CN110323199A - A kind of QFN encapsulating structure of more base island lead frame framves and power conversion module - Google Patents

Abstract

The invention discloses a kind of more base island lead frame framves and the QFN encapsulating structures of power conversion module, encapsulate by using the island Duo Ji and application QFN, improve integrated level, reduce packaging body volume, reduce packaging cost；By the way that Ji Dao is packaged maximum leakage, reach high heat dissipation purpose；Electrical isolation between each base island inside encapsulating structure, and security isolation spacing is provided between Ji Dao and base island, safe spacing design is carried out between encapsulating structure leakage radiating surface, between pin and pin, between separate type pin and radiating surface, high-voltage breakdown can be effectively prevented, and then meet encapsulation or the requirement of reliability.

Description

A QFN package structure of a multi-base island lead frame and a power conversion module

technical field

The invention relates to the technical field of semiconductor packaging, in particular to a QFN packaging structure of a multi-base island lead frame and a power conversion module.

Background technique

With the rapid development of integrated circuit IC design and manufacturing industry, packaging technology has also been greatly improved. Packaging is an important part of the entire integrated circuit manufacturing process, which has the functions of heat dissipation and protection. The packaging process can seal the chip and isolate the damage from external pollution and external force.

With the advancement of technology, it is no longer sufficient to package two chips in one package. Encapsulating multiple chips in one package has become the direction of technological development. In practical application of the existing multi-base island frame with one chip placed on each base island, each pin is very easy to break down due to the large difference in high and low voltage, and thus cannot meet the requirements of packaging or reliability.

Low-cost, ultra-thin, high heat dissipation chip packaging has always been the development direction of semiconductor packaging. With the country's vigorous advocacy of environmental protection and energy conservation, the motor industry has also ushered in the spring, and motor drive technology has developed by leaps and bounds. The chip area is getting smaller and smaller, the power is getting bigger and bigger, the usage environment is getting more and more extreme, the heat dissipation requirement is getting higher and higher, the market competition is getting more and more intense, and the cost competition is particularly prominent. The traditional DIP/SOP IPM package structure has disadvantages such as poor heat dissipation, high cost, poor package compatibility, and few optional suppliers.

At present, the QFN package has also appeared on the market. The traditional QFN package is usually used to package memory chips. Due to a series of problems such as high power consumption, high heat dissipation requirements, and safe spacing between pins, power conversion chips are not suitable for the packaging process of QFN packaging for memory chips. Therefore, how to solve the problems of large volume, high cost, poor compatibility, and poor heat dissipation of the existing DIP/SOP IPM packaging structure has become an urgent technical problem to be solved in the development of multi-base island lead frames and semiconductor packaging.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a QFN package structure of a multi-base island lead frame and a power conversion module in view of the technical problems existing in the prior art, which can realize the package structure with small package volume, low cost, high heat dissipation and integration. High, good compatibility and so on.

In order to achieve the above object, the present invention provides a multi-base island lead frame applied to a QFN package of a power conversion module, which at least includes: a first base island and a second base island that are electrically isolated from each other; the first base island; The base island has a first carrying surface for carrying power devices, and a first heat dissipation surface opposite to the first carrying surface, and the first base island has at least one side disposed on the multi-base island lead frame, A plurality of first pins directly connected to the first base island body; the second base island has a second bearing surface for carrying the main control chip for controlling the power device, and is connected to the first base island. A second heat dissipation surface opposite the two bearing surfaces, the second base island has a plurality of second pins disposed on two adjacent sides of the multi-base island lead frame and separated from the second base island body; Wherein, after the multi-base island lead frame is applied to the QFN package and is plastic-sealed by the plastic-sealed body, a part or all of the corresponding heat dissipation surface is exposed to the plastic-sealed body, and the ends of all the pins and the bottom surface coplanar with the corresponding heat-dissipating surface Parts are exposed to the molding.

