Lead frame structure

Abstract

The utility model discloses a lead frame structure. A plurality of lead frame bodies are continuously arranged along the axial direction to form the lead frame structure. Each lead frame body comprises a lead frame unit, a first side band and a second side band; the lead frame units are arranged in four rows up and down and two columns left and right; the first sidebands are arranged at the upper end and the lower end of each lead frame body; the second sideband is connected between the left lead frame unit and the right lead frame unit; wherein the lead frame unit comprises a base island for bearing a chip, a first pin, a second pin, a third pin, a fourth pin and a fifth pin; the root parts of the first pin, the second pin, the fourth pin and the fifth pin are provided with silver coatings, and the root part of the third pin is connected with the base island. The problems of stress concentration and reliability reduction caused by improper structural design of an existing TO-252 lead frame are solved.

Description

Technical Field

[0001] This utility model belongs to the field of lead frame technology, and more specifically, relates to a lead frame structure. Background Technology

[0002] A semiconductor lead frame is a thin metal frame used to connect the contact points of the internal chip of a semiconductor integrated circuit to external wires. It is a structural material used in semiconductor packaging, accounting for 15% of the semiconductor packaging materials market. As the chip carrier of integrated circuits, the lead frame is a key structural component that uses bonding materials (gold, aluminum, or copper wires) to electrically connect the internal circuit leads (bonding points) of the chip to the external leads, forming an electrical circuit. It acts as a bridge connecting to external wires. Lead frame electroplating is an important semiconductor packaging technology, mainly used to improve the conductivity and heat dissipation of integrated circuit chips.

[0003] The TO-252 package has a relatively small form factor, making it easy to install and layout in compact spaces. However, existing TO-252 leadframes are prone to structural design flaws, leading to stress concentration and reduced reliability. Utility Model Content

[0004] To address the problem of stress concentration and reduced reliability caused by improper design of existing TO-252 leadframe structures, the purpose of this invention is to provide a leadframe structure in which multiple leadframe bodies are continuously arranged along the axial direction to form the leadframe structure. Each leadframe body includes: a leadframe unit, a first side strip, and a second side strip; the leadframe units are arranged in four rows vertically and two columns horizontally; the first side strip is disposed at the upper and lower ends of each leadframe body; the second side strip connects the left and right leadframe units; wherein, the leadframe unit includes: a base island for carrying the chip, a first pin, a second pin, a third pin, a fourth pin, and a fifth pin; the roots of the first pin, the second pin, the fourth pin, and the fifth pin are provided with a silver plating layer, and the root of the third pin is connected to the base island.

[0005] Furthermore, the silver plating layer at the root of the first pin, second pin, fourth pin, and fifth pin has a plating thickness of 2.5 μm.

[0006] Furthermore, semi-circular lead holes are provided on the outer sides of the first pin and the fifth pin.

[0007] Furthermore, the side of the base island closest to the chip is a burred side.

[0008] Furthermore, each of the lead frame units is provided with a plurality of first positioning holes on the first side strip, and a second positioning hole is also provided on one of the first side strips, wherein the second positioning hole is an oblong hole.

[0009] Furthermore, each of the lead frame units is provided with a plurality of third positioning holes and fourth positioning holes on the second side strip; wherein the fourth positioning hole is an oblong hole.

[0010] Furthermore, a first connecting rib is provided between two adjacent lead frame bodies.

[0011] Furthermore, the lead frame body also includes: a second connecting rib and a reinforcing rib, wherein the second connecting rib is connected between two adjacent base islands; and the reinforcing rib is connected between the pins of two adjacent lead frame units.

[0012] Furthermore, the lead frame body also includes a stress-relieving dovetail groove, which is formed between the second connecting rib and the base island.

[0013] Furthermore, the lead frame body also includes: a first V-shaped groove, formed at the edges of the left and right sides of the base island; wherein the first V-shaped groove is located on the side of the base island away from the chip.

[0014] Furthermore, the pin is provided with a stamped arc.

