SMD type micro breaker

Abstract

To prevent a decrease in reliability due to a flux residue of a reflow solder.SOLUTION: A micro breaker includes: a fixed contact metal plate 4 having a fixed contact 5; a movable contact metal plate 6 having a movable contact 7, and a case 1, and the fixed contact metal plate 4 and the movable contact metal plate 6 include an embedded metal plate part 2 in which a solder terminal 3X is provided on both sides. The embedded metal plate part 2 has a planar part 2F, a vertical portion 2V, and a solder terminal 3X. The planar part 2F is connected to the vertical portion 2V through an internal bending line L1, and the vertical portion 2V is connected to the solder terminal 3X through an external bending line L2. The internal bending line L1 is inclined in a direction from an X-axis direction of the case 1 toward a center point of a bottom surface 1F of the case 1, and an intersection point M of the vertical line of the center of the pair of internal bending lines L1 disposed on both sides of the fixed contact 5 is displaced from the center of the fixed contact 5.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a microbreaker that detects temperature and switches to an OFF state, and in particular to an SMD (Surface Mount Device) type microbreaker that is mounted on a circuit board by reflow soldering. [Background technology]

[0002] In order to improve safety, devices such as battery packs and motors can be designed to cut off current when the temperature exceeds a set value. To achieve this, a small microbreaker has been developed that switches off the contacts to cut off current when the set temperature is reached (Patent Document 1).

[0003] The microbreaker in Patent Document 1 is used in protection circuits for battery packs built into mobile phones. The microbreaker in the protection circuit detects abnormally high battery temperatures and cuts off current. This microbreaker detects temperature increases using a thermal deformation element and switches the movable contact away from the fixed contact, switching it to the OFF state. This microbreaker detects temperature using a thermal deformation element and switches the movable contact away from the fixed contact, switching it to the OFF state. When the temperature exceeds a set temperature, the thermal deformation element reverses, deforming to push up the elastic arm plate that secures the movable contact to its tip, separating the movable contact from the fixed contact and switching it to the OFF state, cutting off current. When the temperature drops and the thermal deformation element returns to its original shape, the elasticity of the elastic arm plate brings the movable contact into contact with the fixed contact, restoring the ON state. When the elastic arm plate is not pushed up by the thermal deformation element, i.e., when the thermal deformation element does not reverse due to temperature, it elastically presses the movable contact against the fixed contact. In this state, the movable contact is brought into contact with the fixed contact by the elasticity of the elastic arm plate and is maintained in the ON state. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6967878 Summary of the Invention [Problem to be solved by the invention]

[0005] The microbreaker in Patent Document 1 is soldered to a printed circuit board by reflow soldering. Reflow soldering involves printing cream solder on the surface of a printed wiring board, placing the microbreaker on the cream solder, and heating it in a high-temperature furnace to melt the cream solder and solder the microbreaker to a land on the copper foil wiring pattern on the surface of the printed wiring board. Reflow soldering uses flux to prevent soldering defects caused by an oxide film on the surface of the land to be soldered. While flux is essential for stable soldering, the harmful effects of flux residue after soldering pose a problem. Microbreakers are extremely small electronic components. Flux residue generated during the reflow soldering process can reduce the reliability of the breaker by increasing the on-resistance of the contacts, causing contact failures, and even migration. Microbreakers are manufactured by insert molding a thin movable contact metal plate, a fixed contact metal plate, and other metal plates into a plastic case, but SMD type microbreakers have solder terminals on the bottom of the case that are soldered to the printed wiring board using reflow soldering, so flux seeps into the interior through the gaps between the solder terminals and the plastic case during the reflow soldering process, causing a decrease in the reliability of the microbreaker.

[0006] The breaker in Patent Document 1 has an embedded metal plate with solder terminals at both ends inserted into a plastic case. The solder terminals at both ends of the embedded metal plate are exposed on the bottom surface of the case, and fixed contacts are located on the central flat surface. The embedded metal plate has solder terminals connected to both ends of the flat surface, where the fixed contacts are located on the surface, and the connection between the flat surface and the solder terminals is embedded in the plastic case. Although the connection is embedded in the plastic case, a completely airtight seal between the connection and the plastic case cannot be achieved in all mass-produced microbreakers. These gaps are caused by, for example, differences in the thermal expansion coefficients of plastic and metal, or by relative misalignment during the insert molding process, in which an extremely small metal plate is held in a fixed position in a mold. These tiny gaps provide a path for flux to penetrate the hollow portion of the case during the reflow soldering process, and the flux residue that penetrates into the hollow portion reduces the reliability of the breaker.

[0007] This disclosure was developed with the aim of solving the above problems, and one of the objectives of this disclosure is to provide an SMD type micro breaker that can prevent a decrease in reliability due to flux residue. [Means for solving the problem]

[0008] An SMD type micro breaker according to one embodiment of the present disclosure comprises a fixed contact metal plate having a fixed contact, a movable contact metal plate having a movable contact arranged at a position opposite the fixed contact, and a case in which the fixed contact metal plate and the movable contact metal plate are arranged in fixed positions; Furthermore, it has all of the following configurations (a) to (l). (a) The case is a solder terminal provided on the fixed contact metal plate; The solder terminals on the movable contact metal plate are located at the four corners of the bottom surface. (b) The case has a hollow space with a closed structure inside. (c) the movable contact metal plate has an elastic arm plate with a movable contact at its tip, The elastic arm plate is arranged in a hollow portion of the case so as to be freely deformable. (d) The movable contact and fixed contact are arranged in the hollow part of the case. (e) The moving contact metal plate and the fixed contact metal plate are It has an embedded metal plate portion with solder terminals on both sides. (f) The buried metal plate part is a fixed contact embedded metal plate portion provided on the fixed contact metal plate; The movable contact is provided in a metal plate and has an embedded metal plate portion. (g) The buried metal plate part is A metal plate consisting of a flat section, a vertical section, and solder terminals. Solder terminals are connected to both sides of the flat portion via vertical portions. (h) The buried metal plate part is An internal bending line is formed between the flat and vertical sections. An external bending line is provided between the vertical portion and the solder terminal, The inner and outer folding lines are arranged in parallel. (i) The buried metal plate portion is The vertical part is buried in the case, The flat surface is placed in the hollow part of the case, The solder terminals are located on the bottom of the case. (j) The flat surface of the embedded metal plate of the fixed contact is Fixed contacts are arranged between internal bend lines arranged at opposing positions on both sides. (k) The fixed contact metal plate and the movable contact metal plate are an internal bending line of the buried metal plate portion of the fixed contact; Four internal bend lines, consisting of internal bend lines of the buried metal plate part of the movable contact, are located at the four corners of the case. (l) Internal fold lines are It is tilted from the X-axis direction of the case towards the center point of the bottom of the case, A pair of internal bending lines arranged on both sides of the fixed contacts are The intersection of the central perpendicular lines is displaced from the center of the fixed contact. [Effects of the Invention]

