A packaging method and packaging structure for improving pin glue overflow

Abstract

The application discloses a packaging method and structure for improving pin overflow glue, and the packaging method comprises the following steps: a die bonding step; a film pasting step, in which a glue film is pasted on the back of a lead frame; a wire bonding step; a pressure supplementing step, in which a welding needle of an ultrasonic wire bonding machine acts on the front of a non-functional pin to apply pressure to the glue film; and a plastic packaging step, in which packaging material is used to wrap a wafer and the lead frame. The packaging structure comprises a lead frame, a wafer, a welding object and a package. The lead frame comprises a base island, a wire bonding pin and a non-functional pin. The wafer is combined with the front of the base island. The electrode of the wafer is electrically connected with the wire bonding pin through a metal wire. The welding object is fixed to the front of at least one non-functional pin. The package wraps the lead frame and the wafer, and the back of the lead frame is exposed from the package. The packaging method for improving pin overflow glue can make the non-functional pin and the glue film tightly adhere to each other, effectively improve the pin overflow glue condition, and improve the yield. The packaging structure has a beautiful appearance.

Description

Technical Field

[0001] This invention relates to the field of semiconductor packaging technology, and in particular to a packaging method and packaging structure for improving lead overfill. Background Technology

[0002] Flat package (PSP) is a surface-mount package structure. It features short conductive paths between pins and pads, low self-inductance, and low wiring resistance, resulting in excellent electrical performance. In this package, the base island of the leadframe and the back of the pins need to be exposed to allow the chip's electrodes to be brought out through the leadframe. A film is typically adhered to the back of the leadframe to prevent resin from overflowing and covering the back of the leadframe during injection molding. After molding, the film is removed, exposing the back of the leadframe.

[0003] To improve the versatility of existing packaging structures, several common pin layouts are generally designed. During the packaging process, the circuit designs of different products vary. In some packaging structures, one or more pins do not require wire bonding. These pins are called non-functional pins, which do not need to be electrically connected to the electrodes of the chip, and no metal wires or other electrical connections need to be soldered onto them.

[0004] However, in existing packaging structures, there is a problem of poor adhesion between the non-functional pins and the adhesive film. During molding, the molding material will flow into the gap between the non-functional pins and the adhesive film, causing adhesive overflow. The molding material will also cover the back of the non-functional pins, resulting in poor appearance of the finished packaging structure. Summary of the Invention

[0005] One of the objectives of this invention is to provide a packaging method that improves lead overflow, which can effectively reduce lead overflow and increase yield.

[0006] The second objective of this invention is to provide a packaging structure that improves the situation of excess adhesive on the leads and has an aesthetically pleasing appearance.

[0007] To achieve one of the above objectives, the present invention adopts the following technical solution:

[0008] A packaging method for improving lead overfill, comprising:

[0009] Die bonding step; providing a lead frame and a wafer, and using bonding materials to fix the wafer to the front side of the lead frame;

[0010] Film application step: Apply the adhesive film to the back of the lead frame;

[0011] Wire bonding steps: An ultrasonic wire bonding machine bonds one end of a metal wire to the wafer and the other end to the front of the wire bonding pin of the lead frame to electrically connect the wafer to the wire bonding pin.

[0012] Pressure replenishment step: The welding pin of the ultrasonic wire bonding machine acts on the front of the non-functional foot of the lead frame to apply pressure to the non-functional foot in the direction of the adhesive film;

[0013] Molding step: The wafer and the lead frame are wrapped with encapsulation material.

[0014] Preferably, in the pressure replenishment step, a metal wire is provided inside the welding needle, and the welding needle is used to weld one or more solder joints on the front side of the non-functional foot.

[0015] Preferably, in the pressure replenishment step, a metal wire is provided inside the welding needle, and one or more metal wires are welded to the front of the non-functional foot using the welding needle of the ultrasonic wire welding machine.

[0016] Preferably, the wire bonding step is performed using a first ultrasonic wire bonding machine, wherein the welding needle of the first ultrasonic wire bonding machine contains a metal wire.

