Thick Film Capacitors with Variable Tc on Cu Foils
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1075-J07-10
Thick Film Capacitors with Variable Tc on Cu Foils Byeong Kon Kim1, Dong Joo Shin2, Jun Kwang Song3, and Yong Soo Cho4 1 Materials science & Engineering, Yonsei university, Seoul, 120-749, Korea, Republic of 2 Samsung Electro-Mechanics, Suwon, 442-743, Korea, Republic of 3 Materials analysis team, Korea Testing Laboratory, Seoul, 152-718, Korea, Republic of 4 Materials science & Engineering, Yonsei university, Seoul, 120-718, Korea, Republic of ABSTRACT High k dielectric thick films, consisting of BaTiO3, a low softening glass and fluoride compounds, were studied to apply them as potential low temperature N2-fireable capacitors on commercially-available Cu foils. Different additive combinations of LiF, ZnF2 and BaF2 were specifically compared in terms of dielectric constant, dielectric loss and Curie temperature (Tc) for the purpose of optimizing dielectric performance. The thick film consisting of 95BaTiO31.5LiF-1.5ZnF2-2 bismuth borosilicate glass exhibited the best performance, i.e., a dielectric constant of 2,382 and a dissipation factor of 0.021 at Tc of 27oC at the firing temperature of 950oC. This result can be regarded as one of the best performance, compared to literature reported on embedded capacitors in Cu-PCB applications. No apparent Cu-diffusion was detected across the Cu-thick film-Cu foil structure.
INTRODUCTION New high-performance passive components including capacitors and resistors have been required for successful development of the SOP (system-on-package) technology. There can be two approaches, thin films versus thick films, to embedded capacitors that are applicable for CuPCB substrates [1,2]. It has been recognized, particularly, that the thick film technology is more viable in terms of cost effectiveness and easy-processing as long as it secures a sufficiently high capacitance density. Since high dielectric constant materials such as ferroelectric BaTiO3 and Pbbased relaxors are required for high capacitance density, the control of Tc is believed to be critical in maximizing dielectric performance at room temperature. Several additives having low melting temperatures have been investigated to densify samples at relatively low temperatures below 950oC for the thick film technology utilizing screen printing [3,4]. As one of the solutions to achieve the low temperature densification, low melting glasses or fluoride compounds have been combined with high k BaTiO3 materials [5-11]. For example, Haussonne et al. [9] have reported the effect of 1~2 wt% LiF additions on the dielectric properties of BaTiO3 with variable Ba/Ti ratios. Benziada et al. [10] studied the BaTiO3-BaLiF3 system having a Curie temperature Tc close to 10oC. In this work, several additive combinations based on Bi-borosilicate glass and fluoride compounds were selected for improving dielectric performance of BaTiO3-based thick film capacitors, which were specifically designed for Cu-PCB applications. Understanding of the additive effects on the resultant physical and electrical characteristics of thick film capac
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