[0009] The microbreaker described above has the advantage of being able to prevent a decrease in reliability due to flux residue from reflow soldering. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic perspective view of a microbreaker according to an embodiment of the present invention; [Figure 2] FIG. 2 is a schematic perspective view of the microbreaker shown in FIG. 1, seen obliquely from below. [Figure 3] FIG. 2 is a schematic bottom view of the microbreaker shown in FIG. 1. [Figure 4] 3 is a schematic perspective view of an embedded metal plate portion, a fixed contact metal plate, and a movable contact metal plate. FIG. [Figure 5] FIG. 2 is a schematic plan view of an embedded metal plate portion and a fixed contact metal plate. [Figure 6] 3 is a schematic plan view of an embedded metal plate portion, a fixed contact metal plate, and a movable contact metal plate. FIG. [Figure 7] 6 is a schematic vertical cross-sectional view taken along line VI-VI of the microbreaker shown in FIG. 1. [Figure 8] FIG. 2 is a schematic horizontal cross-sectional view of a micro-breaker. [Figure 9] 1 is an enlarged cross-sectional view showing the self-alignment effect of molten solder in a reflow soldering process. [Figure 10] FIG. 10 is a plan view showing a state in which the solder terminals are self-aligned in the lateral direction with respect to the wiring pattern. [Figure 11] 10 is a plan view showing a state in which the solder terminals are self-aligned in the vertical and horizontal directions with respect to the wiring pattern. FIG. [Figure 12] FIG. 10 is a schematic cross-sectional view showing an example of an undercut shape of a case and a solder terminal. [Figure 13] FIG. 10 is a schematic perspective view of an embedded metal plate portion and a fixed contact metal plate of a conventional microbreaker. [Figure 14]14 is a schematic plan view of the embedded metal plate portion and the fixed contact metal plate of the microbreaker of FIG. 13. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below with reference to the drawings. In the following description, terms indicating specific directions or positions (e.g., "upper," "lower," and other terms including these terms) will be used as necessary. However, the use of these terms is intended to facilitate understanding of the invention with reference to the drawings, and the meaning of these terms does not limit the technical scope of the present invention. Furthermore, parts that appear with the same reference numerals in multiple drawings indicate the same or equivalent parts or components. Furthermore, the embodiments shown below are specific examples of the technical concept of the present invention and are not intended to limit the present invention thereto. Furthermore, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described below are intended as examples and are not intended to limit the scope of the present invention thereto. Furthermore, the content described in one embodiment or example can also be applied to other embodiments or examples. Furthermore, the sizes and positional relationships of components shown in the drawings may be exaggerated for clarity of explanation. The X-axis, Y-axis, and Z-axis directions are shown in the figure. The X-axis and Y-axis directions indicate the extension directions of each side that intersects perpendicularly on the bottom surface of the rectangular case. For example, in Figure 2, the longitudinal direction (long side direction) of the bottom surface 1F of the rectangular case 1 is the X-axis direction, and the lateral direction (short side direction) is the Y-axis direction. The thickness (height) direction of the case 1 is the Z-axis direction.

[0012] The embodiments of the present disclosure may be specified by the following configurations and features. An SMD type micro breaker according to one embodiment of the present disclosure comprises a fixed contact metal plate having a fixed contact, a movable contact metal plate having a movable contact arranged at a position opposite the fixed contact, and a case in which the fixed contact metal plate and the movable contact metal plate are arranged in fixed positions, Furthermore, it has all of the following configurations (a) to (l). (a) The case is a solder terminal provided on the fixed contact metal plate; The solder terminals on the movable contact metal plate are located at the four corners of the bottom surface. (b) The case has a hollow space with a closed structure inside. (c) the movable contact metal plate has an elastic arm plate with a movable contact at its tip, The elastic arm plate is arranged in a hollow portion of the case so as to be freely deformable. (d) The movable contact and fixed contact are arranged in the hollow part of the case. (e) The moving contact metal plate and the fixed contact metal plate are It has an embedded metal plate portion with solder terminals on both sides. (f) The buried metal plate part is a fixed contact embedded metal plate portion provided on the fixed contact metal plate; The movable contact is provided in a metal plate and has an embedded metal plate portion. (g) The buried metal plate part is A metal plate consisting of a flat section, a vertical section, and solder terminals. Solder terminals are connected to both sides of the flat portion via vertical portions. (h) The buried metal plate part is An internal bending line is formed between the flat and vertical sections. An external bending line is provided between the vertical portion and the solder terminal, The inner and outer folding lines are arranged in parallel. (i) The buried metal plate portion is The vertical part is buried in the case, The flat surface is placed in the hollow part of the case, The solder terminals are located on the bottom of the case. (j) The flat surface of the embedded metal plate of the fixed contact is Fixed contacts are arranged between internal bend lines arranged at opposing positions on both sides. (k) The fixed contact metal plate and the movable contact metal plate are an internal bending line of the buried metal plate portion of the fixed contact; Four internal bend lines, consisting of internal bend lines of the buried metal plate part of the movable contact, are located at the four corners of the case. (l) Internal fold lines are It is tilted from the X-axis direction of the case towards the center point of the bottom of the case, A pair of internal bending lines arranged on both sides of the fixed contacts are The intersection of the central perpendicular lines is displaced from the center of the fixed contact.

[0013] The microbreaker described above has the advantage that during the reflow soldering process, the direction of flux entering the hollow portion through the minute gaps formed between the vertical portion 2V and the plastic of the case is shifted away from the direction toward the contacts (fixed and movable contacts), preventing the harmful effects of flux residue adhering to the contacts and preventing a decrease in the reliability of the microbreaker due to flux residue. Arrow X in Figure 5 indicates the direction of flux entering hollow portion 20. As shown in this figure, during the reflow soldering process, flux entering hollow portion 20 through the gaps between vertical portion 2V and the plastic of case 1 enters hollow portion 20 from internal bend line L1 at the top edge of vertical portion 2V.

[0014] As shown in Figures 13 and 14, the fixed contact metal plate 904 of a conventional microbreaker 900 has two parallel rows of internal bending lines L901 extending in the X-axis direction on both sides of the fixed contact 905. In this microbreaker 900, flux penetrates into the hollow space inside the case through the gap between the vertical portion 902V and the plastic of the case, and the flux penetrates into the hollow space through the internal bending lines L901. The flux penetrating into the hollow space from the internal bending lines L901 penetrates in the direction of the opening gap of the internal bending lines L901, i.e., perpendicular to the internal bending lines L901. Therefore, in a microbreaker 900 in which internal bending lines L901 are arranged on both sides of the fixed contact 905 in a parallel orientation in the X-axis direction, the flux penetrates in the direction toward the contacts (fixed contact 905, movable contact) (arrow Y in Figure 14).