[0017] The pressure compensation step is performed using a second ultrasonic wire bonding machine. The welding needle of the second ultrasonic wire bonding machine has no metal wire inside. The welding needle acts on the front of the non-functional pin to apply pressure to the non-functional pin in the direction of the adhesive film.

[0018] Preferably, the copper bridge frame welding step is also included:

[0019] In the die bonding step: at least two of the wafers are respectively fixed to the lead frame;

[0020] In the copper bridge frame welding step: a copper bridge frame is provided, and the copper bridge frame is welded to at least two of the wafers on the side opposite to the lead frame;

[0021] In the film application step: after the adhesive film is applied to the back of the lead frame, a film pressing tool is used to press the copper bridge frame on the side away from the lead frame to apply pressure to the lead frame in the direction of the adhesive film.

[0022] To achieve the second objective mentioned above, the present invention adopts the following technical solution:

[0023] A packaging structure, comprising:

[0024] A lead frame, comprising a base island and a pin assembly, the pin assembly including bonding leads and non-functional leads;

[0025] A wafer, which is bonded to the front side of the base island; the electrodes of the wafer are electrically connected to the bonding wires via metal wires;

[0026] A weldment, which is fixed to the front of at least one of the non-functional feet;

[0027] A package that encloses the lead frame and the wafer, with the back of the lead frame exposed.

[0028] Preferably, the base island includes an adjacent first side and a second side; a plurality of first pins are provided on the side of the first side, and the plurality of first pins are all the solder leads;

[0029] A plurality of second pins and at least one third pin are provided on the side of the second side portion, wherein the plurality of second pins are the solder pins and the third pin is a non-functional pin; the solder is fixed to the front of the third pin by soldering.

[0030] Preferably, the device also includes a copper bridge frame, which is coupled to the side of the at least one wafer facing away from the lead frame.

[0031] Preferably, the welded material is a solder ball, and one or more of the solder balls are fixed to the front of the non-functional foot.

[0032] Preferably, the welded material is a metal wire, and one or more of the metal wires are fixed to the front of the non-functional foot.

[0033] The beneficial effects of this invention are as follows: This packaging method applies a certain pressure to the pins by soldering pins, which can strengthen the adhesion between the lead frame and the adhesive film, and prevent the packaging material from overflowing into the gap between the pins and the adhesive film during plastic encapsulation. Without making major changes to the original process, it improves the situation of glue overflow at the pins and increases the yield rate. This packaging structure has no glue overflow at the pins, and the packaging is good and aesthetically pleasing. Attached Figure Description

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0035] Figure 1 This is a flowchart of the encapsulation method described in an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the die bonding step in the packaging method described in this embodiment of the invention;

[0037] Figure 3 for Figure 2 AA section diagram;

[0038] Figure 4 This is a schematic diagram of the pin distribution of the lead frame used in the packaging method described in this embodiment of the invention;

[0039] Figure 5 This is a schematic diagram of the copper bridge frame welding step in the packaging method described in an embodiment of the present invention;

[0040] Figure 6 for Figure 5 BB section diagram;

[0041] Figure 7 This is a schematic diagram (cross-sectional view) of the film application step in the encapsulation method described in an embodiment of the present invention;

[0042] Figure 8 This is a schematic diagram of the wire bonding step in the packaging method described in an embodiment of the present invention;

[0043] Figure 9 This is a schematic diagram of one embodiment (solder joint) of the pressure compensation step in the packaging method described in this invention.

