PoP MEMS sensor and preparation method thereof

Abstract

The invention discloses a PoP MEMS sensor and a preparation method thereof, and the PoP MEMS sensor comprises a first substrate, the back surface of which is provided with a first solder ball array used for external connection; the second substrate is positioned above the first substrate and is electrically connected with the first substrate through a second solder ball array; the ASIC chip is fixed on the front surface of the first substrate, is interconnected with the first substrate through a first bonding wire, and is completely wrapped by the plastic package body, and the plastic package body is provided with holes corresponding to the second solder ball array so as to expose the second solder balls; the MEMS chip is fixed on the front surface of the second substrate and is interconnected with the second substrate through a second bonding wire; and the metal cover is hermetically adhered to the front surface of the second substrate through box dam glue and covers the MEMS chip to form a cavity structure. According to the invention, the requirements of the market on smaller-size and higher-quality packaging structure products are met.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor packaging, and in particular to a PoP MEMS sensor and a preparation method thereof. Background Art

[0002] With the continuous advancement of semiconductor technology, sensor chip packaging technology is gradually upgrading. Against this backdrop, MEMS (micro-electromechanical systems) products, due to their high degree of integration and miniaturization, have gained an increasingly important position in the market. To meet the urgent demand for smaller, higher-quality packaging structures, new packaging technologies are constantly emerging, providing more diverse options for semiconductor sensor packaging devices.

[0003] Traditional packaging technologies have, to a certain extent, limited the progress of product miniaturization and integration. However, modern electronic applications, such as automotive electronics, industrial control, and consumer electronics, are placing increasingly stringent demands on package size and quality. Therefore, developing a technology that can further reduce package size while maintaining packaging quality has become an urgent need within the industry. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present invention provides a PoP MEMS sensor and a preparation method to meet the market demand for smaller size and higher quality packaging structure products.

[0005] In order to solve the above technical problems, the present invention is implemented through the following technical solutions:

[0006] According to a first aspect of the present invention, there is provided a PoP MEMS sensor, comprising:

[0007] a first substrate, a first solder ball array for external connection being provided on the back side;

[0008] a second substrate, located above the first substrate and electrically connected to the first substrate via a second solder ball array;

[0009] An ASIC chip is fixed to the front surface of the first substrate and interconnected with the first substrate via a first bonding wire, and is completely encapsulated by a plastic package, wherein the plastic package has openings at positions corresponding to the second solder ball array to expose the second solder balls;

[0010] The MEMS chip is fixed to the front surface of the second substrate and interconnected with the second substrate via a second bonding wire;

[0011] The metal cover is sealed and bonded to the front surface of the second substrate by dam glue, and covers the MEMS chip to form a cavity structure.

[0012] In a possible implementation of the first aspect, the ASIC chip is fixed to the front surface of the first substrate by a first adhesive bond, and the first adhesive bond is a non-conductive adhesive film or non-conductive glue.

[0013] In a possible implementation of the first aspect, the MEMS chip is fixed to the front surface of the second substrate by a second adhesive, and the second adhesive is jelly glue.

[0014] In a possible implementation of the first aspect, the jelly glue has a thickness of 60 μm to 100 μm.

[0015] In a possible implementation of the first aspect, the dam glue of the metal cover is solder paste or silver glue, and is applied in a ring shape on the edge of the second substrate.

[0016] In a possible implementation manner of the first aspect, the opening of the plastic package body is formed by a laser ablation process.

[0017] In a possible implementation manner of the first aspect, the first solder ball array and the second solder ball array are both spherical solder structures and are connected by reflow soldering and curing.

[0018] In a possible implementation manner of the first aspect, the bonding wires between the ASIC chip and the MEMS chip are gold wires or copper wires.

[0019] According to a second aspect of the present invention, a method for preparing a PoP MEMS sensor is provided, comprising:

[0020] S1. Soldering a second solder ball array on the front side of the first substrate and curing by reflow;

[0021] S2. The ASIC chip is fixed to the front of the first substrate by a first adhesive, and bonding is performed after curing by baking to interconnect the ASIC chip with the first substrate;

[0022] S3. The ASIC chip is plastic-encapsulated to form a plastic body, and a hole is laser-ablated at the position corresponding to the second solder ball array to expose the second solder ball;

[0023] S4. The second substrate is stacked on the plastic package body and connected to the second substrate by reflow soldering through the second solder ball;

[0024] S5. The MEMS chip is fixed to the front of the second substrate by a second adhesive, and bonding is performed after curing by baking to interconnect the MEMS chip and the second substrate;

[0025] S6. Coating the dam glue in a ring shape on the edge of the second substrate, bonding the metal cover and then baking or reflow curing to form a cavity structure covering the MEMS chip;

[0026] S7. Plant a first solder ball array on the back side of the first substrate and solidify it through reflow soldering.