In order to achieve the above object, the present invention also provides a QFN package structure of a power conversion module, comprising: a multi-base island lead frame, the multi-base island lead frame at least includes a first base island that is electrically isolated from each other; a second base island; the first base island has a first bearing surface and a first heat dissipation surface opposite to the first bearing surface, the first base island has leads disposed on the multi-base island at least one side of the frame and a plurality of first pins directly connected to the first base island body; the second base island has a second bearing surface, and a second heat dissipation surface opposite to the second bearing surface surface, the second base island has a plurality of second pins disposed on two adjacent sides of the multi-base island lead frame and separated from the second base island body; a first power device disposed on the the first carrying surface, and is directly connected to the first pin; a main control chip for controlling the first power device is disposed on the second carrying surface, and the main control chip is respectively connected by metal leads is electrically connected with the second pin and the first power device; and a plastic packaging body, which plastically encapsulates the multi-base island lead frame carrying the first power device and the main control chip; wherein the corresponding heat dissipation Part or all of the surface is exposed to the plastic package, and the ends of all pins and the bottom surface part coplanar with the corresponding heat dissipation surface are exposed to the plastic package; the working voltage of the first pin is the same as that of the second pin. The working voltage of the pins is not the same.

The advantages of the present invention are that: multi-chip/device integrated plane packaging is realized, the integration degree is improved, the volume of the package body is reduced, and the packaging cost is reduced; The PCB is fully contacted to achieve the purpose of high heat dissipation; the base islands inside the package structure are electrically isolated, and a safety isolation distance is set between the base islands and the base islands, and the package structure leaks between the heat dissipation surfaces and between the pins and the pins. , A safe spacing is designed between the separated pins and the heat dissipation surface, which can effectively prevent high-voltage breakdown, thereby meeting the requirements of packaging or reliability.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings can also be obtained from these drawings without creative effort.

FIG. 1 is a schematic plan view of an embodiment of the lead frame of the present invention;

FIG. 2A is a schematic diagram of the wire bonding structure of the first embodiment of the QFN packaging structure of the power conversion module of the present invention;

2B is a bottom view of the QFN package structure shown in FIG. 2A;

FIG. 2C is a side view of the QFN package structure shown in FIG. 2A;

FIG. 3 is a schematic diagram of the wire bonding structure of the second embodiment of the QFN packaging structure of the power conversion module of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, but not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present invention. The terms "first", "second", "third", etc. (if present) in the description and claims of the present invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It is to be understood that the objects so described are interchangeable under appropriate circumstances. Furthermore, the terms "comprising" and "having", and any variations thereof, are intended to cover non-exclusive inclusion.

Please refer to FIG. 1 , which is a schematic plan view of a multi-base island lead frame according to an embodiment of the present invention. The multi-base island lead frame 10 of the present invention is applied to the QFN package of a power conversion module. The multi-base island lead frame 10 can form an independent QFN package structure 20 (marked in FIG. 2A ) after being plastic-sealed with the electronic components through the QFN package. , wherein the packaging lines of the multi-base-island lead frame 10 are schematically indicated by a dotted frame. The multi-base island lead frame 10 includes a plurality of base islands that are electrically isolated from each other. In this embodiment, four base islands that are electrically isolated from each other are schematically depicted, namely, a first base island 11 , a second base island 12 , a third base island 13 and a fourth base island 14 . Wherein, the area of the first base island 11 is larger than the area of the second base island 12 . In other embodiments, the multi-base-island lead frame 10 may also include three base islands that are electrically isolated from each other, such as a first base island 11 , a second base island 12 and a third base island 13 , or include The first base island 11 , the second base island 12 and the fourth base island 14 .

In this embodiment, the first base island 11 has a first carrying surface 111 for carrying the first power device 21 (marked in FIG. 2A ), and a first carrying surface 111 opposite to the first carrying surface 111 . A heat dissipation surface 112 (shown in FIG. 2B ), the first base island 11 has multiple base islands disposed on two adjacent sides of the multiple base island lead frame 10 and directly connected to the first base island body 110 a first pin 113 . Wherein, after the multi-base-island lead frame 10 is applied to the QFN package and is plastic-sealed by the plastic-sealed body, the first heat dissipation surface 112 is partially or completely exposed to the plastic-sealed body, and the ends of all the first pins 113 and A portion of the bottom surface coplanar with the first heat dissipation surface 112 is exposed to the molding body. By encapsulating the base island to maximize external leakage, the external leakage heat dissipation surface can be fully contacted with the PCB in the follow-up to achieve the purpose of high heat dissipation. In this embodiment, nine first pins 113 are schematically drawn. In other embodiments, the number of the first pins 113 is not limited, and the setting positions may only be located in the multi-base island lead frame On one side of 10, as long as the purpose of the present invention is satisfied. The first power device 21 includes, but is not limited to, a triode, a MOS transistor, a thyristor, a combination of an insulated gate bipolar transistor (IGBT) and a fast recovery diode (FRD).

