CONTRACT MANUFACTURING FEATURE MANUFACTURING PCBS QUICKER AND SIMPLER
Rob Hornsblow, Product Manager at Datapaq discusses how thermal profiling and analysis of reflow is enabling quick oven setup in electronics maunfacturing
P
rofit margins can be tight in electronics manufacturing, and the cost of product
failures is often high. Monitoring each process is vital to ensuring continued profitability. Reliable temperature measurement systems are a valuable tool in electronics manufacturing, especially if they are easy to use and oriented at both increasing productivity and minimising operation costs. Datapaq’s Reflow Tracker temperature profiling solutions provide the detail required for accurate process setup. Designed specifically for ease of use, it is suitable for day-to-day monitoring. In the manufacture of printed circuit
boards, melting the solder is a sensitive process: a temperature above the liquid (solder melting point) must be maintained long enough for all of the solder to reflow and for flux and solvents to be released. The temperature must not be so high as to damage any parts; the temperature slope must not be too steep, or parts may crack or discolour; and the slope must not be too slight, either, in order to avoid flux dissipation and drying-out before the solder reflows. Cool-down must be fast enough to ensure the assembly is safe to be handled but without being so fast as to thermally shock the components. Melting the solder with optimal energy use and without damaging the electrical components requires precise temperature control. Based on robust data loggers and application-specific thermal barriers, the Reflow Tracker systems pass through the oven along with the PCBs, obtaining detailed temperature profiles if required, providing the data via a radio link for real- time monitoring. The systems help manufacturing engineers in reducing reject rates and increasing yields. The accompanying Easy Oven Setup (EOS) software automatically determines the optimal oven settings for specific products and ovens, rendering the repeated trial-and- error setup method obsolete and thereby saving considerable time and effort at every new product introduction.
PROFILING AND ANALYSIS SYSTEM At the heart of the temperature profiling system is a data logger that stores all the readings from up to twelve probes. The thermocouples can be placed at strategic locations on the product. The logger features a “machined-from-solid” housing but still needs protection from the heat of
the process. Compact thermal barriers use microporous ceramic insulation to enable the systems to pass through the entire process, profiling all phases while maintaining the logger within its operating temperature
Figure 1: Reflow Tracker systems record complete temperature profiles of reflow soldering processes
programmable alarms instantly show whether the profile is within the required tolerance limits.
USER-FRIENDLY PROCESS SETUP The Easy Oven Setup (EOS) function is an especially valuable tool for process engineers. Usually, achieving the right temperature profile takes a trial-and-error process. Reflow ovens have several zones that can be temperature-controlled individually, combined with different possible line speeds.
TECHNOLOGY IN ACTION Let us look at an example with an oven that has seven zones (figure 2). A profile has been run. EOS checks the temperature data against parameters such as “time above temperature threshold”, “time to reach threshold”, highlighting any alarm conditions in red. In this case, the software detects two out-of-tolerance values: the liquidus temperature has been held for less than the specified 40s at two thermocouple positions. Conventionally, an engineer would at this
range. Datapaq is able to provide highly effective barriers that fit even in very restricted spaces. This includes a highly compact thermal barrier for vapour phase soldering which makes trailing sensor cables
Figure 2: Easy Oven Setup supports both, Ramp-Soak-Spike and Ramp-to-Spike profiles
Figure 3
a thing of the past, increasing functionality and safety. The accompanying Insight software converts the raw data into meaningful and clear information. Automatic analysis, traffic light signals, and
/ ELECTRONICS
Figure 3: Users can preview the predicted profiles for the recommended list of recipes graphically and numerically before deciding on one recipe
point go back to oven setup and manipulate the zone settings to achieve a correct profile in a trial-and-error process that can take hours. Using EOS, however, the engineer can simply enter the process parameters in a template using as much or as little detail as required. The specifications can be saved and shared. EOS automatically calculates from virtually an infinite number of temperature and line speed combinations those which ensure the best thermal profile. Ten possible oven setups are displayed along with their predicted temperature profiles (figure 3). Depending on production requirements, the engineer can select, e.g., an especially fast line speed and high temperature setting or a slower speed/low temperature combination. Once a setting has been selected, the engineer can simply programme the oven and start production. As can be seen, EOS speeds up oven setup by taking the guesswork out of the process. It is a virtual reflow oven that calculates optimal settings and predicts the effect on the temperature profile. This frees up the production line to do what it should be doing, producing good-quality electronic assemblies.
Datapaq
www.datapaq.com 01223 652 400
Enter 214 ELECTRONICS | OCTOBER 2014 29
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