JPH01289307A - Chip noise filter - Google Patents

Abstract

PURPOSE:To obtain an excellent noise attenuation characteristic and to attain automatic mounting by an automatic mounting machine and the surface mounting method altogether by covering the entire component including a drum core whose winding is installed into plural winding slots, a capacitor connected between a neutral terminal and a common terminal and a coil copper wire joint part with an outer forming. CONSTITUTION:An inductor comprising plural windings 2 and a capacitor 3 are contained into a subminiature structure, the inductor is connected between an input/output terminal 6 made of a metallic plate and a neutral terminal 7 and the capacitor 3 is connected between the common terminal 5 and the neutral terminal 7. Thus, a constant K type low pass filter circuit is obtained and acts like an electric function as a noise filter. Thus, excellent mass- productivity is given as the noise filter of subminiature and lead-wire-less suitable for the surface mounting method high reliability and excellent electric performance are provided and the inductance over a wide range is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a noise filter used in various electronic devices such as digital VTRs and digital TVs, and non-4AA devices.

2. Description of the Related Art In recent years, digital circuit processing technology has improved significantly, especially with the advent of high-speed modules, D-M converters, and large-capacity memory ICs.
The application of digital technology to TR, TV, etc. has become highly multifunctional.

On the other hand, as OR parts become chips, high reliability is achieved through surface mounting methods such as automatic mounting machines and reflow soldering machines.
The establishment of a high-density mounting method has greatly contributed to the miniaturization of equipment, and there is a strong desire for all other components to be compatible with this surface mounting method, that is, to be made into chips.

Among these, what is a noise filter?

It is used in the coupling section between the digital signal processing circuit and the analog signal processing circuit, and removes harmonic noise having a wide frequency band included in pulses with sharp rises and falls characteristic of digital signals. It is an effective component that eliminates the negative effects of these noises on analog circuits (deterioration of image and sound quality due to beat noise), prevents malfunction of equipment, and furthermore prevents noise interference to other equipment.

It has become widely used.

The conventional noise filter as described above will be explained below with reference to the drawings.

4 and 6 both show transparent perspective views of typical examples of conventional noise filters. At h in Figure 4, 1
Reference numeral 2 denotes a sleeve core made of ferrite, through which an input/output terminal 14 made of a copper wire is passed through the center to form an inductance. 13 is a cylindrical capacitor, 14 is an input/output terminal, 1
Reference numeral 6 is a common terminal and is normally used by connecting it to GND (earth).

16 is an exterior paint that integrates the whole and protects each internal functional element. Further, in FIG. 6, reference numeral 17 denotes a drum core made of ferrite, and a winding #118 made of coated copper wire is applied to the bump 17 to constitute an inductance. 19 is a cylindrical capacitor, 2o is an input/output terminal, 21 is a common terminal,
22 is an exterior paint. In this way, the fourth factor and the conventional example shown in FIG. 5 are the same except for the method of configuring the inductance.

FIG. 6 shows an electrical equivalent circuit of the noise filter configured as described above. As is clear from the figure, it is a low-pass filter with a fixed shape, and functions as a noise filter by passing necessary signal components (below the cutoff frequency afc) and attenuating unnecessary harmonic noise. be.

Figure 7 shows a typical passband characteristic. In this figure, the characteristic curve ■ shows the characteristics of a filter whose inductance is formed by the sleeve core 12 shown in the fourth factor, and the characteristic curve marked ■ shows the characteristics of a filter whose inductance is formed by winding 18 around the drum core 17 shown in FIG. Indicates %1 raw. The latter has better attenuation characteristics for harmonic noise, but this is because a large value of inductance can be obtained, and the required inductance can be easily achieved by adjusting the number of windings, and the circuit operating impedance. This is because it is possible to match the input and output impedances of the noise filter.

Problems to be Solved by the Invention However, with the above configuration, there is no need for a noise filter! Although good mechanical performance has been achieved, the fan configuration with reeds cannot be applied to the surface mount method, making it impossible to miniaturize and increase the density of the device. There was a problem in that it was difficult to save labor through automatic mounting, and there was a desire for an immediate development of chip components.

In view of the above-mentioned problems, the present invention has the excellent noise attenuation characteristics of a noise filter using a wound inductance with a drum core, and also provides an ultra-small chip noise filter that can be automatically mounted using a surface mounting method and an automatic mounting machine. It provides a filter.

