Planar coil element and method for producing planar coil element
A planar coil element of the present invention includes an insulating base film having a first surface and a second surface opposite to the first surface, a first conductive pattern deposited on the first surface side of the insulating base film, and a first insulating layer covering the first conductive pattern on the first surface side, in which the first conductive pattern includes a core body and a widening layer deposited by plating on the outer surface of the core body, and the ratio of the average thickness of the first conductive pattern to the average circuit pitch of the first conductive pattern is ½ or more and 5 or less.
1. A planar coil element comprising an insulating base film having a first surface and a second surface opposite to the first surface, a first conductive pattern deposited on the first surface side of the insulating base film, and a first insulating layer covering the first conductive pattern on the first surface side,
wherein the first conductive pattern includes a core body and a widening layer deposited on an outer surface of the core body,
a ratio of an average thickness of the first conductive pattern to an average circuit pitch of the first conductive pattern is ½ to 5,
the first conductive pattern includes a rectangular portion that is deposited on the first surface side of the insulating base film and that has a rectangular cross-sectional shape, and a top portion that extends continuously from a surface of the rectangular portion opposite to the surface on which the insulating base film lies and that has a cross section with a semicircular shape, and
an average shortest distance from the top portion of the first conductive pattern to a surface of the first insulating layer on the first surface side of the insulating base film is 3 μm to 40 μm.
2. The planar coil element according to claim 1 , wherein the first conductive pattern has an average circuit pitch of 20 μm to 100 μm.
3. The planar coil element according to claim 1 , wherein a ratio of an average circuit gap width at a height position of ½ the average thickness to an average circuit gap width in a bottom portion of the first conductive pattern is 2 or less.
4. The planar coil element according to claim 3 , wherein a ratio of an average circuit gap width at a height position of ⅔ the average thickness to the average circuit gap width in the bottom portion of the first conductive pattern is 2 or less.
5. The planar coil element according to claim 1 , wherein each of the core body and the widening layer contains copper or a copper alloy as a main component.
6. The planar coil element according to claim 1 , wherein the insulating base film contains a polyimide as a main component, and the first insulating layer contains an epoxy resin as a main component.
7. The planar coil element according to claim 1 , further comprising a second conductive pattern deposited on the second surface side of the insulating base film, and a second insulating layer covering the second conductive pattern on the second surface side,
wherein the second conductive pattern includes a core body and a widening layer deposited on an outer surface of the core body.
8. The planar coil element according to claim 7 , further comprising a through hole electrically connecting the first conductive pattern to the second conductive pattern.
9. The planar coil element according to claim 7 , wherein the first conductive pattern and the second conductive pattern have an identical pattern, and
a difference in position in a width direction between a center line of the first conductive pattern and a center line of the second conductive pattern is 40% or less of the average circuit pitch.