Plastic package DFN package based on Cu-Clip structure

Abstract

The invention provides a plastic package DFN package based on a Cu-Clip structure. The plastic package DFN package comprises a lead frame. A tube core is welded on the lead frame, the tube core is connected with one end of a clip sheet, the other end of the clip sheet is connected with a pin confluence block, through optimization of through-current capability and conduction impedance design, the chip can still keep good performance under high current, and power consumption and heat generation are effectively reduced. Compared with a traditional power package, the package provided by the invention has the advantages of higher integration level, better reliability and longer service life. In addition, the packaging process is relatively simple, large-scale production is easy, and the requirements of the market for high-performance and miniaturized semiconductor packaging can be met. In conclusion, the plastic package DFN package with the CU-Clip structure provided by the invention has remarkable advantages and application value, and is expected to be widely applied and popularized in the field of semiconductor package.

Description

Technical Field

[0001] The present invention relates to a plastic encapsulated DFN package based on a Cu-Clip structure. Background Art

[0002] DFN series plastic encapsulated surface mount products are a new type of package product that has emerged in recent years. They have won the favor of a large number of users due to advantages such as high current, low thermal resistance, and low on-resistance. At present, the internal lead bonding process of traditional plastic encapsulated power devices uses aluminum wires, gold wires, copper wires, aluminum strips, copper strips, etc. as the connection bridges between the chip electrodes and the external pins of the lead frame. Due to the limitation of the package volume, it is difficult to meet the requirements of high current, low thermal resistance, and low on-resistance in small package products. For example, a packaging method and structure of a double-sided heat dissipation power semiconductor disclosed in CN116259549B installs the chip on the frame and connects the chip to the external pins through a copper clip, but no arch is provided on the copper clip, resulting in insufficient connection strength at both ends of the copper clip. Summary of the Invention

[0003] To solve the above technical problems, the present invention provides a plastic encapsulated DFN package based on a Cu-Clip structure.

[0004] The present invention is achieved through the following technical solutions.

[0005] A plastic encapsulated DFN package based on a Cu-Clip structure provided by the present invention includes a lead frame; a die is welded on the lead frame, one end of the die is connected to one end of a clip piece, the other end of the clip piece is connected to a pin bus bar, a chip pole point is further provided on the lead frame, the chip pole point is connected to a second lead-out end through an inner lead, three external pins are evenly and parallelly provided on the pin bus bar, the second lead-out end is parallel to the three external pins and all in the same plane; the lead frame, the die, the pin bus bar, and the second lead-out end are encapsulated into one body.

[0006] Four frame leads are provided at one end of the lead frame far from the pin bus bar, and the positions of the four frame leads correspond to the three external pins and the second lead-out end respectively.

[0007] A groove is machined on the bottom edge of the lead frame.

[0008] A first arch bridge and a second arch bridge are machined on the clip piece, the first arch bridge is machined on the top of the die, and the second arch bridge is machined between the lead frame and the pin bus bar.

[0009] An elliptical through hole is machined on the first arch bridge.

[0010] A fork is machined at the connection between the clip piece and the pin bus bar.

[0011] An inclined bend is processed at the connection between the outer lead and the lead bus bar, so that the top plane of the outer lead is lower than the bottom plane of the lead bus bar.

[0012] Rounded corners are processed at the corners of the Cu-clip.

[0013] The beneficial effects of the present invention are as follows: By optimizing the current-carrying capacity and conduction impedance design, the chip can still maintain good performance under high current, effectively reducing power consumption and heat generation. Compared with traditional power packages, the package of the present invention has higher integration, better reliability and longer service life. In addition, the packaging process is relatively simple and easy for large-scale production, which can meet the market demand for high-performance and miniaturized semiconductor packages. In summary, the plastic-encapsulated DFN package with a CU-clip structure provided by the present invention has significant advantages and application values, and is expected to be widely applied and promoted in the field of semiconductor packaging. Description of the Drawings

[0014] Figure 1 is a schematic structural diagram of the present invention;

[0015] Figure 2 is a schematic side structural diagram of the present invention;

[0016] Figure 3 is a schematic packaging structure diagram of the present invention;

[0017] Figure 4 is a schematic diagram of the bottom groove structure of the lead frame of the present invention;

[0018] Figure 5 is a schematic diagram of the packaging shell structure of the present invention;

[0019] Figure 6 is the sintering process temperature curve of the present invention;

[0020] In the figure: 1 - lead frame, 2 - frame lead, 3 - die, 4 - Cu-clip, 41 - first arch, 42 - second arch, 5 - lead bus bar, 6 - outer lead, 7 - inner lead, 8 - solder layer, 9 - silver-plated area, 10 - chip pole, 11 - second lead-out end. Detailed Embodiments

[0021] The technical solutions of the present invention will be further described below, but the scope of protection is not limited thereto.

