Packaging structure

Abstract

Some embodiments of the present application provide a package structure comprising: a lead frame; a wafer disposed on the lead frame; a metal lead electrically connecting the lead frame and the wafer; the rigid structure is arranged above the lead frame and is separated from the lead frame, and the projections of the rigid structure and the metal wires in the horizontal direction and the vertical direction are overlapped; and the die sealing layer wraps the wafer, the metal wires and part of the rigid structure. According to the packaging structure, the warping amount of the packaging structure is suppressed by adding the rigid structure, and in order to reduce the overall size of the packaging structure, the rigid structure is overlapped with the projections of the metal wires in the horizontal direction and the vertical direction in a sectional view.

Description

Technical Field

[0001] An embodiment of the present application relates to a packaging structure. Background Art

[0002] like Figure 1A As shown, the previous QFN (quad flat no-lead package) package structure 10 uses a chip 11 to wire and uses a metal wire 12 to connect the conductive line, which has the advantages of small size, low cost, and mature technology. However, its IO (input and output) number has gradually become insufficient with the development of IC (integrated circuit) products. Next, see Figures 1B to 3 , Figure 1B shows a top view of the aQFN, and Figure 1C-1 Shown along Figure 1B A cross-sectional view of the line A-A'. Figure 1B As shown, the aQFN (improved quad flat no-lead package) package structure 10' improves the problem of insufficient IO, and its chip 11' has more wire rows (that is, more metal wires 12') and IO points, but the resulting problem is that as the number of wires increases, the curvature between the wires must also be increased to avoid contact with each other. Figure 1C-1 As shown, the increase in the bonding height of the wafer 11 ′ attached to the lead frame 13 via the adhesive layer 15 affects the thickness of the molding layer 14 , which is usually formed of a material with a large CTE (coefficient of thermal expansion), and thus affects the severity of the warpage.

[0003] It can be seen that in the prior art, although the aQFN package structure 10' has the advantage of high IO number, the area of ​​the chip 11' (such as Figure 1B The chip 11' shown in the figure has a smaller coverage area than the chip 11 of the QFN package structure 10, and due to the larger number of wire bonding rows (i.e., more metal wires 12') and the higher arc height, a higher thickness of the mold encapsulation layer (EMC) 14 is required, such as Figure 1C-1 Therefore, the aQFN 10' is easily affected by the shrinkage of the molding layer 14, which causes the aQFN package structure 10' to be warped too much, as shown in FIG. Figure 1C-2 to Figure 1C-4 shown. Figure 1C-2 Shown from another angle Figure 1C-1 A perspective view of an aQFN package structure 10', wherein a chip 11' is covered by a mold sealing layer 14. Figure 1C-2 The middle mold seal layer 14 is shown to be semi-transparent and therefore not shown. Figures 1D to 1F Shows Figure 1C-1The process flow of the aQFN package structure 10' is as follows: specifically, the chip 11' is attached to the lead frame 13, and the metal wire 12' is formed by a wire bonding method commonly used in the art. Then, a mold sealing layer 14 is formed on the lead frame 13 and the chip 11'. Finally, the die is cut to form Figure 1C-1 aQFN package structure 10'.

[0004] also, Figure 1C-3 to Figure 1C-4 The warpage of the aQFN package structure 10' at room temperature (RT) and high temperature (HT) are shown respectively. Figure 1C-3 The warpage of the aQFN package structure 10' shown in FIG. 1 at room temperature (RT) is -31 μm (- indicates that the direction of the warpage is toward the lead frame 13). Figure 1C-4 The warpage of the aQFN package structure 10' shown in the figure at high temperature (HT) is ﹢28μm (﹢ indicates that the direction of the warpage is away from the lead frame 13, which is opposite to "﹢"). It can be seen that in the existing aQFN package structure 10', the warpage variation at room temperature (RT) and high temperature (HT) is 59μm. Therefore, the warpage of the aQFN package structure 10' in the prior art is too large (59μm), >43μm, which leads to the failure of the aQFN package structure 10' to be mounted on the board, resulting in a surface mount technology (SMT) failure rate of >50%.

