A lead frame structure

Abstract

The utility model provides a kind of lead frame structure, including lead frame and multiple horizontal webs being arranged on the lead frame and multiple longitudinal webs being perpendicular to the horizontal web, the horizontal web and the longitudinal web separate the lead frame into multiple groups of lead frame units, each group of lead frame unit includes at least two horizontally adjacent lead frame units, each lead frame unit includes a base island, pin being arranged in the longitudinal side of the base island and being separated from the base island, the pin of the same group of lead frame unit shares a common web, two ends of the common web are connected with the longitudinal web respectively, the tip end of the multiple pins is disconnected with the frame body by pre-cut, the part of the common web close to the longitudinal web is bent upwards and protrudes, the height of the plane where the pin is located is equal to the height of the top surface of chip after the base island welds chip.The lead frame structure of the utility model can be compatible with multiple packaging modes.

Description

Technical Field

[0001] This utility model relates to the field of integrated circuit packaging, specifically a lead frame structure. Background Technology

[0002] In the field of power devices, there is a package name called LFPAK, which originated overseas and has been around for 20 years. Figure 1 As shown, the assembly process of the LFPAK package is as follows: First, the chip 130 is soldered onto the base island 110 of the leadframe 100. Then, the clips 120 and copper clamps 140 of the leadframe 100 are used for assembly and positioning to complete the assembly. Next, the leadframe 100 is encapsulated using a molding compound 150. Finally, lead trimming and pin bending are performed. Its characteristic is that the product has externally bent leads; after being placed on the PCB board, the bent leads can absorb stress and prevent the molding compound from cracking.

[0003] Disadvantages of the existing LFPAK packaging structure:

[0004] 1. The copper clip 140 and the lead frame 100 are positioned in the X and Y directions by the buckle 120. Due to the processing error of each component, the buckle may fail: interference mismatch will cause the copper clip to be unable to be fixed, and the product will be scrapped because it cannot be injection molded; excessive freedom will cause the injection mold to press the pins or the lead cutting mold to cut the pins.

[0005] 2. Because this structure adopts an integrated design of copper clip 140 and pin 141, the copper clip is located directly above the lead frame base island after assembly. This means that this structure can only be made into copper clip type packages and cannot be made into low-cost aluminum ribbon bonding packages available on the market.

[0006] 3. Because this structure uses clips to fix the relative positions of the copper clips and the lead frame, the clip design wastes material and frame area, resulting in a relatively high unit price for this product. Utility Model Content

[0007] The purpose of this invention is to provide a lead frame structure that is compatible with multiple packaging methods.

[0008] In this embodiment of the utility model, a lead frame structure is provided, which includes a lead frame and a plurality of transverse connecting ribs disposed on the lead frame and a plurality of longitudinal connecting ribs perpendicular to the transverse connecting ribs. The transverse connecting ribs and the longitudinal connecting ribs divide the lead frame into a plurality of lead frame units. Each group of lead frame units includes at least two transversely adjacent lead frame units. Each lead frame unit includes a base island and a pin disposed on one longitudinal side of the base island and separated from the base island. The pins of the same group of lead frame units share a common connecting rib. The two ends of the common connecting rib are respectively connected to the longitudinal connecting rib. The tips of the plurality of pins are pre-cut and disconnected from the frame body. The portion of the common connecting rib near the longitudinal connecting rib is bent upward and protrudes. The height of the plane where the pin is located is equal to the height of the top surface of the chip after the chip is soldered to the base island.

[0009] In this embodiment of the utility model, one side of the base island is connected to the longitudinal connecting rib via a transverse support rod, and the other side of the base island is connected to a T-shaped support rod, which is connected to the transverse connecting rib.

[0010] Compared with existing technologies, the lead frame structure of this invention, due to the pre-cutting of the tips of the multiple pins from the frame body, facilitates the bending of the connecting ribs, thereby increasing the height of the plane where the pins are located. Furthermore, during electroplating after molding, the tip surfaces of the pins are also covered with tin, enhancing the bonding strength between the packaged product and the PCB board. Additionally, the portion of the common connecting rib near the longitudinal connecting rib is bent upwards and protrudes, making the height of the plane where the pins are located equal to the height of the top surface of the chip after the chip is soldered to the base island. This allows for direct soldering of copper clips or bonding of aluminum strips and copper wires after chip installation, supporting two different packaging methods. Support rods are provided on both sides of the base island, facilitating mold clamping of the support rods during molding to prevent excess adhesive from spilling onto the base island surface. The elimination of clips for fixing copper clips saves frame area and materials, allowing for the formation of more lead frame units within the same size frame. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of a process for encapsulating a lead frame using existing technology.

[0012] Figure 2 This is a schematic diagram of the overall structure of the lead frame structure according to an embodiment of the present invention.

[0013] Figure 3 This is a partial structural schematic diagram of the lead frame structure according to an embodiment of the present invention.

[0014] Figure 4 yes Figure 3 A cross-sectional view along line AA.

[0015] Figure 5 This is a schematic diagram of the encapsulation process using the lead frame structure of an embodiment of this utility model.

[0016] Figure 6 This is a schematic diagram of another packaging process using the lead frame structure of this utility model embodiment. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.

[0018] The implementation of this utility model will be described in detail below with reference to specific embodiments.

