How to improve the placement rate of smt equipment and maintain the placement rate of SMT equipment is an urgent problem that needs to be solved in the face of the equipment after many years of use. This article takes the rotary head placement machine as an example to elaborate the influence from many aspects. The reason why the device placement rate is low, and the inspection contents of common faults of the SMT device are described in detail. Keywords: placement rate optical recognition attitude detection state monitoring placement machine is to stably, quickly, completely and correctly pick up the device without any damage to the device and the base board, and quickly and accurately place the device in the specified In terms of location, it has been widely used in military, home appliances, communications, computers and other industries. SMT equipment mainly considers its placement accuracy and placement speed when purchasing. In actual use, in order to effectively improve product quality, reduce production cost and improve production efficiency, how to improve and maintain SMT equipment placement rate is The primary issue facing the user.
One: the meaning of the placement rate The so-called placement rate refers to the ratio of the actual number of devices mounted to the number of suctions in a certain period of time, namely: placement rate = &TImes; 100% number of suctions, the total number of discarded items refers to the number of errors, Identify the number of errors, the number of slices, the number of missing, etc., and the recognition error is divided into two types: device size error and device optical recognition. Whether it is a minicomputer, a medium-sized machine, a mainframe, or a medium-speed machine or a high-speed machine, they are mainly composed of a device storage device, an XY table, a mounting head, and a control system. The placement head is the core and key components of the placement machine. The placement head generally has a fixed head and a rotating head. The fixed head is generally arranged in a long position, ranging from 2 to 8 and can be taken at the same time or separately. It is also rotated in the horizontal plane and rotated in the vertical plane. A: device suction nozzle suction height switch
B: θI rotation (±90')
C: device optical identification
D: device attitude detection θ2 rotation (±90')
E: Mounting device / nozzle height switching
F: θ3 rotation (±180'-θ) nozzle origin detection defective product exclusion
G: nozzle conversion
H: The nozzle number detection is based on the entire process of the placement machine from the pick-up machine. From the perspective of the equipment, in the case of correctly setting the nozzle pick-up height, the position of the pick-up nozzle and the relative position of the feeder, The main factor affecting the placement rate of equipment is that at the pick-up location, according to the statistics of production information, the impact of the equipment accounts for more than 80% of the total influencing factors. The reasons are: on the one hand, the feeder on the device storage device, and on the other hand, the nozzle, about 60% of the film in the feeder, about 40% is caused by the suction nozzle pollution.
Second, the influence of the feeder The influence of the feeder is concentrated on the abnormal supply. The drive mode of the feeder is motor drive, mechanical drive and cylinder drive. Here, the mechanical drive is taken as an example to illustrate the effect of the feeder on the placement rate:
1: Drive part wear mechanically drive the feeding mechanism by the cam main shaft, quickly tap the search arm of the feeder, and let the ratchet connected with the connecting rod drive the component to advance a distance and drive the plastic The take-up reel removes the plastic cap from the braid and the nozzle is lowered to complete the pick-up action. However, due to the high-speed access of the feeder to the feeder, after a long period of use, the pawl of the feeder is seriously worn, and the pawl cannot drive the plastic strip of the take-up reel to be normally peeled off, so that the nozzle cannot complete the pickup work. Therefore, the feeder should be carefully inspected before installing the braid. The feeder that has worn out the pawl wheel should be repaired immediately. If it cannot be repaired, it should be replaced in time.
2: Deformation of the structural parts of the feeder due to long-term use or improper operation of the operator, the pressure belt cover, thimble, spring and other moving mechanisms are deformed, rusted, etc., resulting in the device being biased, the vertical piece or the device is not absorbed. Therefore, it should be checked regularly, and the problems should be dealt with in time to avoid a large amount of waste of the device. At the same time, the installation of the hopper should be correctly and firmly installed on the platform of the feeding part, especially the equipment without height detection of the feeder, otherwise it may Causes damage to the feeder or equipment.
