Self-reinforced BGA packaging device structure and assembling method thereof

Abstract

The invention discloses a self-reinforced BGA (Ball Grid Array) packaging device structure and an assembling method thereof. The self-reinforced BGA packaging device structure comprises a BGA packaging tube shell, BGA solder balls, rectangular copper sheets and a PCB (Printed Circuit Board), after the BGA packaging tube shell is coated with soldering paste, a BGA solder ball and a rectangular copper sheet are mounted on the BGA packaging tube shell, and then reflow soldering is carried out; after the PCB is coated with soldering paste, a chip mounter is adopted to mount the BGA device on the PCB; and after reflow soldering, the board-level assembly process of the self-reinforced BGA packaging device structure is realized. According to the invention, the rectangular large-area bonding pad is additionally arranged in the BGA packaging array bonding pad, the copper sheet is welded on the rectangular bonding pad to increase the welding area and improve the mechanical fixation of the BGA packaging device PCB, dispensing reinforcement is not needed, the assembly process is simplified, and the board-level assembly efficiency is improved.

Description

Technical Field

[0001] This invention is an innovation in the structure and assembly process of BGA packaged devices used in the manufacturing of integrated circuit devices, and relates to a self-hardened BGA packaged device structure and its assembly method. Background Technology

[0002] BGA (Block Grid Assembly) structures are used in some newly developed assembly structures and components due to their miniaturization advantages, such as FPGA devices, SIP devices, and devices based on various advanced packaging technologies. However, due to product characteristics, the board-level assembly reliability of BGA packaged devices requires the introduction of dispensing processes. This not only increases the product's production cycle but also risks that the performance of the product after dispensing may not meet the microwave transmission performance requirements of high-frequency products.

[0003] No invention patents addressing the aforementioned problems were found in publicly available literature and publications. Several representative patents and documents are as follows: 1. "Design Method and Structure of Ports for Large-Size Single-Layer Ceramic BGA Package Products", Application No.: CN202311356643.5, Publication / Announcement Date: 2023-12-22. This invention relates to the field of radio frequency circuit technology, specifically disclosing a design method and structure for ports of large-size single-layer ceramic BGA package products. The method includes the following steps: setting multiple sets of arrayed pads on a substrate for mounting BGA solder balls; interconnecting the signal pads in the third ring of pads used for mounting signal attribute BGA solder balls with adjacent pads in the second outer ring of pads through interconnecting pad patterns. This invention achieves the same attribute design for the second outer ring and third ring of BGA pads by binding the signal pads in the second outer ring and third ring of pads at the same position through interconnecting pad patterns. This simultaneously achieves port expansion and solves the reliability design problem after expansion; it improves the integration density of BGA package products with almost unchanged size and design. This invention mainly solves the problem of improving board-level assembly reliability of BGA packaged devices by adding rectangular copper sheets, which is significantly different from the problem solved by the aforementioned patent.

[0004] 2. "Reinforcing Components for CCGA Packages", Authorization Announcement No.: CN219248186U, Publication / Announcement Date: 2023-06-23. This utility model provides a reinforcing component for CCGA packages. The CCGA package includes a printed circuit board assembly and a CCGA ceramic body. The reinforcing components are evenly distributed along the edge of the CCGA ceramic body, and are fixed to both the printed circuit board assembly and the CCGA ceramic body using epoxy resin or silicone rubber. This utility model has the following advantages: by connecting the CCGA ceramic body and the printed circuit board assembly with independent reinforcing components, it solves the technical problem that the existing fixing structures of packaging devices are not suitable for CCGA packages, resulting in a reinforcing component specifically suitable for CCGA packages. This invention is a solution proposed to avoid the impact of the dispensing process on the product's production cycle and high-frequency microwave transmission characteristics, and is completely different from the aforementioned patent.

[0005] The novelty search results show that no content identical to this invention has been found in publicly published patent and non-patent documents, either domestically or internationally. Summary of the Invention

[0006] This invention proposes a self-hardened BGA packaged device structure and its assembly method. By adding rectangular pads to the array pads of the BGA package and employing an integrated solder ball and copper sheet soldering method, a novel BGA packaged device structure is achieved. Finally, board-level soldering is achieved through SMT reflow soldering. In this structure, the BGA solder balls enable signal interconnection, and the copper sheet increases the soldering area of ​​the device, simultaneously satisfying mechanical and thermal stress hardening, and also serving as a heat dissipation path to improve the device's heat dissipation capacity.

