JPH1041152A - Surface mounting type coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve mechanical strength and obtain reliability of an extension line by providing a through hole to a part wherein a lead terminal part is subjected to solder precoating. SOLUTION: A through hole 23 is provided to a lead terminal part 21 of a circular line ring which is extended from an outer shell core structure body 1 comprised of a core case 11 and a lid 12 of a core to a groove part 13 of a core case and molded. (A through hole is similarly provided to a lead terminal part 22.) The lead terminal parts 21, 22 are fused to cover at least the through hole 23 by an electrode 14 of a core case and solder 4. Thereby, mechanical holding force of a lead terminal part is raised and reliability of an extension line is improved. Additionally, since solder after solder precoating enters a through hole, enough required amount of solder attaches and dispersion in fusing strength of a lead terminal of products can be restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a surface mount type (SM)
D) The reliability of the connection between the lead terminals of the flat wire and the electrodes when reflowing to the printed circuit board in a coil, specifically, a surface mount type coil using a flat wire to reduce the resistance of the winding. Regarding high things.

[0002]

2. Description of the Related Art In recent years, with the increase in portable electronic devices such as mobile communication devices, there has been a demand for lower loss and higher efficiency of electronic components and circuits. In particular, in order to reduce the size of the switching power supply and achieve high conversion efficiency, attempts have been made to eliminate the switching loss of the diode by using a synchronous rectification circuit in the circuit. In addition, many attempts have been made to minimize the heat generation of the resistor due to high-frequency loss and current due to the increase in frequency of the switching coil due to miniaturization.

As an example, Japanese Patent Application Laid-Open No. 7-288210 discloses a switching power supply in which a DC resistance of a winding is reduced as much as possible by using a rectangular wire to reduce a loss due to a current in order to increase a space factor of the winding. An SMD choke coil is described. By the way, in the SMD choke coil using the flat wire, a means for connecting the flat wire and the electrode by connecting a conventional inner wire to a lead terminal and soldering is not employed. That is, the method of connecting the flat wire and the electrode of the surface-mount type coil using the flat wire is roughly classified into the following two methods.

(1) A method in which thermocompression bonding (a wire coating is melted by heat to form an alloy of copper and an electrode and fixed) without removing the coating at the winding end.

(2) A method of soldering a flat wire and soldering it to an electrode.

[0006]

However, the above-mentioned 2)
The two methods have the following problems.

In the method (1), the melted residue of the wire coating may remain between the electrode and the wire, and the welding strength is not sufficient. Also, the level of the welded strength of the crimp cannot be confirmed after manufacturing.

In the method (2), since the lead wire is soldered in advance compared with the method (1), the influence of the coating residue is eliminated, but there is a problem in strength due to the variation in the amount of solder attached to the lead wire. There is. In particular, at the time of reflow soldering when mounting, this portion is at 200 to 220 ° C., and it has been difficult to ensure perfect reliability of the connection at this temperature.

Accordingly, the present invention is directed to a surface having high mechanical strength for welding of a rectangular wire lead terminal portion to an electrode, particularly having high reliability of a spliced wire even at a temperature (200 to 220 ° C.) during reflow soldering. A mounting type coil is provided.

[0010]

Specifically, the invention is achieved by the following constitution.

An electrode to be soldered on a printed circuit board is formed on the side or bottom of a ferrite or ceramic case, and a conductor having a rectangular insulating coating is wound in the case, and winding starts and ends. A lead terminal portion having a portion to be soldered to the case, the lead terminal portion being welded to an electrode of the case to make an electrical connection, and having a through hole in a portion of the lead terminal portion to be soldered. A surface mount type coil characterized by the following.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A surface mount type coil according to the present invention will be specifically described below with reference to FIGS.

