Transient voltage suppression diode capable of preventing explosion during open circuit failure

Abstract

The invention provides an explosion-proof transient voltage suppressor diode in open circuit failure, which belongs to the technical field of surge protection devices and comprises a crystal grain, a first electrode and a second electrode. The insulating layer covers the non-protruding part of the inverted-T-shaped first electrode and exposes the protruding part of the first electrode; the fusible alloy sheet layer is connected with the protruding part of the first electrode; the third electrode is connected with the protruding part of the first electrode through a fusible alloy sheet layer; and the plastic package body is used for wrapping the crystal grains, the first electrode, the second electrode and the insulating layer and exposing the surfaces of the insulating layer and the second electrode. The beneficial effects are that when a surge event occurs, heat generated by grain thermal breakdown is transmitted to the fusible alloy sheet layer, the fusible alloy sheet layer is heated and fused, open circuit failure is realized, and plastic package body explosion caused by metal vaporization when the device is in open circuit failure is avoided; in addition, interference peaks generated when the device bears surge thermal breakdown failure and open circuit failure can be avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of surge protection devices, and particularly to a transient voltage suppression diode that prevents explosion during open - circuit failure. Background Art

[0002] A transient voltage suppressor (TVS) device is a semiconductor discrete device widely used in the field of power electronics, specifically for protecting electronic devices from various transient over - voltages. When in use, the TVS device is usually connected across the power supply terminals. When a momentary high - voltage pulse appears in the circuit, the TVS device connected in parallel with the protected circuit can respond quickly and clamp the voltage across its two ends at a predetermined low level, thereby protecting other components in the circuit connected across the TVS device from high - voltage impacts.

[0003] The failure modes of TVS devices are mainly divided into two types: short - circuit failure and open - circuit failure. Among them, the short - circuit failure mode mainly shows that after the device withstands a high - surge impact, the chip is broken down, resulting in a short - circuit at the power supply terminal, and then causing fire or even explosion at the power supply port. Especially with the rise of new - energy vehicles, the charging safety of new - energy vehicle batteries has attracted much attention. The short - circuit failure of TVS devices is extremely likely to cause battery charging fires, posing a great threat to battery charging safety. The open - circuit failure mode will cause the plastic package to explode, generating momentary burr - like transient interference waves at the moment of explosion, which has an adverse effect on the subsequent circuit, thus limiting the application scenarios of the device.

[0004] Most of the existing TVS devices are mainly in the short - circuit failure mode. When a large surge passes through, the short - circuit of the TVS device will cause a short - circuit of the power supply, and in severe cases, phenomena such as device fire, smoke, and explosion will occur. Although open - circuit failure TVS products have been introduced in recent years, their structures are mostly metal bonding (metal wires act as fuses) or simple combined packaging of TVS devices and fuse wires. For example, Chinese Patent Application CN114242692A discloses a transient voltage suppression diode and its circuit and system based on the open - circuit failure mode, which involves a series of fuse wires and transient voltage suppression diodes. Another example is Chinese Patent CN220775393U, which discloses a structure of a protection chip and an electronic device based on the open - circuit failure mode, which involves connecting the cathode of the transient voltage suppression diode to the Vin pin of the package through a first fuse bonding wire. When the fuse is opened due to a surge in the above - mentioned two types of structures, device explosion will occur accompanied by metal vaporization, and the surge limit ability wave of the metal wire or fuse is unstable.

[0005] In addition, when the existing TVS device with an open-circuit failure mode opens while the surge has not completely disappeared, it will cause the microelectronic components (such as MOS transistors) on the back-end integrated circuit (IC) chip to withstand the surge that has not completely disappeared, resulting in damage to the back-end due to lightning strike interference. Moreover, the surge limit capacity of the existing TVS products is also limited by the package. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a transient voltage suppression diode that prevents explosion when an open-circuit failure occurs.

[0007] The technical problems solved by the present invention can be achieved by adopting the following technical solutions:

[0008] A transient voltage suppression diode that prevents explosion when an open-circuit failure occurs, comprising:

[0009] A grain, and a first electrode and a second electrode respectively formed on opposite sides of the grain, wherein the first electrode is in a convex shape;

[0010] An insulating layer formed on a surface of the first electrode facing away from the grain, the insulating layer covering a non-convex portion of the convex-shaped first electrode and exposing a surface of the convex portion of the first electrode;

[0011] A fusible alloy sheet layer formed on a surface of the insulating layer facing away from the second electrode, and the fusible alloy sheet layer is connected to the convex portion of the first electrode; wherein, heat generated by thermal breakdown of the grain melts the fusible alloy sheet layer;

[0012] A third electrode, the third electrode being connected to the convex portion of the first electrode through the fusible alloy sheet layer;

[0013] A plastic package body for wrapping the grain, the first electrode, the second electrode, and the insulating layer therein, and exposing the convex portion of the first electrode, the insulating layer, and the surface of the second electrode.

[0014] Preferably, it further comprises:

[0015] A substrate having a first surface, a second surface opposite to the first surface, a first end portion, and a second end portion opposite to the first end portion;

[0016] A fourth electrode, one end of the fourth electrode is located between the second electrode and the first surface of the substrate, and the other end of the fourth electrode extends from the first end portion of the substrate to the second surface of the substrate;

[0017] A fifth electrode, one end of the fifth electrode is connected to the third electrode, and the other end of the fifth electrode extends from the second end of the substrate to the second surface of the substrate;

[0018] A package housing is disposed on the substrate, and a cavity is formed between the package housing and the substrate. The cavity is used to enclose the plastic package, the fusible alloy sheet layer, the third electrode, part of the fourth electrode, and part of the fifth electrode.