3: Poor lubrication of the feeder Generally, the maintenance and maintenance of the feeder is easy to be ignored, but regular cleaning, cleaning and lubrication are essential tasks.
Third, the influence of the nozzle The nozzle is also another important factor affecting the placement rate, the cause is internal and external.
1: Internal reason: On the one hand, the vacuum negative pressure is insufficient, the mechanical valve on the head is automatically converted before the nozzle is taken, and the air is converted to true by the blowing, which generates a certain negative pressure. When the part is sucked, the negative pressure sensor When the detection value is within a certain range, the machine is normal, and vice versa. Generally, the negative pressure at the pickup position to the placement nozzle should be at least 400mmHg or more. When the negative pressure of the large device is above 70mmHg, the filter inside the vacuum pump should be cleaned regularly to ensure sufficient negative pressure; At the same time, the working state of the negative pressure detecting sensor should be checked regularly. On the other hand, the filter on the placement head and the filter on the nozzle are blackened due to contamination of the surrounding environment or the air source is contaminated. Therefore, the filter should be replaced regularly. Generally, the filter on the nozzle should be replaced at least once every two months. The filter on the placement head should be replaced at least once every six months to ensure smooth airflow.
2: External causes are pressure relief of the air source circuit, such as rubber tube aging, cracking, aging of seals, wear and wear of the nozzle after prolonged use, and dust on the other hand due to adhesive or external environment, especially The large amount of waste generated after the cutting of the tape-wrapped components causes the nozzle to block. Therefore, due to the cleanliness of the nozzles, the pick-up of the nozzles is monitored at any time, and the suction or the pick-up is poor. The mouth should be cleaned or replaced in time to ensure a good condition. At the same time, when installing the nozzle, it must be ensured that the installation is correct and firm, otherwise the nozzle or equipment will be damaged.
Four: device detection system The device detection system is the necessary guarantee for placement accuracy and placement accuracy. Divided into device optical identification system and device attitude detection. 1: Optical recognition system is a fixed installation of an optical camera system, which is used to identify the outline of the component through the camera during the rotation of the placement head for optical imaging, and to measure and record the center position and rotation angle of the device relative to the camera. Down, it is passed to the transmission control system to compensate for the XY coordinate position deviation and the θ angular deviation, which has the advantages of accuracy and flexibility applicable to devices of various specifications and shapes. It has a reflection recognition method to identify the device electrodes, and the recognition accuracy is not affected by the size of the nozzle. Generally, SOP, QFP, BGA, PLCC and other devices adopt reflection recognition. The transmission recognition method is based on the component shape, and the recognition accuracy is affected by the size of the nozzle. When the nozzle shape is larger than the device contour, the contour of the nozzle is recognized in the image. Since the light source of the optical camera system is used after a period of time, the light intensity will gradually decrease, because the light intensity is proportional to the gray value of the solid-state image conversion, and the larger the gray value, the clearer the digital image. Therefore, as the light intensity of the light source decreases, the gray value also decreases, but the gray value stored in the machine does not automatically decrease as the light intensity of the light source decreases, and when the gray value is lower than a certain value At the time of the value, the image cannot be recognized, so the calibration detection must be performed periodically. 1 Re-calibration 2 Adjust the aperture focal length. The gray value will be proportional to the light intensity of the light source. When the light intensity of the light source is too weak to identify the device, the light source must be replaced. At the same time, the lens, the glass piece and the dust and the device on the reflector should be cleaned regularly to prevent the light source from being affected by dust or the device, resulting in poor recognition; The aspect must also correctly set the camera's initial data.
2: The whole attitude detection is a high-speed scanning from the lateral direction of the device through the linear sensor mounted on the frame to detect the sorption state of the device, and accurately detect the thickness of the device. When the thickness value and the measured value are set in the parts library, When the allowable error range is exceeded, the thickness detection may be poor, resulting in parts loss. Therefore, it is important to correctly set the data of the devices in the parts library and the reference data of the thickness detection control. The thickness of the device must be re-tested frequently. At the same time, the linear sensor should be cleaned frequently to prevent the thickness and sorption state of the dust, debris, oil and other components adhering to it.
