Electroless Nickel Plating On The Application Of The Thermal Resistor

PTC thermistor is a kind of semiconductor ceramic components based onbarium titanate（BaTiO₃） as main materials.It is widely used in variouscircuits because of its resistance-temperature characteristics,current-time characteristic and voltage-current characteristics.On theprocess of electrodes on the surface of PTC,need to plate a layer of nickelelectrode on substrate surface using the deposition of electrodes nickelplating and then print silver electrode.Due to the importance of nickelelectrodes properties on electronical properties of PTC thermistor,it isnecessary to study the chemical nickel plating technology and itsformula.At present, Electrodes nickel plating is widely used in indutriessuch as aerospace, chemical, electronic, steel.There are a lot of researchabout nickel plating in the world but few study about electrodes nickelplating on PTC thermistor.This thesis focus on the research of the formula of nickel plating,nickel plating process, properties of nickel electrode and their relatedsystems.On the process of formulation design of nickel plating, we combinedwith the characteristics of PTC thermistor, through experience and effort,first determine the best [Ni²⁺]:[H₂PO^-] molar ratio is0.5. On the basis,we determine Complexing agent、buffer、stabilizer as the best concentrationof stabilizers. In order to reduce contact resistance of electrode, enhancethe resistance to current, voltage capacity of electrode, This study madea bold attempt to add trace copper ion （Cu+） and achieved very good results.As the result, when reducing contact resistance and also enhancing voltagecapability of PTC products.After confirming the formula, throughcontinuous exploration and improvement,we develop a set of matched processand use XRD, AFM, SEM etc modern materials characterization techniques.Westudy the influence of PH value, heat treatment temperature and otherfactors on the properties of electrodes. This study has identified the best formula for nickel plating on PTCThermistors: NiSO₄·6H₂O25g/L,NaH₂PO₂·H₂O20.1g/L,NaCH3COO·3H₂O15g/L,Na₃C₆H₅O₇·2H₂O20g/L,PbAC1mg/L, CuSO₄·5H₂O0.5g/l. Determines theoptimal PH value is5.0and nickel layer thickness1.8².0μ m. Alsoidentified rough melting, activation and sensitization for before nickelplacting and boiling, drying and heat treatment condition for after nickelplating.