In the process of PCB (printed circuit board) sampling, PCB layout design is a key step to ensure smooth subsequent production. Reasonable panel design can not only improve production efficiency, but also reduce quality hazards in the production process. The following are several aspects to pay attention to when designing PCB samples: 1. Advantages and conventional requirements of PCB assembly
Splicing shipment has significant advantages in handling small-sized PCBs. By laying out multiple small-sized PCBs on a large-sized board, the difficulty of positioning can be reduced, the accuracy of positioning can be improved, and shape deformation and edge burrs caused by positioning errors can be effectively prevented. At the same time, panel design is beneficial for solving the cleaning of small-sized circuit boards by machines, improving quality control levels, and providing convenience for subsequent automated assembly of components.
When designing PCB boards, it is necessary to ensure that the PCB size is appropriate, neither too large nor too small, in order to meet the requirements of production equipment. If Jialichuang assists in making V-cut patterns, it will default to processing them according to zero spacing patterns to ensure that the PCB shape tolerance after V-cut patterns is closer to the design dimensions. 2、 Key points of stamp hole design
Stamp holes are common connecting structures in panel design, used to maintain the stability of panels during production and transportation. When designing stamp holes, the following points should be followed:
Quantity and distribution: Stamp holes are usually grouped with 5-8 holes, and a single group of stamp holes should have at least 5 holes to ensure sufficient connection strength. The recommended parameter for the distance between adjacent stamp hole edges is 0.35-0.4mm to avoid excessive connection force or burrs between holes.
Position and shape: The stamp hole should be designed inside the board, with the hole edge tangent to the outer edge, or the stamp hole should be designed on the outer line, with the hole center overlapping the outer line. At the same time, the stamp hole should maintain a minimum distance of 12mil/0.3mm from the internal conductor to ensure quality.
Board splitting efficiency: The design of stamp holes should facilitate board splitting operations. For example, designing the stamp hole at the edge of the PCB shape allows the auxiliary edge to be opened at once, improving the efficiency of board splitting.
The arrangement of stamp holes in Figure 1 requires two breaking operations to completely remove the auxiliary edge.
The stamp hole design in Figure 2 is along the outer edge of the PCB, allowing the auxiliary edge to be opened at once and improving the efficiency of board splitting.
The stamp edge in Figure 3 is close to the process edge, which makes it difficult to effectively separate the auxiliary edge PCB shape.
So the stamp hole in Figure 2 is the most suitable.
When using stamp holes to assemble circular PCBs, the effect in Figure 2 is better than that in Figure 1, but the stability of the assembled PCB in Figure 1 is also sufficient. III. Precautions for V-cut assembly
V-cut splicing is a common splicing method that is suitable for the production of most PCBs. When designing V-cut panels, the following points should be noted:
Board length limit: The vertical length of the V-cut board must not exceed the maximum length of the V-cut equipment guide rail, otherwise the PCB will not be able to fit into the equipment. Therefore, it is necessary to ensure that the length of the board meets the equipment requirements during design.
Panel size and thickness: The PCB panel size for V-cut shipments should be greater than 7cm * 7cm, and the board thickness should be greater than 0.6mm. Thinner PCBs are prone to breakage or deformation during V-cutting, so it is necessary to ensure sufficient board thickness.
Avoid board edge cracking: For PCBs with protruding shapes and widths less than 3mm, using V-cut splicing may increase the risk of board edge cracking. At this point, consideration should be given to using a hollow pattern design to directly form the shape through CNC machining. 4、 Design and requirements for process edge
The process edge is an indispensable part of panel design, which facilitates the placement and soldering of subsequent components. When designing the process edge, the following requirements should be noted:
Width requirement: The width of the process edge should meet the equipment limitations of the PCB board during cutting and processing. Taking Jialichuang as an example, the minimum distance between the blade of the V-cutter and the edge of the track is 3mm, so the width of the process edge should not be less than this parameter. Meanwhile, considering the limitations of SMT processing equipment, the process edge usually requires a width of 4.65mm. To facilitate manufacturing and design uniformity, the process edge width is usually set to 5mm.
Enhance connectivity: When the process edge of the splicing board is suspended beyond 30mm, it is easy to cause a short circuit in the process edge due to collision during processing and transportation. At this point, adding stamp holes and auxiliary edges for connection can be used to enhance the firmness of the external structure.
Positioning holes and Mark points: It is usually necessary to add positioning holes and Mark points on the process edge as an aid to SMT positioning. The position, quantity, and diameter of the positioning holes and Mark points need to be designed reasonably according to the requirements of the production equipment. 5、 Other precautions
Avoid interference between components: In the layout of PCB shipment, it is necessary to avoid interference between components that may affect normal welding. Interference between components affects normal welding, and interval splicing should be used.
Consider the production process: When designing the panel, it is necessary to fully consider the subsequent production processes, such as cleaning, patching, welding, and splitting, to ensure that the panel design meets the requirements of each production process.
Unified design specifications: In order to improve production efficiency and quality, a unified panel design specification should be developed and trained and promoted within the company.
In summary, the PCB layout design during prototyping is a complex and meticulous process that requires comprehensive consideration of multiple factors. Only by designing the splicing structure reasonably can we ensure the smooth progress of subsequent production and the stable improvement of product quality.