Reflow oven

Abstract

The present invention provides a reflow oven used for mounting electronic components onto a circuit board using solder, which has a cooling plate movement mechanism that prevents distortion of the cooling plate. [Solution] In a reflow oven used when mounting electronic components on a wiring board using solder, the oven comprises a base plate 3, a housing 4, a heating plate 30 supported by the housing with a mounting surface for mounting the wiring board as its upper surface and containing a heater 31, a cooling plate 10 provided on the lower side of the heating plate, and a moving mechanism that moves the cooling plate between a position in contact with the lower surface of the heating plate and a position separated from it. The moving mechanism is a lifting device 20 using a tube provided on the lower side of the cooling plate, and the cooling plate contains a cooling pipe 11 that circulates a refrigerant for cooling.

Description

Technical Field

[0001] The present invention relates to a cooling mechanism capable of stably raising and lowering the temperature in a reflow furnace used when mounting electronic components on a wiring board using solder.

Background Art

[0002] Mounting boards on which electronic components are mounted are used in various products and contribute to the电子化 of products. Generally, when mass-producing a completed device after developing a product, a dedicated wiring board is manufactured, and the necessary electronic components are assembled by an automated board mounting device. At that time, various devices have been proposed for applying cream solder to the mounting lands of the wiring board and soldering the electronic components to the wiring board.

[0003] However, those board mounting devices are large-scale ones corresponding to mass production and are not suitable for reflow of mounting boards in prototypes during product development. In addition, recently, electronic components have become extremely miniaturized, and skilled skills are required for manual soldering using a soldering iron on the mounting lands of the wiring board. The method of mounting electronic components on the mounting lands coated with cream solder and performing reflow does not require much skill. By using cream solder corresponding to mass production, it is required to create a temperature profile in reflow during mass production at the prototype stage. When creating a temperature profile, a device capable of raising and lowering the temperature of the mounting board during reflow in a short time is required. However, although the control of temperature rise using a heater is relatively easy, it is not easy to lower the temperature of something that has once become high in a short time.

[0004] Patent Document 1 describes a simple reflow oven apparatus filed by the present inventor in 2024 to solve the above problem. It provides a cooling plate on the underside of a heating plate on which a mounting substrate is mounted, and the cooling plate is provided with a moving mechanism that allows it to move between a position in close contact with the underside of the heating plate and a position separated from it. The moving mechanism moves the cooling plate between a position in close contact with the heating plate and a position separated from it by rotating an eccentric cam provided on the underside of the cooling plate. The cooling plate separates from the heating plate when raising its temperature and makes contact when lowering its temperature, thereby shortening the heating and cooling time. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Utility Model Registration No. 3249042 [Overview of the project] [Problems that the invention aims to solve]

[0006] The cooling plate movement mechanism described in Patent Document 1 uses an eccentric cam to bring the upper surface of the cooling plate and the lower surface of the heating plate into contact. However, only the portion of the eccentric cam surface that makes contact with the lower surface of the heating plate is strongly pressed against it, while other parts only make light contact. Over time, this causes distortion in the cooling plate, resulting in uneven contact across the entire lower surface of the heating plate. This slows down heat conduction from the heating plate, leading to longer cooling times. To resolve this, the number of eccentric cams was increased and their positions were changed, but this did not prevent the occurrence of distortion. The present invention aims to solve the above problems by providing a cooling plate movement mechanism that uniformly brings the upper surface of the cooling plate into contact with the lower surface of the heating plate and prevents distortion of the cooling plate, thereby enabling stable temperature rise and fall during reflow of mounted substrates. [Means for solving the problem]

[0007] In a reflow oven used for mounting electronic components onto a wiring board using solder, the oven comprises a base plate, a housing, a heating plate supported by the housing with a heating element built into it and a mounting surface on which the wiring board is mounted facing upward, a cooling plate provided on the lower side of the heating plate, and a moving mechanism that moves the cooling plate between a position in contact with the lower surface of the heating plate and a position separated from it. The moving mechanism is a lifting device using a tube provided on the lower side of the cooling plate, and the cooling plate has a cooling pipe built into it that circulates a refrigerant for cooling.