[0027] In a possible implementation of the second aspect, in step S5, the second adhesive is jelly glue, and its coating thickness is controlled to be 60 μm to 100 μm.

[0028] Compared with the prior art, the present invention has at least the following beneficial effects:

[0029] The present invention provides a PoP MEMS sensor, which adopts PoP technology to stack and assemble multiple chip packages. Specifically, by stacking the second substrate and the MEMS chip thereon and other structures on the first substrate and the structure thereon, a solution of stacking another packaged product on a packaged product is achieved. This multi-layer stacking method effectively utilizes the vertical space and avoids the problem of traditional packaging methods occupying too much space in the horizontal direction, thereby being able to more significantly reduce the package size of the product and meet the demand for miniaturized packaging structures in modern electronic applications. It is particularly suitable for automotive electronics, consumer electronics and other fields with extremely stringent space requirements. In the present invention, since PoP technology is adopted to achieve close stacking between chips, the signal transmission path is greatly shortened. Compared with the relatively long signal transmission path between chips in traditional packaging technology, the signal transmission between chips in the present invention does not need to go through too many intermediate links and long wires, thereby effectively reducing the delay in the signal transmission process. The present invention optimizes the chip layout by adopting PoP technology, making the arrangement of chips in the package more compact and reasonable, reducing the use of unnecessary packaging materials, and thus reducing material costs. Since the packaging levels are reduced, the packaging process is simplified during the production process, the production steps and the required equipment investment are reduced, and the energy consumption and labor costs in the production process are also reduced.

[0030] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the following is a brief introduction to the drawings required for use in the description of the specific embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figures 1 to 9 This is a schematic diagram of the preparation process of a PoP MEMS sensor according to an embodiment of the present invention.

[0033] In the figure: 1-first substrate; 2-first solder ball array; 3-second substrate; 4-second solder ball array; 5-ASIC chip; 6-first bonding wire; 7-plastic package; 8-MEMS chip; 9-second bonding wire; 10-metal cover; 11-first adhesive tape; 12-first adhesive tape. DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0035] Combine Figures 1 to 9 As shown, the embodiment of the present invention provides a PoP MEMS sensor and a preparation method, which are specifically as follows:

[0036] Step 1: Figure 1 As shown, first prepare a first substrate 1 and a second substrate 3. The material of the first substrate 1 and the second substrate 3 can be selected according to actual needs, such as a common printed circuit board (PCB) substrate, etc., and its size and shape must meet the requirements of subsequent chip mounting and stacking.

[0037] It should be noted that during the substrate preparation process, the substrate surface needs to be cleaned to remove impurities such as oil, dust, etc. on the surface to ensure the quality of chip bonding and welding.

[0038] Step 2: Figure 2 As shown, BGA solder balls are used as the second solder ball array 4 and are soldered to the front surface of the first substrate 1. During the soldering process, a standard BGA soldering process is used to place the BGA solder balls on the preset solder pads on the front surface of the first substrate 1, and then solidify them through reflow equipment. During the reflow process, it is ensured that the BGA solder balls can fully fuse with the solder pads to form a reliable electrical connection. The peak temperature of the reflow soldering is usually controlled between 220℃ and 250℃, and the specific temperature can be adjusted according to the material specifications of the BGA solder balls.

[0039] Step 3: Figure 3As shown, the ASIC chip 5 is fixed to the front of the first substrate 1 through the first adhesive 11. The first adhesive 11 adopts a non-conductive adhesive film (DAF) or non-conductive glue. Its bonding performance must meet the fixing requirements between the chip and the substrate, and at the same time, it must be ensured that it will not interfere with the electrical performance of the chip. During the bonding process, the amount and coating uniformity of the first adhesive 11 must be controlled to avoid problems such as bubbles or glue overflow. After the bonding is completed, the substrate is placed in an oven for baking and curing. The baking temperature and time can be adjusted according to the specifications of the first adhesive 11. Generally, the baking temperature is between 150°C and 180°C, and the baking time is 1 to 2 hours.

