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GAISER CAPILLARY INFORMATION

Figure 7. The zero degree (0°) face angle provides the greatest downward force on the stitch bond; however, it may result in heel cracking problems.
To reduce this problem, 0° face angle capillaries are designed with a larger outside radius of 0.0025"/64u or larger. 0° face angle capillaries have shown to work well for lead frames with lead planarity problems. 

Figure 8. The eight degree (8° ) face angle is probably the most successful dimensional characteristic of modern capillary design. The 8° face angle provides adequate force down on the stitch bond and limits heel crack problems. This is due to the thicker cross-sectional area of the wire under the face up to where the outside radius begins. The 8° face angle capillary works well over the broadest range of moralizations; i.e., thick film, thin film, soft and hard moralizations.  

Figure 9. The four degree (4°) face angle provides a compromise between the 0° face angle and the 8° face angle capillary. The 4° face angle provides more force down on the stitch bond than the 8° face angle. This allows for a stronger stitch bond but can lead to the possibility of heel cracks or chopped off stitches. This is due to the thinner cross-sectional area of the wire under the face.
The 4° face angle is recommended when power and time (instead of force) are used to correct stitch bond nonsticking problems.

Figure 10. Causes for a week transition from the stitch bond to the Wire include:

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