Reflow oven

Abstract

The present invention provides a vacuum reflow furnace used when mounting electronic components on a wiring board using solder, which can prevent damage and contamination of the sealing material and allows workers to work safely. [Solution] A vacuum reflow furnace used when mounting electronic components on a wiring board using solder comprises a base plate having at least a flat upper surface and a heating means inside, a lid body arranged to cover the upper surface of the base plate and forming a vacuum space in cooperation with the base plate, a connecting means for connecting the lid body to the base plate, and a fixing means for fixing the lid body to the base plate so that it can be opened and closed, the lid body being composed of a frame member that surrounds the periphery, a glass plate covering the upper surface of the frame member, and a sealing material attached to the lower surface of the frame member, the connecting means being located at the rear of the vacuum reflow furnace and the fixing means being located at the front of the vacuum reflow furnace.

Description

[Technical field]

[0001] This invention relates to a solder reflow oven that uses solder to mount electronic components on a wiring board, and in particular to a small vacuum reflow oven used for prototyping. [Background technology]

[0002] Mounting boards equipped with electronic components are used in a variety of products, contributing to the electronicization of products. Generally, when developing a product and mass-producing the completed device, a dedicated wiring board is manufactured as the mounting board, and the necessary electronic components are assembled using an automated board mounting device. At this time, various devices have been proposed for applying cream solder to the mounting land of the wiring board and soldering the electronic components to the wiring board. These mass production devices reflow the solder in a vacuum state to remove air bubbles in the cream solder. [Patent Document 1]

[0003] However, these board mounting devices are large-scale and suitable for mass production, and are not suitable for reflowing mounted boards in prototypes during product development. In addition, electronic components have become extremely fine in recent years, and manual soldering with a soldering iron to the mounting lands of a wiring board requires advanced skills. The method of mounting electronic components on mounting lands coated with cream solder and then reflowing does not require much skill. By using cream solder suitable for mass production, it is necessary to create the temperature and vacuum pressure profile for reflow during mass production at the prototype stage. A small, manual vacuum reflow oven is required to create the final profile by prototyping with the profile expected at the prototype stage prior to mass production. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication WO2015 / 011785 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the small vacuum reflow ovens used by engineers on their work benches, the pressure inside the oven changes greatly even though it is negative pressure, and the entire reflow oven becomes hot, so the equipment must be designed with the safety of the operator in mind. In addition, there is a need for equipment that takes into consideration the damage and contamination of the O-rings, which are the sealing material for vacuum sealing. The objective of this invention is to provide a small vacuum reflow oven that allows operators to work safely despite the large pressure fluctuations inside the oven, and that prevents the O-rings, which are the sealing material, from being contaminated and damaged. [Means for solving the problem]

[0006] A vacuum reflow furnace used when mounting electronic components on a wiring board using solder comprises a base plate having at least a flat upper surface and a heating means therein, a lid body arranged to cover the upper surface of the base plate and forming a vacuum space together with the base plate, a connecting means for connecting the lid body to the base plate, and a fixing means for fixing the lid body to the base plate so as to be openable and closable, the lid body being composed of a frame member surrounding the periphery, a glass plate covering the upper surface of the frame member, and a sealant attached to the lower surface of the frame member, the connecting means being arranged at the rear of the vacuum reflow furnace, and the fixing means being arranged at the front of the vacuum reflow furnace. Furthermore, the frame member is provided with a plurality of intake and exhaust ports to which a vacuum pump and other vacuum equipment can be connected.

[0007] The connection means is composed of hinge fittings fixed to both rear side surfaces of the lid, the hinge fittings including long holes, and pins fixed uniaxially to both rear side surfaces of the base plate, the pins corresponding to the long holes of the hinge fittings, so that the lid is rotatably connected to the base plate and can be opened and closed. The hinge fittings corresponding to the pins on both rear side surfaces that serve as the rotation axis have long holes, so that the lid is lifted when the vacuum is broken and hot air is not prevented from escaping. The fixing means is a male screw member provided on the frame member and a female screw portion provided on the base plate, and prevents hot air from spraying out from the front part of the reflow furnace in a fixed state even when the vacuum is broken. Effect of the Invention

[0008] In the vacuum reflow furnace of this invention, the base plate having the heating means and the lid body which covers it and cooperates to form a vacuum space are connected by connecting means at the rear so that they can rotate, and the hinge metal fittings corresponding to the pins on both sides of the rear which act as the pivot axis are long holes, so that when the vacuum is broken the lid body is lifted and hot air flows out, but since the front of the furnace is fixed by the fixing means, the hot air does not flow out, so the hot air does not directly hit the workers and they can work safely. Also, since the vacuum sealant is attached to the underside of the frame member, it is not damaged or contaminated when the wiring board is inserted and removed. [Brief description of the drawings]

