JP4017120B2 - Thermistor mounting structure - Google Patents

Description

  The present invention relates to a mounting structure for a power thermistor (hereinafter referred to as a thermistor) mounted on a printed circuit board on which electronic components are mounted, and more particularly to a mounting structure for reducing the height.

  For example, the thermistor used to prevent the inrush current of the switching power supply is a heat-generating component, so when it is mounted on a printed circuit board and operated, the heat of the thermistor is transferred to the printed circuit board, and the printed circuit board itself is deteriorated or mounted on the printed circuit board. Therefore, it is necessary to suppress the temperature rise of the printed circuit board due to the heat of the thermistor.

  In Patent Document 1, in a mounting structure such as a resistor that generates a large amount of heat, a pair of lead terminals of the resistor is connected to a vertical metal plate that is mounted on a printed circuit board, and the metal plate has an opening for heat dissipation. Are provided.

  Further, in Patent Document 2, as a structure for attaching a thermistor to a printed circuit board, a lead terminal of the thermistor is soldered to the printed circuit board, a portion of the lead terminal in the vicinity of the thermistor body is folded back, and the thermistor body faces downward. The thing which aimed at the suppression and the low profile of the heat transfer to is disclosed.

  Further, in Patent Document 3, in a switching power supply, a heat sink made of a metal plate is mounted on a printed circuit board in the vicinity of an attachment section of the thermistor to the printed circuit board, and is thermally coupled to the mounting section. A device in which a thermistor is prevented from falling is disclosed.

Japanese Utility Model Publication No. 6-11376 JP 10-335112 A JP 2002-142457 A

  Electronic devices such as switching power supplies tend to be thinner, and in order to reduce the thickness, it is necessary to mount electronic components mounted on a printed circuit board with a low profile. However, as described in Patent Document 1, when a vertically long metal plate having a heat radiation opening is used, there is a problem that it is difficult to reduce the height.

  Also, as described in Patent Document 2, in the structure in which the lead terminal is folded and the lead terminal is directly soldered to the printed circuit board so that the thermistor body faces downward, the thermistor body is vertically oriented and has a low profile. In addition, it is difficult to achieve a sufficiently low profile due to the presence of the folded portion of the lead terminal. Also, when an external force is applied to this thermistor, the thermistor body comes into contact with the printed circuit board or other electronic components because the lead terminal is bent, etc., and the heat of the thermistor body is transferred to the printed circuit board or other electronic components. There exists a problem that there exists a possibility that a board | substrate may become high temperature or degrade other electronic components.

  In addition, as described in Patent Document 3, a thermistor lead terminal is soldered to a printed circuit board, and a heat radiator that is thermally coupled to a metal plate is provided in the vicinity of the soldered portion. Although it is good in terms of heat dissipation of the printed circuit board, there is a problem that it is difficult to reduce the height and the structure is complicated.

  In view of the above problems, the present invention provides a thermistor mounting structure that can reduce the height of the thermistor when mounting and can prevent an excessive temperature rise of the printed circuit board due to contact between the thermistor and the printed circuit board. Objective.

The mounting structure of the thermistor according to claim 1 is a structure in which the thermistor is attached to the printed circuit board on which the electronic component is mounted via two metal plates that also serve as a conductive means .
The thermistor has two lead terminals that form a linear shape extending in the same direction from the outer surface of the thermistor body in a direction perpendicular to the thickness direction of the thermistor body and the thermistor body has a flat shape, A bent portion that is bent toward the other side at the ends of the two lead terminals;
Each of the metal plates has a flat plate shape as a whole, and is fixed to the printed circuit board so that the plate surfaces of the two metal plates face each other,
Each of the metal plates is extended so that a gap is formed between a fixed foot soldered to the printed circuit board and an intermediate portion of the fixed foot in parallel to the printed circuit board and the printed circuit board. A thermistor mounting portion formed by extending from the top of the fixed foot in a direction opposite to the stopper portion at a position higher than the stopper portion, and a mounting hole for a lead terminal provided in the thermistor mounting portion And
By inserting and fixing the respective bent portions at the tips of the two lead terminals into the mounting holes of the thermistor mounting portions of the corresponding metal plates, the side surfaces of the thermistor mounting portions of the metal plates and the The thermistor body is positioned in a non-contact state on the stopper portion at the same time as being separated from a portion other than the tip portion of the lead terminal, and the thermistor is flattened by soldering the fixed foot to the printed circuit board. Is attached in a direction substantially parallel to the printed circuit board.

The attachment structure of the thermistor according to claim 2 is characterized in that, in claim 1, the formation portion of the stopper portion in the fixed foot of each metal plate is bent so as to protrude in the extending direction of the stopper portion. And

The mounting structure of the thermistor according to claim 3 is the same as in claim 1 or 2, wherein the lengths of the two lead terminals are different, and the bent portions of the lead terminals are fixed to the corresponding thermistor mounting portions at positions where they do not face each other. It is characterized by that.

