A method and system for preventing tilting of aluminum substrate leads based on segmented welding

Abstract

This invention relates to the field of welding technology, specifically disclosing a method and system for preventing tilting of aluminum substrate leads based on segmented welding. The method includes: S1, welding multiple first leads along the long side of a rectangular aluminum substrate using reflow soldering; S2, preheating the rectangular aluminum substrate and welding multiple second leads along the short side of the rectangular aluminum substrate using a soldering iron with localized heating; wherein the localized heating range of the soldering iron is the pad area corresponding to each second lead. This invention, by first reflow soldering the long side leads and then preheating and soldering the short side leads with a soldering iron, effectively alleviates the problem of thermal deformation and warping of the aluminum substrate during reflow soldering due to temperature cycling. While reducing the tilting of the short side leads, it also improves the upward warping of the long side, thereby improving the verticality of the leads and ensuring the reliability and accuracy of subsequent assembly.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and in particular to a method and system for preventing tilting of aluminum substrate leads based on segmented welding. Background Technology

[0002] Currently, aluminum substrates are widely used for heat dissipation in power devices due to their high thermal conductivity. However, during reflow soldering, aluminum substrates are prone to thermal deformation and warping due to temperature cycling, causing the surface-mount leads (which serve as external connection pins for products) on the aluminum substrate to tilt, especially the leads on the two shorter sides of the aluminum substrate. Traditional solutions rely on tooling fixtures to fix the leads, but the rigid constraint between the fixtures and the aluminum substrate exacerbates uneven thermal stress distribution, causing the long sides of the aluminum substrate to warp upwards, affecting the verticality of the leads and subsequent assembly.

[0003] Therefore, there is an urgent need to provide a technical solution to address the above problems. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method and system for preventing tilting of aluminum substrate leads based on segmented welding.

[0005] In a first aspect, the present invention provides a method for preventing tilting of aluminum substrate leads based on segmented welding, the technical solution of which is as follows:

[0006] S1. Using reflow soldering, multiple first leads are soldered along the long side of a rectangular aluminum substrate.

[0007] S2. Preheat the rectangular aluminum substrate and use a soldering iron for localized heating to solder multiple second leads along the short side of the rectangular aluminum substrate; wherein, the area of ​​localized heating by the soldering iron is the pad area corresponding to each second lead.

[0008] The beneficial effects of the aluminum substrate lead anti-tilting process method based on segmented welding of the present invention are as follows:

[0009] The method of the present invention can effectively alleviate the problem of thermal deformation and warping of aluminum substrates caused by temperature cycling during reflow soldering by first reflow soldering the long side leads and then preheating and soldering the short side leads with a soldering iron. While reducing the tilt of the short side leads, it can also improve the problem of upward warping of the long side, thereby improving the verticality of the leads and ensuring the reliability and accuracy of subsequent assembly.

[0010] Based on the above scheme, the aluminum substrate lead anti-tilting process method based on segmented welding of the present invention can be further improved as follows.

[0011] In one alternative approach, S1 includes:

[0012] S11. Using the first tooling fixture, position the multiple first leads to be welded to the long side of the rectangular aluminum substrate.

[0013] S12. Using the reflow soldering method, the multiple first leads after positioning are soldered along the long side of the rectangular aluminum substrate. After all the first leads are soldered, the first tooling fixture is removed.

[0014] In one alternative approach, the step of preheating the rectangular aluminum substrate includes:

[0015] The rectangular aluminum substrate is placed on a preheating table and preheated to a preset temperature range.

[0016] In one alternative approach, the preset temperature range is 80-100℃.

[0017] In one alternative approach, the preheating area of ​​the rectangular aluminum substrate is the pad area corresponding to a plurality of second leads.

[0018] In one alternative approach, the step of soldering multiple second leads along the short side of the rectangular aluminum substrate using a localized heating soldering method with a soldering iron includes:

[0019] The second tooling fixture is used to position the multiple second leads to be welded to the short side of the rectangular aluminum substrate.

[0020] The local heating soldering method using the electric soldering iron is used to locally heat the area where the multiple second leads are located and to solder the multiple second leads along the short side of the rectangular aluminum substrate.

[0021] Secondly, the present invention provides an aluminum substrate lead anti-tilting process system based on segmented welding, the technical solution of which is as follows:

[0022] A segmented welding-based aluminum substrate lead anti-tilt process system includes: a first welding module and a second welding module;

[0023] The first welding module is used to: weld multiple first leads along the long side of a rectangular aluminum substrate using a reflow soldering method;

[0024] The second welding module is used to: preheat the rectangular aluminum substrate and weld multiple second leads along the short side of the rectangular aluminum substrate using a local heating welding method with a soldering iron; wherein the local heating range of the soldering iron is the pad area corresponding to each second lead.