[0008] Furthermore, the lifting device, which includes a lid to cover the upper surface of the heating plate, is composed of a bottom plate and side plates surrounding it, a tube positioned in the space formed by the bottom plate and the side plates, and an upper plate positioned on top of the tube so as to cover the space. [Effects of the Invention]

[0009] The reflow oven of this invention features a heating plate with a built-in heater, whose upper surface is the mounting surface for the circuit board. This improves the efficiency of heat transfer from the heater to the mounted board during reflow. After the reflow of the mounted board is complete, the heating plate can be rapidly cooled by a cooling plate that is in close contact with its underside. When reheating the heating plate, the lifting mechanism moves the cooling plate to a position away from the heating plate, preventing heat from the heater from being absorbed by the cooling plate and allowing for efficient and stable heating. The cooling plate is pressed uniformly over a wide area against the heating plate by the expansion of a tube inside the lifting mechanism, preventing uneven stress on the cooling plate and thus preventing distortion. When the tube contracts, the cooling plate moves away from the heating plate, allowing the heating plate to heat up without being affected by the cooling plate. [Brief explanation of the drawing]

[0010] [Figure 1] Perspective view of the reflow oven of this invention, excluding the base plate and housing. [Figure 2] Front view showing a cross-section of the reflow oven base plate and casing. [Figure 3] Perspective view of the reflow oven with the lid open. [Figure 4] Diagram illustrating the movement of the cooling plate: (a) Diagram showing the bottom surface of the heating plate and the top surface of the cooling plate in close contact; (b) Diagram showing the bottom surface of the heating plate and the top surface of the cooling plate separated. [Figure 5] Figure 1: Exploded view diagram [Figure 6] Plan view showing the opening for the lifting device. [Figure 7] Cross-sectional view of the lifting device (a) Diagram showing the upper plate of the lifting device in the raised position (b) Diagram showing the upper plate of the lifting device in the lowered position [Figure 8] Diagrams illustrating other embodiments of the lifting device: (a) Plan view of a circular lifting device with the top plate removed (b) Plan view of a lifting device with tubes arranged in a spiral pattern, with the top plate removed [Figure 9] Diagrams illustrating a bellows-type lifting device: (a) Cross-sectional view of the lifting device with the top plate raised (b) Cross-sectional view of the lifting device with the top plate lowered [Best Mode for Carrying Out the Invention]

[0011] The reflow oven 1 of this invention will be explained with reference to the diagram. The reflow oven 1 consists of a base plate 3, a housing 4, a heating plate 30 supported by the housing 4, a lid 40 provided to cover the mounting surface 38 which is the upper surface of the heating plate 30 and on which a mounting board is placed, a cooling plate 10 provided on the lower side of the heating plate 30, and a lifting device 20 using a tube pipe 25, which is a moving mechanism for raising and lowering the cooling plate 10 to a position where it is in contact with the lower surface of the heating plate 30 and a position where it is separated from it. It also has a power supply unit that supplies power to a heater 31 built into the heating plate 30, a cooling unit that supplies cooling water, which is a refrigerant, to a cooling pipe 11 built into the cooling plate 10, an air compressor that supplies compressed air to the tube pipe 25 of the lifting device 20, and a control unit and personal computer to control them externally.

[0012] The heating plate 30 is rectangular in shape and made of copper, with its upper surface serving as the mounting surface 38 on which the mounting board 70 is mounted. In the diagram, the heating plate 30 has six rod heaters 31 built in parallel, with their wires extending from the rear of the device and connected to an external power supply. As a result, the heating plate 30 heats up as the rod heaters 31 generate heat, and this heat is transferred to the mounting board 70 mounted on the mounting surface 38, melting the solder and performing reflow soldering. A thermocouple 32 is inserted into the upper center of the heating plate 30 and connected to an external control unit to sense the temperature of the mounting surface 38 and control the temperature according to instructions from a PC. By using copper, which has good thermal conductivity, as the material for the heating plate 30, the heat from the multiple built-in rod heaters 31 can be efficiently and uniformly distributed across the entire heating plate 30. However, the material for the heating plate 30 does not have to be copper; stainless steel, aluminum, brass, etc., may also be used, and the internal heaters may be of other types, such as flat heaters, instead of rod heaters.

