Lead frame packaging method and packaging structure

Abstract

The invention provides a lead frame packaging method and a packaging structure, and relates to the technical field of chip packaging, and the method comprises the steps: firstly providing a lead frame, and then carrying out the routing of the front surface of each first pseudo pin to form a first connecting line arc, thereby achieving the electric connection between a plurality of first pseudo pins and / or a plurality of connecting pins. And then forming a back glue layer on the back surface of the connecting skeleton, completing chip mounting on the lead frame, and then forming a plastic package layer on the front surface of the connecting skeleton. And removing the back adhesive layer, forming a step groove, and finally forming a back gold layer. Compared with the prior art, the adhesive fixing binding force of the back adhesive layer is improved, and the risk that the back adhesive layer falls off can be effectively reduced in the plastic packaging process, so that the risk that the back surface is polluted by excessive adhesive during plastic packaging can be reduced. And during electroplating, the current skin effect is relieved, the electroplating quality is improved, the process efficiency is improved, the electroplating quality is better, and the process efficiency is higher.

Description

TECHNICAL FIELD

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

[0002] With the rapid development of the semiconductor industry, the dual flat no-leads (DFN) and quad flat no-leads (QFN) structures are widely used in the semiconductor industry. The DFN and QFN structures adopt a wettable flank structure and are plated with a solderable plating layer on the side surface to form a three-dimensional solder joint, thereby enhancing the connection strength between the component and the circuit board, reducing the failure caused by poor soldering, improving the reliability and stability of the product, and enabling the solder joint to flow upward along the pin to form a clear and visible fillet, which facilitates the detection of the quality of the solder joint by using the automatic optical inspection (AOI) technology without relying on the X-ray image, thereby improving the detection efficiency and safety and reducing the detection cost.

[0003] In the existing DFN and QFN structures, the lead frame back adhesive film can prevent the bottom pins from being encapsulated during plastic packaging and can also support the lead frame during the wire bonding process. However, due to the existence of the space gap between the lead frame base island, connecting rod, and pins, the space gap needs to be filled and protected by the plastic encapsulation layer. However, during the plastic packaging process, the adhesive film in the space gap region is easily impacted by the mold flow of the plastic encapsulation layer, which can cause the adhesive film to fail to adhere, and even cause the adhesive film to fall off and form a gap, thereby causing the overflow of the plastic encapsulation layer on the back surface of the lead frame to contaminate the pins and base island regions on the back surface of the lead frame.

[0004] In addition, during the subsequent electroplating process on the back surface of the pins, the gap between the pins can cause the electrical connection performance between the pins to be relatively poor, and the current skin effect can easily occur during electroplating, i.e., the current density on the surface of the pins is too high, and the current density inside the pins is too low, thereby affecting the quality of the plating layer and the process efficiency. SUMMARY

[0005] The present application aims to provide a lead frame packaging method and packaging structure that can reduce the risk of overflow of the plastic encapsulation layer on the back surface and have better electroplating quality and higher process efficiency.

[0006] In a first aspect, the present application provides a lead frame packaging method, comprising: providing a lead frame, wherein the lead frame comprises a connecting skeleton and a plurality of connecting pins, the connecting skeleton is provided with a mounting window, a plurality of the connecting pins are hollowly arranged on at least two side edges of the mounting window and connected to the connecting skeleton, and a first dummy pin connected to the connecting skeleton is further arranged between each adjacent two connecting pins; forming a first connecting line arc on the front surface of each of the first dummy pins, wherein the first connecting line arc is connected to the adjacent first dummy pins and / or the connecting pins; forming a back adhesive layer on the back surface of the connecting skeleton, wherein the back adhesive layer extends to cover the plurality of first dummy pins and the plurality of connecting pins; attaching a chip on the front surface of the lead frame, wherein the chip is electrically connected to the plurality of connecting pins; forming a plastic encapsulation layer on the front surface of the connecting skeleton, wherein the plastic encapsulation layer fills the gaps between the plurality of connecting pins and covers the chip, the first dummy pins, and the plurality of connecting pins; removing the back adhesive layer to expose the back surface of the connecting skeleton, the connecting pins, and the first dummy pins; removing a part of the back surface of the connecting pins to form a stepped groove; electroplating a back gold layer on the back surface of the connecting pins and the base island to extend to the sidewall of the stepped groove; cutting the plastic encapsulation layer and the connecting pins along a cutting path corresponding to the first dummy pins.

[0007] In an optional embodiment, the lead frame further comprises a base island arranged in the mounting window, and a plurality of pins are arranged on at least two sides of the base island. The step of attaching a chip on the lead frame comprises: attaching the back surface of the chip to the front surface of the base island; forming a plurality of connecting line arcs on the front surface of the chip, wherein the plurality of connecting line arcs are connected to the plurality of pins.

[0008] In an optional embodiment, the step of forming a first connecting line arc on the front surface of each of the first dummy pins comprises: forming a first connecting line arc on the front surface of each of the first dummy pins, wherein the first connecting line arc is connected to the adjacent first dummy pins, and the first connecting line arc is arranged in an arc shape above the connecting pins between the adjacent two first dummy pins.

[0009] In an optional embodiment, a second dummy pin connected to the connecting skeleton is arranged between each of the adjacent two connecting pins, and the second dummy pin is arranged on the first dummy pin in a staggered manner. After the step of forming a first connecting line arc on the front surface of each of the first dummy pins, the method further comprises: forming a second connecting line arc on the front surface of each of the second dummy pins, wherein the second connecting line arc is connected to the adjacent second dummy pins and / or the connecting pins.

[0010] In an optional embodiment, the step of wire bonding a first connecting line arc on the front surface of each of the first dummy pins comprises: wire bonding a first connecting line arc on the front surface of each of the first dummy pins, wherein the first connecting line arc is archedly distributed between the connecting pin and the first dummy pin.

[0011] In an optional embodiment, before the step of forming a back adhesive layer on the back surface of the connecting skeleton, the method further comprises: slotting a bonding groove on the back surface of each of the first dummy pins, wherein the bonding groove is used to accommodate the back adhesive layer.

[0012] In an optional embodiment, before the step of forming a back adhesive layer on the back surface of the connecting skeleton, the method further comprises: slotting a cutting groove on the back surface of each of the connecting pins, wherein the cutting groove and the bonding groove extend along the same linear direction, and the depth of the cutting groove is greater than that of the bonding groove, and the width of the cutting groove is less than that of the bonding groove.

[0013] In an optional embodiment, before the step of forming a back adhesive layer on the back surface of the connecting skeleton, the method further comprises: slotting an overflow groove on the back surface of the connecting skeleton, wherein the overflow groove is formed around the mounting window.

[0014] In an optional embodiment, after the step of slotting an overflow groove on the back surface of the connecting skeleton, the method further comprises: attaching a drainage strip to at least a partial area of the overflow groove to divide the overflow groove into at least two overflow sub-grooves, wherein the extension direction of the drainage strip is the same as that of the overflow groove.

[0015] In an optional embodiment, before the step of attaching a drainage strip to at least a partial area of the overflow groove, the method further comprises: forming a tapered flow guide hole and a check hole on the side wall of the drainage strip, wherein the flow guide hole and the check hole are both inclined through the opposite side walls of the drainage strip, and the large hole end of the flow guide hole and the small hole end of the check hole are located on the same side wall of the drainage strip.

