A fritless copper conductor system for power electronic applications

Copper coated aluminium nitride (AlN) ceramic is a preferred substrate material utilized for high power, high frequency electronic applications. The use of metallized ceramic requires bonding of the metallization onto the substrate. AlN, however, is chemically inert to Cu. At present time the direct copper bonding (DCB) technology is used to manufacture such structures.In this project, for reasons of simplicity and economy and as alternative to the standard DCB-technology, the metallization on the AlN ceramic is built up by active metal brazing of a screen printable AgCuTi thick film ink. The mean advantage of this technology is, that the metal/ceramic braze compound can be processed in a conventional belt furnace at inert firing atmosphere usually available at hybrid microelectronics industry.Aspects of paste preparation ranging from the derivation of the metallic powder to the assortment of an appropriate organic screen-printing medium were investigated. The physical properties of the phases occurring at the interface between the TiCuAg metallization and AlN ceramic and their contribution to the thermal conductivity and the thermomechanical performance of the metallized substrate have been characterized theoretically as well as by experiment and compared with different commercial glass frit containing copper thick film metallization systems.     

The influence of finite conductor thickness and conductivity onfundamental and higher-order modes in miniature hybrid MIC's (MHMIC's)and MMIC's

The effect of finite metallization thickness and finite conductivity on the propagation characteristics of conductor-backed CPW on thin substrate is rigorously analyzed. A self-consistent approach is used together with the method of lines (MoL) to determine the propagation constant, losses and field distribution of the fundamental and first two higher-order modes in coplanar waveguides (CPWs) with finite metallization thickness and lossy backmetallization. The method used is general and can be applied to miniature MHMICs and MMICs including lossy semiconductor substrate. It is shown that the onset of higher-order modes limits the usable frequency range of conductor-backed CPWs. The analysis also includes microstrip transmission lines on thin substrate material. It is demonstrated that a resistive strip embedded into the microstrip ground plane may potentially be useful in the design of integrated planar attenuators     

Dispersion and attenuation characteristics of coplanar waveguideswith finite metallization thickness and conductivity

A new approach of modifying the conventional spectral-domain approach is proposed for an analysis of the coplanar waveguide whose signal strip and ground planes have finite thickness and conductivity. By introducing suitable equivalent sources in the slot and signal strip regions, the problem can be significantly simplified by reducing the two-dimensional numerical integration into the one-dimensional one, thus it can be treated as easily as the conventional spectral-domain approach. By this modified approach, both the phase constant and attenuation constant can be determined simultaneously without using the assumption that the metallization thickness is much larger or smaller than the skin depth. In this work, comparison with published theoretical and experimental results is presented to check the accuracy of the new approach's results. In particular, the effective dielectric constant ϵ_eff and attenuation constant a of a coplanar waveguide with finite metallization thickness and finite conductivity are discussed in detail, together with the current distributions along the signal strip and ground planes     

The structure of acoustic modes in piezoelectric plates with free and metallized surfaces

By the example of 128°Y,X + 90°-LiNbO₃ plates and quasi-longitudinal acoustic modes, the effect of one- and two-sided metallization of plates on the depth profiles of elastic displacements of modes is studied theoretically and experimentally. It is shown that, in the modes with the zero electromechanical coupling coefficient K² = 0, the elastic displacement profiles for free and metallized plates are the same; while, in the modes with the nonzero coupling K² ?? 0, they are noticeably different and correspond to either attraction or repulsion of modes from the metallized surface. Correspondingly, the modes become more or less sensitive to surface loading.     

碳纤维天线表面金属化的研究及应用

介绍了碳纤维复合材料天线采用转移法进行表面金属化的技术。通过对高分子转移膜溶液配方、高分子转移膜制作和金属喷涂等进行研究,确定了碳纤维复合材料天线表面金属化的流程。在Ka频段对电磁波的反射特性进行测试,达到了设计指标要求。该方法操作简单,稳定性和可靠性较高,不影响制品精度,而且成本较低,适用于室温固化成型和中温固化成型,具有广泛的应用前景。     

Capacitance computation for CPW discontinuities with finitemetallization thickness by hybrid finite-element method

A variational equation is derived for the capacitances of coplanar waveguide (CPW) structures with finite metallization thickness. The equation is expressed in terms of the static potential in the slot region and is solved by applying the hybrid finite-element method (FEM). In the case of small metallization thickness, it is reduced to a perturbation formula for the incremental capacitances. Numerical results for the equivalent capacitances of various discontinuities with finite metallization thickness are presented and compared with measured data. The reasonable agreement between the measured data and the theoretical results validates the present approach. Being simple and computationally efficient, the method is suitable for dealing with extensive CPW discontinuity problems where the metallization thickness is not negligible     

