• Skip to primary navigation
  • Skip to main content
  • Skip to primary sidebar
  • Skip to footer

Electrical Engineering News and Products

Electronics Engineering Resources, Articles, Forums, Tear Down Videos and Technical Electronics How-To's

  • Products / Components
    • Analog ICs
    • Battery Power
    • Connectors
    • Microcontrollers
    • Power Electronics
    • Sensors
    • Test and Measurement
    • Wire / Cable
  • Applications
    • 5G
    • Automotive/Transportation
    • EV Engineering
    • Industrial
    • IoT
    • Medical
    • Telecommunications
    • Wearables
    • Wireless
  • Learn
    • eBooks / Handbooks
    • EE Training Days
    • Tutorials
    • Learning Center
    • Tech Toolboxes
    • Webinars & Digital Events
  • Resources
    • White Papers
    • Educational Assets
    • Design Guide Library
    • Digital Issues
    • Engineering Diversity & Inclusion
    • LEAP Awards
    • Podcasts
    • DesignFast
  • Videos
    • EE Videos and Interviews
    • Teardown Videos
  • EE Forums
    • EDABoard.com
    • Electro-Tech-Online.com
  • Bill’s Blogs
  • Advertise
  • Subscribe

Via In Pad Guidelines for PCBs

December 3, 2018 By Duane Benson, Chief Technology Champion at Screaming Circuits

Via in pad seems to be one of the hot topics these days. It’s a bit of a tough one too. The SMT guys pretty much always say, “don’t ever do it.” However, with certain parts, the component manufacturer strongly recommends it. You gotta love those mutually exclusive requirements. Rather than just telling you “no, never” here’s a few guidelines on how to do it properly.

PCB assemblers don’t like it, but with some designs, if done properly, there can be a number of compelling reasons for putting vias directly in the SMT pads for BGA and QFN packaged components.

  • It can make routing easier with big or fine pitch BGAs
  • It can allow really close placement of bypass capacitors
  • It can help with thermal management
  • It can help with grounding on high-frequency parts

The primary reason we don’t want to see vias in pads is that when left open, those via holes act like little capillary straws and suck solder off of the pad. A couple of undesirable events can happen depending on the method used during board fab.

  • If your vias are left open, solder will tend to wick down into the via hole. The larger the diameter, the worse the wicking problem can be. You might end up without enough solder left to secure the component, or even a solder bump on the bottom side of the board which could interfere with other components or lead to shorts.
  • If your vias are capped or partially filled, the caps might pop off due to thermal expansion or out-gassing. Internal air bubbles can migrate up, leading to voids in your solder joint.

Open vias in pads are not an industry-accepted practice. In a perfect world, we’d like to never see one. However, the real-world is saying otherwise. Manufacturers of QFN parts are starting to recommend vias in the heat-slug pad for improved thermal conductivity. High frequency designs benefit from the shortest possible routing, which may indicate via in pad. Super fine pitch BGAs may not leave any other options.

My first recommendation would be to re-design the boards so the vias are in between the pads, plug or cap the vias at the board house or to use microvias that don’t go all the way through the board. If you can’t do any of that, use as small a diameter as the design will allow and follow the component manufacturer’s guidelines for placement and via capping or filling.

You Might Also Like

Filed Under: Components

Primary Sidebar

EE Engineering Training Days

engineering

Featured Contributions

zonal architecture

Addressing zonal architecture challenges in the automotive industry

zonal architecture

Addressing zonal architecture challenges in the automotive industry

A2L refrigerants drive thermal drift concerns in HVAC systems

Why outdoor charging demands specialized battery connectors

How Li-ion batteries are powering the shift in off-highway equipment

More Featured Contributions

EE Tech Toolbox

“ee
Tech Toolbox: 5G Technology
This Tech Toolbox covers the basics of 5G technology plus a story about how engineers designed and built a prototype DSL router mostly from old cellphone parts. Download this first 5G/wired/wireless communications Tech Toolbox to learn more!

EE Learning Center

EE Learning Center
“ee
EXPAND YOUR KNOWLEDGE AND STAY CONNECTED
Get the latest info on technologies, tools and strategies for EE professionals.
“bills
contribute

R&D World Podcasts

R&D 100 Episode 10
See More >

Sponsored Content

Designing for Serviceability: The Role of Interconnects in HVAC Maintenance

From Control Boards to Comfort: How Signal Integrity Drives HVAC Innovation

Built to Withstand: Sealing and Thermal Protection in HVAC Sub-Systems

Revolutionizing Manufacturing with Smart Factories

Smarter HVAC Starts at the Sub-System Level

Empowering aerospace E/E design and innovation through Siemens Xcelerator and Capital in the Cloud

More Sponsored Content >>

RSS Current EDABoard.com discussions

  • Can I use TLV75533PDBVR for powering ADC
  • Step Up Push Pull Transformer design / construction
  • connector model question
  • SMPS feedback circuit
  • Snooping Around is All

RSS Current Electro-Tech-Online.com Discussions

  • More fun with ws2812 this time XC8 and CLC
  • Pic18f25q10 osccon1 settings swordfish basic
  • Pickit 5
  • turbo jet fan - feedback appreciated.
  • I Wanna build a robot
Search Millions of Parts from Thousands of Suppliers.

Search Now!
design fast globle

Footer

EE World Online

EE WORLD ONLINE NETWORK

  • 5G Technology World
  • Analog IC Tips
  • Battery Power Tips
  • Connector Tips
  • DesignFast
  • EDABoard Forums
  • Electro-Tech-Online Forums
  • Engineer's Garage
  • EV Engineering
  • Microcontroller Tips
  • Power Electronic Tips
  • Sensor Tips
  • Test and Measurement Tips

EE WORLD ONLINE

  • Subscribe to our newsletter
  • Teardown Videos
  • Advertise with us
  • Contact us
  • About Us

Copyright © 2025 · WTWH Media LLC and its licensors. All rights reserved.
The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with the prior written permission of WTWH Media.

Privacy Policy