Ball bonding chopper tip structure capable of increasing height of convex point of gold ball

Abstract

The invention relates to a unique tip structure suitable for a ball bonding chopper, the unique tip structure comprises a conventional structure and a cavity structure, the conventional structure comprises a wire hole, a first inner tangent plane, a second inner tangent plane, an inner cavity chamfer height, an appearance chamfer, an appearance surface angle and an appearance size, and the cavity structure comprises an upper platform, a platform taper and a platform height. The method has the advantages that an extra cavity structure is added in the tip, the height of a Ball Height above a single-layer gold ball bump Ball Thickness is increased, the overall height of the single-layer gold ball bump is effectively increased, the number of times of a stacking process is reduced, and the production efficiency is improved; the width of the single-layer Top Diameter is increased, the process difficulty of the stacking process is reduced, and the production yield is improved.

Description

Technical Field

[0001] The invention discloses a ball welding chopper tip structure for improving the height of gold ball bumps, belonging to the technical field of advanced packaging. Background Art

[0002] In the advanced packaging field, bumps serve as electrical interconnects and stress buffers between interfaces. Bump fabrication is a key technology in vertical interconnects. In RF flip-chip packaging applications, due to the poor compatibility between the fabrication processes for III-V compound semiconductor chips, primarily based on gallium arsenide, and the copper pillar (CuP) bumping process, the gold stud bump (GSB) process has become the mainstream choice due to its excellent compatibility with both the chip and substrate pads. The ball bond wrench is a key tool in the wafer-level GSB bumping process, directly determining the production efficiency and yield of flip-chip packaging products.

[0003] RF flip-chips have a dielectric cavity on their surface for electromagnetic wave transmission. Simulation results indicate that a 40GHz RF flip-chip requires a dielectric cavity height of at least 70µm. This necessitates that the gold bumps have an initial height of at least 90µm within a 100µm chip pad. Existing ball bonders require a two-step stacking process to achieve height control. This significantly increases the difficulty of wafer ball placement and flip-chip bonding, introducing reliability risks, and results in millions of extra bumps being placed at the wafer level, significantly reducing production efficiency. Summary of the Invention

[0004] The present invention proposes a ball bonding tool tip structure for increasing the height of gold ball bumps. The purpose of the present invention is to address the defects of the two-time stacking in the prior art. In order to achieve the preparation of higher gold ball bumps, only a single stacking process is required, thereby reducing the process difficulty, improving reliability and production efficiency. A ball bonding tool tip structure for increasing the height of gold ball bumps is provided. The ball height above the ball thickness of a single-layer gold ball bump is increased, effectively increasing the overall height of the single-layer gold ball bump, reducing the number of stacking processes, and improving production efficiency; and increasing the width of the top diameter of the single-layer gold ball bump, reducing the process difficulty of the stacking process, and improving production yield.

[0005] The technical solution of the present invention is: a ball welding chopper tip structure for improving the height of the gold ball bump, the tip structure is an inverted truncated cone structure with a cavity structure and a wire hole, the bottom end of the tip structure is a quasi-arc-shaped structure, the bottom surface of the quasi-arc-shaped structure is a plane, the inner side is provided with a chamfer, the outer side is arc-shaped, and from the central axis outward are the outer surface angle 7 and the outer surface chamfer 8, which together constitute the outer dimension 9, and the outer surface chamfer and the outer surface angle cooperate with each other to jointly determine the outer shape of the gold ball bump; the central cavity is recessed to form an upper platform 2, and a wire hole 1 is provided in the middle of the upper platform 2, and the wire hole is connected with the cavity structure; the side wall of the upper platform 2 is inclined, and the plane where the inner chamfer of the quasi-arc-shaped structure intersects with the inner inclined side wall is a first inscribed surface 4, and the bottom plane of the inner chamfer of the quasi-arc-shaped structure is a second inscribed surface 5.

[0006] The side wall of the upper platform is inclined at a certain angle, and the angle between the connecting surface of the upper platform and the first inner tangent surface and the central axis is the platform taper 10, and the platform taper is 20°±5°.

[0007] The vertical distance between the upper platform 2 and the first inscribed surface 4 is the platform height, and the vertical distance between the first inscribed surface 4 and the second inscribed surface 5 is the inner chamfer height 6.