[0044] Figure 10 for Figure 9 CC section diagram in the image;

[0045] Figure 11 for Figure 10 Enlarged view of part a in the image;

[0046] Figure 12 This is a schematic diagram of Embodiment 2 (welding metal wires) of the pressure compensation step in the packaging method described in this invention;

[0047] Figure 13 for Figure 12 Enlarged view of part b in the image;

[0048] Figure 14 for Figure 12 DD cross-section diagram;

[0049] Figure 15 for Figure 14 Enlarged view of part c in the image;

[0050] Figure 16 This is one of the schematic diagrams of the packaging steps in the packaging method described in the embodiment of the present invention (the pressure compensation step uses solder joints for pressure compensation);

[0051] Figure 17 This is one embodiment of the packaging structure of the present invention;

[0052] Figure 18 This is a second schematic diagram of the packaging steps in the packaging method described in the embodiment of the present invention (the pressure compensation step is performed by soldering metal wires);

[0053] Figure 19 This is a second embodiment of the packaging structure of the present invention;

[0054] Figure 20 This is a schematic diagram of the third packaging step in the packaging method described in the embodiment of the present invention (pressure compensation is performed by using solder pins under air pressure in the pressure compensation step);

[0055] Figure 21 The third embodiment of the packaging structure of this invention;

[0056] In the diagram: 10, lead frame; 11, base island; 12, pin assembly; 121, solder pin; 122, non-functional pin; 1221, recess; 101, first side; 102, second side; 103, third side; 104, fourth side; 20, wafer; 30, solder joint; 40, metal wire; 50, copper bridge frame; 60, encapsulant film; 70, package. Detailed Implementation

[0057] To make the technical problems solved by the present invention, the technical solutions adopted, and the technical effects achieved clearer, the technical solutions of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected" and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0059] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0060] For packaged products requiring pre-film bonding followed by wire bonding, a layer of adhesive film 60 is typically applied to the back of the lead frame 10. After the adhesive film 60 and the back of the lead frame 10 are bonded, it prevents packaging material from overflowing onto the back of the lead frame 10 and obstructing the back of the pins during injection molding, ensuring electrode lead-out. For packaged structures where the side of the chip 20 facing away from the lead frame 10 is bonded to the copper bridge frame 50 to achieve electrical connections between chips 20 or between the chip 20 and its pins, the copper bridge frame 50 protects the chip 20. Thus, during film application, a pressing tool can be used to press the film firmly onto the copper bridge frame 50. In the pressed area, the adhesion between the lead frame 10 and the adhesive film 60 is stronger, preventing packaging material from flowing into this area.

[0061] Since some pins of the chip 20 and the lead frame 10 need to be electrically connected by the solder wire 40, the area where the wire needs to be soldered needs to be protected from contamination or scratches. The shape of the laminating tool should be designed to avoid the area where the wire needs to be soldered. Therefore, during the step of pressing with the laminating tool, the lead frame 10 and the adhesive film 60 in the area where the wire needs to be soldered are not subjected to pressure from the laminating tool, and the adhesion is not reliable enough.

[0062] After lamination, wire bonding 40 is performed to electrically connect the lead frame 10 pins 121 to the chip 20. Since the bonding is achieved using ultrasonic thermoforming, the pins 121 are subjected to pressure under the action of the bonding pins, promoting reliable adhesion between the leads and the adhesive film 60 and preventing excess adhesive in this area. However, when the bonding area includes several pins 121 and at least one non-functional pin 122, the non-functional pin 122 does not require electrical connection to the chip 20 and therefore does not require bonding. Consequently, the non-functional pin 122 is not subjected to pressure during lamination and bonding, leading to poor adhesion between the non-functional pin 122 and the adhesive film 60. During encapsulation, encapsulation material flows into the gap between the adhesive film 60 and the back of the non-functional pin 122, causing excess adhesive. After removing the adhesive film 60, excess adhesive covers the back of the non-functional pin 122, resulting in a poor appearance of the encapsulation structure.

[0063] This invention proposes a packaging method to improve lead overflow, which improves the situation of overflow occurring on the back of non-functional pins 122 in the bonding wire area or next to the bonding wire area in flat packaging, and ensures the aesthetic appearance of the packaging structure.