[0005] In summary, in the prior art, the warpage of the aQFN structure 10' can only be improved by selecting a material with a smaller CTE mismatch. Therefore, there is an urgent need for a structure that can reduce the warpage on a product with a high wire bonding volume. Utility Model Content

[0006] In order to solve the above problems, the present application suppresses the warping of the packaging structure by adding a rigid structure. In the present application, the rigid structure is encapsulated in the mold layer of the packaging structure and avoids the position where the metal wire passes; at the same time, in order to reduce the overall volume of the packaging structure, the rigid structure partially overlaps with the horizontal and vertical projections of the metal wire in the cross-sectional view.

[0007] Some embodiments of the present application provide a packaging structure, including: a lead frame; a chip, which is arranged on the lead frame; a metal wire, which electrically connects the lead frame to the chip; a rigid structure, which is arranged above the lead frame and spaced apart from the lead frame, and the rigid structure overlaps with the projection of the metal wire in both the horizontal and vertical directions; and a molding layer, which encapsulates the chip, the metal wire and a portion of the rigid structure.

[0008] In some embodiments, the metal wire includes a vertex and an end point connected to the lead frame, wherein the rigid structure overlaps with a projection of the vertex in a horizontal direction, and the rigid structure overlaps with a projection of the end point in a vertical direction.

[0009] In some embodiments, the molding layer covers an upper surface of the lead frame facing the chip, the chip, the metal wires, and a lower surface of the rigid structure facing the lead frame.

[0010] In some embodiments, the side surface of the molding layer is not flush with the side surface of the rigid structure.

[0011] In some embodiments, a side surface of the molding layer is disposed outside a lateral extent of the rigid structure.

[0012] In some embodiments, the upper surface of the rigid structure is flush with the upper surface of the molding layer, wherein the upper surface of the rigid structure and the upper surface of the molding layer are surfaces away from the lead frame.

[0013] In some embodiments, the thermal expansion coefficient of the rigid structure is smaller than the thermal expansion coefficient of the molding layer.

[0014] In some embodiments, when viewed from above, the rigid structure is an annular structure and defines a receiving space.

[0015] In some embodiments, the vertex is disposed within the receiving space.

[0016] In some embodiments, the rigid structure includes a plurality of corner portions and a plurality of connecting portions connecting the corner portions.

[0017] In some embodiments, the thickness of the corner portion is greater than the thickness of the connecting portion.

[0018] In some embodiments, the thickness of the corner portion is equal to the thickness of the connecting portion.

[0019] In some embodiments, the rigid structure has a chamfered surface conformal to the metal wire, and the chamfered surface is disposed closest to the metal wire.

[0020] In some embodiments, the rigid structure is separated from the lead frame by a molding layer.

[0021] In some embodiments, the metal wires electrically connect the die to pads on the lead frame.

[0022] In some embodiments, the die is attached to the lead frame by an adhesive layer.

[0023] In some embodiments, a side surface of the molding layer is flush with a side surface of the rigid structure.

[0024] Other embodiments of the present application provide a packaging structure, comprising: a lead frame; a chip disposed on the lead frame; a metal wire electrically connecting the lead frame to the chip; a molding layer covering the chip and the metal wire; and a rigid structure covered in the molding layer and spaced apart from the lead frame, wherein the metal wire comprises a vertex and an end point connected to the lead frame, and wherein the vertex is disposed between horizontal surfaces where the upper and lower surfaces of the rigid structure are located, and the end point is disposed between vertical surfaces where opposite sides of the rigid structure are located.

[0025] In some embodiments, the thermal expansion coefficient of the rigid structure is smaller than the thermal expansion coefficient of the molding layer.

[0026] In some embodiments, when viewed from above, the rigid structure is an annular structure and defines a receiving space, wherein the vertex is disposed within the receiving space.

[0027] Through the packaging structure provided in the present application, the warpage variation of the packaging structure can be reduced to 16 μm, thereby increasing the board rate of the corresponding packaging structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] When read in conjunction with the accompanying drawings, various aspects of the present invention can be best understood from the following detailed description. It should be noted that, in accordance with standard practice in the industry, the various components are not drawn to scale. In fact, for the sake of clarity of discussion, the size of the various components can be arbitrarily increased or reduced.

