Composite bonding sheet and preparation method thereof, and semiconductor packaging structure and method

Abstract

The invention discloses a composite bonding sheet and a preparation method thereof, and a semiconductor packaging structure and method, and the method comprises the steps: providing a large-area composite substrate which comprises a conductive metal sheet and a bonding layer; incompletely cutting the large-area composite base material according to the outline of the composite bonding sheet to form a cutting line interrupted by at least one connection point, defining the cutting line to form an area corresponding to the single composite bonding sheet, and keeping the connection between the composite bonding sheet and the rest part of the large-area composite base material through the connection point; the connection points are cut, so that the composite bonding sheet is completely separated from the large-area composite base material and falls off by means of the gravity of the composite bonding sheet; according to the invention, the production efficiency can be remarkably improved, the single-chip cost is reduced, and the high-reliability requirement of the power device is met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, and in particular to a composite bonding sheet and a preparation method thereof, a semiconductor packaging structure and a method. BACKGROUND

[0002] With the rapid development of the fields of electric power, communication, high-speed rail and new energy vehicles, the demand for power semiconductor devices is also rapidly increasing. In order to develop power semiconductor devices with long service life and high reliability, it is required that the upper side connection of the semiconductor chip has high thermal conductivity and electrical conductivity. The traditional aluminum wire bonding method interconnects the chip electrode and the substrate or lead frame to realize current conduction. However, as the power density requirement of power devices increases, aluminum wire bonding is difficult to meet the thermal and electrical requirements, and therefore copper wire bonding is used to replace aluminum wire bonding. In order to solve the problems of soldering point falling off and chip damage caused by direct bonding of copper wire on the upper side of the chip, manufacturers usually use silver paste to sinter a copper foil on the upper side of the chip, and then perform bonding. The composite bonding sheet composed of copper foil and sintered silver is a product that can be applied to chip bonding. At present, the composite bonding sheet has high cost and low efficiency in batch production, and cannot well compatible with the demand of automatic production.

[0003] The above information disclosed in the background section of this document is only included to enhance the understanding of the background of the present disclosure, and therefore can contain information that does not form the prior art known to those of ordinary skill in the art at the present time. SUMMARY

[0004] The present application provides a composite bonding sheet and a preparation method thereof, and a semiconductor packaging structure, to solve the problems of high cost and low efficiency of the composite bonding sheet in batch production, and the inability to well compatible with the demand of automatic production.

[0005] The present application adopts the following technical solutions.

[0006] In a first aspect, the present application provides a preparation method of a composite bonding sheet for chip bonding, the method comprising:

[0007] providing a large-area composite substrate, the large-area composite substrate comprising an electrically conductive metal sheet and a bonding layer for bonding with a chip, which are stacked;

[0008] performing incomplete cutting on the large-area composite substrate according to the contour of the composite bonding sheet, to form a cutting line interrupted by at least one connection point, the cutting line circumscribing an area corresponding to a single composite bonding sheet, and the composite bonding sheet being connected to the remaining part of the large-area composite substrate through the connection point;

[0009] cutting the connection point to completely separate the composite bonding sheet from the large-area composite substrate and make the composite bonding sheet fall off by its own gravity.

[0010] Therefore, the application can significantly improve the production efficiency and reduce the cost of single chip, and meet the high reliability requirement of power devices.

[0011] In a possible implementation manner of the first aspect, the incomplete cutting is implemented based on a first cutting manner, and the cutting of the connection points is implemented based on a second cutting manner different from the first cutting manner.

[0012] In this way, different cutting processes are used in stages (such as stamping first and then laser), taking into account the mass processing efficiency and high-precision separation requirements, and adapting to the strict tolerance of the size of the bonding sheet of the power device.

[0013] In a possible implementation manner of the first aspect, the first cutting manner is a stamping manner, and the second cutting manner is a laser cutting manner. The stamping cutting can realize high-efficiency and continuous cutting, and because the product is not completely detached during stamping in the application, it will not accumulate in the stamping die, and will not affect the continuity of the stamping operation. The laser can accurately cut the connection points, and the cutting manner is much gentler than stamping, so that the product can rely on its own gravity to fall off, facilitating product collection and avoiding product damage. In summary, the method of stamping the main contour first and then laser cutting the small range connection points can avoid the problem that the product falls off uncontrollably and easily accumulates in the die, affecting continuous operation caused by full stamping, and also solves the problem of low production efficiency and easy generation of "black slag" oxide on the edge caused by full laser cutting.

[0014] In a possible implementation manner of the first aspect, the connection points are located in the corner area and / or the edge midpoint area of the bonding sheet. In this way, the strength and stability of the connection points can be improved, and the product main body can be easily removed during subsequent cutting to avoid damage.

[0015] In a possible implementation manner of the first aspect, the number of connection points is 2-4. In this way, the temporary fixing effect and the convenience of subsequent cutting removal can be properly balanced to ensure that the bonding sheet is temporarily fixed stably and reliably.

[0016] With reference to the first aspect, in a possible implementation manner, a length of the connection point on the profile of the composite bonding sheet is less than 1 / 50 of a length of the profile of the composite bonding sheet and greater than 2 times a diameter of a laser cutting focal spot. In this way, the stamping process is ensured to be feasible, and the thermal influence zone is prevented from diffusing to damage the conductivity of the bonding layer during laser cutting, so that the connection strength and the convenience of cutting and removal can be considered, and the overall processing efficiency is improved.

