PTC Thermistor Chip Production Process
Ceramic PTC thermistor basic formula： 【（Ba0.71Pb0.25Ca0.04）Ti1.0103+0.11%(mol)Nb2O5】+0.04%(mol)MnO2+0.06%(mol)Sb2O3+0.5%(mol)SiO2+0.167%(mol)Al2O3+0.1%(mol)Li2CO3。
Polymer PTC thermistor basic formula: Polymer organic polymer (polyolefin, epoxy resin) + Addition of conductive particle materials (carbon black, carbon fiber, metal powder, metal oxide)
1. Preparation Of Powder
Due to the particle size of the powder and the mixing uniformity of the ingredients, will directly affect the PTC function, ceramic firing temperature, quality and performance, according to the maturity of traditional technology, the preparation of the PTC thermistor powder takes the traditional solid phase method. The method has the production equipment is relatively simple, the quality of the product is easier to control, the investment is small and the economic benefits are good. through the vibration mill or grinding mill on the raw materials for grinding, refining, powder particle size of the technical requirements, thus facilitating the sintering and solid phase reaction.
The raw materials were weighed and mixed at a temperature of 1250 ° C for 2 hours. can reduce shrinkage during the final sintered ceramic article, but also can eliminate the raw materials in the high temperature decomposition and crystal transformation, eliminate the difference in volume changes, improve the performance of raw materials.
In the manufacture of PTC thermistor chip, It is generally desirable to obtain ultrafine raw material particles, but the finer powder, the greater the surface area, the worse the liquidity, dry pressure molding can not even fill the mold, often appear molded parts empty, corners are not dense, spallation, elastic effects and other issues, need to use granulation process to solve these problems. granulation process is the grinding of the powder, after drying, plus adhesive, made of good mobility, particle size of about 0.1mm particles.
Dry pressure molding is the method of pressing the powder into a geometric size body, through forming presses and molds, is the most widely used a molding method. Dry pressing production of high efficiency, short production cycle, the process is simple, easy to achieve mechanical automation, forming the size of high precision, small sintering shrinkage, not easily deformed, applicable to sheet-like and other simple geometric shape of the body molding. mold selection, the product size is 30 × 20 × 2mm, the size of the mold to relax a little, the body will shrink when sintering, while preventing loss in the later cold working.
Sintering method: Atmospheric pressure sintering firing system:
① heating stage: to a faster speed to the highest sintering temperature (about 1250 ℃) speed of about 300 ℃ / h. The critical temperature range in the heating stage is 1150 ℃ ~ 1350 ℃, take the rapid warming
② insulation stage: insulation time should not be too long, holding time is about 30min
③ cooling stage: the general cooling with the furnace.
6. Upper Electrode
PTC sheet to the upper electrode, commonly used methods are: infiltration firing method, a chemical plating method and vacuum evaporation method, my company am using silver plating method, forming a metal electrode of the PTC thermistor element,for future testing and use.
Cleaning usually use hydrogen fluoride, trichloroethane or tetrachlorethylene and other cleaning agents are suitable for cleaning, the same can be used ultrasonic cleaning method, However, some of the cleaning agents may impair the performance of the thermistor.
In Ya Xun, equipped with automatic manufacturing equipment, it provided strong support for the development and research products. satisfy the global thermistor supply, effectively reducing costs.
Ya Xun commonly used manufacturing equipment:
Weighing equipment JD-4000-2: Weighing range is usually 0.0001g ~ 120g
Powder grinding equipment: High-speed vibration ball mill SFM-3
Raw material mixing equipment: Vertical planetary mixer SFM-2
Sintering equipment: Protection atmosphere resistance furnace KSL1600X-H2
Cutting equipment: Desktop diamond cutting machine STX-202
Grinding and polishing equipment: Precision grinding and polishing machine unipol-802
PTC film cleaning equipment: Ultrasonic cleaner EQ-VGT-1620QTD-220V
PTC testing equipment: Automatic testing PTC thermistor sorting machine
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