9.4.2 BGA Component Reballing, Braid Ball Removal, Reflow Oven Attachment Method

Outline

This procedure covers the reballing of BGA components.

Minimum Skill Level - Expert

Conformance Level - High

Tools and Materials

Cleaner General purpose cleaner for removing contamination.

Cleaning Brushes Disposable brushes for solvent cleaning and application of coatings.

Cleaning System Batch or inline cleaning system for removing fluxes and contamination.

Desolder Braid Woven copper wire designed to wick solder from surfaces and holes.

Gloves Disposable, puncture-resistant gloves designed for handling mild chemicals.

Microscope Precision microscope with stand and lighting for work and inspection.

Oven General purpose oven for drying, baking and curing epoxies.

Precision Tool Set Nine precision-crafted tools for detailed circuit board work.

Reflow Oven Reflow oven with multiple zones for controlled solder reflow.

Safety Glasses Protect your eyes and your vision with proper safety glasses.

Solder Flux Used to prepare solder surfaces and to prevent formation of oxides during soldering.

Solder Paste Solder paste for component soldering and rework.

Solder Spheres Solder balls or spheres for BGA component reballing and rework.

Soldering Iron Properly maintained soldering iron and properly sized soldering iron tips.

Wipes Nonabrasive, low-linting wipes for cleanup.

Procedure

Procedure - Braid Ball Removal

1. Ensure all BGA components that are processed meet the requirements for acceptable moisture levels.
   Note: For information on baking and moisture level control, see 2.5 Baking and Preheating
2. Remove existing solder spheres on BGA components using desolder braid. Place the de-solder braid on the balls to be removed, and gently place the soldering iron on the desoldering braid. Apply very light pressure to melt the solder balls. As the solder melts, capillary action will draw it onto the copper desoldering braid. Repeat as needed to remove all the solder balls. (See Figure 1) When complete, simutaneously lift both the soldering iron and solder braid. (See Figure 2)
3. Clean the BGA components with an approved cleaning solution. The customer or contract may specify specific cleaning solutions. The typical cleaning process uses a cleaning brush and cleaner. Gently brush the surface until all evidence of flux and debris has been removed. Dry with a clean wipe or blow dry using an air gun.

Procedure - Reflow Oven Attachment

1. Apply tacky flux to the flat BGA component pads using a brush. Flux should be evenly applied across the entire BGA pad surface. Use minimal flux needed to cover the surface thoroughly. Remove any excess flux. (See Figure 3)
2. Place the BGA components into a fixture and cover with a matching stencil. Check to ensure the alignment is correct. (See Figure 4 and 5)
3. Place a quantity of the appropriate size solder spheres onto the fixture and use a clean cleaning brush to distribute them so they fill all the open apertures in the BGA component stencil. Ensure all the apertures are filled with only one solder sphere. Tilt the fixture and pour the excess solder spheres into a collection container for reuse.
   Note: Avoid overloading the solder stencil with excess solder spheres, as they may wedge under the stencil. This will make lifting the stencil to remove any excess solder spheres difficult.
4. Set up the reflow oven with the proper profile and run the oven for 5 minutes to ensure the reflow zone temperatures are stable. (See Figure 6)
   Note: If a profile has not been defined, a profile will need to be created.
5. Place the BGA fixture and BGA components into the reflow oven. As the fixture moves through the oven, the fixture and components will undergo the required preheat, reflow, and cooling cycles.
6. When the fixture and components emerge from the reflow oven, use gloves to remove the fixture and place it on a flat surface. Allow the fixture and components to cool for one minute to ensure package thermal stability before removing the BGA components from the fixture.
7. Inspect the BGA component balls for proper alignment and appearance.
8. Clean the BGA components in an approved cleaning solution.
9. Inspect the body of the BGA components for abnormalities.
10. Inspect the BGA components for cleanliness.

Images

BGA Component Reballing, Braid Ball Removal, Reflow Oven Attachment Method

Remove the existing solder spheres on BGA components using desolder braid.

When complete, simutaneously lift both the soldering iron and solder braid.

Apply tacky flux to flat BGA component pads using a brush.

Place the proper stencil on the fixture and fill the stencil apertures with the proper size solder balls.

Run the fixture and components through the reflow oven.