JP2015069879A - Induction heating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an induction heating apparatus capable of preventing a printed board from being damaged when soldering the printed board by induction heating.SOLUTION: An induction heating apparatus 20 comprising a heating coil 1 for induction heating of a heated body 6 provided therein by power supplied from an induction heating power supply 3, comprises an auxiliary coil 2 having the same center axis as the center axis of the heating coil, and wound so that a magnetic flux is generated in an opposite direction to the magnetic flux of the heating coil, and placed between a printed board 4 and the heating coil. Because the auxiliary coil cancels the magnetic flux emitted by the heating coil to a wiring pattern, heating of the wiring pattern can be suppressed. Therefore, damages to the board at the soldering using the induction heating can be suppressed.

Description

  The present invention relates to an induction heating apparatus for heating a metal body inserted into a hole of a plate body.

  As a method of heating a conductive object such as a metal, there is induction heating using electromagnetic induction. In induction heating, an eddy current is generated in a heated body by magnetic flux supplied from a coil, and the heated body is directly heated by heat generated by the current. For this reason, it has the features of being capable of high temperature increase and high efficiency.

  Since induction heating has the above-mentioned features, there is a demand to apply induction heating to a heating device used for soldering a printed circuit board. The soldering of the printed circuit board takes a configuration in which component leads are inserted into through holes formed on the printed circuit board. At this time, a land is formed in the vicinity of the through hole. The lead is often a columnar metal such as a cylinder. In soldering, it is necessary to heat the lead to an appropriate temperature.

  As a conventional columnar metal induction heating device, there is one using a solenoid coil as a heating coil (see, for example, Patent Document 1). FIG. 7 is a diagram showing a heating coil used in the conventional induction heating apparatus described in Patent Document 1. As shown in FIG.

  In FIG. 7, the heated object 10 that is a metal pipe is fixed from above and below by a jig 13. The heating coil 9 is a solenoid coil. The heating coil 9 is connected to the induction heating power source 3, and the body to be heated 10 is disposed therein. At the time of heating, electric power is supplied from the induction heating power source 3 to the heating coil 9, whereby the heated object 10 is induction heated.

JP 2007-262461 A

  However, when the conventional configuration is applied to the soldering of the printed board, there is a problem that the printed board is burnt and damaged. This cause will be described.

  In the induction heating, the heated body is heated by interlinking magnetic flux with the heated body and causing the heated body to absorb the magnetic energy. The amount of heat generated at this time takes a larger value as the interlinkage magnetic flux increases. Here, the interlinkage magnetic flux increases as the area increases. Therefore, in induction heating, the larger the area of the object to be heated, the greater the interlinkage magnetic flux and the greater the amount of heat generated.

  The printed board is formed of a resin and a wiring pattern. The wiring pattern is a metal plate and can be induction-heated. In soldering a printed circuit board, the wiring pattern often has a larger area than the lead. For this reason, when induction heating is performed from the same heating coil, the wiring pattern generates a larger amount of heat than the lead, and the temperature rises first.

  The resin forming the printed circuit board is damaged at a low temperature, such as scoring, as compared with a metal. Therefore, when soldering is performed using induction heating, the wiring pattern is heated first, and the wiring pattern exceeds the heat resistance temperature of the resin before the lead is heated to a temperature suitable for soldering. To rise. As a result, a phenomenon occurs in which the resin burns and damages the printed circuit board.

  The present invention solves the above-described conventional problems, and an object of the present invention is to provide an induction heating apparatus that does not damage a plate body when a plate body such as a printed circuit board and a metal body are joined by induction heating. .

In order to achieve the above object, the induction heating apparatus of the present invention is configured as follows.

According to one aspect of the invention, an induction heating power source;
A heating coil in which at least a part of a metal body, which is a body to be heated inserted into a hole of a plate body, is disposed inside, and the body to be heated is induction-heated by electric power supplied from the induction heating power source;
Adjacent to the heating coil so as to face the plate body, the central axis of the heating coil is the same as the central axis, and the direction opposite to the magnetic flux generated by the heating coil by the power supplied from the induction heating power source And an auxiliary coil configured to generate a magnetic flux.

