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www.us-
tech.com Measuring Three Levels of
Process Control in Thermal Profiling M
By Patrick McWiggin, Technical Director, Solderstar Ltd.
aintaining process control within tightly defined limits is an important part of achieving high product quality in today’s
electronic manufacturing facilities. The pressures to deliver products in shorter development cycles and with increased capacities pose significant challenges for these facilities, making thermal management a necessary component in an elec- tronic manufacturing process. Proper thermal management can guarantee that products are cor- rectly soldered and process parameters are met. Three levels of process control are commonly
employed at present, with differing benefits and failures. They start with the traditional test board method through to advanced automatic profiling systems. Over the years, thermal profiling has advanced significantly and now offers exact pro- files aiding in the advancement of electronic tech- nology manufacturing. The first level to examine is the traditional manual method of process control.
Manual Method The manual method of passing a device
through an oven for testing, with a test board to assist with the initial temperature profile setup, is still an essential fundamental step in product tem- perature profiling. In this approach, thermocou- ples are placed on crucial components on the test board. When it is passed through the oven for test- ing, measurements are performed to ensure that the product’s thermal profile is within the limits of the target profile. As electronic assemblies grow smaller, more
complex, and more fragile, or when higher volumes of electronic products must be tested, the manual method may no longer be suitable. With higher volumes, verification of the oven profile must be performed more frequently. Using a test board for
Traditional thermal profiling is performed with the help of a great deal of operator labor time.
ly to changes in temperature and not degrade tem- perature measurement accuracy. As a result, they are inherently fragile and must often be replaced, which is time-consuming and can lead to measure- ment repeatability problems. Attaching new sen- sors can be difficult; if placed incorrectly, they can fall off or be caught within the measurement machine. Along with the potential of damaging a PCB as a result of repeated test runs, which can cause inaccurate measurements, the manual ther- mal profiling method suffers many drawbacks.
on-going process checking can be error-prone, resulting in false alarms or thermal measure- ments with poor accuracy and poor repeatability. The main challenge in using the manual
method of thermal processing lies in keeping the test board in proper working order. The thermo- couple sensors that establish the thermal profile during the initial setup stage must respond quick-
The manual thermal profiling method
requires many hours from personnel. The process is labor-intensive and interrupts production. The manual measurement approach is also very dependent on the technician’s skills in correctly attaching thermocouple sensors within the test board and product to be tested. The approach requires the measurement of a “golden standard” to use as a reference for other measurements, and this can be difficult or impossible to do if thermo- couple sensors are improperly placed.
Oven Verification Devices Because of these drawbacks to using tradi-
tional thermal profiling devices, combined with test cards, SolderStar sought thermal profiling solutions that would ease the process of capturing oven verification profiles. There was a need for a device that monitored oven temperatures effective- ly, without putting constraints on the test machine or the technicians working it. There was also the need for software that documented the thermal profile accurately and could provide easily trace- able results. This is especially important with gov- ernment regulations and original equipment man- ufacturers imposing higher standards. The med- ical and automotive industries are among the industries that have pushed demand for more crit- ical thermal management control and traceability; therefore, oven verification devices were born. The DeltaProbe system from SolderStar is an
example of a more advanced thermal profiling solution for electronic manufacturing process con- trol. It was designed and developed to combat the problems of traditional manual profiling and pro- vide manufacturers with a more streamlined method for periodic thermal profiling. The
Continued on next page
March, 2015
Aven Tailors Inspection Systems For The Perfect Fit
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