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2N9 Gold Wire Bonding


Enhanced Stitch Bondability

The use of 2N9 Alloyed Au wire is becoming popular for fine-pitch and ultra-fine pitch bonding. These wires consist of 99% Au purity with 1% Pd and are formulated with dopant to enhance the looping capability and ball bond reliability. However, these wires are generally harder and more prone to wire breakage and non-sticking problem during stitch bond formation resulting in higher yield loss during production, especially for leaded devices. The nature of the lead frame design with certain degree of bouncing effect during bonding further complicates the robustness of the bonding process.

The challenge is to be able to improve the stitch bondability for 2N Alloyed Au wire. The Stitch Integrator capillary helps to improve the bonding performance as shown in the following application.

Bonding Condition:
Capillary SI - 33090-435F - ZB34TP
Bond Pad Pitch 70um
Bonder ASM 339 Eagle
Wire Type 1 mil 2n9 Au Wire
Device Lead Frame base, TQFP

Bonding Responses monitoring for SI capillary
:


Stitch Bond before and after destructive test
 Capillary Condition @ 600K bonds
Wire Pull Process Capability

Key Notes:

  • The enhanced coupling effect between the SI capillary and the alloyed wire has proven to improve the bondability of the stitch bond with minimum interruption to the bonder.

  • At 600K bonds, the load-up on the capillary is satisfactory with no excessive load-up accumulation at the tip of the capillary.
     (Note: standard tool life is set at 500K bonds)

  • Destructive test performed through wire pull @ 1/3 wire length at 1K and 600K bonds did not reveal any abnormality with the stitch bonds as all the wires
      break @ neck location. This indicates that the stitch bond adhesion is satisfactory with no bond reliaability issue. Sample size = 1500 wires.
 
  • Bonder stoppages due to wire open and short tail defect rate were recorded at less than 1000ppm while regular bonder stoppages was encountered with non-SI capillary.
 
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