Lightning protection high-power TVS ceramic chip package method and package structure

Abstract

A lightning protection high-power TVS ceramic chip packaging method and packaging structure, belonging to the technical field of microelectronic device packaging. A structure in which a ceramic shell matches a metal shell is selected as the packaging shell. The periphery of the packaging shell is a ceramic shell, and the upper and lower parts are metal shells; the ceramic shell is designed into a Chinese character "ri" shaped ceramic shell, and a metal heat sink and a metal outer electrode are respectively embedded in two through holes. The lower ends of the two metal blocks serve as ceramic chip packaging electrode pins; the upper ends of the two metal blocks are used for assembling the TVS chip and bonding the bonding copper sheet. The height of the sealing frame is greater than the height after the TVS chip and the bonding copper sheet are bonded, forming a TVS chip assembly inner cavity; the metal cover plate serves as the upper cover plate of the ceramic chip packaging shell. It solves the problems that the existing metal hermetic packaging and plastic packaging transient voltage suppression diodes have small transient peak power and poor heat dissipation capacity, and cannot meet the lightning protection requirements of airborne equipment. It is widely used in the lightning protection technology of equipment.

Description

Technical Field

[0001] This invention belongs to the field of microelectronic device packaging technology, and more specifically relates to the field of high-power transient voltage suppressor diode (TVS) ceramic surface mount packaging technology. In particular, it relates to a lightning protection high-power TVS ceramic surface mount packaging method and packaging structure. Background Technology

[0002] Lightning is a significant factor in the electromagnetic environment, posing a serious threat to the normal operation of airborne equipment and the safety of personnel. With the rapid development of modern electronic information technology, the safety and reliability requirements for airborne equipment in electromagnetic environments are becoming increasingly stringent. To standardize the lightning protection design of airborne equipment and ensure the safety of equipment and personnel, standards concerning "Environmental Conditions and Test Procedures for Airborne Equipment" have been established. Lightning protection testing of airborne equipment involves simulating real lightning environments in a laboratory to examine and verify the ability of airborne equipment, such as the entire aircraft and its components, to withstand direct and indirect effects.

[0003] As airborne equipment has increasingly stringent requirements for lightning protection, existing transient voltage suppressor diodes with metal hermetically sealed or plastic encapsulation have low transient peak power and poor heat dissipation capabilities. Under rapid thermal shock, internal leads (such as bonding wires) may break, the package shell may crack, or even explode. There is an urgent need for a ceramic surface mount package that can withstand extremely high transient power and extremely rapid thermal shock, and has high integration, stability, and reliability.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The technical problem to be solved by this invention is to address the issue that existing metal-sealed and plastic-encapsulated transient voltage suppression diodes have low transient peak power and poor heat dissipation capabilities, which cannot meet the lightning protection requirements of airborne equipment.

[0006] The objective of this invention is to utilize the inherent excellent electrical insulation, high-strength mechanical properties, good airtightness, and superior chemical stability of ceramic materials to design and manufacture integrated, highly stable, and reliable high-power TVS ceramic surface-mount packaged devices for lightning protection of airborne equipment, thereby meeting the following requirements for lightning protection of airborne equipment: (1) Extremely high transient power: The test waveform in the standard "Environmental Conditions and Test Procedures for Airborne Equipment" contains peak currents of hundreds to thousands of amperes. When the TVS is clamped, the huge energy will generate extremely high heat on the chip instantly.

[0007] (2) Extremely rapid thermal shock: Energy is injected within microseconds, causing the chip junction temperature to rise sharply. The package must remove the heat from the chip in a very short time, otherwise the chip will be damaged due to local overheating.

[0008] (3) Huge electrical and mechanical stress: The internal leads (such as bonding wires) of the package are generally made of gold or aluminum wire, which are long and thin. When a transient large current passes through the internal leads, it may cause them to vibrate or even break. At the same time, due to the mismatch of the coefficients of thermal expansion between the package materials, they are prone to cracking or delamination under rapid thermal shock.

[0009] (4) Under lightning conditions, the transient voltage peak that the package withstands is very high, up to several kilovolts, which places high demands on the insulation of the package.

[0010] (5) Extremely low impedance and parasitic inductance are required. The test waveform contains transient peak current of hundreds to thousands of amperes. Otherwise, the package will have an excessively high voltage drop due to impedance and parasitic inductance. This voltage is superimposed on the TVS chip voltage, resulting in the total voltage actually applied to the protected circuit being much higher than the nominal clamping voltage of the TVS chip, thus causing the protection to fail.

