QFN packaging method

Abstract

The invention provides a QFN packaging method, and relates to the technical field of chip packaging. The QFN packaging method comprises the steps that a metal plate is provided, the metal plate is etched to form a lead frame, the lead frame comprises a base island and fingers, and every two adjacent fingers are connected through a connecting part; mounting a chip on the front surface of the base island, enabling the chip to be electrically connected with the front surface of the finger through a bonding lead, forming a tin layer on the back surface of the lead frame, and carrying out plastic packaging on the chip, the lead frame and the bonding lead; and cutting the connecting part and the plastic packaging material above the connecting part to obtain a plurality of packaging bodies. According to the QFN packaging method, when the metal plate is etched, the material between the two adjacent fingers surrounding the different substrates is reserved as the connecting part, so that the two fingers are connected into a whole through the connecting part. Therefore, the strength of the obtained lead frame is higher, the lead frame is not easy to deform during subsequent plastic packaging, and the obtained overall structure is more stable.

Description

TECHNICAL FIELD

[0001] The present application relates to the chip packaging technical field, and in particular to a QFN packaging method. BACKGROUND

[0002] QFN (Quad Flat No-leads Package) packaging is a mainstream packaging form that can realize miniaturization of packaging size. The QFN packaging method mainly includes: etching a metal plate to form a lead frame; welding or bonding a chip on the surface of the base island of the lead frame through a patch material; connecting the circuit on the active surface of the chip to the fingers of the lead frame as the lead pins of the QFN packaging structure through the form of bonding leads; using resin or other plastic packaging materials to package the chip, the lead frame, the bonding leads and the gap therebetween; and cutting the packaged structure to obtain a single QFN packaging structure. However, the existing QFN packaging method has the problem of insufficient strength of the lead frame during packaging, which is prone to deformation. SUMMARY

[0003] The present application aims at the deficiencies in the prior art, and provides a QFN packaging method which can improve the strength of the lead frame and is not prone to deformation during packaging, and has a more stable structure.

[0004] To achieve the above-mentioned purpose, the technical solutions adopted by the embodiments of the present application are as follows: The embodiments of the present application provide a QFN packaging method, which includes: providing a metal plate and etching the metal plate to form a lead frame, wherein the lead frame includes a base island and fingers, and two adjacent fingers are connected through a connecting portion; mounting a chip on the front surface of the base island and electrically connecting the chip and the front surface of the fingers through bonding leads, forming a tin layer on the back surface of the lead frame, and packaging the chip, the lead frame and the bonding leads; and cutting the connecting portion and the packaging material above the connecting portion to obtain a plurality of packaging bodies.

[0005] Optionally, mounting the chip on the front surface of the base island and electrically connecting the chip and the front surface of the fingers through the bonding leads, forming the tin layer on the back surface of the lead frame, and packaging the chip, the lead frame and the bonding leads include: mounting the chip on the front surface of the base island and electrically connecting the chip and the front surface of the fingers through the bonding leads; packaging the chip, the lead frame and the bonding leads; and forming the tin layer on the back surface of the lead frame.

[0006] Optionally, the chip is attached to the front side of the base island and is electrically connected to the front side of the fingers through the bonding leads, a tin layer is formed on the back side of the lead frame, and the encapsulation of the chip, the lead frame and the bonding leads comprises: forming the tin layer on the back side of the lead frame; attaching the chip to the front side of the base island and electrically connecting the chip to the front side of the fingers through the bonding leads; and encapsulating the chip, the lead frame and the bonding leads.

[0007] Optionally, the providing of the metal plate and the etching of the metal plate to form the lead frame comprises: providing the metal plate and forming a through hole on the metal plate, and forming a groove on the back side of the metal plate, wherein the through hole is used to divide the base island and the fingers surrounding the base island on the metal plate, and the groove is used to form the connecting part between the two adjacent fingers.

[0008] Optionally, after the cutting of the connecting part and the encapsulation material above the connecting part, the QFN packaging method further comprises: providing a substrate and welding the package to the substrate.

