Ultra-small common mode filter package can reduce footprint in half

Noise-suppression component saves board space and increases design flexibility

As electronic devices such as smartphones and tablets become ever more sophisticated, the number of components they contain, including the number of common mode filters and other noise-suppression components, increases. In addition, these devices are becoming not only more sophisticated, but also smaller and thinner, which means that component density is also rising. As a result, there is a growing requirement for component miniaturization, in order to increase the system designer's flexibility to optimize the board layout and component placements.

To meet this demand, TDK has introduced the TCM0403R ultra-small thin-film common mode filter, one of the smallest common mode filters available: it is less than half the size (41.5%) of the existing products (TCM0605 series), while maintaining the same characteristics. It has achieved this size reduction through the improvement of thin-film processing techniques and by enhancing the design of the internal structure.

Figure 1 Size comparison between the existing product (TCM0605 Series) and the new product (TCM0403R)

Table 1 Change in the size and conductor dimensions of TDK's thin-film common mode filter products

Product size	1.0x1.25mm	1.0x0.5mm	0.65x0.5mm	0.45x0.3mm
Line width	1	0.67	0.56	0.28
Aspect ratio*2	1.0	1.2	1.0	2.8

*1 Line width is described using a ratio where the 1.0 x 1.25 mm product is set as 1.
*2 Aspect ratio

How TDK has realized an ultra-small common mode filter

In order to realize an ultra-small product with a footprint half the size of existing products, TDK has to optimize its product design and processing techniques. In particular, TDK made the following process and design innovations.

(1) Fine patterning of the coil conductor

In order to produce characteristics equivalent to those of its existing products in a package that is half the size, TDK had to implement fine patterning of the conductor, and achieve a conductor aspect ratio*2 at least twice that of the existing products . The change in the size and conductor dimensions of TDK's thin-film common mode filter products is shown in the table below.

Fine patterning of the conductor has been realized through the adoption of a photolithography technique that supports electronic components, and through the improvement of the electroplating technique, building on thin-film techniques used for HDD head production.

(2) Forming terminal electrodes on the wafer

In general, the terminals of passive components are most often fabricated when they have been cut from the wafer and are in the form of a chip. However, for thin-film electronic components such as the TCM series thin-film common mode filters, the fabrication process provides for terminals to be formed on the wafer. Common mode filters need at least four terminals. The smaller the device, the harder it is to form terminals with the required precision on the chip. In the TCM series, by contrast, terminals may readily be formed on the wafer with very high precision because of the thin-film processing technique used to fabricate the device. This enables TDK to make an ultra-small product with a footprint half the area of existing products' footprint.

TDK has been pursuing the miniaturization of electronic components, achieving breakthroughs ahead of its competitors, through the application of advanced thin-film techniques. TDK will extend its efforts to contribute to reductions in the size, thickness and weight and of devices, as well as to improvements in their operation, while at the same time helping to reduce their impact on the environment.

Figure 2 The example of characteristics of the thin-film common mode filter TCM0403R

TCM0403R ensures common mode characteristics and differential mode characteristics equivalent to those of the existing product TCM0605G-900, while reducing the size to half or less of the existing product.

Main Features, Applications, and Electrical Characteristics of the thin-film common mode filter TCM0403R

Main Features

• One of the smallest common mode filters in the industry, benefiting from the application of advanced thin-film processing techniques
• Characteristics equivalent to those of the existing product, the TCM0605G

Main Applications

• Noise suppression in mobile devices such as smartphones and tablets

Main Electrical Characteristics

Operating temperature range: –25 to +85°C

Frequency Characteristics