A method and apparatus for integrated connection of a multilayer heterogeneous material by ultrafast laser

Abstract

The application provides a kind of multilayer heterogeneous material ultrafast laser integrated connection method and equipment, specifically includes: chip pad, spring pin and quartz glass are stacked and fixed on three-dimensional motion platform, adjust platform to make laser focal plane be located in the central of pin;For pad and pin connection, space shaping obtains high repetition rate ultrafast laser with high Rayleigh length, is acted on the periphery of pin by spiral line or concentric circular scanning of two-dimensional galvanometer, excites metal plasma, forms molten metal, is deposited in the aperture of pin and pad contact, with reverse heating, molten metal continuously accumulates, realizes heterogeneous metal welding;For pin and glass connection, laser transmits through quartz glass, excites plasma at metal interface, forms molten metal with increased volume, fills material interface gap, regulates non-optical contact to optical contact welding;Two kinds of heterogeneous materials are successfully welded by single scanning, until the welding of entire pin array is completed, realizes efficient integrated packaging.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ultrafast laser chip packaging, and particularly relates to a method and equipment for integrating multi-layer heterogeneous materials. BACKGROUND

[0002] System-in-Package (SIP) is an advanced chip packaging technology that integrates multiple integrated circuits and other electronic components into a single package to improve functional density and reduce manufacturing costs. Its structure usually contains multiple functionally different chips, passive elements (such as resistors and capacitors), and various connection technologies (such as flip-chip bonding and ball grid array), ensuring electrical connections between components. The main advantages of SIP packaging include high integration and miniaturization, significantly reducing overall size and improving electrical performance, thus reducing signal delay. In addition, the design of SIP simplifies PCB layout, reduces steps in the manufacturing process, effectively reducing production costs, and enhances the reliability of components within the package. This technology is widely used in consumer electronics, Internet of Things devices, wireless communication, and medical devices, meeting the growing demand for high integration and high performance.

[0003] To further improve the integration of SIP packaging, three-dimensional packaging technology has emerged. Three-dimensional packaging usually uses a multi-layer stacking design to vertically stack chips with different functions (such as processors, memories, and sensors). Using through-silicon via (TSV) technology to manufacture tiny vertical vias on silicon wafers allows direct connections between different layers. TSV technology significantly shortens signal transmission paths, improving data transmission rates and overall performance. The entire SIP packaging process flow includes wafer thinning, wafer dicing, substrate glue coating, chip bonding, bonding glue curing, wire bonding, molding, substrate ball planting, reflow, and laser marking. In the SIP packaging process, according to the connection method of the chip and the substrate, it can be divided into wire bonding packaging and flip-chip bonding. Wire bonding packaging is a packaging form that connects chips and substrates through metal leads, characterized by the connection of leads to chips and substrates through bonding, thus having high reliability. BGA packaging, also known as ball grid array (or solder ball array) packaging, is a large-scale integrated circuit chip packaging technology that uses solder balls or solder bumps as external leads and distributes them in an array on the bottom plane of the packaging substrate. It is a type of surface mount packaging for chips. Its main advantages include high-density connections, which can accommodate more pins in a small area; excellent electrical performance, reducing signal delay; good heat dissipation, helping to prevent overheating. In addition, BGA packaging simplifies the soldering process, improves solder consistency, and enhances mechanical strength, meeting the needs of modern electronic products.

[0004] For high-frequency chip arc surface assembly, the traditional spherical interconnection pin will cause the two end spherical pin to contact the arc surface and the middle part of the spherical pin to be suspended, which is difficult to meet the high reliability assembly requirement. The spring pin provides a new idea by using its compression deformation characteristics. In this regard, the granted patent (CN108666275B) and the published patent (CN108666275A) package the chip in a two-dimensional mode in a package body on the same packaging substrate; the columnar or micro-spring form pin is used as the interconnection pin of the SIP device and the external arc surface PCB substrate, and the columnar or micro-spring form pin is made to match the shape of the arc surface PCB substrate; then the columnar or micro-spring form pin is placed on the SIP device pad in an array form through a pin placement tool, and is fixed after welding and through coaxial detection; then the SIP device with the implanted columnar or micro-spring form pin is attached to the arc surface PCB substrate; finally, the conformal assembly of the arc surface PCB substrate and the SIP device is completed through reflow soldering. This process can reduce the complexity of the printed circuit board, shorten the development cycle, and improve the system integration. However, the lower surface of the columnar or micro-spring form pin is a cylindrical bottom or side, which cannot completely match the arc surface PCB substrate, so it is limited in practical application, resulting in reduced welding quality and reduced packaging reliability. In addition, the above-mentioned patent uses reflow soldering to solder the curved surface material, and the solder flows, so the precision is reduced, and therefore the existing reflow soldering method cannot achieve effective soldering.

