Pin-free packaging structure

Abstract

The invention provides a pin-free packaging structure. The pin-free packaging structure comprises a plastic packaging body; the bonding pad is embedded in the plastic package body, one end face of the bonding pad is exposed on the side face of the plastic package body, the bottom face of the bonding pad is exposed on the back face of the plastic package body, the bonding pad is provided with a groove extending from the end face to the center of the back face of the plastic package body, the groove is provided with an opening located in the end face of the bonding pad, and the opening is located in the plastic package body. The size of the section, perpendicular to the extending direction of the groove, of the groove is gradually reduced in the extending direction. According to the pin-free packaging structure, the problems of metal burrs and metal scraping in the groove of the pin-free packaging structure can be reduced, so that the cutting quality of a monomerization process is improved, and the reliability of the pin-free packaging structure is improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, and in particular to a leadless package structure. Background Technology

[0002] As electronic devices develop towards miniaturization, high integration, and high reliability, leadless packaging, with its advantages in size, excellent heat dissipation, and high soldering reliability due to its leadless design, has been widely used in consumer electronics, industrial control, and automotive electronics.

[0003] In leadless packaging, after the package structure is cut and separated, the copper alloy pad substrate is exposed on the sides. Standard electroplating processes typically only cover the bottom of the pads, failing to protect the bare copper on the newly formed sides. Copper rapidly oxidizes in air, forming a dense copper oxide layer that hinders solder wetting. Since the time from component manufacturing to placement and soldering far exceeds the safe window for preventing oxidation, oxidation is almost unavoidable. Furthermore, contaminants or burrs that may remain from the cutting process further exacerbate wetting difficulties. These factors combined result in solder failing to spread effectively on the sides during reflow, affecting visual inspection and soldering reliability.

[0004] To address the issue of pad wetting in leadless packages, a wettable wing process was developed. This process provides a visual indicator of solderability, reduces inspection time, and improves soldering reliability. The wettable wing process fundamentally solves the industry problem of traditional packages where solder joints are completely obscured by the device, hindering optical inspection, by forming a special metallized plating step on the side of the package structure. During soldering, the solder climbs along this wing, forming a solder joint outline visible to the naked eye or equipment, enabling 100% visual inspection of soldering quality. Simultaneously, this structure significantly enhances solder wettability, greatly improving the mechanical strength of the solder and the reliability of the electrical connection, making it particularly suitable for the stringent quality control standards of demanding applications such as automotive electronics.

[0005] Dimples / cavities at the leadframe pins are a mainstream leadless packaging technology with wettable sidewalls. The process involves: pre-punching or etching grooves on the leadframe pins; surface mounting and molding; and performing a singulation process to cut the large package structure into multiple independent leadless package structures. In the final package structure, the leadframe pins form pads, and the grooves are located on the sides of the package structure. Solder climbs along the sidewalls of the grooved pads, forming solder joint outlines visible to the naked eye or equipment, allowing for 100% visual inspection of soldering quality. Furthermore, the grooves act as tiny reservoirs and provide anchoring points for the liquid solder, enhancing soldering reliability.

[0006] The monolithization process typically involves cutting large package structures with a dicing blade, which passes through the groove. Because these grooves contain conductive materials such as copper, copper residue remains at the edges after cutting. The high-speed rotation of the dicing blade causes compression and friction on this residual copper, forming copper burrs, accompanied by metal smearing. The residual copper burrs can easily lead to short circuits between adjacent pads, while metal smearing can damage the insulating layer on the pad surface, increasing the risk of electrochemical migration. Currently, there is no effective method to remove the copper burrs from the grooves or reduce the metal smearing problem, thus reducing the reliability of the leadless package structure, a problem particularly prominent in automotive-grade packages.

[0007] Therefore, how to reduce metal burrs and metal scratches in the grooves of leadless package structures, thereby improving the cutting quality of the monolithic process and improving the reliability of leadless package structures, is a technical problem that urgently needs to be solved. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a leadless package structure that can reduce metal burrs and metal scratches in the groove of the leadless package structure, thereby improving the cutting quality of the monomerization process and improving the reliability of the leadless package structure.

[0009] To address the above problems, this invention provides a leadless package structure, comprising: Plastic encapsulation; A solder pad is embedded in the molding compound, with one end face of the solder pad exposed on the side of the molding compound and the bottom face of the solder pad exposed on the back of the molding compound. The solder pad has a groove extending from the end face to the center of the back of the molding compound. The groove has an opening located on the end face of the solder pad. The dimension of the cross section of the groove perpendicular to its extension direction gradually decreases along the extension direction.

[0010] In one embodiment, the length and / or width of the cross section of the groove perpendicular to its extension direction gradually decreases along the extension direction, wherein the length refers to the dimension of the cross section in the direction parallel to the back surface of the encapsulant, and the width refers to the dimension of the cross section in the direction perpendicular to the back surface of the encapsulant.

[0011] In one embodiment, the side profile of the opening coincides with the outer side profile of the pad on the side of the molding compound.

[0012] In one embodiment, the opening side profile and the pad have a distance between them and the outer side profile of the side of the molding compound.

[0013] In one embodiment, the bottom edge contour of the opening coincides with the bottom outer contour of the pad on the side of the molding compound.

[0014] In one embodiment, the bottom edge contour of the opening and the pad are separated by a distance from the bottom edge outer contour of the side of the molding compound.

[0015] In one embodiment, the outline of the opening coincides with the outer outline of the pad on the side of the molding compound.

[0016] In one embodiment, the outline of the opening is at a distance from the outer outline of the pad on the side of the molding compound.

[0017] In one embodiment, the distance between the two side walls of the groove gradually decreases along the extension direction of the groove, so that the length of the cross section of the groove perpendicular to its extension direction gradually decreases along the extension direction.

[0018] In one embodiment, along the extending direction of the groove, the sidewalls of the groove are inclined inwards to gradually reduce the distance between the two sidewalls of the groove.

[0019] In one embodiment, along the extension direction of the groove, the sidewalls of the groove converge toward the interior of the groove in a stepped manner, so that the distance between the two sidewalls of the groove gradually decreases.

[0020] In one embodiment, the sidewall includes a plurality of sequentially adjacent stepped surfaces, wherein the same stepped surface extends along the extension direction of the groove.

[0021] In one embodiment, the sidewall includes a plurality of sequentially adjacent stepped surfaces, wherein the same stepped surface is inclined inward into the groove in the extending direction of the groove.

[0022] In one embodiment, the side of the cross-section of the groove perpendicular to its extension direction is parallel to the outer contour of the side of the pad, so that the cross-section has a rectangular configuration.

[0023] In one embodiment, the side of the cross-section of the groove perpendicular to its extension direction is inclined toward the outer contour of the side of the pad, so that the cross-section has an inverted trapezoidal configuration.

[0024] In one embodiment, the distance between the bottom surface and the top surface of the groove gradually decreases along the extending direction of the groove, so that the width of the cross-section of the groove perpendicular to its extending direction gradually decreases along the extending direction.

[0025] In one embodiment, along the extending direction of the groove, the bottom surface of the groove is inclined to the top surface of the groove, so that the distance between the bottom surface and the top surface of the groove gradually decreases.

[0026] In one embodiment, along the extending direction of the groove, the bottom surface of the groove converges towards the top surface of the groove in a stepped manner, so that the distance between the bottom surface and the top surface of the groove gradually decreases.

[0027] In one embodiment, the bottom surface of the groove includes a plurality of sequentially adjacent stepped surfaces, wherein the same stepped surface is parallel to the top surface of the groove in the extending direction of the groove.

[0028] In one embodiment, the bottom surface of the groove includes a plurality of sequentially adjacent stepped surfaces, wherein the same stepped surface is inclined to the top surface of the groove in the extending direction of the groove.

[0029] In one embodiment, the sidewalls and bottom surface of the groove exhibit the same variation pattern along the extension direction of the groove.

