Method for preventing layering of power device after packaging and semiconductor power device

Abstract

The invention discloses a method for preventing a power device from layering after packaging and a semiconductor power device, relates to the technical field of semiconductor device packaging, and can prevent the problem of layering after packaging of the power device. The specific scheme comprises the following steps: aiming at a first power device subjected to pressure welding; according to a lead frame adopted in the pressure welding process of the first power device, the first power device is subjected to cleaning and isolation treatment, a second power device is obtained, the cleaning and isolation treatment comprises plasma cleaning treatment and / or glue spraying treatment, the glue spraying treatment is that a spraying agent is used for spraying the front face area of the power device, and the second power device is obtained; the front area comprises a carrier, a chip, a bonding wire and a pin part of the power device; and sequentially carrying out plastic packaging treatment, curing treatment and rib cutting treatment on the second power device to obtain a target power device.

Description

Technical Field

[0001] The present application relates to the technical field of semiconductor device packaging, and in particular to a method for preventing delamination of a power device after packaging and a semiconductor power device. Background Art

[0002] With the acceleration of the replacement process of semiconductor devices and the gradual and large-scale application of power semiconductor devices in the automotive field, higher requirements are also placed on the reliability of devices.

[0003] However, since the packaging process of plastic encapsulated power devices uses bare copper or silver-plated lead frames, solders and plastic encapsulation materials with large differences in thermal expansion coefficients, these materials are prone to stress mismatch or poor adhesion during the plastic encapsulation process, resulting in delamination or tiny gaps on the bonding surface of the two materials. This delamination can cause device short circuits, poor heat dissipation or abnormal reliability, and will directly affect the use of the device and even cause safety problems. Therefore, a method for preventing delamination of power devices after packaging is urgently needed. Summary of the invention

[0004] The present application provides a method for preventing delamination of a power device after packaging and a semiconductor power device, which can prevent the problem of delamination of the power device after packaging.

[0005] In order to achieve the above objectives, this application adopts the following technical solutions:

[0006] In a first aspect of an embodiment of the present application, a method for preventing delamination of a power device after packaging is provided, the method comprising:

[0007] For the first power device completed by pressure welding;

[0008] According to the lead frame used in the pressure welding process of the first power device, the first power device is cleaned and isolated to obtain a second power device, wherein the cleaning and isolation treatment includes plasma cleaning and / or glue spraying, and the glue spraying is to spray the front area of ​​the power device with a spraying agent, and the front area includes a carrier, a chip, a bonding wire and a pin part of the power device;

[0009] The second power device is subjected to a plastic encapsulation process, a curing process and a rib cutting process in sequence to obtain a target power device.

[0010] In one embodiment, the first power device is cleaned and isolated according to the lead frame used in the pressure welding process of the first power device to obtain the second power device, including:

[0011] If the first power device uses a bare copper lead frame during the pressure welding process, the first power device is subjected to the plasma cleaning process, and the first power device after the plasma cleaning is subjected to a glue spraying process to obtain the second power device;

[0012] If the first power device uses a bare silver lead frame during the pressure welding process, the first power device is subjected to the plasma cleaning treatment to obtain the second power device.

[0013] In one embodiment, the plasma cleaning process is performed on the first power device, including:

[0014] A plurality of the power devices are placed in a hollow material box for the plasma cleaning process, wherein the hollow material box comprises a plurality of open storage areas, each of which is used for placing the first power device.

[0015] In one embodiment, performing a plastic encapsulation process on the second power device includes:

[0016] After placing a plurality of the second power devices in a plastic encapsulation mold by using a plastic encapsulation loading rack for plastic encapsulation, waste materials of the plastic encapsulated second power devices are cut off by using a plastic encapsulation waste punching mold to obtain a third power device.

[0017] In one embodiment, the mold depth of the plastic encapsulation and waste stamping mold is: L+(0.4-0.6) mm, where L is the thickness of the second power device after plastic encapsulation.

[0018] In one embodiment, the method further comprises:

[0019] The third power device is placed in a fully automatic nitrogen-filled active exhaust device for curing treatment to obtain a fourth power device.

