Automatic crystal bonding machine for power semiconductor and crystal bonding process thereof

Abstract

The present invention discloses an automatic die bonding machine for power semiconductors, comprising: a transmission device that runs through the entire device, with a loading area and a unloading area at both ends of the transmission device, a die bonding area between the two areas, the die bonding area being arranged in a gas protection chamber, an ultrasonic solder coating device, an automatic chip mounting device and a cooling device being arranged in sequence in the gas protection chamber along the conveying direction of the transmission device, the ultrasonic solder coating device and the automatic chip mounting device both automatically completing the solder coating and chip mounting actions through a mechanical arm. In the above manner, the present invention utilizes the high-frequency vibration of an ultrasonic soldering iron to break the oxide film, integrates the ultrasonic soldering iron, chip automatic positioning chip mounting and cooling processes, improves production efficiency and welding quality, improves chip stability, can be used for a long time at high temperatures, and also solves the problem of flux causing pollution.

Description

Technical Field

[0001] The present invention relates to the field of semiconductors, and in particular to an automatic crystal bonding machine for power semiconductors and a crystal bonding process thereof. Background Art

[0002] An important step in semiconductor packaging is die bonding, which involves bonding the chip to the lead frame or ceramic circuit board through conductive glue or silver paste to provide a heat dissipation channel, thereby preventing the chip from overheating and improving the reliability of chip operation. Currently, conductive glue, solder paste or silver paste are commonly used in the LED and power semiconductor fields.

[0003] For example, patent CN201810617835 is a fully automatic assembly line method for semiconductor die bonding and curing, which uses die bonding glue to fix the LED chip on the bracket.

[0004] For example, in the patent with application number CN201821242079.6, a dispensing component is used to apply glue to fix the chip.

[0005] These methods can be used in situations where heat dissipation requirements are not high, but they are not enough for high-power, high-temperature LEDs and automotive IGBTs, because the thermal conductivity and high-temperature aging resistance of the glue are poor and cannot be used for a long time at 250°C.

[0006] Another existing method is to use metal solder, such as lead-based solder wire Pb-5Sn-1.5Ag, which has a melting point of 295°C. However, the solder wire contains lead, which is easy to pollute the environment. At the same time, the thermal conductivity of the solder is low, making it difficult to achieve rapid heat dissipation of power semiconductors.

[0007] The patent with application number US9216478B2 mentions a zinc-based solder that can be lead-free, meet environmental protection requirements, and has high thermal conductivity. At present, it is a very suitable solder for power semiconductors. However, the solder is very easy to oxidize during the melting and coating process, thereby affecting its wetting with the chip bracket or ceramic circuit board, and flux cannot be used because the residual flux will bring pollution and other adverse effects. Therefore, the existing conventional crystal bonding method is difficult to apply to this new material. Summary of the invention

[0008] The main technical problem solved by the present invention is to provide an automatic die bonding machine and a die bonding process for power semiconductors. The high-frequency vibration of ultrasound breaks the oxide film of the solder, which meets the application of zinc-based solder in the field of power semiconductors. This can not only overcome the problem of chip stability caused by poor thermal conductivity and aging resistance of the glue, but also avoid the pollution problem of residual flux.

[0009] In order to solve the above technical problems, a technical solution adopted by the present invention is: to provide an automatic die bonding machine for power semiconductors, including: a transmission device running through the entire device, with a loading area and a unloading area at both ends of the transmission device respectively, a die bonding area is provided between the two areas, and the die bonding area is provided in a gas protection chamber, and an ultrasonic solder coating device, an automatic chip bonding device and a cooling device are provided in sequence in the gas protection chamber along the conveying direction of the transmission device, and both the ultrasonic solder coating device and the automatic chip bonding device automatically complete the solder coating and chip bonding actions through a robotic arm.

[0010] In a preferred embodiment of the present invention, the transmission device includes a transmission platform and a conveying track. The transmission platform reciprocates along the conveying track. A laser height measuring device for measuring the height of the ceramic circuit board is provided on the transmission platform.

[0011] In a preferred embodiment of the present invention, a preheating zone is provided between the loading zone and the crystal bonding zone, the temperature of the preheating zone is 150-500° C., and the preheating is performed by an infrared heating tube or a lifting heating platform.

[0012] In a preferred embodiment of the present invention, a gas circulation purification device is further included, and the gas circulation purification device includes a circulation pump and a deoxygenation purification device, and the circulation pump and the deoxygenation purification device are connected in series with the gas protection chamber.

[0013] In a preferred embodiment of the present invention, the gas in the gas protection chamber is nitrogen or argon with an oxygen content lower than 500 PPM.