[0013] A lid 40 is provided on the top of the heating plate 30 so as to cover the mounting surface 38. The lid 40 consists of a frame 41, a glass plate 42, and a glass plate retainer 43. The frame 41 is a frame that surrounds the mounting surface 38 of the heating plate 30, and the glass plate 42 is fixed to the upper opening by the glass plate retainer 43. During reflow soldering, the mounted substrate 70 inside can be observed through the glass plate 42, and the temperature distribution can be measured using an infrared camera. The lid 40 is also supported on the left and right sides of its rear by hinges 44 so as to be openable and closable on the heating plate 30, and the operator can open the lid 40 by holding the opening / closing knob 47 on the front of the frame 41 to insert and remove the mounted substrate 70. Stays 45 are provided on the sides of the frame 41 and, in cooperation with locking pins 35, can maintain the lid 40 at a certain angle with respect to the mounting surface 38. When closing the lid 40, the stay knob 46 of the stay 45 is used to release the lock from the locking pin 35, and the lid is then secured to the heating plate 30 with the lower screw of the opening / closing knob 47.

[0014] The heating plate 30 is fixed with screws to the inside of the housing 4, which is located on the upper surface of the base plate 3, on both sides, with the lid 40 mounted on top. The top of the housing 4 has an opening that is almost the same shape as the mounting surface 38, and the lid 40 protrudes above the opening of the housing 4. The inner surface of the housing 4 and the outer circumference of the heating plate 30 are positioned with sufficient space between them, so that the heat from the heating plate 30 is not easily transferred to the housing 4.

[0015] The cooling plate 10 is rectangular in shape and approximately the same dimensions as the heating plate 30, and is made of stainless steel. Cooling pipes 11, which are also made of stainless steel and are the flow paths for cooling water, are built into the cooling plate 10 in an S-shape and are positioned on the upper surface of the upper plate 24 of the lifting device 20 so as to be movable by the lifting device 20 to a position in contact with the lower surface of the heating plate 30 and a position away from it. The cooling pipes 11 are connected by tubes to an external cooler at the rear end of the cooling plate 10, and the cooling water, which is the refrigerant, circulates between the cooling pipes 11 and the cooler. The heated cooling water is cooled by the cooler and supplied back into the cooling pipes 11, so that the high temperature heating plate 30 can be quickly cooled after the reflow process is completed. Through holes 13 are provided at the four corners of the cooling plate 10, and guide shafts 6, which are supported by the housing 4 and the intermediate plate 5, pass through them to guide the vertical movement.

[0016] As will be described with reference to FIGS. 6 and 7, the lifting device 20 includes a bottom plate 21, side plates 22 surrounding the periphery thereof, a tube 25 bent and disposed in the space formed by the bottom plate 21 and the side plates 22, and an upper plate 24 disposed above the tube 25 so as to cover the space. It is arranged on an intermediate base 5 supported by the housing 4 with the cooling plate 10 placed on the upper surface of the upper plate 24. In order to facilitate arranging the tube 25 in a bent state within the side plates 22 as shown in FIG. 6, a guide plate 23 may be provided on the bottom plate 21. The guide plate 23 regulates the movement of the tube 25 during assembly and during the inflow and discharge of compressed air. The tube 25 is made of a resin material or rubber material with a large shrinkage. Specifically, it is a tube 25 made of silicone rubber. One end of the tube 25 disposed inside the space is connected to a joint 26, and compressed air flows into the inside of the tube 25 from an external air compressor through an air pipe 27. The other end 28 of the tube 25 is sealed. When high-pressure compressed air flows into the tube 25 from the air compressor, the tube 25 expands in the diameter direction, raises the height from the bottom plate 21, and pushes up the upper plate 24. When the pressure of the compressed air is reduced or discharged, the tube 25 contracts, lowers the height from the bottom plate 21, and the upper plate 24 descends. Thereby, the cooling plate 10 disposed on the upper surface of the upper plate 24 moves vertically between a position in contact with the lower surface of the heating plate 30 and a position spaced apart therefrom. When the heating plate 30 cools down, it closely adheres to the lower surface of the heating plate 30 strongly due to the expansion of the tube 25, and when the temperature rises, it is spaced apart.

