A high‐performance broadband ball‐grid‐array (BGA) package transition was designed and implemented from DC up to the Ka‐band frequencies. The vertical BGA‐via transition path starts from an organic motherboard (PCB) and ends at the top surface of a low‐temperature cofired ceramic module package. To assess solder joint reliability, large plastic‐core solder balls with a diameter of 800 μm were employed. The measured insertion loss of the entire vertical transition path, including feedlines, was better than 0.5 dB (1 dB) up to 25 GHz (29 GHz). Moreover, an equivalent circuit model for the complete transition path was developed.