JP7463876B2 - Heating device - Google Patents

Description

The present invention relates to a heating device.

Induction heating involves placing the object to be heated, such as a conductive material such as a metal, in the magnetic flux generated by a coil, which generates eddy currents through electromagnetic induction, allowing for non-contact, fast, and highly efficient heating. Induction heating is used, for example, for preheating the soldering process of printed circuit boards (see Patent Document 1).

JP 2019-47050 A

A printed circuit board contains metal parts such as copper plates that form the electrical circuits, and resin parts that are non-metallic insulators. When preheating a printed circuit board, it is desirable to heat both the metal and resin parts in a balanced manner, for example to expel any moisture that has penetrated them.

However, while induction heating uses eddy currents and can heat metal parts, it is difficult to heat insulators. Therefore, in order to heat the resin parts of a printed circuit board, a heating means separate from induction heating must be provided, making the system complicated.

The present invention was made in consideration of the above problems, and aims to provide a heating device that can heat metal and non-metal parts with a simple configuration.

In order to solve the above problems and achieve the object, the heating device according to the present invention is a heating device for heating an object to be heated, and is provided with a coil made of a metal pipe, a power source for applying an alternating current to the coil, and a fluid source for supplying a fluid from one side of the metal pipe, and is characterized in that the object to be heated is heated by a magnetic flux generated by the coil, and the object to be heated is heated by a fluid ejected from an ejection port on the other side of the metal pipe. In such a heating device, the coil serves as a heating means for the metal part and a heating means for the resin part, and both the metal part and the non-metal part can be heated with a simple configuration.

The device may also include a temperature detection means for measuring the temperature of the object to be heated, and a control unit for adjusting the AC current supplied to the coil based on the temperature of the object to be heated obtained from the temperature detection means.

The device may also include a temperature detection means for measuring the temperature of the object to be heated, and a control unit for adjusting the flow rate of the fluid supplied to the metal pipe based on the temperature of the object to be heated obtained from the temperature detection means.

The device may include a temperature detection means for measuring the temperature of the object to be heated, and a control unit for adjusting the gap between the coil and the object to be heated based on the temperature of the object to be heated obtained from the temperature detection means.

A control unit is provided to adjust the alternating current supplied to the coil and the flow rate of the fluid supplied to the metal pipe, and the control unit may stop the alternating current to the coil while supplying fluid to the metal pipe depending on the conditions of the heated object.

The fluid may be an inert gas.

One end of the metal pipe may be connected directly to the fluid source or via a flexible pipe, and the power source and the coil may be electrically connected by a conductor.

The heated object may be a printed circuit board, multiple coils may be provided, and the nozzle may be directed toward the printed circuit board.

The nozzle may be directed toward a resin portion of the printed circuit board.

The heating device of the present invention can heat an object to be heated by the interaction between the magnetic action of the magnetic flux generated by the coil and the action of the fluid ejected by the coil. In other words, the coil serves as a heating means for both the metal parts and the resin parts, and can heat both the metal parts and the non-metal parts with a simple configuration.

FIG. 1 is a schematic side view of a heating device according to an embodiment of the present invention. FIG. 2 is a schematic bottom view of the heating device. FIG. 3 is a block diagram of a portion of the heating device. FIG. 4 is a graph showing a method of adjusting the heating capacity at the design stage of a heating device, where (a) is a graph showing the heating capacity depending on the length of the coil, (b) is a graph showing the heating capacity depending on the number of turns of the coil, and (c) is a graph showing the heating capacity depending on the material resistivity of the coil. FIG. 5 is a graph showing the heating capacity of the heating device depending on the change in the distance between the coil and the printed circuit board, which is the object to be heated. 6A and 6B are graphs showing the heating capacity of the heating device depending on the state of the fluid supplied from the fluid source and sprayed from the nozzle, where (a) is a graph showing the heating capacity of the heating device depending on the change in flow rate, and (b) is a graph showing the heating capacity of the heating device depending on the specific heat of the fluid. FIG. 7 is a graph showing the heating capacity of the heating device depending on the output current to the coil. FIG. 8 is a schematic side view of a heating device according to a modified example.

Below, an embodiment of a heating device according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to this embodiment.

Figure 1 is a schematic side view of a heating device 10 according to an embodiment of the present invention. Figure 2 is a schematic bottom view of the heating device 10.

As shown in FIG. 1, the heating device 10 is a device that heats a printed circuit board 12, which is an object to be heated. The heating device 10 is used, for example, for preheating the printed circuit board 12 in a process of soldering. The printed circuit board 12 includes a metal part 12a (see FIG. 3), such as a copper plate, that forms an electric circuit, and a resin part 12b (see FIG. 3), which is a non-metallic insulator.

