Packaging structure of large hollow frame and preparation method thereof

Abstract

The application discloses a packaging structure of a large-hole hollow frame, which comprises a frame body, a base island, a heat sink, a pin and a plastic sealing layer. The front surface of the frame body is provided with the base island, the top of the base island is connected with a chip, the bottom of the base island is provided with the heat sink, the chip is connected with the pin through a welding wire, the hollow part of the frame body is provided with a support web, the support web is distributed in a net shape, and the plastic sealing layer is arranged on the top of the frame body and covers the base island, the chip, the welding wire and the support web. The application provides a packaging structure of a large-hole hollow frame and a preparation method thereof, which can increase the strength of the frame, reduce the impact force generated by die flow stamping in the injection molding process, improve the cutting path arc, reduce the cutting path line arc impact bending risk, improve the toughness of the frame after plastic sealing, and reduce the frame deformation risk.

Description

Technical Field

[0001] This invention relates to the field of semiconductor packaging, and more specifically to a packaging structure with a large hollow frame and its preparation method. Background Technology

[0002] With the continuous development of packaging technology integration and to adapt to the diverse functional needs of products, the special characteristics of packaging products and frame designs are increasing, and products with special frame designs are becoming more and more common in the packaging technology field. Currently, large-chip packaging products are a long-term trend. However, the matching of large-chip packaging designs with small heat sinks results in large areas of hollowed-out design in the lead frame design. That is, the hollowed-out part on the frame is relatively large. In the actual production of the entire product, the arc of the cutting track caused by the die stamping exceeds the set value, making fully automatic cutting impossible. There is a risk of arc cutting when cutting the product. Summary of the Invention

[0003] To address the aforementioned issues, the present invention aims to provide a packaging structure and preparation method for a large hollow frame that increases frame strength, reduces the impact force generated by mold flow stamping during injection molding, improves the curvature of the cutting track, reduces the risk of bending of the cutting track line, enhances the toughness of the frame after molding, and reduces the risk of frame deformation.

[0004] According to one aspect of the present invention, a packaging structure for a large-sized hollow frame is provided, comprising: a frame body, a base island, a heat sink, pins, and a molding compound. The base island is provided on the front side of the frame body, a chip is connected to the top of the base island, and a heat sink is provided at the bottom of the base island. The chip is connected to the pins via bonding wires. The hollow portion of the frame body is provided with supporting ribs, which are distributed in a mesh pattern. The molding compound is disposed on the top of the frame body and covers the base island, the chip, the bonding wires, and the supporting ribs. By adding mesh-like supporting ribs to the hollow portion of the frame body, the risk of frame deformation is reduced, and the curvature of the cut track is improved.

[0005] In some implementations, the supporting tie rods connect the base island and the edge of the frame body and are connected to other adjacent frame bodies. The connection to the edge of the frame body and to other adjacent frame units serves to stabilize the connection between units, increase the overall strength of the frame, and reduce the frame curvature.

[0006] In some implementations, the top of the support rib is flush with the surface of the base island, and the thickness of the support rib is half the thickness of the frame body. The back of the support rib is etched to prevent markings from forming after molding.

[0007] In some implementations, the width of the supporting ribs is ≥0.15mm, and the gap between the supporting ribs is ≥0.15mm.

[0008] On the other hand, the present invention also discloses a method for preparing a large-sized hollow frame encapsulation structure, the method comprising the following steps:

[0009] S1: The base island, pins, support ribs and heat sink are etched on the frame body;

[0010] The thickness of the support rib etched away is half the thickness of the frame body.

[0011] The heat sink is etched and formed on the bottom of the base island;

[0012] S2: Chip installation, the chip is placed on top of the base island;

[0013] S3: Wire bonding connection, using wire bonding to connect the chip and the pin;

[0014] S4: Apply film, apply film to the back of the frame body, and expose the film paper at the cutout of the frame body;

[0015] S5: Plasma cleaning, which performs plasma cleaning on products after the film has been applied;

[0016] S6: Molding, which uses molding compound to cover the base island, chip, bonding wires and support ribs;

[0017] S7: Peel off the film, removing the film paper that was applied in S4.

[0018] In some implementations, both the chip and the bonding wires in S6 are completely encapsulated by molding compound.

[0019] In some embodiments, S5 plasma cleaning involves applying a radio frequency voltage to a set of electrodes, forming a high-frequency alternating electric field between the electrodes. Under the oscillation of the alternating electric field, the active plasma physically impacts and chemically reacts with the substrate, causing the surface material of the product after wire bonding to become particles and gaseous substances, which are then discharged through vacuuming.

