JP2009289507A - Load driving device and overheat protective structure for the load driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a load driving device capable of surely stopping the output of a driving current from a current control element when the current control element abnormally generates heat. <P>SOLUTION: A conductive piece 10 is series connected to a switching element 9 which is the current control element for supplying a driving current to a component 2 to be driven. The conductive piece 10 is joined with solder to a land of a printed wiring board 3, and a self-elastic part 10a of the conductive piece 10 energizes a solder joint part 10b to the land in the conductive piece 10 in a direction to separate from the land. When the switching element 9 abnormally generates heat, the solder that joins the solder joint part 10b and the land melts, and the self-elastic part 10a separates the solder joint part 10b from the land. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a load driving device for supplying a driving current to a load and an overheat protection structure of the load driving device.

  For example, the thing of patent document 1 is proposed as a load drive device which uses a solenoid as a load.

In the technique described in Patent Document 1, a power element that is a current control element that supplies a drive current to a solenoid based on a command from a CPU includes an overheat protection circuit that operates when the power element overheats. The overheat protection circuit operates when the power element is in an overheat state exceeding a predetermined set temperature due to the solenoid drive current output from the power element being increased than normal due to the failure of the solenoid. The output of the drive current from the power element is stopped.
JP-A-2005-236100

  However, in the technique described in Patent Document 1, when the overheat protection circuit is activated and the output of the drive current from the power element is stopped, the temperature of the power element is lowered with time. Thus, when the temperature of the power element becomes lower than the set temperature, the drive current output stop by the overheat protection circuit is released, and the output of the drive current from the power element is resumed. Therefore, when the solenoid fails, the power element repeatedly stops and restarts output of the drive current near the set temperature, so that the power element itself may fail and the overheat protection circuit may not operate. It is not preferable.

  The present invention has been made in view of the above-described problems. For example, when the current control element abnormally generates heat due to a load failure, the load drive can reliably stop the output of the drive current from the current control element. It is an object of the present invention to provide an overheat protection structure for a device and its load driving device.

  The invention according to claim 1 is a printed wiring board having a conductor pattern that connects a power source and a load, a current control element that is interposed in the conductor pattern and controls a drive current supplied from the power source to the load, and current control And an overheat protection means for stopping the output of the drive current from the current control element when the element abnormally generates heat, and a conductive piece arranged electrically in series with the current control element The solder is joined to the land with solder, and the overheat protection means is configured by energizing the solder joint portion of the conductive piece in a direction away from the land by the energizing means, and the current control element generates abnormal heat and the solder joining is performed. When the solder for joining the part and the land is melted, the solder joint is separated from the land by the urging force of the urging means, and the drive current from the current control element is It is characterized by being adapted to stop the force.

  The invention according to claim 18 is the one according to claim 1 as an overheat protection structure of the load driving device, wherein the power source and the load are connected to the current control element by the conductor pattern of the printed wiring board. In the overheat protection structure of the load drive device that is connected via the current control element and supplies the drive current to the load by the current control element, the conductive piece connected by solder to the land of the conductor pattern is electrically in series with the current control element. And the solder joint portion of the conductive piece with respect to the land is urged by the urging means in a direction away from the land, and the current control element abnormally generates heat to connect the solder joint portion and the land. When the solder to be joined melts, the urging force of the urging means separates the solder joint from the land and stops the output of the drive current from the current control element. It is characterized in that that is a cormorant.

  According to the present invention, when the current control element abnormally generates heat, the solder for joining the solder joint portion of the conductive piece and the land of the conductor pattern is melted, and the solder joint portion and the land are attached to the above-mentioned attachment. Since it is separated by the biasing means, the output of the drive current from the current control element can be stopped reliably.

  FIG. 1 is a cross-sectional view of an essential part showing a load driving device 1 as a more specific first embodiment of the present invention.

  A load driving device 1 shown in FIG. 1 drives a component 2 to be driven which is a load represented by, for example, a relay or a solenoid. The load driving device 1 includes a printed wiring board 3 on which a driving circuit for driving the component 2 to be driven is formed, and a case 4 that houses the printed wiring board 3. The case 4 includes a box-shaped case body 5 having one open side, and a substantially rectangular plate-like lid body 6 that closes the opening of the case body 5, and the lid body 6 is assembled to the case body 5. A case 4 having an internal space for accommodating the printed wiring board 3 is formed. The case body 5 and the lid body 6 are each formed with an insulator.

