Assembly yield improvement of an asymmetric surface mountable transformer

As microelectronic technology continues to evolve, it is finding increased applications in the medical sector, such as ever increased usage of microelectronics inside implantable medical devices. This market is driven by a set of challenging requirements that include form factor, weight, functionality, battery longevity, cost, and reliability, which requires in many cases custom developed packaging and assembly solutions. [1] A custom-designed surface mountable transformer with higher performance while enabling a smaller and more anatomically shaped device has been developed for a new implantable cardioverter defibrillator. The initial designs and prototypes of this transformer exhibited significant pre-production manufacturability issues and would have resulted in significant yield loss if implemented in high volume hybrid manufacturing. Predicted yield loss in high volume manufacturing was expected to be, on average, 15%. This paper provides an overview of various tools utilized and steps taken to identify root cause of major manufacturability issues, and subsequent yield improvements of this transformer in the surface mount process from 85% to greater than 99%.