Ten Precautions for PCB Assembly

1. The outer frame (clamping edge) of the PCB panel should adopt a closed-loop design to ensure that the PCB panel will not deform after being fixed on the fixture;

2. PCB panel width ≤ 260mm (SIEMENS line) or ≤ 300mm (FUJI line); If automatic dispensing is required, PCB panel width × Length ≤ 125mm × 180mm；

3. The appearance of the PCB panel should be as close to a square as possible, and it is recommended to use 2 × 2、3 × 3. ... Splicing board; But do not assemble yin and yang plates;

4. The center distance between small boards should be controlled between 75mm and 145mm;

5. When setting a benchmark positioning point, a welding free zone 1.5mm larger than it is usually left around the positioning point;

6. There should be no large or protruding components near the connection points between the outer frame of the panel and the internal small board, or between the small board and the small board, and there should be a space greater than 0.5mm between the edges of the components and the PCB board to ensure the normal operation of the cutting tool;

7. Make four positioning holes at the four corners of the outer frame of the panel, with an aperture of 4mm ± 0.01mm; The strength of the hole should be moderate to ensure that it will not break during the process of loading and unloading the plate; The aperture and position accuracy should be high, and the hole wall should be smooth and hairless;

8. Each small board in the PCB assembly must have at least three positioning holes, with a diameter of 3 ≤ 6mm, and no wiring or mounting is allowed within 1mm of the edge positioning holes;

9. The reference symbols used for the positioning of the entire PCB board and for the positioning of fine pitch devices should be set diagonally for QFPs with a spacing less than 0.65mm in principle; The positioning reference symbols used for assembling PCB sub boards should be used in pairs and arranged diagonally on the positioning elements;