April, 2011
www.us-
tech.com Selective Soldering by Laser Continued from previous page
joint and the thermal profile are needed in order to have full traceabil- ity of the process.
Laser Selective Soldering Seica, with experience in axes
motion and control of Flying Probe systems, manufactures the Firefly Line of selective soldering systems, an integration of software, mechan- ics and laser technology. The Firefly soldering system makes it possible to program a specific thermal profile for every single joint. This programming comprises three phases and is char- acterized by the change of tempera- ture over time.
Pre-heat. The first phase measures temperature and time to pre-heat the pad and pin surface.
Alloy melt. In the next phase, a higher temperature melts the alloy, which is automatically dispensed to the joint. The time of the second phase is proportional to the alloy and dispense speed, thus forming the sol- der joint.
Reflow completion. The third phase is used to improve the wetta- bility and to complete the reflow of the solder joint. The thermal profile is controlled using a pyrometer which adjusts the power of the laser source based on the detected temper- ature and the thermal profile that has been previously defined for the specific joint. This couples the real thermal profile with the theoretic thermal profile. To take advantage of the laser
technology used by the Firefly selec- tive soldering systems, all the oper- ating elements are inserted onto a soldering head capable of rotating 180°; this allows targeting the solder joint at any angle, and if necessary, rotating in the soldering phase to improve the wettability, particularly on larger-size joints. The optics of the 50-watt laser source are connected to the soldering head through a fiber optic cable, attached to a motor, which allows focusing the laser beam spot based on the solder joint size. The feeding of solder alloy to the sol- der joint is handled by a motor and sensor combination, which detects the alloy in the nozzle of the wire feeder as well as the amount of alloy fed to the joint. Because of the vary- ing dimensions of electronic compo- nents and circuits, the Firefly system is capable of using 500 gram spools of alloy wire with a diameter that ranges from 0.5 to 1mm.
Your story. Your reprint. From U.S. Tech.
Articles appearing in U.S. Tech are available as reprints. PDFs also available.
Contact Steve Leberstien, 610-783-6100, ext. 2125.
The laser technology requires
that the laser beam must always be perfectly focused on the solder joint. If there is board warpage, the focus may not be accurate. A warpage recovery sensor is located on the sol- dering head to detect and make adjustments to correct for the warpage and properly focus the optics on the joint. A camera mount- ed on the center-line of the soldering head provides fiducial recognition and video storage of the soldering phase, monitoring the entire solder- ing process.
Laser Management Software Among the basic features of the
software, the ability to create a com- prehensive soldering program needs
to be available, as well as the ability to process CAD/CAM data to create the solder joints. VIVA — the man- agement software for the Firefly laser selective soldering system — can create the required parameters working from CAD/CAM data or data manually entered by the operator, using a Macro designed for the sol- dering process. The use of the soft- ware ensures that there are no sur- prises, when using lead-free alloys with flux developed specifically for use with laser technology. The VIVA software can manage PCB features, such as the color, surface finish, and the composition of the alloys creating soldering parameters and thermal profiles for all types of boards and components.
Process traceability is another
important aspect of the software sys- tem. It provides up-to-the-minute results of production accuracy as well as the quality and repetitiveness of results. This monitoring this allows for the detection of possible produc- tion deviation. The VIVA software stores the thermal profile in use for each solder joint, the exact tempera- tures detected, and a video of the sol- dering process. The automation of such a critical part of the manufac- turing process is an important requirement in achieving the highest solder joint quality and repeatability. Contact: Seica, Inc., 50A
Northwestern Drive, Suite 10, Salem, NH 03079 % 603-890-6003 Web:
www.seicausa.com
Page 55
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