Fifth, the device tape bad device placement accuracy is a result of a multi-factor, in addition to the device itself, the device tape has a great impact on it, mainly in: A: perforation error Larger. B: The device shape is poor. C: The braided square hole is irregular or too large in shape, causing the device to be hung or flipped laterally. D: The tape and the plastic hot press tape are too strong to be peeled off properly, or the device is stuck to the bottom tape. E: There is oil on the bottom of the device.
Sixth: How to use the excellent performance equipment to make the maximum profit is the goal pursued by the enterprise. How to achieve the goal depends on the scientific management method:
A: Establish a regular staff training system to improve the quality of employees. People are the soul of enterprises and the foundation of enterprise entrepreneurship and development. Therefore, we must pay attention to the skills training and ideological concept training of the staff team. We should be able to operate the equipment proficiently and correctly, correctly install and use the feeder, and regularly maintain and maintain the equipment to effectively ensure product quality, reduce material consumption and improve production efficiency. .
B: Establish a regular equipment maintenance plan. Promote TPM management, implement preventive performance maintenance and overhaul, thereby reducing equipment downtime due to temporary failure surfaces, and pursuing maximum equipment utilization efficiency.
C: Sound equipment maintenance files. 1: Maintenance record. Record the phenomenon of fault occurrence, analysis process, processing situation, spare parts replacement, etc. 2: Dimensional spare parts replacement record. Analyze the reasons for spare parts replacement, spare parts replacement cycle, reduce spare parts backlog and reduce production costs.
D: Sound equipment operation file. 1: The device running status is timely registered in the table. 2: List of equipment operating status. 3: Operation status monitoring diagram. 4: The maintenance worker monitors the operation status of the equipment on duty. 5: List of equipment monthly operation. 6: Equipment monthly running status summary table.
Seven: Mounter common faults
1: When a fault occurs, it is recommended to solve the problem as follows:
A: Detailed analysis of the working order of the devices and the logical relationship between them.
B: Understand the location, link and extent of the fault, and whether there is abnormal sound.
C: Understand the operation process before the failure occurs.
D: Whether it occurs on a specific placement head or nozzle.
E: Whether it occurs on a specific device.
F: Whether it occurs on a specific batch.
G: Whether it happened at a specific moment.
2: Analysis of common faults.
A: Component placement offset mainly refers to the position shift of XY after the components are mounted on the PCB. The reasons for this are as follows:
(1): Reason for PCB board a: The warpage of the PCB board is beyond the allowable range of the device. The upturn is up to 1.2MM and the downturn is up to 0.5MM. b: The height of the support pins is inconsistent, resulting in uneven printing of the printed board. c: The flatness of the workbench support platform is poor. d: The circuit board has low wiring precision and poor consistency, especially the difference between batch and batch.
(2): The suction pressure of the mounting nozzle is too low, and the pick-up and placement should be above 400mmHG.
(3): The blowing pressure is abnormal at the time of placement.
(4): The amount of adhesive and solder paste applied is abnormal or deviated. This causes the component to drift when the component is mounted or soldered. Too little causes the component to deviate from the original position when the device is mounted at high speed after the device is mounted. The coating position is inaccurate and the corresponding offset occurs due to the tension.
(5): The program data device is incorrect.
(6): The substrate is poorly positioned.
(7): When the mounting nozzle rises, the movement is not smooth, and it is slow.
(8): The coupling between the power piece and the transmission part of the XY table is loose.
(9): The head nozzle is not properly installed.
(10): The blowing timing does not match the placement head down timing.
(11): The initial data setting value of the camera of the nozzle center data and the optical recognition system is poor.
B: The device mounting angle offset mainly refers to the angular rotation offset when the device is mounted. The main reasons for this are as follows: (1): Reasons for the PCB board
a: PCB board warp is beyond the allowable range of the device
b: The height of the support pins is inconsistent, which makes the printed board support uneven.