[0015] The technical effects and advantages of this utility model are as follows:

[0016] 1. By setting the leadframe unit to include a first pin, a second pin, a third pin, a fourth pin, and a fifth pin, and by applying a silver plating layer at the base of the first, second, fourth, and fifth pins, four solder feet can be formed at the base of the first, second, fourth, and fifth pins. Compared to setting only two solder feet, the stress distribution during soldering is more uniform, which improves the reliability of the solder joint and avoids stress concentration that could affect the performance of the leadframe. Furthermore, more solder feet generally mean a larger mechanical connection area, which can improve the mechanical strength of the solder joint, making it more resistant to vibration and impact.

[0017] 2. When the lead frame structure is stamped and bent using a lead frame processing die, the first positioning hole is mainly used to position the entire lead frame structure. The second positioning hole is set as an elongated hole. When the lead frame structure is stamped and bent using a lead frame processing die, the lead frame body can be positioned on the Y-axis according to the second positioning hole, and the lead frame body has a certain degree of freedom on the X-axis to adapt to the tolerance and assembly requirements in the manufacturing process.

[0018] 3. By using a stamping process to create an arc on the pin, it will not be scratched during assembly, which can improve assembly efficiency, enhance the reliability of the lead frame, and extend the service life of the lead frame. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a lead frame structure provided by this utility model;

[0020] Figure 2 yes Figure 1 A schematic diagram of the specific structure of the middle lead frame body;

[0021] Figure 3 yes Figure 1 A schematic diagram of the specific structure of the middle lead frame unit;

[0022] Figure 4 yes Figure 3 A schematic diagram showing the connection between two lead frame units;

[0023] Figure 5 yes Figure 4 AA section view of two lead frame units;

[0024] Figure 6 yes Figure 4 BB cross-sectional view of two lead frame units in the middle;

[0025] Figure 7 yes Figure 4 CC cross-sectional view of two lead frame units;

[0026] Figure 8 yes Figure 4 DD cross-sectional view of two lead frame units in the middle;

[0027] Figure 9 yes Figure 4 EE cross-sectional view of two lead frame units;

[0028] Figure 10 yes Figure 4 FF cross-sectional view of two lead frame units;

[0029] Figure 11 yes Figure 4 GG cross-sectional view of two lead frame units in the middle;

[0030] Figure 12 yes Figure 1 A schematic diagram of an electroplating process for a middle lead frame unit.

[0031] In the picture:

[0032] 100. Lead frame structure; 10. Lead frame body; 20. Lead frame unit; 21. First pin; 22. Second pin; 23. Third pin; 24. Fourth pin; 25. Fifth pin; 26. Base island; 27. Lead hole; 30. First side strip; 31. First positioning hole; 32. Second positioning hole; 40. Second side strip; 41. Third positioning hole; 42. Fourth positioning hole; 50. Silver plating layer; 60. First connecting rib; 70. Second connecting rib; 80. Reinforcing rib; 91. Stress relief dovetail groove; 92. First V-groove. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the present invention to the disclosed forms. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described to better illustrate the principles and practical applications of the present invention, and to enable those skilled in the art to understand the present invention and design various embodiments with various modifications suitable for a particular purpose.

[0034] See Figure 1 This is a schematic diagram of a lead frame structure 100 provided by this utility model. See also... Figures 1 to 12 Multiple lead frame bodies 10 are continuously arranged along the axial direction to form the lead frame structure 100; each lead frame body 10 includes: a lead frame unit 20, a first side strip 30, and a second side strip 40; the lead frame units 20 are arranged in four rows vertically and two columns horizontally; the first side strip 30 is disposed at the upper and lower ends of each lead frame body 10; the second side strip 40 connects the left and right lead frame units 20; wherein, the lead frame unit 20 includes: a base island 26 for carrying the chip, a first pin 21, a second pin 22, a third pin 23, a fourth pin 24, and a fifth pin 25; the roots of the first pin 21, the second pin 22, the fourth pin 24, and the fifth pin 25 are provided with a silver plating layer 50, and the root of the third pin 23 is connected to the base island 26.

[0035] Understandably, by setting the leadframe unit 20 to include a first pin 21, a second pin 22, a third pin 23, a fourth pin 24, and a fifth pin 25, and providing a silver plating layer 50 at the roots of the first pin 21, the second pin 22, the fourth pin 24, and the fifth pin 25, four solder feet can be formed at the roots of the first pin 21, the second pin 22, the fourth pin 24, and the fifth pin 25. Compared to setting only two solder feet, the stress distribution during soldering is more uniform, which can improve the reliability of the solder joint and avoid the problem of stress concentration affecting the performance of the leadframe. In addition, more solder feet usually mean a larger mechanical connection area, which can improve the mechanical strength of the solder joint and make it more resistant to vibration and impact.