[0064] like Figure 1-21 As shown, in one embodiment of the encapsulation method for improving lead overfilling according to the present invention, the encapsulation method includes:

[0065] Die bonding step; providing a lead frame 10 and a wafer 20, the lead frame 10 including a base island 11 and a number of pins, some of which are bonding pins 121 for electrical connection with the wafer 20, and other of which are non-functional pins 122 that do not need to be electrically connected to the wafer 20; using bonding material to fix the wafer 20 to the front side of the lead frame 10;

[0066] Application steps: Apply the adhesive side of the adhesive film 60 to the back of the lead frame 10;

[0067] Plasma cleaning step; Plasma cleaning enhances the reliability of subsequent wire bonding.

[0068] Wire bonding steps: Use an ultrasonic wire bonding machine to bond one end of the metal wire 40 to the chip 20 and the other end to the front of the bonding pin 121 of the lead frame 10, so as to electrically connect the chip 20 and the bonding pin 121 through the metal wire 40.

[0069] Pressure replenishment step: The welding needle of the ultrasonic wire bonding machine is applied to the front of the non-functional pin 122 of the lead frame 10 to apply pressure to the non-functional pin 122 in the direction of the adhesive film 60.

[0070] Molding process: The chip 20 and the lead frame 10 are wrapped with encapsulation material.

[0071] The principle of welding metal wire 40 using an ultrasonic wire welding machine is as follows: adding metal wire 40 inside the welding needle converts the ultrasonic vibration energy into friction between the two metals, causing the metals to heat up to a limited extent and produce plastic deformation. Under a certain static pressure, the two metals are bonded together to achieve a strong weld.

[0072] The principle of applying pressure by using the welding needle of the ultrasonic wire bonding machine to the non-functional pin 122 is as follows: the mechanical vibration energy of the ultrasonic frequency is used to apply a certain pressure to the lead frame 10.

[0073] The bonding material can be either conductive or insulating, depending on the specific requirements. The bonding material can be solder paste or other materials.

[0074] This invention employs an ultrasonic wire bonding machine to weld the metal wire 40 after the film application step. The wire bonding is performed using the principle of ultrasonic thermo-press welding, which can achieve electrical connection between the wire pin 121 and the chip 20. During welding, the welding needle applies a certain pressure to the front of the wire pin 121, which can strengthen the adhesion between the lead frame 10 and the adhesive film 60 in this area and the surrounding area, and avoid adhesive overflow.

[0075] Compared to existing packaging methods, this invention adds a pressure-compensating step, using the welding needle of an ultrasonic wire bonding machine to apply pressure to the non-functional pin 122, thereby strengthening the adhesion between the frame and the adhesive film 60 in this area and the surrounding area. This effectively prevents the packaging material from overflowing into the gap between the non-functional pin 122 and the adhesive film 60 during molding.

[0076] Furthermore, the packaging method of the present invention only requires adding a pressure replenishment step to the original process, which has little impact on the original process, is easy to improve on the basis of existing equipment, has low improvement cost, and can improve yield.

[0077] The packaging method of this invention allows for the design of the number and layout of pins according to certain specifications, thereby improving the versatility of the packaging structure. For non-functional pins 122 that do not require electrical connection to the chip 20 or soldering of metal wires 40, soldering pins are used to address the issue of excess adhesive at the non-functional pins 122. The packaging structure obtained by the packaging method of this invention combines versatility and aesthetics.

[0078] In this embodiment, the wire bonding step is performed before the pressure compensation step.

[0079] In other embodiments, the wire bonding step may also be performed after the pressure compensation step.

[0080] In this embodiment, the metal wire 40 is a gold wire with excellent electrical and thermal conductivity.

[0081] In other embodiments, the metal wire 40 may also be a copper wire or other conductive metal wire 40.

[0082] In one embodiment, during the pressure compensation step, a welding needle with a built-in metal wire 40 is used to weld one, two or more welded objects on the front side of the non-functional pin 122. When welding the welded objects, a certain pressure is applied to the non-functional pin 122 by the welding needle, so that the lead frame 10 at the non-functional pin 122 fits better with the adhesive film 60.

