LTCC Materials Research Articles

Development of New LTCC Material for Low-k/Ultra Low-k Device

Development of New LTCC Material for Low-k/Ultra Low-k Device

Thermal and dielectric properties of glass-ceramics sintered based on diopside and anorthite composition

To develop a low dielectric constant of LTCC substrate, we studied the effect of the sintering and crystallization behavior on the dielectric properties of a sintered body by mixing a CaO–Al2O3–SiO2 frit and a CaO–MgO–SiO2 frit for a low dielectric constant of LTCC substrates. In this work, the two glass frits were mixed at different proportions and sintered at 860~920°C. After sintering at 900oC for 1h, the glass frits crystallized into diopside and anorthite. The sintered bodies exhibited dielectric properties, ɛr = 6~8.6 at 1 GHz, which is an essential condition for a substrate in microwave devices. The results suggest that the glass-ceramic can be applied to low dielectric LTCC materials in the electronics packaging industry.

Preparation and Characterization of Low Temperature Sintered Alumina by CuO-TiO2-Nb2O5-Ag2O Additives

For the purpose of enabling the low-temperature sintering of alumina, the addition of Ag 2 O to CuO-TiO 2 -Nb 2 O 5 type sintering additive was examined. The use of CuO-TiO 2 -Nb 2 O 5 -Ag 2 O type sintering additive by 5 wt% enabled the low-temperature sintering of alumina at 860°C. It is presumed that the formation of Cu 4 TiNb 4 O x solid solution has an important role for low temperature sintering of alumina. The obtained sintered material showed high thermal conductivity of 18 W/mK, higher than that of conventional LTCC materials, and that the material could be co-fired with silver electrodes.

Fabrication of Ba-Ti-B-Si-O Glass-Ceramics for LTCC

This paper studied the dielectric performances and microstructure of the Ba-Ti-B-Si-O glass-ceramics fabricated with different methods. The experimental results showed that the pre-calcined method was an effective way to decrease the sintering temperature in glass-ceramic fabricating process, and the dielectric properties of the LTCC materials were εr ≈10, tanδ ≤ 2×10-3 (@1MHz). This study provided a composite method to fabricate LTCC for different applications that was composed of pre-calcined powders and molten powders with different ratios; Moreover, the dielectric constant and sintering performance of composite LTCC were adjustable by changing the ratio of pre-calcined powders and molten powders.

Low-temperature sintering and microwave dielectric properties of ZnTiO3-based LTCC materials

The low-temperature sintered microwave dielectric ceramics with composition of ZnTiO3-0.25TiO2 were prepared by adding a small amount of low-melting compounds CuO-V2O5-Bi2O3 (CVB). The phase relationship and dielectric properties as a function of sintering temperature and the additional amount were studied. It is demonstrated that the addition of low-melting CVB can suppress the formation of Zn2TiO4 at low temperature, but decrease the decomposition temperature of ZnTiO3. The sintering temperature has a significant effect on the stability of ZnTiO3 and dielectric properties of sintered ceramics. CVB addition can promote the densification of ceramics through liquid-phase sintering. The dense 2wt% CVB-doped ZnTiO3-0.25TiO2 ceramics prepared at 850 °C have excellent dielectric properties of ɛ = 30, Q×f = 32,000 GHz, and τf = +12 ppm/ °C.

LTCC system with new high- ɛr and high- Q material co-fired with conventional low- ɛr base material for wireless communications

The authors have developed a new LTCC material with characteristics of high dielectric constant ( ɛ r), high quality factor ( Q) and low temperature coefficient of capacitance (TCC). This material can be co-fired with a conventional base LTCC material and buried resistors with low temperature coefficient of resistance (TCR). The base material which consists of Al 2O 3 filler and glass, has low ɛ r of 8.7 at 3 GHz. The newly developed LTCC material, which consists of Ba–(Re)–Ti–O filler, Al 2O 3 filler, and glass, has the following characteristics of ɛ r of 15.1, Q of 900 at 3 GHz, and TCC of −10 ppm/K. The buried resistors consist of RuO 2 and glass. Two different LTCC materials, a resistor material and a silver electrode paste can be co-fired as multi-layer substrates and are regarded as a new LTCC system. Constrained sintering could be applied to this LTCC system and the dimensions of substrates could be controlled with quite high accuracy. This LTCC system is expected to contribute to further miniaturization of RF circuits and the reduction of electrical loss.

