CN110961751B - Laser welding tinning device and welding method - Google Patents
Laser welding tinning device and welding method Download PDFInfo
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- CN110961751B CN110961751B CN201911256278.4A CN201911256278A CN110961751B CN 110961751 B CN110961751 B CN 110961751B CN 201911256278 A CN201911256278 A CN 201911256278A CN 110961751 B CN110961751 B CN 110961751B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K3/00—Tools, devices, or special appurtenances for soldering, e.g. brazing, or unsoldering, not specially adapted for particular methods
- B23K3/06—Solder feeding devices; Solder melting pans
- B23K3/0607—Solder feeding devices
- B23K3/063—Solder feeding devices for wire feeding
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K1/00—Soldering, e.g. brazing, or unsoldering
- B23K1/005—Soldering by means of radiant energy
- B23K1/0056—Soldering by means of radiant energy soldering by means of beams, e.g. lasers, E.B.
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K3/00—Tools, devices, or special appurtenances for soldering, e.g. brazing, or unsoldering, not specially adapted for particular methods
- B23K3/08—Auxiliary devices therefor
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Abstract
The invention designs a laser welding tinning device and a welding method, wherein the tinning device comprises a back plate, a laser position correction device, a camera, a laser processing head, a pushing wheel pair, a connecting rod, a tin feeding nozzle, a displacement sensor, an angle sensor, a balance spring, a controller and a residue box, wherein the angle sensor detects the swing angle of the connecting rod, the displacement sensor detects the up-down movement position of the connecting rod, and the controller calculates the movement speed and the acceleration of a detecting head according to the displacement and the angle change value of the detecting head; during laser welding, the position of the detecting head is utilized to perform laser working height closed-loop control, the stress of the detecting head is utilized to perform tin wire feeding speed closed-loop control, and the angle of the detecting head is utilized to perform laser following tin wire position closed-loop control, so that the influence of welding point height difference on the welding effect can be compensated, the product processing fixing requirement is reduced, and the application range of the laser welding is enlarged. Can prevent mechanical collision or burn of the processing base material, has stable process and improves the qualified product rate.
Description
Technical Field
The invention relates to a laser welding tinning device and a welding method, in particular to a laser tin wire welding tinning device and a welding method adopting the device, and belongs to the technical field of laser tin wire welding.
Background
In the field of laser tin wire welding fine processing, along with higher and higher production process requirements, the use conditions of processing equipment are also stricter and stricter, and the existing traditional equipment cannot meet the emerging process requirements. For example, when a particular tiny spot is laser welded, a slight deviation of the laser from the tin wire or spot will burn the spot or scrap the substrate. The difference between the laser soldering and the traditional electric soldering iron welding mode is that no contact force directly acts on a welding spot during laser welding, and if a tin wire is not in good contact with the welding spot or is unstable in contact, the molten tin wire cannot be well attached to the welding spot, the welding spot is easy to float or rosin joint; if the contact force is too large, the tin wire is easy to deform, and normal welding cannot be realized. The method is a key factor influencing the welding yield of the laser tin wire.
The Chinese utility model 'laser tin soldering device for automatically calibrating and feeding tin' (201820105083.4) adopts a laser emitter, a first CCD component and the like, which are respectively used for melting tin wires for welding and obtaining image information of the tin wires; further acquiring the extending length of the tin wire, the deviation degree of the tin wire and the laser facula and the appearance information of the tin wire; and then the tin wire is trimmed by using the control laser transmitter and the tin feeding assembly to solve the problems of tin feeding amount control and automatic correction, and the defects are as follows: the device cannot accurately judge the contact force between the tin wire and the welding spot; the invention relates to a tin wire precision welding device and a control method thereof (201710413205.6) which are invented by China, and the problem that the contact force between a tin wire and a welding point cannot be accurately judged due to the accumulation of tin ball, bending, deformation and length error at the top end of the tin wire is solved by comparing the length, position, posture and other parameters of the tin wire during initial detection and detection to obtain deviation, and then by means of a laser tin cutting process, an automatic tin stroking process and an automatic tin wire pushing and collecting method on the basis of two sets of vision systems for collecting three-dimensional images of the tin wire; the Chinese invention patent 'an automatic tin wire feeding device for laser welding' (201811475586.1) only solves the problems of ensuring that the wire outlet position is always consistent with the laser welding point when the wire feeding mechanism deflects, avoiding the tin wire from generating stress deformation during wire feeding and preventing the wire from being clamped.
In the prior art or the published patent, a vision system is mainly used for processing position correction or process dynamic adjustment, the adopted device or method cannot accurately judge the contact force between a tin wire and a welding point, and cannot adjust the state of the device and the tin wire in real time according to the contact force.