  The printed wiring board 3 is fastened and fixed with screws 7 as fastening members to spacers 5b serving as wiring board mounting portions protruding from the bottom wall 5a of the case body 5 to the lid body 6 side. In detail, the printed wiring board 3 is formed in a substantially rectangular shape in plan view, and a component surface 3a on which each component to be described later is mounted faces the lid 5 side, and is a predetermined distance from the bottom wall 5a of the case body 5. It is accommodated in the case main body 4 in a state of being spaced apart from each other. Although not shown, the case main body 5 has four spacers 5b, and the four corners of the printed wiring board 3 are supported by the spacers 5b.

  The printed wiring board 3 includes a battery terminal 8 to which a battery (not shown) as a power source is connected, a switching element 9 as a current control element that controls a drive current supplied from the battery terminal 8 to the drive target component 2, The conductive piece 10 for stopping the output of the drive current from the switching element 9 when the switching element 9 abnormally generates heat is mounted, and the drive target component 2 also mounted on the printed wiring board 3 A drive circuit for driving the drive target component 2 is configured by connecting the battery terminal 8 in series via the switching element 9 and the conductive piece 10. The drive target component 2 does not need to be mounted on the printed wiring board 3 as in the present embodiment. For example, the drive target component 2 is outside the case 4 like a solenoid of a hydraulic control system in an electronically controlled power steering device for automobiles. It is good also considering what is arrange | positioned as drive object components.

  The switching element 9 is composed of, for example, a transistor, and performs a switching operation based on a command from a CPU (not shown), and outputs a drive current to the drive target component 2. In addition, the switching element 9 includes an overheat protection circuit 9a that operates by detecting when the temperature of the switching element 9 reaches a predetermined set temperature. The output of the driving current from the switching element 9 is stopped by the operation of the circuit 9a.

  2 is an enlarged view of a portion A in FIG. 1, and FIG. 3 is a plan view showing a main part of the printed wiring board 3 in FIG. In FIG. 3, the battery terminal 8 and the drive target component 2 are omitted for convenience.

  As shown in FIGS. 2 and 3 in addition to FIG. 1, the printed wiring board 3 is configured with a substrate 11 made of an insulator as a base, and a conductor pattern made of a conductive material formed on the substrate 11 by etching treatment. 12, the battery terminal 8, the conductive piece 10, the switching element 9, and the drive target component 2 are connected to each other in series. Further, a solder resist 15 made of an insulator is printed on the printed wiring board 3 in a region indicated by diagonal lines in FIG. 3 so as to cover the conductor pattern 12.

  Between the switching element 9 and the battery terminal 8 in the conductor pattern 12, a pair of lands 13 and 14 exposed to the component surface 3 a are formed by the resist openings 15 a and 15 b of the solder resist 15. A portion of the conductor pattern 12 between the lands 13 and 14 is divided by an insertion hole 3b having a substantially rectangular shape in plan view formed through the printed wiring board 3 so that the lands 13 and 14 have the conductive piece 10. Electrically connected.

  FIG. 4 is a side view showing the conductive piece 10 alone, and FIG. 5 is an explanatory view of a method for forming the conductive piece 10.

  As shown in FIG. 4, the conductive piece 10 extends in a direction away from each other from both ends of the self-elastic portion 10 a that is a protruding portion that bulges or bends in a substantially U shape when viewed from the side. Solder joints 10b and 10c. Further, as shown in FIG. 5, this conductive piece 10 is a flat plate-like workpiece by a mold 16 comprising upper and lower molds 17 and 18 each having a molding surface 17a and 18a having a shape corresponding to the self-elastic portion 10a. The copper plate 19 is formed by pressing. In the self-elastic portion 10a, the protruding amount L1 in the free state is set larger than the distance L2 (see FIG. 1) from the component surface 3a of the printed wiring board 3 to the bottom wall 5a of the case body 5.

  As shown in FIGS. 1 to 3, both solder joint portions 10b and 10c are joined to both lands 13 and 14 of the conductor pattern 12 with solder 20 respectively, and the self-elastic portion 10a is printed from the component surface 3a side. The wiring board 3 is inserted through the insertion hole 3 b and elastically deformed in the protruding direction by contact with the bottom wall 5 a of the case body 5. In other words, both the solder joint portions 10b and 10c are urged in a direction away from both the lands 13 and 14 by the restoring force accompanying the elastic deformation of the self-elastic portion 10a. That is, when the switching element 9 abnormally generates heat and the solder 20 joining the solder joint 10b on the switching element 9 side and the land 13 melts, the solder joint 10b and the land 13 are urged by the urging force of the self-elastic part 10a. And the output of the drive current from the switching element 9 is stopped. The melting temperature of the solder 20 is set higher than the set temperature of the overheat protection circuit 9a of the switching element 9.

