A dual heat source vacuum reflow furnace

Abstract

The present invention discloses a dual-heat-source vacuum reflow furnace, comprising a furnace body, wherein a heating zone is arranged in the furnace body; a conveying device, on which a sample is fixed, and wherein the conveying device conveys the sample from one end of the furnace body to the other end of the furnace body; a first heat source and a second heat source, which are arranged in the heating zone and are used to provide a temperature for sample welding, wherein the first heat source provides hot air heating and the second heat source provides radiant heat, and the combined effect of the first heat source and the second heat source causes the furnace body to heat up quickly and the temperature to be more uniform, so as to improve the welding quality of the sample.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, and in particular to a vacuum reflow furnace for eutectic welding of semiconductor elements. Background Art

[0002] Eutectic welding technology is widely used in the electronic packaging industry, such as bonding between chips and substrates, bonding between substrates and tube shells, and tube shell capping. Compared with traditional epoxy conductive adhesive bonding, eutectic welding has the advantages of high thermal conductivity, low thermal resistance, fast heat transfer, strong reliability, and high strength after bonding. It is suitable for the interconnection between chips and substrates, and substrates and tube shells in high-frequency and high-power devices.

[0003] With the rapid development of LED technology, LED chips and packages are increasingly moving towards high power and integration. The traditional silver glue bonding process can hardly meet the welding process requirements of LED chips. Therefore, more and more LED packaging manufacturers have begun to try other more advanced welding processes to achieve the bonding of LED chips and brackets. Among them, eutectic welding technology is generally considered to have good application prospects.

[0004] However, since the eutectic melting point of LED chips is about 300°C or above, the existing LED chip eutectic welding equipment generally uses a hot air reflow furnace as a heating device, which has a slow heating speed and a relatively low maximum temperature. In addition, there is also a solution using infrared welding technology in the prior art. Although this solution has the advantages of convenient heat source control and easy control of heating speed, it also has many disadvantages, such as more photosensitivity points will be shielded, less uniform heating, different quality of components and PCB will affect the heating effect, and large temperature difference. Summary of the invention

[0005] The present invention provides a dual-heat source vacuum reflow furnace, which can solve the above-mentioned defects in the prior art.

[0006] The technical solution of the present invention is as follows:

[0007] A dual-heat source vacuum reflow furnace, comprising

[0008] A furnace body, wherein a heating zone is arranged in the furnace body;

[0009] A conveying device, on which the sample is fixed, and the conveying device transports the sample from one end of the furnace body to the other end of the furnace body;

[0010] The first heat source and the second heat source are arranged in the heating zone to provide a temperature for sample welding, wherein the first heat source provides hot air heating, and the second heat source provides radiant heat. The first heat source and the second heat source work together to make the furnace body heat up quickly and the temperature more uniform, so as to improve the welding quality of the sample.

[0011] Preferably, the first heat source and the second heat source heat the sample from different directions of the conveying device respectively.

[0012] Preferably, the first heat source includes a plurality of resistance wires, which are evenly arranged on the front and back of the conveyor device; the second heat source includes a plurality of infrared quartz lamps, which are evenly arranged on the two sides of the conveyor device. Thermal resistance wires are installed on the top and bottom of the furnace body to generate hot air; infrared quartz lamps are installed on the left and right sides to generate radiation energy; the dual heat sources ensure that the heating plate heats up quickly and the temperature is uniform, which can quickly melt the solder paste and reduce the generation of sample void rate;

[0013] Preferably, a control system is also included, which is connected to the first heat source and the second heat source respectively. The control system controls the heat output ratio of the first heat source and the second heat source to be: 60%~75%:25%~40%, so that the heating zone of the furnace body can heat up quickly and reduce the void rate of the welding sample.

[0014] Preferably, the first heat source is symmetrically arranged at the top and bottom of the furnace body, and the second heat source is symmetrically arranged at both sides of the furnace body, so that the first heat source and the second heat source are evenly arranged in the furnace body to ensure that the heating plate is heated evenly.

[0015] Preferably, a cooling zone is also provided in the furnace body, and the cooling zone is located at the rear end of the furnace body. The sample after welding is cooled in the cooling zone. The cooling zone uses a semiconductor refrigeration chip as a cold source, which has the advantage of rapid cooling.

