Package structure

Abstract

The utility model provides a packaging structure, comprising a lead frame comprising a base island and a first pin arranged at the periphery of the base island, the first pin comprising a first welding zone and a second welding zone; the first chip is arranged on the base island; the conductive strip is connected with the first chip and the first welding area of the first pin; and the conductive welding sheet is arranged on the surface of the first pin and located in the second welding area, and the conductive welding sheet is electrically connected with the first pin. The packaging structure provided by the embodiment of the utility model not only can ensure the welding firmness of the conductive strip and the welding spot of the first pin, but also can avoid the reliability problem of the connection between the conductive lead and the first pin caused by the bad state of the surface of the first pin, thereby improving the reliability of the packaging structure.

Description

Technical Field

[0001] The utility model relates to the technical field of semiconductor packaging, in particular to a packaging structure. Background Art

[0002] As semiconductor packages become smaller, the thick aluminum wire bonding technology commonly used in high-power devices is no longer a viable option. Aluminum ribbon bonding breaks through the limitations of package size and achieves the strength and performance advantages of the bonding process in low-power device packaging. Aluminum ribbon bonding provides a nearly perfect technical alternative.

[0003] In the aluminum ribbon bonding process, the chip is usually mounted on the base island surface of the lead frame, and the aluminum ribbon is bonded from the chip to the solder joints of the lead frame pins. During bonding, the pins need to be pressed firmly with pressure claws to ensure the solder joints are strong. However, the pressure claw pressing will leave pressure claw marks on the pins, destroying the structural layer on the pin surface, and causing poor flatness in the corresponding area of ​​the pins, affecting the next process.

[0004] Therefore, how to ensure the welding strength of the solder joint while avoiding the adverse effects of the pressure claw marks left by the pressure claws on the pins has become a problem that needs to be solved at present. Summary of the invention

[0005] The technical problem to be solved by the utility model is to provide a packaging structure which can ensure the welding fastness of the welding point and avoid the connection reliability problem caused by the bad state of the pin surface.

[0006] In order to solve the above technical problems, an embodiment of the utility model provides a packaging structure, including: a lead frame, including a base island and a first pin arranged on the periphery of the base island, the first pin including a first welding area and a second welding area; a first chip, arranged on the base island; a conductive strip, connected to the first chip and the first welding area of ​​the first pin; a conductive welding sheet, arranged on the surface of the first pin and located in the second welding area, the conductive welding sheet being electrically connected to the first pin.

[0007] In one embodiment, at least a portion of a surface of the conductive solder pad facing away from the first pin has a silver plating layer.

[0008] In one embodiment, the conductive solder sheet is fixed to the surface of the first pin through a conductive layer.

[0009] In one embodiment, the second welding area is disposed at the periphery of the first welding area.

[0010] In one embodiment, the surface of the first pin has a recessed groove that is recessed toward the first pin, and the conductive solder sheet at least covers a portion of the recessed groove.

[0011] In one embodiment, on the surface of the first pin, both sides of the connection between the conductive strip and the first welding area of ​​the first pin have the indentations.

[0012] In one embodiment, the packaging structure further includes a first conductive lead connected to the first chip and the conductive pad.

[0013] In one embodiment, the packaging structure further includes a second chip and a second conductive lead, the second chip is disposed on the base island, and the second conductive lead is connected to the second chip and the conductive pad.

[0014] In one embodiment, the packaging structure further includes a second pin and a third conductive lead, the second pin is disposed at the periphery of the base island, and the third conductive lead is connected to the second chip and the second pin.

[0015] In one embodiment, at least a portion of the surface of the second pin has a silver plating layer, and the third conductive wire is bonded to the silver plating layer.