The thermistor mounting structure of claim 4 is any one of claims 1 to 3, wherein each metal plate has two fixed legs,
The thermistor mounting part is configured as a bridging part between two fixed legs.

According to the invention of claim 1, the thermistor body is flattened, the flat surface is substantially parallel to the printed circuit board, and the thermistor body is positioned on the stopper portion formed lower than the thermistor mounting portion of the metal plate. Therefore, it becomes possible to reduce the height.

In addition , since the stopper provided on the metal plate is interposed between the thermistor body and the printed circuit board, it is possible to reliably prevent the thermistor body from coming into contact with the printed circuit board due to external force even though the height is reduced. At the same time, the wire lead terminal is not in contact with the metal plate between the thermistor body and the connection part of the thermistor mounting part, and the thermistor body is also in contact with the stopper part. In addition, a long heat transfer path of lead terminal-thermistor mounting part-fixed foot is formed, and furthermore, the heat dissipation effect is exerted by the stopper part extended in the opposite direction to the thermistor mounting part. Can be prevented from rising excessively.

According to the second aspect of the present invention, since the formation portion of the stopper portion in the fixed foot of each metal plate is bent so as to protrude in the extending direction of the stopper portion, the transmission from the lead terminal to the printed circuit board is performed. The heat path becomes longer and the temperature rise of the printed circuit board is suppressed.

According to the invention of claim 3, since the lengths of the two lead terminals are different and the bent portions of the lead terminals are fixed to the corresponding thermistor mounting portions at positions where they do not face each other, the metal plates are close to each other. It can arrange | position and an installation space can be narrowed.

According to invention of Claim 4 , since each metal plate has two fixed legs, it can attach to a printed circuit board with the stable attitude | position.

  FIG. 1 is a circuit diagram showing an example of a switching power supply having a thermistor to which the mounting structure of the present invention is applied. In the circuit of FIG. 1, 21 is an AC power supply, 22 is a rectifier circuit, 1 is a thermistor for preventing inrush current, 24 is a transformer that is turned on / off by a switching element 25, 26 is a primary side smoothing capacitor, and 27 and 28 are secondary sides. A rectifying diode 29 is a choke coil provided on the secondary side, and 30 is a secondary side smoothing capacitor. The output voltage on the secondary side is detected by the voltage detection unit 31, and the detection signal is sent to the control unit 33 via the photocoupler 32, and the control unit 33 controls the switching element 25 so that the output voltage becomes constant. .

  In the switching power supply, since a capacitor 26 having a large capacity is installed in the rectifying / smoothing circuit, a large inrush current flows when the power is turned on. When this inrush current becomes excessive, it propagates as noise to peripheral devices and the like, so it is necessary to prevent the inrush current from becoming excessive, and the NTC thermistor 1 is used as a simple means. That is, when the thermistor 1 is at room temperature when the power is turned off, it has a relatively high resistance value. When the power is turned on in this state, the inrush current is suppressed. When the power supply is turned on and in a steady state, the temperature of the thermistor 1 is maintained at a high temperature, for example, exceeding 120 ° C. due to energization, the resistance value of the thermistor 1 decreases, and the power supply operates in a state where the loss caused by the thermistor 1 is reduced. . For this reason, the thermistor 1 is kept at a high temperature while the device is operating.

  2 is a side view showing an example of a metal plate used in the mounting structure of the present invention, FIG. 3 is a side view showing an example of the thermistor, and FIG. 4 is a plan view thereof. 5 is a perspective view showing an embodiment of a thermistor mounting structure according to the present invention, FIG. 6 is a side sectional view thereof, and FIG. 7 is a plan view thereof.

2 to 7, reference numeral 2 denotes a printed board, and 3 denotes a metal plate that also serves as a conductive means for attaching the thermistor 1 to the printed board 2. The metal plate 3 has two linear lead terminals 5 provided so as to extend from the thermistor body 4 having a flat shape in a direction perpendicular to the thickness direction and from the outer surface of the thermistor body in parallel to the same direction. , 6 are provided corresponding to 6 respectively.

Each metal plate 3 is made into a flat plate shape by punching, and the same shape is used for the two metal plates 3 for one thermistor in order to facilitate manufacture. Each metal plate 3 is fixed to the mounting portion 7 of the lead terminals 5 and 6, the fixing legs 9 and 10 to the land 8 of the printed circuit board 2, and the mounting portion 7 of the lead terminals 5 and 6 to the land 8. It has a stopper portion 11 provided between the foot 9. As this metal plate 3, copper, iron, other metals, or alloys thereof can be used, but in this embodiment, iron is tin-plated in consideration of cost reduction and rigidity. Was used.

