7.3.1 Soldering Surface Mount Chip Components, Point To Point Method

Outline
This procedure covers the general guidelines for soldering surface mount chip components. The following surface mount chip components are covered by this procedure. While all of these components are different, the techniques for soldering are relatively similar

Chip Resistors: The component body of chip resistors is made out of alumna; an extremely hard, white-colored material. The resistive material is normally located on the top. Chip resistors are usually mounted with the resistive element facing upwards to help dissipate heat.

Ceramic Capacitors: These components are constructed from several layers of ceramic with internal metalized layers. Because metal heats up much faster than ceramic, ceramic capacitors need to be heated slowly to avoid internal separations between the ceramic and the metal layers. Internal damage will not generally be visible since any cracks will be inside the ceramic body of the component.

Note: Avoid rapid heating of ceramic chip capacitors during soldering operations.

Plastic Body: Another style of chip component has a molded plastic body that protects the internal circuitry. There are a number of different types of components that share this type of exterior package. The termination styles for plastic chip component packages vary considerably.

MELF: MELF - Metal Electrode Face cylindrical components. These may be capacitors, resistors, and diodes. It can be hard to tell them apart - since there is no universal coloring or component designators printed on the component bodies.

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 5.3.1	Solder Paste Method

Kits and Systems

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 Chip Component

Figure 1: Prefill one pad with solder.

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

Figure 3: Solder the other opposite side of the component.

Chip Capacitors generally have solid color bodies.

Procedure

Add liquid flux to one pad.
Prefill one pad with solder. (See Figure 1)
Clean the area.
Add liquid flux to both pads.
Place the component in position and hold it steady with a wooden stick or tweezers so that the soldering iron won't push the component out of alignment.
Place the soldering iron tip at the junction between the prefilled pad and component lead. Flow the solder until the component drops down and is soldered in position. Apply additional solder as needed. (See Figure 2)
Remove the tip. Wait a moment for the solder to solidify before soldering the other side of the component. (See Figure 3)
Clean, if required and inspect.

Solder Joint Acceptable Criteria - Chip Components

Feature	Dim	Class 1	Class 2	Class 3
Maximum Component Side Overhang	1	Less than 50% of the component termination width or 50% of the pad width whichever is less.	Less than 50% of the component termination width or 50% of the pad width whichever is less.	Less than 25% of the component termination width or 25% of the pad width whichever is less.
Maximum Component End Overhang	2	Not permitted.	Not permitted.	Not permitted.
Minimum End Joint Width	3	50% of the component termination width or 50% of the pad width, whichever is less.	50% of the component termination width or 50% of the pad width, whichever is less.	75% of the component termination width or 75% of the pad width, whichever is less.
Minimum Side Joint Length	4	Evidence of proper wetting.	Evidence of proper wetting.	Evidence of proper wetting.
Maximum Fillet Height	5	Solder may overhang the pad but must not touch the non-soldered portion of the component package body.	Solder may overhang the pad but must not touch the non-soldered portion of the component package body.	Solder may overhang the pad but must not touch the non-soldered portion of the component package body.
Minimum Fillet Height	6	Evidence of proper wetting.	Evidence of proper wetting.	Equal to the solder thickness plus 25%, or equal to the solder thickness plus 0.50 mm (.020"), whichever is less.
Minimum Solder Thickness	7	Evidence of proper wetting.	Evidence of proper wetting.	Evidence of proper wetting.
Minimum End Overlap	8	Evidence of any overlap is required.	Evidence of any overlap is required.	Minimum 25% of the termination length.

Procedure for reference only.