A pin for a power module

Abstract

The utility model belongs to the field of semiconductor technology discloses a PIN needle for power module, including needle holder and needle body, needle holder and needle body axial one side link, the position of needle body is close to needle holder and is provided with the boss, the boss ring is equipped on the outside wall of needle body. The PIN needle of the present application increases the boss on the needle body, forms the check structure, prevents the solder from climbing along the needle body, and can effectively inhibit the solder infiltration.

Description

Technical Field

[0001] This utility model belongs to the field of semiconductor technology, and specifically relates to a PIN pin for power modules. Background Technology

[0002] As the core power semiconductor device in power electronic systems, IGBT (Insulated Gate Bipolar Transistor) modules use pins as key connection components for signal and power transmission within the IGBT module. Their core function is to achieve flexible connection between the internal chip and the external circuit.

[0003] like Figure 1 As shown, the existing PIN pins include a first post 1, an S-bend structure 2, a second post 3, and a base 4 connected in sequence. The PIN pins are mostly made of oxygen-free copper (T2) substrate, and the surface is treated with tin (Sn) or tin-lead (Sn-Pb) alloy to optimize the soldering performance. During service, the PIN pins of the IGBT module exhibit brittle fracture failure of IMC induced by solder creep. The failure mechanism is as follows: when the solder creeps along the base 4 and the second column 3 to the S-bend structure 2 area, the Sn element in the solder will undergo an interfacial chemical reaction with the copper substrate of the S-bend structure 2 to generate intermetallic compounds (IMC). Under the action of thermal cycling (ΔT>100℃) and mechanical creep, the IMC layer will induce stress concentration, leading to fatigue cracking of the S-bend structure 2.

[0004] To address the solder creep problem, the most common solution in existing technologies is to use solder resist processes (such as applying solder resist adhesive or attaching solder resist film). However, since the distance between the S-bend structure 2 and the base 4 is only 0.8~2mm, and due to the requirements of the IGBT assembly process, the S-bend structure 2 should be immersed in silicone to provide a certain degree of stability. Therefore, the length of the second column 3 cannot be increased. The confined space places stringent requirements on the precision, material properties, and construction feasibility of the solder resist process, making it difficult for traditional processes to effectively suppress solder wetting. Utility Model Content

[0005] To address the aforementioned issues, this utility model provides a PIN pin for a power module, comprising a pin holder and a pin body. The pin holder is connected to one side of the pin body along its axial direction. The pin body has a boss located near the pin holder, and the boss is arranged around the outer side wall of the pin body.

[0006] Furthermore, the boss is umbrella-shaped, with the convex surface of the umbrella-shaped boss facing away from the needle seat.

[0007] Furthermore, the angle A between the outline of the edge of the boss facing the needle seat and the axial center line of the needle body is an acute angle.

[0008] Furthermore, the surface of the boss facing away from the needle seat is provided with micro-grooves.

[0009] Furthermore, the depth of the microgrooves is 50~100μm.

[0010] Furthermore, the height H between the side of the boss facing the needle seat and the side facing away from the needle seat is 0.3~0.5mm.

[0011] Furthermore, the density of microgrooves is 3~5 per mm. 2 .

[0012] Furthermore, the needle body includes a third column, a connecting plate, and a fourth column; One side of the third column is connected to the needle seat along its axial direction, and the other side of the third column is connected to the connecting plate and the fourth column in sequence. The boss is located on the side of the third column near the connecting plate. The outer diameter of the third column is smaller than the outer diameter of the needle seat.

[0013] Furthermore, the outer diameter of the boss is 1.2 to 1.5 times the outer diameter of the third column.

[0014] Furthermore, the needle base, needle body, and boss are integrally molded.

[0015] The beneficial effects of this utility model are: 1. The PIN pin of this application forms a barrier structure by adding protrusions on the pin body, which prevents solder from climbing along the pin body and can effectively inhibit solder wetting.

[0016] 2. The boss in this application is umbrella-shaped. When the solder flows along the axial direction of the needle body due to temperature during the welding process, the inclined convex surface of the boss can directly block the direction of solder movement.

[0017] 3. The outline of the side of the boss facing the pin seat in this application forms an acute angle with the axial center line of the pin body. The "pinning effect" is achieved by utilizing the sudden change in surface tension of the molten solder, thereby achieving physical barrier.

[0018] 4. This application provides a microgroove on the surface of the boss facing away from the pin seat, which induces the solder to form a crescent-shaped solder joint in the microgroove, thus consuming its climbing kinetic energy.