[0016] In the packaging structure provided by the embodiment of the utility model, the conductive welding sheet is arranged on the surface of the first pin, and in the area corresponding to the conductive welding sheet (e.g., the second welding area), the surface of the first pin connected to the conductive lead and other structures is replaced by the surface of the conductive welding sheet, and the conductive lead and other structures are connected to the surface of the conductive welding sheet, which can ensure the welding strength of the solder joint between the conductive strip and the first pin, and avoid the reliability problem of the connection between the conductive lead and other structures and the first pin caused by the poor state of the surface of the first pin, thereby improving the reliability of the packaging structure. Since the conductive lead and other structures are connected to the surface of the conductive welding sheet, there is no need to set a silver-plated area on the surface of the first pin, which greatly saves the cost of the lead frame, and whether to set the conductive welding sheet can be selected according to the requirements of the packaging structure, thereby improving the application breadth of the lead frame. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1A It is a schematic diagram of a lead frame and chip before aluminum ribbon bonding;

[0019] Figure 1B This is a schematic diagram after bonding with aluminum tape;

[0020] Figure 1C is along Figure 1B Cross-sectional view of line C-C1;

[0021] Figure 2 is a top view of a packaging structure provided by an embodiment of the utility model;

[0022] Figure 3 is along Figure 2 A cross-sectional view of line A-A1;

[0023] Figure 4 is along Figure 2 Cross-sectional view of line B-B1;

[0024] Figure 5 It is a schematic diagram of a packaging structure provided by another embodiment of the utility model. DETAILED DESCRIPTION

[0025] During the aluminum ribbon bonding process, the pressing claws will leave claw marks on the pins after pressing, which will damage the structural layer on the surface of the pins and cause poor flatness in the corresponding area of ​​the pins.

[0026] Specifically, Figure 1A This is a schematic diagram of the lead frame and chip before aluminum ribbon bonding. Figure 1A The lead frame 100 includes a base island 101 and pins 102 disposed on the periphery of the base island 101 . The chip 110 and the chip 120 are disposed on the base island 101 . The pins 102 include an aluminum ribbon welding area 102A and a silver-plated area 102B.

[0027] Figure 1B This is a schematic diagram after aluminum ribbon bonding, please refer to Figure 1B , the aluminum ribbon 130 of the chip 110 is bonded to the aluminum ribbon welding area 102A of the pin 102. In order to ensure the welding strength of the solder joint, it is necessary to use a pressure claw to press the two sides of the pin 102 during bonding. The pressure claw may leave a pressure claw mark 140 on the surface of the pin 102, damaging the silver-plated area 102B on the surface of the pin 102. When the chip 120 and the silver-plated area 102B of the pin 102 are connected by wires, the silver-plated area 102B is damaged, which may cause the wire to fail to achieve reliable electrical connection with the pin 102, affecting the reliability of the packaging structure. In addition, Figure 1C As shown, it is Figure 1B In the cross-sectional view along the C-C1 line, the pressure claw mark 140 is a dent sunken toward the bottom of the pin 102. Due to the existence of the pressure claw mark 140, the surface of the pin 102 is uneven, and the flatness of the pin 102 is affected, which in turn affects the next process (such as wire bonding).

[0028] In view of the defects existing in the packaging structure, the utility model provides a packaging structure, which can ensure the welding fastness of the welding point and avoid the connection reliability problem caused by the bad state of the pin surface.

[0029] The specific implementation of the packaging structure provided by the utility model is described in detail below with reference to the accompanying drawings.

[0030] Figure 2 is a top view of a packaging structure provided by an embodiment of the utility model, Figure 3 is along Figure 2 The cross-sectional view of the A-A1 line, Figure 4 is along Figure 2 For a cross-sectional view of the line B-B1, please refer to Figure 2 , Figure 3 as well as Figure 4 The packaging structure provided by an embodiment of the utility model includes: a lead frame 200, including a base island 201 and a first pin 202 arranged on the periphery of the base island 201, the first pin 202 including a first welding area 202A and a second welding area 202B; a first chip 210, arranged on the base island 201; a conductive strip 220, connected to the first chip 210 and the first welding area 202A of the first pin 202; a conductive welding piece 230, arranged on the surface of the first pin 202 and located in the second welding area 202B, and the conductive welding piece 230 is electrically connected to the first pin 202.