[0025] The beneficial effects of the aluminum substrate lead anti-tilt process system based on segmented welding of the present invention are as follows:

[0026] The system of this invention can effectively alleviate the problem of thermal deformation and warping of aluminum substrates caused by temperature cycling during reflow soldering by first reflow soldering the long side leads and then preheating and soldering the short side leads with a soldering iron. While reducing the tilt of the short side leads, it can also improve the problem of upward warping of the long side, thereby improving the verticality of the leads and ensuring the reliability and accuracy of subsequent assembly.

[0027] Based on the above solution, the aluminum substrate lead anti-tilting process system based on segmented welding of the present invention can be further improved as follows.

[0028] In one alternative embodiment, the first welding module is specifically used for:

[0029] The first tooling fixture is used to position the multiple first leads to be welded to the long side of the rectangular aluminum substrate.

[0030] Using the reflow soldering method, the multiple first leads after positioning are soldered along the long side of the rectangular aluminum substrate. After all the first leads are soldered, the first tooling fixture is removed.

[0031] In one alternative embodiment, the second welding module is specifically used for:

[0032] The rectangular aluminum substrate is placed on a preheating table and preheated to a preset temperature range.

[0033] In one alternative approach, the preset temperature range is 80-100℃.

[0034] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0035] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0036] Figure 1 This is a schematic flowchart of an embodiment of the aluminum substrate lead anti-tilting process method based on segmented welding according to the present invention.

[0037] Figure 2 This is one of the schematic diagrams of the present invention;

[0038] Figure 3 This is the second schematic diagram of the principle of the present invention;

[0039] Figure 4This is a schematic diagram of an embodiment of an aluminum substrate lead anti-tilting process system based on segmented welding according to the present invention. Detailed Implementation

[0040] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0041] Figure 1 This diagram illustrates a flow chart of an embodiment of an aluminum substrate lead anti-tilting process method based on segmented welding provided by the present invention. Figure 1 As shown, it includes the following steps:

[0042] S1. Using reflow soldering, multiple first leads are soldered along the long side of the rectangular aluminum substrate.

[0043] The rectangular aluminum substrate has an aspect ratio of ≥1.5:1, where the long side refers to the two sides along the length of the rectangular aluminum substrate, and the short side refers to the two sides along the width of the rectangular aluminum substrate. Reflow soldering refers to uniformly heating the entire rectangular aluminum substrate in a furnace, melting the pre-coated solder, and then cooling it to form solder joints. This is used to efficiently solder multiple first leads along the long side of the rectangular aluminum substrate.

[0044] S2. Preheat the rectangular aluminum substrate and use a soldering iron for localized heating to solder multiple second leads along the short side of the rectangular aluminum substrate; wherein, the area of ​​localized heating by the soldering iron is the pad area corresponding to each second lead.

[0045] The localized soldering method refers to a manual soldering process where a handheld soldering iron is used to locally heat a specific area of ​​the solder pad. The heating range diameter is ≤5mm to prevent heat from spreading to the entire rectangular aluminum substrate. The second lead refers to the external connection pin soldered to the short side of the rectangular aluminum substrate. The lead height can be set according to the actual situation and is not limited here.

[0046] It should be noted that since rectangular aluminum substrates account for over 80% of the power module, and the aspect ratio of these rectangular aluminum substrates (typically ≥1.5:1) leads to significant anisotropy in thermal deformation: the long side of the aluminum substrate, due to its strong structural rigidity, primarily exhibits localized warping under thermal stress; while the short side, due to its reduced size, experiences a sharp drop in bending stiffness, and the warping amplitude upon release of residual thermal stress can reach 1.5 times that of the long side, concentrating the risk of lead wire tilting. Traditional welding processes struggle to balance the efficiency of the long side and the precision of the short side of the aluminum substrate. Therefore, this embodiment employs a segmented welding method for the rectangular aluminum substrate to address the mechanical weaknesses of this shape. Furthermore, experimental verification shows that the aluminum substrate warping rate decreased from 0.5% to 0.2% and the short-side lead wire tilting angle was optimized from 2° to 0.5° using the segmented welding-based lead wire anti-tilting process method of this embodiment.

