Encapsulation method and light-transmissive encapsulation structure

Abstract

This invention discloses a packaging method and a transparent packaging structure. The method involves aligning the first surface of the bare die containing the pads and the upper surface of the lead frame containing the frame pins, forming a redistribution structure to connect the pads and the frame pins. Simultaneously, when an insulating structure fills the area between the lead frame and the bare die, a portion of the photosensitive area is exposed. A transparent dielectric layer is formed above the photosensitive area and the redistribution structure, allowing light to pass through the transparent dielectric layer to reach the exposed photosensitive area. This packaging structure eliminates the need for wire bonding, improving reliability, reducing size, and lowering packaging costs. Furthermore, the absence of a transparent cover plate further enhances structural strength and improves the overall integrity of the packaging structure.

Description

Technical Field

[0001] This invention relates to the field of advanced chip packaging technology, specifically to a packaging method and a light-transmitting packaging structure. Background Technology

[0002] Currently, traditional optical sensors and image sensors typically use a substrate combined with wire bonding to encapsulate bare wafers, and then install a transparent cover or use a transparent molding compound on top of the sensor wafer to achieve light transmission and sealing protection. However, the above structure has some problems, such as poor heat dissipation and reliability of the encapsulation structure, which affects the performance of the sensor chip. In addition, due to the high coefficient of thermal expansion of transparent molding compounds, electrical connections can only be made using gold wire bonding, resulting in high encapsulation costs. Summary of the Invention

[0003] In view of this, embodiments of the present invention provide a packaging method and a light-transmitting packaging structure, which are expected to improve the reliability of the light-transmitting packaging structure while reducing its size and packaging cost.

[0004] In a first aspect, embodiments of the present invention provide a light-transmitting encapsulation structure, the light-transmitting encapsulation structure comprising: A first bare wafer has a first surface, a first portion of which is configured as a photosensitive area, and a second portion of which is configured to include a set of pads; The patterned lead frame includes a set of frame pins, which are disposed on the outside of the first bare die and do not directly contact the first bare die; A rewiring structure electrically couples the pads and the corresponding frame pins; An insulating structure is provided to fill the area between the lead frame and the first bare wafer, and to expose at least a portion of the photosensitive area; A first transparent dielectric layer is located above the lead frame, the redistribution structure, and the first bare wafer, such that light passes through the first transparent dielectric layer to reach the exposed photosensitive area.

[0005] In a second aspect, embodiments of the present invention provide a packaging method for packaging a first bare wafer, wherein a first portion of a first surface of the first bare wafer is configured as a photosensitive area, and a second portion is configured to include a set of pads, the method comprising: A patterned lead frame is provided, the lead frame including a set of frame pins; The first bare wafer is fixed inside the lead frame, exposing the photosensitive area of ​​the first bare wafer; A redistribution structure is formed between the pads of the first bare die and the frame pins to electrically couple the pads and the corresponding frame pins. A first transparent dielectric layer is formed, which covers the redistribution structure and the first bare wafer, so that light passes through the transparent dielectric layer to reach the exposed photosensitive area.

[0006] The packaging method and transparent packaging structure of this invention fix the first surface of the bare die containing the pads and the upper surface of the lead frame containing the frame pins in the same direction, and form a redistribution structure on the upper surfaces of the pads and the frame pins to connect the pads and the frame pins. Simultaneously, when the area between the lead frame and the bare die is filled with an insulating structure, a portion of the photosensitive area is exposed. A transparent dielectric layer is formed above the photosensitive area and the redistribution structure, allowing light to pass through the transparent dielectric layer to reach the exposed photosensitive area. This packaging structure eliminates the need for wire bonding, improving reliability, reducing size, and lowering packaging costs. Furthermore, the absence of a transparent cover plate further enhances structural strength and improves the overall integrity of the packaging structure. Attached Figure Description

[0007] The above and other objects, features and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings, in which: Figure 1 This is a schematic diagram of a light-transmitting encapsulation structure in the prior art; Figure 2 This is a schematic diagram of another transparent encapsulation structure in the prior art; Figure 3 This is a schematic diagram of another transparent encapsulation structure in the prior art; Figure 4 This is a schematic diagram of another transparent encapsulation structure in the prior art; Figure 5 This is a flowchart of the encapsulation method of the first embodiment of the present invention; Figure 6 These are cross-sectional views of the packaging structure at different steps in the packaging method of the first embodiment of the present invention; Figure 7 This is a cross-sectional view of the light-transmitting encapsulation structure according to the first embodiment of the present invention; Figure 8 This is a flowchart of the packaging method according to the second embodiment of the present invention; Figure 9 These are cross-sectional views of the packaging structures at different steps in the packaging method of the second embodiment of the present invention; Figure 10 This is a cross-sectional view of the light-transmitting encapsulation structure according to the second embodiment of the present invention; Figure 11 This is a flowchart of the packaging method according to the third embodiment of the present invention; Figure 12 These are cross-sectional views of the packaging structures at different steps in the packaging method of the third embodiment of the present invention; Figure 13 This is a cross-sectional view of the light-transmitting encapsulation structure according to the third embodiment of the present invention; Figure 14 This is a cross-sectional view of the light-transmitting encapsulation structure according to the fourth embodiment of the present invention; Figure 15 This is a cross-sectional view of the light-transmitting encapsulation structure according to the fifth embodiment of the present invention. Detailed Implementation

[0008] The present invention is described below based on embodiments, but the invention is not limited to these embodiments. In the detailed description of the invention below, certain specific details are described in detail. Those skilled in the art will fully understand the invention even without these details. To avoid obscuring the essence of the invention, well-known methods, processes, flows, elements, and circuits are not described in detail.

