High-temperature laser welding method for fine-pitch micro-via solder joints

Abstract

The present application relates to a kind of high temperature micro-hole welding spot laser welding method of close pitch, belong to laser welding technical field, solve the problem of one of welding performance in prior art, poor weld appearance consistency, rely on artificial operation.By selecting suitable solder, setting reasonable number and size of spray ball, setting subsection process, automatic welding etc., through laser spray ball automatic welding equipment realizes high temperature welding for close pitch micro-hole welding spot, and welding performance is excellent, weld appearance consistency is good and effectively realizes dehumanization.

Description

Technical Field

[0001] This invention relates to the field of laser welding technology, and in particular to a high-temperature, close-pitch micro-through-hole welding method. Background Technology

[0002] In recent years, laser ball soldering has been gradually applied to various fields such as high-speed data cables, flexible circuit boards, and various connectors. However, the solder used in these applications is almost always lead-free alloy or 6337 alloy (Pb). 63 Sn 37 The corresponding solder joint structures are all PIN (pin) / PAD (pad) type or "L" type. For solder joint types such as through-hole pin type, which have high requirements for solder transmittance, laser ball welding has been rarely used.

[0003] As the application environment of existing dual-polarized antennas becomes increasingly demanding, and the assembly ratio of such antennas is extremely sensitive to the solder joint morphology, the requirements for through-hole pin-type solder joint welding are also increasing. However, due to the special working environment, the high melting point of the solder, poor solderability, and the influence of structural space, as well as limitations on aperture and pads, welding is difficult.

[0004] Existing technologies mostly employ manual welding for welding through-hole pin-type solder joints, especially for welding closely spaced micro-through holes. This method suffers from problems such as high dependence on operators, poor consistency in solder joint morphology, and unstable welding performance, which significantly impacts the subsequent antenna assembly effect and efficiency. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a high-temperature, close-pitch micro-through-hole laser welding method to solve one of the problems of high operator dependence, poor weld joint morphology consistency, and unstable welding performance in the prior art.

[0006] This invention discloses a laser welding method for welding closely spaced micro-through-hole weld joints at high temperatures, comprising the following steps:

[0007] S1: Select the appropriate solder based on the working environment of the solder joint, and estimate the solder volume based on the through-hole size of the pad on the printed circuit board;

[0008] S2: Determine the diameter and number of spray balls based on the estimated solder volume;

[0009] S3: Determine the segmented process based on the number of sprayed balls;

[0010] S4: Set the welding power, time, and gas pressure parameters in the process window of the laser ball spraying automatic welding equipment according to the determined segmented process;

[0011] S5: Adjust the distance between the nozzle and the welding pad, and the laser ball welding equipment will automatically complete the welding to obtain the final product.

[0012] Specifically, the estimated solder volume in step S1 is v is the solder volume, r1 is the radius of the through hole, h is the depth of the through hole, and r2 is the radius of the pad.

[0013] Specifically, the number of sub-process segments in the segmented process described in step S3 corresponds to the number of spray balls.

[0014] Specifically, in step S2, there are two spray balls, and the two spray balls have the same volume.

[0015] Specifically, the diameter of the pad is 0.5 mm, the diameter of the through hole is 0.35 mm, the depth of the through hole is 0.544 mm, and the diameter of the ball is 0.4 mm.

[0016] Specifically, the segmented process described in step S3 is as follows:

[0017] First spray ball: spray pressure: 3±0.5kPa; first stage welding power 90±10W, welding time 2±0.5ms; second stage welding power 30±10W, welding time 50±5ms;

[0018] Second spray ball: spray pressure: 2±0.5kPa; welding power: 30±10w; welding time: 10±2ms.

[0019] Specifically, the liquidus temperature of the solder is ≥300℃.

[0020] Preferably, the solder is Sn5Pb. 95 The liquidus temperature is 312℃.

[0021] Specifically, the distance between the soldering nozzle and the solder pad is 1 to 3 times the corresponding ball diameter.

[0022] Specifically, the diameter of the through-hole of the pad is 0.3 to 0.4 mm, and the center distance between adjacent pads is 0.8 to 1 mm.