[0019] Preferably, the package housing is provided with ventilation holes, and the ventilation holes communicate with the cavity.

[0020] Preferably, the third electrode is formed on the surface of the insulating layer facing away from the second electrode, and the projection of the protruding part of the third electrode and the first electrode on the grain in the perpendicular direction does not coincide.

[0021] Preferably, the fusible alloy sheet layer includes an intermediate layer, an upper layer located above the intermediate layer, and a lower layer located below the intermediate layer. The upper layer and the lower layer are made of silver, the intermediate layer is made of tin, the thickness of the intermediate layer is less than 1.5 mm, and the total thickness of the upper layer and the lower layer is less than 0.5 mm.

[0022] Preferably, the fusible alloy sheet layer is in a planar spiral shape or a planar W shape.

[0023] Preferably, it further includes:

[0024] A flux layer is formed on the surface of the fusible alloy sheet layer facing away from the insulating layer.

[0025] Preferably, the flux layer is in a linear shape. The layout of the linear flux layer is the same as that of the fusible alloy sheet layer. The line width of the flux layer is 0.005 mm - 5 mm, and the thickness is 0.05 mm - 2 mm.

[0026] Preferably, the thickness of the non-protruding part of the first electrode is 0.1 - 0.5 mm; and / or

[0027] The thickness of the protruding part of the first electrode is 0.1 - 1.0 mm; and / or

[0028] The thickness of the second electrode is 0.1 mm - 0.5 mm; and / or

[0029] The thickness of the insulating layer is 0.1 mm - 1 mm; and / or

[0030] The thermal conductivity of the insulating layer is higher than 300 W / m·K; and / or

[0031] The thickness of the fusible alloy sheet layer is less than 2 mm; and / or

[0032] The fusing temperature of the fusible alloy sheet layer is 230°C - 380°C; and / or

[0033] The thickness of the third electrode is 0.1 mm - 0.5 mm; and / or

[0034] The thickness of the fourth electrode is 0.1 mm - 0.5 mm; and / or

[0035] The thickness of the fifth electrode is 0.1 mm - 0.5 mm.

[0036] Preferably, the surge capacity of the fusible alloy sheet layer is greater than that of the grains.

[0037] Preferably, the surge capacity of the fusible alloy sheet layer is 1.5 - 20 times that of the grains.

[0038] The advantages or beneficial effects of the technical solution of the present invention are as follows:

[0039] By providing a fusible alloy sheet layer in the present invention, the fusible alloy sheet layer is connected to the TVS grains through the protruding part of the first electrode. When a surge event occurs, the heat generated by the thermal breakdown of the TVS grains is transferred to the fusible alloy sheet layer, and the fusible alloy sheet layer is heated and fused to achieve open-circuit failure; at the same time, by using the method of heating and fusing the fusible alloy sheet layer to open the circuit, the phenomenon of metal vaporization during the open-circuit failure of the device is avoided, thereby preventing the explosion of the plastic package, solving the problem of the explosion of the device during open-circuit failure, and improving the stability and reliability of the device; in addition, the present invention can ensure that the residual voltage across the device drops instantaneously when the TVS device withstands a large surge thermal breakdown failure, avoiding the interference spikes generated during the surge thermal breakdown failure and open-circuit failure of the device, and improving the anti-interference ability of the circuit system; at the same time, the device uses low thermal resistance materials, increases the heat capacity of the device, reduces the thermal resistance of the device, and thus improves the surge capacity of the device. Description of the Drawings

[0040] Figure 1 It is a cross-sectional structure schematic diagram of a transient voltage suppression diode (excluding the package shell) in the preferred Embodiment 1 of the present invention;

[0041] Figure 2 It is a cross-sectional structure schematic diagram of a transient voltage suppression diode (including the package shell) in the preferred Embodiment 1 of the present invention;

[0042] Figure 3 It is a planar structure schematic diagram of a transient voltage suppression diode after primary packaging in the preferred Embodiment 1 of the present invention;

[0043] Figure 4In the second preferred embodiment of the present invention, it is a schematic cross-sectional structure diagram of a transient voltage suppression diode (excluding the packaging shell);

[0044] Figure 5 In the second preferred embodiment of the present invention, it is a schematic cross-sectional structure diagram of a transient voltage suppression diode (including the packaging shell);

[0045] Figure 6 In the second preferred embodiment of the present invention, it is a schematic plan view of the transient voltage suppression diode after the first encapsulation.

[0046] Description of reference numerals:

[0047] 1. Chip; 2. First electrode; 3. Second electrode; 4. Insulating layer; 5. Plastic package; 6. Fusible alloy sheet layer; 7. Flux layer; 8. Third electrode; 9. Substrate; 10. Fourth electrode; 11. Fifth electrode; 12. Packaging shell. Detailed implementation manners

[0048] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0049] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0050] Next, the present invention will be further described in conjunction with the accompanying drawings and specific embodiments, but it is not a limitation of the present invention.

[0051] In the preferred embodiment of the present invention, in view of the above problems existing in the prior art, a transient voltage suppression diode that prevents explosion during open-circuit failure is provided, as Figure 1 shown, including:

[0052] A chip 1 and a first electrode 2 and a second electrode 3 respectively formed on opposite sides of the chip 1, and the first electrode 2 is in a convex shape;

[0053] An insulating layer 4 is formed on the side of the first electrode 2 facing away from the chip 1. The insulating layer 4 covers the non-projecting part of the convex first electrode 2 and exposes the surface of the projecting part of the first electrode 2;

[0054] A fusible alloy sheet layer 6 is formed on the side of the insulating layer 4 facing away from the second electrode 3, and the fusible alloy sheet layer 6 is connected to the projecting part of the first electrode 2; wherein, heat generated by thermal breakdown of the chip 1 melts the fusible alloy sheet layer 6;

[0055] The third electrode 8, and the third electrode 8 is connected to the protruding portion of the first electrode 2 through the fusible alloy sheet layer 6;

[0056] The plastic package 5 is used to wrap the die 1, the first electrode 2, the second electrode 3, and the insulating layer 4, and expose the surfaces of the protruding portion of the first electrode 2, the insulating layer 4, and the second electrode 3.

