PCB Technical - Precautions of PCB pad circuit

The reflow soldering process of SMT chip requires that the pads of two end chip components should be independent pads. When the pad is connected with a large area of ground wire, the cross paving method and 45 ° paving method should be preferred; the length of the wire leading from the large area ground wire or power line is greater than 0.5mm, and the width is less than 0.4mm; the wire connected with the rectangular pad should be led out from the center of the long side of the pad to avoid a certain angle.

The wire between SMD pads and the lead out wire of pad are shown in the figure. The diagram shows the connection between pad and printed wire.

What should be paid attention to in the direction and shape of PCB pad printed wire.

The direction and shape of printed wire

(1) Do not short circuit, so you can not follow the short circuit. It is very helpful for the quality control of PCB in the later stage.

(2) The direction of printed wire shall not have sharp bending and acute angle, and the angle of printed wire shall not be less than 90 °. This is because it is difficult to corrode the small inner angle when making the plate. The copper foil is easy to peel off or warp at the outer corners that are too sharp. The form of turning is a gentle transition, that is, the inner and outer corners of the corner are radians.

(3) When a wire passes between two gaskets and is not connected to them, it shall be kept at an equal distance from them; similarly, the distance between conductors shall be uniform and equal and maintained.

(4) When connecting wires between PCB pads, when the center distance between pads is less than the outer diameter D of pads, the width of wires can be the same as that of pads; when the center distance between pads is greater than D, the width of wires should be reduced. When there are more than 3 pads on the pad, the distance between wires should be greater than 2D.

(5) Copper foil shall be retained as far as possible for common ground wire.

(6) In order to increase the peeling strength of the liner, a production line without conductive effect can be provided.