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7.5.2 Soldering Surface Mount Gull Wing Components, Continuous Flow 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 5.5.1 Multi-Lead Method - Top of Lead
IPC7711 5.5.2 Multi-Lead Method - Toe Tip
Kits and Systems
201-4150
Soldering Skills Practice Kit
Training kit to practice circuit board soldering skills prior to testing for certification.
201-7100
Precision Tool Set
Nine precision-crafted tools for detailed circuit board work.
Additional Items and Supplies
Cleaner
Cleaner
General purpose cleaner for removing contamination.
Microscope
Microscope
Precision microscope with stand and lighting for work and inspection.
Solderinmg Iron
Soldering Iron
Properly maintained soldering iron and properly sized soldering iron tips.
Wipes
Wipes
Nonabrasive, low-linting wipes for cleanup.
Images and Figures
7.5.2 Soldering Surface Mount Gull Wing Components, Continuous Flow Method
Surface Mount Gull Wing Component
7.5.2 Soldering Surface Mount Gull Wing Components, Continuous Flow Method
Figure 1: Place component and check alignment.
7.5.2 Soldering Surface Mount Gull Wing Components, Continuous Flow Method
Figure 2: Apply solder to the continuous flow solder tip to create a convex bead of molten solder.

7.5.2 Soldering Surface Mount Gull Wing Components, Continuous Flow Method
Figure 3: Slowly move the tip over the row of leads to form proper solder fillets at each joint.
Procedure
  1. Add liquid flux to the corner pads.
  2. 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)
  3. Place the soldering iron tip at the junction between the pad and component lead at one of the corners. Apply additional solder as needed.
  4. Remove the tip. Wait a moment for the solder to solidify before soldering the opposite corner.
  5. Apply solder to the continuous flow solder tip to create a convex bead of molten solder on the tip. (See Figure 2)
  6. Position the solder tip so that the solder bead contacts the top portion of the leads. Slowly move the tip over the row of leads to form proper solder fillets at each joint. (See Figure 3)
  7. Repeat steps 5 and 6 for the remaining sides.
  8. Clean, if required, and inspect.
Solder Joint Acceptable Criteria - Gull Wing Components
Solder Joint Acceptance Criteria
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.