Friday, January 3, 2014

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 attaching electronics to PCB requires heating of soldering paste so that it attaches electronics on the pad on solidifying. This requires a complicated and an efficient technique, and there currently better technology to do this than an SMT reflow soldering model.

The beginning point is making of the soldering paste. This is a mixture of flux, some chemical used as cleaning agent and small solder particles. This makes a sticky paste that is used to loosely hold the electronics on to their predetermined positions on the PCB.

Through a conveyor belt, the PCB and the mounted components are directed into the oven. This requires time and temperature precision to avoid destroying any of the components. There are four phases that these components pass through in the oven. In starts at preheat zone where time/temperature rate (ramp rate) is determined. This is important to the other zones too as it gives the correct temperature to be used. The melting point of solvent is also set here.

At thermal soak zone, the components are exposed to heat for about 60-120 seconds. The heat produced at this stage should be enough to remove all the volatiles of solder paste. The reflow zone then takes over. At this stage, the components get exposed to the maximum possible temperature which is normally set a few degrees below the maximum temperature tolerable by the component with the lowest tolerable temperature. This reduces surface tension at joints, the result of which is the bonding between pads and the electronic components.

The cooling zone is the last phase where controlled cooling is done to avoid thermal shock. This result of this is permanent bonding of the electrical components to PCB ready for use in electronic market after cleaning and testing.

Most of these ovens use ceramic heaters as the source of heat. The heat flows to the assemblies through hot air using fan (radiation) or just the infrared electromagnetic radiation. As the new models are introduces, the techniques of heat transfers are improved.

They are simpler to operate and work much faster with high accuracy level. They also have higher production level with ability to produce more that 136,000 components in a single hour. Attachment of the components can also be done on both sides at the same time with better 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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