Cleaning and Testing
PCB Inspection Process
Some commonly used PCB inspection methods:
1, Manual visual inspection
Manual visual inspection is the most traditional detection methods, compared to other detection methods low cost, does not require complex instrumentation tools to assist, through the use of magnifying glass or has been calibrated microscope visual inspection to determine whether qualified. The disadvantage is the high long-term cost, subjective human error.
2, On-line testing
Such as needle bed tester and flying needle tester, through the electrical performance test to identify PCB manufacturing defects. The main advantage is the low cost of testing, intelligence can quickly check the value of short-circuit, open-circuit and components, in the prototype stage to provide designers with rapid feedback, greatly saving the testing time, the disadvantage is that the test probes and access holes and test pads on the solder physical contact may leave a small crater in the solder.
3, Automatic X-ray inspection
Automatic X-ray inspection is mainly used to detect defects in ultra-fine pitch and ultra-high density circuit boards, as well as bridges, missing chips, poor alignment and other defects generated in the assembly process. The inspection principle uses the difference in X-ray absorption of different substances to inspect the part to be tested and find defects. Internal defects in IC chips can also be detected using tomography, which is the only way to test the solder quality of ball grid arrays and solder balls. The main advantage is the ability to detect BGA solder quality and embedded components without the expense of fixtures.
4, AOI Inspection (Automatic Optical Inspection)
When automatic inspection, the machine automatically scans the PCB through the camera, captures the image, the tested solder joints are compared with the qualified parameters in the database, and after image processing, the defects on the PCB are checked and the defects are displayed/labeled through the display or the automatic sign for the maintenance personnel to fix.
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PCBA Circuit Board Production and Processing Cleaning Methods
A. Artificial Cleaning Methods
- 1, Clean the circuit board in IPA or VIGONEFM, or spray IPA and EFM on the surface of the circuit board, using about 10 ml per 4 square inches.
- 2, The use of moist, soft, short-bristle brush to wipe the circuit board continuously for about 10 seconds.
- 3, Rinse with deionized water, approximately 10 ml per 4 square inches. Effectively remove potential contaminant residues.
- 4, Hand hold the circuit board edge, use a clean lint-free wipe to wipe off the unwanted deionized water.
- 5, Visual inspection of circuit board cleanliness.
- 6, If necessary, the use of air guns to dry the circuit board.
- 7, If you need to store the circuit board or components for a period of time before coating, please put the circuit board or components into a sealed bag containing desiccant.
In the case of manual cleaning, soak the circuit board in acetone with high solubility, which can effectively dissolve the pollutants in the solution. The board is then physically cleaned by placing it in ethanol and tiny flux contaminations are cleared away. Then, the organic solvent must be dewatered with the support of deionized water, etc..
B. Ultrasonic Cleaning Methods
- 1, Acetone solvent for ultrasonic cleaning methods. First, the PCBA board immersed in acetone solvent for about 10 minutes. Subsequently, the board is immersed in a quartz container dedicated to anhydrous ethanol.
- 2, Then, the quartz container is placed into the ultrasonic cleaning tank after ultrasonic cleaning. Ultrasonic cleaning for about 5 minutes continuously, ultrasonic power of 240W, turn off the ultrasonic cleaning switch and then remove the quartz container with a basket. Subsequently, the plates were washed with deionized water for about 5 minutes and dehydrated with anhydrous ethanol, etc. Apply nitrogen to dry the surface layer.
- 3, In the case of ultrasonic cleaning, the circuit board is placed in an ethanol agent, unlike manual cleaning. Ultrasonic cleaning is based on the principle of ultrasonic vibration, deionized water to remove flux residue and dehydration, etc. and designed.
C. Automatic Cleaning Equipment Spray Cleaning Method
- 1, PBT-800P Offline PCBA Cleaning Machine
- Process flow: manually into the product - cleaning basket frame moving back and forth - spray pump pressurized cleaning - filtration and recovery of liquid - spray pump pressurized rinsing (open loop) - select the number of rinsing - heating and drying - manually remove the product. It can effectively clean the organic and inorganic pollutants such as rosin flux, water-soluble flux, no-clean flux/soldering paste and other organic and inorganic pollutants left on the surface of PCBA after soldering in SMT/THT;
- 2, Equipment Features:
- 1) automatic cleaning mode: equipment in operation, the workpiece in the cleaning basket with the cleaning basket to move back and forth, while the spray system high-pressure jet heated cleaning fluid, can make the PCBA all-round to get automatic cleaning, rinsing, drying the whole process;
- 2) the most scientific nozzle design (patented): the use of up and down the staggered, left and right incremental distribution - a complete solution to the cleaning of the blind spot, 3 layers of 610mm x 600mm large area cleaning, spray arm can be removed 3 layers to 2 layers, to solve a variety of sizes of PCBA board placement;
- 3) visualize the nozzle pressure can be adjusted: solved the small size workpiece in the cleaning by high-pressure spray conditions of collision, splash problem;
- 4) comprehensive cleaning system: compatible with running aqueous or chemical cleaning, for SMT, THT PCBA welding surface residues of rosin, water-soluble flux, no-clean flux solder paste and other organic and inorganic pollutants for a thorough and effective cleaning of the body material: the overall stainless steel body, resistant to acid, alkaline, and other cleaning fluids.
Through the observation of PCBA circuit board wiring and surface conditions, PCBA circuit board manual cleaning, ultrasonic cleaning and cleaning equipment spray cleaning methods, comprehensive analysis, spray cleaning equipment has a higher feasibility and higher safety, so that the cleaning is more thorough, resulting in better cleaning results.
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