[0016] Preferably, a plurality of plasma fans are also provided in the furnace body to evenly distribute the heat of the resistance wire and the coldness of the semiconductor refrigeration chip.

[0017] Preferably, a heating plate is fixed on the conveying device, and the sample is placed on the heating plate for heating; the heating plate is made of silicon carbide and coated with an optical coating to increase the absorption of radiation energy so that the heating plate can heat up quickly.

[0018] Preferably, the heating plate is detachably fixed on the conveying device, so that the heating plate can be easily disassembled for cleaning and maintenance.

[0019] Preferably, a power supply is further included, and the power supply is connected to each component via a rectifier bridge to convert alternating current into direct current to supply power to each component.

[0020] Preferably, a temperature sensor is further included, and the control system controls the conveying speed of the conveying device, the output power of the first heat source and the second heat source, and the power of the fan according to the temperature information fed back by the temperature sensor.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] First, thermal resistors are installed on the top and bottom of the furnace to generate hot air; infrared quartz lamps are installed on the left and right sides to generate radiation energy; the heating device uses a heating plate made of silicon nitride and coated with an optical coating to increase the absorption of radiation energy, so that the heating plate can heat up quickly; the synergistic effect between the first heat source, the second heat source and the heating plate ensures that the heating plate heats up quickly and has a uniform temperature, which can quickly melt the solder paste and reduce the generation of sample voids.

[0023] Second, the resistance wires on the top and bottom of the furnace body are symmetrically and evenly distributed, the infrared quartz lamps on the left and right sides are symmetrically and evenly distributed, and the use of plasma fans makes the temperature distribution in the heating area more uniform. The use of resistance wires and infrared quartz lamps as heat sources reduces the cost of the vacuum reflow furnace and makes the welding process safer.

[0024] Third, semiconductor refrigeration chips are set at the top and bottom of the furnace body to achieve rapid cooling of the heating plate and rapid welding of solidified solder paste, thereby improving the welding speed.

[0025] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a cross-sectional schematic diagram of a double-heating vacuum reflow furnace according to Example 1 of the present invention;

[0027] Figure 2 is another cross-sectional schematic diagram of the double-heating vacuum reflow furnace of Example 1 of the present invention;

[0028] Figure 3 1 is a control principle diagram of a double-heating vacuum reflow furnace according to Embodiment 1 of the present invention;

[0029] Figure 4 It is a temperature rise curve diagram of the sample welding in comparative example 1 of the present invention;

[0030] Figure 5 It is a temperature rise curve diagram of the welding of the sample of Example 2 of the present invention.

[0031] Figure numerals: furnace body 100; heating zone 1; cooling zone 2; conveying device 3; temperature sensor 4; rectifier bridge 5; semiconductor refrigeration chip 6; heating plate 7; plasma fan 8; power supply 9; sample 10; first heat source 11; second heat source 12; control system 40. DETAILED DESCRIPTION

[0032] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0033] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of protection of the present invention. Improvements and adjustments made by those skilled in the art in practical applications according to the present invention still belong to the scope of protection of the present invention.

[0035] Example 1

[0036] This embodiment provides a dual heat source vacuum reflow furnace. Figure 1-Figure 3 The reflow furnace includes a furnace body 100, which is a horizontal column with a height of about 2m. A heating zone 1, a cooling zone 2, and a conveying device 3 are arranged in the furnace body 100. The conveying device 3 is located in the furnace body 100. The sample is fixed on the conveying device 3, and the conveying device 3 then transports the sample from one end of the furnace body 100 to the other end. The first heat source 11 and the second heat source 12 are arranged in the heating zone 1 to provide a temperature for sample welding. The first heat source 11 and the second heat source 12 heat the sample from different directions of the conveying device 3 respectively, so that the temperature in the furnace body 100 is more uniform.

[0037] Figure 1 It is a schematic cross-sectional diagram of a vacuum reflow furnace along the axial longitudinal section. Figure 2It is a schematic cross-sectional diagram of a vacuum reflow furnace along the axial direction.