[0040] After curing is complete, bonding is performed to connect the ASIC chip 5 to the first substrate 1. Gold or copper wires are used as the first bonding wires 6. During the bonding process, the connection strength of the first bonding wires 6 is ensured. After bonding is complete, the bonding points are inspected to ensure there are no defects such as cold solder joints or broken wires.

[0041] Step 4: Figure 4 As shown, the first substrate 1 with the ASIC chip 5 fixed thereon is plastic-encapsulated to form a plastic-encapsulated body 7, which completely encapsulates the ASIC chip 5. For example, the plastic-encapsulating material may be epoxy resin or other plastic-encapsulating materials. The molding quality of the plastic-encapsulated body 7 is ensured during the plastic-encapsulating process. After the plastic-encapsulating process is completed, the plastic-encapsulated body 7 needs to be cooled to solidify.

[0042] Step 5: Figure 5 As shown, laser ablation is performed on the surface of the plastic encapsulation body 7 (corresponding to the location of the second solder ball array 4 inside), exposing the second solder balls. During the laser ablation process, the size and shape of the opening must be ensured to meet the requirements, while also avoiding damage to the surrounding plastic encapsulation body 7 and first substrate 1. After the opening is completed, the opening area must be cleaned to remove any residual plastic encapsulation material and impurities.

[0043] Step 6: Figure 6 As shown, the second substrate 3 is stacked on the plastic package 7 so that the bottom of the second substrate 3 contacts the second solder balls exposed on the surface of the plastic package 7. The second solder balls are then reflowed and connected using a reflow soldering device to achieve electrical connection between the second substrate 3 and the first substrate 1.

[0044] Step 7: Figure 7As shown, the MEMS chip 8 is fixed to the front of the second substrate 3 by the second adhesive 12. The second adhesive 12 adopts jelly glue, and its coating thickness is controlled between 60μm and 100μm. Specifically, during the bonding process, a dispensing device is used to evenly apply the jelly glue to a preset position on the front of the second substrate 3, and then the MEMS chip 8 is placed on the jelly glue and pressed to make it fully contact with the jelly glue. After the bonding is completed, the substrate is placed in an oven for baking and curing. The baking temperature and time can be adjusted according to the specifications of the jelly glue. Generally, the baking temperature is between 120℃ and 150℃, and the baking time is 0.5 to 1 hour.

[0045] After curing is complete, bonding is performed to interconnect the MEMS chip 8 and the second substrate 3. The second bonding wire 9 is also made of gold or copper wire. The bonding quality and electrical performance must be ensured during the bonding process. After bonding is complete, the bonding points are inspected.

[0046] Step 8: Figure 8 As shown, solder paste or silver glue is used as the dam glue, and a circle of glue is drawn around the second substrate 3 by scribing. During the scribing process, the amount of glue used and the uniformity of the coating are controlled to ensure that the glue can form a continuous ring structure. The metal cover 10 is then bonded to the scribing area and pressed to make it fully contact with the dam glue. After the bonding is completed, the substrate is placed in an oven for baking or cured by reflow soldering equipment. The baking temperature and time can be adjusted according to the specifications of the solder paste or silver glue. The general baking temperature is between 150 and 180°C, and the baking time is 1 to 2 hours; the peak temperature of the reflow soldering is usually controlled between 220 and 250°C. After the curing is completed, the metal cover 10 and the second substrate 3 form a cavity structure, which wraps the MEMS chip 8 therein.

[0047] Step 9: Figure 9 As shown, a ball implantation operation is performed on the back side of the first substrate 1 to implant a first solder ball array 2. The first solder ball array 2 is the solder ball array on the back side of the final product for external connection. The solder balls are then cured in a reflow oven. During the reflow oven process, it is necessary to ensure that the solder balls are fully fused with the pads on the back side of the first substrate 1 to form a reliable electrical connection.

[0048] Step 10: Print the package structure after the above steps, printing information such as the product model and batch number on the surface of the package. Then, use a cutting device to cut the package structure into individual finished structures. During the cutting process, ensure the flatness and dimensional accuracy of the cut surface.

