Flip-Chip Technologie für Anwendungstemperaturen > 250 °C

In this work the development of a flip chip package with a long term thermal resistance for temperatures above 250 °C and additional high reliability against temperature cycling is shown. Since standard organic underfill materials can not be used at these high temperatures a solder frame structure was added along the chip edges. This leads, analogue to the function principle of an underfill, to a bow of the whole package instead of a lateral prolongation of the joint partners. Thereby the solder bumps stay aligned perpendicular to their joint partners and as a consequence the lateral deformation as well as the thermomechanical tension are reduced. The bump and the frame connections were produced with a gold/tin Solid-Liquid Interdiffuision (SLID) solder process. By the presented concept of an additional solder frame the thermomechanical tension could be reduced and the reliability against thermal cycles is increased significantly. The thermal stability is shown for temperatures up to 300 °C

Ungekühlte Mikrobolometer-Arrays mit einer Pixelgröße von 12 µm basierend auf einer neuartigen thermisch isolierenden Struktur

A novel structure for realization of thermal isolation and electrical contacting of microbolometers is described in this paper. This structure is formed by thin coated hollow tubes (termed as nanotubes in this work), which can be fabricated by processes of microsystems technology. Therefore, commonly used lateral legs as main component of thermal isolation can be excluded in order that the effective absorption area is maximized. The resulting thermal conductance can be tuned independently from the pixel size by varying layer thicknesses, base radius and length of the structured nanotubes. The fabricated12 μm pixel size nanotube microbolometers are characterized with respect to electrical-optical and mechanical properties by means of test structures

Uncooled digital IRFPA-family with 17µm pixel-pitch based on amorphous silicon with massively parallel Sigma-Delta-ADC readout

This paper presents the results of an advanced digital IRFPA-family developed by Fraunhofer IMS. The IRFPA-family compromises the two different optical resolutions VGA (640 ×480 pixel) and QVGA (320 × 240 pixel) by using a pin-compatible detector board. The uncooled IRFPAs are designed for thermal imaging applications in the LWIR (8 .. 14µm) range with a full-frame frequency of 30 Hz and a high thermal sensitivity. The microbolometer with a pixel-pitch of 17µm consists of amorphous silicon as the sensing layer. By scaling and optimizing our previous microbolometer technology with a pixel-pitch of 25µm we enhance the thermal sensitivity of the microbolometer. The microbolometers are read out by a novel readout architecture which utilizes massively parallel on-chip Sigma-Delta-ADCs. This results in a direct digital conversion of the resistance change of the microbolometer induced by incident infrared radiation. To reduce production costs a chip-scale-package is used as vacuum package. This vacuum package consists of an IR-transparent window with an antireflection coating and a soldering frame which is fixed by a wafer-to-chip process directly on top of the CMOS-substrate. The chip-scale-package is placed onto a detector board by a chip-on-board technique. The IRFPAs are completely fabricated at Fraunhofer IMS on 8" CMOS wafers with an additional surface micromachining process. In this paper the architecture of the readout electronics, the packaging, and the electro-optical performance characterization are presented

Polymer tribology by combining ion implantation and radionuclide tracing

Radionuclide tracers were ion implanted with three different techniques into the ultra-high molecular weight polyethylene polymer. Tracer nuclei of (7)Be were produced with inverse kinematics via the reaction p((7)Li,(7)Be)n and caught by polymer samples at a forward scattering angle with a maximum implantation energy of 16 MeV. For the first time, (97)Ru, (100)Pd, and, independently, (111)In have been used as radionuclide tracers in ultra-high molecular weight polyethylene. (97)Ru and (100)Pd were recoil-implanted following the fusion evaporation reactions (92)Zr((12)C,alpha 3n) (97)Ru and (92)Zr((12)C,4n)(100)Pd with a maximum implantation energy of 8 MeV. (111)In ions were produced in an ion source, mass-separated and implanted at 160 keV. The tribology of implanted polymer samples was studied by tracing the radionuclide during mechanical wear. Uni-directional and bi-directional sliding apparatus with stainless steel actuators were used. Results suggest a debris exchange process as the characteristic feature of the wear-in phase. This process can establish the steady state required for a subsequently constant wear rate in agreement with Archard's equation. The nano-scale implantation of mass-separated (111)In appears best suited to the study of non-linear tribological processes during wear-in. Such non-linear processes may be expected to be important in micro- and nanomachines. (C) 2010 Elsevier B.V. All rights reserved

Digital uncooled IRFPAs based on microbolometers with 17 μm and 12μm pixel pitch

This paper presents the results of high-performance infrared detectors (IRFPA – InfraRed Focal Plane Array) based on uncooled microbolometers with 17 μm and 12 μm pixel pitch and a chip-scale-package as the vacuum package developed and fabricated by Fraunhofer-IMS. Like CMOS image sensor IRFPAs also have been following the trend of reducing the pixel size in order to reduce the costs and increase the optical resolution. For microbolometer based uncooled IRFPA the pixel pitch has been reduced from 35 μm pixel pitch ten years ago via 25 μm and 17 μm down to 12 μm. Fraunhofer IMS has developed digital IRFPAs featuring a direct conversion of the microbolometer’s resistance into a 16 bit value by the use of massively parallel on-chip Sigma-Delta-ADCs achieving a high scene temperature dynamic range of more than 300 K and a very low NETD-value below 50 mK. Due to a broadband antireflection coating the digital IRFPAs achieve a high sensitivity in the LWIR (wavelength 8 μm to 14 μm) and MWIR (wavelength 3 μm to 5 μm) range. In this paper the microbolometer, the vacuum-packaging, the architecture of the readout electronics, and the electro-optical performance characterization will be presented