[0009] Optionally, before the cutting of the connecting part and the encapsulation material above the connecting part, the QFN packaging method further comprises: removing the encapsulation material in the groove.

[0010] Optionally, before the cutting of the connecting part and the encapsulation material above the connecting part, the QFN packaging method further comprises: removing the encapsulation material in the groove and removing part of the encapsulation material in the through hole on the back side of the metal plate.

[0011] Optionally, the removal depth of the encapsulation material in the through hole is equal to the depth of the groove.

[0012] Optionally, the thickness of the connecting part is equal to the thickness of the lead frame.

[0013] Optionally, the cutting of the connecting part and the encapsulation material above the connecting part comprises: cutting the connecting part and the encapsulation material above the connecting part by using a cutting knife, wherein the width of the cutting knife is greater than or equal to the width of the connecting part.

[0014] The beneficial effects of the present application include: The application provides a QFN packaging method, comprising the following steps: providing a metal plate, and etching the metal plate to form a lead frame, wherein the lead frame comprises a base island and fingers, and two adjacent fingers are connected through a connecting part; mounting a chip on the front surface of the base island, and electrically connecting the chip and the front surface of the fingers through bonding leads, forming a tin layer on the back surface of the lead frame, and plastic packaging the chip, the lead frame and the bonding leads; and cutting the connecting part and the plastic packaging material above the connecting part to obtain a plurality of packaging bodies. When the metal plate is etched, the material between the two adjacent fingers around different substrates is reserved as the connecting part, so that the two fingers are connected as a whole through the connecting part. The strength of the lead frame obtained in this way is higher, and the lead frame is not easy to deform during subsequent plastic packaging, and the overall structure obtained is more stable. In addition, the connecting part can also be used as a positioning line for cutting, which is beneficial to rapid positioning during cutting. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0016] Figure 1 The flow chart of the QFN packaging method provided by the embodiments of the application; Figure 2 The structural schematic diagram of the lead frame provided by the embodiments of the application; Figure 3 The preparation process schematic diagram one of the QFN packaging structure provided by the embodiments of the application; Figure 4 The preparation process schematic diagram two of the QFN packaging structure provided by the embodiments of the application; Figure 5 The preparation process schematic diagram three of the QFN packaging structure provided by the embodiments of the application; Figure 6 The preparation process schematic diagram four of the QFN packaging structure provided by the embodiments of the application; Figure 7 The preparation process schematic diagram five of the QFN packaging structure provided by the embodiments of the application; Figure 8 The preparation process schematic diagram six of the QFN packaging structure provided by the embodiments of the application; Figure 9 The preparation process schematic diagram seven of the QFN packaging structure provided by the embodiments of the application; Figure 10Fig. 8 is a schematic view of a preparation process of a QFN packaging structure according to an embodiment of the present application; Figure 11 Fig. 9 is a schematic view of a preparation process of a QFN packaging structure according to an embodiment of the present application; Figure 12 Fig. 10 is a schematic view of a preparation process of a QFN packaging structure according to an embodiment of the present application; Figure 13 Fig. 11 is a schematic view of a preparation process of a QFN packaging structure according to an embodiment of the present application; Figure 14 Fig. 12 is a schematic view of a preparation process of a QFN packaging structure according to an embodiment of the present application; Figure 15 Fig. 13 is a schematic view of a preparation process of a QFN packaging structure according to an embodiment of the present application; Figure 16 Fig. 14 is a schematic view of a preparation process of a QFN packaging structure according to an embodiment of the present application.

[0017] Fig. 14 is a schematic view of a preparation process of a QFN packaging structure according to an embodiment of the present application. Fig. 14 is a schematic view of a preparation process of a QFN packaging structure according to an embodiment of the present application. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, but not all the embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0019] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. It should be noted that, in the case of no conflict, each feature in the embodiments of the present application can be combined with each other, and the combined embodiment is still within the protection scope of the present application.