  The auxiliary coil generates a magnetic flux in a direction opposite to the magnetic flux generated by the heating coil. This weakens the magnetic flux generated in the vicinity of the metal plate and suppresses heat generation.

  As described above, according to the induction heating device of the present invention, it is possible to realize bonding such as soldering between a printed board and a metal body such as a lead without damaging a plate body such as the printed board. Can do.

Schematic of the induction heating device in the first embodiment of the present invention The figure of magnetic flux distribution which the heating coil in a 1st embodiment of the present invention generates The figure of magnetic flux distribution which the auxiliary coil in a 1st embodiment of the present invention generates Diagram of magnetic flux distribution generated when heating coil and auxiliary coil are combined in the first embodiment of the present invention Diagram of magnetic flux distribution generated by a coil in the first embodiment of the present invention Graph showing the relationship between the number of turns of the heating coil and the current value when the lead temperature is 250 degrees A graph showing the relationship between the number of turns of the heating coil and the temperature of the wiring pattern when the lead temperature is 250 degrees. The figure of magnetic flux distribution which one turn heating coil in a 1st embodiment of the present invention generates Diagram of magnetic flux distribution generated by one turn auxiliary coil in the first embodiment of the present invention The figure of the magnetic flux distribution which generate | occur | produces when combining the 1-turn heating coil and 1-turn auxiliary coil in 1st Embodiment of this invention. Diagram of magnetic flux distribution generated by a coil in the first embodiment of the present invention The figure which shows the state where the length of the auxiliary coil is shorter than the length of the lead on the printed circuit board Schematic of induction heating device using series coil of the present invention The figure which shows the conventional induction heating apparatus using the solenoid coil described in patent document 1

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
In FIG. 1, the induction heating apparatus 20 which is one embodiment of this invention is shown.

  The induction heating device 20 includes a heating coil 1, an auxiliary coil 2, and an induction heating power source 3.

  Two induction heating power sources 3 are prepared: a heating coil induction heating power source 3a and an auxiliary coil induction heating power source 3b. Here, for example, the object to be heated is a lead 6 as an example of a metal body. The lead 6 is inserted into a through hole (hole) 5 formed in the printed circuit board 4 as an example of a plate body, and the lead 6 is heated by the heating coil 1 to join the lead 6 and the through hole 5. The solder 12 arranged at 22 is melted, and the lead 6 and the through hole 5 are soldered. The printed circuit board 4 has a metal wiring pattern.

  The induction heating power source 3, that is, the heating coil induction heating power source 3 a and the auxiliary coil induction heating power source 3 b are separately connected to the heating coil 1 and the auxiliary coil 2 via the wiring 7. At this time, the induction heating power source 3a for both heating coils and the induction heating power source 3b for the auxiliary coil are driven by the control unit 23 so that the phases are equal to each other.

  The heating coil 1 and the auxiliary coil 2 each have a solenoid shape, and are arranged so that the central axes coincide with each other. The heating coil 1 and the auxiliary coil 2 are arranged at a predetermined interval in the central axis direction. The printed circuit board 4 and the auxiliary coil 2 are arranged at a predetermined interval in the central axis direction. The number of turns of the heating coil 1 and the auxiliary coil 2 is set so that the number of turns of the heating coil 1 is larger than the number of turns of the auxiliary coil 2. Further, the heating coil 1 and the auxiliary coil 2 are arranged so that the directions of the generated magnetic fluxes are opposite to each other.

  The lead 6 is a cylindrical metal member. The lead 6 is disposed by being inserted into the heating coil 1 and the auxiliary coil 2. The lead 6 needs to penetrate the auxiliary coil 2, but the heating coil 1 does not necessarily need to penetrate, and it is only necessary that a part of the lead 6 is disposed inside the heating coil 1 as described later. . The central axis of the heating coil 1 and the central axis of the lead 6 are preferably matched from the viewpoint of heating uniformly and efficiently.

  The induction heating device 20 configured as described above operates as follows.

  First, two induction heating power sources 3 (3a, 3b) are energized, and high frequency currents are individually energized in the heating coil 1 and the auxiliary coil 2, respectively.