[0017] FIGS. 8(a) and (b) show another form of the lifting device 20. In the lifting device 20 of (a), the bottom plate 21 is circular, and the tube 25 is bent in the space surrounded by the side plates 22 and guided by the guide plate 23. The lifting device 20 of (b) also has a circular bottom plate 21, and the tube 25 is arranged in a spiral shape and guided by the guide plate 23 in the space surrounded by the side plates 22. In both forms (a) and (b) of the lifting device 20, the tube 25 is arranged in the space surrounded by the bottom plate 21 and the side plates 22, and the tube 25 expands and contracts in the diameter direction. The lifting device 50 shown in FIGS. 9(a) and 9(b) has a bellows-type tube 56 disposed longitudinally in a space surrounded by a bottom plate 51 and side plates 52, and an upper plate 54 is placed on its upper surface. Different from the tube 25, the tube 56 utilizes a bellows-type tube and thus expands and contracts in the longitudinal direction. Also in the lifting devices 20 shown in FIGS. 8(a) and 8(b) and the lifting device 50 shown in FIG. 9, when high-pressure compressed air flows into the tubes 25 and 56 from an air compressor, the tubes expand, increasing the height from the bottom plates 21 and 51 and pushing up the upper plates 24 and 54, thereby bringing the cooling plate 10 into close contact with the lower surface of the heating plate 30. When the pressure of the compressed air is reduced or discharged, the tubes 25 and 56 contract, decreasing the height from the bottom plate 21 and causing the upper plate 24 to descend, thereby separating the cooling plate 10 from the heating plate 30.

[0018] The reflow furnace of the present invention is configured by the above mechanism. At the end of reflow, the heat of the heating plate 30 is absorbed by the cooling plate 10 in close contact with its lower surface, and the temperature can be decreased in a short time, so that the temperature of the mounting substrate 70 can also be decreased in a short time. Further, during reheating, since the cooling plate 10 is moved to a position separated from the lower surface of the heating plate 30 by the lifting device 20, the heat of the bar heater 31 can be transmitted to the heating plate 30 without waste, so that the temperature can be stably increased in a short time and the temperature profile during reflow in mass production can be accommodated.

Industrial Applicability

[0019] The reflow furnace of the present invention can be used when mounting electronic components on a prototype wiring board or the like using solder, and is particularly effective for creating a profile during reflow in mass production. Further, it can also be used for annealing treatment of metal materials and resin materials.

Explanation of Reference Numerals

[0020] 1 Reflow furnace 3 Base plate 4 Housing 5 Intermediate base 6 Guide shaft 10 Cooling plate 11 Cooling pipe 13 guide holes 20 Lifting device 21 Bottom plate 22 Side panels 23 Guide plate 24 Top plate 25 tubular tubes 26 Fittings 27 Air Piping 28 The other end of the tube 30 heating plate 31 Stick Heater 32 Thermocouples 35 Locking pin 38 Mounting surface 40 Lid 41 frames 42 Glass plate 43 Glass retainer 44 Hinge 45 Stay 46 State knob 47 Cover knob 50 Bellows-type lifting device 51 Bottom plate 52 Side panel 54 Top plate 56 Bellows-type tubular tube 70 Implemented circuit boards

Claims

1. In a reflow oven used when mounting electronic components onto a circuit board using solder, A reflow oven comprising a base plate, a housing, a heating plate supported by the housing with a mounting surface for the wiring board and a built-in heater on its upper surface, a cooling plate provided on the lower side of the heating plate, and a moving mechanism that moves the cooling plate between a position in contact with the lower surface of the heating plate and a position separated therefrom, wherein the moving mechanism is a lifting device using a tube provided on the lower side of the cooling plate, and the cooling plate is characterized by having a built-in cooling pipe for circulating a refrigerant for cooling.

2. The reflow oven according to claim 1, characterized in that it comprises a lid that covers the upper surface of the heating plate.

3. The reflow oven according to claim 1, characterized in that the lifting device using the tube comprises a bottom plate and a side plate surrounding it, a tube placed in the space formed by the bottom plate and the side plate, and a top plate placed on the tube so as to cover the space.

4. The reflow oven according to claim 3, characterized in that the lifting device using the tubes further includes a guide plate for facilitating the arrangement of the tubes.

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