Preparation of the electroplating resist for NTC thermistors

• Main Authors: Yi-hung Lin, 林奕宏
• Other Authors: Hsing-I Hsiang
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/19116520137648605194

碩士 === 國立成功大學 === 資源工程學系碩博士班 === 96 === 　　Owing to the prevalence of portable electronic device in recent years, the development of electronic components trends towards thinner, smaller and much surface adherent. It turns out to ferment the demand for NTC thermistor. When producing NTC termination electrodes, in order to enhance the solder property, we have to 1) attach silver electrodes to components about 40~50μm thickness, 2) co-fire in 600℃∼650℃, and finally 3)coat Ni-layer with 2∼4μm thickness and Sn- or Sn-Pb layer with 5∼10μm thickness. However, NTC thermistor is of semiconducting ceramics, resulting in the diffusion phenomenon in electroplate layer during electroplating. 　　In this research, on the surface of NTC thermistor, we employ phosphate ion conversion treatment, by the reaction of phosphate ion and (Co,Mn)(Mn,Co)2O4, to construct manganese phosphating protection layer, which is resistance and defending for the corrosion due to electroplate liquid. Moreover, we also investigate 1) the effect with respect to the variation of sorts of accelerator and the variation of accelerator concentration, and 2) the influence on the surface structure and material property of manganese phosphating layer by changing temperature and time of conversion treatment. In consequence, on the surface of NTC thermistor, ideal MnPO4•H2O layer can be constructed by 1) utilizing the solution of manganese phosphating as the conversion treatment liquid in which Zn+2 ions are added as accelerator, and by 2) 90℃ and 1 hour conversion treatment. The mechanism of layer producing is in that 1) first the Mn-rich region in the composition of NTC thermistor is dissolved, 2) Mn+3 ions from manganese phosphating solution thus react with PO43- ions within the solutions, and 3) finally the Ni-rich region in the composition of NTC thermistor precipitates MnPO4•H2O, forming the manganese phosphating layer.