[0019] like Figure 2 and Figure 3 As shown in the embodiment of this utility model, a lead frame structure is provided, which includes a lead frame 200 and a plurality of transverse connecting ribs 210 disposed on the lead frame 200 and a plurality of longitudinal connecting ribs 220 perpendicular to the transverse connecting ribs. The transverse connecting ribs 210 and the longitudinal connecting ribs 220 divide the lead frame into multiple groups of lead frame units 230. Each group of lead frame units 230 includes two transversely adjacent lead frame units 240. It should be noted that in other embodiments of this utility model, each group of lead frame units 230 may include three or more transversely adjacent lead frame units 240, the specific number of which depends on actual needs, and this utility model does not limit this.

[0020] Each lead frame unit 240 includes a base island 241 and a plurality of pins 242 disposed on one longitudinal side of the base island 241 and separated from the base island 241. The pins 242 of the same group of lead frame units share a common connecting rib 243, and the two ends of the common connecting rib 243 are respectively connected to the longitudinal connecting rib 220.

[0021] like Figure 4 As shown, the portion of the common connecting rib 243 near the longitudinal connecting rib 220 bends upward and protrudes, making the plane where the pin 242 is located higher than the plane where the base island 241 is located. Specifically, by setting the amplitude of the bend, the height of the plane where the pin 242 is located can be made equal to the height of the top surface of the chip after the chip is soldered to the base island 241. This ensures that when soldering copper clips or bonding aluminum strips, the contact surfaces of the copper clips / aluminum strips, the chip surface, and the pin 242 are on the same plane, facilitating a more reliable electrical connection.

[0022] Furthermore, in this embodiment of the invention, the tips 2421 of the plurality of pins 242 are pre-cut and disconnected from the frame body. This arrangement allows the plurality of pins 242 to be suspended in the air. Only the common connecting rib 243 needs to be bent to move the plane containing the pins 242 upwards, facilitating the overall upward protrusion of the pins 242. Furthermore, in the tin plating process after chip molding, since the tips 2421 of the plurality of pins 242 are pre-cut and exposed, the tips 2421 will also be tin-plated, which can enhance the bonding strength between the packaged product and the PCB board.

[0023] In this embodiment of the invention, one side of the base island 241 is connected to the longitudinal connecting rib 220 via a transverse support rod 244, and the other side of the base island 241 is connected to a T-shaped support rod 245, which is connected to the transverse connecting rib 210. This arrangement ensures that support rods are provided on both the left and right sides of the base island 241, facilitating the sealing mold to press the support rods firmly during molding to prevent excess adhesive from spilling onto the base island surface.

[0024] like Figure 5 As shown in the embodiment of this utility model, a packaging method using the above-described lead frame structure is also provided, which includes the following steps:

[0025] The chip 300 is soldered onto the base island 241;

[0026] A copper clip 400 is soldered onto the chip 300 and the pin 242 so that the chip 300 and the pin 242 are electrically connected through the copper clip 400;

[0027] Injection molding encapsulates the chip 300, the pin 242, and the copper clip 400, and then tin-plats the exposed portion after encapsulation.

[0028] The lead frame after molding is cut to separate each molded chip and each pin of the chip.

[0029] The chip's pins are bent and shaped.

[0030] like Figure 6 As shown in the embodiment of this utility model, another packaging method using the above-described lead frame structure is also provided, which includes the following steps:

[0031] The chip 300 is soldered onto the base island 241;

[0032] Aluminum strip 500 and copper wire 600 are bonded to the chip 300 and the pin 242, so that the chip 300 and the source pin 242 are electrically connected through the aluminum strip 500, and the chip 300 and the gate pin 242 are electrically connected through the copper wire 600.

[0033] Injection molding encapsulates the chip 300, the pin 242, the aluminum strip 500, and the copper wire 600, and then tin-plats the exposed portion after encapsulation.

[0034] The lead frame after injection molding is cut to separate each molded chip and each pin of the chip.

[0035] The chip's pins are bent and shaped.

[0036] In summary, the lead frame structure of this invention, with its pre-cut tips disconnected from the frame body, facilitates bending of the connecting ribs, thereby increasing the height of the plane containing the pins. Furthermore, during electroplating after molding, the tip surfaces of the pins are covered with tin, enhancing the bonding strength between the packaged product and the PCB board. Additionally, the portion of the common connecting rib near the longitudinal connecting rib bends upwards, and the height of the plane containing the pins is equal to the height of the top surface of the chip after bonding it to the base island. This allows for direct soldering of copper clips or bonding of aluminum strips and copper wires after chip installation, supporting two different packaging methods. Support rods are provided on both sides of the base island, facilitating mold clamping during molding to prevent excess adhesive from spilling onto the base island surface. The elimination of clips for fixing copper clips saves frame area and material, allowing for the formation of more lead frame units within the same frame size.

[0037] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A lead frame structure, characterized in that, The device includes a lead frame and multiple transverse connecting ribs disposed on the lead frame, as well as multiple longitudinal connecting ribs perpendicular to the transverse connecting ribs. The transverse connecting ribs and the longitudinal connecting ribs divide the lead frame into multiple groups of lead frame units. Each group of lead frame units includes at least two transversely adjacent lead frame units. Each lead frame unit includes a base island and a pin disposed on one longitudinal side of the base island and separated from the base island. The pins of the same group of lead frame units share a common connecting rib. The two ends of the common connecting rib are respectively connected to the longitudinal connecting ribs. The tips of the multiple pins are pre-cut and disconnected from the frame body. The portion of the common connecting rib near the longitudinal connecting rib is bent upward and protrudes. The height of the plane where the pin is located is equal to the height of the top surface of the chip after the chip is soldered to the base island.

2. The lead frame structure as described in claim 1, characterized in that, One side of the base island is connected to the longitudinal connecting rod via a transverse support rod, and the other side of the base island is connected to a T-shaped support rod, which is connected to the transverse connecting rod.

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