[0022] A plastic-encapsulated DFN package based on a Cu-Clip structure includes a lead frame 1; a die 3 is soldered on the lead frame 1, one end of the die 3 is connected to a clip piece 4, the other end of the clip piece 4 is connected to a pin bus bar 5, and a chip pole 10 is also provided on the lead frame 1. The chip pole 10 is connected to a second lead-out end 11 through an inner lead 7. Three outer pins 6 are evenly and parallelly arranged on the pin bus bar 5. The second lead-out end 11 and the three outer pins 6 are parallel to each other and are all on the same plane; the lead frame 1, the die 3, the pin bus bar 5, and the second lead-out end 11 are encapsulated into one body.

[0023] Four frame leads 2 are provided at one end of the lead frame 1 away from the pin bus bar 5. The positions of the four frame leads 2 are respectively opposite to the three outer pins 6 and the second lead-out end 11. The second lead-out end 11 is partially silver-plated.

[0024] A groove is machined on the bottom edge of the lead frame 1.

[0025] A first arch 41 and a second arch 42 are machined on the clip piece 4. The first arch 41 is machined on the top of the die 3. The second arch 42 is machined between the lead frame 1 and the pin bus bar 5. A groove structure is provided on the back edge of the lead frame strip, which strengthens the bonding force between the plastic encapsulant and the lead frame, thereby improving the reliability of the component. Moreover, the arch can also ensure that the solder adheres evenly to the bottom and around the Cu-clip piece.

[0026] An elliptical through-hole is machined on the first arch 41. The top of the Cu-clip piece is designed as an elliptical hole structure, which is convenient for the plastic encapsulant to penetrate through the entire Cu-clip piece, locking the plastic encapsulant firmly on the front and back sides of the Cu-clip piece, thereby improving the reliability of the component.

[0027] A fork is machined at the connection between the clip piece 4 and the pin bus bar 5 to ensure that the solder does not overflow or flip over to cover the Cu-clip piece.

[0028] An oblique bend is machined at the connection between the outer pin 6 and the pin bus bar 5, so that the top plane of the outer pin 6 is lower than the bottom of the pin bus bar 5 and parallel.

[0029] Round corners are machined at the corners of the Cu-clip piece 4.

[0030] The present invention adopts a package size of 5×6 mm 2 This compact design conforms to the trend of miniaturization of modern electronic devices and can achieve efficient electronic connection in a limited space. The package shape is rectangular, and the four corners adopt a rounded corner design to reduce stress concentration and improve the mechanical strength and reliability of the package, as Figure 5 shown.

[0031] The internal structure of the component is designed according to the product functions and performance requirements. The component structure is designed as a bottom KFC copper lead frame strip + chip + Cu-clip sheet + gold wire bonding + plastic encapsulation combined structure, as Figure 1 shown. The specific structure is realized by evenly applying a layer of lead-tin-silver (or silver) solder on the KFC copper lead frame strip using die bonding equipment, then mounting the chip on the lead frame strip, then applying a layer of lead-tin-silver (or silver) solder on the chip surface and the outer pins of the lead frame strip, then mounting the Cu-clip sheet on the chip surface and the outer pins of the lead frame strip, then using a suitable sintering process to cure the lead-tin-silver (or silver) solder, then using a gold wire bonder to connect the chip gate to the outer pins of the lead frame strip, and finally using a highly reliable epoxy plastic encapsulant to perform plastic encapsulation on the product to be encapsulated using a plastic encapsulation press. The local structure is as Figure 1 , Figure 2 shown.

[0032] The lead frame strip is made of KFC copper alloy material, ensuring the electrical conductivity, heat dissipation ability and certain mechanical strength of the component. For the mass production of components, the lead frame strip is designed as a multi-row structure of 8 rows and 32 columns. The local schematic diagram is as Figure 3 shown.