In the present embodiment, as described above, each metal plate 3 has the two fixed feet 9 and 10 and is horizontally attached between the tops of these fixed feet 9 and 10 (that is, attached to the printed circuit board 2). The bridge portion formed so as to be parallel to the printed circuit board 2 forms the mounting portion 7 of the lead terminals 5 and 6. The stopper portion 11 is formed to extend horizontally from the middle portion of one fixed foot 9 in the opposite direction to the other fixed foot 10. As shown in FIG. 2, there is a height difference ΔH between the upper side of the mounting portion 7 of the lead terminal of the metal plate 3 and the upper side of the stopper portion 11.

Moreover, in this Embodiment, the formation part of the stopper part 11 in the said fixed leg 9 of each metal plate 3 is bent so that it may protrude in the extension direction of the stopper part 11, and, thereby, it fixes to the attachment part 7 only set the lacking part 12 from the inside to the inner corner of the corner portion between the legs 9, configured to heat transfer path from the lead terminals 9 and 10 on the printed circuit board 2 becomes long, the temperature of the printed circuit board 2 The rise is suppressed.

The thermistor 1 of the present embodiment has a structure in which the main body 4 has a flat shape, and the lead terminals 5 and 6 extend in the same direction from both sides of the main body 4 as shown in FIG. . The lead terminals 5 and 6 have bent portions 5a and 6a that are horizontally bent at right angles so as to face each other , and the mounting portion 7 of the metal plate 3 has the bent portions 5a and 6a. Has a mounting hole 13 for inserting and temporarily fixing. The height difference ΔH (see FIG. 2) between the upper side of the mounting portion 7 and the upper side of the stopper portion 11 is preferably set larger than the thickness t (see FIG. 3) of the thermistor body 4.

As shown in FIG. 6, the thermistor 1 is attached by fixing two fixing legs 9 and 10 to the land 8 of the printed circuit board 2 with solder 14 . Thereby, it fixes to the printed circuit board 2 so that the plate | board surface of the two metal plates 3 and 3 may mutually face. The bent portions 5 a and 6 a of the lead terminals are fitted into the mounting holes 13 of these metal plates 3, temporarily fixed laterally, and finally fixed with solder 14. At the time of this soldering, as shown in FIG. 6, the thermistor body 4 is attached to the stopper portion 11 with a gap G in a non-contact manner. In addition, the stopper portion 11 is in a state of floating from the printed board 2. As shown in FIG. 7, a gap g is formed between the lead terminals 5 and 6 and the side surface of the metal plate 3.

  In this way, the thermistor 1 is mounted using the metal plate 3 for mounting the thermistor so as to be in a direction substantially parallel to the printed circuit board 2, so that the height can be reduced. In particular, in the present embodiment, the thermistor body 4 has a flat shape, and the flat surface is attached so as to be substantially parallel to the printed circuit board 2, which is more effective in reducing the height.

  Further, since the stopper portion 11 is provided on the metal plate 3 and the stopper portion 11 is interposed between the thermistor body 4 and the printed board 2, the thermistor body 4 contacts the printed board 2 even when an external force is applied to the thermistor 1. This prevents the temperature of the printed circuit board 2 from rising. Accordingly, it is possible to reliably prevent the thermistor body 4 from coming into contact with the printed circuit board 2 at the same time as reducing the height, preventing deterioration due to excessive rise in the temperature of the printed circuit board 2 and deterioration of other mounted electronic components. A highly thermistor mounting structure is realized.

  Further, according to the present embodiment, even when the thermistor body 4 approaches or comes into contact with the stopper portion 11 and the temperature of the stopper portion 11 rises, the stopper portion 11 is substantially parallel to the printed circuit board 2. Since the fixed foot 9 is separated from the stopper portion 11, the transfer of heat from the stopper portion 11 to the printed circuit board 2 is reduced, and the temperature of the printed circuit board 2 is excessively increased. A rise is avoided.

  Further, according to the present embodiment, the heat transfer path of the thermistor body 4 has a path constituted by the lead terminals 5 and 6 and the horizontal mounting portion 7, and a direction substantially perpendicular to the printed circuit board 2. The heat transfer path (heat transfer resistance) of a predetermined length is formed in total, and a temperature gradient is created by this long path, and a predetermined temperature as an NTC thermistor is formed. Can be maintained (that is, the resistance value of the thermistor is kept low), and heat transfer to the printed circuit board 2 can be prevented from being excessively performed to prevent an excessive temperature rise of the printed circuit board 2.

  Moreover, according to this Embodiment, since the metal plate 3 has the two fixed legs 9 and 10, it can attach to the printed circuit board 2 with the stable attitude | position.

