May, 2018
www.us-tech.com Continued from previous page
of the solder wave. The pump speed is then regu- lated to achieve the preset wave height. As the measuring needle only carries
out a contact measurement and does not dip into the solder, it is important to keep the atmosphere stable. Changes in the surface tension can cause different meas- urement results. The wave height can automatically
be controlled using a laser measuring sys- tem. The measurement procedure is per- formed during production and does not influence cycle time. In addition, any change of the pump speed affects the measuring signal quickly. The direct measurement of the wave height also rec- ognizes soiling in the nozzle system which could affect soldering quality. The wide measuring range of the sensor and the adjustment to zero at the top edge of the solder nozzle allow the use of nozzles with different heights. One newly developed wave
height measurement system is SEHO’s cross sensor that has several functions. It measures, without con- tact, directly at the solder nozzle and is unaffected by the type of solder alloy used. The cross sensor is also used for
automatic tool measurement. Dia - meter, height and mounting position of the solder nozzle are automatical- ly controlled, eliminating potential operator errors. The cross sensor car- ries out another task if additional
One newly developed
wave height measurement system is SEHO’s cross sensor that has several functions. It measures, without contact, directly at the solder nozzle and is unaffected by the type of solder alloy used.
processes, such as a brushing process for the removal of solder balls, are installed in the selective soldering system. The cross sensor can monitor the condition of the brush and auto- matically indicate the need for a replacement if it is worn down to a certain level. Additional automatic monitor-
ing and control functions help to avoid potential soldering defects or to eliminate operator errors. Functions include automatic position correction of the x, y and z values for assemblies that have misalignment or warpage. Intelligent tool management, based on sensors and software, recognizes the solder nozzle and ensures that only PCBs designed designed for that nozzle setup are allowed to enter the soldering system. Selective soldering processes
require high pot temperatures, up to 608°F (320°C), due to the relatively small solder volume available for energy transfer. This also comes with an increased risk of oxidation. Selective soldering is generally done in a nitrogen atmosphere. While the mini-wave in nitrogen has a con- trolled solder flow, the liquid solder rapidly oxidizes once the inert atmos- phere is lost. The solder flow can then be
deflected easily and hardly be con- trolled, making it difficult to create reliable solder connections. Various control methods can ensure a stable nitrogen atmosphere during this process. The quality of the supplied
DESIGN SOLUTIONS … for SMT Threaded Standoffs
Page 67 Zero-Defect Soldering and Quality Management
nitrogen can be monitored by measuring the rest- oxygen value at the nitrogen feed-in. This is partic-
ularly useful if a nitrogen generator is connected. To ensure a stable atmosphere, it is also pos- sible to permanently control the nitrogen quantity at the gas supply of the soldering unit. Here, an individual value that is needed for the specific process can be set in the soldering program (l/min).
Integrated AOI and Rework An AOI system, integrated into the
selective soldering machine, offers 100 percent process control. Soldering defects can be detected early and analysis of trend and series fault information allows process optimization at an early stage, reducing the overall defect rate. This applies mainly to component placement
Automated, zero-defect production line concept. Continued on page 72
™
Designed for Surface Mount use on PC Boards Minimize PCB damage Reduced scrap/handling Faster board assembly Manufactured with tin plate Available in 2-56, 4-40 and 6-32 threads
Lengths from 1/16” up to 3/8” Ideal for automated installations Supplied on tape and reel with Kapton tape for easy pick up Compatible with all reflow operations and vacuum and mechanical pick-&-place assembly systems
IT’S WHAT’S ON THE INSIDE THAT COUNTS ® ELECTRONICS CORP.
www.keyelco.com (516) 328-7500 (800) 221-5510 REQUEST CATALOG M65
See at EDS, Booth 300
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