[0017] With reference to the first aspect, in a possible implementation manner, the connection point is formed by a local avoidance structure of the stamping die. The connection point formed by the local avoidance structure of the stamping die can simplify the structure of the die, reduce the cost of the die, and improve the processing precision and efficiency.

[0018] With reference to the first aspect, in a possible implementation manner, the method further includes: dispensing glue on the bonding layer of the composite bonding sheet obtained by cutting to form at least one adhesive organic polymer glue point; and the glue point is used for preliminary positioning and temporary fixing when the composite bonding sheet is combined with the chip. In this way, the organic polymer glue point is arranged on the composite bonding sheet, so that the composite bonding sheet has the functions of preliminary positioning and temporary fixing when the chip is bonded, the mounting precision and process stability are significantly improved, and the problem that the chip is easily detached or displaced on the side before the bonding layer is sintered is solved.

[0019] With reference to the first aspect, in a possible implementation manner, the method further includes: arranging the plurality of composite bonding sheets on a carrier film based on the respective glue point arrays so as to be uniformly transported. Arranging the plurality of composite bonding sheets on the carrier film based on the glue points facilitates batch transportation and automated production, and effectively improves the production efficiency and yield.

[0020] With reference to the first aspect, in a possible implementation manner, the dispensing glue adopts a pneumatic dispensing or jet dispensing mode. The pneumatic dispensing or jet dispensing mode can realize efficient, accurate and rapid glue point formation, and is more suitable for automated mass production.

[0021] With reference to the first aspect, in a possible implementation manner, the material of the organic polymer glue point is one or more of polyvinyl chloride, polystyrene, ABS resin, and polyethylene. Such a material can ensure that the adhesion of the glue point is controllable and the positioning is reliable, and has good compatibility and processing performance.

[0022] With reference to the first aspect, in a possible implementation manner, the method further includes: arranging a metal film on one side of the conductive metal sheet combined with the bonding layer and arranging an organic film on the other side of the conductive metal sheet. In this way, the conductive metal sheet can be effectively protected from oxidation and pollution, and the electrical performance and long-term stability of the composite bonding sheet are improved.

[0023] In a possible implementation manner of the first aspect, the organic film comprises benzotriazole or imidazole organic crystalline base; and / or, the material of the metal film is silver single layer or nickel-silver double layer. The use of benzotriazole or imidazole organic crystalline base for the organic film and the use of silver single layer or nickel-silver double layer for the metal film can further enhance the oxidation resistance and electrical conductivity of the conductive metal sheet, and improve the reliability of the product.

[0024] In a possible implementation manner of the first aspect, the thickness of the organic film is 5 nm-50 nm; and / or, the thickness of the conductive metal sheet is 50 μm-100 μm; and / or, the thickness of the metal film is 0.5 μm-2 μm; and / or, the thickness of the bonding layer is 30 μm-100 μm.

[0025] In a possible implementation manner of the first aspect, the bonding layer is a sintering layer, and provides a large-area composite substrate, comprising:

[0026] The conductive paste is coated on the high-temperature-resistant film and then subjected to drying treatment to obtain a whole sintering sheet;

[0027] A plurality of conductive metal sheets are cut out from the whole conductive metal sheet according to the size of the large-area composite substrate;

[0028] A plurality of sintering sheets are cut out from the whole sintering sheet according to the size of the large-area composite substrate;

[0029] The single sintering sheet is hot-pressed on the single conductive metal sheet, and the high-temperature-resistant film is removed to form a sintering layer.

[0030] That is, the conductive paste is preformed and then compounded to the conductive metal sheet, the process operation is flexible, the thickness uniformity of the sintering layer is better, the product quality is stable, and the conductive performance is excellent. Moreover, compared with the forming by means of point gluing, printing or spraying, the silver paste is difficult to be flat after point gluing, the doctor blade is easy to deform in the printing manner, leading to that the coating is not flat enough, and the coating is too thin in the spraying manner, the conductive paste is uniformly distributed by coating the conductive paste on the high-temperature-resistant film in the present application, and uneven distribution is avoided.

[0031] In a possible implementation manner of the first aspect, the bonding layer is a sintering layer, and provides a large-area composite substrate, comprising: the conductive paste is coated on the conductive metal sheet and subjected to drying treatment, and the dried conductive paste forms a sintering layer. In this manner, the conductive paste is directly coated on the conductive metal sheet to form a sintering layer, the process is simple and efficient, the process and cost are reduced, and the large-scale batch production is suitable.

[0032] With reference to the first aspect, in a possible implementation manner, the method comprises: when coating, based on the coating tool, the coating tool depth is 100-200 μm of the coating groove; and / or, the coating speed when coating is 15-50 mm / s. By reasonably setting the coating groove depth and the coating speed, the sintering layer thickness uniformity and the slurry coating quality are controlled, and the process repeatability and product consistency are improved.

[0033] With reference to the first aspect, in a possible implementation manner, the conductive slurry is silver slurry, and the sintering layer is a silver sintering layer, and silver particles with a diameter of 0.2-10 μm are used.

[0034] The drying treatment comprises: first drying at 80-100 °C for 5-20 min; and then drying at 120-160 °C for 5-20 min.