[0005] The high-frequency chip curved surface integrated packaging technology includes heterogeneous metal welding between the chip metal pad and the metal spring pin, and transparent / metal heterogeneous material welding between the metal spring pin and the transparent quartz glass. The existing laser welding technology cannot achieve efficient integrated packaging of the above-mentioned multi-layer heterogeneous materials. To solve this technical problem, the present application proposes a new technology of ultra-high repetition rate ultrafast laser oscillation scanning integrated welding, including heterogeneous metal ultrafast laser "limited ablation-deposition-melting" connection technology, transparent / metal heterogeneous material ultrafast laser high-strength connection technology, and multi-layer heterogeneous material ultrafast laser integrated connection technology. SUMMARY

[0006] To solve the problems of low packaging reliability of the new type of pin and complex welding process between the metal spring pin and the metal pad and the quartz glass, the present application provides a multi-layer heterogeneous material ultrafast laser integrated connection method and equipment, including heterogeneous metal ultrafast laser "limited ablation-deposition-melting" connection technology, transparent / metal heterogeneous material ultrafast laser high-strength connection technology, and multi-layer heterogeneous material ultrafast laser integrated connection technology.

[0007] To achieve the above-mentioned purpose, the present application provides a multi-layer heterogeneous material ultrafast laser integrated connection method and equipment, including the following steps:

[0008] (1) The lower chip pad, spring pin array and upper quartz glass are sequentially stacked on the three-dimensional motion platform, and are fixed with a clamp. The focal plane of the laser is located at the central height of the spring pin array by adjusting the three-dimensional motion platform.

[0009] (2) Based on the space-time shaping of ultrafast laser, high repetition rate and high length of ultrafast laser focusing is realized. Through two-dimensional galvanometer, spiral or concentric ring type oscillation scanning path is realized. Under the oscillation scanning path, the ultrafast laser will act on the three-dimensional limited area of the spring pin (limited ablation);

[0010] (3) The ultrafast laser acts on the surface position of the lower chip pad to excite metal plasma. The heat accumulation formed by the ultra-high repetition rate will form molten metal material. The two will actively deposit high-temperature plasma-molten metal mixture in the contact aperture between the spring pin and the lower chip pad pad (limited deposition). Under the oscillation scanning, the above process repeatedly occurs. The deposited high-temperature plasma-molten metal mixture continuously heats and accumulates, reversely heating and melting the spring pin (limited melting), thereby realizing the heterogeneous metal welding between the chip metal pad and the metal spring pin.

[0011] (4) When the ultrafast laser oscillates and scans in a spiral line or concentric ring, the ultrafast laser will simultaneously act on the interface position between the upper quartz glass and the spring pin. In this process, the ultrafast laser will directly transmit through the quartz glass. Because the metal material has high linear absorption to the ultrafast laser, metal plasma will be excited at the interface. Under the effective heat accumulation of the ultra-high repetition rate ultrafast laser, the volume of the molten metal material can be increased to fill the gap between the transparent / metal heterogeneous materials, and the non-optical contact welding is adjusted to optical contact welding. Under the oscillation scanning of the ultrafast laser, the transparent / metal heterogeneous material is realized. High-strength welding of ultrafast laser.

[0012] (5) After the spring pin is successfully connected to the upper quartz glass and the lower chip pad by using the ultrafast laser, move to the next spring pin position to continue welding until the entire spring pin array is completely welded, realizing the efficient integration packaging of the upper quartz glass, spring pin array and lower chip pad.

