Lead frame and power device
By placing a resist on the back of the lead frame substrate, the overflow of molding compound is prevented, thus solving the problem of material overflow during the molding process of power devices and ensuring high product reliability and appearance quality.
Patent Information
- Application Number
- CN202423293424.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-30
- Publication Date
- 2025-12-26
- Estimated Expiration
- 2034-12-30
AI Technical Summary
During the molding process of power devices, overflow often occurs, affecting the solderability and appearance of the product and leading to reliability issues.
A resist is placed on the back of the substrate of the lead frame to prevent the molding compound from overflowing and to prevent the material from spilling onto the side of the semiconductor device. By placing the resist on the back of the substrate, a sealed area is formed to prevent the molding compound from overflowing.
It effectively prevents molding compound from overflowing, ensuring the appearance of semiconductor devices and product reliability, and meeting high reliability requirements.
Smart Images
Figure CN223728777U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The embodiment of the present application relates to the technical field of semiconductor technology, in particular to a lead frame and a power device. BACKGROUND
[0002] The lead frame is a thin metal frame that plays a key role in semiconductor packaging, usually made of alloys such as copper, nickel and iron. It is mainly composed of two parts: chip pads and pins. The chip pad is the area where the chip is directly placed and fixed, with a large area to provide support and good heat dissipation performance for the chip; the pin is an elongated metal part extending from the chip pad, used to connect with external circuit boards or other electronic components to realize the transmission of electrical signals.
[0003] The power device is a key component in electronic devices for power conversion and circuit control, which can handle high voltage and large current. Common power devices include diodes, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), IGBTs (Insulated Gate Bipolar Transistors), etc. To manufacture a power device, in addition to the chip, it is essential to have a lead frame, adhesive, bonding material, packaging material and other materials, and it needs to go through multiple fine processes to complete. Among them, the core role of the lead frame is to provide a stable carrier support for the chip, and has welding pins to realize reliable connection of the circuit.
[0004] During the molding process of the power device, overflow is a common defect. It has no effect on the performance of the product itself, but if the overflowed plastic encapsulation covers the exposed carrier, it will affect the solderability and appearance, and if there is still residue after the flash removal process, it will form a plating defect and affect the product reliability, causing problems such as open circuit or false welding. CONTENT OF THE INVENTION
[0005] The purpose of the embodiment of the present application is to provide a lead frame and a power device to prevent the occurrence of overflow during the molding process of the power device, and to meet the high reliability requirements of the power device product.
[0006] To solve the above technical problems, the embodiment of the present application provides a lead frame, which includes a substrate, a glue-blocking body and a pin end. The substrate includes a front surface provided with a carrier platform and a back surface opposite to the front surface; the glue-blocking body is arranged on the back surface to prevent overflow of the plastic encapsulation during molding of the lead frame; and the pin end is arranged on the side surface of the substrate.
[0007] The embodiment of the present application also provides a power device, which includes the above-mentioned lead frame, and further includes a chip and a pin. The chip is arranged on the carrier platform and electrically connected to the pin end; and the pin is connected to the pin end to conduct the electrical signal of the chip to an external device.
[0008] The lead frame and power device provided by the embodiments of the present application prevent overflow of plastic sealing material by arranging a glue blocking body on the back surface of the lead frame substrate to prevent overflow of plastic sealing material to the side surface of the semiconductor device during the plastic sealing process of the power device, thereby ensuring the appearance of the semiconductor device product and meeting the high reliability requirement of the power device product.
[0009] In some embodiments, the glue blocking body comprises a first glue blocking body arranged around the edge of the back surface.
[0010] In some embodiments, the lead frame further comprises a through hole arranged on the substrate away from the side of the pin end and penetrating the front surface and the back surface.
[0011] In some embodiments, the glue blocking body further comprises a second glue blocking body arranged around the through hole.
[0012] In some embodiments, the glue blocking body has an integrated structure with the substrate.
[0013] In some embodiments, the height of the glue blocking body protruding from the back surface is between 10 um and 20 um, and the width of the glue blocking body is between 50 um and 150 um.
[0014] In some embodiments, the lead frame further comprises an overflow prevention groove arranged around the carrier platform to prevent overflow of the front surface after the solder is melted.
[0015] In some embodiments, the power device further comprises a plastic sealing body covering the entire chip, part of the lead frame and part of the pin. BRIEF DESCRIPTION OF DRAWINGS
[0016] One or more embodiments are illustrated by way of example in the figures that form a part of this patent document, these example are not intended to limit the embodiments, elements having the same reference numbers in the figures indicate like elements, unless otherwise expressly stated, the figures in the drawings do not constitute a proportional limitation.