[0083] The encapsulation method of this embodiment can be implemented through at least the following two methods:

[0084] Implementation Method 1: The welded component is solder joint 30, which has a spherical structure; that is, a ball is implanted on the front side of the non-functional pin 122 using a welding pin. The end of the metal wire 40 vibrates at high frequency under the influence of the reverse rotation, rubbing against the surface of the non-functional pin 122. This causes the surface oxide layer to break down, resulting in plastic deformation. The deformed end of the metal wire 40 forms a spherical structure, which is then bonded and fixed to the non-functional pin 122. The number of solder joints 30 on the front side of the non-functional pin 122 can be one or more.

[0085] Implementation Method 2: The welding material is a metal wire 40. After the end of the metal wire 40 is bonded to the non-functional pin 122 under the action of ultrasonic vibration, the welding needle moves a certain distance and then breaks the metal wire 40 by shearing or melting, so as to weld the metal wire 40 on the front side of the non-functional pin 122. The metal wire 40 can be a short wire. The number of metal wires 40 welded to the front side of the non-functional pin 122 can be one or more.

[0086] In the second embodiment, to reduce material consumption and lower costs, one end of the metal wire 40 is bonded and fixed to the non-functional pin 122, while the other end remains free.

[0087] Of course, in other embodiments, when the welded object is a metal wire 40, both ends of the metal wire 40 can be welded to the non-functional pin 122 by an ultrasonic wire bonding machine.

[0088] In one embodiment, since metal wire 40 needs to be installed inside the welding needle of the ultrasonic wire bonding machine in both the wire bonding step and the pressure replenishment step, in order to reduce the floor space, the same ultrasonic wire bonding machine is used to perform the wire bonding step and the pressure replenishment step. In this way, the processing of the two steps can be achieved by the same ultrasonic wire bonding machine, saving the equipment floor space.

[0089] In other embodiments, different ultrasonic wire bonders may be used to perform the wire bonding step and the pressure compensation step respectively.

[0090] In one embodiment, in order to save materials and reduce costs, during the pressure replenishment step, an empty welding pin is used to apply air pressure to the non-functional pin 122 to apply pressure to the non-functional pin 122.

[0091] The empty welding needle, i.e., the welding needle without metal wire 40 inside, is used to align the welding needle of the ultrasonic wire bonding machine with the non-functional foot 122. Under the action of ultrasonic vibration, the welding needle presses against the front of the non-functional foot 122. In this way, the bonding strength between the non-functional foot 122 and the adhesive film 60 is strengthened, and the metal wire 40 is not wasted, saving materials. Especially when the price of gold wire is high, it can reduce costs.

[0092] In this embodiment, when a welding needle without internal metal wire 40 is used to press air into the non-functional foot 122, a certain plastic deformation is generated on the front side of the non-functional foot 122, forming a recess 1221.

[0093] In other embodiments, when a welding rod with no internal metal wire 40 is used to pneumatically press the non-functional foot 122, the front side of the non-functional foot 122 may remain flat, without plastic deformation or the formation of a recess 1221.

[0094] In this embodiment, since a metal wire 40 needs to be placed inside the welding needle in the wire bonding step, but there is no metal wire 40 inside the welding needle in the pressure compensation step, in order to facilitate assembly line production and improve packaging efficiency, two ultrasonic wire bonding machines are used to perform the wire bonding step and the pressure compensation step respectively.

[0095] The first ultrasonic wire bonding machine is used to perform the wire bonding step, and the second ultrasonic wire bonding machine is used to perform the pressure compensation step. The metal wire 40 material is added into the welding needle of the first ultrasonic wire bonding machine by manual or machine addition, while the metal wire 40 material does not need to be added into the welding needle of the second ultrasonic wire bonding machine.

[0096] Using this packaging method, only one ultrasonic wire bonding machine needs to be added to the original production line. The wire bonding and pressure replenishment steps can be performed by different wire bonding machines. There is no need for manual supervision next to the same ultrasonic wire bonding machine to repeatedly perform the two operations of adding and removing metal wire 40 from the welding needle. This can greatly improve packaging efficiency, reduce packaging costs, and avoid machine wear or poor packaging caused by repeated wire addition and removal.