[0019] 5. The boss, needle body, and needle seat of this application are integrally formed, which is lower in cost and more reliable than the existing solder mask process.

[0020] Other features and advantages of this invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objectives and other advantages of this invention can be realized and obtained through the structures pointed out in the description and the accompanying drawings. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A schematic diagram of the structure of a PIN pin for an IGBT module according to the prior art is shown; Figure 2 A schematic diagram of a PIN pin for a power module according to an embodiment of the present invention is shown; Figure 3 It shows Figure 2 Side view; Figure 4 A schematic diagram of the microgroove structure on the boss according to an embodiment of the present invention is shown.

[0023] In the diagram: 1. First column; 2. S-bend structure; 3. Second column; 4. Base; 5. Needle seat; 6. Needle body; 7. Boss; 61. Third column; 62. Connecting plate; 63. Fourth column; 71. Micro-groove. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0025] It should be noted that the terms "first," "second," etc., used in this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," "longitudinal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings.

[0026] This application provides a PIN pin for a power module to prevent abnormal solder creep and effectively suppress solder wetting.

[0027] like Figure 2As shown, a PIN pin for a power module includes a pin holder 5 and a pin body 6. The pin holder 5 is connected to one side of the pin body 6 along the axial direction. The pin body 6 has a boss 7 near the pin holder 5. The boss 7 is arranged around the outer side wall of the pin body 6. In this embodiment, by adding the boss 7 to the pin body 6, a barrier structure is formed to prevent solder from climbing along the pin body 6 and to effectively suppress solder wetting.

[0028] For example, the boss 7 is umbrella-shaped, and the convex surface of the umbrella-shaped boss 7 faces away from the needle seat 5, forming a "reverse interception" structure: when the solder flows along the axial direction of the needle body 6 due to temperature during the welding process, the inclined convex surface of the boss 7 can directly block the direction of solder movement.

[0029] like Figure 2 As shown, for example, the angle A between the edge contour line of the boss 7 facing the pin seat 5 and the axial center line of the pin body 6 is an acute angle. The edge of the boss 7 facing the pin seat 5 forms an acute angle with the axial center line of the pin body 6. The "pinning effect" is achieved by utilizing the sudden change in surface tension of the molten solder, thereby achieving physical barrier.

[0030] like Figure 4 As shown, for example, the surface of the boss 7 facing away from the pin seat 5 is provided with a microgroove 71, the depth of which is 50~100μm. By providing the microgroove 71, the solder is induced to form a crescent-shaped solder joint in the microgroove 71, thus consuming its climbing kinetic energy.

[0031] When the solder comes into contact with the microgroove 71, the microgroove 71 causes the solder to form a crescent-shaped (meniscus) solder joint: the liquid surface of the solder will adhere to the inner wall of the microgroove 71, forming an arc shape with a "low center and high edges". In this process, the kinetic energy of the solder flow will be converted into surface energy (maintaining the meniscus shape requires overcoming surface tension to do work), thus losing the power to continue climbing.

[0032] If the depth is too shallow (<50μm): the microgroove 71 has insufficient constraint on the solder. The solder can only form a small depression on the surface and cannot stably form a crescent-shaped solder joint. This is equivalent to insufficient resistance, and the solder will continue to climb along the gap.

[0033] Excessive depth (>100μm): The microgroove 71 has an excessively strong ability to absorb solder, and a large amount of solder will fill the interior of the microgroove 71. After the solder in the microgroove 71 cools down, it is easy to form voids, which will affect the stability of electrical connection and heat dissipation performance.

[0034] like Figure 3 As shown, for example, the needle body 6 includes a third column 61, a connecting plate 62, and a fourth column 63. One side of the third column 61 is connected to the needle seat 5 in the axial direction, and the other side of the third column 61 is connected to the connecting plate 62 and the fourth column 63 in sequence.

[0035] The outer diameter of the third column 61 is smaller than the outer diameter of the needle seat 5. The boss 7 is located on the side of the third column 61 near the connecting plate 62. The shape of the connecting plate 62 can be set according to requirements. For example, it can be set as an S-shape or other shapes. The outer diameter of the fourth column 63 is smaller than the outer diameter of the needle seat 5.

[0036] In this embodiment, a boss 7 is provided on the third column 61. When the solder climbs to the boss 7, a molten solder joint is formed, which reduces the solder wetting ability and prevents the solder from continuing to climb to the connecting plate 62.

[0037] For example, the outer diameter of boss 7 is 1.2 to 1.5 times the outer diameter of the third column 61 to ensure the maximum climbing diameter of the covered solder.

