Semiconductor Leadframe Clamping via Wedge Recesses
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Solution Overview
Problem
The semiconductor industry faces challenges in securely constraining highly populated leadframes during ultrasonic wire or ribbon bonding processes, leading to unreliable and poor-quality bonds due to insufficient clamping, especially in densely arranged components where conventional clamping systems fail to provide adequate frictional coupling.
Innovation Solution
A support structure with constraining features, such as wedge-shaped geometry on its upper surface, is introduced to securely hold the leadframe in place during bonding, reducing vibrations and improving clamping through a combination of raised walls and device clamps that apply pressure to force leadframe portions into these features, thereby enhancing the bonding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional clamping systems are used to secure leadframes during bonding operations, then the clamping force is applied through frictional coupling, but the clamping reliability deteriorates due to insufficient frictional coupling in densely arranged components
Solution Approach 1:
Instead of relying on frictional coupling between clamp fingers and leadframe surfaces, the invention inverts the approach by using mechanical interlocking through recesses in the support structure that positively engage with protrusions on the leadframe. This geometric constraint system replaces the ineffective friction-based system, providing reliable clamping without depending on surface friction.
Solution Approach 2:
The invention introduces an intermediary support structure with specifically designed recesses that act as a mediator between the clamp fingers and the leadframe. These recesses receive and constrain leadframe portions, translating the clamping force into effective mechanical constraint. The intermediary structure bridges the gap between the clamping system and the densely arranged leadframe components.
2Loss of substance
If leadframes are made highly populated to reduce material usage and cost, then material consumption decreases, but the difficulty of properly constraining components during bonding increases
Solution Approach 1:
The support structure is segmented into multiple regions with specifically designed recesses positioned to accommodate different portions of the highly populated leadframe. Each recess is strategically located to constrain specific leadframe components, allowing the system to handle dense component arrangements through distributed, localized constraint points rather than requiring a monolithic clamping approach.
Solution Approach 2:
The support structure implements local quality by providing recesses with specific geometries at specific locations tailored to the local requirements of the leadframe portions. Each recess is designed to match the shape and size of the leadframe component it receives, providing optimized constraint at each location rather than using a uniform clamping approach across the entire leadframe.
3Reliability
If the bonding process is made highly dynamic to improve bonding quality, then bonding reliability improves, but the relative displacement between bonding tool and semiconductor device decreases due to device movement
Solution Approach 1:
The support structure with its constrained recesses applies preliminary anti-action by pre-constraining the leadframe portions before the bonding process begins. The recesses are designed to receive and fix the leadframe components in predetermined positions, counteracting the dynamic movements that would otherwise occur during high-velocity bonding operations. This pre-constraint prevents device movement that would compromise bonding precision.
Solution Approach 2:
The clamping system performs preliminary action by securing the leadframe to the support structure before the bonding operation commences. The clamp fingers apply force to press the leadframe portions into the recesses, establishing stable mechanical constraints in advance. This preliminary constraining action ensures that when the dynamic bonding process begins, the device is already properly positioned and constrained.
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
The solution provides a more robust bonding process with consistent deformation values and increased shear strength of bonded wires/ribbons, making the process less dependent on clamp finger design and force, and is suitable for small devices requiring clearance for the bonding tool.
Implementation Method 1
poor clamping (which may result from the density and arrangement of the components) tends to lead to an unreliable process... because the bonding process (e.g., ultrasonic bonding process) is highly dynamic, particularly for large wire and ribbon bonding, the device being bonded (including the leadframe) may be driven at high velocities similar in amplitude to the tip velocity of the bonding tool
Implementation Method 2
A support structure with constraining features, such as wedge-shaped geometry on its upper surface, is introduced to securely hold the leadframe in place during bonding, reducing vibrations and improving clamping through a combination of raised walls and device clamps that apply pressure to force leadframe portions into these features
Implementation Method 3
Exemplary methods of forming the interconnections include ball bonding, wedge bonding, and ribbon bonding. An exemplary wedge or ribbon bonding sequence includes: (1) forming a first wedge/ribbon bond on a die pad of a semiconductor die; (2) extending a length of wire/ribbon in a desired shape between the die pad and a lead of a leadframe; (3) forming a second wedge/ribbon bond on the lead of the leadframe; and (4) severing the wire/ribbon to complete the wire/ribbon loop. In forming the bonds between (a) the respective portion of the wire/ribbon material and (b) the respective bond site (e.g., a die pad, a lead, etc.) varying types of bonding energy may be used including, for example, ultrasonic energy, thermosonic energy, thermocompressive energy, amongst others.
Data Source
AI summary
A support structure for supporting a semiconductor device during a bonding operation is provided. The support structure comprises a body portion defining an upper surface configured to support a semiconductor device during a bonding operation. The upper surface defines a constraining feature for constraining at least a portion of the semiconductor device during the bonding operation.