The heating device 10 comprises a number of coils 16 made of metal pipes 14, an inverter (power source) 18 that applies high-frequency alternating current to each coil 16, and a fluid source 20 that supplies fluid from one side of the metal pipes 14. The metal pipes 14 are made of, for example, copper or stainless steel. The coils 16 are provided below the printed circuit board 12. The coils 16 are formed by winding the metal pipes 14 into a cylindrical spiral shape. The cylinder of the coil 16 is oriented so that its central axis is approximately perpendicular to the underside of the printed circuit board 12.

1, each coil 16 is connected in series to the inverter 18, but it may be connected in parallel or may be a circuit in which serial and parallel parts are mixed. In addition, the direction of voltage application to each coil 16 is shown to be the same, but it may be applied in the opposite direction to some of the coils 16. Furthermore, the spiral direction of each coil 16 is shown to be the same, but it may be reversed for some of the coils 16. The printed circuit board 12 is transported from left to right as indicated by the arrow in FIG. 1, and is set at a predetermined position in the heating device 10 and heated. The printed circuit board 12 may be heated while being transported in the heating device 10. In FIG. 1, the number of coils 16 is provided according to the length of the printed circuit board 12 when viewed from the side, but this is not limited to this, and the number of coils 16 may be set to be more or less in the transport direction.

The length of the coil 16 is H. The gap between the coil 16 and the printed circuit board 12 is G. Although not shown, the heating device 10 is provided with a lifting mechanism that adjusts the gap G by raising and lowering the coil 16 or the printed circuit board 12.

As shown in FIG. 2, the coils 16 are arranged in a staggered manner in each row in the direction perpendicular to the conveying direction. This makes it possible to prevent uneven heating of the printed circuit board 12. The coils 16 may be arranged, for example, in a grid pattern.

Figure 3 is a partial block diagram of the heating device 10. In Figure 3, only one representative coil 16 is shown to avoid clutter.

As shown in FIG. 3, the heating device 10 includes a temperature detection means 22 for measuring the temperature of the printed circuit board 12, and a control unit 24 for controlling the inverter 18 and the fluid source 20 based on the temperature of the printed circuit board 12 obtained from the temperature detection means 22. The temperature detection means 22 is, for example, a non-contact thermometer. The control unit 24 acts as a temperature regulator, and is capable of adjusting the AC current I supplied to the coil 16 by controlling the inverter 18, and is also capable of adjusting the flow rate Q of the fluid supplied to the metal pipe 14. The control unit 24 is preferably configured to be capable of adjusting at least one of the AC current I and the flow rate Q. This allows the temperature of the printed circuit board 12 to be controlled easily and with high accuracy. The control unit 24 is capable of controlling the lifting mechanism. The operation of the control unit 24 will be described later.

The fluid source 20 includes a compressor 20a and a pressure reducing valve 20b. The compressor 20a compresses the fluid. The pressure reducing valve 20b reduces the pressure of the fluid compressed by the compressor 20a under the action of the control unit 24. The pressure reducing valve 20b may be of a manually adjustable type.

The fluid used in the heating device 10 is a gas, specifically air. However, in addition to air, an inert gas such as nitrogen may be used. The inert gas can prevent corrosion of the metal parts of the printed circuit board 12. Depending on the design conditions, the fluid supplied from the fluid source 20 in the heating device 10 may be a liquid. In this case, it is advisable to use a pump instead of the compressor 20a.

The metal pipe 14 and the flexible resin pipe 26 form a pipeline 28. One end of the flexible pipe 26 is connected to the pressure reducing valve 20b, and the other end is connected to the metal pipe 14 via a joint 30. The flexible pipe 26 allows freedom of positioning of the fluid source 20 and the coil 16 relative to each other. The flexible pipe 26 is an insulator and can electrically insulate the coils 16 from each other, allowing electrical series connection as shown in FIG. 1, for example. In the heating device 10, one end of the metal pipe 14 is connected to the fluid source 20 via the flexible pipe 26, but it may be connected directly depending on the design conditions.

Terminals 14a are provided on both ends of the metal pipe 14. The metal pipe 14 and the inverter 18 are connected by a pair of conductors 32. One end of the conductor 32 is connected to the terminal 14a. In this way, the inverter 18 and the coil 16 are electrically connected by the conductor 32. The conductor 32 is, for example, a Litz wire.

A nozzle (spout) 34 is provided at the other end of the metal pipe 14, which is directed toward the printed circuit board 12 above. The direction of the nozzle 34 can be adjusted and it can be replaced with a different type. Depending on the conditions, the nozzle 34 may be omitted.