[0030] In one embodiment, the two side walls of the groove are mirror images of the center line of the groove.

[0031] In one embodiment, the end of the groove away from the opening has an arc-shaped configuration that curves toward the center of the back side of the encapsulated body.

[0032] In one embodiment, the end of the groove away from the opening has a planar configuration.

[0033] In one embodiment, the leadless package structure further includes: Base island, wherein the pads are distributed around the base island; The chip is disposed on the front side of the base island and connected to the pads via bonding wires; The molding compound also covers the base island, the chip, and the bonding wires, with the back side of the base island exposed on the back side of the molding compound.

[0034] In one embodiment, the solder pads are provided on all four sides of the molding compound.

[0035] In one embodiment, the solder pads are provided on opposite sides of the molding compound.

[0036] In one embodiment, the leadless package structure includes a plurality of pads, at least a portion of which have the groove.

[0037] In the above technical solution, the pad is embedded in the molding compound, and one end face of the pad is exposed on the side of the molding compound, while the bottom face of the pad is exposed on the back of the molding compound. The pad has a groove extending from the end face to the center of the back of the molding compound, and the groove has an opening located on the end face of the pad. The cross-sectional dimension of the groove perpendicular to its extension direction gradually decreases along the extension direction. In the leadless package structure of the present invention, the solid structure area of ​​the pad exposed on the side of the molding compound is smaller than the cross-sectional area of ​​the solid structure of the pad located inside the molding compound.

[0038] In the process of forming the leadless package structure provided in this embodiment of the invention, a large package structure needs to be cut into multiple independent leadless package structures. During the cutting process, a cutting blade cuts the pads, and the cut surface of the pads serves as the solid structure of the pads exposed on the side of the molding compound in the leadless package structure. Therefore, the pad design of this embodiment of the invention reduces the amount of metal on the cut surface, thereby reducing metal burrs and metal scratches in the grooves of the leadless package structure, thus improving the cutting quality of the unitization process and improving the reliability of the leadless package structure provided in this embodiment of the invention. Furthermore, the grooves not only increase the contact area between the solder and the pads, thereby improving the welding strength, but also guide the solder flow and improve the solder wetting performance, significantly improving the performance of the leadless package structure.

[0039] Furthermore, when manufacturing the leadless package structure provided in this embodiment of the invention, the process of forming the groove portion can be integrated with the process of removing excess adhesive after the molding process, so that no new process equipment and new process steps are required. It is compatible with the existing manufacturing process and flow of leadless package structures, and there is no additional production capacity loss. This helps to reduce the manufacturing cost of the leadless package structure while improving the manufacturing yield and productivity of the leadless package structure.

[0040] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1This is a three-dimensional schematic diagram of the leadless package structure provided in the first embodiment of the present invention; Figure 2 yes Figure 1 Enlarged view of region A in the middle; Figure 3 It is along Figure 2 Cross-sectional view of line A1-A1 in the middle; Figure 4 It is along Figure 2 Cross-sectional view of line B1-B1 in the middle; Figure 5 yes Figure 1 Top view of the pad area and its surrounding area; Figure 6 It is along Figure 1 Cross-sectional view of line C1-C1; Figure 7 yes Figure 6 Enlarged view of region B in the middle; Figure 8 The leadless package structure provided in the second embodiment of the present invention is as follows: Figure 1 Enlarged view of region A in the middle; Figure 9 The leadless package structure provided in the third embodiment of the present invention is as follows: Figure 1 Enlarged view of region A in the middle; Figure 10 This is a top view of the pad area and surrounding area of ​​the leadless package structure provided in the third embodiment of the present invention; Figure 11 The leadless package structure provided in the fourth embodiment of the present invention is as follows: Figure 1 Enlarged view of region A in the middle; Figure 12 The fifth embodiment of the present invention provides a leadless package structure as shown below. Figure 1 Enlarged view of region A in the middle; Figure 13 This is a top view of the pad area and surrounding area of ​​the leadless package structure provided in the fifth embodiment of the present invention; Figure 14 The leadless package structure provided in the sixth embodiment of the present invention is as follows: Figure 1 Enlarged view of region A in the middle; Figure 15 This is a top view of the pad area and surrounding area of ​​the leadless package structure provided in the sixth embodiment of the present invention; Figure 16 The pinless package structure provided in the seventh embodiment of the present invention is as follows: Figure 1 Enlarged view of region A in the middle; Figure 17 It is along Figure 16Cross-sectional view of line A1-A1 in the middle; Figure 18 The leadless package structure provided in the eighth embodiment of the present invention is along Figure 1 A cross-sectional schematic diagram at the position indicated by line C1-C1; Figure 19 yes Figure 18 Enlarged view of region B in the middle; Figure 20 The leadless package structure provided in the ninth embodiment of the present invention is along Figure 1 A cross-sectional schematic diagram at the position indicated by line C1-C1; Figure 21 yes Figure 20 Enlarged view of region B in the middle; Figure 22 This is a top view of the pad area and its surrounding area in the leadless package structure provided in the tenth embodiment of the present invention; Figure 23 This is a three-dimensional schematic diagram of the leadless package structure provided in the eleventh embodiment of the present invention; Figure 24 This is a three-dimensional schematic diagram of the leadless package structure provided in the twelfth embodiment of the present invention.

[0043] Explanation of reference numerals in the attached figures: 100 molded body 200 pads 210 groove 211 opening 212-step surface 213 steps 214 sidewalls 215 bottom 300 base islands 310 chip 320 bond wire 330 adhesive. Detailed Implementation

[0044] The technical solutions in the embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Figure 1 This is a schematic diagram of the leadless package structure provided in the first embodiment of the present invention. Figure 2 yes Figure 1 Enlarged diagram of region A in the middle. Figure 3 It is along Figure 2 Cross-sectional view of line A1-A1 in the middle. Figure 4 It is along Figure 2 Cross-sectional view of line B1-B1 in the middle. Figure 5 yes Figure 1 Top view of the pad area and its surrounding area. Figure 6 It is along Figure 1 Cross-sectional view of line C1-C1 in the middle. Figure 7 yes Figure 6 Enlarged schematic diagram of region B in the middle.

[0046] Please see Figures 1-7 The leadless package structure includes: 100 mm of encapsulated material; A pad 200 is embedded within the molding compound 100, with its end face exposed to the side of the molding compound 100 and its bottom face exposed to the back of the molding compound 100. The pad 200 has a groove 210 extending from its end face to the center of the back of the molding compound 100. The groove 210 has an opening 211 located on the end face of the pad 200. The cross-sectional dimension of the groove 210 perpendicular to its extending direction gradually decreases along the extending direction.

[0047] The length and / or width of the cross section of the groove 210 perpendicular to its extension direction gradually decreases along the extension direction. The length refers to the maximum dimension of the cross section in the direction parallel to the back surface of the encapsulant 100, and the width refers to the maximum dimension of the cross section in the direction perpendicular to the back surface of the encapsulant 100.

[0048] In the leadless package structure provided in this embodiment of the invention, the pad 200 is embedded within the molding compound 100. The pad 200 has a groove 210. The length and / or width of the groove 210's cross-section perpendicular to its extension direction gradually decreases along the extension direction. That is, the area of ​​the solid structure of the pad 200 exposed to the side of the molding compound 100 is smaller than the cross-sectional area of ​​the solid structure of the pad 200 within the molding compound 100. In the process of forming the leadless package structure provided in this embodiment of the invention, a large package structure needs to be cut into multiple independent leadless package structures. During the cutting process, a cutting blade cuts the pad 200. The cut surface of the pad 200 serves as the solid structure of the pad 200 exposed to the side of the molding compound 100 in the leadless package structure. Therefore, the design of the pad 200 in this embodiment of the invention reduces the amount of metal on the cut surface, thereby reducing metal burrs and metal scratches in the groove 210 of the leadless package structure. This improves the cutting quality of the individualization process and enhances the reliability of the leadless package structure provided in this embodiment of the invention. Furthermore, the groove 210 not only increases the contact area between the solder and the pad 200, thereby improving the welding strength, but also guides the solder flow, improves the solder wetting performance, and significantly improves the performance of the leadless package structure.

