Whether the panel PCB design is reasonable directly affects the efficiency and operability of subsequent SMT production. For example, an unreasonable panel will cause the board to bend and warp after wave-soldering. Too many V-cut designs may cause broken and fall off. If connect the rounded board by stamp holes may cause burrs and unmatched the shell.
Engineers in PCBONLINE have accumulated many secrets(experience)about PCB board design based on years of customer service. Here are ten suggestions to share with PCBONLINE customers. I think these experiences will definitely help you make better decisions when designing the PCB panel.
1. The outline (clamping edge) of the PCB panel shall adopt a closed-loop design to ensure that the PCB panel will not deform after being fixed on the fixture;
2. PCB panel width is less than or equal to 260mm (SIEMENS production line) or is less than or equal to 300mm (FUJ production line); If automatic dispensing is required, PCB panel width * length is less than or equal to 125 mm*180 mm;
3. Trying to make the shape of PCB outline as close as possible to square, recommended to use 2*2, 3*3,......panel way; But do not put top side and bottom side in the same side;
4. The center distance between the single pcs should be controlled between 75 mm to 145 mm;
5. When design the fiducial points, it is common to leave an open welding area 1.5mm larger around the fiducial point;
6. There should be no large components or protruding components near the connection point between the outline of the panel and the internal single pcs, also between each single pcs. Besides, there should be more than 0.5mm space between the components and the edge of the PCB board to ensure the normal operation of the cutting tool.
7. There should be four positioning holes with a diameter of 4mm±0.01mm at the four corners of the outline of each panel. The strength of the hole should be moderate to ensure that the board will not break during the process of up and down; Diameter and position accuracy should be high, the whole wall should be smooth and without burr;
8. Each single pcs in PCB panel shall have at least three positioning holes, the diameter is less than or equal to 6mm, wiring or SMT is not allowed within 1mm of edge positioning hole;
9. In principle, QFP with spacing less than 0.65mm should be set in its diagonal position(The fiducial symbols used for PCB position or components position.) The positioning fiducial symbols used for the PCB subboard shall be used in pairs, arranged diagonally on the positioning elements.
10. If the rounded board has high requirements on the shape tolerance, it is not recommended to use a stamp hole connection. Milling edge + V-cut connection is preferred, as shown in the figure below. The advantage of this is that it is easy to disassemble after mounting and to match the shell without burrs.
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