[0015] In contrast, in the microbreaker of the present disclosure, the internal bend lines located at the four corners of the case are inclined from the X-axis direction of the case toward the center point of the bottom surface of the case, and a pair of internal bend lines located on both sides of the fixed contacts are inclined so that the intersection of their central perpendicular lines is displaced from the center of the fixed contact. Flux that enters the hollow space from the internal bend lines enters toward the opening gap of the internal bend lines. Since the opening gap of the internal bend line is in the direction of the perpendicular line to the internal bend line (opening), the present disclosure displaces the intersection of the central perpendicular lines of the pair of internal bend lines located on both sides of the fixed contacts from the center of the fixed contact, thereby displacing the flux entry direction from the direction toward the fixed contact and away from the fixed contact, thereby preventing the adverse effects of flux residue entering the hollow space and adhering to the contacts and preventing a decrease in the reliability of the microbreaker due to flux residue.

[0016] In a microbreaker according to another embodiment of the present disclosure, the four external bending lines on the fixed contact metal plate and the movable contact metal plate can be inclined in a direction from the X-axis direction of the case toward the center point of the bottom surface of the case, and the tip edges of the solder terminals can be inclined in a direction from the X-axis direction of the case toward the center point of the bottom surface of the case.

[0017] The microbreaker with the above configuration has the advantage that the microbreaker's posture and position can be accurately corrected during the reflow soldering process. In particular, the above microbreaker has the advantage that it can accurately correct any deviation in the rotational posture of the microbreaker when soldered to a printed wiring board. This is because the external bending lines of the solder terminals located at the four corners of the bottom of the case are tilted from a direction parallel to the X-axis direction of the case toward the center point of the bottom of the case, so that the posture of the microbreaker that has been misaligned in the rotational direction can be corrected by self-alignment and soldered to the printed wiring board in the correct posture.

[0018] The conventional micro breaker 900 can be soldered to a printed circuit board by correcting its position using the self-alignment effect of the solder terminals 903X located at the four corners. However, because each solder terminal 903X is a parallelogram, it is possible to efficiently correct misalignment in the vertical and horizontal directions due to the self-alignment effect of reflow soldering, but it is difficult to efficiently correct misalignment in the rotational direction, i.e., misalignment in the rotational posture.

[0019] The cross-sectional view of Figure 9 shows how the self-alignment effect of the molten solder YH during the reflow soldering process corrects the microbreaker 100 to a precise position. The self-alignment effect is the effect of the surface tension of the molten solder YH acting in a direction that minimizes the surface area, correcting the position and soldering. Arrow A in Figure 9 shows how the surface tension of the molten solder YH acts in a direction that corrects the position of the solder terminal 3X. The surface tension indicated by arrow A acts in a direction that minimizes the surface area of ​​the molten solder YH, moving the microbreaker 100 to the right as indicated by arrow B in Figure 10, and moving the solder terminal 3X to a position facing the wiring pattern HP.

[0020] The self-alignment effect acts to bring the outer edges of the solder terminal 3X and the wiring pattern HP closest to each other, minimizing the surface area of ​​the molten solder YH, so that the solder terminal 3X that has shifted position to the lower left of the wiring pattern HP is corrected by the surface tension of the molten solder YH moving it in the direction indicated by arrow C, as shown in Figure 11. This is because the surface tension of the molten solder YH acts in the direction indicated by arrow C to bring the side edges of the solder terminal 3X and the wiring pattern HP closer together, thereby moving and correcting the solder terminal 3X to a position facing the wiring pattern HP.

[0021] Arrow B in the plan view of FIG. 10 and arrow C in the plan view of FIG. 11 indicate the direction of the position correcting force due to the self-alignment effect acting on the solder terminals 3X. As shown in these figures, the position correcting force (arrows B and C) effectively acts in a direction perpendicular to the side edge 3S of each solder terminal 3X. Therefore, the parallelogram-shaped solder terminals 903X provided on the bottom surface of the case of the conventional microbreaker 900 have strong position correcting forces due to the self-alignment effect in both the vertical and horizontal directions, effectively correcting misalignment in the vertical and horizontal directions. However, if there is a misalignment in the rotational direction, the position correcting force due to the self-alignment effect weakens, making it difficult to correct a microbreaker 900 that is misaligned in the rotational direction to the correct rotational direction and posture for soldering.

[0022] In contrast, the microbreaker of the present disclosure has the external bend lines of the four solder terminals located at the four corners inclined from a direction parallel to the X-axis direction of the case toward the center point of the bottom of the case, and the external bend lines of two solder terminals located at diagonal positions on the bottom of the case are parallel to each other, and the external bend lines of two solder terminals located at both ends of the case in the X-axis direction are in a mutually intersecting direction, thereby achieving the feature of being able to effectively correct and move rotational deviations and rotational posture, allowing soldering to be performed in an accurate posture.

[0023] When a solder terminal that has been rotated from its normal position and shifted out of position is moved or corrected, a displacement occurs between the outer bend line of the solder terminal and the outer bend line of the wiring pattern HP. The displacement caused by the rotational position shift is larger in the microbreaker of the present disclosure than in conventional microbreakers, and the self-alignment effect is more effective, allowing the microbreaker to be accurately adjusted for soldering. The displacement between the solder terminal and the wiring pattern HP caused by the rotational position shift of the microbreaker is greatest in the direction in which the outer bend line of the solder terminal is directed toward the center point of the bottom surface of the case, and is smallest in the direction perpendicular to the direction in which the outer bend line is directed toward the bottom surface of the case.

[0024] The microbreaker of the present disclosure can achieve a larger displacement of the external bend line than the external bend line L902 of the conventional microbreaker 900 because, while the external bend line L902 of the solder terminal 903X of the conventional microbreaker 900 is parallel to the X-axis direction of the case, the external bend line of the solder terminal of the microbreaker of the present disclosure is inclined from a direction parallel to the X-axis direction of the case toward the center point of the bottom surface of the case. The external bend line is oriented toward the center point of the bottom surface of the case, which maximizes its displacement in response to rotational misalignment of the microbreaker. This is because the displacement of the external bend line toward the center point of the bottom surface of the case increases in proportion to the rotational direction of the microbreaker, whereas the external bend line parallel to the X-axis direction of the case is inclined relative to the direction toward the center of the bottom surface of the case, and therefore does not increase in proportion to the rotational direction of the microbreaker.

[0025] In a microbreaker according to another embodiment of the present disclosure, the external bending lines of two solder terminals arranged at diagonal positions on the bottom surface of the case can be parallel to each other, and the external bending lines of two solder terminals arranged at both ends of the case in the X-axis direction can be arranged in an intersecting position.

[0026] In a micro breaker according to another embodiment of the present disclosure, the side edges of the solder terminals disposed on the bottom surface of the case can be non-linear.

[0027] In a micro breaker according to another embodiment of the present disclosure, the solder terminals arranged on the bottom surface of the case may have a bent shape in plan view.

