A lead frame structure

Abstract

The utility model discloses a kind of lead frame structures, lead frame unit is arranged to form the lead frame structure in six rows, left and right two columns, the lead frame unit includes: base island, including base island body and protruding setting in the front of base island body chip bearing area;Locking groove, be opened in the chip bearing area, and the locking groove is located at the edge position of the chip bearing area;Pin, bending connection in the side of the base island;Base island connecting rib, connect between two the base island of adjacent upper and lower;Wherein, the chip bearing area is rough surface. Solve the problem that the base island and chip of existing TO-252 lead frame are easy to delaminate.

Description

Technical Field

[0001] This utility model belongs to the field of lead frame design technology, and more specifically, it 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 lay out in a compact space. However, the base island and chip of the existing TO-252 leadframe are prone to being separated. Utility Model Content

[0004] To address the issue of easy delamination between the base island and chip in existing TO-252 leadframes, the purpose of this invention is to provide a leadframe structure. The leadframe units are arranged in six rows vertically and two columns horizontally to form the leadframe structure. Each leadframe unit includes: a base island, comprising a base island body and a chip-carrying area protruding from the front of the base island body; a locking groove, formed in the chip-carrying area and located at the edge of the chip-carrying area; a lead, bent and connected to one side of the base island; and a base island connecting rib, connecting two adjacent base islands vertically. The chip-carrying area has a rough surface.

[0005] Furthermore, the raised chip-carrying area forms a first step on the front side of the base island body; the first step includes a first longitudinal wall and a first transverse wall, the first transverse wall being arc-shaped.

[0006] Furthermore, a second step is provided on the side of the base island body away from the chip carrying area; the width of the second step is smaller than the width of the first step.

[0007] Furthermore, the lead frame unit also includes a through groove formed between the base island connecting rib and the base island.

[0008] Furthermore, the through groove includes a first rectangular groove and a second rectangular groove that are connected, wherein the width of the first rectangular groove is smaller than the width of the second rectangular groove.

[0009] Furthermore, an arc-shaped rib is provided on the side of the first rectangular groove near the second rectangular groove.

[0010] Furthermore, the pin includes an outer pin and an inner pin, the inner pin including a bent section and a base island connection section; wherein, a first stress groove is provided at the connection between the bent section and the base island connection section.

[0011] Furthermore, a second stress groove is provided at the connection between the bent section and the outer pin.

[0012] Furthermore, a third stress groove is provided at the connection between the base island connecting rib and the base island.

[0013] Furthermore, the pin includes a first pin, a second pin, and a third pin; the first pin is provided with a first soldering portion, the third pin is provided with a second soldering portion, and the soldering area of ​​the first soldering portion is larger than the soldering area of ​​the second soldering portion.

[0014] Furthermore, the second welding part is provided with a locking hole.

[0015] Furthermore, the first weld portion and the second weld portion include a bare copper layer and a silver plating layer.

[0016] Furthermore, the silver plating layer comprises a plurality of uniformly distributed silver plating dots.

[0017] The technical effects and advantages of this utility model are as follows:

[0018] 1. By setting the chip carrier area to a rough surface, the bonding area between the chip carrier area and the chip can be increased, thereby improving the bonding strength between them. By creating locking grooves at the edges of the chip carrier area, the bonding strength between the chip edges and the carrier area can be further enhanced, ensuring a tight fit and preventing chip lifting or delamination. The combination of a rough surface and locking grooves effectively prevents chip delamination or detachment from the base islands.

[0019] 2. By applying a silver plating layer to the first weld joint, the conductivity of the first weld joint and the first weld joint can be improved. Compared to full-area electroplating, spot plating can improve performance while reducing the amount of silver used and the time required for electroplating, thus lowering costs. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a lead frame structure provided by this utility model;

[0021] Figure 2 yes Figure 1A schematic diagram of the structure in which two lead frame units are connected together;

[0022] Figure 3 yes Figure 2 A cross-sectional view of two lead frame units connected together;

[0023] Figure 4 yes Figure 3 Enlarged view of point A in the middle;

[0024] Figure 5 yes Figure 3 Enlarged view of point B in the middle;

[0025] Figure 6 yes Figure 3 Enlarged view of point C in the middle;

[0026] Figure 7 yes Figure 3 A detailed structural diagram of the base island;

[0027] Figure 8 yes Figure 7 Sectional view at point D;

[0028] Figure 9 yes Figure 7 Sectional view at point E in the middle.

