A reflow oven is a machine used primarily for reflow soldering of surface mount electronic components to printed circuit boards (PCB).
SMT Reflow Oven Type:
As heating zones is different, SMT reflow oven called 8 heating zones reflow oven, 10 heating zones reflow oven, 12 heating zones reflow oven. By heating method different, SMT Reflow oven called hot air convection reflow oven or infrared Reflow oven, Some reflow oven is Dual lane(2 conveyor in 1 reflow oven), so called Dual lane Reflow Oven, some reflow oven is nitrogen process, so called Nitrogen Reflow oven, Some reflow oven has a Vacuum part in soldering area to reduce the void in solder, this kind reflow oven called Vacuum Reflow oven.
Different Reflow oven used for different soldering process. Like the Pick and place machine is Dual lane, then Reflow oven and conveyor also should be Dual lane model. Some Print Circuit board components is very small, easy to be oxidated in the high temperature environment, so need the nitrogen process to avoid oxidation on the solder surface. Some Reflow Oven for LED industry, 6 heating zones Reflow Oven can be enough for soldering requirement.
The SMT Reflow oven contains multiple zones, which can be individually controlled for temperature. Generally there are several heating zones followed by one or more cooling zones. The PCB moves through the oven on a conveyor belt, and is therefore subjected to a controlled time-temperature profile.
The heat source is normally from ceramic infrared heaters, which transfers the heat to the assemblies by means of radiation. Ovens which also use fans to force heated air towards the assemblies (which are usually used in combination with ceramic infrared heaters) are called infrared convection ovens.
Some ovens are designed to reflow PCBs in an oxygen-free atmosphere. Nitrogen (N2) is a common gas used for this purpose. This minimizes oxidation of the surfaces to be soldered. The nitrogen reflow oven takes a few minutes to reduce Oxygen concentration to acceptable levels within the chamber. Thus nitrogen ovens typically have nitrogen injection in at all times which decreases defect rates.
Thermal processing of solder for electronics manufacturing takes place in a reflow oven. A reflow oven can be a small batch (box) style oven for very small lab scale operations. For larger manufacturers, an inline or conveyor belt reflow oven is the best choice. In the early days of electronics manufacturing, infrared (IR) heating technology was employed. Later on, the industry, switched to convection heat transfer. Convection reflow ovens had many advantages including vast improvements in heating uniformity. The most modern reflow ovens use closed-loop convection.
Vapour phase oven
The heating of the PCBs is sourced by thermal energy emitted by the phase transition of a heat transfer liquid (e. g. PFPE) condensing on the PCBs. The liquid used is chosen with a desired boiling point in mind to suit the solder alloy to be reflowed.
Some advantages of vapour phase soldering are:
· High energy efficiency due to the high heat transfer coefficient of vapour phase media
· Soldering is oxygen-free. There is no need for any protective gas (e.g. nitrogen)
· No overheating of assemblies. The maximum temperature assemblies can reach is limited by the boiling point of the medium.
This is also known as condensation soldering.
HOW ARE REFLOW OVENS CONFIGURED?
Inline reflow ovens are configured with a number of heating zones followed by cooling section(s). Depending on the length and throughput of the oven there may be few zones, 8 or less, or many zones, 12 or more. During the reflow process the zones are programmed with a thermal set point. This set point corresponds to the temperature the circuit board should be exposed to as it passes through that zone. The program with the temperatures for all of the zones, as well as the belt
SMT Reflow Oven Thermal profiling
Reflow oven Thermal profiling is the act of measuring several points on a circuit board to determine the thermal excursion it takes through the soldering process. In the electronics manufacturing industry, SPC (statistical process control) helps determine if the process is in control, measured against the reflow parameters defined by the soldering technologies and component requirements.
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