Large-size wafer surface mount tool

Abstract

The application relates to a large-size wafer surface mounting tool, which comprises a base and two pads, the two pads are slidingly installed on the base, and the two pads move along the base towards each other or away from each other; the two pads are respectively located on two sides of a substrate, each pad presses two corners of the substrate, and the pads are located on the side of the substrate close to a wafer. The application has the effects of improving the warping condition of the substrate, avoiding bridge short circuit, and improving the surface mounting yield.

Description

Technical Field

[0001] This application relates to the field of surface mount technology, and in particular to a surface mount fixture for large-size wafers. Background Technology

[0002] In modern electronics manufacturing, surface mount technology (SMT) is the mainstream process for electronic assembly. As electronic products continue to evolve towards higher performance and more multifunctionality, the application of large-size chips (greater than 60mm x 60mm) in SMT is becoming increasingly widespread. In SMT, reflow soldering is the core process for electrical connections. Through controlled heating, solder balls melt, reflow, and then solidify to form solder joints, achieving a conductive connection between the chip and the PCB substrate.

[0003] Regarding the aforementioned technologies, there is a significant difference in the coefficient of thermal expansion (CTE) and structural inhomogeneity between large-size wafers and PCB substrate materials. The degree of deformation between the two differs considerably, causing the four corners of the PCB substrate to deform downwards due to thermal stress at the peak reflow soldering temperature during the reflow soldering process. This warping deformation causes excessive compression of the solder balls in the corner areas, resulting in deformation of the solder balls, a reduction in the spacing between adjacent solder balls, and even bridging, thereby causing short-circuit defects. Utility Model Content

[0004] To improve substrate warping and prevent short circuits, this application provides a large-size wafer surface mount fixture.

[0005] A surface mount fixture for large-size wafers includes a base and two spacers. The two spacers are slidably mounted on the base and move along the base in a direction toward each other or away from each other. The two spacers are located on opposite sides of a substrate, with each spacer pressing against two corners of the substrate. The spacers are located on the side of the substrate closer to the wafer.

[0006] By adopting the above technical solution, two relatively movable pads can be adapted to substrates of different sizes and simultaneously apply constraint force to the four corners on both sides of the substrate, effectively suppressing the warping deformation caused by thermal stress during high-temperature reflow soldering, thereby avoiding short circuit problems between the chip and the substrate caused by excessive warping.

[0007] Preferably, the base is provided with two parallel sliding grooves, and the bottom of the pad is provided with a slider that matches the sliding groove, and the slider is slidably installed in the sliding groove.

[0008] By adopting the above technical solution, the cooperation between the slider and the groove provides precise guidance for the movement of the pads, ensuring that the two pads can always move in parallel, thereby making the pressure applied to the four corners of the substrate uniform and consistent, and improving the stability and reliability of the tooling.

[0009] Preferably, the base includes a first mounting plate, a second mounting plate, and a connecting plate. The connecting plate connects the first mounting plate and the second mounting plate. The first mounting plate and the second mounting plate are each equipped with the sliding groove. The bottom of each gasket is provided with a slider corresponding to the position of the two sliding grooves.

[0010] By adopting the above technical solution, the split base structure reduces the processing difficulty and cost, while the connecting plate ensures the relative positional accuracy and overall rigidity between the first mounting plate and the second mounting plate, thus guaranteeing the parallelism of the slide.

[0011] Preferably, the lower surfaces of the two pads contact and press against the four corner areas of the substrate, and the upper surfaces of the two pads contact and provide support to the four corner areas of the wafer.

[0012] By adopting the above technical solution, the gasket clamps and supports the critical corner areas of the substrate and the wafer from both the top and bottom directions, forming an effective mechanical balance and maximally offsetting the warping torque caused by the mismatch of the thermal expansion coefficients of the materials.

[0013] Preferably, the upper surfaces of the two gaskets are fitted with counterweights to increase their mass.

[0014] By adopting the above technical solution, the extra mass provided by the counterweight can increase the downward pressure on the substrate, further enhancing the effect of suppressing warping, and is especially suitable for large-sized, easily deformable substrates.

[0015] Preferably, the counterweight and the pad are connected by a detachable structure.

[0016] By adopting the above technical solution, users can flexibly replace counterweights of different masses according to different process requirements, so as to achieve precise control of the applied pressure and enhance the process adaptability and versatility of the tooling.

[0017] Preferably, the base and the two sets of gaskets are made of any one of ceramic, metal, alloy, or carbon fiber composite materials.

[0018] By adopting the above technical solutions, these materials all share the characteristics of high strength, high rigidity and low coefficient of thermal expansion, which can ensure that the tooling itself is not easily deformed in high temperature environment, maintain stable geometric dimensions and mechanical properties, thereby ensuring the suppression effect on product warping.