[0049] The molding compound 100 covers the side and top surfaces of the pad 200. In one embodiment, the leadless package structure further includes a base island 300, a chip 310, and bonding leads 320, in which case the molding compound 100 also covers the base island 300, the chip 310, and the bonding leads 320.

[0050] The molding compound 100 is primarily composed of thermosetting molding compound (EMC) with epoxy resin as the base resin. Its typical formulation includes epoxy resin, phenolic resin curing agent, a high proportion of inorganic fillers, accelerators, flame retardants, and coupling agents, prepared through precise proportioning and mixing processes. After a series of transfer molding processes such as heating and melting, injection into a mold, and pressure curing, this material system forms a dense three-dimensional network cross-linked structure. This structure endows the molding compound 100 with excellent mechanical strength, enabling it to effectively resist external physical impacts and mechanical stresses. Simultaneously, its excellent thermal stability is reflected in its high glass transition temperature (Tg) and low coefficient of thermal expansion (CTE), thereby ensuring the reliability of the device under high-temperature operating environments and preventing delamination or cracking due to thermal fatigue. The encapsulated body 100 forms the first line of defense by completely encapsulating the internal components. Its density can effectively block the intrusion of external moisture and dust, significantly reduce the risk of electrochemical corrosion caused by moisture in the internal circuits, and provide good insulation performance to ensure the long-term stability of electrical connections. For harsh environments, such as high-pressure applications on the seabed, the pressure resistance and resistance to media corrosion can be enhanced by optimizing the elastic modulus of the epoxy resin and the filler system.

[0051] In terms of manufacturing process, the thickness and shape of the molding compound 100 can be precisely controlled through mold design and injection molding parameters. For example, multi-segment injection technology can be used to avoid bubbles and wire breaks, and the frame can be laminated. For QFN, DFN and other packages, their shape design (such as rounded corners) helps to disperse stress, while the thickness directly affects the heat dissipation path and the overall package height, meeting the requirements of portable devices for thinness and the heat dissipation efficiency requirements of high-power devices. As the main carrier of the package, the molding compound 100 provides robust structural support for the internal precision chip 310, bonding wires and pads, maintaining the integrity and dimensional stability of the leadless package structure. Its low moisture absorption also helps to pass the moisture sensitivity test.

[0052] The pad 200 is embedded in the molding compound 100, with one end face exposed on the side of the molding compound 100 and its bottom face exposed on the back of the molding compound 100. It serves as an external connection component of the leadless package structure and is used to electrically connect with the corresponding pad 200 on the external circuit.

[0053] The choice of material for the pad 200 directly affects the welding quality, mechanical connection reliability, and long-term electrical stability. Common pad substrates are copper or copper alloys, mainly due to copper's excellent electrical and thermal conductivity. Its good ductility also facilitates precision cutting, etching, or stamping to form specific configurations (such as grooves or stepped structures), and the cost is relatively low.

[0054] However, copper substrates are prone to oxidation in air, forming a copper oxide layer, which severely degrades solderability, leading to problems such as solder rejection or insufficient solder climb. To address this issue, the surface of the pads 200 typically requires electroplating to provide protection and ensure good solderability. For example, the widely used tin plating process provides good wettability to the surface of the pads 200 (including the bottom surface and specially treated exposed end faces), ensuring that the molten solder can effectively spread and form a reliable connection during reflow soldering. For some high-reliability applications, surface treatments such as chemical nickel plating or hard gold plating are also used. In these applications, the nickel layer acts as a barrier layer to prevent copper diffusion, while the gold layer provides excellent oxidation resistance and contact resistance. However, this method is more expensive and carries the risk of "black pads" due to the presence of nickel plating.

[0055] In addition, organic solderability protectants, as an alternative, prevent oxidation by forming an organic protective film on the copper surface. They have the advantages of low cost and smooth surface, but their storage time and ability to withstand multiple reflow soldering are relatively weak.

[0056] In advanced packaging structures, wettable sidewall technology is employed to enable automated optical inspection of solder joint quality. This allows solder to climb along the sidewalls after reflow soldering, forming a visible meniscus, thus eliminating the need for X-ray inspection. The overall performance of the pad 200 (including electrical interconnection and heat dissipation) is also closely related to the design of the underlying PCB pads. For example, the use of non-solder mask (NSMD) pads and optimized thermal via design are all aimed at synergistically improving the connection reliability and thermal management capabilities of the final assembly.

[0057] The leadless package structure includes multiple pads 200 disposed in the periphery of the molded body 100. The pads 200 serve as key external electrical connection interfaces, and are responsible for enabling stable and reliable electrical signal transmission between the internal chip 310 circuit and the external printed circuit board (PCB).

[0058] The specific layout of the pads 200 can be optimized according to the overall requirements of the package structure, the number of pins, and the signal distribution.

[0059] For example, in the leadless package structure, one pad layout involves evenly distributing the pads 200 along the four sides of the molding compound 100, forming a four-sided surround arrangement. This four-sided surround arrangement is suitable for scenarios with a large number of input / output ports and requiring high-density interconnection, helping to achieve uniform signal distribution and optimize heat dissipation paths. As an example, such as... Figure 1As shown, in the first embodiment, a plurality of pads 200 are provided on all four sides of the molding compound 100, and the plurality of pads 200 are arranged at a specific interval. This leadless package structure is a QuadFlat No-lead Package (QFN).

[0060] For example, another pad layout in the leadless package structure is to concentrate the pads 200 in a portion of the molded body 100, depending on the complexity of the actual circuit connection. For instance, the pads may be arranged only on two opposite sides or specific sides of the molded body 100. This specific layout effectively reduces the overall package size and parasitic parameters, making it suitable for applications with a relatively small number of pins or those requiring isolation for specific signal paths. Furthermore, the structural design helps alleviate stress concentration problems caused by the mismatch in thermal expansion coefficients between the molded body 100 and the PCB substrate. As an example, such as... Figure 23 As shown, in the eleventh embodiment, the pads 200 are provided on two opposite sides of the molding compound 100, while no pads 200 are provided on the other two sides. Multiple pads 200 are provided on both sides of the molding compound 100 where the pads 200 are provided, and the multiple pads 200 are arranged at specific intervals. This leadless package structure is a dual flat no-lead package (DFN).

[0061] The shape and precise dimensions of the pads 200 (such as width, length, and spacing) also need careful consideration to ensure sufficient mechanical anchoring strength and excellent soldering reliability, and to avoid defects such as bridging or cold solder joints during reflow soldering. This flexible and scientific layout and design of the pads 200 allows for improved package integration, reliability, and the ability to handle complex application environments while meeting electrical performance requirements.

[0062] The leadless package structures, such as QFN and DFN, completely eliminate the traditional external leads. Instead, they are directly mounted and soldered to the surface of the printed circuit board (PCB) through the metallized pads 200 arranged in an array at the bottom of the molded body 100. This fundamental design innovation brings multiple significant advantages.

[0063] In terms of physical dimensions, the leadless package structure can be tightly attached to the printed circuit board by eliminating the outward-extending pins, which greatly reduces the overall size and weight of the component, making it suitable for applications with demanding space and weight requirements, such as smartphones and portable devices.

[0064] In terms of electrical performance, the leadless package structure makes the conductive path between the chip 310 and the pads on the printed circuit board extremely short. This effectively reduces the parasitic inductance and resistance in the signal transmission path between the leadless package structure and the printed circuit board, thereby significantly improving signal integrity and reducing noise interference, which is particularly beneficial for high-speed digital circuits and radio frequency applications.