[0097] In one embodiment, the encapsulation method further includes a copper bridge frame 50 welding step and a film pressing step;

[0098] In the die bonding step: at least two wafers 20 are respectively fixed to the lead frame 10, and different wafers 20 are soldered to different base islands 11 within the lead frame 10;

[0099] In the soldering step: a copper bridge frame 50 is provided, and the copper bridge frame 50 is soldered to at least two wafers 20 on the side opposite to the lead frame 10.

[0100] In the lamination step: the lamination tool is pressed onto the side of the copper bridge frame 50 away from the lead frame 10 to apply pressure to the wafer 20 in the direction of the adhesive film 60, thereby applying pressure to the lead frame 10 in the direction of the adhesive film 60 to increase the bonding strength between the lead frame 10 and the adhesive film 60 in this area.

[0101] In one embodiment, for a square lead frame 10, a plurality of pins are formed on each of the four sides of the lead frame 10. When some of the pins on one side of the lead frame 10 are solder pins 121 and the other are non-functional pins 122, in the pressure compensation step, solder pins are used to compensate for the non-functional pins on this side. When all of the pins on one side of the lead frame 10 are non-functional pins, since non-functional pins do not require soldering, in the film application step, all non-functional pins 122 on this side can be pressed with a film pressing tool, which can ensure reliable adhesion between the non-functional pins on this side and the adhesive film 60, and will not contaminate the soldering area.

[0102] In one embodiment, epoxy resin is used as the encapsulation material in the molding step.

[0103] In other embodiments, other encapsulation materials may also be used in the molding step.

[0104] In one embodiment, the operating temperature is 180 to 220 degrees Celsius during the wire bonding and pressure replenishment steps.

[0105] The present invention also proposes a packaging structure formed by the above packaging method. The exposed portion of the non-functional pins of the packaging structure is not covered by packaging material, resulting in an aesthetically pleasing appearance. Furthermore, the chip 20 will not be scratched during the packaging process, but the bonding wire area will not be contaminated, thus ensuring the reliable performance of the packaging structure.

[0106] like Figures 2-21 As shown, in one embodiment of the packaging structure of the present invention, the packaging structure includes:

[0107] The lead frame 10 includes a base island 11 and a pin assembly 12. The pin assembly 12 includes a plurality of pins formed around the lead frame 10. Some of the pins are bonding pins 121, and the other part of the pins are non-functional pins 122. The number of non-functional pins 122 can be one or more.

[0108] The chip 20 is bonded to the front side of the base island 11. The electrodes of the chip 20 are electrically connected to the bonding pins 121 via metal wires 40, so that the electrodes of the chip 20 can be led out via the bonding pins 121.

[0109] The welded material is formed by bonding the welding material to the front side of the non-functional pin 122 using an ultrasonic wire bonding machine;

[0110] Package 70, which is formed by curing encapsulation material, encapsulates lead frame 10, wafer 20 and electrical connectors for electrically connecting lead frame 10 and wafer 20 to provide electrical protection for the components, with the back of lead frame 10 exposed by package 70.

[0111] In this embodiment, the back side of the pins of the lead frame 10 is exposed by the package 70, and the exposed part of the pins is used for electrical connection with other electronic components; the back side of the base island 11 of the lead frame 10 is exposed by the package 70 to achieve good heat dissipation and ensure reliable operation.

[0112] It should be noted that the packaging structure in this embodiment is a flat packaging structure, which can be, but is not limited to, QFN (Quad Flat No-leads Package) or DFN (Double-sided Flat No-leads Package) packaged products. Any packaging structure obtained by using the packaging method of first applying a film and then bonding wires is the subject of protection of this invention.