  On the other hand, the opening areas of the resist openings 15a and 15b are set slightly smaller than the surface areas of the lands 13 and 14. As a result, of the outer peripheral edge portions of the four sides of the lands 13 and 14, the overlapping portions 13 a and 14 a covered with the solder resist 15 are formed on the three sides excluding the side on the insertion hole 3 b side, that is, the side covered with the conductive piece 10. Is formed. Thus, by forming the overlapping portions 13a and 14a at the peripheral edge portions of the lands 13 and 14, respectively, the separation strength of the lands 13 and 14 from the substrate 11 is improved, and the urging force of the self-elastic portion 10a is increased. I try to compete.

  On the other hand, a cover piece 6a having a substantially U-shape in plan view covering the solder joint portion 10b is directed to the printed wiring board 3 side at a position facing the solder joint portion 10b on the switching element 9 side in the lid body 6 of the case 4. Projecting. 3, this cover piece 6a is open to the insertion hole 3b side, that is, the anti-switching element 9 side in a plan view, as indicated by a virtual line in FIG. 3. With this cover piece 6a, the solder joint portion 10b is separated from the land 12. The scattering of the solder 20 during the operation is prevented without hindering the separating operation. The cover piece 6a has a tip abutting against the overlapping portion 13a, supports the printed wiring board 3 against the urging force of the self-elastic portion 10b, and supports the bending of the printed wiring board 3. In addition to functioning as a means, the land 13 is pressed against the substrate 11 and functions to further improve the separation strength of the land 13 from the substrate 11. Needless to say, the self-elastic portion 10b of the conductive piece 10 can effectively exert its urging force by suppressing the bending of the printed wiring board 3 as described above with the cover piece 6a.

  Further, slits 3c and 3d along the longitudinal direction of the conductor pattern 12 are formed on both sides in the width direction of the region where the conductive piece 10 and the switching element 9 are connected with the conductor pattern 12 in the printed wiring board 3, respectively. Yes. Both the slits 3c and 3d communicate with the insertion hole 3b, and the insertion hole 3b functions as a heat insulating portion in addition to the both slits 3c and 3d, so that the heat generated by the switching element 9 is transferred to the switching element 9 side. It transmits efficiently to the solder joint 10b.

  FIG. 6 is an explanatory diagram for explaining a manufacturing process of the load driving device 1. FIG. 7 is an explanatory diagram for explaining a flow soldering process in the manufacturing process of the load driving device 1.

  In order to assemble the load driving device 1 configured as described above, as shown in FIG. 6A, first, the solder paste 21 is applied to both lands 13 and 14, respectively, and the load driving device 1 shown in FIG. As described above, the conductive piece 10 is mounted on the printed wiring board 3 and both solder joint portions 10b and 10c are pressed against the solder paste 21 on both lands 13 and 14, respectively. Thereafter, both solder joint portions 10b and 10c of the conductive piece 10 are soldered to both lands 13 and 14 by a reflow soldering process which is a solder paste melting step. The other components such as the battery terminal 8, the switching element 9, and the driving target component 2 are reflow soldering processing for mounting the conductive piece 10 on the printed wiring board 3, or a flow performed before and after this reflow soldering processing. It is soldered to the printed wiring board 3 by a soldering process.

  After each component is mounted on the printed wiring board 3 in this way, the printed wiring board 3 is inserted into the case body 5 and the self-elasticity of the conductive piece 10 as shown in FIGS. 6 (c) and 6 (b). The portion 10a is compressed and deformed, and the printed wiring board 3 is supported on the case body 5 with the spacers 5b and screws 7 not shown in this state. As a result, the self-elastic portion 10 a of the conductive piece 10 generates a biasing force that biases both the solder joint portions 10 b and 10 c of the conductive piece 10 in a direction away from the lands 13 and 14.

  When other parts are mounted by the flow soldering process after the conductive piece 10 is mounted on the printed wiring board 3, as shown in FIG. 7, the conductive piece 10 of the solder 24 jetted from the flow layer 23 is applied. In order to prevent adhesion of the conductive piece 10, the flow soldering process is performed in a state in which the conductive piece 10 is attached with the metal plate 22 having a relatively large heat capacity having the protrusion 22 a having a shape corresponding to the self-elastic portion 10 a of the conductive piece 10. Good.

