A metal solder layer for diode packaging and a method of manufacturing the same

Abstract

The application relates to a metal welding layer for diode packaging and a preparation method thereof, and belongs to the technical field of semiconductor packaging. The metal welding layer is prepared on the surface of a diode inner electrode by adopting a vacuum magnetron sputtering technology, the metal welding layer is a three-layer structure, and comprises a Ti adhesion layer, a Ni barrier layer and an Ag welding functional layer. The metal welding layer has high bonding strength and good density. The metal welding layer can be directly welded with a chip under a high-temperature state to realize diode packaging with small thermal resistance and low loss, and solves the technical problems in high-grade diode sealing.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power semiconductor packaging, and relates to a metal welding layer for diode packaging and a preparation method thereof, in particular to a metal welding layer suitable for diode chip welding application scenarios, and a diode welded with the metal welding layer has the characteristics of low thermal resistance, low loss and fast response. BACKGROUND

[0002] With the continuous development of modern science and technology, a large number of electronic equipment has appeared in military and civilian fields, and power components matching the electronic equipment are needed on the electronic equipment. Diodes are indispensable as an important category of components. In high-power application scenarios, diodes have a wide range of applications. Because of high conversion frequency and frequent switching, it is easy to cause excessive heat generation of diodes and long response time, causing circuit failure. At the same time, because of short service life, the use of diodes is limited. In view of this, it is necessary to prepare a diode with small thermal resistance, low loss and fast response.

[0003] At present, there are two ways for diode chip welding. One is brazing, that is, a round soldering sheet is placed between the chip and the inner electrode. After the soldering sheet reaches the melting temperature, the soldering sheet is fully melted on the surface of the chip and the inner electrode to spread and wet and diffuse between molecules, and then welding is formed. Because a large number of bubbles and cavities exist in the solder, the heat conduction efficiency is reduced, the thermal resistance value is large, and the size of the solder is not easy to control, which can easily cause short circuit of the chip and make the device fail. The other is a pressing method, that is, the chip and the inner electrode are directly contacted together, and the contact points of the chip and the inner electrode are protected by subsequent processes using glass sealing or plastic sealing. This method has poor heat conduction performance.

[0004] Based on the limitations of the above welding methods, a high-temperature-resistant metal welding layer is prepared on the surface of the inner electrode, so that the metal welding layer and the chip form a silver-silicon eutectic welding, which can effectively improve the heat conduction performance of the welding and meet the packaging requirements of low thermal resistance, low loss and fast response of high-reliability diodes. SUMMARY

[0005] The technical problem of the present application is to overcome the shortcomings of the prior art and provide a metal welding layer for diode packaging and a preparation method thereof. The metal welding layer has high bonding strength and compactness, can form effective welding with the chip at high temperature, and reduces the thermal resistance, power loss and response time of the device.

[0006] The technical solution of the present application is:

[0007] A metal welding layer for diode packaging, the metal welding layer is located on the surface of the diode inner electrode and has a three-layer structure, wherein the bottom layer is a Ti adhesion layer, the middle layer is a Ni barrier layer, and the surface layer is an Ag welding functional layer.

[0008] The thickness of the adhesion layer Ti layer is 0.1-0.3 μm, the thickness of the barrier layer Ni layer is 0.2-1.0 μm, and the thickness of the welding functional layer Ag layer is 1.0-5.0 μm.

[0009] The purity of the adhesion layer Ti layer is ≥99.99 Wt%, the purity of the barrier layer Ni layer is ≥99.99 Wt%, and the purity of the welding functional layer Ag layer is ≥99.999 Wt%.

[0010] The thickness of the metal welding layer of the diode inner electrode end surface is 1.5-2 times the thickness of the metal welding layer of the side surface.