[0029] Figures 1A to 1F The prior art packaging structure and process flow are shown.

[0030] Figures 2 to 4 A packaging structure according to some embodiments of the present application is shown.

[0031] Figure 5 , FIG. 5A to FIG. 5E A packaging structure according to some embodiments of the present application is shown.

[0032] FIG. 6A to FIG. 6C The warpage of the package structure according to some embodiments of the present application is shown.

[0033] Figures 7 and 8 , FIG. 9A to FIG. 9B as well as Fig.10 The process flow of the packaging structure according to some embodiments of the present application is shown. DETAILED DESCRIPTION

[0034] The following disclosure provides many different embodiments or examples for realizing different features of the present invention. Specific examples of components and arrangements are described below to simplify the present invention. Of course, these are merely examples and are not intended to limit the present invention. In addition, when "approximately", "about", "substantially", etc. are used to describe a numerical value or a numerical range, unless otherwise specified, the term is intended to cover a numerical value within ±10% of the described numerical value. For example, the term "about 5nm" covers a size range from 4.5nm to 5.5nm.

[0035] The present application reduces or suppresses the warping of the packaging structure by adding a rigid structure in the mold sealing layer of the packaging structure. Specifically, see Figure 2 , Figure 2 A packaging structure 100 according to some embodiments of the present application is shown, and the packaging structure 100 includes: a lead frame 103; a chip 101 disposed on the lead frame 103, and in some embodiments, the chip 101 is attached to the lead frame 103 by an adhesive layer 105. In some embodiments, the adhesive layer 105 can be a die attach film, or can be an epoxy resin glue, etc. Further, the packaging structure 100 also includes a metal wire 102, and the metal wire 102 electrically connects the lead frame 103 and the chip 101. In addition, the packaging structure 100 also includes a rigid structure 106, which is disposed above the lead frame 103 and is spaced apart from the lead frame 103 (not in contact with the lead frame 103), and the rigid structure 106 overlaps with the projection 102Rh of the metal wire 102 in the horizontal direction H and the projection 102Rv in the vertical direction V, as shown in FIG. Figure 2 In some embodiments, the package structure 100 further includes a mold layer 104, which encapsulates the chip 101, the metal wire 102 and a part of the rigid structure 106. Figure 2 It can be seen that the rigid structure 106 is encapsulated in the encapsulation layer 104, and the encapsulation layer 104 encapsulates the metal wire 102 and the chip 101. Further, the rigid structure 106 is separated from the lead frame 103 by the encapsulation layer 104. Specifically, the encapsulation layer 104 encapsulates the upper surface 103t of the lead frame 103 facing the chip 101, the chip 101, the metal wire 102, and the lower surface 106d of the rigid structure 106 facing the lead frame 103. Figure 2 In the illustrated embodiment, the side 104s of the encapsulation layer 104 is flush with the side 106s of the rigid structure 106. Figure 3In other embodiments shown, the side 104s of the encapsulation layer 104 is not flush with the side 106s of the rigid structure 106. Specifically, the side 104s of the encapsulation layer 104 is disposed outside the lateral extent of the rigid structure 106, that is, the encapsulation layer 104 extends beyond the lateral extent of the rigid structure 106. This may be caused during the cutting process of the package structure 100, which will be described in further detail below. Figure 2 As shown, the upper surface 106t of the rigid structure 106 is flush with the upper surface 104t of the mold encapsulation layer 104. Figure 2 As can be seen from FIG. 1 , the upper surface 106 t of the rigid structure 106 and the upper surface 104 t of the molding layer 104 are surfaces away from the lead frame 103 .