[0011] (6) The lightning environment is very harsh, and the requirements for the integration, stability and reliability of the package are high.

[0012] Therefore, this invention provides a method for high-power TVS ceramic surface mount packaging for lightning protection. The method includes the following steps: (1) Based on the characteristics of lightning protection and high-power efficient heat dissipation, a structure matching the ceramic shell and the metal shell is selected as the encapsulation shell. The four sides of the encapsulation shell are ceramic shells, and the top and bottom are metal shells.

[0013] (2) Based on the structure of the two electrodes of the PN junction of the high-power TVS chip, the ceramic shell is designed as a H-shaped ceramic shell. Two metal blocks with matching shapes and sizes are embedded in the two through holes of the H-shaped ceramic shell. The lower ends of the two metal blocks are higher than the lower end of the ceramic shell, serving as the two electrode pins of the PN junction of the TVS chip, i.e., the electrode pins of the ceramic surface mount package. The upper ends of the two metal blocks penetrate the ceramic shell, with one metal block being higher than the thickness of the TVS chip assembly of the other metal block, forming the TVS chip assembly surface with the upper end of the ceramic shell.

[0014] (3) Mount the TVS chip on the end face of the low metal block.

[0015] (4) A copper sheet is used instead of the bonding wire in conventional bonding as a bonding copper sheet. The size of the bonding copper sheet is matched with the upper electrode and bonding distance of the TVS chip.

[0016] (5) Bond one end of the bonding copper sheet to the upper electrode of the TVS chip and the other end to the upper surface of the high metal block.

[0017] (6)Design a metal frame that matches the shape and size around the ceramic shell as the sealing frame. The height of the sealing frame is greater than the height after the TVS chip is bonded with the bonding copper sheet, forming an inner cavity for assembling the TVS chip.

[0018] (7)Design a metal cover plate that matches the shape and size around the sealing frame as the upper cover plate of the ceramic patch package shell.

[0019] The described lightning protection high-power TVS ceramic patch package structure is as Figures 1-6 shown. It includes: Metal heat sink 1, metal outer electrode 2, ceramic body 3, sealing frame 4, cover plate 5, TVS chip 6, bonding copper sheet 7.

[0020] The metal heat sink is in the shape of a double convex platform. The upper convex platform is the welding area for the TVS chip, and the lower convex platform is the pad for the outer pin of the ceramic patch package.

[0021] The metal outer electrode is in the shape of a double convex platform. The upper convex platform of the metal outer electrode is higher than the upper convex platform of the metal heat sink, and the height difference is consistent with the sum of the thickness of the TVS chip and its welding layer, which is the welding area for one end of the bonding copper sheet. The lower convex platform is the pad for another outer pin of the ceramic patch package.

[0022] The ceramic body is in the shape of a Chinese character 'Ri'. The middle ring plate and the upper convex platform of the metal heat sink, and the middle ring plate and the upper convex platform of the metal outer electrode are embedded in the ceramic body.

[0023] The sealing frame is an annular metal frame that matches the outer ring of the ceramic body. The lower end of the sealing frame is hermetically connected to the upper outer ring of the ceramic body. The height of the sealing frame is greater than the thickness after the TVS chip is bonded with the bonding copper sheet.

[0024] The TVS chip is welded on the surface of the upper convex platform of the metal heat sink.

[0025] One end of the bonding copper sheet is bonded on the upper surface pad of the TVS chip, and the other end is bonded on the upper surface of the upper convex platform of the metal outer electrode.

[0026] The cover plate is a metal cover plate that matches the shape and size of the upper end of the sealing frame. The metal cover plate is hermetically connected to the upper end face of the sealing frame.

[0027] It has insulation with a voltage of up to several thousand volts.

[0028] The metal heat sink and metal outer electrode with large thickness and size, and the TVS chip is directly welded on the metal heat sink, ensuring sufficient heat dissipation capacity.

[0029] The bonding copper sheet is thick and short, with low resistivity and strong ability to withstand transient high currents; the bonding copper sheet has a large contact area with the TVS chip and the metal external electrode 2, the welding is reliable, the bonding strength is high, which can greatly improve the ability to withstand extremely high transient power and extremely fast thermal shock, and avoid melting.

[0030] 4. Under the premise of ensuring insulation, the distance between the metal heat sink and the metal external electrode is close; the resistivity of the bonded copper sheet is low, achieving the shortest current loop and ensuring extremely low impedance and parasitic inductance.

