**9. Tombstone effect**

The tombstone effect (or Manhattan effect, drawbridging or the Grabstein effect) is a phenomenon which is characterised by one of the sides of a small SMD component (typically in a 0805, 0603, 0402 and 0201 package) lifting up during reflow. A photo of the tombstone effect is shown in **Figure 14**.

Tombstone effect is caused by an imbalance of wetting forces during the reflow process [12]. This can be caused by unequal amount of solder paste applied to the connecting pads, differently sized soldering pads, eccentrically mounted component, different wettability of soldering pads, a different time of solder melting on each side of the component, etc. or by upward push by solvent vapours from flux during an asymmetric reflow process [13]. The effect of the wetting force, or upward push force from solvent vapours, is depicted in **Figure 15**.

The frequency of the tombstone effect is also influenced by the reflow technology used. The feedback from industrial practice says that this effect is more frequent in vapour-phase soldering technology. This has been experimentally verified and presented in the publication dealing with tombstone effect [14, 15]. Currently work is being done on a more detailed explanation of the cause of the higher occurrence of the tombstone effect in vapour-phase soldering.

**Figure 14.** *Photo of the tombstone effect.*

**Figure 15.** *Schematic representation of the wetting force (F1); upward push force from solvent vapours (F2).*
