A lead frame

Abstract

The utility model discloses a lead frame, including a plurality of parallelly arranged frame groups, and each frame group includes two frame units, and each frame unit includes a carrier area, and four pins located below the carrier area, the carrier area is divided into left carrier area and right carrier area, and the four pins are same in size and are commonly connected with middle ribs, and the two middle ribs of each frame group are equipped with connecting ribs, and the two frame units of each frame group are centrally symmetric with the center of connecting rib as the symmetry center, and the four pins of one frame unit are staggered with the four pins of another frame unit. The two frame units of each frame group are centrally symmetric with the center of connecting rib as the symmetry center, and the four pins of one frame unit are staggered with the four pins of another frame unit, so that the gap between the pins is fully utilized, thereby making the arrangement of the frame unit more compact, the material utilization rate of the lead frame is higher, and the waste of materials is reduced.

Description

Technical Field

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

[0002] As a chip carrier for integrated circuits, the lead frame is a key structural component that uses bonding materials to achieve electrical connection between the internal circuit leads of the chip and the external leads, forming an electrical circuit. It acts as a bridge connecting to external wires, and most semiconductor integrated circuits require the use of lead frames.

[0003] Lead frames are formed by stamping metal strips using a punch press. Currently, the stamping method using metal strips to form single-row lead frames has the disadvantages of low metal strip utilization, serious resource waste, and high production costs, especially for high-power lead frames.

[0004] Therefore, a new solution is needed to address the above problems. Utility Model Content

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a lead frame.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A lead frame includes several parallel frame groups. Each frame group includes two frame units. Each frame unit includes a substrate area and four pins located below the substrate area. The substrate area is divided into a left substrate area and a right substrate area. There is a spacing between two adjacent pins, and the width of the spacing is greater than the width of the pins. The four pins are of the same size and are connected to a central rib. Adjacent frame groups are connected by the central rib. A connecting rib is provided between the two central ribs of each frame group. The connecting rib is perpendicular to the central rib and its two ends are respectively connected to the two central ribs. The two frame units of each frame group are centrally symmetrical about the center of the connecting rib. The four pins of one frame unit are staggered with the four pins of the other frame unit.

[0008] Furthermore, the left carrier area has a U-shaped structure, the right carrier area has an n-shaped structure, and the two free ends of the left carrier area are staggered with the two free ends of the right carrier area.

[0009] Furthermore, each frame unit has four pins, namely a first pin, a second pin, a third pin, and a fourth pin. The first pin is connected to the left substrate area, the second pin is connected to the first solder pad, the third pin is connected to the second solder pad, and the fourth pin is connected to the right substrate area. The first solder pad and the second solder pad are located below the left substrate area and the right substrate area.

[0010] Furthermore, the lower part of the left substrate area is connected to a left connecting part, and the first pin is connected through the left connecting part. The lower part of the right substrate area is connected to a right connecting part, and the fourth pin is connected through the right connecting part. The first solder pad and the second solder pad are located in the area formed by the combination of the left connecting part, the first pin, the right connecting part and the right pin. This area is connected to the area formed by the combination of the left substrate area and the right substrate area.

[0011] Furthermore, the first welding piece and the second welding piece have the same structure. The first pin forms an angle of 45° with the left connecting part, the second pin forms an angle of 45° with the first welding piece, the third pin forms an angle of 45° with the second welding piece, and the fourth pin forms an angle of 45° with the right connecting part.

[0012] Furthermore, the connecting rib is provided with a plurality of positioning holes along its length direction, and the plurality of positioning holes are arranged vertically.

[0013] Furthermore, in each of the frame groups, the bottom of the four pins of one frame unit is connected to the central rib of another frame unit after being narrowed.

[0014] The beneficial effects of this utility model are:

[0015] 1. In this utility model, by separating the carrier area into sections, the thermal stress path is broken. Compared with an integral carrier area, the stress transmitted to the chip and solder interface is greatly reduced, significantly reducing the risk of chip adhesive layer cracking. At the same time, after separating the carrier area, the effective surface area of ​​the carrier area is increased, that is, the contact surface area with epoxy resin is increased, which helps to dissipate the heat generated by the chip more evenly to the entire package surface, and then dissipate it into the environment through convection and radiation.

