Specific Process Knowledge/Back-end processing/Laser Micromachining Tool/fluence

Fluence definition

The fluence produces by a laser is, by definition, the energy delivered by a laser pulse ($E_{pulse}$) per surface unit ($A$) and it is given in J/cm2.

The function $E_{pulse}$ is defined as :

$E_{pulse}={\frac {\overline {P}}{f}}\,$

Where ${\overline {P}}$ (average power) is measured with the laser sensor power measurement (see manual,section 5.3) and the repetion rate ($f$) is set in the parameter file under " laser frequency".

The fluence is therefore determinated as such :

$Fluence={\frac {E_{pulse}}{A}}\,$

The area ($A$) can be determinate with the theoretical min spot diameter (1/e2), available here

Fluence results measurement

Fluence result for IR wavelength (1064nm, F255mm)	Fluence result for green wavelength (532nm, F255mm)	Fluence result for UV wavelength (355nm, F100mm)

File:140414 FluenceVSrepRate IPG.jpg Fluence result for IR wavelength (IPG 1064nm, F255mm)