[0007] To achieve the above effects, the technical solution adopted by the present invention is as follows: A self-hardened BGA packaged device structure, characterized in that it comprises a BGA package shell, BGA solder balls, rectangular copper sheets, and a PCB board. After applying solder paste to the BGA package, BGA solder balls and multiple rectangular copper sheets are mounted, and then reflow soldering is performed to obtain the BGA device. After solder paste is applied to the PCB board, a pick-and-place machine is used to mount the BGA devices onto the PCB board. The product is obtained after reflow soldering.

[0008] Optionally, a gate array BGA solder balls are arranged on the BGA package shell, and multiple rectangular copper sheets are symmetrically arranged therein.

[0009] Optionally, the rectangular copper sheets are uniformly arranged on the BGA package shell according to at least one of the following symmetry methods: top-bottom symmetry, left-right symmetry, vertical symmetry, horizontal symmetry, diagonal symmetry, axial symmetry, central symmetry, and mirror symmetry.

[0010] Optionally, the center-to-center spacing of the BGA solder balls and the maximum solder joint height are determined according to the product's electrical performance requirements. Then, the layout position and number of rectangular copper sheets are determined according to the layout of the BGA solder balls, ultimately forming a BGA packaged device structure that meets the product's performance requirements.

[0011] Optionally, the layout can be configured such that 370 BGA solder balls are arranged, with a solder ball diameter of 0.45mm. Ten rectangular copper sheets are arranged symmetrically, each measuring 1.4mm x 2.2mm.

[0012] The assembly method of any self-hardened BGA packaged device structure of the present invention includes: Design solder paste printing fixture: The solder paste printing fixture thickness is 0.1mm, the opening size of the BGA solder ball is 100% of the pad size, the opening size of the rectangular copper sheet is 90% of the pad size, and the solder paste is applied to the BGA package using a printing machine; the thickness of the rectangular copper sheet is 0.05~0.1mm lower than the height of the BGA solder ball, and the flatness of the rectangular copper sheet is less than 0.05mm. Design the ball-leaking fixture: the thickness is 0.5 to 1 times the diameter of the BGA solder ball, and the mesh size is the solder ball diameter + 0.05 mm. Place the BGA solder ball (3) on the BGA package shell. After mounting a rectangular copper sheet (2) onto the BGA package using a chip mounter, it is placed in a reflow soldering machine. Solder paste is applied to the PCB board, BGA devices are mounted on the PCB board, and board-level assembly is achieved through reflow soldering.

[0013] The advantages of this invention compared to the prior art are as follows: (1) A large rectangular pad was added to the BGA package array pad. Copper sheets were welded on the rectangular pad to increase the welding area and improve the mechanical fixation of the BGA package device PCB board. No further glue reinforcement was required, which simplified the assembly process and improved the board-level assembly efficiency.

[0014] (2) BGA solder balls have small size and good microwave transmission characteristics, but the CTE mismatch between the CBGA device body and the PCB board is serious, resulting in poor board-level reliability. By placing rectangular pads in the locations of high thermal stress of the device to increase the soldering strength, the thermal stress on the spherical solder joints is dispersed to increase product reliability. At the same time, the introduction of underfill is avoided or the solder joint height is increased to ensure high reliability while maintaining high-frequency microwave transmission characteristics. Attached Figure Description

[0015] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the self-hardened BGA packaged device structure of the present invention; Thermodynamic simulations were performed on the BGA casing before and after the addition of copper strips under conditions ranging from -55℃ to 125℃. The specific results are as follows. Figure 2 and Figure 3 As shown; Figure 2 Before adding the rectangular copper sheet, the stress (top two images) and strain (bottom two images) results at 125℃ and -55℃ temperatures; Figure 3 The images show the stress (top two) and strain (bottom two) results at 125℃ and -55℃ after adding rectangular copper sheets. The labels in the diagram represent: 1-BGA package shell, 2-rectangular copper sheet, 3-BGA solder ball. Detailed Implementation

[0016] The present invention will be described in detail below with reference to specific embodiments and accompanying drawings: This invention develops a novel self-hardened BGA package structure based on BGA packaging. This structure adds large rectangular pads to the gate array pads, and rectangular copper sheets are soldered onto these pads to increase the soldering area, improve the mechanical fixation of the BGA packaged device on the PCB board, and distribute the stress on the spherical solder joints. Furthermore, the layout can be customized according to heat dissipation requirements to enhance heat dissipation capabilities.

