A solid ball mounting method for integrated circuit manufacturing

Abstract

The application provides a solid ball mounting method for integrated circuit manufacturing, which comprises the following steps: providing an inner recess on a rigid anvil plate for accommodating a to-be-mounted ball and limiting displacement of the to-be-mounted ball; placing the to-be-mounted ball into the inner recess of the rigid anvil plate and fixing the rigid anvil plate, at this time, a partial region of the to-be-mounted ball protrudes from the surface of the rigid anvil plate; arranging a substrate of an integrated circuit in front of the to-be-mounted ball and adjusting the to-be-mounted ball region of the substrate so as to be opposite to the to-be-mounted ball; and applying a force to the substrate so that the substrate hits the to-be-mounted ball under the action of the force, thereby realizing combination of the substrate and the to-be-mounted ball and obtaining a micro-ball bump structure. The application provides a brand-new solid ball mounting method for integrated circuit manufacturing, which does not need the whole melting and wetting process of solder in traditional reflow soldering, can reduce or avoid dependence on flux, UBM layer and complex surface metallization process, and is especially suitable for preparing micro-ball bumps / connections directly on the surface of an easily-oxidized substrate such as aluminum or aluminum alloy.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit manufacturing technology, and more specifically to a solid-state ball-mounting method for integrated circuit manufacturing. Background Technology

[0002] In the integrated circuit manufacturing process, the main techniques for soldering or bumping electronic devices include reflow soldering, electroplating bumping, thermoforming, ultrasonic bonding, and laser micro-soldering. However, these methods have significant shortcomings when directly forming connection points on the surface of aluminum substrates or dissimilar metal substrates, including: The oxide film on the surface of aluminum substrate makes direct ball bonding difficult: A dense and stable Al2O3 oxide film naturally exists on the surface of aluminum and aluminum alloys. This oxide film will hinder the direct contact and interfacial bonding between the solder ball and the aluminum substrate. Traditional reflow soldering usually requires flux, surface activation treatment or UBM metallization layer, otherwise it is difficult to achieve reliable connection of solder ball on the surface of aluminum substrate. Traditional thermal processes are prone to thermal damage and interface contamination: methods such as reflow soldering, brazing or laser soldering rely on high heat input, which can easily cause solder ball oxidation, substrate thermal deformation, generation of brittle phases at the interface, flux residue and thermal damage to the packaging structure, which is not conducive to the manufacturing of high-reliability electronic packaging and heat-sensitive devices. Micro solder ball positioning is difficult: Micro solder balls are prone to rolling, shifting, stacking or scattering before being placed, especially for arrayed bump structures. The positional accuracy and height consistency of the solder balls directly affect the reliability of subsequent interconnection, making it difficult to achieve stable positioning and effective bonding of solder balls under high-speed impact conditions.

[0003] Therefore, it is necessary to develop a novel solid-state ball-planting method that does not rely on solder melting and wetting spreading technology, has no thermal damage, and has good stability. Summary of the Invention

[0004] One objective of this invention is to provide a solid-state ball-mounting method for integrated circuit manufacturing. Solid-state ball-mounting, as described in this invention, refers to a method where the balls to be mounted are fixedly connected to the integrated circuit substrate without melting or molten wetting.

[0005] To achieve the above objectives, the present invention adopts the following technical solution.

[0006] A method for solid-state ball mounting in integrated circuit manufacturing, comprising the following steps: Step 1: Select a rigid cutting board. The rigid cutting board has a concave part to accommodate the planted bulb and limit its displacement. Step 2: Place the planted bulb into the concave part of the rigid cutting board and fix the rigid cutting board in place. At this time, part of the planted bulb protrudes from the surface of the rigid cutting board. Step 3: Place the integrated circuit substrate in front of the sphere to be implanted, and adjust the area of ​​the substrate to be implanted so that it faces the sphere to be implanted. Step 4: Apply a force to the substrate so that the substrate impacts the sphere to be implanted under the force, thereby achieving the bonding between the substrate and the sphere to be implanted, and obtaining the microsphere bump structure. Step 5: Remove the rigid anvil and perform post-processing on the workpiece after ball planting.

