PCB Layout Design Considerations

In order to facilitate production, PCB stitching generally need to design Mark point, V-slot, process edge.

I. The shape of the spelling plate

1. The outer frame of the PCB splicing board (clamping edge) should be closed-loop design to ensure that the PCB splicing board will not be deformed after it is fixed on the fixture.

2. PCB splice width ≤ 260mm (SIEMENS line) or ≤ 300mm (FUJI line); if automatic dispensing is required, PCB splice width x length ≤ 125 mm x 180 mm.

3. PCB splicing board shape as close to the square as possible, recommended 2 × 2, 3 × 3, …… splicing board; but do not spell into the yin and yang board.

II. V-slot

1. after opening the V-slot, the remaining thickness X should be (1/4 ~ 1/3) board thickness L, but the minimum thickness X must be ≥ 0.4mm. The upper limit of the heavier load-bearing board can be taken, the lower limit of the lighter load-bearing board.

2. V-slot on both sides of the upper and lower notches of the misalignment S should be less than 0.1mm; due to the minimum effective thickness of the restrictions, the thickness of less than 1.2mm board, should not use V-slot spell board way.

III. Mark point

1. Set the reference positioning point, usually in the positioning point around the leave 1.5 mm larger than its non-resistant soldering area.

2. Used to help the optical positioning of the placement machine has a chip device PCB board diagonal at least two asymmetric reference points, the whole PCB optical positioning with the reference point is generally in the whole PCB diagonal corresponding position; piece of PCB optical positioning with the reference point is generally in the piece of PCB diagonal corresponding position.

3. for lead spacing ≤ 0.5mm QFP (square flat package) and ball spacing ≤ 0.8mm BGA (ball grid array package) devices, in order to improve the placement accuracy, the requirements of the IC two diagonal set of reference points.

IV. The process edge

1. The outer frame of the patching board and the internal small board, small board and small board between the connection point near the device can not be large or protruding devices, and components and the edge of the PCB board should be left with more than 0.5mm of space to ensure the normal operation of the cutting tool.

V. the board positioning holes

1. for PCB positioning of the whole board and for the positioning of fine-pitch devices benchmark symbols, in principle, a pitch of less than 0.65mm QFP should be set in its diagonal position; PCB subboard positioning benchmark symbols should be used in pairs, arranged at the diagonal of the positioning elements.

2. Large components should be left with positioning columns or positioning holes, focusing on such as I/O interfaces, microphones, battery interfaces, microswitches, headphone interfaces, motors, etc..

A good PCB designer, in the collocation design, to consider the factors of production, to facilitate processing, improve production efficiency and reduce production costs.