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PCB Design Guidelines

With the popularization of electronic products and the expansion of market scale, as one of the core components of electronic products, printed circuit boards are used more and more. According to different end products and usage scenarios, PCB production process limitations, the design of PCB circuit boards should also follow certain rules.

Printed Circuit Board

Below are several Guideline Rules to follow and keep in mind when designing PCBs. These are general rules that apply to most PCB manufacturers, but it is advisable to check with your fabricator.

  • Board Size

PCB manufacturers have a maximum size board they can handle. Typically this is also their panel size. The PCB fabrication house’s panel size is also important when mass producing boards. In this situation, one would want to fit as many boards as possible on a panel with as little wasted board space (to reduce costs). Normal board spacing for routing (how boards are separated on a panel) is 0.3″, plus there is typically a 1.0″ to 2.0″ border on the board for handling it during processing.

Board thickness may also be specified. A standard thickness and type of board is .062″ FR4. Other typical board thickness are .010″, .020″, .031″, and .092″.

  • Trace Width and Spacing

The chemical and photographic processes used to produce a PCB put requirements on the minimum width of trace and the minimum spacing between traces. If a trace is made smaller than this minimum width, there is some chance it will open (no connection) when manufactured. If two traces are closer together than the minimum spacing, there is some chance they will short when manufactured. These parameters are usually specified as “x/y rules,” where x is the minimum trace width, and y is the minimum trace spacing. For example, “8/10 rules” would indicate 8 mil minimum trace width and 10 mil minimum trace spacing. These rules (especially spacing) apply to any metal on the PCB, including a pad to track spacing and line widths for strings on the PCB.

Typical modern process rules are 8/8 rules with values as small as 2/2 rules being available. For Press-n-Peel, people have had success using 12/12 rules, but values a little larger are easier to make work consistently. However, keep in mind that the board must be soldered, and a trace within 8 mils (8/8 rules) of a pad is easier to short than one with greater spacing when hand soldered. For hand soldering, 10/10 rules are much easier to solder (if the design density can spice this large).

  • Pad Sizes

The biggest issues with pad size are solderability and manufacturability. Solderability is really just a matter of skill and will not be discussed here. Manufacturability is concerned with whether the pad will be broken when the hold is drilled in it. This is mainly a function of the accuracy of the PCB manufacturer’s drilling. If a drill hole is slightly off-center, the pad may be broken at one edge, possibly leading to an open circuit. A standard requirement for pad sizes is a 5 mil annulus. This means there must be .005″ all around the hole (i.e., a 28 mil hole would require a 38 mil pad). Something a little larger than this (maybe 10 mils) is recommended for solderability. AP Circuits states they have had relatively consistent success with a 2.5 mil annulus (i.e., a 20 mil hole with only a 25 mil pad), but they don’t recommend it.

  • Hole Sizes

Most PCB manufacturers have a wide selection of drill (hole) sizes available. Some charge per drill size used; others offer a standard set of drill sizes for no charge and then charge for non-standard drill sizes. AP Circuits uses the latter approach. When choosing a hole size, remember that the plate-through will cause the hole to be more narrow effectively. The plate-through thickness varies from .001″ to .003″. AP Circuits’ plate-through thickness is approximately .015″ (meaning the “finished hole” diameter is 3 mils smaller).

Standard Drill Sizes

 

Drill Number

Hole Size

Finished Hole Size

70

.028″

.025″

65

.035″

.032″

58

.042″

.039″

55

.052″

.049″

53

.0595″

.056″

44

.086″

.083″

1/8″

.125″

.122″

24

.152″

.149″

  • Hole Density

Hole density is purely a cost issue. The more holes there are on a board, the more wear and tear manufacturing will put on the equipment (and the more the board will cost). Most PCB manufacturers have a maximum hole density, and boards with greater density are charged more. For AP Circuits, there is a per-hole charge for densities above 24 holes per square inch.

Drill Chart

Drill No.

Inches

Drill No.

Inches

Drill No.