[0047] The technical solution of this embodiment can effectively alleviate the problem of thermal deformation and warping of aluminum substrate caused by temperature cycling during reflow soldering by first reflow soldering the long side leads and then preheating and soldering the short side leads with a soldering iron. While reducing the tilt of the short side leads, it can also improve the problem of upward warping of the long side, thereby improving the verticality of the leads and ensuring the reliability and accuracy of subsequent assembly.

[0048] In one alternative approach, S1 includes:

[0049] S11. Using the first tooling fixture, position the plurality of first leads to be welded to the long side of the rectangular aluminum substrate.

[0050] The first tooling fixture is a detachable metal fixture that only clamps the first lead wire in the long side area of ​​the rectangular aluminum substrate, thereby positioning the first lead wire vertically.

[0051] Specifically, a rectangular aluminum substrate is placed on a worktable, and multiple first leads in the long side area are clamped using the limiting groove of the first tooling fixture to ensure that all first leads are perpendicular to the plane of the rectangular aluminum substrate (perpendicularity tolerance ≤ 0.1°).

[0052] S12. Using the reflow soldering method, the multiple first leads after positioning are soldered along the long side of the rectangular aluminum substrate. After all the first leads are soldered, the first tooling fixture is removed.

[0053] The immediate removal of the first tooling fixture after welding can avoid creating a continuous rigid constraint on the aluminum substrate.

[0054] Specifically, the clamped rectangular aluminum substrate is fed into a reflow oven and heated according to a standard curve (peak temperature 245±5℃) to melt the solder and connect the first lead to the long side pad. After soldering, the first tooling fixture is removed before cooling to 100℃ to eliminate the rigid constraint of the first tooling fixture on the rectangular aluminum substrate and prevent thermal stress concentration during the cooling stage.

[0055] In the above-mentioned optional methods, by using the first tooling fixture to position the lead wire during long-side lead wire welding and removing it after welding, the accuracy of the lead wire welding position can be ensured, the uneven distribution of thermal stress caused by the rigid constraint of the tooling fixture can be avoided, the risk of warping of the long side of the aluminum substrate can be reduced, and the verticality of the lead wire can be guaranteed.

[0056] In one alternative approach, the step of preheating the rectangular aluminum substrate includes:

[0057] The rectangular aluminum substrate is placed on a preheating table and preheated to a preset temperature range.

[0058] The preset temperature range is 80-100℃. Experiments have verified that a preheating temperature strictly below 100℃ ensures uniform heating of the rectangular aluminum substrate without triggering the warping critical point. It should be noted that the lower limit of the preset temperature range, 80℃, ensures sufficient release of residual thermal stress within the aluminum substrate (stress release rate <90% below this temperature); the upper limit of the preset temperature range, 100℃, is strictly below the thermal deformation critical point of the aluminum substrate (warping rate >0.3% at ≥120℃), preventing secondary thermal deformation.

[0059] The preheating area of ​​the rectangular aluminum substrate is the pad area corresponding to multiple second leads. The heating range of the preheating station is limited to the pad area corresponding to the short side second lead (width is 10mm beyond the pad), avoiding the already soldered first lead (long side lead) and the central area, thus protecting the soldered lead structure.

[0060] In the aforementioned optional methods, further preheating the aluminum substrate to a preset temperature range on a preheating table can uniformly heat the aluminum substrate, reduce the temperature difference with subsequent soldering, make the soldering more stable, reduce deformation of the aluminum substrate due to temperature differences, ensure the soldering quality of short-side leads, and improve lead perpendicularity. Further preheating the aluminum substrate to 80-100℃ can better balance preheating effect and energy consumption, effectively reducing the temperature difference with reflow soldering and soldering iron soldering, avoiding thermal shock deformation of the aluminum substrate, while avoiding excessive heat waste, ensuring lead soldering quality and efficiency. Simultaneously, preheating only the pad area corresponding to the second lead achieves precise local preheating, reducing unnecessary heating of other areas of the aluminum substrate, accurately controlling thermal stress distribution, reducing the risk of overall deformation, ensuring minimal thermal deformation of the aluminum substrate during short-side lead soldering, and guaranteeing lead perpendicularity.

[0061] In one alternative approach, the step of soldering multiple second leads along the short side of the rectangular aluminum substrate using a localized heating soldering method with a soldering iron includes:

[0062] The second tooling fixture is used to position the multiple second leads to be welded to the short side of the rectangular aluminum substrate.