[0020] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0021] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship commonly used when the product of the application is used, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third" and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0022] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "set", "mount", "connect", "connect" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0023] Please refer to Figure 1 The embodiment of the present application provides a QFN packaging method, comprising: S100: providing a metal plate and etching the metal plate to form a lead frame, wherein the lead frame comprises a base island and a finger, and two adjacent fingers are connected by a connecting part.

[0024] Please refer to Figure 2 The metal plate 10 is etched to process the metal plate 10 into a lead frame 20. The lead frame 20 comprises a base island 21 and a finger 22, the number of base islands 21 is multiple, and multiple fingers 22 are surrounded around each base island 21. The two adjacent fingers 22 surrounding different base islands 21 are connected together by a connecting part 23.

[0025] S200: mounting a chip to the front surface of the base island, and electrically connecting the chip and the front surface of the finger through a bonding lead, forming a tin layer on the back surface of the lead frame, and plastic packaging the chip, the lead frame and the bonding lead.

[0026] Please refer to Figure 3The lead frame 20, the base island 21 and the fingers 22 all have opposite front and back surfaces, and the front surfaces of the lead frame 20, the base island 21 and the fingers 22 face the same side, and the back surfaces also face the same side. After the lead frame 20 is formed, the chip 30 needs to be attached to the front surface of the lead frame 20, and the tin layer 50 needs to be formed on the back surface of the lead frame 20. In this embodiment, the order of attaching the chip 30 and forming the tin layer 50 is not limited, and the chip 30 can be attached first, and then the tin layer 50 is formed, or the tin layer 50 can be formed first, and then the chip 30 is attached.

[0027] The chip 30 is attached to the front surface of the base island 21, and then the circuit on the active surface of the chip 30 is connected to the fingers 22 surrounding the base island 21 by wire bonding, so that the chip 30 is electrically connected to the fingers 22 through the bonding wires 40. The fingers 22 will be used as the pins of the QFN package structure 100 in the future.

[0028] After the chip 30 is attached, the chip 30, the lead frame 20 and the bonding wires 40 are encapsulated by the encapsulation material 60. It can be understood that the encapsulation operation can be performed before the tin layer 50 is formed, or can be performed after the tin layer 50 is formed.

[0029] S300: cutting the connection part and the encapsulation material above the connection part to obtain a plurality of package bodies.

[0030] Please refer to Figure 4 and Figure 5 , the whole structure after encapsulation is cut, the cutting position is opposite to the connection part 23, and the connection part 23 and the encapsulation material 60 above the connection part 23 are removed during cutting, so that a plurality of independent package bodies are obtained.

[0031] The above QFN packaging method retains the material between the adjacent two fingers 22 surrounding the different base plates 90 as the connection part 23 when etching the metal plate 10, so that the two fingers 22 are connected as a whole through the connection part 23. The strength of the lead frame 20 obtained in this way is higher, the lead frame 20 is not easy to deform during subsequent encapsulation, and the overall structure obtained is more stable. In addition, the connection part 23 can also be used as a positioning line for cutting, which is beneficial to rapid positioning during cutting.

[0032] Optionally, please refer to Figure 3 and Figure 4 , the thickness of the connection part 23 is equal to the thickness of the lead frame 20.

[0033] That is to say, when etching the metal plate 10, the area where the connection part 23 is located is not removed. The thickness of the connection part 23 is equal to the thickness of the lead frame 20, which can further improve the strength of the lead frame 20 and simplify the etching step. That is to say, when etching the metal plate 10, the area where the connection part 23 is located is not removed. The thickness of the connection part 23 is equal to the thickness of the lead frame 20, which can further improve the strength of the lead frame 20 and simplify the etching step. That is to say, when etching the metal plate 10, the area where the connection part 23 is located is not removed. The thickness of the connection part 23 is equal to the thickness of the lead frame 20, which can further improve the strength of the lead frame 20 and simplify the etching step.

[0034] Optionally, the cutting of the connecting part and the plastic encapsulation material above the connecting part comprises: S310: cutting the connecting part and the plastic encapsulation material above the connecting part by using a cutting knife, wherein the width of the cutting knife is greater than or equal to the width of the connecting part.