Inches

80

.0135

53

.0595

27

.1440

79

.0145

52

.0635

26

.1470

78

.0160

51

.0670

25

.1495

77

.0180

50

.0700

24

.1520

76

0200

49

.0730

23

.1540

75

.0210

48

.0760

22

.1570

74

.0225

47

.0785

21

.1590

73

.0240

46

.0810

20

.1610

72

.0250

45

.0820

19

.1660

71

.0260

44

.0860

18

.1695

70

.0280

43

.0890

17

.1730

69

.0292

42

.0935

16

.1770

68

.0310

41

.0960

15

.1800

67

.0320

40

.0980

14

.1820

66

.0330

39

.0995

13

.1850

65

.0350

38

.1015

12

.1890

64

.0360

37

.1040

11

.1910

63

.0370

36

.1065

10

.1935

62

.0380

35

.1100

09

.1960

61

.0390

34

.1110

08

.1990

60

.0400

33

.1130

07

.2010

59

.0410

32

.1160

06

.2040

58

.0420

31

.1200

05

.2055

57

.0430

1/8″

.1250

04

.2090

56

.0465

30

.1285

03

.2130

55

.0520

29

.1360

02

.2210

54

.0550

28

.1405

01

.2280

dBm – Volts – Watts Conversion

dBm

V

Po

dBm

V

Po

dBm

UV

Po

+53

100.0

200W

+7

0.50

5mW

-37

3.2

+50

70.0

100W

+6

0.445

4mW

-38

2.85

+49

64.0

80W

+5

0.40

3.2mW

-39

2.5

+48

58.0

64W

+4

0.355

2.5mW

-40

2.25

0.1uW

+47

50.0

50W

+3

0.320

2.0mW

-41

2.0

+46

44.5

40W

+2

0.280

1.6mW

-42

1.8

+45

40.0

32W

+1

0.252

1.25mW

-43

1.6

+44

32.5

25W

0

0.225

1.00mW

-44

1.4

+43

32.0

20W

-1

0.200

0.80mW

-45

1.25

+42

28.0

16W

-2

0.180

0.64mW

-46

1.18

+41

26.2

12.5W

-3

0.160

0.50mW

-47

1.00

+40

22.5

10W

-4

0.141

0.40mW

-48

0.90

+39

20.0

8W

-5

0.125

0.32mW

-49

800

+38

18.0

6.4W

-6

0.115

0.25mW

-50

710

0.01uW

+37

16.0

5W

-7

0.100

0.20mW

-51

640

+36

14.1

4W

-8

0.090

0.16mW

-52

570

+35

12.5

3.2W

-9

0.080

0.125mW

-53

500

+34

11.5

2.5W

-10

0.071

0.10mW

-54

450

+33

10.0

2W

-11

64

-55

0.40

+32

9.0

1.6W

-12

58

-56

351

+31

8.0

1.25W

-13

50

-57

320

+30

7.10

1.0W

-14

45

-58

286

+29

6.40

800mW

-15

40

-59

251

+28

5.80

640mW

-16

35.5

-60

225

0.001uW

+27

5.00

500mW

-17

31.5

-61

200

+26

4.45

400mW

-18

28.5

-62

180

+25

4.00

320mW

-19

25.1

-63

160

+24

3.55

250mW

-20

22.5

0.01mW

-64

141

+23

3.20

200mW

-21

20.0

-65

128

+22

2.80

160mW

-22

17.9

-66

115

+21

2.52

125mW

-23

15.9

-67

100

+20

2.25

100mW

-24

14.1

-68

90

+19

2.00

80mW

-25

12.8

-69

80

+18

1.80

64mW

-26

11.5

-70

71

0.1nW

+17

1.60

50mW

-27

10.0

-71

65

+16

1.41

40mW

-28

8.9

-72

58

+15

1.25

32mW

-29

8.0

-73

50

+14

1.15

25mW

-30

7.1

0.001mW

-74

45

+13

1.00

20mW

-31

6.25

-75

40

+12

0.90

16mW

-32

5.8

-76

35

+11

0.80

12.5mW

-33

5.0

-77

32

+10

0.71

10mW

-34

4.5

-78

29

+9

0.64

8mW

-35

4.0

-79

25

+8

0.58

6.4mW

-36

3.5

-80

22.5

0.01nW

Getek® Laminates – Epoxy / Polyphenylene Oxide Resin

(Type: NEMA FR-4, IPC-L-108B/04)

Nominal thickness

Thickness tolerance

GE grade

E-Glass construction

Dk@1MHz.