[0063] The second tooling fixture is a special fixture for the short side. It is installed after preheating and only fixes the vertical position of the second lead on the short side. A 0.5mm thermal expansion gap is maintained between the support arm of the second tooling fixture and the aluminum substrate to avoid rigid contact.

[0064] Specifically, after preheating is completed, the second tooling fixture is installed. The positioning pin of the second tooling fixture is inserted into the short side lead mounting hole to fix the vertical posture of multiple second leads (the angle between the second lead and the rectangular aluminum substrate is 90±0.5°).

[0065] The local heating soldering method using the electric soldering iron is used to locally heat the area where the multiple second leads are located and to solder the multiple second leads along the short side of the rectangular aluminum substrate.

[0066] Specifically, a constant temperature soldering iron (temperature set at 300±10℃) is used to locally heat the pad area corresponding to the second lead, meeting the following conditions: ① the contact area of ​​the soldering iron tip is ≤ 80% of the pad size; ② the single-point heating time is ≤ 3 seconds to avoid heat accumulation; ③ after the solder melts, the verticality of the lead is automatically corrected by the surface tension of the molten solder, and a metallurgical connection is formed after cooling.

[0067] In the above-mentioned optional methods, the short-side lead is further positioned by using a second tooling fixture to ensure accurate lead position. Then, a soldering iron is used for local heating and soldering, concentrating the heat in the lead area to avoid large-scale heat deformation of the aluminum substrate, effectively reducing the tilt of the short-side lead, and improving the verticality of the lead and the assembly quality.

[0068] In this embodiment, as Figure 2 As shown, the heights of the multiple first leads can be the same or different, and they are unevenly distributed along the long side of the rectangular aluminum substrate. A first fixture has lead positioning holes for positioning (fixing) the first leads. Similarly, the heights of the multiple second leads can be the same or different, and they are unevenly distributed along the short side of the rectangular aluminum substrate. A second fixture has lead positioning holes for positioning (fixing) the second leads. After sequentially welding and fixing the first and second leads, the following is obtained: Figure 3 The aluminum substrate shown in this embodiment uses manual soldering of the short side leads of the aluminum substrate instead of reflow soldering. This avoids the tooling fixture forming a rigid constraint with the aluminum substrate through the short side leads and the external mechanical constraint when the whole is heated, thus releasing thermal stress.

[0069] It should be noted that, in this embodiment, in addition to being welded along the long side of the rectangular aluminum substrate, the multiple first leads can also be set in the middle area of ​​the rectangular aluminum substrate. The specific arrangement can be adapted according to the application scenario of the aluminum substrate to be prepared, and no limitations are set here. The aluminum substrate obtained by the segmented welding-based aluminum substrate lead anti-tilt process method of this embodiment is suitable for high-reliability power supplies, spacecraft power distribution systems, and 5G base station RF power amplifier modules. The short-side leads, as high-density I / O interfaces, need to withstand mechanical vibration (≥10G acceleration), thermal cycling (-40℃~125℃), and insertion / extraction stress. The method of this embodiment controls the lead tilt angle on the aluminum substrate within 0.5°, ensuring connector mating accuracy (tolerance ±0.1mm), avoiding contact failure or arc discharge caused by pin misalignment, and significantly improving the reliability and accuracy of the system power supply and power supply unit.

[0070] Figure 4 This diagram illustrates a structural schematic of an embodiment of an aluminum substrate lead anti-tilting process system 200 based on segmented welding provided by the present invention. Figure 4 As shown, the aluminum substrate lead anti-tilt process system 200 based on segmented welding includes: a first welding module 210 and a second welding module 220.

[0071] The first welding module 210 is used to: weld multiple first leads along the long side of a rectangular aluminum substrate using a reflow soldering method;

[0072] The second welding module 220 is used to: preheat the rectangular aluminum substrate and weld multiple second leads along the short side of the rectangular aluminum substrate using a local heating welding method with a soldering iron; wherein the local heating range of the soldering iron is the pad area corresponding to each second lead.

[0073] In one alternative embodiment, the first welding module 210 is specifically used for:

[0074] The first tooling fixture is used to position the multiple first leads to be welded to the long side of the rectangular aluminum substrate.

[0075] Using the reflow soldering method, the multiple first leads after positioning are soldered along the long side of the rectangular aluminum substrate. After all the first leads are soldered, the first tooling fixture is removed.

[0076] In one alternative embodiment, the second welding module 220 is specifically used for:

[0077] The rectangular aluminum substrate is placed on a preheating table and preheated to a preset temperature range.