  By applying a high-frequency current to the heating coil 1 and the auxiliary coil 2, magnetic flux is generated from the coils 1 and 2. The leads 6 are heated by these magnetic fluxes. The solder 12 is melted by supplying the solder 12 to the joint 22 and heating the lead 6 to a temperature suitable for the solder 12.

  After the solder 12 is melted, the energization of the two induction heating power sources 3 (3a, 3b) is stopped by the control unit 23.

  Thereafter, the solder 12 of the joint portion 22 is cooled, so that the melted solder 12 is solidified at the joint portion 22, and a soldering joint is formed between the through hole 5 and the lead 6 of the printed circuit board 4. The

  The heating coil 1 and the auxiliary coil 2 interact with each other to realize a magnetic flux distribution suitable for the printed circuit board 4. Below, this effect | action is demonstrated.

  FIG. 2A shows the magnetic flux 8a generated by the heating coil 1 alone. 2B shows the magnetic flux 8b generated by the auxiliary coil 2 alone. As shown in FIGS. 2A and 2B, the magnetic fluxes 8a and 8b generated by the heating coil 1 and the auxiliary coil 2 are opposite to each other. Since the number of turns of the heating coil 1 is larger than the number of turns of the auxiliary coil 2, the magnetic flux 8 a generated by the heating coil 1 alone is stronger than the magnetic flux 8 b generated by the auxiliary coil 2 alone.

  FIG. 2C shows the magnetic flux distribution when the heating coil 1 and the auxiliary coil 2 are combined. Since the magnetic fluxes can be superposed, the superposition of the magnetic flux 8a generated by the heating coil 1 alone and the magnetic flux 8b generated by the auxiliary coil 2 alone becomes a magnetic flux when the heating coil 1 and auxiliary coil 2 are combined, and heating The magnetic flux 8c near the coil 1 and the magnetic flux 8d near the auxiliary coil 2 are obtained.

  Since the magnetic flux 8a generated by the single heating coil 1 is stronger than the magnetic flux 8b generated by the single auxiliary coil 2, the influence of the heating coil 1 is dominant even in the vicinity of the auxiliary coil 2. For this reason, the direction of the magnetic flux 8d near the auxiliary coil 2 is equal to the direction of the magnetic flux 8a generated by the heating coil 1. However, the magnetic flux 8d in the vicinity of the auxiliary coil 2 is weaker than the magnetic flux 8c in the vicinity of the heating coil 1 because the auxiliary coil 2 generates and cancels out the magnetic flux 8b having a direction different from that of the magnetic flux 8d. As described above, the heating coil 1 and the auxiliary coil 2 interact with each other to form a magnetic flux distribution in which the magnetic flux 8c in the vicinity of the heating coil 1 is strong and the magnetic flux 8d in the vicinity of the auxiliary coil 2 is weak.

  FIG. 2D shows the magnetic flux distribution during soldering to the printed circuit board 4. Since the magnetic flux 8c in the vicinity of the heating coil 1 is strong, the upper portion of the lead 6 is strongly induction-heated. On the other hand, since the magnetic flux 8d in the vicinity of the auxiliary coil 2 is weak, the magnetic flux linked to the wiring pattern of the printed circuit board 4 is weak, heat generation is reduced, and heating of the printed circuit board 4 by induction heating is suppressed.

  As described above, by combining the heating coil 1 and the auxiliary coil 2, the lead 6 can be heated while suppressing heating of the printed circuit board 4.

  Here, the conditions of the shape and arrangement of the auxiliary coil 2 will be described. Analysis was used to derive the conditions. Femtet 2013 (Murata Software Co., Ltd.) was used for the analysis.

  The analysis model was created to have the same configuration as in FIG.

  The heating coil 1 and the auxiliary coil 2 have the same coil diameter and the same wire diameter, the coil diameter is 18 mm, and the wire diameter is 3 mm. In addition, it is assumed that the heating coil 1 and the auxiliary coil 2 are both sufficiently densely wound and that there is no leakage magnetic flux. Therefore, if the number of turns of each of the heating coil 1 and the auxiliary coil 2 is N, the width of each coil is 3 × N mm. The coil wire material is copper. However, N is an integer greater than or equal to 1.

