PCB DESIGN – TYPICAL LAYOUT CHARACTERISTICS

Electronics & Software

INTRODUCTION

The ever increasing requirements for small volume envelopes contribute to integrating electronics to the mechanical design. Although there are numerous solutions this sheet provides the JPE standard in designing PCB’s

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Electrical layout characteristics
  • Guidelines for outer layers (top/bottom), but also suitable for inner layers
  • Copper base thickness: 18 um
  • Suitable for PCB thickness of: ≤ 2.4 mm
PCB design - PCB Classification
TypeMinimalRecomm.Note
Trace Width0.15 mmRecommended values: see “PCB trace widths”
Edge-Trace0.45 mm1.0 mm
Trace-Trace0.15 mm0.35 mm
Trace-Pad0.15 mm0.35 mm
Pad-Pad0.15 mm0.5 mm
Pad-Hole0.20 mm0.5 mmAlso for Trace-Hole
Finished hole ø for PTH0.25 mmInitial drill hole ø will be +0.1 mm to accommodate through hole plating
Finished hole ø for NPTH0.35 mm
OAR PTH0.125 mm0.35 mm
OAR NPTH0.30 mm0.5 mmFor non-plated hole but with pad on top/bottom
Via ø0.45 mm0.6 mmA PTH to connect traces from/to different layers
PCB trace widths
  • Copper base thickness: 18 um
  • Temperature rise of trace: ≤ 15 °C
  • Ambient temperature: ~25 °C
  • For outer layer traces only (top/bottom)
Signal typeMinimal RecommendedApplication
Low current0.5 mm1.0 mmLow voltage DC power supply lines
High current1.5 mm≥ 2.5 mmMains, high power DC
Digital0.2 mm0.5 mmI/O, logic, microcontroller, CPLD
Analog0.5 mm0.8 mmADC, low power op-amps
PCB build up

A standard build up of a 4-layer, thickness of 1.55 mm:

PCB design - PCB Build Up

In a 2-layer design, the Copper Inner and Prepreg layers are left out but the base FR4 is thicker.

Mechanical design characteristics
TypeValueNote
PCB Dimensionsmin. 5 x 5 mmPCB does not have to be rectangular!
max. 425 x 425 mm
Board thickness1.55 mmIndustry standard
1.00 mmAlso a standard for ceramic PCBs
2.00 mmHeavy components
Width for slotsmin. 0.5 mm
Radius inside corners PCB edgemin. 1.0 mm
Drill size increments0.05 mm
Standard tolerancesEnd-size drill ø NPTH:
±0.05 mm
End-size drill ø PTH:
±0.1 mm
Contour dim. : ±0.2 mm
Position contour / holes:
±0.2 mm
Slot dimensions:
width: ±0.1 mm
length: ±0.2 mm
Surface finish on solderable pads and tracesHAL Lead-freeGood solderability, for standard PCB thickness
ENIG (chem. Ni/Au)Flat surface, for connectors and contacts, expensive
Immersion Silver
(chem. Ag)
Flat surface, long shelf life, cheap