[0065] In terms of thermal management, the bottom center of the leadless package structure typically features a large exposed base island (e.g., Figure 6 The base island 300 shown serves as a large-area heat dissipation pad, directly connected to the back of the chip 310. During mounting, it is directly soldered to the corresponding heat dissipation pad on the printed circuit board, thus creating an efficient heat conduction path from the chip 310 to the printed circuit board. This significantly improves the heat dissipation capacity of the package structure and the reliability of the system at high temperatures. Furthermore, the leadless package structure is typically assembled using a reflow soldering process, which has a high degree of automation and helps reduce production costs.

[0066] The pad 200 has a groove 210 that is recessed towards the interior of the pad 200 and extends from the end face of the pad 200 to the center of the back surface of the molding compound 100. The recessed direction of the groove 210 is as follows: Figure 2 As shown in the D1 direction, the extension direction of the groove 210 is as follows: Figure 2 As shown in the D2 direction, the recessed direction (D1 direction) of the groove 210 is perpendicular to the extension direction (D2 direction). When the leadless package structure is mounted on an external structure such as a printed circuit board, the solder will climb along the side of the pad 200 with the groove 210, forming a solder joint outline (e.g., a meniscus) visible to the naked eye or equipment, enabling 100% visual inspection of the soldering quality; furthermore, the groove 210 acts as a tiny reservoir and provides an anchoring point for the liquid solder, enhancing the reliability of the soldering.

[0067] In some embodiments, the leadless package structure includes a plurality of pads 200, at least a portion of which have the groove 210. That is, all of the pads 200 of the leadless package structure have the groove 210, or some of the pads 200 of the leadless package structure have the groove 210 while another portion of the pads 200 do not have the groove 210.

[0068] As an example, such as Figure 1 As shown, in the first embodiment, the leadless package structure includes a plurality of pads 200, all of which have the groove 210. The plurality of pads 200 are spaced apart to comprehensively improve the mechanical anchoring effect and wetting performance of the soldering interface.

[0069] As an example, such as Figure 24 As shown, in the twelfth embodiment, the leadless package structure includes multiple pads 200, which are spaced apart. Some pads 200 have the groove 210, while others do not. The bottom and side surfaces of the pads 200 without the groove 210 are flat. This differentiated design of the pads 200 allows for optimization of pads 200 with different functions within the same leadless package structure, thereby ensuring the reliability of critical connection points while considering manufacturing costs and process complexity. In the twelfth embodiment, the pads 200 with the groove 210 and those without the groove 210 can be alternately arranged to ensure the reliability of critical connection points.

[0070] The groove 210 has an opening 211 located on the end face of the solder pad 200, that is, the end of the groove 210 away from the interior of the molding compound 100 is the opening 211, making the groove 210 an open groove. The opening 211 provides a direct channel for the solder to fill in the groove 210, thereby significantly improving the wetting effect of the solder on the sidewalls and bottom surface of the groove 210, ensuring the formation of reliable electrical connection and mechanical anchoring.

[0071] The cross-sectional dimension of the groove 210 perpendicular to its extending direction gradually decreases along the extending direction. Specifically, the groove 210 perpendicular to its extending direction (the extending direction is as follows) Figure 2 The length and / or width of the cross-section (in the D2 direction) gradually decreases along the extending direction, causing the area of ​​the solid structure of the pad 200 along the extending direction of the groove 210 to gradually increase. The length refers to the dimension of the cross-section perpendicular to its extending direction in the direction parallel to the back surface of the molding compound 100, and the width refers to the dimension of the cross-section perpendicular to its extending direction in the direction perpendicular to the back surface of the molding compound 100. In other words, in the leadless package structure, the length and / or width of the cross-section of the groove 210 perpendicular to its extending direction at the opening 211 is the largest, and the solid structure area of ​​the pad 200 at its end face located on the side of the molding compound 100 is the largest.

[0072] As an example, Figure 3 This is a cross-sectional view of the first location of the pad 200 (i.e., at line A1-A1). Figure 4 This is a cross-sectional view of the second position (i.e., at line B1-B1) of the pad 200, where the first position is adjacent to the opening 211 and the second position is away from the opening 211, as shown below. Figure 3 and Figure 4As shown, the length H1 and width W1 of the cross section of the groove 210 perpendicular to its extension direction at the first position are both greater than the length H2 and width W2 of the cross section of the groove 210 perpendicular to its extension direction at the second position. Correspondingly, the outer contour dimensions of the pad 200 at the first position and the second position remain unchanged, which makes the area S1 of the solid structure of the pad 200 at the first position smaller than the area S2 of the solid structure of the pad 200 at the second position.

[0073] In the leadless package structure provided in this embodiment of the invention, when comparing the length and width of the cross-section of the groove 210 perpendicular to its extension direction, the dimensions of the cross-sections obtained at different regions of the groove 210 at the same location are compared. As an example, such as... Figure 16 and Figure 17 As shown, in the seventh embodiment, the cross-section of the groove 210 is an inverted trapezoid. When comparing the length and width of the cross-section of the groove 210 perpendicular to its extension direction, the upper or lower base of the inverted trapezoid is used as the length of the cross-section perpendicular to its extension direction obtained at different regions of the groove 210 for comparison, and the height of the inverted trapezoid is used as the width of the cross-section perpendicular to its extension direction obtained at different regions of the groove 210 for comparison.

[0074] In the leadless package structure provided by the present invention, the length and / or width of the cross section of the groove 210 perpendicular to its extension direction at the opening 211 is the largest, and the area of ​​the solid structure of the pad 200 at its end face located on the side of the molded body 100 is the smallest, so as to reduce the amount of metal at the end face of the pad 200 located on the side of the molded body 100, thereby reducing the amount of metal on the cutting surface in the process of forming the leadless package structure, thereby reducing the metal burrs and metal scratches in the groove 210 of the leadless package structure.

[0075] Furthermore, in some embodiments of the present invention, the outline of the opening 211 and the outer outline of the pad 200 on the side of the molding compound 100 have a positional relationship of overlapping, partially overlapping, or not overlapping at all, so as to meet the personalized requirements of the leadless package structure.

[0076] As an example, such as Figure 8 As shown, it is a leadless package structure provided in the second embodiment of the present invention. Figure 1 An enlarged schematic diagram of region A in the middle, and a top view of the pad 200 region and its surrounding area can be referenced. Figure 5In the second embodiment, the side profile of the opening 211 coincides with the outer side profile of the pad 200 on the side of the molded package 100, and there is a distance between the bottom profile of the opening 211 and the outer bottom profile of the pad 200 on the side of the molded package 100. That is, the outline of the opening 211 coincides with the outer profile of the pad 200 on the side of the molded package 100. Starting from the end face of the pad 200, along the extension direction of the groove 210, the thickness of both the side and bottom of the pad 200 gradually increases, causing the area of ​​the pad 200 solid structure to gradually increase. This gradual structure effectively suppresses the risk of metal burrs and metal scratches caused by material separation during the processing of the groove 210, while ensuring that the pad 200 structure has continuously enhanced conductive path performance and mechanical strength performance in the extension direction of the groove 210. Thus, it balances the manufacturability of the leadless package structure with the connection reliability of the final component.

[0077] As an example, such as Figure 9 and Figure 10 As shown, where, Figure 9 The leadless package structure provided in the third embodiment of the present invention is as follows: Figure 1 Enlarged diagram of region A in the middle. Figure 10 This is a top view of the pad 200 area and its surrounding area of ​​the leadless package structure provided in the third embodiment of the present invention. In the third embodiment, there is a distance between the side contour of the opening 211 and the outer side contour of the pad 200 on the side of the molded body 100, and there is a distance between the bottom contour of the opening 211 and the outer bottom contour of the pad 200 on the side of the molded body 100. That is, there is a distance between the contour of the opening 211 and the outer contour of the pad 200 on the side of the molded body 100, meaning that the contour of the opening 211 and the outer contour of the pad 200 on the side of the molded body 100 do not coincide at all. Starting from the end face of the pad 200, along the extension direction of the groove 210, the thickness of both the side and bottom edges of the pad 200 gradually increases, causing the area of ​​the pad 200 solid structure to gradually increase. This gradual structure effectively suppresses the risk of metal burrs and scratches caused by material separation during the processing of the groove 210, while ensuring that the pad 200 structure has continuously enhanced conductive path performance and mechanical strength performance in the extension direction of the groove 210. Thus, it balances the manufacturability of the leadless package structure with the connection reliability of the final component.

