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GAISER CAPILLARY INFORMATION

12. FINE PITCH BONDING PAGE 1 (2)

Continued improvements in wire bonding technology have resulted in new packages with lead counts of up to 304 leads. ASICS and VLSICS are increasing the lead counts and the density of the new packages. This results in die pad sizes, lead widths and the center to center spacing (pad pitch) becoming smaller and smaller. Lead pitches are also being reduced. However, due to the wire approaching the lead at a very low angle, the lead pitch is typically not considered a critical capillary design consideration. 

GTC Figure 41

Figure 41. This drawing identifies the primary design constraints. 
 

Today's bonders are equipped with pattern recognition systems that allow them to bond advanced packages at a rate of up to 9 wires per second. The capillary must be designed to allow clearance into bonding areas without damaging the previous bonds or adjacent loops.
Fine pitch (0.006in/152µm or less) ball bonding has become common as applications approach pad pitch requirements of 0.004in./102µm and below. 

GTC Figure 42

Figure 42. Many software algorithms utilize sophisticated bonder head movements that provide looping profiles that produce the clearance required for fine pitch bonding. This drawing shows how the wire adjacent to the cone of the capillary is the critical loop height even though the overall loop height is considerably higher. 

Bonding application elements to be considered in the design of the capillary include: 

bullet Bond pad size and pitch
bullet Wire diameter
bullet Loop height adjacent to capillary
bullet The wire span or loop length
bullet The metallization material and thickness on both the die and lead, (Is it considered to have good or poor bondability?)
bullet Is the die higher or lower with respect to the lead bonds?
bullet Bonder speed
bullet Wire elongation

GTC Figure 43

Figure 43. This photo shows fine pitch low loop bonds. The pad pitch can be reduced by forming loops with the wire bending just at or above the ball bond. This region is commonly referred to as the neck of the ball bond.

(Photo courtesy ASM Corporation)

GTC Figure 44

Figure 44. Many fine pitch applications incorporate staggered die pads. In the photo above, the row of pads closest to the pad's edge are low-loop bonds. The row of pads bonded directly behind are higher loop bonds. On some of the new packages lead bonds are on two tiers, often referred to as a multilevel package.

(Photo courtesy Kaijo Corporation)

Get the BASIC CAPILLARY BONDING and DESIGN document in BASIC CAPILLARY BONDING/ DESIGN format

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Last modified: 2011-11-12