Fabrication method of flip chip and face-up chip interconnectable stacked structure

Abstract

The application discloses a preparation method of a flip-chip and vertical-chip interconnectable stacking structure, which comprises the following steps: S1, preparing a substrate; S2, preparing a flip-chip, and mounting a chip with metal bumps and metal bumps on the substrate; S3, preparing a vertical-chip, and interconnecting the metal bumps on the back of the chip with the metal bumps on the back of the flip-chip; S4, filling and protecting the stacking structure of S1 to S3 with an underfill; S5, ball bonding the front of the vertical-chip, and connecting the substrate with the welding line; and S6, plastic packaging the whole. The method has the advantages that the interconnection path distance between the stacked chips is reduced, the electrical performance and packaging reliability are improved, the number of substrate layers is reduced, and the packaging size is reduced.

Description

Technical Field

[0001] This invention relates to a method for fabricating a stackable structure for interconnecting flip-chip and conventional chips. Background Technology

[0002] Currently, it is impossible to achieve functional interconnection between flip-chips on the bottom and conventional chips on the top, or it is necessary to achieve this by expanding the packaging or increasing the number of substrate layers. This results in a significant increase in the interconnection length between stacked chips, which affects the electrical performance and reliability of the product.

[0003] Existing technology: Flip-chip at the bottom, with a ball-bonded chip on top; the interconnect between the top ball-bonded chip and the bottom flip-chip requires more routing space, such as... Figure 1 As shown, Figure 1 In the middle, the components are: 1. Substrate; 2. Aluminum pad window; 3. Metal protrusion; 4. Flip chip; 5. Orthogonal chip; 6. Bonding wire; 8. Molding material; 9. Die-mount adhesive; 10.

[0004] In an existing stacked structure with a top-mounted chip and a bottom-mounted chip, interconnection between the chips requires the top-mounted chip to have a bonding wire pulled out and routed through a substrate to connect with the functional aluminum pads of the bottom-mounted chip (e.g., Figure 1 The interconnection of the two aluminum pads shown requires increasing the number of substrate layers, using internal traces within the substrate, and expanding the package. This results in a long interconnection path, poor electrical performance, and the addition of more traces to the top-mounted chip, increasing the overall thickness of the package and making the entire package structure larger. Summary of the Invention

[0005] To improve the interconnection path between aluminum pads in stacked chips, enhance electrical performance and packaging reliability, reduce the number of substrate layers, and decrease package size, this invention proposes a method for fabricating a stackable structure with interconnectable flip-chip and conventional chips. This method reduces the interconnection path distance between aluminum pads in stacked chips, improves electrical performance and packaging reliability, reduces the number of substrate layers, and decreases package size.

[0006] The technical solution adopted is as follows: A method for fabricating a stackable structure for interconnection between flip-chip and conventional chips, comprising the following steps: S1. Prepare the substrate; S2. Prepare for flip-chip bonding: flip-chips with metal bumps and metal dots are flipped onto the substrate. S3. Prepare the upright chip, and interconnect the chip with metal bumps on the back with the metal bumps on the back of the flip chip. The stacked structure of S4, S1 to S3 is used for bottom filling and protection with adhesive. S5. Ball bonding is performed on the front side of the upright chip located on the upper layer of the structure, and the bonding wire is connected to the substrate; S6. Complete the entire process by plastic sealing.

[0007] A further optimization of the technical solution of the present invention is that the flip chip has aluminum pad windows on both the front and back sides, metal bumps are made on the back side, and metal protrusions are made on the front side. Both the metal bumps and metal protrusions are made inside the aluminum pad windows, which facilitates signal interconnection between chips.

[0008] A further optimization of the technical solution of the present invention is that the front and back of the chip have aluminum pad windows, and metal bumps are made on the back. The metal bumps are made inside the aluminum pad windows to facilitate signal interconnection between chips.

[0009] A further optimization of the technical solution of the present invention is that the bottom filler glue fills the gaps between the chips and the gaps of the metal protrusions on the front side of the flip chip in the lower layer. After filling the gaps and curing, the upright chip has better support during wire bonding.

[0010] In a further preferred embodiment of the technical solution of the present invention, the substrate includes a base island and functional pins, the base island is arranged between the functional pins, and the functional pins are electrically connected by wire bonding.

[0011] A further optimization of the technical solution of the present invention is to completely encapsulate the entire structure with a molding compound.

[0012] This invention also proposes a stacked structure for interconnecting flip-chips and standard-mount chips, comprising a substrate, a lower flip-chip, an upper standard-mount chip, and an underfill. The flip-chip is flipped onto the substrate, and the back side of the standard-mount chip is interconnected with the back side of the flip-chip. The underfill fills the gaps, and the front side of the upper standard-mount chip is ball-bonded to the substrate. A molding compound covers the interconnected stacked structure. This stacked structure is suitable for a specific configuration where a flip-chip is at the bottom and a standard-mount chip is on top. It improves the interconnectivity between stacked chips, reduces the package size, and the underfill process ensures stable support during wire bonding (WB).

[0013] The advantages of this invention compared to the prior art are: The method of the present invention reduces the interconnection path distance between aluminum pads between stacked chips, improves electrical performance and packaging reliability, reduces the number of substrate layers, and reduces package size. Attached Figure Description

[0014] Figure 1 This is a cross-sectional schematic diagram of a known product.

[0015] Figure 2 This is a schematic diagram of the substrate used in step S1 of the method in Example 1.

