Rosidah Alias

Rheological Behaviors and Their Correlation with Printing Performance of Silver Paste for LTCC Tape

Low Temperature Co-fired Ceramic (LTCC) technology has attracted much attention for high frequency applications due to the advantages in preparing 3D circuits within a ceramic block that enables burying of passive elements; resistor, inductor and capacitor (Jantunen et al., 2003). This technology also offers another advantages such as low fabrication cost due to parallel process, utilizing high conducting metal, higher interconnect density, high performance thermal management system, shrinking of circuit dimensions and high level of passive integration (Lin and Jean, 2004; Gao et al., 2010). The LTCC multilayer technology process generally consists of cutting the green tape ceramic into the required dimension, via punching, via filling, screen printing, stacking, lamination and co-firing process. All these steps are important to achieve a good quality of the final structure. Furthermore, LTCC technology requires cofiring process of conductor and ceramic-glass substrate. The co-firing mismatch should be avoided to make sure the resulting product has good appearance. The key point of LTCC technology is the screen printing process of thick-film technology which strongly depends on the optimization of the conductor paste rheological behavior. Besides, the characteristics and the quality of printed conductor lines are greatly affected by some process variables such as screen printing speed, angle and geometry of the squeegee, snapoff and screen mesh parameter including the paste characteristics (Hoornstra et al., 1997; Yin et al., 2008). The performance of the paste depends on the variety of factors including storage, how easily and accurately it can be deposited (printing) and the flow characteristics (rheology) (Nguty and Ekere, 2000). Thick-film paste must maintain good printability throughout the time on the screen and the screen parameters must allow for high throughput and repeatability results (Harper, 2001; Buzby & Donie, 2008). The successful story of making multilayer substrate is depends on this steps. Consequently, a thorough understanding of the influence of the paste rheological behavior and the combination with other parameters is essential if this objective is to be met.

The microstrip coupled line Bandpass filter using LTCC technology for 5GHz wireless LAN application

This paper presents a top-down design of the microstrip coupled line Band pass filter (BPF) embedded in low temperature co-fired ceramic (LTCC) for 5 GHz wireless LAN applications. It includes the design, simulation, fabrication and measurements. The filter circuit was designed and simulated based on Agilent Advanced Automation (ADS2005A) software. Then, the physical dimensions of components and the filter itself is subsequently determined and the physical design is later performed in the layout window of Empire XcCEL. All measured simulations are analyzed and compared to design specifications and characteristics (curve fitting). Any inaccuracy is taken into account where corrected design is further recovered.

Characterization of alumina-based LTCC composite materials: Thermal and electrical properties

The study on Low temperature co-fired ceramic (LTCC) has been widely investigated due to its potential as an advanced approach for packaging of electronics devices. This paper evaluates and discusses about the firing temperatures effect on the densification, thermal and electrical properties of the prepared LTCC material. The LTCC tape, which consists mostly of Al2O3 was fabricated using tape casting technique. Five layers of tapes were then stacked and air-fired at different temperatures of 840, 880, 920 and 960°C. All samples were characterized for thermal and electrical properties. The crystallinity and microstructure of all samples were studied using XRD and SEM respectively. Current investigations show that the changing of density or volume fraction of pores is the main reason for the dielectric properties shift. Meanwhile, the changing in lattice parameters is observed as the main reason in thermal diffusivity shift. The sample fired at 880°C has the best thermal and electrical properties with thermal diffusivity of about 0.62 mm2/s, dielectric constant (εr) of about 5.65 and dielectric loss, tan (δ) of about 0.003.

Design of Interdigital Band Pass Filter for WLAN applications using LTCC technology

The paper presents the design of Interdigital Band Pass Filter (IBPF) for WLAN applications at center frequency 2.45GHz. It was designed using a 3D EM simulation tool and fabricated on substrate Ferro A6S by using in-house process of Low Temperature Co-fired Ceramic (LTCC) technology. Simulated and measured results were presented. The pass band insertion loss of the filter was measured to be −1.66dB at 2.45GHz within the specification, S21< −3dB. The return loss was measured at −15.57dB which better than specification, S11>−10dB.