A LTCC Material with Low Temperature Coefficient of Resonance Frequency

For high frequency packaging applications, LTCC materials are required to have a low loss tangent to reduce the total microwave loss. For multi-layered ceramic devices with embedded passive components, besides a loss tangent, a small temperature coefficient of resonance frequency (TCF) is an important factor. To meet these demands, we developed a new LTCC material with a smaller TCF, less than +/-3ppm/oC, and a low loss tangent, 0.0012 at 15GHz. We designed the glass composition to precipitate two low-loss crystal phases during firing at 900 oC. One phase has a plus TCF and the other phase has a minus TCF. We also controlled the amount of the two crystal phases, so these crystal phases and the fixed amount of alumina filler make the sum of TCF for the LTCC material close to zero.

Ca[Ti1-x(Ni1/3Nb2/3)x]O3세라믹스의 저온소결 및 마이크로파 유전특성

The microwave dielectric properties and low temperature sintering of Ca［Ti 1-x (Ni ⅓ Nb ⅔ ) x ］O₃ system were investigated at the sintering temperature 1,200~1,350℃. The density and quality factors (Q×f) increased while dielectric constants slightly decreased with the decrease of Ti. The dielectric constant, quality factor, and temperature coefficient of resonance frequency (τ f ) were 64, 17,000 ㎓, and -9.1 ppm/℃ respectively, when CaTi ½ (Ni ⅓ Nb ⅔ )O₃ ceramics were sintered at 1,300℃ for 4 h. 2Li₂O-B₂O₃ was added to CaTi ½ (Ni ⅓ Nb ⅔ )O₃ to decrease the sintering temperature for LTCC application. The microwave dielectric properties of the samples sintered at 925℃ for 2h with the addition of 6 wt% 2Li₂O-B₂O₃ were e r ＝48.7, Q×f＝8,460 ㎓, and τ f ＝＋5.6 ppm/℃, Compatibility test of the composition with silver electrode shows no reaction with silver electrode, implying the feasibility as a high-K LTCC material.

Novel microwave dielectric LTCCs based uponV 2O 5 doped M 2+Cu 2Nb 2O 8 compounds (M 2+ = Zn, Co, Ni, Mg and Ca)

The copper-niobates, M 2+Cu 2Nb 2O 8 (M 2+ = Zn, Co, Ni, Mg or Ca) have good microwave dielectric properties when sintered between 985–1010 °C and 1110 °C for CaCu 2Nb 2O 8. Therefore, they would be potential dielectric LTCC materials if they could be made to sinter below 960 °C (melting point of silver). To this end, additions of 3 wt.% V 2O 5 were made to ZnCu 2Nb 2O 8, CoCu 2Nb 2O 8, NiCu 2Nb 2O 8, MgCu 2Nb 2O 8 and CaCu 2Nb 2O 8, and their sintering and dielectric behaviour was investigated for samples fired between 800 and 950 °C. Doping lowered sintering temperatures to below the 960 °C limit in all cases. Doping had the general effect of reducing ɛ r, density, Qf and τ f, although doped CaCu 2Nb 2O 8 had a Qf value of 9300 GHz, nearly four times that of the best undoped sample. Doped ZnCu 2Nb 2O 8 fired to 935 °C had Qf = 10,200 GHz, and for doped CoCu 2Nb 2O 8 fired to 885 °C Qf = 7500 GHz. When doped and undoped samples all fired to 935 °C were compared, all doped samples had greater ɛ r and density, and all except ZnCu 2Nb 2O 8 had a smaller τ f. All doped samples had a more linear relationship between frequency and temperature in the range 250–300 K.

