User-Manual-of-NeoDen4-PNP-machine.pdf - 第51页

46 a. Nozzle had bee n wearing or bec ome aging, the cra ck cau ses leakage. - replac e with a new no zzle b. The nozzle’s bottom surfa ce is uneven or get suck b y sold er paste or other d irt Please wipe it off and use…

5.5

Placement failure analysis and troubleshooting

Placement failure analysis

Whether Pick and Place machine can run normally or not, which will directly impact on production

quality and volume. To make the machine run properly, we must fully understand the structure and

characteristics of the machine, master every kinds of failure patterns of manifestation, reason and

troubleshooting methods. Finding problems and reasons in time and timely troubleshooting can help

ensure efficiency of the machine during working.

（1）

Common failures

a. not start boot failure

b. head doesn’t move

c. fail to feed forward a board

d. Pick failure

e. Place failure

（2）

Main reasons of failure

a. transmission systems-driven PCB and head movement transmission system and the

corresponding sensors.

b. Air Route-Air pipe, nozzle

c. Nozzle size not suit to the component

d. No info in Footprint library

e. Irregular component

f. Incorrect values setting of component’s heights or pick height

（3）

placement troubleshooting

Failure patterns of manifestation, Reasons, troubleshooting methods

head doesn’t move

Solutions:

a. Sensor is poor connected or short-circuited. Please wipe off the dust or lubrication on

sensor or even exchange a sensor

b. Longitudinal sensor or sensor poor connect or short circuit, check and repair the transmitter or

add too much lubricating oil on sensor-clean the sensor

c. Rails fail to advance the board feed forward after uploading the PCB

Solutions:

a. The rails belt gets loose or broken, need to be adjusted or exchanged.

b. The rails drive motor doesn’t work.

c. Nozzle can’t pick up component

d. Pick up position offset

e. Components fall down during moving

Solutions:

a. Nozzle had been wearing or become aging, the crack causes leakage. - replace with a new nozzle

b. The nozzle’s bottom surface is uneven or get suck by solder paste or other dirt Please wipe it

off and use cleaning needle to clean the nozzle

c. Current nozzle size is not suit to component, change another one

d. Surface uneven on the component, replace with a qualified one

e. Component is sticking to the bottom tape;

f. Burrs on tape hole stuck component;

g. Component’s pin gets stuck in the corner of the den;

h. Gap between components and tape package hole is not big enough, uncover the plastic tape and

upside down to check if the components can fall down or not.

i. Plastic adhesive tape is too sticky or flimsy and then cannot be unfolded. Or plastic adhesive tape

has been tearing down from edge side.

j. Pick up position offset. Actual Feed box is offset from Feeding center, check X, Y, Z data and do

reprogram.

Placement offset

Solutions:

a. Programming issue (some components’ positions are inaccurate), amend the coordinates; If all

components are offset, please modify fiducials.

b. The components’ thickness setting errors, modify components information on Footprint Library

c. Pick height is too high that causes components being dropped. Please reset the Pick Height value

d. Pick height is too low that causes slide problem during placement

e. High speed issue. Lower the speed to achieve a more accurate rotation and placement effect.

5.6

Related issues during solder paste printing process

(1)

Stencil Printing Technology

Screen printing technology refer to using ready-made stencil, directly contact to the printer in a

certain way, make the solder paste evenly flow on the stencil and then leak into the mesh through

the holes. When getting the stencil away, solder paste had been covered to the printed circuit board

solder graphics, corresponding, thus complete the solder paste printing on the PCB.

(2)

Inspecting of solder paste printing

Printing process is one of the key working procedures to ensure the quality of surface mounting.

According to the statistics, under the premise of guaranteed quality about components and PCB,

correctly PCB design, 70% of the surface quality problem caused during printing process. In order

to ensure the quality of SMT assembly, it is necessary to strictly control the quality of the solder

paste printing. The amount of solder paste printing requirements are as follows:

a. The using amount of solder paste should be uniform, good consistency. Solder paste graphics

should be clear, try to avoid adhesion between adjacent graphics. Solder paste graphics and solder

graphics should be consistent.

b. In general, keep unit area amount of solder paste about 0.8 mg/mm². For fine pitch components,

should be 0.5 mg/mm²(using stencil thickness and hole size to control in the actual operation).

c. Printed on the substrate of solder paste compared with required value, a certain deviation is

permissible, the covering area of the solder paste on each solder pad should be more than 75%.

d. Should be no seriously collapsing problem and edges neatly after solder paste had been printed,

the dislocation shouldn’t be larger than 0.2 mm, for solder pad of fine pitch components, dislocation

shouldn’t be larger than 0.1MM, pollution by solder paste is not permitted to the PCB.

(3)

The defects of solder paste printing, reasons andsolutions

Excellent printing graphics should be uniform in both vertical and horizontal direction, full, clean

all round, solder paste fill solder pad. Using above such printing graphics device, after reflow

soldering, will get good welding effect then.

a. Solder paste graphics dislocation

Reasons: Holes on the stencil not good match with solder pad; No enough precision of the Printing

machine

Issues: easily cause bridge connection

Solutions: Adjust the stencil position; Adjust the printing machine.

b. Solder paste graphics have icicles and dents

Reasons: Scraper’s pressure is too large; Rubber scraper’s hardness is not enough; Holes are too big

in the stencil

Issues: Solder paste’s required volume is not enough, easy to appear faulty soldering; solder joint

strength is not enough.

Solutions: Adjust the printing pressure; Use metal scraper; Improved holes designing in the stencil.

c.Too much solder paste

Reasons: Holes are too big in the stencil; The gap is too big between stencil and PCB. Issues: easily

cause bridge connection

Solutions: Check the holes size in stencil; Adjust the parameters of printing, especially the gap

between PCB and stencil

d. Graphic uneven (havebreakpoints)

Reasons: Holes’ wall are not smoothness enough; not wipe residual solder paste in using for many

times; Solder paste’s thixotropy is bad.

Issues: Easy cause no enough solder paste, lead to the problem such as faulty soldering. Solutions:

Wipe the stencil

e. Contamination of thegraphics

Reasons: Not wipe residual solder paste in stencil after using for many times; Poor quality of solder

paste; Shake problem when getting the stencil way

Issues: easily cause bridge connection

Solutions: Wipe and clean stencil; replace solder paste; adjust the machine.