Specifically, each of the first pins 113 is directly connected to the first base island body 110 , and is electrically connected to the outside world as a main heat dissipation pin and a functional pin of the first base island 11 . Since the first pin 113 is directly connected to the first base island body 110, in subsequent use, the pin can be coupled to the ground or a high-voltage pin; or the pin can only be used as a high-voltage pin pin usage. At the same time, all the first pins 113 also play a supporting role for the first base island 11 with a larger area when the multi-base island lead frame 10 is applied to the QFN package for plastic packaging.

In a further embodiment, all the first pins 113 on one side of the multi-base-island lead frame 10 may have a wider width (greater than a first predetermined width, for example, less than or equal to the first The width of the base island body 110 ) is divided into directly connected pins. Due to the large stress of the direct-connected pins with a wide width, it is not easy to cut off during the cutting process, which brings difficulties to the forming of the cutting ribs, and there is a risk of dark cracking of the plastic package; and the width is too narrow, which affects the package body after plastic sealing. The ability to dissipate heat out through the pins. In the present invention, by dividing the direct-connected lead into a plurality of first leads 113 with narrower widths (less than a second predetermined width), the stress of the rib forming of the first leads 113 is reduced. , and the total width of the plurality of first pins 113 is relatively wide, which improves the performance of the plastic-encapsulated package body to dissipate heat outward through the pins, and can solve the problem of difficulty in cutting ribs on the premise of ensuring that the heat dissipation performance is basically unchanged. The problem of molding is also avoided, and the risk of cracking of the plastic body is avoided. Further, in the present invention, the direct connection pins directly connected to the first base island body 110 on the two adjacent sides of the multi-base island lead frame 10 are divided into a plurality of the first pins 113 ; or the direct-connected pins on one side are divided into a plurality of the first pins 113, and the direct-connected pins on the other side are not divided.

In a further embodiment, at least one rough surface area 119 is provided on the first bearing surface 111 outside the area for bearing the first power device 21 . The rough surface area 119 can be realized by adopting a half-etching process in the corresponding area on the first bearing surface 111. Through the half-etching process, the surface roughness of the rough surface area 119 is increased, and its function is to enhance the multi-base surface roughness. The bonding force between the island lead frame 10 and the plastic encapsulation body of the subsequent encapsulation process. Compared with the existing package body, the product corresponding to the present invention has smaller package volume, weaker package strength, and the product is easy to be delaminated. The bonding force between the base island lead frame 10 and the plastic packaging body avoids product delamination and improves product reliability. In this embodiment, the first bearing surface 111 is provided with two rough surface areas 119 , which are respectively located at the included angle between two adjacent edges of the frame body and close to the third base island 13 . side, which further improves the bonding force between the multi-base island lead frame 10 and the plastic package. In other embodiments, the roughened surface area 119 may be provided only at the included angle between two adjacent edges of the frame body, or only at the side close to the third base island 13 . The present invention does not limit the shape, quantity and setting position of the rough surface area 119 , the shape can be designed according to the setting position, and the quantity can be adjusted as required.

In a further embodiment, at least one wire bonding area 118 is provided on the first carrying surface 111 outside the area for carrying the first power device 21 for passing through the metal leads 25 (marked in FIG. 2A ) The electrical connection between the first base island 11 and the chips or devices carried on other base islands is realized. For example, in this embodiment, the first carrying surface 111 is provided with two of the wire bonding areas 118 , one of which uses the metal lead 25 and the second power device 23 disposed on the third base island 13 . (marked in FIG. 2A ) is connected, and the other is connected with the main control chip 22 (marked in FIG. 2A ) disposed on the second base island 12 by using metal leads 25 . The wire bonding area 118 may be implemented by silver plating or tin plating or other processes on the corresponding area on the first bearing surface 111 .

In this embodiment, the second base island 12 has a second carrying surface 121 for carrying the main control chip 22 for controlling the first power device 21 , and a second carrying surface 121 opposite to the second carrying surface 121 . The second heat dissipation surface 122 (shown in FIG. 2B ) has a plurality of second base islands 12 disposed on two adjacent sides of the multi-base island lead frame 10 and separated from the second base island body 120 The second pin 123 . Wherein, after the multi-base-island lead frame 10 is applied to the QFN package to be molded by the molded body, the second heat dissipation surface 122 is partially or completely exposed to the molded body, and the ends of all the second pins 123 and A portion of the bottom surface coplanar with the second heat dissipation surface 122 is exposed to the molding body. By encapsulating the base island to maximize external leakage, the external leakage heat dissipation surface can be fully contacted with the PCB in the follow-up to achieve the purpose of high heat dissipation. In this embodiment, ten second pins 123 are schematically shown, which may include a spare pin (which may be used to connect the thermistor). In other embodiments, the number of the first pins 113 is not limited, and the arrangement position may only be located on one side of the multi-base island lead frame 10, as long as the purpose of the present invention is satisfied. The main control chip 22 is an integrated circuit chip (IC) for controlling the first power device 21 .

