SOP32 lead frame
By setting recessed structures and guiding areas on the damping ribs of the SOP32 lead frame, the problem of uneven cutting stress distribution was solved, improving cutting accuracy and chip yield.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-28
- Publication Date
- 2026-03-31
AI Technical Summary
When cutting damping ribs, the existing SOP32 lead frame has a wide range of cutting stress distribution, forming multiple high stress points, which makes the frame unit easy to deform and the yield rate of chip mass production is low.
The damping rib is designed with a recessed structure on the front surface that is recessed to the rear, with the recessed direction perpendicular to the cutting direction. First and second guide areas are set on the damping rib. The first guide area provides main guidance, and the second guide area provides buffering, so as to evenly distribute the cutting stress and reduce the concentration of mechanical stress.
By guiding the cutting path and buffering stress fluctuations, the risk of microcracks and fatigue damage to the pins is reduced, improving the yield of chip mass production and ensuring cutting accuracy and stability.
Smart Images
Figure CN224069093U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of chip molding technology, and in particular to an SOP32 lead frame. Background Technology
[0002] The existing SOP32 leadframe includes a main frame and several frame units. Each frame unit includes a wafer island, connecting ribs, and damping ribs. The chip is connected to the wafer island, and two connecting ribs are located on the left and right sides of the wafer island. The connecting ribs are connected to the main frame. Sixteen pins are respectively set on the upper and lower sides of the wafer island. The damping ribs are connected between two adjacent pins. When the leadframe is sealed with adhesive and the pins are separated, the leadframe is placed on a cutting device. The cutting device cuts the damping ribs along the cutting direction to separate adjacent pins. The damping ribs are all flat. When the damping ribs are cut in a straight line, the cutting stress distribution range is wide, and multiple high stress points are formed near the cutting path. The frame units are prone to deformation during the cutting process, resulting in a low yield rate for chip mass production.
[0003] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Utility Model Content
[0004] To address the shortcomings of existing technologies, this utility model discloses an SOP32 lead frame to solve the problems that damping ribs are all flat, and when the damping ribs are cut in a straight line, the cutting stress distribution range is wide, multiple high stress points are formed near the cutting path, the frame unit is easy to deform during the cutting process, and the yield rate of chip mass production is low.
[0005] The technical solution adopted in this utility model is as follows:
[0006] An SOP32 lead frame includes:
[0007] The main framework;
[0008] A frame unit, comprising a plurality of such units, is connected within the frame body. The frame unit includes:
[0009] A wafer carrier island, on which a chip is disposed, and sixteen pins extend from the wafer carrier island to the top and bottom sides respectively, and thirty-two pins are bonded to the chip;
[0010] There are two connecting ribs, which are symmetrically arranged on the left and right sides of the carrier island and connect the frame body.
[0011] A damping rib is provided, comprising several damping ribs connected between two adjacent pins. The front surface of the damping rib is provided with a recessed structure that is recessed to the rear, and the recessed direction is perpendicular to the cutting direction.
[0012] A further technical solution is that the damping rib includes two first guide areas and one second guide area; the two first guide areas are symmetrically arranged on the upper and lower sides of the damping rib, and each first guide area has two first plates, with one end of the two first plates connected being lower than the opposite end of the two first plates; the second guide area is located between the two first guide areas and connects the two first guide areas, and the second guide area is an arc-shaped plate with the arc-shaped plate recessed towards the rear end.
[0013] A further technical solution is that the recess depth of the second guide area is less than the recess depth of the first guide area.
[0014] A further technical solution is that the recess depth of the first guide area is 40% to 50% of the thickness of the damping rib.
[0015] A further technical solution is that the frame unit also includes two side ribs, one side rib is located above the sixteen pins on the upper side of the substrate island, and the other side rib is located below the sixteen pins on the lower side of the substrate island, and the side ribs are connected to the frame body.
[0016] A further technical solution is that a bonding area is set on one end of the 32 pins on both sides of the wafer island, and the bonding area is bonded to the chip on the wafer island through bonding wires.
[0017] A further technical solution is that, of the sixteen pins on the upper side of the substrate island, the middle eight pins extend from directly above the substrate island, and the other eight pins extend symmetrically from the upper ends of both sides of the substrate island and bend upwards; of the sixteen pins on the lower side of the substrate island, the middle eight pins extend from directly below the substrate island, and the other eight pins extend symmetrically from the lower ends of both sides of the substrate island and bend downwards.
[0018] A further technical solution is that the sixteen pins on the upper and lower sides of the substrate island have a rectangular bonding area for the middle eight pins, and the width of the rectangular bonding area is greater than the width of the pin.