[0019] In summary, this application includes at least one of the following beneficial technical effects: 1. The adjustable double-shield design enables compatibility with substrates of different sizes and simultaneously applies uniform constraints to the four corners of the substrate, effectively suppressing solder warping and preventing short circuits. 2. The dovetail slide block mechanism ensures the smoothness and directional accuracy of the shim movement and prevents it from detaching during operation, thus improving the reliability and stability of the tooling. 3. The design of the detachable counterweight allows users to flexibly adjust the applied pressure according to process requirements, enhancing the tooling's process adaptability and applicability. Attached Figure Description

[0020] Figure 1 This is a three-dimensional structural diagram of the tooling in Embodiment 1 of this application; Figure 2 This is a schematic diagram of the substrate and wafer mounted on the tooling in Embodiment 1 of this application; Figure 3 This is a schematic diagram of the tooling in Embodiment 1 of this application, used to highlight the relative positions of the substrate, the wafer, and the spacer. Figure 4 This is a schematic diagram of the tooling in Embodiment 1 of this application, designed to highlight the shapes of the groove and the slider.

[0021] Reference numerals: 1. Base; 11. First mounting plate; 12. Second mounting plate; 13. Connecting plate; 14. Slide groove; 2. Gasket; 3. Slider; 4. Counterweight; 5. Substrate; 6. Wafer. Detailed Implementation

[0022] The following is in conjunction with the appendix Figure 1 -Appendix Figure 4 This application will be described in further detail.

[0023] This application discloses a surface mount fixture for large-size wafers, as described in the embodiments below. Figure 1 and Figure 2 It includes a base 1 and two pads 2 that are slidably mounted on the base 1. The two pads 2 are used to press against the corners of the substrate 5. During the reflow soldering process, the pads 2 always act on the corners of the substrate 5, applying a force to the corners to suppress the warping deformation of the corners of the substrate 5 during temperature changes.

[0024] Reference Figure 3 In this embodiment, two pads 2 are located on both sides of the substrate 5. Each pad 2 is used to press on the two corners of each side of the substrate 5. At the same time, the two pads 2 can slide towards each other or away to adjust the distance between the two pads 2, so as to realize the mounting limit of the substrate 5 of different sizes and the wafer 6 in the reflow soldering process.

[0025] The base 1 includes a first mounting plate 11, a second mounting plate 12, and a connecting plate 13. The first mounting plate 11 and the second mounting plate 12 are both rectangular flat plates, placed horizontally and parallel to each other. The connecting plate 13 is also a rectangular flat plate, with both ends of the connecting plate 13 fixedly connected to the same side of the first mounting plate 11 and the second mounting plate 12 by welding. Together, they form a U-shaped structure. The inner area of ​​the U-shaped structure is the accommodating area of ​​the substrate 5. In other embodiments, the first mounting plate 11, the second mounting plate 12, and the connecting plate 13 can also be integrally formed.

[0026] The base 1 has a first mounting plate 11 and a second mounting plate 12, each with a groove 14. The two grooves 14 are parallel to each other and have identical structural parameters. A slider 3, matching the groove 14, is installed at the bottom of each pad 2 at a position corresponding to the two grooves 14. The cross-sectional shape of the slider 3 is adapted to the opening of the groove 14. By pushing the two pads 2, the operator can move the slider 3 synchronously along the groove 14 on the base 1, driving the two pads 2 to achieve linear motion towards or away from each other. This adjustable structure of the fixture allows for flexible changes in the spacing between the two pads 2, thus adapting to substrates 5 and wafers 6 of different sizes and specifications. This improves the versatility of the fixture and reduces the cost and time required to change fixtures due to variations in the dimensions of substrates 5 and wafers 6.

[0027] Both gaskets 2 are rectangular flat plates, and each gasket 2 has a trapezoidal notch on its side closest to the other. The rectangular side of each gasket 2 closest to the other is the bottom edge of the trapezoidal notch. The trapezoidal notch design ensures that when the two gaskets 2 are attached and pressed against the substrate 5 to be mounted, four triangular pressing areas are formed at the corners, exerting force only on the four corners of the substrate 5 that are prone to warping and deformation.

[0028] Each pad 2 is also fitted with two counterweights 4, and all four counterweights 4 are placed on the triangular pressing areas on both sides of the two pads 2, corresponding one-to-one with the four corner areas of the substrate 5 to be mounted. The counterweights and pads are connected by bolts to enable detachable replacement. In other embodiments, the counterweights and pads can be integrally molded.

[0029] The weights of the four counterweights 4 are designed and selected based on the specific reflow soldering process. These counterweights 4 increase the weight of the pads 2, thereby ensuring that the downward pressure applied by the two pads 2 to the substrate 5 during the reflow soldering process can effectively suppress the warping deformation of the substrate 5 during the reflow soldering process.

[0030] The base 1 and the two gaskets 2 are made of high-strength materials with low coefficients of thermal expansion, such as ceramics, metals or alloys, and composite materials. These materials exhibit minimal warping deformation during the reflow soldering process, even after undergoing drastic temperature changes from room temperature to high temperature and back to room temperature, thus ensuring the dimensional stability and mechanical reliability of the tooling in high-temperature environments. In this embodiment, the counterweight 4 is made of the same material as the gaskets 2.

