Automatic optical inspection systems
In the SMT process, the migration to smaller components are driving the implementation of AOI machines.
1. Passive components: smaller components (0402/0201) utilization
1206 =
0805=
0603 =
0402 =
0201 =
3.2 x 1.6 mm
2.0 x 1,3 mm
1.6 x 0.8 mm
1.0 x 0.5 mm
0.6 x 0.3 mm
2. Large utilization of ultrafinepitch and BGA and uBGA components.
3. Higher speed placement equipment.
Automatic optical inspection systems
 The issue is not if we have to use an AOI machine, but understand where in the process it is most
profitable: after the screen printer, after the pick and place or after the oven? The list of the main failures
that can be caught with the use of the AOI machine can help us on this analysis.
Fail
Excessive paste
Missing solder paste
Misaligned solder paste
Poor solder paste
Smashed solder paste
Missing components
Reversed components
Misaligned Components
Wrong Polarity
Wrong component
Cracked component
Aoi after screen printer
X
X
X
X
X
Aoi after pick and place
( X)
(X)
(X)
(X)
( X)
X
X
X
X
X
X
Missing/ bent lead(s)
Tombstoned
Poor solder joint
No solder joint
Short circuit
(X)
AOI after the oven
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Automatic optical inspection systems
1. AOI after the screen printer
Since the screen printer is the first stage, every defect created will be passed on to the next process. The
strategy behind using post print AOI is to perform 2D or 3D paste inspection. The volume measurement is
critical in the smaller componets (0201) and the ultra fine pitch components.
2. AOI after placement
Placement of an AOI at this location will identify a high percentage of defects during the SMT process
including some caused at screen printing .The failures detected at this step can be easily detected and
reworked.
3. AOI after the oven
The system can theorically give you the opportunity to identify all defects caused during the SMT process
but inherently has these disadvantages:
- Failures identified have a high rework cost.
- The feedback on the process is not in real time ....all boards in reflow oven be defective.
- The overkill factor is critical due to inherent variability of the solder joint image. Bad, missing and
cold solder joints are not detected with high repeatability. Consequently, much time is spent fine
tuning each AOI program.
- The pick and place operation cannot be controlled by SPC analysis because the addition of reflow
masks problems otherwise contained by real time SPC feedback
Automatic optical inspection systems: VIM II
Failure sample: Insufficient
capacitor metallization
The machine controls component positioning after placement. The system verifies by pattern matching at the
component level giving us the opportunity to inspect with high accuracy. Additionally, since it utilizes
centroid data as an integral part of that inspection, it offers real time Statistical Process Control of placement
accuracy.
Automatic optical inspection systems: VIM II
Main Features
Each point represents
individual placements
of the component
selected.
Max speed
0,085 sec/comp
Accuracy
(+/- 0,015 mm)
Near Zero Overkilling
Easy to be programmed
Easy maintenance
Real Time SPC.
With this graph, you can immediately evaluate placement
performance for each component real time.
This feature assists not only with placement program
optimization, but also provides immediate feedback, relative to
all types of process changes. ( program variations, feeders,
nozzles etc.)
Reports have been developed to analyze positioning accuracy
by product, by lot, by hours. Additional reports can be added as
desired by the customer.
Features
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Max speed: 0.085 sec/comp
Accuracy: (+/- 0.015 mm)
Near Zero Overkill
Easy programming
Inspects for missing, misplaced, wrong, polarization, cracked, broken, and more.
Easy, flexible programming. Individual components can be reprogrammed easily without reprogramming an entire area.
Standard Library for passive components. (Passive components have “don’t care area’ pre-programmed)
Executes 45,000 tests per hour
CAD Data or machine data may be downloaded to minimize downtime.
Programmable rail width
In line or off-line capability
Test optimization function determines fastest path.
8 camera lighting sections may be individually programmed for best contrast
Tests individual cards or multiple panels
Unique components can be added to the component library
Markings Identification. This can be programmed for “spot checking” for statistical analysis.
Statistical symbolization checking.
Statistical control prior to reflow . SPC can measure the deviation and provide real time feedback.
Component model images are optimized to produce near zero overkill.
Can check 0201 with no modifications to camera
Extremely low maintenance.
Affordable cost
Data reporting. All data can be used for statistical analysis.
SMEMA compatible
Questions /Answers
1. Who is Protech? Protech Electronics is a sales / engineering firm based near Rome, Italy. Protech has exclusive rights as marketing reps in
Italy for Ersa, Philips, Knodel. VIM II , and Optitest. Protech engineering is responsible for development, and ongoing support for VIM II
and Optitest as well as development of new products.
2. How many units in operation worldwide? 67 Units currently in operation worldwide. Most units are located in Italy. The machine was
developed by Protech specifically for EEMS, Inc. Rieti , Italy. It was so successful that it is now being marketed worldwide.
3. What companies currently use the system? Currently, EEMS (formerly Texas Instruments), a large memory house has 8 units in production.
Others machines are located throughout Europe. Additionally, a VIM II is currently under evaluation by JBIL.
4. How many units in operation in USA? Recon has recently been awarded exclusive rights to market the machines in North America. Several
companies are strongly considering the machine at this time.
5. Who is going to support the machine in the USA? Recon / Protech have a longstanding partnership. Upon delivery of the first machine in
the USA, 3Q 2004, Protech Electronics provided on-site training Recon engineering. Additionally, Protech Engineering has the capability to
access each machine’s onboard software via the internet from anywhere in the world. However, since thousands of hours have been logged
on the machines, little or no offline support is anticipated.
6. Spare parts and service. Recon will stock a complete inventory of consumable spare parts, along with an inventory of complete machines.
7. Warranty? 1 Year Parts / service warranty.
8. Website? www.protechelettronica.it The VIMII is featured.