Disclosure of Invention
The invention aims to solve the problems in the prior art and designs a tin applying device and a welding method for laser welding. The tin feeding device is a device which takes a tin wire tip (tin tip for short) as a detection head and feeds back parameters such as the position, the angle and the like of the detection head to a controller through a displacement sensor and an angle sensor; the laser welding method is a method for performing laser working height closed-loop control by using the position of a detecting head, performing tin wire feeding speed closed-loop control according to the stress condition of the detecting head, and performing laser following tin wire position closed-loop control by using the angle of the detecting head. The method dynamically adjusts the laser focus coordinate by utilizing the position feedback function of the tin tip, can compensate the influence of the height difference of the welding point on the welding effect, reduces the fixed requirements of product processing and enlarges the application range of laser welding; the tin wire is ensured to be in good contact with the welding spot through the force feedback function of the tin tip, the stability of the processing technology is further ensured, meanwhile, the speed and the acceleration of the tin tip in contact with the welding spot are calculated through the force feedback device, and the device is emergently stopped to act when the speed or the acceleration is too large, so that the mechanical collision is prevented. The feeding state of the tin wire accords with the processing technology, the laser processing system can be better suitable for complex working conditions, and the processing consistency and the qualified rate are improved.
The technical scheme of the invention is as follows: a laser welding tinning device comprising: the backplate and install laser position correction device, visual system on the backplate still includes: the device comprises a laser processing head, a tin feeding mechanism, a detection mechanism, a controller and a residue box; the residue box is used for containing chopped tin wire residues; the laser processing head is fixedly connected below the laser position correcting device and used for hot melting tin or cutting tin wires; the laser position correction device is used for driving the laser processing head to carry out space position adjustment; the send tin mechanism includes: the pushing wheel pair, the connecting rod and the tin feeding nozzle are hinged to the lower end of the connecting rod; the front end of a tin wire for welding penetrates through a tin delivery nozzle to be in contact with a welding pad, the rear end of the tin wire penetrates through a pushing wheel pair, and the pushing wheel pair is used for pushing or withdrawing the tin wire; setting: a small section of tin wire extending forwards along the lower part of the tin feeding nozzle is a probe head; the vision system comprises a camera which is fixed on the back plate and used for shooting the detecting head, and then the straightness and the length of the detecting head are detected.
The detection mechanism includes: displacement sensor, angle sensor, balance spring; the connecting rod is arranged along the vertical direction, a set angle is formed between the tin feeding nozzle and the axial direction of the connecting rod, the angle sensor is fixed on the back plate and is positioned at the upper end of the connecting rod, the balance spring penetrates through the connecting rod and is positioned at the lower part of the connecting rod, the upper end of the balance spring is fixedly connected with the connecting rod, the displacement sensor is fixed on the back plate, and the lower end of the balance spring is fixedly connected with the displacement sensor; a sliding sleeve for accommodating the connecting rod to slide up and down is arranged on the displacement sensor, and the connecting rod can drive the tin feeding nozzle to move up and down and rotate and swing; the angle sensor is used for detecting the swing angle of the connecting rod, the displacement sensor is used for detecting the up-down moving position of the connecting rod, and the controller calculates the movement speed and the acceleration of the detecting head according to the displacement and the angle change value of the detecting head detected by the displacement sensor and the angle sensor in real time. The method comprises the steps that the state of the top end of the tin wire is detected through a vision system before welding, when the top end of the tin wire is seriously deformed, the tin wire is cut off through laser pulses, cut tin wire residues automatically fall into a residue box, the reliability of the tin wire as a detection head is guaranteed, a laser position correction device, the vision system, a displacement sensor, an angle sensor and the like are connected with a controller, and the controller is responsible for orderly operation of the whole device.
Further, the connecting angle between the tin feeding nozzle and the axial direction of the connecting rod is 90-150 degrees and can be manually adjusted.
Further, the length of the probe head is set to be less than or equal to 5 times the diameter of the tin wire.
A laser welding method is a closed-loop control method which utilizes the position of a detecting head to perform laser working height closed-loop control, utilizes the stress of the detecting head to perform tin wire feeding speed closed-loop control and utilizes the angle of the detecting head to perform laser following tin wire position closed-loop control.
When the detecting head is contacted with the bonding pad, the force applied to the detecting head makes the balance spring generate axial and radial deformation, and the balance spring provides restoring force. At this time, the balance spring absorbs the contact force, and the tin wire is not deformed. When the force of the probe disappears, the restoring force can restore the deflection angle of the probe to the initial state; the balance spring is simultaneously used for improving the reliability and the sensitivity of the tin wire as a probe;
setting the minimum bending force of the tin wire as M, the weight G of the detection mechanism and the contact force f of the balance spring to satisfy the following conditions:
f＝G-M*β
wherein β represents: equilibrium coefficient, 0< β < 1.