[0029] In the picture:

[0030] 200. Leadframe structure; 100. Leadframe unit; 10. Base island; 11. Chip carrier area; 12. Base island body; 13. First step; 14. Second step;

[0031] 15. Locking groove; 21. First pin; 22. Second pin; 23. Third pin; 24. Outer pin; 251. Bending section; 252. Base island connecting section; 261. First welding part;

[0032] 262. Second welding section; 263. Locking hole; 30. Base island connecting rib; 31. Through groove;

[0033] 311. First rectangular groove; 312. Second rectangular groove; 313. Arc-shaped rib; 41. First stress groove; 42. Second stress groove; 43. Third stress groove. Detailed Implementation

[0034] 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.

[0035] See Figure 1 This is a schematic diagram of a lead frame structure 200 provided by this utility model, combined with... Figures 1 to 9 The lead frame units 100 are arranged in six rows vertically and two columns horizontally to form the lead frame structure 200. The lead frame unit 100 includes a base island 10 and pins. The base island 10 includes a base island body 12 and a chip carrier area 11 protruding on the front side of the base island body 12. During semiconductor packaging, the chip is first attached to the chip carrier area 11, and then the bonding solder joints of the chip and the solder joints of the lead frame are soldered together with wires. Finally, it is encapsulated with a molding compound such as resin.

[0036] The chip-carrying area 11 has a rough surface and a locking groove 15 is provided therein. Specifically, the locking groove 15 is located at the edge of the chip-carrying area 11. For example, the chip-carrying area 11 is a rectangular area, and the locking groove 15 is located at the outer edge of the rectangular area, that is, around the perimeter of the chip. In a specific embodiment, the cross-section of the locking groove 15 is V-shaped, and the angle of the V-shaped groove is 60°.

[0037] It is understandable that by setting the chip carrier area 11 to a rough surface, the bonding area between the chip carrier area 11 and the chip can be increased, thereby improving the bonding force between the chip carrier area 11 and the chip. By creating a locking groove 15 at the edge of the chip carrier area 11, the bonding force between the chip edge and the chip carrier area 11 can be further improved in a targeted manner, ensuring that the chip edge and the chip carrier area 11 can fit tightly together, avoiding problems such as chip lifting or delamination at the chip edge. The combination of the rough surface and the locking groove 15 can effectively prevent the chip from delaminating or falling off from the base island 10.

[0038] Furthermore, the pin is bent and connected to one side of the base island 10, creating a height difference between the pin and the base island 10. For example, this height difference is 1.067 ± 0.050 mm; the bending angle between the pin and the base island 10 is 30°.

[0039] In one specific embodiment, the lead frame unit 100 includes a first pin 21, a second pin 22, and a third pin 23 arranged sequentially from left to right. The first pin 21 and the third pin 23 are side pins, and the second pin 22 is a center pin. In one specific embodiment, the first pin 21 has a first solder portion 261, and the third pin 23 has a second solder portion 262. The soldering area of ​​the first solder portion 261 is larger than the soldering area of ​​the second solder portion 262, and the second solder portion 262 has a locking hole 263. The first solder portion 261 and the second solder portion 262 include a bare copper layer and a silver plating layer. The silver plating layer includes multiple uniformly distributed silver plating dots. For example, the silver plating thickness is 2.0-6.0 μm.

[0040] It is understandable that by applying a silver plating layer to the first weld portion 261, the conductivity of the first weld portion 261 can be improved. Compared to full-area electroplating, spot plating can improve performance while reducing the amount of silver used and the time required for electroplating, thus lowering costs.

[0041] The base island connecting rib 30 connects two adjacent base islands 10. For example, the base island connecting rib 30 has a rectangular through hole.

[0042] Furthermore, the raised chip-carrying area 11 forms a first step 13 on the front side of the base island body 12. For example, the first step 13 includes a first longitudinal wall and a first transverse wall, the first transverse wall being arc-shaped, so that the portion of the base island body 12 extending beyond the chip-carrying area 11 forms an arc-shaped rounded corner structure to avoid stress concentration.