[0007] Preferably, after the implantable bulb is placed into the concave part, there is no gap or almost no gap between the implantable bulb and the surface of the concave part.

[0008] Preferably, the recessed portion is a blind hole or a through hole.

[0009] Preferably, the surface of the concave portion is a curved surface adapted to the surface of the sphere to be planted.

[0010] Preferably, the rigid anvil is provided with a plurality of said recesses arranged in an array.

[0011] In this invention, in step 4, the rigid cutting board provides reaction force and support to the ball during the ball planting process and restricts the ball's displacement.

[0012] In this invention, during the ball-planting process, the substrate is first moved to a new position, and the ball is transferred from the rigid anvil to the substrate and fixed on the substrate.

[0013] Preferably, the rigid cutting board is made of stainless steel, tool steel, cemented carbide, tungsten alloy, ceramic, or other materials that meet the requirements for rigidity and impact resistance; the substrate is made of aluminum plate, aluminum alloy plate, or other materials that meet the requirements for use in integrated circuits; and the sphere to be implanted is replaced by metal microspheres or cylindrical bodies.

[0014] Preferably, an electromagnetic pulse device is used to apply force to the substrate, and the substrate moves as a driven component or a flyboard during the electromagnetic pulse action.

[0015] In an optional embodiment of the present invention, when the ball to be implanted is a SAC305 solder ball with a diameter of 1 mm, the discharge energy of the electromagnetic pulse device is controlled to be 20-24 kJ.

[0016] Beneficial Effects: This invention provides a novel solid-state ball-mounting method for integrated circuit manufacturing. This method eliminates the need for the overall melting and wetting process of solder in traditional reflow soldering, reducing or avoiding reliance on flux, UBM layers, and complex surface metallization processes. It is particularly suitable for directly preparing microsphere bumps / connections on easily oxidized substrates such as aluminum or aluminum alloys. This invention uses a rigid anvil to temporarily accommodate, position, and support the balls to be mounted, and utilizes electromagnetic pulse force to drive the substrate as a flying plate to impact the balls at high speed. This allows the balls to be transferred and bonded to the substrate surface without flux, without overall reflow melting, and with little or no reliance on UBM layers, thereby forming a microsphere bump structure with controllable position, high stability, and high reliability. Unlike traditional ball-mounting methods that melt and wet the balls to be mounted onto the substrate surface, this invention utilizes the instantaneous pressure, local plastic flow, and interfacial shearing generated by high-speed impact to break and disturb the oxide film on the substrate surface, forming a microsphere bump structure with high stability and reliability between the balls to be mounted and the substrate. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the rigid cutting board in this invention; Figure 2 This is a schematic diagram of the solid-state ball-planting process in this invention; Figure 3 This is a diagram of the microsphere bump structure obtained after solid-state implantation in Example 1; Figure 4 The figure shows the interface characterization results of SAC305 solder ball / aluminum plate in Example 1. In the figure, (a) is the SEM image of the interface cross section, (b) is the magnified image of the interface bonding area, and (c) is the EDS line scan result. Figure 5 The image shows the fracture morphology of the SAC305 solder ball / aluminum plate in Example 1. Figure 6 To compare the interface characterization results of SAC305 solder ball / aluminum plate in Example 1, in the figure, (a) is the SEM image of the interface cross section, (b) is the enlarged view of the interface bonding area, and (c) is the EDS line scan result. Figure 7 For comparison, see the fracture morphology of SAC305 solder ball / aluminum plate in Example 1; Figure 8 To compare the interface characterization results of SAC305 solder balls / aluminum plates in Example 2, in the figure, (a) is a SEM image of the interface cross section; (b) is a magnified view of the interface bonding area; and (c) is the EDS line scan result. Figure 9 For comparison, the fracture morphology of SAC305 solder ball / aluminum plate in Example 2 is shown. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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. Example 1

[0019] A solid-state ball-mounting method for integrated circuit manufacturing involves using an electromagnetic pulse device to implant SAC solder balls 2 (balls to be mounted) onto the surface of a 6061 aluminum plate (substrate 3). It should be understood that, in addition to SAC305 solder balls 2 and 6061 aluminum plates, this method is also applicable to other metal microspheres, alloy microspheres, surface-coated microspheres, and substrates 3 with conductive layers or conductive driving layers.