[0023] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0024] 1. High-efficiency welding of micro-hole solder joints with close spacing at high temperatures was achieved, with excellent welding performance. By rationally selecting the diameter and number of spray balls, the total volume of the spray balls was matched with the capacity of the through-hole solder pads, resulting in good solder penetration and surface uniformity of the through-hole solder joints. By using a fiber laser and setting reasonable spray pressure, time, and segmented process curves corresponding to the number of spray balls, fast and efficient welding was achieved, with good weld morphology consistency, excellent welding performance, and fast welding response speed, enabling the welding of micro-holes with close spacing.

[0025] 2. Reduced reliance on manual labor. Laser welding uses fixed power, air pressure, and time to weld closely spaced micro-holes, effectively avoiding individual differences inherent in traditional manual welding, resulting in more consistent weld morphology.

[0026] 3. The welding process is highly efficient and fast, with a small heat-affected zone. In the past, it took about 2 seconds to weld a single point manually. Now, the time to weld a single point is controlled within 70ms, which effectively avoids heat damage to the solder pads, greatly reduces the risk of solder pads falling off and failing, and also provides effective protection for the solder points of the socket components.

[0027] 4. Laser welding uses a φ0.4mm micro-spot for irradiation, which can achieve continuous welding of closely spaced micro weld points without weld defects such as bridging, remelting, or spikes.

[0028] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0029] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0030] Figure 1 A schematic diagram of the process for laser welding of closely spaced micro-through holes at high temperatures;

[0031] Figure 2 This is a schematic diagram of a 100% tinned through-hole pad in Example 1;

[0032] Figure 3 This is a photograph of the initial state of the pads in Example 1;

[0033] Figure 4 Photograph of solder joints on the pad surface in Example 1;

[0034] Figure 5 This is a photograph of the solder pads on the back side in Example 1.

[0035] Figure 6 Metallographic image of the through-hole solder joint in Example 1;

[0036] Figure 7 Here is a SEM image of the through-hole solder joint in Example 1;

[0037] Figure 8 Photograph of solder joints on the pad surface in Comparative Example 1;

[0038] Figure 9 Photograph of solder joints on the pad surface in Comparative Example 2;

[0039] Figure 10 This is a photograph of the solder joints on the surface of the pads in Comparative Example 3. Detailed Implementation

[0040] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0041] This invention discloses a laser welding method for welding closely spaced micro-through-hole weld joints at high temperatures, comprising the following steps:

[0042] S1: Select the appropriate solder based on the working environment of the solder joint, and estimate the solder volume based on the through-hole size of the pad on the printed circuit board;

[0043] S2: Determine the diameter and number of spray balls based on the estimated solder volume;

[0044] S3: Determine the segmented process based on the number of sprayed balls;

[0045] S4: Set the welding power, time, and gas pressure parameters in the process window of the laser ball spraying automatic welding equipment according to the determined segmented process;

[0046] S5: Adjust the distance between the nozzle and the welding pad, and the laser ball welding equipment will automatically complete the welding to obtain the final product.

[0047] This invention achieves 100% tinning rate and fast response welding for through-hole pads by setting appropriate spray ball diameter, quantity, segmentation process, and welding parameters. While ensuring welding effect, it avoids thermal damage or even desoldering of the original solder joints attached to the through-hole components.

[0048] In step S1, the solidus of the selected solder must be 10°C higher than the working environment to prevent the solder joints from melting during operation and affecting reliability. The via dimensions refer to the pad diameter, via depth, and via diameter. The estimated solder volume is the sum of the surface solder joint volume and the volume of solder inside the via.

[0049] In step S2, the solder ball size and number are determined based on the estimated solder volume and a standard industry conversion table for solder ball size and mass. Currently, most equipment manufacturers support discrete solder ball sizes. Based on the approximate size range of standard parts in the application field of this invention, solder ball diameters of 0.25, 0.29, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, and 0.60 mm (unit: mm) are generally selected. The number of solder balls is then determined based on the estimated solder volume and the volume of a single solder ball.

[0050] Before starting the soldering process in step S4, a layer of flux should be applied to the surface of the solder pads (a standard industry practice). It is preferable to use a medium-activity rosin-based flux (RMA type) as specified in GB / T9491, which remains active above the solder solidus line.

