JPH01277012A - Filter device - Google Patents

Abstract

PURPOSE:To obtain a thin and miniature filter device by generating coils by plating to a magnetic-substance substrate. CONSTITUTION:A substrate 10 is formed out of magnetic substance and conductive layers are provided on its both faces by electric plating of copper, etc. A through hole is pierced in the substrate 10 and the inside of the through hole is electrically plated and a through hole electrode 11 is formed. By etching the conductive layers, spiral coils L5-L7 are formed on a surface 10a of the substrate 10, a conductive pattern 12 is provided on a rear face 10b and electricity is conducted between the two faces of the substrate 10 through the electrode 11. Further, capacitors C5-C8 are fitted between the pattern 12 and the electrode 11 and a filter is formed. Thus, the coils are formed by the plating processing, therefore, they becomes high-density coils, and the substrate is formed out of the magnetic substance, therefore, permeability becomes large and the coils are miniaturized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a filter device used in electronic equipment, and particularly relates to a thin (miniaturized) filter device for use in communications or VTRs. .

[Prior art] Audio electronic equipment such as tuners and amplifiers, or V
A large number of various filters are used in TR, etc., and the filters include LPF (low pass filter) and HI'F (
Bypass filter) and BI'F (band pass filter).

Attachment Figure 12 shows an LPF, in which a shield plate (2) is provided inside a metal case (1), and connectors (3) and (4) are connected to both sides of the metal case (1). Installation. Then, coils (Ll) (L2) are connected in series between the connectors (3) and (4), and a capacitor (
Connect CIIC2) (C3). This capacitor (C
I) (C3) uses a disc type ceramic capacitor, and the capacitor (C2) uses a feedthrough type capacitor.

Figure 13 shows an equivalent circuit of the LPF, in which a capacitor (CI) is connected to each contact of the coil (Ll) (L2).
(C2) (C3) are connected and grounded. Further, as shown in FIG. 14, a coil (L3) is formed by winding a copper wire around a bobbin (5), and the coil (L3) is placed on a substrate (6).
L3) and a capacitor (C4) were attached to form a filter device.

[Problem to be solved by the invention] As mentioned above, the conventional filter device consists of a single coil (
Ll) (L2) and (L3), and the capacitor (CII
C2), (C3) and (C4) are combined, and it takes time to solder the individual parts.

In addition, it is necessary to shield the coils (Ll) (C2) and (C3), and they are large because they are housed in the metal case (1) or shielded with a shield plate, and the bobbin (5
) was an obstacle to thinning.

Therefore, it is an object of the present invention to provide a thinner (smaller) filter device.

[Means for Solving the Problems] The present invention has been proposed to achieve the above object, and includes plating and etching a magnetic substrate to form a coil on its front surface, and forming a coil on its back surface. A conductive pattern is provided on the substrate, and both sides are electrically connected through the through-hole electrode, and a capacitor is installed between the through-hole electrode and the conductive pattern on the back side, and a magnetic plate is further covered on the surface of the magnetic substrate. The present invention aims to provide a filter device having the following characteristics.

[Function] In the present invention, a substrate is formed of a magnetic material, and conductive layers are provided on both sides of the substrate by electroplating of copper or the like. A through hole is pre-drilled in the substrate, and the inside of this through hole is also electroplated to form a through hole electrode. and,
By etching the conductive layer, a spiral coil is formed on the front surface of the substrate, and a conductive pattern is provided on the back surface, so that the two surfaces of the substrate are electrically connected via the through-hole electrodes. Furthermore, a capacitor is attached between the conductive pattern on the back surface and the through-hole electrode to form a filter. Since the above-mentioned coil is formed by plating at °C, it becomes a fine pitch and a high-density coil. Furthermore, since the substrate is made of a magnetic material, the magnetic permeability is increased and the coil can be made smaller. Since the surface of the substrate is covered with a magnetic plate, there is no leakage of lines of magnetic force to the outside and no inductive coupling between the coils, making it possible to obtain a thin and compact filter device.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the accompanying drawings. 1 to 5 show a filter device, in which a coil (I, 5
) (C6) (L?), and provide through-hole electrodes Q +)Q9... at both ends of each coil, and
It is electrically connected to the conductive pattern 0b).

The surface (IOa) of the board (1) is covered with two magnetic plates θ except for the connection terminals (1), and H
Each through-hole electrode θl) θ+) on the back surface (10b)...
Chip-type capacitors (C5), (C6), (C7), and (C8) are soldered between .

