Rotatable Capillary Stitch Bonding for Small-Pitch Connection Points
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Solution Overview
Problem
As semiconductor packages get smaller, the risk of stitch bonds lifting off or not fully bonding to the bonding surface increases, and current solutions to address this, such as forming additional balls or bumps, increase the complexity and cost of the fabrication process.
Innovation Solution
A rotatable capillary in the XY plane is used to secure the stitch bond by rotating it to ensure at least a portion of the bond is bonded to the side walls of the connection point, thereby increasing the bond area and reducing the risk of lift-off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional balls or bumps are formed on the stitch bond to prevent lift-off, then the reliability of the bond is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent transitions from a single-point bonding approach to a multi-dimensional bonding approach by rotating the capillary around the connection point. This allows the bond wire to contact not only the top surface but also the side walls of the connection point, effectively utilizing three-dimensional space to create multiple bonding zones without adding extra balls or bumps to the process
Solution Approach 2:
The capillary is made rotatable rather than fixed, allowing dynamic adjustment of the bonding position. The rotation mechanism enables the capillary to sweep across the connection point and deposit bond wire on multiple surfaces (top surface and side walls), providing adaptability to varying connection point geometries and ensuring reliable bonding without complex additional structures
2Productivity
If the pitch between connection points is reduced to accommodate smaller packages, then the productivity is improved, but the reliability of the stitch bond deteriorates due to increased lift-off risk
Solution Approach 1:
By utilizing the vertical dimension and side wall surfaces in addition to the top surface, the effective bonding area is increased without requiring larger horizontal spacing between connection points. This allows smaller pitch between connection points while maintaining adequate bond reliability through multi-surface contact
3Productivity
If the bonding surface area on the connection point is reduced, then the productivity is improved by enabling smaller packages, but the manufacturing precision required increases to ensure proper bond formation
Solution Approach 1:
The rotatable capillary provides dynamic positioning capability that compensates for variations in connection point geometry. By adjusting the rotation angle and sweep path, the system can adapt to different connection point sizes and shapes, ensuring consistent bond formation even with reduced bonding surface area
Solution Approach 2:
The bonding process is segmented into multiple contact zones: bonding to the top surface and bonding to the side walls. This segmentation of the bonding function across different surfaces allows the system to achieve reliable total bonding area even when individual surface areas are reduced
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method reduces the risk of stitch bonds lifting off the bonding surface and simplifies the semiconductor fabrication process by eliminating the need for additional balls or bumps.
Implementation Method 1
Wire bonding is a process in semiconductor packaging in which electrical connections are established between a semiconductor die or an integrated circuit and a connection point on a circuit board or a substrate
Implementation Method 2
A high-voltage electric arc is applied to the bond wire, which causes a ball to be formed at the end of the bond wire
Implementation Method 3
As the capillary rotates, at least a portion of the stitch bond and/or at least a portion of the bond wire is bonded to one or more side walls of the connection point
Data Source
AI summary
A wire bonder has a rotatable capillary for forming a stitch bond on a bonding surface of a connection point. When the stitch bond is formed, a bond head of the wire bonder causes the capillary to rotate in a XY plane. Rotation of the capillary causes at least a portion of the stitch bond to contact one or more side walls of the connection point. As a result, an entire surface area of the stitch bond contacts one or more surfaces of the connection point.