[0028] In a microbreaker according to another embodiment of the present disclosure, the solder terminals disposed on the bottom surface of the case can be embedded in the case with undercut edges on both sides, preventing the solder terminals from coming loose from the bottom surface of the case. (Embodiment 1)

[0029] The micro breaker 100 shown in Figures 1 to 12 below is an SMD-type breaker that is reflow soldered to a printed wiring board. SMD-type micro breakers are primarily used as safety components for battery packs and the like. The micro breaker 100 mounted on a battery pack deforms its built-in thermal deformation element 8 to switch it to the OFF state and cut off the current when the battery or ambient temperature exceeds a set temperature or when the battery pack is used in an abnormal condition. However, this disclosure does not specify the use of the micro breaker 100, and can be used for all micro breakers that detect temperature rises and cut off current, such as in motors, heaters, etc. (Micro Breaker 100)

[0030] Figures 1 to 12 show an SMD-type microbreaker 100. This microbreaker 100 has a fixed contact metal plate 4 with a fixed contact 5 and a movable contact metal plate 6 with a movable contact 7 located opposite the fixed contact 5, both embedded in a plastic case 1. The fixed contact metal plate 4 and the movable contact metal plate 6 are provided with an embedded metal plate portion 2 that is insert-molded and embedded in the case 1. The fixed contact metal plate 4 in Figures 4 to 6 is a single metal plate including an embedded metal plate portion 2 (2X), and the movable contact metal plate 6 has a resilient arm plate 6P welded to the embedded metal plate portion 2 (2Y). The microbreaker 100 also has a thermal deformation element 8 that switches the resilient arm plate 6P of the movable contact metal plate 6 on and off. The fixed contact 5 provided on the fixed contact metal plate 4 and the movable contact 7 on the elastic arm plate 6P are arranged in opposing positions, and when the movable contact comes into contact with the fixed contact, the microbreaker 100 is switched to the ON state, and when the movable contact moves away from the fixed contact, the microbreaker 100 is switched to the OFF state.

[0031] When the ambient temperature of this microbreaker 100 rises to a high temperature, it detects this temperature rise and deforms the thermal deformation element 8, which then presses the elastic arm plate 6P, moving the movable contact 7 away from the fixed contact 5 and switching the contact to the OFF state. When the ambient temperature of the microbreaker 100 falls to a predetermined temperature, the elastic arm plate 6P and the thermal deformation element 8 return to their original position, bringing the movable contact 7 into contact with the fixed contact 5 and switching the contact to the ON state. (Fixed contact metal plate 4, movable contact metal plate 6, buried metal plate part 2)

[0032] The fixed contact metal plate 4 and the movable contact metal plate 6 form an embedded metal plate portion 2 that is insert-molded and embedded in the plastic case 1. The embedded metal plate portion 2 is a metal plate having a flat portion 2F, a vertical portion 2V, and solder terminals 3X, with the solder terminals 3X connected to both sides of the flat portion 2F via the vertical portions 2V. Furthermore, the embedded metal plate portion 2 has an internal bending line L1 formed by bending between the flat portion 2F and the vertical portion 2V, and an external bending line L2 formed by bending between the vertical portion 2V and the solder terminals 3X. The flat portion 2F is connected to the vertical portion 2V via the internal bending line L1, and the vertical portion 2V is connected to the solder terminals 3X via the external bending line L2.

[0033] The buried metal plate portion 2 has a flat portion 2F in the center, and vertical portions 2V are connected to both sides of the flat portion 2F via internal bending lines L1, and the vertical portions 2V are connected to solder terminals 3X via external bending lines L2. The vertical portions 2V of the buried metal plate portion 2 are embedded in the plastic of the case 1, the flat portion 2F is located in the hollow portion 20, and the solder terminals 3X are located on the bottom surface 1F of the case 1. The internal bending lines L1 connected to the upper edge of the vertical portions 2V are connected to both side edges of the flat portion 2F, and the external bending line L2 connected to the lower edge of the vertical portions 2V is connected to the solder terminals 3X and is located at the tip edge of the solder terminals 3X. The fixed contact metal plate 4 has a fixed contact 5 located on the flat portion 2F of the buried metal plate portion 2 (the buried metal plate portion 2X of the fixed contact). The movable contact metal plate 6 is a tip 6D of the elastic arm plate 6P, and has a movable contact 7 arranged at a position opposite the fixed contact 5. The embedded metal plate portion 2 has a vertical portion 2V that passes vertically through the bottom closing portion 1G of the plastic case 1, with an internal bending line L1 at the upper edge of the vertical portion 2V positioned in the hollow portion 20 and an external bending line L2 at the lower edge of the vertical portion 2V positioned on the bottom surface 1F of the case 1.

[0034] The buried metal plate portion 2 consists of a buried metal plate portion 2X of the fixed contact provided in the fixed contact metal plate 4, and a buried metal plate portion 2Y of the movable contact provided in the movable contact metal plate 6. The buried metal plate portion 2X of the fixed contact in Fig. 4 has a fixed contact 5 provided on the surface of the flat portion 2F. The buried metal plate portion 2Y of the movable contact in Figs. 4 and 6 has an elastic arm plate 6P welded to the flat portion 2F by a method such as a laser.

[0035] The fixed contact metal plate 4 and the movable contact metal plate 6 are fixed in place in the case 1 by insert molding. The fixed contact metal plate 4 and the movable contact metal plate 6 are embedded in the case 1 so that the vertical portion 2V of the embedded metal plate portion 2 (2X, 2Y) penetrates the case 1 from the inside to the outside, with the flat portion 2F located in the hollow portion 20 within the case 1 and the solder terminal 3X located on the bottom surface 1F of the case 1. During manufacturing, it is difficult to mold the vertical portion 2V embedded in the plastic case 1 so that it adheres tightly to the plastic of the case 1 without any gaps, resulting in tiny gaps between the vertical portion 2V and the plastic of the case 1. These gaps are caused by differences in the thermal expansion coefficients of the plastic and the metal, as well as by misalignment during insert molding. These tiny gaps serve as a path for flux to penetrate into the hollow portion 20 of the case 1 during the reflow soldering process. Flux residue that penetrates through these gaps and adheres to the contacts (fixed contact 5, movable contact 7) can reduce the reliability of the microbreaker 100. Flux residue on the contacts increases the on-resistance of the contacts in the on-state and can also cause poor contact. Furthermore, the harmful effects of migration caused by flux residue cannot be ignored. Migration of flux residue can cause an internal short circuit between the fixed contact metal plate 4 and the moving contact metal plate 6, which are close to each other with a narrow gap, further reducing the reliability of the micro breaker 100.

[0036] To solve the problem of reduced reliability of the microbreaker 100 due to flux residue entering the hollow portion 20, the embedded metal plate portion 2X of the fixed contact shown in the plan view of Fig. 5 has a pair of internal bend lines L1 connected to both sides of the flat portion 2F where the fixed contact 5 is provided, which are not parallel to the X-axis direction as in the conventional case (Figs. 13 and 14), but are inclined from the X-axis direction of the case 1 toward the center point 1C (intersection of the diagonal lines) of the bottom surface 1F of the case 1, and the intersection point M of the perpendicular lines at the center of each internal bend line L1 on both sides is displaced in the X-axis direction (vertical direction) of the case 1 from the center of the fixed contact 5. In Fig. 5, the intersection point M is displaced from the center of the fixed contact 5 toward the end surface 1T. The internal bending lines L1 in Figure 5 are inclined from the X-axis direction (towards the side surface 1S of the case 1) in the diagonal direction of the case 1, and the distance (width in the Y-axis direction) between the pair of internal bending lines L1 is wider (wider) on the side closer to the nearest end face 1T than on the farther side, and becomes wider as it approaches the nearest end face 1T (short side). The pair of internal bending lines L1 are in a V-shape when viewed from the nearest end face 1T side.

