7.5.3 Soldering Surface Mount Gull Wing Components, Hot Gas Method
This procedure covers the general guidelines for soldering surface mount Gull Wing components. There is basically only one type of Gull Wing component. Whether leads are on two sides or four sides, or whether the component is large or small, the soldering principles are the same.
Minimum Skill Level - Intermediate
Recommended for technicians with skills in basic soldering and component rework, but may be inexperienced in general repair/rework procedures.
Conformance Level - High
This procedure most closely duplicates the physical characteristics of the original, and most probably complies with all the functional, environmental and serviceability factors.
General purpose cleaner for removing contamination.
Hot Air Tool
Tool and nozzles to deliver precise flow of hot air.
Precision microscope with stand and lighting for work and inspection.
Solder paste for component soldering and rework.
Nonabrasive, low-linting wipes for cleanup.
During component rework, protection of nearby components is often mandatory to avoid collateral heat damage or inadvertent reflow. Collateral heat damage or unintended reflow of adjacent component solder connections can result in component damage, oxidation, de-wetting, pad damage, wicking, starved joints, and scorching. The rework technician must constantly be aware of the effect of heat on the target device or circuit, plus how it affects components near the target device on both sides of the assembly.
235-4010 Heat Shield Blanket
These are 5" x 7" sheets of fiberglass fabric, aluminum foil laminate with a pressure-sensitive adhesive backing. Heat Shield Blanket is designed to reflect 90% of the radiant heat energy. It will withstand continuous heat in the leaded and lead-free solder melt temperature range and short-term exposure at temperatures up to 1000°F/538°C. Heat Shield Blankets can be used in conjunction with Heat Shield Plates to create a more robust thermal shield with a more rigid structure.
235-4060 Heat Shield Plates
These are light gauge 5" x 7" aluminum sheets used primarily when simple heat deflection is required. Heat Shield Plates are easy to size, cut, form, and bond or tape into place using the high-temperature mask or high-temperature tape supplied in the kit. When using Heat Shield Plate material to deflect heat, leave a small space between the Heat Shield Plate and the protected component or area to avoid direct contact transfer of heat.
115-9010 Mask, High Temperature
This product is a high-temperature, quick cure, synthetic latex, peel-able solder mask supplied in syringes with dispensing needles. This mask can create free-form heat shielding or seal the edges of the Heat Shield Blanket or Heat Shield Plates. This mask cures at room temperature in 5 minutes. Once dried, it can be peeled off after use.
Images and Figures
Surface Mount Gull Wing Component
Figure 1: Add a small bead of solder paste along the row of pads.
Figure 2: Move the tool back and forth to heat all the solder joints until complete solder melt is observed.
Add a small bead of solder paste along the row of pads. (See Figure 1)
Place the component in position.
Adjust the pressure and temperature output of the hot air tool.
Direct the hot air over the component with the hot air tool tip approximately 2.50 cm (1.00") from the solder joint. This initial heating will pre-dry the solder paste.
Note: Solder paste has a dull flat appearance when dried.
When the solder paste has dried, move the hot air tooltip to approximately 0.50 cm (0.20") above the component. Move the tool back and forth to heat all the solder joints until complete solder melt is observed. (See Figure 2)
Remove the tool. Wait a moment for the solder to solidify.