As the fluid boils, a thick blanket of vapour is created which is used to transfer the heat to PCBAs. This is not an accident, the fluid is specifically engineered to have this boiling point as it is the optimum temperature to melt solder paste. A heater boils the liquid at a typical lead-free solder paste melting point of 235C. On switch on, the vapour phase fluid is liquid at room temperature at the bottom of the fluid tank. How Does This Soldering Method Work?Ī Vapour Phase Reflow Machine works as follows. In contrast to other soldering processes, with VPR, heat is transferred by condensing vapour and not by radiation, or forced convection gas or conduction from a soldering iron. This has to be done without overheating the components. In addition, it is essential that PCB pads and the component itself also reach a temperature above the melting point of the solder paste otherwise a cold solder joint will arise, i.e. For a good solder joint, all the solder must be melted completely. Reflow soldering of SMD PCBAs may appear simple because all you need to do is apply some heat to melt the solder paste. Here at Newbury Electronics, we selected and installed an IBL BLS 420 VPR machine because of its adaptability to all the types of PCBs we might see. As a result, Electronic Manufacturers are now taking advantage of this reflow soldering method for its simple and effective process. Handling is automated and temperature profiles can be monitored and controlled precisely. Modern VPR machines, however, are entirely enclosed and recover most of the vapour medium. Handling through the process was usually manual and they could only process small batches of PCBAs (printed circuit board assemblies). The reflow profile was limited to the vapour phase fluid medium used and the time in the tank. They also had limited temperature profiles available. Early machines lost a lot of the vapour phase fluid medium in the process, making them environmentally unfriendly and also unhealthy. VPR ovens have been around for a long time, but they once fell out of favour. This process provides a high heat transfer and ensures very little temperature difference occurs between components of different thermal mass. Unlike Convection Reflow machines, which use hot air to apply heat to the PCB as it travels through a conveyor belt, Vapour Phase machines use the latent heat of condensation from a vapour layer, which is created by boiling a liquid at 235C. This takes time, and risks damaging the test board which may be precious if it is a small run. Profiling is where you monitor the temperature rise through an HACR oven with a thermocouple attached to the test PCB assembly. These change the rate at which heat is conducted from hot air in the oven. Hot air convection reflow (HACR) profiles are influenced by the thermal mass of the PCB and its components, and the “colour” of the components. Convection Reflow ProfilesĮvery PCB assembly may need a unique reflow profile and Convection Reflow as a method of SMT reflow soldering is not always suitable. We wanted to improve the efficiency of our SMD process as the current set-up was causing delays and production bottlenecks, and Vapour Phase ovens have proven to be the best investment to eliminate these hold-ups. In our search for a Surface Mount Device (SMD) Reflow System that would not require constant profiling every time we ran a new job, Newbury Electronicswas reintroduced to Vapour Phase Reflow machines. Aug 30th 2019 Why We’re Using A Vapour Phase Reflow Machine Why Vapour Phase Reflow?
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