[0035] The width of the connecting part is set as W1 which is less than or equal to the width W2 of the cutting knife, so that the connecting part 23 can be completely removed during cutting, and cutting burrs are reduced.

[0036] Optionally, the chip is attached to the front surface of the base island, and the chip is electrically connected to the front surface of the finger through the bonding lead, a tin layer is formed on the back surface of the lead frame, and the chip, the lead frame and the bonding lead are encapsulated comprising: S210: attaching the chip to the front surface of the base island, and electrically connecting the chip to the front surface of the finger through the bonding lead.

[0037] S220: encapsulating the chip, the lead frame and the bonding lead.

[0038] S230: forming a tin layer on the back surface of the lead frame.

[0039] Please refer to Figures 6 to 8 In the embodiment, the attachment of the chip 30 is performed first, and then the encapsulation operation is performed. Please refer to Figure 2 Finally, the tin layer 50 is formed.

[0040] Exemplarily, please refer to Figures 6 to 8 The encapsulation of the chip, the lead frame and the bonding lead comprises: S221: providing a release film, and placing the lead frame on the release film, wherein the back surface of the lead frame faces the release film.

[0041] S222: encapsulating the chip, the lead frame and the bonding lead by using a plastic encapsulation material.

[0042] S223: removing the release film.

[0043] The surface of the release film 80 has adhesion, and the lead frame 20 is fixed by the adhesion of the release film 80 during encapsulation, so that the structure remains stable. After the encapsulation is completed, the release film 80 can be peeled off without residue.

[0044] Optionally, the chip is attached to the front surface of the base island, and the chip is electrically connected to the front surface of the finger through the bonding lead, a tin layer is formed on the back surface of the lead frame, and the chip, the lead frame and the bonding lead are encapsulated comprising: S224: forming a tin layer on the back surface of the lead frame.

[0045] S225: mounting the chip on the front surface of the base island, and electrically connecting the chip with the front surface of the finger through the bonding wire.

[0046] S226: plastic packaging the chip, the lead frame and the bonding wire.

[0047] Please refer to Figures 9 to 11 In the embodiment, the tin layer 50 is formed first, then the chip 30 is mounted, and finally the plastic packaging is performed. The tin layer 50 is generally formed by electroplating. After the etching of the lead frame 20, the tin layer 50 is formed first, so that the etching and electroplating steps can be performed in the frame factory. After entering the packaging factory, only the plastic packaging, the removal of the plastic packaging material 60 and the singulation steps are needed, which reduces the requirement for the process capability of the packaging factory. The packaging factory does not need to purchase a high-precision etching machine and establish a perfect electroplating production line, the equipment investment cost is reduced, and the saved funds can be transferred to the optimization of the plastic packaging process or the improvement of the cutting precision.

[0048] For example, please refer to Figure 3 The plastic packaging of the chip, the lead frame and the bonding wire includes: S224: providing a release film, and placing the lead frame on the release film, wherein the tin layer on the back surface of the lead frame is attached to the surface of the release film.

[0049] S225: plastic packaging the chip, the lead frame and the bonding wire by using a plastic packaging material.

[0050] S226: removing the release film.

[0051] Since the tin layer 50 is formed before the chip 30 is mounted, when the release film 80 is used to fix the lead frame 20, the tin layer 50 needs to be attached to the surface of the release film 80, and then the chip 30 is mounted and plastic packaged. After the plastic packaging, the area of the release film 80 is removed, and the tin layer 50 is exposed again.

[0052] Optionally, the metal plate is provided, and the metal plate is etched to form the lead frame, which includes: S110: providing a metal plate, and forming a through hole on the metal plate, and forming a groove on the back surface of the metal plate, wherein the through hole is used to divide the base island and the fingers surrounding the base island on the metal plate, and the groove is used to form the connecting part between the adjacent two fingers.

