Cleaning under BGAs: Best practices
BGAs have multiple internal solder joints and some routing under the ball grid. Use:
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tumble or spray-in-air cleaning with azeotrope solvents that penetrate via capillary action
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ultrasonic cleaning with controlled energy
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flux selection that minimizes tack and rosin deposition under balls.
Validate by dye-penetrant inspection or cross-sectioning sample BGAs and by ionic contamination testing on coupons that mimic BGA land patterns.