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www.us-
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Production Environments Continued from page 50
verification profiles run to ensure proper operation. For such products, clients and manufacturers are con- stantly in discussion regarding the required frequency of profiling. Opinions can vary greatly on how much profiling is enough, since some feel modern reflow ovens are stable and require less profiling while some feel that there can never be enough accurate knowledge about the char- acteristics of a reflow oven and a sol- der reflow process.
Automatic and continuous
profiling that measures the profile in real-time for
each and every PCB being produced is becoming popular among many manufacturers
Common variations like
changes in the exhaust system, ther- mal loading, pressure changes, and human errors may affect the thermal process significantly. Automatic and continuous profiling that measures the profile in real-time for each and every PCB being produced is becom- ing popular among many manufac- turers because the technology pro- vides traceability, eliminates the problem of running blind in between spot checks, and eliminates the pro- duction downtime associated with periodic manual profiling. The sys- tems will further reduce downtime by monitoring the oven during the
Reflow in Today’s High Mix
changeover phase and alert the tech- nician the moment that the oven is ready for production. Another source of downtime can
be the time required to troubleshoot a production run that has stopped due to a yield problem. Although typ- ically less than 5 to 10 percent of defects are attributed to the reflow process, many factories will run a profile to troubleshoot a yield prob- lem. This is due to the lack of process information about the reflow oven. Automatic profiling will inform the engineer immediately whether the problem is in the reflow process or not, reducing troubleshooting time. If the problem is in the thermal process, the system provides infor- mation to identify the problems in the oven.
Automatic Profiling It is not uncommon for SMT
production lines to spend more time on setup and line changeover than actually running production. Ad - ditionally, following best manufac- turing practices for the reflow process may not be possible or acceptable at these factories. Today, process engineers and managers are doing their best with what they have. They can use techniques like scheduling the production batches to run cooler oven recipes in the morn- ing and progress towards hotter recipes at the end of the day. To sig- nificantly improve profitability, how- ever, high-mix/low-volume manufac- turers are taking advantage of new
Continued on page 57
August, 2015
Reflow Soldering: With or Without Vacuum?
Continued from previous page
mechanical construction of the sys- tem offers the opportunity to use the vacuum as a true option, or to use the VisionXP+ Vac system as a classic convection soldering system without the vacuum.
Reduced Maintenance The vacuum chamber
is
installed in the VisionXP+ Vac reflow solder system as an enhancement to the available peak zones. The inte- grated pyrolysis and separate filter- ing of the atmosphere extracted from
maintenance efforts. The VisionXP+ reflow solder
system has a tripartite transport sys- tem: pre-heating/peak area, vacuum unit, and cooling zone. All three areas of the transport system can be optionally equipped with a central support for handling particularly wide circuit boards. The possibility of reducing the transportation speed in the cooling zone when using the vac- uum enables the extension of the cooling time of components and therefore guarantees an optimum temperature for subsequent process
The x-ray images show a QFN44 solder joint with and without
vacuum using the VisionXP+ Vac soldering system. Note all the voids in the non-vacuum soldering.
the vacuum chamber are additional plus points in terms of maintenance and cleaning. A generously dimen- sioned vertical travel range of the vacuum chamber in the service posi- tion enables ready access to the internal mechanisms during mainte- nance periods. The automatic run- ning of the process chamber into the processing or maintenance positions minimizes downtimes and simplifies
steps. The throughput of the system is additionally increased with the expansion of the transport system by a second track.
Precise Pressure All heating zones of
the
VisionXP+ Vac are regulated individ- ually and separated from each other thermally, guaranteeing flexible pro-
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