An Assembly Quality Inspection System for Bone Conduction Implant Transducers

We designed and implemented a two-axis measurement system to inspect the assembly quality condition of a bone conduction implant (BCI) transducer. The system consists of a laser Doppler vibrometer (LDV), XY manual stage, and two digital scale calipers capable of displaying a position coordinate system. To measure the vibration of the cantilever constituting the transducer vibrational membrane, an XY coordinate system was obtained using FEA software. Based on the derived XY coordinate system, the cantilever vibration displacement of the vibrational membrane was measured for each coordinate using the LDV at 0.5, 0.9, and 2 kHz. To visualize the measured area, we developed a Matlab-based application and then visualized the motion of the cantilever. The alignment and misalignment models of the vibrational membrane and permanent magnet were designed using finite element analysis (FEA) software, and the measured cantilever motions of the vibrational membrane were then compared. Finally, to numerically compare the vibration magnitude of the cantilever, the standard deviation was calculated based on the displacement of each edge of the cantilever. The fabricated BCI transducer had a higher standard deviation (3.5 times at 0.5 kHz, 2.3 times at 0.9 kHz) than the ideally aligned FEA model, but the standard deviation was about eight times lower (at 0.5 and 0.9 kHz) than that of the misaligned case. The results of the numerical comparison indicated that the manufactured BCI transducer was very well assembled.