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Wiring design rules of PCB

Release Date:2020-01-10

How to make a good design in PCB pads and wire to avoid manufacturing or functional problem, That is the question many of the PCB designer asked, there are some basic rule and tips to share.

1.1.1 line width and distance of printed wire


The line width of  printed wire shall be determined according to the wiring density and the current passing through the wire. The commonly used line width is 0.3mm (12mil), 0.2mm (8mil), 0.15mm (6mil), 0.12mm (5MIL). Generally, the thickness of signal line shall be uniform as far as possible to avoid sudden change of thickness and sharp turn. The design of power line, ground wire and large area copper-clad can refer to relevant regulations. Refer to table 7 for pad spacing, line to line spacing, line to pad, line to hole, pad to hole distance during Pad lead out design

Table1 Recommended spacing for several lineweights                        mmmil

line width

0.312

0.28

0.156

0.125

PCB layer

Spcing

Outer

Inner

Outer

Inner

Outer

Inner

Outer

Inner

Pad  Spacing

0.2510

0.25

10

0.2

8

0.2

8

0.15

6

0.15

6

0.12

5

0.12

5

Line to Line

0.2510

0.25

10

0.2

8

0.2

8

0.15

6

0.15

6

0.12

5

0.12

5

Line to Pad

0.2510

0.25

10

0.2

8

0.2

8

0.15

6

0.15

6

0.12

5

0.12

5

Line to Hole

0.38

15

0.45

18

0.3

12

0.4116

0.18

7

0.3313

0.15

6

0.3313

Pad  to Hole

0.38

15

0.45

18

0.3

12

0.4116

0.2

8

0.3313

0.18

7

0.3313



The outgoing line of the pad shall be led out vertically from the middle as precisely as possible, as shown in Figure 19



Figure1   Schematic diagram of pad outgoing line




1.1.2 Design of connection between pad and pad

The wire between adjacent pin pads of the same multi pin component shall be short circuited through outgoing wire, as shown in Figure 16 (a). Generally, the method of direct short-circuit of pad is not adopted, as shown in FIG. 20 (b).


A. recommend                                                          B.Not recommend

FIG20  Wiring diagram of pad

1.1.3 Design of connecting wire between pad and through hole

Lead  wire connection shall be adopted  between  the  pad  and  the through hole, and  the

distance between the through hole and the pad edge shall be greater than 0.5mm..No through holes are allowed in and on the edge of the surface assembly welding pad, as shown in Figure 21


Figure 21. wiring diagram of pad and through hole (unit: mm)

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