[0019] A further technical solution is to provide positioning holes and stepping holes on both sides of the main frame body.
[0020] A further technical solution is that the frame body is connected with several double-row frame units. The double-row frame unit includes two rows of frame units arranged horizontally at intervals. Each row of frame units includes several frames arranged vertically at intervals. Several waist-shaped holes are opened vertically at intervals between the two rows of frame units. Several through slots are opened vertically at intervals between two adjacent double-row frame units.
[0021] The beneficial effects of this utility model embodiment are as follows:
[0022] (I) An SOP32 lead frame includes a frame body and several frame units. The frame units include a chip island, connecting ribs, and damping ribs. The chip is connected to the chip island. Two connecting ribs are located on the left and right sides of the chip island and are connected to the frame body. Sixteen pins are respectively arranged on the upper and lower sides of the chip island. The damping ribs are connected between two adjacent pins. The front surface of the damping rib has a recessed structure that is recessed to the rear, and the recessed direction is perpendicular to the cutting direction. When the cutting device cuts the damping rib along the cutting direction, so that the adjacent pins are separated, the cutting point is located in the recessed structure. The recessed structure set along the cutting direction induces mechanical stress to be distributed along the recessed structure during cutting, and concentrates the mechanical stress generated by cutting in the recessed structure, reducing the excess stress in the pin body area, avoiding microcracks or fatigue damage to the pins, and improving the yield of chip mass production.
[0023] (II) Further, the damping rib includes two first guiding zones and one second guiding zone. The two first guiding zones are symmetrically located on the upper and lower sides of the damping rib. Each first guiding zone has two first plates, with one end connecting the two first plates lower than the opposite end of the two first plates. The second guiding zone is located between the two first guiding zones and connects them. The second guiding zone is an arc-shaped plate, concave towards the rear end. During the cutting process, the first guiding zones guide the tool along a predetermined path, quickly initiating cracks and guiding the cutting direction. The two sides of the first guiding zones effectively constrain the cutting device, ensuring accurate cutting paths, reducing errors or deviations during the cutting process, enhancing cutting stability, and ensuring cutting precision and quality. The second guiding zone provides a transition area, buffering stress fluctuations and preventing unstable crack propagation. The shape of the second guiding zone reduces excessive stress concentration during cutting, evenly distributing cutting stress, thereby reducing the risk of material fracture.
[0024] (iii) Furthermore, the depth of the second guide zone is less than that of the first guide zone. Because the second guide zone is shallower, it does not exert excessive constraint on the cutting device, resulting in a more flexible and stable cutting path. While the first guide zone provides primary guidance, the second guide zone ensures that the cutting device is not excessively constrained, thereby reducing friction and vibration during cutting movement and helping to improve cutting accuracy. The first guide zone, by providing a deeper cutting path, allows the cutting point to be better maintained in the center position, reducing cutting errors and improving the accuracy and stability of the cutting process. Attached Figure Description
[0025] Figure 1 This is a schematic diagram of the main structure of an SOP32 lead frame according to the present invention.
[0026] Figure 2 This is a schematic diagram of the main structure of a double-row frame unit in an SOP32 lead frame according to this utility model.
[0027] Figure 3 This is a schematic diagram of the main structure of the frame unit in the SOP32 lead frame of this utility model.
[0028] Figure 4 This is a schematic diagram of the internal structure of the frame unit in an SOP32 lead frame according to this utility model.
[0029] Figure 5 for Figure 3 Enlarged view at point A.
[0030] Figure 6 This is a top view schematic diagram of the recessed structure in the SOP32 lead frame of this utility model.
[0031] In the picture:
[0032] 100. Frame body; 101. Waist-shaped hole; 102. Through groove; 103. Stepping hole; 104. Positioning hole; 200. Frame unit; 210. Carrier island; 211. Lead; 212. Bonding area; 220. Connecting rib; 230. Damping rib; 240. Edge rib; 310. First guide area; 320. Second guide area. Detailed Implementation
[0033] The specific embodiments of this utility model are described below with reference to the accompanying drawings.
[0034] To make the objectives, technical solutions, and advantages of this utility model clearer, the device proposed by this utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of this utility model will become clearer according to the following description. It should be noted that the accompanying drawings are in a very simplified form and use non-precise proportions, only used to conveniently and clearly assist in illustrating the purpose of the embodiments of this utility model. Please refer to the accompanying drawings to make the objectives, features, and advantages of this utility model more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only used to complement the content disclosed in the specification, for those skilled in the art to understand and read, and are not intended to limit the implementation conditions of this utility model. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and objectives that this utility model can produce, should still fall within the scope of the technical content disclosed in this utility model.