In a further embodiment, the second pin 123 is provided with a wire bonding area 1231 for realizing the second pin 123 and the main control chip 22 carried on the second bearing surface 121 through the metal lead 25 . , or the electrical connection with the first power device 21 carried on the first carrying surface 111 . Wherein, in subsequent use, the working voltage of the second pin 123 is different from the working voltage of the first pin 113, and the two base islands are electrically isolated to avoid the large difference between the pins due to the high and low voltage. The resulting breakdown occurs between each other, thereby meeting the requirements of packaging or reliability. The second pin 123 is not directly connected to the second base island body 120, and is provided with a wire bonding area. After silver plating or tin plating, it can be connected with the main body disposed on the second base island 12. The control chip 22 or the first power device 21 disposed on the first base island 11 is connected with metal leads 25, and is electrically connected to the outside as a functional pin of the subsequently formed QFN package structure 20. For example, in this embodiment, five second pins 123 are connected to the main control chip 22 disposed on the second base island 12 by using metal leads 25 , and the other three second pins 123 are connected to the main control chip 22 provided on the second base island 12 by using metal leads 25 . The first power device 21 disposed on the first base island 11 is connected. There is at least a predetermined safety distance between the second pin 123 and the first pin 113 on the same side, so as to reduce the risk of breakdown caused by the difference in operating voltage between the two pins.

In a further embodiment, the second base island 12 further has at least one support structure 124 for supporting the second base island 12 when the multi-base island lead frame 10 is applied to the QFN package for plastic packaging. Specifically, the support structure 124 is directly connected to the second base island body 120 and extends to two adjacent sides of the multi-base island lead frame 10 . For example, a frame structure close to a second lead 123 of the fourth base island 14 is directly connected to the second base island body 120 to form a support structure; a second lead close to the first base island 11 The frame structure on the side of the feet 123 is also directly connected with the second base island body 120 to form a support structure. Preferably, in addition to the supporting structures extending from the second pins 123 on both sides, at least one frame structure on the side of the second pin 123 may also be directly connected to the second base island body 120 to form a supporting structure (eg The part enclosed by the dashed circle in the figure).

In this embodiment, the third base island 13 has the same structure as the first base island 11 and is symmetrically disposed on the multi-base island lead frame 10 .

Specifically, the third base island 13 has a third carrying surface 131 for carrying the second power device 23 , and a third heat dissipation surface 132 (marked in FIG. 2B ) opposite to the third carrying surface 131 ), the third base island 13 has a plurality of third pins 133 disposed on two adjacent sides of the multi-base island lead frame 10 and directly connected to the third base island body 130 . Wherein, after the multi-base-island lead frame 10 is applied to the QFN package and is molded by the molded body, the third heat dissipation surface 132 is partially or completely exposed to the molded body, and the ends of all the third pins 133 and A portion of the bottom surface coplanar with the third heat dissipation surface 132 is exposed to the molding body. By encapsulating the base island to maximize external leakage, the external leakage heat dissipation surface can be fully contacted with the PCB in the follow-up to achieve the purpose of high heat dissipation. In this embodiment, nine third pins 133 are schematically drawn. In other embodiments, the number of the third pins 133 is not limited, and the setting positions may only be located in the multi-base island lead frame On one side of 10, as long as the purpose of the present invention is satisfied. The second power device 23 includes, but is not limited to, a triode, a MOS transistor, a thyristor, a combination of an insulated gate bipolar transistor (IGBT) and a fast recovery diode (FRD).