[0009] Furthermore, those skilled in the art should understand that the accompanying drawings provided herein are for illustrative purposes only and are not necessarily drawn to scale.

[0010] Furthermore, it should be understood that in the following description, "circuit" refers to a conductive loop consisting of at least one element or sub-circuit connected by electrical or electromagnetic connections. When an element or circuit is said to be "connected" to another element or "connected" between two nodes, it can be directly coupled or connected to another element, or there may be intermediate elements. The connection between elements can be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected" to another element, it means that there are no intermediate elements between them.

[0011] In the description of this invention, it should be understood that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0012] Figure 1 This is a schematic diagram of a light-transmitting encapsulation structure in existing technology. For example... Figure 1 As shown, the prior art transparent packaging structure includes a substrate 11 and a bare die 12 with a photosensitive area. The bare die 12 is fixed to the substrate 11 by conductive adhesive or insulating adhesive 13. The pads of the bare die 12 are electrically connected to the pads or pins on the substrate 11 by bonding wires 14. The bare die 12 and the partially exposed substrate 11 are covered by a transparent molding compound 15. Because the transparent molding compound 15 has a large coefficient of thermal expansion, it limits the type of material for wire bonding, resulting in higher packaging costs.

[0013] Figure 2This is a schematic diagram of another transparent encapsulation structure in the prior art. For example... Figure 2 As shown, the prior art transparent packaging structure includes a substrate 21 and a bare die 22 with a photosensitive area. The bare die 22 is fixed to the substrate 21 by conductive adhesive or insulating adhesive 23. The pads of the bare die 22 are electrically connected to the pads or pins on the substrate 21 by bonding wires 24. A transparent glass cover plate 25 is placed on the photosensitive area of ​​the bare die 22. The other areas of the bare die, the bonding wires, and the exposed portion of the substrate 21 are covered by an opaque molding compound 26. Figure 2 The transparent encapsulation structure shown can solve the problem caused by the thermal expansion coefficient of the transparent molding compound. However, the processing and assembly of the transparent glass cover, as well as the flatness of the product surface, require fine adjustment, resulting in complex processes, low product yield, and high encapsulation costs.

[0014] Figure 3 This is a schematic diagram of another transparent encapsulation structure in the prior art. For example... Figure 3 As shown, the prior art transparent packaging structure includes a substrate 31 and a bare die 32 with a photosensitive area. The bare die 32 is fixed to the substrate 31 by conductive adhesive or insulating adhesive 33. The pads of the bare die 32 are electrically connected to the pads or pins on the substrate 31 by bonding wires 34. The bare die 32 and the partially exposed substrate 31 are covered by a transparent molding compound 35. A light-shielding layer 36 made of black molding compound or light-shielding adhesive is formed on the edges of the sides and top surface of the transparent molding compound 35. This transparent packaging structure is relative to... Figure 1 It can avoid the negative impact of side light on the photosensitive chip; however, the packaging process is complex and the problem of the large thermal expansion coefficient of transparent molding compound cannot be overcome.

[0015] Figure 4 This is a schematic diagram of another transparent encapsulation structure in the prior art. For example... Figure 4 As shown, the prior art transparent packaging structure includes a substrate 41, a bare die 42 with a photosensitive area, and a transparent carrier plate 43. Solder balls 41a for external connections are formed on the underside of the substrate 41, and a redistribution layer 41b is formed inside the substrate 41. The photosensitive area and solder pads of the bare die 42 face the transparent carrier plate 43. The bare die 42 is connected to the redistribution layer 41b in the substrate 41 through a connection structure including conductive pillars 44, a redistribution layer 43a formed on the transparent carrier plate 43, and conductive pillars 45, thereby forming an electrical connection from the bare die 42 to the solder balls 41a. The entire area containing the connection structure is encapsulated by a packaging material 46, and light transmission is achieved by covering it with the transparent carrier plate 43. Figure 4 The transparent packaging structure shown requires the fabrication of a wafer-level transparent substrate. Additionally, two redistribution layers need to be fabricated inside the substrate and on the transparent substrate, resulting in a complex and costly process.

[0016] In view of this, embodiments of the present invention propose a packaging method for packaging a bare wafer with a photosensitive area to form a light-transmitting packaging structure, thereby solving many problems related to the size of the photosensitive sensor product, packaging process, packaging cost, etc.

[0017] Figure 5 This is a flowchart of the encapsulation method according to the first embodiment of the present invention. Figure 6 This is a cross-sectional schematic diagram of the encapsulation structure at different steps in the encapsulation method of the first embodiment of the present invention. For example... Figure 5 and Figure 6 As shown, the packaging method of this embodiment includes the following steps: In step S510, a patterned lead frame is provided, the lead frame including a set of frame pins.

[0018] In an embodiment, such as Figure 6 As shown in step S510, the bare die to be packaged includes at least a first bare die 61 with a photosensitive surface. The first bare die 61 has a first surface 61a. A portion of the first surface 61a is configured as a photosensitive area 61b for receiving visible or invisible light from the outside, thus achieving light sensing. Simultaneously, a set of pads 61c is configured on the first surface 61a that does not overlap with the photosensitive area 61b. The pads 61c are used to establish electrical connections between the photosensitive area 61b and other circuits in the first bare die 61 and external circuits.

[0019] The lead frame plays a crucial triple role in integrated circuit (IC) packaging, providing mechanical support, electrical connection, and heat dissipation channels. In this embodiment, the lead frame 62 includes a set of frame pins 62a for connection to pads. The lead frame 62a also includes a receiving space 62b for placing a first bare die 61 and an opening 62c on one side of the receiving space 62b. In this embodiment, the frame pins 62a of the lead frame 62 are disposed on planes on both sides of the opening 62c. Since the frame pins 62a are not necessarily planar, they may extend to different surfaces in space depending on the design requirements of the lead frame. However, in this embodiment, the frame pins 62a have an upper surface that is the surface of the lead frame after packaging, facing the same direction as the photosensitive area 61b of the first bare die 61. This surface is subsequently used for connection to a redistribution structure, achieving low-cost, high-reliability pad-frame pin electrical coupling.

