PCBA repair process
We have a job as a PCBA maintenance engineer in our JY electronics assembly shop. Since the production and use of SMT patches is a relatively complex process, it is inevitable that these problems will arise, including factors such as mishandling, misuse and component aging, which will result in abnormal working or even actual use of the product. Because many products just don't need to be replaced. This requires some repair and maintenance of the internal circuit boards. Then, it involves circuit board maintenance!
Today, the editors of Jiang Yuan Electronics are here to share some experience and tips on circuit board repair techniques. To learn circuit board repair techniques in a systematic way, you can click on JY Electronics' official website. We will regularly share with you some practical small parts of SMT processing plant. Tips, including but not limited to repair.
Usually, our maintenance technical engineers will perform the following operations.
1. Check the parts
When it is necessary to repair the product in SMT chip processing plant, the first step is to determine whether each solder joint components have errors, leaks, inversions, etc.. Confirming that there is no material authenticity is also a situation that needs to be considered. Given that the chips imported by Jingbang Electronics from Sweden were inbound in 2011, the supply from Europe and the United States is not necessarily stronger than the supply from Huaqiangbei. If issues such as errors, leaks, inversions, authenticity, etc. are eliminated and the board in question is obtained, the board is first checked to see if it is in good condition, if individual components are obviously burned in, and if it is properly inserted. .
2. Solder state analysis
Basically, 80% of the board defects are solder joint defects. Whether the solder joints are full and whether there are abnormalities, the first must refer to the ISO9001 quality system management standards and various SMT processing soldering quality standards. Solder defects, false solder, short circuit, whether the copper skin is obviously raised and other visible defects. If so, the product needs to be repaired for defects, if not, then you can proceed to the next step
3. Detection of component orientation
In the process of this link, we have basically eliminated some defects visible to the naked eye. Now, we must carefully check the specified orientation of diodes, electrolytic capacitors and the most commonly used components on the board. Otherwise, will the positive and negative required components inserted in the wrong direction?
4. Tool check of the parts
If there is no problem with the naked eye, then at this time we need to borrow some auxiliary tools. The most common in SMT chip processing factory is to use a multimeter to simply measure our resistors, capacitors, transistors and other components. The most important thing about a multimeter is to check if the resistance values of these components do not meet normal values and become larger or smaller. Whether the circuit is disconnected, inductor is disconnected, etc.
5. Power on test
After completing all of the above processes, you can basically eliminate routine problems with the components. If the power is turned on, the circuit board will not be damaged by short circuit or bridging and ablation. You can turn on the power and check whether the corresponding function of the board is normal.
Basically, after all processes are completed, the customer's BOM and Gerber will be eradicated. These schematics can be used to determine and fix customer product defects. The technicians in our repair department are carefully selected professionals from the shop floor. They are experienced in solving these problems.
6. The last step is the most important comprehensive PCBA testing
A. ICT (In-Circuit Test) test. It mainly detects the voltage/current data of the test points after the PCB is powered on, and does not involve the testing of function buttons or inputs and outputs.
B. FCT (Functional Test) Test: The programmed microcontroller program (MCU) must be burned into the program IC through a burner (e.g. ST-Link, JTAG) to achieve the corresponding functional test. For example, the LED lights up when the button is pressed; pressing two buttons at the same time will restore the factory settings, etc. Of course, whether it is possible to test all functions by PCB soldering normal and circuit conduction, otherwise it will not be achieved.
C. Combustion test. PCBA boards programmed and passed by FCT must simulate user inputs and outputs for a long time and be tested regularly for durability and solder reliability. In special cases, it is also necessary to expose the PCBA board to specific temperature and humidity environments.
After completing the above steps, we can fix most of the PCBAs with abnormal functions. Thank you for your patience and cooperation, and hope this article will be helpful to you.