[0113] In one embodiment, the base island 11 in the lead frame 10 and the distribution of the leads adopt... Figure 4 , Figure 8 The arrangement is as shown in the image, where, for ease of description, in... Figure 4 In the pin assembly 12, the pins are labeled on the side of the pins; the lead frame 10 includes four sides, which are respectively the first side 101, the second side 102, the third side 103 and the fourth side 104.

[0114] In this embodiment, among the pins within the first side portion 101, some are solder pins 121, and some are non-functional pins 122. Pins 932 to 939 are all functional pins, requiring soldering on their front sides. Pin 931 is a non-functional pin 122, and its front side does not require soldering. Since pin 931 and pin 932, which requires soldering, are located on the same side and are close together, it is difficult for the laminating tool to press only onto pin 931 without contaminating or scratching pin 932. In existing packaging structures, adhesive overflow often occurs on the back of pin 931, resulting in defective products. Therefore, in this embodiment, a pressure compensation operation is performed on pin 931, leaving additional structures (such as solder joints 30, metal wires 40, or recesses 1221 caused by air pressure) in the packaging structure after the pressure compensation operation.

[0115] In this embodiment, pins 91 to 96 of the second side 102 are solder pins 121, which are pressed by soldering pins during the soldering process; pins 97 to 99 are non-functional pins 122, which are covered by the copper bridge frame 50 and pressed by the pressing tool.

[0116] In this embodiment, the pins of the third side 103 and the fourth side 104 are directly pressed by the film pressing tool during the film application step.

[0117] In other embodiments, pin assemblies 12 may be provided only on both sides.

[0118] In one embodiment, when two or more chips 20 are packaged in the same package structure, in order to meet the interconnection requirements between the chips 20 and reduce the connection resistance and improve the heat dissipation performance, the package structure further includes a copper bridge frame 50, through which the chips 20 are electrically connected.

[0119] In this embodiment, the copper bridge frame 50 covers the side of the two wafers 20 that need to be interconnected that is away from the lead frame 10. Furthermore, the copper bridge frame 50 covers the part of the wafer 20 that does not require wire bonding. The copper bridge frame 50 is electrically connected to the electrodes of the two wafers 20 respectively, thereby realizing the interconnection between the wafers 20.

[0120] In this embodiment, the copper bridge frame 50 is also electrically connected to a portion of the pins.

[0121] In one embodiment, when the ultrasonic wire bonding machine performs a pressure compensation operation on the non-functional pin 122, the additional pressure compensation structure formed on the non-functional pin 122 is a welded material.

[0122] The number of solder objects formed on the front side of the non-functional pin can be one, two or more; the solder objects formed on the front side of the non-functional pin can be only solder balls, only metal wires 40, or both solder balls and metal wires 40.

[0123] The weld is formed by bonding the welding material to the front side of the non-functional pin 122 using an ultrasonic wire bonding machine.

[0124] In one embodiment, when the non-functional pin 122 is subjected to pressure compensation operation by an ultrasonic wire bonder, the additional pressure compensation structure formed on the non-functional pin 122 is a recess 1221. During the pressure compensation step of the package, when a bonding pin without internal metal wire 40 is used to apply air pressure to the non-functional pin 122, a certain amount of plastic deformation will occur on the front side of the non-functional pin, forming the recess 1221.

[0125] In one embodiment, the package structure includes three chips 20. The first and second chips can be transistor chips, and the third chip can be a control chip. The control chip is electrically connected to the transistor via a metal wire 40.

[0126] In one embodiment, the metal wire 40 used to electrically connect the chip 20 to the bonding pin 121 is a gold wire, which has better electrical and thermal conductivity.

[0127] In one embodiment, the metal wire 40 soldered to the front side of the non-functional pin 122 is a copper wire. Since this part of the metal wire 40 does not need to be conductive, a lower-cost copper wire can be used.

[0128] In the description herein, it should be understood that the terms "upper," "lower," "left," and "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings, and are used only for ease of description and simplification of operation. They do not 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 limiting the present invention. Furthermore, the terms "first" and "second" are used merely for descriptive distinction and have no special meaning.

