Sunday, 13 July 2014

Utilizing Tabletop Reflow Oven To Connect Electric Components

By Coleen Torres


Manufacturing a variety of different electrical components often requires a process called reflow soldering. In addition to being great DIY components producers, tabletop reflow oven makes up a key portion in the soldering process. The oven is hassle-free for both home and commercial users in terms of installation and operation thanks to its simple bench top design.

Re-flow soldering is most often used to fix surface mounted components onto circuit boards. Through-hole components can be fixed onto the boards using this method as well. In order to ensure accuracy, a paste made from solder and flux is set between the component and contact pad. The combined piece then requires a higher temperature for the paste to meld. In order to do this safely, the piece is put inside this kind of soldering machine.

Reflow ovens must be used so that the areas other than the paste aren't burnt or heated to the point of damage. The four specific features of the oven successfully targets the paste. These consist of preheat, soak, reflow, and cooling stages.

The preheat zone takes the longest time out the four stages. During preheating, the heat increases between 1 to 3 degrees Celsius per second. This rate of increase in heat is called the ramp-up rate. The equipment offer a controlled ramp-up rate so that the component is gradually heated, rather than giving it a heat shock that can cause damage.

The thermal soak zone follows the preheat stage, which typically lasts one to two minutes. This short exposure allows for the removal of solder paste volatiles and activation of the fluxes. The thermal soak temperature must be within a narrow range, since too high a temperature will cause splattering as well as oxidation of the paste, attachment pads and component terminals. Additionally, too low a temperature will not allow for the activation of the fluxes.

Peak temperatures are reached in the re-flow zone. Temperatures in the oven goes as high as 20 to 40 degrees Celsius. There is a 20 degree difference in range because the specific degree depends on the lowest heat tolerance of the electric components. In order to bring about any damages, the oven will never heat up higher than 60 degrees.

The temperature will never exceed 60 degrees Celsius in the machine because the parts inside may burn up at that point. The time above liquidus (TAL) comes to play in determining the required length of time of this stage that will properly meld the component together. Incomplete TAL may cause the paste to stay dry instead of melting, thus creating a defective connection.

The re-flow oven finishes the entire molding process in its cooling stage. The melted paste between the components need to cool gradually to create a cohesive unit. If the component isn't cooled with proper measures, the unit might produce intermetallic accumulation or even go into thermal shock. Proper cooling actually requires a faster temperature change rate than heating for it to achieve the best durability. This faster cooling rate usually lies around 4 degrees Celsius per second.




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