[0053] Please refer to Figure 12 and Figure 13 The metal plate 10 is etched to form the through hole 11 penetrating through the front surface and the back surface of the metal plate 10, and the groove 12 on the back surface of the metal plate 10. Please refer to Figure 2The number of the through holes 11 is multiple, and the multiple through holes 11 divide the metal plate 10 into the base islands 21 and the fingers 22 surrounding the base islands 21. The number of the grooves 12 is also multiple, and the multiple grooves 12 divide the metal plate 10 into the fingers 22 surrounding different base islands 21. The area between two adjacent grooves 12 on the metal plate 10 and the area directly above the area are the connecting portions 23.

[0054] For example, the metal plate is provided, and the through hole is formed on the metal plate, and the groove is formed on the back surface of the metal plate, which comprises: S111: etching the groove and the first half hole on the back surface of the metal plate.

[0055] S112: etching the second half hole corresponding to the first half hole on the front surface of the metal plate, wherein the first half hole and the second half hole jointly form the through hole penetrating the metal plate.

[0056] The through hole 11 is prepared by machining the half hole on the front surface and the back surface of the metal plate 10, which can make the machining precision of the through hole 11 higher and the hole wall smoother.

[0057] Further, the depth of the first half hole 111 is equal to the depth of the groove 12, so as to facilitate machining of the two simultaneously. The edge of the first half hole 111 and the second half hole completely coincide, so that the hole wall of the obtained through hole 11 is smoother and no step exists.

[0058] Optionally, please refer to Figure 1 After the connecting portion and the plastic encapsulation material above the connecting portion are cut, the QFN packaging method further comprises: S400: providing a substrate and welding the packaging body to the substrate.

[0059] Please refer to Figure 4 and Figure 5 After the overall structure after plastic encapsulation is cut, a plurality of mutually independent packaging bodies are obtained, and then the side of the packaging body provided with the tin layer 50 is welded on the substrate 90 to obtain the QFN packaging structure 100. The welding generally uses tin paste, and the tin paste can be combined with the tin layer 50 on the packaging body to realize reliable connection of the packaging body 70 and the substrate 90.

[0060] Optionally, before the connecting portion and the plastic encapsulation material above the connecting portion are cut, the QFN packaging method further comprises: S510: removing the encapsulation material in the groove.

[0061] Please refer to Figure 7In the process of plastic packaging, the recess 12 and the through hole 11 are also filled with plastic packaging material 60, at this time, the finger 22 is surrounded by the plastic packaging material 60, and when the package is welded to the substrate 90, the solder cannot contact the side of the finger 22. When the packaging material in the recess 12 is removed, the side of the finger 22 is exposed, and when welding, the solder can climb to the side of the finger 22, thereby enhancing the welding strength.

[0062] Further, please refer to Figure 14 When the packaging material in the recess 12 is removed, part of the packaging material in the through hole 11 on the back of the metal plate 10 is also removed.

[0063] In this way, the finger 22 can be exposed on all sides, please refer to Figure 15 When welding, the solder can climb around the finger 22, further enhancing the welding strength.

[0064] Optionally, the removal depth of the packaging material in the through hole 11 is equal to the depth of the recess 12, so as to avoid too much or too little removal of the packaging material in the through hole 11.

[0065] It can be understood that if the packaging material in the through hole 11 is removed too much, the reliability of the package can be affected; if the packaging material in the through hole 11 is removed too little, the area exposed around the finger 22 is less, and the welding strength cannot be significantly enhanced.

[0066] It should be understood that although each step in the flowchart is shown in sequence according to the direction of the arrow, these steps are not necessarily executed in sequence according to the direction of the arrow. Unless otherwise stated herein, the execution of these steps is not strictly limited in sequence, and these steps can be executed in other sequences. Moreover, at least part of the steps in the flowchart can include multiple steps or multiple stages, which are not necessarily executed at the same time, but can be executed at different times, and the execution sequence of these steps or stages is not necessarily sequential, but can be executed in rotation or alternation with at least part of other steps or steps or stages in other steps.

