Glass frit bonding is an important technology for the hermetical encapsulation of microsensors. During manifactiring processes and in application the bonding layer is repeatedly exposed to temperature changes. Therefore a meaningful stability assessment must consider possible temperature dependent fracture toughness parameters. This work shows that the influence of temperature changes on the fracture toughness depends on whether the bonding layer is subjected to externally pure tensile or combined tensile and shear loading. The reasons for this effect are discussed by use of finite element simulations. Two different kinds of cracks are compared with regard to the residual stresses that result from the wafer bonding process. These residual stresses have a high influence on the loading conditions at the crack tip, when the crack is kinking into the glass frit material. However, the influence of residual stresses on an interfacial crack that propagates parallel to the plan e of the bonding layer is almost negligible
Platinum I 8300Modulated Crystal Structures and Phase Transitions -The Compounds SrPt2As2 and EuPt 2 As 2 . -The new title compounds are synthesized from the elements at 1050°C and characterized by single crystal XRD. Both compounds crystallize with modulated crystal structures at room temperature. The average structures belong to the orthorhombic space group Pmmn (Z = 2). The modulated structure of SrPt2As2 is described in the superspace group Pmmn(α00)0s0 (Z = 2). SrPt2As2 undergoes a phase transition at about 60 kbar. The high pressure phase crystallizes in the monoclinic space group P21/c with Z = 4. The high temperature phase of EuPt2As2 crystallizes in the space group P4/nmm with Z = 2. SrPt2As2 is further characterized by DFT band structure calculations. -(IMRE, A.; HELLMANN, A.; WENSKI, G.; GRAF, J.; JOHRENDT, D.; MEWIS*, A.
The reaction of rhodium(III) chloride trihydrate with 1, 4‐diazacycloheptane in concentrated hydrochloric acid results in the formation of tris(1, 4‐diazoniacycloheptane) hexaaquahydrogen(1+) bis(hexachlororhodate(III)) chloride, [C5H14N2]3[H13O6][RhCl6]2Cl (1). Dark red crystals of 1 are obtained by diffusion‐controlled crystallization at room temperature. Slow evaporation of the mother liquor over a period of several days yields a few tiny crystals of the bis(1, 4‐diazoniacycloheptane) hexachlororhodate(III) chloride hydrate, [C5H14N2]2[RhCl6]Cl˙1.75 H2O (2), as red thin squared plates. In the context of crystal engineering, compounds 1 and 2 are inorganic‐organic hybrid materials built up from octahedral [RhCl6]3‐, simple Cl‐ and semi‐flexible heterocyclic 1, 4‐diazoniacycloheptane ions, incorporating either the [H13O6]+ and further Cl‐ ions or portions of simple water molecules. Both compounds crystallize in the space group type P21/c. Compound 1 contains isolated [H13O6]+ ions with a linear chain‐like configuration enclosed in the cavities of the inorganic‐organic framework. The presence of a strong central O···H···O hydrogen bond within the [H13O6]+ ions in 1 is confirmed by the short O···O separation of 2.47Å and by characteristic IR absorption bands at 1626 (s), ∼ 1250 (m) and 668 (m) cm‐1. During the thermal decomposition, compound 1 looses at first five equivalents of water and one equivalent of hydrochloric acid in a two‐step process at 37 °C and 67 °C. This is followed by the decomposition of the 1, 4‐diazoniacycloheptane cations and the hexachlororhodate(III) anions, starting at 190 °C and proceeding intensified at 240 °C.
Inorganic-organic hybrid polymers (ORMOCE®s) combine very good optical and dielectricproperties in the frequency range up to 1 MHz (εr = 3.1 and tanδ = 0.004, both at 1 MHz). Thisis particularly promising for electro-optical (e/o) applications. Multi-layer microwave circuits forhigh frequency applications up to 100 GHz demand extraordinary material properties such as alow permittivity εr < 3 and a dielectric loss tanδ of about 10-3. For low-cost processing, direct UVpatterning would be particularly advantageous. Additionally, the material should be thermallystable at least up to temperatures around 300°C.We have developed a series of novel ORMOCE® materials for high frequency applications.Using these ORMOCE®s, thick film coatings (up to 150 m) can be produced and directlypatterned by UV lithography with sufficiently high resolution. The synthesis has been carried outusing styrene-substituted organosilanes and silanediols as precursors reacted by simplified solgel-processing in combination with organic cross-linking of polymerizable organic functions.The materials have been characterized at high frequencies up to 40 GHz, exhibiting verypromising dielectric properties of εr = 2.5 and tanδ = 0.0035.
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