LC composite component

An LC composite component of the combination of a coil inductor and a capacitor, in which a bobbin having first and second flanges formed at both ends of a coil winding portion is provided on at least one of the flanges with first and second lead-out electrodes, and both lead-out terminals of the coil wound around the coil winding portion being connected to the first and second lead-out electrodes. The flanges provided with the first and second lead-out electrodes is made from a dielectric material. A ground electrode is provided on the flange between both the electrodes, and capacitors are formed between the first lead-out electrode and the ground electrode and between the second electrode and the ground electrode. Thus, the combination of the capacitor and coil inductor is small and easy to produce.

FIELD OF THE INVENTION 
The present invention relates to an LC composite component, and more 
particularly to an LC composite component of the combination of a coil 
inductor and a capacitor, and suitable for use as a low-pass filter. 
BACKGROUND OF THE INVENTION 
Conventionally, this kind of LC composite component, for example, as shown 
in FIG. 5, has a cylindrical capacitor 5 comprising electrodes 2 and 3 
disconnected from each other and formed inside a cylindrical dielectric 1 
(hereinafter referred to as the inside electrodes 2 and 3) and an 
electrode 4 (hereinafter referred to as the outside electrode 4) opposite 
in common to the inside electrodes 2 and 3 and provided outside the same, 
and a ferrite bead 7 through which a central conductor 6 is inserted, so 
that solder 8 filled at both openings of the cylindrical capacitor 5 
connects the inside electrodes 2, 3 and central conductor 6 respectively. 
Reference numeral 9 designates an eyelet member which is, as needed, 
fitted onto the outside electrode 4 at the capacitor 5 and connected to 
the electrode 4 by solder 10. 
Such a conventional LC composite component constructed as above-mentioned 
comprises the combination of the capacitor 5 and a ferrite bead 7 separate 
therefrom, and is thereby both large and complicated to manufacture. 
OBJECT OF THE INVENTION 
An object of the invention is to provide an LC composite component of an 
inductor and a capacitor integral with each other and being both small and 
easy to manufacture.

DETAILED DESCRIPTION OF THE INVENTION 
In the first embodiment of the invention shown in FIGS. 1 and 2, a bobbin 
21 is made from a dielectric material and provided at both ends of a 
prismatic coil winding portion 22 with a first flange 23 and a second 
flange 24. 
The second flange 24 is at the mounting side of a printed circuit board or 
the like, and is larger in width than the first flange 23. Pairs of 
recesses 25 and 26 are provided at a pair of lengthwise ends of the second 
flange 24. Reference numerals 27 and 28 designate first and second 
lead-out electrodes formed at both lengthwise end sides of the lower 
surface of the second flange 24 serving as the mounting surface therefor. 
29 designates a ground electrode provided between the lead-out electrodes 
27 and 28 on the lower surface of the second flange 24, and 30 designates 
a coil wound around the coil winding portion 22. A pair of lead-out 
terminals 31 and 32 of the coil 30 are connected by soldering or the like 
(not shown) with the first and second lead-out electrodes 27 and 28 
through the recesses 25 and 26 respectively. 
The first embodiment of the LC composite component constructed as 
above-mentioned forms an equivalent circuit comprising an inductor L of 
the coil 30, a capacitor C.sub.1 formed between the first lead-out 
electrode 27 and the earth electrode 29, and a capacitor C.sub.2 formed 
between the second lead-out electrode 28 and the ground electrode 29 as 
shown FIG. 3. 
The first embodiment of the LC composite component of the invention, which 
forms such equivalent circuit, connects by soldering or the like the first 
and second lead-out electrodes 27 and 28 and ground electrode 29 formed on 
the lower surface of the second flange 24 with a predetermined pattern 
formed on a mounting substrate such as a printed circuit board or the 
like, and is mounted thereon, thereby being used as a low-pass filter. 
Referring to FIG. 4, a second embodiment of the LC composite component of 
the invention is shown. 
The fundamental construction of the second embodiment is the same as that 
of the first embodiment shown in FIGS. 1 and 2, in which like components 
are designated by like reference numerals and omitted by way of 
explanation. Only the differences between the first embodiment and the 
second embodiment will be described. 
In the second embodiment, first and second lead-out electrodes 27 and 28 
are formed in a continuing manner at both lengthwise end sides of the 
upper surface of the second flange 24 and both lengthwise end faces. A 
ground electrode 29 is formed on the lower surface of the second flange 24 
and between the first and second lead-out electrodes 27 and 28, and 
includes portions opposite to the first and second lead-out electrodes 
formed on the upper surface of the second flange 24, and bridges both 
lateral side surfaces in part of the flange 24. In a case where the second 
embodiment of the LC composite component in FIG. 4 is mounted on a printed 
circuit board, the first and second lead-out electrodes 27 and 28 formed 
at both the lengthwise end faces at the second flange 24, the ground 
electrode 29 formed at the lower surface serving as the mounting surface 
for the second flange 24 and at both the lateral side surfaces thereof, 
and the predetermined pattern on the printed circuit board, need only be 
connected by soldering or the like with each other. Hence, even when the 
portion of the ground electrode 29 formed on the lower surface of the 
second flange 24 is made larger, intervals between the ground electrode 29 
and the first and second lead-out electrodes 27 and 28 formed at both the 
lengthwise end faces of the same can be made larger respectively, thereby 
facilitating mounting of the composite component and improving the 
reliability of the mounting. 
The portions of the ground electrode 29 formed at both the lateral side 
surfaces of the second flange 24 are used for an improvement in the 
reliability of soldering the component to the printed circuit board or the 
like. Therefore, when reliability of mounting by soldering or the like is 
not especially required, the portion of ground electrode 29 at both the 
lateral surfaces of the flange 24 need not be formed. Also, both lead-out 
terminals 31 and 32 of a coil 30 are connected by soldering with the 
portions of first and second lead-out electrodes 27 and 28 formed on the 
upper surface of the flange 24. Accordingly, in the second embodiment, 
both the lead-out terminals 31 and 32 of the coil 30 need not extend 
toward the lower surface of the flange 24, thereby requiring no recesses 
25 and 26 as in the flange 24 as in the first embodiment of FIG. 1. 
In addition, the LC composite component of this invention is not defined 
solely by the aforesaid embodiments and may be changed without departing 
from the scope of the invention. 
For example, the shapes and positions of the first and sescond lead-out 
electrodes are optional, and the ground electrode may properly be changed 
in the same manner. 
The bobbin need not be made from a dielectric material in its entirety, but 
at least the flange on which the first and second lead-out electrodes and 
ground electrode are formed need be made from a dielectric material. Other 
portions of the flange may be made from other materials, such as magnetic 
substance. 
Furthermore, the first and second lead-out electrodes and the earth 
electrode may be provided on both the first and second flanges. 
Also, one of the first and second flanges need not be larger in width than 
the other, but they may be similar in size. 
The LC composite component of the invention is not restricted to being 
low-pass filter. 
As seen from the above, the LC composite component of the invention need 
not be formed in the combination of the capacitor and the inductor 
separate therefrom, and is both small and easy to manufacture. 
Although several embodiments have been described. they are merely exemplary 
of the invention and not to be construed as limiting, the invention being 
defined solely by the appended claims.