[0035] The second aspect, the application further provides a composite bonding sheet for chip bonding, which is prepared based on the preparation method in the first aspect or any of the optional implementation manners of the first aspect, and comprises a conductive metal sheet and a bonding layer.

[0036] The third aspect, the application further provides a semiconductor packaging method, which comprises:

[0037] The composite bonding sheet of the second aspect is positioned and placed on the chip, and the bonding layer is in contact with the chip;

[0038] The bonding layer and the chip are combined and fixed by sintering.

[0039] The fourth aspect, the application further provides a semiconductor packaging structure, which comprises:

[0040] A substrate;

[0041] A chip disposed on the substrate, and an external conductive structure for electrically connecting with the chip is further disposed on the substrate;

[0042] The composite bonding sheet prepared based on the preparation method in the first aspect or any of the optional implementation manners of the first aspect, the bonding layer in the composite bonding sheet is combined with a side surface of the chip away from the substrate, and the conductive metal sheet in the composite bonding sheet is electrically connected with the external conductive structure through a metal wire.

[0043] The beneficial effects of the above second aspect to the fourth aspect can refer to the first aspect or any of the possible implementation manners of the first aspect, and will not be repeated here. On the basis of the implementation manners provided in the above aspects, the application can be further combined to provide more implementation manners.

[0044] Other advantages, objects, and features of the application will be apparent to those skilled in the art from the following specification. BRIEF DESCRIPTION OF DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related art, the following will briefly introduce the drawings needed to be used in the embodiments or the related art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from the structures shown in the drawings without creative labor.

[0046] Figure 1 is one of the flowcharts of the composite bonding sheet preparation method provided by the embodiments of the present application;

[0047] Figure 2 is the second flowchart of the composite bonding sheet preparation method provided by the embodiments of the present application;

[0048] Figure 3 is the third flowchart of the composite bonding sheet preparation method provided by the embodiments of the present application;

[0049] Figure 4 is one of the flowcharts of providing large-area composite substrates;

[0050] Figure 5 is the second flowchart of providing large-area composite substrates;

[0051] Figure 6 is a schematic diagram of a coating tool;

[0052] Figure 7 is a schematic diagram of a cutting line;

[0053] Figure 8 is one of the structural schematic diagrams of the composite bonding sheet provided by the embodiments of the present application;

[0054] Figure 9 is the second structural schematic diagram of the composite bonding sheet provided by the embodiments of the present application;

[0055] Figure 10 is the structural schematic diagram of the semiconductor packaging structure provided by the embodiments of the present application;

[0056] Reference signs in the drawings:

[0057] 1, large-area composite substrate; 2, cutting line; 3, connection point; 4, composite bonding sheet; 41, conductive metal sheet; 42, bonding layer; 43, organic film; 44, metal film; 45, glue point; 5, chip; 6, external conductive structure; 7, substrate; 8, metal wire. DETAILED DESCRIPTION

[0058] It should be noted that the terms "exemplary" and / or "for example" are used herein to mean "an example of" rather than "an ideal". Any implementation described herein as "exemplary" and / or "for example" is not necessarily to be construed as preferred or advantageous over other implementations. A specific implementation described as "exemplary" and / or "for example" is intended merely to present an example of the described subject matter. The term "exemplary" and / or "for example" is not intended to convey that the described subject matter is limited to a particular implementation.

[0059] The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. In the present application, "at least one" means one or more and "multiple" means two or more. The terms "first", "second", and the like as used herein to describe various constitutional elements constitute ordinal terms and can be used to distinguish one constitutional element from another. However, these terms are not intended to limit the scope of the present application. The use of these terms is intended to convey the relative importance of the associated constitutional elements. For example, without departing from the scope of the present application, a first constitutional element can be named as a second constitutional element, and similarly, a second constitutional element can be named as a first constitutional element.

[0060] Before introducing the embodiments of the present application, the technical terms and background art related to the present application are introduced.

[0061] Wire bonding: Wire bonding is the most common chip packaging bonding technology, which mainly connects the chip pads with the corresponding pads on the packaging carrier through fine metal wires (usually gold wires, aluminum wires or copper wires). Common wire bonding schemes include aluminum wire bonding and copper wire bonding.

[0062] Sintering: In the field of chip packaging, it generally refers to an advanced packaging technology that realizes reliable interconnection and heat conduction connection between chips and packaging substrates by using special sintering materials (such as sintering silver paste) and specific sintering processes (such as pressure sintering or pressureless sintering). Compared with traditional welding or bonding methods, sintering has more excellent electrical conduction performance, heat conduction performance and reliability, and is particularly suitable for packaging of high-power and high-performance semiconductor devices.

[0063] Silver paste: Also known as silver paste, it is a functional electronic material that is essentially a suspension paste formed by uniformly dispersing micron or nanoscale silver (Ag) particles in an organic carrier (or binder) system.

[0064] Semiconductor packaging: a technology that encapsulates a manufactured semiconductor chip into a specific structure, enabling it to work stably and efficiently in the actual environment. In simple terms, it is to protect the manufactured chip and provide electrical connection, thermal management and mechanical protection for reliable use in electronic devices. Semiconductor chips are generally very fragile and cannot be directly exposed to air or the outside environment, and the chip itself cannot be directly installed on the circuit board. Therefore, the chip must be protected, connected and integrated through packaging technology.