Mechanical reliability of metallized optical fiber for hermeticterminations

Hermetic packaging requirements for high-reliability fiber-optic devices can be met through the use of solder-sealed fibre penetrations. Local metallization of the fiber surface facilitates soldering but also modifies the fiber's strength and fatigue properties. A significant body of research addresses the properties of fibers coated with metal during fiber drawing, but the mechanical properties of fibers locally metallized after drawing have not been discussed. These properties were evaluated by means of dynamic fatigue tensile testing for fibres having a multilayer metallization applied by a vacuum deposition process. The results show that fiber strength reduction resulting from metallization is compensated by an increased resistance to static fatigue. Use of the results in reliability assurance is discussed     

Optical Fibers With a Finite Metallic Core

Optical step index fibers can be produced that include a thin metal wire in the centre of the core. Such fibers are particularly interesting with respect to their guiding properties. With the goal to theoretically analyse their modes, we summarize three analytic solutions for dielectric media containing a thin metallic wire. In addition, we present a solution for the most general case of a step index fiber containing a metallic wire with finite conductivity. The analytic solutions serve as model cases which are used to evaluate the accuracy of numerical simulations and to find the most appropriate simulation parameters. Given those, more complex structures can be investigated.      

Analysis of the Characteristics of an Earthed Fin Line

This paper presents a theoretical and experimental investigation of the effective permittivity and the characteristic impedance of the earthed unilateral fin line. Using the Ritz-Galerkin method, the eigenvalue equation for a fin line with finite metallization thickness as well as a longitudinal slit in the metal waveguide mount is derived. The numerical solution converges very rapidly in all the cases investigated. Experimental checks are reported, which verify the results of this method and stress the importance of the effects of the finite metallization thickness and longitudinal slit in the mount at higher frequencies. The theoretical results are compared with results by Hofmann, and they are found to correspond closely.     

PTFE基复合介质表面金属化的研究

采用真空蒸发、溅射和化学镀铜的方法分别对研制的ＰＴＦＥ基复合介质进行了金属化处理。试验结果表明：经萘钠溶液处理后的介质，镀铜后铜层致密光亮，且剥离强度明显高于物理方法金属化的剥离强度。     

印制电路孔金属化

印制电路是电子工业重要部件,印制电路金属化孔要有良好的机械韧性和导电性,孔金属化涉及生产全过程,特别是钻孔,活化,化学镀铜尤为重点,必须做到孔内无钻屑,胶体色活性好,化学镀铜层为红棕色,才能生产出高质量优孔的印制板。     

The performance of GaAs power MESFET’s using backside copper metallization

The performance of GaAs power MESFET’s using backside copper metallization has been evaluated. 10 nm Ta metal was used as the diffusion barrier between GaAs and Cu for copper film metallization in this study. Microstructural characterization shows that the Cu/Ta films with GaAs remained stable up to 400 °C, indicating that Ta is a good diffusion barrier for Cu in GaAs MESFET’s. A copper metallized 6 mm power MESFET was thermal stressed to test the device stability. After annealing at 200 °C for 3 h, the devices showed very little degradation in power performance, and the thermal resistance of the device was 65 °C mm/W with 1.4 W/mm DC input power. Results in this study demonstrate that the feasibility of using Cu/Ta films for the backside metallization of GaAs power devices with stable electrical and thermal characteristics.     

Analysis of discontinuities in an open dielectric slab waveguide bycombination of finite and boundary elements

A combination of the finite-element and boundary-element methods is proposed for the solution of arbitrarily shaped discontinuities in an open dielectric slab waveguide. The discontinuity region is divided into two regions. One is a finite region with arbitrary inhomogeneities, and the other is a semi-infinite and homogeneous region. The finite-element and boundary-element methods are applied to the former and the latter regions, respectively. For uniform waveguide regions connected to discontinuities, analytical solutions in which both the guided and the radiated modes are taken into account are used. To show the validity and usefulness of this approach, computed results are given for several kinds of discontinuities, and the accuracy of the solutions is investigated in detail     

一种分析有限金属厚度和有限电导率的共面波导结构的有效方法

采用分区直线法与渐近拟合阻抗边界条件相结合的方法,对一种具有限金属厚度和有限电导率的共面波导结构的相对介电常数和损耗特性进行了分析,这是一种全波分析方法,并且可以适用于趋肤深度与金属厚度之比为任意数值的情况。计算实例证明了该方法的正确性和有效性。     