[0078] As an example, such as Figure 11 As shown, Figure 11 It is the leadless package structure provided in the fourth embodiment of the present invention, such as Figure 1 An enlarged schematic diagram of region A in the middle, and a top view of the pad 200 region and its surrounding area can be referenced. Figure 10 In the fourth embodiment, the side profile of the opening 211 and the outer side profile of the pad 200 on the side of the molded body 100 are separated by a distance, and the bottom profile of the opening 211 coincides with the outer bottom profile of the pad 200 on the side of the molded body 100, that is, the profile of the opening 211 coincides with the outer profile of the pad 200 on the side of the molded body 100. Starting from the end face of the pad 200, along the extension direction of the groove 210, the thickness of both the side and bottom of the pad 200 gradually increases, causing the area of ​​the pad 200 solid structure to gradually increase. This gradual structure effectively suppresses the risk of metal burrs and metal scratches caused by material separation during the processing of the groove 210, while ensuring that the pad 200 structure has continuously enhanced conductive path performance and mechanical strength performance in the extension direction of the groove 210, thus taking into account both the manufacturability of the leadless package structure and the connection reliability of the final component.

[0079] As an example, such as Figure 1 and Figure 5 As shown, in the first embodiment, the side profile of the opening 211 coincides with the outer side profile of the pad 200 on the side of the molding compound 100, and the bottom profile of the opening 211 coincides with the outer bottom profile of the pad 200 on the side of the molding compound 100. That is, the profile of the opening 211 completely coincides with the outer profile of the pad 200 on the side of the molding compound 100. Starting from the end face of the pad 200, along the extension direction of the groove 210, the thickness of both the side profile and the bottom profile of the pad 200 gradually increases, causing the area of ​​the pad 200 solid structure to gradually increase. This gradual structure not only minimizes the risk of metal burrs and metal scratches caused by material separation during the processing of the groove 210, but also ensures that the pad 200 structure has continuously enhanced conductive path performance and mechanical strength performance in the extension direction of the groove 210, thus taking into account both the manufacturability of the leadless package structure and the connection reliability of the final component.

[0080] In some embodiments of the present invention, the distance between the two side walls 214 of the groove 210 gradually decreases along the extending direction of the groove 210, so that the length of the cross section of the groove 210 perpendicular to its extending direction gradually decreases along the extending direction.

[0081] As an example, such as Figure 1 and Figure 5As shown, in the first embodiment, the sidewall 214 of the groove 210 is inclined inwards towards the interior of the groove 210, so that the distance between the two sidewalls 214 of the groove 210 gradually decreases. That is, the sidewall 214 of the groove 210 has an inclined surface at an angle relative to the extending direction of the groove 210 (as shown by direction D2 in the figure), such that the vertical distance between the two sidewalls 214 of the groove 210 monotonically decreases along the extending direction of the groove 210, thereby increasing the length of the cross-section of the groove 210 perpendicular to its extending direction (e.g., ...). Figure 3 The length H1 in and Figure 4 The length H2 in the groove gradually decreases along the extension direction. Specifically, by adjusting the process parameters for forming the groove 210, the sidewall 214 is controlled to have a continuous inclined surface with a constant tilt angle relative to the extension direction of the groove 210. This inclined surface configuration causes the length of the cross-section of the groove 210 perpendicular to its extension direction to gradually decrease, thereby forming a tapered structure. The tilt angle of the sidewall 214 can be set according to actual functional requirements to ensure effective guidance of solder flow, enhanced mechanical anchoring effect, and optimized stress distribution in the packaging process. Furthermore, the tilt angle of the sidewall 214 can be changed by adjusting the process parameters for forming the groove 210, thereby controlling the rate of change of the length of the cross-section of the groove 210 along the extension direction of the groove 210, and thus optimizing the wetting and conductivity of the solder pad.

[0082] As an example, such as Figure 12 and Figure 13 As shown, where, Figure 12 The fifth embodiment of the present invention provides a leadless package structure as shown below. Figure 1 Enlarged diagram of region A in the middle. Figure 13This is a top view of the pad 200 area and its surrounding area of ​​the leadless package structure provided in the fifth embodiment of the present invention. In the fifth embodiment, along the extension direction of the groove 210 (as shown in direction D2 in the figure), the sidewalls 214 of the groove 210 converge toward the interior of the groove 210 in a stepped manner, so that the distance between the two sidewalls 214 of the groove 210 gradually decreases, thereby causing the length of the cross section of the groove 210 perpendicular to its extension direction to gradually decrease along the extension direction. Specifically, at least one sidewall 214 of the groove 210 includes a plurality of sequentially adjacent stepped surfaces 212. These stepped surfaces 212 are arranged sequentially along the extension direction of the groove 210, and each subsequent stepped surface 212 has a smaller vertical distance to the other sidewall 214 than the previous stepped surface 212, so that the sidewall 214 as a whole converges toward the interior of the groove 210 in a stepped manner, causing the vertical distance between the two sidewalls 214 of the groove 210 to decrease step by step as the groove 210 extends. This stepped convergence configuration precisely controls the gradual gradient of the length of the groove 210 cross section through the hierarchical changes of the stepped surface 212. This is beneficial for optimizing material filling and stress distribution in the packaging process, and can also guide the directional flow and filling of solder during welding, thereby enhancing the mechanical anchoring strength and connection reliability of the welding interface.

[0083] In some embodiments of the present invention, along the extending direction of the groove 210, the same step surface 212 extends along the extending direction of the groove 210, or the same step surface 212 is inclined toward the interior of the groove 210.

[0084] As an example, such as Figure 12 and Figure 13 As shown, in the fifth embodiment, in the extending direction of the groove 210 (as shown by direction D2 in the figure), the same step surface 212 extends along the extending direction of the groove 210. That is, the vertical distance from different positions of the same step surface 212 to the other sidewall of the groove 210 along the extending direction of the groove 210 is equal. Each subsequent step surface 212 among the plurality of step surfaces 212 has a smaller vertical distance to the other sidewall compared to the previous step surface 212.

[0085] As an example, such as Figure 14 and Figure 15 As shown, where, Figure 14 The leadless package structure provided in the sixth embodiment of the present invention is as follows: Figure 1 Enlarged diagram of region A in the middle. Figure 15This is a top view of the pad 200 area and its surrounding area of ​​the leadless package structure provided in the sixth embodiment of the present invention. In the sixth embodiment, along the extension direction of the groove 210 (as shown in direction D2 in the figure), the same step surface 212 is inclined inward towards the interior of the groove 210, that is, the vertical distance from the same step surface 212 to the other sidewall 214 of the groove 210 along the extension direction of the groove 210 shows a monotonically decreasing trend. Each subsequent step surface 212 among the plurality of step surfaces 212 has a smaller vertical distance to the other sidewall 214 compared to the previous step surface 212, that is, the maximum vertical distance from each subsequent step surface 212 to the other sidewall 214 of the groove 210 along the extension direction of the groove 210 is less than the minimum vertical distance from the previous step surface 212 to the other sidewall 214 of the groove 210.

[0086] In some embodiments of the present invention, the cross section of the groove 210 perpendicular to its extension direction can be constructed in different geometric configurations, such as a rectangular configuration or an inverted trapezoidal configuration.

[0087] As an example, such as Figures 1-4 As shown, in the first embodiment, the side of the cross-section of the groove 210 perpendicular to its extending direction is parallel to the outer contour of the side of the pad 200, giving the cross-section a rectangular configuration. In this embodiment, the side of the cross-section is approximately perpendicular to the bottom surface of the pad 200, forming a right-angled groove 210 structure with a defined corner, or a groove 210 structure with a chamfered corner.

