In our JY electronic assembly workshop, there is a job as a PCBA maintenance engineer. Because the production and use of SMT patch processing is a relatively complicated process, these problems will inevitably occur, including processing errors, improper use and aging of components, and other factors will cause abnormal work or even the use of real products. Because many products just don’t need all replacements. This requires some repair and maintenance of the circuit board inside. Then it involves the repair of the circuit board! Today, the editor of JY Electronics is here to share some experience and skills of circuit board repair technology for you. If you want to learn the technology of circuit board repair system systematically, you can click on the official website of JY Electronics. We will regularly share some practical small parts of SMT processing plants for you. Tips, including but not limited to maintenance:
Under normal circumstances, our maintenance technical engineer will perform the following operations.
1. Check components
When the product needs to be repaired in the SMT patch processing plant, we must first determine whether the components of each solder joint have errors, leaks, and inversions. Confirming the authenticity of no materials is also a situation that needs to be considered. In view of Jingbang Electronics Chips imported from Sweden were pitted in 2011, so the supply of European and American countries may not necessarily be stronger than Huaqiangbei. If the problems of error, leakage, inversion and authenticity are ruled out, you can get a faulty circuit board and first check whether the circuit board is intact and whether the various components are obviously burned out and inserted correctly.
2. Analysis of welding status
Basically, 80% of the defects of the circuit board are the defects of the solder joints. Whether the solder joints are full and whether there are xabnormalities, first of all, we must refer to the management standards of the ISO9001 quality system, and various SMT processing welding quality standards. Defective welding, false welding, short circuit, whether the copper skin is obviously raised and other defects that are visible to the naked eye. If there is, you need to repair the defective points of this product, if not, you can proceed to the next step!
3. Detection of component direction
In the process of this link, we have basically ruled out some of the defects that can be seen by the naked eye. Now we must carefully check the diodes, electrolytic capacitors, the most used components on the circuit board, and other regulations on the direction, or positive Are the required components of the negative pole inserted in the wrong direction?
4. Tool inspection of components
If all the naked eye judges that there is no problem, then we need to borrow some auxiliary tools at this time. The most commonly used in SMT patch processing factory is to use a multimeter to simply measure our resistance, capacitance, triode and other components, use a multimeter The most important thing to check is to check whether the resistance value of these components does not meet the normal value, becomes larger or smaller, whether the capacitor is open, whether the inductance is open, etc.
5. Power-on test
After all the above processes are completed, the conventional problems of the components can be basically eliminated. If the power is turned on, the circuit board will not be ablated and damaged due to short circuit or bridging. You can turn on the power and check whether the corresponding function of the circuit board is normal.
Basically, after all the processes are completed, the BOM and Gerber of the customer are eradicated. The schematic diagrams can be used to judge and repair the defects of the customer’s products. The technicians in our maintenance department are carefully selected professional players from the workshop. They solve These questions are very experienced.
6. The last step is the most important comprehensive PCBA test
A. ICT (In-Circuit Test) test:
It mainly detects the voltage/current data of the test point after the PCB circuit board is energized, and does not involve the test of function buttons or input and output.
B. FCT (Functional Test) test:
you need to burn the programmed single chip microcomputer (MCU) program into the program IC through the burner (such as ST-Link, JTAG) to achieve the corresponding functional test. For example, after pressing the button, the LED light is on; press the two buttons at the same time to restore the factory settings and so on. Of course, whether all functions can be tested must be based on PCB soldering OK and line conduction, otherwise it cannot be achieved.
C. Burn-in test:
The PCBA board that has been programmed and passed by FCT is subjected to long-term and periodic simulation of user input and output to test its durability and welding reliability. In special cases, it is also necessary to expose the PCBA board to a specific temperature and humidity environment.
After the above steps, we can repair most of the PCBA with dysfunction. Thank you for your patience and hope this article can bring you some help.
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