Six Precautions before Using Chip Resistors

Six Precautions before Using Chip Resistors
As we all know, the detection and selection of chip resistance is a crucial link in chip processing. SMD resistor is one of the most common electronic components in SMD processing industry. However, some SMD resistors are packaged in small sizes, which makes it easy to confuse SMD resistors in use.
Next, the SMT technicians of kingford will briefly introduce some precautions before using SMT resistors.
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(1) When the SMT technology operator of PCBA manufacturer works, use a multimeter to measure the resistance of the patch. At this time, the power supply in the circuit shall be disconnected, and one end of the patch resistor shall be disconnected from the circuit to avoid parallel connection with other circuit elements, which will affect the accuracy of the measured value. Smt technicians cannot touch both ends of the instrument with both hands when measuring the resistance, which will form a parallel connection between the patch resistance and the human body resistance, thus affecting the accuracy of the measured value. If high-precision measurement of chip resistance is required, a resistance bridge is required.

(2) Smt technicians use a multimeter to measure the resistance before use. Use only after proper inspection. The chip resistor with text mark shall be installed with the marked side facing up for later inspection.
(3) Potentiometers are prone to noise and other faults after use, and the probability of unpacked potentiometers with switches is higher. The unstable contact resistance is mainly due to the damage of the resistance film. If the condition is slight, the resistance film can be cleaned with alcohol to effectively remove the dirt and carbon powder generated by friction. If the condition is serious, consider replacing the potentiometer.
(4) Selecting rated power and high-power chip resistors will increase the volume and cost, which is unfavorable to circuit design. In addition, the power should not be too small, which will affect the normal use of the circuit; Generally, the value of rated power is twice the actual power.
(5) For the selection of error size, the selection of chip resistance is generally (+) 10% of the circuit diagram value. Some of them require high accuracy and can be marked separately.
(6) Because small and ultra small resistors are widely used in electronic equipment, relevant SMT technicians need to use thin and sharp welding heads with power lower than 30W in welding operations; Do not cut the wire too short to avoid heat transfer to the resistance during welding, which may lead to errors.

The above is the explanation given by the editor of pcb circuit board company.
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