  FIG. 8 is an explanatory diagram for explaining the operation of the present embodiment.

  In the load driving device 1 configured as described above, as shown in FIG. 8A, the resistance value of the driving target component 2 decreases due to the failure of the driving target component 2, and an overload current is generated in the switching element 9. When the switching element 9 flows abnormally and flows, first, the temperature of the switching element 9 exceeds the set temperature of the overheat protection circuit 9a, the overheat protection circuit 9a is activated, and the drive current from the switching element 9 to the drive target component 2 is activated. Output is stopped.

  When the overheat protection circuit 9a is activated and no current flows through the switching element 9, and the temperature of the switching element 9 decreases with time and becomes lower than the set temperature of the overheat protection circuit 9a, the overheat protection circuit 9a 9 is released, and output of drive current from the switching element 9 is resumed. As described above, when the output of the drive current from the switching element 9 is repeatedly stopped and restarted, if the switching element 9 itself fails due to a thermal failure and the overheat protection circuit 9a does not operate, the temperature of the switching element 9 Exceeds the set temperature of the overheat protection circuit 9a and further rises.

  On the other hand, since the heat generated by the switching element 9 is transmitted to the solder 20 that joins the solder joint portion 10b and the land portion 13 on the switching element 9 side of the conductive piece 10, the temperature of the switching element 9 is as described above. When the temperature further exceeds the set temperature of the overheat protection circuit 9a, the solder 20 that joins the solder joint portion 10b and the land portion 13 on the switching element 9 side reaches the melting temperature and melts. When the solder 20 is thus melted, the solder joint 10b on the switching element 9 side is separated from the land 13 by the urging force of the self-elastic portion 10a as shown in FIG. The drive current output is cut off.

  Therefore, according to the present embodiment, the solder joint portion 10b on the switching element 9 side and the land 13 are joined by the solder 20, and the solder joint portion 10b on the switching element 9 side is separated from the land 13 by the self-elastic portion 10a. Therefore, when the switching element 9 abnormally generates heat, the solder 20 melts and the solder joint portion 10b is separated from the land 13, and the drive current output from the switching element 9 is output. It can be stopped reliably.

  Further, since the conductive piece 10 is disposed between the switching element 9 and the battery terminal 8, the printed wiring is formed in a state where the switching element 9 abnormally generates heat and the solder joint portion 10 b of the conductive piece 10 is separated from the land 13. The range to which the power supply voltage of the plate 3 is applied can be narrowed, and the safety of the load driving circuit 1 can be further improved.

  Further, since the self-elastic portion 10a of the conductive piece 10 generates a biasing force only when the printed wiring board 3 is accommodated in the case 4, the mounting of the conductive piece 10 on the printed wiring board 3 is not possible. It can be done easily.

  In addition, since the cover piece 6a that covers the solder joint portion 10b is formed integrally with the lid 6 of the case 4, the lid 6 of the case 4 is closed after the conductive piece 10 is mounted on the printed wiring board 3. Before, the visual confirmation of the joining state of the solder joint part 10b of the conductive piece 10 and the land 13 can be easily performed.

  Further, since the periphery of the switching element 9 is insulated by the insertion holes 3b in addition to the slits 3c and 3d and the heat transfer path generated by the switching element 9 is restricted, the anti-switching element is generated when the switching element 9 is abnormally heated. Without melting the solder 20 that joins the solder joint 10c on the 9 side to the land 14, the solder 20 that joins the solder joint 10b on the switching element 9 side to the land 13 is surely melted, and the conductive piece 10 is printed wiring. It is possible to prevent the occurrence of secondary problems caused by dropping from the plate 3.

  In the present embodiment, the solder joints 10b and 10c are soldered to the lands 13 and 14, respectively. However, the joint of the conductive piece 10 to the land 14 on the side opposite to the switching element 9 is, for example, resistance welding. The joining state may be maintained at a temperature higher than the melting temperature of the solder joining the solder joint portion 10b on the switching element 9 side and the land 13. In this case, when the switching element 9 is abnormally heated, the end of the conductive piece 10 on the side opposite to the switching element 9 can be reliably prevented from separating from the land 14, and the conductive piece 10 falls off the printed wiring board 3. Occurrence of secondary problems due to this can be prevented more reliably.

