Circuit Board Repair and Rework Guide > 8.0 Rework Procedures > 8.1.1 Component Removal, Through Hole Components, Vacuum Method

8.1.1 Component Removal, Through Hole Components, Vacuum Method

Printed Board Type: R/F/W/C
Skill Level: Intermediate
Conformance Level: High
Revision: E
Revision Date: Oct 18, 2001

Outline

This procedure covers the general guidelines for through hole component removal using a powered vacuum desoldering tool. There is basically only one style of through hole component. Whether there are a few leads or many, or whether the component is large or small, the component removal principles are the same.

Acceptability References
IPC-A-610	5.0	Component Installation
IPC-A-610	6.0	Soldering

Through Hole Component

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	3.1.1	Through-Hole Desoldering - Continuous Vacuum Method

Tools and Materials
Cleaner
Flux
Microscope
Solder
Solder Removal Tool, Vacuum Type with Tips
Soldering Iron with Tips
Wipes

When solder melts, activate vacuum to remove solder while oscillating tip.

Figure 1: When the solder melts, activate the vacuum to remove the solder while oscillating the tip.

Procedure - Straight Leads, Standard Method

1.	Inspect the size of the solder joints on the component to be removed. If the size of the solder joint fillets are minimal, it may be desirable to add additional solder to form an "excess solder" joint. This will improve the thermal linkage.

2.	Apply a small amount of liquid flux to the solder joints of the component to be removed.

3.	Align the desolder tip with a component lead end and lightly make contact with the solder joint. Keep the desolder tip off the pad by allowing it to slide around on a film of solder.

	Caution Do not apply pressure with the solder extractor tip to the lands or other conductive patterns.

4.	After the solder has melted, start a rotating or oscillating motion with the desolder tip. Continue the rotating motion until a change in the "feel" of the rotating motion occurs. At this instant the solder in the solder joint is completely molten. Immediately activate the vacuum, extracting the solder from the solder joint. (See Figure 1).

5.	Maintain rotation of the desolder tip while continuous vacuum is being applied. This allows air to cool both the component lead and the plated-through hole preventing the component lead from resweating to the side of the hole.

6.	After the solder has been extracted from the solder joint, remove the desolder tip from the component lead while maintaining continuous vacuum.

7.	Maintain continuous vacuum for a few seconds to clear the desolder tip.

8.	Turn off the vacuum.

9.	Desolder each of the remaining component leads individually using a skipping method to reduce thermal buildup at adjacent hole locations.

10.	Probe each component lead to be sure that they are not soldered to the side of the plated hole and then remove component.

	Note If each lead is not completely free, resolder the joint and repeat steps 2 - 10.

11.	Clean the area.

Lower tip to melt solder, then gently straighten lead to a vertical position.

Figure 2: Lower the tip to melt the solder, then gently straighten the
lead to a vertical position.

Procedure - Partial Clinch Leads, Standard Method

1.	Inspect the size of the solder joints on the component to be removed. If the size of the solder joint fillets are minimal, it may be desirable to add additional solder to form an "excess solder" joint. This will improve the thermal linkage.

2.	Apply a small amount of liquid flux to the solder joints of the partially clinched leads.

3.	Align the desolder tip with the partially clinched lead. Lower the tip to melt the solder. Then gently straighten the lead to a vertical position. (See Figure 2). After each lead has been straightened, continue desoldering each lead as described beginning in step 3 above.

Lower tip to melt solder and activate vacuum to remove solder from joint.

Figure 3: Align the desolder tip
with the fully clinched lead. Lower
the tip to melt the solder and
activate the vacuum to remove the solder from the joint.

Procedure - Fully Clinch Leads, Standard Method

1.	Apply a small amount of liquid flux to the solder joints of the fully clinched leads.

2.	Align the desolder tip with the fully clinched lead. Lower the tip to melt the solder and activate the vacuum to remove the solder from the joint. (See Figure 3).

Use flat nose pliers to gently rotate lead laterally break any remaining solder sweat joints.

Figure 4: Use a flat nose pliers to gently rotate the lead laterally
break any remaining solder sweat joints.

3.	Use a flat nose pliers to gently rotate the lead laterally break any remaining solder sweat joints. (See Figure 4).

4.	Probe each component lead to be sure that they are not soldered to the side of the plated hole and then remove component.

	Note If each lead is not completely free, resolder the joint and repeat steps 2 - 4.

Figure 5: Place a soldering iron tip against the component lead and the desoldering tip over the lead end..

Procedure - Straight Leads, Auxiliary Heat Method
Auxiliary heating may be required on solder joints with a large thermal mass. This is most common on multilayer circuit boards.

1.	Inspect the size of the solder joints on the component to be removed. If the size of the solder joint fillets are minimal, it may be desirable to add additional solder to form an "excess solder" joint. This will improve the thermal linkage.

2.	Apply a small amount of liquid flux to the solder joints of the component to be removed.

3.	Place a soldering iron tip against the lead of the component side of the circuit board. (See Figure 5).

4.	Align the desolder tip with a component lead end and lightly make contact with the solder joint. Keep the desolder tip off the pad by allowing it to slide around on a film of solder.

	Caution Do not apply pressure with the solder extractor tip to the lands or other conductive patterns.

5.	After the solder has melted, start a rotating or oscillating motion with the desolder tip. Continue the rotating motion until a change in the "feel" of the rotating motion occurs. At this instant the solder in the solder joint is completely molten. Immediately activate the vacuum, extracting the solder from the solder joint.

6.	Maintain rotation of the desolder tip while continuous vacuum is being applied. This allows air to cool both the component lead and the plated-through hole preventing the component lead from resoldering to the side of the hole.

7.	After the solder has been extracted from the solder joint, remove the desolder tip and the soldering iron tip from the component lead while maintaining continuous vacuum on the desoldering tip.

8.	Maintain continuous vacuum for a few seconds to clear the desolder tip.

9.	Turn off the vacuum.

10.	Desolder each of the remaining component leads individually using a skipping method to reduce thermal buildup at adjacent hole locations.

11.	Probe each component lead to be sure that they are not soldered to the side of the plated hole and then remove component.

	Note If each lead is not completely free, resolder the joint and repeat steps 2 - 11.

12.	Clean the area.

Evaluation

1.	In-process QA Inspection should be conducted to ensure component was removed without evidence of damage to circuit board assembly or plated through hole.