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CHAPTER 4 NOTES ON MOUNTING
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In the reflow process, a cold solder joint (a mechanically weak incomplete joint with high electrical resistance) may form if solder in a semi-molten state is subject to vibration or shock while the molten solder joint is cooling down. Also, if the device or printed circuit board warps considerably during reflow heat application, some solder balls may squashed down. However, while in a semi-molten state in the cooling process after heat application, the solder balls may be pulled upward as the warped device or board starts to return to normal, causing the formation of a cold solder joint. |
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Figure 4-13. Mechanism for Inferring Cause of Cold Solder Joint
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The following measures can be implemented to prevent the problem of cold solder joints.
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