Setting the parameters of the balance spring: the deformation coefficient of the balance spring is lambda, and the minimum deformation lambdaminCorresponding minimum working load of Fmin(ii) a Maximum working load FmaxThe corresponding maximum distortion is λmax. At (lambda)min，λmax) Within the range, the actual load F of the balancing spring is proportional to the deformation λ, i.e.:
F＝K*λ
setting: the contact force between the detecting head and the bonding pad is f, and the displacement sensor feeds back a value Z in real time, so that:
in the formula, z0The feedback value of the displacement sensor is that the contact force f is zero, wherein the contact force f is calculated by the deformation quantity of the spring, and the deformation quantity of the spring is obtained by the displacement sensor.
Further, the laser welding method comprises the following four stages:
1-processing preparation, 2-tin wire positioning, 3-light extraction welding and 4-processing completion, wherein the method specifically comprises the following steps:
1. preparation phase of the process
Setting a Z-direction offset Z of a detecting head acquired by a displacement sensor, acquiring an X-direction offset X and a Y-direction offset Y of the detecting head by an angle sensor, and acquiring a speed V and an acceleration A of the detecting head through the Z-direction offset and unit response time t of the displacement sensor; and the vision system acquires the straightness s and the length l of the tin wire on the processing surface.
Under the standard state, the set reference parameter comprises contact force fbX-direction offset X of the probebY-offset YbZ-direction offset ZbMaximum velocity VmaxMaximum acceleration AmaxThe vision system obtains the reference straightness s of the tin wire on the processing surfacebAnd length lbThe allowable deviations are set to Δ f, Δ X, Δ Y, Δ Z, Δ s, and Δ l, respectively.
In the preparation stage of processing, the vision system acquires the straightness s and the length l of the tin wire on the processing surface and compares the straightness s with the reference straightness sbAnd length lbAnd (6) comparing. If the straightness deviation s-sbIf the value of the angle of the laser beam is beyond the range of +/-Delta s, the deformed tin wire is cut off by the pulse laser, and after the tin wire is fed by the tin feeding mechanism, the vision system acquires the straightness s and the length l of the probe on the processing surface again until the probe meets the reference requirement, so that the effectiveness and the precision of the probe are ensured. If the length of the probe head deviates by l-lbWhen the value of (d) is out of the range of +/-delta l, the length l of the tin wire is adjusted to be within the standard range through the tin feeding mechanism.
2. Tin wire positioning stage
And in the tin wire positioning stage, the controller updates the data of the displacement sensor and the angle sensor in real time, and calculates the movement speed and the acceleration of the detection head according to the displacement variation in unit time. If the moving speed V of the tin tip at the front end of the probe head exceeds VmaxOr acceleration A exceeding AmaxIf so, judging that the tin tips collide and stopping the device in an emergency. If the contact force difference f-f is poor during the positioning processbIf. + -. Δ f is exceeded, then f-f is passedbDynamically adjusting the position of the tin applying device, keeping the contact force within +/-delta f by recording Z-direction deviation m of the device through a position sensor, synchronously adjusting the Z-axis coordinate of laser through a laser position correcting device, and keeping the laser focus and the laser additionThe relative position of the working point is stable, and the positioning is finished.
3. Welding stage of light extraction
The contact force f between the detecting head and the welding spot is reduced along with the gradual melting of the tin wire by the laser, in the process, the feeding speed of the tin wire needs to be dynamically adjusted according to the feedback contact force f, a classical PID closed-loop control method is adopted in the process, and the control model is as follows:
wherein t is processing time, f (t) is contact force corresponding to the time t, u (t) is feeding speed of the tin wire corresponding to the time t, Kp is proportional coefficient, Ki is integral coefficient, and Kd is differential coefficient.
In the positioning and laser welding process of the probe, when the processing track is not a straight line or other factors cause the tin point to deflect under stress, the laser position needs to be synchronously adjusted to prevent poor welding caused by the deviation of laser and welding spots. Specifically, the rotation radius r of the tin tip around the center of the detection mechanism is set, and the rotation rule accords with a polar coordinate system equation. The latest plane coordinates of the tin tip after the deflection angle θ are:
and (3) dynamically adjusting the model of the laser position according to the deflection angle theta of the tin tip to accord with the position follow-up control process, wherein the process adopts a classical PID closed-loop control method.
4. Stage of completion of processing
Before the laser is closed, a pushing wheel of the tin feeding mechanism quickly retracts the tin wire, so that the tin wire is prevented from balling or being adhered to a processing point; and completing the whole processing process, entering the next welding point, and circulating and reciprocating.