[0017] For molded BGA devices that may deform during reflow soldering, a collapsible solder ball process is used in conjunction with the copper strip. After soldering the solder balls and copper strip, the solder balls are slightly higher than the copper strip to ensure that the device is supported on the printed circuit board after mounting. During subsequent reflow soldering, the solder balls stop collapsing after touching the copper strip, ensuring effective soldering between the copper strip and the solder balls. For ceramic-encapsulated BGA devices that do not deform during reflow soldering, both collapsible and non-collapsible solder ball processes can be used. When using the non-collapsible solder ball process, the height of the solder joints must be consistent after the solder balls and copper strip are installed.

[0018] Specifically, this invention innovates the structure and board-level assembly process of BGA packaged devices, significantly improving the board-level assembly reliability and high-frequency transmission performance of BGA packaged devices. For example... Figure 1As shown, the self-hardened BGA packaged device structure and its assembly method of the present invention include BGA package housing 1, BGA solder balls 3, rectangular copper sheets 2, and PCB board. After solder paste is applied to the BGA package housing 1, BGA solder balls 3 and multiple rectangular copper sheets 2 are mounted, and then reflow soldering is performed to obtain the BGA device. After solder paste is applied to the PCB board, the BGA device is mounted on the PCB board using a pick-and-place machine. After reflow soldering, the device is obtained.

[0019] In an embodiment of the present invention, a gate array BGA solder balls 3 are arranged on a BGA package 1, and a plurality of rectangular copper sheets 2 are symmetrically arranged therein.

[0020] In an embodiment of the present invention, rectangular copper sheets 2 are uniformly arranged on the BGA package shell 1 according to at least one of the following symmetry methods: top-bottom symmetry, left-right symmetry, vertical symmetry, horizontal symmetry, diagonal symmetry, axial symmetry, central symmetry, and mirror symmetry.

[0021] In an embodiment of the present invention, the center spacing of the BGA solder balls 3 and the maximum solder joint height are determined according to the electrical performance requirements of the product. Then, the layout position and number of the rectangular copper sheets 2 are determined according to the layout of the BGA solder balls 3, and finally a BGA packaged device structure that can meet the product performance is formed.

[0022] A novel BGA package structure was achieved by adding rectangular pads to the array pads of the BGA package and using an integrated solder ball and copper sheet soldering method. Finally, board-level soldering was achieved through SMT reflow soldering. This structure can simultaneously meet mechanical and thermal stress reinforcement requirements. The device uses array BGA pads for signal points and array rectangular pads for areas outside the signal points. First, electrical performance simulation is needed to determine the center-to-center spacing of the BGA solder balls and the maximum tolerable solder joint height. Then, based on the layout of the BGA solder balls, force and thermal simulations are used to determine the layout position and quantity of the copper sheets, ultimately forming a BGA package structure that meets product performance requirements.

[0023] Design solder paste printing fixture: The solder paste printing fixture thickness is 0.1mm. The BGA array pad opening size is 100% of the pad size, and the copper pad opening size is 90% of the pad size. A solder paste printer is used to apply solder paste to the device. The copper pad thickness is determined based on the solder ball diameter. The height of the copper pad after soldering should be slightly lower than the solder ball height, with a height difference of 0.05–0.1mm, and the flatness of the copper pad soldering should be better than 0.05mm. A pick-and-place machine is used to mount the copper pad onto the device.

[0024] The solder ball fixture is designed with a thickness of 0.5 to 1 times the solder ball diameter. The mesh size is: solder ball diameter + 0.05 mm. The mesh spacing and number are the same as the BGA pad spacing and number on the substrate. A fully automated ball placement machine is used to place the solder balls onto the device array pads, and a pick-and-place machine is used to place rectangular copper sheets onto the rectangular pads of the device. The device with solder balls and copper sheets mounted is then placed in a reflow soldering machine to achieve soldering of the BGA solder balls to the copper sheets.

[0025] Solder paste is applied to the PCB board using a printer, BGA devices are mounted onto the PCB board using a pick-and-place machine, and then board-level assembly is achieved through a reflow soldering process.

[0026] Example 1: Combination Figure 1 The self-hardened BGA package structure of this embodiment includes a BGA package shell 1, BGA solder balls 3, rectangular copper sheets 2, and a PCB board. After solder paste is applied to the BGA package shell 1, BGA solder balls 3 and rectangular copper sheets 2 are mounted, and then reflow soldering is performed to obtain the BGA device. After solder paste is applied to the PCB board, the BGA device is mounted on the PCB board using a pick-and-place machine. After reflow soldering, the board-level assembly process of the self-hardened BGA package structure is realized.

