• 55degC bake and room temperature aging – 3 to 6 months with readouts every month
• Unbiased 55degC/85% RH, 10 weeks with readout every after 4 weeks.

Criteria:

• No Pass/ Fail Criteria established yet. Will be complying with the NEMI, JEITA and Soldertec Organization once standard criteria is released.
• Whisker growth > 50 microns (> 2mils) is considered not good.

SEM Inspection: (Whisker Growth Classification)

• This is to be done at each readouts and document whisker data such as type of whisker, length of whisker, number of whiskers, etc.

Sampling Plan Recommendation

• Lots to be run/selected based on the following variables:
  • Lead frame material/shape
  • Plating alloy
  • Plating bath vendor
  • Assembly site
  • Plating bath age ( new, 50% aged and 100% aged)
• Sample Size: At least 5 packaged units each lot for each test.

Stereoscope Inspection
At 100 – 200X magnification, identify one location per sample unit with the highest concentration of whiskers. (Use of Stereoscope is optional if it is found to be easier to scan the units in the SEM which provides greater depth of field)

SEM Inspection:

Attach double – sided conductive tape to SEM work holder (See Fig. 1) Using a vacuum wand or tweezers, attach the package/sample onto the conductive tape With the SEM at approximately 300X magnification (250 x250 micron field of view), scan each location selected for the greatest density of whiskers and record the number of whiskers, by type. Take pictures for later review. At 1000X – 2000X magnification, measure and record the longest whiskers Take higher magnification pictures as appropriate

Fig 1. No carbon or Au coating

Needle Whiskers

Flowers

Lumps

Artifacts