Further, when the surface mount welding is carried out, the tin tip is contacted with the welding point, and the contact force f is always kept to be f in the welding process0Said f0Selecting the value according to the characteristics of the tin wire and the welding process; in the positioning stage, when the tin wire and the bonding padContact force at fbWhen the range is +/-delta f, immediately stopping positioning; in the welding process, the tin wire pushing speed is regulated through a PID algorithm, and when the tin tip is not molten, the tin wire feeding speed is reduced; when the tin wire is melted too fast, the tin feeding speed is increased.
Furthermore, when the contact pin is welded, if the contact pin is deformed, in the positioning stage of the detecting head, the tin point is deflected due to stress after contacting the top end of the contact pin, the deflection angle of the detecting head is recorded by the angle sensor, the connecting rod continues to move downwards, and the tin point is always contacted with the contact pin in the moving process until the contact force f is fbIn the range of +/- Δ f; and in the process of contacting the tin point with the pin of the pin, the running track of the tin point is close to the shape of the pin.
The invention has the advantages and beneficial effects that:
(1) the invention dynamically adjusts the laser focus coordinate by utilizing the position feedback function of the probe, can compensate the influence of the height difference of the welding point on the welding effect, reduces the fixed requirement of product processing and enlarges the application range of laser welding.
(2) The good contact of the tin tip and a processing point is the basic requirement of laser welding, the good contact of the tin tip and a welding point is ensured through the force feedback function of the tin tip, the stability of the processing technology is further ensured, and meanwhile, the contact speed and the contact acceleration of the tin tip and the welding point are calculated through a force feedback device. When the speed or the acceleration is overlarge, the emergency stop device acts to prevent mechanical collision.
(3) The laser irradiation position is adjusted in real time through the angle feedback function, so that the device can be successfully applied to pin welding occasions, the influence of pin bending on the tin wire is eliminated, the laser is ensured to be always irradiated on the tin wire, and the base material is prevented from being burned by the laser.
(4) The tinning device can ensure that the relative positions of laser and tin tips in the machining process are stable, and the tin wire feeding state accords with the machining process, so that the laser machining system is better suitable for complex working conditions, and the machining consistency and the production yield are effectively improved.
Drawings
FIG. 1 is a schematic structural diagram of a soldering apparatus of a laser soldering apparatus according to an embodiment of the present invention;
FIG. 2 is a schematic view of the detection mechanism of FIG. 1;
FIG. 3 is a schematic diagram illustrating bending forces of the probe head;
FIG. 4 is a flow chart of the "one laser welding method" of the present invention;
FIG. 5 is a force feedback diagram of a probe head relative to a pad during laser welding in accordance with one embodiment;
FIG. 6 is a schematic diagram of pin welding positioning traces during laser welding according to a second embodiment.
Description of the reference symbols in the drawings:
in fig. 1: the device comprises a back plate 1, an angle sensor 2, a connecting rod 3, a balance spring 4, a pushing wheel pair 5, a displacement sensor 6, a tin feeding nozzle 7, a welding disc 8, a controller 9, a laser position correcting device 10, a laser processing head 11, a vision system 12, a residue box 13, a detection head 14, a probe 15, a probe pin 16, a tin point D1, a fixed point 1 and a fixed point 2D 2.
Detailed Description
Embodiments of the invention will be further described with reference to the accompanying drawings, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below are exemplary and are intended to be illustrative, but not limiting, of the present invention, and any modifications, equivalents, or improvements made within the spirit and principle of the present invention, which are not described in detail in the technical solutions below, are known in the art, and are intended to be included within the scope of the claims of the present invention.
Referring to fig. 1 to 3, the invention provides a laser welding and tin-coating device, comprising: the back plate 1, the laser position correction device 10 and the vision system 12 are mounted on the back plate, and the device further comprises: the device comprises a laser processing head 11, a tin feeding mechanism, a detection mechanism, a controller 9 and a residue box 13; the residue box 13 is used for containing chopped tin wire residues; the laser processing head 11 is fixedly connected below the laser position correcting device 10, and the laser processing head 11 is used for hot melting tin-coating or cutting tin wires; the laser position correction device 10 is used for driving a laser processing head 11 to carry out spatial position adjustment; the send tin mechanism includes: the pushing wheel pair 5, the connecting rod 3 and a tin feeding nozzle 7 which is hinged and fixed at the lower end of the connecting rod; in the embodiment of the invention, the axial connecting angle between the connecting rod 3 and the tin feeding nozzle 7 is 120 degrees, and the connecting rod can be manually adjusted as required in practical application. The front end of a tin wire for welding passes through a tin feeding nozzle 7 to be in contact with a welding pad 8, the rear end of the tin wire passes through a pushing wheel pair 5, and the pushing wheel pair 5 is used for pushing or withdrawing the tin wire; setting: a small section of tin wire extending downwards along the front end of the tin feeding nozzle is a probe head 14; the vision system 12 includes a camera fixed on the back plate 1, and the camera is used for shooting the detecting head 14, so as to detect the straightness and length of the detecting head 14.