[0020] In this embodiment, multiple lead frames 62 are attached to the surface of the frame pins 62a for connection with the pads 61c (also referred to as the upper surface) on the surface of the surface tape or carrier 63, thereby forming a surface at the opening 62c that can fix the first bare die 61 or other bare dies in the same package.

[0021] In step S520, the first bare wafer is fixed inside the lead frame, exposing the photosensitive area of ​​the first bare wafer.

[0022] The purpose of this step is to fix the first bare die 61 and the lead frame 62 relative to each other so as to facilitate the subsequent connection of the pads 61c and the frame pins 62a.

[0023] In this embodiment, step S520 includes the following steps: In step S521, the first surface 61a of the first bare wafer 61 is attached to the patch tape or carrier plate 63 on the inner side region of the lead frame 62.

[0024] like Figure 6 As shown in step S521, after the first surface 61a of the first bare wafer 61 is adhered to the patch tape or carrier 63 on the inner region of the lead frame 62, the first surface 61a is fixed to be substantially coplanar with the upper surface of the frame pin 62a. Simultaneously, a gap exists between the first bare wafer 61 and the lead frame 62.

[0025] In step S522, insulating material is filled between the first bare wafer 61 and the lead frame 62 to form an insulating structure 64.

[0026] The insulating structure 64 serves two purposes: firstly, it relatively fixes the first bare wafer 61 and the lead frame 62; secondly, it provides insulation between the two. Simultaneously, the insulating structure 64 can also shield the first bare wafer 61 from the negative impact of side-transmitted light. In one alternative implementation, the insulating material can be an opaque material, such as a black epoxy molding compound or a black epoxy thermosetting film. In another alternative implementation, the insulating material can also be a translucent material, such as polyvinylimide (PVI) or an epoxy thermosetting composite film.

[0027] like Figure 6 As shown in step S522, after filling with insulating material, the insulating material forming surface is flush with or slightly higher than the back surface of the lead frame. If it is slightly higher than the back surface of the lead frame, the protruding portion of the insulating structure can be removed or thinned after step S522 or S523, exposing the back surface of the lead frame. The back surface of the lead frame is opposite to the upper surface of the lead frame, and the back surface of the lead frame is also the back surface of the frame pins. The upper surface of the lead frame is also the upper surface of the frame pins.

[0028] In step S523, the patch tape or carrier 63 is removed to expose the photosensitive area 61b of the first bare wafer 61.

[0029] Specifically, such as Figure 6As shown in step S523, the transparent packaging structure is also flipped. Since the upper surfaces of the first surface 61a and the frame pins 62a are both adhered to the surface mount tape or carrier 63, the insulating material will not overflow from the first surface 61a or the upper surface of the frame pins 62a during the filling process. Therefore, by simply removing the surface mount tape or carrier 63, a relatively flat surface formed by the first surface 61a, the upper surface of the lead frame 62, and the surface of the filled insulating structure 64 can be obtained. The photosensitive area 61b and the pad 61c of the first bare die 61 are located on this surface. The insulating structure 64 fixes the first bare die 61 and the lead frame 62 relatively, such that the first surface 61a and the upper surface of the lead frame 62 are substantially coplanar. In the description herein, substantially coplanar means that two planes are coplanar within the allowable error range of engineering.

[0030] In step S530, a redistribution structure 65 is formed between the pad 61c and the frame pin 62a of the first bare die 61 to electrically couple the pad 61c and the corresponding frame pin 62a.

[0031] Redistribution layers (RDLs) are a core technology in advanced packaging, designed to address the challenge of densely spaced internal pads that prevent direct external interconnection after chip miniaturization. Utilizing thin-film processes similar to those used in semiconductor front-end development, RDLs deposit dielectric layers and construct multi-layered metal circuitry on the chip surface or reconstructed wafer. This "fans out" and rearranges the previously dense or space-constrained I / O pads to wider spacing suitable for external soldering. RDLs not only achieve spacing transformation and layout optimization but also significantly reduce signal latency and improve high-frequency performance.

[0032] In this embodiment, as Figure 6 As shown in step S530, based on the coplanar pads 61c and frame pins 62a, a redistribution structure 65 can replace the bonding wires in the prior art, forming an electrical coupling between the pads 61c and frame pins 62a. Since the redistribution structure 65 is in close contact with the first surface 61a and the upper surface of the lead frame 62, the package size can be reduced. Simultaneously, the redistribution structure 65 is more robust than bonding wires and will not be damaged by the thermal expansion coefficient of the encapsulating packaging material. Using a redistribution layer (RDL) to connect the pads and frame pins further reduces the connection path length for external electrical connections to the bare die, resulting in shorter signal paths and better performance. Furthermore, since there is no wire bonding, the product's reliability is improved.

[0033] Meanwhile, since the pads 61c are usually formed on the edge of the first surface 61a or on both sides or around the photosensitive area, surrounding the photosensitive area 61b, the formed redistribution structure 65 will not block the photosensitive area 61b.

[0034] Specifically, the rewiring structure 65 may include multiple rectangular structures extending in the horizontal direction, with one end of the rectangular structure connected to the pad 61c and the other end connected to the upper surface of the frame pin 62a.

[0035] In step S540, a first transparent dielectric layer 66 is formed. The first transparent dielectric layer 66 covers the redistribution structure 65 and the first bare wafer 61, so that light passes through the transparent dielectric layer 66 to reach the exposed photosensitive area 61b.