[0020] Combination Figure 1 and Figure 2 As shown, the solid-state ball-planting method in this embodiment includes the following steps: Step 1, select 304 stainless steel plate as rigid cutting board 1, such as Figure 1 As shown, the rigid cutting board 1 is provided with a concave portion 4 for accommodating the planted bulb and restricting its displacement. The concave portion 4 is provided with vacuum suction holes, and the structure of the concave portion 4 is as follows. Figure 1 As shown, a spherical recess is used (the surface of the recess 4 is a curved surface adapted to the surface of the ball to be implanted). The opening of the recess 4 is chamfered to reduce the detachment resistance of the SAC305 solder ball 2 during the subsequent transfer process. Multiple recesses 4 are arranged in an array. 6061 aluminum plate is selected as the substrate 3 of the integrated circuit. The material types and specifications of each embodiment are shown in Table 1. Among them, the 304 stainless steel rigid anvil 1 has high rigidity and impact resistance stability. In the subsequent ball implantation process, it is used to accommodate and position the SAC305 solder ball 2 and provide reaction force support for the SAC305 solder ball 2. Table 1. Materials and specifications used in this embodiment.

[0021] Step 2: Place the sphere to be planted into the concave part 4 of the rigid cutting board 1, and use vacuum adsorption to adsorb and fix the sphere to be planted, and fix the rigid cutting board 1. At this time, part of the sphere to be planted protrudes from the surface of the rigid cutting board 1. After the sphere to be planted is placed into the concave part 4, there is no gap or almost no gap between the sphere to be planted and the surface of the concave part 4. Step 3: Arrange the integrated circuit substrate 3 in front of the sphere to be implanted (in this example, substrate 3 is arranged below the rigid anvil 1, such as...). Figure 2 As shown), adjust the area of ​​the substrate 3 to be planted so that it is aligned with the sphere to be planted, and adjust the distance between the substrate 3 and the sphere to be planted (initial gap 2mm). Step 4: Turn on the electromagnetic pulse device and apply force to the substrate 3, so that the substrate 3 impacts the ball to be implanted under the action of the force, thereby achieving the bonding between the substrate 3 and the ball to be implanted. During this process, the SAC305 solder ball 2 undergoes local plastic deformation under the combined action of the high-speed impact of the aluminum plate and the reaction support of the rigid anvil 1, and is bonded to the surface of the aluminum plate. Step 5: Remove the rigid anvil 1. After the aluminum plate separates from the rigid anvil 1, the SAC305 solder balls 2 detach from the recess 4 and remain on the surface of the aluminum plate, forming a raised structure of the solder balls 2 as shown in the figure. Figure 3 As shown, the workpiece after ball planting is then post-processed.