[0020] In one embodiment, the curing process has a heating rate of 2.0 to 2.3° C. / min, a heat preservation time of 5.5 to 6.5 hours, and a cooling rate of 1.7 to 2.0° C. / min.

[0021] In one embodiment, the method further comprises:

[0022] The fourth power device is subjected to a rib cutting process by using a rib cutting die to obtain the target power device.

[0023] In one embodiment, a distance of 0.25-0.4 mm exists between the cutting surface of the rib cutting die and the root of the pin of the fourth power device.

[0024] According to a second aspect of an embodiment of the present application, a semiconductor power device is provided, which is packaged using a method for preventing delamination of a power device after packaging according to the first aspect of an embodiment of the present application.

[0025] The beneficial effects brought by the technical solution provided by the embodiment of the present application include at least:

[0026] The method for preventing delamination of power devices after packaging provided by the embodiment of the present application is to clean and isolate the first power device after pressure welding according to the lead frame used in the pressure welding process of the first power device to obtain a second power device, wherein the cleaning and isolation treatment includes plasma cleaning and / or glue spraying, wherein the glue spraying is to spray the front area of ​​the power device with a spraying agent, wherein the front area includes the carrier, chip, welding wire and pin part of the power device; and to perform plastic encapsulation, curing and rib cutting treatment on the second power device in sequence to obtain a target power device. For the power device after pressure welding, plasma cleaning is first performed before plastic encapsulation, which can remove foreign organic matter on the surface of the lead frame, improve the cleanliness of the lead frame, and avoid delamination caused by abnormality of the frame surface due to organic contamination. In addition, a bonding transition layer can be formed on the surface of different materials through glue spraying, and the transition layer can increase the bonding strength with the plastic encapsulation material, and further improve the bonding strength between the plastic encapsulation material and the lead frame. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A flow chart of a method for preventing delamination of a power device after packaging provided by an embodiment of the present application;

[0028] Figure 2 A schematic diagram of a glue spraying process for a power device provided in an embodiment of the present application;

[0029] Figure 3 A schematic diagram of a plastic sealing waste punching mold provided in an embodiment of the present application;

[0030] Figure 4 A schematic diagram of a hollow material box provided in an embodiment of the present application;

[0031] Figure 5 A schematic diagram of a frame-type loading rack provided in an embodiment of the present application;

[0032] Figure 6 A schematic diagram of a baking curve for a curing process provided in an embodiment of the present application. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0034] In the following, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present disclosure, unless otherwise specified, "plurality" means two or more.

[0035] Additionally, the use of “based on” or “according to” is meant to be open and inclusive, as a process, step, calculation, or other action “based on” or “according to” one or more conditions or values ​​may, in practice, be based on additional conditions or beyond values.

[0036] As a core component of the electronic industry chain, the development of power devices is not only closely related to technological progress, but also inseparable from the continuous expansion of market demand. The emergence of wide-bandgap third-generation semiconductor materials such as silicon carbide and gallium nitride provides power devices with higher voltage and high temperature resistance, as well as lower on-resistance and faster switching speed. With the development of packaging technology, power devices have also evolved towards low impedance, high power, and high frequency characteristics. Traditional packaging technology has been difficult to meet the requirements of fast switching characteristics and reliability under high temperature operation, which has prompted the innovation and development of packaging technology. At the same time, in order to improve the performance and reliability of power devices, the manufacturing process is also being continuously optimized, such as the use of environmentally friendly materials such as halogen-free and antimony oxide, and the use of special materials and processes such as roughening or spraying. Driven by market demand, the rise of new energy vehicles: The demand for power semiconductors in new energy vehicles has increased significantly, driving power devices to develop in the direction of high efficiency and high stability.

[0037] With the acceleration of the replacement process of semiconductor devices and the gradual and large-scale application of power semiconductor devices in the automotive field, higher requirements are also placed on the reliability of devices. However, since the packaging process of plastic-encapsulated power devices uses bare copper or silver-plated lead frames and plastic encapsulation materials with large differences in thermal expansion coefficients, these two materials are prone to stress mismatch or poor adhesion during the plastic encapsulation process, resulting in delamination or tiny gaps on the bonding surface of the two materials. This delamination can cause device short circuits, poor heat dissipation, or abnormal reliability, and will directly affect the use of the device and even cause safety problems.