FIG. 1 is an external perspective view of a surface mount coil according to the present invention. Accordingly, the outer shell core structure 1 including the core case 11 and the core lid 12 is
3, a through-hole 23 is provided in the lead terminal portion 21 of the formed annular wire loop (a through-hole is also provided in the lead terminal portion 22).
Reference numerals 1 and 22 are welded so that at least the through hole 23 is covered by the electrode 14 and the solder 4 of the core case. FIG. 2A is a cross-sectional view taken along the line AA ′ in FIG. 1, and FIG. 2B is a partially omitted cross-sectional view centering on the lead terminal portion 21 of the annular loop. Here, in the figure, reference numeral 2 denotes an annular wire loop, and reference numeral 3 denotes a columnar magnetic material. FIG. 4A is an external perspective view of an example of a conventional surface-mount type coil, that is, an example in which a through-hole is not provided in a lead terminal portion of an annular wire loop, and FIG. B- in (a)
FIG. 4 shows a partial cross-sectional view of B ′. In this figure, 5 is an outer shell core structure, 51 is a core case, 52 is a core lid, and 5 is a core cover.
3 is a groove of the core case, 54 is an electrode of the core case,
Reference numeral 6 denotes an annular wire, 61 and 62 denote lead terminal portions, and 8 denotes solder. Thus, the conventional surface mount type coil
The solder is welded to the electrode only in such a form that the solder covers the lead terminal portion of the annular wire loop. However, in the surface-mount type coil according to the present invention, the solder is welded to the electrode in such a state that the solder covers the lead terminal portion of the annular wire loop, and the solder is also present in the through hole of the lead terminal portion. As a result, the solder is in a state in which the electrodes are so-called "caulked", the mechanical holding force of the lead terminal portion is increased, and the reliability of the connecting wire is improved.
In addition, by providing the through-holes in the lead terminal portions, the amount of solder attached after the solder is lifted into the through-holes becomes a necessary and sufficient amount, and the variation in the welding strength of the lead terminal portions between products can be suppressed.

[0014] In addition, a soldered portion of the lead terminal portion processed into a wavy shape can similarly obtain high reliability of the connecting wire.

Next, referring to an exploded perspective view shown in FIG. 3, the surface mounting type coil according to the present invention will be described in more detail while explaining an assembling method.

First, an annular wire ring 2 having lead terminal portions 21 and 22 provided with through holes 23 and 24 in a wire housing recess 15 of a ferrite or ceramic core case 11 having a predetermined shape and having an electrode 14. Is stored. The lead terminal portions 21 and 22 are bent and drawn out so as to be parallel to the bottom surface of the lead terminal portion lead-out groove portion 13, and are welded to the electrode 14 by soldering. Next,
The columnar magnetic body 3 is inserted and arranged in the center hole 25 of the annular loop 2, and in order to fix them, the core lid 12 made of the same material as the core case 11 is fixed thereon using an adhesive or the like. By providing the outer core structure provided, a surface-mounted coil according to the present invention as shown in FIG. 1 is obtained.

Here, the material and the like of each component will be described.

The material of the outer core structure is ferrite or ceramics as described above. As the ferrite, a Ni—Zn ferrite or the like is used as a high-resistance material, and as the ceramic, alumina or the like is used. The ferrite or ceramic core case is manufactured by powder press molding.

The electrodes are manufactured by baking a conductive metal paste. Alternatively, it may be manufactured by a vacuum evaporation method. Examples of the conductive metal include Ag and Cu.
In addition, plating is performed on the baked metal for the purpose of improving solder wettability and the like. For example, apply Ag paste,
After baking, Cu-Ni-Sn plating or Cu-Ni-solder plating is applied.

The toroidal wire uses a rectangular wire with an insulating coating as a wire, and the surface of the insulating coating is further coated with an adhesive resin having tackiness by heat or an alcohol-based solvent. . Then, the annular wire loop is formed by winding the rectangular wire into a roll shape so that the wide surface of the rectangular wire becomes the inner and outer peripheral surfaces, and fusing the adhesive resin coating on the insulating coating surface of the rectangular wire to form an annular shape. To be obtained. Further, the annular wire loop is drawn out after the lead terminal portion at the start of winding and the lead terminal portion at the end of winding are bent and formed, and each of the lead terminal portions is provided with a through hole. The material of the rectangular wire may be a normal coil material, for example, Cu, Au, Ag, Fe, Pt, S
n, Ni, Pb, Al, Co, or an alloy thereof can be used, and Cu is preferably used. Further, ordinary materials may be used for the insulating coating and the adhesive resin.

