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Wirebond Workmanship: Wedge (Ultrasonic) Bonding

Wirebond Workmanship Contents

Bond Wire Placement and Tail

Wedge bond width (W) , on the die pad or package post should not be less than 1.2 times or more than 3.0 times the wire diameter (D).

Wedge bond length (L) , on the die pad or package post should not be less than 1.5 times or more than 5.0 times the wire diameter (D).

Note: Wire tail is not considered part of the bond when determining physical bond dimensions.

No bonding wire shall make a straight line run from the die pad to package post without a visible arc.(see wedge bond strain relief section for diameter requirements)

Note: Some wedge bonding tools have a built in cross groove to improve bonding. The cross groove may leave a tooling mark which is not a defect.


There shall be no lifting of the bond heel

 

There shall be no lifting of the bond toe that reduces the bond foot to below the minimum required length.

The wire, as it exits from the bond foot, shall not form an angle of less than 80 degrees to the bond foot within five wire diameters of the bond foot.

 

Die: Bond foot shall be at least 50 percent on the bonding pad.

 

Substrate: Bond foot shall be completely within the bonding pad area.

 

Substrate: If pad size is smaller than 1.5 X the minimum bond size, the bond shall be at least 75 percent in the bond pad area.

 

When bonding to a pad there shall be at least 1.0 mil of a line of undisturbed connecting metal between the bond pad and conductor.

 

Note: An exception is when:

  • entering metal width is greater than 2 mils, and
  • pad dimension is greater than 3.5 mils, and
  • at least 50 percent of bond is on the pad, and
  • NO visible line of undisturbed connecting metal is required.

Wire bond tails shall not prevent the bonding pad/conductor joint from being visible, unless the following conditions are met:

Bond (excluding the tail) has clearance greater than or equal to 0.1 mil from the inter-section of the conductor and the bonding pad, and

No visual evidence of disturbed pad at the bonding pad and connector joint.

Bond tails shall not extend over or make contact with any adjacent uninsulated metallization, except when metallization areas connected together. No wire tail overhang is allowed over unglassivated conductors.

 

Wire bond tails shall not exceed:

  • two wire diameters in length at bond pad, and
  • four wire diameters in length at package post, or 10 mils, whichever is less.

Courtesy Rockwell Collins