PCBA Tech - Poor device placement and placement machine failure

The placement accuracy of SMT equipment is the result of a combination of multiple factors. In addition to the equipment itself, poor device taping also has a great impact on it, mainly in:  

A. The pitch error of the tooth hole is relatively large.

B. The shape of the device is not good.

C. The shape of the square hole of the braid is irregular or too large, which causes the device to be hung or flipped laterally.

D. The adhesive force between the paper tape and the plastic hot-pressing tape is too large and cannot be peeled off normally, or the device is stuck on the bottom tape.

E. There is oil stain on the bottom of the device.

Six, common faults of the placement machine

1. When a fault occurs, it is recommended to solve the problem according to the following ideas:

A. Detailed analysis of the working sequence of the equipment and the logical relationship between them.

B. Understand the location, link and extent of the fault, and whether there is any 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 in a specific batch.

G. Does it happen at a specific moment?

2. Analysis of common faults

A. Component placement offset mainly refers to the position offset in X-Y after the components are mounted on the PCB. The causes are as follows:

(1) Reasons for PCB board a: PCB warpage exceeds the allowable range of the equipment. The maximum upturn is 1.2MM, and the maximum downturn is 0.5MM. b: The height of the support pins is inconsistent, resulting in uneven support of the printed board. c: The flatness of the workbench support platform is poor. d: The circuit board has low wiring accuracy and poor consistency, especially the large difference between batch and batch.

(2) The suction pressure of the placement nozzle is too low, and the pickup and placement should be above 400mmHG.

(3) The blowing pressure is abnormal during placement.

(4) The amount of adhesive and solder paste applied is abnormal or deviated. This leads to component placement or welding when the position drifts. Too few components cause the component to deviate from the original position when the worktable moves at high speed after placement, the coating position is inaccurate, and the corresponding deviation occurs due to its tension.

(5) The program data device is incorrect.

(6) Poor positioning of the substrate.

(7) The movement of the mounting nozzle is not smooth and slow when it rises.

(8) The coupling between the power part and the transmission part of the X-Y worktable is loose.

(9) Poor installation of the nozzle of the placement head.

(10) The blowing sequence does not match the placement head descending sequence.

(11) The initial data settings of the nozzle center data and the camera of the optical recognition system are poor.

B. Device mounting angle deviation mainly refers to the angular direction rotation deviation when the device is mounted. The main reasons for it are as follows:

(1) The reason for the PCB board a: The warpage of the PCB board exceeds the allowable range of the equipment 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 circuit board has low wiring accuracy and poor consistency, especially the large difference between batch and batch.

(2) The suction pressure of the placement nozzle is too low, and the pickup and placement should be above 400mmHG.

(3) The blowing air pressure is abnormal during placement.

(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 suction nozzle is worn, blocked or stuck with foreign matter.

(7) The uptake or rotation of the mounting nozzle is not smooth and slow.

(8) The parallelism between the nozzle unit and the X-Y table is poor or the nozzle origin detection is poor.

(9) Improper installation of optical cameras or improper data equipment.

(10) The blowing sequence does not match the placement head descending sequence.

C. Loss of components: mainly refers to the loss of components between the suction position and the placement position.

The main reasons for this are as follows:

(1) Program data device error

(2) The pressure of the mounting nozzle is too low. It should be more than 400MMHG during removal and placement.

(3) The blowing sequence does not match the placement sequence

(4) The posture detection sensor is bad, and the reference equipment is wrong.

(5) Cleaning and maintenance of reflectors and optical recognition cameras.

D. The pickup is abnormal:

(1) The tape specification does not match the feeder specification.

(2) The vacuum pump is not working or the suction pressure of the suction nozzle is too low or too low.

(3) The plastic hot pressing tape braided at the pickup position is not peeled off, and the plastic hot pressing tape is not pulled up normally.

(4) The vertical movement system of the suction nozzle is slow.

(5) The placement speed of the placement head is selected incorrectly.

(6) The feeder is not firmly installed, the feeder thimble does not move smoothly, the quick switch and the press belt are not good.

(7) The paper cutter cannot cut the braid normally.

(8) The braid cannot follow the normal rotation of the gear or the feeder is not running continuously.

(9) The suction nozzle is not at the low point at the suction position, the lowering height is not in place or there is no movement.

(10) In the pickup position, the center axis of the suction nozzle does not coincide with the center axis of the feeder, and there is a deviation.

(11) The falling time of the suction nozzle is not synchronized with the suction time.

(12) Vibration in the feeding part

(13) The component thickness data device is incorrect.

(14) The initial value of the suction piece height is wrong.

E. Random non-attachment mainly refers to the fact that the suction nozzle is not attached at the low point of the patch position and there is a missed attachment.

The main reasons for this are as follows:

(1) The warpage of the PCB board exceeds the allowable range of the equipment, the maximum warpage is 1.2mm, and the maximum warpage is 0.4mm.

(2) The height of the support pins is inconsistent or the flatness of the support platform of the worktable is poor.

(3) There is liquid on the suction nozzle or the suction nozzle is severely magnetized.

(4) The vertical movement system of the L nozzle runs slowly.

(5) The blowing sequence does not match the placement head descending sequence.

(6) The amount of glue on the printed board is insufficient, missing points, or the machine pins are too long.

(7) The nozzle mounting height equipment is defective.

(8) The solenoid valve is poorly switched and the blowing pressure is too small.

(9) When a certain suction nozzle appeared NG, the device placement STOPPER cylinder did not move smoothly and was not reset in time

F. Poor posture for picking up: Mainly refers to the presence of standing or oblique films.

The main reasons for this are as follows:

(1) The vacuum suction pressure is poorly adjusted.

(2) The vertical movement system of smt placement nozzle is slow.

(3) The falling time of the suction nozzle is not synchronized with the suction time.

(4) The initial value of the height of the suction piece or the thickness of the component is set incorrectly, and the distance between the suction nozzle and the feeder platform when the suction nozzle is at a low point is incorrect.

(5) The packaging specifications of the braid are not good, and the components are shaking in the installation belt.

(6) The feeder thimble does not move smoothly, the fast closing device and the press belt are not good.

(7) The center axis of the feeder does not coincide with the vertical center axis of the suction nozzle, and the deviation is too large.