[0057] Specifically, for the existing TVS devices with open - circuit failure modes, a metal bonding (metal wire acts as a fuse) or a simple combined packaging structure of a TVS device and a fuse is adopted. When a surge comes and causes the fuse to open, it will be accompanied by metal vaporization, resulting in device explosion, and the surge limit ability wave of the metal wire or fuse is unstable; moreover, when the device opens while the surge has not completely disappeared, it will cause the MOS transistor on the backend IC chip to withstand the surge that has not completely disappeared, thus causing damage to the backend due to lightning strike interference.

[0058] The TVS device shown in this embodiment includes a die 1, a first electrode 2, a second electrode 3, an insulating layer 4, a plastic package 5, a fusible alloy sheet layer 6, and a third electrode 8; among them, the plastic package 5 is used to wrap the die 1, the first electrode 2, the second electrode 3, and the insulating layer 4 to protect and fix the corresponding structures.

[0059] In this embodiment, the die 1 is a TVS die 1, and the TVS die 1 is a planar chip or a mesa chip. The TVS die 1 can quickly conduct and clamp the over - voltage within a safe range when subjected to a transient over - voltage impact, thereby protecting subsequent circuit elements from over - voltage damage.

[0060] The first electrode 2 is formed above the TVS die 1, and the first electrode 2 is electrically connected to the upper surface of the TVS die 1 through a welding material. The welding material can be a solder sheet, solder paste, or other materials with the same function. Further, the first electrode 2 has a convex - shaped structure. The convex - shaped first electrode 2 includes a non - protruding portion and a protruding portion. Among them, the lower surface of the non - protruding portion is in close contact with the upper surface of the TVS die 1, the upper surface of the non - protruding portion is in close contact with the insulating layer 4, and the upper surface of the protruding portion is in close contact with the lower surface of the fusible alloy sheet layer 6 to form an electrical connection. The non - protruding portion and the protruding portion are integrally formed, and the protruding portion is located at any position on the entire surface of the first electrode 2. The thickness of the non - protruding portion of the first electrode 2 is preferably 0.1 - 0.5 mm, and the thickness of the protruding portion is 0.1 - 1.0 mm.

[0061] More specifically, the material of the first electrode 2 can be made of a conductive material with low thermal resistance. The low-thermal-resistance conductive material can reduce the resistance of heat dissipation when the current flows through the first electrode 2, thereby reducing the heat accumulation generated by the current passing through, reducing the risk of device damage due to overheating, and improving the reliability and stability of the TVS device.

[0062] The second electrode 3 is formed under the TVS die 1, and the second electrode 3 is also electrically connected to the lower surface of the TVS die 1 through a welding material. The welding material can also be a solder sheet, solder paste or other materials with the same function. The thickness of the second electrode 3 is preferably 0.1 mm - 0.5 mm.

[0063] The insulating layer 4 is formed on the upper surface of the non-protruding part of the first electrode 2 and completely covers the non-protruding part of the first electrode 2 to achieve electrical isolation. In this embodiment, the insulating layer 4 is made of an insulating material with low thermal resistance. The insulating material with low thermal resistance has a high thermal conductivity, which can reduce the thermal resistance and improve the heat dissipation efficiency of the device. By way of example and not limitation, the insulating material with low thermal resistance can be diamond material, aluminum nitride material or other materials with a thermal conductivity higher than 300 W / m·K.

[0064] In this embodiment, the thickness of the insulating layer 4 is in the range of 0.1 mm - 1 mm, which can not only ensure that the insulating layer 4 isolates the non-protruding part of the first electrode 2 from the external environment and achieve a good insulation effect, but also increase the device heat capacity and reduce the device thermal resistance under the synergistic effect of thermal resistance and thickness, thereby improving the surge capacity of the TVS device. Specifically, when the TVS device encounters a surge current, due to the low-thermal-resistance characteristic and appropriate thickness of the insulating layer 4, the heat can be quickly transferred to the fusible alloy sheet layer 6, ensuring that under the specified surge conditions, the fusible alloy sheet layer 6 can be heated and melted to achieve open-circuit failure and play a role in protecting the circuit. The thermal resistance and thickness of the insulating layer 4 ensure the device fusing time and are also essential conditions for improving the surge capacity of the TVS device.

[0065] The fusible alloy sheet layer 6 is formed on the upper surface of the low-thermal-resistance insulating layer 4. One end of the fusible alloy sheet layer 6 is electrically connected to the protruding part of the first electrode 2, and the other end is electrically connected to the third electrode 8. By only contacting the protruding part of the first electrode 2, the fusible alloy sheet layer 6 can reduce the contact area between the fusible alloy sheet layer 6 and the first electrode 2, so that the connection between the third electrode 8 and the TVS die 1 can be disconnected more quickly after the TVS die 1 fails. Specifically, when the TVS die 1 is thermally broken down due to a surge impact, a large amount of heat will be generated at the failure point of the TVS die 1. Due to the existence of the low-thermal-resistance insulating layer 4, this heat can be quickly transferred to the fusible alloy sheet layer 6. As the heat accumulates continuously, when the melting temperature of the fusible alloy sheet layer 6 is reached, the fusible alloy sheet layer 6 will quickly melt, thus achieving the state of open-circuit failure.

