Electronic packaging welding substrate and welding method capable of removing bubbles

Abstract

The present invention provides an electronic packaging welding substrate and a welding method capable of removing bubbles. The electronic packaging welding substrate comprises a substrate. A micro-nano structure is provided on the welding surface of the substrate, forming a wettability that gradually decreases from the center of the substrate toward the outside, and a plurality of grooves are provided. The plurality of grooves divide the welding surface of the substrate into a plurality of wettability gradient areas. A plurality of wetting grooves extending from the welding surface of the substrate to the bottom of the grooves are formed on the inner side surfaces of the grooves. On the one hand, bubbles in the molten solder are moved from the center to the periphery under the action of the wetting gradient force during high-temperature welding. On the other hand, the shape of the grooves can form Laplace pressure, further strengthening the movement of bubbles from the center to the periphery. The wetting grooves can enable bubbles to move from the bottom of the grooves to the welding surface of the substrate, preventing bubbles from being deposited in the grooves. Since the bubbles move from the center of the substrate to the periphery and escape in time, the effective contact area is increased, thereby improving the reliability of the chip and having good practicality.

Description

Technical Field

[0001] The invention relates to the technical field of electronic packaging welding, and in particular to an electronic packaging welding substrate capable of removing bubbles and a welding method. Background Art

[0002] Packaging technology utilizes a series of techniques to lay out, affix, and connect chips to a frame, then lead out the terminals and secure them with insulating plastic or ceramic potting to create an integrated three-dimensional structure. Packaging is crucial for chips. This is because packaging protects and supports the chip, creating a favorable operating environment to prevent airborne impurities from corroding the chip's circuitry and degrading electrical performance. Packaged chips also facilitate installation and transportation. Furthermore, given that all semiconductor products generate heat during operation, packaging technology can enhance heat dissipation, improve chip reliability, and extend chip lifespan. Because the quality of packaging technology directly impacts both the performance of the chip itself and the design and manufacture of the PCB (printed circuit board) to which it connects, it is a crucial component of many integrated circuit products.

[0003] During the packaging process, components are typically connected via soldering. As modern electronic packaging devices continue to move toward higher density, higher integration, and smaller form factors, thermal stress and alternating cycling caused by chip power cycling can degrade solder joint performance, reduce reliability, and even cause chip failure. Therefore, solder joint reliability is crucial. During the soldering process, due to the varying vaporization temperatures of various solder components, flux vaporizes during heating, and the molten solder easily incorporates air. This can lead to bubbles forming within the solder, creating voids. These bubbles reduce the chip's heat dissipation area and increase its ground impedance, compromising soldering reliability and product performance. This can even lead to package failure, resulting in defective products, impacting product yield, and compromising product quality stability. Subsequent soldering steps are required, making the soldering process cumbersome and complex, impacting production efficiency.

[0004] Therefore, how to remove bubbles in solder, prevent empty soldering and cold soldering, ensure full and uniform soldering, improve product yield, improve heat dissipation efficiency, enhance reliability and extend product life, is a technical problem that needs to be solved urgently in the field of electronic packaging. Summary of the Invention

[0005] The purpose of the present invention is to address the shortcomings of the existing technology and provide an electronic packaging welding substrate that can remove bubbles, including a substrate, a plurality of grooves are provided on the welding surface of the substrate, and the plurality of grooves divide the welding surface of the substrate into multiple wetting gradient areas, and a plurality of wetting grooves are formed on the inner side surfaces of the grooves, extending from the welding surface of the substrate to the bottom of the grooves.

[0006] Optionally, a plurality of wetting grooves are arranged side by side in sequence along the extension direction of the groove.

[0007] Optionally, a plurality of wetting tanks are arranged at equal intervals.

[0008] Optionally, the cross-sectional shape of the groove is trapezoidal, rectangular, triangular or semicircular.

[0009] Optionally, the shapes of the multiple wettability gradient regions are trapezoidal, triangular or polygonal.

[0010] Optionally, the wetting groove is formed by a plurality of pattern grooves connected in sequence, and the shape of the pattern groove is trapezoidal, triangular or semicircular.

[0011] Optionally, a micro-nano structure is formed on the welding surface of the substrate, and the roughness of the welding surface of the substrate varies from the center to the outside.

