aging factor (default we take 3) are needed to calculate the maximum voltage or minimum spacing required between layers with that particular dielectric in between the two layers