For PCB assembly,kingford can provide components sourcing service for our customers.
Small size and light weight;
Adapt to reflow and wave soldering;
Stable electrical performance and high reliability;
Low assembly cost and match with automatic mounting equipment;
High mechanical strength and superior high frequency characteristics.
At present, the type of chip resistors is not uniform and is set by each manufacturer, and the model is particularly long (consisting of a dozen English letters and numbers). If various parameters and specifications of the chip resistor can be correctly presented during the purchase, it can be easily selected (or ordered) to the required resistance.
Patch resistors have five parameters, namely size, resistance, tolerance, temperature coefficient, and packaging.
- Size series SMD resistor series generally have 7 sizes, which are represented by two size codes. A size code is an EIA (American Electronic Industry Association) code represented by 4 digits. The first two digits and the last two digits represent the length and width of the resistor, respectively, in inches. The other is the metric code, which is also represented by 4 digits and its unit is mm. Different size resistors have different power ratings. Table 1 lists the code and power ratings for these seven resistance dimensions.
- Resistance series Nominal resistance is determined by series. Each series is divided by the tolerance of the resistor (the smaller the tolerance is, the more the resistance is divided). The most commonly used is E-24 (tolerance of resistance value is ±5%).The surface of the chip resistor is represented by a three-digit number, where the first and second digits are valid numbers, and the third digit indicates the number of zeros to be followed by zeros. When there is a decimal point, it is represented by “R” and it occupies one significant digit. Nominal resistance code indicates the method .
- The tolerance of the tolerance chip resistor (carbon film resistor) has four levels, namely, F level, ±1%; G level, ±2%; J level, ±5%; K level, ±10%.
- Temperature coefficient The temperature coefficient of the chip resistor has two grades, namely w grade, ±200ppm/°C, X grade, ±lOOppm/°C. Only resistors with an F-class tolerance are used with x-level resistors, and other-level resistors with tolerances are generally of the w-level.
- There are two types of packaging, bulk and ribbon packages.
The most widely used chip resistor size code is 0805 and 1206. And there is a gradual trend towards 0603. Both package 0402 and 0201 are commonly used in products with higher integration, and they also impose higher requirements on the SMT process level.