Microstructure for Printed Multilayer LTCC Tape of Different Paste Rheology

Screen printing is the most common method of transferring silver thick film paste to a low temperature co-fired ceramic tape. Silver paste with varying rheology will have a varying print quality. The effect of silver paste rheology on the microstructure is investigated. Although there are many parameters to be considered, this parameter is a critical parameter which will control the line width and roughness on the substrate. To study the effect of paste rheology, a test pattern design was printed on the Heraeus CT2000 LTCC tape using silver paste. Then the LTCC tape was stacked and laminated at pressure of 28 MPa and temperature of 65 oC for 10 minutes. The laminated sample then was fired up to 850 oC. The fired silver conductor printed on the LTCC tape then was analyzed. Prints were evaluated by scanning electron microscopy. It was found that silver paste with high viscosity produce a good microstructure.

Designing 5GHz microstrip coupled line bandpass filter using LTCC technology

A top-down detail design of a 5 GHz micro strip coupled line band pass filter in LTCC is presented in this paper. LTCC, which stands for low temperature co-fired ceramic is especially used for wireless and high-frequency applications. Now, the importance of LTCC is becoming more prominent in views of the fact a lot organizations has been funding R&D-projects regarding this new technology that focuses on larger implementation of functionality in LTCC substrates. Although Malaysia is new to this technology, its industry has certainly high hopes on the LTCC innovation to make a breakthrough and contribute significant benefits to the technology, industry, market and also, the country itself. The filter circuit was designed and simulated by using ADS2005A. Then, the physical dimensions of components and the filter itself is subsequently determined and the physical design is later performed in the layout window of Empire XcCEL. All measured simulations are analyzed and compared to design specifications and characteristics (curve fitting). Any inaccuracy is taken into account where corrected design is further recovered.

Defect Observation of Embedded Components of a Low Temperature Co-Fired Ceramic

This paper reports observations of defects in laminated eight layers of a glass-ceramic composite system fabricated by a standard low temperature co-fired ceramic (LTCC) technology. The layers were laminated at 3000 psi and 70 °C for 10 minutes and were fired at 850 °C for 15 minutes. Material characterizations of the green compact and fired substrate were carried out on density, surface roughness and microstructure. The crack and warpage of the substrate were related to the microstructure and densification process of the system. It was found that the presence of these defects could be due to a mismatch of the sintering kinetics of the glass-ceramic composite system and silver conductor materials which lead to the development of stresses which act on both materials. The detailed microscopic observation of the internal and surface defects is explained.

Screen Printing Parameter Effect on the Surface Roughness Measurement of Printed Gold Paste on LTCC Tape

Effect of screen printing parameter such as squeegee speed was studied in this paper for the surface roughness of gold paste on the Ferro A6M LTCC tape. Roughness measurement was evaluated by 3D profilometer of the Ferro A6M LTCC tape co-fired with Au conductor paste.

The Effects of Sintering Temperature Variations on some Physical Properties of Al2O3-SiO2-PbO-MgO Laminated Tape System

An Al2O3-SiO2-PbO-MgO laminated tape system was prepared to investigate the dependence of some physical properties on various sintering temperatures, 840 °C, 880 °C, 920 °C and 960 °C. The results show that the effect of the increasing sintering temperatures was a fluctuating in the density value of the laminates. It was also observed that the dielectric constant and dielectric loss showed the lowest value for the sintering temperature of 880 °C. SEM micrographs of the laminate samples shows a mixture of grain sizes and the samples had a combination of small and large pores with the average grain size around 2.20-2.64 m.

Methods of measurement of LTCC metallization thickness

Metallization provides electrical routing and serves as thermal via in LTCC (Low Temperature Cofired Ceramic) technology. High electrical and thermal conductivity is desirable. It is often achieved with the use of low electrical resistance materials, such as gold, silver and copper. The conductive paste made of these materials is expensive. Hence, the fabrication of LTCC has to be performance-wise and cost effective. The width, length and thickness of metallization are associated with the amount of conductor paste used. The thickness of metallization governs the functionality and performance of some components, such as resistor. In this paper, the physical attributes of LTCC substrate and its metallization was studied. Due to the constraint brought by the physical attributes of LTCC samples, various methods had been carried out. This paper also summarized the pros and cons of each method. The methods are limited to the equipment available.