Printed Circuit Board Design
Sung Yeul Park
Dept. of Electrical and Computer Eng
University of Connecticut
September 24, 2014
What can you see from an electrical
engineering perspective?
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Three Elements to be considered
 Components :
- How to select components?
- What values are needed?
- What kind of package will be?
 Printed Circuit Board :
- Schematic Design
- PCB Layout Design
- Prototype board
 Case or Box for the prototype board :
- Purchase or build by yourself
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Printed Circuit Board ?
 A printed circuit board (PCB) mechanically supports and electrically
connects electronic components using conductive tracks, pads and
other features etched from copper sheets laminated onto a nonconductive substrate.
 PCBs can be single sided (one copper layer),double sided (two
copper layers) or multi-layer.
 Conductors on different layers are connected with plated-through
holes called vias.
 Advanced PCBs may contain components - capacitors, resistors or
active devices - embedded in the substrate.
Printed Circuit Board Design
A PCB as a design on a computer (left) and realized as a board assembly
populated with components (right). The board is double sided, with through-hole
plating, green solder resist and a white legend. Both surface mount and
through-hole components have been used.
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Printed Circuit Board Design
Schematic Design
PCB Layout
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Key terms for PCB design
 Pads are where the components are soldered
to the PCB.
 Traces are the copper tracks that
connect pads together.
 Via are small holes through the board
that link a bottom and top trace
together electrically. Traces on the
same layer cannot cross, so often,
when you are laying out a PCB, you
need to a signal to jump from one
layer to another.
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Key terms for PCB design
 Silk-screen refers to any lettering that
will appear on the final board.
 Solder-mask is a layer of insulating
lacquer that covers both sides of the
board except where there are pads.
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Multi-layer PCB design
 2 Layer PCB design: Top layer and bottom layer
 4 Layer PCB design: Top, Bottom, and two middle layers.
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PCB design procedure
 Design specification
 Circuit diagram
 Schematic design  Select components
Check the dimension  Build a footprint 
Make a PCB library  Add parts
 Export schematic design to layout design
 Route all connection
 Design rule check
 Generate Gerber files and drill file and zip them
 Upload zip file to PCB order
website
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PCB Library design
 Are you Ready to build a library?
 Component datasheet
 Dimension: mil (imperial unit) vs mm (metric)
1 inch =1000 mil, 1 mil = 0.0254 mm
1 mm = 39.3700787 mil
DIP component and connector: 100 mil or 2.54 mm
 Symbol in schematic vs Exact dimension in Layout
 Pad number should be matched in schematic symbol
and layout footprint
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PCB Library dimension example
 Male header
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PCB manufacturing procedure
http://www.pa-international.com/images/stories/Multilayer%20Metal%20Plate%20PCB%20Process%20Flow%20Chart.JPG
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Tips for PCB design
 Keep traces straight,
 Try to avoid 90o turns use two 45o’s.
 Double, even triple check layout,
 Having a fresh pair of eyes look it over,
 “measure twice, cut once” idea.
 Trace thickness & spacing
 Spacing of at least .010”,
 0.030” for In-house
 ~0.025” per 1 Amp carrying lines,
 Don’t use anything smaller than 0.010” for traces,
 0.030” for In-house milling.
 Try to keep all connections
on one side of PCB
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 Take into account component package
Free PCB design program
 EAGLE PCB Design Software:
http://www.cadsoftusa.com/download-eagle/freeware/
 Express PCB:
http://www.expresspcb.com/expresspcbhtm/download.htm
 Free PCB:
http://www.freepcb.com/
 Advanced Circuits:
http://www.4pcb.com/free-pcb-layout-software/
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Making PCBs
 Layout your circuit / circuits
 Check out http://www.expressPCB.com for some
great tips on component layout and power
distribution.
 Layout is more of an art.
 Tight spaces
 Lots of connections
 Make a 2 level board into a 3 level with vias
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PCB Design Example
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Top and Bottom Layer
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Middle Layers(2nd & 3rd)
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DSP Board
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DC-AC Inverter
DC-DC Converter
PCB Design Assignment
 Every senior design team need to design one printed circuit board
during fall semester.
 The number of components should be more than 10 components
with connectors, surface mount components, through-hole
components, and ICs.
 The number of layers should be 2 or more.
 Report due date is November 19th 2014
 Report: Schematic, Layout, and Free dfm Check result
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https://www.my4pcb.com/net35/FreeDFMNet/FreeDFMHome.aspx