0.0027″

±0.0005″

ML200D

1080

3.8

0.004″

±0.0005″

ML200D

2313

3.9

0.005″

±0.0007″

ML200M

2313/106

3.8

0.006″

±0.0007″

ML200D

2313/1080

3.9

0.007″

±0.0010″

ML200M

(2)2313

3.8

0.008″

±0.0010″

ML200D

2313/2116

3.9

0.010″

±0.0010″

ML200D

(2)2116

3.9

0.012″

±0.0010″

ML200D

1080/7628/1080

3.9

0.014″

±0.0015″

ML200D

(2)7628

4.2

0.018″

±0.0015″

ML200D

7628/2313/7628

4.1

0.021″

±0.0020″

ML200D

(3)7628

4.2

0.024″

±0.0020″

ML200C

2116/(2)7628/2116

4.1

0.028″

±0.0020″

ML200D

(4)7628

4.2

0.028″(Alt.)

±0.0020″

ML200C

1080/2313/(3)2116/2313/1080

3.8

0.031″

±0.0030″

ML200C

2116/(3)7628/2116

4.1

0.031″1

±0.0040″

ML200D

(4)7628

4.2

0.044″1

±0.0050″

ML200D

(6)7628

4.2

0.059″1

±0.0050″

ML200D

(8)7628

4.2

VSWR Vs. Return Loss

VSWR

Ret. Loss

VSWR

Ret. Loss

VSWR

Ret. Loss

VSWR

Ret. Loss

VSWR

Ret. Loss

1.01

-46.064

1.51

-13.842

1.79

-10.960

2.18

-8.611

2.57

-7.135

1.02

-40.086

1.52

-13.708

1.80

-10.881

2.19

-8.565

2.58

-7.105

1.03

-36.608

1.53

-13.577

1.81

-10.804

2.20

-8.519

2.59

-7.074

1.04

-34.151

1.54

-13.449

1.82

-10.729

2.21

-8.474

2.60

-7.044

1.05

-32.256

1.55

-13.324

1.83

-10.654

2.22

-8.430

2.61

-7.014

1.06

-30.714

1.56

-13.201

1.84

-10.581

2.23

-8.386

2.62

-6.984

1.07

-29.417

1.57

-13.081

1.85

-10.509

2.24

-8.342

2.63

-6.954

1.08

-28.299

1.58

-12.964

1.86

-10.437

2.25

-8.299

2.64

-6.925

1.09

-27.318

1.59

-12.849

1.87

-10.367

2.26

-8.257

2.65

-6.896

1.10

-26.444

1.60

-12.736

1.88

-10.298

2.27

-8.215

2.66

-6.867

1.11

-25.658

1.61

-12.626

1.89

-10.230

2.28

-8.173

2.67

-6.839

1.12

-24.943

1.62

-12.518

1.90

-10.163

2.29

-8.132

2.68

-6.811

1.13

-24.289

1.63

-12.412

1.91

-10.097

2.30

-8.091

2.69

-6.783

1.14

-23.686

1.64

-12.308

1.92

-10.032

2.31

-8.051

2.70

-6.755

1.15

-23.127

1.65

-12.207

1.93

-9.968

2.32

-8.011

2.71

-6.728

1.16

-22.607

1.66

-12.107

1.94

-9.904

2.33

-7.972

2.72

-6.700

1.17

-22.120

1.67

-12.009

1.95

-9.842

2.34

-7.933

2.73

-6.673

1.18

-21.664

1.68

-11.913

1.96

-9.780

2.35

-7.894

2.74

-6.646

1.19

-21.234

1.69

-11.818

1.97

-9.720

2.36

-7.856

2.75

-6.620

1.20

-20.828

1.70

-11.725

1.98

-9.660

2.37

-7.818

2.76

-6.594

1.21

-20.443

1.71

-11.634

1.99

-9.601

2.38

-7.781

2.77

-6.567

1.22

-20.079

1.72

-11.545

2.00

-9.542

2.39

-7.744

2.78

-6.541

1.23

-19.732

1.73

-11.457

2.01

-9.485

2.40

-7.707

2.79

-6.516

1.24

-19.401

1.74

-11.370

2.02

-9.428

2.41

-7.671

2.80

-6.490

1.25

-19.085