[0031] 5. The ceramic-encapsulated components have highly matched coefficients of thermal expansion, preventing cracking or delamination under rapid thermal shock, thus ensuring airtightness and structural integrity. Furthermore, each component possesses high mechanical strength and excellent chemical stability, ensuring stability and reliability.

[0032] 6. The bonding area within the ceramic package cavity adopts a stepped geometric configuration. One electrode of the TVS chip is soldered to the metal heat sink 1, and the other electrode is soldered to one end of the bonding copper sheet. The other end of the bonding copper sheet is soldered to the external metal electrode 2. The metal heat sink 1 and the external metal electrode 2 form a hierarchical topology, one low and one high, which greatly solves the influence of different chip thicknesses on the height difference of the bonding surface, thereby ensuring that the device achieves excellent structural reliability.

[0033] 7. Adjusting the number of TVS chips integrated into the package can achieve both integration and meet the different lightning protection requirements of airborne equipment, providing flexibility and forming a series of packages that meet different peak power requirements.

[0034] High-power TVS (Transient Voltage Suppressor) ceramic surface mount packages for lightning protection of airborne equipment require good electrical isolation, highly matched thermal expansion coefficients between package materials, the ability to withstand transient high current or high voltage, good heat dissipation, extremely low impedance and parasitic inductance, bonding copper sheets as internal leads, high bonding strength, strong ability to withstand transient high current, and integrated protection functions.

[0035] Under high-voltage conditions, it can withstand extremely high transient power and rapid thermal shock, protecting downstream loads from damage caused by abnormally high voltages while maintaining its own structural and electrical integrity. It is widely used in lightning protection technology for equipment. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the ceramic surface mount package.

[0037] Figure 2 This is a schematic diagram showing the structural relationship of the components in a ceramic surface mount package.

[0038] Figure 3 This is a schematic diagram of a metal heat sink and a metal external electrode structure.

[0039] Figure 4 This is a schematic diagram showing the structural relationship between various components, TVS chip, and bonding copper sheet in a ceramic surface mount package.

[0040] Figure 5 This is a schematic diagram of the assembly of a ceramic surface mount TVS chip and its bonding copper sheet.

[0041] Figure 6 This is a schematic diagram of the internal cavity, bottom surface, cross-section, and connection relationship between the inner and outer surfaces of a ceramic surface mount packaging frame.

[0042] Figure 7 This is a schematic diagram of the current-time variation waveform in the standard "Environmental Conditions and Test Procedures for Airborne Equipment".

[0043] Figure 8 This is a schematic diagram illustrating the working principle of the PN junction VI characteristic of a TVS transient voltage suppressor diode.

[0044] Figure 9 This is a schematic diagram showing the current-voltage variation over time after the reverse breakdown of the PN junction of a TVS transient voltage suppressor diode.

[0045] Figure 10 A schematic diagram of a circuit structure in which a ceramic surface mount package is connected in parallel across the load terminals of an airborne device.

[0046] In the diagram: 1 is the metal heat sink, 2 is the metal external electrode, 3 is the ceramic body, 4 is the sealing frame, 5 is the cover plate, 6 is the TVS chip, and 7 is the bonding copper sheet.

[0047] A is the top surface of the metal heat sink, A1 is the bottom surface of the metal heat sink, B is the top surface of the metal external electrode, and B1 is the bottom surface of the metal external electrode. Detailed Implementation

[0048] like Figures 1-10 As shown, the specific implementation method of the high-power TVS ceramic surface mount package structure and packaging method for lightning protection is as follows: The metal heat sink 1, metal external electrode 2, ceramic body 3, sealing frame 4, cover plate 5, and bonding copper sheet 7 are square in shape.

[0049] The metal heat sink 1 is a CPC copper-molybdenum copper-copper composite material.

[0050] The outer metal electrode 2 is made of 4J29 iron-nickel alloy.

[0051] The ceramic body 3 is alumina ceramic.

[0052] The sealing frame 4 is made of 4J29 iron-nickel alloy.

[0053] The cover plate 5 is made of 4J42 iron-nickel alloy.

[0054] The sealing frame 4 and the cover plate 5 are connected by parallel seam welding.

[0055] The bonding copper sheet 7 is a gold-plated bonding copper sheet.

