PCB Footprints

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Contents

Standard Footprints

Footprints for common packages used by many different components.

Special Footprints

Footprints for components that don't necessarily use a standardized package or layout.

Manufacturer Description Available footprints
Trimble Lassen iQ GPS Module Protel
(none) Compact Flash IDE Connector Protel
Linx Technologies RF transmitters, RF receivers and USB transcievers Protel
Spark Fun Electronics Old SFE Footprint Library Protel
Spark Fun Electronics Updated Eagle SFE Footprint Library Eagle
Cypress PSoC microcontrollers Protel, Eagle
Microchip PIC microcontrollers gEDA ? ORCAD ?
Atmel Atmel AVR Protel (dead link)
Philips ARM microcontrollers in LQFP-48 package Eagle
Various Sarang: Many Protel libraries from Altium Protel
Misc. Variety of footprints for gEDA/PCB PCB Protel


QFN Footprints

I'm a little intimidated by these little QFN packages. Alas, I've been asked to use a chip that doesn't have any alternative package.

"QFN/SON PCB Attachment Application Report: SLUA271"

"QFN Layout Guidelines: sloa122"

prototyping boards for Chip Scale (QFN) Packages from SchmartBoard

Any other tips?

high-power footprints

When MOSFETs and image sensors get warm, they don't work as well. Many ICs are guaranteed to work only up to 85 °C. "Automotive grade" ICs are typically guaranteed to work only up to 125 °C.

Several of the most popular ways to keep a part cool involve footprints:

  • In general, larger packages (such as "Power-SO8 LFPAK"[1][2], TO-220, and D2PAK packages), with larger footprints, can handle more power than smaller packages (such as TO-92 and SOT23 packages). Often people don't know ahead of time if the small, cheap voltage regulator will be adequate, or if they will need the larger part.
    • Some people prefer a "universal layout" that supports practically any 3-pin voltage regulator.[3]
  • Some heatsinks are designed to mount in holes drilled through the PCB.
    • Some people make a separate "heatsink footprint", often with a corresponding "heatsink schematic component".
    • Other people make a single footprint such as "TO220_plus_heatsink" that has all the holes for a TO-220 package and a TO-220 heatsink all lined up perfectly relatively to each other.
  • Many people use a square inch or more of PCB copper as a heat sink. Enlarged copper mounting pads, on one or both sides of the PCB, help keep the component closer to ambient temperature. ... thermal vias ? ...
    • Some people make a "power footprint" that includes a big patch of PCB copper as a heat sink.
    • Some people make a "power footprint" that includes a big patch of PCB copper on both the top and bottom as a heat sink, and thermal vias between them.
    • Many people add a "flood fill"/"filled poly" on the PCB. Zhang. "PCB layout considerations for non-isolated switching power supplies".[4]
    • AN1028: "Maximum Power Enhancement Techniques for SOT-223 Power MOSFETs".[5]
    • "Soldering and Mounting Techniques: Reference Manual"[6], in particular, "Figure 2. Thermal Resistance versus Drain Pad Area for the DPAK Package" and "Figure 3. Thermal Resistance versus Drain Pad Area for the D2PAK Package".
    • "Filling in empty spaces on your printed circuit board with copper areas [helps] heat dissipation. This is true even if the copper fills are not electrically connected" -- David Cook[7]


The Open Symbol Project

"The Open Symbol Project aims to create an open collection of schematic symbols and PCB footprints released under a license that does not interfere with use in either commercial or free projects. ... can easily be modified to accommodate various design rules."

What can we do to help the Open Symbol Project?

Links to Footprints

  • un-tested gEDA symbols and footprints
    • All of these Symbols are heavy symbols. gEDA has already provided most of the above symbols in light format for us to modify. The above symbols include more information than normal to save some time instead of configuring each symbol every time you use them.

Contributing

Yes, please do! Hit the "Upload file" link in the left column, and select your PCB footprint file.

Please take a look at Talk:PCB_Footprints#Contributing.

Further reading

  • Obtaining PCB footprints -- even if you have to manually draw them yourself -- is a key part of designing Printed Circuit Boards.
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