7.5.1 Soldering Surface Mount Gull Wing Components, Point To Point Method

Outline
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.

Acceptability References
IPC-A-610 12.0	Surface Mount Assemblies
Procedure References
1.0	Foreword
2.1	Handling Electronic Assemblies
2.2	Cleaning
2.5	Baking And Preheating
7.1.1	Soldering Basics
7.1.2	Preparation For Soldering And Component Removal
7.1.3	Solder Joint Acceptability Criteria
IPC7711 5.5.3	Point-To-Point Method

Kits and Systems

Flex-Rack PCB Holder
Sturdy holder supports PCBs for rework, drilling, pad repair, and positioning.

Soldering Skills Practice Kit
Training kit to practice circuit board soldering skills prior to testing for certification.

Precision Tool Set
Nine precision-crafted tools for detailed circuit board work.

Additional Items and Supplies

Cleaner
General purpose cleaner for removing contamination.

Microscope
Precision microscope with stand and lighting for work and inspection.

Soldering Iron
Properly maintained soldering iron and properly sized soldering iron tips.

Wipes
Nonabrasive, low-linting wipes for cleanup.

Images and Figures

Surface Mount Gull Wing Component

Figure 1: Place component and check alignment.

Figure 2: Place the soldering iron tip at the junction between the pad and component lead.

Procedure

Add liquid flux to the corner pads.
Place the component in position and hold it steady. The leads must be aligned with the pads. On large components, this is best done by aligning the leads on opposite corners. (See Figure 1)
Place the soldering iron tip at the junction between the pad and component lead at one of the corners. The soldering iron tip may rest at the junction of the component lead and pad or on top of the lead. Apply additional wire solder as needed. (See Figure 2)
Remove the tip. Wait a moment for the solder to solidify before soldering the opposite corner.
After the opposite corner is soldered, solder the remaining leads.
Clean, if required, and inspect.

Solder Joint Acceptable Criteria - Gull Wing Components

Feature	Dim	Class 1	Class 2	Class 3
Maximum Lead Side Overhang	1	No more than 50% of the lead width or 0.50 mm (.020") whichever is less.	No more than 50% of the lead width or 0.50 mm (.020") whichever is less.	No more than 25% of the lead width or 0.50 mm (.020") whichever is less.
Maximum Toe Overhang	2	Does not violate minimum electrical clearance.	Not acceptable.	Not acceptable.
Minimum End Joint Width	3	50% of the lead width.	50% of the lead width.	75% of the lead width.
Minimum Side Joint Length: Lead thickness greater than 3X lead width	4	Equal to the lead width or 0.50 mm (.020") whichever is less.	3 times the formed foot length or 75% of the formed foot length, whichever is longer.	3 times the formed foot length or 75% of the formed foot length, whichever is longer.
Minimum Side Joint Length: Lead thickness less than 3X lead width	4	Equal to the lead width or 0.50 mm (.020") whichever is less.	Equal to 100% of formed foot length.	Equal to 100% of formed foot length.
Maximum Heel Fillet Height	5	No maximum, but solder must not touch the component package body.	No maximum, but solder must not touch the component package body.	No maximum, but solder must not touch the component package body.
Minimum Heel Fillet Height	6	Evidence of proper wetting.	Equal to the solder thickness plus 50% of lead thickness.	Equal to the solder thickness plus 100% of lead thickness.
Solder Thickness	7	Evidence of proper wetting.	Evidence of proper wetting.	Evidence of proper wetting.

Procedure for reference only.