Journal of Alloys and Compounds 478 (2009) 858–862 Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jallcom Synthesis and characterization of CBS glass/ceramic composites for LTCC application Guo-hua Chen ∗ , Lin-jiang Tang, Jun Cheng, Min-hong Jiang School of Information Materials Science and Engineering, Guilin University of Electronic Technology, Guilin 541004, PR China article info Article history: Received 6 August 2008 Received in revised form 16 November 2008 Accepted 19 November 2008 Available online 24 December 2008 Keywords: Glass–ceramics Sintering Dielectric properties Thermal expansion X-ray diffraction SEM abstract CBS (CaO–B 2 O 3 –SiO 2 ) glass/cordierite (Mg 2 Al 4 Si 5 O 18 ) ceramic composites were prepared using standard ceramic process. Effects of cordierite on crystallization behavior of the CBS glass powder were investi- gated. Results showed that crystalline phases like pseudowollastonite (CaSiO 3 ) and quartz (SiO 2 ) were formed during the firing of glass alone. For the composites with ≥45 vol. % cordierite at 780–1200 ◦ C, the above crystalline phases were completely prevented but new phase of anorthite (CaAl 2 Si 2 O 8 ) was formed. For all the composites, the intensity of peaks characterizing cordierite gradually decreases and that of characterizing anorthite synchronously enhances with increasing sintering temperature. Microstructural changes of all the samples with sintering temperature were in good agreement with the relative den- sity and an optimum firing temperature for maximum densification existed for each glass/ceramic ratio. The thermal expansion coefficient (TEC) of the composites decreases with increase in cordierite ceramic volume percent. The TEC of all the composites was in the range of 2.2 × 10 -6 K -1 to 5.2 × 10 -6 K -1 . The dielectric constant of the fabricated composites was between 5.2 and 6.2. The precipitation of anorthite has no bad effect on the dielectric constant and the TEC of the resulting composites because anorthite has low dielectric constant (6.2) and low thermal expansion coefficient (4.82 × 10 -6 K -1 ). The prepared glass/ceramic composites were well suited for LTCC application. © 2009 Published by Elsevier B.V. 1. Introduction It has been well documented that materials for electronic pack- aging application should meet stringent requirements in terms of dielectric, electrical, thermal, and mechanical properties [1–3]. Cur- rently, low-temperature co-fired ceramic (LTCC) substrates with a low dielectric constant (k < 10) and thermal expansion coefficient (TEC) matching that of silicon (3.1 ppm/ ◦ C) are widely accepted as materials for electronic packaging [4–6]. Commercially available LTCC systems are either glass/ceramic or glass–ceramic. Controlled crystallization in the case of crystallizable glass based glass/ceramic LTCC shows: (1) improved mechanical behavior due to reduction in effective glass content and (2) lower dielectric constant, loss, and TCE due to crystallization of suitable phase from the glass matrix [7]. Most commercial crystallizable glass type LTCC systems are based on cordierite glass–ceramics [8,9]. Recently, CaO–B 2 O 3 –SiO 2 glass–ceramics as a candidate substrate material in the electronic packaging field are investigated due to its low sintering and a rel- atively low dielectric constant (6.5), but the thermal expansion coefficient is relatively high (8.0 × 10 -6 K -1 ) [10,11]. This, in com- ∗ Corresponding author. Tel.: +86 773 5601434; fax: +86 773 5605903. E-mail addresses: cgh1682002@163.com, chengh@gliet.edu.cn (G.-h. Chen). bination with crystalline filler materials, can be tailored to achieve the required properties for LTCC substrates. Identification of suitable ceramic filler for a glass/ceramic composition is equally important as it determines the substrate properties [12]. This filler may also influence the crystallization behavior of glass. For the present study, cordierite was chosen as the filler material in view of its low dielectric constant and TEC. In this paper, we report the details of synthesis, characterization, and phase evaluation of crystallizable CBS glass in the presence of cordierite as a ceramic filler for LTCC application. 2. Experimental procedure 2.1. Preparation of glass and ceramic Low-softening CBS glass with the composition 30–50 wt% CaO, 15–25 wt% B2O3, 35–40 wt% SiO2, 1–3 wt% (ZnO + P2O5) was prepared by melting powders contain- ing appropriate amounts of reagent grade SiO2,H3BO3, CaCO3, NH4H2PO4 and ZnO in an corundum crucible for 1 h at 1320 ◦ C in an electric furnace. The melt was rapidly quenched in distilled water, crushed and ground into fine glass powders (D50 =2 m). The softening point of CBS glass is about 700 ◦ C. MgO, Al2O3 and SiO2 (+99%) were used to synthesize a stoichiometric cordierite ceramic powder. Magnesia was preserved in a desiccator to prevent moisture absorp- tion. The raw materials were mixed together in absolute ethanol and milled for 24h in a planetary ball mill. The mixtures were completely dried in an oven at 120 ◦ C and sintered at 1400 ◦ C for 5 h to obtain cordierite. The calcined ceramic was placed in a corundum container and ball milled for 8 h to obtain desired particle size (D50 =4 m). 0925-8388/$ – see front matter © 2009 Published by Elsevier B.V. doi:10.1016/j.jallcom.2008.11.163