[0016] In an optional embodiment, the step of removing a partial area of the back surface of the connecting pin comprises: forming a protective layer on the back surface of the pin; forming an etching opening on the protective layer; etching the back surface of the pin along the etching opening to form a stepped groove.

[0017] In an optional embodiment, the step of removing the back surface portion of the lead includes: cutting and removing the back surface portion of the lead to form a stepped groove.

[0018] In a second aspect, the present application provides a packaging structure prepared by the lead frame packaging method as described above, which includes: a lead frame including a plurality of leads; a chip mounted on the lead frame and electrically connected to the plurality of leads; a plastic encapsulation layer covering the lead frame and the chip, and the back surface of the plurality of leads exposed outside the plastic encapsulation layer; a back gold layer plated on the back surface of the lead.

[0019] In an optional embodiment, the lead frame further includes an island, the plurality of leads are distributed on at least two sides of the island, the chip is mounted on the front surface of the island, the plastic encapsulation layer covers the front surface and the sidewall of the island, and the back gold layer is further plated on the back surface of the island.

[0020] In an optional embodiment, the back surface of each lead forms a stepped groove, and the back gold layer extends to the sidewall of the stepped groove.

[0021] In an optional embodiment, the plastic encapsulation layer is protrudingly arranged between two adjacent stepped grooves.

[0022] In an optional embodiment, the back surface of the lead further forms a structural groove, and the structural groove is communicated to the stepped groove.

[0023] In an optional embodiment, the back surface of the lead further forms a structural groove, and the structural groove extends to the edge sidewall of the lead.

[0024] The beneficial effects of the embodiments of the present application include: The lead frame packaging method and packaging structure provided by the embodiment of the present application first provides a lead frame, the connecting skeleton of the lead frame is provided with a mounting window, a plurality of connecting pins are hollowed out on at least two side edges of the mounting window and are connected to the connecting skeleton, and a first dummy pin connected to the connecting skeleton is further arranged between every two adjacent connecting pins. Then, a first connecting line arc is formed by wire bonding on the front surface of each first dummy pin, wherein the first connecting line arc can be connected to the adjacent first dummy pin and / or connecting pin, so as to realize the electrical connection between the plurality of first dummy pins and / or the plurality of connecting pins. Then, a back adhesive layer is formed on the back surface of the connecting skeleton, the back adhesive layer can extend and cover the first dummy pin and the connecting pin, and the setting of the first dummy pin can improve the bonding strength of the back adhesive layer. Then, the chip is mounted on the front surface of the lead frame, and then a plastic encapsulation layer is formed on the front surface of the connecting skeleton, wherein the plastic encapsulation layer can fill the gap between the plurality of connecting pins and is wrapped between the chip, the first dummy pin and the connecting pin. Then, the back adhesive layer is removed to expose the back surface of the connecting pin, the first dummy pin and the connecting skeleton, and then the back surface of the connecting pin and the first dummy pin is cut to remove the partial area, so as to form a stepped groove, and finally, a back gold layer extending to the sidewall of the stepped groove is formed by electroplating on the back surface of the connecting pin and the base island. Compared with the prior art, the lead frame packaging method and packaging structure provided by the embodiment of the present application can make the back adhesive layer adhere and cover the first dummy pin by setting the first dummy pin, improve the bonding area, and thus improve the bonding strength of the back adhesive layer. In the plastic encapsulation process, the risk of the back adhesive layer falling off can be effectively reduced, so that the risk of back overflow pollution during plastic encapsulation can be reduced. In the electroplating process, the first dummy pin or the connecting pin is electrically connected by the first connecting line arc, the internal current density is improved, the plurality of pins are directly electrically connected to each other, the skin effect of the current is slowed down, the electroplating quality is improved, the process efficiency is improved, the electroplating quality is better, and the process efficiency is higher. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present 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 present 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.

[0026] Figure 1 The step block diagram of the lead frame packaging method provided by the first embodiment of the present application; Figure 2a The front surface schematic diagram corresponding to step S1 in the lead frame packaging method provided by the first embodiment of the present application; Figure 2b And Figure 2cThe partial schematic view corresponding to step S1 in the lead frame packaging method provided by the first embodiment of the present application is shown in different views; Figure 3a 、 Figure 3b and Figure 3c The partial schematic view corresponding to step S2 in the lead frame packaging method provided by the first embodiment of the present application is shown in different views; Figure 4a and Figure 4b The partial schematic view corresponding to step S3 in the lead frame packaging method provided by the first embodiment of the present application is shown in different views; Figure 4c and Figure 4d The schematic view corresponding to the step of preparing the cutting groove and the bonding groove before step S3 in the lead frame packaging method provided by the first embodiment of the present application is shown; Figure 5a and Figure 5b The partial schematic view corresponding to step S4 in the lead frame packaging method provided by the first embodiment of the present application is shown in different views; Figure 6a and Figure 6b The partial schematic view corresponding to step S5 in the lead frame packaging method provided by the first embodiment of the present application is shown in different views; Figure 7a and Figure 7b The partial schematic view corresponding to step S6 in the lead frame packaging method provided by the first embodiment of the present application is shown in different views; Figure 8a The cross-sectional schematic view corresponding to the first process of step S7 in the lead frame packaging method provided by the first embodiment of the present application is shown; Figure 8b The cross-sectional schematic view corresponding to the second process of step S7 in the lead frame packaging method provided by the first embodiment of the present application is shown; Figure 9 The partial schematic view corresponding to step S8 in the lead frame packaging method provided by the first embodiment of the present application is shown; Figure 10a and Figure 10b The partial schematic view corresponding to the step of preparing the overflow groove before step S8 is shown in different views; Figure 11a The schematic view corresponding to step S9 in the lead frame packaging method provided by the first embodiment of the present application is shown; Figure 11b 、 Figure 11c 、 Figure 11d 、 Figure 11e 、 Figure 11f 、 Figure 11g The schematic view of different products obtained by step S9 in the lead frame packaging method provided by the first embodiment of the present application is shown; Figure 12 A schematic view of a package structure provided by a first embodiment of the present application; Figure 13 A partial schematic view corresponding to step S2 in a lead frame packaging method provided by a second embodiment of the present application; Figure 14 A partial schematic view corresponding to step S1 in a lead frame packaging method provided by a third embodiment of the present application; Figure 15 A partial schematic view corresponding to step S2 in a lead frame packaging method provided by a third embodiment of the present application.

[0027] Figure: 100 - package structure; 110 - lead frame; 111 - connecting skeleton; 112 - base island; 113 - connecting pin; 114 - cutting groove; 115 - structure groove; 116 - connecting rod; 120 - first dummy pin; 121 - first connecting line arc; 122 - bonding groove; 130 - back adhesive layer; 140 - chip; 141 - structure line arc; 150 - plastic packaging layer; 160 - step groove; 161 - protective layer; 170 - back gold layer; 180 - overflow groove; 181 - drainage strip; 182 - flow hole; 183 - check hole; 190 - second dummy pin; 191 - second connecting line arc. DETAILED DESCRIPTION

[0028] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in 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 only some of the embodiments of the present application, but not all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0029] 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. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0030] 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.

[0031] In the description of the present application, it should be noted that if the terms "upper", "lower", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, or the orientation or positional relationship commonly used when the product of the present application is used, only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying 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 limiting the present application.

