JP2007019065A - Printed circuit board unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed circuit board unit of which a power element is not rotated at the same time by preventing, at screwing, rotation when it is attached to a heatsink with a screw. <P>SOLUTION: When an IGBT17 is attached to a heatsink 30 using a screw 31, a step 33 provided to the heatsink is contacted to the upper end of the IGBT17, for use as a guide, or to function as a stopper for preventing rotation. So the IGBT17 is prevented from rotating when screwing, allowing inserting into a printed circuit board 38. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is an inverter-type microwave generator using a magnetron such as a microwave oven, and attaches heat generating parts such as IGBT which is a switching element constituting the main circuit of the inverter and a diode bridge which rectifies a power source to dissipate heat. The present invention relates to a printed circuit board unit having a heat radiating plate having a role of promoting.

  FIG. 2 is a control circuit diagram of a conventional inverter type microwave oven.

  In the figure, the alternating current from the commercial power source 11 is rectified to a direct current by the rectifying circuit element 13 and smoothed by the choke coil 14 and the smoothing capacitor 15 on the output side of the rectifying circuit element 13, and the resonant capacitor 16 and the IGBT 17 high voltage (step-up) transformer 18. That is, it is converted into a high voltage of a desired high frequency (20 to 40 kHz) by an inverter constituted by: The inverter is controlled by an IGBT (Insulated Gate Bipolar Transistor) that switches DC at high speed and an inverter control circuit 29 that drives and controls the IGBT, and the current flowing through the primary side of the step-up transformer 18 is switched on and off at high speed. The

  In the step-up transformer 18, a high frequency voltage is applied to the primary winding 181, and a high voltage corresponding to the winding ratio is obtained in the secondary winding 182. A winding 183 with a small number of turns is provided on the secondary side of the step-up transformer 18 and is used for heating the filament 121 of the magnetron 12. The secondary winding 182 of the step-up transformer 18 includes a voltage doubler full wave rectification circuit 19 that rectifies the output. The voltage doubler full wave rectifier circuit 19 includes two high voltage diodes 191 and 192 and high voltage capacitors 193 and 194.

  Further, the AC from the commercial power source 11 is rectified to DC by rectifier circuits (diodes) 201 and 202, dropped in voltage by a cement resistor 21, and connected in series by a voltage adjusting resistor 22, a smoothing capacitor 23, and a Zener diode 24, the inverter described above. A low voltage (power supply) circuit 25 of the control circuit 29 is configured.

  Further, the rectifier circuit 13 and the IGBT 17 require a heat sink because a large current flows when the microwave oven is operated, that is, when the inverter is operated. Therefore, a heat sink is required. As a mounting method, the rectifier circuit and the IGBT are mounted on one heat sink. There is a method of attaching (see, for example, Patent Document 1).

FIG. 3 shows a mounting state according to a conventional method, in which a heat sink 30 is attached with screws 31 to prevent temperature destruction due to overheating. In addition, silicon 32 is applied between the rectifier circuit element 13 and the IGBT 17 and the heat sink 30 in order to improve thermal conductivity.
JP-A 63-271881

However, in the conventional configuration, when the rectifier circuit 13 or the IGBT 17 is attached to the heat sink 30 with the screw 31, the IGBT 17 and the rectifier circuit element 13 are dragged and rotated as shown in FIG. Since the silicon 31 is applied, the rotation is further facilitated. As a subsequent work, it is inserted into a mounting hole on the printed circuit board 38 (the mounting hole 34 for the IGBT 17 and the mounting hole 35 for the rectifier circuit element 13) and soldered. Alternatively, there is a problem that the insertion work into the printed circuit board 38 is very difficult even if it is rotated a little and an attachment inclination occurs.