  For the printed circuit board 4, only a wiring pattern that is directly affected by induction heating is modeled. The wiring pattern was a 10 mm square and the thickness was 0.5 mm. The through hole 5 was arranged at the center of the wiring pattern, and the hole diameter was 2.5 mm. The material of the wiring pattern is copper.

  The lead 6 has a diameter of 2 mm and a length of 50 mm. The material of the lead 6 is copper.

  The center of the lead 6 in the longitudinal direction and the center of the height of the wiring pattern were arranged to coincide. The auxiliary coil 2 is disposed at a position 1 mm away from the printed circuit board 4 on the upper part of the printed circuit board 4 so that the central axis of the auxiliary coil 2 coincides with the central axis of the lead 6. The central axis of the heating coil 1 is aligned with the central axis of the lead 6, and is arranged above the auxiliary coil 2 so as to have a gap of 1 mm from the auxiliary coil 2.

  Analysis was performed by coupled analysis of magnetic field and heat. In the magnetic field analysis, the frequency from the induction heating power source 3 was fixed at 200 kHz, and AC analysis was performed. In the thermal analysis, only the wiring pattern and the lead 6 are subjected to the thermal analysis. The reason why the coils 1 and 2 are not included in the thermal analysis is that the coils 1 and 2 are water-cooled in the actual induction heating device 20 because the temperature is constant and the influence on the temperature rise of the wiring pattern or the lead 6 is small. It is.

  In order to prevent the printed circuit board 4 from being damaged, the turn ratio between the heating coil 1 and the auxiliary coil 2 is important. This is because the ratio of the magnetic flux in the vicinity of the heating coil 1 and the magnetic flux in the vicinity of the auxiliary coil 2 is determined by this ratio, and the ratio of heat generation of the REIT 6 and the wiring pattern is determined.

  Therefore, in the analysis, conditions for the turn ratio of the coils 1 and 2 that do not damage the printed circuit board 4 are derived. Here, the number of turns of the auxiliary coil 2 was fixed to 1 and the number of turns of the heating coil 1 was changed to various values. By obtaining the correlation between the number of turns at this time and the temperature of the printed circuit board 4, a condition of the number of turns ratio that does not damage the printed circuit board 4 is derived.

  The resin of the printed circuit board 4 is assumed to be glass epoxy, and the heat resistant temperature is 250 degrees. In addition, assuming that lead-free solder is used for soldering, the soldering temperature is 250 degrees. In the soldering process, it is required to keep the temperature rising time constant. Here, it is assumed that the temperature rising time is 10 seconds.

  From the above, the condition under which the printed circuit board 4 is not damaged is that the temperature of the lead 6 as the joint 22 becomes 250 degrees after 10 seconds, and the temperature of the wiring pattern at this time becomes lower than 250 degrees.

  In the analysis, first, calculation was performed using two steps of deriving a current value for the lead 6 to be 250 degrees in 10 seconds and deriving the temperature of the wiring pattern at the current value.

  FIG. 3A shows the analysis result of the current value for the lead 6 to be 250 degrees in 10 seconds when the auxiliary coil 2 is fixed with one turn and the number of turns of the heating coil 1 is changed. Moreover, the analysis result of the temperature of the wiring pattern at this time is shown in FIG. 3B. From this graph, for example, when the number of turns of the heating coil 1 is 3, the lead temperature after 10 seconds at a current value of 400 A is 250 degrees, and the temperature of the wiring pattern at this time can be read as 155 degrees. .

  From the graph of FIG. 3B, it can be seen that the greater the number of turns of the heating coil 1, the lower the temperature of the wiring pattern. The reason for this will be described with reference to FIGS. 2A to 4D.

  First, a phenomenon when the number of turns of the heating coil 1 is small will be described. Here, a case where the heating coil 1 has one turn is shown as an example.

  FIG. 4A shows the magnetic flux 8a generated by the heating coil 1 when the heating coil 1 has one turn. At this time, the magnetic flux 8b generated by the auxiliary coil 2 is shown in FIG. 4B. These magnetic fluxes 8a and 8b have the same size because the number of turns of the coils 1 and 2 is equal. Therefore, when these are superposed, they weaken each other, and the magnetic flux 8c in the vicinity of the heating coil 1 and the magnetic flux 8d in the vicinity of the auxiliary coil 2 are both equal in magnitude and small in magnitude as shown in FIG. 4C. Become. Note that the direction of the magnetic flux is the same in both coils 1 and 2, so that one of them does not become dominant and remains in the opposite direction.