[0036] In the above embodiment, the lead frame 103 may be a metal frame, such as a frame made of metal such as copper, aluminum, etc., and the lead frame 103 includes a plurality of rows of finger pads 103P connected to the metal wires 102, such as Figure 2 As shown, the metal wire 102 electrically connects the wafer 101 to the pads on the lead frame 103 (i.e., respectively connected to the multiple rows of finger pads 103P). In some embodiments, the multiple rows of finger pads 103P are formed integrally with the lead frame 103. In other embodiments, the multiple rows of finger pads 103P are formed separately from the lead frame 103. In addition, the multiple rows of finger pads 103P may include the same or different materials as the lead frame 103. In the above embodiments, the metal wire 102 may include metals such as copper, tin, and alloys thereof. In the above embodiments, the rigid structure 106 may be made of a material with high strength such as silicon and copper, and the mold layer 104 may be made of a molding compound, a molding compound, and the like. In an embodiment, the modulus of the rigid structure 106 is greater than the modulus of the mold layer 104, because a larger modulus can make the rigid structure 106 more rigid, thereby better resisting deformation of the package structure 100. In some embodiments, the wafer 101 may include a die, etc.

[0037] In addition, see Figure 2 The metal wire 102 includes a vertex 102t and an end point 102d connected to the lead frame 103 (specifically, one of the multiple rows of finger pads 103P of the lead frame 103), Figure 2 As can be seen in FIG. 1 , the rigid structure 106 overlaps with a projection 102th of the vertex 102t in the horizontal direction H, and the rigid structure 106 overlaps with a projection 102dv of the end point 102d in the vertical direction V. In some embodiments, the coefficient of thermal expansion (CTE) of the rigid structure 106 is smaller than that of the molding layer 104, thereby further reducing the warpage of the package structure 100.

[0038] See also Figure 4In some other embodiments, the rigid structure 106 has a chamfered surface 106x that is substantially conformal to the metal wire 102 (in some embodiments, it may not be conformal), and the chamfered surface 106x is arranged closest to the metal wire 102. In the present application, the chamfered surface 106x (triangular cross section) can better avoid the metal wire 102 and can be made thicker, so as to have a better ability to suppress warping.

[0039] Figures 5 to 5E Shows Figure 2 The package structure 100 and Figure 4 A top view of the package structure 300 and a corresponding partial cross-sectional view are shown. Figure 5 As shown, in a top view, the rigid structure 106 is an annular structure and defines a receiving space V. Further, Figure 2 The package structure is 100 to Figure 4 The vertex 102 t of the metal wire 102 in the package structure 300 is disposed in the receiving space V. Figure 5A and Figure 5B Shown along Figure 5 A partial cross-sectional view of the rigid structure 106 along line BB', from Figure 5A and Figure 5B As can be seen in the figure, the rigid structure 106 can have different cross-sectional shapes, and the rigid structure 106 is filled with the molding layer 104 . FIG. 5C to FIG. 5E Shown along Figure 5 A partial cross-sectional view of the rigid structure 106 along the line CC', from FIG. 5C to FIG. 5E As can be seen from the figure, the rigid structure 106 includes a plurality of corner portions 106c and a plurality of connecting portions 1061 connecting the corner portions 106c. Figure 5C and Figure 5E As shown, the thickness of the corner portion 106c is greater than the thickness of the connecting portion 1061. Figure 5D As shown, the thickness of the corner portion 106c is equal to the thickness of the connecting portion 1061.

[0040] It can be seen from the above embodiments that in the present application, the rigid structure 106 may be a sheet-shaped and hollow annular structure when viewed from above (see FIG. Figure 5 ), the hollow portion can accommodate the metal wire 102 to reduce the volume of the package structure 100-300. FIG. 5A to FIG. 5E In the cross-sectional view of the corner portion 106c of the rigid structure 106 shown (each of the annular rigid structures 106 of the packaging structures 100-300 has four corner portions 106c respectively), the thickness of the corner portion 106c can be increased, and the shape can be set according to actual conditions, and is not limited to a square shape. In the present application, the shape of the corner portion 106c can be satisfied to avoid the metal wire 102, and the thicker the thickness, the better the ability to suppress warping.