Figure 6 shows an equivalent circuit of the above filter device.
To explain this in comparison to the component configuration described above, the connection terminal (
Coil (C5) (C6) placed between +1 ($4)
(C7) are electrically connected on the back surface side via through-hole electrodes Q +)Q Q... and connected in series. One end of a capacitor (C5) (CB) (C?HC8) is connected to each through-hole electrode (l I) (I +)..., and each capacitor (C5) (C6) (C7) (C
8) Lead the other end 1? It is connected to the li group 7 (12 (12.) and grounded. Therefore, the circuit constitutes a low-pass filter, and the current with a frequency lower than a specific cutoff frequency is attenuated (passed through), and the current with a frequency lower than a certain cutoff frequency is is cut off with large attenuation.

The manufacturing procedure of the filter device will be explained with reference to FIGS. 7 to 1O. In Fig. 7, through holes (
H) is opened. Next, as shown in FIG.
Copper plating is applied to both sides of 0) to form a conductive layer (+119 (+
(9 is provided. At that time, the inside of the through hole (H) is also electroplated to form a through hole electrode 01). Furthermore, a spiral coil (C7) is provided on the surface (IOa) of the substrate (10) by etching, and
) A conductive pattern (1) is formed on the back surface (10b) of the conductive pattern (1).

Then, as shown in FIG. 10, resist films (r7) (r7) are provided on the coils (1, 7) and the conductive pattern 02 formed on both sides of the substrate (10) to insulate them, and the through-hole electrodes ( 11) Attach a chip-type capacitor (C?) (CB) between the conductive pattern θ and the conductive pattern θ by soldering. Thereafter, the present filter device is formed by bonding one magnetic plate to the surface (loa) side of the substrate (10) and covering the coil (C7).

Here, the through-hole electrode (
11) (11)... and conductive pattern 0 exposure... by changing the position and connection, as shown in Figure 11 (capacitor (
C5) (C6) (c?) (ca) is arranged in series with the terminal (1), and the through-hole electrode (I +)
(l l) Coil (L5) (L6) (L7)
Connect and ground. In this case, the circuit constitutes a bypass filter, allowing currents with frequencies higher than a specific cutoff frequency to pass through without attenuation, and cutting off currents with lower frequencies with large attenuation. Although not shown, it is also possible to form a bandpass filter that passes current within a band between two specific frequencies by changing the combination of a coil and a capacitor.

In this embodiment, the coils (I, 5) (1, 6) (L?) are formed on the substrate (10) by plating and etching.
) and a conductive pattern (+2 (+2...), it is possible to form a coil without winding the conductive wires individually.

Therefore, it is possible to obtain a thin and compact filter device, and it is also possible to obtain a connecting substrate (
(not shown), it is possible to simultaneously manufacture a large number of filter devices in the same process. In addition, the substrate (10
) is covered with a magnetic plate (one piece glued), and the magnetic lines of force of each coil (L5) (L6) (L?) are shielded and do not leak outside or are induced between each coil. There is no possibility of binding occurring.

[Effects of the Invention] As described in detail in the above embodiment, the present invention generates a coil by plating a magnetic substrate, so that a thin and small filter device can be formed. By setting through-hole electrodes and conductive patterns, H
Various filter devices such as PF and BPF can be easily formed. Furthermore, since the coil surface is covered with a magnetic plate, interference of magnetic lines of force with the outside can be prevented, and there is no inductive coupling between each coil. In addition, a large number of filter device substrates can be manufactured in the same process, which improves product yield and improves reliability, and contributes to cost reduction.

[Brief explanation of the drawing]

1 to 11 show an embodiment of the present invention. Fig. 1 is a plan view showing the surface of the filter device, Fig. 2 is a bottom view thereof, Fig. 3 is a sectional view taken along the line A-A in Fig. 1, and Fig. 4 is a sectional view taken along the line B-B in Fig. 2. Figure 5 is C- of Figure 1.
C-line cross section, Figure 6 is an electrical equivalent circuit diagram of this device, Figures 7 to 10 are longitudinal sectional views of main parts explaining the procedure for forming the substrate of the filter device, and Figure 11 is an electrical diagram of HP F. FIG. 12 to 14 show a conventional example, in which FIG. 12 is a plan view of the LPF, FIG. 13 is an electrical equivalent circuit diagram of the same, and FIG. 14 is a slope of the main part of the board with the bobbin attached. It is a diagram. (10)... Board (10...
...Front side (10b)...Back side (L5)
(L6) (L?)... Coil (C5) (C
B) (C?) (CB)... Capacitor (I
+)...Through hole electrode (I2...
・Conductive pattern: 0... Magnetic material plate Applicant Mitsumi Electric Co., Ltd. Agent Patent Attorney Hayashi
Takayoshi 1I Figure 12 Figure 13 Figure 14

Claims (1)

[Claims] A magnetic substrate is plated and etched to form a coil on its surface, a conductive pattern is provided on the back surface, and both surfaces are electrically connected via through-hole electrodes.
A filter device characterized in that a capacitor is attached between the through-hole electrode and the conductive pattern on the back side, and a magnetic plate is further covered on the surface of the magnetic substrate.