As a platform for the transmission of many components and circuit signals, the printed circuit board (PCB) has always been regarded as a key part of electronic information products, and its quality determines the quality and reliability of the final product. Due to the development trend of high density, lead-free and halogen-free environmental requirements, if professional and timely inspections are not completed, various failure problems may occur, such as poor wettability, cracks, delamination, etc.
Detection Technology
Generally, PCBA assembly inspection technology is divided into two types: visual inspection and automatic process inspection.
A. Visual inspection
After a large number of steps in the PCB assembly process, visual inspection can be used, and the visual inspection equipment is selected according to the position of the inspection target. The effectiveness of the visual inspection depends on the competence of the inspectors, the consistency and applicability of the inspection standards.
Inspectors must be fully aware of the technical requirements for each type of solder joint, as each type of solder joint may contain up to 8 defect criteria, and there may be more than 6 solder joints on different assembly equipment. Therefore, visual inspection is not suitable for quantitative measurement of effective structural process control.
B. Structural Process Test System (SPTS)
Digitization and analysis systems for real-time and automatic video capture can significantly improve the tolerance and repeatability of visual inspection. Therefore, structural process test systems rely on certain forms of emitted light, such as visible light, laser beams, and X-rays. All of these systems process images to obtain information to identify and measure defects related to solder joint quality.
C. Automatic / Automatic Optical Inspection (AOI)
The AOI system relies on multiple light sources, a programmable LED library, and some cameras to illuminate the solder joints and shoot. Under reflected light, the leads and solder joints reflect, reflecting most of the light, while PCB and SMD reflect very little light. The light reflected from the solder joint does not provide actual height data, while the pattern and intensity of the reflected light provides information about the curvature of the solder joint. A professional analysis is then performed to determine if the solder joints are complete, whether the solder is sufficient, and if wetting has not occurred.
D. Automatic laser test (ALT) measurement
ALT is a more direct technique for testing height and shape solder joints or paste deposits. When the image of the laser beam is focused on one or more position-sensitive detectors at an angle to the laser beam, the system is used to measure the height and reflectance of some surface parts.
During the ALT measurement, the surface height is determined by the position of the light reflected by the position-sensitive detector, and the surface reflectance is calculated from the power of the reflected beam. Due to the secondary reflection, the beam may illuminate a position-sensitive detector at multiple locations, which requires a solution to distinguish the correct measurement.
In addition, when traveling along the light of the position sensitive detector, the reflected light beam may be shielded or interfered by interfering materials. To eliminate multiple reflections and prevent shielding, the system should test the reflected laser beam along an adjusted independent optical path.
How to determine the PCB assembly inspection method?
Despite the variety of detection methods, there is a big difference between AOI inspection and X-ray inspection. The three factors to consider when determining the inspection method are defect type, cost, and inspection speed. When it comes to defect types AOI and X-ray coverage, AOI is usually used for inner layer testing before lamination. Defect items include solder paste amount, component location, missing and polarity, and solder joint defects.
The above is a detailed introduction to the common methods of testing printed circuit boards. If you have any questions about our answer, you can contact us.
With the development of the times, the purse is a vital decoration for everyone. A distinctive purse can enhance one's temperament invisibly.
However, how to maintain the leather bag to keep it shiny? Let's take a look at the common sense of leather goods maintenance!.jpg)
Wipe the dust every day
As we all know,customized leather handbags are easily stained with dust. Dust will reduce the color of the bag and affect its appearance. Therefore, after you use the bag yourself, you must find a clean rag and carefully remove the dust from the bag. If you can persist, your purse will last longer.
Buy special leather oil
The maintenance of genuine leather goods requires everyone to be more troublesome. Generally, you need to take care of it once every one month. You can go to the supermarket to buy a bottle of special purse oil, and then clean the purse thoroughly, so that you can easily protect the "face" of the purse.
Don't put it in a damp place
Neither the leather bag nor the leather bag can be placed in a damp place. Because the humid environment will cause the bag to harden, and at the same time, it may appear discolored, which not only affects the beauty of the bag but also damages the leather, so everyone must pay attention.
Clean with a wipe
When we are cleaning the purse, it is best to use something that is not corrosive. Wet wipes can prevent the case from corroding the bag. When using, just wipe the stains slowly, and then dry the remaining moisture with a dry towel.
Avoid being pinched by heavy objects
During the use of the bag, you must avoid being pressed by heavy objects, because this will cause your bag to deform and it will be difficult to recover.
Under normal circumstances, it is best not to put hard objects in the bag, such as scissors, screwdrivers, etc., because these metals can easily puncture your bag. At the same time, don't put the bag in too hot place, to prevent the leather of the bag from getting worse.
I believe that after reading the little general knowledge of leather goods maintenance, you have a certain understanding of the daily maintenance of the bag! In fact, although the maintenance of the bag is very simple, but it is expensive. Clean the stains on the surface of the bag from time to time!