Impact of sintering conditions on solderability and wire bondability of thick-film metallizations for Silicon-Ceramic composite substrates

Over the last years, the Low Temperature Co-fired Ceramic (LTCC) technology has proven its extreme efficiency for compact and reliable radio-frequency (RF) modules for wireless communication. LTCC technology is widely present in switches, power amplifiers and Bluetooth modules for handsets. No doubt that this technology will also be adopted for the WLAN (wireless local area network) modules in a very short term. However LTCC solutions often suffers from the reputation to be difficult to design, few flexible and expensive specially versus the very well known solutions based on printed circuit boards (PCB). DT Microcircuits and Thales Microelectronics launched together an important study to simplify the design and reduce the cost of WLAN modules based on LTCC technology. This paper summarizes this 12 months study. RF designers studied the different architectures and integration levels applied to WLAN modules. Fundamental elementary blocks, like baluns, filters, power amplifiers (PA) and switches were identified and described as a function of possible architectures, specifications and pre-selected technologies. They were implemented in LTCC substrates individually and all together. Several more or less complex LTCC modules were designed, simulated, manufactured and tested. The study proved the ability to efficiently implement the different components of a WLAN front-end module (FEM) in LTCC, whatever the chosen technologies and architectures: embedded LTCC components (filters, switches), surface acoustic waves (SAW) filters, PIN diodes or GaAs switches and PA. It allows customers to save an important time in the design of their WLAN LTCC modules.

Purpose – The purpose of this paper is to focus on development and electrical characterization of miniature ion-selective electrode (ISE) for application in micro total analysis system or lab-on-chip devices. The presented ISE is made using low temperature co-fired ceramics (LTCC). It shows possibility of integration chemically sensitive layers with structures fabricated using modern microelectronic technology. Design/methodology/approach – The presented ISEs were fabricated using LTCC microelectronic technology. The possibility of ISE fabrication on multilayer ceramic substrate made of two different LTCC material systems (CeramTec GC, Du Pont 951) with deposited thick-film silver pad is studied. Different configurations of LTCC/silver pad (surface, embedded) are taken into account. Electrical performance of all LTCC-based structures with integrated ISE was examined experimentally. Findings – The preliminary measurements made for ammonium ions have shown good repeatability and linear response with slope of about 30-35 mV/dec. Moreover, no significant impact of the LTCC material system and silver pad configuration on fabricated ISEs’ electrical properties was noticed. Research limitations/implications – The presented research is a preliminary work. The authors focused on ISE fabrication on LTCC substrates without any microfluidic structures. Therefore, further research work will be needed to evolve ion-selective membrane deposition inside microfluidic structures made in LTCC substrates. Practical implications – Development of the LTCC-based ISE makes the fabrication of detection units for integrated microfluidic systems possible. These devices can find practical applications in analytical diagnosis and continuous monitoring of various biochemical parameters. Originality/value – This paper shows design, fabrication and performance of the novel ISE fabrication using LTCC technology.

In this paper, two broadband rectangular waveguide to microstrip transitions at W-band with LTCC (Low Temperature Co-fired Ceramic) technology are proposed: WLWMT(WR-10 to LTCC Waveguide to Microstrip Transition), and a novel probe transition of WR-10 to Microstrip using LTCC technology. To widen the bandwidth of WLWMT, two matching structures which are composed of stripline on different substrate layers connected by the staggered via side walls are buried. For the novel probe transition, inner conducting ground is used as waveguide backshort comparing with that in HIMCs(Hybrid Integrated Microwave Circuits). According to EM simulation, the WLWMT illustrates a 19% effective bandwidth (ranging from 91.6 to 98.2 GHz); the probe transition illustrates a 29% effective bandwidth (ranging from 90 to 100 GHz).

Small, light weight and multifunctional electronic components are attracting much attention because of the rapid growth of the wireless communication systems and microwave products in the consumer electronic market. The component manufacturers are thus forced to search for new advanced integration, packaging and interconnection technologies. One solution is the low temperature cofired ceramic (LTCC) technology enabling fabrication of three-dimensional ceramic modules with low dielectric loss and embedded silver electrodes. During the past 15 years, a large number of new dielectric LTCCs for high frequency applications have been developed. About 1000 papers were published and ∼500 patents were filed in the area of LTCC and related technologies. However, the data of these several very useful materials are scattered. The main purpose of this review is to bring the data and science of these materials together, which will be of immense help to researchers and technologists all over the world. The commercially available LTCCs, low loss glass phases and researched novel materials are listed with properties and references. Additionally, their high frequency and thermal performances are compared with the other substrate material options such as high sintering temperature ceramics and polymers, and further improvements in materials' development required are discussed.

