1. Size series SMD resistor series generally have 7 sizes, which are represented by two size codes. One size code is an EIA code represented by a 4-digit number. The first two digits and the last two digits indicate the length and width of the resistor, in inches. The other is the metric code, which is also represented by 4 digits, and its unit is millimeters. Different sizes of resistors have different power ratings. Table 1 lists the codes and power ratings of these 7 resistor sizes.
2. Resistance series The nominal resistance is determined by series. Each series is divided by the tolerance of the resistance (the smaller the tolerance, the more the resistance value is divided), and the more commonly used one is E-24 (the tolerance of the resistance value is ±5%).
The surface of the chip resistor uses three digits to indicate the resistance value, the first two digits are valid digits, and the third digit indicates the number of zeros followed. When there is a decimal point, it is represented by "R" and occupies one effective digit. Nominal resistance code representation method.
3. Tolerance SMD resistors (carbon film resistors) have 4 levels of tolerance, namely F level, ±1%; G level, ±2%; J level, ±5%; K level, ±10%.
4. Temperature coefficient The temperature coefficient of chip resistors has 2 levels, namely w level, ±200ppm/℃; X level, ±100ppm/℃. Only resistors with tolerances of class F use class x, and resistances with tolerances of other classes are generally class w.
5. There are two main types of packaging: bulk and strip rolls.
The working temperature range of SMD resistors is -55--+125℃. The larger working voltage is related to the size: 0201 is lower, 0402 and 0603 are 50V, 0805 is 150V, and other sizes are 200V.
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