4OM-1208-011_w.pdf - 第231页
5-10 AIVEMT -ID 0606-009 3.1 Cause and Remedy of Placement Errors (2) Missing Components on PCB (2-1) Situational Grasp of Error Generation The following three symptoms can be assumed regarding why some components are mi…
5-9
AIVEMT-ID
0606-009
(1-3) Positional and Angular Deviations in Process D or E
When a positional deviation is not generated on the double-faced tape,
it in
dicates that positional and angular deviations occur in Process D or E.
As a symptom at this time
•
The component is dislocated right after it is placed.
•
The component is dislocated during operation subsequent to the
placement.
•
The component is dislocated during PCB discharge operation
subsequent to the placement.
The causes in the above cases lie in the factors affected commonly by
the shape of the component, the condition of the PCB, or the condition
of solder paste or glue.
Fig. 4E8 is an example, which shows that a component is dislocated
right after it is placed due to the upper and lower surfaces of the
component not parallel to each other
.
A force is generated and moves the component in the X direction at the
moment when the lower surface touches the PCB during placement.
This leads to the positional and angular deviations of the component
placement.
When this type of component is used, this failure may be avoided by
slowing down the placement speed or slightly increasing the nozzle
descent level for the placement.
Some components may be dislocated easily during the backup base
movement or a PCB discharge operation after they are placed.
The factor may be weak holding power of solder paste or glue or
imperfect fixation of PCB.
It is required to check these conditions and take individual
countermeasures.
Fig. 4E8 Easily-Dislocated Component during Placement (Example 2)
3.1 Cause and Remedy of Placement Errors
5-10
AIVEMT-ID
0606-009
3.1 Cause and Remedy of Placement Errors
(2) Missing Components on PCB
(2-1) Situational Grasp of Error Generation
The following three symptoms can be assumed regarding why some
components are missing.
•
Some components were lifted up during placement.
•
Some components sprang out due to vibrating PCB or vacuum break
during placement.
•
A component sprang out while the PCB is being discharged after
placement.
The smaller the touch area with the PCB (solder paste) is in comparison
with the component size, the more frequently this type of failure occurs.
This applies commonly to these symptoms.
As shown in Fig. 4E9, power enough to hold a component will be given
when square components (resistors, capacitors, etc.) are used. However,
the above symptoms may appear more frequently when leaded
components (transistors, diodes, etc.) are handled because of the small
touch areas.
Square Component
Leaded Component
Shadowed are the touch areas between the components
and the solder paste.
Solder Paste
PCB
Note
Fig. 4E9
5-11
AIVEMT-ID
3.1 Cause and Remedy of Placement Errors
0606-009
(2-2) Machine-Based Factors
Shown below are the assumable main factors based on the machine.
When trouble occurs in some of the components (the components of the
same type that have been used in the past actual production), check for
the following factors.
•
Worn, Clogged, or Dirty Vacuum Nozzle
•
Vacuum Nozzle Up/Down Movement Error
•
Flow Rate of Broken Vacuum and Performance Error
•
Improper Placement Height Level
•
Imperfect Holding Power for Z Clamping
•
Dirt and/or Nicks on Linear Measure Sensor
(3) Other Factors
The factors other than the machine-based ones are assumed to be the
shape of the component, the condition of the PCB, or the condition of
solder paste or glue.
The factors are shown in the table below
.
Check each item and take measures if necessary.
If no quick improvement can be made due to the condition of the PCB
or solder paste, failures can be avoided by slowing down the speed of
the component placement or the PCB transfer.
Table 4E2
Component
A foreign substance exists on the upper surface
of a component and adheres to the vacuum
nozzle.
There is a protruding portion on the upper
surface of a component, causing the lower
surface of the vacuum nozzle to wear out and
an error during the teaching operation through
component recognition lighting.
Oil or mold lubricant adheres to the lower
surface of a component.
PCB
S
ome
PCBs vibrate during component placement
because the warpage is great.
Some PCBs are fixed imperfectly due to
variations in shape.
Glue
Shortage of
Applied Glue
Solder Paste
Shortage of
Applied Solder Paste
Shortage of Adhesion