JPH03272111A - Bobbin for surface package type transformer - Google Patents

Abstract

PURPOSE:To relax stress at a soldered joint part in the land of the terminal and the printed wiring plate caused by the difference in expansion coefficient, and to miniaturize a bobbin by reducing the area of soldering by a method wherein the terminal is fixed by giving the degree of freedon aginst the bobbin. CONSTITUTION:The terminal part 3, which is engaged to the lower flange of a bobbin 1 has a stepping face 5 and a stepping side face 6, a groove Q having a terminal-fitting groove 8 is provided on a plane surface part P, and a U-shaped terminal 4, having a terminal protruding part 7 on the rear side, is inserted into the groove Q. The terminal 4 is couplded to the terminal part 3 using the protruding part 7 and the groove 8, but as the cross-section of the protruding part is semi-circularly shaped and the cross-section of the groove 8 is crescent-shaped, the degree of coupling of each surface of the terminal 4 and the groove Q is low, and there is a gap excepting the protruding part 7 and the groove 8. Then, the terminal 4 is placed on the land 11 located on a printed wiring board 10, the board 10 and the terminal 4 are fixed using a solder junction part 12 which is formed by soldering, and the terminal 4 and the bobbin 1 are fixed by giving the degree of freedom between the protruding part 7 and the groove 8. As a result, the stress of the junction part 12 generated by the difference of expansion coefficient of material is absorbed, the area of soldering is reduced, and the bobbin can be made small in size.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a bobbin for a surface-mounted transformer, and particularly to a bobbin for a surface-mounted transformer mounted on a substrate.

[Conventional technology]

Conventionally, as this type of apparatus, those shown in FIGS. 5 to 8 are known.

1) FIG. 5 is a perspective view showing a bobbin in which a terminal and a bobbin are integrally molded, and FIG. 6 is a detailed perspective view of the terminal portion of FIG. 5. In the figure, 1 is a bobbin, 2 is one rib of this bobbin 1, 3 is a terminal portion engaged with this one rib 2, 10 is a printed wiring board which is a board on which the bobbin 1 is mounted, 11
is the land printed on this printed wiring board 10, 1
2 is a solder joint, and 13 is an integrally molded terminal.

2) FIG. 7 is a perspective view showing the bobbin 1 with the terminal 4 press-fitted therein, and FIG. 8 is a detailed perspective view of the terminal portion of FIG. 7.

In the figure, reference numeral 14 denotes a press-fitting terminal that is press-fitted into the terminal portion 3 that is engaged with the lower collar 2 of the bobbin 1.

Next, the configuration will be explained.

1) An integrally molded terminal 1 that is integrally molded with the terminal portion 3 that is engaged with the lower collar 2 of the bobbin 1 shown in FIGS. 5 and 6.
3, a coil (not shown) is wound around the bobbin 1 for a transformer, a ferrite core is attached, and the bobbin 1 is attached to the land 11 printed on the printed wiring board 10.
An integrally molded terminal 13 is placed on the bobbin 1 and soldered, and the bobbin 1 and the printed wiring board 10 are fixed by the solder joint 12 formed by this soldering.

2) Winding a coil around a transformer bobbin 1 having a press-fitting terminal 14 press-fitted into a terminal portion 3 engaged with a lower collar 2 of the bobbin 1 shown in FIGS. 7 and 8, After attaching the ferrite core, place the press-fit terminal 14 on the bobbin 1 on the land 11 printed on the printed wiring board 10, solder it, and connect the bobbin 1 and the print with the solder joint 12 formed by the soldering. It was supposed to fix the wiring board.

[Problem to be solved by the invention]

However, since the conventional bobbin is constructed as described above, stress generated due to the difference in expansion coefficients between the printed wiring board material and the bobbin material is applied to the solder joint between the printed wiring board land and the bobbin terminal. Because it acts on
When creating a bobbin for surface mounting, a structure must be created that can withstand the stress, such as by increasing the area of the solder joint, and there is a problem in that it is difficult to miniaturize and save space.