[0031] Reference Figure 4 The grooves 14 formed on the first mounting plate 11 and the second mounting plate 12 of the base 1 have a cross-sectional profile consisting of two parts: a rectangular groove at the top and a trapezoidal groove at the bottom, wider at the top and narrower at the bottom. Correspondingly, the sliders 3 at the bottom of the two pads 2 are designed as square blocks with trapezoidal protrusions that match the grooves 14. The dimensions of the grooves 14 and the sliders 3 correspond to each other, ensuring that they can fit tightly together. This allows the sliders 3 to slide along the grooves 14, thereby adjusting the distance between the two pads 2 to accommodate substrates 5 and wafers 6 of different sizes.

[0032] In other embodiments, the cross-section of the groove 14 can be triangular, trapezoidal, semi-circular, or other shapes. Correspondingly, the cross-sectional shape of the slider 3 is adapted to the cross-section of the groove 14 to allow the slider 3 to slide within the groove 14 and adjust the position of the pad 2.

[0033] In the actual placement process, the fixture is first placed stably on the carrier table of the pick-and-place machine. The substrate 5, pre-printed with solder balls, is placed in the receiving area of ​​the base 1. According to the size of the substrate 5 and the chip 6 to be placed, the positions of the two spacers 2 are adjusted so that the spacing between the two spacers 2 matches the size of the substrate 2. The triangular pressing areas of the two spacers 2 press against the four corners of the substrate 5. Then, the chip 6 is aligned and placed on the substrate 5. The two spacers 2, the substrate 5, and the chip 6 form a stacked structure. The two spacers 2 apply uniform pressure simultaneously, tightly pressing against the four corner areas of the substrate 5, effectively preventing the substrate from shifting or deforming during reflow soldering. At the same time, the upper surfaces of the two spacers 2 also provide reliable and stable support for the four corners of the chip 6.

[0034] Subsequently, the entire fixture, along with substrate 5 and wafer 6, is sent into a reflow oven for soldering. At high temperatures, the solder balls on substrate 5 melt. The fixture, through the restraint of two spacers 2 and the pressure applied by the counterweight 4, effectively counteracts the thermal stress generated on substrate 5 due to the high temperature, effectively suppressing warping deformation. After the reflow oven completes the soldering process and cools, the molten solder balls gradually solidify, forming a reliable electrical connection between substrate 5 and wafer 6. At this point, the fixture can be removed from substrate 5 and wafer 6, completing the entire mounting process.

[0035] The implementation principle of this embodiment is as follows: Two adjustable pads 2, along with the sliding cooperation of slider 3 and groove 14, achieve adaptive support for substrates 5 and wafers 6 of different sizes. Combined with the weight-increasing design of counterweight 4, the weight mass is controlled according to the actual needs of the reflow soldering process, increasing the pressure on substrate 5 and effectively suppressing warpage deformation. The tooling is made of high-strength, low-thermal-expansion-coefficient materials, effectively maintaining the dimensional stability of the tooling itself under the high-temperature environment of reflow soldering, avoiding adverse effects on the mounting accuracy of substrate 5 and wafer 6 due to tooling deformation. Ultimately, effective suppression of substrate warpage deformation is achieved, significantly improving soldering yield and interconnect reliability, providing strong technical support for high-quality mounting of large-size wafers.

[0036] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A surface mount fixture for large-size wafers, characterized in that, Includes a base (1) and two pads (2), the two pads (2) are slidably mounted on the base (1), and the two pads (2) move along the base (1) in a direction that is closer to or further away from each other; the two pads (2) are respectively located on both sides of the substrate (5), each pad (2) presses against two corners of the substrate (5), and the pads (2) are located on the side of the substrate (5) closer to the wafer (6).

2. The large-size wafer surface mount fixture according to claim 1, characterized in that, The base (1) is provided with two parallel sliding grooves (14), and the bottom of the pad (2) is provided with a slider (3) that is adapted to the sliding groove (14). The slider (3) is slidably installed in the sliding groove (14).

3. The large-size wafer surface mount fixture according to claim 2, characterized in that, The base (1) includes a first mounting plate (11), a second mounting plate (12) and a connecting plate (13). The connecting plate (13) connects the first mounting plate (11) and the second mounting plate (12). The first mounting plate (11) and the second mounting plate (12) are provided with the sliding groove (14). The bottom of each gasket (2) is provided with the slider (3) corresponding to the two sliding grooves (14).

4. The large-size wafer surface mount fixture according to claim 1, characterized in that, The lower surfaces of the two pads (2) contact and press against the four corner areas of the substrate (5), and the upper surfaces of the two pads (2) contact and provide support to the four corner areas of the wafer (6).

5. The large-size wafer surface mount fixture according to claim 1, characterized in that, The upper surfaces of the two gaskets (2) are fitted with counterweights (4) for increasing mass.

6. The large-size wafer surface mount fixture according to claim 5, characterized in that, The counterweight (4) and the pad (2) are connected by a detachable structure.

7. A large-size wafer surface mount fixture according to any one of claims 1-6, characterized in that, The base (1) and the two gaskets (2) are both made of any one of ceramic, metal, alloy, or carbon fiber composite materials.

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