1.75

-11.285

2.03

-9.372

2.42

-7.635

2.81

-6.465

1.26

-18.783

1.76

-11.202

2.04

-9.317

2.43

-7.599

2.82

-6.440

1.27

-18.493

1.77

-11.120

2.05

-9.262

2.44

-7.564

2.83

-6.415

1.28

-18.216

1.78

-11.039

2.06

-9.208

2.45

-7.529

2.84

-6.390

1.29

-17.949

1.40

-15.563

2.07

-9.155

2.46

-7.494

2.85

-6.366

1.30

-17.692

1.41

-15.385

2.08

-9.103

2.47

-7.460

2.86

-6.341

1.31

-17.445

1.42

-15.211

2.09

-9.051

2.48

-7.426

2.87

-6.317

1.32

-17.207

1.43

-15.043

2.10

-8.999

2.49

-7.393

2.88

-6.293

1.33

-16.977

1.44

-14.879

2.11

-8.949

2.50

-7.360

2.89

-6.270

1.34

-16.755

1.45

-14.719

2.12

-8.899

2.51

-7.327

2.90

-6.246

1.35

-16.540

1.46

-14.564

2.13

-8.849

2.52

-7.294

2.91

-6.223

1.36

-16.332

1.47

-14.412

2.14

-8.800

2.53

-7.262

2.92

-6.200

1.37

-16.131

1.48

-14.264

2.15

-8.752

2.54

-7.230

2.93

-6.177

1.38

-15.936

1.49

-14.120

2.16

-8.705

2.55

-7.198

2.94

-6.154

1.39

-15.747

1.50

-13.979

2.17

-8.657

2.56

-7.167

2.95

-6.131

VSWR Vs. Return Loss (Continued)

VSWR

Ret. Loss

VSWR

Ret. Loss

VSWR

Ret. Loss

VSWR

Ret. Loss

VSWR

Ret. Loss

2.96

-6.109

3.07

-5.872

3.18

-5.654

3.29

-5.452

3.40

-5.265

2.97

-6.086

3.08

-5.852

3.19

-5.635

3.30

-5.435

3.41

-5.248

2.98

-6.064

3.09

-5.832

3.20

-5.617

3.31

-5.417

3.42

-5.232

2.99

-6.042

3.10

-5.811

3.21

-5.598

3.32

-5.400

3.43

-5.216

3.00

-6.021

3.11

-5.791

3.22

-5.579

3.33

-5.383

3.44

-5.200

3.01

-5.999

3.12

-5.771

3.23

-5.561

3.34

-5.365

3.45

-5.184

3.02

-5.977

3.13

-5.751

3.24

-5.542

3.35

-5.348

3.46

-5.168

3.03

-5.956

3.14

-5.732

3.25

-5.524

3.36

-5.331

3.47

-5.152

3.04

-5.935

3.15

-5.712

3.26

-5.506

3.37

-5.315

3.48

-5.137

3.05

-5.914

3.16

-5.693

3.27

-5.488

3.38

-5.298

3.49

-5.121

3.06

-5.893

3.17

-5.674

3.28

-5.470

3.39

-5.281

3.50

-5.105

WIRE DATA CHART

 

AWG

Diam
(In.)

AWG

Diam
(In.)

AWG

Diam
(In.)

AWG

Diam
(In.)

4/0

0.4600

9

0.1144

21

0.0285

33

0.0071

3/0

0.4096

10

0.1019

22

0.0253

34

0.0063

2/0

0.3648

11

0.0907

23

0.0226

35

0.0056

1/0

0.3249

12

0.0808

24

0.0201

36

0.0050

1

0.2893

13

0.0720

25

0.0179

37

0.0045

2

0.2576

14

0.0641

26

0.0159

38

0.0040

3

0.2294

15

0.0571

27

0.0142

39

0.0035

4

0.2043

16

0.0508

28

0.0126

40

0.0031

5

0.1819

17

0.0453

29

0.0113

41

0.0028

6

0.1620

18

0.0403

30

0.0100

42

0.0025

7

0.1443

19

0.0359

31

0.0089

43

0.0022

8

0.1285

20

0.0320

32

0.0080

44

0.0020

 

PCMCIA CONNECTOR PIN OUT

 