Specifically, each of the third pins 133 is directly connected to the third base island body 130 , which is used as a main heat dissipation pin and a functional pin of the third base island 13 to be electrically connected to the outside world. Since the third pin 133 is directly connected to the third base island body 130 , it can be used as a low-voltage pin (for example, a grounding function) or a high-voltage pin in subsequent use. Wherein, in subsequent use, the working voltage of the third pin 133 is different from the working voltage of the first pin 113; for example, the first pin 113 may be a low voltage (voltage less than or equal to a predetermined Set a voltage, such as 0V) pin, the corresponding third pin 133 is a high-voltage (voltage greater than or equal to a preset voltage, such as 500V) pin; or the first pin 113 can be a high-voltage pin, the corresponding The third pin 133 is a low voltage pin. In this exemplary embodiment, since the two power chips on the first base island 11 and the third base island 13 work alternately in the high and low voltage states, therefore, between the first base island 11 and the third base island 13 A preset safe distance needs to be maintained to prevent breakdown from occurring when the power devices on the first base island 11 and the third base island 13 work alternately under high and low voltage states. All the third pins 133 also play a role of supporting the third base island 13 when the multi-base island lead frame 10 is applied to the QFN package for plastic packaging. For the setting method and function of the third pin 133, reference may be made to the description of the first pin 113, which will not be repeated here.

Correspondingly, at least one rough surface area 139 and at least one wire bonding area 138 are also provided on the third carrying surface 131 outside the area used to carry the second power device 23 , please refer to the first base The records corresponding to the island 11 will not be repeated here.

In this embodiment, the fourth base island 14 has a fourth carrying surface 141 for carrying the discrete devices 24 (marked in FIG. 2A ), and a fourth heat dissipation surface opposite to the fourth carrying surface 141 On the surface 142 (marked in FIG. 2B ), the fourth base island 14 has a plurality of fourth pins 143 disposed on two adjacent sides of the multi-base island lead frame 10 . The fourth pin 143 can be directly connected to the fourth base island body 140 , or be separated from the fourth base island body 140 , and electrically connected to pins, chips or devices on other base islands through the metal leads 25 . connect. In some embodiments, if the discrete device is a power-type device, such as a diode, which has high requirements for heat dissipation, it is recommended that the fourth pin 143 be directly connected to the fourth base island body 140 to improve the heat dissipation of the fourth base island 14 efficiency. Wherein, after the multi-base-island lead frame 10 is applied to the QFN package and is molded by the molded body, part or all of the fourth heat dissipation surface 142 is exposed to the molded body, and the ends of all the fourth pins 143 and A portion of the bottom surface coplanar with the fourth heat dissipation surface 142 is exposed to the molding body. By encapsulating the base island to maximize external leakage, the external leakage heat dissipation surface can be fully contacted with the PCB in the follow-up to achieve the purpose of high heat dissipation. The fourth bearing surface 141 is further provided with a wire bonding area 148 . For the arrangement and function of the wire bonding area 148 , reference may be made to the description corresponding to the wire bonding area 118 on the first base island 11 , which will not be repeated here. The discrete device 24 may be a diode chip, such as a freewheeling diode.

In this embodiment, the area of the first base island 11 is larger than the areas of the second base island 12 and the fourth base island 14 , so as to facilitate placement of power devices. If the package structure needs to package two power devices at the same time, a third base island 13 that is symmetrical with the first base island 11 may also be provided. The first base island 11 and the third base island 13 are disposed on the same side of the multi-base lead frame 10 , and the second base island 12 and the fourth base island 14 are disposed on the multi-base lead frame 10 . On the same side of the island lead frame 10 , a multi-chip/device integrated plane package is realized, the integration degree is improved, and the package volume is reduced. In other embodiments, a four-base island design or a three-base island design with different sizes and different base island positions from the present embodiment may be derived.

In this embodiment, the power devices on the first base island 11 and the third base island 13 work alternately in high and low voltage states. In order to prevent high voltage breakdown, the base islands are electrically isolated, and the base islands are A safety isolation distance is set between the base island and the base island, as shown in the figure, the safety isolation distance a between the first base island 11 and the second base island 12, the first base island 11 and the third base island 12 The safety isolation distance b between the base islands 13 , the safety isolation distance c between the second base island 12 and the fourth base island 14 , and the third base island 13 and the fourth base island 14 The safety isolation distance d between them; when the pins on the third base island 13 are used as high-voltage output pins, the values of b and d are greater than the values of a and c. The safety isolation distance needs to consider both the fluidity of the molding compound during packaging and the safety of high voltage between the base islands.

The invention realizes the multi-chip/device integrated plane package, improves the integration degree, and reduces the volume of the package body; by encapsulating the base island to maximize the external leakage, the external leakage heat dissipation surface can be fully contacted with the PCB in the follow-up, so as to achieve the purpose of high heat dissipation; The base islands are electrically isolated, and a safety isolation distance is set between the base islands, which can effectively prevent high-voltage breakdown, thereby meeting the requirements of packaging or reliability. In addition, the base island where the power device is placed can be provided with a number of pins directly connected to the base island to improve heat dissipation.

