7.3.2 Soldering Surface Mount Chip Components, Hot Gas Method

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Printed Board Type: R/F/C
Skill Level: Intermediate
Conformance Level: Medium
Revision: D
Revision Date: Jul 7, 2000

OUTLINE

Surface Mount Chip Component

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

Figure 1: Add a small bead of solder paste to each pad.

These components are constructed from several layers of ceramic with internal metallized 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.

ACCEPTABILITY REFERENCES
IPC-A-610 12.0	Surface Mount Assemblies
PROCEDURE REFERENCE
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

Figure 2: Move the tool back and forth to heat both solder joints until complete solder melt is observed.

TOOLS & MATERIALS
Cleaner
Flux
Hot Air Tool with Tips
Microscope
Solder
Wipes

PROCEDURE    Preview a Video Clip   (Size - 500KB)

1. Add a small bead of solder paste to each pad. (See Figure 1).
   
   
2. Place the component in position.
   
   

3. Chip Capacitors generally have solid color bodies.

   Adjust the pressure and temperature output of the hot air tool.
   
   
4. 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
   When the solder paste has pre-dried, the paste will have a dull flat appearance
   
   

5. When the solder paste has dried, move the hot air tool tip to approximately 0.50 cm (0.20") above the component. Move the tool back and forth to heat both solder joints until complete solder melt is observed. (See Figure 2).
   
   

6. A - Stripe

   Remove the tool. Wait a moment for the solder to solidify.
   
   
7. Clean, if required and inspect.