[0129] In the description of this specification, references to terms such as "an embodiment," "example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0130] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style of the specification is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0131] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A packaging method for improving lead overfill, characterized in that, include: Die bonding step; providing a lead frame (10) and a wafer (20), and using a bonding material to fix the wafer (20) to the front side of the lead frame (10); Application step: Apply the adhesive film (60) to the back of the lead frame (10); Wire bonding step: The ultrasonic wire bonding machine bonds one end of the metal wire (40) to the wafer (20) and the other end to the front of the bonding pin (121) of the lead frame (10) to electrically connect the wafer (20) and the bonding pin (121). Pressure replenishment step: The welding needle of the ultrasonic wire bonding machine acts on the front of the non-functional foot (122) of the lead frame (10) to apply pressure to the non-functional foot (122) in the direction of the adhesive film (60); Molding step: The wafer (20) and the lead frame (10) are wrapped with encapsulation material; In the pressure replenishment step, a metal wire (40) is provided inside the welding needle, and one or more solder points (30) are welded to the front of the non-functional foot (122) using the welding needle; or, in the pressure replenishment step, a metal wire (40) is provided inside the welding needle, and one or more solder points (30) are welded to the front of the non-functional foot (122) using the welding needle; or, the wire bonding step is performed using a first ultrasonic wire bonding machine, the welding needle of the first ultrasonic wire bonding machine is provided with a metal wire (40), the pressure replenishment step is performed using a second ultrasonic wire bonding machine, the welding needle of the second ultrasonic wire bonding machine is not provided with a metal wire (40), and the welding needle acts on the front of the non-functional foot (122) to apply pressure to the non-functional foot (122) in the direction of the adhesive film (60).

2. The encapsulation method for improving lead overfill according to claim 1, characterized in that, This also includes the welding steps for the copper bridge frame (50): In the die bonding step: at least two of the wafers (20) are respectively fixed to the lead frame (10); In the copper bridge frame (50) welding step: a copper bridge frame (50) is provided, and the copper bridge frame (50) is welded to at least two of the wafers (20) on the side opposite to the lead frame (10); In the film application step: after the adhesive film (60) is applied to the back of the lead frame (10), a film pressing tool is used to press the copper bridge frame (50) on the side away from the lead frame (10) to apply pressure to the lead frame (10) in the direction of the adhesive film (60).

3. A packaging structure, characterized in that, The encapsulation structure is formed by the encapsulation method for improving lead overflow as described in claim 1 or 2, and the encapsulation structure includes: A lead frame (10) includes a base island (11) and a pin assembly (12), the pin assembly (12) including bonding pins (121) and non-functional pins (122); A wafer (20) is bonded to the front side of the base island (11); the electrodes of the wafer (20) are electrically connected to the bonding pins (121) via metal wires (40); A weldment, which is fixed to the front of at least one of the non-functional feet (122); A package (70) encloses the lead frame (10) and the wafer (20), with the back of the lead frame (10) exposed.

4. The packaging structure according to claim 3, characterized in that, The base island (11) includes an adjacent first side (101) and a second side (102); a plurality of first pins are provided on the side of the first side (101), and the plurality of first pins are all the solder pins (121); A plurality of second pins and at least one third pin are provided on the side of the second side (102), wherein the plurality of second pins are all solder pins (121), and the third pin is a non-functional pin (122); the solder is fixed to the front of the third pin by soldering.

5. The packaging structure according to claim 3, characterized in that, It also includes a copper bridge frame (50) which is coupled to the side of the at least one wafer (20) opposite to the lead frame (10).

6. The packaging structure according to any one of claims 3-5, characterized in that, The welded material is a solder ball, and one or more of the solder balls are fixed to the front side of the non-functional foot (122).

7. The packaging structure according to any one of claims 3-5, characterized in that, The welded material is a metal wire (40), and one or more of the metal wires (40) are fixed to the front of the non-functional foot (122).

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