[0036] In step S550, the first transparent dielectric layer 66 is exposed and developed to expose the cutting area of ​​the lead frame, and the lead frame is cut to obtain a discrete light-transmitting encapsulation structure.

[0037] In one alternative implementation, the first transparent dielectric layer 66 is made of polyimide. This results in a packaging structure with numerous advantages over existing technologies, such as... Figure 7 As shown.

[0038] Figure 7 This is a cross-sectional view of the light-transmitting encapsulation structure according to the first embodiment of the present invention. Figure 7 As shown, the light-transmitting packaging structure of this embodiment includes a first bare die 61, a patterned lead frame 62, a redistribution structure 65, an insulating structure 64, and a first transparent dielectric layer 66. The first bare die 61 has a first surface 61a. A first portion of the first surface 61a is configured as a photosensitive area 61b, and a second portion is configured to include a set of pads 61c.

[0039] The patterned lead frame 62 includes a set of frame pins 62a. The frame pins 62a are positioned outside the first bare die 61 and do not directly contact it. A redistribution structure 65 electrically couples the pads 61c and the upper surfaces of the corresponding frame pins 62a. An insulating structure 64 fills the area between the lead frame 62 and the first bare die 61, exposing at least a portion of the photosensitive area 61b. A first transparent dielectric layer 66 is located above the lead frame 62, the redistribution structure 65, and the first bare die 61, allowing light to pass through the first transparent dielectric layer 66 to reach the exposed photosensitive area 61b.

[0040] In this embodiment, the first surface 61a and the upper surface of the frame pin are substantially coplanar. Furthermore, the redistribution structure 65 is configured as a horizontally placed rectangular structure and is connected to the upper surfaces of the pad 61c and the frame pin 62a, respectively.

[0041] In this embodiment of the packaging structure, the first surface where the pads of the first bare die are located and the upper surface where the frame pins of the lead frame are located face the same direction, forming a redistribution structure to connect the pads and the frame pins. Simultaneously, when the area between the lead frame and the first bare die is filled with an insulating structure, a portion of the photosensitive area is exposed. A transparent dielectric layer is formed above the photosensitive area and the redistribution structure, allowing light to pass through the transparent dielectric layer to reach the exposed photosensitive area. This packaging structure eliminates the need for wire bonding, improving reliability, reducing size, and lowering packaging costs. Furthermore, the absence of a transparent cover plate further enhances structural strength and improves the overall integrity of the packaging structure.

[0042] Meanwhile, the first bare die and pins are distributed on both sides of the lead frame. The first surface of the first bare die is filled with a first transparent dielectric layer, eliminating the need for a transparent carrier or substrate window design, making the application scenarios of the packaged sensor more flexible. Furthermore, the first bare die is located inside the lead frame, with an insulating structure filling the area between the lead frame and the bare die, while exposing part of the photosensitive area. This blocks lateral light from entering the photosensitive area of ​​the chip, eliminating the need for additional side-shielding structures and simplifying the process. Moreover, the photosensitive surface of the first bare die is no longer encapsulated with molding compound, improving front-side light sensing capability while ensuring product reliability is not limited by molding compound. This simplifies the complexity of the packaging process and reduces packaging costs.

[0043] Figure 8 This is a flowchart of the encapsulation method according to the second embodiment of the present invention. Figure 9 This is a cross-sectional schematic diagram of the packaging structure at different steps in the packaging method of the second embodiment of the present invention. For example... Figure 8 and Figure 9 As shown, the encapsulation method in this embodiment includes the following steps: In step S810, a patterned lead frame is provided, the lead frame including a set of frame pins.

[0044] In this embodiment, multiple lead frames 92 are attached to the surface of the frame pins 92a (also referred to as the upper surface) by means of adhesive tape or carrier board 93, thereby forming a surface at the opening 92c that can fix the first bare die 91 or other bare dies in a common package.

[0045] In step S820, the first surface 91a of the first bare wafer 91 is attached to the patch tape or carrier plate 93 on the inner side region of the lead frame 92.

[0046] In step S830, insulating material is filled between the first bare wafer 91 and the lead frame 92 to form an insulating structure 94.

[0047] In step S840, the patch tape or carrier 93 is removed to expose the photosensitive area 91b and pad 91c of the first bare wafer 91.

[0048] Specifically, step S840 further includes flipping the light-transmitting packaging structure. Since the first surface 91a and the upper surface where the frame pins 92a are located are both adhered to the patch tape or carrier plate 93, the insulating material will not overflow from the first surface 91a or the upper surface of the lead frame 92 during the filling process. Therefore, by simply removing the patch tape or carrier plate 93, a relatively flat surface formed by the first surface 91a, the upper surface of the lead frame 92, and the surface of the filled insulating structure 94 can be obtained. The photosensitive area 91b and the pad 91c of the first bare die 91 are located on this surface. That is, the insulating structure 94 fixes the first bare die 91 and the lead frame 92 relatively, making the first surface 91a and the upper surface of the lead frame 92 substantially coplanar.

[0049] In step S850, a second transparent dielectric layer 95 is formed on the upper surface of the photosensitive area 91b and the lead frame, covering the photosensitive area 91b and the upper surface.

[0050] In step S860, the second transparent dielectric layer 95 is removed from the pads 91b of the first surface 91a and at least a portion of the upper surfaces of each of the frame pins 92a to expose the pads 91b of the first surface 91a and at least a portion of the upper surfaces of each of the frame pins 92a.

[0051] In one alternative implementation, the material of the second transparent dielectric layer is polyimide, and more specifically, photosensitive polyimide (PSPI). Thus, a portion of the second transparent dielectric layer can be removed by exposure and development.