[0027] The specific layout of this embodiment is as follows: the BGA package shell 1 has a size of 21mm*16mm; the number of BGA solder balls 3 is 370, arranged uniformly in an array; the diameter of the solder balls is 0.45mm, and the center-to-center spacing of the solder balls is 0.8mm; the rectangular copper sheets 2 are symmetrically arranged, numbering 10, with a size of 1.4mm*2.2mm. See details for the structure. Figure 1 As shown; for example, on a rectangular BGA package 1, two rectangular copper sheets 2 are symmetrically arranged along one width side with the center line of the width side; two are symmetrically arranged along one length side with the center line of the length side; and another set is mirror-symmetrically arranged along the center line of the other width side and length side; at the same time, two rectangular copper sheets 2 are symmetrically arranged vertically on the center line of the length side at the intersection of the center line of the length center line and the center line of the width center line of the BGA package 1.

[0028] Figure 2 Before adding the rectangular copper sheet, the stress (top two images) and strain (bottom two images) results at 125℃ and -55℃ temperatures; Figure 3 The images show the stress (top two) and strain (bottom two) results at 125℃ and -55℃ after adding rectangular copper sheets. Table 1

[0029] Thermodynamic simulations were performed on the BGA casing before and after adding the copper strip under conditions of -55℃ to 125℃. The specific results are as follows. Figure 2 , Figure 3 As shown in Table 1, the results indicate that increasing the copper sheet reduced the minimum stress at the solder ball position by approximately 16% and the minimum strain by approximately 30% at low temperatures, demonstrating a significant effect.

[0030] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A self-hardened BGA packaged device structure, characterized in that, It includes a BGA package (1), BGA solder balls (3), rectangular copper strips (2) and a PCB board; After applying solder paste to the BGA package (1), BGA solder balls (3) and multiple rectangular copper sheets (2) are mounted, and then reflow soldering is performed to obtain the BGA device. After solder paste is applied to the PCB board, a pick-and-place machine is used to mount the BGA devices onto the PCB board. The product is obtained after reflow soldering.

2. The self-hardened BGA packaged device structure according to claim 1, characterized in that, A gate array BGA solder balls (3) are arranged on the BGA package shell (1), and multiple rectangular copper sheets (2) are symmetrically arranged therein.

3. The self-hardened BGA packaged device structure according to claim 1 or 2, characterized in that, The rectangular copper sheet (2) is uniformly arranged on the BGA package shell (1) according to at least one of the following symmetry methods: top-bottom symmetry, left-right symmetry, vertical symmetry, horizontal symmetry, diagonal symmetry, axial symmetry, central symmetry and mirror symmetry.

4. The self-hardened BGA packaged device structure according to claim 1 or 2, characterized in that, The center spacing and maximum solder joint height of the BGA solder balls (3) are determined according to the electrical performance requirements of the product. Then, the layout position and quantity of the rectangular copper sheet (2) are determined according to the layout of the BGA solder balls (3), and finally, a BGA packaged device structure that can meet the product performance is formed.

5. The self-hardened BGA packaged device structure according to claim 1 or 2, characterized in that, The specific layout is as follows: the number of BGA solder balls (3) is 370, and the diameter is 0.45mm; Ten rectangular copper sheets (2) are arranged symmetrically, with a size of 1.4mm*2.2mm.

6. The assembly method of the self-hardened BGA packaged device structure according to any one of claims 1-5, characterized in that, include: Design of solder paste printing fixture: The thickness of the solder paste printing fixture is 0.1mm. The opening size of the BGA solder ball (3) is 100% of the pad size. The opening size of the rectangular copper sheet (2) is 90% of the pad size. Solder paste is applied to the BGA package shell (1) using a printing machine. The thickness of the rectangular copper sheet (2) is 0.05 to 0.1mm lower than the height of the BGA solder ball (3). The flatness of the rectangular copper sheet (2) is less than 0.05mm. Design the ball-leaking fixture: the thickness is 0.5 to 1 times the diameter of the BGA solder ball, and the mesh size is the solder ball diameter + 0.05 mm. Place the BGA solder ball (3) on the BGA package shell. After mounting a rectangular copper sheet (2) onto the BGA package using a chip mounter, it is placed in a reflow soldering machine. Solder paste is applied to the PCB board, BGA devices are mounted on the PCB board, and board-level assembly is achieved through reflow soldering.

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