[0051] Specifically, the estimated solder volume in step S1 is v is the solder volume, r1 is the radius of the through-hole, h is the depth of the through-hole, and r2 is the radius of the pad. The first part of the formula... The formula for calculating the volume of a through-hole is shown in the second half. The formula for calculating the volume of a hemisphere with a radius equal to the pad radius r² is used. This estimation formula serves as a preliminary estimate of the solder volume, thus eliminating the need for corrections for the volume occupied by the through-hole component and for solder joint morphology that is not a standard hemisphere. In reality, because the through-hole component occupies a portion of the through-hole volume, and the solder joint morphology is a spherical cap with a volume smaller than a standard hemisphere, this estimated solder volume is still excessive, even considering the small amount of solder passing through the printed circuit board. Experiments have verified that good soldering results can be achieved when the total volume of the sprayed balls (volume of a single sprayed ball * number of sprayed balls) is 75%–100% of the estimated solder volume.

[0052] Specifically, the number of sub-process segments in the segmented process corresponds to the number of spray balls. The number of sub-process segments is equal to the number of spray balls, and the process parameters for a single sub-process segment are closely related to the process objective to be achieved by the corresponding spray ball. For example, if the preset technical objective of a certain spray ball is to complete through-hole soldering, then the welding power in the parameter settings of that sub-process segment should ensure that the spray ball can fully melt and the ejected gas pressure is sufficient to enable the spray ball to complete through-hole soldering.

[0053] It is worth emphasizing that a single sub-process segment can contain multiple welding stages. For example, in Example 1, the sub-process segment corresponding to the initial solder ball spraying contains two welding stages, which respectively achieve the technical objectives of solder through-hole tinning and surface solder joint formation.

[0054] Preferably, the number of spray balls described in step S2 is 2, and the volumes of the 2 spray balls are equal. When determining the size and number of spray balls based on the through-hole diameter of the pad and the estimated solder volume, it is necessary to consider that the more the number of spray balls, the greater the thermal shock to the pad; while single-spray-ball soldering is likely to generate large air bubbles, resulting in poor solder penetration. Experiments have proved that when the number of laser spray balls is 2, the welding effect is optimal. The first sprayed spray ball completes the through-hole solder penetration, and the second sprayed spray ball forms the solder joint on the pad surface. In addition, according to the inherent characteristics of the solder cartridge and the solder spraying device of the laser spray ball welding related equipment, the spray ball size is a preset standard value, and the spray ball sizes ejected during the welding process are the same within the tolerance range, that is, spraying solder balls with different sizes is not supported during the rapid welding process.

[0055] Specifically, the diameter of the pad is 0.5 mm, the through-hole diameter of the pad is 0.3 - 0.4 mm. For example, the through-hole diameter is 0.35 mm, and the through-hole depth is 0.544 mm. According to the determined number of laser spray balls being 2, the spray ball diameter of 0.4 mm is obtained by querying the solder ball size-quality conversion table. That is, this spray ball diameter is obtained by querying the solder ball size-quality conversion table when the estimated solder volume and the number of spray balls are 2.

[0056] Specifically, the segmented process described in step S3 is as follows:

[0057] The first spray ball: ejection air pressure: 3 ± 0.5 kPa; primary welding power 90 ± 10 W, welding time 2 ± 0.5 ms; secondary welding power 30 ± 10 W, welding time 50 ± 5 ms;

[0058] The second spray ball: ejection air pressure: 2 ± 0.5 kPa; welding power 30 ± 10 W, welding time 10 ± 2 ms.

[0059] The spray ball air pressure refers to the pressure difference between the nitrogen gas filled into the pump head and the outside world, which is adjusted by the gas proportion valve supporting the pump head. This parameter controls the pressure difference between the inside and outside of the nozzle cavity during spray ball spraying, as well as the oxygen content of the gas around the nozzle. It has an impact on the spray ball landing accuracy, the oxidation degree of the solder joint surface, and the temperatures of the solder ball and the solder joint during welding. If the air pressure is too high, the spray ball position accuracy will be worse. In mild cases, the top of the solder joint will be beveled, and in severe cases, most of the spray ball will fall outside the pad area, resulting in the solder joint not forming at all. If the air pressure is too low, it can be observed that there is obvious firelight at the nozzle during spray ball spraying, serious dust accumulation, the oxidation layer on the solder joint surface becomes thicker, and even cracks appear on the solder joint surface. After testing, when the ejection air pressure of the first spray ball is within the range of 3 ± 0.5 kPa, sufficient solder penetration can be achieved while taking into account the landing accuracy; for the second spray ball, since it does not need to pass through the through-hole, the ejection air pressure within the range of 2 ± 0.5 kPa is sufficient.