  When these coils 1 and 2 are used for soldering, the result is as shown in FIG. 4D. Since the magnetic flux 8c in the vicinity of the heating coil 1 and the magnetic flux 8d in the vicinity of the auxiliary coil 2 are equal to each other, the temperature of the printed circuit board 4 that is easily heated rises first. Since the magnetic flux 8c in the vicinity of the heating coil 1 is small, in order to heat the lead 6, it is necessary to apply a large current to generate a large magnetic flux. It can be seen from FIG. 3A that the amount of current required to set the temperature of the lead 6 to 250 degrees is 1202A. The temperature of the wiring pattern at this time is 9532 degrees from FIG. 3B.

  Thus, when soldering is performed under conditions where the number of turns of the heating coil 1 is small, it can be seen that the wiring pattern is heated to a higher temperature than the soldering temperature.

  Next, a phenomenon when the number of turns of the heating coil 1 is large will be described. Here, a case where the heating coil 1 has four turns is shown as an example.

FIG. 2A shows the magnetic flux 8a generated by the heating coil 1 when the heating coil 1 has four turns. At this time, the magnetic flux 8b generated by the auxiliary coil 2 is shown in FIG. 2B. These magnetic fluxes 8a and 8b have a larger value in the magnetic flux 8a generated by the heating coil 1 because the heating coil 1 has more turns. Therefore, when these are superposed, the magnetic flux 8c near the heating coil 1 takes a large value, and the magnetic flux 8d near the auxiliary coil 2 takes a small value. When these coils 1 and 2 are used for soldering, as shown in FIG. become. Since the magnetic flux 8c in the vicinity of the heating coil 1 is larger, the lead 6 is heated first by induction heating. As a result, the current value required to heat the lead 6 is also reduced, and it can be seen from FIGS. 3A to 400A. The temperature of the wiring pattern at this time is 77 degrees from FIG. 3B.

  Thus, when soldering is performed under conditions where the number of turns of the heating coil 1 is large, it can be seen that the temperature of the wiring pattern is lower than the soldering temperature.

  From the above analysis results, the conditions of the heating coil 1 for preventing the printed circuit board 4 from being damaged are derived.

From FIG. 3B, when the condition of the heating coil 1 where the temperature of the wiring pattern is 250 degrees or less is read, it is when the number of turns of the heating coil 1 is larger than two. Calculate the ratio from here,
(Number of turns of heating coil 1 / number of turns of auxiliary coil 2)> 2
Satisfying the conditions is a condition that does not damage the printed circuit board 4.

  However, depending on the arrangement conditions of the leads 6, there is a possibility that the printed circuit board 4 may be damaged even if the winding ratio is satisfied. This is when the lead 6 is not disposed inside the heating coil 1. This is shown in FIG. The auxiliary coil 2 is longer than the length of the lead 6 at the top of the printed circuit board, whereby the heating coil 1 is disposed above the upper end of the lead 6. At this time, the heating coil 1 cannot heat the lead 6. As a result, the magnetic flux 8b generated by the auxiliary coil 2 heats the leads 6 and the wiring pattern, and the wiring pattern that is easily heated is overheated, and the printed circuit board 4 is damaged.

  From the above, in order not to damage the printed circuit board 4, the lead 6 needs to be disposed inside the heating coil 1. Further, in order to reliably heat the lead 6 with the heating coil 1, it is necessary that at least the tip of the lead 6 penetrating the auxiliary coil 2 is in the heating coil 1.

  According to the embodiment, the lead 6 inserted into the through hole 5 of the printed circuit board 4 penetrates the auxiliary coil 2 with the central axis of the heating coil 1 and the central axis of the auxiliary coil 2 being the same and adjacent to each other. Then, a part of the lead 6 is disposed inside the heating coil 1, and the auxiliary coil 2 generates magnetic flux in the opposite direction to the magnetic flux generated by the heating coil 1 by the power supplied from the induction heating power source 3. The lead 6 is induction-heated by the heating coil 1.