In this paper, we present design, analysis and simulation of a front-end of a transceiver which works in Ku-band (15.5GHz) based on multi-layer LTCC (low temperature co-fire ceramic) technology. The superheterodyne structure is selected and some GaAs bare chips from Hittite company such as mixer, power amplifier, LNA, drive amplifier are used in this MCM (multi-chip module). Some considerations about the system design are considered first, by the simulation of the system we can got the following results: NF 26dB, Sensitivity about −80dBm. Most of the passive devices including filters, power dividers, transmission lines, impedance matching network are integrated in the LTCC substrate. The active devices are mounted on the surface of LTCC substrate. The entire module is achieved with 15-layer LTCC substrate and the area is about 50mm*30mm.

Today LTCC (Low Temperature Co-fired Ceramics) Technology is established as a key technology for ceramic based interconnects on modules and components. Known for their excellent thermal and high frequency electrical performance, LTCC Technology is gaining new applications e.g. in the automotive and telecommunications market. Over the last years, LTCC materials and production processes have been further developed to meet the needs of these applications. As a result, the layouts of LTCC-modules are characterized by increasing circuit complexity and packaging density. Accordingly, the numbers of layers and vias are increasing, while the dimensions of the circuitry (lines and spaces) are decreasing. On the other side, conventional screen printing is limited to approximately 100 mum of line width (in volume production). This is why photoimageable thick film technology is used in applications requiring high packaging density. Another consequence of shrinking circuit dimensions is the need to reduce the size of via holes, which are usually fabricated by punching or laser drilling. This paper reports results regarding the formation of vias in LTCC tapes. Different methods, i.e. mechanical punching and laser drilling, as well as different lasers (CO2, Nd-YAG and UV) are compared..

Modern advanced 3D microelectronic packages are in many cases made as multilayer ceramic modules with integrated electronic components and sub-circuits. The Low Temperature Co-Fired Ceramics (LTCC) technology is considered as one of more advanced technologies for fabrication of these structures. The increasing versatility of LTCC technology applications is a consequence of such attractive features of this technology as possibility of creation of three-dimensional structures as many of applications demand possibility of structuring of channels, cavities and reaction chambers, membranes and free-standing beams within LTCC ceramics. To obtain these buried structures without delamination and/or sagging during lamination processes (compressing of green LTCC foils at around 70°C) so called sacrificial layers are often used. During lamination sacrificial layers (screen printed thick film pastes or tapes) support buried cavities. During firing layers must burn out before LTCC tapes are densely sintered to enable the diffusion of air into structures. Six different carbon based materials (four pastes and two tapes) were evaluated. The thermo gravimetrical analysis (TGA) was used to determine the optimised burn-out temperatures and times. LTCC test structures were designed to evaluate the “quality” of buried cavities with different sacrificial materials and with different processing parameters.

A wideband low noise amplifier integrated into a LTCC (Low Temperature Co-Fired Ceramic) environment is presented in this paper. 50ohm microstrip lines are simulated using 3D full-wave simulator, which takes into account the electromagnetic effects caused by top conductors recess. To integrate bare chips into LTCC substrates, an entire passive structure of the LNA including bond wires and via arrays is designed and optimized, with bond wires for interconnection from MMIC chips to microstrip lines and via arrays for grounding between different ground planes. An equivalent π-type model for two-parallel bond wires is analyzed and parameters of the model are extracted. The pitch of via arrays is studied to obtain good grounding performance. To implement an overall simulation of the LNA, EM (electromagnetic)-based data of the full passive structure are exported into ADS and are cascaded with S parameter data of MMIC. The measured results show the LNA has a 20dB gain, a 7dB return loss and a 2.6dB noise figure from 8 GHz to 20 GHz. Good agreement between simulated and measure results is achieved.

In developing low-temperature cofired ceramic (LTCC) technology for high-density packaging or advanced packaged electronics, matching the coefficient of thermal expansion (CTE) among the packaged components is a critical challenge to improve reliability. The CTEs of solders and organic laminates are usually larger than 16.0 ppm of °C1-, while most low-permittivity (εr) dielectric ceramics have CTEs of less than 10.0 ppm °C1-. Therefore, a good CTE match between organic laminates and dielectric ceramics is required for further LTCC applications. In this paper, we propose a high-CTE BaSO4-BaF2 LTCC as a potential solution for high-reliability packaged electronics. The BaSO4-BaF2 ceramics have the advantages of a wide low-temperature sintering range (650-850 °C), low loss, temperature stability, and Ag compatibility, ensuring excellent performance in LTCC technology. The 95 wt %BaSO4-5 wt %BaF2 ceramic has a εr of 9.1, a Q × f of 40,100 GHz @11.03 GHz (Q = 1/tan δ), a temperature coefficient of the resonant frequency of -11.2 ppm °C1-, a CTE of +21.8 ppm °C1-, and a thermal conductivity of 1.3 W mK-1 when sintered at 750 °C. Furthermore, a dielectric resonant antenna using BaSO4-BaF2 ceramics, a typically packaged component of LTCC and laminate, was designed and used to verify the excellent performance by a gain of 6.0 dBi at a central frequency of 8.97 GHz and a high radiation efficiency of 90% over a bandwidth of 760 MHz. Good match and low thermal stress were found in the packaged components of BaSO4-BaF2 ceramics, organic laminates, and Sn-based solders by finite element analysis, proving the potential of this LTCC for high-reliability packaged electronics.

