PCB design and fabrication

Lin ZhongELEC424, Fall 2010

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Alternatives to PCB

• Breadboard

Breadboard prototype of the first IBM PC motherboard (1981)http://www.yourdictionary.com/computer/breadboard

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Alternative to PCB (Contd.)

• Prefabricated PCB

Digikey.com

Outline

• Basic concepts• Introduction to EAGLE• A small design project

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PCB design concepts

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Function Design Schematic

Layout

Routing

Form factor constraints

Production

Assembly

Component library

Design tools

PCBexpress.com

Any local workshops

Design rules

Schematic Capture

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Layout and Routing

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Layout and Routing (Contd.)

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Component Library

• Component packaging– Surface mount technology (SMT)– Through-hole packaging

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Chip packaging

• Through-hole– Dual in-line(DIP)– Pin grid array (PGA)

• Surface mount– Quad flat (QFP)– Ball grid array (BGA)

• Socket-based– Land grid array (LGA)

Core 2 Duo E6700

XC68020

PCB design concepts

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Function Design Schematic

Layout

Routing

Form factor constraints

Production

Assembly

Component library

PCB design tool

PCBexpress.com

Any local workshops

Design rules

Production• Patterning (etching)

– Subtractive process to remove copper cover from a preimpregnated substrate

– Silk-screen printing of etch-resistant inks• Lamination

– Multilayer PCBs• Drilling (vias and holes)• Coating (Solder and Solder mask /resist)• Printing text and symbols

12http://www.unitechelectronics.com

Assembly• Pick & place machine

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http://www.europlacer.com

Assembly (Contd.)

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Assembly (Contd.)• Soldering– Wave soldering– Reflow oven

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Wave soldering

• Waves of liquid solder• Board passes the waves• Large devices, high pin count, through-hole

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Reflow Oven

• Heat the board up (infrared)• Small, surface mounted components

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Further Reading

• How motherboards are made– http://www.pcstats.com/articleview.cfm?articleid=1722

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Caveats

• Locations of components• Orientation of components• Height of components• Polarity of components• SMT vs. Through-hole components

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PCB vs. IC

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Function Design Schematic

Layout

Routing

Form factor constraints

Production

Assembly

Component library

Design rules

Synthesis

Integrated

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PCB vs. IC production• Polymer composite board

• Silkscreen printing, photoengraving – Etch away copper

• Copper wires

• Place components on top of board

• Soldering

• Silicon wafer

• Photolithography

• Metallic (copper) wires

• Make devices such as transistors on the wafer

• Modification– Ion implantation, furnace anneal

• Deposition– Physical vapor deposition (PVD)– Chemical vapor deposition (CVD)

Small scale and large # of devices