## PCB Thermal Copper AreaFebruary 16, 2007

I published the following Zoho Sheet to calculate the PCB copper surface area to cool a device based on its power dissipation.

It is embedded below and can also be opened in its own window.

## Current vs. Trace Thickness and Temperature vs. Copper DensityDecember 15, 2006

Regarding the PCB Trace Width Calculator [1], Regit asks:

(a.) What is the relationship between current and trace thickness? And, (b.) what is the relationship between temperature and copper density?

## PCB Via Thermal ResistanceMay 22, 2006

By popular demand, Iâ€™ve also added thermal resistance calculation to the PCB Via Calculator. Thanks for the good suggestions!

## PCB Trace Thermal ResistanceMay 17, 2006

I had a request to calculate the thermal resistance of a PCB trace, so I updated the trace resistance calculator to add this feature.

## PCB Via CalculatorMarch 12, 2006

This Javascript web calculator calculates the resistance, voltage drop, and power loss of printed circuit board vias. Note that vias are made out of plated copper which typically has a resistivity of 1.7E-6 to 2.2E-6 Ohm-cm. The calculator has an input box for the resistivity which defaults to 1.9E-6 Ohm-cm.

May 22, 2006 - Added thermal resistance calculation.
January 19, 2007 - Minor Clarifications.
March 28, 2007 - Updated resistivity. See comment 12.
June 21, 2007 - Added estimated ampacity. See comment 17.

Inputs:

 Finished Hole Dia mil mm um Plating Thickness oz/ft^2 mil mm um Via Length mil mm um

Optional Inputs:

 Applied Current Amps Plating Resistivity Ohm-cm

Electrical Results:

 Resistance Ohms Voltage Drop Volts Power Loss Watts Estimated Ampacity Amps

Thermal Results:

 Thermal Resistance Deg. C/Watt

Notes:
Resistance = Resistivity*Length/Area
Area = pi*(Inner_dia + Plating_thk)*Plating_thk
Resistivity = 1.9E-6 Ohm-cm (plated copper)
(plated copper is much more resistive than pure copper)
Copper Thermal_Resistivity = 0.249 cm-K/W (at 300K)
Est_Ampacity [Amps] = k*(Temp_Rise [deg C])^b*(Area [mils^2])^c
For IPC-2221 external layers: k = 0.048, b = 0.44, c = 0.725

References:
[1] "Constructing Your Power Supply - Layout Considerations", by Robert Kollman
http://focus.ti.com/lit/ml/slup230/slup230.pdf
[2] "Current Carrying Capacity of Vias", by Doug Brooks and Dave Graves