[0036] Furthermore, the silver plating layer 50 disposed at the root of the first pin 21, the second pin 22, the fourth pin 24, and the fifth pin 25 has a plating thickness of 2.5 μm.

[0037] Understandably, by setting the electroplating thickness of the silver plating layer 50 to 2.5μm, the base material can be better protected, preventing it from oxidizing or corroding at high temperatures, thereby extending the service life of the lead frame.

[0038] Furthermore, a semi-circular lead hole 27 is provided on the outer side of the first pin 21 and the fifth pin 25.

[0039] It is understandable that by providing semi-circular lead holes 27 on the outside of the two side pins (first pin 21 and fifth pin 25) of the lead frame unit 20, when the chip is soldered onto the base island 26, the lead wires can be inserted into the lead holes 27 before soldering, thereby improving the adhesion between the chip and the lead frame and enhancing the packaging reliability of the lead frame structure 100.

[0040] Furthermore, the side of the base island 26 closest to the chip is a rough surface. For example, the rough surface of the base island 26 has multiple pits (not shown in the figures), and the conductive adhesive or solder will fill the pits after melting, improving the bonding force between the base island 26 and the chip.

[0041] It is understandable that since the side of the base island 26 closest to the chip is a burr side, it can increase the bonding area between the base island 26 and the chip, thereby increasing the bonding strength between the two parts of the base island 26 and the chip, and avoiding the problem of delamination between the base island 26 and the chip.

[0042] Furthermore, each of the lead frame units 20 has multiple first positioning holes 31 on the first side strip 30, and one of the first side strips 30 also has a second positioning hole 32, which is an elongated hole. For example, the first positioning hole 31 is a circular hole; the extension direction of the second positioning hole 32 is the X-axis.

[0043] Understandably, when the lead frame structure 100 is stamped and bent using a lead frame processing die, the first positioning hole 31 is mainly used to position the entire lead frame structure 100; the second positioning hole 32 is set as an elongated hole so that when the lead frame structure 100 is stamped and bent using a lead frame processing die, the lead frame body 10 can be positioned on the Y-axis according to the second positioning hole 32, and the lead frame body 10 has a certain degree of freedom on the X-axis to adapt to the tolerance and assembly requirements in the manufacturing process.

[0044] Furthermore, each of the lead frame units 20 is provided with a plurality of third positioning holes 41 and fourth positioning holes 42 on the second side strip 40; wherein, the fourth positioning hole 42 is an oblong hole.

[0045] It is understandable that by setting multiple fourth positioning holes 42 with third positioning holes 41 and elongated holes on the second side strip 40, the lead frame body 10 can be positioned on the X axis according to the fourth positioning holes 42, and the lead frame body 10 has a certain degree of freedom on the Y axis to adapt to the tolerance and assembly requirements in the manufacturing process.

[0046] Furthermore, a first connecting rib 60 is provided between two adjacent lead frame bodies 10. For example, the first connecting rib 60 connects the fifth pin 25 and the first pin 21 of two adjacent lead frame units 20.

[0047] It is understandable that by providing a first connecting rib 60 between the side pins of two adjacent lead frame units 20, the overall strength and stability of the lead frame can be improved.

[0048] Furthermore, the lead frame body 10 also includes a second connecting rib 70 and a reinforcing rib 80, wherein the second connecting rib 70 is connected between two adjacent base islands 26; and the reinforcing rib 80 is connected between the pins of two adjacent lead frame units 20.

[0049] It is understandable that by providing a second connecting rib 70 between two adjacent base islands 26, the two adjacent base islands 26 can be connected by the second connecting rib 70; by providing a reinforcing rib 80 between the pins of two adjacent lead frame units 20, the overall strength and stability of the lead frame can be further improved.

[0050] Furthermore, the lead frame body 10 also includes a stress-relieving dovetail groove 91, formed between the second connecting rib 70 and the base island 26. For example, a rectangular groove on the surface and a trapezoidal groove on the bottom surface are connected to form the stress-relieving dovetail groove 91.