[0012] The present invention also provides an electronic packaging welding method capable of removing bubbles, comprising the following steps:

[0013] Processing grooves and wetting grooves on the substrate to form the above-mentioned electronic packaging soldering base capable of removing bubbles;

[0014] Apply solder paste on the substrate and perform the first reflow to fill the grooves and wet the slots with solder paste;

[0015] Clean the substrate and remove the welding slag on the substrate;

[0016] Solder paste is applied to the substrate again, and the chip is attached to the substrate coated with solder paste, and a second reflow process is performed.

[0017] Optionally, reflow can be performed under vacuum or inert atmosphere.

[0018] The beneficial effects of the present invention are as follows: the electronic packaging soldering substrate capable of removing bubbles of the present invention has a plurality of grooves formed on the soldering surface of the substrate, which divide the soldering surface of the substrate into a plurality of wetting gradient areas. The inner side surfaces of the grooves are formed with a plurality of wetting grooves extending from the soldering surface of the substrate to the bottom of the grooves, thereby converting the original integral substrate into a gradient wetting area and a groove area. On the one hand, bubbles in the molten solder are moved from the center to the periphery under the action of the wetting gradient force during high-temperature soldering. On the other hand, the grooves can form Laplace pressure, further strengthening the movement of bubbles from the center to the periphery. The wetting grooves can move bubbles from the bottom of the grooves to the surface of the substrate, so that bubbles move from the center of the substrate to the periphery and escape in time. After the first reflow soldering is completed, the solder fills the groove area, reducing bubbles trapped in the grooves, cleaning and smoothing the substrate surface, and improving the contact surface condition of the second reflow soldering. The method effectively reduces the area and number of bubbles, ensures that the chip has sufficient heat dissipation area, and improves its heat dissipation effect. At the same time, due to the reduction in the area of the bubbles, the effective area of the substrate forming the conductor is increased, thereby reducing the grounding impedance of the chip, thereby improving the reliability of the chip and having good practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic structural diagram of the electronic packaging welding substrate capable of removing bubbles in Example 1 provided by the present invention;

[0020] Figure 2 A schematic structural diagram of the wetting tank in Example 1 provided by the present invention;

[0021] Figure 3 This is a schematic structural diagram of the electronic packaging welding substrate capable of removing bubbles in the second embodiment provided by the present invention;

[0022] Figure 4 This is a schematic structural diagram of the wetting tank in the second embodiment provided by the present invention;

[0023] Figure 5 This is a schematic structural diagram of the electronic packaging welding substrate capable of removing bubbles in the third embodiment provided by the present invention;

[0024] Figure 6 This is a flow chart of the electronic packaging welding method capable of removing bubbles in the second embodiment provided by the present invention. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0026] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0027] The present invention will be further described below with reference to specific embodiments and drawings, but they are not intended to limit the present invention.

[0028] Example 1

[0029] Combine Figure 1 and Figure 2 As shown, an embodiment of the present invention discloses an electronic packaging welding base capable of removing bubbles, including a substrate 1, and a plurality of grooves 2 are provided on the welding surface of the substrate 1. In this embodiment, the cross-sectional shape of the grooves 2 is rectangular. Of course, according to actual needs, the cross-sectional shape of the grooves 2 can also be trapezoidal, triangular or semicircular.

[0030] Furthermore, a plurality of grooves 2 separate the soldering surface of the substrate 1 into a plurality of wetting gradient regions 3. In this embodiment, the plurality of wetting gradient regions 3 are trapezoidal in shape. This embodiment replaces the original monolithic substrate with gradient wetting regions and grooves 2. This allows bubbles in the molten solder to move from the center to the periphery under the action of the wetting gradient force during high-temperature soldering. Furthermore, the specific wetting gradient regions 3 separated by the grooves 2 generate Laplace pressure, further enhancing the movement of bubbles from the center to the periphery.