[0038] In order to solve the above problems, the present application embodiment provides a method for preventing delamination of a power device after packaging, such as Figure 1 As shown, the method comprises the following steps:

[0039] Step 101, for a first power device that has been pressure-welded;

[0040] Step 102: performing a cleaning and isolation treatment on the first power device according to the lead frame used in the pressure welding process of the first power device to obtain a second power device, wherein the cleaning and isolation treatment includes a plasma cleaning treatment and / or a glue spraying treatment, wherein the glue spraying treatment is to spray a front area of ​​the power device with a spraying agent, and the front area includes a carrier, a chip, a bonding wire, and a pin portion of the power device;

[0041] Step 103 , performing a plastic encapsulation process, a curing process and a rib cutting process on the second power device in sequence to obtain a target power device.

[0042] It is understandable that the packaging process of semiconductor power devices is generally: dicing, bonding, pressure welding, plastic sealing, curing and rib cutting. This application mainly adds cleaning and isolation treatment after pressure welding and before plastic sealing, and the cleaning and isolation treatment includes plasma cleaning and / or spraying.

[0043] The method for preventing delamination of power devices after packaging provided by the embodiment of the present application is to clean and isolate the first power device after pressure welding according to the lead frame used in the pressure welding process of the first power device to obtain a second power device, wherein the cleaning and isolation treatment includes plasma cleaning and / or glue spraying, wherein the glue spraying is to spray the front area of ​​the power device with a spraying agent, wherein the front area includes the carrier, chip, welding wire and pin part of the power device; and to perform plastic encapsulation, curing and rib cutting treatment on the second power device in sequence to obtain a target power device. For the power device after pressure welding, plasma cleaning is first performed before plastic encapsulation, which can remove foreign organic matter on the surface of the lead frame, improve the cleanliness of the lead frame, and avoid delamination caused by abnormality of the frame surface due to organic contamination. In addition, a bonding transition layer can be formed on the surface of different materials through glue spraying, and the transition layer can increase the bonding strength with the plastic encapsulation material, and further improve the bonding strength between the plastic encapsulation material and the lead frame.

[0044] Optionally, the process of performing cleaning and isolation treatment on the first power device according to the lead frame used in the pressure welding process of the first power device in step 102 to obtain the second power device may be:

[0045] If the first power device uses a bare copper lead frame during the pressure welding process, the first power device is subjected to the plasma cleaning process, and the first power device after the plasma cleaning is subjected to the first glue spraying process to obtain the second power device;

[0046] If the first power device uses a bare silver lead frame during the pressure welding process, the first power device is subjected to the plasma cleaning treatment to obtain the second power device.

[0047] In addition, if the first power device uses a bare silver lead frame during the pressure welding process, the first power device can also be plasma cleaned, and then the first power device after plasma cleaning is subjected to a second glue spraying process to obtain the second power device.

[0048] like Figure 2 FIG. 1 is a schematic diagram of the glue spraying process. In addition, the spraying agent used in the first glue spraying process may be a spraying agent with a bonding force that matches the copper material. The spraying agent used in the second glue spraying process may be a spraying agent with a bonding force that matches the silver material.

[0049] Specifically, the process of performing plasma cleaning on the first power device may be:

[0050] Placing a plurality of the power devices in a hollow material box for plasma cleaning, wherein the hollow material box includes a plurality of open storage areas, each of which is used to place the first power device. Figure 3 As shown, it is a schematic diagram of a hollow material box. Placing a plurality of the power devices in the hollow material box and performing the plasma cleaning process can improve the cleaning efficiency of the plurality of power devices.

[0051] Optionally, the step 103 of sequentially performing plastic encapsulation processing on the second power devices includes:

[0052] After placing a plurality of the second power devices in a plastic encapsulation mold by using a plastic encapsulation loading rack for plastic encapsulation, waste materials of the plastic encapsulated second power devices are cut off by using a plastic encapsulation waste punching mold to obtain a third power device.

