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Joined: 12 Jun 2026
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 Posted: Sun Jun 22, 2026 11:03 pm Post subject: |
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Reposted from SFE's old Assembly Forum
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Date: 25 Apr 2026
Time: 02:54:57
Remote Name: 137.71.23.54
Remote User:
Hello Wbeng,
Welcome to the Assembly forum!
Don't worry - most new WB engineers get their baptism of fire from ball lifting. Here are things that you need to look for: 1) anomalies in the set-up of the wirebond equipment - parameter settings, mechanical stability, etc.; 2) anomalies on the bond pad: bond pad contamination, bond pad corrosion, excessive and/or multiple probe marks, topography imperfections; 3) anomalies in the bonding itself: misplaced bond.
Before suspecting any other cause, you must establish that there is nothing wrong with your set-up. Equipment problems would usually manifest in the ball bond formation itself, i.e., you may see signs of: size abnormality, insufficient or excessive aspect ratio (ball too high or ball too flat, respectively), or excessive non-symmetry of the ball.
Once you're sure that the equipment/set-up is OK, you may suspect that something on the bond pad is interfering with the proper formation of ball bond intermetallics. Usually this 'something' is a contaminant. Note that contaminants on bond pads are not always visible, so don't conclude immediately that the bond pad is clean if it looks clean. For example, an unetched layer of glass on the bond pad may look invisible to you, so you need to do some compositional or elemental analysis on the bond pad (usually EDX analysis) before writing up your report.
Ball lifting encompasses a wide range of manufacturing issues that can not be covered completely in this response. The good news is that ball lifting is a fairly well-understood mechanism already, and there are hundreds of engineers out there who can add to this thread to help you.
Good luck!
-EE
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