Circuit Board Repair and Rework Guide > 8.0 Rework Procedures > 8.2.1 Component Removal, Surface Mount Chip Components, Forked Tip Method

8.2.1 Component Removal, Surface Mount Chip Components, Forked Tip Method

Printed Board Type: R/F/C | Skill Level: Intermediate | Conformance Level: High | Rev.: D | Rev. Date: Jul 7, 2000

Outline

This procedure covers one commonly used method for removing surface mount chip components.

Note
The goal when removing any component is to remove the component as quickly as possible.

Caution - Glued Components
A small dot of epoxy is often used to hold chip components in position during wave soldering processing. Typically these components will be located on the bottom side of a circuit board that has through hole components located on the other side. Whenever you see a board like this, you can generally assume that the chip components will be glued onto the board. You'll need to leave the tip on the component for one or two additional seconds in order to transfer enough heat to overcure or soften the adhesive. If required take a wooden stick or curved tweezers and push the component sideways until the glue joint finally gives way.

Surface Mount Chip Component

Acceptability References
IPC-A-610	12.0	Surface Mount Assemblies
Procedure References
CTC	2.1	Handling Electronic Assemblies
CTC	2.2.1	Cleaning, Local
CTC	2.2.2	Cleaning, Aqueous Batch Process
CTC	2.5	Baking and Preheating
CTC	7.1.1	Soldering Basics
CTC	7.1.2	Preparation For Soldering
IPC7711	3.3.1	Bifurcated tip
Tools and Materials
Caliper Cleaner Flux, Liquid		Microscope Soldering Removal Tool with Tips Wipes

Figure 1: Forked tip shown with solder added to cavity to enhance removal operation.

Tip Preparation

Forked tips are designed to fit over the top of chip components, and to reflow both solder joints at once. The ends of the forked tip fit over the component with just a slight amount of extra space for solder. Measure the overall length and width of the component with a caliper to select the proper size tip. Check the tip for proper fit prior to processing the part.

The tip should not fit the component so tightly that it will get lodged in the tip, but the tip should not be so loose that it will not conduct heat to the leads simultaneously. The size and shape of the forked tip will have an effect on the rate of heat transfer. Larger tips with more surface area will transfer heat faster than smaller tips.

Forked tips can be used to remove a number of different styles of chip components but the component must fit properly in the tool cavity. Since forked tips have a cavity, they require special cleaning and tinning procedures.

1.	Remove any solder from inside the tip cavity with a fiber tool.

	Caution Do not use a wire brush for any tip cleaning procedure. A wire brush can severely scratch a metal tip. Scratches allow oxidation to form on the base metal of the tip and this will severely decrease the useful life.

2.	Remove any oxidized solder by shocking the tip on a wet sponge.

3.	Add solder to the properly prepared tip. Fill the cavity until there is a fillet on each side of the tip. (See Figure 1). Add enough solder to help transfer the heat quickly but not so much that it will fall out when the tip is turned upside down.

The solder provides surface tension to lift the component off the pads after reflow. Since the tip has more metal surface area than the pads on the circuit board, the solder will be drawn toward the metal tip and so will the component.

	Note Determine the direction the part is to be swept off the circuit board surface. Densely packed circuit board assemblies often leave only one direction for the rework tool to follow when sweeping the part off the surface.

Figure 2: Removing SMT chip component with forked tip. After
solder has melted lift tip out and up.

Chip Capacitors generally have solid color bodies.

Striped or beveled end is positive (+) or anode end.

A - Stripe
B - Beveled Surface
The striped or beveled end is
the "positive" (+) or "anode end".

1.	Apply a small amount of liquid flux to both ends of the component.

2.	Place the forked tip directly over the top of the component. The extra solder on the tip will melt both solder joints. When the solder has melted slide the component out and up. (See Figure 2). Once the component is removed from the circuit board it can be removed from the tip by the shocking sponge or with a dull blunt instrument applying downward pressure on the component.

3.	Clean the area.