[0053] Among them, the present application optimizes the glue opening of the plastic encapsulation mold. Since the lead frame of the power device is generally designed with an asymmetric structure and is affected by the number of wires of different pins, when the product is placed in the plastic encapsulation mold and during the injection molding process, under the same process parameters, the injection molding pressure will have attenuation differences, resulting in poor filling at the far end of the glue inlet, resulting in poor bonding between the plastic encapsulation material and the lead frame and stratification. Therefore, the glue opening of the plastic encapsulation mold of the present application is designed to change in a step-by-step manner from the glue inlet to the far end, that is, the glue opening size is small near the glue inlet, and the glue opening size is larger at the far end, which ensures the consistency of the plastic encapsulation material filling of the product during the plastic encapsulation injection molding process, thereby improving the bonding strength between the plastic encapsulation material and the lead frame.

[0054] Furthermore, the present application optimizes the plastic sealing and waste flushing mold. Figure 4 As shown, the mold depth of the plastic encapsulation and waste stamping mold of the present application is L+(0.4~0.6)mm, where L is the thickness of the second power device after plastic encapsulation. Compared with the existing plastic encapsulation and waste stamping mold, the mold depth of the plastic encapsulation and waste stamping mold of the present application is small, which can ensure that the waste falls smoothly while optimizing the gap between the plastic encapsulation body and the mold, thereby avoiding stratification due to mechanical stress on the product.

[0055] In addition, the present application optimizes the design of the loading rack used for plastic packaging, and improves the existing ordinary loading rack into a supporting frame type loading rack. Figure 5 As shown, when the product is separated from the mold by the improved support frame loading rack, the force is more evenly distributed, avoiding the delamination caused by the product tilting and the interference with the fixed position of the mold.

[0056] Optionally, the method further comprises: placing the third power device in a fully automatic nitrogen-filled active exhaust device for curing to obtain a fourth power device. The curing process has a heating rate of 2.0 to 2.3°C / min, a heat preservation time of 5.5 to 6.5 hours, and a cooling rate of 1.7 to 2.0°C / min.

[0057] It is understandable that during the curing process, considering that the lead frame and the plastic packaging material need to be cooled from high temperature to room temperature in a short period of time after high temperature baking, the sudden change in temperature will increase the risk of stratification and air oxidation. The site adopts a fully automatic nitrogen-filled active exhaust baking process to extend the closed cooling time, control the cooling rate, and reduce the risk of stratification. Specifically, the curing baking curve can be as follows: Figure 6 shown.

[0058] Optionally, the method further comprises: performing rib cutting processing on the fourth power device using a rib cutting die to obtain the target power device, wherein a distance of 0.25 to 0.4 mm exists between a cutting surface of the rib cutting die and a root of a pin of the fourth power device.

[0059] It should be noted that a redesigned rib cutting mold is used in the rib cutting process. A certain distance is reserved between the punch of the rib cutting mold and the root of the tube pin. This can avoid mechanical stress caused by contact between the tool and the plastic package or too close distance, thereby preventing delamination.

[0060] The present application also provides a semiconductor power device, which is packaged using the method for preventing delamination of a power device after packaging provided by the present application. The method for preventing delamination of a power device after packaging includes:

[0061] For the first power device completed by pressure welding;

[0062] According to the lead frame used in the pressure welding process of the first power device, the first power device is cleaned and isolated to obtain a second power device, wherein the cleaning and isolation treatment includes plasma cleaning and / or glue spraying, and the glue spraying is to spray the front area of ​​the power device with a spraying agent, and the front area includes a carrier, a chip, a bonding wire and a pin part of the power device;

[0063] The second power device is subjected to a plastic encapsulation process, a curing process and a rib cutting process in sequence to obtain a target power device.

[0064] In one embodiment, the first power device is cleaned and isolated according to the lead frame used in the pressure welding process of the first power device to obtain the second power device, including:

[0065] If the first power device uses a bare copper lead frame during the pressure welding process, the first power device is subjected to the plasma cleaning process, and the first power device after the plasma cleaning is subjected to a glue spraying process to obtain the second power device;

[0066] If the first power device uses a bare silver lead frame during the pressure welding process, the first power device is subjected to the plasma cleaning treatment to obtain the second power device.