Means for Solving the Problem In order to solve this problem, the chip noise filter of the present invention has two input/output terminals facing each other on both sides of one common terminal (grounding terminal) made of a metal plate, and one midpoint. Terminals are arranged on the same plane, and one drum core with a plurality of winding grooves covered with windings is arranged so that its central axis is perpendicular to the terminal surface and extends across two or more terminals on the surface. , connect each coil copper wire between the input/output terminal and the midpoint terminal, and connect a capacitor between the midpoint terminal and the common terminal, and connect the whole including the coil copper wire joint, the drum core, and the capacitor. The terminals made of the plurality of metal plates covered with an exterior molded body and led out of the exterior molded body are shaped along the exterior molded body to form a terminal for connecting to and reading an external circuit.

Function: With this configuration, multiple wound inductors and capacitors are housed in an ultra-small integrated structure, and the inductor is placed between the input/output terminal and the midpoint terminal made of gold steel plate, and between the common terminal and the midpoint terminal. By wiring a capacitor, it becomes equivalent to a low-pass filter and performs the electrical function of a noise filter. At the same time, the metal plate terminal is led out of the exterior molded body and shaped into a terminal for external circuit connection as a leadless chip component.

EXAMPLE An example of the present invention will be described below with reference to the drawings. FIG. 1 is a transparent perspective view showing the internal structure of a chip noise filter in an embodiment of the present invention.

In FIG. 1, 1 is a drum core with windings 2 arranged in a plurality of winding grooves, and 3 is a square chip capacitor.

4 and 6 are input/output terminals, and 6 is a common terminal, which is normally connected to BID (earth) for grounding. Reference numeral 7 denotes a mid-point terminal, which is normally provided for configuring a low-pass filter circuit and is used as a wiring terminal inside the chip noise filter, but is not connected to an external circuit. 8 is an exterior molded body which is usually completely sealed with a highly heat resistant resin such as epoxy resin. FIG. 2 is an electrical equivalent circuit of the chip noise filter constructed according to the above embodiment. FIG. 3 is a perspective view showing the state of the manufacturing process before exterior molding of this embodiment. Items 1 to 8 in the figure are the same as those in FIG. 1, and their explanation will be omitted.

21L, 2b, 20, 211 are coil lead wires at the beginning and end of the plurality of windings 2, and 4N and 61L are input/output terminals 4.
6 and the coil leads 21L and 2 (1); 7m is the protrusion that connects the midpoint terminal 7 and the coil leads 2b and 2G; 9 is the input/output terminal 4°6, the common terminal 6, and the midpoint. A terminal frame 10 is used to maintain the relative positions of the terminals 7, and numeral 10 is a protrusion for fixing a copper wire temporarily provided on the terminal frame 9 in order to continuously perform winding wiring.

Next, an example of a method for manufacturing the chip noise filter of this embodiment will be described. A plurality of one set of terminals integrated in the terminal frame 9 are lined up to form a long hoop-shaped terminal, and the drum core 1
Fix it in place on the terminal with adhesive, etc. Next, after winding the copper wire 11 around the protrusion 10 and temporarily fixing it, the rear drum core Winding 2 is performed in the groove on the terminal surface side among the plurality of winding grooves. After winding, the copper wire 11 is hooked along the back surface of the protrusion 7& of the midpoint terminal 7, and then the wire is wound again in the other winding groove of the drum core 1. Thereafter, the copper a11 is hooked along the back surface of the protrusion e& of the input/output terminal 6, and is temporarily fixed around the rear protrusion 1o. The coiled copper wire and the respective terminals 4, 6.7 are connected to their protrusions 41.
Solder the back sides of 6a and 7a using cream solder or the like.

Extra lines from the protrusions 4&, 6& of the input/output terminals 4.6 to the temporarily fixed protrusion 1o are cut and removed. Next, solder the chip capacitor 3 between the midpoint terminal 7 and the common terminal 6 using cream solder, etc., and use epoxy! The exterior molded body 8 is formed by transfer or injection molding using a heat-resistant resin such as Ii resin. After that, each terminal 4, 5, 6.7 is separated from the hoop terminal frame 9, and the outer molded body 8 is removed.
Shape it separately to form each terminal.