[0037] The embedded metal plate portion 2X of the fixed contact described above changes the intrusion direction (the direction of the perpendicular line at the center of the internal bend line L1) of flux that penetrates into the hollow portion 20 through the minute gap between the vertical portion 2V and the plastic of the case 1 from a direction toward the contact (the center of the fixed contact 5) to the direction of arrow X, which is inclined from the Y-axis direction toward the end face 1T side, rather than toward the contact. The intersection point M of the perpendicular lines at the centers of the pair of internal bend lines L1 is set to a position away from the center of the fixed contact 5, displaced in the X-axis direction toward the end face 1T side in Figure 5. As described above, in the micro breaker 100, during the reflow soldering process, flux that penetrates into the hollow portion 20 through the gap between the vertical portion 2V and the plastic penetrates from the internal bend line L1 into the hollow portion 20, or more precisely, from the gap between the surface of the internal bend line L1 and the plastic, in the direction indicated by arrow X. The flux penetrates in the direction of the opening of the gap between the vertical portion 2V and the plastic of the case 1, in other words, in the direction perpendicular to the internal bending line L1, which is orthogonal to the internal bending line L1. Therefore, by arranging the internal bending line L1 in a non-parallel position, tilted with respect to the X-axis direction, the flux penetrating in this direction is redirected from a direction toward the contacts to a direction away from the contacts (the direction of arrow X in Figures 4 and 5), and penetrates into the hollow portion 20, preventing the adverse effects of flux residue adhering to the contacts. The microbreaker 100, in which flux residue does not adhere to the contacts, has the advantage of being able to prevent a decrease in reliability due to flux residue.

[0038] In the embedded metal plate portion 902X of the fixed contact of the fixed contact metal plate 904 of the conventional micro breaker 900, flux penetrates from the internal bend lines L901 arranged in parallel on both sides of the contact toward the contact 905, as indicated by arrows Y in the plan views of Figures 13 and 14. Flux flowing in this direction deposits flux residue on the surface of the contact 905, increasing the on-resistance of the contact and causing contact failure, reducing the reliability of the micro breaker 900. However, the embedded metal plate portion 2X of the fixed contact can solve this problem.

[0039] The fixed contact metal plate 4 and the movable contact metal plate 6 shown in Figures 4 and 5 have four internal bending lines L1, consisting of the internal bending lines L1 of the buried metal plate portion 2X of the fixed contact and the internal bending lines L1 of the buried metal plate portion 2Y of the movable contact, arranged at the four corner portions 1E near the four corners of the case 1, and all four internal bending lines L1 are inclined in a direction from the X-axis direction of the case 1 (the longitudinal side surface 1S in Figure 5) toward the center point 1C of the bottom surface 1F of the case 1. The four solder terminals 3X in Figure 5, namely, in addition to the solder terminals 3X (31X, 32X) of the fixed contact metal plate 4, the solder terminals 3X (33X, 34X) of the movable contact metal plate 6 also have an internal bend line L1 that is inclined from the X-axis direction of the case 1 toward the center point 1C of the bottom surface 1F of the case 1, and an external bend line L2 that forms the tip edge of the solder terminal 3X that is inclined from the X-axis direction of the case 1 toward the center point 1C of the bottom surface 1F of the case 1. Furthermore, of the four solder terminals 3X arranged on the bottom surface 1F of the case 1, two solder terminals 3X (31X and 34X, 32X and 33X) arranged at diagonal positions on the bottom surface 1F of the case 1 have their internal bend lines L1 and external bend lines L2 parallel to each other, while the internal bend lines L1 and external bend lines L2 of two solder terminals 3X (31X and 33X, 32X and 34X) arranged at both ends 1D of the case 1 in the X-axis direction are in intersecting directions.

[0040] The fixed contact metal plate 4 and the movable contact metal plate 6 have solder terminals 3X arranged on both end portions 1D near the end faces 1T of the bottom face 1F of the case 1. Of the four solder terminals 3X (31X, 32X, 33X, 34X) connected to the fixed contact metal plate 4 and the movable contact metal plate 6, two solder terminals 3X are provided in the X-axis direction of the case 1 (31X and 33X, 32X and 34X on each longitudinal side face 1S). The two solder terminals 3X (31X and 33X, 32X and 34X) arranged in the X-axis direction of each case 1 are displaced toward the center from the end face 1T of the case 1. With this structure, parts of the fixed contact metal plate 4 and the movable contact metal plate 6 connected to the solder terminals 3X are embedded in the case 1, allowing the solder terminals 3X to be arranged in fixed positions on the bottom face 1F of the bottom closing portion 1G. A pair of solder terminals 3X (31X and 32X) arranged on one end face 1T of the case 1 are electrically connected to the fixed contact metal plate 4, and a pair of solder terminals 3X (33X and 34X) arranged on the other end are electrically connected to the movable contact metal plate 6, and the fixed contact metal plate 4 and the movable contact metal plate 6 are partially embedded in the case 1, positioning the solder terminals 3X in fixed positions on the bottom face 1F of the bottom closing portion 1G.

[0041] The solder terminal 3X has both side edges 3S parallel to the Y-axis direction of the case 1, a rear edge 3L positioned on the side surface 1S of the case 1 parallel to the X-axis direction, and a leading edge forming an external bend line L2. The external bend line L2 is inclined from a direction parallel to the X-axis direction of the case 1 toward the center point 1C of the bottom surface 1F of the case 1. While the four solder terminals 3X can have straight side edges 3S, the solder terminal 3X of FIG. 3 does not have straight side edges 3S, but rather has both side edges 3S that are partially bent in a dogleg shape, resulting in a bent shape with a bent middle in the planar shape. In the solder terminal 3X of FIG. 3, the total length (and the straight portion) of the side edge 3S away from the end face 1T is longer than the side edge 3S closer to the end face 1T.

[0042] The vertical portion 2V can be positioned vertically or inclined relative to the flat portion 2F and / or the solder terminal 3X. The vertical portions 2V connected to both sides of the flat portion 2F can be inclined surfaces with the distance between them narrowing at the top (widening at the bottom). The vertical portion 2V configured in this manner can ensure the width required for embedding in the plastic of the case 1 in the Y-axis direction. The external bending line L2 and the internal bending line L1 are parallel to each other, making the top and bottom widths of the vertical portion 2V equal. The vertical portion 2V is insert-molded into the plastic of the case 1, and the vertical portion 2V is connected to the solder terminal 3X via the external bending line L2, with the solder terminal 3X positioned on the bottom surface 1F of the bottom closing portion 1G.