[0065] In related technologies, silver paste is usually used to sinter copper foil on the upper side of the chip, and then copper wire bonding is performed. The composite bonding sheet composed of copper foil and sintered silver is a product that can be applied to chip bonding. Currently, the composite bonding sheet has high cost and low efficiency in batch production, and cannot well compatible with the demand of automatic production. In order to solve the above problems, the embodiment of the present application provides a preparation method of a composite bonding sheet for chip bonding.

[0066] In a first aspect, as shown in Figure 1 , a preparation method of a composite bonding sheet is provided, and the purpose is to prepare a composite bonding sheet. The structure of the composite bonding sheet can refer to Figure 8 、 9 . Referring to Figure 10 , the composite bonding sheet can be used for bonding of the chip 5, as shown in Figure 10 .

[0067] The method of the embodiment includes:

[0068] S101: providing a large-area composite substrate, the large-area composite substrate including a conductive metal sheet and a bonding layer for bonding with a chip, which are stacked;

[0069] In some embodiments, the conductive metal sheet is copper, with a thickness of 50μm-100μm and a hardness of 40Hv-120Hv. The bonding layer is a sintering layer. For example, the bonding layer is a silver sintering layer, using silver particles with a diameter of 0.2μm-10μm, with a thickness of 30μm-100μm.

[0070] S103: performing incomplete cutting on the large-area composite substrate according to the contour of the composite bonding sheet, forming a cutting line interrupted by at least one connection point, the cutting line enclosing an area corresponding to a single composite bonding sheet, and the composite bonding sheet being connected to the remaining part of the large-area composite substrate through the connection point;

[0071] Referring to Figure 7 , Figure 7 , the cutting of 6 composite bonding sheets 4 on the large-area composite substrate 1 is shown. Of course, this figure is only illustrative. In fact, the number of composite bonding sheets 4 cut from a single large-area composite substrate 1 is set according to the situation and is not limited.

[0072] S105: cutting the connection points to completely separate the composite bonding sheet from the large-area composite substrate and rely on its own gravity to fall off.

[0073] In this way, the present application can cut a large number of products (i.e. composite bonding sheets) from the large-area substrate in batches. Through the design of the cutting line and the connection points by batch incomplete cutting of the large-area substrate, the cutting can be performed in two steps of incomplete cutting and connection point cutting. Since the incomplete cutting does not need to consider the collection of the falling products, a faster cutting method can be selected for fast and continuous cutting. The connection point cutting can be performed by a relatively mild cutting method, so that the composite bonding sheet can rely on its own gravity to fall off. In this way, the work of the cutting equipment is not affected, the product collection is facilitated, and the product damage is avoided, thereby meeting the high reliability requirement of the power device. Therefore, in general, the present application can significantly improve the production efficiency and reduce the cost of a single sheet, and meet the high reliability requirement of the power device.

[0074] In some embodiments, the incomplete cutting in step S103 is implemented based on a first cutting method, and the cutting of the connection points in step S105 is implemented based on a second cutting method different from the first cutting method. In this way, different cutting processes (such as stamping first and then laser) are used in stages to balance the mass production efficiency and the high-precision separation requirement, and to adapt to the strict tolerance of the bonding sheet size of the power device.

[0075] For example, the first cutting method is a stamping method, and the second cutting method is a laser cutting method. The stamping cutting can achieve high-efficiency and fast continuous cutting. Since the product is not completely fallen off during stamping in the present application, the product will not accumulate in the stamping die, and the continuity of the stamping operation will not be affected. The laser can accurately cut the connection points, and this cutting method is much milder than stamping, so that the product can rely on its own gravity to fall off, facilitating product collection and avoiding product damage. In general, the method of stamping the main contour first and then laser cutting the small range connection points can avoid the problem that the product falls off uncontrollably and easily accumulates in the die, affecting continuous operation caused by full stamping. It also solves the problem of low production efficiency and the generation of "black slag" oxides at the edge caused by full laser cutting.

[0076] With reference to Figure 7 , the planar shape of the composite bonding sheet 4 is generally rectangular according to the chip design, and can also be other shapes. In this embodiment, the planar shape of the composite bonding sheet 4 is rectangular, so the cutting line 2 is a discontinuous rectangle.

[0077] In this embodiment, the connection points are formed by the local avoidance structure of the stamping die. Forming the connection points through the local avoidance structure of the stamping die can simplify the die structure, reduce the die cost, and improve the processing precision and efficiency. For example,Figure 7 As shown, the four corners are laser cutting areas, and the shaded areas are punching areas. The punching die cuts the punching areas while avoiding the laser cutting areas in a single punching action, thereby cutting the line 2 in one step.

[0078] In some embodiments, the number of connection points is 2-4. In this way, the temporary fixing effect and the convenience of subsequent cutting removal can be properly balanced, ensuring that the composite bonding sheet is temporarily fixed stably and reliably.

[0079] In some embodiments, the connection points 3 are located in the corner regions and / or edge midpoint regions of the composite bonding sheet 4 profile, such as Figure 2 As shown in the middle, connection points 3 are arranged in the four corner regions of the rectangle. Here, the edge can be understood as the line connecting adjacent corners along the profile of the composite bonding sheet 4, such as Figure 2 In the middle, the composite bonding sheet 4 corresponds to the long side and short side of the rectangular shape. In this way, the strength and stability of the connection points can be improved, and the composite bonding sheet can be easily removed during subsequent cutting, avoiding damage to the product body.