[0035] Example:
[0036] Figure 1 This is a schematic diagram of the main structure of an SOP32 lead frame according to the present invention. Figure 2 This is a front view schematic diagram of a double-row frame unit in an SOP32 lead frame according to this utility model. Figures 1-2 As shown, an SOP32 lead frame includes a frame body 100 and several frame units 200, with the frame units 200 connected within the frame body 100. For example, the frame body 100 contains several double-row frame units, each double-row comprising two horizontally spaced rows of frame units 200. Each row of frame units 200 includes several vertically spaced frame units 200, and several waist-shaped holes 101 are vertically spaced between the two rows of frame units 200. Several through slots 102 are vertically spaced between two adjacent double-row frame units.
[0037] Figure 3 This is a schematic diagram of the main structure of the frame unit in the SOP32 lead frame of this utility model. Figure 4 This is a schematic diagram of the internal structure of a frame unit in an SOP32 lead frame according to this utility model. Figures 3-4As shown, the frame unit 200 includes a chip carrier island 210, two connecting ribs 220, and several damping ribs 230. The chip carrier island 210 has a chip mounted on it, and sixteen pins 211 extend from its upper and lower sides. Specifically, of the sixteen pins 211 on the upper side of the chip carrier island 210, the middle eight pins 211 extend from directly above the island, and the other eight pins 211 extend symmetrically from the upper ends of both sides of the island and bend upwards. Similarly, of the sixteen pins 211 on the lower side of the chip carrier island 210, the middle eight pins 211 extend from directly below the island, and the other eight pins 211 extend symmetrically from the lower ends of both sides of the island and bend downwards. All thirty-two pins 211 are bonded to the chip. For example, a bonding area 212 is provided near one end of the thirty-two pins 211 on both sides of the wafer island 210. The bonding area 212 is bonded to the chip on the wafer island 210 via bonding wires. Two connecting ribs 220 are symmetrically provided on the left and right sides of the wafer island 210, and the connecting ribs 220 are connected to the frame body 100. For example, the frame unit 200 also includes two side ribs 240. One side rib 240 is provided above the sixteen pins 211 on the upper side of the wafer island 210, and the other side rib 240 is provided below the sixteen pins 211 on the lower side of the wafer island 210. The side ribs 240 are connected to the frame body 100.
[0038] Figure 5 for Figure 3 A magnified view at point A. (See image below.) Figure 3 and Figure 5 As shown, the damping rib 230 is connected between two adjacent pins 211. The front surface of the damping rib 230 has a recessed structure that is recessed to the rear, and the recessed direction is perpendicular to the cutting direction.
[0039] Figure 6 This is a top view schematic diagram of the recessed structure in an SOP32 lead frame according to this utility model. Figures 5-6As shown, the damping rib 230 further includes two first guide areas 310 and one second guide area 320. The two first guide areas 310 are symmetrically arranged on the upper and lower sides of the damping rib 230. Each first guide area 310 has two first plates, with one end of the two first plates connected to the other end of the two first plates being lower than the opposite end of the two first plates. The second guide area 320 is located between the two first guide areas 310 and connects the two first guide areas 310. The second guide area 320 is an arc-shaped plate with the arc-shaped plate concave towards the rear end. During the cutting process, the first guide area 310 can guide the tool to cut along a predetermined path, quickly initiating cracks and guiding the cutting direction. The two sides of the first guide area 310 can effectively constrain the cutting device, ensuring accurate cutting path, reducing errors or deviations during the cutting process, enhancing cutting stability, and ensuring cutting accuracy and quality. The second guide area 320 provides a transition area, buffering stress fluctuations and preventing unstable crack propagation. The shape of the second guide area 320 reduces excessive stress concentration during the cutting process, evenly distributing cutting stress, thereby reducing the risk of material fracture.
[0040] like Figure 6 As shown, the recess depth of the second guide area 320 is less than that of the first guide area 310. Because the second guide area 320 has a shallower recess depth, it does not exert excessive constraint on the cutting device, resulting in a more flexible and stable cutting path. While the first guide area 310 provides primary guidance, the second guide area 320 ensures that the cutting device is not excessively constrained, thereby reducing friction and vibration during cutting movement and helping to improve cutting accuracy. The first guide area 310, by providing a deeper cutting path, allows the cutting point to be better maintained in the center position, reducing cutting errors and improving the accuracy and stability of the cutting process.