[0041] Continue to see Figure 2 Some other embodiments of the present application provide a package structure 100, comprising: a lead frame 103; a wafer 101 disposed on the lead frame 103; a metal wire 102 electrically connecting the lead frame 103 to the wafer 101; a mold layer 104 covering the wafer 101 and the metal wire 102; and a rigid structure 106 covered in the mold layer 104 and spaced apart from the lead frame 103. In the package structure 100, the metal wire 102 includes a vertex 102t and an end point 102d connected to the lead frame 103, and wherein the vertex 102t is disposed between horizontal surfaces h1 and h2 where the upper surface 106t and the lower surface 106t of the rigid structure 106 are located, and the end point 102d is disposed between vertical surfaces v1 and v2 where opposite sides of the rigid structure 106 are located. In some embodiments, the coefficient of thermal expansion (CTE) of the rigid structure 106 is less than the coefficient of thermal expansion of the mold layer 104, thereby further reducing the warpage of the package structure 100. Likewise Figure 5 As shown, in a plan view, the rigid structure 106 is an annular structure and defines an accommodation space V, and the vertex 102t is disposed in the accommodation space V.

[0042] The following shows Figure 2 The warpage variation of the package structure 100 shown in FIG. FIG. 6A to FIG. 6C As shown, Fig. 6A Shown from another angle Figure 2 A perspective view of a package structure 100, wherein a chip 101 is covered by a mold sealing layer 104. Fig. 6A The middle mold sealing layer 104 is shown to be semi-transparent and therefore not shown. FIG. 6B to FIG. 6C The warpage of the package structure 100 at room temperature (RT) and high temperature (HT) are shown respectively, wherein: Figure 6B The warpage of the package structure 100 at room temperature (RT) is -24 μm (- indicates that the direction of the warpage is toward the lead frame 103 (such as Figure 2 direction shown), Figure 6CThe warpage of the package structure 100 shown in the figure at high temperature (HT) is +40μm. It can be seen that for the package structure 100 provided in the present application, the warpage variation at room temperature (RT) and high temperature (HT) is 16μm (much less than 43μm). Therefore, the present application increases the rigidity by adding a rigid structure 106 to the mold layer 104, thereby reducing the overall deformation and warpage of the package structure 100, and by making the rigid structure 106 partially overlap with the projection 102Rh of the metal wire 102 in the horizontal direction H and the projection 102Rv in the vertical direction V in the cross-sectional view, the volume of the mold layer 104 is reduced, and the shrinkage of the mold layer 104 is reduced. Therefore, through the package structure 100-300 provided in the present application, the warpage variation can be reduced to 16μm, which is much less than 43μm, and the reduced warpage variation increases the board rate of the corresponding package structure 100-300.

[0043] The following will refer to Figure 7-10 To introduce Figure 2 and Fig. 6A The process flow of forming the package structure 100 is shown.

[0044] See also Figure 7 , attaching a plurality of wafers 101 to a lead frame 103 such as a copper frame, as Figure 2 As shown, a plurality of wafers 101 (such as dies) may be attached to a lead frame 103 by adhesive layers 105, respectively. Figure 8 A metal wire 102 (such as a copper wire) is formed by a wire bonding method commonly used in the art to make a wire bond, thereby connecting the chip 101 to the lead frame 103.

[0045] See also Fig.9A , attach the rigid structure 106 above the wafer 101, such as fixing the rigid structure 106 above the wafer 101 through a bracket 107, and space the rigid structure 106 from the wafer 101 and the lead frame 103. In some embodiments, the bracket 107 can be made of the same material as or different from that of the rigid structure 106, and can be a metal bracket, such as a copper bracket. Fig. 9B Shows Fig.9A An enlarged cross-sectional view of region A, from Fig. 9B It can be seen that the thickness of the connecting rigid structure 106e between the corner portions 106c of the rigid structure 106 of each unit of the packaging structure 100 is thinned, that is, the thickness of the connecting rigid structure 106e is less than the thickness of the corner portion 106c and the connecting portion 106l, to facilitate subsequent cutting.

