Current sensor and current sensor manufacturing method
View Patent ↗A low-cost, current sensor suitable for mass production and a manufacturing method thereof are provided. The current sensor is small with high sensitivity and can be packaged in a standard assembly line which is normally used when an integrated circuit is manufactured. Further, it is possible to obtain a sufficient shielding effect against a disturbance flux without degrading the detecting sensitivity of a flux. A first magnetic material 50 is bonded to the lower part of a current conductor 22 C. The first magnetic material 50 has the function of converging and amplifying a flux 3 generated by the current to be measured. A second magnetic material 51 is bonded above a magnetic sensor chip 20 . The second magnetic material 51 has a shielding function against a disturbance flux entering from the outside.
1. A current sensor comprising:
a housing of molded plastics;
a metallic current conductor through which a current to be measured flows;
a magnetic field sensor chip containing at least one magnetic field detection element, the magnetic field sensor chip being placed on a side of the current conductor;
a flux concentrator placed on the magnetic field sensor chip for urging a flux generated by the current flowing through the current conductor to pass through the at least one magnetic field detection element;
a plurality of input and output terminals, each of the input and output terminals having an end that is electrically connected to a corresponding terminal of the magnetic field sensor chip, wherein a portion of the current conductor carrying the magnetic field sensor chip lies in a first plane and said ends of the input and output terminals lie in a second plane oriented substantially parallel to the first plane, and wherein a distance between the first and second plane substantially disappears or is substantially the same as a thickness of the magnetic field sensor chip;
a first magnetic material located on a backside of the current conductor, said backside located opposite to the side that the magnetic field sensor chip is placed on; and
a second magnetic material located above the magnetic field sensor chip.
2. The current sensor as claimed in claim 1 , wherein a position of the second magnetic material is set so as to satisfy 0.1α≦X≦3.6α where α represents a whole length of the flux concentrator along a direction of the flux generated by the current flowing through the current conductor and X represents a distance between a magnetic detecting surface of the at least one magnetic field detection element and the second magnetic material.
3. The current sensor as claimed in claim 1 , wherein the flux concentrator is composed of a pair of members having a gap of a predetermined width.
4. The current sensor as claimed in claim 2 , wherein the flux concentrator is composed of a pair of members having a gap of a predetermined width.
5. A method of manufacturing a current sensor, comprising the steps of:
forming a thin plate-like metal into a leadframe containing a current conductor and input and output terminals;
placing a magnetic field sensor chip containing at least one magnetic field detection element on a side of the current conductor;
connecting electrical terminals of the magnetic field sensor chip to the input and output terminals;
forming a plastic housing by molding the current conductor, the magnetic field sensor chip and the input and output terminals;
separating the current conductor and the input and output terminals from each other;
providing a first magnetic material on a backside of the current conductor, said backside being located opposite to the side that the magnetic field sensor chip is placed on; and
providing a second magnetic material located above the magnetic field sensor chip.
6. The method according to claim 5 , wherein a position of the second magnetic material is set so as to satisfy 0.1α≦X≦3.6α where α represents a whole length of the flux concentrator along a direction of the flux generated by the current flowing through the current conductor and X represents a distance between a magnetic detecting surface of the magnetic field detection element and the second magnetic material.
7. The method according to claim 5 , wherein the first and second magnetic material is provided before the plastic housing is formed.
8. The method according to claim 5 , wherein the second magnetic material is provided after the plastic housing has been formed.