[0080] In some embodiments, the length of the connection point on the profile of the composite bonding sheet is less than 1 / 50 of the length of the profile of the composite bonding sheet, and greater than 2 times the diameter of the laser cutting focal spot. In this way, the feasibility of the punching process is ensured, and the thermal influence zone is prevented from diffusing and damaging the conductivity of the bonding layer during laser cutting. The connection strength and the convenience of cutting removal can be considered, and the overall processing efficiency can be improved.

[0081] Reference Figure 2 In some embodiments, the method further comprises:

[0082] S201: dispensing glue on the bonding layer of the cut composite bonding sheet to form at least one adhesive organic polymer glue point.

[0083] Reference Figure 8 , 9 The glue point 45 is used for preliminary positioning and temporary fixing when the composite bonding sheet is combined with the chip. In this way, the organic polymer glue point is provided on the composite bonding sheet, so that the composite bonding sheet has preliminary positioning and temporary fixing function when the chip is bonded, which significantly improves the mounting precision and process stability, and solves the problem of easy falling off or displacement of the chip on the side before the bonding layer is sintered.

[0084] In one possible implementation, the dispensing adopts pneumatic dispensing or jet dispensing. The pneumatic dispensing or jet dispensing can realize efficient, accurate and fast glue point formation, and is more suitable for automatic mass production.

[0085] Exemplarily, the material used by the organic polymer adhesive dots is one or more of polyvinyl chloride, polystyrene, ABS resin, and polyethylene. Such material can ensure controllable adhesion of the adhesive dots, reliable positioning, and good compatibility and processing performance.

[0086] Reference Figure 3 In some embodiments, the method further comprises:

[0087] S301: arranging the plurality of composite bonding pieces on the carrier film based on the respective array of adhesive dots for unified transportation.

[0088] Arranging the plurality of composite bonding pieces on the carrier film (such as a blue film) based on the adhesive dots facilitates batch transportation and automated production, effectively improves production efficiency and yield, and avoids product friction during transportation affecting product quality.

[0089] Reference Figure 4 In some embodiments, a large-area composite substrate is provided, comprising:

[0090] S401: providing a metal film on one side of the conductive metal sheet that is combined with the bonding layer, and providing an organic film on the other side of the conductive metal sheet.

[0091] In one possible implementation, the thickness of the organic film is 5-50 nm, and the thickness of the metal film is 0.5-2 μm.

[0092] In one possible implementation, the organic film includes a benzotriazole or imidazole organic crystalline base, and the metal film is made of a silver single layer or a nickel-silver double layer, thereby further enhancing the oxidation resistance and electrical conductivity of the conductive metal sheet and improving product reliability.

[0093] Before the organic film and the metal film are provided, the conductive metal sheet needs to be pretreated to remove surface oxides, oil stains, and other impurities, mainly including:

[0094] (1) Oil removal: using a cleaning agent to remove grease and dirt on the surface of the conductive metal sheet.

[0095] (2) Water washing: washing away the cleaning agent remaining in the oil removal step.

[0096] (3) Micro-etching: using a micro-etching solution to slightly etch the conductive metal sheet to remove surface oxides and roughen the surface for subsequent adhesion of the organic film.

[0097] (4) Water washing: again washing away the micro-etching solution remaining in the micro-etching step.

[0098] (5) Acid pickling: using an acid pickling solution to further treat the surface of the conductive metal sheet to improve the adhesion and uniformity of the organic film.

[0099] (6) Pure water washing: using pure water to clean the residual pickling solution in the pickling step.

[0100] After the pretreatment is completed, the organic film and the metal film can be coated.

[0101] The organic film coating includes:

[0102] (1) The conductive metal sheet is immersed in an organic coating solution, and by controlling the temperature, concentration and time of the solution, a protective layer that prevents oxidation is formed on the surface of the conductive metal sheet.

[0103] (2) Pure water washing: cleaning the excess organic coating solution.

[0104] (3) Drying: placing the conductive metal sheet in a drying device to remove the surface moisture and solvent, and solidifying the organic film.

[0105] When the metal film is a silver single layer, the metal film is plated, including:

[0106] (1) The treated conductive metal sheet is immersed in a silver plating solution to perform plating;

[0107] (2) The plated layer is cleaned and dried.

[0108] When the metal film is a nickel-silver double layer, the metal film is plated, including:

[0109] (1) The treated conductive metal sheet is immersed in a nickel plating solution to perform nickel plating;

[0110] (2) The plated layer is cleaned and dried.

[0111] (3) The conductive metal sheet plated with nickel is immersed in a silver plating solution to perform silver plating;

[0112] (4) The plated layer is cleaned and dried.

[0113] In this way, by arranging the metal film on the side of the conductive metal sheet that is combined with the bonding layer and arranging the organic film on the other side of the conductive metal sheet, the conductive metal sheet can be effectively protected from oxidation and pollution, and the electrical performance and long-term stability of the composite bonding sheet can be improved.

