Magnetic control type anti-inclination copper needle structure and packaging process thereof

Abstract

The invention discloses a magnetic control type anti-inclination copper needle structure and a packaging technology thereof, and the technology comprises the following steps: S1, providing a plurality of copper needles, and forming a ferromagnetic metal layer at one end of each copper needle; s2, forming a solder paste layer at a welding spot on the substrate; s3, in an environment where a first magnetic field is applied, the copper needle is transferred to the substrate, and the end, provided with the ferromagnetic metal layer, of the copper needle stands on the solder paste layer in the direction away from the substrate; and S4, in an environment where a second magnetic field is applied, reflow soldering is carried out on the substrate, the solder paste layer is melted and then solidified, the copper needle is fixed, and the second magnetic field generates a directional force which enables the copper needle to be kept upright on the ferromagnetic metal layer. By actively applying the controllable directional force, the unstable mode of passively depending on solder paste supporting in the traditional process is replaced, and the placement precision of the copper needle and the product yield are fundamentally improved.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor packaging technology, and in particular relates to a copper pin structure and corresponding process method for improving the tilting of mass transfer copper pins during reflow soldering in advanced packaging processes. Background Technology

[0002] In advanced packaging processes, such as 2.5D / 3D ICs and wafer-level packaging (WLP), mass transfer technology is often used to implant a large number of tiny copper pins onto a substrate. These copper pins, as vertical interconnect conductors, are crucial to the electrical performance and reliability of the package.

[0003] The currently common process in the industry involves first printing solder paste onto a substrate, then placing copper pins on the solder paste, and finally reflow soldering to melt and solidify the solder paste, thus firmly soldering the copper pins to the substrate. However, this existing technology has a significant problem: during the reflow soldering process, when the solder paste melts and becomes liquid or semi-liquid, its fixing effect on the copper pins weakens considerably. The copper pins thus lose effective support and positioning, making them prone to tilting in any direction due to various factors (such as uneven surface tension of the liquid solder paste, equipment vibration, etc.). Since there is no directional restoring force to pull the tilted copper pins back to an upright position during the cooling and solidification stage, the finished soldered copper pins ultimately suffer from tilting defects.

[0004] Tilting of copper pins can cause a series of problems such as electrical short circuits, impedance changes, and insufficient mechanical strength, which seriously affect the yield and long-term reliability of packaged products. Summary of the Invention

[0005] The purpose of this invention is to provide a magnetically controlled anti-tilting copper pin structure and its packaging process, which aims to solve the technical problem that the copper pins lose support due to the softening of solder paste during the reflow soldering process, causing the copper pins to tilt.

[0006] The objective of this invention is achieved through the following technical solution: A magnetically controlled anti-tilt copper pin packaging process includes the following steps: S1. Provide a plurality of copper needles, each of which has a ferromagnetic metal layer formed at one end; S2. Form a solder paste layer at the solder joints on the substrate; S3. In an environment where a first magnetic field is applied, the copper needle is transferred to the substrate, so that the copper needle stands upright on the solder paste layer with the end having the ferromagnetic metal layer facing away from the substrate. S4. In an environment where a second magnetic field is applied, the substrate is reflow soldered to melt and solidify the solder paste layer, thereby fixing the copper needle. The second magnetic field generates an directional force on the ferromagnetic metal layer that keeps the copper needle upright.

[0007] As a further improvement of the present invention, in step S4, when performing the reflow soldering, the substrate is set so that the copper pins on it face downwards, so that the copper pins are simultaneously subjected to the orientation force and their own weight to maintain uprightness.

[0008] As a further improvement of the present invention, the ferromagnetic metal layer is a nickel or nickel alloy layer or other ferromagnetic materials.

[0009] As a further improvement of the present invention, the ferromagnetic metal layer is formed on the end of the copper needle by electroplating.

[0010] A copper needle structure prepared using the above process includes: The copper needle body; and A ferromagnetic metal layer is formed at one end of the copper needle body. The ferromagnetic metal layer can be attracted by an external magnetic field to provide orientation force for the copper needle body during reflow soldering.

[0011] As a further improvement of the present invention, the material of the ferromagnetic metal layer is nickel or a nickel alloy.