[0020] In some embodiments, during S5, argon gas impacts the film paper surface from above the frame body surface during the molding process, causing a physical reaction that roughens the film paper surface and creates a gap between the film paper and the frame body, allowing the molding compound to flow into the gap.

[0021] In some implementations, the plastic sealant wraps around the frame body, and the back of the frame body does not expose the mesh support ribs.

[0022] Compared with existing technologies, this invention adds a grid-like supporting rib design to the hollowed-out portion of the frame body. However, simply adding the grid-like supporting rib to the hollowed-out portion results in the added grid-like supporting rib forming a mark on the back of the frame body after product encapsulation. This invention improves the appearance of the supporting rib by etching away part of the bottom of the supporting rib. By adding a grid-like supporting rib design to the hollowed-out portion, combined with etching and plasma cleaning before encapsulation, the frame strength can be increased without affecting the product's appearance. This can minimize the impact force generated by the mold flow during injection molding, improve the curvature of the cutting track, reduce the risk of bending of the cutting track line, and improve the frame's toughness after encapsulation, reducing the risk of frame deformation, thereby improving product performance and production efficiency. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the encapsulation structure of the large hollow frame of the present invention;

[0024] Figure 2 This is a schematic diagram of the entire frame body of the encapsulation structure of the large hollow frame of the present invention;

[0025] Figure 3 This is a cross-sectional view of the supporting ribs of the encapsulation structure of the large hollow frame of the present invention.

[0026] Figure 4 This is a schematic diagram of the supporting ribs and frame unit structure of the encapsulation structure of the large hollow frame of the present invention. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the embodiments shown in the accompanying drawings. However, it should be noted that these embodiments are not intended to limit the present invention. Equivalent transformations or substitutions in function, method, or structure made by those skilled in the art based on these embodiments are all within the scope of protection of the present invention.

[0028] In the description of this invention, it should be noted that, unless otherwise specified and limited, the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the terms according to the specific circumstances.

[0029] like Figure 1 and Figure 4As shown, the encapsulation structure of the large-sized hollow frame includes: a frame body 1, a base island 2, a heat sink 3, pins 4, and a molding compound 5. The base island 2 is located on the front of the frame body 1, the top of the base island 2 is connected to the chip 6, and the heat sink 3 is located at the bottom of the base island 2. The chip 6 is connected to the pins 4 via bonding wires 7. The hollow portion of the frame body 1 has supporting ribs 8, which are distributed in a mesh pattern. The molding compound 5 is located on the top of the frame body 1 and covers the base island 2, the chip 6, the bonding wires 7, and the supporting ribs 8. By adding mesh-like supporting ribs 8 to the hollow portion of the frame body 1, the risk of frame deformation is reduced, and the curvature of the cut track is improved.

[0030] like Figure 2 As shown, the supporting rib 8 connects the base island 2 and the edge of the frame body 1 and is also connected to other adjacent frame bodies 1. Connecting to the edge of the frame body 1 and other adjacent frame units serves to stabilize the connection between units, increase the overall frame strength, and reduce the frame curvature.

[0031] like Figure 3 As shown, the top of the support rib 8 is flush with the surface of the base island 2, and the thickness of the support rib 8 is half the thickness of the frame body 1. The back of the support rib 8 is etched to prevent marks from forming after molding.

[0032] According to the existing design standards for the base island support reinforcement, the width of the support reinforcement 8 is ≥0.15mm, and the gap between the support reinforcement 8 is ≥0.15mm.

[0033] A method for fabricating a large-sized hollow frame encapsulation structure, characterized by comprising the following steps:

[0034] S1: On the frame body 1, the base island 2, pins 4, support ribs 8 and heat sink 3 are etched out;

[0035] The thickness of the support rib 8 etched away is half the thickness of the frame body 1.

[0036] The heat sink 3 is etched and formed on the bottom of the base island 2;

[0037] S2: Chip 6 installation, wherein the chip 6 is placed on top of the base island 2;

[0038] S3: Connect the chip 6 and the pin 4 using the bonding wire 7;

[0039] S4: Apply film, apply film to the back of the frame body 1, and expose the film at the cutout of the frame body 1;

[0040] S5: Plasma cleaning, which performs plasma cleaning on products after the film has been applied;

[0041] S6: Molding, which uses molding compound to cover the base island 2, chip 6, bonding wire 7 and support rib 8;

[0042] S7: Peel off the film, removing the film paper that was applied in S4.