[0114] S403: After the conductive paste is coated on the high-temperature-resistant film, drying treatment is performed to obtain a whole sintered sheet;

[0115] During coating, the conductive paste is first coated on the high-temperature-resistant film, and then the conductive paste is spread and leveled on the surface of the high-temperature-resistant film based on the movement of the coating tool on the high-temperature-resistant film, to form a uniform and continuous wet film.

[0116] Reference Figure 6The cross-sectional shape of the coating tool is roughly an inverted "concave" character. The side surface of the coating tool facing the surface 200 of the carrier to be coated is a flat surface, and a coating groove is recessed on the surface. The coating groove is a rectangular groove open in the coating direction parallel to the surface 200.

[0117] For example, the coating speed during coating is 15 mm / s-50 mm / s, and the depth D of the coating groove is 100 μm-200 μm. By reasonably setting the depth of the coating groove and the coating speed, the sintered layer thickness uniformity and the slurry coating quality can be controlled, and the process repeatability and product consistency can be improved. Moreover, compared with the forming by means of dispensing, printing or spraying, the silver paste dispensed out is difficult to be flat, the doctor blade of the printing method is easy to deform, resulting in an uneven coating, and the coating by the spraying method is too thin. In the present application, the conductive paste is coated on the high-temperature-resistant film by the coating method, so that the conductive paste is uniformly distributed, and uneven distribution is avoided.

[0118] The conductive paste is silver paste, also known as silver paste. For example, the silver paste uses silver particles with a diameter of 0.2 μm-10 μm. Correspondingly, the sintered layer to be prepared is a silver sintered layer.

[0119] For example, the high-temperature-resistant film can be a PET film, and can also be a PI, PTFE, FEP or the like.

[0120] In some embodiments, the drying treatment includes: first drying at 80℃-100℃ for 5 min-20 min to realize solvent volatilization; and then drying at 120℃-160℃ for 5 min-20 min to cause the silver particles in the silver paste to be pre-sintered, facilitating subsequent silver sintering.

[0121] S405: cutting a whole piece of conductive metal sheet into multiple pieces of conductive metal sheet according to the size of the large-area composite substrate;

[0122] S407: cutting a whole piece of sintered sheet into multiple pieces of sintered sheet according to the size of the large-area composite substrate;

[0123] S409: hot pressing a single piece of sintered sheet on a single piece of conductive metal sheet, and removing the high-temperature-resistant film to form a sintered layer.

[0124] If the conductive metal sheet and the sintered sheet are too large, the hot pressing effect will be affected. Therefore, in the present embodiment, the pieces are cut and then hot pressed, so as to guarantee the hot pressing effect and make the sintered sheet tightly combined with the conductive metal sheet.

[0125] In the present embodiment, the conductive paste is pre-formed and then compounded on the conductive metal sheet, so that the process operation is flexible, the sintered layer thickness uniformity is better, the product quality is stable, and the conductive performance is excellent.

[0126] Reference Figure 5 In some embodiments, a large-area composite substrate is provided, comprising:

[0127] S401: A metal film is arranged on one side of the conductive metal sheet combined with the bonding layer, and an organic film is arranged on the other side of the conductive metal sheet.

[0128] S501: The conductive paste is coated on the conductive metal sheet for drying treatment, and the dried conductive paste forms a sintering layer.

[0129] For example, the coating speed during coating is 15-50 mm / s. During coating, it is realized based on a coating tool. For details, refer to the part of step S501, which will not be repeated here.

[0130] In some embodiments, the drying treatment includes: first drying at 80-100℃ for 5-20 min to realize solvent volatilization; and then drying at 120-160℃ for 5-20 min for pre-sintering of silver particles in the silver paste, facilitating subsequent silver sintering.

[0131] In this way, since the conductive paste is directly coated on the conductive metal sheet to form a sintering layer, the process is simple and efficient, reducing the process and cost, and being suitable for large-scale batch production.

[0132] In some embodiments, the conductive metal sheet 41 is a copper foil, and the bonding layer 42 is a silver sintering layer. Figure 8 Based on the same technical concept, the embodiments of the present application also provide a composite bonding sheet 4 for chip bonding, which is prepared by the preparation method of the present application and comprises a conductive metal sheet 41 and a bonding layer 42.

[0133] In some embodiments, the conductive metal sheet 41 is a copper foil, and the bonding layer 42 is a silver sintering layer.

[0134] The bonding layer 42 is provided with a plurality of glue points 45. The glue points 45 can not only position the composite bonding sheet on the carrier film during transportation, but also realize preliminary positioning and temporary fixing with the chip before the bonding layer 42 is sintered and fixed with the chip.

[0135] The composite bonding sheet of the embodiments of the present application can realize front surface interconnection of the chip and can be compatible with ultrasonic bonding of copper wires with a wire diameter of 300-400 μm. Compared with aluminum wires, copper has good mechanical properties, electrical conductivity and reliability, and can realize higher current density and longer service life.

[0136] Reference Figure 9 In some embodiments, a metal film 44 is arranged on one side (lower surface) of the conductive metal sheet 41 combined with the bonding layer 42, and an organic film 43 is arranged on the other side (upper surface) of the conductive metal sheet 41, avoiding oxidation of the copper foil.

[0137] It can be understood that, Figure 8 , 9 Only the relative position relationship of each layer structure in the stacking direction is shown, and does not have any dimensional meaning.