  Further, the mounting hole 35 of the rectifier circuit element 13 has a large hole diameter so that the inter-lead pitch between the lead terminals 39 is wide and the eyelet 36 can be attached, so that the inclination of the lead terminal 39 due to a slight rotation can be inserted without any problem. In particular, since the mounting holes 34 of the IGBT 17 have a narrow pitch between the leads of the lead terminals 37 and a small hole diameter, it is difficult to insert them. Further, since the length of the lead terminal 37 of the IGBT 17 itself is long, a slight rotation is not allowed when the IGBT 17 is attached, and the heat sink 30 is attached with a screw 31 of the IGBT 17 with considerable accuracy. As a countermeasure, there is a method of fixing with a screw when attaching with a screw, but there is a problem that man-hours are required and mass productivity is poor.

  The present invention solves the above-described conventional problems, and when the rectifier circuit element 13 or the IGBT 17 is attached to the heat sink 30 with the screw 31, the IGBT 17 and the rectifier circuit element 13 are rotated by being dragged by the tightening torque of the screw 31. In the subsequent insertion operation into the mounting hole on the printed circuit board 38, it is prevented that the insertion cannot be performed because the directions do not match. Further, the present invention provides a structure of a heat radiating plate that prevents the insertion work into the printed circuit board 38 from becoming very difficult even if a slight rotation, that is, a mounting inclination occurs.

  The present invention has been made to solve the above-described problems, and a power element that generates heat, a heat dissipation plate that can be attached to the power element and dissipates heat, and a print that solders the power element. The heat sink has a structure in which a step is provided along the upper end of the power element attachment, and rotation can be prevented when a structural screw is attached to which the power element is attached along the step.

  According to the printed circuit board unit of the present invention, when attaching a rectifier circuit element or IGBT, which is a power element that generates heat, to the heat sink with screws, the step provided on the heat sink is applied to the upper end of these power elements, that is, as a guide, or The structure is used as a stopper function to prevent rotation, and these heat generating power elements are also dragged and rotated by the torque of screw tightening, and the direction does not match in the subsequent insertion into the mounting hole on the printed circuit board. Therefore, it can be prevented that the insertion becomes impossible. In addition, it is possible to provide a structure of a heat sink that prevents the insertion work into the printed circuit board from becoming very difficult even if a slight rotation, that is, a mounting inclination occurs.

  1st invention has the power element which heat-generates, the heat sink to which the said power element is attached, and radiates the heat_generation | fever part, and the printed circuit board which solder mounts the said power element, The said heat sink Is a structure in which a step is provided along the upper end of the power element. The step provided on the heat radiating plate is attached to the upper end of the power element and used as a stopper function for preventing rotation.

  In the second invention, two or more heat generating power elements are attached to the heat sink, the sizes of the power elements are different, and the position of the step is the tallest, that is, the attachment of the large power element. The structure is adapted to the upper end.

In the third aspect of the present invention, two or more power elements that generate heat have a longer height of about 5 mm between the lead terminals, whereas a shorter length between the lead terminals is about 7.5 mm.

  According to a fourth aspect of the present invention, the lower power element is a diode bridge for full-wave rectification of the power source, and is soldered through a grommet attached to the printed circuit board in order to ensure high current performance and mounting strength. It is a thing.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 shows the mounting state of the printed circuit board according to the first embodiment, and FIG. 2 is a control circuit diagram of the inverter printed circuit board unit for microwave oven according to the present invention.

  In FIG. 2, the alternating current from the commercial power source 11 is rectified to a direct current by the rectifier circuit 13, smoothed by the choke coil 14 and the smoothing capacitor 15 on the output side of the rectifier circuit 13, and by the resonant capacitor 16 and the IGBT 17 high voltage (step-up) transformer 18. That is, it is converted into a high voltage of a desired high frequency (20 to 40 kHz) by the inverter configured. The inverter is controlled by an IGBT (Insulated Gate Bipolar Transistor) that switches DC at high speed and an inverter control circuit 29 that drives and controls the IGBT, and the current flowing through the primary side of the step-up transformer 18 is switched on and off at high speed. The

  In the step-up transformer 18, a high-frequency voltage that is the output of the inverter 16 is applied to the primary winding 181, and a high-voltage voltage corresponding to the winding ratio is obtained in the secondary winding 182. A winding 183 with a small number of turns is provided on the secondary side of the step-up transformer 18 and is used for heating the filament 121 of the magnetron 12. The secondary winding 182 of the step-up transformer 18 includes a voltage doubler full wave rectification circuit 19 that rectifies the output. The voltage doubler full-wave rectifier circuit 19 includes two high voltage diodes 191 and 192 and high voltage capacitors 193 and 194.