  9 and 10 show a second embodiment of the present invention. FIG. 9 is a plan view showing the main part of the printed wiring board 3, and FIG. 10 is a cross-sectional view taken along line BB in FIG. In FIG. 9, only one land 13 is shown as a representative example of the pair of lands 13, 14, but the other land 14 is configured similarly.

  In the second embodiment shown in FIG. 9, a via 25 penetrating the printed wiring board 3 is provided in the overlapping portion 13 a where the land 13 and the solder resist 15 are overlapped. A plurality of vias 25 are arranged along the longitudinal direction of the overlapping portion 13a.

  As shown in FIG. 10, each via 25 is a conductor layer 25 b formed by copper plating on the outer wall surface of the through hole 25 a penetrating the printed wiring board 3, and the conductor layer 25 b is connected to the land 13. The conductor pattern 12 on the side opposite to the component surface 3a is connected to each other. Moreover, solder is filled in the inner peripheral side of the conductor layer 25b in each via 25, and the fastening body 26 is formed with the solder. A pair of heads 26a and 26b are formed at both ends in the axial direction in the fastening body 26, and the substrate 11 and the land 13 and the conductor pattern 12 on the side opposite to the component surface 3a are sandwiched between the heads 26a and 26b. Yes. Other parts are the same as those in the first embodiment described above.

  Therefore, according to the second embodiment, in addition to the same effects as the first embodiment described above, by pressing the land 13 against the substrate 11 with the copper plating 25b and the fastening body 26 of each via 25, There is an advantage that the separation strength of the land 13 with respect to the substrate 11 can be further improved.

  FIG. 11 is a plan view showing a main part of the printed wiring board 3 as a modification of the above-described second embodiment. Note that, in FIG. 11, as a representative example, only the joint portion between the solder joint portion 10 b on the switching element 9 side and the land 13 is illustrated, but the joint portion between the solder joint portion 10 c on the anti-switching element 9 side and the land 14 is illustrated. Is similarly configured.

  In the modification shown in FIG. 11, the solder joint portion 10b of the conductive piece 10 is formed wider than the self-elastic portion 10a of the conductive piece 10, and other portions are the second embodiment described above. It is configured in the same way. Therefore, according to this modification, the same effects as those of the second embodiment described above can be obtained, and the bonding strength between the solder bonding portion 10b and the land 13 can be increased by increasing the bonding strength. There is a merit that can be done.

  FIG. 12 is a plan view showing a main part of the printed wiring board 3 as the third embodiment of the present invention.

  In the third embodiment shown in FIG. 12, the conductive piece 10 is mounted on the outer peripheral edge of the printed wiring board 3, and the insertion hole 3 b of the printed wiring board 3 extends to the side of the printed wiring board 3. It is open. Further, a slit 3 e is formed on one side of the printed wiring board 3 where the conductive pattern 10 is connected to the switching element 9 with the conductor pattern 12, that is, on the opposite outer peripheral side of the printed wiring board 3. Other parts are the same as those in the first embodiment described above.

  Therefore, in the third embodiment, since the outer peripheral edge of the printed wiring board 3 functions as a heat insulating portion, the switching element 9 is connected to the solder 20 that joins the solder joint portion 10b and the land 13 by a single slit 3e. The heat generated can be transmitted efficiently, and the substantially same effect as the first embodiment can be obtained.

  FIG. 13: is principal part sectional drawing which shows the load drive device 1 as the 4th Embodiment of this invention.

  In the fourth embodiment shown in FIG. 13, instead of the cover piece 6a in the first embodiment, a substantially columnar columnar projection 6b as a supporting means is projected from the lid 6 toward the printed wiring board 3 side. Is. The tip of the columnar protrusion 6b is brought into contact with the printed wiring board 3, so that the bending of the printed wiring board 3 is suppressed against the urging force of the self-elastic portion 10a.

  Therefore, according to the fourth embodiment, since the bending of the printed wiring board 3 can be suppressed by the support portion 6b having a simple shape, the solder 20 accompanying the separation of the solder joint portion 10b from the land 12 can be prevented. Although the effect of preventing scattering cannot be obtained, the other parts can obtain substantially the same effect as the first embodiment described above.

  FIG. 14 shows a modification of the above-described fourth embodiment, and is a cross-sectional view of a main part of the load driving device.

