Through <NTC Thermistor for Substrate-1> and <NTC Thermistor for Substrate-2>, we learned the basic situation of NTC thermistor for substrate. Now, let’s introduce its manufacturing methods. This method includes the production of NTC thermistor billet of internal electrode and the formation of external electrode on the NTC thermistor billet. The specific actions are as follows:
Production of NTC thermistor billet of internal electrode
1. Add organic adhesives to the presintering raw material powder and mix them into slurry as needed;
2. Doing shape forming with Knife Coating method, making ceramic raw slices;
3. The internal electrode with conductive paste on the ceramic raw slices for screen printing, forming electrode pattern;
4. After stacking a plurality of ceramic slices with electrode patterns, the ceramic raw films that are not printed with electrode patterns are clamped and pressed up and down, thus making the laminated bodies;
5. The obtained laminated body is treated with a debonding agent and sintered to create a thermistor billet with an alternating of internal electrodes and thermistor billet layers.
Formation of external electrode on the NTC thermistor billet
1. The two end surfaces of the thermistor billet alternating of internal electrodes and thermistor billet layers are impregnated in the conductor paste and sintered to form the first electrode layer;
2. By sputtering method, a pair of second electrode layer are formed on each main surface of thermistor billet that one end connect to one end of the first electrode layer, a pair of second electrode layers that the other end is extending along the direction of the other end surface; And one end connect to the other end of the first electrode layer, an other pair of second electrode layers that the other end is extending along the direction of the other end surface.
3. The third electrode layer is formed by electrochemical plating method.
After forming the second electrode layer, the external surface of the central part of the thermistor billet, that is, the non-covering area which is not covered by the second electrode layer, is removed by acid treatment, grinding treatment, electroplating treatment or grinding treatment. Thus, when electroplating treatment used to form the third electrode layer, it’s able to suppress the production of island-like electroplating in the central part of the thermistor billet.
Only the forming of the second electrode layer is flatter than the first electrode layer can form the third electrode layer flatly, and can prevent unnecessary clearance between the NTC thermistor and the sealing body in the installation of the built-in substrate of the components. In addition, the directional stability of the reflected light of the laser and the stable shape of the through hole can also be obtained.
According to this method, it is able to provide NTC thermistor which can be easily embedded in the built-in substrates of components.