February, 2016 Continued from page 54
Materials Processing In the production of stencils for PCB assem-
bly, the precision and speed requirements are quite high. Material must be removed with exactly defined edges. Traditional laser deflection tech- niques such as galvo scanners are suitable, but for two-axis motion, two single-axis systems have to be “stacked.” This results in differing and variable pivot points, beam polarization rotation, and takes up more space. Piezo-driven tip/tilt mirror systems are more compact and provide higher acceleration and bandwidth. Due to a parallel kinematics design, there is only one moving optic with a fixed pivot point, leading to less inertia, higher dynam- ics, and better accuracy.
Medical Technology: Ophthalmology Benefits
This technology also has benefits for medical
technology. In ophthalmology it is possible to correct ametropia —a con- dition of the eye in which it is unable to focus — by reshaping the cornea using refractive operation tech- niques. For this purpose, the cornea
The Evolution of Cleaning Methods in
PCB Rework Continued from previous page
control thermal profiles. Also, the vacuum collection nozzle automates the task of solder removal for more consistent and complete removal, and with less chance of molten solder flowing into the wrong areas.
All-in-One Designs Until recently, contact-less
cleaning could only be performed on very large, high-end machines, or as an optional, retrofittable add-on that would allow the cleaning function to become part of the removal and replacement steps on a single rework machine. Stand-alone contact-less cleaning machines present a sub- stantially lower capital investment and other benefits. Perhaps most significantly,
stand-alone machines can offer great throughput. They can be run by a single operator, and when used next to a standard rework machine, offer the opportunity for the establish- ment of an assembly line operation to increase speed. These stand-alone machines
offer the opportunity for manufactur- ers to flexibly add contact-less capa- bility to their operations. If they have more recently invested in a standard rework machine lacking a scavenger add-on, they can readily add a con- tact-less cleaning machine to work side-by-side with their current sys- tem. This is a useful option if sudden- ly the manufacturer is forced to quickly add the capability because of customer demand. Scavenging can eliminate the
risks that come with manual cleaning. As chip sizes shrink, and production struggles to keep up with an ever- expanding demand for smaller and more powerful electronics, rework processes must develop as well. Contact: Metcal, 12151 Monarch
Street, Garden Grove, CA 92841 % 714-799-9910 Web:
www.metcal.com r
www.us-tech.com Piezo Mechanisms in Optics and Laser Technology
is modeled in the optical axis by shaving away small corneal particles and allowing the eye to refocus. Piezo tip/tilt mirror systems are suitable for these applications. Ultrasonic ceramic piezo motors also open up new possibilities for laser applications.
Set-and-Forget Laser Alignment Components In addition to the applications mentioned,
there are a number of “set-and-forget” tasks where an optic or mirror in a laser system needs to be checked on occasionally. The focus in this area is on stability and
smooth motion. PiezoMike type inertial actuators combine resolutions of 30 nanometers with holding forces of 100N and reliable start-up, even after long downtimes. The field of piezo motion devices for laser
applications has expanded rapidly in recent years. Today’s optical engineers have a wealth of differ- ent piezo technologies at their fingertips, from small piezo stacks for cavity tuning, to tip/tilt plat- forms, as well as long-travel motors with high dynamics and precision. Contact: Physik Instrumente L.P. (PI), 16
PiezoMike inertial linear motors replace conventional micrometers in a tip/tilt mirror mechanism.
Albert Street, Auburn, MA 01501 % 508-832-3456 fax: 508-832-0506 E-mail:
stefanv@pi-usa.us Web:
www.pi-usa.us r
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