[0011] The diode inner electrode material is tungsten or molybdenum, and the purity is ≥99.92 wt%. The diode inner electrode diameter is 0.4-3 mm, the height is 1-4 mm, and the surface roughness is not more than

[0012] A preparation method of a metal welding layer for diode packaging, comprising the following steps:

[0013] S1 surface treatment of the diode inner electrode;

[0014] S2 the diode inner electrode after surface treatment is loaded into a vacuum magnetron sputtering device for vacuum baking. The vacuum degree needs to reach 5×10 -7 torr below, the baking temperature is set at 120°C, and the holding time is 30 minutes;

[0015] S3 after the baking time reaches, Ar gas is passed, and after stabilization, the ion source is opened. The power is set at 200-300 W, ion beam cleaning is carried out, and the cleaning time is 5-10 minutes;

[0016] S4 the adhesion layer Ti layer is prepared by using the sputtering table sputtering method. The sputtering power is 200-300 W, the sputtering time is 600-1800 s, and the sputtering table rotation speed is 25 revolutions / minute. When the time reaches, the sputtering is stopped;

[0017] S5 the barrier layer Ni layer is prepared by using the sputtering table sputtering method. The sputtering power is 200-300 W, the sputtering time is 1000-5000 s, and the sputtering table rotation speed is 25 revolutions / minute. When the time reaches, the sputtering is stopped;

[0018] S6 the welding functional layer Ag layer is prepared by using the sputtering table sputtering method. The sputtering power is 150-230 W, the sputtering time is 3000-5000 s, and the sputtering table rotation speed is 25 revolutions / minute. After the sputtering time reaches, it is stopped for 600 s;

[0019] S7 repeat step S6, sputter the welding functional layer Ag layer twice, and complete the sputtering;

[0020] S8 high temperature test is conducted on the prepared metal soldering layer:

[0021] The diode inner electrode is placed in a graphite fixture, and then the temperature is heated to 860-880 DEG C through a high temperature sintering furnace for 5 minutes, if the diode inner electrode has no discoloration and peeling phenomenon, it shows that the quality of the prepared metal soldering layer is qualified.

[0022] In the step S1, the process of surface treatment of the diode inner electrode is as follows:

[0023] 1) cleaning agent cleaning:

[0024] Firstly, the diode inner electrode is placed in anhydrous acetone for ultrasonic cleaning for 10-20 minutes, then taken out, and the diode inner electrode cleaned by anhydrous acetone is cleaned by deionized water for at least 5 times to make the surface of the diode inner electrode free of residues;

[0025] Then the diode inner electrode is placed in anhydrous ethanol for ultrasonic cleaning for 10-20 minutes, then taken out, and the diode inner electrode cleaned by anhydrous ethanol is cleaned by deionized water for at least 5 times to make the surface of the diode inner electrode free of residues;

[0026] Continue to place the diode inner electrode in ammonia water with a concentration of 10%-15% for at least 10 minutes;

[0027] After taking out, the diode inner electrode cleaned by ammonia water is cleaned by deionized water for 5 times until the surface is free of residues.

[0028] 2) drying:

[0029] The diode inner electrode cleaned by the cleaning agent is placed in a nitrogen-filled oven for drying, and the drying temperature is set to 100-120 DEG C, and the time is at least 2 hours.

[0030] Compared with the prior art, the present application has the following beneficial effects:

[0031] (1) The present application provides a preparation method of metal soldering layer for diode packaging, which prepares a Ti / Ni / Ag three-layer structure metal soldering layer by a magnetron sputtering process. The metal soldering layer has high density, good uniformity, good bonding strength and high temperature resistance. The diode packaged by the metal layer has the characteristics of small thermal resistance, low loss and fast response.

[0032] (2) The present application provides a surface cleaning method for tungsten / molybdenum cylindrical diode inner electrode, which greatly improves the cleanliness and surface activity of the surface through cleaning agent cleaning and ion beam cleaning, and lays a foundation for high strength bonding of the metal soldering layer.

[0033] (3) The application formulates a reliable metal welding layer sputtering process control method, realizes low stress and uniformity growth of the metal welding layer, and ensures the bonding strength and high temperature resistance of the metal welding layer. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 High-temperature-resistant metal welding layer structure

[0035] Figure 2 Tungsten / molybdenum cylindrical diode inner electrode surface treatment process schematic diagram

[0036] Figure 3 High-temperature-resistant metal welding layer preparation process schematic diagram. DETAILED DESCRIPTION

[0037] The embodiments will be described below according to the drawings.

[0038] A metal welding layer for diode packaging is located on the surface of a diode inner electrode 1 and has a three-layer structure, wherein the bottom layer is a Ti adhesion layer 2, the middle layer is a Ni barrier layer 3, and the surface layer is an Ag welding functional layer 4.