Based on the same inventive concept, the present invention also provides a QFN package structure of a power conversion module, which adopts the above-mentioned multi-base island lead frame 10 of the present invention.

Please refer to FIGS. 2A-2C together, wherein FIG. 2A is a schematic diagram of a wire bonding structure of the first embodiment of the QFN package structure of the power conversion module of the present invention, FIG. 2B is a bottom view of the QFN package structure shown in FIG. 2A , and FIG. 2C It is a side view of the QFN package structure shown in FIG. 2A . Among them, in order to clearly describe the structure of the QFN package structure 20 of the present invention, in FIG. 2A , the structure of the multi-base island lead frame inside the plastic package is shown.

QFN (Quad Flat No-lead Package) is a leadless package, which is square or rectangular, and has the advantages of small package size, low cost, high heat dissipation, high integration, and good compatibility. It makes up for the shortcomings of traditional DIP/SOPIPM modules such as large size, high cost, poor compatibility, and poor heat dissipation. The mounting area of the QFN package structure is smaller than that of the QFP, and the height is lower than that of the QFP. Due to the short conductive path between the internal pins and the pads of the QFN package structure, the self-inductance coefficient and the internal wiring resistance are very low, so it can provide excellent electrical performance. In addition, it provides excellent thermal dissipation through exposed leadframe pads (thermal planes) with direct thermal paths for dissipating heat within the package. Thermal pads are usually soldered directly on the board, and thermal vias in the PCB help to spread excess power dissipation into the copper ground plane, which absorbs excess heat. The QFN package structure 20 of the present invention adopts an ultra-thin low-cost design. The area (S=9mm*9mm) of the single QFN package structure 20 of the 4-base island frame structure is only 23% of the area of the traditional DIP23/SOP23, and the packaging cost is only the traditional DIP23/ 60% of SOP23.

In this embodiment, the power conversion module is a half-bridge rectifier or inverter power conversion module. The QFN package structure 20 includes a multi-base island lead frame 10, a first power device 21, a main control chip 22, a second power device 23, a diode chip 24 and a plastic package (not shown in the drawings). ). The structure, function and effect of the multi-base island lead frame 10 are the same as those of the above-mentioned multi-base island lead frame 10 , which will not be repeated here. Wherein, part or all of the corresponding heat dissipation surface is exposed to the plastic packaging body, and the ends of all the pins and the bottom surface part coplanar with the corresponding heat dissipation surface are exposed to the plastic packaging body. By encapsulating the base island to maximize external leakage, the external leakage heat dissipation surface can be fully contacted with the PCB in the follow-up to achieve the purpose of high heat dissipation. In other embodiments, the power conversion module may also be a DC-DC power conversion module, and the QFN package structure 20 includes a multi-base island lead frame 10 , a first power device 21 , a control device for the first power The device 21 has a main control chip 22 , a diode chip 24 and a plastic package. Correspondingly, the multi-base island lead frame 10 includes the first base island 11 , the second base island 12 and the fourth base island 14 .

In this embodiment, the first power device 21 is pasted on the first bearing surface 111 by an adhesive such as conductive glue, and is directly connected to the first pin 113 , and is connected to multiple Some of the second pins 123 are electrically connected to the second power device 23 . The first power device 21 is a MOS transistor. The main control chip 22 is pasted on the second carrying surface 121 by adhesives such as conductive glue, and the main control chip 22 is connected to some of the plurality of second pins 123 through metal leads 25 respectively. , the first power device 21 , the second power device 23 and the diode chip 24 are electrically connected. The main control chip 22 is an integrated circuit chip (IC) for controlling other devices, such as controlling the first power device 21 , the second power device 23 and the diode chip 24 . The second power device 23 is pasted on the third bearing surface 131 with an adhesive such as conductive glue, and is directly connected to the third pin 133, and is connected to the fourth pin 143 through the metal lead 25 at the same time. Electrical connection. The second power device 23 is a MOS transistor. The diode chip 24 is pasted on the fourth bearing surface 141 by using an adhesive such as conductive glue, and is directly connected to the fourth pins 143 , and is connected to a plurality of the second pins 123 through the metal leads 25 at the same time. One of the pins is electrically connected; the fourth bearing surface 141 is also provided with a wire bonding area, which is electrically connected to the main control chip 22 through the metal leads 25 .