[0067] Hereinafter, three representative embodiments of QFN packaging methods are given: Embodiment 1 Please refer to Figure 12 and Figure 13 The recess 12 and the first half hole 111 are etched on the back of the metal plate 10, and the second half hole corresponding to the first half hole 111 is etched on the front of the metal plate 10, wherein the first half hole 111 and the second half hole together form a through hole 11 penetrating the metal plate 10. Please refer to Figure 6 The chip 30 is attached to the front of the base island 21, and the chip 30 is electrically connected to the front of the finger 22 through the bonding wire 40. Please refer toFigure 7 and Figure 8 A release film 80 is provided and the lead frame 20 is placed on the release film 80, with the back of the lead frame 20 adhering to the release film 80. The chip 30, the lead frame 20 and the bonding wires 40 are encapsulated with the encapsulation material 60, and then the release film 80 is removed. Please refer to Figure 8 The encapsulation material in the recess 12 is removed. Please refer to Figure 3 A tin layer 50 is formed on the back of the lead frame 20, which can be formed by electroplating and covers the bottom of the island 21, the finger 22 and the inner wall of the recess 12. Please refer to Figure 4 The connecting portion 23 and the encapsulation material 60 above the connecting portion 23 are cut to obtain a plurality of packages. Please refer to Figure 5 A substrate 90 is provided and the package 70 is soldered to the substrate 90.

[0068] Embodiment 2 Please refer to Figure 12 and Figure 13 The recess 12 and the first half-hole 111 are etched on the back of the metal plate 10, and the second half-hole corresponding to the first half-hole 111 is etched on the front of the metal plate 10, wherein the first half-hole 111 and the second half-hole together form the through-hole 11 penetrating the metal plate 10. Please refer to Figure 6 The chip 30 is attached to the front of the island 21, and the chip 30 is electrically connected to the front of the finger 22 through the bonding wire 40. Please refer to Figure 7 and Figure 14 A release film 80 is provided and the lead frame 20 is placed on the release film 80, with the back of the lead frame 20 adhering to the release film 80. The chip 30, the lead frame 20 and the bonding wires 40 are encapsulated with the encapsulation material 60, and then the release film 80 is removed. Please refer to Figure 14 The encapsulation material in the recess 12 is removed, and part of the encapsulation material in the through-hole 11 on the back of the metal plate 10 is removed. A tin layer 50 is formed on the back of the lead frame 20, which can be formed by electroplating and covers the bottom of the island 21, the finger 22 and the inner wall of the recess 12. Please refer to Figure 16 The connecting portion 23 and the encapsulation material 60 above the connecting portion 23 are cut to obtain a plurality of packages. Please refer to Figure 15 A substrate 90 is provided and the package 70 is soldered to the substrate 90.

[0069] The main difference between Embodiment 2 and Embodiment 1 is that in Embodiment 2, not only the encapsulation material 60 in the recess 12 is removed, but also part of the encapsulation material 60 in the through-hole 11 is removed. When soldering, the solder can climb around the finger 22 to improve the soldering strength between the package 70 and the substrate 90.

[0070] Embodiment 3 Referring to Figure 12 and Figure 13 A groove 12 and a first half-hole 111 are etched on the back surface of the metal plate 10, and a second half-hole corresponding to the first half-hole 111 is etched on the front surface of the metal plate 10, wherein the first half-hole 111 and the second half-hole together form a through-hole 11 penetrating the metal plate 10. Referring to Figure 9 A tin layer 50 is formed on the back surface of the lead frame 20, which can be formed by electroplating and covers the bottom surface of the base island 21, the finger 22 and the inner wall of the groove 12. Referring to Figure 10 The chip 30 is attached to the front surface of the base island 21, and the chip 30 is electrically connected to the front surface of the finger 22 through the bonding wire 40. Referring to Figure 11 and Figure 3 A release film 80 is provided, and the lead frame 20 is placed on the release film 80, wherein the tin layer 50 on the back surface of the lead frame 20 is attached to the release film 80; the chip 30, the lead frame 20 and the bonding wire 40 are encapsulated by the encapsulating material 60, and then the release film 80 is removed. Referring to Figure 3 The encapsulating material in the groove 12 is removed. Referring to Figure 4 The connecting portion 23 and the encapsulating material 60 above the connecting portion 23 are cut to obtain a plurality of packages. Referring to Figure 5 A substrate 90 is provided, and the package 70 is soldered to the substrate 90.