[0017] Figure 1 is a schematic diagram of the front surface structure of the lead frame provided by some embodiments of the present application;
[0018] Figure 2 is a schematic diagram of the side surface structure of the lead frame provided by some embodiments of the present application;
[0019] Figure 3 is a schematic diagram of the back surface structure of the lead frame provided by some embodiments of the present application;
[0020] Figure 4 is a schematic diagram of the front surface structure of the power device provided by some embodiments of the present application;
[0021] Figure 5Fig. 1 is a schematic diagram of a back structure of a power device provided by some embodiments of the present application.
[0022] Reference signs: 11-substrate; 111-substrate table; 112-front surface; 113-back surface; 12-adhesive; 121-first adhesive; 122-second adhesive; 13-pin end; 14-via hole; 15-overflow prevention groove; 16-pin; 17-plastic package; 18-radiator. DETAILED DESCRIPTION
[0023] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the embodiments of the present application will be described in detail below with reference to the drawings. However, those skilled in the art can understand that, in the embodiments of the present application, many technical details are presented in order to make the readers better understand the present application. However, the technical solutions claimed by the present application can be implemented even without these technical details and based on various changes and modifications of the following embodiments. The division of the following embodiments is for the convenience of description, and should not constitute any limitation on the specific embodiments of the present application, and the embodiments can be combined and referenced with each other without contradiction.
[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application; the description and the claims of this application and the above description of drawings, the terms "comprising" and "having" and any variations thereof, are intended to cover not exclusively containing.
[0025] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited.
[0026] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the technical terms "mounting", "connecting", "connecting" and other terms should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.
[0027] Lead frame is a thin metal frame that plays a key role in semiconductor packaging, usually made of alloys such as copper, nickel and iron. It is mainly composed of two parts: chip pads and pins. Chip pads are areas where chips are directly placed and fixed, with a larger area to provide support and good heat dissipation performance for chips. Pins are slender metal parts extending from the chip pads, used to connect with external circuit boards or other electronic components to transmit electrical signals.
[0028] Power devices are key components in electronic devices for power conversion and circuit control, which can handle high voltage and large current. Common power devices include diodes, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), IGBTs (Insulated Gate Bipolar Transistors), etc. To manufacture a power device, in addition to the chip, lead frame, adhesive, bonding, packaging material and other materials are essential, and multiple fine processes are required to complete. Among them, the core role of the lead frame is to provide a stable carrier support for the chip, and has welding pins to achieve reliable connection of the circuit.
[0029] During the molding process of power devices, overflow is a common defect. It has no effect on the performance of the product itself. If the overflowed plastic encapsulation covers the exposed carrier, it will affect the solderability and appearance. If there is still residue after the flash removal process, it will form a plating defect and affect the product reliability, causing problems such as open circuit or false welding.
[0030] To prevent the occurrence of overflow during the molding process of power devices and meet the high reliability requirements of power device products, the embodiments of the present application provide a lead frame, which includes a substrate, a glue blocking body and a pin end. The substrate includes a front surface provided with a carrier platform and a back surface opposite to the front surface; the glue blocking body is arranged on the back surface to prevent overflow of the plastic encapsulation during molding of the lead frame; and the pin end is arranged on one side of the substrate.
[0031] The embodiments of the present application also provide a power device including the above-mentioned lead frame. The power device further includes a chip and a pin, the chip is arranged on the carrier platform and electrically connected to the pin end; and the pin is connected to the pin end to conduct the electrical signal of the chip to an external device.
[0032] The lead frame and power device provided by the embodiments of the present application prevent overflow of the plastic encapsulation by arranging a glue blocking body on the back surface of the lead frame substrate during the molding process of the power device. The glue blocking body prevents the overflow of the plastic encapsulation to the side surface of the semiconductor device, ensuring the appearance of the semiconductor device product and meeting the high reliability requirements of the power device product.
[0033] The following will be described in conjunction with Figure 1 , Figure 2 , Figure 3 ,Figure 4 and Figure 5 The lead frame provided by some embodiments of the present application is illustrated.
