Teardrop (electronics)

Short description: Printed circuit board feature

Teardrops and trace necking as seen in a PCB layout design tool

Teardrop vias on printed circuit boards

A teardrop is typically drop-shaped feature on a printed circuit board and can be found on the junction of vias or contact pads.

## Contents

* 1 Purpose
* 2 Shape
* 3 Necking
* 4 References
* 5 External links

## Purpose

The main purpose of teardrops is to enhance structural integrity in presence of thermal or mechanical stresses,[1][2][3] for example due to vibration or flexing.[4] Structural integrity may be compromised, e.g., by misalignment during drilling, so that too much copper may be removed by the drill hole in the area where a trace connects to the pad or via.[2][3][5] An extra advantage is the enlarging of manufacturing tolerances, making manufacturing easier and cheaper.[3]

## Shape

While a typical shape of a teardrop is straight-line tapering, they may be concave.[2] This type of teardrop is also called filleting or straight.[3] To produce a snowman-shaped teardrop, a secondary pad of smaller size is added at the junction overlapping with the primary pad (hence the nickname).[3][6]

## Necking

For similar reasons, a technique called trace necking reduces (or necks down[7][8][9]) the width of a trace that approaches a narrower pad of a surface-mounted device or a through-hole with a diameter that is less than the width of the trace, or when the trace passes through bottlenecks (for example, between the pads of a component).[8][9][10][11]

## References

1. ↑ "Component placement tips and strategies". EDN Network. 2014-02-21. http://www.edn.com/design/pc-board/4428665/2/Component-placement-tips-and-strategies.
2. ↑ 2.0 2.1 2.2 "Removing Unused Pads and Adding Teardrops". Altium Designer technical documentation. Altium. 2017-05-30. http://www.altium.com/documentation/17.1/display/ADES/((Removing+Unused+Pads+and+Adding+Teardrops))_AD.
3. ↑ 3.0 3.1 3.2 3.3 3.4 "Why Where When and how teardrops should be added to PCB?". KaiZen Technologies. 2010. http://www.kaizen-t.com/technical/teardropinpcb.html.
4. ↑ Ruth (2023-04-28). "Introduction to high speed PCB and is it same as high frequency PCB". IBE Electronics. https://www.pcbaaa.com/an-ultimate-introduction-to-high-speed-pcb-and-is-it-same-as-high-frequency-pcb/.
5. ↑ "Empfehlung zu Tear-drops" (in German). AT&S AG. October 2002. http://wiki.fed.de/images/5/50/Empfehlung_zu_Tear-drops.pdf.
6. ↑ "PCB Design Guidelines for 0.5mm Package-on-Package Applications Processor, Part I". Texas Instruments. June 2010. http://www.ti.com/lit/an/sprabb3/sprabb3.pdf.
7. ↑ "Interactive Routing". Altium Designer technical documentation. Altium. 2017-04-25. http://www.altium.com/documentation/17.1/display/ADES/((Interactive+Routing))_AD.
8. ↑ 8.0 8.1 Printed Circuit Board Design with Microcomputers (1 ed.). McGraw-Hill Book Company. 1991-08-01. p. 102. ISBN 0070095582. https://dl.acm.org/citation.cfm?id=114661.
9. ↑ 9.0 9.1 "11.1.3 Packaging Electronic Systems - Design of Printed Wiring Boards". The Electronics Handbook (2 ed.). CRC Press. 2005. p. 1266. ISBN 978-0-8493-1889-4. http://s1.downloadmienphi.net/file/downloadfile6/192/1385077.pdf. Retrieved 2017-09-25.
10. ↑ Abrams, Halle, "Packaging Electronic Systems", US patent 3560256, published 1971-02-02
11. ↑ High-Speed Circuit Board Signal Integrity (1 ed.). Artech House, Inc.. 2004. pp. 104–105. ISBN 1580531318.

## External links

* High Frequency PCB

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