[0032] In addition, if the terms "first", "second" and the like appear, they are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0033] As disclosed in the background art, in the existing lead frame packaging process, due to the existence of the space gap between the pin, the connecting rod, the base island and the like, the plastic encapsulation layer needs to be filled for protection and to realize structural support. However, during plastic encapsulation, due to the large plastic encapsulation pressure, the mold flow impact is easy to occur, the back adhesive film of the space gap area is easy to be impacted by the mold flow of the plastic encapsulation layer, and then the back adhesive film is easy to cause adhesion failure, and even the back adhesive film is easy to fall off to form a gap, thereby causing the overflow of the back of the plastic encapsulation layer to contaminate the pin / base island area of the back of the lead frame, and affecting the subsequent electroplating effect.

[0034] In addition, in the subsequent pin back electroplating process, since the pins are independent of each other and are not directly electrically connected, that is, there is a gap between the pins, the pins can only play the role of conductive lead through the connecting frame skeleton, but the transverse contact area between the skeleton and the pin is small, so the electrical connection performance between the pins is poor, and the current skin effect is easy to occur, which causes the surface current density of the pin to be too high and the internal current density to be too low, thereby affecting the plating layer quality and process efficiency.

[0035] In order to solve the above problems, the present application provides a lead frame packaging method and packaging structure, and it should be noted that the features in the embodiments of the present application can be combined with each other without conflict.

[0036] First embodiment Referring to Figure 1 The present application provides a lead frame packaging method, which is used for preparing a packaging structure, and can reduce the risk of back overflow pollution during plastic encapsulation, and has better electroplating quality and higher process efficiency.

[0037] The lead frame packaging method provided by the present application comprises the following steps: S1: providing a lead frame 110.

[0038] Referring to Figure 2a , Figure 2b and Figure 2cThe lead frame 110 includes a connecting skeleton 111, a base island 112, and a plurality of connecting pins 113. The connecting skeleton 111 is provided with a mounting window, the base island 112 is arranged in the mounting window, and the base island 112 is provided with a connecting rod 116 around the base island 112, the connecting rod 116 is connected to the connecting skeleton 111, the plurality of connecting pins 113 are arranged on at least two sides of the base island 112 in a hollow manner, and the plurality of connecting pins 113 are connected to the connecting skeleton 111. Between every two adjacent connecting pins 113, a first dummy pin 120 connected to the connecting skeleton 111 is further arranged. It should be noted that the lead frame 110 can be provided with a plurality of rectangularly distributed mounting windows, and the base island 112 and the plurality of pins are arranged in each mounting window. The plurality of pins can be distributed around the base island 112, thereby facilitating the subsequent formation of the QFN packaging structure 100. Of course, the plurality of pins can also be distributed only on two opposite sides of the base island 112, thereby facilitating the subsequent formation of the DFN packaging structure 100. In the embodiment, the plurality of pins are distributed around the base island 112.

[0039] It should be noted that when step S1 is performed, the lead frame 110 needs to be prepared. The base island 112, the connecting pin 113, and the first dummy pin 120 are formed through a conventional lead frame 110 preparation process. The preparation process of the first dummy pin 120 is consistent with that of the connecting pin 113, and the first dummy pin 120 and the connecting pin 113 are both connected to the connecting skeleton 111. The protruding length of the first dummy pin 120 is less than that of the connecting pin 113.

[0040] S2: A first connecting line arc 121 is formed by wire bonding on the front surface of each first dummy pin 120.

[0041] Referring to Figure 3a , Figure 3b and Figure 3c The first connecting line arc 121 is connected to the adjacent first dummy pin 120 and / or connecting pin 113. Specifically, the first connecting line arc 121 can be connected to the adjacent first dummy pin 120, can be connected to the adjacent first dummy pin 120 and connecting pin 113, or can be connected to the adjacent connecting pin 113. In the embodiment, the first connecting line arc 121 is connected to the adjacent two first dummy pins 120.

[0042] In actual wire forming the first connecting line arc 121, the first connecting line arc 121 can be formed on the front surface of each first dummy pin 120 to connect to the adjacent first dummy pin 120, wherein the first connecting line arc 121 is arched and distributed above the connecting pin 113 between the adjacent two first dummy pins 120. The fence structure can be formed by the plurality of first connecting line arcs 121, which can connect the plurality of first dummy pins 120 into one on the one hand, improve the current density during subsequent electroplating, and thus improve the electroplating effect, especially the flow of current inside the packaging structure, improve the internal current density and electrical connection performance, thereby slowing down the skin effect and improving the electroplating effect. On the other hand, it can slow down the mold flow impact during plastic packaging, further preventing the mold flow impact from causing the back adhesive film to fall off.

[0043] S3: Forming a back adhesive layer 130 on the back of the connecting skeleton 111.

[0044] Referring to Figure 4a and Figure 4b , wherein the back adhesive layer 130 extends to cover the base island 112, the plurality of first dummy pins 120 and the plurality of connecting pins 113. Specifically, the back adhesive film can be attached to the back of the connecting skeleton 111 by using a film attachment machine, which can prevent the back of the connecting pin 113 from being encapsulated during plastic packaging, and can also support the chip 140 during the wire bonding process of the chip 140. The back adhesive film can cover the back of the base island 112 and the plurality of connecting pins 113, and cover the first dummy pin 120. By providing the first dummy pin 120, the adhesion of the back adhesive film can be further improved, so that the adhesion and fixing effect of the back adhesive film is better.

[0045] Referring to Figure 4c and Figure 4d , further, before step S3 is performed, a bonding groove 122 can be formed on the back of each first dummy pin 120 by laser slotting or mechanical slotting process, wherein the bonding groove 122 is used to accommodate the back adhesive layer 130. Specifically, the back adhesive layer 130 can cover the bonding groove 122 on the back of the first dummy pin 120. By providing the bonding groove 122, the adhesion between the back adhesive layer 130 and the first dummy pin 120 can be further improved, thereby further improving the adhesion and fixing effect of the back adhesive layer 130.

[0046] It is worth noting that after the groove forming the bonding groove 122, and before forming the back adhesive layer 130, the back of each connecting pin 113 can also be grooved to form a cutting groove 114, wherein the cutting groove 114 extends in the same direction as the bonding groove 122, and the depth of the cutting groove 114 is greater than the bonding groove 122, and the width of the cutting groove 114 is less than the bonding groove 122. Specifically, the cutting groove 114 is relatively narrower and deeper, and the bonding groove 122 is relatively wider and shallower. Both the bonding groove 122 and the cutting groove 114 can be in contact with the back adhesive layer 130, thereby improving the bonding force of the back adhesive layer 130, and also improving the flowability of the electroplating solution during the subsequent electroplating process.

[0047] It should be noted that the preparation sequence of the bonding groove 122 and the cutting groove 114 can not be limited, as long as it is completed before the back adhesive layer 130 is attached.

[0048] S4: Attaching the chip 140 on the lead frame 110, wherein the chip 140 is electrically connected to the plurality of connecting pins 113.