[0038] In this embodiment, the furnace body 100 is a hollow column with two ends open, the conveyor 3 is a conveyor belt, the first heat source 11 includes a plurality of resistance wires, and the first heat sources 11 are evenly arranged on the front and back of the conveyor 3; the second heat source 12 includes a plurality of infrared quartz lamps, and the second heat sources 12 are evenly arranged on the two sides of the conveyor 3. The heat provided by the first heat source 11 is convected up and down in the furnace body 100, and the second heat source 12 provides radiant heat, so that the heating zone 1 can achieve rapid temperature rise.

[0039] In this embodiment, a control system 40 is also included. The control system 40 is connected to the first heat source 11 and the second heat source 12 respectively. The control system 40 controls the first heat source 11 and the second heat source 12 to output a predetermined heat ratio, so that the heating area 1 can achieve rapid temperature rise.

[0040] The resistance wires are evenly distributed on the front and back sides of the conveyor 3 and fixed on the top and bottom of the furnace body 100. The resistance wires are symmetrically distributed on the top and bottom of the furnace body 100, and can evenly heat the heating plate. The infrared quartz lamps are evenly distributed on both sides of the conveyor 3, fixed on the left and right side walls of the furnace body 100, and symmetrically distributed on the left and right sides to provide uniform radiation energy.

[0041] In this embodiment, a cooling zone 2 is also provided in the furnace body 100, and the cooling zone 2 is located at the rear end of the furnace body 100, i.e., the outlet end of the furnace body 100. The sample after welding is cooled in the cooling zone; the cooling zone 2 uses a semiconductor refrigeration chip 6 as a cold source. The semiconductor refrigeration chip 6 is used to cool the heating plate 7. When direct current passes through a chip made of two different semiconductor materials connected in series, heat is absorbed and released at both ends of the chip. The semiconductor refrigeration chip 6 is small in size, suitable for the limited space of the furnace body 100, has high reliability, does not generate refrigerant pollution, and can achieve a rapid cooling effect.

[0042] In this embodiment, a plurality of plasma fans 8 are also provided in the furnace body 100. The plasma fans 8 are evenly arranged at the top and bottom of the furnace body 100. The plasma fans 8 circulate the heat generated by the resistance wire in the furnace body 100, so that the sample is heated by hot air on the front and back sides. The heating zone 1 and the cooling zone 2 are arranged at the same time. The plasma fans 8 can evenly distribute the heat generated by the resistance wire in the heating zone 1, and evenly distribute the cold air generated by the semiconductor refrigeration chip 6 to the cooling zone 2. At the same time, the plasma fans 8 can also purify the atmosphere in the furnace body 100 to ensure the quality of sample welding.

[0043] Specifically, the plasma fan 8 is directly fixed to the upper and lower side walls of the furnace body 100, and the resistance wire is suspended in the furnace body 100 and located between the conveying device 3 and the plasma fan 8. For example, the resistance wire can be fixed to the upper and lower side walls of the furnace body 100 through a support rod. At the same time, the semiconductor refrigeration chip 6 is suspended in the furnace body 100 and located between the conveying device 3 and the plasma fan 8. When the plasma fan 8 located at the top of the furnace body 100 is working, the heat generated by the resistance wire and the cold generated by the semiconductor refrigeration chip 6 can be transported from top to bottom, while the plasma fan 8 located at the bottom of the furnace body 100 can transport the heat generated by the resistance wire and the cold generated by the semiconductor refrigeration chip 6 from bottom to top, which is conducive to the formation of an upper and lower circulation of hot air and cold, and improves the heating and cooling efficiency of hot air and cold.

[0044] The heating zone 1 includes a preheating zone, a constant temperature zone and a vacuum zone. The first heat source 11 is evenly arranged in the preheating zone, the constant temperature zone and the vacuum zone. The number, density and specific arrangement positions of the first heat source 11, the second heat source 12 and the plasma fan 8 can be set according to actual needs and are not used to limit the protection scope of the present invention. No further restrictions are imposed here. The vacuum can be created by filling the vacuum zone with hot inert gas, or by setting a baffle in the vacuum zone and creating the vacuum zone by evacuating. The specific method of creating the vacuum should be set according to actual needs and is not used to limit the protection scope of the present invention.