[0039] The thickness of the Ti adhesion layer 2 is 0.1-0.3 μm, the thickness of the Ni barrier layer 3 is 0.2-1.0 μm, and the thickness of the Ag welding functional layer 4 is 1.0-5.0 μm.

[0040] The purity of the Ti adhesion layer 2 is ≥99.99 Wt%, the purity of the Ni barrier layer 3 is ≥99.99 Wt%, and the purity of the Ag welding functional layer 4 is ≥99.999 Wt%.

[0041] The diode inner electrode 1 is made of tungsten or molybdenum, and the purity is ≥99.92 wt%. The diode inner electrode has a diameter of 0.4-3 mm and a height of 1-4 mm, and the surface roughness is not more than

[0042] The metal welding layer for diode packaging has high-temperature resistance, and the metal welding layer can be used at a high temperature of 800-900℃. The metal welding layer does not have abnormal changes such as melting, delamination, blistering, discoloration, and peeling.

[0043] A method for preparing a metal welding layer for diode packaging, comprising the following steps:

[0044] a) Process tungsten / molybdenum metal material into a cylindrical body of corresponding size as a sputtered diode inner electrode;

[0045] b) Surface treatment of tungsten / molybdenum cylindrical diode inner electrode;

[0046] c) Sputtering of a metal soldering layer on the surface of the tungsten / molybdenum diode inner electrode by vacuum magnetron sputtering technology;

[0047] d) Post-evaluation of the plating layer to obtain the finished product.

[0048] In the b) step, the specific process is as follows:

[0049] 1) Cleaning with a cleaning agent, first, the tungsten / molybdenum cylindrical diode inner electrode is placed in anhydrous acetone for ultrasonic cleaning for 10 minutes, and the diode inner electrode cleaned with anhydrous acetone is cleaned with deionized water for 5 times until the surface is free of residues; then the tungsten / molybdenum cylindrical diode inner electrode is placed in anhydrous ethanol for ultrasonic cleaning for 10 minutes, and the diode inner electrode cleaned with anhydrous ethanol is cleaned with deionized water for 5 times until the surface is free of residues; continue to place the tungsten / molybdenum cylindrical diode inner electrode in 10% ammonia water for 10 minutes, and clean the diode inner electrode cleaned with ammonia water with deionized water for 5 times until the surface is free of residues.

[0050] 2) Drying, place the tungsten / molybdenum cylindrical diode inner electrode in a nitrogen-filled drying oven for drying, set the drying temperature at 120°C, and the time for 2 hours.

[0051] In the c) step, the specific process is as follows:

[0052] 1) Pre-sputtering baking, place the tungsten / molybdenum cylindrical diode inner electrode into the vacuum magnetron sputtering equipment for vacuum baking, the vacuum degree needs to reach 5×10 -7 torr below, set the baking temperature at 120°C, and keep the temperature for 30 minutes.

[0053] 2) Ion beam cleaning, after the baking time reaches, pass Ar gas (20 L / min), open the gas path valve, adjust the flowmeter to the valve control notch, and after stabilization, open the ion source, set the power at 200W-300W for ion beam cleaning, and after cleaning for 5-10 minutes, start sputtering;

[0054] 3) Preparation of the adhesion layer Ti layer (2), the sputtering power is 200-300W, the sputtering time is 1200s, and the sputtering table rotation speed is 25 revolutions / minute, and when the time reaches, stop sputtering;

[0055] 4) Preparation of the barrier layer Ni layer (3), the sputtering power is 200-300W, the sputtering time is 4000s, and the sputtering table rotation speed is 25 revolutions / minute, and when the time reaches, stop sputtering

[0056] 5) Preparation of the soldering functional layer Ag layer (4), the sputtering power is 150-230W, the sputtering time is 1500-2000s, the sputtering table rotation speed is 25 revolutions / minute, and when the time reaches, stop for 600s, repeat sputtering of the Ag layer (4) twice, and complete sputtering.

[0057] Step d) involves conducting a high-temperature test on the prepared metal weld layer. The inner electrode is placed in a graphite fixture, and then heated to 860–880°C in a high-temperature sintering furnace and held for 5 minutes. Once it is confirmed that the inner electrode does not exhibit discoloration or peeling, the quality of the prepared metal weld layer is deemed qualified.

