Friday 20 December 2013

SMT Reflow Soldering Oven: Efficiency And Profitability

By Harriett Crosby


Surface Mount Technology (SMT) is a technology of soldering electrical components onto the pre-printed circuit boards. In order to make the whole process possible, SMT reflow soldering oven is usually used. This is a machine that employs high level of technology and bonding principles in its functionality. It is very complex but offers reliability and better alternative in the field of electrical assembly. This comes with advantages such as reduced board cost, controlled manufacturing and assembling process and reduced material handling.

This is one of the machines that get used more often than any other machines in the electrical line of assembly. Before passing over to the oven, the solder paste made of flux, small solder particles and chemical cleaning agents is used to loosely attach the electrical components on to the printed circuit board (PCB) and then sent to the next step.

It all starts by making of solder paste. This is a mixture of small solder particles, flux and some solvent that also work as a cleaning agent. This forms a sticky substance that is used to loosely attach electrical components on to specific points on the circuit board.

The PCB and loosely attached components is then drawn into the heating chambers through a conveyor belt. This then undergoes into four distinct phases in this machine. The first phase is known as preheat zone. This is where the melting point of the solvent is set. The ramp rate (time/temperature rate) is also determined and used to control heating in the following stages.

The second zone is the thermal soak zone. Removal of paste volatiles takes place here through a 60 to 120 second heat exposure of the PCB at a predetermined temperature. This is followed by the reflow stage, the stage in which the whole thing happens. Printed circuit board and components are exposed to the highest possible temperatures. The tolerable (liquidus) temperature for each of the component is determined and the maximum temperature is set just below it. This forces reduction between the surface tension between solder particles so that they melt at the point of contact on the pad.

The 4th zone is the cooling stage where control cooling ensures that the components are correctly placed and fixed. In all these stages, both heating and cooling process is keenly controlled to avoid any thermal shock that may damage the components or the PCB.

The heaters in these types of oven are made of ceramic materials with various options through which heat reaches the heating zones. The heat transfer can either be through hot air (radiation) and infrared electromagnetic radiation among other alternatives.

SMT reflow soldering oven comes with a number of advantages such as simpler and much faster automated assemblies, very small levels of errors in component mounting, high level of production rate (some capable of placing up to 136,000 components per hour), possible to mount components on both side of the PCB, and electrical efficiency.

In order to remain relevant in electrical assembly industry, just like any other industry, it is important to use highly efficient and most up-to-date technology. There are latest models SMT reflow soldering oven that offers efficiency level that results to high productivity and profitability to a firm.




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2 comments:

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