[0014] In a preferred embodiment of the present invention, the ultrasonic solder coating device includes an ultrasonic soldering iron and a wire feeding device, and the wire feeding device feeds the solder wire into the surface of the ceramic circuit board below the ultrasonic soldering iron.

[0015] In a preferred embodiment of the present invention, a heating device is provided on the ultrasonic soldering iron, and the heating device heats the soldering iron to 150-600°C.

[0016] In a preferred embodiment of the present invention, the frequency of the ultrasonic soldering iron is 30-80KHZ.

[0017] In order to solve the above technical problems, another technical solution adopted by the present invention is: to provide a die bonding process of an automatic die bonding machine for power semiconductors, comprising the following steps:

[0018] 1) Load the ceramic circuit board onto the conveyor table in the loading area;

[0019] 2) The conveyor carries the ceramic circuit board into the gas protection chamber;

[0020] 3) The conveyor moves the ceramic circuit board to the bottom of the ultrasonic solder coating device and coats the solder;

[0021] 4) The conveyor table continues to move under the automatic placement device, which picks up the chip and places it at the designated position on the ceramic circuit board;

[0022] 5) After cooling by the cooling device, the crystal bonding is completed, and the conveyor moves out of the gas protection chamber and enters the unloading area for unloading.

[0023] In a preferred embodiment of the present invention, the cooling device is an air cooling device or a cooling plate with water cooling, and the cooling plate is a cooling plate that can be raised and lowered.

[0024] The beneficial effects of the present invention are as follows: the present invention utilizes the high-frequency vibration of an ultrasonic soldering iron to break the oxide film, integrates the ultrasonic soldering iron, automatic chip positioning and patching, and cooling processes, thereby improving production efficiency and welding quality, improving chip stability, enabling long-term use at high temperatures, and solving the problem of pollution caused by flux. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0026] Figure 1 It is a structural schematic diagram of a preferred embodiment of an automatic die bonding machine for power semiconductors of the present invention;

[0027] Figure 2 It is a structural schematic diagram of another preferred embodiment of the automatic die bonding machine for power semiconductors of the present invention;

[0028] Figure 3 yes Figure 1 or Figure 2 A three-dimensional diagram of a gas protection chamber in an automatic die bonding machine for power semiconductors shown;

[0029] Figure 4 It is a structural schematic diagram of a preferred embodiment of an ultrasonic solder coating device in an automatic die bonding machine for power semiconductors of the present invention.

[0030] The components in the accompanying drawings are marked as follows: loading area 1; unloading area 2; solid crystal area 3; gas protection chamber 3-1; lift cover 3-1-1; ultrasonic solder coating device 3-2; automatic mounting device 3-3; cooling device 3-4; ultrasonic soldering iron 3-2-1; wire feeding device 3-2-2; heating device 3-2-3; conveying platform 4; conveying track 5; infrared heating tube 6-1; lifting heating platform 6-2; ceramic circuit board 7; circulation pump 8; deoxygenation purification device 9. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The embodiments of the present invention include:

[0033] An automatic die bonding machine for power semiconductors, such as Figure 1 As shown, including:

[0034] The transmission device runs through the entire device, and the two ends of the transmission device are respectively a loading area 1 and a unloading area 2, and a crystal fixing area 3 is arranged between the two areas.

[0035] The transmission device includes a transmission platform 4 and a conveying track 5. The transmission platform 4 moves back and forth along the conveying track 5. Figure 3 A laser height measuring device for measuring the height of the ceramic circuit board 7 is provided on the conveying platform 4 .

[0036] A preheating zone is provided between the material loading zone 1 and the crystal bonding zone 3, and the temperature of the preheating zone is 150-500° C. The preheating is performed by an infrared heating tube 6-1 or a lifting heating platform 6-2. Figure 1 Optimize the infrared heating tube preheating method, Figure 2 The preheating method using a lifting heating table is preferred.

[0037] The solid crystal area 3 is arranged in a gas protection chamber 3 - 1 , and the gas in the gas protection chamber 3 - 1 is nitrogen or argon with an oxygen content lower than 500 PPM.

[0038] The gas protection chamber 3-1 is provided with a flip cover 3-1-1, and the flip cover 3-1-1 is made of transparent plastic or glass. Figure 3 shown.

[0039] The gas protection chamber 3-1 is provided with an ultrasonic solder coating device 3-2, an automatic patch device 3-3 and a cooling device 3-4 in sequence along the conveying direction of the transmission device. The ultrasonic solder coating device 3-2 and the automatic patch device 3-3 both automatically complete the solder coating and patching actions through a robotic arm.

[0040] like Figure 4 As shown, the ultrasonic solder coating device 3-2 includes an ultrasonic soldering iron 3-2-1 and a wire feeding device 3-2-2. The wire feeding device 3-2-2 feeds the solder wire into the surface of the ceramic circuit board 7 below the ultrasonic soldering iron 3-2-1.

