5 Rework Guidelines

TI strongly recommends that the PCB with already-mounted SMT devices be baked prior to any rework so that absorbed moisture is removed. See J-STD-033 for more details. The rework process should be characterized such that the temperature of the MicroSiP device and the surrounding PCB area are controlled. Either an attached thermocouple or an infrared camera works well to determine a repeatable heating profile.

Component removal process example:

• Align nozzle over part to be removed
• Maintain nozzle 1.27 mm over the package
• Preheat board to 90°C, nozzle warming at 20% airflow, 125°C
• Soak stage at 20% air flow, 225°C, 90 seconds
• Ramp stage at 25% air flow, 335°C, 30 seconds
• Reflow stage at 25% air flow, 370°C, 65 seconds
• Enable vacuum, lower nozzle, remove inductor and capacitors from MicroSiP
• Discard inductor and capacitors
• Reposition nozzle, reheat at 25% air flow, 370°C, 20 seconds
• Enable vacuum, lower nozzle, remove MicroSiP from PCB
• Cool down stage at 40% air flow, 25°C, 50 seconds
• Turn off vacuum and remove MicroSiP from nozzle
• Avoid handling damage of the removed unit
• Do not reuse or repair the removed unit

Component replacement process example:

• Apply solder paste to board using a micro-stencil
• Align MicroSiP over board land pads
• Place MicroSiP on board. Care should be taken to prevent overtravel during placement which may damage the package or vacuum tip
• Raise nozzle 1.27 mm
• Preheat board to 90°C, nozzle warming at 20% air flow, 125°C
• Soak stage at 20% air flow, 225°C, 90 seconds
• Ramp stage at 25% air flow, 335°C, 30 seconds
• Reflow stage at 25% air flow, 370°C, 65 seconds
• Cool down stage at 40% air flow, 25°C, 50 seconds

Air-Vac Engineering:

Air-Vac Engineering (www.air-vac-eng.com) has established heating profiles and tooling recommendations for their Hot Gas (convection) rework equipment, DRS-24NC.

Nozzle NMX188DVG:

• 0.18 in exhaust opening
• VTMX020-35 vacuum tip

Comparable hot gas (convection heating) rework equipment from other vendors can also be used successfully.