[0138] More details can be referred to the foregoing embodiments, which will not be repeated here.

[0139] The scheme of the present application can be applied to the packaging of various semiconductor devices, such as SiC module and IGBT module packaging applications. In a third aspect, based on the same technical concept, the embodiments of the present application also provide a semiconductor packaging method, comprising:

[0140] The composite bonding sheet prepared based on the preparation method of the present embodiment is positioned and placed on the chip, and the bonding layer is in contact with the chip;

[0141] The bonding layer and the chip are combined and fixed by sintering.

[0142] More details can be referred to the foregoing embodiments, which will not be repeated here.

[0143] In a fourth aspect, referring to Figure 10 , based on the same technical concept, the embodiments of the present application also provide a semiconductor packaging structure, comprising: a substrate 7, a chip 5, and a composite bonding sheet 4 prepared based on the preparation method of the present embodiment.

[0144] The substrate 7 is a carrier material or structure for supporting the chip, realizing the electrical connection of the chip with the external circuit, and providing a heat dissipation channel. Common types of substrates: lead frame, ceramic substrate, organic substrate, metal substrate, etc. In some embodiments, the ceramic substrate is selected as the substrate, specifically the Direct Bonded Copper (DBC substrate).

[0145] The chip 5 can be an IGBT, SiC module, etc., which is arranged on the substrate, and the substrate is also provided with an external conductive structure for electrical connection with the chip. The side of the chip facing away from the substrate provides a bonding surface. The bonding surface is the functional surface of the chip for mounting the composite bonding sheet, and the size and shape of the bonding surface and the size and shape of the composite bonding sheet are designed according to the specific application scenario of the chip.

[0146] The composite bonding sheet 4, wherein the bonding layer 42 is combined with the side surface of the chip 5 facing away from the substrate 7, and the conductive metal sheet 41 is electrically connected to the external conductive structure 6 through the metal wire 8. In some embodiments, the conductive metal sheet 41 in the composite bonding sheet 4 is a copper foil, the bonding layer 42 in the composite bonding sheet 4 is a silver sintering layer, and the metal wire 8 is a copper wire.

[0147] The application scenario of the present application is not limited, and the external conductive structure is determined according to the packaging architecture and application scenario requirements.

[0148] For example, the external conductive structure 6 can be a lead frame. For example, the composite bonding sheet 4 and the copper wire of the present application are used to connect the chip with the lead frame to realize the current transmission through the electrode or pin.

[0149] For example, the external conductive structure 6 can be an external electrode or terminal of the chip 5. For example, the composite bonding sheet 4 and the copper wire of the present application are used to directly connect the chip to the external electrode or terminal on the package shell, so as to realize the electrical connection between the chip and the external circuit or the printed circuit board (PCB).

[0150] For example, the external conductive structure 6 can be a printed circuit board (PCB) pad or substrate electrode. For example, in some power semiconductor packages, the composite bonding sheet 4 and the copper wire of the present application are used to directly connect the chip 5 with the PCB pad or the electrode on the ceramic or metal substrate, to provide an efficient current path and good heat dissipation performance.

[0151] For example, the external conductive structure 6 can be other chips or semiconductor elements. In a multi-chip or modular packaging structure, the composite bonding sheet 4 and the copper wire of the present application can also realize the electrical connection between the chip and other chips, between the chip and the power module.

[0152] More details can be referred to the foregoing embodiments, which will not be repeated here.

[0153] It can be understood that the application field of the present application includes but is not limited to the fields of automotive electronics, power electronics, industrial frequency converters, power modules, rail transit or new energy, etc.

[0154] It should be noted that the description order of the embodiments of the present application is not limited as the priority order of the embodiments. In this text, the phrase "embodiments" means that the specific features, structures or characteristics described in combination with the embodiments can be contained in at least one embodiment of the present application. The appearance of this phrase in the specification does not necessarily mean the same embodiment, nor is it an independent or alternative embodiment that is not mutually exclusive with other embodiments. The skilled person in the art explicitly and implicitly understands that the embodiments described herein can be combined with other embodiments.

[0155] 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 in the specification of the present application is only for the purpose of describing specific embodiments and is not intended to limit the present application.

[0156] It should be noted that the "connection" or "connection" described in the present application includes not only the direct connection of two entities, but also the indirect connection through other entities with beneficial improvement effect.

[0157] The embodiments of the present application are described above in conjunction with the drawings, but the present application is not limited to the specific embodiments described above, which are only illustrative but not restrictive. Those skilled in the art can make many forms without departing from the purpose of the present application and the scope protected by the claims under the inspiration of the present application. Any equivalent transformation made by using the content of the present application specification and drawings, or direct / indirect application in other related technical fields is included in the patent protection scope of the present application.

Claims

1. A method for preparing a composite bonding sheet for chip bonding, characterized in that: The method comprises: Providing a large-area composite substrate, the large-area composite substrate comprising stacked conductive metal sheets and a bonding layer for bonding with a chip; Incompletely cutting the large-area composite substrate according to the outline of the composite bonding sheet to form a cutting line interrupted by at least one connection point, wherein the cutting line encloses an area corresponding to a single composite bonding sheet, and the composite bonding sheet remains connected to the remaining portion of the large-area composite substrate through the connection point; The connection points are cut so that the composite bonding sheet is completely separated from the large-area composite substrate and falls off by its own gravity.

