/Circuit board manufacturing inspection, cleaning, and repairing
1.Inspection requirements for pcb manufacturing
In the process of pcb manufacturing, first check the printing solder paste whether it is in the storage period; after printing the solder paste, check whether there are any defects such as leakage,tailing; after the component is mounted, check whether there is any missing piece, solder paste contaminating the pad of the pcb, etc.; after curing, check the shearing force of the component. Each process should establish a process qualification rate statistical table to record the inspection condition. Inspection methods include manual visual inspection and AIO inspection.
(1) Cleaning of metal stencil
In order to avoid the erosion of the cleaning agent on the stencil and the screen adhesive, it is recommended to use a special cleaning agent. When printing small glue dots, such as 0.6mm or less, or when the stencil is heavily contaminated by the patch glue, it is recommended to use the pre-cleaning process firstly, using a stronger cleaning agent, and manually operate to avoid contact the cleaning agent and the patch glue. And then clean the stencil with a regular cleaning agent.
(2) Cleaning of plastic stencil
Electrostatic discharge may occur during the cleaning of the plastic stencil, so special anti-static cleaners should be used. Do not use a rag to clean by hand because the plastic is easily scratched. In addition, manual cleaning is not easy to thoroughly clean the through holes, and the residue accumulates, which affects the printing quality.
(3) Cleaning of the needle
One method is to soak the needle in a compatible solvent, then use a high-pressure spray to blow the glue out of the inner hole of the needle, Then use dry pressure air to blow the inner hole and let the needle dry. Another method is ultrasonic plus static soaking. Firstly, the uncured glue is mechanically removed by using a small tool such as a wire or a drill with an appropriate diameter in the inner hole of the needle; the second step is to soak the needle to be cleaned in a cleaning solvent for a while and stirring; the third step is to set the ultrasonic machine to 40 ° C, ultrasonic cleaning at maximum power for 3 min; the fourth step is to wash the cleaned needle with cleaning solvent, for the nozzle with very small inner hole, available High pressure spray; finally dry the needle with a dry compressed air blow pin,
3.Circuit board repair
The components that have been cured and need to be repaired can be uniformly heated by a heat gun. If the components have been soldered, it is necessary to increase the temperature to melt the solder joints, and remove the components with tweezers in time. Large ICs need to be heated by a service station. After removing the components, the residual glue should be slowly removed with a small knife under the cooperation of the heat gun, and the PCB printed wires and pads should not be damaged.
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① Standard components should pay attention to the dimensional tolerances of components from different manufacturers. Non-standard components must be designed in accordance with the actual size of the components and the land pattern and the space between the land. ② When designing high-reliability...
The water cleaning process of PCB circuit board uses water as the cleaning medium. A small amount (usually 2% to 10%) of surfactants, corrosion inhibitors and other chemicals can be added to the water. The PCBA cleaning process is completed by washing, washing and drying the source of pure water ...