[0033] For the convenience of subsequent wire bonding of the component, the second solder joint of the lead frame strip lead-out end is locally silver-plated, as Figure 3 shown.

[0034] A groove structure (width 0.1 - 0.3 mm, depth 0.1 - 0.2 mm) is provided at the back edge of the lead frame strip. When the component is injection-molded through a mold, the plastic encapsulant fills the groove to form mechanical locking, preventing delamination and glue overflow, strengthening the bonding force between the plastic encapsulant and the lead frame, and improving the reliability of the component, as Figure 4 shown.

[0035] The cross-section of the Cu-clip sheet is trapezoidal (the top width is designed as 1.0 - 3.0 mm according to the current-carrying capacity of the product, the chip source PAD size and the on-state voltage drop of the product, and the bottom width is designed as 1.5 - 2.3 mm according to the bonding area of the lead frame), increasing the contact area with the chip and the lead frame and reducing the current density, as Figure 1 , Figure 2 shown.

[0036] The edge chamfer of the Cu-clip sheet is optimized: the edge is chamfered with an arc (radius 0.05 - 0.1 mm) to reduce stress concentration, as Figure 1 , Figure 2 shown.

[0037] For the Cu-clip, the middle part of the Cu-clip is designed as an arched trapezoidal structure, which enhances the mechanical strength and disperses the thermal stress, thereby improving the reliability of the components. The tail of the Cu-clip is designed as a split structure to ensure that the solder does not overflow or flip over to cover the Cu-clip, as Figure 1 shown.

[0038] For the Cu-clip, the middle of the arched trapezoidal top of the Cu-clip is designed as an elliptical hole structure, which facilitates the encapsulant to penetrate through the entire Cu-clip and firmly locks the encapsulant on both the front and back sides of the Cu-clip, thereby improving the reliability of the components, as Figure 5 shown.

[0039] When die bonding for the packaging structure, lead-tin-silver (or silver) solder is used, and different sintering processes are selected according to different solders. In order to ensure that the overall temperature of the product rises and falls in a stepped manner during sintering in the present invention, a 13-zone sintering process is selected, as Figure 6 shown.

Claims

1. A plastic-encapsulated DFN package based on a Cu-Cl ip structure, comprising a lead frame (1), characterized in that: A die (3) is soldered onto the lead frame (1). One end of a clip (4) is connected to the die (3), and the other end of the clip (4) is connected to a pin bus bar (5). A chip pole (10) is also provided on the lead frame (1), and the chip pole (10) is connected to a second lead-out end (11) through an inner lead (7). Three outer pins (6) are evenly and parallelly provided on the pin bus bar (5). The second lead-out end (11) and the three outer pins (6) are parallel to each other and are all on the same plane. The lead frame (1), the die (3), the pin bus bar (5), and the second lead-out end (11) are encapsulated into one body.

2. The plastic-encapsulated DFN package based on the Cu-Clip structure according to claim 1, wherein: Four frame leads (2) are provided at one end of the lead frame (1) away from the pin bus bar (5), and the positions of the four frame leads (2) are respectively opposite to the three outer pins (6) and the second lead-out end (11).

3. The plastic-encapsulated DFN package based on the Cu-Clip structure according to claim 2, wherein: A groove is machined on the bottom edge of the lead frame (1).

4. The plastic-encapsulated DFN package based on the Cu-Clip structure according to claim 1, characterized in that: A first arch (41) and a second arch (42) are machined on the clip (4). The first arch (41) is machined on the top of the die (3), and the second arch (42) is machined between the lead frame (1) and the pin bus bar (5).

5. The plastic-encapsulated DFN package based on the Cu-Clip structure according to claim 4, wherein: An elliptical through hole is machined on the first arch (41).

6. The plastic-encapsulated DFN package based on the Cu-Clip structure according to claim 1, wherein: A fork is machined at the connection between the clip (4) and the pin bus bar (5).

7. The plastic encapsulated DFN package based on the Cu-Clip structure according to claim 1, wherein: An oblique bend is machined at the connection between the outer pin (6) and the pin bus bar (5), so that the top plane of the outer pin (6) is lower than the bottom of the pin bus bar (5) and is parallel.

8. The plastic-encapsulated DFN package based on the Cu-Clip structure according to claim 1, wherein: Rounded corners are machined at the corners of the Cu-clip (4).

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