[0078] In one alternative approach, the preset temperature range is 80-100℃.

[0079] In one alternative approach, the preheating area of ​​the rectangular aluminum substrate is the pad area corresponding to a plurality of second leads.

[0080] In one alternative embodiment, the second welding module 220 is specifically used for:

[0081] The second tooling fixture is used to position the multiple second leads to be welded to the short side of the rectangular aluminum substrate.

[0082] The local heating soldering method using the electric soldering iron is used to locally heat the area where the multiple second leads are located and to solder the multiple second leads along the short side of the rectangular aluminum substrate.

[0083] It should be noted that the beneficial effects of the aluminum substrate lead anti-tilt process system 200 based on segmented welding provided in the above embodiments are the same as those of the aluminum substrate lead anti-tilt process method based on segmented welding, and will not be repeated here. Furthermore, the system provided in the above embodiments is only illustrated by the division of the above functional modules. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the system can be divided into different functional modules according to the actual situation to complete all or part of the functions described above. In addition, the system and method embodiments provided in the above embodiments belong to the same concept, and their specific implementation process is detailed in the method embodiments, and will not be repeated here.

[0084] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. Similarly, for the sake of brevity and to aid in understanding one or more aspects of the invention, in the description of exemplary embodiments of the invention above, various features of the embodiments are sometimes grouped together in a single embodiment, figure, or description thereof. The claims, which follow the detailed description, are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the invention.

[0085] It should be noted that the above embodiments are illustrative of the invention and not restrictive, and that those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names. The steps in the above embodiments, unless otherwise specified, should not be construed as limiting the order of execution.

Claims

1. A method for preventing tilting of aluminum substrate leads based on segmented welding, characterized in that, include: The first tooling fixture is used to position multiple first leads to be welded to the long side of the rectangular aluminum substrate. A reflow soldering method is used to solder multiple first leads along the long side of the rectangular aluminum substrate after positioning. After all the first leads are soldered, the first tooling fixture is removed. The reflow soldering method refers to uniformly heating the entire rectangular aluminum substrate in a heating furnace to melt the pre-coated solder and form solder joints after cooling, which is used to efficiently solder multiple first leads along the long side of the rectangular aluminum substrate. The rectangular aluminum substrate is placed on a preheating table and preheated to a preset temperature range; wherein, the preset temperature range is 80-100℃; the preheating area of ​​the rectangular aluminum substrate is the pad area corresponding to multiple second leads. The second tooling fixture is used to position the multiple second leads to be welded to the short side of the rectangular aluminum substrate. A localized heating soldering method using a soldering iron is employed to locally heat the areas where multiple second leads are located after positioning, and then solder the multiple second leads along the short side of the rectangular aluminum substrate. The localized heating range of the soldering iron is the pad area corresponding to each second lead. The localized heating soldering method refers to a manual soldering process in which a handheld soldering iron is used to locally heat a specific pad area, with a heating range diameter ≤ 5mm, to avoid heat diffusion to the entire rectangular aluminum substrate.

2. A process system for preventing tilting of aluminum substrate leads based on segmented welding, characterized in that, include: First welding module and second welding module; The first welding module is used to: position multiple first leads to be welded to the long side of a rectangular aluminum substrate using a first tooling fixture; weld the positioned multiple first leads along the long side of the rectangular aluminum substrate using a reflow soldering method; and remove the first tooling fixture after all the first leads have been welded. The reflow soldering method refers to: uniformly heating the entire rectangular aluminum substrate in a heating furnace to melt and cool the pre-coated solder to form solder joints, which are used to efficiently weld multiple first leads along the long side of the rectangular aluminum substrate. The second welding module is used to: place the rectangular aluminum substrate on a preheating platform and preheat it to a preset temperature range; position multiple second leads to be welded to the short side of the rectangular aluminum substrate using a second tooling fixture; and use a soldering iron for localized heating to locally heat the area where the positioned multiple second leads are located and weld the positioned multiple second leads along the short side of the rectangular aluminum substrate; wherein, the preset temperature range is 80-100℃; the preheating area of ​​the rectangular aluminum substrate is the pad area corresponding to the multiple second leads; the localized heating range of the soldering iron is the pad area corresponding to each second lead; the localized heating soldering method refers to a manual welding process in which a handheld soldering iron is used to locally heat a specific pad area, with a heating range diameter ≤ 5mm, to avoid heat diffusion to the entire rectangular aluminum substrate.

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