Six Precautions for resistance in Polychlorinated Biphenyl Production
As we all know, in the PCBA board manufacturer of PCBA manufacturing technology, the detection and selection of chip resistance is one of the most important links; Chip resistor is one of the most commonly used electronIC components in PCBA factory installation However, some SMD resistors are packaged in a miniaturized way. In retrOSPect, it is easy to confuse chip resistors in use Next, kingford engineers will explain the precautions that should be taken before using SMD resistors in PCBA processing and production
1. When PCBA technICians use a multimeter to measure the chip resistance, they need to disconnect the power supply in the circuit, and then disconnect one end of the chip resistance from the circuit to avoid parallel connection with other PCBA circuit components, which will affect the measurement accuracy. When measuring the resistance, do not touch both ends of the instrument with both hands at the same time, which will lead to the patch resistance and the human body resistance in parallel, affecting the accuracy of the measurement parameters. If high-precision measurement of chip resistance is required, a resistance bridge is required.
2. Before using the resistance, PCBA technicians use a multimeter to measure the resistance value. After inspection, it can be used normally. For patch resistors with text MARKs, make sure that the marking side is upward, which helps to ensure the accuracy of later inspection.
3. Potentiometers are prone to high noise and other faults after use. Potentiometers without package and switch have a high probability of occurrence; The main reason is that the contact resistance is unstable due to the damage of its resistance film. If the condition is relatively light, the resistance film can also be cleaned with alcohol to remove the dirt and carbon powder caused by friction. If the condition is serious, you can also consider replacing a new potentiometer for treatment.
4. For the selection of rated power, if high-power chip resistors are selected, the volume and cost will increase. This is unfavorable to the design of PCBA circuit, and the power should not be too SMAll. This low power will affect the normal use of PCBA circuit board. Generally, the value of rated power is twice the actual power.
5. The selection of error size and chip resistance is usually ± 10% of the median value of the circuit diagram. Some places requiring high precision can be marked separately.
6. Because a large number of small and ultra small resistors are used in the pads of PCBA circuit board electronic equipment during surface mounting, the operators related to PCBA chip processing PCBA technology in PCBA factories use sharp soldering heads to adjust the power to PCBA circuit boards below 30W during welding; At this time, during the welding of PCBA board, the wire shall not be cut too short to avoid heat transfer to the resistance, which may lead to errors