[0016] 2. In this utility model, the two frame units of each frame group are arranged in a centrally symmetrical manner with the center of the connecting rib as the center of symmetry. The four pins of one frame unit are staggered with the four pins of the other frame unit, so that the gap between the pins is fully utilized, thereby making the arrangement of the frame units more compact, the material utilization rate of the lead frame is higher, the waste of materials is reduced, and the cost can be effectively reduced. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of one structure of the lead frame in this embodiment;

[0018] Figure 2 This is a schematic diagram of one structure of the frame group in this embodiment;

[0019] Figure 3 This is a schematic diagram of a right-view structure of the frame group in this embodiment.

[0020] Reference numerals: Frame group 1, Frame unit 2, Left carrier area 21, Left connecting part 211, Right carrier area 22, Right connecting part 221, First pin 23, Second pin 24, Third pin 25, Fourth pin 26, First welding piece 27, Second welding piece 28, Middle rib 3, Connecting rib 4, Positioning hole 41. Detailed Implementation

[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0022] Example: A lead frame, such as Figures 1-3 As shown, it includes several parallel frame groups 1, each frame group 1 includes two frame units 2, and one frame unit 2 corresponds to one chip, which is used in high-power electrical equipment.

[0023] like Figure 2 As shown, each frame unit 2 includes a wafer carrier area and four pins located below the wafer carrier area. The wafer carrier area is used to mount the chip and is divided into a left wafer carrier area 21 and a right wafer carrier area 22. The left wafer carrier area 21 has a U-shaped structure, and the right wafer carrier area 22 has an n-shaped structure. Both the left wafer carrier area 21 and the right wafer carrier area 22 have two free ends. The two free ends of the left wafer carrier area 21 and the two free ends of the right wafer carrier area 22 are staggered. Specifically, the left free end of the right wafer carrier area 22 extends beyond the right free end of the left wafer carrier area 21 and into the area enclosed by the two free ends of the left wafer carrier area 21. The right free end of the left wafer carrier area 21 extends beyond the left free end of the right wafer carrier area 22 and into the area enclosed by the two free ends of the right wafer carrier area 22.

[0024] By dividing the carrier into a left carrier area 21 and a right carrier area 22, a split configuration is formed to break the thermal stress path. Compared with a single carrier area, the stress transmitted to the chip and solder interface is greatly reduced, significantly reducing the risk of chip bonding layer cracking and improving device life and reliability. At the same time, after the carrier is split, the effective surface area of ​​the carrier area increases, that is, the contact surface area with epoxy resin increases, which helps to dissipate the heat generated by the chip more evenly to the entire package surface, and then dissipate it into the environment through convection and radiation.

[0025] Furthermore, such as Figure 2As shown, in frame unit 2, there is a gap between two adjacent pins, and the width of the gap is greater than the width of the pin. The four pins are the same size and are connected by a central rib 3. Two adjacent frame groups 1 are connected by the central rib 3, and multiple frame groups 1 are connected together by the central rib 3 to form a whole, i.e., a lead frame. A connecting rib 4 is provided between the two central ribs 3 of each frame group 1. The width of the connecting rib 4 is greater than the width of the central rib 3 and the pin, and the length of the connecting rib 4 is equal to the length of the pin. The connecting rib 4 is set perpendicular to the central rib 3, and its two ends are connected to two central ribs 3 respectively.

[0026] Since the bottom of the four pins of one frame unit 2 in each frame group 1 is connected to the middle rib 3 of another frame unit 2 after being narrowed, in order to improve the integrity of each frame group 1, a connecting rib 4 is set between the two middle ribs 3, and the two frame units 2 are connected by the connecting rib 4, which further improves the stability of the connection between the two frame units 2, thereby ensuring the integrity of the frame group 1.

