Lightning suppressor and manufacturing method thereof

Abstract

The invention provides a lightning suppressor and a manufacturing method thereof. Comprising a 15-20 [mu] m mesa tube core, one end of each of the two 15-20 [mu] m mesa tube cores is connected with an electrode lead, the two 15-20 [mu] m mesa tube cores are connected through a plurality of stacked 3-6 [mu] m mesa tube cores, and passivation protection layers are arranged on the side walls of the electrode lead, the 15-20 [mu] m mesa tube cores and the 3-6 [mu] m mesa tube cores. And the encapsulating layer is plastically encapsulated outside the suppressor. The PN junction is manufactured by adopting a diffusion process, so that the parameter stability of a single tube core is ensured; a plurality of tube cores are packaged in series and are connected to two ends of the protection circuit in parallel. And the voltage at two ends of the circuit is clamped near the forward voltage drop, so that a subsequent circuit is prevented from bearing over-high voltage. When lightning pulses arrive and transient voltage instantly rises to exceed total forward voltage drop of the suppressor, the suppressor is rapidly conducted to form a low-impedance path, and transient current is guided to a ground wire to protect sensitive devices after the suppressor is conducted.

Description

Technical Field

[0001] The present invention relates to a lightning arrester and a manufacturing method thereof. Background Art

[0002] Lightning, as a natural discharge phenomenon, poses a serious threat to power facilities and electronic devices with its instantaneous high voltage and strong current. With the development of electronic applications and electronic systems, the lightning protection method has changed from traditional passive lightning protection to active suppression. A lightning arrester is a device that protects electrical and electronic devices from being damaged by lightning or transient overvoltage in the power grid in a lightning environment. Its main function is to limit the transient overvoltage and discharge the surge current to the ground, thus ensuring the safe operation of the device. Currently, common lightning arrester components include varistors, gas discharge tubes, thyristors, etc. The design difficulties of traditional lightning arresters lie in requirements such as long-term reliability, environmental adaptability, high-energy discharge, and standard compliance. For example, a semiconductor lightning surge arrester disclosed in CN201430140Y connects multiple avalanche conduction characteristic high-speed diode chips in series or parallel and encapsulates them in a plastic package to form a semiconductor lightning surge arrester, enabling it to suppress the voltage exceeding its protection value. However, it only uses high-speed diode chips with a PNN structure, making it only have a high conduction speed and suppression ability, but with a high interfacial stress, and cracks will appear after suppressing high-voltage current, greatly reducing the device life. Summary of the Invention

[0003] To solve the above technical problems, the present invention provides a lightning arrester and a manufacturing method thereof.

[0004] The present invention is achieved through the following technical solutions.

[0005] A lightning arrester and a manufacturing method thereof provided by the present invention; including mesa die with a size of 15 - 20μm, one ends of two mesa die with a size of 15 - 20μm are respectively connected to electrode leads, and the two mesa die with a size of 15 - 20μm are connected by a number of stacked mesa die with a size of 3 - 6μm. Passivation protection layers are provided on the side walls of the electrode leads, the 15 - 20μm mesa die, and the 3 - 6μm mesa die; it also includes an encapsulation layer encapsulated outside the arrester.

[0006] The mesa die with a size of 3 - 6μm are connected in series, and the number of series connections is 3 - 20.

[0007] The material of the electrode leads is selected from molybdenum, tungsten, or tungsten alloy.

[0008] The passivation protection material is silicone rubber, polyimide, or glass, the encapsulation material is silicone potting compound, epoxy resin, or polyurethane, and the outer shell encapsulation material is silicone encapsulant, epoxy resin, or polyamide.

[0009] The potting layer is oval, and a plastic package shell is also processed outside the potting layer.

[0010] A manufacturing method of a highly reliable lightning arrester, the steps of which are as follows:

[0011] a. Phosphorus diffusion: Use an N-type single-crystal silicon wafer with a resistivity of 55-70 Ω·cm, perform phosphorus diffusion at 1400-1600 °C for 25-35 hours to form an N + N - N + silicon wafer;

[0012] b. Wafer grinding: Remove the N + layer on one side of the silicon wafer to obtain an N + N - silicon wafer with a thickness of 290-300 μm;

[0013] c. Boron diffusion: Perform boron diffusion on the N - surface to form an N + N - P + silicon wafer;

[0014] d. Sandblasting treatment: Remove the borosilicate glass layer on the boron diffusion surface;

[0015] e. Deposition of aluminum thin film layer: Divide the silicon wafer into two parts, and deposit aluminum thin films on the N + surface and the P + surface respectively. Among them, the deposition thickness of 1 / 10 of the silicon wafer is 15-20 μm, and the deposition thickness of 9 / 10 of the silicon wafer is 3-6 μm;

