Design, manufacture and application of in-board magnetic devices

Transformers and inductors can be integrated within a multilayer printed circuit board as described in [1]. These devices offer great advantages in packaging density. The planar type form factor provides for a large surface area to volume ratio, allowing for effective heat transfer from the magnetic device. This paper takes a tilt factor for winding resistances into consideration, and develops a more accurate design methodology for in-board magnetic devices. Manufacture challenges includes burying of magnetic cores, controlling internal stress and plating through deep vias. A propose manufacture process is described in detail. Finally a transformer and an inductor were designed for an example dc-dc converter demonstrating the manufacturability of in-board magnetic devices. Measured parameters match fairly well with the simple models.