[0009] [Figure 1] A perspective view of the vacuum reflow furnace of the present invention with the lid open. [Diagram 2] Bottom view of the lid [Diagram 3] Left side view of the vacuum reflow furnace of this invention [Figure 4] FIG. 4 shows the cover in FIG. 3 open. [Diagram 5] Cross-sectional view of the lid closed and vacuum drawn [Figure 6] Cross-section of the moment the vacuum is broken [Figure 7] (a) Diagram explaining the state of the hinge metal fittings when a vacuum is applied. (b) Diagram explaining the state of the hinge metal fittings at the moment the vacuum is released. BEST MODE FOR CARRYING OUT THEINVENTION

[0010] To explain the vacuum reflow furnace 1 of the present invention with reference to the drawings, the vacuum reflow furnace 1 is composed of a base plate 10 having a flat upper surface and a heating means 12 inside, a lid body 20 arranged to cover the upper surface of the base plate 10 and forming a vacuum space in cooperation with the base plate 10, a connecting means 30 connecting the lid body 20 to the base plate 10, and a fixing means 40 for fixing the lid body 20 to the base plate 10 so that it can be opened and closed.

[0011] The base plate 10 has a rectangular plate shape with the flat surface on which the wiring board 5, which is the target of solder reflow, is mounted as the upper surface, and has built-in heating means 12. In the figure, the heating means 12 has multiple rod heaters 12 built in parallel, with their conductors 13 extending from the rear and connected to an external power supply. A thermocouple (not shown) is inserted into the base plate 10 from the side to measure the temperature, and the signal is sent to an external control device to control the temperature of the base plate 10. The material of the base plate 10 can be, but is not limited to, stainless steel or copper. The heating means 12 is not limited to a rod heater, but may be a surface heater or a device that circulates hot air.

[0012] A lid 20 is provided on the base plate 10 so as to cover the upper surface of the base plate 10 and can be opened and closed. The lid 20 is composed of a frame member 21, a glass plate 22, a glass plate holder 23, and an O-ring 26, which is a sealant, attached to the lower surface of the frame member. The frame member 21 is a frame that surrounds the upper surface of the base plate 10, and the glass plate 22 is fixed by the glass plate holder 23 via an O-ring 28, closing the upper opening of the frame member 21. The gap between the frame member 21 and the glass plate 22 is sealed by the O-ring 28, which is a sealant, provided on the upper inner peripheral surface of the frame member 21. The O-ring 26, which is a sealant, is fitted into a groove 27 and attached to the lower surface of the frame member 21, as shown in FIG. 2. By disposing the lid 20 so as to cover the upper surface of the base plate 10, the lid 20 and the upper surface of the base plate 10 are sealed via the O-ring 26, and together form a vacuum space. By attaching the O-ring 26, which is a sealing material, to the underside of the frame member 21, the O-ring 26 is not damaged or soiled with solder chips when the lid 20 is opened to insert or remove the wiring board, as compared with the case where the O-ring 26 is attached to the base plate 10 side. By making the upper opening of the lid 20, which covers the upper surface of the base plate 10 on which the wiring board 5 is mounted, into a glass plate 22, it is possible to observe the internal mounting board 5 through the glass plate 22 during reflow and to measure the temperature distribution using an infrared camera. Note that the glass plate 22 may be sealed by other means such as an adhesive without using the O-ring 28.

[0013] The frame member 21 is provided with a plurality of intake and exhaust ports 25 penetrating from the inside to the outside, allowing air to flow in and out of the vacuum space. In the perspective view of FIG. 1, two intake and exhaust ports 25 are provided on the right side of the frame member 21, and the front intake and exhaust port 25 is connected to a valve 63 that lets in air when the vacuum is broken. A filter 62 and a valve 61 are connected in series to the rear intake and exhaust port 25, and an external vacuum pump is used to suck in air from the vacuum space formed by the lid body 20 and the base plate 10 to create a vacuum state. In addition, a relief valve 63 is attached to the left side of the frame member 21, which serves to release the internal gas if the vacuum space becomes high pressure instead of a vacuum state for some reason. Other vacuum-related devices such as a compound pressure gauge can be attached.

[0014] The lid 20 also has connection means 30 on the left and right side surfaces of its rear portion. Hinge fittings 31 having long holes 33 are fixed by screws to the left and right side surfaces of the rear portion of the frame member 21, and pins 32 provided on the left and right side surfaces of the rear portion of the base plate 10 fit into the long holes 33, so that the lid 20 is supported rotatably relative to the base plate 10 about the left and right pins 32 as axes. Furthermore, the lid body 20 and the base plate 10 have fixing means 40 at their front parts. A male screw member 41, which is provided at the front part of the frame member 21 and has a knob 42 at its head and a male screw at its tip, corresponds to a female screw portion 45 provided at the front part of the base plate 10, and serves as a fixing means for fixing the lid body 20 to the base plate 10, enabling the lid body 20 to be opened and closed relative to the base plate 10. By lifting the knob 42 upward, the lid body 20 rotates and opens due to the action of the connecting means 30, and by screwing the male screw of the male screw member 41 into the female screw portion 45, the lid body 20 is fixed to the base plate 10, and the lower part of the O-ring 26 is in a state of being pressed against the upper surface of the base plate 10. A stay 51 is provided on the side of the frame member 21, and a recess at the tip of the stay 51 fits into a locking pin 53 on the side of the base plate 10, thereby maintaining the lid body 20 at a constant angle relative to the base plate 10. When closing the lid body 20, the stay knob 52 of the stay 51 is held to release the lock with the locking pin 53, and the knob 42 is turned to fix the lid body to the base plate 10.