  In the modification shown in FIG. 14, instead of the support portion 6 b in the fourth embodiment, a spacer 5 c that supports a portion of the printed wiring board 3 that is close to the land 13 protrudes from the bottom wall 5 a of the case body 5. Is. The spacers 5c are provided separately from the spacers 5b (see FIG. 1) that support the four corners of the printed wiring board 3. Then, a portion of the printed wiring board 3 that is close to the land 13 is fastened to the spacer 5c by a screw 27 that is a fastening member, thereby suppressing the bending of the printed wiring board 3 against the urging force of the self-elastic portion 10a. It is like that. Other parts are the same as those in the fourth embodiment.

  Therefore, in this modified example, substantially the same effect as that of the above-described fourth embodiment can be obtained.

  FIG. 15 is a plan view showing an outline of the printed wiring board 3 as another modification of the above-described fourth embodiment. In FIG. 15, components other than the conductive piece 10 mounted on the printed wiring board 3 are omitted for convenience.

  In the modification shown in FIG. 15, the conductive piece 10 is arranged at a corner portion of the printed wiring board 3. As a result, the spacer 5b (see FIG. 1) that fastens and supports the corner portion of the printed wiring board 3 together with the screw 7 functions as a support means that suppresses the bending of the printed wiring board 3 against the urging force of the self-elastic portion 10a. Will do. Other parts are the same as those in the fourth embodiment described above. Further, the solder joint portion 10b on the side of the switching element 9 is disposed at a position closest to the spacer 5b functioning as a support means as compared with other components not shown in the figure mounted on the printed wiring board 3.

  Therefore, according to this modification, it is possible to suppress the bending of the printed wiring board 3 without newly providing a support means. Therefore, in addition to substantially the same effect as the fourth embodiment, it is advantageous in terms of cost. There are benefits.

  FIG. 16 is a plan view showing a main part of the printed wiring board 3 as the fifth embodiment of the present invention. FIG. 17 is a perspective view showing a cover member 28 described later in FIG. 16 alone.

  In the fifth embodiment shown in FIGS. 16 and 17, instead of the cover piece 6a of the lid body 6 in the first embodiment, an independent cover member 28 separate from the lid body 6 is provided. . The cover member 28 includes a substantially U-shaped side wall portion 28a that opens to one side in a plan view, an upper wall portion 28b, and claw portions that are respectively formed at the lower ends of a pair of walls that face each other. 28c. Then, with the opening of the side wall portion 28a facing the insertion hole 3b, both the claw portions 28c are inserted into a pair of engagement holes (not shown) formed in the printed wiring board 3, and the claw portions 28c are printed. The cover member 28 is attached to the printed wiring board 3 by being engaged with the wiring board 3. As a result, the solder joint 10 b on the switching element 9 side is covered with the cover member 28. Other parts are the same as those in the first embodiment described above.

  Therefore, according to the present embodiment, the cover member 28 prevents the solder 20 from being scattered during the operation without inhibiting the operation of separating the solder joint portion 10b from the land 13. The substantially same effect as the embodiment can be obtained.

  FIG. 18 is a plan view showing an outline of a printed wiring board 3 as a sixth embodiment of the present invention.

  In the sixth embodiment shown in FIG. 18, a cover layer 29 made of an insulator is formed on the surface layer portion of the printed wiring board 3 in a region electrically on the side opposite to the switching element 9 from the conductive piece 10. is there. That is, the cover layer 29 prevents the conductor from being exposed to a region of the printed wiring board 3 that is electrically opposite the switching element 9 from the conductive piece 10. In other words, the solder 20 scattered due to the separation of the solder joint portion 10 b from the land 13 when the switching element 9 is abnormally heated by the cover layer 29 is more electrically than the conductive piece 10 in the printed wiring board 3. Further, it is possible to prevent the portion on the switching element 9 side and the portion on the side opposite to the switching element 9 electrically from the conductive piece 10 from being short-circuited. Other parts are the same as those in the first embodiment described above.

  Therefore, the present embodiment can provide substantially the same effect as that of the first embodiment.

  In the present embodiment, the cover layer 29 is formed on the surface layer portion of the printed wiring board 3 in the region on the side opposite to the switching element 9 electrically from the conductive piece 10. It goes without saying that the cover layer 29 may be formed in the surface layer portion of the region closer to the switching element 9 than the piece 10.

  FIG. 19 shows a seventh embodiment of the present invention and is a cross-sectional view of the main part of the printed wiring board 3.

  A conductive piece 30 according to the seventh embodiment shown in FIG. 19 includes a self-elastic portion 31 that is a substantially channel-shaped biasing means, and the self-elastic portion 31 from the tip of one side wall 31a. A solder joint 32 extending outward and a claw 33 extending from the tip of the other side wall 31b of the self-elastic part 31 to the outside of the self-elastic part 31 are provided.