[0052] Specifically, for steps S850-S860, an exemplary process includes firstly, coating and pre-baking: liquid photosensitive polyimide is spin-coated onto the surface of the photosensitive surface, and then baked at 80-120°C to remove the solvent, forming a solid film. At this time, the photosensitive groups in the material (such as diazonaphthoquinone (DNQ) for positive adhesives, or acrylates for negative adhesives) are in an unreacted state. Then, in step S860, exposure is performed, i.e., ultraviolet light (UV) is used to irradiate the film through a photomask. If a positive photosensitive polyimide is used, the photosensitizer in the exposed area undergoes a photodecomposition reaction, generating polar groups such as carboxylic acids, making the polyimide precursor in that area soluble in an alkaline developer. If a negative photosensitive polyimide is used, the exposed area undergoes a photocrosslinking reaction, the molecular chains form a network structure, and become insoluble; while the unexposed area remains soluble. To "remove" a specific patterned area, positive adhesives remove the exposed area, and negative adhesives remove the unexposed area. Next, after exposure, development is performed by immersing the exposed wafer in a developing solution. Positive processes typically use a weakly alkaline aqueous solution (such as dilute tetramethylammonium hydroxide, TMAH) as the developing solution. The exposed areas dissolve rapidly due to increased polarity, while the unexposed areas remain, thus "removing" the polyimide layer from the exposed areas and exposing the underlying substrate. Negative processes typically use organic solvents (such as butyl acetate or propylene glycol methyl ether acetate, PGMEA) as the developing solution. The unexposed areas are dissolved and removed, while the exposed cross-linked areas remain. After development, the wafer is usually rinsed with deionized water and dried, and finally cured at high temperature (250-350℃) to completely imidize the remaining polyimide, forming a stable insulating pattern. The entire process utilizes the property of light energy to alter the chemical structure of polymers, achieving precise pattern removal without physical etching.

[0053] In step S870, a redistribution structure 96 is formed between the pad 91c and the frame pin 92a of the first bare die 91 to electrically couple the upper surfaces of the pad 91c and the corresponding frame pin 92a.

[0054] After forming the pattern on the upper surface of the exposed pad 91c and frame pin 92a through steps S850-S860, a horizontally extending rectangular structure is fabricated to electrically connect the pad 91c and the corresponding frame pin 92a. Optionally, since the second transparent dielectric layer 95 has a certain thickness, the redistribution structure 96 may include not only the horizontal rectangular structure but also a vertically located bump structure connected to the rectangular structure. The bump structure is connected to the pad 91c and the horizontal rectangular structure, or the bump structure is connected to the frame pin 92a and the horizontal rectangular structure.

[0055] In step S880, a first transparent dielectric layer 97 is formed. The first transparent dielectric layer 97 covers the redistribution structure 96 and the first bare wafer 91, so that light passes through the first transparent dielectric layer 97 and the second transparent dielectric layer 95 to reach the exposed photosensitive area 91b.

[0056] In one alternative implementation, the first transparent dielectric layer 97 and the second transparent dielectric layer 95 are made of the same material, namely polyimide.

[0057] In subsequent steps, the first and second transparent dielectric layers can be exposed and developed to remove the cut areas of adjacent parts of different lead frames, thereby obtaining discrete transparent encapsulation structures through cutting.

[0058] In this embodiment, the thickness of the second transparent dielectric layer 95 is less than the thickness of the first transparent dielectric layer 97. Increasing the thickness of the second transparent dielectric layer 95 improves the connection performance between the thicker first transparent dielectric layer 97 and the underlying layer, preventing peeling defects and improving packaging reliability. Simultaneously, the second transparent dielectric layer 95 protects the photosensitive area during the fabrication of the rewiring structure, improving yield.

[0059] Figure 10 This is a cross-sectional view of the light-transmitting encapsulation structure according to the second embodiment of the present invention. Figure 10 As shown, the light-transmitting packaging structure of this embodiment includes a first bare die 91, a patterned lead frame 92, a redistribution structure 96, an insulating structure 94, a second transparent dielectric layer 95, and a first transparent dielectric layer 97. The first bare die 91 has a first surface 91a. A first portion of the first surface 91a is configured as a photosensitive area 91b, and a second portion is configured to include a set of pads 91c.

[0060] The patterned lead frame 92 includes a set of frame pins 92a. The frame pins 92a are positioned outside the first bare die 91 and do not directly contact the first bare die 91. A redistribution structure 96 electrically couples the pads 91c and the corresponding frame pins 92a. An insulating structure 94 fills the area between the lead frame 92 and the first bare die 91, exposing at least a portion of the photosensitive area 91b. A second transparent dielectric layer 95 covers the photosensitive area 91b and the upper surfaces of the frame pins 92a, exposing at least a portion of the upper surfaces of the pads 91c and each of the frame pins 92a. The redistribution structure 96 includes horizontally oriented rectangular structures formed on the second transparent dielectric layer 95. A first transparent dielectric layer 97 is located above the second transparent dielectric layer 95 and the redistribution structure 96, allowing light to pass through the first transparent dielectric layer 97 and the second transparent dielectric layer 95 to reach the exposed photosensitive area 91b.

[0061] In this embodiment, the first surface 91a and the upper surface of the frame pin are substantially coplanar. Furthermore, the redistribution structure 96 is configured to connect to the upper surfaces of the pad 91c and the frame pin 92a.

[0062] In this embodiment, the thickness of the second transparent dielectric layer 95 is less than the thickness of the first transparent dielectric layer 97. Increasing the thickness of the second transparent dielectric layer 95 improves the connection performance between the thicker first transparent dielectric layer 97 and the underlying layer, preventing peeling defects and improving packaging reliability. Simultaneously, the second transparent dielectric layer 95 protects the photosensitive area during the fabrication of the rewiring structure, improving yield.

