- Many manufacturers have made great strides in defect reduction through process control and continual improvement. Statistical process control shows that because of inherent variation, defects can be greatly reduced but not completely eliminated.
- There are two technologies (IR and Hot Air) are being used in soldering and de soldering Process
- Here there are the most common defects could occur during using advanced controlled hot air and Dark Infrared Technologies:-
Adjacent Components defect :
- Hot air convection systems offer good reliability and repeatability but care must be taken in tip and barrier selection to ensure adjacent components are not damaged by air flow which needs greater technical expertise where the nozzle is required to be placed flush against the PCB surface in order to have a proper convective atmosphere, the nozzle wall cannot fit into this small gap. The escaping hot air can overheat or blow away the adjacent device
- IR Technology is a True Protection of adjacent components as providing a source of localized heating on the spot of heat directly on top of the part requiring rework so minimal heat is delivered outside this spot that could affect the surrounding components of approximately 1 cm (0.4 in). Heat shielding is the solution for Controlled IR heating by using heat resistant tape or aluminum foil and small or lightweight components cannot be "blasted away" as no air is required in an IR system thereby insuring a higher reliability rework process
Plastic or heat sensitive components :
- Hot air system is described as a sudden heat source which causes deformation in plastic SMD sockets which is sensitive to high temperature heat sources.
- Dark IR is an ideal use for the Plastic Parts Components so no discrepancies could be occurred during any Process.
Hot and Cold Spots :
- Hot air System where nozzle is required so different in heat will occur on PCB which produces hot and cold spots.
- IR guaranteed uniform heat to create a homogeneous temperature of the repair area and reduce thermal shock during removal which guarantees no occurrence of hot or cold Spots.
Heat Absorption Reflection :
- Main Disadvantage of IR was absorption /reflection differences between light and dark colors which lead to a temperature gradient across the PCB but this only occurring when using Light IR system, On the contrary, Dark IR technology) used for rework has only the positive effects as minimum reflections between different colors occurs and limited shadowing effects occur as well.
- Main advantage in using Controlled Hot Air is no radiation heat absorption/reflection occurs where specific nozzle is required
Widely spreaded low cost Hot Air Systems Disadvantages :
• No Preheat stage
• No controlled heat across PCB
• Excess Heat could damage the components itself and wire tracks
• Bad joints could occur with low heat due to non controlled heat
Adjacent Components defect :