  Then, the solder joint portion 32 is joined to the pair of lands 34 and 35 exposed on the component surface 3a side of the printed wiring board 3 by the solder 20, and the side wall 31b on the claw portion 33 side of the self-elastic portion 31 is printed wiring. The nail | claw part 33 is engaged with the land 36 exposed to the non-component surface 3a side of the printed wiring board 3 through the insertion hole 3b of the board 3. As a result, the land 36 and the lands 34 and 35 are electrically connected via the conductive piece 30. That is, both the solder-bonded lands 34 and 35 of the solder joint portion 32 are connected to the switching element 9 (not shown) via the conductor pattern 12 formed on the printed wiring board 3, while the claw portion 33 is engaged. The mating land 36 is connected to the battery terminal 8 (not shown) via the conductor pattern 12 formed on the printed wiring board 3, and the battery terminal 8 (not shown) and the switching element 9 are connected via the conductive piece 30. Has been.

  FIG. 20 is an explanatory diagram for explaining a procedure for mounting the conductive piece 30 on the printed wiring board 3.

  In order to mount the conductive piece 30 on the printed wiring board 3, first, as shown in FIG. 20, the solder joint portion 32 is solder-bonded to the lands 34, 35 on the component surface 3a side by reflow soldering processing. 19, the side wall 31 b on the claw 33 side is inserted into the insertion hole 3 b of the printed circuit board 3 while being elastically deformed so as to constrict the self-elastic part 31, and the claw 33 is connected to the opposite part of the printed circuit board 3. Engage with the land 36 on the surface 3a side. Thereby, the solder joint portion 32 is urged in the direction away from the lands 34 and 35 by the restoring force based on the elastic deformation of the self-elastic portion 31.

  FIG. 21 is an explanatory diagram for explaining the operation of the present embodiment.

  Therefore, also in the present embodiment, when an overload current flows through the switching element 9 (not shown), the switching element 9 abnormally generates heat, and the solder 20 joining the solder joint 32 and the lands 34 and 35 melts. As shown in FIG. 21, the solder joint portion 32 is separated from the lands 34 and 35 by the urging force of the self-elastic portion 31, and substantially the same effect as that of the first embodiment described above can be obtained.

1 is a main part sectional view showing a load driving device 1 as a first embodiment of the present invention. The enlarged view of the A section in FIG. The top view of the printed wiring board 3 in FIG. The side view which shows the electrically-conductive piece in FIG. 1 alone. Explanatory drawing of the shaping | molding method of the electrically-conductive piece shown in FIG. Explanatory drawing of the manufacturing process of the load drive device shown in FIG. Explanatory drawing of a flow soldering process process among the manufacturing processes of the load drive device shown in FIG. Action | operation explanatory drawing of 1st Embodiment. The top view which shows the principal part of a printed wiring board as the 2nd Embodiment of this invention. BB sectional drawing in FIG. The top view which shows the principal part of a printed wiring board as a modification of 2nd Embodiment. The top view which shows the principal part of a printed wiring board as the 3rd Embodiment of this invention. Sectional drawing which shows the principal part of a load drive device as the 4th Embodiment of this invention. Sectional drawing which shows the principal part of a load drive device as a modification of 4th Embodiment. The top view which shows the outline of a printed wiring board as another modification of 4th Embodiment. The top view which shows the principal part of a printed wiring board as the 5th Embodiment of this invention. The perspective view which shows the cover member in FIG. 16 alone. The top view which shows the outline of a printed wiring board as the 6th Embodiment of this invention. Sectional drawing which shows the principal part of a printed wiring board as the 7th Embodiment of this invention. Explanatory drawing for demonstrating the mounting procedure to the printed wiring board of the electroconductive piece shown in FIG. Explanatory drawing for demonstrating the effect | action of the 7th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Load drive device 2 ... Drive object component (load)
3 ... Printed wiring board 3b ... Insertion hole 3c ... Slit (heat insulation part)
3d ... Slit (heat insulation part)
3e ... Slit (heat insulation part)
4 ... Case 5b ... Spacer (wiring board mounting part)
5c ... Spacer (support means)
6a ... Cover piece (support means)
6b ... Columnar protrusion (supporting means)
9: Switching element (current control element)
9a ... Overheat protection circuit 10 ... Conductive piece 10a ... Self-elastic part (biasing means)
DESCRIPTION OF SYMBOLS 10b ... Solder junction 12 ... Conductor pattern 13 ... Land 15 ... Solder resist 20 ... Solder 25 ... Via 28 ... Cover member 29 ... Cover layer 30 ... Conductive piece 31 ... Self-elastic part (biasing means)
32 ... Solder joint 34 ... Land 35 ... Land 36 ... Land