[0060] Excessive power and prolonged soldering time can lead to excessive heat on the solder joints, causing overheating, damage to the adhesive layer between the solder pad and the substrate, and even solder pad detachment. Additionally, excessive solder penetration results in insufficient solder on the front side, poor appearance, and heat damage or even solder joint breakage at the soldering end. Conversely, insufficient power and short time result in insufficient heat, inadequate solder penetration, incomplete melting of the solder ball during ejection, sticking to the nozzle, and causing the solder joint surface to become pointed, resulting in poor wettability and a short solder joint. Testing showed that the following process parameters achieved high-quality soldering for the first ball ejection: a first-stage soldering power of 90±10W and a soldering time of 2±0.5ms; a second-stage soldering power of 30±10W and a soldering time of 50±5ms; and a second ball ejection with a soldering power of 30±10W and a soldering time of 10±2ms.

[0061] The first section of the ball-spraying process involves welding to melt the solder and ensure it penetrates the tin completely. Therefore, the welding power is relatively high. On the other hand, to prevent thermal damage to the material, the welding time is strictly controlled to around 2ms.

[0062] This invention overcomes the problems of large heat source area, unstable welding performance, and poor weld morphology consistency associated with manual welding by setting a segmented process (corresponding to step S3) that gradually reduces welding power, ejection gas pressure, and time, and by using an automated laser ball welding device. Specifically, the solder liquidus temperature is ≥300℃. This method can be widely applied to the welding and assembly of dual-polarized antenna components. For example, such antennas need to operate in a high-temperature environment of around 280℃, and the printed circuit board requires high-density welding of various electronic components. Therefore, it is necessary to select solder with a liquidus temperature of not less than 300℃ for welding to avoid problems such as solder joint melting under operating conditions.

[0063] Preferably, the solder is Sn5Pb. 95 Its liquidus temperature is 312℃. This type of solder has stronger solderability than other high-temperature solders, better solder joint wettability, and is beneficial for subsequent metallographic and SEM analysis.

[0064] Specifically, the distance between the welding nozzle and the pad is 1 to 3 times the corresponding laser ball diameter, preferably 2 times the laser ball diameter. The distance between the welding nozzle and the pad is set according to industry standards, ensuring the stability of the welding effect.

[0065] Specifically, the diameter of the via on the pad is 0.3–0.4 mm, and the center-to-center distance between adjacent pads is 0.8–1 mm. For example, the via diameter can be 0.31 mm, 0.32 mm, 0.33 mm, 0.34 mm, 0.35 mm, 0.36 mm, 0.37 mm, 0.38 mm, or 0.39 mm; the center-to-center distance between adjacent pads on the printed circuit board can be 0.85 mm, 0.90 mm, or 0.95 mm. This via diameter and pad center-to-center distance are preset by the designer before the printed circuit board is manufactured, based on electrical performance requirements.

[0066] Specific embodiments and comparative examples:

[0067] The standard parameters of the laser automatic welding equipment used in all the following embodiments and comparative examples are shown in Table 1:

[0068] Table 1. Standard parameters of laser automatic welding equipment

[0069]

[0070]

[0071] Example 1:

[0072] Step 1: For the dual-polarized antenna operating environment of 300℃, select Sn5Pb solder alloy composition. 95 The liquidus temperature is 312℃.

[0073] Step 2: The pad diameter is 0.5mm, the pad thickness is 18μm, the through hole diameter is 0.35mm, the through hole depth is 0.544mm (the through hole depth is the sum of the printed circuit board thickness and the pad thickness, and the printed circuit board thickness is 0.526mm), and the center distance between adjacent pad holes is 0.8mm.

[0074] like Figure 2 As shown, the estimated solder volume after 100% tinning can be estimated as 0.085mm. 3 .

[0075] Step 3, estimate the solder volume as 0.085mm. 3 It can spray three 0.35mm diameter balls, two 0.4mm diameter balls, or one 0.5mm diameter ball. Experiments showed that the more balls sprayed, the greater the thermal shock to the pad, and a single ball is prone to generating large bubbles, leading to poor solder adhesion. Ultimately, spraying two 0.4mm diameter balls was selected as the preferred method for single-hole pad soldering. Figure 5 As shown, the first solder ball completes the solder penetration through the via, and the second solder ball completes the solder joint morphology on the pad surface. This ensures consistent solder joint morphology and guarantees that the solder ball quality deviation is less than 1%.

[0076] Step four: Fix the printed circuit board to the special fixture and mount it onto the welding equipment. The round copper wires to be welded must be trimmed flush with the solder pads before welding.

[0077] Step 5: Set the ball-spraying welding parameters as shown in Table 2. The welding power process window is ±10W. A 150W fiber laser is used for laser welding.

[0078] Table 2 Welding process parameters

[0079]

[0080] Step six: Adjust the distance between the nozzle and the pad. The nozzle height from the pad is generally 1 to 3 solder ball diameters. In this embodiment, the distance between the nozzle and the pad is set to 2 solder ball diameters, or 0.8 mm.

[0081] Step 7: Perform laser ball welding on the closely spaced micro-through hole weld points according to the above process.

[0082] Solder joint morphology as follows Figure 5 and Figure 6 As shown, in accordance with IPC-TM-650 and GB / T 16594-2008, a professional testing institution was commissioned to conduct metallographic microscopy observation of the solder joints and SEM to measure the thickness of the IMC. The inspected solder joints showed no abnormalities such as non-wetting or cracking. The tin-lead two-phase distribution and diffusion were uniform, and the solder filling degree within the through-holes was 100%. The SEM images showed obvious IMC formation between the round copper wires and the printed circuit board pads. The IMC layer formed a tin-silver alloy on the round copper wire side and a tin-copper alloy on the pad side, with an IMC thickness of 1-2 μm and a uniform morphology. This analysis verifies that the solder joint quality is qualified, and the morphology of continuous solder joints is highly consistent, significantly improving the production capacity of this type of antenna.

[0083] The solder joints have good wetting, with a wetting angle of no more than 90 degrees. When observed under 100x magnification using a microscopic inspection device (capable of 360-degree inspection), there are no defects such as pinholes or spikes. The height difference between solder joints is no more than 0.2 mm, and there are no bridging or slag between solder joints.

[0084] Example 2:

[0085] The power and time for the first solder ball soldering are set as follows:

[0086] First stage: 80W / 2ms; Second stage: 20W / 50ms, the remaining steps and parameter settings are the same as in Example 1. The solder joint morphology is qualified, and the amount of solder on the bottom is slightly less than in Example 1.

[0087] Example 3:

[0088] The ejection pressure of the second solder ball was set to 2.5 kPa, and the remaining steps and parameter settings were the same as in Example 1. The solder joint morphology was acceptable. Because the second solder ball mainly affected the external solder joint, the ejection pressure increased, resulting in a slightly flattened top and a wetting angle close to 90 degrees.

[0089] Comparative Example 1:

[0090] The laser power corresponding to the first solder ball was increased to 120W, while other parameters and operations remained exactly the same as in Example 1. Figure 8 As shown, due to excessive power, the solder pads lifted, and the solder joint failed.

[0091] Comparative Example 2:

[0092] Using 3 φ0.35mm solder balls, the soldering process curve is set as follows:

[0093] First solder ball: Air pressure 3kPa, soldering power and time, first stage: 90W / 2ms; second stage: 30W / 50ms;

[0094] Second solder ball: ejected air pressure 2kPa, soldering power 30W, soldering time 10ms;

[0095] The third solder ball: air pressure 2 kPa, welding power 30 W, welding time 10 ms.

[0096] Other parameters and operations are exactly the same as in Example 1. Figure 9 As shown, since the amount of solder is equivalent to that of two φ0.4mm solder balls, the solder joint morphology is similar. However, due to the three solder balls, the soldering time is longer, resulting in greater thermal shock to the pads and a significant increase in the proportion of pad detachment. Moreover, due to the small diameter of the solder balls, the solder joints cannot cover the outer edge of the pads.

[0097] Comparative Example 3:

[0098] Using a φ0.5mm solder ball, the ejection pressure is 3kPa. The soldering power and time are: first stage: 90W / 2ms; second stage: 30W / 60ms. Other parameters and operations are exactly the same as in Example 1.

