Large size substrate vertical interconnect structure and method of fabrication

Abstract

The application discloses a large-size substrate vertical interconnection structure and a manufacturing method, and belongs to the technical field of electronic products.The application realizes signal interconnection through BGA solder balls, uses copper sheets as mechanical supports and forms heat dissipation channels, plates the surface of the copper sheets with tin and lead, and makes the copper sheets into a braided material to realize efficient and accurate mounting of the copper sheets through a chip mounter, and realizes fast mounting of the substrate and guarantees welding precision through design of process holes on the substrate and use of positioning guide pins.Through the structure and the manufacturing method, high-reliability vertical interconnection of the large-size substrate is realized.

Description

Technical Field

[0001] This invention relates to a vertical interconnect structure and manufacturing method for a large-size substrate, belonging to the field of electronic product technology. Background Technology

[0002] POP (Package on Package) packaging involves three-dimensionally stacking packaged chips with different functions to form electrical connections, achieving high integration and miniaturization. Conventional POP packaging uses BGA solder balls to interconnect the bottom and top modules. With the development of active phased array antennas, the structural integration method of phased array antennas is gradually shifting towards a "watt-type" approach. A certain type of active phased array antenna has high integration, high power consumption, and high heat dissipation requirements. This product integrates most of the phased array antenna functions onto two printed circuit boards (PCBs), which are then stacked and soldered together. Therefore, compared to conventional POP devices, the weight, power consumption, and size of this T / R module structure will increase significantly. The BGA solder ball interconnection method cannot meet the support and heat dissipation requirements of the substrate. Summary of the Invention

[0003] The technical problem solved by this invention is to overcome the shortcomings of existing technologies and provide a vertical interconnect structure and fabrication method for large-size substrates. This involves a strategy of achieving signal interconnection through BGA solder balls, a strategy of using copper sheets as mechanical supports and forming heat dissipation pathways, and efficient and precise placement of the copper sheets using a pick-and-place machine after tin-lead plating and fabrication into tape and ribbon. Furthermore, the invention utilizes process holes designed on the substrate and positioning guide pins to achieve rapid substrate stacking while ensuring soldering accuracy. Through the above structure and fabrication method, highly reliable vertical interconnection of large-size substrates is achieved.

[0004] The technical solution of the present invention is: a large-size substrate vertical interconnect structure, including an upper substrate, BGA solder balls, positioning guide pins, copper sheets and a lower substrate;

[0005] The upper and lower substrates are provided with positioning holes for use with positioning guide pins to align the two substrates.

[0006] Solder paste is coated on the upper substrate, and the BGA solder balls and copper sheets are mounted on the upper substrate.

[0007] Solder paste is applied to the lower substrate, and positioning guide pins are used to stack and solder it to the upper substrate on which BGA solder balls and copper sheets are mounted.

[0008] Furthermore, the positioning holes are provided in at least three locations, distributed at the three corners of the upper and lower substrates.

[0009] Furthermore, the diameter of the positioning guide pin is 0.01mm to 0.03mm smaller than the diameter of the positioning hole on the printed circuit board.

[0010] Furthermore, the thickness of the copper sheet is determined based on the diameter of the BGA solder ball.

[0011] Furthermore, the height of the copper sheet after welding is lower than the height of the BGA solder ball, with a height difference of 0.03 to 0.1 mm.

[0012] The method for fabricating a large-size substrate vertical interconnect structure includes:

[0013] After applying solder paste to the upper substrate, BGA solder balls and copper sheets are mounted, and then reflow soldering is performed.

[0014] After applying solder paste to the lower substrate, a positioning guide pin is inserted into the process hole. The upper substrate after reflow soldering is aligned with the positioning guide pin on the lower substrate. The upper substrate is moved along the positioning guide pin until it contacts the lower substrate, thus aligning the two substrates.

[0015] After reflow soldering, the positioning guide pins are removed to achieve stacked soldering of vertical interconnects of the substrates.