The columnar magnetic material is, for example, Fe--Si--Al
Any type of metal dust core may be used as long as the diameter is slightly smaller than the center hole of the annular wire loop.

A solder having a composition having a melting temperature of 250 ° C. or higher is used. This is because the temperature at the time of reflow (usually 200 to 220) is required for mounting the coil by reflow.
This is because a material having a melting point higher than (° C.) is required.

[0023]

EXAMPLES Specific examples of the present invention will be described below.

The mechanical strength of the surface-mounted coil according to the present invention, that is, the coil having a through-hole in the lead terminal portion, is compared with the conventional surface-mount coil, that is, the coil having no through-hole in the lead terminal portion. To do this, a tensile test after soldering was performed.

(Evaluation Method) A flat wire (with a φ.0 at the tip) having a through hole soldered to the electrode portion of a ferrite case core having an electrode coated with an Ag paste, baked, and then plated with Cu—Ni—Sn. A 3 mm through-hole is provided, or a normal rectangular wire (normally shaped rectangular wire, that is, without a through hole) is thermocompressed at 350 ° C., soldered, and welded by a tensile tester. The tensile stress when the part was broken was measured. Here, the measurement temperature is 150 ° C.
The following samples were measured three times in order to see the variation between products.

(Evaluation Results) Table 1 shows the measurement results. Here, the sample name BF is obtained by soldering a normal rectangular wire together with a flux, and the sample name A is obtained by soldering the flat wire provided with the through hole without using the flux. In this case, the sample name B is obtained by soldering a normal rectangular wire without using a flux.

From this, it can be seen that the tensile strength after soldering of the rectangular wire provided with the through hole has a tensile strength of about twice that of the conventional rectangular wire. Also, 3
There is little variation in the number of measurements. Further, it is easily considered that the variation in the measurement, that is, the variation between products is further improved by using the flux. Therefore, the surface-mount type coil according to the present invention having the rectangular wire having the through hole has excellent connection reliability.

[0028]

[Table 1]

[0029]

The surface mount type coil according to the present invention has a high mechanical strength for welding the flat wire lead terminal portion to the electrode,
Has high connection reliability. In addition, by providing the through-holes in the lead terminal portions, the amount of solder attached after soldering becomes necessary and sufficient, so that the variation in the welding strength of the lead terminal portions between products can be suppressed.

[Brief description of the drawings]

FIG. 1 is an external perspective view of a surface mount coil according to the present invention.

FIG. 2A is a sectional view taken along line AA ′ in FIG.
(B) is a partially omitted cross-sectional view centering on the lead terminal portion of the annular wire loop.

FIG. 3 is an exploded perspective view of the surface mount coil according to the present invention.

FIG. 4A is an external perspective view of a conventional surface mount coil, and FIG. 4B is a partial cross-sectional view taken along the line BB ′ in FIG.

[Explanation of symbols]

 1, 5; outer core structure 11, 51; core case 12, 52; core lid 13, 53; lead terminal portion lead-out groove 14, 54; electrode 15; coil storage recess 2, 6; Rings 21, 22, 61, 62; lead terminal portions 23, 24; through holes 25; center holes 3; cylindrical magnetic bodies 4, 8;

Claims (1)

[Claims] An electrode to be soldered on a printed circuit board is formed on a side or bottom of a ferrite or ceramic case, and a conductor having a rectangular insulating coating is wound in the case,
A lead terminal portion having a portion to be soldered at the beginning and end of winding of the winding, wherein the lead terminal portion is welded to an electrode of the case to make an electrical connection; A surface-mount type coil having a through hole in a portion to be mounted.