The detection mechanism includes: a displacement sensor 6, an angle sensor 2 and a balance spring 4; the connecting rod 3 is arranged in the vertical direction, the angle sensor 2 is fixed on the back plate 1 and is positioned at the upper end of the connecting rod 3, the balance spring 4 penetrates through the connecting rod 3 and is positioned at the lower part of the connecting rod 3, the upper end of the balance spring 4 is fixedly connected with the connecting rod 3 through a fixing point D1, the displacement sensor 6 is fixed on the back plate 1, and the lower end of the balance spring 4 is fixedly connected with the displacement sensor 6 through a fixing point D2; as can be seen from fig. 1, the fixed point D2 is actually a structural supporting point of the connecting rod 3 and the tin feeding nozzle 7 hinged and fixedly connected to the connecting rod 3, and the connecting rod 3 can drive the tin feeding nozzle 7 to move up and down and swing rotationally, so as to drive the probe head 14 to move up and down and swing around the connecting rod 3; the angle sensor 2 is used for detecting the rotation angle of the connecting rod 3, the displacement sensor 6 is used for detecting the up-down movement position of the connecting rod 3, and the controller 9 calculates the movement speed and the acceleration of the detecting head 14 according to the displacement amount and the angle change value of the detecting head 14 detected by the displacement sensor 6 and the angle sensor 2 in real time. The method comprises the steps that the state of the top end of a tin wire, namely the front end of a detecting head 14, is detected through a vision system 12 before welding, when the top end of the tin wire is seriously deformed, a laser processing head 11 sends out laser pulses to cut off the top end of the tin wire, and tin wire residues after cutting off automatically drop into a residue box, so that the reliability of the tin wire serving as the detecting head is guaranteed, the laser position correction device 10, the vision system 12, a displacement sensor 6, an angle sensor 2 and the like are connected with a controller 9, and the controller 9 controls the orderly operation of a tin feeding device for laser welding.
In the embodiment of the present invention, the length of the solder wire extending from the front end of the solder feeding nozzle and used as the probing tip 14 is set to be equal to 3 times the diameter of the solder wire.
Referring to fig. 4 to 6, the method for welding by using the laser welding and tinning device of the invention comprises the following steps: the method comprises the steps of performing laser working height closed-loop control by using the position of a detection head 14, performing tin wire feeding speed closed-loop control by using the stress condition of the detection head 14, and performing laser following tin wire position closed-loop control by using the angle of the detection head 14.
After the probe head contacts the pad, the probe head 14 is forced to deform the balance spring 4 axially and radially, and the balance spring 4 provides a restoring force. At this time, the balance spring 4 absorbs the contact force, and the tin wire as the proximity head 14 is not deformed. When the force applied to the probing tip 14 disappears, the restoring force of the balance spring 4 can restore the deflection angle of the probing tip 14 to the initial state; the balance spring 4 is used for improving the reliability and the sensitivity of the tin wire as a probe head at the same time;
the minimum bending force of the detecting head 14 is set to be M, the weight G of the detecting mechanism and the contact force f of the balance spring meet the following conditions:
f＝G-M*β
wherein β represents: equilibrium coefficient, 0< β < 1.
Setting the parameters of the balance spring 4: the deformation coefficient of the balance spring 4 is lambda, and the minimum deformation lambdaminCorresponding minimum working load of Fmin(ii) a Maximum working load FmaxThe corresponding maximum distortion is λmax. At (lambda)min，λmax) Within the range, the actual load F of the balancing spring 4 is proportional to the deformation λ, i.e.:
F＝K*λ
setting the contact force between the detecting head 14 and the bonding pad 8 as f, and the real-time feedback value of the displacement sensor 6 as Z, then:
in the formula, z0The feedback value of the displacement sensor 6 is zero when the contact force f is zero.
The laser welding method of the laser welding tinning device comprises the following four stages:
1-processing preparation, 2-tin wire positioning, 3-light extraction welding and 4-processing completion, wherein the method specifically comprises the following steps:
1. preparation phase of the process
Acquiring Z-direction offset Z of the detecting head through a displacement sensor, acquiring X-direction offset X and Y-direction offset Y of the detecting head through an angle sensor, and acquiring speed V and acceleration A of the detecting head through the Z-direction offset and unit response time t of the displacement sensor; the vision system acquires the straightness s and the length l of the probe on the bonding pad;
in a standard state, setting reference parameters, including: contact force f between probe and padbX-direction offset X of the probe headbY-offset YbZ-direction offset ZbMaximum velocity VmaxMaximum acceleration AmaxThe vision system obtains the reference straightness s of the probe on the bonding padbAnd length lbThe allowable deviations are set to Δ f, Δ X, Δ Y, Δ Z, Δ s, and Δ l, respectively.
In the preparation stage of processing, the vision system first obtains the straightness s and length l of the probe head above the bonding pad and compares the straightness s with a reference straightnessbAnd length lbComparing, detecting the top state of the tin wire by a vision system before welding, and if the straightness deviation s-sbWhen the value of the tin wire is beyond the range of +/-Delta s, the tin wire is cut off by laser pulse when the top end of the detecting head is seriously deformed, the cut tin wire residue automatically falls into a residue box, the reliability of the tin wire as the detecting head is ensured, and after the tin wire is fed by a tin feeding mechanism, the straightness s and the length l of the tin wire on a processing surface are obtained again by a vision system until the tin wire meets the standard requirement, so that the effectiveness and the precision of the detecting head are ensured. If the length of the probe head deviates by l-lbWhen the value of (d) is out of the range of +/-delta l, the length l of the tin wire is adjusted to the standard by the tin feeding mechanismWithin the range.
2. Tin wire positioning stage
The controller updates data of the displacement sensor and the angle sensor in real time, and calculates the movement speed and the acceleration of the detecting head according to the displacement variation in unit time. If the moving speed V of the tin tip at the front end of the probe head exceeds VmaxOr acceleration A exceeding AmaxJudging that the tin tips collide and emergently stopping the operation of the device; if the contact force difference f-f is poor during the positioning processbIf. + -. Δ f is exceeded, then f-f is passedbAnd dynamically adjusting the position of the tin coating device, keeping the contact force within +/-delta f through Z-direction deviation m of the position sensor recording device, synchronously adjusting the Z-axis coordinate of the laser through a laser position correcting device, keeping the relative position of the laser focus and the processing point stable, and finishing positioning.
3. Welding stage of light extraction
The contact force f between the detecting head and the welding spot is reduced along with the gradual melting of the tin wire by the laser, in the process, the feeding speed of the tin wire needs to be dynamically adjusted according to the feedback contact force f, a classical PID closed-loop control method is adopted in the process, and the control model is as follows:
wherein t is processing time, f (t) is contact force corresponding to the time t, u (t) is feeding speed of the tin wire corresponding to the time t, Kp is a proportional coefficient, Ki is an integral coefficient, and Kd is a differential coefficient.
During positioning and laser welding of the probe 14, when the machining track is not a straight line or other factors cause the tin tip to deflect under stress, the laser position needs to be adjusted synchronously to prevent poor welding caused by deviation of the laser and the welding spot. Specifically, the rotation radius r of the tin tip around the center of the detection mechanism, namely the axis of the connecting rod, is set, and the rotation rule conforms to the polar coordinate system equation. The latest plane coordinates of the tin tip after the deflection angle θ are:
and (3) dynamically adjusting the model of the laser position according to the deflection angle theta of the tin tip to accord with the position follow-up control process, wherein the process adopts a classical PID closed-loop control method.
4. Stage of completion of processing
Before the laser is closed, the tin feeding mechanism quickly returns the tin wire, so that the tin wire is prevented from balling or being adhered to a processing point; the whole processing process is completed, and then the next welding point is entered, and the cycle is repeated.
In the actual operation process, because the method for bonding the patch and the method for bonding the pin are different, the following two specific embodiments are described in detail:
the first embodiment is as follows: patch welding
Referring to fig. 4 and 5, when the surface mount device is used for surface mount welding, it is required to ensure that the tin wire is in good contact with the welding point, i.e. the contact force f is always kept at f during welding0，f0Can be selected according to the characteristics of the tin wire and the welding process. In the positioning stage, when the contact force between the tin wire and the bonding pad is fbWhen the range is +/-delta f, the positioning is immediately stopped. In the welding process, the pushing speed of the tin wire is regulated through a PID algorithm, when the tin tip is not molten, if tin is continuously fed, the contact force f of the tin wire and the bonding pad is increased, and at the moment, the tin feeding speed is reduced; when the tin wire is melted too fast, the contact force f between the tin wire and the bonding pad is reduced, and the tin feeding speed is increased.