[0016] Furthermore, a pick-and-place machine is used to mount copper sheets onto the upper substrate, and a ball-drilling fixture or pick-and-place machine is used to place BGA solder balls onto the upper substrate; the upper substrate with BGA solder balls and copper sheets mounted is then placed in a reflow soldering machine to achieve soldering of the BGA solder balls and copper sheets.

[0017] Furthermore, the thickness of the ball-drilling tool is 0.5 to 1 times the diameter of the BGA solder ball, and the mesh size is the diameter of the BGA solder ball + 0.05 mm.

[0018] Furthermore, the spacing and number of arrayed mesh holes on the ball-drilling fixture are the same as the spacing and number of BGA pads on the upper substrate.

[0019] Furthermore, after the lower substrate is printed with solder paste, it is placed flat on the worktable. The positioning guide pin is inserted into the lower substrate, the BGA solder balls and copper sheets of the upper substrate are facing down, and the positioning holes on the substrate are aligned with the positioning guide pin. Then the upper substrate is moved vertically so that it falls onto the lower substrate to achieve alignment.

[0020] The advantages of this invention compared to the prior art are:

[0021] (1) The copper pads used in this invention can provide mechanical support while meeting high heat dissipation requirements, and can ensure high reliability of large-size substrate stacking and welding.

[0022] (2) In this invention, BGA solder balls are matched and soldered to copper sheets. After soldering on the upper substrate, the BGA solder balls are slightly higher than the copper sheets. After stacking, the substrate is supported by the BGA solder balls. During subsequent stacking and soldering, the BGA solder balls stop collapsing after touching the copper sheets during the collapse process, thus achieving effective soldering of different materials and solder end shapes.

[0023] (3) The present invention uses a tin-lead plating layer on the surface of copper sheet to avoid the easy oxidation of bare copper and improve the solderability of copper sheet; in addition, the copper sheet after tin-lead plating is processed by tape and then mounted by a pick and place machine, which greatly improves production efficiency.

[0024] (4) The positioning guide pin used in this invention can quickly align the upper and lower substrates. During welding, the positioning pin limits the offset of the substrate to ensure welding accuracy. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a large-size substrate vertical interconnect structure according to the present invention. Detailed Implementation

[0026] To better understand the above technical solutions, the technical solutions of this application will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of this application and the specific features in the embodiments are detailed descriptions of the technical solutions of this application, rather than limitations on the technical solutions of this application. In the absence of conflict, the embodiments of this application and the technical features in the embodiments can be combined with each other.

[0027] The following description, in conjunction with the accompanying drawings, provides a more detailed account of a large-size substrate vertical interconnect structure and its fabrication method provided in this application. Specific implementation methods may include (e.g.) Figure 1 As shown): upper substrate 1, BGA solder balls 2, positioning guide pins 3, copper sheet 4, and lower substrate 5; the upper substrate 1 and lower substrate 5 are provided with positioning holes for aligning the two substrates in cooperation with the positioning guide pins 3; solder paste is coated on the upper substrate 1, and the BGA solder balls 2 and copper sheet 4 are mounted on the upper substrate 1; solder paste is coated on the lower substrate 5, and the positioning guide pins 3 are used to stack and solder the upper substrate 1 with the BGA solder balls 2 and copper sheet 4 mounted on it.

[0028] Furthermore, the positioning holes are provided in at least three locations, distributed at the three corners of the upper substrate 1 and the lower substrate 5.

[0029] Optionally, in one possible implementation, the diameter of the positioning guide pin is 0.01 mm to 0.03 mm smaller than the diameter of the positioning hole on the printed circuit board.

[0030] In one possible implementation, the thickness of the copper sheet 4 is determined based on the diameter of the BGA solder ball 2.

[0031] Optionally, the height of the copper sheet 4 after welding is lower than the height of the BGA solder ball 2, with a height difference of 0.03 to 0.1 mm.

[0032] Based on and Figure 1With the same inventive concept, the present invention also provides a method for fabricating a large-size substrate vertical interconnect structure, comprising the following steps:

[0033] After applying solder paste to the upper substrate 1, BGA solder balls 2 and copper sheets 4 are mounted, and then reflow soldering is performed.