[0043] In S6, both chip 6 and bonding wire 7 are completely encapsulated by molding compound. A design incorporating a grid-like support rib 8 in the hollowed-out portion of the frame body 1 is used. However, simply adding the grid-like support rib 8 to the hollowed-out portion results in the added grid-like support rib 8 forming a mark on the frame body 1 on the back of the product after encapsulation. Etching away part of the bottom of the support rib 8 improves the appearance of the support rib 8 forming a mark on the frame body 1. This design of adding grid-like support rib 8 to the hollowed-out portion, combined with etching and plasma cleaning before encapsulation, increases frame strength without affecting the product's appearance. It minimizes the impact force generated by the mold flow during injection molding, improves the curvature of the cutting track, reduces the risk of bending of the cutting track line, and enhances the frame's toughness after encapsulation, reducing the risk of frame deformation, thereby improving product performance and production efficiency.

[0044] S5 plasma cleaning utilizes a set of electrodes to apply radio frequency voltage, forming a high-frequency alternating electric field between the electrodes. Under the excitation of the alternating electric field, the active plasma physically impacts and chemically reacts with the frame body 1, turning the surface material of the product after wire bonding into particles and gaseous substances, which are then discharged through vacuuming.

[0045] In S5, during the molding process, argon gas impacts the film paper surface from above the surface of the frame body 1, producing a physical reaction that roughens the film paper surface and creates a gap between the film paper and the frame body 1, allowing the molding material to flow into the gap.

[0046] The gap between the film paper and the frame body 1 allows for better flow of the molding compound, increasing the bonding strength between the molding compound and the film paper and enabling the molding compound to better wrap the frame. The molding layer 5 wraps the frame body 1, and the mesh support ribs 8 are not exposed on the back of the frame body 1.

[0047] In the specific implementation process: the existing frame body 1, after being encapsulated, does not meet the requirements for cutting operations, with a maximum arc of 0.04mm-0.05mm, and the short side arc is within the control range; the frame body 1 disclosed in this invention, after being coated with film, meets the requirements for cutting operations, with a maximum arc of 0.003mm-0.006mm; the frame body 1 disclosed in this invention, after being plastic-sealed, meets the requirements for cutting operations, with a maximum arc of 0.01mm-0.025mm.

[0048] The above descriptions are merely some embodiments of the present invention. It should be noted that those skilled in the art can make other modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A packaging structure for a large hollow frame, characterized in that, It includes: a frame body, a base island, a heat sink, pins, and a molding compound. The front of the frame body has a base island, the top of the base island is connected to a chip, the bottom of the base island has a heat sink, the chip is connected to pins via bonding wires, the hollow part of the frame body has supporting ribs, the supporting ribs are distributed in a mesh, and the molding compound is set on the top of the frame body and covers the base island, chip, bonding wires, and supporting ribs. The supporting rib connects the base island and the edge of the frame body and is connected to other adjacent frame bodies; the top of the supporting rib is flush with the surface of the base island, and the thickness of the supporting rib is half the thickness of the frame body; the width of the supporting rib is ≥0.15mm, and the gap between the supporting ribs is ≥0.15mm.

2. The method for preparing the encapsulation structure of the large hollow frame according to claim 1, characterized in that, Includes the following steps: S1: The base island, pins, support ribs and heat sink are etched on the frame body; The thickness of the support rib etched away is half the thickness of the frame body. The heat sink is etched and formed on the bottom of the base island; S2: Chip installation, the chip is placed on top of the base island; S3: Wire bonding connection, using wire bonding to connect the chip and the pin; S4: Apply film, apply film to the back of the frame body, and expose the film paper at the cutout of the frame body; S5: Plasma cleaning, which performs plasma cleaning on products after the film has been applied; S6: Molding, which uses molding compound to cover the base island, chip, bonding wires and support ribs; S7: Peel off the film, removing the film paper that was applied in S4.

3. The method for preparing the encapsulation structure of the large hollow frame according to claim 2, characterized in that, In S6, both the chip and the bonding wires are completely encapsulated by molding compound.

4. The method for preparing the encapsulation structure of the large hollow frame according to claim 3, characterized in that, The S5 plasma cleaning process involves applying a radio frequency voltage to a set of electrodes, creating a high-frequency alternating electric field between the electrodes. Under the oscillation of the alternating electric field, the gas in the region forms active plasma. The active plasma physically impacts and chemically reacts with the frame body, causing the surface material of the product after wire bonding to become particles and gaseous substances. The particles and gaseous substances are then discharged through vacuuming.

5. The method for preparing the encapsulation structure of the large hollow frame according to claim 3, characterized in that, In step S5, during the molding process, argon gas impacts the exposed film paper surface at the frame cutout from above the frame body surface, generating a physical reaction that roughens the film paper surface and creates a gap between the film paper and the frame body, allowing the molding material to flow into the gap.

6. The method for preparing the encapsulation structure of the large hollow frame according to claim 5, characterized in that, The plastic sealant wraps around the frame body, and the mesh support ribs are not exposed on the back of the frame body.

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