[0015] The use of the vacuum reflow furnace 1 in a vacuum state and the operation of the furnace will be described with reference to FIGS. FIG. 5 shows a state in which the mounting board 5 is mounted on the upper surface of the base plate 10 and the cover 20 is closed. When the male screw member 41 is screwed into the female screw portion 45 of the base plate 10 and tightened, the lower part of the O-ring 26, which is a sealing material, is pressed against the upper surface of the base plate 10, and the vacuum space is sealed. In this state, the air in the vacuum space is exhausted by an external vacuum pump, and the vacuum pressure can be set to the set value. After that, the temperature of the furnace is raised to the set temperature by the action of the built-in rod heater 21, and the solder reflow of the mounting board 5 is performed. As the exhaust of the vacuum space progresses, the O-ring 26 is pressed further by the vacuum pressure and sinks, and the gap between the upper surface of the base plate 10 and the lower surface of the frame member 21 becomes smaller as shown in FIG. 7(a). At that time, the hinge metal fitting 31 and the pin 32 that rotatably connect the base plate 10 and the frame member 21 have a play in the vertical direction due to the long hole 32, so they can accommodate the sinking of the O-ring 26.

[0016] When the solder reflow is completed, valve 63 is opened to break the vacuum and introduce air into the vacuum space. At that time, the temperature of the furnace remains high as it was during reflow, so the air that entered the furnace momentarily becomes hot and expands, breaking the pressure connection between O-ring 26 and the top surface of base plate 10 and ejecting hot air. At that time, the pressure connection between the front O-ring 26 and the top surface of base plate 10 is fixed by the screwing of male screw member 41 and female screw portion 45, so hot air does not eject, but the internal hot air ejects from the gaps that have formed at the rear and both sides, as shown in Figure 6. After releasing the atmosphere, male screw member 41 is loosened, lid 20 is opened, and mounting board 5 is removed.

[0017] As explained above, in the vacuum reflow furnace of the present invention, the O-ring 26, which is the sealing material, is attached to the underside of the frame member 21, so that when the lid 20 is opened to insert and remove the wiring board, the O-ring 26 is not damaged and is not contaminated with solder chips, etc. In addition, although the hot air generated when the vacuum is broken is blown out from the sides and rear, it is prevented from being blown out from the front where the worker is located by the action of the fixing means 40, allowing safe work. [Industrial Applicability]

[0018] The vacuum reflow furnace of this invention can be used when mounting electronic components on prototype wiring boards using solder, and is particularly effective for creating profiles during reflow in mass production. It can also be used for annealing metal and resin materials. [Explanation of symbols]

[0019] 1 Vacuum reflow oven 5 Mounting board 10 Base plate 12 Heating means (rod heater) 20 Lid 21 Frame members 22 Glass Plate 23 Glass plate holder 25 Intake and exhaust vents 26 Sealing material (O-ring) 27 Groove 28 Sealing material (O-ring) 30 Connection means 31 Hinge fittings 32-pin 33 long hole 40 Fixing means 41 Male threaded member 42 Knob 45 Female thread 51 Stay 52 States Mami 53 Locking pin

Claims

1. A vacuum reflow furnace used when mounting electronic components on a wiring board using solder comprises: a base plate having at least a flat upper surface and a heating means inside; a lid body arranged to cover the upper surface of the base plate and forming a vacuum space in cooperation with the base plate; a connecting means for connecting the lid body to the base plate; and a fixing means for fixing the lid body to the base plate so that it can be opened and closed, wherein the lid body is composed of a frame member that surrounds the periphery, a glass plate that covers the upper surface of the frame member, and a sealing material attached to the lower surface of the frame member, the connecting means being located at the rear of the vacuum reflow furnace, and the fixing means being located at the front of the vacuum reflow furnace.

2. 2. The vacuum reflow furnace according to claim 1, wherein the frame member is further provided with a plurality of intake and exhaust ports extending from the inside to the outside.

3. 3. The vacuum reflow furnace according to claim 2, wherein the connection means is composed of hinge fittings fixed to both rear side surfaces of the lid body, the hinge fittings including long holes, and pins fixed to both rear side surfaces of the base plate, the pins corresponding to the long holes of the hinge fittings.

4. 4. The vacuum reflow furnace according to claim 3, wherein said fixing means comprises a male screw member provided on said frame member and a female screw portion provided on said base plate.

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