The microstructure of Sn-Ag-Cu (SAC) solder joints plays an important role in the reliability of electronics, and interlaced twinning has been linked with improved performance. Here, we study the three-dimensional (3-D) shape of interlaced regions in Sn-3.0Ag-0.5Cu (SAC305) solder balls by combining serial sectioning with electron backscatter diffraction. In solder balls without large Ag3Sn plates, we show that the interlaced volume can be reasonably approximated as a hollow double cone with the common 〈100〉 twinning axis as the cone axis, and the 〈110〉 from all three twinned orientations making up the cone sides. This 3-D morphology can explain a range of partially interlaced morphologies in past work on 2-D cross-sections.