# PCB trace height to width ratio

I came across the Isola IsoStack website that lets me test PCB stack-up using Isola substrates:

https://www.isola-group.com/isostack

My project is using a stripline design with a 1oz copper inner layer and trace width of 0.010". The tool calculated impedance at 50 ohms for my stackup but it complains that it violates an IPC-2141A constraint where trace height over trace width must be less than or equal to 0.11. The tool used 0.00125" for 1 oz copper height and my width of 0.010" to get a ratio of 0.125.

Can someone give me an overview on how this ratio applies to trace/signal behavior? If my signal is only DC-50Mhz, does it still apply or can be ignored? I tried to search for IPC-2141A and any term matching height/width ratio and most results talk more about current capacity or, oddly, hole aspect ratios.

Below is a screenshot of the parameters and constraints, the T/W is the constraint in question:

• The "height" is the thickness of the dielectric between the trace and the ground plane. You need to share what number you plugged in for that parameter, not just what you used for the thickness of the copper. A screen shot showing your complete geometry would be helpful. Oct 6, 2020 at 21:18
• Also, to know whether you can ignore transmission line effects at 50 MHz, we need to know how long your traces are. Oct 6, 2020 at 21:19
• If I understand your question correctly, you don't care for the tickness, you care for the length and width? The height and dimensions do matter. Increasing the capacitance will require more current, it will also increase the interferences. Here are the explanations pcbcart.com/article/content/… Also the technology that the manufacturer uses might not allow it. Oct 6, 2020 at 21:38
• The tool showed two constraints: T/H which is trace height (copper weight) over dielectric height, and T/W defined as trace height over trace width. T/W is the constraint that I don't fully understand and W changes to match the trace width. I will try to add a screen shot to clarify. Oct 6, 2020 at 21:59
• Please share a screen shot showing how these parameters are defined. (Usually they provide a diagram, but I don't know Isola's tool) Oct 6, 2020 at 23:29