2. The method according to claim 1, characterized in that The incomplete cutting is achieved based on a first cutting method; and the cutting of the connection points is achieved based on a second cutting method that is different from the first cutting method.

3. The method according to claim 2, characterized in that The first cutting method is a punching method, and the second cutting method is a laser cutting method.

4. The method according to any one of claims 1 to 3, characterized in that The connection point is located in a corner area and / or an edge midpoint area of ​​the composite bonding sheet outline.

5. The method according to any one of claims 1 to 4, characterized in that The number of the connection points is 2-4.

6. The method according to any one of claims 1 to 5, characterized in that The cutting of the connection point is achieved based on laser cutting; the length of the connection point on the outline of the composite bonding sheet is less than 1 / 50 of the length of the outline of the composite bonding sheet and greater than 2 times the diameter of the laser cutting focal spot.

7. The preparation method according to any one of claims 1 to 6, characterized in that The connection point is formed by the local clearance structure of the punching die.

8. The preparation method according to any one of claims 1 to 7, characterized in that The method further comprises: dispensing glue on the bonding layer of the cut composite bonding sheet to form at least one adhesive organic polymer glue dot; The glue dots are used for preliminary positioning and temporary fixation when the composite bonding sheet is combined with the chip.

9. The preparation method according to claim 8, characterized in that The method further includes: arranging the plurality of composite bonding sheets on a carrier film based on their respective glue dot arrays for unified transportation.

10. The preparation method according to any one of claims 8 to 9, characterized in that: The dispensing method is pneumatic dispensing or jet dispensing.

11. The preparation method according to any one of claims 8 to 10, characterized in that: The material of the organic polymer glue dots is one or more of polyvinyl chloride, polystyrene, ABS resin, and polyethylene.

12. The preparation method according to any one of claims 1 to 11, characterized in that: The method further includes: providing a metal film on one side of the conductive metal sheet that is bonded to the bonding layer, and providing an organic film on the other side of the conductive metal sheet.

13. The preparation method according to any one of claims 1 to 12, characterized in that: The organic film includes benzotriazole or imidazole organic crystalline base; and / or the metal film is made of a silver single layer or a nickel-silver double layer.

14. The preparation method according to any one of claims 1 to 13, characterized in that: The thickness of the organic film is 5nm-50nm; and / or, The conductive metal sheet has a thickness of 50 μm to 100 μm; and / or, The thickness of the metal film is 0.5 μm-2 μm; and / or, The thickness of the bonding layer is 30 μm-100 μm.

15. The preparation method according to any one of claims 1 to 14, characterized in that: The bonding layer is a sintered layer, and the large-area composite substrate is provided, comprising: The conductive paste is coated on the high temperature resistant film and then dried to obtain a whole sintered sheet; Cutting a plurality of conductive metal sheets from a whole piece of the conductive metal sheet according to the size of the large-area composite substrate; Cutting a whole piece of the sintered sheet into multiple pieces of the sintered sheet according to the size of the large-area composite substrate; The single sintered sheet is hot-pressed onto the single conductive metal sheet, and the high-temperature resistant film is removed to form the sintered layer.

16. The preparation method according to any one of claims 1 to 14, characterized in that: The bonding layer is a sintered layer. The process of providing a large-area composite substrate includes: coating a conductive paste on the conductive metal sheet and performing a drying process, wherein the dried conductive paste forms the sintered layer.

17. The preparation method according to claim 15 or 16, characterized in that: The method comprises: during coating, the coating is achieved based on a coating tool, wherein the coating tool has a coating groove with a depth of 100 μm to 200 μm; and / or, The coating speed during coating is 15 mm / s-50 mm / s.

18. The preparation method according to claim 15 or 16, characterized in that: The conductive metal sheet is copper foil, the conductive paste is silver paste, the sintered layer is a silver sintered layer, and silver particles with a diameter of 0.2 μm-10 μm are used; The drying process includes: firstly baking at 80° C.-100° C. for 5 min-20 min; and then baking at 120° C.-160° C. for 5 min-20 min.

19. A composite bonding sheet for chip bonding, characterized in that: It is prepared based on the preparation method described in claims 1-18, and includes a conductive metal sheet and a bonding layer.

20. The composite bonding sheet according to claim 19, wherein: The conductive metal sheet is copper foil, and the bonding layer is a silver sintered layer.

21. A semiconductor packaging method, characterized in that: include: Positioning the composite bonding sheet prepared by the preparation method according to claims 1 to 18 on the chip, and making the bonding layer contact the chip; The bonding layer and the chip are fixed together by sintering.

22. A semiconductor packaging structure, characterized in that: include: substrate; A chip is provided on the substrate, and the substrate is also provided with an external conductive structure for electrically connecting to the chip; The composite bonding sheet is prepared by the preparation method described in claims 1-18, wherein the bonding layer in the composite bonding sheet is bonded to the surface of the chip facing away from the substrate, and the conductive metal sheet in the composite bonding sheet is electrically connected to the external conductive structure through a metal wire.

23. The semiconductor package structure according to claim 22, wherein: The conductive metal sheet is copper foil, the bonding layer is a silver sintered layer, and the metal wire is a copper wire.

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