This invention was made to solve the above-mentioned problems, and it is possible to obtain a bobbin for a surface mount transformer that can absorb stress without increasing the space by increasing the area of the solder joint. The purpose is

[Means to solve the problem]

Therefore, in the bobbin for a surface mount type transformer according to the present invention, the terminal is fixed to the bobbin with a degree of freedom.

[Effect]

The bobbin for a surface-mounted transformer according to the present invention has terminals fixed to the bobbin with a degree of freedom.
Works to prevent stress from acting on the solder joint between the terminal and the land of the printed wiring board due to the difference in expansion coefficient between the bobbin material and the printed wiring board material due to temperature changes,
Therefore, the solder area can be reduced, and the bobbin can be made smaller.

(Example) Below, a bobbin for a surface mount type transformer according to an example of the present invention will be described based on the drawings. FIG. 1 is a perspective view showing a bobbin for a surface mount type transformer according to an embodiment of the present invention, and FIG. 2 is an enlarged detailed view of the terminal portion in FIG. 1. The same or equivalent parts as in the conventional example and FIGS. 5 to 8 are denoted by the same reference numerals to avoid duplication of explanation.

In FIGS. 1 and 2, 4 is a terminal fitted to this terminal portion 3, 5 is a stepped surface of the portion where this terminal 4 is fitted, 6 is a stepped side surface with an opposing surface, and 7 is a terminal protrusion, and 8 is a terminal fitting groove into which this terminal protrusion 7 is fitted. 10 is a printed wiring board which is a board on which the bobbin 1 is mounted, 11 is a land printed on this printed wiring board 10, and 12 is this land! ■This is the solder joint between the terminal and the pattern when the terminal 4 is placed on top and soldered.

In one embodiment of the present invention, a bobbin for a surface-mounted transformer has Ili! due to the heat of the material of the bobbin 1. A case where the bobbin 1 is a transformer bobbin in which the expansion coefficient differs depending on the tensile coefficient and the heat of the material of the printed wiring board 10 and the terminals 4 of the bobbin 1 are surface mounted will be described.

The terminal portion 3 engaged with the lower collar 2 of the bobbin 1 has a stepped surface 5 and a stepped side surface 6 having opposing surfaces, as shown in FIG. 2, and the flat portion P has a terminal fitting groove. Groove Q with 8
are provided on at least one of the upper and lower sides. 1 and 2 show the case where grooves Q are provided on both the upper and lower sides.

A U-shaped terminal 4 having a terminal protrusion 7 on the back surface is inserted into the groove Q. The inserted terminal 4 is connected to the terminal part 3 by the terminal protrusion 7 and the terminal fitting groove 8. The terminal protrusion 7 has a semicircular cross section, and the terminal fitting groove 8 has a crescent shape in cross section. Therefore, the degree of coupling is low.

Each surface of the terminal 4 inserted into the terminal portion 3 of the bobbin 1 and each surface of the groove Q having the stepped surface 5 and the stepped side surface 6 are, except for the terminal convex portion 7 and the terminal fitting groove 8. It has a gap.

With this structure, a coil (not shown) is wound around the bobbin 1, and the terminal 4 of the transformer equipped with the ferrite core is placed on the land 11 printed on the printed wiring board 10 and soldered. The printed wiring board 10 and the terminal 4 are fixed by the solder joint 12 formed by this soldering, and the terminal protrusion 7 and the terminal fitting groove 8 are fixed.
By connecting terminal 4 with a degree of freedom only between
is not integrated with the bobbin 1, but is fixed with a degree of freedom.