Example two: pin welding
Referring to fig. 4 and 6, when the pin 15 is deformed, the tin tip 16 is forced to deflect rightward after contacting the top end of the pin 15 during the positioning stage of the probing tip 14, and the angle sensor 2 records the deflection angle of the tin wire 14, but the vertical contact force of the balance spring 4 is 0, so that the device continues to move downward. During the movement, the tin point 16 is always contacted with the pin 15 under the restoring force of the balance spring 4 until the contact force f is fbIn the range of ± Δ f. In the process of contacting the tin tip 16 with the pin 15, the running track of the tin tip 16 is close to the shape of the pin 15, as shown in fig. 6, the tin tip 16 can effectively avoid the interference of the pin 15 and accurately position to the pad 8 to be welded.
The invention dynamically adjusts the laser focus coordinate by utilizing the position feedback function of the probe, can compensate the influence of the height difference of the welding point on the welding effect, reduces the fixed requirement of product processing and enlarges the application range of laser welding.
The laser welding is the most basic requirement when the tin point is in good contact with a processing point, the tin point is ensured to be in good contact with a welding spot through the force feedback function of the tin point, the stability of the processing technology is further ensured, and meanwhile, the contact speed and the contact acceleration of the tin point and the welding spot are calculated through the force feedback device. When the speed or the acceleration is overlarge, the emergency stop device acts to prevent mechanical collision.
The laser irradiation position is adjusted in real time through the angle feedback function, so that the device can be successfully applied to pin welding occasions, the influence of pin bending on the tin wire is eliminated, the laser is ensured to be always irradiated on the tin wire, and the base material is prevented from being burned by the laser.
The tinning device can ensure that the relative positions of laser and tin tips in the machining process are stable, and the tin wire feeding state accords with the machining process, so that the laser machining system is better suitable for complex working conditions, and the machining consistency and the production yield are effectively improved.
In the description of the present invention, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention.
In the present invention, unless otherwise specifically stated or limited, the terms "mounted," "connected," "fixed," "secured," and the like are to be construed broadly, e.g., as meaning a fixed connection, a removable connection, or an integral part; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
Claims (6)
1. A laser welding tinning device comprising: the backplate and install laser position correction device, visual system on the backplate still includes: the device comprises a laser processing head, a tin feeding mechanism, a detection mechanism, a controller and a residue box; the residue box is used for containing chopped tin wire residues; the laser processing head is fixedly connected below the laser position correcting device and used for hot melting tin or cutting tin wires; the laser position correction device is used for driving the laser processing head to carry out space position adjustment; the send tin mechanism includes: the pushing wheel pair, the connecting rod and the tin feeding nozzle are hinged to the lower end of the connecting rod; the front end of a tin wire for welding penetrates through a tin delivery nozzle to be in contact with a welding pad, the rear end of the tin wire penetrates through a pushing wheel pair, and the pushing wheel pair is used for pushing or withdrawing the tin wire; setting: a small section of tin wire extending forwards along the lower part of the tin feeding nozzle is a probe head; the vision system comprises a camera which is fixed on the back plate and is used for shooting the detecting head so as to detect the straightness and the length of the detecting head; the method is characterized in that:
the detection mechanism includes: displacement sensor, angle sensor, balance spring; the connecting rod is arranged along the vertical direction, a set angle is formed between the tin feeding nozzle and the axial direction of the connecting rod, the angle sensor is fixed on the back plate and is positioned at the upper end of the connecting rod, the balance spring penetrates through the connecting rod and is positioned at the lower part of the connecting rod, the upper end of the balance spring is fixedly connected with the connecting rod, the displacement sensor is fixed on the back plate, and the lower end of the balance spring is fixedly connected with the displacement sensor; a sliding sleeve for accommodating the connecting rod to slide up and down is arranged on the displacement sensor, and the connecting rod can drive the tin feeding nozzle to move up and down and rotate and swing; the angle sensor is used for detecting the swing angle of the connecting rod, the displacement sensor is used for detecting the up-down moving position of the connecting rod, and the controller is connected with the laser position correction device, the vision system, the displacement sensor and the angle sensor respectively.
2. The laser welding tinning device of claim 1, wherein: the connecting angle between the tin feeding nozzle and the axial direction of the connecting rod is 90-150 degrees and can be manually adjusted.
3. The laser welding tinning device of claim 1, wherein: the length of the probe is set to be less than or equal to 5 times the diameter of the tin wire.
