The patch resistor consists of four main parts.
The substrate material is generally 96% aluminum oxide ceramic. In addition to good electrical insulation, the substrate should have good thermal conductivity at high temperatures. Electrical properties and mechanical strength. In addition, the substrate should be flat and accurate. Standard to fully guarantee resistance. Electrode paste printing in place.
2) Resistance film:
The ceramic substrate is printed with a certain resistivity of resistance paste, and then sintered. Dioxide is usually used in resistance slurry.
3) Protective film:
The protective film is covered with the resistance film, mainly to protect the resistance body. On the one hand, it plays a mechanical protection role, on the other hand, it insulates the surface of the resistance body, avoiding the fault caused by the contact between the resistance and the adjacent conductor. In the process of electric crossing the intermediate electrode, it can also prevent the electric crossing liquid from eroding the resistance film, resulting in the degradation of resistance performance. Protective film is generally low melting point glass slurry, printing sintering.
In order to ensure that the resistance has good weldability and reliability, generally three layers of electrode structure: internal. In the middle. External electrodes. The internal electrode is the internal electrode connected to the resistor body. The electrode material should have little contact with the resistance film, strong bonding force with the ceramic substrate, good chemical resistance and easy electroplating. Generally silver palladium alloy printing sintering. The intermediate electrode is nickel-plated, also known as the barrier layer. Its function is to improve the heat resistance of the resistance in the welding process and buffer the thermal shock in the welding process. It also prevents silver ions from migrating to the resistance film layer, avoids corrosion of the internal electrode (which is corroded by the solder), makes the electrode have good weldability, and extends the storage life of the electrode. Tin-lead alloys are commonly used in electroplating.
Rectangular sheet resistance is divided into thin film resistance and thick film resistance according to the resistance material. Among them, the film resistance precision is high, resistance temperature coefficient is small. Good stability, but narrow resistance range, suitable for precision and high frequency fields. Thick film resistors are widely used in circuits.