Semiconductor Wire Bonding with Sloped Wedge Bump
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Solution Overview
Problem
Conventional wire bonding methods face challenges in achieving high bondability between gold wires and materials like copper or nickel, leading to bonding defects due to insufficient slope and flat surface on bumps, and issues with wire cutting causing bends and adjacent wire contact.
Innovation Solution
A semiconductor device and wire bonding method that form a bump with bent wire convex portions and a sloped wedge, allowing the wire to be bonded along the wedge with a cut surface smaller than its cross-section, improving bondability and cutting properties by reducing tensile stress during cutting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bump is formed with sufficient slope and flat surface for gold wire bonding, then bondability between gold wire and bump is improved, but the wire cutting process causes bends and adjacent wire contact due to increased tensile stress
Solution Approach 1:
The invention applies local quality by creating a sloped wedge structure on the bump surface where the slope gradually decreases from the base toward the top. This localized variation in slope angle allows the wire bonding process to occur on a surface with optimal local characteristics - steeper slopes near the base for structural support and gentler slopes at the bonding area for improved wire adhesion, thereby resolving the contradiction between bondability and wire deformation during cutting
Solution Approach 2:
The invention employs asymmetry by designing the bump surface with an asymmetric sloped wedge profile rather than a symmetric or uniform surface. The asymmetric slope distribution - with varying angles across different regions of the bump surface - enables differentiated functionality where certain areas provide mechanical support while others optimize bonding conditions, thus improving bondability without causing wire bends during cutting
2Device complexity
If gold wire is bonded directly on copper, nickel, or flash gold plating without a bump, then the bonding process is simplified, but bondability is insufficient due to material incompatibility
Solution Approach 1:
The invention uses the sloped wedge structure on the bump as an intermediary between the gold wire and the underlying copper, nickel, or flash gold plating materials. This intermediate structure provides a transition zone that improves mechanical interlocking and bonding surface area, enabling reliable bonding between incompatible materials while maintaining process simplicity
Solution Approach 2:
The invention applies preliminary action by pre-forming the bump with the sloped wedge structure before wire bonding. This preliminary preparation of the bonding surface creates optimal geometric conditions for subsequent wire attachment, improving bondability through enhanced surface area and mechanical interlocking without requiring complex bonding procedures
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
Enhances bonding quality by improving bondability between the wire and bump, while also improving the cutting property of the wire, reducing the occurrence of bends and preventing wire contact with the chip or lead frame.
Implementation Method 1
a discharge from a flame off electrode forms a ball at a tip end of the wire protruding from the capillary
Data Source
AI summary
A semiconductor device with improved bondability between a wire and a bump and cutting property of the wire to improve the bonding quality. In the semiconductor device, a wire is stacked on a pad as a second bonding point to form a bump having a sloped wedge and a first bent wire convex portion, and a wire is looped from a lead as a first bonding point to the bump and is pressed to the sloped wedge of the bump with a face portion of a tip end of a capillary to bond the wire to the bump. At the same time, the wire is pressed to the first bent wire convex portion using an inner chamfer of a bonding wire hole in the capillary to form a wire bent portion having a bow-shaped cross section. The wire is pulled up and cut at the wire bent portion.