[0041] The ultrasonic soldering iron 3-2-1 is provided with a heating device 3-2-3, which heats the soldering iron to 150-600° C. The frequency of the ultrasonic soldering iron is 30-80KHZ.

[0042] The ultrasonic soldering iron structure in the present invention or the ultrasonic low-temperature brazing device disclosed in the preferred patent number CN201420273661.7, the specific structure is not repeated here.

[0043] The automatic die bonding machine for power semiconductors may also include a gas circulation purification device, which includes a circulation pump 8 and a deoxygenation purification device 9. The circulation pump 8 and the deoxygenation purification device 9 are connected in series with the gas protection chamber 3-1 to form a gas circulation purification circuit to ensure a pollution-free processing environment in the gas protection chamber.

[0044] A die bonding process of an automatic die bonding machine for power semiconductors comprises the following steps:

[0045] 1) Loading the ceramic circuit board 7 onto the conveying table 4 in the loading area 1 .

[0046] 2) The conveyor platform 4 carries the ceramic circuit board 7 into the gas protection chamber 3 - 1 . The conveyor platform 4 is preheated to 150-500° C. before entering the gas protection chamber 3 - 1 .

[0047] 3) The conveyor 4 moves the ceramic circuit board 7 to the bottom of the ultrasonic solder coating device 3-2, and the ultrasonic soldering iron coats the ceramic circuit board with solder.

[0048] 4) The conveyor platform 4 continues to move under the automatic chip placement device 3 - 3 , and the automatic chip placement device 3 - 3 picks up the chip and places it at a designated position on the ceramic circuit board 7 .

[0049] 5) After cooling by the cooling device 3-4, the crystal bonding is completed, and the conveyor moves out of the gas protection chamber 3-1 and enters the unloading area 2 for unloading.

[0050] The cooling device 3-4 is an air cooling device or a cooling plate with water cooling, and the cooling plate may be a cooling plate that can be lifted and lowered.

[0051] The present invention utilizes the characteristic that high-frequency vibration of an ultrasonic soldering iron can break the oxide film, integrates the ultrasonic soldering iron, automatic chip positioning and patching, and cooling processes, thereby improving production efficiency and welding quality, improving chip stability, enabling long-term use at high temperatures, and solving the problem of pollution caused by flux.

[0052] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. An automatic die bonding machine for power semiconductors, characterized in that: include: A transmission device running through the entire device, with a loading area and a unloading area at both ends of the transmission device, a crystal solidification area being arranged between the two areas, the crystal solidification area being arranged in a gas protection chamber, an ultrasonic solder coating device, an automatic patch device and a cooling device being arranged in sequence in the gas protection chamber along the conveying direction of the transmission device, the ultrasonic solder coating device and the automatic patch device both automatically complete the solder coating and patching actions through a mechanical arm; the gas in the gas protection chamber is nitrogen or argon with an oxygen content of less than 500PPM; the ultrasonic solder coating device comprises an ultrasonic soldering iron and a wire feeding device, the wire feeding device feeds the solder wire into the surface of the ceramic circuit board below the ultrasonic soldering iron; a heating device is arranged on the ultrasonic soldering iron, the heating device heats the soldering iron to 150-600°C; the frequency of the ultrasonic soldering iron is 30-80KHZ; The transmission device includes a transmission platform and a conveying track. The transmission platform reciprocates along the conveying track. A laser height measuring device for measuring the height of the ceramic circuit board is provided on the transmission platform. A preheating zone is provided between the feeding zone and the crystal bonding zone, and the temperature of the preheating zone is 150-500°C, and the preheating is performed by an infrared heating tube or a lifting heating table; A gas circulation purification device, the gas circulation purification device comprises a circulation pump and a deoxygenation purification device, the circulation pump and the deoxygenation purification device are connected in series with the gas protection chamber; The die bonding process of the automatic die bonding machine for power semiconductors includes the following steps: 1) Load the ceramic circuit board onto the conveyor table in the loading area; 2) The conveyor table carries the ceramic circuit board into the gas protection chamber. The conveyor table is preheated to 150-500℃ before entering the gas protection chamber; 3) The conveyor moves the ceramic circuit board to the bottom of the ultrasonic solder coating device and coats the solder; 4) The conveyor table continues to move under the automatic placement device, which picks up the chip and places it at the designated position on the ceramic circuit board; 5) After cooling by the cooling device, the crystal bonding is completed, and the conveyor moves out of the gas protection chamber and enters the unloading area for unloading.

2. The die bonding process of the automatic die bonding machine for power semiconductors according to claim 1, characterized in that: The cooling device is an air cooling device or a cooling plate with water cooling, and the cooling plate may be a cooling plate that can be lifted and lowered.

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