[0016] Figure 3 This is a schematic diagram of step S2 of the method in Example 1.

[0017] Figure 4 This is a schematic diagram of step S3 of the method in Example 1.

[0018] Figure 5 This is a schematic diagram of step S4 of the method in Example 1.

[0019] Figure 6 This is a schematic diagram of step S5 of the method in Example 1.

[0020] Figure 7 This is a schematic diagram of the encapsulation process using the molding compound in Example 1. Detailed Implementation

[0021] The technical solution of the present invention will be described in detail below, but the scope of protection of the present invention is not limited to the embodiments described.

[0022] To make the content of this invention clearer and easier to understand, the following description is in conjunction with the appendix. Figures 1-7 The specific implementation methods will be further described below.

[0023] Example 1 like Figure 2-6 As shown in the figure, this embodiment describes a method for fabricating a stackable structure for interconnecting flip-chip and conventional chips, comprising the following steps: S1. Prepare substrate 1; substrate 1 includes base island 11 and functional pins 12, with base island 11 arranged between two functional pins 12; S2. Prepare flip chip 5. Flip chip with metal bumps and metal dots is flipped onto substrate 1. S3. Prepare the upright chip 6, and interconnect the chip with metal bumps on the back with the metal bumps on the back of the flip chip 5. The stacked structure of S4, S1 to S3 is filled and protected by Underfill 7; Underfill 7 fills the gaps between chips and the gaps of the metal protrusions 4 on the front side of the flip chip 5 of the lower layer.

[0024] S5. Ball bonding is performed on the front side of the upright chip 6 located on the upper layer of the structure, and bonding wire 8 is connected to the substrate 1. The substrate 1 includes a base island 11 and functional pins 12. The base island 11 is arranged between the functional pins 12, and the bonding wire 8 is connected to the functional pins 12 for electrical connection.

[0025] S6. Complete the entire process by encapsulating it with molding compound 9 for protection.

[0026] like Figure 3 As shown, the flip chip 5 has aluminum pad windows 2 on both the front and back sides, metal bumps 3 on the back side and metal protrusions 4 on the front side. Both metal bumps 3 and metal protrusions 4 are made inside the aluminum pad windows 2.

[0027] like Figure 3As shown, the front and back of the chip 6 have aluminum pad windows 2, and the back has metal bumps 3 inside the aluminum pad windows 2.

[0028] This embodiment describes a stacked structure that allows interconnection between flip-chip and conventional chips. This stacked structure is suitable for a special structure with a flip-chip 5 at the bottom and a conventional chip 6 on top. It can improve the interconnection between stacked chips, reduce the package size, and use the underfill process to fill the structure, making the support stable during WB wire bonding.

[0029] like Figure 2-7 As shown, a stacked structure for interconnecting flip-chips and regular chips includes a substrate 1, a lower flip-chip 5, an upper regular chip 6, and an underfill 7. The substrate 1 is a substrate or frame. The flip-chip 5 is flip-mounted onto the substrate 1. The flip-chip 5 has aluminum pad openings 2 on both its front and back sides, metal bumps 3 on its back side, and metal protrusions 4 on its front side. The back side of the regular chip 6 is interconnected with the back side of the flip-chip 5. The regular chip 6 also has aluminum pad openings 2 on both its front and back sides, and metal bumps 3 on its back side. The metal bumps 3 on the back side of the regular chip 6 are interconnected with the metal bumps 3 on the back side of the flip-chip 5. The underfill 7 fills the gaps between the chips and the gaps between the metal protrusions 4 on the front side of the lower flip-chip 5. The front side of the upper regular chip 6 is ball-bonded, and bonding wires 8 connect to functional pins 12 for electrical connection. A molding compound 9 encapsulates the stacked structure for interconnecting the chips.

[0030] The above embodiments are merely illustrative of the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solutions based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A method for fabricating a stackable structure for interconnecting flip-chip and conventional chips, characterized in that: Includes the following steps: S1. Prepare substrate (1). Substrate (1) includes base island (11) and functional pins (12). Base island (11) is arranged between functional pins (12). Solder wire (8) is used to connect functional pins (12) for electrical connection. S2. Prepare flip chip (5). Flip chip (5) has aluminum pad openings (2) on both the front and back sides. Metal bumps (3) are made on the back side and metal protrusions (4) are made on the front side. The metal bumps (3) and metal protrusions (4) are both made inside the aluminum pad openings (2). The chip with metal protrusions and metal bumps is flip-chipped onto the substrate (1). S3. Prepare the upright chip (6). The upright chip (6) has aluminum pad windows (2) on both the front and back sides. Metal bumps (3) are made on the back side. The metal bumps (3) are made inside the aluminum pad windows (2). The chip with metal bumps on the back side is interconnected with the metal bumps on the back side of the flip chip (5). The stacked structure of S4, S1 to S3 is used as an underfill (7) for filling and protection; S5. Ball bonding is performed on the front side of the upright chip (6) located on the upper layer of the structure, and the bonding wire (8) is connected to the substrate (1). S6. Complete the entire process by plastic sealing.

2. The method for fabricating a stackable structure for interconnecting flip-chip and conventional chip according to claim 1, characterized in that: Underfill (7) fills the gaps between chips and the gaps between the flip chips (5) on the front side of the metal protrusion (4).

3. The method for fabricating a stackable structure for interconnecting flip-chip and conventional chip according to claim 1, characterized in that: The entire structure is covered with plastic sealant (9).

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