[0034] After applying solder paste to the lower substrate 5, a positioning guide pin 3 is inserted into the process hole. The upper substrate 1 after reflow soldering is aligned with the positioning guide pin 3 on the lower substrate 5. The upper substrate 1 is moved along the positioning guide pin 3 to make it contact the lower substrate 5, thereby aligning the two substrates.

[0035] After reflow soldering, the positioning guide pin 3 is removed to achieve stacked soldering of vertical interconnection of the substrate.

[0036] Furthermore, a pick-and-place machine is used to mount copper sheets onto the upper substrate 1, and a ball-drilling fixture or a pick-and-place machine is used to place BGA solder balls 2 onto the upper substrate 1; the upper substrate 1 with BGA solder balls 2 and copper sheets 4 mounted is placed in a reflow soldering machine to achieve soldering of BGA solder balls 2 and copper sheets 4.

[0037] Optionally, in one possible implementation, the thickness of the ball-drilling fixture is 0.5 to 1 times the diameter of the BGA solder ball 2, and the mesh size is the diameter of the BGA solder ball 2 + 0.05 mm.

[0038] In one possible implementation, the spacing and number of arrayed mesh holes on the ball-drilling fixture are the same as the spacing and number of BGA pads on the upper substrate 1.

[0039] Furthermore, after the lower substrate 5 is printed with solder paste, it is placed flat on the worktable. The positioning guide pin 3 is inserted into the lower substrate 5, the BGA solder balls 2 and copper sheets 4 of the upper substrate 1 are facing down, and the positioning holes on the substrate are aligned with the positioning guide pin 3. Then the upper substrate 1 is moved vertically so that it falls onto the lower substrate 5 to achieve alignment.

[0040] In the solution provided in this application embodiment, three process holes with a diameter of 1mm are designed on the substrate. The process holes are distributed at the three corners of the printed circuit board. The diameter of the positioning guide pin is 0.01mm to 0.03mm smaller than the diameter of the process hole. The signal points on the substrate are designed with array BGA pads. The pad diameter is determined according to the design requirements. The area outside the signal points is set with array rectangular pads.

[0041] Design a solder paste printing fixture with a thickness of 0.1mm and an aperture size of 90% of the pad size. Use a printer to apply solder paste to the upper substrate 1 and lower substrate 5. The copper sheet thickness is determined based on the solder ball diameter. The height of the copper sheet after soldering should be slightly lower than the solder ball height, with a height difference of 0.03-0.1mm. The size is designed based on the space on the substrate and heat dissipation requirements. Use a pick-and-place machine to mount the copper sheet onto the substrate. Design a ball drain fixture with a thickness of 0.5-1 times the solder ball diameter and a mesh size of solder ball diameter + 0.05mm. The mesh spacing and number are the same as the BGA pad spacing and number on the substrate. Align the ball drain fixture with the substrate and adjust the gap between the substrate and the ball drain fixture (between 0.05-0.1mm). Guide the solder ball into the ball drain fixture and use a brush to sweep the solder ball into the mesh. Use a vacuum gun to remove excess solder ball. Lower the substrate height and remove the lower ball drain fixture to achieve the mounting of the BGA solder ball on the upper substrate 1. The upper substrate 1, after mounting the solder balls and copper sheets, is placed in a reflow soldering machine to achieve the soldering of BGA solder balls and copper sheets.

[0042] After the lower substrate 5 is printed with solder paste, it is placed flat on the worktable. The positioning guide pin is inserted into the lower substrate 5, and the solder balls and copper sheets of the upper substrate 1 are placed downwards. The process holes on the substrate are aligned with the positioning guide pin. Then, the upper substrate 1 is moved vertically so that it falls onto the lower substrate 5 to achieve alignment. The above assembly is placed in a reflow soldering machine. After soldering is completed, the positioning guide pin is removed, thus realizing the vertical interconnection process of large-size substrates.

[0043] like Figure 1 As shown, the components of the large-size substrate vertical interconnect structure and manufacturing method of the present invention include an upper substrate 1, BGA solder balls 2, positioning guide pins 3, copper sheets 4, and a lower substrate 5.