[0031] In the package structure, the conductive welding piece 230 is arranged on the surface of the first pin 202. Then, in the area corresponding to the conductive welding piece 230 (e.g., the second welding area 202B), the surface of the first pin 202 connected to the conductive lead and other structures is replaced by the surface of the conductive welding piece 230. The conductive lead and other structures are connected to the surface of the conductive welding piece 230, which can ensure the welding strength of the solder joint between the conductive strip 220 and the first pin 202, and avoid the reliability problem of the connection between the conductive lead and other structures and the first pin 202 caused by the poor state of the surface of the first pin 202, thereby improving the reliability of the package structure. Since the conductive lead and other structures are connected to the surface of the conductive welding piece 230, there is no need to set a silver-plated area on the surface of the first pin 202, which greatly saves the cost of the lead frame, and whether to set the conductive welding piece 230 can be selected according to the requirements of the package structure, thereby improving the application breadth of the lead frame.

[0032] In this embodiment, the lead frame 200 includes a base island 201 and a first pin 202 disposed on the periphery of the base island 201, and the first pin 202 is independent of the base island 201. The base island 201 is used to carry the first chip 210, and the first pin 202 is used to realize the electrical connection between the first chip 210 and an external device. It can be understood that the lead frame 200 may include a plurality of pins disposed on the periphery of the base island 201, and the first pin 202 is one of the pins.

[0033] The first pin 202 includes a first welding area 202A and a second welding area 202B. The first welding area 202A is used as an area for welding the conductive strip 220 and the first pin 202, and the second welding area 202B is used as an area for arranging the conductive pad 230. The second welding area 202B is arranged at the periphery of the first welding area 202A. For example, according to the design requirements of the packaging structure, the second welding area 202B can be arranged at both sides of the first welding area 202A, or the second welding area 202B is arranged at one side of the first welding area 202A. In this embodiment, the second welding area 202B is arranged at one side of the first welding area 202A as an example for description.

[0034] The first chip 210 is fixed to the surface of the base island 201 through an adhesive layer (not shown in the drawings). The adhesive layer may be a conductive layer or an insulating layer. The surface of the first chip 210 away from the base island 201 has a plurality of pads (not shown in the drawings), and the first chip 210 is electrically connected to the conductive strip 220 through the pads. In this embodiment, the first chip 210 is a power chip.

[0035] One end of the conductive strip 220 is connected to the pad of the first chip 210, and the other end is connected to the first welding area 202A of the first pin 202, forming a bridge structure between the first chip 210 and the first pin 202. A conductive strip bonding process can be used to achieve the connection between the conductive strip 220 and the first chip 210 and the first pin 202. The conductive strip bonding process breaks through the limitation of the package size and realizes the strength and performance advantages of the bonding process in the packaging of low-power devices. In this embodiment, the conductive strip 220 is an aluminum strip, and in other embodiments, the conductive strip 220 can also be a copper strip.

[0036] The conductive solder sheet 230 is disposed on the surface of the first pin 202 and electrically connected to the first pin 202, serving as an intermediate structure for electrically connecting the first pin 202 to a conductive lead (eg, the first conductive lead 500 or the second conductive lead 270). In one embodiment, the conductive solder sheet 230 is a preformed solder sheet.

[0037] In this embodiment, the surface of the first pin 202 has a dent 240 that is recessed toward the first pin 202, and the conductive solder sheet 230 at least covers a portion of the dent 240. In this embodiment, the dent 240 is a claw mark left by a claw when performing the conductive strip bonding step, which causes an uneven surface of the first pin 202. The conductive solder sheet 230 at least covers a portion of the dent 240, and a conductive lead (such as the first conductive lead 500 or the second conductive lead 270) is connected to the conductive solder sheet 230, thereby avoiding the connection reliability problem caused by the uneven surface of the first pin 202.

[0038] In one embodiment, when performing the conductive strip bonding step, the pressing claws are pressed on both sides of the first pin 202, and both sides of the connection between the conductive strip 220 and the first welding area 202A of the first pin 202 have the indentations 240. According to the design requirements of the packaging structure, the conductive soldering pad 230 can be arranged corresponding to the indentation 240 area that needs to be connected to the conductive lead.

