Stud Bump Formation via Wire Notching and Breaking
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Solution Overview
Problem
As integrated circuit device density increases, there is a need for improved packaging schemes that require smaller solder bumps without compromising the quality of solder-containing bonds, necessitating more precise and efficient methods for forming stud bumps.
Innovation Solution
The formation of stud bumps involves pre-notching or in-situ notching of wires, followed by bonding and controlled breaking at the notch points to achieve precise control over the height of the tail and overall stud bump, using various apparatuses such as rollers, capillaries, clamps, and spring blades to ensure efficient integration into packaging processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If solder bump size is reduced to accommodate increased IC device density, then connector density increases, but bond quality deteriorates
Solution Approach 1:
The wire is segmented into two distinct regions: a stud bump region that bonds to the electrical connector and a tail region that extends upward. This segmentation allows the stud bump to be small for high density while the tail provides sufficient material for reliable solder bonding, resolving the contradiction between connector density and bond quality
Solution Approach 2:
A notch is formed in the wire at a predetermined location before bonding occurs. This preliminary action defines the exact height and shape of the stud bump, ensuring consistent dimensions that maintain bond quality while enabling reduced overall wire size for higher density applications
2Reliability
If stud bump height is increased for better solder bonding, then bond quality improves, but manufacturing precision requirements increase
Solution Approach 1:
The notch is formed in advance at a precisely controlled depth and position, which predetermined the exact height of the stud bump before bonding. This preliminary dimensioning ensures that the stud bump achieves optimal height for solder bonding while maintaining tight dimensional control through the notching process
Solution Approach 2:
The wire itself serves as the forming tool - by notching the wire at a specific depth, the unnotched portion automatically forms the stud bump with the correct height when bonded. The wire's own material properties and the notch geometry self-determine the final stud bump dimensions, reducing the need for additional precision control mechanisms
Data Source
AI summary
An apparatus includes a spool configured to supply a wire, a cutting device configured to form a notch in the wire, and a capillary configured to bond the wire and to form a stud bump. The apparatus is further configured to pull the wire to break at the notch, with a tail region attached to the stud bump.