[0045] In this embodiment, a heating plate 7 is fixed on the conveying device 3, and the sample 10 is placed on the heating plate 7 for heating. The heating plate 7 is made of silicon nitride and coated with an optical coating to increase the absorption of radiation energy. The synergistic effect of the first heat source 11, the second heat source 12 and the heating plate 7 enables the heating plate 7 to heat up quickly.

[0046] The heating plate 7 is detachably fixed on the conveying device 3, which is convenient for disassembly and cleaning of the heating plate 7 and reduces maintenance costs. The heating plate 7 is provided with a clamping foot, and a corresponding clamping port is provided on the conveyor belt, and the heating plate 7 is detachably fixed on the conveyor belt through the clamping foot.

[0047] In this embodiment, a power supply 9 is also included. The power supply 9 is connected to various components through a rectifier bridge 5 to supply power to the first heat source 11 , the second heat source 12 , the semiconductor refrigeration chip 6 , and the plasma fan 8 .

[0048] The furnace body 100 also includes a temperature sensor 4. The control system 40 controls the conveying speed of the conveying device 3, controls the output power of the first heat source 11 and the second heat source 12, and controls the power of the plasma fan 8 according to the temperature information fed back by the temperature sensor 4. Specifically, the temperature sensor 4 immediately feeds back the temperature of the heating zone 1. When the temperature in the heating zone 1 is lower than the preset value, an electrical signal is given to the control system 40. The control system 40 controls to reduce the conveying speed of the conveying device 3, increase the power of the first heat source 11 and the second heat source 12, or reduce the power of the plasma fan 8 according to the size of the received electrical signal, until the temperature of the heating zone 1 reaches the preset value.

[0049] Specifically, the preheating zone, constant temperature zone, vacuum zone, and cooling zone may be provided with the temperature sensors 4 to detect the temperatures of the corresponding zones. The location and quantity of the temperature sensors 4 should be set according to actual needs and are not limited here.

[0050] The vacuum welding equipment used for semiconductor chips is high-end equipment with high equipment cost. The existing equipment uses resistance wire heating. Due to the high cost and high power of resistance wire, when too many resistance wires are laid, the cost of the equipment increases, and the layout of the circuit is high, which poses risks.

[0051] Comparative Example 1

[0052] LED chips were selected as welding samples, and eutectic welding was performed using the hot air reflow heating equipment FCR3003-0203FCR produced by Anhui Funais Electromechanical Technology Co., Ltd., with single resistance wire heating and a heating rate of 120°C / min in the preheating zone. The time it took for the sample to pass through heating zone 1 and cooling zone 2 was 6 minutes.

[0053] In this comparative example, the heating curve of heating zone 1 is shown in FIG. Figure 4 , the void rate of the sample after welding is 10%.

[0054] Example 2

[0055] Four LED chips were selected as welding samples, and eutectic welding was performed respectively using the dual heat source vacuum reflow furnace in Example 1. Four groups of experiments were performed, wherein:

[0056] Group A: The heat output of the first heat source 11 and the second heat source 12 in the heating zone 1 is: 60% hot air + 40% radiant heat, the heating rate in the preheating zone is 185℃ / min, the cooling rate in the cooling zone is 100℃ / min, and the time for the sample to pass through the heating zone 1 and the cooling zone 2 is 250-300 seconds. The void rate of the sample after welding is tested to be 8%.

[0057] Group B: The heat output of the first heat source 11 and the second heat source 12 in the heating zone 1 is: 65% hot air + 35% radiant heat. The heating rate in the preheating zone is 190℃ / min, the cooling rate in the cooling zone is 100℃ / min, and the time for the sample to pass through the heating zone 1 and the cooling zone 2 is 250-300 seconds. The void rate of the sample after welding is 6%.

[0058] Group C: The heat output of the first heat source 11 and the second heat source 12 in the heating zone 1 is: 70% hot air + 30% radiant heat. The heating rate in the preheating zone is 200℃ / min, the cooling rate in the cooling zone is 100℃ / min, and the time for the sample to pass through the heating zone 1 and the cooling zone 2 is 250-300 seconds. The void rate of the sample after welding is tested to be 3%.