[0088] As an example, such as Figure 16 and Figure 17 As shown, where, Figure 16 The pinless package structure provided in the seventh embodiment of the present invention is as follows: Figure 1 Enlarged diagram of region A in the middle. Figure 17 It is along Figure 16 In the cross-sectional view of line A1-A1 in the seventh embodiment, the side of the cross-section of the groove 210 perpendicular to its extension direction (as shown by direction D2 in the figure) is inclined towards the outer contour of the side of the pad 200, giving the cross-section an inverted trapezoidal shape. In this embodiment, the sidewall of the cross-section is constructed as an inclined surface sloping from the bottom of the groove 210 to the outer side of the top surface of the groove 210, thereby forming a tapered cross-section structure that is wider at the top and narrower at the bottom. The corners of the inverted trapezoidal structure can be right-angled corners or corners with chamfers. In some embodiments, the inverted trapezoidal configuration can be set with a specific sidewall inclination angle according to design requirements to meet the personalized needs of the leadless package structure.

[0089] The rectangular or inverted trapezoidal configurations described are merely illustrative examples of the cross-sectional shape of the groove 210 perpendicular to its extension direction, and are not intended to limit the scope of protection of this invention. The cross-sectional shape of the groove 210 perpendicular to its extension direction is not limited to the two configurations described above, and may also be other irregular cross-sections, such as including but not limited to V-shapes, U-shapes, arcs, polygons, or composite shapes of any combination thereof. The specific contours of these irregular cross-sections can be customized according to actual welding requirements, mechanical anchoring strength requirements, or specific stress distribution optimization objectives, thereby exhibiting different advantages in enhancing the capillary effect of solder, improving the flowability of molding compound filling, or dispersing local stress concentration.

[0090] In some embodiments of the present invention, along the extending direction of the groove 210, the distance between the bottom surface 215 and the top surface of the groove 210 gradually decreases, so that the width of the cross section of the groove 210 perpendicular to its extending direction gradually decreases along the extending direction.

[0091] As an example, such as Figures 1-7 As shown, in the first embodiment, along the extending direction of the groove 210 (as shown in direction D2 in the figure), the bottom surface 215 of the groove 210 is inclined towards the top surface of the groove 210, so that the distance between the bottom surface 215 and the top surface of the groove 210 gradually decreases. That is, the bottom surface 215 of the groove 210 has an inclined surface at an angle relative to the top surface of the groove 210, such that the vertical distance between the bottom surface 215 and the top surface of the groove 210 monotonically decreases along the extending direction of the groove 210, thereby increasing the width of the cross-section of the groove 210 perpendicular to its extending direction (e.g., ...). Figure 3 Width W1 and Figure 4 The width W2 in the groove gradually decreases along the extending direction. Specifically, by adjusting the process parameters for forming the groove 210, the bottom surface 215 of the groove 210 is controlled to have a continuous inclined surface with a constant angle relative to the top surface of the groove 210. This inclined surface configuration causes the width of the cross-section of the groove 210 perpendicular to its extending direction to gradually decrease, thereby forming a tapered cross-section structure. The inclination angle of the bottom surface 215 of the groove 210 can be set according to actual functional requirements to ensure effective guidance of solder flow, enhanced mechanical anchoring effect, and optimized stress distribution in the packaging process. Furthermore, by adjusting the process parameters for forming the groove 210, the inclination angle of the bottom surface 215 of the groove 210 can be changed, thereby controlling the rate of change of the width of the cross-section of the groove 210 along the extending direction of the groove 210, thereby optimizing the wetting performance and conductivity of the solder pad.

[0092] As an example, such as Figure 18 and Figure 19As shown, where, Figure 18 The leadless package structure provided in the eighth embodiment of the present invention is along Figure 1 A cross-sectional schematic diagram at the location indicated by line C1-C1. Figure 19 yes Figure 18 In the enlarged schematic diagram of region B in the eighth embodiment, along the extension direction of the groove 210 (as shown in direction D2 in the figure), the bottom surface 215 of the groove 210 converges towards the top surface of the groove 210 in a stepped manner, so that the distance between the bottom surface 215 and the top surface of the groove 210 gradually decreases, thereby causing the width of the cross-section of the groove 210 perpendicular to its extension direction to gradually decrease along the extension direction. Specifically, the bottom surface 215 of the groove 210 includes a plurality of sequentially adjacent stepped surfaces 213. These stepped surfaces 213 are arranged sequentially along the extension direction of the groove 210, and each subsequent stepped surface 213 has a smaller vertical distance from the top surface of the groove 210 compared to the previous stepped surface 213. This causes the sidewall to converge towards the top surface of the groove 210 in a stepped manner, resulting in the vertical distance between the bottom surface 215 and the top surface of the groove 210 decreasing step by step as the groove 210 extends. This stepped convergence configuration precisely controls the gradual gradient of the width of the groove 210 cross section through the hierarchical changes of the stepped surface 213. This is beneficial for optimizing material filling and stress distribution in the packaging process, and can also guide the directional flow and filling of solder during welding, thereby enhancing the mechanical anchoring strength and connection reliability of the welding interface.

[0093] In some embodiments of the present invention, in the extending direction of the groove 210, the same step surface 213 is parallel to the top surface of the groove 210 or inclined toward the top surface of the groove 210.

[0094] As an example, such as Figure 18 and Figure 19 In the eighth embodiment, the bottom surface of the groove 210 includes a plurality of sequentially adjacent stepped surfaces 213. In the extending direction of the groove 210, the same stepped surface 213 is parallel to the top surface of the groove 210. That is, the vertical distance from different positions of the same stepped surface 213 to the top surface of the groove 210 is equal along the extending direction of the groove 210. Each subsequent stepped surface 213 has a smaller vertical distance to the top surface of the groove 210 compared to the previous stepped surface 213.

[0095] As an example, such as Figure 20 and Figure 21 As shown, where, Figure 20 The leadless package structure provided in the ninth embodiment of the present invention is along Figure 1 A cross-sectional schematic diagram at the location indicated by line C1-C1. Figure 21 yes Figure 20 An enlarged schematic diagram of region B shows that, in the ninth embodiment, the bottom surface 215 of the groove 210 includes a plurality of sequentially adjacent stepped surfaces 213. Along the extension direction of the groove 210 (as shown in direction D2 in the figure), the same stepped surface 213 slopes towards the top surface of the groove 210. That is, along the extension direction of the groove 210, the vertical distance from the same stepped surface 213 to the top surface of the groove 210 exhibits a monotonically decreasing trend. Each subsequent stepped surface 213 has a smaller vertical distance to the top surface of the groove 210 compared to the previous stepped surface 213; specifically, the maximum vertical distance from each subsequent stepped surface 213 to the top surface of the groove 210 along the extension direction of the groove 210 is less than the minimum vertical distance from the previous stepped surface 213 to the top surface of the groove 210.

[0096] In some embodiments of the present invention, the sidewall 214 and bottom surface 215 of the groove 210 have the same variation pattern along the extension direction of the groove 210, thereby forming a consistent gradient profile, maintaining the uniformity of stress distribution, which helps to optimize the filling behavior and flow characteristics of the solder in the groove 210, thereby enhancing the mechanical anchoring effect and connection reliability of the welding interface.

[0097] For example, in the first embodiment, such as Figures 1-7 As shown, the sidewall 214 of the groove 210 is inclined toward the interior of the groove 210 so that the distance between the two sidewalls 214 of the groove 210 gradually decreases, and the bottom surface 215 of the groove 210 is inclined toward the top surface of the groove 210 so that the distance between the bottom surface 215 of the groove 210 and the top surface of the groove 210 gradually decreases.

