![]() A poorly-designed nozzle leaves a temperature gradient in the hot air source thereby leading to inconsistent results. ![]() Too large a gap between the edge of the package and the nozzle and then the neighboring parts will tend to go in to reflow. Secondly, to make sure the hot air blows effectively on the package and not onto the neighboring components, a customized nozzle is required. This is especially true for 0201, μBGA and other micro packages. First, due to the nature of the hot air source and the ever-decreasing mass of SMT components, solder joints can be disturbed or parts can be skewed during reflow. While there are many advantages to using a hot air rework system, there are some drawbacks the user needs to be aware of when trying to decide which reflow source to use. Finally, a hot air convection system quickly delivers heat energy into thermally massive boards.įigure 1: Nozzle delivers hot air in and around the package during rework cycle. Inducing nitrogen during this step displaces the oxygen and limits the oxide layer forming around the molten solder. In air-atmosphere rework, an oxide layer forms around the solder sphere as it reflows. Additionally, inducing nitrogen to the site during component reflow has the advantage of making sure the metallurgical structure of the solder joint is the most reliable. The absorption of heat by the component and circuit board is independent of a material’s color or texture. Hot air convection heating for PCB rework is advantageous for a variety of reasons. ![]() There are numerous levels of such a hot air system, including a completely manual, a semi-automatic, and an automatic system, each with its own features. This electromagnetic radiation, safe to the operators, is absorbed by the package, thereby sending the solder into reflow.Ī typical hot air rework system employs a heat source and an air source that forces the heated air through a nozzle (Figure 1) configured to the area of interest, which heats up the component to be reworked. A second much-used heating technology relies on infrared energy. The first method employs the use of hot air gas to heat up the component through the package-this may or may not include the injection of nitrogen. There are two prevalent heating technologies in use throughout most electronic assembly operations for advanced component rework.
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