You got it exactly right.

Lifted lands are NOT allowed when you are inspecting the board visually. If you can see the lift during a visual examination (usually done before thermal stress), then there is a problem and cause for reject.

The thermal stress test method requires inspection by microsection. If you can't see lifted lands during the visual inspection, but you see it in the microsection...it is still okay.

In fact a major OEM has postulated that if the lands lift during thermal stress the reliability of the PTH actually increases, because the FR4 can expand and contract independently of the copper (in other words the copper will not undergo as much mechanical stress).

Lisa Williams
IPC

>>> APeder01 <[log in to unmask]> 10/21/97 03:15PM >>>
     I'm a bit confused (not unusual) by two paragraphs in IPC-6012
     regarding lifted lands.

     3.3.4  Lifted Lands.  The finised board SHALL not exhibit any lifted
     lands.

     3.6.2.9  Lifted Lands.  Lifted lands are allowed after thermal stress
     provided that the visual criteria of section 3.3.4 are met.

     So, is this telling me that lifted lands are okay as long as I can't
     see them?  (If I can't see them, how would I know they were lifted?)
     Therefore, if there is visual evidence of a lift is it rejectable?
     Was the intent to allow or dis-allow lifted lands after thermal
     stress?

     Thank you for any clarification.

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