[0049] Referring to Figure 5a and Figure 5b , specifically, the back of the chip 140 can be first attached to the base island 112, and the front of the chip 140 is formed with a pad for realizing electrical connection, and then a plurality of structure wire arcs 141 are formed on the front of the chip 140 by wire bonding process, wherein the plurality of structure wire arcs 141 can be respectively connected to the plurality of connecting pins 113. In the present embodiment, connecting wire arcs can be formed around the chip 140 to form a QFN structure, and when a DFN structure is used, connecting wire arcs can be formed only on the two side edges of the front of the chip 140.

[0050] In other preferred embodiments of the present application, the lead frame 110 can also be designed without a base island, i.e. no base island and connecting rod are arranged in the mounting window, and the chip 140 can be directly attached to the plurality of connecting pins 113 by flip-chip process, also realizing the electrical connection between the chip 140 and the plurality of connecting pins 113.

[0051] S5: Forming a plastic encapsulation layer 150 on the front of the connecting skeleton 111.

[0052] Referring to Figure 6a and Figure 6bWherein the plastic sealing layer 150 fills the gap between the plurality of connecting pins 113 and covers the base island 112, the chip 140, the first dummy pin 120 and the plurality of connecting pins 113. Specifically, the plastic sealing liquid is filled and then pressure-injected by using the plastic sealing process, so as to fill the pin gap and protect the chip 140 structure to form the plastic sealing layer 150. Since the bonding force of the back adhesive layer 130 is enhanced by the bonding groove 122 on the first dummy pin 120 and the cutting groove 114 on the connecting pin 113, the mold flow impact generated during the plastic sealing will not cause the bonding failure of the back adhesive layer 130, thereby avoiding the situation that the back adhesive layer 130 falls off to form a gap and causes the plastic sealing overflow pollution.

[0053] S6: Remove the back adhesive layer 130 to expose the back surface of the connecting pin 113, the first dummy pin 120 and the connecting skeleton 111.

[0054] Referring to Figure 7a and Figure 7b , specifically, the back adhesive layer 130 can be removed by using a film tearing machine, so as to expose the back surface of the connecting pin 113, the base island 112 and the connecting skeleton 111, and expose the first dummy pin 120 and the bonding groove 122.

[0055] S7: Remove the back surface of the connecting pin 113 to form a step groove 160.

[0056] Referring to Figure 8a , the step groove can be formed by using an etching process. Specifically, a protection layer 161 can be first formed on the back surface of the connecting pin 113, which can be a photoresist and cover the back surface of the entire lead frame 110, then an etching opening is formed on the protection layer 161, which exposes a part of the connecting pin 113, and then the back surface of the pin is etched along the etching opening, so as to form the step groove. The depth of the step groove 160 is less than the depth of the bonding groove 122, and the width of the step groove 160 is greater than the minimum distance between the bonding grooves 122 in the adjacent two mounting windows, so that the step groove 160 can expose the bonding groove 122, thereby forming a half-cut state.

[0057] Referring to Figure 8b , of course, in other preferred embodiments of the present application, a cutting process (using a laser cutting machine, a plasma cutting machine or a mechanical cutting machine, etc.) can be used to complete the first wider area cutting, and a wider cutting knife can be used for local cutting after the first cutting, so as to form the step groove 160. The step groove 160 needs to extend to the connecting skeleton 111, and the depth of the step groove 160 is less than the depth of the bonding groove 122, and the width of the step groove 160 is greater than the minimum distance between the bonding grooves 122 in the adjacent two mounting windows, so that the step groove 160 can expose the bonding groove 122, thereby forming a half-cut state.

[0058] It should be noted that the step groove 160 can expose the cutting groove 114 and the bonding groove 122, facilitating subsequent plating operations.

[0059] S8: Back plating of the connecting pin 113 to form a back gold layer 170 extending to the sidewall of the step groove 160.

[0060] Referring to Figure 9 , specifically, the lead frame 110 is plated by using a plating process, and the lead frame 110 is electrically coupled to the negative pole of the conductive plating device, and the positive pole is coupled to the conductive plating material, and an electric current is applied to the lead frame 110, so that the plating material is deposited on the metal surface of the lead frame 110, i.e. on the surface of the connecting pin 113, the base island 112, the connecting skeleton 111, and the first pseudo pin 120 exposed from the plastic encapsulation layer 150, to form a metal layer. At this time, since the first connecting line arc 121 electrically connects the plurality of first pseudo pins 120 into one, the current density between the plurality of first pseudo pins 120 during plating can be improved, the internal current density is improved, the generation of skin effect is reduced, and the quality of the plated metal layer is improved. The back gold layer 170 can be at least one of tin, gold, silver, palladium, and nickel.

[0061] It should be noted that since the cutting groove 114 and the bonding groove 122 are both exposed to the step groove 160, an electroplating flow channel can be formed during plating, the conductive bonding groove 122 is wide and shallow, and the plating liquid can flow along the electroplating flow channel to improve the flowability of the plating liquid. And since the cutting groove 114 is narrow and deep, the plating liquid can be fully immersed in the connecting pin 113, and the electroplated metal layer can be better formed on the sidewall of the pin.

[0062] Referring to Figure 10a and Figure 10b , further, before step S8 is performed, a overflow groove 180 can also be formed by grooving the back surface of the connecting skeleton 111. Specifically, the overflow groove 180 can be formed by a laser grooving process on the back surface of the connecting skeleton 111, and the overflow groove 180 is formed around the mounting window. After forming the overflow groove 180, a drainage strip 181 can also be attached to at least part of the area of the overflow groove 180 to divide the overflow groove 180 into at least two overflow sub-grooves, wherein the extension direction of the drainage strip 181 is the same as the extension direction of the overflow groove 180. The preparation of the overflow groove 180 can improve the flowability of the plating liquid in the subsequent plating process, and the arrangement of the drainage strip 181 can form a plurality of flow channels to increase the contact area between the plating liquid and the lead frame 110, further reduce the skin effect, and improve the plating efficiency.

[0063] It should be noted that before the drainage strip 181 is attached, the drainage strip 181 can also be formed with a tapered flow guide hole 182 and a check hole 183 on the side wall, wherein the flow guide hole 182 and the check hole 183 are both inclined through to the opposite two side walls of the drainage strip 181, and the large hole end of the flow guide hole 182 and the small hole end of the check hole 183 are located on the same side wall of the drainage strip 181. Specifically, the flow guide hole 182 and the check hole 183 are both inclined holes, that is, the opening direction of the flow guide hole 182 and the check hole 183 is inclined to the extension direction of the drainage strip 181, and the designed inclination angle can be between 30-60°, for example, it can be 30°, 45° or 60°. And here the flow guide hole 182 and the check hole 183 are both tapered holes, and have relatively large and small hole ends, the large hole ends of the flow guide hole 182 and the check hole 183 are located on the two sides of the drainage strip 181 respectively, and the small hole ends of the two are also located on the two sides of the drainage strip 181 respectively, so here the flow guide hole 182 can be used as a flow guide hole to accelerate the flow of the electroplating solution in the overflow sub-tank on both sides of the drainage strip 181, and the check hole 183 can be used as a blocking hole to block the backflow of the liquid. Through the hole design, it can ensure that the flow rate of the electroplating solution in the overflow sub-tank on both sides is consistent, and the uniformity of electroplating is ensured.

[0064] S9: cutting the plastic sealing layer 150 and the connecting pin 113 along the cutting groove.