[0022] The samples obtained in this embodiment were tested, and the results are as follows: Figure 4 As shown. Wherein: SEM images of the specimen cross-section, as shown Figure 4 As shown in section (a), a continuous bonding interface is formed between the SAC305 solder ball and the aluminum plate. Plastic interlocking and interface interlocking features are observed in local areas. The SAC305 solder ball is embedded in the surface layer of the aluminum plate, and the cross-section of the solder ball still maintains a near-circular outline. No large-scale spreading or collapse morphology caused by overall melting is observed. A continuous contact area is formed between the lower part of the solder ball and the aluminum plate, indicating that the high-speed impact can enable the SAC305 solder ball to directly enter the surface layer of the aluminum substrate and form a stable implantation structure. SEM magnification of solder ball / aluminum plate interface, such as Figure 4 As shown in section (b), the interface is not flat and straight, but rather has a fine and irregular undulating morphology. This interface morphology indicates that during the high-speed impact of the aluminum plate with the SAC305 solder ball, the surface material of the aluminum plate undergoes local plastic flow and forms an interlocking contact area at the bottom of the solder ball. Its irregular interface profile is conducive to improving the mechanical interlocking effect between the SAC305 solder ball and the aluminum plate, which is significantly different from the traditional solder ball connection method that relies on the melting and wetting of solder. EDS line scan results are as follows Figure 4 As shown in section (c), Al is mainly distributed on one side of the aluminum plate, Sn is mainly distributed on one side of the SAC305 solder ball, and Ag and Cu, as alloying elements in the SAC305 solder ball, are mainly distributed on the solder ball side and in the area near the interface. When crossing the SAC305 solder ball / aluminum plate interface, the Al and Sn element signals undergo significant conversion, and there is a finite-width element transition zone near the interface. This result indicates that the scheme of this embodiment can promote the SAC305 solder ball to form a tight contact with the aluminum plate, which may be accompanied by local material mixing, interface disturbance, or local solid bonding.

[0023] To evaluate the connection reliability between the SAC solder balls and the aluminum plate obtained in this embodiment, tensile shear tests and fracture morphology analysis were performed on the aluminum substrate after ball implantation. The implantation area had a nearly circular outline, and obvious contact marks of the implanted balls were retained at the fracture surface. Irregular deformation and tearing characteristics caused by impact implantation were observed around the perimeter. Figure 5 As shown, a push-shear test was performed on the implanted SAC solder ball, with a maximum push force of 49.17 N. Using the projected area of ​​the near-circular implantation region at the fracture point as the nominal bonding area, the apparent shear strength was calculated to be 66.2 MPa. This result indicates that the SAC solder ball / aluminum plate solid implantation structure formed using the method of this embodiment has high interfacial shear capacity. After the shear test, the fracture location was located within the SAC solder ball body, with material tearing and residue characteristics at the edge region, rather than complete detachment along the SAC / Al interface. This indicates that the solder ball has a certain bonding area with the aluminum substrate after implantation and possesses good interfacial bonding strength.

[0024] In this embodiment, the SAC solder ball can be transferred from the concave part of the rigid anvil and bonded to the surface of the aluminum plate after the electromagnetic pulse is applied, proving that the method can realize the solid-state transfer of SAC solder balls to the surface of the aluminum plate. Therefore, this invention can achieve direct implantation of solder balls onto an aluminum substrate without flux, UBM layer, or overall melting, simplifying the aluminum substrate bumping process and ensuring the stability of the heterogeneous metal micro-connection structure.

[0025] Compared with Example 1, the difference between this comparative example and Example 1 is that electromagnetic pulse discharge energy (19kJ) is used for ball planting.

[0026] The samples obtained in this comparative example were tested, and the results are as follows: Figure 6 As shown. Wherein: like Figure 6 As shown in section (a), although the SAC305 solder ball can be transferred to the surface of the aluminum plate, the solder ball is embedded in the surface layer of the aluminum plate at a shallow depth, the continuous bonding area between the solder ball and the aluminum plate is small, and there are local areas with insufficient bonding or interface gaps. like Figure 6 As shown in section (b), the surface of the aluminum plate undergoes only limited plastic deformation, the interface undulation is weak, and the mechanical interlocking effect between the solder ball and the aluminum plate is insufficient.

[0027] EDS line scan results are as follows Figure 6As shown in section (c), Al is mainly distributed on one side of the aluminum plate, while Sn is mainly distributed on the SAC305 solder ball side. The Al and Sn element signals convert when crossing the interface, but the element transition region at the interface is narrow. Solder ball alloying elements such as Ag and Cu are mainly concentrated on the SAC305 solder ball side. This result indicates that in this comparative example, the SAC305 solder ball and the aluminum plate mainly form localized contact, and the interface mixing, plastic interlocking, and mechanical interlocking are insufficient.