[0099] The volume of one φ0.5mm solder ball is equivalent to that of two φ0.4mm solder balls, but the solder joint with one φ0.5mm solder ball has a higher proportion of voids. For example... Figure 10 As shown, large pores are easily generated on the surface of the weld joint, or large bubbles are formed due to incomplete gas release during the welding process. Such weld joints are prone to rupture of bubbles on the surface after temperature changes and vibration impacts, resulting in unqualified weld joint quality.

[0100] Comparative Example 4:

[0101] Three φ0.4mm solder balls are used, and the specific process parameters are set as follows:

[0102] First solder ball: Air pressure 3kPa, soldering power and time, first stage: 90W / 2ms; second stage: 30W / 50ms;

[0103] The second solder ball: the ejection pressure is 2 kPa, and the soldering power and time are 30 W / 10 ms;

[0104] The third solder ball: the ejection pressure is 2 kPa, and the soldering power and time are 30 W / 10 ms.

[0105] Other parameters and operations are exactly the same as in Example 1. The three φ0.4mm solder balls are too large, the wetting angle of the solder joint is greater than 90 degrees, and due to the large volume of solder, bridging between solder joints is easy to form. In addition, due to the long heating process, the solder pads are easy to fall off, and the solder joints are unqualified.

[0106] Comparative Example 5:

[0107] Except for the laser power of the second solder ball being reduced to 10W, the other parameters and operations were exactly the same as in Example 1. The solder joint surface of this comparative example had poor wetting, was not smooth, had some under-soldering, and was of poor quality and unqualified.

[0108] This invention preferably uses two solder balls (spray balls) for through-hole soldering. The first solder ball primarily fills the interior of the through-hole and tins the non-soldering surfaces, with the solder level of the first ball essentially flush with the pad surface. The second ball shapes the solder joint morphology on the pad surface. Microscopic and metallographic examinations revealed no damage to the pad structure. The total solder volume should be commensurate with the pad and through-hole capacity. Excessive volume can lead to a wetting angle greater than 90 degrees and inadequate bridging between solder joints. Insufficient volume results in incomplete solder coverage of the pad or insufficient tinning on the non-soldering surfaces. With laser power, time, and gas pressure within the range specified in this invention, and with a suitable solder volume, the solder joint yield can be significantly improved, meeting production requirements.

[0109] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A laser welding method for welding closely spaced micro-through holes at high temperatures, characterized in that, Includes the following steps: S1: Select the appropriate solder based on the working environment of the solder joint, and estimate the solder volume based on the through-hole size of the pad on the printed circuit board; S2: Determine the diameter and number of spray balls based on the estimated solder volume; the number of spray balls is 2 and the 2 spray balls have equal volumes; S3: Determine the segmentation process based on the number of sprayed balls; the segmentation process is as follows: First spray ball: spray pressure: 3±0.5kPa; first stage welding power 90±10W, welding time 2±0.5ms; second stage welding power 30±10W, welding time 50±5ms; Second spray ball: spray pressure: 2±0.5kPa; welding power: 30±10w; welding time: 10±2ms; S4: Set the welding power, time, and gas pressure parameters in the process window of the laser ball spraying automatic welding equipment according to the determined segmented process; S5: Adjust the distance between the nozzle and the welding pad, and the laser ball welding equipment will automatically complete the welding to obtain the final product; The diameter of the pad is 0.5 mm, the diameter of the through hole is 0.35 mm, the depth of the through hole is 0.544 mm, and the diameter of the spray ball is 0.4 mm.

2. The laser welding method according to claim 1, characterized in that: The estimated solder volume in step S1 is , For solder volume, The radius of the through-hole is the pad. The depth of the through hole. Where is the radius of the solder pad.

3. The laser welding method according to claim 1, characterized in that: The number of sub-process segments in the segmented process corresponds to the number of spray balls.

4. The laser welding method according to claim 1, characterized in that: The solder liquidus temperature is ≥300℃.

5. The laser welding method according to claim 1, characterized in that: The solder is Sn5Pb. 95 .

6. The laser welding method according to claim 1, characterized in that: The distance between the nozzle and the pad is 1 to 3 times the corresponding diameter of the spray ball.

7. The laser welding method according to claim 1, characterized in that: The diameter of the through-hole of the pad is 0.3-0.4 mm, and the center distance between adjacent pads is 0.8-1 mm.

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