[0012] As a further improvement of the present invention, the ferromagnetic metal layer and the copper needle body are integrally formed or combined through a surface treatment process.

[0013] The above technical solution offers the following advantages: By adding a ferromagnetic metal layer to one end of the copper pin, the pin can be attracted by an external magnetic field. During the pin placement and reflow soldering steps, a stable magnetic field with a specific direction is applied. This magnetic field attracts the copper pin, forming a continuous directional force that "straightens" and fixes the copper pin while the solder paste is molten, preventing it from tilting arbitrarily. By actively applying a controllable directional force, the unstable method of passively relying on solder paste support in traditional processes is replaced, fundamentally improving the placement accuracy of the copper pin and the product yield. Attached Figure Description

[0014] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0015] The structures, proportions, sizes, etc. shown in this specification are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0016] Figure 1 This is a schematic diagram of the first state structure provided by the present invention.

[0017] Figure 2 This is a schematic diagram of the copper pins assembled on the substrate according to the present invention.

[0018] In the picture: 1. Copper needle body; 2. Ferromagnetic metal layer. Detailed Implementation

[0019] In this invention, unless otherwise stated, directional terms such as "upper," "lower," "top," and "bottom" are generally used in relation to the direction shown in the accompanying drawings, or in relation to the vertical, perpendicular, or gravitational direction of the component itself; similarly, for ease of understanding and description, "inner" and "outer" refer to the inner and outer contours of each component itself, but the above directional terms are not intended to limit this invention.

[0020] First embodiment, such as Figure 1 As shown, a magnetically controlled anti-tilt copper pin packaging process includes the following steps: S1. Prepare copper needles: Prepare a large number of cylindrical copper needles with micron-sized components. Use an electroplating process to precisely form a ferromagnetic metal layer with a thickness of approximately 1 micron on one end of each copper needle.

[0021] The copper needle in this design is primarily made of highly conductive copper. The key improvement lies in forming a ferromagnetic material layer, such as nickel (Ni) or a nickel alloy, or other ferromagnetic materials, on one end face of the copper needle through electroplating, deposition, or other feasible surface treatments. The application of this ferromagnetic material layer allows one end of the copper needle, which was originally unaffected by a magnetic field, to be strongly attracted by an external magnetic field.

[0022] S2. Substrate preparation: Print solder paste layer at the predetermined solder joints on the substrate; S3. Applying a Magnetic Field and Plating the Pins: In the pin placement process, a first magnetic field is applied above the substrate. Under this magnetic field, a large number of copper pins are transferred onto the pre-printed solder paste substrate using a pin placement stencil (such as a stencil). Under the influence of the magnetic field, the copper pins with nickel caps automatically adjust their orientation due to the upward attraction of the caps, ensuring that the caps face upwards and the other end (the soldering end) is inserted into the solder paste. This ensures that all copper pins stand in a uniform and correct orientation (i.e., the end with the ferromagnetic metal layer faces away from the substrate on the solder paste layer).

[0023] Specifically, the first magnetic field is composed of an array of electromagnets or permanent magnets. When in use, its position is adjusted so that it can generate a stable magnetic field with uniform intensity and direction perpendicular to the substrate surface.

[0024] S4. The substrate with the copper pins attached is sent to a reflow oven for soldering. A magnetic field generator is also installed in the heating chamber of the reflow oven, which forms a second magnetic field. In the environment of the applied second magnetic field, the substrate is reflow soldered. When the solder paste melts due to heat during reflow soldering and loses its ability to hold the copper pins, the vertically upward attractive force (i.e., directional force) generated by the second magnetic field on the nickel cap will continue to act, effectively counteracting the random forces that may cause the copper pins to tilt (i.e., the second magnetic field generates a directional force on the ferromagnetic metal layer that keeps the copper pins upright).

[0025] The solder paste melts and then cools and solidifies after being heated according to the temperature curve inside the furnace, firmly welding the upright copper pins to the solder joints of the substrate, resulting in a packaging intermediate with extremely high copper pin uprightness.