According to a surface-mounted transformer bobbin according to an embodiment of the present invention, the bobbin 1 is surface-mounted on a printed wiring board 10 made of a material having a different coefficient of expansion from the material of the bobbin 1, and the bobbin 1 and the terminal 4 connected to the printed wiring board 10 are not integrated with the bobbin 1 but are fixed with a degree of freedom, so that the coefficient of thermal expansion of the material of the bobbin 1 and the material of the printed wiring board 10 is Since the stress generated due to the difference between This has the effect of providing a bobbin for a surface-mounted transformer at a low cost.

(Other Embodiments) In one embodiment of the present invention, the case where the terminal is a flat plate has been explained, but in the case of a round bar or a square bar, the terminal is shown in FIGS. 3 and 4.
As in the other embodiment shown in the figure, a terminal part insertion hole 9 is provided in the terminal part 3 that is engaged with the lower collar 2 of the bobbin 1, and the terminal part 4 having a smaller diameter than the terminal part insertion hole 9 is inserted into the terminal part 3. insert into the insertion hole 9 and fold the top and bottom.

The terminal insertion hole 9 has a stepped surface 5 on at least one of the upper and lower sides.
The terminal 4 is provided in a groove Q having a stepped side surface 6 having opposing surfaces, and the stepped side surface 6 prevents the terminal 4 from shifting from side to side. A coil (not shown) is wound around the bobbin 1 configured as described above, and the terminal 4 of the transformer equipped with the ferrite core is placed on the land 11 printed on the printed wiring board 10 and soldered. The printed wiring board 10 and the terminal 4 are fixed by the solder joint formed by the soldering, and the spring pressure of the terminal 4 allows the terminal 4 to be freely attached without being integrated with the bobbin. It can be fixed with great precision and has the same effect as the above embodiment.

In one embodiment of the present invention, the case where the terminal is a flat plate has been described, but it goes without saying that the same effect can be achieved even if the terminal is oval or flat.

In one embodiment of the present invention, the bobbin for a surface-mounted transformer is one in which the expansion coefficient of the material of the bobbin is different from that of the material of the printed wiring board, which is the substrate, and the surface-mounted transformer is Although we have explained the case of a bobbin for a transformer, it goes without saying that the same effect can be achieved even when the expansion coefficients of the bobbin material and the material of the printed wiring board are the same, and the terminal can be integrated with the bobbin. By fixing the bobbin with a degree of freedom, stress will not be generated due to the difference in expansion coefficient between the bobbin material and the printed wiring board. Even if the terminal is fixed to the bobbin with a degree of freedom, this stress can be absorbed and a bobbin for a surface mount type transformer can be obtained in which the stress does not act.

(Effects of the Invention) As described above, according to the present invention, the bobbin and the terminal are not integrally formed by molding or press-fitting, but are configured to be fixed with a degree of freedom. Since the stress generated due to the difference in thermal expansion coefficient between the material of the terminal and the board is absorbed by the component, the stress applied to the solder joint between the terminal and the land on the board is reduced, and the solder joint with the land on the board is reduced. This has the effect that the area of the part can be reduced and a miniaturized bobbin for a surface mount transformer can be obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a bobbin according to an embodiment of the present invention, FIG. 2 is an enlarged detailed perspective view of the terminal portion, and FIG.
0 A perspective view showing a bobbin according to another embodiment of the present invention, FIG. 4 is an enlarged detailed perspective view of the terminal portion, and FIG. 5 is a perspective view showing a conventional terminal integrally molded bobbin.
FIG. 6 is a detailed perspective view of the terminal portion, FIG. 7 is a perspective view showing another conventional terminal press-fit type bobbin, and FIG. 8 is a detailed perspective view of the terminal portion. 1 is a bobbin, 3 is a terminal part, 4 is a terminal, 7 is a terminal convex part, 8
10 is a terminal fitting groove, and 10 is a printed wiring board. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A transformer bobbin surface-mounted on a board made of a material with a different expansion coefficient from that of the bobbin, in which the terminals connected to the bobbin and the board are fixed with a degree of freedom without being integrated with the bobbin. A bobbin for surface-mounted transformers characterized by: