Automatic welding process for rigid-flexible combined part

Abstract

The invention relates to the technical field of automatic welding processes, in particular to an automatic welding process for a rigid-flexible combined component, which can be applied to welding of connector pins in the rigid-flexible combined component and comprises the following steps of: feeding a rigid-flexible combined component carrier; the carrier flows to a spraying station, and scaling powder spraying operation is conducted on the welding area; preheating is conducted; and after preheating is completed, transferring to a welding station, and carrying out automatic pin welding. The welding quality of the rigid-flexible combined part can be greatly improved, manual welding is avoided, the welding consistency is guaranteed, the production efficiency is further improved, and the labor cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of automatic welding technology, and is an automatic welding technology for rigid-flexible combination components. The automatic welding technology can be applied to the welding of connector pins in the rigid-flexible combination components. Background Art

[0002] With the development of lightweight, precision and modularization of electronic complete products, the filling density and precision requirements of products are getting higher and higher, the difficulty of mechatronic assembly is also increasing, and the problems of assembly consistency and reliability are becoming more and more prominent. Cables, as an important component inside the chassis, are subject to more and more constraints. Traditional cables are mainly composed of wires, connectors and other materials. Their weight and space occupy a considerable proportion of the whole machine. In addition, the failure rate of traditional cables is quite high, and disconnection and short circuit are common. They have gradually been replaced by rigid-flexible components (Note: modular components composed of rigid-flexible boards and mechanical structure panels), which greatly improves assembly efficiency, reduces weight, and fully utilizes the internal space, making them neat and beautiful, which is conducive to mass production.

[0003] Rigid-flexible components have become important components of the equipment's external interface, and it is particularly important to ensure the stability and reliability of their electrical interconnection. In order to prevent the connector solder joints on the rigid-flexible components from being affected by assembly stress during the assembly process, the connector is first fixed to the structural parts according to the principle of first installation and then welding, and then the printed circuit board is installed to form a rigid-flexible component, which is finally welded. The entire process is done manually, and manual welding has problems such as poor consistency, low efficiency, and easy to cause welding defects such as pull tips, bridging, insufficient solder, and excessive solder, resulting in low pass rates, and cannot meet mass production requirements. Summary of the invention

[0004] In order to overcome the above-mentioned deficiencies in the prior art, the present invention aims to provide an automatic welding process for rigid-flexible combined components, comprising the following steps:

[0005] Step 1: Feeding the rigid-flexible component carrier;

[0006] Step 2: The carrier is transferred to the spraying station to spray flux on the welding area;

[0007] Step 3: preheating;

[0008] Step 4: The track flows to the welding station for automatic pin welding.

[0009] Furthermore, in step one, a pallet-type carrier is selected to clamp rigid-flexible components of different sizes, and the carrier is made of alloy stone material.

[0010] Furthermore, in step 2, the flux spraying operation adopts a spray method, and the flux spraying amount is determined by an orthogonal test method.

[0011] Furthermore, the orthogonal test method is used to determine the flux spraying amount, specifically including: taking the flux spraying amount as a variable, welding temperature and welding time as quantitative factors, performing post-welding analysis, analyzing the influence of the flux spraying amount on welding quality, and determining a suitable flux spraying amount.

[0012] Furthermore, the flux spraying amount is set to 25% to 40%.

[0013] Furthermore, in step three, the preheating temperature is set to 120° C. and the preheating time is set to 60 s.

[0014] Furthermore, step 4 also includes the following steps:

[0015] Step 4.1, set the equipment parameters, including setting the nozzle diameter, setting the nozzle height, setting the welding height, setting the welding wave peak, setting the tin collection height and setting the tin collection time;

[0016] Step 4.2, set welding parameters, including setting welding mode, setting welding area, setting welding temperature and welding time.

[0017] Further, in step 4.1, the nozzle diameter is set to φ+2mm, where φ is the diameter of the welding area; the nozzle height is set to -H, where H is the thickness of the rigid-flexible component; the welding height is set to 3mm; for ordinary pin solder joints, the welding wave peak is set to 70%×3mm~90%×3mm; for typical solder joints of large-area copper-clad layers and ground pin solder joints, the welding wave peak is set to 95%×3mm; the tinning height is set to 10%×3mm; and the tinning time is set to 1s;

[0018] In step 4.2, set the welding to be performed by drag soldering or spot soldering; set the welding area to the maximum length × width of the rigid-flexible component; according to the different pin sizes and spacings of different plug-in devices, keep the nozzle specifications and welding methods as constants, take the flux spraying amount as a constant, and take the welding temperature and welding time as variables. Define each variable parameter at a high and low level, that is, define the parameter as "minimum value", "median value" and "maximum value", and use another item as a quantitative value for post-welding analysis to obtain the influence of parameter changes in welding temperature and welding time on welding quality, and obtain the welding temperature and welding time.

[0019] Furthermore, in step 4.2, the welding temperature is set to 280° C. to 300° C., and the welding time is set to 3s to 5s.

[0020] Furthermore, in step 4.2, the welding temperature is set to 300° C. and the welding time is set to 4 s.

[0021] The present invention is an efficient welding process applicable to the welding of connector pins in rigid-flexible components. The present invention has the following beneficial effects: the automatic welding method of rigid-flexible components can avoid welding defects such as pull-point, bridge, insufficient solder, and excessive solder during manual welding. The local spraying of flux and preheating method are adopted to better stimulate the activation of flux, avoid the stress of rigid-flexible components caused by rapid temperature rise during welding, and further improve the welding quality. The automatic welding process of the present invention welds rigid-flexible components, effectively ensures the welding consistency and qualified rate of rigid-flexible components, and improves production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the process of the present invention;

[0023] Figure 2 This is the production line diagram of automatic welding equipment;

[0024] Figure 3 Schematic diagram of the rigid-flexible combination component in the present invention, wherein: Figure 3 (a) is the front view of the rigid-flexible component. Figure 3 (b) is a side view of the rigid-flexible component;

[0025] Figure 4 This is a trend chart of tin penetration rate for 9 groups of orthogonal test welding parameters. DETAILED DESCRIPTION

[0026] In order to better understand the purpose, technical solution and function of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings, but the present invention can be implemented in a variety of different ways as defined and covered by the claims. The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0027] like Figure 1 As shown, in a specific embodiment of the present invention, the following steps are included:

[0028] Step 1: Feed the rigid-flexible component carrier.

[0029] Specifically, the design style belongs to the tray type carrier used to clamp rigid-flexible components of different sizes (length × width × height). Because the size of each rigid-flexible component is quite different, it is designed as an adjustable universal carrier. The designed universal carrier meets the following three points:

[0030] a) The rigid-flexible components can be quickly assembled and disassembled from the carrier. The carrier can meet the needs of various sizes of rigid-flexible components. One side of the carrier is designed as a movable beam, and butterfly nuts are used as adjustment mechanisms. Spring pressure plates are installed around the carrier for quick assembly and disassembly of rigid-flexible components, which meets the needs of repeated use and mass production and improves the production efficiency of the welding process.

[0031] b) The carrier must ensure that the rigid-flexible components are level and flat, so that the welding surface height is consistent, which can meet the requirements of automatic welding, precise control of welding height and welding.

[0032] c) The carrier material is made of alloy stone, which can avoid panel scratches, poor heat absorption performance, high temperature resistance, not easy to deform and high cost performance.

[0033] Step 2: The carrier is transferred to the spraying station to spray flux on the welding area.

[0034] The control of flux spraying amount has a significant impact on the solderability of the solder joints of the aviation plug-in board components. A small amount of spraying is prone to defects such as pull tips and bridges. Too much flux will cause residual flux on the PCB surface to corrode the substrate. Specifically, the spray method is used to better control the amount of flux. The amount of flux is generally 25% to 40%, and the amount of flux is divided into three amounts of 25%, 30% and 40%, which is 25%, 30% and 40% of the one-time spray amount of the nozzle.

[0035] Through the orthogonal test method, the amount of flux is used as a variable, and the welding temperature and welding time are used as quantities. Post-welding analysis is performed to analyze the effect of flux amount on welding quality and determine the optimal flux coating amount for rigid-flexible components.

[0036] Step 3: Preheat.

[0037] Since automatic welding is local welding, the PCB board is directly welded without preheating. Rapid temperature rise will produce thermal stress, resulting in defects such as poor welding quality and easy deformation of the board. Preheating also helps to activate the flux. Therefore, the preheating process is an indispensable process. According to the recommended PCB preheating process parameters: 110-130℃, the surface temperature of the PCB board (85-100℃) is measured with a thermocouple (temperature recorder). This test sets different preheating temperatures of 110℃, 120℃, and 130℃, and preheats for 2min. The temperature is detected on the aviation plug-in board. The specific test results are shown in Table 1. The temperatures of 120℃ and 130℃ both meet the preheating time. Excessive preheating temperature may weaken the effect of the flux, so the preheating temperature is selected as 120℃. The temperature on the board can reach the preheating value after preheating for 1min. After reaching the value, the temperature is basically stable, and the preheating time can be set to 60s; the verification results determine that the preheating temperature is 120℃ and the preheating time is 60s.

[0038] Table 1 Preheating temperature test results

[0039]

[0040]

[0041] Step 4: The track flows to the welding station for automatic pin welding.

[0042] Set the process parameters. The process parameters are divided into two categories: equipment parameters (including nozzle model, nozzle height, tin collection height and tin collection time) and welding parameters (variables affecting welding parameters include flux spraying amount, welding temperature, and welding time).

[0043] 4.1 Set equipment parameters: Equipment parameters include nozzle specifications, nozzle height, tin collection height and time. Use the default parameters of the equipment for verification. During the verification process, it is found that the following equipment parameters need to be adjusted:

[0044] 4.1.1 Specifications of soldering nozzles: The automatic soldering equipment is equipped with a set of standard soldering nozzles as shown in Table 2. The inner diameter of the soldering nozzle directly determines the diameter of the tin column, thereby determining the size of the spot welding area. The selection of soldering nozzles should take into account the following points:

[0045] Table 2 Welding nozzle specifications

[0046]

[0047] a) The larger the diameter of the soldering nozzle, the greater the heat capacity, the higher the stability of the tin column, and the excess tin slag will not block the inner wall of the soldering nozzle, ensuring the smooth flow of solder and better avoiding defects such as solder joint tipping and bridging.

[0048] b) When choosing a welding nozzle, you should consider its compatibility as much as possible. Use one welding nozzle for welding a certain aviation plug-in board. Changing the welding nozzle will affect the efficiency.

[0049] c) The selection of the soldering nozzle must also ensure a safe distance from adjacent devices (≥2mm), that is, the outer diameter of the soldering nozzle must also ensure a safe distance from adjacent devices (≥2mm) during soldering; if there are no surface-mount devices around the welding area, the soldering nozzle model with the largest connector can be selected for spot welding.

[0050] d) According to the welding area φ of the connector, the inner diameter of the solder nozzle is selected to be φ+2mm to ensure that there is no leakage of solder joints around the connector. If there are no devices around the connector (that is, without considering the safety distance), select the solder nozzle of the largest connector of the product.

[0051] 4.1.2 Welding nozzle height: The default height 0 point of the equipment is the track chain surface. For printed circuit boards, since the track chain surface and the printed circuit board surface coincide, the height reference point provided by the equipment can be used without adjusting the welding nozzle height value; however, since the rigid-flexible component welding has structural parts, and the surface of the structural parts coincides with the track chain surface, the welding surface of the rigid-flexible component is lower than the track surface. After using the height reference point provided by the equipment, there will be interference between the welding nozzle and the product. The welding nozzle height value needs to be adjusted. The adjusted value is the distance h from the rigid-flexible component to the track overlap surface to the aviation plug board surface, which is equal to the thickness H of the rigid-flexible component. After adding the distance h to the equipment height reference point, welding verification was performed, and no interference or welding failure occurred.

[0052] 4.1.3 Tinning height and tinning time: To ensure that the solder joints are not bridged or pointed after welding, the parameters of tinning height and tinning time should be set for the soldering nozzle after welding. For drag soldering, if the tinning is performed outside the solder joint, the default values ​​of the equipment can be used. For tinning on the solder joint, the default values ​​(tinning height 1mm, tinning time 1s) are used. It was found in the experiment that for pins that are densely packed (spacing = 2.15) and the length of the pins above the board surface is greater than 1mm, different degrees of tinning and tipping will occur after welding. Analysis shows that since the pins are too long above the board surface, the default tinning height of 1mm is less than the pin height, resulting in continuous welding at the pin ends. In addition, the dense pins lead to tinning. By adjusting the tinning time from 1s to 0.5s, the tinning height is increased from 1mm to 2mm, solving the problems of bridging and tipping.

[0053] 4.2 Set welding parameters.

[0054] The main parameters that affect welding quality are welding temperature, welding time and flux dosage. According to the different pin sizes and spacings of different plug-in devices, the nozzle specifications and welding methods are kept as constants, and the welding temperature, welding time and flux dosage are used as variables. Each variable parameter is defined at high and low levels, and the parameters are defined as "minimum value", "median value" and "maximum value". The remaining two items are used as quantitative analysis after welding to analyze the influence of changes in welding temperature, welding time and flux dosage parameters on welding quality, improve the tin filling rate of through-hole solder joints, and obtain the optimal process parameters for automatic welding through this orthogonal test method.

[0055] In this step, only the welding temperature and welding time are analyzed and set. The amount of flux (spraying amount) has been determined and set in the same way as before.

[0056] 4.2.1 Welding methods: There are two main welding methods: drag welding and spot welding.

[0057] a) Drag soldering: The drag soldering process is completed on a single small solder nozzle solder wave. It is suitable for soldering in very tight spaces. However, the heat required to form a weld connection is transferred by the solder wave, but the solder wave of a single solder nozzle has a small mass. Only when the temperature of the solder wave is relatively high can the requirements of the drag soldering process be met. The disadvantage is that the welding time is the longest among the three processes of flux spraying, preheating and welding. And because the solder joints are drag soldered one by one, as the number of solder joints increases, the welding time will increase significantly, and the welding efficiency cannot be compared with the traditional wave soldering process.

[0058] b) Spot welding: For devices with a small safety distance between components, or devices with a small number of pins and a long distance, dip soldering can be used for welding. In addition, spot welding can be used for soldering points that are difficult to penetrate with tin and have a copper layer in the middle of the device pins.

[0059] Comparing the above two welding methods, combined with the characteristics of rigid-flexible components, due to the small number of pins and the long distance between the pins of module devices, and the difficulty of tin penetration due to the connection of individual pins of the device to the large area of ​​copper layer, spot welding is preferred.

[0060] 4.2.2 Welding process parameters

[0061] Through the above analysis, the decision is based on three factors: flux spraying amount, welding temperature, and welding time. By studying the typical solder joint process parameters of selective wave soldering, it is determined that the flux spraying amount should be controlled at 25% to 40%, the welding temperature at 250℃ to 300℃, and the welding time at 2s to 4s. The setting factor level table is shown in Table 3:

[0062] Table 3 Factor level table

[0063]

[0064] 4.2.3 Design of experimental plan

[0065] The L9(33) orthogonal table is used to arrange the orthogonal experiment, as shown in Table 4:

[0066] Table 4 Orthogonal test parameter ranking table

[0067]

[0068] Theoretically, the greater the amount of flux sprayed, the higher the welding temperature, and the longer the welding time, the better the corresponding welding effect. Therefore, firstly, the group with the worst test effect in theory (i.e., group 1 in Table 4) and the group with the best test effect (i.e., group 8 in Table 4) are compared. The image of the tin penetration rate of the through-hole solder joint is observed under X-RAY; in addition to the tin penetration rate, the quality of the solder joint also has surface quality requirements, and bridging and insufficient solder are not allowed.

[0069] By examining the tin penetration rate and solder joint appearance quality, it was found that when the flux dosage was 25% or 30%, solder shortage occurred to varying degrees regardless of the welding temperature, and the severity was relatively less with longer welding time. The results of the 9 parameters were filled in the table to obtain Table 5.

[0070] Table 5 Orthogonal test welding parameters

[0071]

[0072] 4.2.4 Analysis of test results

[0073] First, the greater the amount of flux sprayed, the higher the preheating temperature, the higher the welding temperature, and the longer the welding time, the better the corresponding welding effect. Through metallographic section analysis, the solder joint has excellent filling performance (no pores, inclusions and other welding defects), and a good metallurgical bond is formed between the solder and the pin, and between the solder and the pad hole, indicating the reliability of welding under this parameter condition. On the contrary, under the worst test effect parameter condition, the solder did not wet the metallized hole 100%, there was a welding void defect, and the welding reliability was poor.

[0074] a) Since there are two types of pins: thick pins and thin pins, the above uses thick pins, and the following is an exploration of the welding parameters of thin pins. It is found that the lowest conditions can meet the welding requirements, that is, the welding parameter group of low welding temperature, small amount of flux spraying, low preheating temperature, and short welding time.

[0075] b) For large-area copper cladding points, according to the test results of the aforementioned plug-in connector pin welding, the quality of the solder joints was explored and analyzed by considering the two main factors of welding temperature and flux spraying amount during welding.

[0076] Under the parameters of the maximum temperature and the maximum amount of flux sprayed within the selected range, the tin penetration rate of the through hole reaches 100%. Keeping other parameters unchanged, only changing the amount of flux sprayed does not have a great impact on the welding quality. If other parameters are kept unchanged, only changing the welding temperature can obviously show poor welding quality.

[0077] c) For the nickel-plated grounding solder pins, since the nickel-plated grounding solder pins are connected to the shell, they will dissipate heat. Therefore, based on the above results and the typical characteristics of this solder joint, the main focus is on exploring the effect of welding temperature on it. Two sets of experiments were designed respectively, keeping other variable parameters unchanged and changing the effect of its welding temperature on it. It can be seen that the higher the temperature, the better the tin penetration rate. Therefore, when welding such nickel-plated grounding solder pins, try to choose parameters with a high welding temperature within a certain range.

[0078] In summary, within a certain parameter range, welding can be divided into three situations: for ordinary solder joints with pins of φ0.6mm, the parameter group with lower welding temperature, less flux spraying amount, lower preheating temperature and shorter welding time (speed) is generally selected; the welding quality of large-area copper-clad solder joints and nickel-plated grounding solder joints with pins of >φ1.2mm generally depends on the welding temperature during welding, and the parameter group with the highest welding temperature is generally selected.

[0079] Directly comparing the tin penetration rates of the 9 tests, it can be seen that the 8th test group has the best effect, with a tin penetration rate of 100% and a round and full solder joint, and its process conditions are A3B2C3. In the 3rd and 6th tests, although the tin penetration rate can reach 100%, the appearance quality of the solder joint is unqualified.

[0080] From the sum of the three-time tin penetration rates of the bit level (the larger the better), it can be calculated that the best process conditions should be A3B3C3.

[0081] The influence of each factor on the result: It can be seen from the range R that the influence of each factor on the tin penetration rate is: C>B>A. Draw a trend chart, such as Figure 4 shown.

[0082] The orthogonal test verified that the best process combination is A3B3C3, that is, the preheating temperature is 120℃, the preheating time is 60s; the flux coating amount is 40%; the welding temperature is 300℃, and the welding time is 4s.

[0083] Based on the process parameters and the characteristics of rigid-flexible component products, the optimal reference table of automatic welding parameters is finally obtained as shown in Table 6.

[0084] Table 6 Automatic welding parameter reference table

[0085]

[0086] By verifying the final welding process parameters, the appearance quality of the solder joints was inspected in accordance with QJ 3011A-2016 "General Technical Requirements for Welding of Aerospace Electronic and Electrical Products". No defects such as bridging and pulling tips were found in the solder joints of the samples.

[0087] a) Tin penetration rate: After welding, the tin penetration rate is detected by X-Ray. The following is an X-Ray inspection photo of the connector pin after welding. The solder joint has a good tin penetration rate (100%) and there is no air hole inside the solder joint.

