Tombstoning happens when solder on one end of a small chip component melts and wets before the other end, and its surface tension pulls the part upright on that pad like a headstone. It is common on 0402 and smaller parts and is driven by unequal pad sizes, uneven heating from a plane or nearby large part, placement offset and paste imbalance. Symmetrical pads, thermal reliefs on plane connections and a proper soak in the profile prevent it.
Tombstoning on C14 again, the ground pad is tied solid into the plane and the other one isn't.
Also heard as
- Manhattan effect
- drawbridging
- tombstone
Related terms
Reflow
Soldering surface mount parts by melting printed solder paste in an oven that follows a set temperature profile.
Pad
Exposed copper area on a board where a component lead or terminal is soldered.
Thermal relief
Spoked connection between a pad and a copper plane that limits heat flow so the joint can be soldered.
AOI
Automated optical inspection: camera system that checks boards for missing, shifted or badly soldered parts.