[0034] As shown in Figure 1 , the lead frame provided by some embodiments of the present application includes a substrate 11, a glue blocking body 12, and a pin end 13. The substrate 11 includes a front surface 112 provided with a carrier table 111 and a back surface 113 opposite to the front surface 112; the glue blocking body 12 is arranged on the back surface 113 and used to prevent overflow of plastic encapsulation material when the lead frame is encapsulated; and the pin end 13 is arranged on a side surface of the substrate 11.
[0035] It should be noted that the substrate 11 is a functional plate with insulation and heat dissipation functions, and can be single-layer, double-layer or triple-layer. The triple-layer structure can separate the functions of mounting, insulation and heat dissipation, each layer has different functions, and ensures the stable functions of the power device frame. The main body of the substrate 1111 can be copper material, which has good heat conduction function. As shown in Figure 1 , the front surface 112 of the substrate 1111 is a functional area, and a large area close to the lower side is the carrier table 111, on which a suitable chip can be mounted and fixed, and the chip is provided with mechanical support during the encapsulation process. The glue blocking body 12 can be of the same material as the substrate 11, and is a region punched out by a special mold during production of the frame, has a certain height and width, and can intercept the flow direction of the plastic encapsulation material. The glue blocking body 12 arranged on the back surface 113 forms a closed area with the encapsulation mold, so that the plastic encapsulation material is blocked outside and does not overflow to the back surface 113.
[0036] Some embodiments of the present application also provide a power device including the above-mentioned lead frame, and the power device further includes a chip (not shown in the figure) and a pin 16. The chip is arranged on the carrier table 111 and electrically connected to the pin end 13; and the pin 16 is connected to the pin end 13 to conduct the electrical signal of the chip to an external device.
[0037] It should be noted that the chip can be fixed on the carrier table 111 by solder, sintering material or conductive glue. The chip and the pin end 13 can be connected by a bonding wire or a metal sheet and the like to transmit the electrical signal of the chip.
[0038] The lead frame and the power device provided by the embodiments of the present application prevent overflow of the plastic encapsulation material by arranging the glue blocking body 12 on the back surface 113 of the substrate 11 of the lead frame, which hinders the overflow of the plastic encapsulation material to the side surface of the semiconductor device during the encapsulation process of the power device, ensures the appearance of the semiconductor device product, and meets the high reliability requirement of the power device product.
[0039] In some embodiments of the present application, the glue barrier 12 comprises a first glue barrier 121, which is arranged around the edge of the back surface 113.
[0040] It should be noted that, as shown in Figure 3 the pin end 13 is located below the substrate 11, the first glue barrier 121 is located above the pin end 13, the first glue barrier 121 is arranged around the back surface 113, the shape of the first glue barrier 121 is consistent with the contour shape of the back surface 113, and the size of the first glue barrier 121 is slightly smaller than the substrate 11. During the plastic packaging, the semiconductor device containing the lead frame is placed in the plastic packaging mold, the back surface 113 is attached to the lower mold, and the sealing structure formed by the first glue barrier 121 and the mold prevents the plastic packaging material from overflowing to the back surface 113.
[0041] In addition, the lead frame is in the shape of a whole strip, and after being installed in the plastic packaging mold, the plastic packaging material will flow according to the designed flow channel after being melted due to the generation of plastic packaging pressure, Figure 3 The plastic package 17 has the most common TO247 shape, and the power device is packaged from top to bottom during plastic packaging, until the entire mold is completely filled, and leakage of the plastic package 17 is prone to occur at the bottom. Therefore, the first glue barrier 121 can also be designed in a U shape near the pin end 13. In fact, the shape of the glue barrier 12 is determined according to the shape of the plastic package 17 and the flow channel of the mold during plastic packaging.
[0042] In some embodiments of the present application, the lead frame further comprises a through hole 14, which is arranged on the side of the substrate 11 away from the pin end 13 and penetrates the front surface 112 and the back surface 113.
[0043] It should be noted that the through hole 14 can be used as a mounting hole for the mounting screw of the power device product, and can be mounted and fixed to different equipment. On the other hand, the heat sink 18 or other heat dissipation devices can be connected through the through hole 14 on the back.
[0044] In some embodiments of the present application, the glue barrier 12 further comprises a second glue barrier 122, which is arranged around the through hole 14.
[0045] It should be noted that the second glue barrier is arranged around the through hole 14 to prevent the plastic packaging material at the through hole 14 from overflowing to the back surface 113 of the welding area of the chip, causing overflow.
[0046] In some embodiments of the present application, the glue barrier 12 and the substrate 11 have an integrated structure.