Claims (18)

A printed wiring board having a conductor pattern for connecting a power source and a load;
A current control element that is interposed in the conductor pattern and controls the drive current supplied from the power source to the load;
Overheat protection means for stopping output of drive current from the current control element when the current control element abnormally generates heat;
In a load drive device comprising:
The conductive piece arranged in series with the current control element is joined to the land of the conductive pattern by soldering, and the solder joint portion of the conductive piece is energized in a direction away from the land by the energizing means. Protective measures are configured,
When the current control element abnormally generates heat and the solder joining the solder joint and the land melts, the solder joint is separated from the land by the biasing force of the biasing means, and the drive current from the current control element is reduced. A load driving device characterized in that output is stopped. While the printed wiring board is housed in the case,
The conductive piece is inserted through an insertion hole formed in the printed wiring board and comes into contact with the case, and has a self-elastic portion that compresses and deforms with the contact.
2. The self-elastic portion as a biasing means biases the solder joint portion in a direction away from the land by a restoring force accompanying elastic deformation of the self-elastic portion. The load driving device described.   The load driving device according to claim 2, wherein the solder joint portion is formed wider than the self-elastic portion.   The load driving apparatus according to claim 1, wherein a resist is applied to a specific area of the printed wiring board, and the outer peripheral edge of the land is covered with the resist.   The load driving device according to claim 1, wherein a via penetrating the printed wiring board is provided in an outer peripheral edge portion of the land.   The load driving device according to claim 5, wherein the via is filled with solder.   Both ends on the current control element side and the countercurrent control element side of the conductive piece are respectively joined to a pair of lands of the conductor pattern, and the junction part on the current control element side of both the junction parts to the land of the conductive piece The load driving device according to claim 1, wherein the load driving device is joined to the land as a solder joint.   Of the conductive pieces, the joint between the end on the side of the anti-solder joint and the land can be maintained at a temperature higher than the melting temperature of the solder joining the solder joint of the conductive piece and the land. The load driving device according to claim 7.   The load according to any one of claims 1 to 8, wherein a heat insulating portion is formed on both sides in a width direction of a region connecting the solder joint portion of the conductive piece and the current control element in the printed wiring board. Drive device.   The load driving device according to claim 1, further comprising a cover that covers the solder joint portion.   The load driving device according to claim 10, wherein the cover is provided integrally with a case that accommodates the printed wiring board.   Insulate at least one surface layer portion of the printed wiring board on the current control element side electrically from the conductive piece and the printed wiring board on the counter current control element side electrically than the conductive piece. The load driving device according to any one of claims 1 to 9, wherein a cover layer made of a body is formed.   The load driving device according to any one of claims 1 to 12, further comprising support means for supporting the printed wiring board against an urging force of the urging means.   The case that accommodates the printed wiring board has a wiring board mounting portion for fastening and fixing the printed wiring board, and the solder mounting portion is disposed at a position close to the wiring board mounting portion of the printed wiring board. The load drive device according to claim 13, wherein the wiring board mounting portion functions as the support means. The current control element has an overheat protection circuit that detects and operates when the temperature of the current control element reaches a predetermined set temperature and stops the output of the drive current from the current control element. ,
The load driving device according to any one of claims 1 to 14, wherein a melting temperature of solder for joining the solder joint and the land is set higher than a set temperature of the overheat protection circuit.   The load driving device according to claim 1, wherein the conductive piece is disposed between a current control element and a power source.   The load driving apparatus according to claim 1, wherein the conductive piece is formed of copper. In the overheat protection structure of the load driving device that connects the power source and the load via the current control element by the conductor pattern of the printed wiring board and supplies the driving current to the load by the current control element,
A direction in which the conductive piece connected to the land of the conductor pattern by solder is electrically arranged in series with the current control element, and the solder joint of the conductive piece to the land is separated from the land by the biasing means Being energized by
When the current control element abnormally generates heat and the solder joining the solder joint and the land melts, the solder joint is separated from the land by the biasing force of the biasing means, and the drive current from the current control element is reduced. An overheat protection structure for a load driving device, wherein output is stopped.

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