[0026] To further enhance the effect, during the reflow soldering process, the product can be passed through the reflow oven with the substrate facing up and the copper needles facing down (i.e., product side down). In this way, the copper needles are attracted downward by the magnetic field and also acted upon by their own gravity. These two forces are coaxial and work together to straighten the copper needles, greatly enhancing the anti-tilting effect (when the substrate side is down, the magnetic field attracts the ferromagnetic material layer from below).

[0027] In this embodiment, the directions of the first magnetic field and the second magnetic field are both perpendicular to the substrate surface, resulting in a significantly higher degree of copper needle uprightness compared to traditional methods, which effectively improves the yield and reliability of packaged products.

[0028] like Figure 2 As shown, a copper needle structure prepared by the above process has a core innovation in that a ferromagnetic metal layer 2 is provided at one end of the copper needle body 1.

[0029] The ferromagnetic metal layer 2 is made of nickel or a nickel alloy. Nickel and nickel alloys have good ferromagnetism and can be stably attracted by an external magnetic field, providing reliable directional force for the copper needle body 1. In terms of mechanical structure, there are two feasible solutions for combining the ferromagnetic metal layer 2 with the copper needle body 1. One is to use an integral molding process, where the ferromagnetic metal layer 2 is directly fused with the copper needle body 1 into a single unit during the manufacturing process of the copper needle body 1 using specific molds and process conditions. This structure has good compactness and stable mechanical properties. The second is to combine it with surface treatment processes, such as electroplating or chemical plating, to deposit the ferromagnetic metal layer 2 on one end of the surface of the copper needle body 1. This method is flexible and allows for precise control of the thickness and composition of the ferromagnetic metal layer 2 according to actual needs.

[0030] In practical applications, a stable magnetic field with a specific direction is applied during the pin placement and reflow soldering steps. This magnetic field attracts the copper pins with the ferromagnetic metal layer 2, forming a continuous directional force. When the solder paste is molten, this directional force "straightens" and firmly fixes the copper pins, effectively preventing them from tilting arbitrarily. Compared to the unstable method of passively relying on solder paste support in traditional processes, this structure, by actively applying a controllable directional force, fundamentally improves the placement accuracy of the copper pins, reduces product defects caused by pin tilting, and significantly improves product yield, demonstrating significant economic benefits and practical value.

[0031] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0032] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0033] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A magnetically controlled anti-tilt copper pin packaging process, characterized in that, Includes the following steps: S1. Provide a plurality of copper needles, each of which has a ferromagnetic metal layer formed at one end; S2. Form a solder paste layer at the solder joints on the substrate; S3. In an environment where a first magnetic field is applied, the copper needle is transferred to the substrate, so that the copper needle stands upright on the solder paste layer with the end having the ferromagnetic metal layer facing away from the substrate. S4. In an environment where a second magnetic field is applied, the substrate is reflow soldered to melt and solidify the solder paste layer, thereby fixing the copper needle. The second magnetic field generates an directional force on the ferromagnetic metal layer that keeps the copper needle upright.

2. The magnetically controlled anti-tilt copper pin packaging process according to claim 1, characterized in that, During the reflow soldering process in step S4, the substrate is positioned so that the copper pins on it face downwards, thereby subjecting the copper pins to both the orientation force and their own weight to maintain their upright position.

3. The magnetically controlled anti-tilt copper pin packaging process according to claim 1, characterized in that, The ferromagnetic metal layer is a nickel or nickel alloy layer or other ferromagnetic materials.

4. The magnetically controlled anti-tilt copper pin packaging process according to claim 1, characterized in that, The ferromagnetic metal layer is formed on the end of the copper needle by electroplating.

5. A copper needle structure prepared using the process described in any one of claims 1 to 4, characterized in that, include: Copper needle body; as well as A ferromagnetic metal layer is formed at one end of the copper needle body. The ferromagnetic metal layer can be attracted by an external magnetic field to provide orientation force for the copper needle body during reflow soldering.

6. The magnetically controlled anti-tilt copper pin packaging process according to claim 5, characterized in that, The material of the ferromagnetic metal layer is nickel or a nickel alloy.

7. The magnetically controlled anti-tilt copper pin packaging process according to claim 5, characterized in that, The ferromagnetic metal layer is integrally formed with the copper needle body or is combined through a surface treatment process.

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