[0013] Further, the three-dimensional motion platform includes an electric Z-axis and a two-dimensional galvanometer, which can move or rotate independently or in linkage on X, Y and Z axes, thereby realizing the precise position and attitude adjustment of the workpiece in three-dimensional space.

[0014] Further, the ultrafast laser is a high repetition rate picosecond laser or femtosecond laser, with a wavelength of 532-1064nm, a repetition rate of 200kHz-2MHz, and a power of 10-100W.

[0015] Further, the Rayleigh length is the distance over which the laser beam maintains its minimum cross-sectional dimension (i.e., beam waist) during propagation. High Rayleigh length is achieved by spatial shaping, so that the laser beam maintains good focusing performance over a longer propagation distance, improving the precision and efficiency of integrated connection.

[0016] Further, the oscillation scanning path is a spiral line or a concentric circular ring, and the size is between the inner diameter and the outer diameter of the spring.

[0017] Further, the connection between the metal pad and the spring pin is based on the new connection mode of ultrafast laser "limited ablation-deposition-melting", realizing high-strength welding between the chip metal pad and the metal spring pin.

[0018] Further, the connection between the spring pin and the quartz glass is non-optical contact regulation to optical contact, which focuses laser energy into a very small range by reducing the interface gap, realizing high-precision and low-heat-affected welding of transparent / metal heterogeneous materials by ultrafast laser.

[0019] Further, the new technology of ultra-high repetition rate ultrafast laser oscillation scanning integrated welding includes heterogeneous metal ultrafast laser "limited ablation-deposition-melting" connection technology, transparent / metal heterogeneous material ultrafast laser high-strength connection technology and multi-layer heterogeneous material ultrafast laser integrated connection technology.

[0020] Further, the upper workpiece is transparent material, the middle is a spring pin array, and the lower workpiece is a metal pad. The transparent material is quartz glass or sapphire, which can be straight or arc-shaped curved surface, and both sides are polished. The metal pad is copper, aluminum alloy or titanium alloy, which is a straight surface.

[0021] Further, the spring pin array is arranged by spring pins, wherein the height of the spring pin is 1-2.5mm, the diameter of the spring is 0.06-0.1mm, the pitch of the spring is 0.025-0.15mm, and the outer diameter of the spring is 0.4-0.6mm.

[0022] Overall, compared with the prior art, the above technical solutions of the present application mainly have the following advantages:

[0023] The use of spring pins expands the application range of chip packaging. For high-frequency chip arc-shaped curved surface assembly, traditional spherical interconnection pins will cause the two end spherical pins to contact the arc-shaped curved surface and the middle part of the spherical pin to be suspended, which is difficult to meet the high reliability assembly requirements. The spring pin provides a new idea for high-frequency chip arc-shaped curved surface assembly by using its compression deformation characteristics. At the same time, the spring pin can also meet the heat dissipation demand of high-power chips, which is conducive to further improving the reliability of chip packaging.

[0024] The use of laser welding enhances the reliability of chip packaging. Compared with traditional technologies such as reflow soldering, ultrafast laser can realize the connection of heterogeneous materials by using heat accumulation under high frequency, and has advantages such as high precision, low heat influence and high connection strength, and is the best choice to enhance the reliability of chip packaging.

[0025] The use of integrated connection technology shortens the development cycle and reduces the manufacturing cost. The glass through via (TGV) is an effective supplement to the through silicon via (TSV) technology, and has significant advantages in high-frequency chips, and can be used as a packaging substrate for conformal assembly of high-frequency chip arc curved surfaces. By selecting a suitable oscillation scanning path, the focused ultrafast laser with a long length can act on the spring pin and the lower chip pad contact aperture to form an ultrafast laser "limited ablation-deposition-melting" connection of heterogeneous metals, and can also simultaneously act on the contact position of the upper quartz glass and the spring pin to weld transparent / metal heterogeneous materials, achieving efficient integrated welding of multi-layer heterogeneous materials, which shortens the development cycle and reduces the manufacturing cost. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The present application is a multi-layer heterogeneous material ultra-high repetition rate ultrafast laser welding system. In the figure: 1-ultrafast laser; 2-collimating light path; 3-two-dimensional galvanometer; 4-field lens; 5-upper quartz glass; 6-lower chip pad; 7-three-dimensional motion platform.