[0039] In one embodiment, the conductive pad 230 is fixed to the surface of the first pin 202 through a conductive layer 400. The conductive layer 400 includes but is not limited to a conductive solder layer or a conductive adhesive layer. In this embodiment, the conductive layer 400 is also filled in the dent 240 to avoid forming a cavity at the dent 240 to affect the flatness of the surface of the conductive pad 230 away from the first pin 202, and to improve the support strength of the first pin 202 to the conductive pad 230.

[0040] In one embodiment, at least a portion of the surface of the conductive soldering pad 230 away from the first pin 202 has a silver plating layer 250, and a conductive lead (such as the first conductive lead 500 or the second conductive lead 270) is connected to the silver plating layer 250. The silver plating layer 250 can reduce the contact resistance between the conductive lead (such as the first conductive lead 500 or the second conductive lead 270) and the conductive soldering pad 230. In this embodiment, the entire surface of the conductive soldering pad 230 away from the first pin 202 has the silver plating layer 250. In other embodiments, the silver plating layer 250 may be provided only on a portion of the surface of the conductive soldering pad 230 away from the first pin 202.

[0041] In another embodiment, see Figure 5, which is a schematic diagram of a packaging structure provided by another embodiment of the utility model, the packaging structure also includes a first conductive lead 500, and the first conductive lead 500 is connected to the first chip 210 and the conductive welding piece 230. One end of the first conductive lead 500 is welded to the pad of the first chip 210, and the other end is connected to the conductive welding piece 230, so that different pads of the first chip 210 are mixed with the conductive strips and welding wires of the same pin. The first conductive lead 500 can be a single metal lead or a metal alloy lead. Among them, the first conductive lead 500 can be connected to the first chip 210 and the conductive welding piece 230 by a wire bonding process.

[0042] Please continue reading Figure 2 to Figure 4 , the package structure also includes a second chip 260 and a second conductive lead 270, the second chip 260 is arranged on the base island 201, and the second conductive lead 270 is connected to the second chip 260 and the conductive solder pad 230, thereby realizing the mixing of conductive strips and solder wires of different chips with the same pin. On the base island 201, the first chip 210 and the second chip 260 are arranged independently of each other, and the second chip 260 can be a chip different from the first chip 210. For example, the first chip 210 is a power chip, and the second chip 260 is a logic chip. In some embodiments, the first chip 210 and the second chip 260 can also be connected by a conductive lead. One end of the second conductive lead 270 is connected to the second chip 260, and the other end is connected to the conductive solder pad 230. The second conductive lead 270 can be a single metal lead or a metal alloy lead. Among them, the second conductive lead 270 can be connected to the second chip 260 and the conductive solder pad 230 by a wire bonding process.

[0043] In this embodiment, the package structure further includes a second pin 280 and a third conductive lead 290, wherein the second pin 280 is disposed on the periphery of the base island 201, and the third conductive lead 290 is connected to the second chip 260 and the second pin 280. It is understood that the lead frame 200 may include a plurality of pins disposed on the periphery of the base island 201, and the second pin 280 is one of the pins. In this embodiment, the first pin 202 is disposed adjacent to the second pin 280. One end of the third conductive lead 290 is connected to the second chip 260, and the other end is connected to the second pin 280. The third conductive lead 290 may be a single metal lead or a metal alloy lead. It is understood that the package structure may include a plurality of the third conductive leads 290 to achieve connection between different pads of the second chip 260 and the second pin 280. The third conductive lead 290 may be connected to the second chip 260 and the second pin 280 by a wire bonding process.

[0044] Optionally, at least a portion of the surface of the second pin 280 has a silver plating layer 250, and the third conductive lead 290 is connected to the silver plating layer 250. In this embodiment, the entire surface of the second pin 280 has a silver plating layer 250 to provide more sufficient space for the connection of the second conductive lead 270. In other embodiments, the silver plating layer 250 is only provided on a portion of the surface of the second pin 280 to reduce the cost of the packaging structure.