[0066] In the embodiment of the present invention, when the TVS device is subjected to a surge impact, the fuse alloy sheet layer 6 can be melted in time to cut off the circuit, preventing excessive current from continuing to pass through the TVS grain 1, effectively protecting the entire circuit system from surge damage, and improving the reliability and safety of the TVS device.

[0067] As a preferred embodiment, as Figure 1 and Figure 2 shown, it further includes:

[0068] A substrate 9 having a first surface, a second surface opposite to the first surface, a first end portion, and a second end portion opposite to the first end portion;

[0069] A fourth electrode 10, one end of the fourth electrode 10 is located between the second electrode 3 and the first surface of the substrate 9, and the other end of the fourth electrode 10 extends from the first end portion of the substrate 9 to the second surface of the substrate 9;

[0070] A fifth electrode 11, one end of the fifth electrode 11 is connected to the third electrode 8, and the other end of the fifth electrode 11 extends from the second end portion of the substrate 9 to the second surface of the substrate 9;

[0071] A packaging shell 12 is disposed on the substrate 9, and a cavity is formed between the packaging shell 12 and the substrate 9 for enclosing the plastic package 5, the fuse alloy sheet layer 6, the third electrode 8, a part of the fourth electrode 10, and a part of the fifth electrode 11.

[0072] Specifically, in this embodiment, the TVS device further includes a substrate 9, a fourth electrode 10, a fifth electrode 11, and a packaging shell 12; wherein, the fourth electrode 10 is located above the substrate 9 and extends to below the substrate 9, and the fourth electrode 10 is connected to the second electrode 3; the fifth electrode 11 is located on the other side of the substrate 9 and extends to below the substrate 9, and the fifth electrode 11 is connected to the third electrode 8; the packaging shell 12 is disposed above the substrate 9 to cover all parts above the substrate 9 inside the packaging shell 12, preventing damage from the external environment and ensuring the stability and reliability of the device during operation.

[0073] The TVS device is covered with the packaging shell 12, and only the parts of the fourth electrode 10 and the fifth electrode 11 extending to below the substrate 9 are exposed, serving as the pins after the TVS device is packaged, for use in being mounted on a circuit board or other mounting substrate in an application to realize the connection and integration of the TVS device with the externally protected circuit, and further providing surge protection for the protected circuit.

[0074] The encapsulation housing 12 is disposed on the upper surface of the substrate 9, and a specific space, namely a cavity, is formed between the upper surface of the self - solvent layer 7 and the lower surface of the encapsulation housing 12. The distance of this cavity (the dimension in the direction perpendicular to the grain 1) is between 2 mm and 20 mm, which can provide space for the melting and shrinkage of the fusible alloy metal.

[0075] As a preferred embodiment, there are vent holes provided on the encapsulation housing 12, and the vent holes are in communication with the cavity.

[0076] Specifically, in this embodiment, vent holes are provided on the encapsulation housing 12, so that the internal cavity is in communication with the external environment through the vent holes. Through the setting of the vent holes, it is possible to prevent the device from bursting due to the vaporization and expansion of the metal.

[0077] As a preferred embodiment, the third electrode 8 is formed on the side of the insulating layer 4 facing away from the second electrode 3, and the projection of the protruding part of the third electrode 8 and the first electrode 2 on the plane perpendicular to the grain 1 do not overlap.

[0078] Specifically, in this embodiment, the third electrode 8 is formed on the upper surface of the insulating layer 4. Through the setting of the insulating layer 4, and the projection of the third electrode 8 and the protruding part of the first electrode 2 exposed from the insulating layer 4 do not overlap in the vertical projection, electrical isolation between the third electrode 8 and the first electrode 2 can be achieved.

[0079] Moreover, the third electrode 8 is electrically connected to the fusible alloy sheet layer 6 formed on the upper surface of the insulating layer 4, so that the third electrode 8 is connected to the first electrode 2 through the fusible alloy sheet layer 6. When the TVS grain 1 is subjected to abnormal conditions such as a surge impact and the temperature rises, the fusible alloy sheet layer 6 will be heated to its melting temperature and quickly melt, disconnecting the connection between the TVS grain 1 and the third electrode 8 (or the fifth electrode 11), achieving an open - circuit failure state.

[0080] As a preferred embodiment, the fusible alloy sheet layer 6 includes an intermediate layer, an upper layer located above the intermediate layer, and a lower layer located below the intermediate layer. The upper layer and the lower layer are made of silver, the intermediate layer is made of tin, the thickness of the intermediate layer is less than 1.5 mm, and the total thickness of the upper layer and the lower layer is less than 0.5 mm.

[0081] In this embodiment, the melting temperature of the fusible alloy sheet layer 6 is higher than the maximum operating temperature during the normal operation of the TVS device and lower than the local temperature of the failure point on the TVS grain 1.

[0082] Specifically, in this embodiment, the fusible alloy sheet layer 6 adopts a three-layer structure of upper layer - middle layer - lower layer. Among them, the upper and lower layers are silver layers, and the total thickness of the double-sided silver layers is less than 0.5 mm; the middle layer is a tin layer, and the thickness of the tin layer is less than 1.5 mm. That is, the fusible alloy sheet layer 6 adopts a silver-tin-silver structure, and its total thickness is less than 2 mm, so that the fusing temperature of the fusible alloy sheet layer 6 is between 230°C and 380°C.

[0083] After the TVS device fails short-circuit, the local temperature at the failure point on the TVS grain 1 can reach above 800°C. In order to control the fusing time and prevent mis-fusing, it is ensured that it does not fuse below the highest stable operating temperature of the device (generally 150°C).

