Characterising the amount and the purity of nucleic acid is an important step in state of the art polymerase chain reaction (PCR). In most cases, the analysis is done by stand-alone equipment. For the measurement, a small amount out of the PCR-process has to be removed. Furthermore, the evaluation of the measured spectra occurs only at three wavelengths (230 nm, 260 nm, 280 nm). Therefore, it should be possible to monitor the PCR-process in situ. We demonstrate an illumination unit with three UV-LEDs (245 nm, 265 nm and 280 nm). Every LED is collimated by two lenses. Two longwave-pass filters merge the optical axes of the different wavelength. Lenses and filters are commercial available. The illumination unit is available with and without fiber coupling. The optical behavior of the illumination unit will be shown and discussed. Further, we investigate the observed peak position of the supporting points in dependence of the impurity concentration of an example solution.
UV LEDs are usually mounted in flip-chip technology by soldering or thermocompression bonding to allow the UV light to be emitted through the sapphire substrate. The thermal conductivity of solders is considerably smaller than that of the typical metals used for packaging such as Cu, Ag or Au. For thermosonic- or thermocompression bonding pure metals can be used, however, the contact area is reduced in comparison to soldered contacts. Thermal simulations with different ratios of the number and size of stud bumps to the total area illustrate the direct influence of these parameters on the thermal resistance. The deformation during the bonding process as a function of the processing temperature and the applied force is discussed together with the influence of preprocessing, e.g. coining. Approaches are presented to increase the bonding area to 70 % of the total pad area of the chip. The improvements in the thermal resistance are demonstrated by lock-in-thermography and SEM investigations.
KEYWORDS: Optical sensors, Sensors, Calibration, Silicon, Diffusion, Manufacturing, Photodiodes, Control systems, Artificial neural networks, Solids, Microopto electromechanical systems, Diodes, Signal analysis, General lighting, Signal analyzers, Semiconducting wafers, Solar energy systems
A novel device for detecting the intensity and the angles of incoming light is presented. The silicon chip with 1 mm edge length comprises a segmented photo diode with four active areas within the inclined surfaces of a deep etched cavity. Simple signal difference analysis of these signals allow for accurate azimuth and inclination measurement in the range of 0 to 360° and 0 to 55°, respectively. Using an artificial neural network (ANN) calibration strategy the operation range of inclination can be increased up to 85° with typical angle errors below 2°. In this report we present details on design, fabrication, signal analysis and calibration strategies.
High power LEDs have conquered the mass market in recent years. Besides the main development focus to achieve higher productivity in the field of visible semiconductor LED processing, the wavelength range is further enhanced by active research and development in the direction of UVA / UVB / UVC. UVB and UVC LEDs are new and promising due to their numerous advantages. UV LEDs emit in a near range of one single emission peak with a width (FWHM) below 15 nm compared to conventional mercury discharge lamps and xenon sources, which show broad spectrums with many emission peaks over a wide range of wavelengths. Furthermore, the UV LED size is in the range of a few hundred microns and offers a high potential of significant system miniaturization. Of course, LED efficiency, lifetime and output power have to be increased . Lifetime limiting issues of UVB/UVC-LED are the very high thermal stress in the chip resulting from the higher forward voltages (6-10 V @ 350 mA), the lower external quantum efficiency, below 10 % (most of the power disappears as heat), and the thermal resistance Rth of conventional LED packages being not able to dissipate these large amounts of heat for spreading. Beside the circuit boards and submounts which should have maximum thermal conductivity, the dimension of contacts as well as the interconnection of UV LED to the submount/package determinates the resolvable amount of heat . In the paper different innovative interconnection techniques for UVC-LED systems will be discussed focused on the optimization of thermal conductivity in consideration of the assembly costs. Results on thermal simulation for the optimal contact dimensions and interconnections will be given. In addition, these theoretical results will be compared with results on electrical characterization as well as IR investigations on real UV LED packages in order to give recommendations for optimal UV LED assembly.