[0049] The above steps can be used to prepare the PoP MEMS sensor of the present invention. This sensor uses PoP technology to achieve high integration and miniaturized stacking between chips, further reducing the package size while maintaining packaging quality, meeting market demand for smaller, higher-quality packaging structures.

[0050] It should be noted that PoP refers to Package on Package ("package on package", stacked assembly, stacked packaging). MEMS refers to Micro-Electro-Mechanical Systems.

[0051] In the description of the present invention, it should be understood that the terms "upper", "lower", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0052] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0053] In the present invention, unless otherwise specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can mean fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0054] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0055] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0056] Finally, it should be noted that the above-described embodiments are only specific implementation methods of the present invention, which are used to illustrate the technical solutions of the present invention rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the above-mentioned embodiments, ordinary technicians in this field should understand that any technician familiar with this technical field can still modify the technical solutions recorded in the above-mentioned embodiments within the technical scope disclosed by the present invention, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered by the protection scope of the present invention.

Claims

1. A PoP MEMS sensor, characterized in that: include: A first substrate (1) having a first solder ball array (2) on its back for external connection; A second substrate (3) is located above the first substrate (1) and is electrically connected to the first substrate (1) via a second solder ball array (4); An ASIC chip (5) is fixed to the front surface of the first substrate (1) and interconnected with the first substrate (1) via a first bonding wire (6), and is completely wrapped by a plastic package (7), wherein the plastic package (7) is provided with openings at positions corresponding to the second solder ball array (4) to expose the second solder balls; A MEMS chip (8) is fixed on the front surface of the second substrate (2) and interconnected with the second substrate (2) via a second bonding wire (9); The metal cover (10) is sealed and bonded to the front surface of the second substrate (2) by means of dam glue, and covers the MEMS chip (8) to form a cavity structure.

2. A PoP MEMS sensor according to claim 1, characterized in that: The ASIC chip (5) is fixed to the front surface of the first substrate (1) via a first adhesive (11), and the first adhesive (11) is a non-conductive adhesive film or non-conductive glue.

3. The PoP MEMS sensor according to claim 1, characterized in that: The MEMS chip (8) is fixed to the front surface of the second substrate (2) via a second adhesive (12), and the second adhesive (12) is jelly glue.

4. The PoP MEMS sensor according to claim 3, characterized in that: The thickness of the jelly glue is 60 μm to 100 μm.

5. The PoP MEMS sensor according to claim 1, characterized in that: The dam glue of the metal cover (10) is solder paste or silver glue, and is coated in a ring shape on the edge of the second substrate (2).

6. The PoP MEMS sensor according to claim 1, characterized in that: The openings of the plastic package body (7) are formed by a laser ablation process.

7. The PoP MEMS sensor according to claim 1, characterized in that: The first solder ball array (2) and the second solder ball array (4) are both spherical solder structures and are connected by reflow soldering and solidification.

8. The PoP MEMS sensor according to claim 1, characterized in that: The bonding wires between the ASIC chip (5) and the MEMS chip (8) are gold wires or copper wires.

9. A method for preparing a PoP MEMS sensor, characterized in that: include: S1. Soldering a second solder ball array (4) on the front surface of the first substrate (1) and curing the solder ball array by reflow soldering; S2. The ASIC chip (5) is fixed to the front of the first substrate (1) by a first adhesive (11), and after curing by baking, bonding is performed to interconnect the ASIC chip (5) and the first substrate (1); S3. The ASIC chip (5) is plastic-encapsulated to form a plastic encapsulation body (7), and a hole is laser-ablated at a position corresponding to the second solder ball array (4) to expose the second solder ball; S4. stacking the second substrate (2) on the plastic package (7), and performing reflow soldering connection with the second substrate (2) via the second solder ball; S5. The MEMS chip (8) is fixed to the front of the second substrate (2) by a second adhesive (12), and after baking and curing, bonding is performed to interconnect the MEMS chip (8) and the second substrate (2); S6. Coating a dam glue in an annular shape on the edge of the second substrate (2), bonding the metal cover (10), and then baking or reflow curing to form a cavity structure covering the MEMS chip (8); S7. Plant a first solder ball array (2) on the back side of the first substrate (1) and solidify it through reflow soldering.

10. The method for preparing a PoP MEMS sensor according to claim 9, characterized in that: In step S5, the second adhesive (12) is jelly glue, and its coating thickness is controlled to be 60 μm to 100 μm.

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