[0084] When the TVS device is operating normally, the temperature usually does not exceed 150°C, and at this time the fusible alloy sheet layer 6 remains stable. When an abnormal situation such as a short-circuit failure occurs in the TVS device and the local temperature rapidly rises to between 230°C and 380°C, the tin in the middle layer will melt, causing the silver in the upper and lower layers to separate, thereby realizing the fusing of the fusible alloy sheet layer 6, disconnecting the electrical connection with the third electrode 8 and the fifth electrode 11, and thus disconnecting the connection between the TVS device and the protected circuit, playing a role in protecting the device and the circuit.

[0085] As a preferred embodiment, among them, the fusible alloy sheet layer 6 is in a planar spiral shape or a planar W shape.

[0086] Specifically, the fusible alloy sheet layer 6 can partially or completely cover the low thermal resistance insulating layer 4.

[0087] By way of example and not limitation, the fusible alloy sheet layer 6 can be in a planar spiral shape or can also be in a planar W shape. Adopting a planar spiral shape or a W-shaped layout can increase the contact area with the insulating layer 4, thereby transferring heat to the fusible alloy sheet layer 6 and improving the thermal stability of the TVS device.

[0088] In addition, the fusible alloy sheet layer 6 can also adopt other layouts, such as a square layout, an S-shaped layout, etc.

[0089] Since the failure point of the TVS chip may exist at various positions on the chip, the fusible alloy sheet layer 6 in a planar spiral shape or a planar W shape covers the chip surface, and at the same time limits the thickness of the first electrode 2 and the low thermal resistance insulating layer 4, controls the thermal resistance of the device, and can ensure that the heat at the chip failure point is transferred to the fusible alloy sheet layer 6.

[0090] As a preferred embodiment, among them, it further includes:

[0091] A flux layer 7, and the flux layer 7 is formed on the side of the fusible alloy sheet layer 6 facing away from the insulating layer 4.

[0092] Specifically, in order to further optimize the device performance, in this embodiment, a flux layer 7 is disposed above the fusible alloy sheet layer 6, and the layout of the flux layer 7 is similar to that of the fusible alloy sheet layer 6.

[0093] When the fusible alloy sheet layer 6 is spiral, the flux layer 7 will also be spiral accordingly and is disposed in the middle of the spiral of the fusible alloy sheet layer 6.

[0094] Similarly, when the fusible alloy sheet layer 6 is W-shaped, the flux layer 7 will also be W-shaped and located in the middle of the W-shape of the fusible alloy sheet layer 6.

[0095] By disposing the flux layer 7 above the fusible alloy sheet layer 6, it can promote the diffusion and reaction of solutes during the heating and melting process of the fusible alloy sheet layer 6, and improve the melting efficiency and performance stability of the fusible alloy sheet layer 6.

[0096] As a preferred embodiment, the flux layer 7 is linear, the layout of the linear flux layer 7 is the same as that of the fusible alloy sheet layer 6, the line width of the flux layer 7 is 0.005 mm - 5 mm, and the thickness is 0.05 mm - 2 mm.

[0097] Specifically, the flux layer 7 is linear and has the same layout as the fusible alloy sheet layer 6, which can uniformly promote the fusing process of the fusible alloy, accelerate the fusing speed, and improve the response speed of the device.

[0098] The width of the flux layer 7 is between 0.005 mm and 5 mm, and the thickness is between 0.05 mm and 2 mm, which can avoid uneven distribution or unnecessary interference with other components caused by too little or too much flux, thus affecting its fluxing effect.

[0099] Furthermore, considering that both the fusible alloy sheet layer 6 and the flux layer 7 being too thin or too thick will have adverse effects on the mechanical strength, electromagnetic shielding effect, and thermal resistance of the device. In this embodiment, by controlling the line width, line thickness, and line spacing (i.e., the line width of the flux layer 7) of the fusible alloy sheet layer 6 and the line thickness of the flux layer 7, it is ensured that the fusible alloy sheet layer 6 can be melted when heated, and it is prevented that the fusible alloy sheet layer 6 is wrongly connected to the adjacent side after fusing due to too wide line width or too narrow line spacing, resulting in the device being unable to open circuit and fail normally.

[0100] As a preferred embodiment, the thickness of the third electrode 8 is 0.1 mm - 0.5 mm; and / or

[0101] The thickness of the fourth electrode 10 is 0.1 mm - 0.5 mm; and / or

[0102] The thickness of the fifth electrode 11 is 0.1 mm - 0.5 mm.

[0103] Specifically, the TVS chip 1 is wrapped by the first electrode 2, the second electrode 3, and the low thermal resistance insulating layer 4, and is hermetically sealed by the plastic package 5. The TVS chip 1 forms an electrical connection with the fusible alloy sheet layer 6 only through the first electrode 2, and at the same time forms an electrical connection with the fourth electrode 10 only through the second electrode 3. The fusible alloy sheet layer 6 forms an electrical connection with the fifth electrode 11 through the third electrode 8.

[0104] The thicknesses of the second electrode 3, the third electrode 8, the fourth electrode 10, and the fifth electrode 11 are between 0.1 and 0.5 mm. The thicknesses of the second electrode 3, the third electrode 8, the fourth electrode 10, and the fifth electrode 11 may be the same or different.

[0105] As a preferred embodiment, the surge capacity of the fusible alloy sheet layer 6 is greater than that of the chip 1.

[0106] As a preferred embodiment, the surge capacity of the fusible alloy sheet layer 6 is 1.5 - 20 times that of the chip 1.