Along with the development of the electrical technology, the power of the circuit rises rapidly, heat dissipation becomes a key problem in the design of the circuit. The 3D microchannel coolers made with LTCC (low temperature co-fire ceramic) technology can absorb the heat of the chip and pass it to the external environment by the liquid circulation. In this paper, the critical manufacturing processes of LTCC multilayer substrate with 3D micro-channel embedded: lamination and sintering are studied mainly. The special lamination sacrificial layer technique can prevent the 3D micro-channel from collapsing and deforming during the lamination. In addition, the sintering profile is optimized which helps avoid the crazing and delamination of the multi-layer substrate. In conclusion, the intact LTCC substrate with 3D micro-channel embedded can be fabricated using the optimized lamination and sintering process parameters, which makes the following heat dissipation experiment and design optimization more conveniently.

Low Temperature Cofired Ceramics (LTCC) has been a popular multi-layer ceramic (MCM) packaging material for many electronic applications. The main advantage with LTCC would be its ability to embed a major part of the electronic circuit within itself, apart from its enhanced RF functionality as against many lossy materials used. The advantages of LTCC in terms of frequency response, cost, ease of fabrication, etc. over many other packaging materials are presented. The applicability of LTCC as a packaging material, circuit mounting material, substrate material or a base material for micro devices is discussed. Low temperature co-fired ceramics (LTCC) is a key technology assets for MEMS/ MOEMS/RF-MEMS packaging. The tolerance of device alignment is the key issue of integration. In order to be able to use mass-manufacturing tools, the primary aim is to process 3D structures, such as, grooves, cavities, holes, bumps and alignment fiducials, which can be used for the passive alignment of devices. The tolerances of LTCC structures are typically ±5μm and in some specific cases ±2μm. Thermal management by the use of thermal vias in LTCC is a well-established technique, and liquid cooling channels in the LTCC substrate provide efficient additional means for high-power laser cooling. When targeting for thermally controlled systems, thermal bridge structures can be used to isolate critical devices from main structures. LTCC provides inherently hermetic substrate allowing for the possibility to hermetic encapsulation. Hermetic fiber feed throughs and transparent windows can be integrated in LTCC structures. Cavities, channels and sealed gas cells can be fabricated, also. RF antennas and coil structures for electro-magnetic field control can be integrated in the LTCC substrate. Therefore, 3D packaging of MEMS and RF MEMS is enabled by LTCC.

In recent years, with the development of wireless communication systems and intelligent auxiliary equipment, the development of various wireless sensors has attracted more and more scientific and commercial attention. A new type of LC (Lenz (inductor) – Capacitor) wireless sensor was designed and fabricated using Low Temperature Co-fired Ceramics (LTCC) technology, including the advantages of low-cost wireless sensing of radio frequency (RF) communications and high operating temperature, miniaturisation, low weight, excellent thermal management, and multilayer printed circuit board of LTCC technology. LTCC technology offers functionalities such as high/low permittivity, low dielectric loss in a single multilayer package and multi-functional features by integration and interconnections. It also offers the highest interconnect density for the fabrication of 3D structures with multilayer additive fabrication of ceramic 2D sheets. In this article, an introduction to the LTCC technology and the mechanism of LC resonance wireless interrogation are overviewed. Then, we summarise the latest developments in wirelessgas, pressure, proximity and microfluidic sensors based on LTCC technology.

Preparation of high-performance Bi-YG ferrite based on LTCC technology and theoretical analysis of its sintering mechanism

A specialized mixing structure incorporating LTCC (Low Temperature Cofired Ceramic) technology was designed and fabricated. Such structures can be applied in a wide range of chemical and biological microsystems. In order to achieve the best fluid mixing efficiency, few different geometries were tested and evaluated. Solutions of phenolphthalein and sodium hydroxide in ethyl alcohol were used in the performed experiments. A customized method of evaluation was proposed and successfully applied. In general, mixing performance varied with shape and dimensions of the mixing structure. The mixing channel technology, evaluation experiment as well as obtained results are presented in this article.

This paper describes technique for the design of Substrate Integrated Waveguide (SIW) filter using multilayer Low Temperature Co-fired Ceramic (LTCC) technology at Q-band frequency region. The design is based on a circular cavity structure operating at TM 010 mode. A single order filter is chosen to demonstrate the feasibility of using in-house LTCC fabrication technology. Measured insertion loss of −1.954 dB and passband return loss of more than 10 dB at 38 GHz were achieved. Good filtering response is observed which shows that SIW filter using LTCC technology is a suitable candidate for implementation of filtering devices for a millimeter-wave uplink/downlink Remote Antenna Unit for a Radio-over-Fibre (RoF) system.