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Are parts falling incorrectly from the feeder?

This month we illustrate what can happen when dropped chip components are permitted to remain on the board surface. In reality, parts can be dropped or misplaced, but in this case it has led to more significant errors. During placement of the BGA, one of the balls may have contacted the chip component, causing misplacement.

During soldering, solder paste reflowed on the BGA pads. The capacitor, which was still in contact with the paste, has wetted and reflowed toward the pad. If lucky, none of the BGA balls has soldered to the board, hence rework will be easy.

FIGURE 1 shows a BGA misplaced on the surface of the board. In this case the misplaced chip capacitor has prevented the correct placement. The capacitor is very well-soldered to a pad but not the BGA, so we know reflow is working!

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Figure 1. Misplaced BGA due to a misplaced capacitor.

This type of fault highlights the importance in looking at machine placement data or the number of non-placements and any trend from a particular feeder or head. This may indicate the need for preventive maintenance, or correction of a tape material problem.

We have presented live process defect clinics at exhibitions all over the world. Many of our Defect of the Month videos are available online at youtube.com/user/mrbobwillis.

Bob Willis is a process engineering consultant; bob@bobwillis.co.uk. His column appears monthly.

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