[0063] Figure 11 This is a flowchart of the packaging method according to the third embodiment of the present invention; Figure 12 This is a cross-sectional schematic diagram of the packaging structure at different steps in the packaging method of the third embodiment of the present invention. For example... Figure 11 and Figure 12 As shown, the encapsulation method in this embodiment includes the following steps: In step S1110, a patterned lead frame is provided, the lead frame including a set of frame pins.

[0064] In this embodiment, the back surface of each lead frame 122, that is, the surface opposite to the opening 122c of the lead frame for exposing the photosensitive area, which is also the surface opposite to the upper surface of the frame pin 122a, is adhered to the surface-mount tape or carrier 123. The opening 122c of the lead frame 122 is placed upwards, and its opposite surface is adhered and fixed. The exposed area on the back surface of the lead frame 122 forms the surface of the tape or carrier for fixing the first bare die 61 or other co-packaged bare dies.

[0065] In step S1120, the second surface 121d of the first bare wafer 121 is adhered to the patch tape or carrier plate 123 on the inner region of the lead frame 122. The second surface 121d is the surface opposite to the first surface 121a of the first bare wafer 121.

[0066] After the second surface 121d of the first bare wafer 121 is attached to the patch tape or carrier 123 on the inner region of the lead frame 122, the second surface 121d is fixed substantially coplanar with the back surface of the frame pin 122a. Since the height of the first bare wafer 121 is less than the height of the lead frame 122a, the first surface 121a of the first bare wafer 121 is lower than the upper surface of the frame pin 122a.

[0067] In step S1130, insulating material is filled between the first bare wafer 121 and the lead frame 122 to form an insulating structure 124.

[0068] In this embodiment, the insulating material is a polyvinylimide (PVI) or epoxy-based thermosetting composite film. Since the insulating material is semi-transparent, the photosensitive area of ​​the first bare wafer can be exposed in subsequent exposure and development steps.

[0069] After the insulating structure 124 is filled and formed, the upper surface of the insulating structure 124 is basically flush with the upper surface of the frame pin 122a. Therefore, the insulating structure 124 will block the opening 122c of the lead frame 122, and the insulating structure covering the photosensitive area 121b needs to be removed in a subsequent step.

[0070] In step S1140, the patch tape or carrier plate 123 is removed.

[0071] In step S1150, the insulating material above the photosensitive area 121b of the first bare wafer 121 is removed to expose the photosensitive area 121b of the first bare wafer 121.

[0072] As described above, the insulating material can be removed by exposure and development. Alternatively, other methods, such as laser etching, can be used to remove the insulating material covering the photosensitive area while protecting it.

[0073] In step S1160, a redistribution structure 125 is formed between the pads 121c and the frame pins 122a of the first bare die 121 to electrically couple the pads 121c and the corresponding frame pins 122a.

[0074] In this embodiment, the upper surfaces of the pad 121c and the frame pin 122a are not coplanar. Therefore, in addition to the horizontal rectangular structure 125a, the redistribution structure 125 also includes bump structures 125b that extend at different heights to form electrical connections.

[0075] Step S1160 may include the following steps: Step S1161: Remove part of the insulating material above the first surface to expose the pad 121c.

[0076] Specifically, the insulating material can be removed by laser drilling. Optionally, step S1161 can be combined with the step of exposing the photosensitive area in step S1150, both of which are performed by exposure and development.

[0077] Step S1162: Create a bump structure 125b above the pad 121c that is electrically connected to the pad 121c.

[0078] Step S1163: Create a horizontal rectangular structure, one end of which is connected to the bump structure and the other end is connected to the upper surface of the frame pin.

[0079] Since the pad 121c is typically formed at the edge of the first surface 121a, surrounding the photosensitive area 121b, the formed redistribution structure 125 will not obstruct the photosensitive area 121b.

[0080] In an alternative implementation, before forming the redistribution layer in step S1160, a thinner second transparent dielectric layer (not shown in the figure of this embodiment) can be formed above the photosensitive area 121b to enhance the bonding strength of the subsequent transparent dielectric layer. This also protects the photosensitive area during the fabrication of the redistribution structure.

[0081] In step S1170, a first transparent dielectric layer 126 is formed. The first transparent dielectric layer 126 covers the redistribution structure 125 and the first bare wafer 121, so that light passes through the first transparent dielectric layer 126 to reach the exposed photosensitive area 121b.

[0082] In subsequent steps, the first and second transparent dielectric layers can be exposed and developed to remove the cut areas of adjacent parts of different lead frames, thereby obtaining discrete transparent encapsulation structures through cutting.

[0083] Figure 13 This is a cross-sectional view of the light-transmitting encapsulation structure according to the third embodiment of the present invention. Figure 13 As shown, the light-transmitting packaging structure of this embodiment includes a first bare die 121, a patterned lead frame 122, a redistribution structure 125, an insulating structure 124, and a first transparent dielectric layer 126. The first bare die 121 has a first surface 121a. A first portion of the first surface 121a is configured as a photosensitive area 121b, and a second portion is configured to include a set of pads 121c.

[0084] The patterned lead frame 122 includes a set of frame pins 122a. The frame pins 122a are disposed outside the first bare die 121 and do not directly contact the first bare die 121. The first surface 121a is lower than the upper surface of the frame pins 122a. That is, the first bare die 121 is embedded within the lead frame 122.

