Worst-Case Coupling Estimation to a Complex Printed Circuit Board (PCB) System Typically Requires an Expensive Computational And/or Experimental Approach. Therefore, there is a Strong Need for a Deterministic Approach that Can Accurately Predict the Worst-Case Coupling with the Least Computational and Experimental Cost. This Work Uses a Hybrid Equivalent Circuit Approach Coupled with Experimental Measurements to Simplify Predicting the Worst-Case Coupling to an Accelerometer Board. the Predictions of the Proposed Methodology Are Validated using Experimental Measurements with Excellent Agreement.