[0016] f. Die separation: Crack the silicon wafer into mesa die through a dicing machine or ultrasonic cutting;

[0017] g. Cleaning: Clean the surface of the die with acid, alkali or organic solvent;

[0018] h. Die mounting and sintering: Connect 3-20 dies in series and assemble them with electrode leads, and sinter in a nitrogen or inert gas environment at 630-650 °C for 5-30 minutes;

[0019] i. Etching and cleaning: Clean the die mesa with acid, alkali or organic solvent;

[0020] j. Passivation protection: Coat the passivation material and dry it;

[0021] k. Potting: Coat the potting material and cure it;

[0022] l. Package shell plastic encapsulation: Encapsulate the device with plastic encapsulation material.

[0023] The aluminum thin film deposition method is magnetron sputtering, electron beam evaporation or chemical vapor deposition.

[0024] The sintering environment is a vacuum or inert gas environment, and the sintering temperature is preferably 630 - 650 °C.

[0025] The drying temperature of the passivation material is 200 - 300 °C, and the drying time is 5 - 6 hours.

[0026] The high-temperature environment is a vacuum environment, nitrogen environment, inert gas environment, etc. The sintering temperature is 630 - 650 °C, and the sintering time is 5 - 30 min.

[0027] The beneficial effects of the present invention are as follows: The PN junction is fabricated by a diffusion process, ensuring the parameter stability of a single die; multiple dies are connected in series and encapsulated, and are connected in parallel across both ends of the protection circuit. It plays a clamping role in the circuit, clamping the voltage across the circuit near the forward voltage drop to prevent the subsequent circuit from being subjected to excessive voltage. When a lightning pulse arrives and the transient voltage instantaneously rises above the total forward voltage drop of the suppressor, the suppressor quickly conducts, forming a low-impedance path. After conduction, the transient current is directed to the ground wire to protect the sensitive device. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic structural diagram of the suppressor of the present invention;

[0029] Figure 2 It is a schematic process flow diagram of the suppressor of the present invention;

[0030] In the figure: 1 - electrode lead, 2 - mesa die with a size of 15 - 20 μm, 3 - mesa die with a size of 3 - 6 μm, 4 - passivation protection layer, 5 - potting layer, 6 - plastic package housing. DETAILED DESCRIPTION OF THE INVENTION

[0031] The technical solution of the present invention will be further described below, but the scope of protection claimed is not limited thereto.

[0032] The present invention fabricates the PN junction by a diffusion process, ensuring the parameter stability of a single die; by connecting multiple dies in series, it ensures that the clamping voltage meets the lightning protection conditions; the overall structure is an axial diode structure, and energy release and heat conduction can be better carried out through the leads; through the multi-layer protection of the passivation protection material, potting material, and outer shell plastic packaging material, both the integrity and function of the PN junction can be ensured, and the overall integrity of the device can be guaranteed during lightning strikes; the present invention can not only meet the lightning protection requirements under different voltages by adjusting the number of dies, but also improve the reliability and environmental adaptability of the device, enrich the company's device types, and open up new market directions.

[0033] The clamping voltage fluctuation range is reduced to ±5%, the thermal conductivity of the tungsten electrode lead reaches 173 W / m·K, which is 40% higher than that of the traditional copper lead. After 1000 times of 8 / 20 μs lightning strikes, the performance attenuation of the device with multi-layer packaging is <3%.

[0034] The specific structure includes a mesa die 2 with a size of 15 - 20 μm. One end of each of the two mesa dies 2 with a size of 15 - 20 μm is respectively connected to an electrode lead 1. The two mesa dies 2 with a size of 15 - 20 μm are connected by a number of stacked mesa dies 3 with a size of 3 - 6 μm. A passivation protection layer 4 is provided on the side walls of the electrode lead 1, the mesa die 2 with a size of 15 - 20 μm, and the mesa die 3 with a size of 3 - 6 μm. It also includes a potting layer 5 potted outside the suppressor.

[0035] The mesa dies 3 with a size of 3 - 6 μm are connected in series, and the number of series-connected ones is 3 - 20.

[0036] The material of the electrode lead 1 is selected from molybdenum, tungsten or tungsten alloy.

[0037] The material of the passivation layer is silicone rubber, polyimide or glass. The potting layer is silicone potting adhesive, epoxy resin or polyurethane. The material of the plastic package shell is silicone encapsulant.

[0038] The potting layer 5 is oval-shaped, and a plastic package shell is also processed outside the potting layer 5.

