Microminiature power converter

1. A microminiature power converter comprising:

a semiconductor substrate on which a semiconductor integrated circuit is formed;

a thin film magnetic induction element; and

a capacitor,

wherein the thin film magnetic induction element includes a magnetic insulating substrate, and a solenoid coil conductor in which a first conductor is formed on a first principal plane of the magnetic insulating substrate, a second conductor is formed on a second principal plane of the magnetic insulating substrate, and a connection conductor is formed in a through hole passing through the magnetic insulating substrate are connected; and

wherein a relationship of a length L of the magnetic insulating substrate in a direction vertical to a magnetic field generated by the solenoid coil and a length d of the coil conductor is d≧L/2.

2. A microminiature power converter according to claim 1 , wherein the magnetic insulating substrate comprises a ferrite substrate.

3. A microminiature power converter according to claim 1 , wherein a surface of the coil conductor is covered with at least one of an insulating film and a resin in which magnetic fine particles are dispersed.

4. A microminiature power converter according to claim 1 , wherein the first principal plane and the second principal plane of the magnetic insulating substrate of the thin film magnetic induction element are provided with electrodes electrically connected through a through hole.

5. A microminiature power converter according to claim 4 , wherein the semiconductor substrate is electrically connected to the electrodes formed on the magnetic insulating substrate of the thin film magnetic induction element.

6. A microminiature power converter according to claim 5 , wherein the electrode electrically connected to the semiconductor substrate is disposed on an inside surface separate from an outer peripheral end of the magnetic insulating substrate.

7. A microminiature power converter according to claim 6 , wherein the principal plane of the magnetic insulating substrate on which the electrode electrically connected to the semiconductor substrate is disposed is covered with a protection film which is in direct contact with a peripheral part surface of a whole outer periphery of the principal plane.

8. A microminiature power converter according to claim 7 , wherein the protection film is a resist protection film.

9. A microminiature power converter according to claim 6 , wherein a part of the semiconductor substrate and a peripheral part surface of a whole outer periphery of the principal plane of the magnetic insulating substrate on which the electrode electrically connected to the semiconductor substrate is disposed are covered with a direct contact binder.

10. A microminiature power converter according to claim 9 , wherein the binder is an under filling.

11. A microminiature power converter according to claim 7 , wherein a part of the semiconductor substrate and a peripheral part surface of a whole outer periphery of the principal plane of the magnetic insulating substrate on which the electrode electrically connected to the semiconductor substrate is disposed are covered with a direct contact binder.

12. A microminiature power converter according to claim 11 , wherein the binder is an under filling.

13. A microminiature power converter according to claim 8 , wherein a part of the semiconductor substrate and a peripheral part surface of a whole outer periphery of the principal plane of the magnetic insulating substrate on which the electrode electrically connected to the semiconductor substrate is disposed are covered with a direct contact binder.

14. A microminiature power converter according to claim 13 , wherein the binder is an under filling.