[0031] Furthermore, a plurality of wetting grooves 4 extending from the welding surface of the substrate 1 to the bottom of the groove 2 are formed on the inner side surface of the groove 2 of the present embodiment. The plurality of wetting grooves 4 are arranged side by side in sequence along the extension direction of the groove 2, and the plurality of wetting grooves 4 are arranged at equal intervals. The wetting groove 4 is formed by a plurality of graphic grooves connected in sequence. In the present embodiment, the shape of the graphic groove is a trapezoid. The wetting groove 4 can move bubbles from the bottom of the groove 2 to the surface of the substrate, and move bubbles from the center of the substrate to the surroundings and escape in time. It is worth noting that a micro-nano structure is formed on the welding surface of the substrate 1, and the roughness of the welding surface of the substrate 1 is different from the center to the outside. Different roughnesses can form different wettabilities, and finally form a wetting gradient in which the wettability of the solder gradually decreases from the center to the surroundings. The construction method of the micro-nano structure can be sandblasting, strong acid etching, anodizing, sintering and photolithography.

[0032] Example 2

[0033] Combine Figure 3 and Figure 4As shown, as another embodiment of the present invention, unlike the first embodiment, the grooves 2 disclosed in this embodiment are connected to form a dendritic structure, which can generate Laplace pressure and has the function of transporting bubbles from the center to the surrounding area, so that there are no bubbles in the central area of the substrate. The grooves 2 are relatively evenly distributed, thereby making the heat dissipation and welding effects of the central area of each substrate more uniform. The grooves 2 separate the multiple wettability gradient areas 3 into polygonal shapes, while the shape of the graphic grooves in this embodiment is semicircular.

[0034] Example 3

[0035] Combine Figure 5 As shown in FIG. , as another embodiment of the present invention, unlike the first embodiment, the grooves 2 disclosed in this embodiment separate the multiple wettability gradient regions 3 into triangular shapes. The grooves 2 are arranged circumferentially with the center of the substrate 1 as the center. This structure can also generate Laplace pressure. The shape of the patterned grooves in this embodiment is triangular.

[0036] Example 4

[0037] Combine Figure 6 As shown, as another embodiment of the present invention, this embodiment discloses an electronic packaging welding method capable of removing bubbles, comprising the following steps:

[0038] Step 1: Form grooves and wetting grooves on the substrate to form the electronic packaging welding base capable of removing bubbles as described above; the cross-sectional shape of the grooves can be trapezoidal, rectangular, triangular, or semicircular, and the shape of the wetting grooves can be trapezoidal, triangular, or semicircular.

[0039] Step 2: Apply solder paste to the substrate and perform the first reflow process to fill the grooves and wet the slots. Specifically, reflow is performed in a reflow oven. First, the solder paste parameters must be determined, including the starting temperature and heating slope range of the reflow oven's preheating zone. The reflow oven parameters are then adjusted to match the solder paste's characteristic curve using the solder paste's characteristic curve. Finally, a stencil contact printing method is used to apply the solder paste to the entire substrate and fill all grooves. Reflow is performed under a vacuum or inert atmosphere.

[0040] Step 3: Clean the substrate to remove the welding slag, precipitated flux and other impurities on the substrate to make the surface of the substrate smooth after welding;

[0041] Step 4: Solder paste is re-coated on the substrate, and the chip is bonded to the solder-coated substrate for a second reflow process. Specifically, the chip is first placed in the sealed chamber of the reflow oven. The appropriate parameters are input, and the reflow oven is controlled to the desired profile. High-pressure nitrogen gas is then introduced into the sealed chamber, flowing through it. Simultaneously, the workpiece is heated to the reflow soldering temperature, maintaining a constant temperature for the semiconductor chip and melting the solder paste for reflow soldering. Within the reflow oven, the solder-coated substrate passes through the preheating zone, the holding zone, the reflow zone, and the cooling zone. Preheating activates the solder paste and prevents undesirable heating behavior caused by sudden high-temperature heating. The goal of the preheating zone is to heat the room-temperature component as quickly as possible. However, the heating rate must be kept within an appropriate range. A too rapid rate can cause thermal shock, potentially damaging both the substrate and the component. A too slow rate can result in insufficient solvent evaporation, impacting soldering quality. The main purpose of the holding phase is to stabilize the temperature of each component within the reflow oven, minimizing temperature differences. This allows sufficient time for larger components to catch up to the temperature of smaller components within the holding zone, ensuring that the flux in the solder paste is fully volatilized. When the component enters the reflow zone, the temperature rises rapidly, melting the solder paste. In the cooling zone, the temperature cools below the solidus temperature, solidifying the solder joints and allowing the chip to be removed.