[0085] A redistribution structure 125 electrically couples the pads 121c and the corresponding frame pins 122a. An insulating structure 124 fills the area between the lead frame 122 and the first bare die 121, exposing at least a portion of the photosensitive area 121b. The redistribution structure 125 is formed on the upper surfaces of the first bare die 121 and the lead frame 122. The redistribution structure 125 includes a horizontally oriented rectangular structure 125a and a vertically oriented bump structure 125b connected to one end of the rectangular structure 125a. The bump structure 125b is connected to the pads 121c, and the other end of the rectangular structure 125a is connected to the frame pins 122a. A first transparent dielectric layer 126 is located above the lead frame 122, the redistribution structure 125, and the first bare die 121, allowing light to pass through the first transparent dielectric layer 126 to reach the exposed photosensitive area 121b.

[0086] In this embodiment, an alternative implementation to the first embodiment is provided. Meanwhile, since the photosensitive surface 121b is lower than the upper surface of the lead frame 122, the influence of side light on the first bare wafer 121 is further weakened, which is beneficial for application scenarios where it is desirable to minimize the influence of side light.

[0087] Figure 14 This is a cross-sectional view of the light-transmitting encapsulation structure according to the fourth embodiment of the present invention. Figure 14 As shown, the transparent packaging structure of this embodiment encapsulates multiple bare dies. In addition to the first bare die 61, each bare die includes at least one second bare die 67. The second bare die 67 may not have a photosensitive area. The second bare die 67 also has pads 67a. The pads 67a of the second bare die 67 are connected to the pads 61c and / or frame pins 62a of the first bare die 61 via a redistribution structure. As an example, the pads of the second bare die 67 are substantially coplanar with the pads of the first bare die 61. The second bare die 67 is used to control the first bare die 61. It can send control commands or receive photosensitive signals through electrical connection with the first bare die 61, and obtain external commands or send signals through electrical connection with the frame pins 62a.

[0088] In order to achieve such Figure 14 The transparent encapsulation structure shown can be implemented in step S521 of the first embodiment, i.e., before filling the insulating material to fix the bare wafer, by attaching the first bare wafer 61 and the second bare wafer 67 to the patch tape or carrier plate 63 on the inner region of the lead frame 62, and then proceeding to step S522. The number of second bare wafers can be one or more. Since the second bare wafers do not require photosensitive properties, it is not necessary to remove the shielding material layer on them in subsequent steps.

[0089] This embodiment can encapsulate multiple bare wafers in a transparent packaging structure, increasing the adaptability and flexibility of the packaging process while reducing production costs.

[0090] It should be understood that, as a further variation of the fourth embodiment, a second transparent dielectric layer may be added before forming the redistribution structure while packaging multiple bare wafers, in order to enhance the bonding strength of the first transparent dielectric layer.

[0091] Figure 15 This is a cross-sectional view of the light-transmitting encapsulation structure according to the fifth embodiment of the present invention. Figure 15 As shown, the transparent packaging structure of this embodiment encapsulates multiple bare dies. In addition to a first bare die 121, each bare die includes at least one second bare die 127. The second bare die 127 may not have a photosensitive area. The second bare die 127 also has pads 127a. The pads 127a of the second bare die 127 are connected to the pads 121c of the first bare die 121 and / or the frame pins 122a via a redistribution structure 125. In this embodiment, the pads of the second bare die 127 are substantially coplanar with the pads of the first bare die 121. The upper surfaces of the first bare die 121 and the second bare die 127 are not coplanar with the upper surface of the lead frame and are lower than the upper surface of the frame pins 122a, thus being embedded in the lead frame 122. In an optional implementation, the back surfaces of the first bare die 121 and the second bare die 127 are coplanar with the back surface of the lead frame 122.

[0092] In order to achieve such Figure 15 The transparent packaging structure shown can be implemented in step S1120 of the third embodiment, i.e., before filling the insulating material to fix the bare wafer, by attaching the second surface of the first bare wafer 121 and the back surface of the second bare wafer 127 to the patch tape or carrier plate 123 of the inner region of the lead frame 122, and then proceeding to step S1130 of the third embodiment. The number of second bare wafers can be one or more. Since the second bare wafers do not require photosensitive properties, it is not necessary to remove the material layer (e.g., insulating structure 124) covering their upper surface in subsequent steps. When forming the redistribution structure, through-holes need to be formed to expose the pads 127a of the second bare wafer 127 for electrical connection.

[0093] This embodiment can encapsulate multiple bare wafers in a transparent packaging structure, increasing the adaptability and flexibility of the packaging process while reducing production costs.

[0094] It should be understood that, as a further variation of the fifth embodiment, a second transparent dielectric layer may be formed before the redistribution layer is formed while encapsulating multiple bare wafers, in order to enhance the bonding strength of the first transparent dielectric layer.

[0095] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can be modified and varied in various ways. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of protection of the present invention.

Claims

1. A light-transmitting encapsulation structure, characterized in that, The light-transparent encapsulation structure includes: A first bare wafer has a first surface, a first portion of which is configured as a photosensitive area, and a second portion of which is configured to include a set of pads; The patterned lead frame includes a set of frame pins, which are disposed on the outside of the first bare die and do not directly contact the first bare die; A rewiring structure electrically couples the pads and the corresponding frame pins; An insulating structure is provided to fill the area between the lead frame and the first bare wafer, and to expose at least a portion of the photosensitive area; A first transparent dielectric layer is located above the lead frame, the redistribution structure, and the first bare wafer, such that light passes through the first transparent dielectric layer to reach the exposed photosensitive area.

2. The light-transmitting encapsulation structure according to claim 1, characterized in that, The first surface and the upper surface of the frame pin are substantially coplanar.

3. The light-transmitting encapsulation structure according to claim 2, characterized in that, The rewiring structure includes a horizontal rectangular structure, which is connected to the upper surfaces of the pads and the frame pins, respectively.

4. The light-transmitting encapsulation structure according to claim 1, characterized in that, The first surface is lower than the upper surface of the frame pin.