[0028] The fracture morphology of the samples obtained in this comparative example was observed, such as... Figure 7 As shown, near-circular ball implantation marks are visible in the fracture area, but the implantation marks are shallow. Plastic tearing and material residue characteristics at the fracture edge are not obvious, and some areas show characteristics of detachment along the SAC305 solder ball / aluminum plate interface. Push-shear test results show that the maximum push-shear force of the low-discharge-energy sample is 25.43 N; estimated based on the same equivalent bonding area as the preferred embodiment, its apparent shear strength is approximately 29.7 MPa, significantly lower than the 66.2 MPa of the sample in Example 1.

[0029] The results of the comparison with Example 1 show that when the electromagnetic pulse discharge energy is too low, the electromagnetic driving force on the aluminum plate is insufficient, the impact velocity and interface pressure are low, and sufficient plastic flow cannot be generated on the surface of the aluminum plate, making it difficult to form a stable interlocking contact area at the bottom of the SAC305 solder ball. Therefore, although local transfer or attachment of SAC305 solder balls can be achieved under low discharge energy conditions, the bonding area of ​​the resulting solder ball bumps, the degree of interfacial mechanical interlocking, and the shear bearing capacity are all significantly reduced, making them prone to detachment during separation, slight contact, or push-shear tests.

[0030] Compared with Example 1, Example 2 differs from Example 1 in that it uses electromagnetic pulse discharge energy (25kJ) for ball planting.

[0031] The samples obtained in this comparative example were tested, and the results are as follows: Figure 8 As shown. Wherein: like Figure 8 As shown in section (a), the SAC305 solder ball can be transferred to the surface of the aluminum plate, but the solder ball undergoes obvious excessive plastic deformation, and local areas show characteristics of collapse, extrusion or morphological instability. like Figure 8 As shown in section (b), excessive impact loads under high discharge energy conditions can lead to a significant reduction in solder ball height and may cause excessive indentation or localized damage to the aluminum plate surface. like Figure 8As shown in section (c), the EDS line scan results show that when crossing the SAC solder ball / aluminum plate interface, the Al and Sn element signals still undergo significant conversion, but the element signals near the interface fluctuate greatly, indicating that the local contact and material deformation at the interface are uneven under excessively high energy, making it difficult to form a stable and consistent effective bonding area.

[0032] The fracture morphology of the obtained samples in this comparative example was observed, such as... Figure 9 As shown, the fracture area exhibits obvious irregular deformation and material residue characteristics, with poor integrity and consistency in the fracture morphology. The shear test results show that the maximum shear force of the high-discharge-energy sample is 32.71 N, corresponding to an apparent shear strength of approximately 34.1 MPa, significantly lower than the 66.2 MPa in Example 1.

[0033] The results of Comparative Example 2 show that while excessively high electromagnetic pulse discharge energy can increase the instantaneous contact pressure between the aluminum plate and the SAC305 solder balls, excessive impact loads can lead to excessive plastic deformation, collapse, local extrusion, or structural damage of the SAC305 solder balls, and may cause excessive surface depression, local tearing, or overall deformation of the aluminum plate. This excessive deformation not only compromises the integrity and uniformity of the solder ball protrusions but also introduces stress concentration at the interface and within the solder balls, reducing the effective load-bearing capacity. Therefore, the shear resistance of the SAC305 solder ball / aluminum plate structure obtained under high discharge energy conditions actually decreases.

[0034] The foregoing embodiments only illustrate the core technical route of the present invention. In other embodiments, the rigid cutting board may also be made of tool steel, cemented carbide, tungsten alloy, ceramic, or other materials that meet the requirements for rigidity and impact resistance; the substrate may be made of aluminum plate, aluminum alloy plate, or other materials that meet the requirements for use in integrated circuits; and the sphere to be implanted may also be cylindrical.

[0035] In other embodiments, the substrate can be positioned above the rigid anvil or on the side at the same height as the rigid anvil.

