This paper presents a novel D-band interconnect implemented in a low-cost embedded Wafer Ball Grid Array (eWLB) commercial process. The transition is realized through a patch slot antenna directly radiating to a standard waveguide opening. The interconnect achieves low insertion loss and good bandwidth. The measured minimum Insertion Loss (IL) is 2 dB and the average is 3 dB across a bandwidth of 22% covering the frequency range 110-138 GHz. In addition, the structure is easy to integrate as it does not require any special assembly nor any galvanic contacts. Adopting the low-cost eWLB process and standard waveguides makes the transition an attractive solution for interconnects beyond 100 GHz.