[0088] b) Metallographic analysis: Metallographic sectioning was performed and the bonding between the solder and the pin metallization layer was observed under an electron microscope. It was found that the solder and the metallization layer of the component pin were well bonded without any microcracks. The quality of the solder joints could meet the standard requirements.

[0089] The present invention improves welding quality by locally spraying flux and preheating the bottom to activate the activity of the flux. The automatic welding station improves welding quality, efficiency and consistency by effectively setting welding temperature and welding time parameters, thereby ensuring the reliability and stability of the product electrical interconnection transmission signal.

[0090] In order to realize automatic welding of rigid-flexible components, ensure the quality of the solder joints of the rigid-flexible components, avoid defects such as solder joint tipping, bridging, pores, cracks, etc., the present invention sets the carrier, flux spraying, preheating and welding parameters, and accurately controls the quality of each solder joint to achieve the best welding effect of each solder joint.

[0091] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. An automatic welding process for rigid-flexible components, characterized in that: The steps include: Step 1: Feeding the rigid-flexible component carrier; Step 2: The carrier is transferred to the spraying station to spray flux on the welding area; Step 3: preheating; Step 4: The track flows to the welding station for automatic pin welding.

2. The automatic welding process for rigid-flexible components according to claim 1, characterized in that: In step one, a pallet-type carrier is selected to clamp rigid-flexible components of different sizes, and the carrier is made of alloy stone material.

3. The automatic welding process for rigid-flexible components according to claim 1, characterized in that: In step 2, the soldering flux spraying operation adopts a spray method, and the amount of soldering flux spraying is determined by an orthogonal test method.

4. The automatic welding process for rigid-flexible components according to claim 3, characterized in that: The orthogonal test method is used to determine the flux spraying amount, specifically including: taking the flux spraying amount as a variable, welding temperature and welding time as quantitative, performing post-welding analysis, analyzing the influence of the flux spraying amount on welding quality, and determining a suitable flux spraying amount.

5. The automatic welding process for rigid-flexible components according to claim 4, characterized in that: Set the flux spraying amount to 25% to 40%.

6. The automatic welding process for rigid-flexible components according to claim 1, characterized in that: In step 3, the preheating temperature is set to 120°C and the preheating time is set to 60s.

7. The automatic welding process for rigid-flexible components according to claim 1, characterized in that: Step 4 also includes the following steps: Step 4.1, set the equipment parameters, including setting the nozzle diameter, setting the nozzle height, setting the welding height, setting the welding wave peak, setting the tin collection height and setting the tin collection time; Step 4.2, set welding parameters, including setting welding mode, setting welding area, setting welding temperature and welding time.

8. The automatic welding process for rigid-flexible components according to claim 7, characterized in that: In step 4.1, set the nozzle diameter to φ+2mm, where φ is the diameter of the welding area; set the nozzle height to -H, where H is the thickness of the rigid-flexible component; set the welding height to 3mm; for ordinary pin solder joints, set the welding wave peak to 70%×3mm~90%×3mm; for typical solder joints of large-area copper-clad layers and ground pin solder joints, set the welding wave peak to 95%×3mm; set the tinning height to 10%×3mm; set the tinning time to 1s; In step 4.2, set the welding to be performed by drag welding or spot welding; set the welding area to the maximum length × width of the rigid-flexible component; according to the different pin sizes and spacings of different plug-in devices, keep the nozzle specifications and welding methods as constants, take the flux spraying amount as a constant, and take the welding temperature and welding time as variables. Define each variable parameter at a high and low level, that is, define the parameter as "minimum value", "median value" and "maximum value", and use another item as a quantitative item for post-welding analysis to obtain the influence of parameter changes in welding temperature and welding time on welding quality, and obtain the welding temperature and welding time.

9. The automatic welding process for rigid-flexible components according to claim 8, characterized in that: In step 4.2, set the welding temperature to 280°C to 300°C and the welding time to 3s to 5s.

10. The automatic welding process for rigid-flexible components according to claim 9, characterized in that: In step 4.2, set the welding temperature to 300°C and the welding time to 4s.

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