[0065] Referring to Figure 11a , Figure 11b and Figure 11c , the cutting groove corresponds to the first dummy pin 120. Specifically, the cutting groove corresponds to the cutting groove 114, that is, the cutting groove 114 can be used as a cutting groove positioning mark to make the cutting more accurate and prevent cutting deviation. A narrower cutting knife can be used for secondary cutting, thereby retaining the metal layer formed by the side wall of the cutting groove in the connecting pin 113 and retaining the side wall of the stepped groove 160 after cutting. After cutting, a single packaged product can be formed, which can be a QFN product ( Figure 11b ), or a DFN product ( Figure 11c ).

[0066] Referring to Figure 11d , of course, in other preferred embodiments of the application, the connecting pin 113 can be cut again to form a structure groove 115 before electroplating, which can be connected to the stepped groove 160, thereby forming a dimple structure after cutting.

[0067] Referring to Figure 11eIn other preferable embodiments of the present application, the position of the cutting path can also be redefined, for example, the cutting path corresponds to the sidewall of the step groove 160. Furthermore, before electroplating, the structure groove 115 can be cut again on the connecting pin 113, which can be connected to the step groove 160, thereby forming a dimple structure after cutting. Specifically, the bottom wall of the step groove 160 is not reserved after cutting, and no step structure is formed. That is, a second cutting can be performed by using a narrower cutting tool, and the position of the cutting path corresponds to the sidewall of the step groove 160, so that the structure groove 115 can be cut along the sidewall of the step groove 160, and the packaging structure 100 is cut into a single product, and the process is completed.

[0068] Referring to Figure 11f In other preferable embodiments of the present application, when the step groove 160 is formed by etching, only the connecting pin 113 can be etched, that is, the opening on the protection layer 161 only exposes the connecting pin 113, thereby reserving the plastic sealing layer 150, that is, the plastic sealing layer 150 protrudes between two adjacent step grooves 160, and the plastic sealing layer 150 does not need to be removed additionally, thereby saving the process steps.

[0069] Referring to Figure 11g In other preferable embodiments of the present application, when the step groove 160 is formed by etching, the etching liquid also etches the sidewall of the step groove 160 in a different direction, thereby etching a round corner structure or a groove undercut phenomenon on the sidewall, which can further improve the welding bonding force of the connecting pin 113.

[0070] Referring to Figure 2a , Figure 3a , Figure 4b , Figure 5a , Figure 6a , Figure 10a and Figure 12The packaging structure 100 is prepared by the method, and specifically prepared by steps S1-S8. The packaging structure 100 comprises a lead frame 110, a first connecting wire arc 121, a back adhesive layer 130, a chip 140, a plastic sealing layer 150, and a back gold layer 170. The lead frame 110 comprises a connecting skeleton 111, a base island 112, and a plurality of connecting pins 113. The connecting skeleton 111 is provided with a mounting window. The base island 112 is arranged in the mounting window. The plurality of connecting pins 113 are arranged in at least two sides of the base island 112 in a hollow manner and connected to the connecting skeleton 111. A first dummy pin 120 connected to the connecting skeleton 111 is further arranged between each adjacent two connecting pins 113. The first connecting wire arc 121 is formed by wire bonding on the front surface of each first dummy pin 120, wherein the first connecting wire arc 121 is connected to adjacent first dummy pins 120 and / or connecting pins 113. The back adhesive layer 130 is formed on the back surface of the connecting skeleton 111, wherein the back adhesive layer 130 extends and covers the base island 112, the plurality of first dummy pins 120, and the plurality of connecting pins 113. The chip 140 is attached to the front surface of the base island 112, and the chip 140 is electrically connected to the pins. The plastic sealing layer 150 is arranged on the front surface of the connecting skeleton 111. The plastic sealing layer 150 fills the gap between the plurality of pins. The plastic sealing layer 150 covers the base island 112, the chip 140, the first dummy pin 120, and the plurality of connecting pins 113. The back surface of the connecting pin 113 is formed with a stepped groove 160 extending to the connecting skeleton 111. The back gold layer 170 is formed by electroplating on the back surface of the connecting pin 113 and the base island 112, and the back gold layer 170 extends to the sidewall of the stepped groove 160.

[0071] In other preferable embodiments of the present application, the lead frame 110 can also adopt a design without the base island, that is, the mounting window is not provided with the base island and the connecting rod. The chip 140 can be directly attached to the plurality of connecting pins 113 by flip-chip technology, and the electrical connection between the chip 140 and the plurality of connecting pins 113 is also achieved.

[0072] Further, the two ends of each first connecting wire arc 121 are respectively connected to the adjacent two first dummy pins 120, and the first connecting wire arc 121 is arranged in an arc shape on the connecting pin 113 between the adjacent two first dummy pins 120.

[0073] In the present embodiment, the back surface of each first dummy pin 120 is formed with an adhesive groove 122 by slotting, and the adhesive groove 122 is used to accommodate the back adhesive layer 130. The back surface of each connecting pin 113 is formed with a cutting groove 114 by slotting, the cutting groove 114 extends in the same direction as the adhesive groove 122, the depth of the cutting groove 114 is greater than that of the adhesive groove 122, and the width of the cutting groove 114 is less than that of the adhesive groove 122.

[0074] Further, the back surface of the connecting skeleton 111 is slotted to form an overflow groove 180, which is located around the mounting window. At least part of the overflow groove 180 is attached with a drainage strip 181 to divide the overflow groove 180 into at least two overflow sub-grooves, wherein the extension direction of the drainage strip 181 is the same as the extension direction of the overflow groove 180. The side wall of the drainage strip 181 is formed with a tapered flow guide hole 182 and a check hole 183, wherein the flow guide hole 182 and the check hole 183 are both inclined through to the opposite two side walls of the drainage strip 181, and the large hole end of the flow guide hole 182 and the small hole end of the check hole 183 are located on the same side wall of the drainage strip 181.

[0075] It should be noted that the flow guide hole 182 and the check hole 183 are both inclined holes, that is, the opening direction of the flow guide hole 182 and the check hole 183 is inclined to the extension direction of the drainage strip 181, and the design inclination angle can be between 30-60°, for example, it can be 30°, 45° or 60°. Moreover, the flow guide hole 182 and the check hole 183 are both tapered holes here, and have opposite large hole ends and small hole ends, the large hole ends of the flow guide hole 182 and the check hole 183 are located on the two sides of the drainage strip 181 respectively, and the small hole ends of the two are also located on the two sides of the drainage strip 181 respectively, so the flow guide hole 182 here can be used as a flow guide hole to accelerate the flow of the electroplating solution in the overflow sub-grooves on both sides of the drainage strip 181, and the check hole 183 can be used as a blocking hole to block the backflow of the liquid. Through the opening design, it can ensure that the flow rates of the electroplating solution in the overflow sub-grooves on both sides are consistent during the electroplating process, and the uniformity of electroplating is ensured.

[0076] Referring to Figure 11a , Figure 11b and Figure 11c , the application further provides another packaging structure 100, which is prepared by the above method, specifically by the above steps S1-S9. The packaging structure 100 comprises a lead frame 110, a chip 140 and a back gold layer 170. The lead frame 110 comprises a base island 112 and a plurality of connecting pins 113, and the plurality of connecting pins 113 are hollowly arranged on at least two sides of the base island 112. The chip 140 is attached to the front surface of the base island 112 and is electrically connected with the connecting pins 113. The back gold layer 170 is electroplated on the back surface of the connecting pins 113 and the base island 112.