Low-sintering ceramic materials based on Bi 2O 3–ZnO–Nb 2O 5 compounds

In this work, sintering behaviour of Bi 2O 3–ZnO–Nb 2O 5 compounds was investigated in order to develop LTCC materials with suitable microwave properties. Structure, dielectric properties and sintering were studied for ceramic dielectrics based on the system: Bi 2ZnNb 2O 9 with the pyrochlore structure and ZnNb 2O 6 with a columbite one. The work was carried out over a wide range of initial components concentration. Ceramic samples of these materials were prepared by the mixed oxide technique. The effect of adding glass to the materials have been discussed. The sintering behaviour, dielectric permittivity, quality factor and crystal structures have been characterized for ceramic samples depending on compositions. Low-temperature co-firable ceramic material with ɛ ∼ 30, τ ɛ = 0 and Q × f = 3500 GHz based on the above system was synthesized.

Co-firing of Low- and Middle Permittivity Dielectric Tapes in Low-Temperature Co-fired Ceramics

AbstractCompatibility in cofiring low-κ and middle-κ based on a same glass composition for the hybrid LTCC material systems was investigated. Designing of appropriate lithium borosilicate glass frit systems allowed us to develop an optimized glass frit system used for low-κ and middle-κ dielectric fillers, commonly. The effects of glass addition on the densification and electrical properties in low-κ and middle-κ dielectric materials were also examined. Controlling glass compositions and contents we tried to match low-κ and middle-κ tapes physically and chemically.

Material properties and RF applications of high k and ferrite LTCC ceramics

The continuous trend in modern electronic applications towards smaller size, higher integration density and enhanced functionality requires new materials, which allow embedding passive functions into the substrate. In this paper an LTCC material system with specialized dielectric and magnetic LTCC tapes cofireable in a low-shrinkage process for RF-passive integration is reported. An LTCC dielectric with a dielectric constant of up to 80 is presented. The material is successfully used in a cofired multi-material stack to realize a fully integrated band-pass filter for Bluetooth applications of 1.3 mm 3 volume. A ferroelectric LTCC ceramic with a maximum dielectric constant of 3000 is presented and the reduction of the dielectric constant to a maximum value of 1100 under constrained-sintering is discussed. Magnetic permeabilities of 14 for a NiZnCo-ferrite and 3.5 for a Ba 3Co 2Fe 24O 41 (Co 2Z) ferrite have been realized under LTCC processing conditions, with gyromagnetic resonance frequencies above 1 GHz and 3 GHz respectively. The permeability of these materials is determined for constrained and unconstrained sintering conditions. A maximum absorption of 27 dB/cm and 30 dB/cm is measured for an embedded stripline in NiZnCo- and Co 2Z ferrite respectively. Two-winding planar RF-chokes in different multi-layer stacks are compared. A maximum of 14.3 nH inductance is realized for a 1.8 mm × 2 mm coil in an LTCC research pilot line.

New Generation of LTCC Materials

To reduce the complexity of LTCC systems and so accelerate the development of LTCC tapes with new functionalities it is necessary to reduce the number of phases within a particular tape. This can best be done by using glass-free single-phase ceramic systems. Such a material system consisting of low- and high-permittivity LTCC materials was developed based on Bi eulytite (permittivity; K'=16) and sillenite (K'=40) compounds and the δ-Bi 2 O 3 solid solution with Nb 2 O 5 (K'=90). The Ge and Si analogues of the sillenites and eulytites, and the 0.75Bi 2 O 3 .0.25Nb 2 O 5 solid solution meet the main requirements for LTCC with respect to their sintering behavior (T s =850-900°C), their mutual chemical compatibility, their compatibility with a silver electrode as well as their dielectric properties.