  Moreover, the alternating current from the commercial power supply 11 is rectified to direct current by rectifier circuits (diodes) 201, 202, and the voltage is dropped by two cement resistors 212, R213, and the voltage adjusting resistor 22, the smoothing capacitor 23, and the Zener diode connected in series. 24 constitutes the low voltage (power supply) circuit 25 of the inverter control circuit 29 described above.

  During microwave oscillation, a large current of about 14 A flows through the diode bridge 13 which is a rectifier circuit element, and the IGBT 17 switches a current of about 80 A at a peak and a voltage of about 600 V at a high speed, so these losses are large and quite large. As shown in FIG. 1, it is attached to the heat dissipation plate 30 with screws 31 to promote heat dissipation and prevent thermal destruction.

  Further, the heat radiating plate is provided with a step 33, and when the screw 31 is attached, the step is applied to the upper end of the IGBT 17, that is, used as a guide or as a stopper function for preventing rotation. Therefore, it is possible to prevent the IGBT 17 from being rotated by being dragged by the tightening torque of the screw 31 and being unable to be inserted because the direction does not match in the subsequent insertion operation into the mounting hole on the printed circuit board 38.

In addition, even if a slight rotation, that is, a mounting inclination occurs, it is possible to prevent the insertion operation to the printed circuit board 38 from becoming very difficult. Silicon 32 is often applied between the heat sink and the IGBT 17 or the diode bridge 13 in order to improve the heat conduction effect. However, when this silicon 32 is applied, it is easy to slip and rotate when screwed, but the step 33 is effective as a stopper. Therefore, even when the silicon 32 is applied, it is possible to realize an efficient screw tightening operation and an accurate attachment without problems.

  Further, even if the package (outer shape) dimensions of the IGBT 17 vary, there is no problem in that the screw mounting hole of the IGBT 17 has a hole diameter margin that can absorb the variation tolerance, so that it does not match the screw hole position of the heat sink.

  On the other hand, as a manufacturing method of the heat sink, in order to make it cheap and to realize mass production, the extrusion manufacturing method is general, that is, there is a restriction that all must be the same in the drawing direction. It is not tolerated with a straight line step only in the extruding direction, and if it is pulled out by extruding and then subjected to another processing, it seems to have hollowed out the shape to the extreme according to the external shape such as IGBT or diode bridge It can be easily processed, and it is easy to do as the work at the time of installation, and the accuracy of the installation is also good.

  Further, since the IGBT 17 is tall and the diode bridge 13 is short compared to the diode bridge 13, it is not possible to provide the step as a stopper with the step and the diode bridge 13 alone. That is, both stoppers or guides can be provided. However, when post-processing is performed, the cost cannot be reduced, and mass productivity is deteriorated. This disadvantage becomes a major obstacle in the larger purpose of realizing microwave heating by an inverter system that can realize energy saving and high efficiency as a microwave oven.

  In the above description, since the IGBT 17 is tall and the diode bridge 13 is short compared to the above, it has been stated that the step can be provided as a stopper and the step can be provided only by the IGBT 17, but the diode bridge 13 cannot be formed. It is possible to provide a step along the upper end of the diode bridge 13 by processing. At this time, the workability and accuracy of mounting the diode bridge 13 are improved, but conversely, a step is formed across the body of the IGBT 17 and the step of the IGBT 17 is performed. The heat dissipation performance is greatly impaired, so that a step is provided only at the upper end of the IGBT 17, which is a tall component. Instead, the diode bridge 13 and the heat dissipation plate when viewed in FIG. Align the left end of 30 and tighten the screws It is a consideration, such as to facilitate providing a stopper on the outside.

