Photovoltaic diode

Abstract

A photovoltaic diode relates to the technical field of semiconductors. Comprising a radiating seat, a radiating part and a lead, a chip placing position is arranged on the outer side of the radiating seat, and radiating grooves are formed in the inner side; the heat dissipation part is fixedly arranged in the heat dissipation groove; one end of the lead is fixedly connected with the heat dissipation groove, and the other end extends out of the heat dissipation groove. The heat dissipation ring and the heat dissipation part are additionally arranged, so that the heat dissipation effect is better, the temperature of the chip after being electrified is reduced, meanwhile, the stress area of the chip is reduced after the area of the lead heat dissipation platform is increased, and the probability of failure caused by extrusion of plastic package materials is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of semiconductors, in particular to an improved photovoltaic diode structure. Background Art

[0002] At present, in bypass applications of traditional photovoltaic diodes, Schottky barrier rectifiers can take advantage of low forward voltage drop and have lower power dissipation than ordinary PN junction rectifiers. However, in the chip packaging process, a variety of materials with different thermal expansion coefficients are often used. Due to the thermal mismatch between materials and temperature changes during manufacturing and later application, each layer of material and interface will be subjected to different thermal stresses. Since Schottky barrier rectifiers are surface-type devices, the Schottky junction depth is only about 0.05-0.5 microns, and the PN junction depth at the guard ring is only about 1-5 microns. Therefore, the thermal stress at the interface between layers and at the ends, especially at the edge of the chip, is concentrated due to the extrusion effect of the plastic packaging material, which often causes product performance degradation or even failure. Generally speaking, when reliability performance evaluation is performed according to standard methods in the semiconductor industry such as MIL-STD 750D METHOD1051.5 Test Condition G, GJB128A-97 Method 1051- Experimental Condition G, and JESD22-A104E Test Condition H, it is impossible to fully meet the harsh -55 °C to +150 °C hot and cold temperature cycle assessment requirements, which actually results in product reliability and product life failing to meet expectations.

[0003] In response to such problems, in existing patent documents, such as the utility model patent for "A stress-improved axial bypass photovoltaic diode" authorized and announced on July 10, 2018, the patent number is 201610646090.0. It includes at least one bypass diode chip, at least one anode lead, and at least one cathode lead. The anode lead and the cathode lead are respectively connected to the anode and cathode of the chip by soldering to form a structure sealed by plastic packaging material; the anode lead is an inverted convex platform structure from the anode lead to the chip; the cathode lead is a platform structure. The inverted boss structure of the anode lead and the platform structure of the cathode lead are used to concentrate the relevant thermal stress on the anode surface of the chip. In actual use, due to the boss structure, the chip part outside the boss will be affected by the thermal stress of the plastic package material and cause failure. In addition, since the contact area between the boss and the platform and the chip is small and not proportionally enlarged according to the plastic package body (8.7mm), the chip will have poor heat dissipation. When the diode switches from forward conduction to reverse cutoff, the high chip temperature will cause large leakage, thereby increasing the risk of reverse breakdown.

[0004] The following table shows the temperature rise test. The new national standard requires Tj≤200°

[0005]

[0006] It can be seen from the above table that the three junction boxes in the temperature rise experiment all exceed the national standard, and there is a risk of the diode being broken down during the reverse cutoff.

[0007] In the existing patent literature, for example, the utility model patent "A diode with good heat dissipation effect" applied for and published on August 22, 2017, application number 201710280678.3. It consists of a diode chip and electrode parts distributed at both ends of the diode chip. The electrode parts are circular, and a boss is formed on the inner end face of the electrode parts. The boss rests on the electrode contact surface of the diode chip. An electrode lead is formed on the outer end face of the electrode parts. The diode chip and the outer side of the boss are coated with a protective adhesive layer. The diode chip and the electrode parts are both plugged into a cylindrical outer shell, which is filled with epoxy insulating glue. A number of heat dissipation holes are formed on the outer wall of the electrode parts. A number of support rods are formed on the outer wall of the electrode parts. The support rods are plugged into the heat dissipation holes of the outer shell. A graphite heat conductive sheet is glued and fixed to the inner wall of the outer shell. In actual use, the following problems mainly exist:

[0008] 1. The chip exposed outside the boss will be squeezed by stress and cause failure;

[0009] 2. The process of adding inner glue, outer glue, and graphite lead-in sheet to the inner wall of the shell is complicated and the cost is doubled;

[0010] 3. Graphite is conductive. If the support rod is also made of metal, it will cause the positive and negative poles to be conductive, and the heat dissipation effect will be poor. Utility Model Content

[0011] In view of the above problems, the utility model provides a photovoltaic diode which can achieve temperature rise compliance and reduce TC failure rate without changing its volume.