[0077] It should be noted that the packaging structure 100 here is a packaging product, which can be a QFN packaging structure 100 (such as Figure 11b ), or a DFN packaging structure 100 (such as Figure 11c ).

[0078] Further, the back surface of each connecting pin 113 is formed with a stepped groove 160, and the back gold layer 170 can extend to the side wall of the stepped groove 160.

[0079] Referring to Figure 11d Of course, in other preferred embodiments of the present application, the back surface of the connecting pin 113 is also cut to form a structure recess 115 which is connected to the step groove 160, so that a dimple structure is formed after cutting. Specifically, the back surface of the connecting pin 113 is also formed with a structure recess 115 which is connected to the step groove 160, and the structure recess 115 can be formed by a laser drilling process, and the bottom wall of the step groove 160 can be used as a stop layer to improve the welding performance.

[0080] Referring to Figure 11e In other preferred embodiments of the present application, the back surface of the connecting pin 113 is also formed with a structure recess 115 which extends to the edge side wall of the connecting pin 113, and specifically, the structure recess 115 can be formed on the connecting pin 113 by a laser drilling process to form a dimple structure. In the preparation process, the position of the cutting path can also be redefined, for example, the cutting path corresponds to the side wall of the step groove 160. Furthermore, before electroplating, the connecting pin 113 can be cut again to form a structure recess 115 which is connected to the step groove 160, so that a dimple structure is formed after cutting. Specifically, the bottom wall of the step groove 160 is not reserved after cutting, and no step structure is formed. That is, a narrower cutting knife can be used for secondary cutting, and the position of the cutting path corresponds to the side wall of the step groove 160, so that the connecting pin 113 can be cut along the side wall of the step groove 160, the structure recess 115 is reserved, and the packaging structure 100 is cut into a single product to complete the process.

[0081] Of course, the structure recess 115 can not be formed here, and the cutting path can directly correspond to the side wall of the step groove 160, and a single product can also be obtained.

[0082] In summary, the lead frame 110 packaging method and packaging structure 100 provided by the embodiment of the present application first provides a lead frame 110, the connecting frame 111 of the lead frame 110 is provided with a mounting window, the base island 112 is arranged in the mounting window, a plurality of connecting pins 113 are hollowly arranged on at least two sides of the base island 112 and are connected to the connecting frame 111, and a first dummy pin 120 connected to the connecting frame 111 is further arranged between each two adjacent connecting pins 113. Then, the first connecting line arc 121 is formed by wire bonding on the front surface of each first dummy pin 120, wherein the first connecting line arc 121 can be connected to the adjacent first dummy pin 120 and / or connecting pin 113, so as to realize the electrical connection between the plurality of first dummy pins 120 and / or the plurality of connecting pins 113. Then, the back adhesive layer 130 is formed on the back surface of the connecting frame 111, which can extend and cover the base island 112, the first dummy pin 120 and the connecting pin 113. Through the arrangement of the first dummy pin 120, the adhesion and fixing strength of the back adhesive layer 130 can be improved. Then, the chip 140 is attached on the front surface of the base island 112, and then the plastic sealing layer 150 is formed on the front surface of the connecting frame 111, wherein the plastic sealing layer 150 can fill the gap between the plurality of connecting pins 113 and coat between the base island 112, the chip 140, the first dummy pin 120 and the connecting pin 113. Then, the back adhesive layer 130 is removed to expose the back surface of the connecting pin 113, the first dummy pin 120, the base island 112 and the connecting frame 111, and then the back surface part area of the connecting pin 113 and the first dummy pin 120 is cut off to form the stepped groove 160, and finally the back gold layer 170 extending to the sidewall of the stepped groove 160 is electroplated on the back surface of the connecting pin 113 and the base island 112. Compared with the prior art, the lead frame 110 packaging method and packaging structure 100 provided by the embodiment of the present application can make the back adhesive layer 130 adhere and cover the first dummy pin 120 by arranging the first dummy pin 120, so as to improve the adhesion area and the adhesion and fixing force of the back adhesive layer 130, effectively reduce the risk of the back adhesive layer 130 falling off during the plastic sealing process, and thus reduce the risk of back overflow pollution during plastic sealing. Moreover, the first dummy pin 120 or the connecting pin 113 is electrically connected by the first connecting line arc 121 during electroplating, which improves the internal current density and electrical connection performance, directly connects the plurality of pins during the electroplating process, slows down the skin effect, improves the electroplating quality, improves the process efficiency, and has better electroplating quality and higher process efficiency.

[0083] Second embodiment The embodiment of the present application provides a lead frame 110 package method, and basic steps and principles, and generated technical effects and the first embodiment are same, for brief description, the part of the embodiment not mentioned can refer to the corresponding content in the first embodiment. Compared with the first embodiment, the difference in the embodiment is that step S2.

[0084] The lead frame 110 package method provided by the embodiment of the present application comprises the following steps: S1: providing a lead frame 110.

[0085] The lead frame 110 provided in step S1 is same as the first embodiment.

[0086] S2: wire bonding a first connecting line arc 121 on the front surface of each first dummy pin 120.

[0087] Referring to Figure 13 The first connecting line arc 121 is connected to the adjacent connecting pin 113. When the first connecting line arc 121 is formed by wire bonding, the first connecting line arc 121 connected to the adjacent connecting pin 113 can be formed by wire bonding on the front surface of each first dummy pin 120, wherein the first connecting line arc 121 is in an arc shape and is distributed between the connecting pin 113 and the first dummy pin 120. Specifically, two first connecting line arcs 121 can be formed by wire bonding on the front surface of each first dummy pin 120, so as to be connected to the connecting pins 113 on both sides respectively, thereby enabling the plurality of connecting pins 113 and the plurality of first dummy pins 120 to be electrically connected as an integrated structure.

[0088] When the first connecting line arc 121 is actually formed by wire bonding, the first connecting line arc 121 connected to the adjacent connecting pin 113 can be formed by wire bonding on the front surface of each first dummy pin 120, wherein the first connecting line arc 121 is in an arc shape and is distributed on the gap between the adjacent first dummy pin 120 and the connecting pin 113. The plurality of first connecting line arcs 121 can form a fence structure, which can enable the plurality of first dummy pins 120 and the plurality of connecting pins 113 to be connected as an integrated structure, improve the current density during subsequent electroplating, thereby improving the electroplating effect, and on the other hand, can slow down the mold flow impact during plastic packaging, and further prevent the back adhesive film from falling off due to the mold flow impact.

[0089] Steps S3-S9 can refer to the first embodiment.

