PCBA Tech - Six precautions of resistance in PCBA manufacturing

As we all know, in the PCBA manufacturing process of PCBA board manufacturer, the detection and selection of patch resistance is one of the very important links; Chip resistor is one of the most commonly used electronic components in the mounting process of PCBA factory. However, some SMD resistors are packaged in miniaturization, so it is easy to confuse the SMD resistors in the process of use. Next, ipcb engineers are here to explain the precautions that should be paid attention to before using the SMD resistors in the process of PCBA processing and production.

1. When PCBA technicians use a multimeter to measure the patch resistance, they need to disconnect the power supply in the circuit, and then disconnect one end of the patch resistance from the circuit to avoid parallel connection with other PCBA circuit elements, which will affect the accuracy of measurement. When measuring the resistance, they cannot use two hands to contact both ends of the meter at the same time, which will cause parallel connection between the patch resistance and human body resistance, It affects the accuracy of measuring parameter values. If it is necessary to measure the patch resistance with high precision, it is necessary to use a resistance bridge for measurement.

2. Before using the resistance, PCBA technicians use a multimeter to measure the resistance value. After checking, it can be used normally. For the patch resistance with text marks, ensure that the marked side is upward, which helps to ensure the accuracy of later inspection.

3. The potentiometer is prone to high noise and other faults after use, and the potentiometer without package and switch has a higher probability of occurrence; The main reason is that the contact resistance is unstable due to the damage of its resistance film. If the situation is relatively light, you can also use alcohol to clean the resistance film to remove the dirt and toner caused by friction. If it is serious, you can also consider replacing a new potentiometer for treatment.

4. For the selection of rated power, if high-power chip resistor is selected, the volume will increase and the cost will increase. This is not conducive to the design of PCBA circuit, and the power can not be too small. This small power will affect the normal use of PCBA circuit board circuit. Generally, the value of rated power is twice the actual power.

5. The selection of error size and chip resistance is generally ± 10% of the value in the circuit diagram. A few places with high accuracy requirements can be marked separately.

6. Since the surface mounting process of PCBA circuit board pad in electronic devices uses a large number of small and ultra-small resistors, the operators related to PCBA technology of PCBA chip processing in PCBA plant use a sharp soldering iron head to adjust the power below 30W when welding PCBA circuit board; At this time, the lead shall not be cut too short to avoid heat transfer into the resistance during PCBA board welding, resulting in error.