[0008] The inner cavity chamfer formed by the second inner section 5 and the first inner section 4 is in a trumpet shape, and the small end thereof is connected to the cavity structure.

[0009] The diameter of the first inner section 4 is 30-40 microns less than the chip pad length.

[0010] The outer dimension 9 is equal to the chip pad length, or increases by 30-40 microns.

[0011] The diameter of the upper platform 2 is 1.8 to 2.2 times the diameter of the bonding wire.

[0012] Beneficial effects of the present invention: The present invention is different from the existing ball welding tool tip structure. Based on the design requirements of the ball welding tool tip structure, a unique tip structure is designed, an additional cavity structure is constructed inside the tip, and a gold ball bump with a truncated cone structure shape is effectively constructed.

[0013] The gold ball bumps with increased height prepared by the present invention effectively reduce the number of stacking processes, can reduce the number of ball planting operations by millions during wafer-level ball planting, and greatly improve production efficiency.

[0014] The gold ball bumps with increased upper end plane size prepared by the present invention provide a larger support plane for the stacking ball planting process, can reduce the process difficulty of the stacking process, and improve the production yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1It is a schematic diagram of the unique tip structure of the ball welding wrecker.

[0016] Figure 2 This is a photo of the unique tip structure of the ball welding cutter.

[0017] Figure 3 This is a real picture of the gold ball bump.

[0018] Figure 4 This is a real picture of stacked gold ball bumps.

[0019] In the figure, 1 is the wire hole, 2 is the upper platform, 3 is the platform height, 4 is the first internal cutting surface, 5 is the internal cutting surface, 6 is the inner cavity chamfer height, 7 is the outer surface angle, 8 is the outer chamfer, 9 is the outer size, and 10 is the platform taper. DETAILED DESCRIPTION

[0020] In the present invention, unless otherwise expressly specified or limited, terms such as "installed," "connected," "connected," and "fixed" should be understood broadly. For example, they can refer to fixed connections, detachable connections, or integrated connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to internal communication between two components or interactions between two components. The terms "first," "second," and similar terms mentioned in this application do not indicate any order, quantity, or importance, but are simply used to distinguish different components. Similarly, terms such as "one" or "a" do not indicate a quantitative limitation, but rather indicate the presence of at least one. In the implementation of this application, "and / or" describes an association relationship between associated objects, indicating that three relationships can exist. For example, "A and / or B" can mean: A exists alone, A and B exist simultaneously, or B exists alone. In the description of the embodiments of this application, unless otherwise specified, "plurality" means two or more. For example, "plurality" refers to two or more positioning posts. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0021] The technical solution of the present invention is further described below in conjunction with the accompanying drawings. Figure 1 As shown, a unique tip structure suitable for a ball welding wrecking tool is provided. The unique tip structure includes a conventional structure and a cavity structure. The conventional structure includes a wire hole, a first inner section, a second inner section, an inner cavity chamfer height, an outer chamfer, an outer surface angle, and outer dimensions. The cavity structure includes an upper platform, a platform taper, and a platform height.

[0022] In the unique tip structure, the wire hole is connected to the cavity structure, and is sequentially connected to the upper platform, the first inner section, and the second inner section.

[0023] The semi-enclosed area formed by the upper platform, the first inner tangent surface and the connecting surface of the two planes constitutes the entire cavity structure.

[0024] The vertical distance between the upper platform and the first inner tangent surface is the platform height.

[0025] The vertical distance between the first inner tangent surface and the second inner tangent surface is the inner chamfer height.

[0026] The angle between the connecting surface of the upper platform and the first inscribed surface and the central axis is the platform taper.

[0027] The outer contour of the tip is composed of an outer face angle and an outer chamfer from the central axis outward, which together constitute the outer dimensions.

[0028] In some possible implementations, the diameter of the first inner section is 30-40 microns less than the chip pad length.

[0029] In some possible implementations, the inner cavity chamfer formed by the second inner tangent surface and the first inner tangent surface is trumpet-shaped, and the small end thereof is connected to the cavity structure.

[0030] In some possible implementations, the outer dimensions are equal to the chip pad length, or increased by 30 to 40 microns.

[0031] In some possible implementations, the outer chamfer and the outer face angle cooperate with each other to jointly determine the outer shape of the gold ball bump.