[0107] Specifically, in this embodiment, the surge capacity of the fusible alloy sheet layer 6 is stronger than that of the TVS chip 1. When the surge current exceeds a certain threshold, the TVS chip 1 first reaches its failure limit and shorts out and fails first. With the continuous action of the surge, the heat (up to 800 °C) generated after the failure of the TVS chip 1 is transferred to the fusible alloy sheet layer 6, causing the fusible alloy sheet layer 6 to melt and break, thereby achieving the protection of the subsequent circuit, and the fusible alloy sheet layer 6 fails open.

[0108] At the same time, the surge current carrying limit value corresponding to the waveform of the fusible alloy sheet layer 6 is more than 1.5 times and less than 20 times that of the TVS chip. If the surge capacity is too strong, that is, the surge current carrying limit value exceeds 20 times, it will cause the melting point of the fusible alloy sheet layer 6 to be too high, making it difficult to melt after the failure of the TVS chip 1 and unable to play a protective role in time; or the retracted solder ball is too large after melting. If the surge current carrying limit value is less than 1.5 times, the surge protection advantage of the fusible alloy sheet layer 6 cannot be fully exerted, and it cannot effectively cope with the surge impact. Through a large number of experiments and practical applications, the range between 1.5 - 20 times is the most preferred, which can achieve the best balance between surge protection performance and device reliability.

[0109] In the above-mentioned preferred embodiment, the TVS device is encapsulated with a low thermal resistance material, and the fusible alloy sheet layer 6 is connected to one side of the TVS chip 1 after encapsulation. The low thermal resistance material can transfer the heat to the fusible alloy sheet layer 6 after the TVS chip 1 undergoes thermal breakdown caused by a large surge, causing the fusible alloy sheet layer 6 to melt and break, achieving open circuit failure.

[0110] By using the method of the fusible alloy sheet layer 6 being heated and melted to open the circuit, when the TVS device fails open, there is no instantaneous gasification phenomenon, which will not cause the explosion of the plastic package 5, thus solving the problem of the explosion of the device when it fails open.

[0111] Through the optimization of the structure, the surge capacity of the fusible alloy sheet layer 6 is more than 1.5 times higher than that of the TVS chip 1. After the TVS chip 1 fails due to surge, the principle of DC melting and opening the circuit is adopted, that is, after the TVS chip 1 is short-circuited, the fusible alloy sheet layer 6 is heated and melted under DC to achieve an open circuit. This open-circuit failure scheme can ensure that the residual voltage across the device drops instantaneously when the TVS chip withstands a large surge thermal breakdown failure, avoiding the interference spikes generated when the device withstands a surge thermal breakdown failure and when it fails open.

[0112] The front of the TVS device has a metal electrode and a low thermal resistance insulating layer 4, which increases the heat capacity of the device and reduces the thermal resistance of the device, thereby improving the surge capacity of the device.

[0113] Two specific embodiments are provided below to further elaborate and illustrate the technical solution of the present invention:

[0114] Embodiment 1:

[0115] As Figures 1-3 shown, the embodiment of the present invention provides a TVS device that does not explode when it fails open. The device includes:

[0116] A TVS chip 1, which is a planar chip; under the surge condition of 8 / 20 μs, the ultimate current-carrying capacity of the TVS chip 1 is 1 KA.

[0117] A first electrode 2, which is arranged above the TVS chip 1 and is electrically connected to the upper surface of the TVS chip 1 through a solder chip, solder paste or other materials with the same function. The first electrode 2 is a copper electrode and has a convex shape. The thickness of the non-convex part is 0.1 mm, and the thickness of the convex part is 0.2 mm. The convex part is located in the middle of the first electrode 2.

[0118] A second electrode 3, which is arranged below the TVS chip 1 and is electrically connected to the lower surface of the TVS chip 1 through a solder chip, solder paste or other materials with the same function. The thickness of the second electrode 3 is 0.2 mm.

[0119] An insulating layer 4, which is connected to the non-convex part of the first electrode 2 and completely covers the non-convex part of the first electrode 2; among them, the insulating layer 4 uses a low thermal resistance insulating material, such as diamond material, and the thickness of the insulating layer 4 is 0.1 mm.

[0120] The plastic package 5 wraps the TVS chip 1, the first electrode 2, the second electrode 3 and the insulating layer 4 to protect and fix the corresponding structures.

[0121] The fusible alloy sheet layer 6 is connected to the surface of the low thermal resistance insulating layer 4. One end is connected to the protruding part of the first electrode 2, and the other end is connected to the third electrode 8. The layout of the fusible alloy sheet layer 6 is in a planar spiral shape and partially or completely covers the low thermal resistance insulating layer 4. The line width of the fusible alloy sheet layer 6 is 0.06 mm, the line interval is 0.02 mm, and the thickness is 0.05 mm. The fusible alloy sheet layer 6 adopts a silver-tin-silver structure, where the structure is a silver layer with a thickness of 200 μm, a tin layer with a thickness of 600 μm, and a silver layer with a thickness of 200 μm, and its fusing and retracting temperature point is between 260 °C and 280 °C. The fusible alloy sheet layer 6 has a limiting current-carrying capacity of 5 KA under the surge condition of 8 / 20 μs.

[0122] The flux layer 7 is arranged above the fusible alloy sheet layer 6, and its layout is the same as that of the fusible alloy sheet layer 6, in a planar spiral shape. The line width of the flux layer is 3 mm and the thickness is 1 mm.

[0123] The third electrode 8 is arranged on the surface of the low thermal resistance insulating layer 4 at a position not covered by the fusible alloy sheet layer 6, and the third electrode 8 is electrically isolated from the first electrode 2.