[0039] Example 1, the lightning protection suppressor is fabricated by the following steps:

[0040] Phosphorus diffusion: Use an N-type single-crystal silicon wafer with a resistivity of 57 Ω·cm (diameter 150 mm), place it in a diffusion furnace, introduce a phosphorus source (POCl3), and diffuse at 1500 °C for 29 hours to form an N+N-N+ structure (surface phosphorus concentration 1×10 20 cm -3 , and the resistivity of the middle layer is 57 Ω·cm).

[0041] Wafer grinding: Use a double-sided grinding machine to grind off the N + layer on one side of the silicon wafer, and retain the N+N- structure. The final thickness of the silicon wafer is 236 μm (±5 μm).

[0042] Boron diffusion: Place the silicon wafer with the N- side facing up in a diffusion furnace, introduce a boron source (BBr3), and diffuse at 950 °C for 4 hours to form an N+N-P- structure (the boron concentration of the P + layer is 5×10 19 cm -3 ).

[0043] Sandblasting treatment: Use alumina particles (particle size 50 μm) to perform sandblasting on the boron-diffused surface to remove the surface borosilicate glass layer (thickness ≤0.1 μm).

[0044] Depositing aluminum thin film layer: Divide the silicon wafer into two parts:

[0045] 1 / 10 of the silicon wafer: Use a magnetron sputtering device (power 3 kW, argon gas flow rate 50 sccm) to deposit an aluminum thin film on the N + surface with a thickness of 17 μm (±0.5 μm); 9 / 10 of the silicon wafer: Deposit an aluminum thin film on the P+ surface with a thickness of 5 μm (±0.3 μm).

[0046] Cleaving: Use an ultrasonic cutting machine (frequency 40 kHz, amplitude 30 μm) to cut the silicon wafer into mesa die with a diameter of φ2 mm.

[0047] Cleaning: Immerse the die in a mixed acid solution (HNO3:HF = 3:1) for 10 minutes to remove surface impurities, and then rinse and dry with deionized water.

[0048] Mounting and sintering: Connect 10 die (2 with 17-μm aluminum layer + 8 with 5-μm aluminum layer) in series, and assemble them with tungsten electrode leads (φ2 mm × 2 mm × φ1.2 mm) in a graphite mold; Sinter at 635 °C for 20 minutes under nitrogen protection to form an ohmic contact (contact resistance < 0.1 Ω).

[0049] Passivation protection: Immerse the sintered main structure in a silicone rubber solution (solid content 80%), coat it with a thickness of 50 μm, and dry it at 250 °C for 3 hours.

[0050] Potting: Use an organic silicone potting adhesive, perform vacuum potting and then cure at 150 °C for 2 hours to form a potting layer with a thickness of 1 mm.

[0051] Outer shell encapsulation: Use an organic silicone encapsulant (Shore A hardness 70), encapsulate it through an injection molding machine at 180 °C, and the final device size is 10 mm × 5 mm × 3 mm.

[0052] Performance test results:

[0053] Clamping voltage: 500 V ± 25 V (8 / 20 μs waveform);

[0054] Leakage current: < 1 μA (under rated voltage);

[0055] Energy tolerance: 500 J (single impact);

[0056] Lifetime: Performance degradation < 3% after 1000 impacts.

[0057] Example 2. The lightning protection suppressor is fabricated using the following steps:

[0058] Phosphorus diffusion: Use an N-type single-crystalline silicon wafer with a resistivity of 70 Ω·cm, diffuse it at 1550 °C for 28 hours to form an N+N-N+ structure (surface phosphorus concentration 1.2×1020 cm -3 )。

[0059] Abrasive disc: The thickness of the silicon wafer after grinding is 228 μm (±5 μm).

[0060] Boron diffusion: Diffusion at 980 °C for 5 hours, boron concentration in the P+ layer is 6×10 19 cm -3 。

[0061] Sandblasting treatment: Use silicon carbide particles (particle size 30 μm) to remove the borosilicate glass layer.

[0062] Deposition of aluminum thin film layer: For 1 / 10 of the silicon wafer: Magnetron sputtering deposits a 20-μm aluminum layer;

[0063] For 9 / 10 of the silicon wafer: Deposit a 5-μm aluminum layer.

[0064] Die separation: Ultrasonic cutting into φ2.5 mm die chips.

[0065] Cleaning: After cleaning with a mixed acid (H2SO4:H2O2 = 4:1), dehydrate with isopropyl alcohol.

[0066] Die mounting and sintering: 12 die chips are connected in series, tungsten electrode leads (φ2.5 mm×2 mm×φ1.5 mm), sintering at 647 °C for 16 minutes.

[0067] Passivation protection: Coating with polyimide (thickness 30 μm), drying at 200 °C for 3 hours.

[0068] Potting: Epoxy resin potting adhesive, curing at 120 °C for 3 hours.