[0047] It should be noted that the blocking glue 12 and the substrate 11 can be punched out by a special mold in the process of making the lead frame. After the plastic packaging, this area is not plastic packaged. It is usually covered by the electroplated layer outside the frame heat sink 18. After the plastic packaging, the blocking glue 12 will be retained and will become part of the back 113 of the frame. The ideal state of a single long strip-shaped blocking glue 12 is a cuboid. Due to the current process capability of the frame manufacturing and the material properties of copper, the angle actually punched out should be an ellipsoid, not an absolute right angle.
[0048] In some embodiments of the present application, the height of the blocking glue 12 protruding from the back 113 is between 10um and 20um; and the width of the blocking glue 12 is between 50um and 150um.
[0049] It should be noted that the height and width of the blocking glue 12 only need to form a certain space in the inner wall of the mold to prevent the plastic packaging material from leaking. The specific width and height mainly depend on the capability of the frame manufacturer and the capability of the frame mold. The width and height are generally not particularly limited, and the ideal state is as thin as possible. The plastic packaging mold setting, plastic packaging parameter setting, and plastic packaging material properties, such as the resin type of the plastic packaging material, the particle size of the plastic packaging material, and the particle type of the plastic packaging material, are comprehensively considered.
[0050] In some embodiments of the present application, the lead frame further comprises an anti-overflow groove 15 arranged around the carrier table 111 to prevent the solder on the front 112 from overflowing after melting.
[0051] It should be noted that the anti-overflow groove 15 is a few groove-shaped structures on the front 112 to prevent too much solder on the front 112 from overflowing to the side or the back 113 after melting.
[0052] In some embodiments of the present application, the power device further comprises a plastic packaging body 17 covering the entire chip, part of the lead frame, and part of the pin 16.
[0053] It should be noted that the lead frame, the chip, and the pin 16 are connected and fixed according to the designed positions to form a structure with a certain function. After the whole is formed into a structure to be plastic packaged, the structure to be plastic packaged is placed in a plastic packaging mold, and the epoxy resin is poured to form the appearance of the power device.
[0054] In some embodiments of the present application, the power device further comprises a heat sink 18 arranged on the back 113 and leaking out the blocking glue 12.
[0055] It should be noted that after the power device is molded, a layer of heat sink 18 is formed on the back surface 113 of the power device which is not molded, and is exposed outside the molded body 17, so that the heat generated by the chip can be dissipated to the ambient environment, and the heat dissipation effect of the lead frame is increased. The resist glue 12 surrounds the heat sink 18, and to some extent, the resist glue 12 on the back surface 113 also has a certain heat dissipation function. The resist glue 12 will eventually be covered by pure tin during subsequent electroplating, so as to prevent subsequent oxidation of the material and affect the heat conduction or welding performance during subsequent use.
[0056] Those skilled in the art can understand that the above-mentioned various embodiments are specific embodiments for implementing the present application, and in actual application, various changes can be made in form and details without departing from the spirit and scope of the present application.
Claims
1. A leadframe, characterized by, Comprising: a substrate, including a front surface provided with a die pad and a back surface opposite to the front surface; an adhesive-preventing body provided on the back surface, for preventing overflow of encapsulation material when the lead frame is encapsulated; a pin end provided on a side surface of the substrate.
2. The leadframe of claim 1, wherein, The adhesive-preventing body comprises a first adhesive-preventing body provided around the edge of the back surface.
3. The leadframe of claim 2, wherein, Further comprising a through hole provided on the substrate away from the pin end and penetrating the front surface and the back surface.
4. The leadframe of claim 3, wherein, The adhesive-preventing body further comprises a second adhesive-preventing body provided around the through hole.
5. The leadframe of claim 1, wherein, The adhesive-preventing body has an integrated structure with the substrate.
6. The leadframe of claim 5, wherein, The height of the adhesive-preventing body protruding from the back surface is between 10 um and 20 um; the width of the adhesive-preventing body is between 50 um and 150 um.
7. The leadframe of claim 1, wherein, Further comprising an overflow-preventing groove provided around the die pad to prevent overflow of the front surface after the solder is melted.
8. A power device comprising the lead frame according to any one of claims 1 to 7, the power device further comprising: a chip provided on the die pad and electrically connected to the pin end; a pin connected to the pin end to conduct the electrical signal of the chip to an external device.
9. The power device of claim 8, wherein, Further comprising an encapsulation body covering the chip, part of the lead frame and part of the pin.