[0059] Group D: The heat output of the first heat source 11 and the second heat source 12 in the heating zone 1 is: 75% hot air + 25% radiant heat. The heating rate in the preheating zone is 200℃ / min, the cooling rate in the cooling zone is 100℃ / min, the time for the sample to pass through the heating zone 1 and the cooling zone 2 is 250-300 seconds, and the void rate of the sample after welding is tested to be 5%.

[0060] Draw the temperature rise curves of group A, group B, group C, and group D respectively, as shown in Figure 5 shown.

[0061] The samples welded by the existing equipment have high void rate, slow heating speed, and unstable temperature fluctuation in the furnace, resulting in poor quality of the samples after welding. Figure 4 In comparative example 1, the temperature fluctuation range in the constant temperature zone reaches ±3-4 degrees. However, the device of embodiment 1 is used to heat the sample from the front, back, left and right sides at the same time through dual heat sources, and when the sample is heated by hot air heating and radiation heating, the furnace body 100 can maintain the heating zone at a constant temperature after reaching the preset temperature, and the heating speed is fast and the temperature in the furnace is uniform, thereby improving the quality of sample welding and reducing the void rate. Figure 5 , which is a temperature rise curve diagram of the four groups of experiments in Example 2, among which the temperature rise rates of Group A and Group C are fast, and the soldering void rates of Group C and Group D are low. When the heat of the vacuum reflow furnace is 70% hot air + 30% radiant heat, the temperature rise rate is fast and the void rate generated is as low as 3%, which greatly improves the reliability of the device and reduces the thermal resistance.

[0062] The test method for void ratio is as follows: the baked filament sample is placed into XRD, and the ratio of the void area to the overall area is the void ratio. The void ratio can be directly read from XRD.

[0063] The above disclosure is only the preferred embodiment of the present invention. The preferred embodiment does not describe all the details in detail, nor does it limit the invention to the specific implementation method described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A dual heat source vacuum reflow furnace, characterized in that: include A furnace body, wherein a heating zone is arranged in the furnace body; A conveying device, on which the sample is fixed, and the conveying device transports the sample from one end of the furnace body to the other end of the furnace body; The first heat source and the second heat source are arranged in the heating zone to provide a temperature for sample welding, wherein the first heat source provides hot air heating, and the second heat source provides radiant heat, and the first heat source and the second heat source work together to make the furnace body heat up quickly and the temperature more uniform, so as to improve the welding quality of the sample; A control system, wherein the control system is connected to the first heat source and the second heat source respectively, and the control system controls the heat ratio of the first heat source to the second heat source to be 70%:30%.

2. The dual heat source vacuum reflow furnace according to claim 1, characterized in that: The first heat source and the second heat source heat the sample from different directions of the conveying device respectively.

3. The dual heat source vacuum reflow furnace according to claim 1 or 2, characterized in that: The first heat source includes a plurality of resistance wires, which are evenly arranged on the front and back sides of the conveying device; the second heat source includes a plurality of infrared quartz lamps, which are evenly arranged on two sides of the conveying device.

4. The dual heat source vacuum reflow furnace according to claim 1, characterized in that: A cooling zone is also provided in the furnace body, and the cooling zone is located at the rear end of the furnace body. The sample after welding is cooled in the cooling zone. The cooling zone uses a semiconductor refrigeration chip as a cold source.

5. The dual heat source vacuum reflow furnace according to claim 1, 2 or 4, characterized in that: A plurality of plasma fans are also arranged in the furnace body.

6. The dual heat source vacuum reflow furnace according to claim 1, characterized in that: A heating plate is fixed on the conveying device, and the sample is placed on the heating plate for heating; the heating plate is made of silicon nitride and coated with an optical coating.

7. The dual heat source vacuum reflow furnace according to claim 6, characterized in that: The heating plate is detachably fixed on the conveying device.

8. The dual heat source vacuum reflow furnace according to claim 1, characterized in that: It also includes a power supply, which is connected to various components through a rectifier bridge.

9. The dual heat source vacuum reflow furnace according to claim 1, characterized in that: It also includes a temperature sensor. The control system controls the conveying speed of the conveying device, the output power of the first heat source and the second heat source, and the power of the fan according to the temperature information fed back by the temperature sensor.

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