Low-temperature deposited Cu electrode on chip inductors by abnormal glow discharge plasma with arc source Yaowen Wang a, * , Hongguo Zhang b , Qiang Chen a , Junde Pan c , Longtu Li b a Mechanical Engineering Department, Tsinghua University, Beijing 100084, China b State Key Laboratory of New Ceramics and Fine Processing, MSE Department, Tsinghua University, Beijing 100084, China c Taiyuan University of Technology, Taiyuan 030024, China Received 3 July 2000; received in revised form 23 July 2001; accepted 4 August 2001 Abstract A new preparation method of Cu electrodes of chip inductors by an abnormal glow discharge technique with arc source at low temperature is presented. SEM observed the microstructure of the Cu electrode joints and EDX detected the interfacial diffusion between the electrodes and the ceramic matrix. The results show that the new technique can effectively suppress interfacial diffusion and Cu oxidation whereas reserve good adhesion in the electrode layer due to low deposition temperature, which can be achieved by suitable control of glow discharge voltage. Consequently, the compromise magnetic properties of the samples can be obtained. D 2002 Published by Elsevier Science B.V. Keywords: Abnormal glow discharge; Electric arc; Low-temperature deposition; Cu electrode; Chip inductors 1. Introduction Recently, the surface mounting devices, of which multilayer chip inductors (MLCI) are one of the most important passive components, has been rapidly developed in modern electronic industry. Polycrystal- line ferrite ceramics are increasingly being used in fabricating chip inductors due to their low cost and high properties [1–4]. With the rapid development of the preparation of ferrite ceramics, the joining tech- nology of ferrites to metal electrode materials should also keep pace. However, because of the thermal expansion mismatch and the surface energy distinc- tion between the ferrite and the electrode metal, the high residual stress between them readily causes unreliable joints, and consequently degrades the prop- erties of chip inductors. Therefore, developing the ferrite-electrode joints with high quality and high reliability is becoming increasingly crucial. Ag or Ag–Pd alloy pastes are usually used as electrode-joining material by means of various print- ing processes [5]. Nevertheless, high temperature cofiring causes unexpected lowing of the inductance due to interfacial diffusion and reaction between the ferrite and the Ag electrode. Moreover, the cost of Ag and Pd is so high that the expense of fabricating MLCI rises sharply. Therefore, the applications of cheap metal electrodes (Cu or Ni) and low cost electrode-fabricating methods at a temperature lower than the cofiring temperature of MLCI have become more and more interesting in recent years. In this letter, a novel method is presented, in which the deposition of Cu electrodes on ferrite ceramics by 0167-577X/02/$ - see front matter D 2002 Published by Elsevier Science B.V. PII:S0167-577X(01)00566-3 * Corresponding author. E-mail address: eywwang@ntu.edu.sg (Y. Wang). www.elsevier.com/locate/matlet May 2002 Materials Letters 54 (2002) 217 – 221