A simple metal-semiconductor substructure for the advanced thermo-mechanical numerical modeling of the power integrated circuits

The metallization of double-diffused metal-oxide semiconductor (DMOS) power devices, which operate under fast thermal cycling (FTC), undergoes thermal induced plastic metal deformation (TPMD). The design of the metallization has a significant impact on the device lifetime and thus requires a thorough understanding of the temperature, stress and strain distribution. A simple three-dimensional (3D) transistor substructure which is commonly found in various high integration Bipolar-CMOS-DMOS (BCD) technologies is analysed. The thermomechanical behaviour is studied with the finite element method (FEM) for investigation of two potential failure mechanisms: delamination of power metal and accumulation of plastic deformation in signal metallization layer (which leads to inter-metal dielectric cracking). These failure mechanisms are analysed on two versions of the structure: the first one has only signal and power metal lines and the second one has vias, in addition to the signal and power metal lines. The target of the paper is to propose an efficient finite element analysis (FEA) model that can be used for a qualitative assessment of thermo-mechanical phenomena in the metal system of high integration BCD technologies.     

Full-wave analysis of coplanar waveguide discontinuities using thefrequency domain TLM method

This paper presents a full-wave analysis of a variety of coplanar waveguide discontinuities using the frequency domain TLM method. The finite metallization thickness is taken into account as well as metal losses and the interaction of fundamental and higher order modes between cascaded discontinuities. Numerical results are presented for the frequency-dependent s-parameters of transitions between CPW and slotline, CPW and microstrip line and CPW-microstrip overlap transition. The effect of interactions between the CPW discontinuities and the CPW airbridges is also investigated     

Propagation Constant Below Cutoff Frequency in a Circular Waveguide with Conducting Medium

Exact and approximate propagation characteristics of normal modes in the cutoff region of a circular waveguide surrounded by a medium of finite conductivity are discussed. An exact solution is obtained by numerical analysis, and an approximate one is derived by expanding the characteristic equation considering the finite conductivity of the cylinder wall. The computed values are compared with experimental ones. It is shown that the attenuation of TM/sub 01/ mode at frequencies that are much lower than the cutoff frequency is constant, i.e., independent of frequency and the material constants of the external medium, and this mode is the most suitable one for realizing a precision circular piston attenuator.     

Analysis of shielded striplines and finlines with finitemetallization thickness containing magnetized ferrites

The applicability of the spectral domain approach is extended to analyze various types of shielded planar transmission lines, taking the anisotropy of the magnetized ferrites and the finite metallization thickness into consideration. The numerical computations include the propagation characteristics of finlines and striplines and the metallization thickness effect in these lines. Numerical data of simpler structures are compared with the available exact solution as well as with published data     

Large Multipurpose Exceptionally Conductive Polymer Sponges Obtained by Efficient Wet‐Chemical Metallization

Exceptionally conductive (250 S cm^?1), very fast electrically heatable, thermally insulating, antimicrobial 3D polymeric sponges with very low density (≈30 mg cm^?3), superhydrophobicity, and high porosity, their method of preparation, and manifold examples for applications are presented here. The electrical heatability is reversible, reaching 90 °C with 4.4 W in about 19–20 s and cooling immediately on switching off the voltage. The sponges show high contact angles >150° against water on the sponge surface as well as inside the sponge. Water droplets injected into the sponges are ejected. A facile wet‐chemical method established for macroscopic melamine–formaldehyde sponges is the key for the thorough in‐depth surface metallization of the sponges. The coating thickness and uniformity depend on the metallization formulation, conditions of metallization, and the type of metal used. A scanning electron microscope is used for morphology characterization. A reduced metallization rate in air is highly critical for the in‐depth uniform coating of metals. The resulting metallized sponges could be highly interesting for heating as well as insulation devices in addition to oil/water separation membranes.     

Calculating the Characteristic Impedance of Finlines by Transverse Resonance Method

The characteristic impedance of finlines with up to three slots is calculated by a rigorous hybrid-mode analysis which includes the finite metallization thickness and finite depth of the mounting grooves. The transverse resonance principle utilized reduces considerably the order of the involved matrix eigenvalue problem. The propagation constants for the fundamental HE/sub 1/ mode (and EH/sub 0/ mode at related structures), as well as for the higher order modes (up to HE/sub 7/), and the characteristic impedances for the fundamental modes are computed as a function of frequency for the bilateral and unilateral finline, as well as for the unilateral finline with two coupled slots, and an additional slot on the opposite side of the substrate surface. The finite metallization thickness and mounting groove depth considered show significant influence on the behavior of the characteristic impedance.