PCB sample production is a crucial link in the PCB production process. It is not only a key step to verify the feasibility of the design plan, but also an important reference for subsequent mass production. However, due to the complexity of PCB design and production processes, various problems are inevitable after sample production. How to quickly rework after discovering problems has become the core point to shorten the product development cycle and reduce costs.
- Problem location and analysis
(I) Comprehensive inspection to determine the scope of the problem
Once a problem is found in the sample PCB, the first task is to use professional inspection tools and methods to conduct a comprehensive «physical examination» of the PCB. The use of automatic optical inspection (AOI) equipment can quickly scan the surface of the PCB and detect obvious appearance defects such as short circuits, open circuits, missing or offset components. For some internal problems that are difficult to detect with the naked eye, such as poor connection of the inner layer circuits and copper plating defects of vias, in-depth inspection is required with the help of X-ray inspection equipment. Through these detection methods, the location and scope of the problem can be accurately determined, providing a clear direction for subsequent rework.
(II) Multi-dimensional analysis of the root cause of the problem
After determining the scope of the problem, it is necessary to analyze the root cause of the problem from multiple dimensions such as design, production process, and raw materials. If it is a short circuit problem, it may be that the line spacing is too small during the design, and the line adhesion occurs during the production etching process; it may also be that the solder mask is missed during the production process, resulting in solder bridging. For the problem of poor component welding, it may be due to improper setting of process parameters such as welding temperature and time, or raw material factors such as oxidation of component pins and poor quality of solder paste. Only by accurately finding the root cause of the problem can an effective rework strategy be formulated.
II. Formulate a rework plan
(I) Formulate targeted strategies based on the type of problem
For different types of problems, corresponding rework strategies need to be formulated. If it is found that individual components are poorly welded, manual welding can be used for rework. Use a high-precision soldering iron, with appropriate solder wire and flux, to re-weld the bad solder joints under the premise of accurately controlling the welding temperature and time. For the circuit short circuit problem, if it is a surface circuit short circuit and the short circuit position is easy to operate, you can try to use microetching agent to perform local etching repair on the short circuit part; if the short circuit occurs in the inner layer circuit, the situation is more complicated, and you may need to use the layered processing method, carefully peel off the relevant layers, repair the short circuit point and then re-press it.
(II) Consider the impact of rework on the surrounding area
When formulating the rework plan, you must fully consider the impact of the rework operation on the surrounding area of PCB. For example, during the manual soldering rework process, you must pay attention to controlling the transfer of soldering heat to avoid thermal damage to the surrounding components and circuits. For the method of using etching to repair circuit short circuits, the use range and time of microetching agent must be accurately controlled to prevent excessive etching of the surrounding normal circuits. Before each step of rework operation, a risk assessment must be carried out to ensure that the rework process will not introduce new problems.
III. Implement rework operations
(I) Professional operation and advanced tool assistance
Rework operations need to be performed by experienced and skilled professionals with the help of advanced tools and equipment. For example, when reworking tiny components, using a welding workbench with a microscope allows operators to observe the solder joints more clearly and improve welding accuracy. For operations involving circuit repair, high-precision micro-machining equipment, such as laser repair equipment, can achieve accurate repair of the circuit and reduce the impact on the surrounding area.
(II) Strictly follow operating specifications and procedures
In the process of implementing rework operations, it is crucial to strictly follow established operating specifications and procedures. Each step of the operation must be carried out in accordance with the standard process flow to ensure the accuracy and consistency of the operation. For example, After soldering rework, the PCB should be cleaned according to the standard cleaning process and special cleaning agents should be used to remove residual flux and impurities to prevent them from having adverse effects on PCB performance. At the same time, during the entire rework process, detailed operation records should be kept, including the location of the rework, operation steps, tools and materials used, etc., for subsequent quality traceability and problem analysis.
IV. Quality Verification and Testing
(I) Comprehensive testing to ensure problem resolution
After the rework is completed, the PCB needs to be fully tested again to ensure that the problems found before have been completely solved and no new problems have been introduced. Use AOI equipment and X-ray inspection equipment to scan the PCB again to check whether the line connection, component welding, etc. are normal. For some PCBs with high electrical performance requirements, electrical performance tests such as impedance testing and signal transmission testing are also required to ensure that the electrical performance of the PCB meets the design requirements.
(II) Small-batch trial production to verify stability
For some sample PCBs that have undergone major rework or have a greater impact on product performance, small-batch trial production can also be carried out after completing comprehensive testing. Through small-batch trial production, the stability and reliability of the reworked PCB in the mass production environment are further verified. Strict quality inspection is carried out on the trial-produced products, and data and feedback information in the production process are collected to provide reference for subsequent mass production.
Hongxin Circuit（HXPCB) has profound technical accumulation and rich practical experience in the field of PCB production. In the face of problems after the production of sample PCBs, the company has formed a professional rework team that can quickly locate problems, formulate scientific rework plans, and efficiently implement rework operations. Through strict quality verification and testing processes, it is ensured that each reworked PCB meets high quality standards. Hongxin Circuit (HXPCB)has always been customer-oriented and is committed to providing customers with high-quality and efficient PCB production and rework services to help customers innovate and develop in the field of electronics. Hongxin Circuit (HXPCB)specializes in the production of 2-30 layer PCBs. Now the service upgrade provides 1-6 layer PCB free proofing services, PCB assembly services, and one-stop PCBA services. We sincerely welcome your consultation and cooperation.
HXPCB provides 1-6 layer PCB free proofing services sales@hongxincircuit.com