In the heating device 10 configured in this manner, first, the transported printed circuit board 12 is set in a predetermined position. Then, fluid is supplied from the fluid source 20 to the pipeline 28. Furthermore, an AC current I is supplied to the coil 16 by the inverter 18. The AC current I supplied from the inverter 18 causes the coil 16 to generate a magnetic flux Φ. The magnetic flux Φ generates eddy currents in the metal part 12a of the printed circuit board 12 through the action of induction heating, which can heat the metal part 12a.

The coil 16 generates a magnetic flux Φ and generates heat due to copper loss caused by its own resistance. In the heating device 10, the fluid supplied from the fluid source 20 absorbs the heat generated by the copper loss in the coil 16, increases in temperature, and is ejected from the nozzle 34 and hits the printed circuit board 12, thereby heating the resin portion 12b.

Furthermore, the control unit 24 measures the temperature of the printed circuit board 12 using the temperature detection means 22, and controls the inverter 18 and pressure reducing valve 20b based on the measured temperature. When the printed circuit board 12 reaches a predetermined temperature, the predetermined temperature is maintained until the printed circuit board 12 is discharged from the heating device 10, and heating is terminated after the board is discharged. The control unit 24 may control the inverter 18 and pressure reducing valve 20b based on the temperature deviation (e.g., proportional control), or may simply control them on and off.

The heating device 10 can heat the printed circuit board 12 by the interaction between the magnetic action and the fluid action of the coil 16. In other words, the heating device 10 has a simple structure because the coil 16 serves both as a heating means for the metal part 12a and the heating means for the resin part 12b. The heating device 10 can be constructed using inexpensive parts.

The coil 16 is cooled by the fluid supplied from the fluid source 20, so it is not overheated, and the allowable current value of the AC current I is increased. Waste heat generated in the coil 16 can be recovered by the fluid and ejected from the nozzle 34 in the appropriate direction, resulting in good energy efficiency. The fluid ejected from the nozzle 34 hits the printed circuit board 12 directly without any heat storage medium in between, resulting in good temperature controllability. The metal part 12a and the resin part 12b of the printed circuit board 12 are heated in a balanced manner, so that the occurrence of warping or cracking in the printed circuit board can be suppressed. In addition, the balanced heating allows the temperature to be freely adjusted to a temperature suitable for expelling moisture from the printed circuit board and activating the flux, improving the quality of the soldering.

Depending on the conditions of the manufacturing process, the printed circuit board 12 may be cooled after heating. In this case, in the heating device 10, the control unit 24 stops the AC current I to the coil 16 while supplying fluid to the metal pipe 14. This stops the generation of magnetic flux Φ and eliminates waste heat due to copper loss, but if fluid supply from the fluid source 20 continues, the fluid will not heat up as it passes through the coil 16 and will strike the printed circuit board 12 at a low temperature, allowing the printed circuit board 12 to be cooled. In this way, the heating device 10 can also be used as a cooling device.

The heating device 10 heats the printed circuit board 12 by magnetic action and fluid action, but the magnetic action and fluid action can be adjusted depending on the type and specifications of the printed circuit board 12. Various adjustment means for heating the printed circuit board 12 by the heating device 10 are described below.

Figure 4 is a graph showing a method of adjusting the heating capacity at the design stage of the heating device 10, where (a) is a diagram showing the heating capacity according to the length H of the coil 16 (see Figure 1), (b) is a diagram showing the heating capacity according to the number of turns of the coil 16, and (c) is a diagram showing the heating capacity according to the material resistivity of the coil 16. In Figures 4 to 7, the thick line L1 indicates the heating capacity due to fluid action, specifically the temperature of the fluid ejected from the nozzle 34. Similarly, the thin line L2 indicates the heating capacity due to magnetic action, specifically the strength of the magnetic flux Φ generated by the coil 16.

As shown in FIG. 4(a), as the length H of the coil 16 increases, L1 due to the fluid effect increases proportionally, and L2 due to the magnetic effect decreases proportionally. Here, the length of the metal pipe 14, which is the wire of the coil 16, and other parameters are assumed to be constant. In the following graphs, parameters other than the horizontal axis quantity are assumed to be constant.

As shown in FIG. 4(b), as the number of turns of the coil 16 increases, L1 due to the fluid effect increases proportionally, and L2 due to the magnetic effect increases proportionally to the square of the number of turns.

As shown in FIG. 4(c), as the material resistivity of the coil 16 increases, L1 due to the fluid effect increases proportionally, while L2 due to the magnetic effect remains constant.

Figure 5 is a graph showing the heating capacity of the heating device 10 as a function of changes in the distance between the coil 16 and the printed circuit board 12, which is the object to be heated, i.e., the gap G (see Figure 1). As shown in Figure 5, as the gap G increases, L2 due to magnetic action decreases inversely proportionally. As the gap G increases, L1 due to fluid action increases, showing an opposite trend to L2, but the rate of increase gradually decreases. As described above, the gap G can be adjusted by the control unit 24 controlling the adjustment mechanism.