The electrical equivalent circuit of the chip noise filter configured as described above is as shown in FIG. 2 as described above, and is the same as that in FIG. It is. Therefore, nothing is connected to the midpoint terminal 7, and the input/output terminals 4, 6 and the common terminal 6 constitute a cedar low-pass filter circuit, which operates as a noise filter.

- If the filter is miniaturized, stray coupling will occur between the input and output, and the characteristics of the filter in the high frequency range will deteriorate; however, according to this embodiment, the input and output terminals 4. Since stray coupling due to stray capacitance between the input and output terminals 4 and 6 is reduced, connecting the common terminal 6 to GND (earth) can further isolate the input and output, allowing high frequency Good attenuation characteristics can be obtained in this region. Further, as mentioned above, continuous winding wiring is possible, mass production can be easily realized, and production costs can be lowered.

Incidentally, a recessed portion is formed in advance by bending or drawing in accordance with the shape of the drum core 1 in the part where the drum core is fixed to the plurality of terminals made of scrap metal plate, and the drum core 1 is fixed in the recessed portion. The fixed state of No. 1 is further stabilized.

By mixing ferrite powder into the exterior molded body 8, it is possible to magnetically shield the entire noise filter, reducing the electromagnetic coupling between the two coils wound around the same drum core 1, and improving the passband characteristics. High frequency attenuation characteristics are further improved, and direct radiation noise from the chip noise filter can be significantly reduced.

Effects of the Invention As described above, the present invention provides one common terminal (
Two input/output terminals and one center point terminal facing each other on both sides of the grounding terminal are arranged on the same plane, and one drum core with wires wound in a plurality of winding grooves is arranged so that its center axis is the same as the terminal. It is fixed perpendicular to the surface and spans the surface between two or more terminals, and each coiled copper wire is wired and connected between the input/output terminal and the midpoint terminal, and a capacitor is connected between the midpoint terminal and the common terminal. The entire body, including the coil copper wire joint, drum core, and capacitor, is covered with an exterior molded body, and the terminals made of the plurality of four gold plates led out of the exterior molded body are shaped along the exterior molded body, and then the outer molded body is formed. By configuring the chip noise filter as a terminal for connection to the circuit, it can be used in a wide range of applications as a miniature leadless noise filter that is suitable for surface mounting methods, has high mass productivity, high reliability, and excellent electrical performance. Since it is possible to use inductance, it is possible to realize filter configurations that are optimal for various circuit operating conditions, and this has great practical effects.

[Brief explanation of the drawing]

Fig. 1 is a transparent perspective view showing the internal structure of a chip noise filter in an embodiment of the present invention, Fig. 2 is an electrical equivalent circuit diagram of the embodiment, and Fig. 3 shows the state of the embodiment in the process of being manufactured. 4 and 6 are both transparent perspective views showing the internal structure of a conventional noise filter, FIG. 6 is an electrical equivalent circuit diagram of the conventional example, and FIG. 7 is a typical example of the conventional noise filter. It is a graph showing frequency attenuation characteristics. 1...Drum core, 2...Winding, 3.
... Chip capacitor, 4.6 ... Input/output terminal, 5 ... Common terminal (GND), 7 ...
...Middle point terminal, 8...Exterior molded body, 9...
...Terminal frame, 1o...Protrusion for temporarily fixing copper wire,
11... Steel wire. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 - 5 "34 Terminal"

Claims (1)

[Claims] (1) 2 opposing sides of one common terminal made of a metal plate
One input/output terminal and one midpoint terminal are arranged on the same plane, and one drum core with wires wound in a plurality of winding grooves has its central axis perpendicular to the terminal surface, and two or more Each coil copper wire is wired and bonded between the input/output terminal and the midpoint terminal, and a capacitor is bonded between the midpoint terminal and the common terminal. A chip noise filter in which the entire body including the drum core and capacitor is covered with an exterior molded body, and the terminals made of the plurality of metal plates led out of the exterior molded body are shaped along the exterior molded body and used as connection terminals to an external circuit. . (2) The chip noise filter according to claim 1, wherein the two input/output terminals are fixed to the drum core, a narrow protrusion is provided at the tip of the fixed part, and a coiled copper wire is wired to the protrusion. (2) The chip noise filter according to claim 1, wherein the drum core and capacitor fixing portions of the plurality of metal plate terminals are bent into concave shapes along the respective shapes, and are fixedly held in the concave portions. (4) The chip noise filter according to claim 1, wherein the exterior molded body is made of a thermosetting resin containing ferrite powder.