## PCB Thermal Copper Area
*February 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 Density
*December 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?

Answers: (more…)

## PCB Via Thermal Resistance
*May 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 Resistance
*May 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 Calculator
*March 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.

Updates:

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 | ||

Plating Thickness | ||

Via Length |

**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

http://www.ultracad.com/articles/viacurrents.pdf

## PCB Trace Resistance Calculator
*January 24, 2006*

This online web calculator finds the resistance of copper PCB traces (a.k.a. tracks) of given width, thickness, length, and temperature. It can also be used for copper bars (e.g. bus bars). Several choices of common units are available. Enter the Width and Thickness below. Optionally, enter the Temperature and Length, or just leave the default values. (To find the needed trace width based on current, see the PCB Trace Width Calculator.)

May 17, 2006 - Added (lateral) thermal resistance calculations.

January 18, 2007 - Clarified equations.

**The Calculator**

(more...)