Common BGA welding phenomena are described as follows.
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(1) Blow holes: holes or circular pits appear on the surface of the tin ball.
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Blow hole diagnosis: During reflow welding, there is gas overflow in the pores of BGA tin ball.
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Blow hole treatment: Use X-Ray to check whether there are pores inside the raw material and adjust the temperature curve.
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(2) Cold welding: the surface of the solder joint is dull and not completely dissolved.
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Cold welding diagnosis: insufficient heat during welding, vibration caused by bare solder joints.
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Cold welding treatment: Adjust the temperature curve during cooling to reduce vibration.
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(3) Crystallization rupture: the surface of the solder joint shows a glass crack state.
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Crystal rupture diagnosis: When gold is used as the welding pad, the crystal rupture occurs when gold is fused with tin\/lead.
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Crystallization cracking treatment: tin is pre-coated on the welding pad of gold and the temperature curve is adjusted.
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(4) Offset: the BGA solder joint is misaligned with the PCB pad.
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Offset diagnosis: The patch is inaccurate, conveying vibration.
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Offset diagnosis: strengthen the maintenance and maintenance of the mounter, improve the accuracy of the mounter, and reduce the vibration error.
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(5) Bridge: The solder flows from the welding pad to another welding pad to form a bridge or short circuit.
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Bridge diagnosis: solder paste, tin ball collapse, poor printing.
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Bridge processing: Adjust the temperature curve, reduce the return pressure, improve the printing quality.
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(6) Tin splash: There is a tiny tin ball near or between two solder joints on the PCB surface.
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Spatter diagnosis: Solder paste quality is not good, heating up too fast.
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Spatter treatment: check the storage time and conditions of the solder paste, select the appropriate solder paste according to the requirements, and adjust the temperature curve.