[0045] In some embodiments, when forming the packaging structure, the conductive strip 220 is first led from the first chip 210 to the first welding area 202A of the first pin 202 for bonding. In order to ensure the welding strength of the solder joint, it is necessary to use a pressure claw to press the two sides of the first pin 202 during bonding. The pressure claw may leave an indentation 240 on the second welding area 202B of the first pin 202. After the aluminum strip is bonded, the conductive welding sheet 230 is set in the second welding area 202B. The conductive welding sheet 230 can cover at least part of the indentation 240. The first conductive lead 500, the second conductive lead 270, the third conductive lead 290 and other structures are connected to the conductive welding sheet 230 and the surface of the second pin 280.

[0046] The packaging structure provided by the embodiment of the utility model can not only ensure the welding strength of the welding point between the conductive strip 220 and the first pin 202, but also avoid the reliability problem of the connection between the conductive lead and other structures and the first pin 202 caused by the poor state of the surface of the first pin 202, thereby improving the reliability of the packaging structure.

[0047] It should be noted that the terms "including" and "having" and their variations involved in the documents of the present utility model are intended to cover non-exclusive inclusions. The terms "first", "second", etc. are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence, unless the context clearly indicates, and it should be understood that the data used in this way can be interchanged under appropriate circumstances. The term "one or more" depends at least in part on the context, and can be used to describe features, structures or characteristics in a singular sense, or can be used to describe a combination of features, structures or features in a plural sense. The term "based on" can be understood as not necessarily intended to express a set of exclusive factors, but can alternatively, also at least in part depending on the context, allow the presence of other factors that are not necessarily explicitly described. In addition, in the absence of conflict, the embodiments of the present utility model and the features in the embodiments can be combined with each other. In addition, in the above description, the description of known components and technologies is omitted to avoid unnecessary confusion of the concept of the present utility model. In the above embodiments, each embodiment focuses on the differences from other embodiments, and the same / similar parts between the embodiments can be referred to each other.

[0048] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A packaging structure, characterized in that: include: A lead frame, comprising a base island and a first pin arranged at the periphery of the base island, wherein the first pin comprises a first welding area and a second welding area; A first chip is arranged on the base island; a conductive strip connected to the first chip and the first welding area of ​​the first pin; A conductive soldering pad is disposed on the surface of the first pin and located in the second soldering area, and the conductive soldering pad is electrically connected to the first pin.

2. The packaging structure according to claim 1, characterized in that: At least a portion of a surface of the conductive solder pad facing away from the first pin has a silver plating layer.

3. The packaging structure according to claim 1, characterized in that: The conductive soldering sheet is fixed on the surface of the first pin through a conductive layer.

4. The packaging structure according to claim 1, characterized in that: The second welding area is disposed at the periphery of the first welding area.

5. The packaging structure according to claim 1, characterized in that: The surface of the first pin has a recessed groove recessed toward the first pin, and the conductive solder sheet at least covers a portion of the recessed groove.

6. The packaging structure according to claim 5, characterized in that: On the surface of the first pin, both sides of the connection between the conductive strip and the first welding area of ​​the first pin have the indentations.

7. The packaging structure according to claim 1, characterized in that: The packaging structure further includes a first conductive lead connected to the first chip and the conductive pad.

8. The packaging structure according to claim 1, characterized in that: The packaging structure further includes a second chip and a second conductive lead. The second chip is disposed on the base island, and the second conductive lead is connected to the second chip and the conductive solder pad.

9. The packaging structure according to claim 8, characterized in that: The packaging structure further includes a second pin and a third conductive lead, wherein the second pin is arranged at the periphery of the base island, and the third conductive lead is connected to the second chip and the second pin.

10. The packaging structure according to claim 9, characterized in that: At least a portion of the surface of the second pin has a silver plated layer, and the third conductive wire is bonded to the silver plated layer.

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