SLDA021B March   2014  – February 2020 AM3892 , AM3894

 

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9 Troubleshooting Guide

The troubleshooting guide shown as Table 4 lists some common assembly defects and typical causes for each. It is possible that other factors may cause these defects – if none of the recommended solutions resolves the defect, more extensive failure analysis may be required to determine the root cause.

Table 4. Troubleshooting Guide

Defect Recommended Solutions
Head on Pillow ● Check Solder Paste Volumes to ensure that there are no insufficient prints
● Check the temperature gradient across the BGA. It should be 10°C or less, with lower temperature gradients preferred
● Check with the solder paste manufacturer to ensure that the solder paste is designed to minimize head in pillow defects
● Check that the reflow profile meets the paste manufacturer’s guidelines. Generally, the time to peak temperature should be less than 6 minutes and the soak should be less than 2 minutes, but these guidelines may vary by paste. Incorrect profiling may exhaust the flux, or may insufficiently activate it.
● Use nitrogen as a reflow environment. Ensure that the oxygen levels are within specification when using nitrogen
● Check the lot number, date code and storage conditions for the component
● Ensure that the maximum recommended bakeout time has not been exceeded.
Solder Shorts or Bridges ● Check solder paste prints for excessive volume or mis-registration
● Check that the stencil underwiping frequency is adequate and the wiping process is effective
● Verify placement accuracy and ensure that placement pressure is not excessive
● Ensure that the printed circuit assemblies do not experience sudden acceleration or deceleration prior to reflow
Opens or Insufficients ● Check Stencil for apertures clogged with solder paste
● Verify that the stencil apertures and the PCB pads are within the designed specification.
● Check the temperature gradient across the BGA and ensure that it is 10°C or less, with lower temperature gradients preferred
Voids ● Check to ensure that the reflow profile matches the paste supplier’s recommendations
● Ensure that microvias are filled. If microvia filling does not meet specification, contact the PCB manufacturer.
● If planar microvoids near the printed circuit board are detected, contact the PCB manufacturer, as these may be signs of a surface finish defect