Tuesday, January 7, 2014

Reflow Soldering Oven: The Techniques And Working

By Harriett Crosby


Assembling electronic components on to printed circuit board (PCB) traditionally depends on soldering them on to that motherboard. In a well functioning reflow soldering oven, the best possible results are usually achieved. The technique is one of the most modern the widely used for this kind of attachments although just like other forms of technologies, it is too undergoing revolution.

The oven should be able to heat the adjoining surface melting all the solder into their correct positions without overheating or damaging the electrical components. One or more ceramic infrared heater are used as the source of heat that is then directed to heat the assemblies through radiation process although some ovens(Infrared types) uses fans to direct heat to the assemblies.

The process starts with loose attachments of the components to the desired positions on the PCB using sticky solder powder and flux mixture. This is then directed to first of the four phases through which the process undergoes. The first of this is the preheat zone which involves determination of temperature/time relationship (ramp rate). This significance of this comes in other stages as the maximum temperature and time exposure should be maintained to avoid destroying the PCB and the components on it.

The PCB is then taken to the thermal soak zone where the removal of solder paste volatiles takes place. Flux activation which involves freeing of leads and pads of any oxide then follows. The temperature range is anywhere between 60 to 120 degrees primary depending on the predetermined ramp rate.

The third phase is the reflow zone where the maximum possible temperatures are reached. The objective is to reduce the surface tension of the flux at the points of metal juncture which leads to metallurgical bonding involving combination of all the available solder powder. The maximum possible operating temperature is set slightly below the maximum tolerable temperature of that component with the lowest operating temperatures. The oven should therefore be efficient in heat control and monitoring.

Cooling takes place in the last phase also known as the cooling zone from where the molten solder solidifies into the precise target points permanently fixing the electronic components on to the PCB. The temperature control is still significant as such problems like thermal shock or the excessive metallic formation must be avoided I order to obtain a mechanically sound devices attached with fine grained structured solder.

With the modern sophisticated ovens, the most up to date technologies are employed to give the best possible yields. These are operated by modern setup processes that identify the best possible combination of zonal temperatures and conveyor speed. Among other things, the production time has been significantly minimized greatly increasing efficiency.

The high rate of the change in business environment reflected by changing consumer needs, shifting technology, market changes and increasing competition all calls for drastic measures such as investing in highly efficient and optimally performing devices such as a reflow soldering oven which should drive production levels and increase profitability for the survival of the business.




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