In a state of subsequent use, the working voltage of the first pin 113 is lower than the working voltage of the second pin 123 , and the working voltage of the second pin 123 is lower than that of the third pin 133 working voltage. The working voltage range of the fourth pin 143 is basically the same as that of the second pin 123 . That is, the first pin 113 is used as a low voltage (voltage less than or equal to a preset voltage, such as 0V) pin, and the second pin 123 is connected to a working voltage or a high/low voltage input signal (usually several tens of volts) , the corresponding third pin 133 is a high-voltage (voltage greater than or equal to a predetermined voltage, such as 500V) pin. The low-voltage pins and the high-voltage pins are arranged on both sides of the base island respectively, and are electrically isolated to avoid the breakdown between the pins due to the large difference between the high and low voltages, so as to meet the packaging or reliability requirements. requirements.

In this embodiment, in order to meet the requirements of high heat dissipation and prevent high-voltage breakdown at the same time, in addition to setting a safety isolation distance between the base island and the base island inside the package structure, the outer leakage and heat dissipation surfaces of the package, pins and pins Safety spacing design is carried out between the separated pins and the heat dissipation surface. As shown in FIG. 2B , there is a preset isolation distance k1 between the first heat dissipation surface 112 and the second heat dissipation surface 122 , and preset isolation distances k and k2 between the second pins 123 on different sides and the second heat dissipation surface 122 , there is a preset isolation distance k3 between the third pin 133 serving as the high voltage pin and the second heat dissipation surface 122 , and a preset isolation distance k4 between the first heat dissipation surface 112 and the third heat dissipation surface 132 . Because the voltage difference between the high-voltage pin and the heat dissipation surface where the control chip is located is large, which can generally reach several hundred volts, the value of k3 can be set to the maximum.

The QFN packaging structure of the present invention realizes multi-chip/device integrated plane packaging, improves the integration degree, reduces the volume of the package body, and reduces the packaging cost; by encapsulating the base island to maximize the external leakage, the external leakage heat dissipation surface can be used in the follow-up with The PCB is fully contacted to achieve the purpose of high heat dissipation; the base islands inside the package structure are electrically isolated, and a safety isolation distance is set between the base islands and the base islands, and the package structure leaks between the heat dissipation surfaces and between the pins and the pins. , A safe spacing is designed between the separated pins and the heat dissipation surface, which can effectively prevent high-voltage breakdown, thereby meeting the requirements of packaging or reliability.

Please refer to FIG. 3 , which is a schematic diagram of the wire bonding structure of the second embodiment of the QFN package structure of the power conversion module of the present invention. The difference from the embodiment shown in FIG. 2A is that in this embodiment, the first power device 21 includes a first insulated gate bipolar transistor (IGBT) 311 electrically connected by a metal wire 25 and a first Fast recovery diode (FRD) 312 ; the second power device 23 includes a second insulated gate bipolar transistor (IGBT) 331 and a second fast recovery diode (FRD) 332 electrically connected by metal leads 25 . For other structures and functions of the QFN package structure, reference may be made to the above-mentioned QFN package structure, which will not be repeated here.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications can also be made, and these improvements and modifications should also be regarded as It is the protection scope of the present invention.

Claims (16)