[0043] Furthermore, a through groove 31 is provided between the base island connecting rib 30 and the base island 10. The through groove 31 includes a first rectangular groove 311 and a second rectangular groove 312 that are connected. The width of the first rectangular groove 311 is smaller than the width of the second rectangular groove 312, and an arc-shaped rib 313 is provided on the side of the first rectangular groove 311 closest to the second rectangular groove 312. During encapsulation, the molding compound such as resin can be cured and formed within the through groove 31, preventing the encapsulation shell and lead frame from becoming one unit. By setting the width of the first rectangular groove 311 to be smaller than the width of the second rectangular groove 312, the cured molding compound can be prevented from falling out of the through groove 31, improving the bonding strength between the molding compound and the through groove 31.

[0044] Furthermore, the pins include outer pins 24 and inner pins. The inner pins include a bent section 251 and a base island connection section 252. A first stress groove 41 is provided at the connection between the bent section 251 and the base island connection section 252 to optimize stress distribution, prevent stress concentration at the connection, and reduce the risk of fracture. For example, the first stress groove 41 is a V-groove with an angle of 60°.

[0045] Furthermore, a second stress groove 42 is provided at the connection between the bent section 251 and the outer pin 24, which can optimize stress distribution and avoid stress concentration at the connection between the bent section 251 and the outer pin 24. For example, the second stress groove 42 is a V-groove with an angle of 60°.

[0046] Furthermore, a third stress groove 43 is provided at the connection between the base island connecting rib 30 and the base island 10. For example, the second stress groove 42 is a dovetail groove, which can further improve the molding bonding force and prevent chip delamination or detachment. Preferably, a V-shaped groove with an angle of 60° is also provided next to the dovetail groove.

[0047] 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.

[0048] 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, characterized by, The lead frame unit (100) is arranged in six rows from top to bottom and two columns from left to right to form the lead frame structure (200), and the lead frame unit (100) comprises: a base island (10) comprising a base island body (12) and a chip bearing area (11) protruding on the front of the base island body (12); a locking groove (15) arranged on the chip bearing area (11), and the locking groove (15) is located at the edge of the chip bearing area (11); a pin bent and connected to one side of the base island (10); a base island connecting rib (30) connected between two adjacent base islands (10) from top to bottom; wherein the chip bearing area (11) is a matte surface.

2. The leadframe structure of claim 1, wherein, The protruding chip bearing area (11) forms a first step (13) on the front of the base island body (12); the first step (13) comprises a first longitudinal wall and a first transverse wall, and the first transverse wall is arc-shaped.

3. The leadframe structure of claim 2, wherein, The base island body (12) is provided with a second step (14) on the side away from the chip bearing area (11); the width of the second step (14) is smaller than the width of the first step (13).

4. The leadframe structure of claim 1, wherein, The lead frame unit (100) further comprises a through groove (31) arranged between the base island connecting rib (30) and the base island (10).

5. The leadframe structure of claim 4, wherein, The through groove (31) comprises a first rectangular groove (311) and a second rectangular groove (312) in communication, and the width of the first rectangular groove (311) is smaller than the width of the second rectangular groove (312).

6. The leadframe structure of claim 5, wherein, The first rectangular groove (311) is provided with an arc-shaped convex rib (313) on the side close to the second rectangular groove (312).

7. The leadframe structure of claim 1, wherein, The pin comprises an outer pin (24) and an inner pin, and the inner pin comprises a bent section (251) and a base island connecting section (252); wherein a first stress groove (41) is arranged at the connection between the bent section (251) and the base island connecting section (252).

8. The leadframe structure of claim 7, wherein, A second stress groove (42) is arranged at the connection between the bent section (251) and the outer pin (24).

9. The leadframe structure of claim 1, wherein, A third stress groove (43) is arranged at the connection between the base island connecting rib (30) and the base island (10).

10. The leadframe structure of claim 1, wherein, The pin comprises a first pin (21), a second pin (22) and a third pin (23); the first pin (21) is provided with a first welding part (261), and the third pin (23) is provided with a second welding part (262); the welding area of the first welding part (261) is larger than the welding area of the second welding part (262).

11. The leadframe structure of claim 10, wherein, The second welding part (262) is provided with a locking hole (263).

12. The leadframe structure of claim 10, wherein, The first welding part (261) and the second welding part (262) comprise a bare copper layer and a silver plating layer.

13. The leadframe structure of claim 12, wherein, The silver plating layer comprises a plurality of uniformly distributed silver plating points.

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