[0032] In some possible implementations, the diameter of the upper platform is 1.8 to 2.2 times the diameter of the bonding wire.

[0033] In some possible implementations, the platform taper is 20°±5°.

[0034] Compared to existing technologies, this approach adds an additional cavity structure within the tip and increases the volume of the gold ball (Free Air Ball). During the bonding process, the gold ball begins to plastically deform under vertical downward pressure, subjecting it to additional compression from the cavity structure. This newly added volume fills the entire cavity structure, forming a frustum-shaped gold ball bump, effectively increasing the height of the gold ball bump. Furthermore, as the gold ball contacts and fills the upper surface of the cavity structure, it forms a platform, effectively increasing the upper surface dimension of the gold ball bump. This provides a larger support surface for the subsequent stacking process, contributing to the stability and consistency of the stacking process.

[0035] The present invention is not limited to the aforementioned specific embodiments, but extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed. Example

[0036] like Figure 2 As shown: Zirconia ceramic cylinder is selected as the ball welding wedge material for processing, with a diameter of 1.58 mm; After design, the tip structure information is: wire hole diameter 30um, upper platform diameter 55um, platform height 40um, first inner section diameter 70um, second inner section diameter 85um, inner cavity chamfer height 5um, outer surface angle 0°, outer chamfer radius 12um, outer dimension diameter 130um, platform taper 21.239.

[0037] like Figure 3-Figure 4 As shown: Reasonable settings were made for the wafer ball placement machine's ultrasonic power, bonding pressure, bonding time, bonding temperature and other process parameters. After process debugging, good bonding results were achieved.

[0038] After measurement, the diameter of the platform on the gold ball bump is 45um, the height of the gold ball bump is 50um, and the height of the stacked gold ball bump is 90um. The wafer planting achieved good results.

[0039] After a period of practical use, the stacked gold ball bumps prepared by the present invention can meet the design requirement that the dielectric cavity height is at least 70 μm.

Claims

1. A ball welding tool tip structure for increasing the height of gold ball bumps, characterized by The tip structure is an inverted truncated cone structure with a cavity structure and a wire hole. The bottom end of the tip structure is a quasi-arc-shaped structure. The bottom surface of the quasi-arc-shaped structure is a plane, the inner side is provided with a chamfer, and the outer side is an arc. From the central axis to the outside, there are the outer surface angle and the outer chamfer, which together constitute the outer size. The outer chamfer and the outer surface angle cooperate with each other and jointly determine the outer shape of the gold ball bump; the middle cavity is recessed to form an upper platform, and a wire hole is provided in the middle of the upper platform, and the wire hole is connected with the cavity structure; the side wall of the upper platform is inclined, and the plane where the inner chamfer of the quasi-arc-shaped structure intersects with the inner inclined side wall is the first internal tangent surface, and the bottom plane of the inner chamfer of the quasi-arc-shaped structure is the second internal tangent surface.

2. A ball bonding tool tip structure for increasing the height of a gold ball bump according to claim 1, characterized in that The side wall of the upper platform is inclined at a certain angle, and the angle between the connecting surface of the upper platform and the first inner tangent surface and the central axis is the platform taper, and the platform taper is 20°±5°.

3. A ball bonding tool tip structure for increasing the height of a gold ball bump according to claim 1, characterized in that The vertical distance between the upper platform and the first inscribed surface is the platform height, and the vertical distance between the first inscribed surface and the second inscribed surface is the inner chamfer height.

4. A ball bonding tool tip structure for increasing the height of a gold ball bump according to claim 1, characterized in that The inner cavity chamfer formed by the second inner tangent surface and the first inner tangent surface is in a trumpet shape, and the small end of the trumpet is connected to the cavity structure.

5. A ball bonding tool tip structure for increasing the height of a gold ball bump according to claim 1, characterized in that The diameter of the first inner section is 30-40 microns less than the chip pad length.

6. A ball bonding tool tip structure for increasing the height of a gold ball bump according to claim 1, characterized in that The outer dimensions are equal to the chip pad length, or increased by 30 to 40 microns.

7. The ball bonding tool tip structure for increasing the height of gold ball bumps according to claim 1, characterized in that The diameter of the upper platform is 1.8 to 2.2 times the diameter of the bonding wire.

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