4. A method for performing laser welding by using the device for tin coating by laser welding as claimed in claim 1, which is a closed-loop control method for performing laser working height closed-loop control by using the position of a detecting head, performing tin wire feeding speed closed-loop control by using the stress of the detecting head, and performing laser following the position of the detecting head by using the angle of the detecting head, and is characterized by comprising the following four stages:
s1, preparation stage of processing
Acquiring Z-direction offset Z of the detecting head through a displacement sensor, acquiring X-direction offset X and Y-direction offset Y of the detecting head through an angle sensor, and acquiring speed V and acceleration A of the detecting head through the Z-direction offset and unit response time t of the displacement sensor; the vision system acquires the straightness s and the length l of the probe on the bonding pad;
in a standard state, setting reference parameters, including: contact force f between probe and padbX-direction offset X of the probe headbY-offset YbZ-direction offset ZbMaximum velocity VmaxMaximum acceleration AmaxThe vision system obtains the reference straightness s of the probe on the bonding padbAnd length lbSetting tolerance deviations as delta f, delta X, delta Y, delta Z, delta s and delta l respectively;
in the preparation stage of processing, the vision system first obtains the straightness s and length l of the probe head above the bonding pad and compares the straightness s with a reference straightnessbAnd length lbComparing, detecting the top state of the tin wire by a vision system before welding, and if the straightness deviation s-sbThe value of the angle of the tin wire is beyond the range of +/-Delta s, when the top end of the detecting head is seriously deformed, the tin wire is cut off through laser pulse, the cut tin wire residues automatically fall into a residue box, the reliability of the tin wire as the detecting head is ensured, after a tin wire feeding mechanism feeds the tin wire, the straightness s and the length l of the tin wire on a processing surface are obtained again by a vision system until the tin wire meets the standard requirement, the effectiveness and the precision of a tin tip as the detecting head are ensured, and if the length deviation of the tin wire is l-lbWhen the value of the tin wire is beyond the range of +/-delta l, the length l of the tin wire is adjusted to be within the standard range through the tin feeding mechanism;
s2 tin wire positioning stage
The controller updates the data of the displacement sensor and the angle sensor in real time, calculates the movement speed and the acceleration of the probe according to the displacement variation in unit time, and if the movement speed V of the tin tip at the front end of the probe exceeds VmaxOr acceleration A exceeding AmaxJudging that the tin tips collide and emergently stopping the operation of the device; if the acting force is poor f-f in the positioning processbIf. + -. Δ f is exceeded, then f-f is passedbDynamically adjusting the position of a tinning device, recording Z-direction deviation m of the device through a position sensor to keep the acting force within +/-delta f, synchronously adjusting the Z-axis coordinate of laser through a laser position correction device, keeping the relative position of a laser focus and a processing point stable, and completing positioning;
s3, laser welding stage
Along with the gradual melting of the tin wire by laser, the contact force f between the detecting head and the welding spot is reduced, in the process, the feeding speed of the tin wire needs to be dynamically adjusted according to the feedback contact force f, a classical PID closed-loop control method is adopted in the process, and the control model is as follows:
in the above formula, t is the processing time, f (t) is the acting force corresponding to the time t, u (t) is the feeding speed of the tin wire corresponding to the time t, Kp is the proportional term coefficient, Ki is the integral term coefficient, Kd is the differential term coefficient,
in the positioning and laser welding process of the probe, when the processing track is not a straight line or other factors cause the tin point to deflect under stress, the laser position needs to be synchronously adjusted; specifically, setting: the rotation radius of the tin tip around the axis of the connecting rod is r, and the rotation rule accords with a polar coordinate system equation; the latest plane coordinates of the tin tip after the deflection angle θ are:
dynamically adjusting a model of the laser position according to the deflection angle theta of the tin tip to accord with a position follow-up control process, wherein the process adopts a classical PID closed-loop control method;
s4, finishing the processing
Before the laser is closed, the pushing wheel pair quickly retracts the tin wire; and completing the whole processing process, entering the next welding point, and circulating and reciprocating.
5. The laser welding method according to claim 4, wherein: when the surface mount welding is carried out, the tin tip is contacted with the welding point, and the contact force f is always kept as f in the welding process0Said f0Selecting the value according to the characteristics of the tin wire and the welding process; in the positioning stage, when the contact force between the tin wire and the bonding pad is fbWhen the range is +/-delta f, immediately stopping positioning; in the welding process, the tin wire pushing speed is regulated through a PID algorithm, and when the tin tip is not molten, the tin wire feeding speed is reduced; when the tin wire is melted too fast, the tin feeding speed is increased.
6. The laser welding method according to claim 4, wherein: when the contact pin is welded, if the contact pin is deformed, in the locating stage of the detecting head, the tin point is deflected due to stress after contacting the top end of the contact pin, the deflection angle of the detecting head is recorded by the angle sensor, the connecting rod continues to move downwards, and the tin point is always contacted with the contact pin in the moving process until the contact force f is fbIn the range of +/- Δ f; and in the process of contacting the tin point with the pin of the pin, the running track of the tin point is close to the shape of the pin.
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| CN113814623B (en) * | 2021-11-23 | 2022-02-22 | 大族激光科技产业集团股份有限公司 | Welding force correction method and correction device |
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