Thin-film Shielded Loop Coil for Magnetic Near Field Measurement of High Densely Packaged PCBs

A miniature thin‐film shielded‐loop probe with a flip‐chip bonding for magnetic near field measurements

“…In the measurement, the transmission line terminated with 50 Ω is excited by a sinusoidal wave at 1 GHz. In the distribution by a thin-film magnetic field probe reported previously [13], the overall tendencies of the measured and computed results are similar. However, two minima generated by mutual cancellation of the current on the strip and its image current did not appear in the numerical results.…”

“…In the frequency characteristics of the thin-film magnetic field probe with a wire bonding connection, the output voltage difference between θ = 0° and 90° is only about 10 dB. Hence, the output voltage due to the magnetic field detected outside the loop is reported not to be small [13]. With the flip-chip connection, the electromagnetic shielding capability is considered to be improved by about 20 dB.…”

“…In the bonding structure reported previously [13], the strip lines on the probe chip and on the chip carrier are converted to coplanar lines which are then bonded with gold wires as shown in Fig. 4, with both pads oriented to the same side without facing each other.…”

“…Specifically, the authors have developed a multilayered magnetic field probe fabricated with low-temperature co-fired ceramic (LTCC) and a printed circuit board made of glassepoxy material [11,12]. Further, by using a thin film process, an ultra-miniature magnetic field probe with a similar configuration has been developed [13][14][15]. In these magnetic field probes, the loop is rectangular so that the near magnetic field of the interconnections can be detected efficiently.…”

“…The previously tested magnetic field probe fabricated by the thin film process [13] has been able to improve the resolution of the near magnetic field profile for interconnections due to the reduction of the loop aperture area to about 1/70 in comparison with the magnetic field probe of LTCC form [14]. However, there is a problem that the effect of magnetic fields detected by structures other than the loop cannot be neglected.…”