[0046] Afterwards, see Fig.10The molding compound is filled into the space between the rigid structure 106 and the wafer 101 and the lead frame 103 by compression molding or other suitable molding or filling processes, thereby forming a molding layer 104 in which the wafer 101, the metal wire 102 and the lead frame 103 are molded / encapsulated. After the molding layer 104 is formed, the rigid structure 106 is further encapsulated in the molding layer 104.

[0047] After the mold encapsulation layer 104 is formed, the Fig.10 The structure shown in FIG. 1 is formed by cutting the rigid structure 106 with a relatively hard tool (such as a knife edge) and cutting the mold sealing layer 104 with a blade or the like. Fig. 6A and Figure 2 The package structure 100 is shown. During the cutting process, as shown above, FIG. 9A to FIG. 9B As described above, for the convenience of cutting, the thickness of the rigid structure 106 between the units of each packaging structure 100 can be thinned, that is, the thickness of the connecting rigid structure 106e can be thinned. In addition, during the cutting process, using different cutting tools for the rigid structure 106 and the encapsulation layer 104 may cause the side 104s of the encapsulation layer 104 to be not flush with the side 106s of the rigid structure 106, as described above. Figure 3 described.

[0048] In summary, the present application suppresses the amount of warping of the package structure 100-300 by adding a rigid structure 106. Specifically, the rigid structure 106 is encapsulated in the mold layer 104 of the package structure 100-300, and avoids the position where the metal wire 102 passes; at the same time, in order to reduce the overall volume of the package structure 100-300, the rigid structure 106 overlaps with the projection 102Rh of the metal wire 102 in the horizontal direction H and the projection 102Rv in the vertical direction V in the cross-sectional view. In addition, through the package structure 100-300 provided by the present application, the warping change can be reduced to 16μm, which is much less than 43μm. The reduced warping change increases the board rate of the corresponding package structure 100-300.

[0049] The features of several embodiments are summarized above so that those skilled in the art can better understand aspects of the present invention. Those skilled in the art should understand that they can easily use the present invention as a basis to design or modify other processes and structures for implementing the same purpose and / or achieving the same advantages as the embodiments described herein. Those skilled in the art should also appreciate that such equivalent constructions do not deviate from the spirit and scope of the present invention, and that they can make various changes, substitutions, and modifications herein without departing from the spirit and scope of the present invention.

Claims

1. A packaging structure, characterized in that: include: Lead frame; A chip is arranged on the lead frame; A metal wire electrically connects the lead frame to the chip; A rigid structure, disposed above the lead frame and spaced apart from the lead frame, wherein the rigid structure overlaps with the projection of the metal wire in both the horizontal direction and the vertical direction; as well as The molding layer encapsulates the chip, the metal wire and a part of the rigid structure.

2. The packaging structure according to claim 1, characterized in that: The metal wire includes a vertex and an end point connected to the lead frame, The rigid structure overlaps with the projection of the vertex in the horizontal direction, and the rigid structure overlaps with the projection of the endpoint in the vertical direction.

3. The packaging structure according to claim 1, characterized in that: The molding layer further covers the upper surface of the lead frame facing the wafer.

4. The packaging structure according to claim 1, characterized in that: The side surface of the molding layer is not flush with the side surface of the rigid structure.

5. The packaging structure according to claim 1, characterized in that: The upper surface of the rigid structure is flush with the upper surface of the molding layer, wherein the upper surface of the rigid structure and the upper surface of the molding layer are surfaces away from the lead frame.

6. The packaging structure according to claim 1, characterized in that: The thermal expansion coefficient of the rigid structure is smaller than the thermal expansion coefficient of the molding layer.

7. The packaging structure according to claim 2, characterized in that: When viewed from above, the rigid structure is an annular structure and defines a receiving space.

8. The packaging structure according to claim 7, characterized in that: The vertex is disposed in the accommodation space.

9. The packaging structure according to claim 1, characterized in that: The rigid structure includes a plurality of corner portions and a plurality of connecting portions connecting the corner portions, wherein the thickness of the corner portions is greater than the thickness of the connecting portions.

10. The packaging structure according to claim 1, characterized in that: The rigid structure has a chamfered surface conforming to the metal wire, and the chamfered surface is disposed closest to the metal wire.

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