Power supply packaging system
View Patent ↗A packaging system for a high current, low voltage power supply. The power supply uses bare die power FETs which are directly mounted to a thermally conductive substrate by a solder attachment made to the drain electrode metallization on the back side of the FETs. The source electrode and gate electrode of each FET are coupled to the circuitry on an overhanging printed circuit board, using CSP solder balls affixed to the front side of the FET die. The heat generated by the FETs is effectively dissipated by the close coupling of the FETs to the thermally conductive underlying substrate. High interconnect densities are achieved through the use of a multilayer printed circuit board. This high interconnect density, with the addition of a magnetic core element, allows the power supply packaging system to incorporate transformer windings for an isolation transformer or an inductor.
1. A power supply package comprising:
a thermally conductive substrate, electrically coupled to a first current handling terminal on a first surface of a semiconductor die;
a multilayer printed circuit board, electrically coupled to a second current handling terminal on an opposing surface of the semiconductor die; and
a magnetic core element;
wherein the thermally conductive substrate is attached to the multilayer printed circuit board, and wherein the multilayer printed circuit board further comprises primary windings etched within layers of the multilayer printed circuit board and the thermally conductive substrate contains at least one secondary turn, the primary windings and the at least one secondary turn being magnetically coupled by the magnetic core element.
2. The power supply package of claim 1 , wherein the multilayer printed circuit board further comprises at least four layers.
3. The power supply package of claim 1 , wherein the magnetic core element comprises an E-shaped core having three legs and an I-shaped core and wherein the multilayer printed circuit board and the thermally conductive substrate each comprise at least one hole configured to mate with a corresponding one of said legs of the E-shaped core.
4. The power supply package of claim 1 , wherein the magnetic core element comprises a first and second E-shaped core having three legs and wherein the multilayer printed circuit board and the thermally conductive substrate each comprise at least one hole configured to mate with a corresponding one of said legs of the E-shaped core.
5. The power supply package of claim 1 , wherein the magnetic core element is comprised of a magnetic polymer material.