· · · Repository hosted by TU Delft Library

An experimental setup built in 1995 measures the spectral absorptioncoefficient of glass as a function of temperature and wavelength bythe emissive method. The setup was improved, as well as the softwarefor processing the measurement data. The measurement results of quartzwere validated by comparison with several literature sources. Theabsorption spectra of Philips 360, GE 180, Schott 8486 Suprax, Corning1724 and Philips 441 glass were determined as a function of temperature.

LEDs will become competitive with regards to classical lamps in fewyears for office lighting applications. In order to create such a device, we need to use a polymer having a low price and an excellentoptical transparency. Polymethylmethacrylate fulfill these requirements, but in order to use it in LEDs office lighting devices, we need to know more about its thermal, and hygroscopic properties. It has to support humidity and temperature fluctuations during more than 10 years, without undue deformation. As Philips has a good knowledge about polycarbonate because of optical storage disks, we can do similar experiments in order to compare the results. Sagging, shrinkage and swell by water sorption experiments have been made to predict and understand PMMA deformation behavior. Six different grades of PMMA were used, coming from 2 suppliers. Experiments were made at maximum used temperature given by the suppliers, and 10ºC below. Sagging and shrinkage were followed as a function of heating time.

The market of LEDs increases exponentially over the years as well as their power. However, at the same time the mean time to failure should remain superior to 100,000 hours. The major difficulty comes from the mechanical stress in the LED structure, which is roughly proportional to the inverse of the thermal conductivity. Consequently, it is really important to determine thermal conductivity of the materials used in LEDs. In the same way, the thermal conductivity of films is lower than the thermal conductivity of the bulk material. Unfortunately, thermal conductivity measurement is difficult on two-dimensional structures. Then an appropriate method had to be developed. The 3 omega thermal conductivity measurement method has been used extensively to measure the thermal properties of bulk and thin film dielectric materials. Tests on different materials will allow to find materials with a higher thermal conductivity. The thermal conductivity measurement will be elaborated by two different methods defined the isotropic and anisotropic properties, the "slope method" and the 2D heat conduction.

ABSTRACT Minority carrier lifetime imaging by lock-in thermography of passivated silicon wafers for photovoltaic cells has been developed for the public Pieken in de Delta project geZONd. CONCLUSIONS Minority carrier lifetime imaging by lock-in thermography of passivatedsilicon wafers is released to MiPlaza : · Exploratory experiments &checks are satisfactory · Modulation with <1 sun ±5% intensity @0.94 µm wavelength · 0.1 m image out of 0.15 m wafer with 1 mm spatial resolution · Calibration with Sinton WCT-120 with 22% relativeaccuracy and R²=0.982 goodness of fit · Image details · agree with high temperature thermography · recognize neighboring wafers andcrystals · disagree with Freiberg Instruments MDPmap · Synergy enables new imaging opportunities of: · severe delamination · patterned indium tin oxide (ITO) · thermal bridges by e.g. oil droplet

ABSTRACT: The power of LEDs increases exponentially over the years,while the mean time to failure (MTTF) should remain >100000 hours. The reliability requirement limits the junction temperature and the thermo elastic stresses, which are roughly inversely proportional tothe thermal conductivity of the heat spreaders. The 3omega method has been set up to measure dynamically the thermal conductivity of anisotropic thin layers preferably in situ. CONCLUSIONS: The 3omega method measurement set up is operational from 10 Hz to 10 kHz The measured thermal conductivity of silicium deviates 50%, so the set upneeds to be improved. The length of the heater has already been checked. The goodness of fit of the sensor/heater calibration R² = 0.99998 The goodness of fit of the 3omega slope method R² = 0.99

An acceptance test for thermography of semi-transparent materials by a FLIR ThermaCAM SC3000 infrared camera with 8.0 µm low-wavelength-pass filter has been developed and performed on polycarbonate, PEN, quartz, Corning 1737 glass, G427 cone glas, G443 screen glass, Schott Zerodur, silicon and a black-body on a hotplate. Effective emis-sivities have been calculated from reflectivity spectra measurements of these materials. The temperature measurement accuracy with 8.0 µm low-wavelength-pass filter is ±6 K, whereas the acceptance criterion of ±2 K is easily met by the old Agema 470 camera. Temperature non-uniformity is up to 5 K. The 8.0 µm low-wavelength-pass filter suppresses reflections of glass and polymer surfaces due to molecular stretching vibrations well. Temperature measurements with 8.0 µm low-wavelength-pass filter are fortunately insensitive to practical mechanical stresses and to lead evaporation of lead glass. Parasitic reflections of the crycooled detector and of the hot camera housing impede display inspection and the location of shorts wit hout filter. FLIR ThermaCAM Researcher software has a couple of bugs. Saving and reopening even corrupts the analysis.