[0012] The technical solution of the utility model is:

[0013] Lead assembly, including:

[0014] The heat sink has a chip placement position on the outside and a heat sink slot on the inside;

[0015] A lead has one end fixedly connected to the heat dissipation slot and the other end extending out of the heat dissipation slot.

[0016] Specifically, it also includes a heat dissipation portion fixedly arranged in the heat dissipation groove.

[0017] Specifically, the cross section of the heat sink is circular, and its diameter is larger than the diameter of the lead.

[0018] Specifically, the lead is cylindrical and located in the middle of the heat dissipation slot.

[0019] Specifically, the heat dissipation part is provided with a plurality of heat dissipation columns which are cylindrical in shape and are evenly and fixedly arranged around the lead wire.

[0020] Specifically, the heat dissipation portion is annular and is fixedly arranged on the outside of the lead.

[0021] Specifically, the heat dissipation portion is a plurality of arc-shaped sheets arranged at intervals and fixedly arranged on the outside of the lead.

[0022] Specifically, the heat dissipation part is a plurality of connecting pieces respectively fixedly connected to the leads and the inner side walls of the heat dissipation grooves.

[0023] Specifically, the heat dissipation groove has a depth of 1-1.5 mm.

[0024] Specifically, the wall thickness of the heat dissipation slot is 1-1.2 mm.

[0025] The ratio of the lead diameter to the heat sink diameter in this case is 4:17.

[0026] Specifically, the lead assembly is provided with a pair;

[0027] A pair of lead assemblies are symmetrically arranged, with a fixedly connected chip disposed between the two.

[0028] The utility model comprises a heat sink, a heat sink and a lead; a chip placement position is arranged on the outside of the heat sink, and a heat sink is arranged on the inside; the heat sink is fixedly arranged in the heat sink; one end of the lead is fixedly connected to the heat sink, and the other end extends out of the heat sink. By adding a heat sink ring and a heat sink, the heat dissipation effect is better, and the temperature of the chip after power is turned on is reduced. At the same time, after the area of ​​the lead heat sink platform is increased, the area of ​​the chip subjected to stress is reduced, thereby reducing the probability of failure caused by extrusion of the plastic packaging material.

[0029] In this case, the heat sink, heat dissipation part and lead wire are made of pure copper respectively; the heat sink is provided with a heat dissipation slot, and the material cost of copper is reduced by 10% for products of the same specifications, while the heat dissipation area is effectively increased, and the overall reliability is further enhanced after plastic sealing. Through thermal simulation tests, the chip temperature of the device with heat dissipation strip is 1° lower than that of the device without heat dissipation strip when working. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a three-dimensional structural schematic diagram of a pair of lead components in connection state;

[0031] Figure 2 It is a schematic diagram of the structure after plastic packaging;

[0032] Figure 3 It is a schematic diagram of the semi-cut three-dimensional structure of a photovoltaic diode;

[0033] Figure 4It is a structural schematic diagram when the heat dissipation part is a heat dissipation column;

[0034] Figure 5 It is a schematic diagram of a ring-shaped structure of the heat dissipation part;

[0035] Figure 6 1. It is a schematic diagram of the structure of the heat dissipation part being an arc-shaped sheet;

[0036] Figure 7 1. It is a schematic diagram of the structure of the heat dissipation part as a connecting piece;

[0037] In the figure, 100 is a lead assembly;

[0038] 110 is a heat sink, 111 is a heat sink, 112 is a heat sink, 120 is a heat sink.

[0039] 130 is a heat dissipation part, 131 is a heat dissipation column, 132 is a heat dissipation ring, 133 is an arc-shaped sheet, 134 is a connecting sheet,

[0040] 140 is the lead, 200 is the chip, and 300 is the plastic package. DETAILED DESCRIPTION

[0041] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0042] In the description of the present invention, it should be understood that the terms "upper", "lower", "left", "right", "vertical", "horizontal", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0043] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] Reference below Figure 1-7Describe the utility model;

[0045] The lead assembly 100 (or referred to as a lead nail head) includes:

[0046] The heat sink 110 has a chip 200 placement position on the outside and a heat sink 120 on the inside. The heat sink 110 in this embodiment includes a heat sink 111 and a heat sink wall 112 fixedly disposed on the heat sink 111.