[0027] Preferably, the two frame units 2 of each frame group 1 are arranged symmetrically with the center of the connecting rib 4 as the center of symmetry, and the four pins of one frame unit 2 are staggered with the four pins of the other frame unit 2. By adopting the above design, the staggered arrangement of the pins of the frame units 2 makes full use of the gaps between the pins, thereby making the arrangement of the frame units 2 more compact, the material utilization rate of the lead frame is higher, the material waste is reduced, and the cost can be effectively reduced.

[0028] Preferably, the connecting rib 4 has multiple positioning holes 41 along its length, and the multiple positioning holes 41 are arranged vertically. For example Figure 2 As shown, in this embodiment, three positioning holes 41 are provided, with the center of the middle positioning hole 41 being the center of symmetry. The positioning holes 41 are provided to facilitate effective positioning of the lead frame and the mold used.

[0029] Furthermore, such as Figure 2 As shown, the four pins of each frame unit 2 are pin 23, pin 24, pin 25, and pin 26. The upper parts of pins 23, 24, 25, and 26 are connected to a central rib 3, and the bottom parts of pins 23, 24, 25, and 26 are connected to another central rib 3. The two central ribs 3 work together to constrain pins 23, 24, 25, and 26 to prevent pin bending during subsequent operations, which would affect chip mounting and frame packaging.

[0030] The first pin 23 is connected to the left substrate area 21, the second pin 24 is connected to the first bonding pad 27, the third pin 25 is connected to the second bonding pad 28, and the fourth pin 26 is connected to the right substrate area 22. The first bonding pad 27 and the second bonding pad 28 have the same structure and are both located below the substrate area formed by the combination of the left substrate area 21 and the right substrate area 22. There are gaps between the first bonding pad 27 and the substrate area, and between the second bonding pad 28 and the substrate area. The first bonding pad 27 is connected to the chip mounted on the substrate area by bonding wires in a flying wire soldering manner, and the second bonding pad 28 is connected to the chip mounted on the substrate area by bonding wires in a flying wire soldering manner.

[0031] By setting gaps between the first solder pad 27 and the substrate area, and between the second solder pad 28 and the substrate area, two purposes are achieved: first, to electrically isolate the four pins from each other; and second, during injection molding, the epoxy resin fills these gaps, forming a solid insulating barrier that increases the creepage distance and clearance between the pins and the substrate area. Simultaneously, the horizontal arrangement of the first solder pad 27 and the second solder pad 28 provides a larger, flatter platform for wire bonding, making the bonding process easier and reducing the risk of wire detachment or breakage. Furthermore, the combination of the first solder pad 27 and the second pin 24, and the second solder pad 28 with the third pin 25, forms a T-shape, which better resists mechanical stress and vibration during packaging and subsequent processing, preventing pin or solder pad deformation.

[0032] Preferably, the lower part of the left substrate area 21 is connected to a left connecting portion 211, and the first pin 23 is connected through the left connecting portion 211. The lower part of the right substrate area 22 is connected to a right connecting portion 221, and the fourth pin 26 is connected through the right connecting portion 221. The first solder pad 27 and the second solder pad 28 are located in the area formed by the combination of the left connecting portion 211, the first pin 23, the right connecting portion 221, and the fourth pin 26, and this area is connected to the area formed by the combination of the left substrate area 21 and the right substrate area 22. This design facilitates the flow of epoxy resin, allowing it to better encapsulate the frame and improve the consistency and insulation performance of the encapsulation.

[0033] Furthermore, such as Figure 3As shown, the first pin 23 forms a 45-55° angle with the left connecting portion 211, the second pin 24 forms a 45-55° angle with the first solder pad 27, the third pin 25 forms a 45-55° angle with the second solder pad 28, and the fourth pin 26 forms a 45-55° angle with the right connecting portion 221. This structure achieves several advantages: first, it shortens the distance between the solder pad and the chip solder joint, thus shortening the bonding wire, which has higher mechanical strength; second, the angle between the pins and the substrate area facilitates epoxy resin flow, reducing the risk of turbulence or dead zones, thereby avoiding defects such as bubbles and material shortages caused by uneven filling; and third, the 45-55° angle reduces the bending amplitude during subsequent molding, disperses stress, and maintains the mechanical integrity of the pins.

