Package-related Failure Mechanisms and Attributes (Page 3 of 3)

 

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Seal Cracking

 

Solder seal cracking is the occurrence of fracture(s) anywhere in the solder seal of a ceramic package that uses a combo lid, e.g., sidebrazed, LCC, and JLCC packages.  Seal glass cracking is the occurrence of fracture(s) anywhere in the seal glass of a Cerdip package. 

See separate article on seal cracking.

      

Wedge Lifting

                

Wedge lifting is the detachment of a wedge bond from the bond pad or bonding post,  or the crescent bond from the leadframe bonding finger.

See separate article on wedge lifting.

                   

Wire Breaking, Midspan

   

A midspan wire break, or broken wire, is simply the disconnection of the first bond from the second bond, because of a total fracture somewhere along the length of the wire itself.  Broken wires are often due to package mishandling, particularly when the package has not yet been encapsulated or sealed. Wires being hit by the lid or cap during capping, or accidentally touched by the operator prior to encapsulation/sealing, or smashed by an equipment tool getting out of control, all suffer a midspan break after the incident.

 

Wire nicks and similar defects can act as crack initiation points on the wire.  Incipient cracks can easily propagate during thermomechanical stressing once they have formed from these defects.  Broken wires can also be caused by corrosion, which is often brought about by Cl contamination of the wires.  Wiresweeping during molding is another primary cause of broken wires.

 
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Wire Depression   

  

Wire depression is a condition wherein one or more wires of the device are deformed or pressed downwards.  Wire depression is caused by purely mechanical means, usually by mishandling. Wirebonded leadframes prior to encapsulation are very vulnerable to wire depression, especially if these are being handled manually. Improper stacking of the leadframes, fingers coming into contact with wires, or leadframes slipping out of control prior to or during the molding process are common causes of depressed wires.

      

Equipment problems can also result in wire depression. For example, overcoat dispense tools that are improperly set up can land on the wires and depress them.  

      

Wire-to-Die Shorting

  

Wire-to-die shorting is the presence of an unintended electrical connection between one or more wires and the die.

See separate article on wirebond-related shorts.

   

Wire-to-Wire Shorting   

  

Wire-to-wire shorting is the presence of an unintended electrical connection between two wires.

See separate article on wirebond-related shorts.

   

Wrong Bonds

  

Bond Mis-assignment, or wrong bonding, is simply the bonding of the first or second bond to the wrong bond pad or bonding post/finger, respectively.  It may be considered as a misrouting of the bonds, such that the bond pads are not connected to their corresponding external terminations.  Bond misassignment can only happen if a wrong bonding program is retrieved and used.

   

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See Also:  Die Failures Failure AnalysisBasic FA Flows Reliability Models

    

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