[0043] The fixed contact metal plate 4 is insert-molded and placed in a fixed position in the main case 1A. The fixed contact metal plate 4 in FIGS. 4 and 6 has a bottom closing portion 1G at the front end 4A that closes the opening 15A in the bottom 13 of the hollow portion 20, and a fixed contact embedded metal plate portion 2X at the rear end 4C that is integral with the front end 4A. The fixed contact metal plate 4 shown in the cross-sectional view of FIG. 7 has the bottom closing portion 1G closing the opening 15A in the bottom 13, and the fixed contact 5 located on the surface of the flat portion 2F of the fixed contact embedded metal plate portion 2X at the rear end 4C. This fixed contact metal plate 4 is placed in a fixed position with its vertical portion 2V embedded in the case 1. The fixed contact metal plate 4 shown in the cross-sectional view of FIG. 7 has a step portion 4D between the front end 4A and the flat portion 2F of the fixed contact embedded metal plate portion 2X, and the step portion 4D is embedded in the bottom 13 of the main case 1A.

[0044] The fixed contact metal plate 4 can be formed into the fixed contact 5 by press-fitting a silver inlay material into a metal plate. The metal plate of the fixed contact 5 is copper, a copper alloy, or nickel, or a nickel alloy. The inlay material can be made thicker to extend the contact life, so its thickness is set to 20 μm. However, the surface of the fixed contact metal plate 4 can be silver-plated, and the silver-plated layer can be used as the fixed contact 5. The silver-plated layer of the fixed contact 5 is thicker than the silver-plated layer of the movable contact 7, for example, 6 μm. However, the film thickness of the silver-plated layer of the fixed contact 5 can be set to 5 μm to 100 μm, preferably 3 μm to 50 μm, and can be thicker than the movable contact 7. By making the silver-plated layer of the fixed contact 5 thicker, the fixed contact 5 can be connected to a polarity that is easily damaged, thereby extending the connection life.

[0045] The fixed contact metal plate 4 has solder terminals 3X (31X and 32X) on both ends of the embedded metal plate portion 2X of the fixed contact. As shown in FIGS. 1 to 3, pairs of solder terminals 3X (31X and 32X, 33X and 34X) are arranged at the four corners 1E of the bottom surface 1F of the bottom closed portion 1G. The solder terminals 3X (31X, 32X, 33X, 34X) at the four corners 1E are exposed on the bottom surface 1F of the bottom closed portion 1G so that they can be fixed to the wiring pattern HP on the surface of the circuit board by soldering such as reflow soldering. This microbreaker 100 is reflow soldered with the solder terminals 3X arranged on the solder surface of the circuit board.

[0046] By embedding the side edges 3S of each solder terminal 3X arranged on the bottom surface 1F of the case 1 in an undercut shape within the plastic case 1, it is possible to prevent the solder terminals 3X from slipping out or becoming unintentionally detached from the bottom surface 1F of the plastic case 1. The example solder terminal 3X shown in FIG. 12 has recessed portions 3a on both side edges 3S. The recessed portions 3a are recessed portions that are recessed inward in a vertical cross-sectional view of the solder terminal 3X in the thickness direction. The shape of the recessed portions 3a is not limited and can be, for example, a step, unevenness, grooves, chamfers, slopes, curved surfaces, etc. During insert molding, the resin flowing into the recessed portions 3a hardens, and as a result, a portion of the outer surface of the solder terminal 3X is embedded in the plastic case 1, forming an undercut shape. The side edges 3S on both sides in Figure 3 have non-linear portions in addition to parallel straight portions, and are also bent in shape, so that at least one side edge 3S of the solder terminal 3X (the side edge 3S on the side away from the end face 1T in Figure 3) can be made longer than the conventional solder terminal 903X shown in Figure 14, whose side edges 903S on both sides are linear and parallel, thereby improving the effect of preventing the solder terminal 3X from coming loose due to the undercut shape. (Elastic arm plate 6P)

[0047] The elastic arm plate 6P shown in Figures 4, 6, and 7 has a movable contact 7 at its tip 6D, which faces the fixed contact 5, and a rear end 6E welded to the embedded metal plate portion 2Y of the movable contact. The elastic arm plate 6P is layered on the flat portion 2F of the embedded metal plate portion 2Y of the movable contact and fixed by laser welding, with the movable portion 6A in the middle being disposed inside the hollow portion 20. The elastic arm plate 6P is made of an elastically deformable conductive metal plate. A Cu-Cr-Ag-Si alloy can be used for the metal plate of the elastic arm plate 6P. The Cu-Cr-Ag-Si alloy contains Cu as a base material, and 0.01 to 5 wt%, preferably 0.01 to 2.5 wt%, of Cr, 0.01 to 5 wt%, preferably 0.01 to 2.5 wt%, of Ag, and 0.01 to 5 wt%, preferably 0.01 to 2.5 wt%, of Si. The elastic arm plate 6P may also be made of an elastic metal plate, such as a copper alloy containing Ni, P, Zn, and Fe, a copper alloy containing Fe, P, and Zn, a copper alloy containing Cr and Mg with an IACS of 75% to 95%, a copper alloy containing Zr with an IACS of 80% to 95%, or a copper alloy containing Sn with an IACS of 80% to 95%. However, IACS (International Annealed Copper Standard) is an internationally adopted standard for electrical resistance or electrical conductivity, and is based on annealed standard soft copper (volume resistivity 1.7241 x 10 -2 This notation defines conductivity as 100%.

[0048] Furthermore, the elastic arm plate 6P has a movable contact 7 at the tip 6D of the movable part 6A. The movable contact 7 of the elastic arm plate 6P is provided with a silver-plated layer in the area facing the fixed contact 5, thereby reducing the contact resistance with the fixed contact 5. When the thermal deformation element 8 is not thermally deformed, the movable contact 7 of the elastic arm plate 6P is in contact with the fixed contact 5 and is in the ON state, and when the thermal deformation element 8 is thermally deformed, the movable contact 7 is separated from the fixed contact 5 and is in the OFF state. (Case 1)

[0049] The case 1 is made of plastic and has a hollow section 20 with a closed structure inside. The bottom surface 1F of the hollow section 20 is closed by the bottom closing portion 1G of the case 1. The hollow section 20 accommodates and houses the fixed contact 5, the movable contact 7, and the elastic arm plate 6P. The embedded metal plate section 2 has all or part of its vertical section 2V embedded in the case 1, and all or part of its flat section 2F disposed in the hollow section 20 of the case 1. The plastic case 1 has solder terminals 3X electrically connected to the fixed contact metal plate 4 and to the movable contact metal plate 6 disposed on its bottom surface 1F. The movable contact metal plate 6 has an elastic arm plate 6P with a movable contact 7 at its tip, and the elastic arm plate 6P is disposed in the hollow section 20 of the plastic case 1 so as to be freely deformable. Furthermore, the plastic case 1 has the fixed contact 5 and the movable contact 7 arranged in a hollow portion 20, and the elastic arm plate 6P, which deforms in the hollow portion 20, switches between an ON state in which the movable contact 7 contacts the fixed contact 5, and an OFF state in which the movable contact 7 is separated from the fixed contact 5.

