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Emerging Horizontal Convection Reflow Technologies

Emerging Horizontal Convection Reflow Technologies
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Emerging Horizontal Convection Reflow Technologies - 1

Emerging Horizontal Convection Reflow Technologies - 2

Forced-air convection, being the preferred technology' for solder reflowing surface mount assemblies, represents a shift from infrared (IR) and other methods for reasons solidly based on principles of physics and highlighted by the accelerated push to lead-free soldering. For example, the varying emissivities of components populating a printed circuit board (PCB) assembly make IR-heater technology undesirable in many cases. Also, because IR emits its effect via radiation, its straight-line energy transfer creates shadowing, a condition in which smaller and lower profiled components in...

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Emerging Horizontal Convection Reflow Technologies - 3

This phenomenon poses several inconsistencies: 1. The air volume to which a given point on the PCB is exposed is different than that of a point in another (longitudinal) position. Under differing air-volume flows, the volatiles escape from the solder paste at different rates, thus creating inconsistent flux activation and flux dry-out conditions. 2. The periphery of the PCB is exposed to higher air volumes but at lower temperatures, further aggravating the center hot-spot/cool-outside condition. 3. Most convection ovens use a system of evenly distributed ports that create streams of air...

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Emerging Horizontal Convection Reflow Technologies - 4

HORIZONTAL CONVECTION 'ACROSS THE BOARD;, tions where airflow is required between the component body and the PCB surface. For example, BGA packages, located proximally on the board, are exposed to less airflow below the component bodies than those located distally. In summary, while there is a nearly unanimous consensus that forced-air convection is a superior method for reflowing surface mount assemblies, many experts agree that issues worthy of improvement remain with the technology. These can be addressed by impro\ing the oven’s ability to produce more uniform and consistent air...

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