“The miniaturization of Electronic components and the application of SMT technology and equipment in electronic products all mark the rapid development of modern science and technology. SMT manufacturing equipment has the characteristics of full automation, high precision and high speed. With the improvement of automation, higher requirements are put forward for PCB design. The PCB design must meet the requirements of SMT equipment, otherwise it will affect the production efficiency and quality, and may even fail to complete the computer automatic SMT. Today, the editor has invited professional technicians from JEDOBANG to introduce the PCB design elements that affect SMT manufacturing. Let’s take a look!
The miniaturization of electronic components and the application of SMT technology and equipment in electronic products all mark the rapid development of modern science and technology. SMT manufacturing equipment has the characteristics of full automation, high precision and high speed. With the improvement of automation, higher requirements are put forward for PCB design. The PCB design must meet the requirements of SMT equipment, otherwise it will affect the production efficiency and quality, and may even fail to complete the computer automatic SMT. Today, the editor has invited professional technicians from JEDOBANG to introduce the PCB design elements that affect SMT manufacturing. Let’s take a look!
PCB Design Elements Affecting SMT Manufacturing
PCB design is a key link in SMT technology, and SMT technology is an important factor determining the quality of SMT manufacturing. This article will analyze the PCB design elements that affect its quality from the perspective of SMT equipment manufacturing. The design requirements of SMT manufacturing equipment for PCB mainly include: PCB pattern, size, positioning hole, clamping edge, MARK, panel routing, etc.
In the SMT automatic production line, the PCB production starts from the loader and goes through printing, chip mounting and soldering. Finally, the unloader will generate the finished board. During this process, the PCB is transmitted on the device path, which requires that the PCB pattern should be consistent with the path transmission between the devices.
For the PCB design in Figure 3, the path clamping edge is not a straight line, so the position of the PCB and transmission in the device will be affected. The open space in Figure 3 can be supplemented to make its clamping edge a straight line as shown in Figure 4. Another way is to add crack edges to the PCB as shown in Figure 5.
The PCB design size must meet the maximum and minimum size requirements of the placement machine. Most devices so far are in the 50mmx50mm to 330mmx250mm (or 410mmx360mm) range.
If the thickness of the PCB is too thin, its design size should not be too large. Otherwise, the reflow temperature will cause the PCB to deform. The ideal aspect ratio is 3:2 or 4:3.
If the PCB size is smaller than the minimum size requirement of the device, it should be panelized. 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 and edge positions and edge positions. However, the most commonly used positioning method is Mark point alignment.
Since the PCB is transported on the path of the device, the component must not be placed in the direction of the clamping edge, otherwise the component will be squeezed by the device, affecting the mounting of the chip.
PCB marking is the identification point for all fully automatic equipment identification and location to correct PCB manufacturing errors.
One. Shapes: square, triangle, filled circle, hollow circle, ellipse, diamond, cross, etc. The first choice is the filled circle.
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: The surface is the same as the welding plane of the PCB pad, the welding plane is uniform, neither thick nor thin, and the reflection effect is excellent.
A no-cloth area should be placed around the Marks and other pads that do not contain screen printing and solder mask.
The silkscreen characters and silkscreen lines are arranged around the MARK, which will affect the equipment’s recognition of the MARK point, and will cause frequent alarms due to MARK recognition, 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 double-sided PCBs, the top and bottom can be designed as one panel, which allows for stenciling, which reduces costs. This approach also helps to reduce top and bottom movement time, thereby increasing manufacturing efficiency and equipment utilization.
The connection method of the panel includes punching holes and V-grooves, as shown in Figure 10.
One requirement of the V-groove connection 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 away, the cutout can crack from the heat of the reflow soldering, causing the PCB to fall off and the PCB to burn in the reflow oven.
PCB design technology is complex, efficient, and rigorous, and this technology must consider device requirements and device layout, pad design, and circuit design at the same time. Excellent PCB design is an important factor to ensure product quality. This article presents some issues that should be considered in PCB design from the perspective of SMT manufacturing. Fully automated SMT fabrication of SMT devices can be achieved as long as sufficient attention is paid to these issues.
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