Figure 6 is a graph showing the heating capacity of the heating device 10 depending on the state of the fluid supplied from the fluid source 20 and sprayed from the nozzle 34, where (a) is a diagram showing the heating capacity of the heating device 10 depending on the change in flow rate Q, and (b) is a diagram showing the heating capacity of the heating device 10 depending on the specific heat of the fluid.

As shown in FIG. 6(a), as the flow rate Q increases, L1 due to the fluid action decreases proportionally, and L2 due to the magnetic action remains constant. As described above, the flow rate Q can be adjusted by the control unit 24 controlling the pressure reducing valve 20b.

As shown in Figure 6(b), as the fluid specific heat increases, L1 due to fluid action decreases proportionally, and L2 due to magnetic action remains constant.

Figure 7 is a graph showing the output current to the coil 16, i.e., the heating capacity of the heating device 10 due to the AC current I described above. As shown in Figure 7, as the AC current I increases, L1 due to the fluid action and L2 due to the magnetic action each increase in proportion to the square. As described above, the AC current I can be adjusted by the control unit 24 controlling the inverter 18.

In this way, the heating capacity due to fluid action and the heating capacity due to magnetic action can be adjusted not only in the design stage but also during operation in the heating device 10. For example, if the printed circuit board 12 contains significantly more metal parts 12a than resin parts 12b, or if it is desired to heat the metal parts 12a with a focus, it is advisable to relatively strengthen the magnetic action. Conversely, if the printed circuit board 12 contains significantly more resin parts 12b than metal parts 12a, or if it is desired to heat the resin parts 12b with a focus, it is advisable to relatively strengthen the fluid action. The horizontal axis parameters in the above graphs can be adjusted not only independently, but also in a cooperative manner with multiple parameters, or can be linked to the temperature measured by the temperature detection means 22.

The coils 16 described above are configured so that fluid supplied from the lower end is sprayed from the upper end through the nozzle 34, but as with the coil 16a in the heating device 10A according to the modified example of FIG. 8, the fluid supplied from the end may be directed upward from the lower end and then sprayed through the nozzle 34. The object to be heated by the heating devices 10 and 10A is not limited to the printed circuit board 12, and the heating devices 10 and 10A can be used suitably and generally for objects that include metal and non-metal parts.

The present invention is not limited to the above-described embodiment, and can of course be freely modified without departing from the spirit of the present invention.

10, 10A Heating device 12 Printed circuit board (object to be heated)
12a: Metal part 12b: Resin part (non-metal part)
14 Metal pipe 16, 16a Coil 18 Inverter (power source)
20 Fluid source 20a Compressor 20b Pressure reducing valve 22 Temperature detection means 24 Control unit 26 Flexible pipe 28 Pipe 32 Conductor 34 Nozzle

Claims (9)

A heating device for heating an object to be heated,
A coil made of a metal pipe;
A power source that applies an alternating current to the coil;
a fluid source that supplies a fluid from one side of the metal pipe;
Equipped with
A heating device characterized in that the object is heated by a magnetic flux generated by the coil, and the object is heated by a fluid ejected from a nozzle which is the other end of the metal pipe. A temperature detection means for measuring the temperature of the object to be heated;
A control unit that adjusts an AC current supplied to the coil based on the temperature of the object obtained from the temperature detection means;
The heating device according to claim 1 , further comprising: A temperature detection means for measuring the temperature of the object to be heated;
a control unit that adjusts a flow rate of the fluid supplied to the metal pipe based on the temperature of the object obtained from the temperature detection means;
The heating device according to claim 1 or 2, further comprising: A temperature detection means for measuring the temperature of the object to be heated;
A control unit that adjusts a gap between the coil and the object to be heated based on the temperature of the object to be heated obtained from the temperature detection means;
The heating device according to any one of claims 1 to 3, further comprising: a control unit that adjusts the AC current supplied to the coil and the flow rate of the fluid supplied to the metal pipe;
The heating device according to claim 1 , wherein the control unit stops the AC current to the coil while supplying the fluid to the metal pipe according to a condition of the object to be heated. The heating device according to any one of claims 1 to 5, characterized in that the fluid is an inert gas. One end of the metal pipe is directly connected to the fluid source or is connected to the fluid source via a flexible pipe;
7. The heating device according to claim 1, wherein the power source and the coil are electrically connected by a conductor. The object to be heated is a printed circuit board,
8. The heating device according to claim 1, wherein a plurality of the coils are provided, and the nozzle is directed toward the printed circuit board. The heating device according to claim 8, characterized in that the nozzle is directed toward the resin portion of the printed circuit board.

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