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Challenging Substrate


Enhanced Stitch Bondability

The pressure to reduce the cost of products has indirectly instilled certain elements of inconsistency to the lead frame and substrate materials, which directly affect the bond reliability of the stitch bonds. Inconsistent lead frame and substrate quality often results in NSOL, short tail or low stitch pull readings during wire bond. Most of the time, the problem is only known after die attach and during wire bond.

The challenge is to be able to improve the stitch bondability for these types of lead frames/substrates. The Stitch Integrator capillary helps to improve the bonding performance as shown in the following application.

Bonding Condition :
Capillary         SI -  30080-385F-ZB34TP
Bond Pad Pitch 60um
Bonder KNS 8028
Wire Type 1mil Au wire
Device Lead frame base

Bonding responses monitoring for SI capillary :
 Wire Pull readings and CpK
Bonder Stoppage Statistic Open / Short Test Statistic

Key Notes:

  • Destructive test for both ball shear and wire pull has shown that the bondability for the ball and stitch bonds was within the manufacturing specification with good Cpk control.

  • Visually, the ball and stitch bonds at 800K bonds did not show any symptoms of golf ball, irregular ball squashed out or damaged stitch bonds. This indicates that SI + Infinty is capable of extending the tool life of the capillary.

  • Bonder stoppages throughout the life of the SI capillary was recorded at, NSOL: 614ppm, short tail: 512ppm. No EFO open was encountered.

  •  During the O/S test, device failure bonded using the SI capillary showed a substantial reduction in ppm as compared to non-SI capillary on the same device type. Overall, the SI capillary showed an improvement of more than 70% with reduced second bond failure. This indicates that the stitch bondability has improved using the SI capillary.
 
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