Ask the Experts
March 3, 2008
Laser alignment vs. vision centering for Pick & Place
In comparing Pick & Place systems with "laser centering" vs. "vision centering" technology, what are their advantages and disadvantages?
Expert Panel Responses
I guess as the President of Juki, I'm the right guy to answer this question.
The reasons we use Laser Cameras to center the small parts on the head during motion are as follows:
Of course, we use bottom cameras for large parts in combination with our on-head laser cameras. This combination gives us the ability to apply the best technology to the task, assuring top quality and accuracy. Bottom cameras cost less than the high resolution laser camera, so it would be to our advantage price wise to just go that way. But to do it better, we use the laser technology. Juki became number one in the world in machines shipped last year, so the industry has endorsed our approach with their business.
If you'll be at APEX come by and watch us place 100 01005 parts for you. You'll quickly see the advantages.
- Accuracy. The laser camera we use has about 10 times more pixels in its CCD array as a bottom vision camera. On a small component such as an 01005, a bottom camera may have 2 to 3 pixels across the part. We will have 20 to 30 pixels. This higher resolution allows us to measure the part more accurately and place it more accurately.
- Speed. Because we measure in-flight, during head movement from the feeder to the board, we do not have to divert to a camera position and then go to the board.
- Extras. We can do a 100% side pick or tombstone check with no time lost. Camera systems can't do that.
President and CEO
Mr. Black was the President and Co-Founder of Zevatech in 1977 and introduced first Pick and Place System at Nepcon West 1980. Bob is now the President, CEO and Co-Founder of Juki Automation Systems. He is also a Co-Founder of the SMEMA Council of IPC. He serves as a member of SMTA and SEMI..
Good Question, but difficult to answer because it depends on what you want to do.
Laser systems work by rotating the component through a laser system and finding the flat sides of the component. It works pretty well on R's & C's. The laser is usually mounted on the placement head so the processing can be done while the head is moving from the pick-up point to the placement point. This makes the system fast, however, the information the machine has to work withis very limited.
For example; if you are placing an SOT-23, you can square the component based on the long side, but you can't tellif the component ispackaged out of rotation.
Example 2; You could be placing an SOIC that the leads are within tolerance, but swept back, a laser system will place the component based on the body and the leads may be off the pads. A camera will identify the leads are swept back, but within tolerance and adjust the placement so all the leads are perfectly on the pads.
Many equipment companies that use laser alignment systemsas a standard also offer camera systems as an option. I think that says it all, If you want to check lead length, lead width, lead center tolerance, number of leads, absence/presence of leads or balls, orientate by features or inspect BGA's, you need to use a camera vision system.
If you going to have a camera, then why have a laser, it's just one more system to maintain. More information translates to better accuracy, I highly recommend camera.
Fuji America Corporation
Scott Wischoffer has been in the SMT industry since 1986 with experience in service, training, sales & applications, and marketing.