Planar transformer

A planar transformer comprising:

• a core comprising a ferromagnetic material, the core including a first part and a second part, at least one of the first and second parts having a center post;
• a printed wiring board having an aperture in which resides the center post, the printed wiring board comprising one or more laminates that each have a first side surface and an opposite second side surface, each of the first and second side surfaces including one of a primary winding and a secondary winding that are magnetically coupled by the core, the primary and secondary windings being electrically independent and surrounding the center post, the printed wiring board having an uppermost primary or secondary winding that is separated from the first part of the core by a first prepreg structure and a lowermost primary or secondary winding that is separated from the second part of the core by a second prepreg structure, each of the first and second prepreg structures comprising multiple prepreg layers, there being no primary or secondary windings disposed between the first prepreg structure and the first part of the core, there being no primary or secondary windings disposed between the second prepreg structure and the second part of the core, the printed wiring board including a first solder mask layer deposited on an uppermost surface of the first prepreg structure and a second solder mask layer deposited on a lowermost surface of the second prepreg structure, the first and second parts of the core being respectively bonded to the first and second solder mask layers;
• the first and second parts of the core being respectively bonded to the first and second solder mask layers by a respective first and second pre-form adhesive sheet that each has a hardness in the Shore D hardness scale at a temperature of 70 degrees Fahrenheit;
• each of the first and second prepreg structures and each of the first and second pre-form adhesive sheets being configured to inhibit the primary and secondary windings from electrically shorting through the core when the planar transformer is subjected to shock or vibration.