[0050] Plastic case 1 has solder terminals 3X electrically connected to fixed contact metal plate 4 and movable contact metal plate 6 at the four corners 1E of bottom surface 1F of bottom closing portion 1G, which is the bottom surface 1F of the case. Case 1 arranges fixed contact metal plate 4 and movable contact metal plate 6 in fixed positions, and solder terminals 3X electrically connected to fixed contact metal plate 4 and solder terminals 3X electrically connected to movable contact metal plate 6 are arranged exposed on bottom surface 1F of bottom closing portion 1G. Bottom surface 1F of bottom closing portion 1G is rectangular, and two solder terminals 3X (31X and 32X) located at one end of the rectangle are electrically connected to fixed contact metal plate 4, and two solder terminals 3X (33X and 34X) located at the other end are electrically connected to movable contact metal plate 6. The microbreaker 100 is fixed in place by reflow soldering the four solder terminals 3X (31X, 32X, 33X, 34X) to the wiring pattern HP of the printed wiring board. During the reflow soldering process, the self-alignment effect of the molten solder YH corrects the posture and position of the microbreaker 100 when soldered to the printed wiring board.

[0051] The case body 1A has the fixed contact metal plate 4 and the movable contact metal plate 6 insert-molded into the case, and the fixed contact 5, the movable contact 7, and the solder terminal 3X are arranged in fixed positions in the case body 1. The case body 1A has both the movable contact metal plate 6 and the fixed contact metal plate 4 arranged in fixed positions, and the movable contact 7 and the fixed contact 5 arranged in opposing positions. This structure of the case body 1A, which arranges the fixed contact 5 and the movable contact 7 in fixed positions, is characterized by preventing misalignment of the contact positions between the movable contact 7 and the fixed contact 5. The movable contact 7 is connected to the case body 1A via an elastically deformable elastic arm plate 6P, which reliably connects the elastic arm plate 6P to the embedded metal plate portion 2Y of the movable contact, preventing misalignment relative to the fixed contact 5. Relative misalignment of the connection position between the embedded metal plate portion 2Y of the movable contact and the elastic arm plate 6P, which are fixed in a fixed position in the case body 1A, causes misalignment of the movable contact 7, and therefore, causes misalignment of the movable contact 7 and the fixed contact 5. The relative positional deviation between the fixed contact 5 and the movable contact 7 causes an increase in the contact resistance between the movable contact 7 and the fixed contact 5 that reciprocates.

[0052] 7, the upper welding plate 6C of the buried metal plate portion 2Y of the movable contact is connected to the main case 1A by a fitting structure and placed in a fixed position. The main case 1A with this structure has the advantage that the movable contact metal plate 6 is placed in a fixed position by a fitting structure, and the upper welding plate 6C can be laser-welded to the flat portion 2F of the buried metal plate portion 2Y of the movable contact to place it in the fixed position without misalignment.

[0053] The bottom surface 1F of the storage recess 29 of the hollow portion 20 is closed by the bottom portion 13 and fixed contact metal plate 4 that are molded integrally with the main case 1A, and the outer bottom surface 1F of the storage recess 29 is closed by the plastic of the main case 1A. The main case 1A is fixed to the main case 1A by insert molding the fixed contact metal plate 4 into the plastic bottom portion 13 that closes the bottom of the hollow portion 20 on the outside of the storage recess 29. The top surface of the hollow portion 20 is closed by the cover case 1B that is connected to the main case 1A, making the hollow portion 20 a closed hollow.

[0054] The main case 1A has an outer peripheral wall 10 that surrounds the hollow portion 20. The outer peripheral wall 10 in FIG. 8 has a pair of outer walls 11A, 11B and opposing walls 12 that connect both ends of the pair of outer walls 11A, 11B. As shown in FIG. 7, the lid case 1B is disposed above the main case 1A, covering the upper side of the elastic arm plate 6P. The lid case 1B shown in the figure is made of plastic, and is fixed to the main case 1A by fixing its outer peripheral edge to the upper surface of the outer peripheral wall 10 of the main case 1A. As shown in FIGS. 7 and 8, the lid case 1B has an outer peripheral wall 22 that protrudes toward the main case 1A at its outer peripheral edge facing the outer peripheral wall 10 of the main case 1A. The inside of this outer peripheral wall 22 has a downwardly opening recessed shape that serves as a storage compartment for storing the elastic arm plate 6P that is elastically deformed when pressed by the thermal deformation element 8. An outer peripheral wall 22 of the lid case 1B is fixed to outer walls 11A and 11B provided at both ends of the main case 1A, and is further fixed to the opposing wall 12. The plastic lid case 1B is connected to the main case 1A by ultrasonic welding.

[0055] The case 1 shown in FIGS. 7 and 8 has mating connecting protrusions and connecting recesses to accurately position and connect the case body 1A and the case lid 1B. The case lid 1B shown in FIG. 7 has connecting protrusions that protrude from the underside of the outer peripheral wall 22 toward the case body 1A on both sides of the end of the outer wall 11A on the fixed contact side of the case body 1A. As shown in FIG. 7, the case body 1A has connecting recesses on the upper surface of the outer peripheral wall 10 opposite these connecting protrusions to guide the connecting protrusions. Furthermore, the case lid 1B shown in FIG. 7 can have a mating protrusion that fits into the opening end of the recess provided on the outer wall 11B side of the case body 1A and is positioned on the upper surface of the laminated portion 40 of the elastic arm plate 6P. The outer shape of this mating protrusion is similar to the planar shape of the recess and can be fitted into a stepped recess formed on the upper surface of the upper welding plate 6C of the elastic arm plate 6P fitted into the recess. In the above case 1, at the end of the outer wall 11A on the fixed contact side of the main case 1A, the connecting protrusions on both sides of the lid case 1B are guided into the connecting recesses of the main case 1A, and at the end of the outer wall 11B side of the main case 1A, the mating protrusions of the lid case 1B are guided into the stepped recesses formed on the upper surface side of the laminated portion 40 of the elastic arm plate 6P, so that the lid case 1B is connected to the main case 1A in the correct position. (Thermal deformation element 8)

[0056] The microbreaker 100 has a fixed contact metal plate 4 and a movable contact metal plate 6 fixed to a case 1 and a thermal deformation element 8 that deforms the elastic arm plate 6P of the movable contact metal plate 6. The thermal deformation element 8 is made of laminated metals with different thermal expansion coefficients so that it deforms when heated. The thermal deformation element 8 is disposed between a heater 9 and the elastic arm plate 6P. When heated, the thermal deformation element 8 deforms and reverses, separating the movable contact 7 from the fixed contact 5 and switching the microbreaker 100 to the OFF state. The thermal deformation element 8 has a convex curved shape at the center. When not thermally deformed, i.e., when the movable contact 7 is in contact with the fixed contact 5, the central alignment protrusion protrudes toward the elastic arm plate 6P. When thermally deformed and reversed, the central alignment protrusion protrudes toward the heater 9. When the thermal deformation element 8 is thermally deformed and inverted, the central alignment protrusion contacts the heater 9, and both end portions contact and press against the elastic arm plate 6P, pushing up the movable part 6A of the elastic arm plate 6P and separating the movable contact 7 from the fixed contact 5 to switch it off.