[0051] Understandably, by creating a stress-relieving dovetail groove 91 between the second connecting rib 70 and the base island 26, the molten conductive adhesive or solder can fill the stress-relieving dovetail groove 91 during welding and encapsulation, improving the bonding force between the base island 26 and the chip and preventing delamination and cracking. On the other hand, the stress-relieving dovetail groove 91 can effectively prevent damage to the chip caused by the stress during solder shrinkage, thereby improving the reliability of the lead frame body 10 and extending its service life.

[0052] Furthermore, the lead frame body 10 also includes a first V-groove 92, which is formed at the edges of the left and right sides of the base island 26; wherein the first V-groove 92 is located on the side of the base island 26 away from the chip.

[0053] Understandably, by opening the first V-groove 92 at the edges on both sides of the base island 26, the adhesion between the lead frame and the molding compound can be further improved.

[0054] Furthermore, the pin is provided with a stamped arc.

[0055] Understandably, creating an arc on the pins through stamping prevents them from being scratched during assembly, thereby improving assembly efficiency, enhancing the reliability of the lead frame, and extending its service life.

[0056] In the description of this utility model, it should be understood that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this utility model and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0057] Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. All other embodiments obtained by those skilled in the art and related fields based on the embodiments of this utility model without creative effort should fall within the protection scope of this utility model. Structures, devices, and operating methods not specifically described and explained in this utility model, unless otherwise specified or limited, shall be implemented according to conventional means in the art.

Claims

1. A lead frame structure (100), characterized in that, Multiple lead frame bodies (10) are continuously arranged along the axial direction to form the lead frame structure (100); each lead frame body (10) includes: lead frame unit (20), first side strip (30), and second side strip (40); the lead frame unit (20) is arranged in four rows up and down and two columns left and right; the first side strip (30) is disposed at the upper and lower ends of each lead frame body (10); the second side strip (40) is connected between the left and right lead frame units (20); wherein, the lead frame unit (20) includes: a base island (26) for carrying the chip, a first pin (21), a second pin (22), a third pin (23), a fourth pin (24), and a fifth pin (25); the roots of the first pin (21), the second pin (22), the fourth pin (24), and the fifth pin (25) are provided with a silver plating layer (50), and the root of the third pin (23) is connected to the base island (26).

2. The lead frame structure (100) according to claim 1, characterized in that, The silver plating layer (50) provided at the root of the first pin (21), the second pin (22), the fourth pin (24), and the fifth pin (25) has an electroplating thickness of 2.5 μm.

3. The lead frame structure (100) according to claim 1, characterized in that, The first pin (21) and the fifth pin (25) have semi-circular lead holes (27) on their outer sides.

4. The lead frame structure (100) according to claim 1, characterized in that, The side of the base island (26) closest to the chip is a burr side.

5. The lead frame structure (100) according to any one of claims 1-4, characterized in that, Each of the lead frame units (20) has a plurality of first positioning holes (31) on the first side strip (30), and a second positioning hole (32) is also provided on one of the first side strips (30), and the second positioning hole (32) is an elongated hole.

6. The lead frame structure (100) according to claim 5, characterized in that, Each of the lead frame units (20) is provided with a plurality of third positioning holes (41) and fourth positioning holes (42) on the second side strip (40); wherein the fourth positioning hole (42) is an oblong hole.

7. The lead frame structure (100) according to claim 6, characterized in that, A first connecting rib (60) is also provided between two adjacent lead frame bodies (10).

8. The lead frame structure (100) according to claim 5, characterized in that, The lead frame body (10) further includes: a second connecting rib (70) and a reinforcing rib (80), wherein the second connecting rib (70) is connected between two adjacent base islands (26); and the reinforcing rib (80) is connected between the pins of two adjacent lead frame units (20).

9. The lead frame structure (100) according to claim 8, characterized in that, The lead frame body (10) further includes a stress-relieving dovetail groove (91) formed between the second connecting rib (70) and the base island (26).

10. The lead frame structure (100) according to claim 8, characterized in that, The lead frame body (10) further includes: a first V-groove (92) formed at the edges of the left and right sides of the base island (26); wherein the first V-groove (92) is located on the side of the base island (26) away from the chip.

11. The lead frame structure (100) according to claim 8, characterized in that, The pin has an arc formed by stamping.

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