The miniaturization of components and the application of SMT technology and equipment in electronic products both mark the rapid development of modern science and technology. SMT manufacturing equipment has the characteristics of full automation, high precision and high speed. PCB design must meet the requirements of SMT equipment, otherwise it will affect production efficiency and quality, and may not even be able to complete computer-automated SMT. today, I invited the professional technical staff of Jie Duo Bang to introduce you to the PCB design elements that affect SMT manufacturing, let’s take a look!
PCB design elements that affect SMT manufacturing
PCB design is a key part of SMT technology, SMT technology is an important factor in determining the quality of SMT manufacturing. This article will analyze the PCB design elements that affect the quality of SMT equipment manufacturing. SMT manufacturing equipment for PCB design requirements mainly include: PCB pattern, size, positioning holes, clamping edges, MARK, panel alignment, etc.
In the SMT automatic production line, PCB production starts from the loader and is completed by printing, chip mounting and soldering. Finally, the unloader will generate the finished board. In this process, the PCB is transferred on the device path, which requires that the PCB pattern should be consistent with the path transfer between devices.
For the PCB design in Figure 3, the path clamping edge is not a straight line, so the location of the PCB and the transfer in the device will be affected. The open space in Figure 3 can be supplemented so that its clamping edge becomes a straight line as shown in Figure 4. Another approach is to add cracked edges to the PCB that
PCB design dimensions must meet the maximum and minimum size requirements of the mounter. By far, most devices are in the 50mmx50mm to 330mmx250mm (or 410mmx360mm) size range.
If the thickness of the PCB is too thin, the design size should not be too large. Otherwise, the reflow temperature will cause PCB deformation. The ideal length to width ratio is 3:2 or 4:3.
If the PCB size is smaller than the minimum size required for the device, the panel should be put together. The number of panels depends on the size and thickness of the PCB.
PCB positioning holes
There are two types of SMT positioning methods: positioning holes as well as edge locations and edge locations. However, the most common positioning method is Mark point alignment.
Since the PCB is transferred in the path of the device, the component must not be placed in the direction of the clamping edge, otherwise the component will be crushed by the device, thus affecting the chip mounting.
PCB Marking is the identification point for all fully automated device identification and location for modifying PCB manufacturing errors.
One. Shape: square, triangle, solid circle, hollow circle, ellipse, diamond, cross, etc. Which is preferred to solid circles.
1, size: the size must be within the range of 0.5mm to 3mm. A solid circle with a diameter of 1mm is preferred.
2, surface: its surface is the same as the PCB pad welding plane, welding plane is uniform, neither thick nor thin, excellent reflection effect.
A forbidden area should be arranged around the Mark point and other pads, which cannot contain screen printing and solder resist layer.
Screen printing characters and screen printing lines are arranged around the MARK, which will affect the identification of the MARK point by the equipment and will lead to frequent alarms due to MARK identification, which will seriously affect the manufacturing efficiency.
The purpose of combining multiple small PCBs with the same or different shapes to form a panel is to improve manufacturing efficiency. For some PCB double-sided, the top and bottom can be designed as one panel so that templates can be made, thus reducing costs. This method also helps to reduce the movement time of the top and bottom, thus improving manufacturing efficiency and equipment utilization.
Joining methods for pieced panels include punched holes and V-grooves
One requirement of the V-slot joining method is to keep the rest of the board (uncut) equal to one-quarter to one-third of the board thickness. If too much of the board is cut off, the cut slots may break due to the high temperatures of reflow, resulting in a dropped PCB that will burn in the reflow oven.
PCB design technology is complex, efficient and demanding, and this technology must consider both device requirements and device layout, pad design and circuit design. Excellent PCB design is an important factor in ensuring product quality. This paper presents some of the issues that should be considered in PCB design from the perspective of SMT manufacturing. With sufficient attention to these issues, fully automated SMT manufacturing of SMT devices can be achieved.