  Further, the pitch between the lead terminals 39 of the diode bridge 13 is generally larger than that of the lead terminal 37 of the IGBT 17 due to the restriction that the pitch between the lead terminals 39 is electrically connected to the commercial power source and the insulation distance must be increased and the current is large. It is a value. In other words, the pitch between the lead terminals is often such that an eyelet 36 can be used to achieve a highly reliable structure in terms of strength, current resistance and temperature resistance. Also in this embodiment, the eyelet 36 is mounted on the printed circuit board 38 to have a highly reliable structure in terms of strength, current resistance, and temperature resistance. Incidentally, the pitch between the lead terminals of the IGBT is 5 mm and that of the diode bridge is 7.5 mm.

  Therefore, the mounting hole diameter 35 of the diode bridge 13 is considerably larger than the hole diameter 34 of the IGBT 17, and the length of the lead terminal 19 of the diode bridge 13 is shorter than the lead terminal 37 of the IGBT 17, so that the diode bridge 13 is slightly dissipated. When tightening the screws to the plate 30 Even if the screws are slightly rotated, that is, tilted, the mounting workability to the printed circuit board 38 will not be hindered. That is, if there is a step as a stopper for restraining at the upper end of the IGBT 17 which is a taller power element, the effect can be sufficiently exerted.

As described above, according to the present invention, when a rectifier circuit element or IGBT, which is a power element that generates heat, is attached to a heat sink with a screw, the step provided on the heat sink is applied to the upper end of these power elements, that is, as a guide or rotated. The structure is used as a stopper function for prevention, and these heat generating power elements are also dragged and rotated due to the tightening torque of the screw, and the direction does not match in the subsequent insertion into the mounting hole on the printed circuit board. It is possible to prevent a situation in which the insertion becomes impossible. In addition, it is possible to provide a structure of a heat sink that prevents the insertion work into the printed circuit board from becoming very difficult even if a slight rotation, that is, a mounting inclination occurs.

  Even if silicon for improving the heat dissipation effect is applied between the heat sink and the IGBT or diode bridge, efficient screw tightening work and accurate mounting can be realized without any problem.

  Since the heat sink uses only the extrusion method, which is a general method, except for drilling and cutting, it can be made inexpensive and mass production can be realized.

  In addition, even in the case of mounting a combination of a tall IGBT and a short diode bridge, the mounting of the diode bridge to the printed circuit board will not interfere with workability by using a configuration that uses eyelets. It goes without saying that it has a highly reliable structure in terms of strength, current resistance, and temperature resistance, that is, with a stopper for suppressing one line at the upper end of the IGBT, which is the taller power element. If there is a certain step, work improvement can be realized.

  As described above, according to the printed circuit board according to the present invention, it is possible to prevent rotation of components to be mounted using the steps of the heat sink, and it can be applied to prevent rotation when various components are mounted.

The mounting block diagram of the printed circuit board unit of Embodiment 1 of this invention Control circuit diagram of inverter according to embodiment 1 of the present invention Mounting diagram of conventional printed circuit board unit Conventional PCB mounting diagram

Explanation of symbols

13 Diode bridge (power element)
17 IGBT (Power element)
29 Inverter control circuit 30 Heat sink 33 Level difference 36 Eyelet 38 Printed circuit board

Claims (4)

A power element that generates heat; a heat sink that can be attached to the power element to dissipate heat; and a printed circuit board to which the power element is attached by soldering. A printed circuit board unit that has a structure along which a step is provided. Two or more power elements that generate heat are attached to the heat radiating plate, the sizes of the power elements are different, and the position of the step is aligned with the upper end of the tallest power element, that is, the large power element. The printed circuit board unit according to claim 1, wherein the printed circuit board unit is structured. The printed circuit board unit according to claim 1 or 2, wherein the two or more heat generating power elements have a longer height of about 5 mm between the lead terminals, whereas the shorter length of the power terminals is about 7.5 mm. 4. The lower power element is a diode bridge for full-wave rectification of a power supply, and is configured to be soldered through eyelets attached on the printed circuit board in order to secure a large current performance and mounting strength. The printed circuit board unit according to any one of the above.