Teardrop (electronics)

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

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

Teardrop vias on printed circuit boards

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

See also: Necking (engineering)

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]}