[0098] For example, in another embodiment, the sidewalls 214 of the groove 210 converge in a stepped manner towards the interior of the groove 210, so that the distance between the two sidewalls 214 of the groove 210 gradually decreases, as can be referred to Figure 12 and Figure 13 As shown; the bottom surface 215 of the groove 210 converges towards the top surface of the groove 210 in a stepped manner, so that the distance between the bottom surface 215 and the top surface of the groove 210 gradually decreases. (See reference...) Figure 18 and Figure 19 As shown. The sidewall 214 and the bottom surface 215 change in a stepped manner with the same step distance.

[0099] In other embodiments of the present invention, the variation patterns of the sidewalls 214 and bottom surface 215 of the groove 210 along the extending direction of the groove 210 are different. The variation pattern refers to the arrangement of the sidewalls 214 and bottom surface 215 of the groove 210 along the extending direction in order to achieve a gradual decrease in the cross-sectional dimension of the groove 210 perpendicular to its extending direction.

[0100] For example, in one embodiment, the sidewalls 214 of the groove 210 are inclined inwards to gradually reduce the distance between the two sidewalls 214 of the groove 210. (See reference...) Figures 1-7 As shown; the bottom surface 215 of the groove 210 converges towards the top surface of the groove 210 in a stepped manner, so that the distance between the bottom surface 215 and the top surface of the groove 210 gradually decreases. (See reference...) Figure 18 and Figure 19 As shown.

[0101] For example, in one embodiment, the sidewalls 214 of the groove 210 converge in a stepped manner towards the interior of the groove 210, so that the distance between the two sidewalls 214 of the groove 210 gradually decreases. (See reference...) Figure 12 and Figure 13 As shown; the bottom surface 215 of the groove 210 is inclined towards the top surface of the groove 210, so that the distance between the bottom surface 215 and the top surface of the groove 210 gradually decreases. (Refer to...) Figures 1-7 As shown.

[0102] In some embodiments of the present invention, the two side walls 214 of the groove 210 are mirror images of the center line of the groove 210. Specifically, the two side walls 214 of the groove 210 are symmetrically arranged, and the variation pattern of the two side walls 214 is the same in the extending direction of the groove 210. For example, both side walls 214 of the groove 210 are inclined inwards towards the interior of the groove 210, or they converge towards the interior of the groove 210 in a stepped manner with the same step distance.

[0103] In some embodiments of the present invention, the end of the groove 210 away from the opening 211 may be an arc-shaped configuration or a planar configuration to adapt to different requirements of the leadless package structure.

[0104] For example, you can refer to Figure 1As shown, the end of the groove 210 away from the opening 211 has an arc-shaped configuration that curves towards the center of the back surface of the molded body 100. Specifically, the end of the groove 210 away from the opening 211 has a smooth arc-shaped configuration that curves towards the center of the back surface of the molded body 100. This effectively disperses and reduces stress concentration in the end region of the groove 210, preventing cracks from forming at this point when the package is subjected to thermal or mechanical stress. Furthermore, the arc-shaped end facilitates solder filling, reducing the risk of incomplete solder filling, thereby enhancing the bonding force between the solder and the pad 200 and improving the reliability and integrity of the solder interface.

[0105] For example, such as Figure 22 As shown, it is a top view of the pad 200 area and its surrounding area in the leadless package structure provided in the tenth embodiment of the present invention. The end of the groove 210 away from the opening 211 is a planar configuration. Specifically, the end of the groove 210 away from the opening 211 is a planar configuration perpendicular to the back of the molded body 100, so as to meet the personalized needs of the leadless package structure.

[0106] The pad design of the leadless package structure provided in this embodiment of the invention effectively controls burr and scratch problems, and ensures the wettability of the sidewalls of the pad 200, ensuring that the solder can rise evenly during reflow soldering to form a reliable connection.

[0107] For reference Figure 6 As shown, in some embodiments of the present invention, the leadless package structure further includes: Base island 300, the pads 200 are distributed around the base island 300; Chip 310 is disposed on the front side of the base island 300 and connected to the pad 200 via bonding wire 320; The molding compound 100 also covers the base island 300, the chip 310, and the bonding wires 320, with the back side of the base island 300 exposed on the back side of the molding compound 100.

[0108] The base island 300, serving as a support and heat dissipation component for the leadless package structure, is located in the central region of the back side of the molding compound 100. The chip 310 is fixed to the front side of the base island 300 by adhesive material, while the back side of the base island 300 is directly exposed to the molding compound 100 to maximize heat dissipation efficiency. The heat generated by the chip 310 during operation is conducted to the external environment (such as a PCB board) through the base island 300, thereby improving the heat dissipation performance of the leadless package structure.

[0109] The base island 300 is typically made of a high thermal conductivity copper alloy, and its surface may be covered with an electroplated layer such as nickel, palladium, or gold to enhance oxidation resistance and solderability. Its thickness can be adjusted according to heat dissipation requirements; for example, in ultra-thin packages, it can be reduced to half the thickness of the lead layer to achieve lower thermal resistance. The base island 300 can be made of the same material as the solder pad 200.

[0110] The chip 310 is mounted on the front side of the base island 300 using adhesive 330 and serves as the active unit for realizing circuit functions. The electrodes of the chip 310 are connected to the surface of the pads 200 surrounding the base island 300 via bonding leads 320 (gold or copper wires), thus achieving electrical interconnection with the pads 200. The power consumption and integration level of the chip 310 are directly related to the package design. For example, high-power chips rely on the efficient heat dissipation capability of the base island 300 to maintain stable junction temperature, while multi-chip integration schemes (such as placing the main control chip, driver chip, and MOSFET chip on multiple base islands) optimize system performance through functional allocation. The molding compound 100 covers the chip 310 and the bonding leads 320 to provide physical protection for them.

[0111] In leadless package structures, the chip 310 is diverse, including highly integrated logic and computing chips with a large number of pins and high operating frequencies (such as CPUs, GPUs, MCUs, and ASICs). These chips require packages to provide high-density interconnects and stable power integrity. They also include power semiconductor chips that withstand high current and high voltage (such as power MOSFETs, GaNHEMTs, and IGBTs), whose package designs need to focus on extremely low thermal resistance and high heat dissipation efficiency, and minimize parasitic parameters to improve switching performance. In addition, there are RF and analog chips that are extremely sensitive to signal integrity and noise (such as RF front-end modules, power amplifiers, and power management chips), which rely on short-path interconnects to ensure high-frequency characteristics. And there are memory chips that pursue high bandwidth and small size (such as DRAM and NAND Flash), which can achieve high-density integration through three-dimensional stacking or system-in-package technology. The power consumption, performance, and integration of these chips directly determine the choice of packaging scheme. For example, high-power chips rely on efficient heat dissipation of the base island to maintain stable junction temperature, while multi-chip integration (such as placing the main controller, driver, and power chips together) optimizes system-level performance through functional allocation. Therefore, the packaging design must be optimized in conjunction with the chip characteristics to meet the comprehensive requirements of electrical connection, thermal management, and mechanical reliability.

[0112] The chip 310 is mounted on the front side of the base island 300 using adhesive 330. Adhesive 330 is a key material for achieving mechanical support, thermal pathways, and electrical connections under specific conditions. Main types include: epoxy resin-based adhesives with an epoxy resin matrix and the addition of conductive fillers such as silver powder or thermally conductive fillers such as alumina, which exhibit high bonding strength and good process adaptability; silicone-based adhesives with excellent elasticity and resistance to high and low temperatures, suitable for power devices and other applications requiring stress buffering; polyimide-based adhesives 330 with extremely high heat resistance and good dimensional stability, suitable for high-end chips and high-temperature processes; acrylate adhesives that can achieve rapid curing, meeting the needs of high-efficiency production; and anisotropic conductive adhesives containing fine conductive particles that enable Z-axis directional conduction, suitable for high-density fine-pitch interconnects.