[0067] In one embodiment, the plasma cleaning process is performed on the first power device, including:

[0068] A plurality of the power devices are placed in a hollow material box for the plasma cleaning process, wherein the hollow material box comprises a plurality of open storage areas, each of which is used for placing the first power device.

[0069] In one embodiment, performing a plastic encapsulation process on the second power device includes:

[0070] After placing a plurality of the second power devices in a plastic encapsulation mold by using a plastic encapsulation loading rack for plastic encapsulation, waste materials of the plastic encapsulated second power devices are cut off by using a plastic encapsulation waste punching mold to obtain a third power device.

[0071] In one embodiment, the mold depth of the plastic encapsulation and waste stamping mold is L+(0.4-0.6) mm, where L is the thickness of the second power device after plastic encapsulation.

[0072] In one embodiment, the method further comprises:

[0073] The third power device is placed in a fully automatic nitrogen-filled active exhaust device for curing treatment to obtain a fourth power device.

[0074] In one embodiment, the curing process has a heating rate of 2.0 to 2.3° C. / min, a heat preservation time of 5.5 to 6.5 hours, and a cooling rate of 1.7 to 2.0° C. / min.

[0075] In one embodiment, the method further comprises:

[0076] The fourth power device is subjected to a rib cutting process by using a rib cutting die to obtain the target power device.

[0077] In one embodiment, a distance of 0.25-0.4 mm exists between the cutting surface of the rib cutting die and the root of the pin of the fourth power device.

[0078] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0079] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A method for preventing delamination of a power device after packaging, characterized in that: The method comprises: For the first power device completed by pressure welding; According to the lead frame used in the pressure welding process of the first power device, the first power device is cleaned and isolated to obtain a second power device, wherein the cleaning and isolation treatment includes plasma cleaning and / or glue spraying, and the glue spraying is to spray the front area of ​​the power device with a spraying agent, and the front area includes a carrier, a chip, a bonding wire and a pin part of the power device; The second power device is subjected to a plastic encapsulation process, a curing process and a rib cutting process in sequence to obtain a target power device.

2. The method according to claim 1, characterized in that: The method of cleaning and isolating the first power device according to the lead frame used in the pressure welding process of the first power device to obtain the second power device includes: If the first power device uses a bare copper lead frame during the pressure welding process, the first power device is subjected to the plasma cleaning process, and the first power device after the plasma cleaning is subjected to a glue spraying process to obtain the second power device; If the first power device uses a bare silver lead frame during the pressure welding process, the first power device is subjected to the plasma cleaning treatment to obtain the second power device.

3. The method according to claim 2, characterized in that The plasma cleaning process is performed on the first power device, comprising: A plurality of the power devices are placed in a hollow material box for the plasma cleaning process, wherein the hollow material box comprises a plurality of open storage areas, each of which is used for placing the first power device.

4. The method according to claim 1, characterized in that: The second power device is plastic-sealed, comprising: After placing a plurality of the second power devices in a plastic encapsulation mold by using a plastic encapsulation loading rack for plastic encapsulation, waste materials of the plastic encapsulated second power devices are cut off by using a plastic encapsulation waste punching mold to obtain a third power device.

5. The method according to claim 4, characterized in that The mold depth of the plastic-sealed waste mold is: L+(0.4-0.6) mm, where L is the thickness of the second power device after plastic sealing.

6. The method according to claim 4, characterized in that The method further comprises: The third power device is placed in a fully automatic nitrogen-filled active exhaust device for curing treatment to obtain a fourth power device.

7. The method according to claim 6, characterized in that The curing treatment has a heating rate of 2.0 to 2.3°C / min, a heat preservation time of 5.5 to 6.5 hours, and a cooling rate of 1.7 to 2.0°C / min.

8. The method according to claim 5, characterized in that The method further comprises: The fourth power device is subjected to a rib cutting process by using a rib cutting die to obtain the target power device.

9. The method according to claim 8, characterized in that There is a distance of 0.25 to 0.4 mm between the cutting surface of the rib cutting die and the root of the pin of the fourth power device.

10. A semiconductor power device, characterized in that: The device is encapsulated by using the method for preventing delamination of a power device after encapsulation as described in any one of claims 1 to 9.

Images