[0038] like Figure 3 As shown, for example, the height H between the side of the boss 7 facing the pin seat 5 and the side facing away from the pin seat 5 is 0.3~0.5mm, forming an effective surface tension abrupt change zone, which also meets the current compact design requirements of electronic components.

[0039] like Figure 4 As shown, for example, the density of microgrooves 71 is 3~5 per mm. 2 This enhances the ability to retain solder.

[0040] The density of microgrooves 71 is too low (<3 grooves / mm). 2 The problem is that there are insufficient "resistance points" per unit area, causing solder to form crescent-shaped solder joints only in a few microgrooves 71. Most areas remain planar, leading to localized overflow (in areas not constrained by the microgrooves 71, the solder continues to rise). For example, 1mm... 2 There are only two micro-grooves 71 inside, with a spacing of about 0.7mm between them. The solder in the gaps is unrestrained and is prone to forming "flow marks".

[0041] Density too high (>5 particles / mm) 2 The processing difficulty increases dramatically, especially if the density is higher (e.g., 6 particles / mm). 2 When the spacing is reduced to 0.4mm, "roughness of the groove edge" is likely to occur during laser etching (interference of the etching path of adjacent micro-grooves 71), which will damage the wetting performance of the solder (the rough surface is prone to residual impurities, resulting in the solder not adhering); the surface bearing capacity will decrease: too many micro-grooves 71 will "encroach" on the effective plane area of ​​the back surface of the boss 7.

[0042] Compared with the existing solder mask process, the solder climb height of the PIN pins in this application embodiment is reduced by more than 55%. In the related technology, the solder climb height of the solder mask process is greater than or equal to 1.8mm, while the solder climb height of the PIN pins in this application embodiment is less than or equal to 0.8mm by setting the boss 7.

[0043] For example, the needle base 5, needle body 6, and boss 7 are integrally formed, or the needle base 5, needle body 6, and boss 7 are simultaneously die-cast, requiring no secondary processing.

[0044] Existing solder resist processes require the application / curing of solder resist at the S-bend structure 2, which is costly. In this embodiment, the needle holder 5, needle body 6, and boss 7 are integrally formed, without adding processing steps, resulting in low cost.

[0045] Furthermore, existing solder resist processes carry the risk of solder resist aging and falling off, while the boss 7 and the pin body 6 are made of the same material (copper-based), making the structure more reliable.

[0046] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A PIN pin for a power module, characterized in that, It includes a needle seat (5) and a needle body (6). The needle seat (5) is connected to one side of the needle body (6) in the axial direction. The needle body (6) has a boss (7) near the needle seat (5). The boss (7) is arranged around the outer side wall of the needle body (6).

2. The PIN pin for a power module according to claim 1, characterized in that, The boss (7) is umbrella-shaped, with the convex surface of the umbrella-shaped boss (7) facing away from the pin seat (5).

3. The PIN pin for a power module according to claim 2, characterized in that, The angle A between the outline of the side edge of the boss (7) facing the needle seat (5) and the axial center line of the needle body (6) is an acute angle.

4. The PIN pin for a power module according to claim 1, characterized in that, The surface of the boss (7) facing away from the needle seat (5) is provided with a micro-groove (71).

5. The PIN pin for a power module according to claim 4, characterized in that, The depth of the microgroove (71) is 50~100μm.

6. The PIN pin for a power module according to claim 2, characterized in that, The height H of the boss (7) between the side facing the needle seat (5) and the side facing away from the needle seat (5) is 0.3~0.5mm.

7. The PIN pin for a power module according to claim 4, characterized in that, The density of the microgrooves (71) is 3~5 per mm. 2 .

8. The PIN pin for a power module according to any one of claims 1-7, characterized in that, The needle body (6) includes a third column (61), a connecting plate (62), and a fourth column (63); One side of the third column (61) is connected to the needle seat (5) along its axial direction, and the other side of the third column (61) is connected to the connecting plate (62) and the fourth column (63) in sequence. The boss (7) is located on the side of the third column (61) close to the connecting plate (62). The outer diameter of the third column (61) and the outer diameter of the third column (61) are both smaller than the outer diameter of the needle seat (5).

9. The PIN pin for a power module according to claim 8, characterized in that, The outer diameter of the boss (7) is 1.2 to 1.5 times the outer diameter of the third column (61).

10. The PIN pin for a power module according to any one of claims 1-7, characterized in that, The needle base (5), the needle body (6), and the boss (7) are integrally formed.

Images