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AN-994-1 Datasheet(PDF) 6 Page - International Rectifier |
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AN-994-1 Datasheet(HTML) 6 Page - International Rectifier |
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6 / 7 page  6 of 7 Section V: Heat profiles Reflow Soldering Heat Profiles A major problem associated with surface mounting of electronic components, especially those with mismatched internal expansion coefficients is the thermal shock of the soldering process. The advent of lead free assemblies has driven the requirement to develop and implement new handling techniques for surface mounting devices. Typical lead free solders have higher melting point temperatures than the traditional Pb based solders. Whereas previously, assemblies could be mounted at peak reflow temperatures in the range of 220 °C to 245°C, Pb free assemblies require reflow temperatures in the range of 245 °C to 260°C. The higher peak reflow temperatures require careful control of the reflow environment to prevent over temperature conditions that can severely degrade the reliability of surface mount devices. Caution must be taken when choosing the reflow profile in order to optimize the thermal stresses that are applied to either Pb based or Pb free assemblies. In addition to the over temperature considerations, under temperature conditions can in turn result in a failure of the mechanical attachment of the device during the reflow profile. A carefully controlled preheat and post-cooling sequence is necessary. Properly controlling the preheat cycle will remove any volatile component of the solder paste such as alcohol or water by evaporation prior to the solder fusing cycle. This will reduce the chances of forming void or solder ball. This thermal conditioning can be applied in several ways such as using Infrared/Convection ovens, Vapor Phase, or Wave Solder equipments. The recommended thermal conditioning method is the Infrared/Convection Soldering Temp / Time Profile described below: Infrared/Convection Soldering Temp/Time Profile. The critical parameters shown below are defined in table 2 by solder paste type and device volume. TSmax TSmin tp TL TP ts preheat tL Ramp down Ramp up t 25°C to peak Time Temperature Figure 5: Soldering & Test Profile |
Similar Part No. - AN-994-1 |
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Similar Description - AN-994-1 |
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