  According to this configuration, by installing the auxiliary coil 2 in addition to the heating coil 1, heating of the wiring pattern of the printed circuit board 4 due to induction heating can be suppressed. This makes it possible to suppress damage to the printed circuit board 4 that occurs when soldering the printed circuit board 4 using induction heating. Therefore, it is possible to prevent the printed circuit board 4 from being damaged when the printed circuit board 4 and the lead 6 are soldered by induction heating.

  As a modification of the embodiment, the heating coil 1 and the auxiliary coil 2 may be connected in series. Hereinafter, a coil in which the heating coil 1 and the auxiliary coil 2 are connected in series is referred to as a series coil 11. In FIG. 6, the schematic of the induction heating apparatus 20B using the serial coil 11 is shown.

  The induction heating device 20B includes a series coil 11 in which the heating coil 1 and the auxiliary coil 2 are connected in series by a wiring 7B, and an induction heating power source 3 connected through the series coil 11 and the wiring 7. . As an example, the object to be heated is composed of leads 6 inserted into through holes 5 of the printed circuit board 4.

  The series coil 11 is configured by connecting the heating coil 1 and the auxiliary coil 2 in series. The induction heating power source 3 is connected to both ends of the series coil 11 via the wiring 7, and supplies power to the series coil 11. Other arrangements of the lead 6 and the like are the same as those described above.

  In the configuration in which power is supplied from the separate power sources 3a and 3b to the heating coil 1 and the auxiliary coil 2 as shown in FIG. 1, two induction heating power sources 3a and 3b are required, which increases the cost of the equipment. There was a problem that. In addition, it is necessary to control the control unit 23 so that the two induction heating power sources 3a and 3b have the same phase.

  According to this configuration, the induction heating power source 3 can be made one by connecting the heating coil 1 and the auxiliary coil 2 in series, and the problem of equipment cost and the problem of control can be solved. Further, similarly to the configuration shown in FIG. 1, damage to the printed circuit board 4 that occurs when the printed circuit board 4 is soldered using induction heating can be suppressed.

  In addition, it can be made to show the effect which each has by combining arbitrary embodiment or modification of the said various embodiment or modification suitably.

  The induction heating apparatus of the present invention is a plate body adjacent to a heated body when a plate body having a holed metal wiring pattern such as a printed circuit board and a metal body that is a heated body such as a lead. It can be applied to joining applications such as soldering or brazing of a heated object inserted into a hole in a plate, for example, a cylindrical metal body.

DESCRIPTION OF SYMBOLS 1 Heating coil 2 Auxiliary coil 3 Induction heating power source 3a Induction heating power source for heating coil 3b Induction heating power source for auxiliary coil 4 Printed circuit board 5 Through hole 6 Lead 7, 7B Wiring 8a Magnetic flux generated by heating coil 1 8b Auxiliary coil 2 Generated magnetic flux 8c Magnetic flux in the vicinity of the heating coil 1 8d Magnetic flux in the vicinity of the auxiliary coil 2 9 Solenoid coil 10 Heated object 11 Series coil 12 Solder 13 Jig 20, 20B Induction heating device 22 Joint

Claims (3)

An induction heating power supply;
A heating coil in which at least a part of a metal body, which is a body to be heated inserted into a hole of a plate body, is disposed inside, and the body to be heated is induction-heated by electric power supplied from the induction heating power source;
Adjacent to the heating coil so as to face the plate body, the central axis of the heating coil is the same as the central axis, and the direction opposite to the magnetic flux generated by the heating coil by the power supplied from the induction heating power source And an auxiliary coil configured to generate magnetic flux. At least a portion of the lead that is the metal body is disposed inside the heating coil;
The ratio of the heating coil to the auxiliary coil is
2 <(number of turns of heating coil ÷ number of turns of auxiliary coil)
The induction heating apparatus according to claim 1, wherein   The induction heating apparatus according to claim 1 or 2, wherein the heating coil and the auxiliary coil are connected in series, and electric power is supplied from the one induction heating power source to the heating coil and the auxiliary coil.

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