[0027] Figure 2 It is a heterogeneous metal ultrafast laser "limited ablation-deposition-melting" technology. In the figure: 1-oscillating scanning path (concentric ring type); 2-focused ultrafast laser; 3-spring pin array; 4-limited ablation deposition particles; 5-lower chip pad.

[0028] Figure 3 It is a heterogeneous metal ultrafast laser "limited ablation-deposition-melting" technology. In the figure: 1-oscillating scanning path (spiral line type); 2-focused ultrafast laser; 3-spring pin array; 4-limited ablation deposition particles; 5-lower chip pad.

[0029] Figure 4 It is a transparent / metal heterogeneous material ultrafast laser high-strength connection technology. In the figure: 1-focused ultrafast laser; 2-upper quartz glass; 3-spring pin array; 4-lower chip pad.

[0030] Figure 5 It is a multi-layer heterogeneous material ultrafast laser integrated connection technology. In the figure: 1-focused ultrafast laser; 2-upper quartz glass; 3-spring pin array; 4-lower chip pad. DETAILED DESCRIPTION

[0031] In order to make the technical problems, technical solutions and advantages of the present application clearer, the following will be described in detail in conjunction with the drawings and specific embodiments. It should be noted that the description of these embodiments is used to help understand the present application, but does not constitute a limitation on the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0032] The high-frequency chip curved surface integrated packaging technology includes heterogeneous metal welding between the chip metal pad and the metal spring type pin, and transparent / metal heterogeneous material welding between the metal spring type pin and the transparent quartz glass. The existing laser welding technology cannot realize the efficient integrated packaging of the above-mentioned multi-layer heterogeneous materials. To solve this technical problem, the project proposes a new technology of ultrahigh repetition rate ultrafast laser oscillation scanning integrated welding, including heterogeneous metal ultrafast laser "limited ablation-deposition-melting" connection technology, transparent / metal heterogeneous material ultrafast laser high-strength connection technology and multi-layer heterogeneous material ultrafast laser integrated connection technology. They are introduced as follows:

[0033] (1) Heterogeneous metal ultrafast laser "limited ablation-deposition-melting" connection technology: based on the time shaping of ultrafast laser, the output of ultrafast laser with ultrahigh repetition rate is realized, and the spiral line or concentric circular ring oscillation scanning path is realized by two-dimensional galvanometer; based on the spatial shaping of ultrafast laser, the focused ultrafast laser with high Rayleigh length is realized, and the ultrafast laser will act on the three-dimensional limited area (limited ablation) around the spring pin in the oscillation scanning path; the surface position of the lower chip pad will be excited by the ultrafast laser with ultrahigh repetition rate, and the heat accumulation formed by the ultrafast laser with ultrahigh repetition rate will form molten metal material, which will actively deposit the high-temperature plasma-molten metal mixture in the contact gap between the spring type pin and the lower chip pad pad (limited deposition); under oscillation scanning, the above process repeatedly occurs, and the deposited high-temperature plasma-molten metal mixture continuously heats and accumulates, reversely heating and melting the spring type pin (limited melting), thereby realizing the heterogeneous metal welding between the chip metal pad and the metal spring type pin.

[0034] (2) Transparent / metal heterogeneous material ultrafast laser high-strength connection technology: when the ultrafast laser oscillates and scans in a spiral line or concentric circular ring, it will simultaneously act on the interface position between the upper quartz glass and the spring pin. In this process, the ultrafast laser will directly transmit through the quartz glass, and the metal material will excite metal plasma at the interface due to its high linear absorption of ultrafast laser. Under the effective heat accumulation of the ultrafast laser with ultrahigh repetition rate, the volume of the molten metal material can be increased to fill the gap between the transparent / metal heterogeneous materials, and the non-optical contact welding can be adjusted to optical contact welding. Under the oscillation scanning of the ultrafast laser, the transparent / metal heterogeneous material ultrafast laser high-strength connection is realized.

