**11.2 Planar microvoids**

Microvoids are characterised by their small diameter, less than 25 μm. Their occurrence is typical for Ni/Au, OSP and Ag finishes [27]. There are planar (one plane) on the solder pad/solder alloy interface; due to this, the joint's mechanical strength is significantly reduced. The cause of these voids' formation is not yet fully clarified. An example of planar microvoids on the interface of the solder pad/solder alloy is shown in **Figure 19**.