[0113] The bonding wires 320 are components that enable electrical interconnection between the chip 310 and the pads 200 distributed around the base island 300. They are typically made of metals such as gold, aluminum, or copper, and their two ends are connected to the pads on the surface of the chip 310 and the top surface of the pads 200 around the base island 300, respectively, using processes such as thermo-ultrasonic bonding. The wire diameter, arc height, and material selection of the bonding wires 320 (e.g., gold wires offer excellent conductivity and stability, aluminum wires are less expensive, and copper wires achieve a good balance between conductivity and heat dissipation) directly affect the electrical performance, thermal management, and reliability of the package. In applications requiring high current carrying capacity, rectangular aluminum or copper strips are sometimes used instead of traditional round wires to increase current carrying capacity and improve heat dissipation within a limited space. The molding compound 100 protects these fine bonding wires 320 by encapsulating them, preventing mechanical damage and environmental impacts, thereby ensuring the long-term stability of the internal connections.

[0114] The leadless package structure provided in this invention effectively reduces metal burrs and metal scratches in the groove 210 through innovative design. Before forming the leadless package structure, the cutting area of ​​the lead frame is optimized to form a groove 210 with a specific configuration to reduce the amount of metal removed during cutting. This reduces the volume of metal contacted by the cutting tool during operation, not only lowering cutting resistance but also effectively dispersing stress. This avoids the metal burrs and metal scratches caused by material ductility during traditional continuous cutting, directly reducing the risk of short circuits between pads 200 due to burr connections.

[0115] The leadless package structure provided by this invention effectively controls burr and scratch problems and ensures the wettability of the sidewalls of the pad 200, ensuring that the solder can rise evenly during reflow soldering to form a reliable connection, thereby improving the overall electrical performance stability and reliability of the leadless package structure.

[0116] It should be noted that references to "an embodiment," "an embodiment," "an exemplary embodiment," "some embodiments," etc., in the specification indicate that the described embodiments may include specific features, structures, or characteristics, but each embodiment may not necessarily include that specific feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. In addition, when a specific feature, structure, or characteristic is described in connection with an embodiment, whether explicitly described or not, implementing such a feature, structure, or characteristic in conjunction with other embodiments is within the knowledge of those skilled in the art.

[0117] It should be noted that the terms "comprising" and "having," and their variations, used in this invention document are intended to cover non-exclusive inclusion. The terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence, unless explicitly indicated by the context. It should be understood that such data used interchangeably where appropriate. Furthermore, embodiments and features within embodiments of this invention can be combined with each other unless otherwise specified. In addition, descriptions of well-known components and technologies have been omitted in the above description to avoid unnecessarily obscuring the concepts of this invention. In the various embodiments described above, each embodiment focuses on its differences from other embodiments; similar or identical parts between embodiments can be referred to interchangeably.

[0118] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications 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 leadless package structure, characterized in that, include: Plastic encapsulation; A solder pad is embedded in the molding compound, with one end face of the solder pad exposed on the side of the molding compound and the bottom face of the solder pad exposed on the back of the molding compound. The solder pad has a groove extending from the end face to the center of the back of the molding compound. The groove has an opening located on the end face of the solder pad. The dimension of the cross section of the groove perpendicular to its extension direction gradually decreases along the extension direction.

2. The leadless package structure according to claim 1, characterized in that, The length and / or width of the cross section of the groove perpendicular to its extension direction gradually decreases along the extension direction, wherein the length refers to the dimension of the cross section in the direction parallel to the back surface of the encapsulant, and the width refers to the dimension of the cross section in the direction perpendicular to the back surface of the encapsulant.

3. The leadless package structure according to claim 1, characterized in that, The side profile of the opening coincides with the outer side profile of the pad on the side of the molding compound.

4. The leadless package structure according to claim 1, characterized in that, The opening side profile and the pad are separated by a distance from each other on the side profile of the molding compound.

5. The leadless package structure according to claim 1, characterized in that, The bottom edge contour of the opening coincides with the bottom outer contour of the pad on the side of the molding compound.

6. The leadless package structure according to claim 1, characterized in that, The bottom edge contour of the opening and the pad are separated by a distance from the bottom outer contour of the side of the molding compound.

7. The leadless package structure according to claim 1, characterized in that, The outline of the opening coincides with the outer outline of the pad on the side of the molding compound.

8. The leadless package structure according to claim 1, characterized in that, The outline of the opening is at a distance from the outer outline of the pad on the side of the molding compound.

9. The leadless package structure according to claim 2, characterized in that, Along the extending direction of the groove, the distance between the two side walls of the groove gradually decreases, so that the length of the cross section of the groove perpendicular to its extending direction gradually decreases along the extending direction.

10. The leadless package structure according to claim 9, characterized in that, Along the extending direction of the groove, the sidewalls of the groove are inclined inwards, so that the distance between the two sidewalls of the groove gradually decreases.

11. The leadless package structure according to claim 9, characterized in that, Along the extension direction of the groove, the sidewalls of the groove converge toward the interior of the groove in a stepped manner, so that the distance between the two sidewalls of the groove gradually decreases.

12. The leadless package structure according to claim 11, characterized in that, The sidewall includes a plurality of sequentially adjacent stepped surfaces, and the same stepped surface extends along the extension direction of the groove.

13. The leadless package structure according to claim 11, characterized in that, The sidewall comprises a plurality of sequentially adjacent stepped surfaces, wherein the same stepped surface is inclined inward into the groove in the extending direction of the groove.

14. The leadless package structure according to claim 1, characterized in that, The side of the cross section of the groove perpendicular to its extension direction is parallel to the outer contour of the side of the pad, so that the cross section has a rectangular configuration.

15. The leadless package structure according to claim 1, characterized in that, The side of the cross section of the groove perpendicular to its extension direction is inclined toward the outer contour of the side of the pad, so that the cross section has an inverted trapezoidal configuration.

16. The leadless package structure according to claim 2, characterized in that, Along the extending direction of the groove, the distance between the bottom surface and the top surface of the groove gradually decreases, so that the width of the cross-section of the groove perpendicular to its extending direction gradually decreases along the extending direction.

17. The leadless package structure according to claim 16, characterized in that, Along the extending direction of the groove, the bottom surface of the groove is inclined to the top surface of the groove, so that the distance between the bottom surface and the top surface of the groove gradually decreases.

18. The leadless package structure according to claim 16, characterized in that, Along the extension direction of the groove, the bottom surface of the groove converges towards the top surface of the groove in a stepped manner, so that the distance between the bottom surface and the top surface of the groove gradually decreases.

19. The leadless package structure according to claim 18, characterized in that, The bottom surface of the groove includes a plurality of sequentially adjacent stepped surfaces, and in the extending direction of the groove, the same stepped surface is parallel to the top surface of the groove.

20. The leadless package structure according to claim 18, characterized in that, The bottom surface of the groove includes a plurality of sequentially adjacent stepped surfaces, and in the extending direction of the groove, the same stepped surface is inclined to the top surface of the groove.

21. The leadless package structure according to claim 1, characterized in that, Along the extension direction of the groove, the sidewalls and bottom surface of the groove exhibit the same variation pattern.

22. The leadless package structure according to claim 1, characterized in that, The two side walls of the groove are mirror images of the center line of the groove.

23. The leadless package structure according to claim 1, characterized in that, The end of the groove away from the opening has an arc-shaped configuration that curves toward the center of the back of the encapsulated body.

24. The leadless package structure according to claim 1, characterized in that, The end of the groove away from the opening has a planar configuration.

25. The leadless package structure according to claim 1, characterized in that, Also includes: Base island, wherein the pads are distributed around the base island; The chip is disposed on the front side of the base island and connected to the pads via bonding wires; The molding compound also covers the base island, the chip, and the bonding wires, with the back side of the base island exposed on the back side of the molding compound.

26. The leadless package structure according to claim 25, characterized in that, The solder pads are provided on all four sides of the molding compound.

27. The leadless package structure according to claim 25, characterized in that, The solder pads are provided on opposite sides of the molding compound.

28. The leadless package structure according to claim 1, characterized in that, The leadless package structure includes multiple pads, at least a portion of which have the groove.

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