Miniature Tight-tolerance Chip Inductors

Miniature Tight-tolerance Chip Inductors

Toko America Inc.
Mt. Prospect, IL

Today’s trend toward smaller circuits and automated assembly is pushing component manufacturers to develop new and innovative ways to reduce the size and cost of their products while maintaining or improving performance. High frequency inductors traditionally have been a difficult component to manufacture in small, mass-produced configurations without sacrificing Q or temperature stability. A new single-layer ceramic chip inductor series has been developed that utilizes a photolithographic etching process to achieve superior performance and repeatability with a low cost construction technique. Each inductor is manufactured with a unique fine electrode forming process using photophosphorous etching on low dielectric constant ceramics laminated on alumina substrates. Figure 1 shows a simplified diagram of the chip inductor’s construction.

The PTL-series chip inductors are fabricated using a proprietary design that provides a high self-resonant frequency (SRF), excellent Q and superior temperature stability when compared to other miniature inductors in the same frequency range. The devices are more economical than similar thin-film or screened wire-wound inductors and feature the tight tolerance required for use in today’s high performance VCO circuits or for matching GaAs FET devices utilized in low noise amplifiers and other sophisticated high frequency circuits.

The new inductor series comprises three distinct size groupings: the PTL1005F series in an EIA standard 0402 (1.0 mm x 0.5 mm) footprint, the PTL1608F series in a 0603 (1.6 mm x 0.8 mm) footprint and the PTL2012F series in a 0805 (2.0 mm x 1.25 mm) footprint. Inductance ranges from 1 nH at the low end for each of the three groups to a maximum of 12, 27 and 100 nH, respectively, at the high end. All of the inductors are rated to operate over a –40° to +100°C temperature range and can be supplied in a tape-and-reel configuration for production quantities.

The PTL1005F Series

The smallest of the inductor families is the PTL1005F series. These inductors are flow and reflow solderable and feature a ±0.2 nH or two percent inductance tolerance over the full temperature range and a low 100 ppm/°C temperature coefficient. Figure 2 shows the change in inductance over temperature of the PTL  series as compared to inductors manufactured using other technologies.

In addition, each device’s SRF is controlled to within ±10 percent with an inductance specified at 800 as well as 100 MHz. Figure 3 shows the inductance vs. frequency characteristics of a typical PTL-series inductor under three conditions of stray capacitance. The data clearly show the effects on the device’s SRF.

Qs for the PTL1005 are typically 30 at 1800 MHz with SRFs ranging from 3.6 to > 13.5 GHz. Table 1 lists specifications for individual part numbers in the PTL1005F series. Most part types are available from stock.

Toko America Inc.,
Mt. Prospect, IL
(847) 297-0700.