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)

Fluence result for IR wavelength (IPG 1064nm, F255mm). The fluence at 100% and 10kHz must be expected around 25J/cm2