JPH07123094B2 - Small coil manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small coil used in various electric devices, and more particularly to a method of manufacturing a small coil of a type in which terminals are directly attached to a core.

[0002]

[Prior art and its problems] On a base with terminals implanted,
A coil having a structure in which a core formed by winding a wire is attached is generally used. However, in recent years, by removing the base and directly attaching the terminals to the core, a small coil which is further miniaturized has been used. FIG. 1 shows an example of such a coil. The flange 2 of the ferrite core 1 has two plate-like terminals 3 and 4 made of phosphor bronze or the like.
Is bonded and the ends 6 and 7 of the wire 5 wound around the core 1 are connected to the terminals 3 and 4 by soldering or welding. However, since the terminals 3 and 4 and the core 1 are conventionally bonded using an organic adhesive such as an epoxy-based adhesive,
This joint part is weak to heat, and the terminal may peel off from the core due to the heat of the solder near 300 ° C. when mounting on the printed board.

[0003]

SUMMARY OF THE INVENTION It is a first object of the present invention to provide a method for manufacturing a small coil capable of firmly joining a ferrite core and a lead frame. A second object of the present invention is to provide a method for manufacturing a small coil of the type in which the terminals are directly attached to the core, which prevents the terminals from being separated from the core due to heat when soldering to the printed circuit board. It is in.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a method of manufacturing a small coil in which a core and a terminal are joined by glass, which is an inorganic material which is difficult to melt at high temperature, instead of a conventional organic adhesive. That is, according to the present invention, a strip-shaped metal plate is punched to form a lead frame, and a glass paste containing crystalline glass powder as a main component is applied to at least one of the tip of the terminal portion provided on the lead frame or the lower surface of the core. The method of manufacturing a small coil is characterized by heating the glass paste in an inert gas atmosphere having a low oxygen concentration with the core placed on the tip of the terminal portion.

[0005]

EXAMPLE An example of the manufacturing method according to the present invention will be described with reference to FIGS. First, as shown in a cross section in FIG. 2, a strip-shaped metal plate 8 made of a clad material having a three-layer structure in which copper 8b is adhered on both surfaces of Kovar 8a which is an alloy of cobalt, nickel and iron is prepared. The coefficient of thermal expansion of Kovar alone is around 54 × 10 ^-7 / ° C at 300 ° C, but by applying copper to both sides of Kovar to form a clad material, the coefficient of thermal expansion can be changed to glass or ferrite. You can get closer. In particular, the coefficient of thermal expansion of the clad material when the thickness ratio of the three layers of copper, kovar, and copper is 1: 2: 1 is about 93 × 10 ⁻⁷ / 300 ° C., for example.
The temperature becomes ° C, which is extremely close to the value of 95 × 10 ^-7 / ° C of glass. The metal plate 8 made of such a clad material is punched out to form the lead frame 10 in which the opposing terminal portions 11 and 12 are provided at predetermined intervals in the longitudinal direction as shown in FIG.

Next, a glass paste made by mixing crystalline glass powder and water and a drum-shaped core 20 made of a ferrite material are prepared, and the glass paste is applied to the tips 11a, 12a of the terminals 11, 12 or the core 20. On the bottom surface or both of the
The tips 11a and 12a are placed on the tips 11a and 12a as shown in FIG. Then, pass the lead frame 10 with the core 20 through a firing furnace,
The glass paste is fired in an atmosphere in which an inert gas such as nitrogen or helium is slightly mixed with oxygen. By this baking treatment, the water content of the glass paste evaporates, and the molten glass melts the core 20 and the terminal portion 1 of the lead frame 10.
1 and 12 are firmly joined.

After this, the wire 30 is wound around the core 20, the ends 31 and 32 thereof are welded or soldered to the terminals 11 and 12, and then the terminals 11 and 12 are separated from the lead frame 10.
11 and 12 are made of a clad material having a three-layer structure in which both sides of Kovar are coated with copper, and a small coil as shown in FIG. 5 in which the terminals 11 and 12 and the core 20 are joined via glass is provided. Complete.

In the present invention, the glass paste is fired in an atmosphere in which a small amount of oxygen is mixed with an inert gas, and the oxygen concentration in this atmosphere is preferably as low as 50 ppm to 200 ppm. If the oxygen concentration is increased higher than this, the copper surface of the lead frame 10 will be oxidized and the terminal 1
Solderability of 1 and 12 deteriorates. On the other hand, if the oxygen concentration is lower than this, the chemical bond between the surfaces of the copper and the glass is not sufficiently performed, and the bonding strength between the lead frame 10 and the glass becomes insufficient. Further, in order to melt the glass component and obtain a sufficient bonding effect, it is preferable to bake at a high temperature of about 600 ° C. for about 10 minutes.

A glass paste prepared by mixing lead-boron-based crystalline glass powder and industrial pure water was fired at 610 ° C. for 10 minutes, and a force was applied to the upper brim of the core 20 in the lateral direction.
When the value of the limit force at which 20 peels from the lead frame 10 was measured, when it was fired in an atmosphere of nitrogen without addition of oxygen, only an adhesive strength of up to 120 g was obtained, whereas the oxygen concentration was It was confirmed that the product fired in a mixed atmosphere of 100 ppm of nitrogen and oxygen had a strength capable of withstanding a force of 300 g. The glass paste may be made by mixing an organic solvent such as thinner with glass powder instead of water. However, in this case, oxygen for vaporizing the organic solvent is required, so it is necessary to increase the oxygen concentration during firing, but since it is difficult to strictly control the oxygen concentration, the surface of the lead frame 10 is easily oxidized. The lead frame 10 may need to be cleaned after firing. Further, the material of the lead frame 10 is not necessarily limited to the Kovar and copper clad material, and other iron-based alloy and copper or a copper-based clad material, or a known metal conventionally used for terminals is used. Good.

[0010]

According to the present invention, the bonding strength between the terminal and the glass can be enhanced without impairing the solderability of the terminal, and the core and the terminal are bonded with the glass having a high melting point and soldered to the printed circuit board. In this case, it is possible to obtain a small coil in which the terminals are not likely to come off from the core.

[0011]

[Brief description of drawings]

FIG. 1 is a perspective view of a conventional coil.

FIG. 2 is a partial cross-sectional view showing an enlarged metal plate according to an embodiment of the present invention.

FIG. 3 is a plan view of the lead frame.

FIG. 4 is a perspective view of the assembly process.

FIG. 5 is a perspective view of a small coil

[Explanation of reference symbols] 10 lead frame 11 terminal portion 12 terminal portion 20 core 30 wire rod

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Susumu Utsunomiya 18 Tsurugashima-cho, Iruma-gun, Saitama Omi Gomigaya Toko Co., Ltd. Saitama Plant (56) Reference JP-A-58-87810 (JP, A)

Claims (2)

[Claims] 1. A method of manufacturing a small coil, in which terminals are directly attached to a core made of a ferrite material, a strip-shaped metal plate is punched out to form a lead frame having a plurality of terminal portions provided at predetermined intervals, and crystallinity is provided. After applying a glass paste containing glass powder as a main component to at least one of the tip of the terminal portion of the lead frame or the lower surface of the core, the core is placed on the tip of the terminal portion, and then the core and the lead frame are lowered. A method for producing a small coil, which comprises heating a glass paste by heating in an atmosphere of an inert gas having an oxygen concentration. 2. A low-oxygen concentration inert gas is nitrogen.
The method for producing a small coil according to claim 1, wherein oxygen is mixed in the range of ppm to 200 ppm.