Calculating Desorption Kinetics and Activation Energy in Polymer Microcircuits
Calculating desorption kinetics and activation energy via multi-ramp thermal testing determines safe reflow limits and prevents package popcorning.
TDS
Analysis Method
Vacuum systems measure the gases released from a solid sample as it is heated at a controlled rate.
Vacuum Requirement
Base pressures in the ultra high vacuum range prevent the contamination of the sample surface during the measurement. In a typical tds experiment, the environment must be clean enough that the rate of gas re-adsorption is negligible compared to the rate of desorption. This ensures that the detected signals originate from the bulk or the surface of the specimen rather than the residual gas in the chamber.
High vacuum pumps maintain the pressure low enough to ensure that the mean free path of the desorbed molecules is larger than the distance to the detector.
Desorption Profile
Thermograms show peaks of gas evolution at temperatures that correspond to specific molecular states. A tds plot reveals whether a gas was physically adsorbed with weak bonds or chemically bonded with higher energy.
Detection Sensitivity
Quadrupole mass filters allow for the measurement of extremely small quantities of gas, often down to a fraction of a monolayer. While tds is highly sensitive to surface species, it can also detect hydrogen or other small atoms diffusing out of the bulk of a metal. Calibration with known gas leaks or calibrated samples is necessary to convert the ion current into an absolute molar quantity.