16-Bit Pin

32-bit Memory

16-Bit I/O+Mem

32-bit CardBus

Pin

Memory

I/O+Mem

CardBus

1

GND

GND

GND

35

GND

GND

GND

2

D3

D3

CAD0

36

CD1#

CD1#

CCD1#

3

D4

D4

CAD1

37

D11

D11

CAD2

4

D5

D5

CAD3

38

D12

D12

CAD4

5

D6

D6

CAD5

39

D13

D13

CAD6

6

D7

D7

CAD7

40

D14

D14

RSRVD

7

CE1#

CE1#

CCBE0#

41

D15

D15

CAD8

8

A10

A10

CAD9

42

CE2#

CE2#

CAD10

9

OE#

OE#

CAD11

43

VS1#

VS1#

CVS1

10

A11

A11

CAD12

44

RSRVD

IORD#

CAD13

11

A9

A9

CAD14

45

RSRVD

IOWR#

CAD15

12

A8

A8

CCBE1#

46

A17

A17

CAD16

13

A13

A13

CPAR

47

A18

A18

RSRVD

14

A14

A14

CPERR#

48

A19

A19

CBLOCK#

15

WE#

WE#

CGNT#

49

A20

A20

CSTOP#

16

READY

IREQ#

CINT#

50

A21

A21

CDEVSEL#

17

Vcc

Vcc

Vcc

51

Vcc

Vcc

Vcc

18

Vpp1

Vpp1

Vpp1

52

Vpp2

Vpp2

Vpp2

19

A16

A16

CCLK

53

A22

A22

CTRDY#

20

A15

A15

CIRDY#

54

A23

A23

CFRAME#

21

A12

A12

CCBE2#

55

A24

A24

CAD17

22

A7

A7

CAD18

56

A25

A25

CAD19

23

A6

A6

CAD20

57

VS2#

VS2#

CVS2

24

A5

A5

CAD21

58

RESET

RESET

CRST#

25

A4

A4

CAD22

59

WAIT#

WAIT#

CSERR#

26

A3

A3

CAD23

60

RSRVD

INPACK#

CREQ#

27

A2

A2

CAD24

61

REG#

REG#

CCBE3#

28

A1

A1

CAD25

62

BVD2

SPKR#

CAUDIO

29

A0

A0

CAD26

63

BVD1

STSCHG#

CSTSCHG

30

D0

D0

CAD27

64

D8

D8

CAD28

31

D1

D1

CAD29

65

D9

D9

CAD30

32

D2

D2

RSRVD

66

D10

D10

CAD31

33

WP

IOIS16#

CCLKRUN#

67

CD2#

CD2#

CCD2#

34

GND

GND

GND

68

GND

GND

GND

 

TRACE SPACING GUIDELINE

Voltage Between Conductors

VDC or Peak

A1

A2

A3

A4

A5

A6

A7

0 thru
15 0

.004

0.025

0.025

0.005

0.005

0.005

0.005

16 thru
30 0

.004 0

.025

0.025

0.005

0.005

0.010

0.005

31 thru
50 0

.004

0.025

0.025

0.005

0.005

0.015

0.005

51 thru 100

0.004

0.025

0.060

0.005

0.005

0.020

0.005

101 thru 150

0.008

0.025

0.125

0.015

0.015

0.030

0.015

151 thru 170

0.008

0.050

0.125

0.015

0.015

0.030

0.015

171 thru 250

0.008

0.050

0.250

0.015

0.015

0.030

0.015

251 thru 300

0.008

0.050

0.500

0.015

0.015

0.030

0.015

301 thru 500

0.010

0.100

0.500

0.030

0.030

0.060

0.030

More than 500

0.0001/V

0.0002/V 0.001/V

0.00012/V

0.00012/V

0.00012/V

0.00012/V

A1 – Internal Conductors
A2 – External Conductors, uncoated, sea level to 10,000 ft.
A3 – External Conductors, uncoated, over 10,000 ft.
A4 – External Conductors, with permanent polymer coating (Solder Mask).
A5 – External Conductors, with a conformal coating over the assembly.
A6 – External Component lead/termination, uncoated.
A7 – External Component lead/termination, with conformal coating.

  • Electrical Design Factors

Conductor Capacitance

C = 0.31 a/b + 0.23(1 + k) log10 (1 + 2b/d +2b + b2/d2)

Where
k = Substrate dielectric constant
a = Conductor thickness
b = Width of conductor in inches
d = Distance between conductors in inches

Conductor Resistance

R = 0.000227W

Where
W = Width of conductor

Characteristic Impedance

Zo = R + jwL / G + kwC

Where
Zo = Apparent Z of an infinitely long line in ohms
R = Resistance in ohms
L = Inductance in Henries
G = Conductor per unit length of line in mhos
C = Capacitance in farads

Characteristic Impedance for a Micro Strip

Zo = (h/W) (377 / (Sqrt. er) {1 + (2h/PI W)[1 + ln(PI W/h)]}

Where
h = Dielectric thickness
W = Micro Strip width
er = Effective dielectric constant of substrate

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