[0056] CPC copper-molybdenum copper-copper composite material features high thermal conductivity, adjustable coefficient of thermal expansion, excellent mechanical strength and reliability, making it an ideal heat sink material. It can effectively dissipate heat, ensure stable operation of TVS chips, reduce thermal stress, and is suitable for the harsh environment of airborne equipment.

[0057] 4J29 iron-nickel alloy has the characteristics of high matching with the thermal expansion coefficient of alumina ceramic, excellent airtightness and good mechanical strength. It ensures that the interface stress is minimal after sealing from room temperature to high temperature, without cracking or leakage, achieving long-term reliable airtight sealing, and is easy to process and seal.

[0058] Alumina ceramics are characterized by excellent insulation, high thermal conductivity, good mechanical strength, and excellent chemical stability, making them suitable for the harsh environments of airborne equipment.

[0059] 4J42 iron-nickel alloy has the characteristics of high thermal expansion coefficient matching with alumina ceramic, excellent airtightness, and good mechanical strength.

[0060] like Figure 1 , 2 As shown, the 4J29 sealing frame is tightly connected to the alumina ceramic shell, the CPC heat sink is welded to the ceramic substrate, and the 4J42 cover plate is connected to the 4J29 sealing frame through parallel seam welding. These three key interfaces have minimal stress due to the high matching of their thermal expansion coefficients, ensuring airtightness and structural integrity.

[0061] like Figures 3-5 As shown, the TVS chip is directly soldered onto the metal heat sink, which has a large thickness and size, forming a highly efficient heat dissipation system with a short heat conduction path and a large heat dissipation area. The instantaneous high heat generated by the TVS is transferred to the CPC heat sink below through solder or sintering layer. The CPC utilizes its high lateral thermal conductivity to rapidly diffuse the heat, which is then transferred to the alumina ceramic substrate or the external environment. It has a strong ability to withstand extremely high transient power and extremely fast thermal shock. The large soldering area between the TVS chip and the metal heat sink ensures excellent bonding shear force.

[0062] like Figure 5As shown, the bonding copper sheet is thick and short, and gold-plated, resulting in low resistivity and strong ability to withstand transient high currents. The bonding copper sheet has a large contact area with the TVS chip and the external metal electrode 2, ensuring a strong weld and high bonding strength. This significantly enhances the ability to withstand extremely high transient power and rapid thermal shock, preventing melting. One electrode of the TVS chip is bonded to the metal heat sink 1, and the other electrode is bonded to the bonding copper sheet and then led to the external metal electrode 2. The assembly process is simple, with high process stability and reliability.

[0063] like Figure 7 The image shows the current / voltage waveforms in the standard "Environmental Conditions and Test Procedures for Airborne Equipment".

[0064] like Figure 8 , 9 As shown, the working principle of a transient voltage suppressor diode (TVS) is to utilize the characteristic that the current can change over a wide range while the voltage remains basically unchanged before and after the PN junction reverse breakdown state, thus playing a role in voltage stabilization.

[0065] like Figure 10 As shown, the ceramic surface mount package is connected in parallel across the load terminals of the airborne equipment. When the load is operating normally, the TVS is in the off state (high impedance state), which does not affect the normal operation of the load; when... Figure 7 The current / voltage waveform shown is applied to the airborne equipment and rapidly changes from a high-resistance state to a low-resistance state, discharging the instantaneous large current caused by the abnormally high voltage to ground, while clamping the abnormally high voltage at a lower level, thereby protecting the downstream load from damage caused by the abnormally high voltage. When the abnormally high voltage disappears, the TVS resistance returns to the high-resistance state.

[0066] Finally, it should be noted that the above embodiments are merely examples for clear illustration. This invention includes, but is not limited to, the above embodiments, and it is neither necessary nor possible to exhaustively describe all possible implementations. Those skilled in the art can make other variations or modifications based on the above description. All implementation schemes that meet the requirements of this invention are within the protection scope of this invention.