[0042] The beneficial effects of the present invention are as follows: since a plurality of grooves are provided on the welding surface of the substrate, the plurality of grooves divide the welding surface of the substrate into a plurality of wetting gradient areas, and a plurality of wetting grooves extending from the welding surface of the substrate to the bottom of the grooves are formed on the inner side surfaces of the grooves, the original welding surface of the substrate is divided into a gradient wetting area and a groove area, and a micro-nano structure is formed on the welding surface of the gradient wetting area, and the roughness of the micro-nano structure is different from the center to the outside, and different roughnesses can form different wettabilities, and finally form a wetting gradient in which the wettability of the solder gradually decreases from the center to the surrounding areas; on the one hand, the bubbles in the molten solder in the high-temperature welding process move from the center to the surrounding areas under the action of the wetting gradient force, and on the other hand, the grooves can form Laplace pressure, further strengthening the bubbles from the center to the surrounding areas. The wetting groove can move bubbles from the bottom of the groove to the surface of the substrate, so that bubbles move from the center of the substrate to the surrounding areas and escape in time. After the first reflow soldering is completed, the solder fills the groove area, reducing bubbles trapped in the groove, cleaning and smoothing the substrate surface, and making the contact surface condition of the second reflow soldering better. This method effectively reduces the area and number of bubbles, ensuring that the chip has sufficient heat dissipation area and improving its heat dissipation effect. At the same time, according to the resistance law of conductor materials, the formula is R = ρL / S, where ρ is the resistivity of the conductor material, L is the conductor length, and S is the conductor cross-sectional area. Since the area of the bubbles is reduced, the effective area of the substrate forming the conductor is increased, thereby reducing the ground impedance of the chip and improving the reliability of the chip. Furthermore, the soldering effect of the substrate is also improved compared to the original integral substrate structure. This is because the reduction of bubbles improves the density of each solder joint, ensuring full and uniform soldering, eliminating the need for a re-soldering process, and thus ensuring the actual soldering quality of each solder joint.

[0043] The above are only preferred embodiments of the present invention and do not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of the present invention specification should be included in the protection scope of the present invention.

Claims

1. An electronic packaging welding substrate capable of removing bubbles, characterized in that: The invention comprises a substrate, wherein a plurality of grooves are formed on the welding surface of the substrate, wherein the plurality of grooves divide the welding surface of the substrate into a plurality of wetting gradient regions, and a plurality of wetting grooves are formed on the inner side surfaces of the grooves, extending from the welding surface of the substrate to the bottom of the grooves, wherein the wetting grooves are used to move bubbles from the bottom of the grooves to the welding surface of the substrate; Several of the wetting grooves are arranged side by side in sequence along the extension direction of the groove, and several of the wetting grooves are arranged at equal intervals. The wetting groove is formed by multiple graphic grooves connected in sequence, and the shape of the graphic groove is trapezoidal, triangular or semicircular.

2. The electronic packaging soldering substrate capable of removing bubbles as claimed in claim 1, wherein: The cross-sectional shape of the groove is trapezoidal, rectangular, triangular or semicircular.

3. The electronic packaging soldering substrate capable of removing bubbles as claimed in claim 1, wherein: The shapes of the plurality of wettability gradient regions are trapezoidal, triangular or polygonal.

4. The electronic packaging soldering substrate capable of removing bubbles as claimed in claim 1, wherein: A micro-nano structure is formed on the welding surface of the substrate, and the roughness of the welding surface of the substrate varies from the center to the outside.

5. An electronic packaging welding method capable of removing bubbles, characterized in that: The following steps are involved: Processing grooves and wetting grooves on the substrate to form the bubble-removable electronic packaging soldering substrate as claimed in claim 1; Coating solder paste on the substrate and performing a first reflow process to allow the solder paste to fill the groove and the wetting slot; Cleaning the substrate to remove welding slag on the substrate; Solder paste is coated on the substrate again, and the chip is attached to the substrate coated with solder paste, and a second reflow process is performed.

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