In construction and manufacturing the surface roughness and their control plays a major role. The mechanical test
probes are used in many applications, because the advantage of the higher resolution of optical systems often plays no
role. But in all cases the measurement systems were uses outside of fabrication processes due to the complex and
expensive equipment. To overcome these we developed a roughness sensor suitable for an automated control of
machined surfaces. The sensor is able to handle high throughput and parallel systems is due to the low cost available.
Our solution is compact stand-alone sensors that can be simple integrated in existing systems like machine tools or
transport systems. The sensor is based on a diode laser, focusing optics and a special silicon photo diode array in a stable
housing. The single-mode VCSEL at 670 nm emission wavelength is focused on the surface of the sample at distance of
5mm. The light was reflected from the test surface and detected with an 8-channel photodiode array. The position of the
main reflex allows an optimization of the sensor distance to the surface. During the movement of the sample with a
known velocity roughness depended signals over time were recorded at 8 cannels. This allows a detection of the angular
distribution of the scattered light in combination of position dependent refection. It was shown here that we be able to
achieve resolution below the spot diameter (30μm FWHM). We verify the sensor capabilities for real world applications
on drilled samples with typical roughness variations in micro meter range.
Opto-chemical transducer almost offers unlimited possibilities for detection of physical quantities. New technologies and research show a steady increasing of publications in the area of sensoric principles. For transfer to real world applications the optical response has to be converted into an electrical signal. An exceptional opto chemical transducer loses the attraction if complex and expensive instruments for analysis are requires. Therefore, the readout system must be very compact and producible for low cost. In this presentation, the technology platform as a solution for these problems will be presented. We combine micro structuring of silicon, photodiode fabrication, chip in chip mounting and novel assembly technologies for creation of a flexible sensor platform. This flexible combination of technologies allows fabricating a family of planar optical remission sensors. With variation of design and modifications, we are able to detect colorimetric, fluorescent properties of an sensitive layer attached on the sensor surface. In our sensor with typical size of 6mm x 6mm x 1mm different emitting sources based on LED's or laser diodes, multiple detection cannels for the remitted light and also measurement of temperature are included. Based on these sensors we proof the concept by demonstrating sensors for oxygen, carbon dioxide and ammonia based on colorimetric and fluorescent changes in the transducer layer. In both configurations, LED's irradiated the sensitive polymer layer through a transparent substrate. The absorption or fluorescence properties of dyed polymer are changed by the chemical reaction and light response is detected by PIN diodes. The signal shift is analyzed by using a computer controlled evaluation board of own construction. Accuracy and reliability of the remission sensor system were verified and the whole sensor system was experimentally tested in the range of concentrations from 50 ppm up to 100 000 ppm for CO2 and O2 Furthermore, we develop concepts to use the sensor also for interferometric detection of layer properties and the combination with capacitive structures on the surface. This allows detecting of thickness or refractive index variation of layers in future.
In chemical, oil, and food industries, there are still higher requirements on miniaturization of optical sensors for
a concentration measurement of gases e.g. a
CO<sub>2</sub>, O<sub>2</sub>, and NH<sub>3</sub>. The paper deals with development of miniaturised
optical sensor for an aqueous carbon dioxide measurement using a sensitive polymer layer. The optical sensor module
consists of two parts, a remission sensor and a removable layered structure (with incorporated dyed polymer) which is
closely placed on the surface of a remission sensor. A dyed polymer film is used as an optical-chemical transducer
working on a principle of colour changes caused by a chemical reaction of an analyte and indicator dye. A novel
remission sensor module was developed for an evaluation of the spectral absorption changes of sensitive polymer layer.
The remission sensor module composed of LED diodes located in a central cavity of the sensor module and PIN diodes
situated around the cavity. The LEDs emit light with optimised wavelengths and irradiate the polymer film. Light
response (the changes of the spectral absorption) of the irradiated polymer film is detected by PIN diodes. A colour shift
is further analyzed and evaluated by electronics without using a photometer.