[0090] The packaging structure 100 includes a lead frame 110, a first connecting wire arc 121, an adhesive layer 130, a chip 140, a plastic sealing layer 150, and a back gold layer 170. The lead frame 110 includes a connecting skeleton 111, an island 112, and a plurality of connecting pins 113. The connecting skeleton 111 is provided with a mounting window, the island 112 is arranged in the mounting window, the plurality of connecting pins 113 are arranged in at least two sides of the island 112 in a hollow manner and are connected to the connecting skeleton 111, and a first dummy pin 120 connected to the connecting skeleton 111 is further arranged between each adjacent two connecting pins 113. The first connecting wire arc 121 is formed by wire bonding on the front surface of each first dummy pin 120, wherein the first connecting wire arc 121 is connected to the adjacent first dummy pin 120 and / or connecting pin 113. The adhesive layer 130 is formed on the back surface of the connecting skeleton 111, wherein the adhesive layer 130 extends and covers the island 112, the plurality of first dummy pins 120, and the plurality of connecting pins 113. The chip 140 is attached to the front surface of the island 112, and the chip 140 is electrically connected to the pins. The plastic sealing layer 150 is arranged on the front surface of the connecting skeleton 111, fills the gap between the plurality of pins, and covers the island 112, the chip 140, the first dummy pin 120, and the plurality of connecting pins 113. The back surface of the connecting pin 113 is formed with a stepped groove 160 extending to the connecting skeleton 111. The back gold layer 170 is formed by electroplating on the back surface of the connecting pin 113 and the island 112, and the back gold layer 170 extends to the sidewall of the stepped groove 160.

[0091] Further, the two ends of each first connecting wire arc 121 are respectively connected to the adjacent connecting pin 113 and first dummy pin 120, and the first connecting wire arc 121 is distributed in an arc shape between the connecting pin 113 and the first dummy pin 120.

[0092] In summary, the lead frame 110 packaging method and packaging structure 100 provided by the embodiment of the present application connect the first connecting wire arc 121 to the adjacent first dummy pin 120 and connecting pin 113, can sequentially connect the plurality of first dummy pins 120 and the plurality of connecting pins 113 into one, thereby improving the overall electrical connection performance, can further improve the current density when the back gold layer 170 is formed by electroplating, reduce the skin effect, and improve the electroplating effect.

[0093] Third embodiment The lead frame 110 packaging method provided by the embodiment of the present application has the same basic structure and principle, technical effects and the first embodiment. For brief description, the part not mentioned in this embodiment can refer to the corresponding content in the first embodiment.

[0094] The lead frame 110 packaging method provided by the embodiment of the present application includes the following steps: S1: providing a lead frame 110.

[0095] Referring to Figure 14 The lead frame 110 provided in step S1 is different from the first embodiment, wherein the lead frame 110 comprises a connecting skeleton 111, a base island 112 and a plurality of connecting pins 113, the connecting skeleton 111 is provided with a mounting window, the base island 112 is arranged in the mounting window, the plurality of connecting pins 113 are arranged in at least two sides of the base island 112 in a hollow manner and are connected to the connecting skeleton 111, and a first dummy pin 120 connected to the connecting skeleton 111 is further arranged between every two adjacent connecting pins 113. A second dummy pin 190 connected to the connecting skeleton 111 is further arranged between every two adjacent connecting pins 113, the second dummy pin 190 is connected to the first dummy pin 120 in a staggered manner and is arranged on the first dummy pin 120. Wherein, the second dummy pin 190 is connected to the first dummy pin 120 in a staggered manner, which means that the two side edges of the second dummy pin 190 are not aligned with the edges of the first dummy pin 120, preferably, the second dummy pin 190 is located in the middle of the first dummy pin 120, thereby forming a stepped structure on both sides to facilitate wire bonding.

[0096] Further, the bottom of the second dummy pin 190 can also form a groove structure, which can make the bonding force between the plastic sealing layer and the connecting skeleton 111 better and the structural strength higher during plastic sealing.

[0097] S2: wire bonding a first connecting line arc 121 on the front surface of each first dummy pin 120.

[0098] Referring to Figure 15 Specifically, the first connecting line arc 121 can be connected to the adjacent first dummy pin 120, and when actually wire bonding the first connecting line arc 121, the first connecting line arc 121 connected to the adjacent first dummy pin 120 can be wire bonded on the front surface of each first dummy pin 120, wherein the first connecting line arc 121 is arranged in an arc shape on the connecting pin 113 between the adjacent two first dummy pins 120.

[0099] After the wire bonding action of the first connecting line arc 121 is completed, a second connecting line arc 191 can be wire bonded on the front surface of each second dummy pin 190, wherein the second connecting line arc 191 is connected to the adjacent second dummy pin 190 and / or connecting pin 113. Wherein the second connecting line arc 191 can be connected to the adjacent second dummy pin 190, or connected to the adjacent connecting pin 113, or connected to the adjacent connecting pin 113 and second dummy pin 190. Preferably, the second connecting line arc 191 can be connected to the adjacent two second dummy pins 190.

[0100] Steps S3-S9 can refer to the first embodiment.

[0101] It should be noted that, by setting the second connecting line arc 191, the connection of the second pseudo pin 190 can be realized, and a line arc with different heights is formed with the first connecting line arc 121, further improving the bonding force of the lead frame 110 and the plastic sealing layer 150, and improving the overall structural strength. At the same time, the first pseudo pin 120 and the second pseudo pin 190 are designed to be staggered, which can also form a stepped structure, which can also improve the bonding force of the plastic sealing body, and further improve the overall structural strength. Moreover, the first connecting line arc 121 and the second connecting line arc 191 can further improve the internal conductive performance and current density, thereby improving the electroplating effect. The plurality of first connecting line arcs 121 and the plurality of second connecting line arcs 191 can form a more dense fence structure, which can better buffer the mold flow impact.

[0102] The application further provides a packaging structure 100 prepared by the above method. The packaging structure 100 comprises a lead frame 110, a first connecting line arc 121, an adhesive layer 130, a chip 140, a plastic sealing layer 150 and a back gold layer 170. The lead frame 110 comprises a connecting skeleton 111, an island 112 and a plurality of connecting pins 113. The connecting skeleton 111 is provided with a mounting window, the island 112 is arranged in the mounting window, and the plurality of connecting pins 113 are arranged in at least two sides of the island 112 in a hollow manner and are connected to the connecting skeleton 111. A first pseudo pin 120 connected to the connecting skeleton 111 is further arranged between every two adjacent connecting pins 113. The first connecting line arc 121 is wire-bonded on the front surface of each first pseudo pin 120, wherein the first connecting line arc 121 is connected to adjacent first pseudo pins 120 and / or connecting pins 113. The adhesive layer 130 is formed on the back surface of the connecting skeleton 111, wherein the adhesive layer 130 extends and covers the island 112, the plurality of first pseudo pins 120 and the plurality of connecting pins 113. The chip 140 is attached to the front surface of the island 112, and the chip 140 is electrically connected to the pins. The plastic sealing layer 150 is arranged on the front surface of the connecting skeleton 111, and the plastic sealing layer 150 fills the gap between the plurality of pins. The plastic sealing layer 150 covers the island 112, the chip 140, the first pseudo pin 120 and the plurality of connecting pins 113, and the back surface of the connecting pin 113 is formed with a stepped groove 160 extending to the connecting skeleton 111. The back gold layer 170 is electroplated on the back surface of the connecting pin 113 and the island 112, and the back gold layer 170 extends to the sidewall of the stepped groove 160.

[0103] Further, a second dummy pin 190 connected with the connecting skeleton 111 is arranged between every two adjacent connecting pins 113, the second dummy pin 190 is connected with the first dummy pin 120 in staggered manner, and is arranged on the first dummy pin 120, and a second connecting line arc 191 is formed on the front surface of each second dummy pin 190 by wire bonding, wherein the second connecting line arc 191 is connected with the adjacent second dummy pin 190 and / or connecting pin 113. Preferably, the two ends of the second connecting line arc 191 are connected with the adjacent second dummy pin 190 respectively, so that the second connecting line arc 191 can be distributed in an arc shape on the first connecting line arc 121.