1. A multi-base island lead frame applied to a QFN package of a power conversion module is characterized in that, at least comprising: a first base island and a second base island electrically isolated from each other; The first base island has a first carrying surface for carrying power devices, and a first heat dissipation surface opposite to the first carrying surface, and the first base island has leads disposed on the multi-base island a plurality of first pins directly connected to the first base island body on at least one side of the frame; The second base island has a second carrying surface for carrying the main control chip for controlling the power device, and a second heat dissipation surface opposite to the second carrying surface, and the second base island has a set of a plurality of second pins on two adjacent sides of the multi-base island lead frame and separated from the second base island body; Wherein, after the multi-base island lead frame is applied to the QFN package and is plastic-sealed by the plastic-sealed body, a part or all of the corresponding heat dissipation surface is exposed to the plastic-sealed body, and the ends of all the pins and the bottom surface coplanar with the corresponding heat-dissipating surface Parts are exposed to the molding. 2 . The multi-base island lead frame of claim 1 , wherein the second base island further has at least one support structure to support the second base island. 3 . 3 . The multi-base island lead frame of claim 2 , wherein the support structure is directly connected to the second base island body and extends to two adjacent sides of the multi-base island lead frame. 4 . 4 . The multi-base island lead frame of claim 1 , wherein the area of the first base island is larger than that of the second base island. 5 . 5 . The multi-base island lead frame according to claim 1 , wherein at least one rough surface area is provided on the first carrying surface outside the area used for carrying power devices. 6 . 6 . The multi-base island lead frame according to claim 1 , wherein at least one wire-bonding area is provided outside the area on the first carrying surface for carrying power devices, for realizing all the The electrical connection between the first base island and the chips or devices carried on other base islands. 7 . The multi-base island lead frame according to claim 1 , wherein a wire bonding area is provided on the second pin for realizing the second pin and the second load through metal leads. 8 . The electrical connection of the main control chip carried on the surface, and/or the electrical connection with the power device carried on the first carrying surface. 8 . The multi-base island lead frame according to claim 1 , wherein the multi-base island lead frame further comprises a third base island, and the third base island has the same structure as the first base island and Symmetrically arranged on the multi-base island lead frame. 9 . The multi-base island lead frame of claim 1 , wherein the multi-base island lead frame further comprises a fourth base island having a fourth base island for carrying discrete devices. 10 . A carrying surface, and a fourth heat dissipation surface opposite to the fourth carrying surface, the fourth base island has a plurality of fourth pins disposed on two adjacent sides of the multi-base island lead frame. 10. The multi-base island lead frame of claim 9, wherein the discrete device is a diode chip. 11. A QFN package structure of a power conversion module, characterized in that, comprising: A multi-base island lead frame, the multi-base island lead frame at least includes a first base island and a second base island that are electrically isolated from each other; the first base island has a first bearing surface, and is connected to the A first heat dissipation surface opposite to the first bearing surface, the first base island has a plurality of first pins disposed on at least one side of the multi-base island lead frame and directly connected to the first base island body ; The second base island has a second bearing surface and a second heat dissipation surface opposite to the second bearing surface, the second base island has two adjacent sides arranged on the multi-base island lead frame , and a plurality of second pins separated from the second base island body; a first power device, disposed on the first bearing surface, and directly connected with the first pin; a main control chip for controlling the first power device, disposed on the second bearing surface, and the main control chip is electrically connected to the second pin and the first power device respectively through metal leads; as well as a plastic encapsulating body, plastic encapsulating the multi-base island lead frame carrying the first power device and the main control chip; Wherein, part or all of the corresponding heat dissipation surface is exposed to the plastic packaging body, and the ends of all the pins and the bottom surface part coplanar with the corresponding heat dissipation surface are exposed to the plastic packaging body; The working voltage of the first pin is different from the working voltage of the second pin. 12. The QFN package structure according to claim 11, wherein there is a first preset isolation distance between any two adjacent heat dissipation surfaces, and/or the second lead and the second heat dissipation surface There is a second preset isolation distance therebetween. 13 . The QFN package structure according to claim 11 , wherein the first power device is a power MOS transistor, or comprises an insulated gate bipolar transistor and a fast recovery diode that are electrically connected. 14 . 14 . The QFN package structure according to claim 11 , wherein the power conversion module is a half-bridge rectifier or inverter power conversion module, the multi-base island lead frame further comprises a third base island, the The third base island has the same structure as the first base island and is symmetrically arranged on the multi-base island lead frame; The QFN package structure further includes a second power device, the second power device is disposed on the third bearing surface of the third base island, and is directly connected to the third pin of the third base island; The working voltage of the first pin is lower than the working voltage of the second pin, and the working voltage of the second pin is lower than the working voltage of the third pin. 15 . The QFN package structure according to claim 14 , wherein the multi-base island lead frame further comprises a fourth base island, the fourth base island has a fourth bearing surface, and is connected with the fourth base island. 16 . A fourth heat dissipation surface opposite to the four bearing surfaces, the fourth base island has a plurality of fourth pins disposed on two adjacent sides of the multi-base island lead frame; The QFN package structure further includes a diode chip, and the diode chip is disposed on the fourth carrying surface and directly connected to the fourth pin. 16 . The QFN package structure according to claim 11 , wherein the power conversion module is a DC-DC power conversion module, and the multi-base island lead frame further comprises a fourth base island, the fourth base island. The island has a fourth carrying surface and a fourth heat dissipation surface opposite to the fourth carrying surface, and the fourth base island has a plurality of fourth leads disposed on two adjacent sides of the multi-base island lead frame. foot; In the QFN package structure, the power conversion module further includes a diode chip, and the diode chip is disposed on the fourth bearing surface and directly connected to the fourth pin.