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]
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]
^Lobner, Wilhelm (October 2002).
"Empfehlung zu Tear-drops" [Recommendations for tear-drops] (PDF) (in German). AT&S AG.
Archived(PDF) from the original on 2017-09-24. Retrieved 2017-09-24.