[0047] The heat dissipation portion 130 is fixedly disposed in the heat dissipation slot 120;

[0048] A lead 140 has one end fixedly connected to the heat dissipation slot 120 and the other end extending out from the heat dissipation slot 120 .

[0049] The heat dissipation effect is improved by adding the heat dissipation ring 132 and the heat dissipation part 130, and the temperature of the chip 200 after power is turned on is reduced. At the same time, the area of ​​the lead heat dissipation platform is increased, and the area of ​​the chip 200 subjected to stress is reduced, thereby reducing the probability of failure caused by extrusion of the plastic packaging material.

[0050] In this case, the heat sink 110, the heat dissipation part 130 and the lead 140 are respectively made of pure copper; a heat dissipation groove 120 is arranged in the heat sink 110. Under the condition of the same specification products, the material cost of copper is reduced by 10%, and at the same time, the heat dissipation area is effectively increased. The overall reliability is further enhanced after plastic packaging. Through thermal simulation tests, the device with heat dissipation strips has a chip 200 with a working temperature 1° lower than that of the device without heat dissipation strips.

[0051] The heat sink 110 further defines:

[0052] The cross section of the heat sink 110 is circular, and the diameter thereof is larger than the diameter of the lead 140 .

[0053] The heat dissipation groove 120 has a groove depth of 1-1.5 mm.

[0054] The wall thickness of the heat dissipation slot 120 is 1-1.2 mm.

[0055] The diameter of the axial plastic package body 300 is 8.7±0.1mm, and the optimal diameter of the heat sink 110 is 8.5mm. If it is larger, there is a risk of leakage of the internal structure. The heat sink 120 extends 1.5mm downward from the outermost side of the heat sink 110, and has a wall thickness of 1mm. If the thickness is too thin, it will be easily deformed. The thicker the thickness, the better the heat dissipation. However, the cost will increase significantly, making the product uncompetitive.

[0056] Lead 140 further defines:

[0057] The lead 140 is cylindrical and located in the middle of the heat dissipation slot 120 .

[0058] In the present case, the ratio of the diameter of the lead 140 to the diameter of the heat sink 120 is 4:17.

[0059] In this case, the lead wire 140 diameter is selected as 2 mm, and the heat sink 120 diameter is selected as 8.5 mm. The thicker the lead wire 140 diameter, the better the heat dissipation effect, as shown in Table 1, the simulated data of the lead wire 140 diameter. However, the thicker the lead wire, the more expensive it is, so a 2.0 mm diameter is selected.

[0060] Table 1 sets the lead 140 diameters to 2.28mm, 2mm, 1.9mm, 1.8mm, 1.7mm, 1.6mm and 1.5mm for simulation, the ambient temperature is 75°C, there is no auxiliary heat dissipation, and the chip 200 power is 1W:

[0061] Lead wire diameter Shell temperature Junction temperature 2.28mm 140.796℃ 144.147℃ 2.0mm 143.301℃ 146.781℃ 1.9mm 144.046℃ 147.538℃ 1.8mm 145.062℃ 148.6℃ 1.7mm 145.934℃ 149.517℃ 1.6mm 147.083℃ 150.726℃ 1.5mm 148.205℃ 151.906℃

[0062] In summary, the junction temperature increases by 7.76° C. when the lead 140 diameter is reduced from 2.28 mm to 1.5 mm.

[0063] The heat dissipation unit 130 further defines:

[0064] Implementation method 1:

[0065] like Figure 4 As shown, the heat dissipation portion 130 is provided with a plurality of cylindrical heat dissipation columns 131 , which are evenly distributed and fixedly arranged around the lead 140 .

[0066] Implementation method 2:

[0067] like Figure 5 As shown, the heat dissipation portion 130 is annular, that is, a heat dissipation ring 132, which is fixedly arranged on the outside of the lead 140, that is, the cross-section of the heat dissipation portion 130 is circular, elliptical or polygonal. Figure 5 The circular ring structure has a gap between it and the lead 140. If it is directly connected to the outer cylindrical surface of the lead 140, it also falls within the protection scope of this case.

[0068] Implementation method three:

[0069] like Figure 6 As shown, the heat dissipation portion 130 is a plurality of arc-shaped pieces 133 arranged at intervals and fixedly arranged on the outer side of the lead 140 .

[0070] Implementation method 4:

[0071] like Figure 7 As shown, the heat dissipation portion 130 is a plurality of connection pieces 134 respectively fixedly connected to the leads 140 and the inner wall of the heat dissipation slot 120 .

