The liquid used is chosen with a desired boiling point in mind to suit the solder alloy to be reflowed. The heating of the PCBs is sourced by thermal energy emitted by the phase transition of a heat transfer liquid (e. Thus nitrogen ovens typically have nitrogen injection in at all times which decreases defect rates. The nitrogen reflow oven takes a few minutes to reduce Oxygen concentration to acceptable levels within the chamber. This minimizes oxidation of the surfaces to be soldered. Nitrogen (N 2) is a common gas used for this purpose. Some ovens are designed to reflow PCBs in an oxygen-free atmosphere. Ovens may use a combination of infrared radiative heating and convection heating, and would then be known as 'infrared convection' ovens. This indirect heating using air allows more accurate temperature control than directly heating PCBs by infrared radiation, as PCBs and components vary in infrared absorptance. They may be fan assisted to control the airflow within the oven. In infrared reflow ovens, the heat source is normally ceramic infrared heaters above and below the conveyor, which transfer heat to the PCBs by means of radiation.Ĭonvection ovens heat air in chambers, using that air to transfer heat to the PCBs by means of convection and conduction. Types of reflow ovens Infrared and convection ovens The profile in use may vary depending on the requirements of the PCBs being processed at the time. Technicians adjust the conveyor speed and zone temperatures to achieve a known time and temperature profile. PCBs being processed travel through the oven and through each zone at a controlled rate. For prototyping or hobbyist use PCBs can be placed in a small oven with a door.Įxample of reflow soldering thermal profile.Ĭommercial conveyorised reflow ovens contain multiple individually heated zones, which can be individually controlled for temperature. In commercial high-volume use, reflow ovens take the form of a long tunnel containing a conveyor belt along which PCBs travel. A reflow oven is a machine used primarily for reflow soldering of surface mount electronic components to printed circuit boards (PCBs).
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