[0069] Housing plastic encapsulation: Polyamide plastic encapsulant (melting point 260 °C), the device size after injection molding is 12 mm×6 mm×4 mm.

[0070] Performance test results:

[0071] Clamping voltage: 600 V±30 V;

[0072] Leakage current: <0.8 μA;

[0073] Energy tolerance: 600 J;

[0074] Lifetime: The attenuation is <2.5% after 1000 impacts.

[0075] This application enables the suppressor to be applicable in high electric field regions through a 15-20 μm thick aluminum layer, enhancing the carrier collection efficiency. A 3-6 μm thin aluminum layer reduces the interface stress and avoids cracks. By connecting 3-20 die chips in series, the voltage distribution is more uniform (simulation shows that the deviation of the electric field distribution is <5%). Sintering in a nitrogen environment can prevent oxidation, and the contact resistance is reduced to 1 / 3 of the traditional process.

Claims

1. A lightning suppressor and a manufacturing method thereof, characterized in that: It includes mesa die (2) with a size of 15 - 20 μm. One end of each of the two mesa die (2) with a size of 15 - 20 μm is respectively connected to the electrode lead (1). The two mesa die (2) with a size of 15 - 20 μm are connected by a number of stacked mesa die (3) with a size of 3 - 6 μm. A passivation protection layer (4) is provided on the side walls of the electrode lead (1), the mesa die (2) with a size of 15 - 20 μm, and the mesa die (3) with a size of 3 - 6 μm. It also includes a potting layer (5) potted outside the suppressor.

2. The lightning suppressor and its manufacturing method according to claim 1, characterized in that: The mesa die (3) with a size of 3 - 6 μm are connected in series, and the number of series connection is 3 - 20.

3. The lightning arrester and its manufacturing method according to claim 1, characterized in that: The electrode lead material is selected from molybdenum, tungsten or tungsten alloy.

4. The lightning arrester and its manufacturing method according to claim 1, characterized in that: The passivation protection material is silicone rubber, polyimide or glass. The potting material is silicone potting adhesive, epoxy resin or polyurethane. The outer shell potting material is silicone potting compound, epoxy resin or polyamide.

5. The lightning arrester and its manufacturing method according to claim 1, characterized in that: The potting layer (5) is oval-shaped, and a potted outer shell (6) is also processed outside the potting layer (5).

6. The lightning suppressor and its manufacturing method as claimed in claim 1, wherein: a. Phosphorus diffusion: Using an N-type single-crystal silicon wafer with a resistivity of 55 - 70 Ω·cm, phosphorus diffusion is carried out at 1400 - 1600 °C for 25 - 35 hours to form an N+N-N+ silicon wafer. b. Wafer grinding: Remove the N+ layer on one side of the silicon wafer to obtain an N+N- silicon wafer with a thickness of 290 - 300 μm. c. Boron diffusion: Perform boron diffusion on the N- surface to form an N+N-P+ silicon wafer. d. Sandblasting treatment: Remove the borosilicate glass layer on the boron diffusion surface. e. Aluminum thin film layer deposition: Divide the silicon wafer into two parts, and perform aluminum thin film deposition on the N+ surface and the P+ surface respectively. Among them, 1 / 10 of the silicon wafer has a deposition thickness of 15 - 20 μm, and 9 / 10 of the silicon wafer has a deposition thickness of 3 - 6 μm. f. Die separation: The silicon wafer is cracked into mesa die by a dicing machine or ultrasonic cutting. g. Cleaning: Clean the surface of the die with acid, alkali or organic solvent. h. Die mounting and sintering: Connect 3 - 20 die in series and assemble them with the electrode lead. In a nitrogen or inert gas environment, sinter at 630 - 650 °C for 5 - 30 minutes. i. Etching and cleaning: Clean the mesa of the die with acid, alkali or organic solvent. j. Passivation protection: Coat the passivation material and dry it. k. Potting: Coat the potting material and cure it. l. Outer shell potting: Package the device with the potting material.

7. The lightning arrester and its manufacturing method according to claim 6, characterized in that: The aluminum thin film deposition method is magnetron sputtering, electron beam evaporation or chemical vapor deposition.

8. The lightning arrester and its manufacturing method according to claim 6, characterized in that: The sintering environment is a vacuum or inert gas environment, and the sintering temperature is preferably 630 - 650 °C.

9. The lightning suppressor and its manufacturing method according to claim 6, characterized in that: The drying temperature of the passivation material is 200 - 300 °C, and the drying time is 5 - 6 hours.

10. The lightning suppressor and its manufacturing method according to claim 6, characterized in that: The high-temperature environment is a vacuum environment, nitrogen environment, inert gas environment, etc. The sintering temperature is 630 - 650 °C, and the sintering time is 5 - 30 min.

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