Effects of composition on low temperature sinterable Ba–Nd–Sm–Ti–O microwave dielectric materials

This work investigated the effects of MgO and ZnO additives on the microwave properties of BRT 114=[(BaO·R 2O 3·4TiO 2)·0.06(2Bi 2O 3·3TiO 2)] materials. Incorporation of small amount of ZnO (≦1 wt.%) markedly lowered the temperature coefficient of resonant frequency ( τ f ), to around τ f ≒1 ppm/°C, slightly increased the density and dielectric constant ( ε r ) of the materials, but degraded the Q× f factor . Doping 2.5 mol% of MgO, in addition to ZnO, further improved the τ f -value for the BRT 114 materials. The dielectric constant and the Q×f factor of the materials degrade pronouncedly when doped with too abundant ZnO. Microstructure and EDX analyses indicated that the main factor for degrading the microwave properties is the induction on formation of secondary phases. Moreover, sol–gel and fused Ba–B–Si glass reacted with BRT 114 in quite a different way. Fused glass wets BRT 114 materials more easily than the sol–gel derived glass, resulting in composite materials with higher density and larger dielectric constant. Precalcining the glass-dielectrics mixture, greatly improved the wetting ability of the glass and markedly increased the microwave properties of the glass/dielectric composite, i.e. LTCC materials.

Glass-free low-temperature cofired ceramics: calcium germanates, silicates and tellurates

To reduce the complexity of LTCC systems, and so accelerate the development of LTCC tapes with new functionalities, it is necessary to reduce the number of phases within a particular tape. This can best be done by using glass-free single-phase ceramic systems. We performed a basic characterization of several low-temperature-sintered calcium silicates, germanates and tellurates in order to evaluate their potential as glass-free low-permittivity substrate LTCC materials. Special attention was focused on their microwave and 1 MHz dielectric properties, their sintering behavior and their compatibility with Ag. Two Ca-germanates, which were found to be the most interesting for LTCC applications exhibit a permittivity of ∼10 and low dielectric losses; however, the temperature dependence of permittivity and the sintering temperature must be further reduced. For CaGeO 3 the temperature dependence of permittivity was fully suppressed by the addition of 10 mol% of CaTiO 3.

Measurements of loss tangent and relative permittivity of LTCC ceramics at varying temperatures and frequencies

Abstract Precise knowledge of microwave properties of LTCC materials is crucial for efficient design of microwave systems, especially for design of communication filters. In this paper relative permittivity e r and loss tangent tan δ of a variety of LTCC ceramics manufactured by Heraeus Circuit Materials Division are presented for frequencies of 3.3 and 5.5 GHz at room temperature and also for temperatures varying from −33 °C to 22 °C at a frequency of 3.3 GHz. The measurement system for microwave characterisation of LTCC materials was based on the split post dielectric resonator and the Transmission Mode Q -factor techniques with random uncertainty in e r and in tan δ better than 0.5 and 2.6% respectively.

Effect of processing route on thermomechanical properties of low temperature firing ceramic for electronic packaging

Mechanical properties and thermal expansivities of two compositionally identical ceramics intended for use in 'low temperature cofired ceramic' (LTCC) technology were investigated. Both were based on a commercial MgCaTiO3 dielectric ceramic with the sintering temperature reduced by addition of ZnO-B2O3-SiO2, either in the glassy state or as separate glass forming oxides. Although in each case the additions were accompanied by decreases in elastic modulus, flexural strength, hardness, fracture toughness, and linear thermal expansivity, the values remained close to those for commercial LTCC materials. The route which involved mixing the separate oxides produced a slightly tougher material, which also had a thermal expansivity closer to the optimum value. The study demonstrates that an acceptable LTCC ceramic can be produced starting from glass forming oxides as sintering aids, thus avoiding the need for glass melting and comminution steps.

Measurement techniques for the evaluation of thick‐film materials used in wireless applications

A review of the dielectric measurement techniques that are currently available for the characterization of thick film and LTCC materials at microwave and millimeter wave frequencies is presented. The intention is to show the relative advantages and limitations of the various methods, and to provide some practical guide to the particular technique that is most suitable for a given type of material, for use in a particular application. In addition, a novel slit cavity resonator method is proposed to enable substrate parameters to be more easily measured, whilst retaining high measurement accuracy. Measured data on materials from a variety of manufacturers are presented to show the validity and usefulness of this method.

New cost-effective LTCC materials from Ferro

New cost-effective LTCC materials from Ferro

A6 S Microwave LTCC materials system for high frequency low cost applications

A6 S Microwave LTCC materials system for high frequency low cost applications