What is the composition of chip resistors
The chip resistor is one of the metallic glass uranium resistors. It is a high-power chip resistor made of mixed metal powder and glass uranium powder and printed on the substrate by screen printing. It is resistant to humidity, high temperature, and has a small temperature coefficient. SMD resistors are mainly composed of four major parts. Today, we will introduce the details of these four major structures:
Substrate. The substrate material is generally 96% alumina ceramic. In addition to good electrical insulation, the substrate should also have excellent thermal conductivity at high temperatures.
Features such as electrical performance and mechanical strength. In addition, the substrate is required to be flat, and the scribing accuracy standards are required to fully ensure that the resistance and electrode paste are printed in place.
Resistive film. Brush the resistive paste with resistivity on the ceramic substrate, and then sinter it. The resistive paste is generally made of ruthenium dioxide.
Protective film. The protective film is covered on the resistive film, mainly to protect the resistor. On the one hand, it serves as a mechanical protection, and on the other hand, it makes the surface of the resistor insulative to prevent the resistor from contacting adjacent conductors and causing malfunctions. In the process of electro-transmitting the middle electrode, it can also prevent the electro-trans liquid from corroding the resistive film and causing the resistance performance to decrease. The protective film is generally a glass paste with a low melting point, which is made by printing and sintering.
Electrode. In order to ensure that the resistor has good solderability and reliability, a three-layer electrode structure is generally used: inner, middle, outer electrode. The inner electrode is the inner electrode connected to the resistor, and the electrode material should be selected with the resistance The membrane has low contact resistance, strong bonding force to the ceramic substrate, and good chemical resistance, making it easy to perform electroplating operations.
It is generally made of silver-palladium alloy printing and sintering. The middle electrode is a nickel-plated layer, also known as a barrier layer. Its function is to improve the heat resistance of the resistor during soldering and buffer the thermal shock during soldering. It can also prevent silver ions Migration to the resistive film layer to avoid corrosion of the internal electrode. The tin-lead layer of the outer electrode, also known as the solderable layer, is used to make the electrode have good solderability and extend the shelf life of the electrode. Generally, tin-lead is used. Alloy electroplated.
Rectangular chip resistors are divided into thin film resistors and thick film resistors according to the resistance material. Thin film resistors have high precision and low resistance temperature coefficient, good stability, but a narrow resistance range, which is suitable for precision and high frequency fields. Thick film resistors It is the most widely used in the circuit.