[0034] Furthermore, in each frame group 1, the bottom of the four pins of one frame unit 2 is narrowed and connected to the central rib 3 of another frame unit 2. Specifically, in this embodiment, the width of the first pin 23, the second pin 24, the third pin 25, and the fourth pin 26 is 1mm, and the bottom of the pins is narrowed to 0.5mm before connecting to the central rib 3 of another frame unit 2. This structure serves two purposes: first, it uses the cooperation of two central ribs 3 to constrain the first pin 23, the second pin 24, the third pin 25, and the fourth pin 26, preventing pin bending during subsequent operations that could affect chip mounting and frame packaging; second, while ensuring the constraint effect of the pins, the narrowing of the bottom of the pins facilitates the subsequent separation of the two frame units 2.

[0035] The above description is merely a preferred embodiment of this utility model. The protection scope of this utility model is not limited to the above embodiments. All technical solutions falling within the scope of this utility model's concept are protected. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of this utility model should also be considered within the protection scope of this utility model.

Claims

1. A lead frame, characterized in that, The system includes several parallel frame groups (1), each frame group (1) includes two frame units (2), each frame unit (2) includes a substrate area and four pins located below the substrate area. The substrate area is divided into a left substrate area (21) and a right substrate area (22). There is a gap between two adjacent pins, and the width of the gap is greater than the width of the pin. The four pins are the same size and are connected to a central rib (3). Two adjacent frame groups (1) are connected by the central rib (3). A connecting rib (4) is provided between the two central ribs (3) of each frame group (1). The connecting rib (4) is set perpendicular to the central rib (3), and the two ends of the connecting rib (4) are respectively connected to the two central ribs (3). The two frame units (2) of each frame group (1) are arranged in a centrally symmetrical manner with the center of the connecting rib (4) as the center of symmetry. The four pins of one frame unit (2) are staggered with the four pins of the other frame unit (2).

2. A lead frame according to claim 1, characterized in that, The left carrier area (21) has a U-shaped structure, and the right carrier area (22) has an n-shaped structure. The two free ends of the left carrier area (21) and the two free ends of the right carrier area (22) are staggered.

3. A lead frame according to claim 1, characterized in that, Each frame unit (2) has four pins: a first pin (23), a second pin (24), a third pin (25), and a fourth pin (26). The first pin (23) is connected to the left substrate area (21), the second pin (24) is connected to the first solder pad (27), the third pin (25) is connected to the second solder pad (28), and the fourth pin (26) is connected to the right substrate area (22). The first solder pad (27) and the second solder pad (28) are located below the left substrate area (21) and the right substrate area (22).

4. A lead frame according to claim 3, characterized in that, The lower part of the left substrate area (21) is connected to the left connecting part (211), and the first pin (23) is connected through the left connecting part (211). The lower part of the right substrate area (22) is connected to the right connecting part (221), and the fourth pin (26) is connected through the right connecting part (221). The first solder piece (27) and the second solder piece (28) are located in the area formed by the combination of the left connecting part (211), the first pin (23), the right connecting part (221) and the fourth pin (26). This area is connected to the area formed by the combination of the left substrate area (21) and the right substrate area (22).

5. A lead frame according to claim 4, characterized in that, The first welding piece (27) and the second welding piece (28) have the same structure. The first pin (23) forms an angle of 45-55° with the left connecting part (211), the second pin (24) forms an angle of 45-55° with the first welding piece (27), the third pin (25) forms an angle of 45-55° with the second welding piece (28), and the fourth pin (26) forms an angle of 45-55° with the right connecting part (221).

6. A lead frame according to claim 1, characterized in that, The connecting rib (4) is provided with a plurality of positioning holes (41) along its length direction, and the plurality of positioning holes (41) are arranged vertically.

7. A lead frame according to claim 1, characterized in that, In each of the frame groups (1), the bottom of the four pins of one frame unit (2) is connected to the central rib (3) of another frame unit (2) after being narrowed.

Images