[0072] like Figure 1 As shown, a photovoltaic diode, the lead assembly 100 is provided with a pair;

[0073] A pair of lead assemblies 100 are symmetrically arranged, and a chip 200 is fixedly connected therebetween.

[0074] The diameter of the heat sink 110 must be larger than the diameter of the chip 200 to avoid damage to the chip 200 caused by impact by external objects during loading and transportation. The diameter of the heat sink 110 must be smaller than the diameter of the plastic package body (8.7±0.1mm) to avoid leakage of the internal structure. Therefore, the size of the heat sink 110 depends on the chip 200 and the plastic package body. Taking a 180mil chip 200 as an example, the size of the heat sink 110 is ≥5.4mm and ≤8.5mm; considering the temperature rise effect, it is set to 8.5mm.

[0075] The chip 200 is packaged between a pair of lead components 100 through a plastic package 300 .

[0076] In this case, the positive and negative electrodes of the chip 200 are connected to the lead pin head 100 through a welding piece, and the chip 200 is located on the chip placement position; the amount of the plastic package 300 in this case is reduced by about 40% compared with the prior art.

[0077] In order to further prove the structural advantages of this case, a thermal simulation test was conducted on the product structure. The test results are shown in Table 1. From top to bottom in the figure, the first and second are conventional structure diodes, the third and fourth are diodes of this case structure, the first and third are equipped with 180mil chips, and the second and fourth are equipped with 150mil chips. Under this simulation condition, the junction temperature dropped by 1~2℃; and the junction-to-case thermal resistance of the new design is smaller.

[0078] Shell temperature Junction temperature 1. Conventional structure + 180mil chip 97.7℃ 100.778℃ 2. Conventional structure + 150mil chip 97.75℃ 101.021℃ 3. New design structure + 180mil chip 98.029℃ 99.07℃ 4. New design structure + 150mil chip 98.046℃ 99.1249℃

[0079] Table 1 is a thermal simulation comparison test table

[0080] As shown in Table 2, according to the stress simulation results, the stress value of the chip with the new design structure (the product on the right side of Table 2) is significantly smaller, and the average stress value decreases by about 8.9%.

[0081] -55~150℃ device thermal stress General structure New Structure Stress value at the center of the chip 356.72MPa 312.98MPa Maximum stress value 411.8MPa 388.45MPa Average stress value 304.96MPa 277.08MPa

[0082] Table 2 is a stress simulation comparison test table

[0083] Regarding the contents disclosed in this case, there are a few points that need to be explained:

[0084] (1) The drawings of the embodiments disclosed in this case only involve the structures involved in the embodiments disclosed in this case. Other structures can refer to the general design;

[0085] (2) In the absence of conflict, the embodiments and features of the embodiments disclosed in this case may be combined with each other to obtain new embodiments;

[0086] The above are only specific implementation methods disclosed in this case, but the protection scope of the present disclosure is not limited thereto. The protection scope disclosed in this case should be based on the protection scope of the claims.

Claims

1. A photovoltaic diode, characterized in that It comprises a pair of symmetrically arranged lead components, between which a fixedly connected chip is arranged; the lead component comprises: The heat sink has a chip placement position on the outside and a heat sink slot on the inside; A lead has one end fixedly connected to the heat dissipation slot and the other end extending out of the heat dissipation slot.

2. The photovoltaic diode according to claim 1, characterized in that: A heat dissipation portion is arranged in the heat dissipation groove.

3. The photovoltaic diode according to claim 1, characterized in that: The cross section of the heat sink is circular, and the diameter thereof is larger than the diameter of the lead.

4. The photovoltaic diode according to claim 1, characterized in that: The lead is cylindrical and located in the middle of the heat dissipation slot.

5. The photovoltaic diode according to claim 2, characterized in that: The heat dissipation part is provided with a plurality of heat dissipation columns which are cylindrical in shape and are evenly and fixedly arranged around the lead wire.

6. The photovoltaic diode according to claim 2, characterized in that: The heat dissipation portion is annular and fixedly arranged on the outside of the lead.

7. The photovoltaic diode according to claim 2, characterized in that: The heat dissipation part is a plurality of arc-shaped sheets arranged at intervals and fixedly arranged on the outside of the lead.

8. The photovoltaic diode according to claim 2, characterized in that: The heat dissipation part is a plurality of connecting pieces which are respectively fixedly connected to the leads and the inner side walls of the heat dissipation grooves.

9. The photovoltaic diode according to claim 1, characterized in that: The depth of the heat dissipation groove is 1-1.5 mm.

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