[0058] Example:

[0059] Figure 1 As shown, the high-temperature resistant metal weld layer structure is located on the surface of the inner electrode 1 of the diode. It is a three-layer structure, with the bottom layer being an adhesion layer Ti layer 2, the middle layer being a barrier layer Ni layer 3, and the top layer being a welding functional layer Ag layer 4. The thickness of the adhesion layer Ti layer 2 is 0.2 μm, the thickness of the barrier layer Ni layer 3 is 0.7 μm, and the thickness of the welding functional layer Ag layer 4 is 3 μm. The thicknesses of the end-face adhesion layer Ti layer, barrier layer Ni layer, and welding functional layer Ag layer are all greater than the thicknesses of the corresponding layers on the sides. Generally, the thickness of the metal weld layer on the end face is 1.5-2.0 times that of the metal weld layer on the sides.

[0060] The diode's internal electrode diameter is 2.25 mm, its height is 1.95 mm, and its surface roughness is within [specific range missing].

[0061] Figure 2 The diagram shows the surface treatment process of the internal electrode of a tungsten / molybdenum cylindrical diode: ① Anhydrous acetone cleaning: The internal electrode 1 of the diode is ultrasonically cleaned in anhydrous acetone for 10 minutes, and then rinsed with deionized water 5 times until no residue remains on the surface; ② Anhydrous ethanol cleaning: The internal electrode 1 of the diode is ultrasonically cleaned in anhydrous ethanol for 10 minutes, and then rinsed with deionized water 5 times until no residue remains on the surface; ③ Ammonia water standing: The internal electrode 1 of the diode is placed in 10% ammonia water and left to stand for 10 minutes, and then rinsed with ammonia water and deionized water 5 times until no residue remains on the surface; ④ Deionized water cleaning: The internal electrode 1 of the diode is placed in deionized water and cleaned for 5 minutes; ⑤ Drying: The internal electrode 1 of the diode is placed in a nitrogen-filled oven for drying at 120℃ for 2 hours.

[0062] Figure 3 The diagram shows the preparation process of the high-temperature resistant metal welding layer. ① Pre-sputtering baking: The inner electrode of the tungsten / molybdenum cylindrical diode is installed in the vacuum magnetron sputtering equipment and vacuum baked. The vacuum degree needs to reach below 5×10-7 torr. The baking temperature is set at 120℃ and held for 30 minutes.

[0063] ② Ion beam cleaning: After the baking time is reached, purge Ar gas (20L / min), open the gas valve, adjust the flow meter to the valve control setting, and turn on the ion source after stabilization. Adjust the anode and cathode voltages to perform ion beam cleaning. Sputtering will begin after 8 minutes of cleaning.

[0064] 3) Preparation of the adhesion layer Ti layer 2, the sputtering power is 250W, the sputtering time is 1200s, the sputtering table rotation speed is 25r / min, when the time reaches, stop sputtering;

[0065] 4) Preparation of the barrier layer Ni layer 3, the sputtering power is 250W, the sputtering time is 4000s, the sputtering table rotation speed is 25r / min, when the time reaches, stop sputtering;

[0066] 5) Preparation of the welding functional layer Ag layer 4, the sputtering power is 200W, the sputtering time is 3600s, pause 600s, repeat sputtering twice for the Ag layer 4, and the sputtering is completed.

[0067] 6) High temperature test for the prepared metal welding layer, the inner electrode is placed in the graphite fixture, then the temperature is heated to 865℃ through the high temperature sintering furnace and kept for 5 minutes, after confirming that the inner electrode has no discoloration and peeling phenomenon, it is determined that the quality of the prepared metal welding layer is qualified.

[0068] The metal welding layer can directly form effective welding with the chip under high temperature state, realizes the packaging of diode with small thermal resistance and low loss, and solves the technical problem in the packaging of high-grade diode.

[0069] The part not described in detail in the application is the common knowledge of the person skilled in the art.