[0041] like Figure 6 As shown, the recess depth of the first guide zone 310 is 40% to 50% of the thickness of the damping rib 230. This ensures that vibrations during the cutting process are effectively absorbed, avoiding resonance problems that may be caused by an excessively deep first guide zone 310. An excessively deep groove may lead to increased local vibrations in the material, thus affecting the cutting quality. A recess depth between 40% and 50% can better balance vibration absorption and structural rigidity, ensuring the stability of the material during the cutting process.
[0042] like Figure 4As shown, further, the sixteen pins 211 on the upper and lower sides of the substrate island 210 have a rectangular bonding area 212 for the middle eight pins 211, and the width of the rectangular bonding area 212 is greater than the width of the pins 211. The wider rectangular bonding area 212 allows the bonding area 212 to effectively cover more of the pin 211 surface, providing a more stable connection point and increasing the reliability of the solder joint or connection, thus avoiding electrical failures caused by weak bonding.
[0043] like Figure 1 As shown, furthermore, positioning holes 104 and stepping holes 103 are provided on both sides of the frame body 100. The positioning holes 104 and stepping holes 103 play a role in positioning and supporting during actual placement, while avoiding unnecessary deviations. Through these holes, positioning pins, screws or other fasteners can be used more conveniently to stably fix it in the designated position, preventing loosening or misalignment.
[0044] In this embodiment, during fragmentation:
[0045] The chip is connected to the wafer island 210. The bonding area 212 of the pin 211 is bonded to the wafer island 210 through bonding wires. The frame body 100 is placed in the molding die. The frame body 100 is positioned through the waist-shaped hole 101. The frame unit 200 is then molded. After all the frame units 200 are molded, the lead frame is positioned and transported through the positioning hole 104 and step hole 103 on the frame body 100. The cutting device is then used to cut the frame unit 200. The cutting device first cuts all the damping ribs 230 to separate all the pins 211. Then, the cutting device cuts all the edge ribs 240 to separate the upper and lower sides of the frame unit 200 from the frame body 100. Finally, the connecting ribs 220 are cut to separate the left and right sides of the frame unit 200 from the frame body 100, thus completing the dicing of the frame unit 200.
[0046] In this embodiment, when the cutting device cuts the damping rib 230 along the cutting direction to separate adjacent pins 211, the cutting point is located in the recessed structure. The recessed structure set along the cutting direction induces mechanical stress to be distributed along the recessed structure during cutting, concentrating the mechanical stress generated by cutting in the recessed structure, reducing the excess stress in the pin 211 body area, avoiding microcracks or fatigue damage to the pin 211, and improving the yield of chip mass production.
[0047] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0048] The embodiments described above are merely illustrative of several implementations of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.
Claims
1. A SOP32 lead frame, characterized in that, The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip. The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip. The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip. The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip. The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip. The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip.
2. The SOP32 lead frame of claim 1, wherein: The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip.
3. The SOP32 lead frame of claim 2, wherein: The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip.
4. The SOP32 leadframe of claim 3, wherein: The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip.
5. The SOP32 leadframe of claim 1, wherein: The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip.
6. The SOP32 leadframe of claim 1, wherein: The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip.
7. The SOP32 leadframe of claim 6, wherein: The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip. The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip. The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip. The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip. The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip. The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip. The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip. The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip. The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip. The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip. The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip. The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip. The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip. The utility model relates to a frame unit (200) is connected in the frame main part (100), and the frame unit (200) includes the slide (210) and the slide (210) is provided with the chip, and the slide (210) extends the sixteen pins (211) towards the upper and lower sides respectively, and the thirty two pins (211) are bonded with the chip. The utility model relates to a frame unit (200) is connected in the frame main part (100), and the 8. The SOP32 leadframe of claim 7, wherein: Sixteen pins (211) are arranged on the upper and lower sides of the slide island (210), wherein the bonding areas (212) of the middle eight pins (211) are rectangular, and the width of the rectangular bonding area (212) is greater than the width of the pin (211).
9. The SOP32 leadframe of claim 1, wherein: Positioning holes (104) and step holes (103) are arranged on both sides of the frame body (100).
10. The SOP32 leadframe of claim 1, wherein: A plurality of double-row frame units are connected in the frame body (100), wherein the double-row frame unit comprises two rows of frame units (200) arranged transversely; each of the two rows of frame units (200) comprises a plurality of frame units (200) arranged vertically, and a plurality of waist-shaped holes (101) are arranged vertically between the two rows of frame units (200); a plurality of through grooves (102) are arranged vertically between two adjacent double-row frame units.