[0035] (3) Multi-layer heterogeneous material ultrafast laser integrated connection technology: by selecting a suitable oscillation scanning path, the focused ultrafast laser with high Rayleigh length can act on the spring pin and the lower layer chip pad contact aperture to form an ultrafast laser "limited ablation-deposition-melting" connection of heterogeneous metals, and can also act on the contact position of the upper layer quartz glass and the spring pin. Therefore, the transparent / metal heterogeneous material welding between the spring pin and the transparent quartz glass and the heterogeneous metal welding between the chip metal pad and the metal spring pin can occur synchronously, achieving the purpose of efficient integrated welding of multi-layer heterogeneous materials.

[0036] Specific examples:

[0037] An example structure provided by the present application is shown in Figure 1 , which is a multi-layer heterogeneous material ultrafast laser integrated connection method and equipment. The equipment is composed of an ultrafast laser 1, a collimating light path 2, a two-dimensional galvanometer 3, a field lens 4, an upper layer quartz glass 5, a lower layer chip pad 6, and a three-dimensional motion platform 7.

[0038] In this example, the ultrafast laser 1, the collimating light path 2, the two-dimensional galvanometer 3, and the field lens 4 are located on the same light path. The ultrafast laser 1 is collimated through the collimating light path 2, moved through the two-dimensional galvanometer 3, and focused through the field lens 4, and finally acts on the upper layer quartz glass 5, the lower layer chip pad 6, and the spring pin array (not shown in the figure) between them. The two-dimensional galvanometer 3 controls the horizontal movement of the ultrafast laser, and the three-dimensional motion platform 7 controls the vertical movement of the multi-layer heterogeneous material.

[0039] In this example, the multi-layer heterogeneous material takes transparent quartz glass, spring pin, and metal chip pad as an example, wherein the transparent quartz glass has a size of 20mm×10mm×2mm, is double polished, the spring pin is phosphor copper compression spring with a size of 0.2mm×1mm×5mm×13 turns, and the metal chip pad has a size of 20mm×10mm×2mm and is double polished.

[0040] In the ultrafast laser integrated connection experiment, a femtosecond pulse laser is used, the wavelength is 1035nm, the repetition frequency is set to 1MHz, the power is set to 30W, the scanning speed of the scanning galvanometer is set to 20mm / s, the focal length of the field lens is 80mm, the laser defocusing amount can be set between plus and minus 100um, a low clamping force or natural stacking can be applied between the workpieces, and the welding times is 1.

[0041] First, the lower layer chip pad, the spring pin array, and the upper layer quartz glass are stacked and fixed on the three-dimensional motion platform, and the laser focal plane is located at the center of the pin by adjusting the platform.

[0042] As shown in Figure 2 , Figure 3As shown, the high repetition rate ultrafast laser 1 is used to scan the interface between the spring pin 3 and the chip pad 4 by a two-dimensional galvanometer to generate a spiral or concentric circular oscillation scanning path 2, excite metal plasma, and heat accumulation to form molten metal particles 5, which are deposited in the contact gap between the pin and the pad. With reverse heating, the plasma-molten metal mixture continuously accumulates to achieve heterogeneous metal welding.

[0043] As shown, Figure 4 As shown, the high repetition rate ultrafast laser 1 is used to scan the interface between the spring pin 3 and the chip pad 4 by a two-dimensional galvanometer to generate a spiral or concentric circular oscillation scanning path 2, excite metal plasma, and heat accumulation to form molten metal particles 5, which are deposited in the contact gap between the pin and the pad. With reverse heating, the plasma-molten metal mixture continuously accumulates to achieve heterogeneous metal welding.

[0044] As shown, Figure 5 As shown, the high repetition rate ultrafast laser 1 is used to scan the interface between the spring pin 3 and the chip pad 4 by a two-dimensional galvanometer to generate a spiral or concentric circular oscillation scanning path 2, excite metal plasma, and heat accumulation to form molten metal particles 5, which are deposited in the contact gap between the pin and the pad. With reverse heating, the plasma-molten metal mixture continuously accumulates to achieve heterogeneous metal welding.

