Item Subject: Re: Assisted visual inspection of fine-pitch solder connecti
Hi Gordon,
The resolution (nos of pixels) of the camera is also important as the
clarity of the image is dependent primarily on this. There are various
'grades' with the highest one at about 400x700 (guess!) pixels. The
cost of the camera also increases.
Besides the frame grabber (as described by Vijay Sankaran), the
software is also another important aspect.
The output monitor may also affect the final image seen. Your monitor
should be of high resolution as well. I have tried with normal TV but
the effect is terrible.
The last but not least is the conditions of lighting (angle,
intensity). If your surfaces are very reflective, you might want to
consider the use of filters (eg. polarisers). This would reduce the
intensity of the light received (you may need to increase the
intensity of the light) but will generally give better edge defination
and less glare.
regards
Jeff-MH Tan
________________________ Reply Separator _____________________________
Hi Gordon:
You have two related issues in your problem. 1. Sufficient resolution
for decision making 2. Intuitive control of positioning
The former can be easily addressed by using the right optics
with the existing TV camera. Incidentally, the NTSC-based TV camera
alone has a good enough resolution for most inspection tasks.
It is the frame grabber, used to acquire and analyze the images
automatically, that decides the maximum detail for decision making. I
agree that there is no unique solution to looking at the heel fillet
other than the mirror arrangement that you investigated and
another microscope lens that I saw at NEPCON. This lens rotates about
the joint in focus giving you a sort of 3D feel for the joint.
I'll post the name of the company that makes /distributes that lens as
soon as I can get hold of it.
For the positioning, we have developed a point-and-click interface for
our Integrated SMT Inspection and Rework Cell which uses a scanned-in
bitmap of the board as a guide. The user simply
clicks on the image at the pin he/she wants to inspect, and
the X-Y table moves there. We have implemented on a PC with a number
of table drivers and it is fully extendible. Depending on the
calibration (which has been greatly simplified), and the accuracy
of the table, the software can position boards with high accuracy. We
are currently using it to create defect maps based on X-ray
Laminography for communicating with our automated Rework cell. That's
one way to take care of the problem you described.
--
Vijay Sankaran (518) 276-2721 [log in to unmask]
Research Associate
Center for Integrated Electronics and Electronics Manufacturing
Renssleaer Polytechnic Institute
Troy, NY 12180
______________________________ Reply Separator _________________________________
Subject: Re: Assisted visual inspection of fine-pitch solder connec
Author: Non-HP-James.terveen ([log in to unmask]) at
HP-Singapore,shargw19
Date: 12/7/96 6:47 AM
Try a system made by Vision Engineering, which uses a camera and
lenses to view different sides of a component with a very slick
system. CA Number is 714-974-6966, CT number is 860-355-3776. I've
uses the system $35K and it is great for visual inspection
______________________________ Reply Separator _________________________________
Subject: Assisted visual inspection of fine-pitch solder connections
Author: [log in to unmask] at _internetcc
Date: 12/6/96 9:14 AM
I was recently asked to help evaluate two systems designed to assist in
visual inspection of solder connections on board assemblies. Both use a TV
camera and automatic X-Y positioning. The latter is important help an
inspector identify a particular connection of a fine-pitch component that
may have fifty or more connections on a side. One, made by Omron, uses a
patented arrangement of three concentric ring lights, each of a different
color. The colored reflection pattern allows interpretation of the fillet
contour. The other, made by I Systems, uses a motor-driven mirror to allow
inspecting connections from any angle, although the TV camera remains
oriented to look straight down.
I found things I liked and things I didn't like about each system, and I
got to wondering whether there might be other commercially available
systems not a whole lot more expensive than these two (say ~ $50K), which
we should evaluate as well. In particular, I find that a TV camera results
in a poorer image quality than conventional optics, and would recommend
just using a microscope, looking at connections at a variety of
orientations, if it weren't for three difficulties with fine-pitch parts:
identifying the pin number, holding the assembly still enough to interpret
what's there, and getting a good view of heel fillets.
Of course, we could try to get our customer to change our acceptance
requirements so that a connection that looks OK to the camera is OK, but
we're not sure we could do that. Also, it may not be necessary to identify
the exact pin number but only to report the approximate location to help the
rework operator to find it.
Comments?
Gordon Davy
Northrop Grumman ESSD
Baltimore, MD
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