Using the existing formula and technology, NTC chip can only achieve ultra-low resistance value, ultra-low B value, that is, the resistivity to achieve 0.3 to 0.6 (kΩ.mm), then the B value can only do 2700 to 2900K. If the B value is small, it will result in poor sensitivity and inability to meet the special requirements of the customer. In order to overcome the shortcomings of existing technology, EXSENSE Electronics introduces a low-resistance-value high-B-value NTC chip，which has better linear and can be used in a wide temperature range. This chip has a resistivity of 0.3 to 0.6 (kΩ.mm), and the B value is 3250 to 3400K. It is manufactured as follows:
1) Ratio of materials: MnO25-45%, CoO30-50%, CuO5-10%, MgO1-5%, CrO1-5%, TiO1-5%;
2) Preparation of ceramic slurry: First, the above materials are mixed into powder according to the weight percentage; Then, add ethanol, adhesive, dispersant to make the slurry; Among them, the weight ratio of powder: ethanol: adhesive: dispersant is 1: 0.3 to 0.5: 0.5 to 0.7: 05 to 0.1;
3) Tape casting: The prepared slurry is placed in the vacuum box, a catheter is used to draw the slurry onto the bearing film, to get a film which thickness is 20 to 70 μm; Then, circular transmission and through the oven at 30~60℃ drying each layer, cycle to produce to designed number of layers and thickness;After drying, the ceramic chip is got by separation, cutting, tape-ranked, sintered;
4) Making electrodes: Silver electrodes are coated on both sides of the sintered ceramic chip;
5) Dicing: According to resistance requirements, the ceramic chips are diced into the required size, to obtain the NTC chips which resistivity is 0.3 to 0.6(kΩ. mm), B value is 3250 to 3400 k.
Low-resistance-value high-B-value NTC chip, its linearity is better, which is better to be used in the industry of temperature monitoring. And the resistivity of the chip reached 0.3 to 0.6 (kΩ.mm), B-value reached 3250 to 3400K, which can be used in the temperature range below -60℃ or lower.
Detection: Algorithm of resistance: ρ=RS/T
In the formula: R is the resistance measured by the NTC chip at a temperature of 25℃; S is the area of the NTC chip (length*width); T is the thickness of the NTC chip.
Algorithm of B value: B=(T1*T2/(T2-T1))*ln(R1/R2)
In the formula: T1/T2 is generally 25/85, or 25/50, or 25/100; R1 is the resistance value at temperature T1; R2 is the resistance value at temperature T2; T1 is 298.15K (273.15+25℃); T2 is 323.15K (273.15+50℃)