[0104] In summary, the lead frame 110 packaging method and packaging structure 100 provided by the embodiments of the present application can realize the connection of the second dummy pin 190 by arranging the second connecting line arc 191, and form line arcs with different heights with the first connecting line arc 121, further improve the bonding force of the lead frame 110 and the plastic encapsulation layer 150, and improve the overall structural strength. Meanwhile, the staggered design of the first dummy pin 120 and the second dummy pin 190 can also form a stepped structure, which can also improve the bonding force of the plastic encapsulation body, and further improve the overall structural strength. Moreover, the first connecting line arc 121 and the second connecting line arc 191 can further improve the internal conductive performance and current density, so as to improve the electroplating effect. The plurality of first connecting line arcs 121 and the plurality of second connecting line arcs 191 can form a more dense fence structure, which can better buffer the mold flow impact.

[0105] The above merely provides a specific implementation of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method of leadframe packaging, characterized by, The method comprises the following steps: providing a lead frame, wherein the lead frame comprises a connecting skeleton and a plurality of connecting pins, the connecting skeleton is provided with a mounting window, a plurality of the connecting pins are hollowed out on at least two side edges of the mounting window and connected to the connecting skeleton, and a first dummy pin connected to the connecting skeleton is further arranged between every two adjacent connecting pins; forming a first connecting line arc on the front surface of each first dummy pin by wire bonding, wherein the first connecting line arc is connected to adjacent first dummy pins and / or connecting pins; forming a back adhesive layer on the back surface of the connecting skeleton, wherein the back adhesive layer extends and covers a plurality of the first dummy pins and a plurality of the connecting pins; attaching a chip on the front surface of the lead frame, wherein the chip is electrically connected to a plurality of the connecting pins; forming a plastic encapsulation layer on the front surface of the connecting skeleton, wherein the plastic encapsulation layer fills the gaps between a plurality of the connecting pins and covers the chip, the first dummy pins and a plurality of the connecting pins; removing the back adhesive layer to expose the back surface of the connecting pins, the first dummy pins and the connecting skeleton; removing a part of the back surface of the connecting pins to form a stepped groove; forming a back gold layer on the back surface of the connecting pins by electroplating, wherein the back gold layer extends to the sidewall of the stepped groove; cutting the plastic encapsulation layer and the connecting pins along a cutting path, wherein the cutting path corresponds to the first dummy pin.

2. The leadframe packaging method of claim 1, wherein, The lead frame further comprises an island, the island is arranged in the mounting window, a plurality of the pins are hollowed out on at least two sides of the island, and the step of attaching a chip on the lead frame comprises: attaching the back surface of the chip on the front surface of the island; forming a plurality of connecting line arcs on the front surface of the chip by wire bonding, wherein a plurality of the connecting line arcs are connected to a plurality of the pins.

3. The leadframe packaging method of claim 2, wherein, The step of forming a first connecting line arc on the front surface of each first dummy pin comprises: forming a first connecting line arc on the front surface of each first dummy pin by wire bonding, wherein the first connecting line arc is connected to adjacent first dummy pins, and the first connecting line arc is arched and distributed above the connecting pins between two adjacent first dummy pins.

4. The leadframe packaging method according to claim 2 or 3, wherein, A second dummy pin connected to the connecting skeleton is further arranged between every two adjacent connecting pins, the second dummy pin is staggered with the first dummy pin and arranged on the first dummy pin, and after the step of forming a first connecting line arc on the front surface of each first dummy pin, the method further comprises: forming a second connecting line arc on the front surface of each second dummy pin by wire bonding, wherein the second connecting line arc is connected to adjacent second dummy pins and / or connecting pins.

5. The leadframe packaging method of claim 2, wherein, The step of forming a first connecting line arc on the front surface of each first dummy pin comprises: forming a first connecting line arc on the front surface of each first dummy pin by wire bonding, wherein the first connecting line arc is connected to adjacent connecting pins, and the first connecting line arc is arched and distributed between the connecting pins and the first dummy pin.

6. The leadframe packaging method of claim 2, wherein, Before the step of forming a back adhesive layer on the back surface of the connecting skeleton, the method further comprises: A groove is formed on the back of each of the first pins to form an adhesive groove, wherein the adhesive groove is used to accommodate the adhesive layer.

7. The leadframe packaging method of claim 6, wherein, Before the step of forming the adhesive layer on the back of the connecting skeleton, the method further comprises: A groove is formed on the back of each of the connecting pins to form a cutting groove, wherein the cutting groove extends in the same direction as the adhesive groove, and the depth of the cutting groove is greater than that of the adhesive groove, and the width of the cutting groove is less than that of the adhesive groove.

8. The leadframe packaging method of claim 2, wherein, Before the step of forming the adhesive layer on the back of the connecting skeleton, the method further comprises: A groove is formed on the back of the connecting skeleton to form an overflow groove, wherein the overflow groove is formed around the mounting window.

9. The method of claim 8, wherein, After the step of forming the overflow groove on the back of the connecting skeleton, the method further comprises: A drainage strip is attached to at least part of the area of the overflow groove to divide the overflow groove into at least two overflow sub-channels, wherein the extension direction of the drainage strip is the same as that of the overflow groove.

10. The method of claim 9, wherein, Before the step of attaching the drainage strip to at least part of the area of the overflow groove, the method further comprises: A tapered flow guide hole and a check hole are formed on the side wall of the drainage strip, wherein the flow guide hole and the check hole are inclined through to the opposite side walls of the drainage strip, and the large hole end of the flow guide hole and the small hole end of the check hole are located on the same side wall of the drainage strip.

11. The leadframe packaging method of claim 1, wherein, The step of removing part of the area of the back of the connecting pin comprises: A protective layer is formed on the back of the pin; An etching opening is formed on the protective layer; The back of the pin is etched along the etching opening to form a stepped groove.

12. The method of claim 1, wherein, The step of removing part of the area of the back of the pin comprises: The part of the area of the back of the pin is cut to form a stepped groove.

13. A package structure prepared by the lead frame packaging method according to claim 1, characterized in that, The package structure comprises: A lead frame comprising a plurality of pins; A chip attached to the lead frame and electrically connected to the plurality of pins; A plastic encapsulation layer covering the lead frame and the chip, and the back of the plurality of pins exposed outside the plastic encapsulation layer; A back gold layer electroplated on the back of the pins.

14. The package structure of claim 13, wherein, The lead frame further comprises a base island, and the plurality of pins are distributed on at least two sides of the base island, the chip is attached to the front of the base island, the plastic encapsulation layer covers the front and side walls of the base island, and the back gold layer is also electroplated on the back of the base island.

15. The package structure of claim 13 or 14, wherein, The back of each of the pins forms a stepped groove, and the back gold layer extends to the side wall of the stepped groove.

16. The package structure of claim 15, wherein, The plastic encapsulation layer is protrudingly arranged between two adjacent stepped grooves.

17. The package structure of claim 15, wherein, The back of the pin further forms a structural groove, and the structural groove is connected to the stepped groove.

18. The package structure of claim 15, wherein, The back of the pin further forms a structural groove, and the structural groove extends to the edge side wall of the pin.

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