[0044] like Figure 1 First, solder paste is applied to the upper substrate 1, followed by mounting BGA solder balls 2 and copper sheets 4, and then reflow soldering is performed. Solder paste is applied to the lower substrate 5, and positioning guide pins 3 are inserted into the process holes. The reflow-soldered upper substrate 1 is aligned with the positioning guide pins on the lower substrate, and the upper substrate 1 is moved along the positioning guide pins until it contacts the lower substrate 5, thus aligning the two substrates. After reflow soldering, the positioning guide pins are removed, thus completing the stacking and soldering process for vertical interconnection of large-size substrates.

[0045] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

[0046] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A vertical interconnect structure for a large-size substrate, characterized in that, It includes an upper substrate (1), BGA solder balls (2), positioning guide pins (3), copper sheets (4) and a lower substrate (5); The upper substrate (1) and the lower substrate (5) are provided with positioning holes for use in conjunction with positioning guide pins (3) to achieve alignment of the two substrates; Solder paste is coated on the upper substrate (1), and the BGA solder balls (2) and copper sheets (4) are mounted on the upper substrate (1); Solder paste is applied to the lower substrate (5), and positioning guide pins (3) are used to stack and solder the upper substrate (1) on which BGA solder balls (2) and copper sheets (4) are mounted. The positioning holes are provided in at least three locations, distributed at the three corners of the upper substrate (1) and the lower substrate (5); The diameter of the positioning guide pin is 0.01mm to 0.03mm smaller than the diameter of the positioning hole on the printed circuit board; The thickness of the copper sheet (4) is determined according to the diameter of the BGA solder ball (2); The height of the copper sheet (4) after welding is lower than the height of the BGA solder ball (2), and the height difference is 0.03~0.1mm; After the solder paste is printed on the lower substrate (5), it is placed flat on the worktable. The positioning guide pin (3) is inserted into the lower substrate (5). The BGA solder balls (2) and copper sheets (4) of the upper substrate (1) are facing down. The positioning holes on the substrate are aligned with the positioning guide pin (3). Then the upper substrate (1) is moved vertically so that it falls onto the lower substrate (5) to achieve alignment.

2. The method for fabricating a large-size substrate vertical interconnect structure according to claim 1, characterized in that, include: After applying solder paste to the upper substrate (1), BGA solder balls (2) and copper sheets (4) are mounted, and then reflow soldering is performed; After applying solder paste to the lower substrate (5), insert the positioning guide pin (3) into the process hole, align the reflow soldered upper substrate (1) with the positioning guide pin (3) on the lower substrate (5), and move the upper substrate (1) along the positioning guide pin (3) to make it contact the lower substrate (5) to achieve alignment of the two substrates. After reflow soldering, the positioning guide pin (3) is removed to achieve stacking soldering of vertical interconnection of substrates; The copper sheet is mounted on the upper substrate (1) using a pick-and-place machine, and the BGA solder ball (2) is placed on the upper substrate (1) using a ball-drilling fixture or a pick-and-place machine. The upper substrate (1) after mounting the BGA solder ball (2) and the copper sheet (4) is placed in a reflow soldering machine to achieve the soldering of the BGA solder ball (2) and the copper sheet (4).

3. The manufacturing method according to claim 2, characterized in that, The thickness of the ball-leaking fixture is 0.5 to 1 times the diameter of the BGA solder ball (2), and the mesh size is the diameter of the BGA solder ball (2) + 0.05 mm.

4. The manufacturing method according to claim 3, characterized in that, The spacing and number of arrayed mesh holes on the ball-drilling fixture are the same as the spacing and number of BGA pads on the upper substrate (1).

5. The manufacturing method according to claim 2, characterized in that, After the solder paste is printed on the lower substrate (5), it is placed flat on the worktable. The positioning guide pin (3) is inserted into the lower substrate (5). The BGA solder balls (2) and copper sheets (4) of the upper substrate (1) are facing down. The positioning holes on the substrate are aligned with the positioning guide pin (3). Then the upper substrate (1) is moved vertically so that it falls onto the lower substrate (5) to achieve alignment.

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