[0071] The main difference between Embodiment 3 and Embodiment 1 is that, in Embodiment 3, the tin layer 50 is formed on the back surface of the lead frame 20 after the lead frame 20 is processed, and then the chip 30 is attached to the front surface of the lead frame 20 and encapsulated. In this way, the etching and electroplating steps can be performed in the frame factory, and after entering the packaging factory, only the encapsulation, removal of the encapsulating material 60 and singulation steps need to be performed, which reduces the requirement for the process capability of the packaging factory. The packaging factory does not need to purchase high-precision etching machines and establish a complete electroplating production line, the equipment investment cost is reduced, and the saved funds can be transferred to the optimization of the encapsulation process or the improvement of the cutting precision.

[0072] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Those skilled in the art can make various changes and modifications to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A QFN packaging method, characterized in that, The QFN packaging method comprises the following steps: providing a metal plate and etching the metal plate to form a lead frame, wherein the lead frame comprises a base island and fingers, and two adjacent fingers are connected by a connecting part; mounting a chip on the front surface of the base island, and electrically connecting the chip and the front surface of the finger by a bonding lead, forming a tin layer on the back surface of the lead frame, and plastic packaging the chip, the lead frame and the bonding lead; cutting the connecting part and the plastic packaging material above the connecting part to obtain a plurality of packaging bodies.

2. The QFN packaging method of claim 1, wherein, The step of mounting a chip on the front surface of the base island, and electrically connecting the chip and the front surface of the finger by a bonding lead, forming a tin layer on the back surface of the lead frame, and plastic packaging the chip, the lead frame and the bonding lead comprises: mounting a chip on the front surface of the base island, and electrically connecting the chip and the front surface of the finger by a bonding lead; plastic packaging the chip, the lead frame and the bonding lead; forming a tin layer on the back surface of the lead frame.

3. The QFN packaging method of claim 1, wherein, The step of mounting a chip on the front surface of the base island, and electrically connecting the chip and the front surface of the finger by a bonding lead, forming a tin layer on the back surface of the lead frame, and plastic packaging the chip, the lead frame and the bonding lead comprises: forming a tin layer on the back surface of the lead frame; mounting a chip on the front surface of the base island, and electrically connecting the chip and the front surface of the finger by a bonding lead; plastic packaging the chip, the lead frame and the bonding lead.

4. The QFN packaging method of claim 1, wherein, The step of providing a metal plate and etching the metal plate to form a lead frame comprises: providing a metal plate, forming a through hole on the metal plate, and forming a groove on the back surface of the metal plate, wherein the through hole is used to divide the base island and the fingers surrounding the base island on the metal plate, and the groove is used to form the connecting part between two adjacent fingers.

5. The QFN packaging method of claim 4, wherein, After the step of cutting the connecting part and the plastic packaging material above the connecting part, the QFN packaging method further comprises: providing a substrate and welding the packaging body on the substrate.

6. The QFN packaging method of claim 5, wherein, Before the step of cutting the connecting part and the plastic packaging material above the connecting part, the QFN packaging method further comprises: removing the packaging material in the groove.

7. The QFN packaging method of claim 5, wherein, Before the step of cutting the connecting part and the plastic packaging material above the connecting part, the QFN packaging method further comprises: removing the packaging material in the groove and removing part of the packaging material in the through hole on the back surface of the metal plate.

8. The QFN packaging method of claim 7, wherein, The removal depth of the packaging material in the through hole is equal to the depth of the groove.

9. The QFN packaging method of claim 1, wherein, The thickness of the connecting part is equal to the thickness of the lead frame.

10. The QFN packaging method of claim 1, wherein, The step of cutting the connecting part and the plastic packaging material above the connecting part comprises: cutting the connecting part and the plastic packaging material above the connecting part by using a cutting knife, wherein the width of the cutting knife is greater than or equal to the width of the connecting part.

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