[0036] This invention provides a novel solid-state ball-mounting method for integrated circuit manufacturing. This method eliminates the need for the overall melting and wetting process of solder in traditional reflow soldering, reducing or avoiding reliance on flux, UBM layers, and complex surface metallization processes. It is particularly suitable for directly fabricating microsphere bumps / connections on easily oxidized substrates such as aluminum or aluminum alloys. This invention uses a rigid anvil to temporarily accommodate, position, and support the balls to be mounted, and utilizes electromagnetic pulse force to drive the substrate as a high-speed impactor to the balls, enabling the balls to be mounted without flux, without overall reflow melting, and with little or no reliance on UBM. Under the condition of layering, the microspheres are transferred and bonded to the substrate surface, thereby forming a microsphere bump structure with controllable position, good stability and reliability. Unlike the traditional ball-planting method of melting and wetting the surface of the substrate with the ball to be planted, the present invention uses an electromagnetic pulse device to apply force to the substrate. The substrate acts as a driven part or flyboard in the electromagnetic pulse process. The instantaneous pressure, local plastic flow and interfacial shearing generated by high-speed impact break and disturb the oxide film on the surface of the substrate. During the ball-planting process, the substrate is first transferred in position. The ball to be planted is transferred from the rigid anvil to the substrate and fixed on the substrate. A microsphere bump structure with good stability and reliability is formed between the ball to be planted and the substrate.

Claims

1. A method for solid-state ball mounting in integrated circuit manufacturing, characterized in that the steps include... include: Step 1: Select a rigid cutting board. The rigid cutting board has a concave part to accommodate the planted bulb and limit its displacement. Step 2: Place the planted bulb into the concave part of the rigid cutting board and fix the rigid cutting board in place. At this time, part of the planted bulb protrudes from the surface of the rigid cutting board. Step 3: Place the integrated circuit substrate in front of the sphere to be implanted, and adjust the area of ​​the substrate to be implanted so that it faces the sphere to be implanted. Step 4: Apply a force to the substrate, causing the substrate to impact the sphere to be implanted, thereby achieving the bonding between the substrate and the sphere to be implanted. Step 5: Remove the rigid anvil and perform post-processing on the workpiece after ball planting.

2. The solid-state ball-planting method according to claim 1, characterized in that: After the implantable bulb is placed into the concave part, there is no gap or almost no gap between the implantable bulb and the surface of the concave part.

3. The solid-state ball-planting method according to claim 1, characterized in that: The recessed portion is constructed using blind holes or through holes.

4. The solid-state ball-planting method according to claim 1, characterized in that: The concave surface is a curved surface adapted to the surface of the sphere to be implanted.

5. The solid-state ball-planting method according to claim 1, characterized in that: The rigid anvil is provided with a plurality of recesses arranged in an array.

6. The solid-state ball-planting method according to claim 1, characterized in that: In step 4, the rigid cutting board provides reaction force and support to the ball during the planting process and limits the ball's displacement.

7. The solid-state ball-planting method according to claim 1, characterized in that: During the ball-planting process, the substrate is first moved to a new position, and the ball is transferred from the rigid anvil to the substrate and fixed on the substrate.

8. The solid-state ball-planting method according to claim 1, characterized in that: The rigid cutting board is made of stainless steel, tool steel, hard alloy, tungsten alloy, ceramic or other materials that meet the requirements for rigidity and impact resistance; the substrate is made of aluminum plate, aluminum alloy plate or other materials that meet the requirements for integrated circuit use; the sphere to be implanted is replaced by metal microspheres or cylindrical bodies.

9. The solid-state pelleting method according to any one of claims 1-8, characterized in that: An electromagnetic pulse device is used to apply force to the substrate.

10. The solid-state ball-planting method according to claim 9, characterized in that: When the sphere to be implanted is a 1mm diameter SAC305 welding ball, the discharge energy of the electromagnetic pulse device is controlled to be 20~24kJ.

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