Claims

1. A method for producing a metal bonding layer for diode packaging, characterized by, The metal welding layer is located on the surface of the diode inner electrode (1) and has a three-layer structure, wherein the bottom layer is a Ti adhesion layer (2), the middle layer is a Ni barrier layer (3), and the surface layer is an Ag welding functional layer (4); the thickness of the Ti adhesion layer (2) is 0.1-0.3 μm, the thickness of the Ni barrier layer (3) is 0.2-1.0 μm, and the thickness of the Ag welding functional layer (4) is 1.0-5.0 μm; The preparation method comprises the following steps: S1, surface treatment of the diode inner electrode; S2 surface treatment of the diode electrode into the vacuum magnetron sputtering equipment, vacuum baking, vacuum degree to reach 5 x 10 -7 torr below, baking temperature set at 120 °C, 30 minutes; S3, after the baking time reaches, Ar gas is passed, and after stabilization, the ion source is opened, the power is set to 200-300 W, ion beam cleaning is performed, and the cleaning lasts for 5-10 minutes; S4, the Ti adhesion layer (2) is prepared by sputtering, the sputtering power is 200-300 W, the sputtering time is 600 s-1800 s, and the self-rotation speed of the sputtering table is 25 revolutions / minute; when the time reaches, the sputtering is stopped; S5, the Ni barrier layer (3) is prepared by sputtering, the sputtering power is 200-300 W, the sputtering time is 1000-5000 s, and the self-rotation speed of the sputtering table is 25 revolutions / minute; when the time reaches, the sputtering is stopped; S6, the Ag welding functional layer (4) is prepared by sputtering, the sputtering power is 150-230 W, the sputtering time is 3000-5000 s, the self-rotation speed of the sputtering table is 25 revolutions / minute, and the sputtering time reaches, and then stops for 600 s; S7, the step S6 is repeated, the Ag welding functional layer (4) is sputtered twice, and the sputtering is completed; S8, high-temperature test of the prepared metal welding layer: The diode inner electrode is placed in a graphite fixture, and then the temperature is heated to 860-880 ℃ through a high-temperature sintering furnace and kept for 5 minutes; if the diode inner electrode has no discoloration and peeling phenomenon, it indicates that the quality of the prepared metal welding layer is qualified.

2. The method for preparing a metal bonding layer for diode packaging according to claim 1, characterized in that, In the step S1, the surface treatment of the diode inner electrode is as follows: 1) cleaning agent cleaning: Firstly, the diode inner electrode (1) is placed in anhydrous acetone for ultrasonic cleaning for 10-20 minutes, then taken out, and the diode inner electrode (1) cleaned by anhydrous acetone is cleaned by deionized water for at least 5 times to make the diode inner electrode surface free of residues; Then, the diode inner electrode (1) is placed in anhydrous ethanol for ultrasonic cleaning for 10-20 minutes, then taken out, and the diode inner electrode (1) cleaned by anhydrous ethanol is cleaned by deionized water for at least 5 times to make the diode inner electrode surface free of residues; Then, the diode inner electrode (1) is placed in anhydrous ethanol for ultrasonic cleaning for 10-20 minutes, then taken out, and the diode inner electrode (1) cleaned by anhydrous ethanol is cleaned by deionized water for at least 5 times to make the diode inner electrode surface free of residues; Then, the diode inner electrode (1) is placed in anhydrous ethanol for ultrasonic cleaning for 10-20 minutes, then taken out, and the diode inner electrode (1) cleaned by anhydrous ethanol is cleaned by deionized water for at least 5 times to make the diode inner electrode surface free of residues; 2) drying: The diode inner electrode (1) cleaned by the cleaning agent is placed in a nitrogen-filled drying oven for drying, the drying temperature is set to 100-120 ℃, and the time is at least 2 hours.

3. The method for preparing a metal bonding layer for diode packaging according to claim 1, characterized in that, The purity of the Ti adhesion layer (2) is ≥99.99 Wt%, the purity of the Ni barrier layer (3) is ≥99.99 Wt%, and the purity of the Ag welding functional layer (4) is ≥99.999 Wt%.

4. The method for preparing a metal bonding layer for diode packaging according to claim 1, characterized in that, The metal solder layer thickness of the diode inner electrode (1) end face is 1.5-2 times of the side face metal solder layer thickness.

5. The method for preparing a metal bonding layer for diode packaging according to claim 1, characterized in that, The diode inner electrode (1) is made of tungsten or molybdenum with purity ≥ 99.92 wt%, the diode inner electrode has a diameter of 0.4 mm - 3 mm and a height of 1 mm - 4 mm, and the surface roughness is not more than 0.5 μm

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