[0057] As shown in FIG. 7, the microbreaker 100 is fixed to a circuit board by soldering the solder terminals 3X (33X and 34X) of the embedded metal plate portion 2Y of the movable contact, which extends from both sides of the case 1 to the outside, and the solder terminals 3X (31X and 32X) of the fixed contact metal plate 4. The microbreaker 100 is placed on the circuit board with the bottom surface 1F of the bottom closing portion 1G, i.e., the bottom surface 1F of the main case 1A, facing the top surface of the circuit board, and then reflow soldered. The microbreaker 100 is reflow soldered by heating with the solder terminals 3X (31X, 32X, 33X, 34X) provided at the four corners 1E of the case 1 aligned with the wiring pattern HP on the surface of the circuit board. The microbreaker 100 is soldered to the wiring pattern HP of the circuit board via the solder terminals 3X at the four corners 1E, and is self-aligned and fixed in place on the circuit board.

[0058] The microbreaker 100 can incorporate a heater 9 for heating the thermal deformation element 8 in the storage recess 29 below the elastic arm plate 6P. This configuration is ideal for applications where the heater 9 heats the thermal deformation element 8 to maintain a current-blocking state. However, the microbreaker 100 is not necessarily limited to a structure incorporating a heater 9. In a microbreaker 100 without a built-in heater 9, when the thermal deformation element 8 exceeds a set temperature and deforms, deforming the elastic arm plate 6P and switching the contacts to the OFF state, the microbreaker 100 does not heat the thermal deformation element 8 to maintain the OFF state, but instead returns the thermal deformation element 8 and elastic arm plate 6P to their original positions once the thermal deformation element 8 drops to a predetermined temperature, switching the microbreaker 100 to the ON state. [Industrial Applicability]

[0059] The present disclosure can be suitably used as an SMD type micro breaker that can prevent a decrease in reliability due to flux residue from reflow soldering. [Explanation of symbols]

[0060] 100, 900...Micro breaker 1. Case 1A...Main unit case 1B...lid case 1C…Center point 1D...both ends 1E...Four corners 1F...bottom 1G…Bottom obstruction part 1S...Side 1T...end face 2...Buried metal plate section 2X: Buried metal plate part of fixed contact 2Y: Buried metal plate part of moving contact 2F…Flat area 2V…Vertical section L1: Internal bending line L2: External bending line 3X, 31X, 32X, 33X, 34X...Solder terminals 3S...Side edge (of solder terminal) 3L...rear edge (of solder terminal) 3a...recess 4…Fixed contact metal plate 4A…Tip 4C…Rear end 4D…Step part 5…Fixed contact 6…Movable contact metal plate 6P...Elastic arm plate 6A…Movable parts 6C...Upper welding plate 6D...Tip 6E…Rear end 7…Movable contact 8...Thermal deformation element 9...Heater 10...Outer wall 11A, 11B...exterior wall 12...Opposite wall 13...Bottom 15A…Opening 20...Hollow part 22...Outer wall 29...Storage recess 40...Laminated part HP...wiring pattern YH: molten solder 902X: Buried metal plate part of fixed contact 902V…Vertical section 903S...Side edge (of solder terminal) 903X...Solder terminals 904…Fixed contact metal plate 905…Fixed contact L901...Internal bending line L902…External bending line

Claims

1. a fixed contact metal plate having a fixed contact; a movable contact metal plate having a movable contact arranged at a position opposite to the fixed contact; a case in which the fixed contact metal plate and the movable contact metal plate are arranged in fixed positions; Furthermore, an SMD type micro breaker having all of the following configurations (a) to (l). (a) the case is a solder terminal provided on the fixed contact metal plate; The solder terminals provided on the movable contact metal plate are arranged at the four corners of the bottom surface. (b) The case has a hollow portion with a closed structure inside. (c) the movable contact metal plate includes an elastic arm plate having the movable contact at its tip, The elastic arm plate is arranged in the hollow portion of the case so as to be deformable. (d) The fixed contact and the movable contact are disposed in the hollow portion of the case. (e) the fixed contact metal plate and the movable contact metal plate are The solder terminals are provided on both sides of an embedded metal plate portion. (f) the embedded metal plate portion is a fixed contact embedded metal plate portion provided in the fixed contact metal plate; and a movable contact embedded metal plate portion provided in the movable contact metal plate. (g) the embedded metal plate portion is A metal plate consisting of a flat portion, a vertical portion, and the solder terminals, The solder terminals are connected to both sides of the flat portion via the vertical portions. (h) the embedded metal plate portion is An internal bend line is formed between the planar portion and the vertical portion. An external bending line is provided between the vertical portion and the solder terminal, The inner and outer folding lines are arranged in a parallel orientation. (i) the embedded metal plate portion is The vertical portion is embedded in the case, The planar portion is disposed in the hollow portion of the case, The solder terminals are disposed on the bottom surface of the case. (j) the flat surface of the embedded metal plate portion of the fixed contact is The fixed contacts are disposed between the internal bending lines disposed at opposing positions on both sides. (k) the fixed contact metal plate and the movable contact metal plate are the internal bending line of the embedded metal plate portion of the fixed contact; Four internal bending lines consisting of the internal bending lines of the buried metal plate portion of the movable contact, They are arranged at the four corners of the case. (l) the internal fold line is The case is inclined in a direction from the X-axis direction toward the center point of the bottom surface of the case, The pair of internal bending lines disposed on both sides of the fixed contact point are The intersection of the central perpendicular lines is displaced from the center of the fixed contact.

2. 2. The micro-breaker of claim 1, The four external bending lines provided on the fixed contact metal plate and the movable contact metal plate are inclined in a direction from the X-axis direction of the case toward the center point of the bottom surface of the case, The tip edge of the solder terminal is An SMD type microbreaker that is inclined in a direction from the X-axis direction of the case toward the center point of the bottom surface of the case.

3. 2. The micro-breaker of claim 1, the outer bending lines of the two solder terminals arranged at diagonal positions on the bottom surface of the case are parallel to each other; The SMD type micro breaker is configured such that the external bending lines of the two solder terminals arranged at both ends of the case in the X-axis direction intersect with each other.

4. 4. The micro-breaker according to claim 1, The solder terminals arranged on the bottom surface of the case have non-linear side edges.

5. 5. The micro-breaker of claim 4, The solder terminals arranged on the bottom surface of the case are bent in plan view.

6. 2. The micro-breaker of claim 1, The solder terminals disposed on the bottom surface of the case are embedded in the case with both side edges undercut.

Images