Document ID: TOS-TOOL-REF-017 Revision: 1.0 Author: ThisOldScot
Section_1: Overview#
Ball Grid Array (BGA) components differ from QFPs in that their electrical connections are located entirely underneath the chip package in a grid of solder “balls.” In the Highlands Lab, we perform Reballing when a chip’s internal connections have fractured (thermal fatigue) or when a high-value IC must be harvested from a donor board.
This is a high-stakes surgical procedure requiring absolute thermal control; if the chip or the PCB warps by even a fraction of a millimeter during the process, the entire grid will fail to make contact.
Section_2: Essential Equipment & Materials#
| Item | Specification | Function |
|---|---|---|
| BGA Rework Station | Dark Infrared (IR) or Hot Air | Controlled bottom and top heating. |
| Direct Heat Stencils | Stainless Steel | Precision alignment for the solder balls. |
| Solder Balls | Leaded (Sn63/Pb37) | Replacing the brittle factory lead-free balls. |
| High-Tacky Flux | RMA-223 / NC-559-ASM | Holding balls in place during the reflow. |
| Pre-heater | Large Surface Area | Preventing PCB “Popcorning” and delamination. |
Section_3: The Reballing Protocol#
STAGE_3: 01 // Component Extraction#
- The Profile: Unlike manual rework, BGAs require a specific Thermal Profile. The board is pre-heated to 150°C, then the top heater brings the chip to the “Liquidous” point (approx. 183°C for leaded, 217°C for lead-free).
- The Lift: Use a vacuum pickup tool to lift the chip vertically. Never use tweezers, as sliding the chip will smear molten solder across the pads.
STAGE_3: 02 // Pad Grooming (The Clean Slate)#
- Apply flux to the chip’s underside.
- Use a “Hoof” tip to gently wick away the old solder balls.
- Protocol: The pads must be flush with the substrate. Any protrusion will cause the stencil to sit unevenly, leading to “bridging” during the reballing phase.
STAGE_3: 03 // The Stenciling Procedure#
- Secure the chip in a reballing jig.
- Apply a microscopic layer of tacky flux.
- Place the Direct Heat Stencil over the chip. Align every hole with the corresponding pad under the microscope.
- Pour the fresh solder balls onto the stencil and vibrate the jig until every hole is occupied.
STAGE_3: 04 // The Reflow (Ball Attachment)#
- Remove excess balls.
- Using a hot air station at low airflow (to avoid blowing the balls away), heat the stencil.
- The Transformation: You will see the balls “pop” into place as they melt and bond to the pads. Once cooled, remove the stencil and verify the height of the new “Grid.”
Section_4: Re-Installation & Alignment#
Because you cannot see the pins, alignment relies on Silkscreen Markers.
- Place the chip within the white corner brackets on the PCB.
- Apply the final thermal profile.
- The “Self-Alignment” Phenomenon: As the solder balls melt, the surface tension will actually pull the chip into perfect alignment with the pads. A successful install is often characterized by a slight “settling” motion of the chip.
Section_5: Technical Warning#
Safety_Warning
MOISTURE SENSITIVITY ALERT: ICs are hygroscopic (they absorb moisture from the air). If you apply rework heat to a “wet” chip, the internal moisture will turn to steam and expand, causing the chip to crack internally (Popcorning). Always “Bake” your BGAs at 100°C for 2-4 hours before attempting a full reflow.
Section_6: Practical Application: Modern Retro Mods#
Many modern HDMI and ODE mods utilize BGA-packaged FPGAs. If a device is DOA or develops “glitchy” behavior after being dropped:
- Perform a Reflow (heating the existing balls until they liquefy).
- If symptoms persist, perform the full BGA Reballing Protocol to replace the solder interface entirely.