  In addition, according to the present embodiment, the height difference ΔH between the mounting portion 7 and the stopper portion 11 is set to be larger than the thickness t of the thermistor body 4. A gap G (see FIG. 6) can be formed between the thermistor body 4 and the stopper portion 11 in a state where the height is equal to the height of the upper surface of the mounting portion 7, that is, in a state where the height is reduced.

  FIG. 8 shows another embodiment of the present invention, in which the metal plate 3A is provided with only one fixed foot 9 and the other fixed foot 10 is eliminated. With this configuration, the effect of preventing the temperature rise of the printed circuit board 2 can be obtained by reducing the height and preventing the contact of the thermistor body 4 with the printed circuit board 2.

FIG. 9 is a side view showing another example of the metal plate 3B according to the present invention, and FIG. 10 is a plan view showing another embodiment of a thermistor mounting structure using the metal plate 3B. In the present embodiment, the mounting portion 7 of the metal plate 3B is provided with two mounting holes 13a and 13b with a distance L in the lateral direction, and the bent portions 5a and 6a of the lead terminals 5 and 6 are also provided with the distance. The lengths of the bent portions 5a and 6a are set so as not to oppose each other. The bent portion 5a of one lead terminal 5 is inserted into one mounting hole 13a of the metal plate 3B and fixed with solder 14, and the bent portion 6a of the other lead terminal 6 is inserted into the other mounting hole 13b. And fixed with solder 14. According to this embodiment, even if the metal plates 3B are arranged close to each other, it is possible to prevent the bent ends 5a and 6a of the lead terminals 5 and 6 from coming into contact with each other and causing a short circuit.

  The present invention can also be applied to a PTC thermistor mounting structure.

It is a circuit diagram which shows an example of the switching power supply to which the attachment structure of the thermistor by this invention is applied. It is a side view which shows an example of the metal plate used for the attachment structure of this Embodiment. It is a side view which shows an example of the thermistor used for the attachment structure of this Embodiment. FIG. 4 is a plan view of FIG. 3. It is a perspective view which shows one Embodiment of the attachment structure of the thermistor by this invention. It is side surface sectional drawing of this Embodiment. It is a top view of this Embodiment. It is a perspective view which shows other embodiment of the attachment structure of the thermistor by this invention. It is a side view which shows the other example of the metal plate by this invention. FIG. 10 is a plan view showing another embodiment of the thermistor mounting structure using the metal plate of FIG. 9 according to the present invention.

Explanation of symbols

1: thermistor, 2: printed circuit board, 3, 3A, 3B: metal plate, 4: thermistor body, 5, 6: lead terminal, 5a, 6a: bent portion, 7: mounting portion, 8: land, 9, 10 : Fixed foot, 11: stopper portion, 12: notched portion, 13, 13a, 13b: mounting hole, 14: solder

Claims (4)

A thermistor is attached to a printed circuit board on which electronic components are mounted via two metal plates that also serve as conductive means ,
The thermistor has two lead terminals that form a linear shape extending in the same direction from the outer surface of the thermistor body in a direction perpendicular to the thickness direction of the thermistor body and the thermistor body has a flat shape, A bent portion that is bent toward the other side at the ends of the two lead terminals;
Each of the metal plates has a flat plate shape as a whole, and is fixed to the printed circuit board so that the plate surfaces of the two metal plates face each other,
Each of the metal plates is extended so that a gap is formed between a fixed foot soldered to the printed circuit board and an intermediate portion of the fixed foot in parallel to the printed circuit board and the printed circuit board. A thermistor mounting portion formed by extending from the top of the fixed foot in a direction opposite to the stopper portion at a position higher than the stopper portion, and a mounting hole for a lead terminal provided in the thermistor mounting portion And
By inserting and fixing the respective bent portions at the tips of the two lead terminals into the mounting holes of the thermistor mounting portions of the corresponding metal plates, the side surfaces of the thermistor mounting portions of the metal plates and the The thermistor body is positioned in a non-contact state on the stopper portion at the same time as being separated from a portion other than the tip portion of the lead terminal, and the thermistor is flattened by soldering the fixed foot to the printed circuit board. mounting structure for a thermistor but which is characterized in that mounted in a direction forming substantially parallel to the printed circuit board. In the thermistor mounting structure according to claim 1,
The thermistor mounting structure characterized in that the formation portion of the stopper portion in the fixed foot of each metal plate is bent so as to protrude in the extending direction of the stopper portion . The thermistor mounting structure according to claim 1 or 2,
2. A thermistor mounting structure in which the lengths of the two lead terminals are made different, and the bent portions of the lead terminals are fixed to corresponding thermistor mounting portions at positions where they do not face each other . In the thermistor mounting structure according to any one of claims 1 to 3 ,
Each metal plate has two fixed legs,
The thermistor mounting portion is configured as a bridging portion between two fixed feet.

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