C: The flatness of the workbench support platform is poor.
d: The board layout has low precision and poor consistency, especially the difference between batch and batch.
(2): The suction pressure of the mounting nozzle is too low, and the pick-up and placement should be above 400mmHG.
(3): The air pressure is abnormal at the time of mounting.
(4): The amount of adhesive and solder paste applied is abnormal or deviated.
(5): The program data device is incorrect.
(6): The end of the nozzle is worn, clogged or stuck with foreign matter.
(7): The rising or rotating motion of the mounting nozzle is not smooth and slow.
(8): The parallelism between the nozzle unit and the XY table is poor or the nozzle origin detection is poor.
(9): The optical camera is installed with agitation or improper data equipment.
(10): The blowing timing does not match the placement head down timing.
C: Loss of components: mainly refers to the loss of components between the position of the suction pad and the position of the patch. The main reasons for its emergence are as follows:
(1): Program data device error (2): The suction pressure of the mounting nozzle is too low. In the removal and placement should be 400MMHG or more.
(3): The blowing timing and the placement should be delayed. (4): The attitude detection sensor is defective, and the reference device is incorrect.
(5): Cleaning and maintenance of reflectors and optical recognition cameras.
D: The pickup is not normal:
(1): The tape size does not match the feeder specifications.
(2): The vacuum pump is not working or the suction pressure of the nozzle is too low.
(3): The plastic hot pressing belt braided at the take-up position is not peeled off, and the plastic hot pressing belt is not pulled up normally.
(4): The vertical movement system of the nozzle is slow.
(5): The placement speed of the placement head is incorrectly selected.
(6): The feeder is not installed firmly, the feeder ejector is not moving smoothly, the quick-opener and the pressure belt are bad.
(7): The paper cutter cannot cut the tape normally.
(8): The braid cannot rotate normally with the gear or the feeder does not run continuously.
(9): When the suction position is at the suction position, the suction nozzle is not at the low point, and the drop height is not in place or no action.
(10): The center axis of the nozzle at the take-up position does not coincide with the lead of the center axis of the feeder, and a deviation occurs.
(11): The nozzle drop time is not synchronized with the suction time.
(12): There is vibration in the feeding section (13): The component thickness data device is incorrect.
(14): The initial value of the suction height is incorrect.
E: Randomness is not a patch. It mainly means that the nozzle is not attached at the low position of the patch. The main reasons for its emergence are as follows:
(1): The warpage of the PCB board is beyond the allowable range of the device, the maximum tilt is 1.2MM, and the lower bend is 0.4MM.
(2): The height of the support pins is inconsistent or the flatness of the support platform is poor.
(3): The nozzle is stuck with the fluid or the nozzle is severely magnetized.
(4): The vertical movement system of the L nozzle is slow to run.
(5): The blowing timing does not match the placement head down timing.
(6): The amount of glue on the printed board is insufficient, the leak point or the machine pin is too long.
(7): The nozzle placement height is poor.
(8): The solenoid valve is poorly switched, and the blowing pressure is too small.
(9): When NG occurs in a nozzle, the STOPPER cylinder of the device is not working properly and is not reset in time.
F: Poor pickup posture: mainly refers to the appearance of slabs, slanting sheets, etc. The main reasons for its emergence are as follows:
(1): The vacuum suction pressure is poorly adjusted.
(2): The vertical movement system of the nozzle is slow to run.
(3): The nozzle drop time is not synchronized with the suction time.
(4): The initial value of the suction piece height or the component thickness is set incorrectly, and the distance between the suction nozzle and the feeding platform is incorrect at the low point.
(5): The tape packaging specifications are poor, and the components are shaken in the mounting tape.
(6): The ejector pin movement is not smooth, the quick loader and the pressure belt are bad.
(7): The center axis of the feeder does not coincide with the vertical center axis of the nozzle, and the offset is too large.
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