[0124] The substrate 9 is connected to the fourth electrode 10 and the fifth electrode 11 on both sides respectively. The fourth electrode 10 is connected to the second electrode 3, and the fifth electrode 11 is connected to the third electrode 8.

[0125] The thicknesses of the third electrode 8, the fourth electrode 10, and the fifth electrode 11 are all 0.5 mm.

[0126] The encapsulation shell 12 is arranged above the substrate 9 to cover each structure. At the corresponding position of the flux layer 7, the lower surface and the upper surface of the encapsulation shell 12 have a cavity with a height of 15 mm, and the encapsulation shell 12 is provided with air vents to connect the cavity and the external air.

[0127] Specifically, aiming at the problems of open-circuit failure and explosion of existing TVS devices and the generation of instantaneous burr-like transient interference waves during the failure moment, the embodiment of the present invention uses low thermal resistance materials for encapsulation in the encapsulation structure, and connects a fusible alloy sheet layer on one side of the chip after encapsulation. The low thermal resistance material can transfer heat to the fusible alloy sheet layer after the TVS chip withstands a large surge-induced thermal breakdown, causing the fusible alloy sheet layer to melt and break due to heat, and open-circuit failure can be achieved.

[0128] Adopting the scheme of the fusible alloy sheet layer melting and opening the circuit due to heat, there is no gasification phenomenon during the open-circuit failure of the device, and it will not cause the explosion of the plastic package, broadening its application scenarios.

[0129] After a surge failure, the device uses the principle of self-heating DC open circuit, that is, after the TVS chip is short-circuited, the fusible alloy sheet layer is heated and melted under DC to achieve an open circuit. This solution can ensure that when the TVS chip withstands a large surge thermal breakdown failure, the residual voltage across the device drops instantaneously, avoiding the interference spikes generated when the device withstands surge thermal breakdown failure and open circuit failure, and preventing abnormal conditions in the backend circuit when the TVS device fails.

[0130] There are metal electrodes and a low thermal resistance material insulation layer on the front side of the device. These two materials optimize the heat capacity and thermal resistance of the device, thereby improving the surge capacity of the device.

[0131] Embodiment 2:

[0132] As Figures 4-6 shown, the embodiment of the present invention provides a TVS device that does not explode during open circuit failure. The device includes:

[0133] A TVS die 1, and the TVS die 1 is a mesa chip; under the surge condition of 10 / 1000 μs, the ultimate current-carrying capacity of the TVS die 1 is 500 A.

[0134] A first electrode 2, which is arranged above the TVS die 1. The first electrode 2 is electrically connected to the upper surface of the TVS die 1 through a solder tab, solder paste or other materials with the same function. The first electrode 2 is a silver electrode and has a convex shape. The thickness of the non-convex part is 0.2 mm, and the thickness of the convex part is 0.5 mm. The convex part is located at the upper left corner of the first electrode 2.

[0135] A second electrode 3, which is arranged below the TVS die 1 and is electrically connected to the lower surface of the TVS die 1 through a solder tab, solder paste or other materials with the same function. The thickness of the second electrode 3 is 0.5 mm.

[0136] An insulation layer 4, which is connected to the non-convex part of the first electrode 2 and completely covers the non-convex part of the first electrode 2. Among them, the insulation layer 4 uses a low thermal resistance insulation material, such as aluminum nitride material, and the thickness is 0.3 mm.

[0137] A plastic package 5, which wraps the TVS die 1, the first electrode 2, the second electrode 3 and the insulation layer 4 to protect and fix the corresponding structures.

[0138] The fusible alloy sheet layer 6 is connected to the surface of the insulating layer 4, with one end connected to the protruding part of the first electrode 2 and the other end connected to the third electrode 8. The fusible alloy sheet layer 6 is arranged in an S-shaped layout, and can also be specifically in an M-shaped layout, and covers part or all of the insulating layer 4. The line width of the fusible alloy sheet layer 6 is 0.5 mm, the line interval is 0.25 mm, and the thickness is 0.075 mm. The fusible alloy sheet layer 6 adopts a silver-tin-silver structure, specifically, a silver layer with a thickness of 300 μm, a tin layer with a thickness of 100 μm, and a silver layer with a thickness of 200 μm, and its fusing and retracting temperature point is between 350 °C and 370 °C. The fusible alloy sheet layer 6 has a limit current-carrying capacity of 750 A under the surge condition of 10 / 1000 μs.

[0139] The flux layer 7 is arranged above the fusible alloy sheet layer 6, with the same layout as the fusible alloy sheet layer 6. The line width of the flux layer is 0.25 mm and the thickness is 0.05 mm.

[0140] The third electrode 8 is arranged at a position on the surface of the insulating layer 4 that is not covered by the fusible alloy sheet layer 6.

[0141] The substrate 9 is connected to the fourth electrode 10 and the fifth electrode 11 on both sides respectively. Among them, the fourth electrode 10 is connected to the second electrode 3, and the fifth electrode 11 is connected to the third electrode 8.

[0142] The thicknesses of the third electrode 8, the fourth electrode 10, and the fifth electrode 11 are all 0.15 mm.

[0143] The encapsulation housing 12 is arranged above the substrate 9, covering each structure, and at the corresponding position of the flux layer 7, the lower surface and the upper surface of the encapsulation housing 12 have a cavity with a height of 5 mm, and the encapsulation housing 12 is provided with ventilation holes to connect the cavity and the external air.

[0144] For the TVS device prepared in Embodiments 1-2 of the present invention, by setting the fusible alloy sheet layer, the fusible alloy sheet layer is connected to the TVS grain through the protruding part of the first electrode. When a surge event occurs, the heat generated by the thermal breakdown of the TVS grain is transferred to the fusible alloy sheet layer, and the fusible alloy sheet layer is heated and fused to achieve open-circuit failure. When the TVS grain fails, the device can achieve open-circuit disconnection within 1 minute.