Claims

1. A method for high-power TVS ceramic surface mount packaging for lightning protection, characterized in that, It includes the following methods: (1) According to the characteristics of lightning protection and high-power efficient heat dissipation, a structure with a ceramic shell matching a metal shell is selected as the encapsulation shell. The four sides of the encapsulation shell are ceramic shells, and the top and bottom are metal shells; (2) According to the structures of the two electrodes of the high-power TVS chip PN junction, the ceramic shell is designed as a "day" - shaped ceramic shell. Two metal blocks with matching shapes and sizes are respectively embedded in the two through - holes of the "day" - shaped ceramic shell. The lower ends of the two metal blocks protrude from the lower end of the ceramic shell and serve as the two electrode pins of the TVS chip PN junction, that is, the ceramic patch - type encapsulation electrode pins. The upper ends of the two metal blocks penetrate through the ceramic shell. One metal block protrudes from the other metal block by the thickness of the TVS chip assembly, and together with the upper end of the ceramic shell, it forms the TVS chip assembly surface; (3) Mount the TVS chip on the end face of the lower metal block; (4) Use a copper sheet instead of the bonding wire in the conventional bonding as the bonding copper sheet. The size of the bonding copper sheet matches the upper - end electrode of the TVS chip and the bonding distance; (5) Bond one end of the bonding copper sheet to the upper - end electrode of the TVS chip and the other end to the upper - end face of the higher metal block; (6) Design a metal frame matching the shape and size of the four sides of the ceramic shell as the sealing frame. The height of the sealing frame is greater than the height after the TVS chip and the bonding copper sheet are bonded, forming the TVS chip assembly inner cavity; (7) Design a metal cover plate matching the shape and size of the four sides of the sealing frame as the upper cover plate of the ceramic patch - type encapsulation shell.

2. The packaging structure of the high-power TVS ceramic surface mount packaging method for lightning protection as described in claim 1, characterized in that... , including: A metal heat sink, a metal outer electrode, a ceramic body, a sealing frame, a cover plate, a TVS chip, a bonding copper sheet; The metal heat sink is in the shape of a double - convex platform. The upper convex platform is the welding area for the TVS chip, and the lower convex platform is the solder pad for the external pins of the ceramic patch - type encapsulation; The metal outer electrode is in the shape of a double - convex platform. The upper convex platform of the metal outer electrode is higher than the upper convex platform of the metal heat sink, and the height difference is consistent with the sum of the thickness of the TVS chip and its welding layer. It is the welding area for one end of the bonding copper sheet, and the lower convex platform is the solder pad for another external pin of the ceramic patch - type encapsulation; The ceramic body is in the shape of a "day". The middle ring plate and the upper convex platform of the metal heat sink, and the middle ring plate and the upper convex platform of the metal outer electrode are embedded in the ceramic body; The sealing frame is an annular metal frame, matching the outer ring of the ceramic body. The lower end of the sealing frame is hermetically connected to the upper - end outer ring of the ceramic body, and the height of the sealing frame is greater than the thickness after the TVS chip and the bonding copper sheet are bonded; The TVS chip is welded on the surface of the upper convex platform of the metal heat sink; One end of the bonding copper sheet is bonded to the pad on the upper surface of the TVS chip, and the other end is bonded to the upper surface of the upper convex platform of the metal outer electrode; The cover plate is a metal cover plate, matching the shape and size of the upper end of the sealing frame. The metal cover plate is hermetically connected to the upper - end face of the sealing frame.

3. The packaging structure of the high-power TVS ceramic surface mount packaging method for lightning protection as described in claim 2, characterized in that: The shapes of the metal heat sink, the metal outer electrode, the ceramic body, the sealing frame, the cover plate, and the bonding copper sheet are square.

4. The packaging structure of the high-power TVS ceramic surface mount packaging method for lightning protection as described in claim 2, characterized in that: The material of the metal heat sink is CPC copper - molybdenum - copper composite material.

5. The packaging structure of the high-power TVS ceramic surface mount packaging method for lightning protection as described in claim 2, characterized in that: The material of the metal outer electrode is 4J29 iron - nickel alloy.

6. The packaging structure of the high-power TVS ceramic surface mount packaging method for lightning protection as described in claim 2, characterized in that: The material of the ceramic body is alumina ceramic.

7. The packaging structure of the high-power TVS ceramic surface mount packaging method for lightning protection as described in claim 2, characterized in that: The material of the sealing frame is 4J29 iron - nickel alloy.

8. The packaging structure of the high-power TVS ceramic surface mount packaging method for lightning protection as described in claim 2, characterized in that: The material of the cover plate is 4J42 iron - nickel alloy.

9. The packaging structure of the high-power TVS ceramic surface mount packaging method for lightning protection as described in claim 2, characterized in that: The sealing frame and the cover plate are connected by parallel seam welding.

10. The packaging structure of the high-power TVS ceramic surface mount packaging method for lightning protection as described in claim 2, characterized in that: The bonding copper sheet is a gold-plated bonding copper sheet.

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