5. The light-transmitting encapsulation structure according to claim 4, characterized in that, The rewiring structure includes a horizontal rectangular structure and a vertical bump structure connected to one end of the rectangular structure. The bump structure is connected to the pad, and the other end of the rectangular structure is connected to the frame pin.

6. The light-transmitting encapsulation structure according to claim 1, characterized in that, The light-transparent encapsulation structure further includes: A second transparent dielectric layer covers the first surface and the upper surface of the frame pins, and exposes at least a portion of the upper surface of the pads and each of the frame pins, the redistribution structure being formed on the second transparent dielectric layer.

7. The light-transmitting encapsulation structure according to claim 1, characterized in that, The light-transparent encapsulation structure further includes: At least one second bare wafer, the second bare wafer having pads; The pads of the second bare die are connected to the pads and / or frame pins of the first bare die via the redistribution structure.

8. The light-transmitting encapsulation structure according to claim 7, characterized in that, The pads of the second bare wafer are substantially coplanar with the pads of the first bare wafer.

9. The light-transmitting encapsulation structure according to claim 4, characterized in that, The first bare wafer has a second surface opposite to the first surface, the second surface of the first bare wafer being coplanar with the back surface of the frame pin, and the back surface of the frame pin being opposite to the upper surface of the frame pin.

10. The light-transmitting encapsulation structure according to claim 2, characterized in that, The insulation structure is made of opaque or semi-transparent materials.

11. The light-transmitting encapsulation structure according to claim 4, characterized in that, The insulation structure is made of a semi-transparent material.

12. The light-transmitting encapsulation structure according to claim 1, characterized in that, The first transparent dielectric layer is a polyimide layer.

13. The light-transmitting encapsulation structure according to claim 6, characterized in that, Both the first transparent dielectric layer and the second transparent dielectric layer are polyimide layers.

14. A packaging method for packaging a first bare wafer, wherein a first portion of a first surface of the first bare wafer is configured as a photosensitive area, and a second portion is configured to include a set of pads, characterized in that... The method includes: A patterned lead frame is provided, the lead frame including a set of frame pins; The first bare wafer is fixed inside the lead frame, exposing the photosensitive area of ​​the first bare wafer; A redistribution structure is formed between the pads of the first bare die and the frame pins to electrically couple the pads and the corresponding frame pins. A first transparent dielectric layer is formed, which covers the redistribution structure and the first bare wafer, so that light passes through the transparent dielectric layer to reach the exposed photosensitive area.

15. The method according to claim 14, characterized in that, Before forming the redistribution structure, the method further includes: A second transparent dielectric layer is formed on the first surface and the upper surface of the frame pins; and, Remove the second transparent dielectric layer from the pads on the first surface and at least a portion of the upper surface of each of the frame pins to expose the pads and at least a portion of the upper surface of each of the frame pins.

16. The method according to claim 15, characterized in that: The second transparent dielectric layer on the pads on the first surface and at least a portion of the upper surface of each of the frame pins is removed by exposure and development.

17. The method according to claim 14, characterized in that, The patterned lead frame includes: The upper surface of the frame pins is attached to the patch tape or carrier board; Fixing the first bare wafer to the inside of the lead frame includes: The first surface of the first bare wafer is attached to the inner region of the lead frame using adhesive tape or a carrier plate. An insulating material is filled between the first bare wafer and the lead frame to form an insulating structure; Remove the adhesive tape or carrier to expose the photosensitive area of ​​the first bare wafer.

18. The method according to claim 14, characterized in that, The patterned lead frame includes: The back side of the frame pin is attached to the patch tape or carrier board, with the back side of the frame pin facing the top surface of the frame pin; Fixing the first bare wafer to the inside of the lead frame includes: The second surface of the first bare wafer is attached to the patch tape or carrier plate of the inner region of the lead frame, and the second surface is the surface opposite to the first surface of the first bare wafer. An insulating material is filled between the first bare wafer and the lead frame to form an insulating structure; Remove the patch tape or carrier plate; Remove the insulating material above the photosensitive area of ​​the first bare wafer to expose the photosensitive area of ​​the first bare wafer.

19. The method according to claim 15, characterized in that, Forming a redistribution structure between the pads of the first bare die and the frame pins includes: fabricating a horizontal rectangular structure, one end of which is connected to the pads and the other end of which is connected to the upper surface of the frame pins.

20. The method according to claim 18, characterized in that, Forming a redistribution structure between the pads of the first bare die and the frame pins includes: Remove the insulating material above the first surface to expose the solder pads; A bump structure electrically connected to the pad is formed above the pad; A horizontal rectangular structure is constructed, with one end of the rectangular structure connected to the bump structure and the other end connected to the upper surface of the frame pin.

21. The method according to claim 17, characterized in that, The insulating material is an opaque or semi-transparent material.

22. The method according to claim 18, characterized in that, The insulating material is a semi-transparent material.

23. The method according to claim 14, characterized in that, The first transparent dielectric layer is a polyimide layer.

24. The method according to claim 15, characterized in that, Both the first transparent dielectric layer and the second transparent dielectric layer are polyimide layers.

25. The method according to claim 17, characterized in that, The method further includes: Before filling with insulating material, the pad side of the second bare die is attached to the patch tape or carrier plate inside the lead frame to fix the second bare die inside the lead frame.

26. The method according to claim 18, characterized in that, The method further includes: Before filling with insulating material, the back side of the second bare die is attached to the patch tape or carrier plate inside the lead frame area, wherein the back side of the second bare die is the side opposite to the side where the second bare die pad is located.

27. The method according to claim 14, characterized in that, The method further includes: The first transparent dielectric layer is exposed and developed to reveal the cutting area of ​​the lead frame, and the lead frame is then cut to obtain a discrete transparent encapsulation structure.

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