[0145] Moreover, by adopting the method of heating and fusing the fusible alloy sheet layer to open the circuit, the phenomenon of metal vaporization during the open-circuit failure of the device is avoided, thereby preventing the explosion of the plastic package, that is, there will be no explosion phenomenon when the device has a surge failure.

[0146] Moreover, since the TVS grains fail due to surge first and then the fusible alloy sheet layer 6 is heated and melted to achieve open-circuit failure, when the chip experiences surge and open-circuit failure, no transient interference spikes will be generated to the devices at the back end.

[0147] Compared with the traditional packaged TVS devices, the embodiments of the present invention improve the surge capability of the devices. That is to say, under the same TVS chip area, the surge capability of the TVS devices in the embodiments of the present invention is better than that of the traditional TVS devices (such as SMA / SMB / SMC).

[0148] Meanwhile, the device uses low thermal resistance materials to increase the device heat capacity and reduce the device thermal resistance, thereby improving the surge capability of the device.

[0149] The above are only the preferred embodiments of the present invention, and do not limit the implementation manners and protection scope of the present invention accordingly. For those skilled in the art, it should be realized that all the equivalent replacements and obvious changes made by using the content of this specification and the drawings should be included in the protection scope of the present invention.

Claims

1. A transient voltage suppression diode that prevents explosion during open - circuit failure, characterized in that, Comprising: A crystal grain, and a first electrode and a second electrode respectively formed on opposite two surfaces of the crystal grain, wherein the first electrode is in a convex shape; An insulating layer formed on a surface of the first electrode facing away from the crystal grain, the insulating layer covering a non-convex portion of the convex-shaped first electrode and exposing a surface of the convex portion of the first electrode; A fusible alloy sheet layer formed on a surface of the insulating layer facing away from the second electrode, and the fusible alloy sheet layer is connected to the convex portion of the first electrode; wherein, heat generated by thermal breakdown of the crystal grain fuses the fusible alloy sheet layer; A third electrode, the third electrode being connected to the convex portion of the first electrode through the fusible alloy sheet layer; A plastic package body for wrapping the crystal grain, the first electrode, the second electrode and the insulating layer therein, and exposing surfaces of the convex portion of the first electrode, the insulating layer and the second electrode.

2. The transient voltage suppression diode according to claim 1, wherein Further comprising: A substrate having a first surface, a second surface opposite to the first surface, a first end portion and a second end portion opposite to the first end portion; A fourth electrode, one end of the fourth electrode being located between the second electrode and the first surface of the substrate, and the other end of the fourth electrode extending from the first end portion of the substrate to the second surface of the substrate; A fifth electrode, one end of the fifth electrode being connected to the third electrode, and the other end of the fifth electrode extending from the second end portion of the substrate to the second surface of the substrate; A package housing provided on the substrate, and a cavity is formed between the package housing and the substrate, the cavity for wrapping the plastic package body, the fusible alloy sheet layer, the third electrode, a part of the fourth electrode and a part of the fifth electrode therein.

3. The transient voltage suppression diode according to claim 2, characterized in that, The package housing is provided with a vent hole, and the vent hole communicates with the cavity.

4. The transient voltage suppression diode according to claim 1, wherein The third electrode is formed on a surface of the insulating layer facing away from the second electrode, and the third electrode and the convex portion of the first electrode do not coincide in projection on the crystal grain in a perpendicular direction.

5. The transient voltage suppression diode according to claim 1, characterized in that, The fusible alloy sheet layer includes an intermediate layer, an upper layer located above the intermediate layer and a lower layer located below the intermediate layer, the upper layer and the lower layer are made of silver, the intermediate layer is made of tin, the thickness of the intermediate layer is less than 1.5 mm, and the total thickness of the upper layer and the lower layer is less than 0.5 mm.

6. The transient voltage suppression diode according to claim 1, wherein The fusible alloy sheet layer is in a planar spiral shape or a planar W shape.

7. The transient voltage suppression diode according to claim 1, wherein Further comprising: A flux layer formed on a surface of the fusible alloy sheet layer facing away from the insulating layer.

8. The transient voltage suppression diode according to claim 7, characterized in that, The flux layer is in a linear shape, the layout of the linear flux layer is the same as the layout of the fusible alloy sheet layer, the line width of the flux layer is 0.005 mm - 5 mm, and the thickness is 0.05 mm - 2 mm.

9. The transient voltage suppression diode according to claim 2, characterized in that, The thickness of the non-convex portion of the first electrode is 0.1 - 0.5 mm; and / or The thickness of the convex portion of the first electrode is 0.1 - 1.0 mm; and / or The thickness of the second electrode is 0.1 mm - 0.5 mm; and / or The thickness of the insulating layer is 0.1 mm - 1 mm; and / or The thermal conductivity of the insulating layer is higher than 300 W / m·K; and / or The thickness of the fusible alloy sheet layer is less than 2 mm; and / or The fusing temperature of the fusible alloy sheet layer is 230°C - 380°C; and / or The thickness of the third electrode is 0.1 mm - 0.5 mm; and / or The thickness of the fourth electrode is 0.1 mm - 0.5 mm; and / or The thickness of the fifth electrode is 0.1 mm - 0.5 mm.

10. The transient voltage suppression diode according to claim 1, characterized in that, The surge capacity of the fusible alloy sheet layer is greater than that of the crystal grains.

11. The transient voltage suppression diode according to claim 10, wherein, The surge capacity of the fusible alloy sheet layer is 1.5 - 20 times that of the crystal grains.

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