Claims

1. A multi-layer heterogeneous material ultrafast laser integrated connection method for high-frequency chip arc curved surface ultrafast laser packaging, characterized in that, The application relates to a method for realizing high-efficiency integrated packaging of upper quartz glass, spring pin array and lower chip metal pad. Step one: sequentially stack the lower chip metal pad, spring pin array and upper quartz glass on a three-dimensional motion platform, the height of the spring pin is in the range of 1.0-2.5 mm, and the spring pin is fixed by a clamp, and the focal plane of the laser is located at the central height of the spring pin array by adjusting the three-dimensional motion platform; Step two: based on the space-time shaping of the ultrafast laser, high-repetition-frequency and high Rayleigh length ultrafast laser focusing is realized, wherein the high-repetition-frequency of the ultrafast laser is 200 kHz-2 MHz, the spiral line or concentric ring type oscillation scanning path is realized by a two-dimensional galvanometer, and the ultrafast laser acts on the three-dimensional limited area of the periphery of the spring pin in the oscillation scanning path, that is, limited ablation is formed; Step three: the ultrafast laser acts on the surface position of the lower chip metal pad to excite metal plasma, and the heat accumulation formed by the high-repetition-frequency forms molten metal material, and the two will actively deposit the high-temperature plasma-molten metal mixture in the contact gap between the spring pin and the lower chip metal pad, that is, limited deposition is formed; under the oscillation scanning, the above process repeatedly occurs, the deposited high-temperature plasma-molten metal mixture continuously heats and accumulates, and the spring pin is reversely heated and melted, that is, limited melting is formed, thereby realizing the heterogeneous metal welding between the lower chip metal pad and the spring pin; Step four: when the ultrafast laser oscillates and scans in the spiral line or concentric ring, the ultrafast laser simultaneously acts on the interface position between the upper quartz glass and the spring pin; in the process, the ultrafast laser directly transmits through the upper quartz glass, and metal plasma is excited at the interface due to the high linear absorption of the metal material to the ultrafast laser; under the effective heat accumulation of the high-repetition-frequency ultrafast laser, the molten metal material with increased volume can be formed to fill the gap between the transparent / metal heterogeneous materials, to regulate the non-optical contact welding to the optical contact welding, to focus the laser energy into a very small range by reducing the interface gap, and to realize the high-precision and low-heat-affected welding of the transparent / metal heterogeneous materials by the ultrafast laser; Step five: after the spring pin is successfully connected to the upper quartz glass and the lower chip metal pad by the ultrafast laser, the spring pin is moved to the next spring pin position for welding, until the whole spring pin array is completely welded, thereby realizing the high-efficiency integrated packaging of the upper quartz glass, the spring pin array and the lower chip metal pad.

2. The method of claim 1, wherein the method is a method of ultrafast laser integrated joining of a multilayer heterogeneous material. The three-dimensional motion platform comprises a motorized Z-axis and a two-dimensional galvanometer, and can independently or jointly move or rotate on the X, Y and Z axes, so as to realize the accurate position and attitude adjustment of the workpiece in the three-dimensional space.

3. The method of claim 1, wherein the method is a multi-layer heterogeneous material ultrafast laser integrated connection method. The ultrafast laser is a picosecond laser or a femtosecond laser, the wavelength is 532-1064 nm, and the power is set to 10-100 W.

4. The method of claim 1, wherein the method is a multi-layer heterogeneous material ultrafast laser integrated connection method. The Rayleigh length is the distance at which the laser beam maintains its minimum cross-sectional size during propagation, and the high Rayleigh length is realized by space shaping, so that the laser beam maintains good focusing performance in a longer propagation distance, and the precision and efficiency of the integrated connection are improved.

5. The method of claim 1, wherein the method is a multi-layer heterogeneous material ultrafast laser integrated connection method. The upper quartz glass material is an arc-shaped curved surface and is double-side polished, and the lower chip metal pad is made of copper, aluminum alloy or titanium alloy and is a straight surface.

6. The method of claim 1, wherein the method is a multi-layer heterogeneous material ultrafast laser integrated connection method. The spring pin array is arranged in a spring pin array, wherein the diameter of the spring is 0.06-0.1mm, and the pitch of the spring is 0.025-0.15mm.

7. A multi-layered heterogeneous material ultrafast laser integrated joining apparatus, characterized by, The method is used for the arc-shaped curved surface packaging of high-frequency chips.

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