Fact 2: Best combination of placement speed and quality
Published on 11-Nov-2008
It's not just a promise, it's a fact!
Parallel placement with full Pick & Place cycle control gives the best combination of placement speed and quality. In-depth analysis of a number of applications shows that parallel placement can give up to a factor of 3.3 savings on rework costs. As the results on this web page show, the design concept gives intrinsically better placement quality through its total Pick & Place placement process control.
Sequential placement increases the risk of missed, misplaced or damaged components
On most machines, all the Pick & Place actions are sequential. That leaves limited time available per individual pick & place action. Most sequential pick & place machines use revolver heads or multiple nozzle heads where continuous individual component monitoring is impossible or very expensive to realize. Component monitoring is particularly needed, though, because of the high acceleration and deceleration forces acting on each individual component that increase the risk of component shift or loss. With typically 48 to 80 pipettes/nozzles per machine, there is a relatively high risk of nozzle contamination and condition variation, and a higher risk of component loss.
That means more missed components, and more variation in the placement process. Sequential machines have a positional uncertainty in component position, measurement position and component placement position. There is no component position monitoring between component alignment and placement position. There is usually no placement force control, either.
| Pick & Place technique | Sequential | Parallel |
| Process times | restricted | relaxed |
| Acceleration/deceleration forces | high | low |
| Continuous component monitoring | no | yes |
| Component positional uncertainty | high | low |
| Placement force control | rare | yes |
| Component cracking | high risk | low risk |
| Risk of component shift/loss | high | low |
| Risk of nozzle contamination | high | low |
| Rework costs | high | low |
Parallel placement allows for total pick & place process control
With parallel placement, all actions are executed in parallel. That means
‘relaxed’ process times with low acceleration forces and continuous
component monitoring. There is an individual component presence check, with
placement force control. Only 12 to 20 pipettes/nozzles are typically
needed to obtain comparable outputs to sequential Pick & Place machines
with 48 to 80 pipettes/nozzles. Possible nozzle contamination is constantly
monitored, with lower costs because there are fewer nozzles in the nozzle
changer.
Placement quality is intrinsically better with multiple placement robots
working in parallel and indexed substrate transport. The single placement
head per robot allows continuous process monitoring. More time available
per process step means lower risks and tighter variation. The result is a
typical single digit DPMO performance, and that means huge savings on
rework costs.
Assembléon’s placement head uses laser alignment, with force control to
cut out any risk of component cracking
