Gold Bump Inner Lead Bonding with Eutectic Sidewall Coverage
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Solution Overview
Problem
Existing chip packaging structures face challenges in achieving high pin count and fine pitch designs due to issues such as damage risk from thermo-compression bonding, increased production costs, and reduced channel density.
Innovation Solution
A chip packaging structure utilizing a gold bump with a first bonding surface and side walls, where a eutectic material coverage is formed between the gold bump and a lead on a film substrate without applying stress, enhancing bonding strength and reducing material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thermo-compression bonding is applied to embed the lead into the gold bump, then bonding strength is improved, but damage risk to chip elements increases
Solution Approach 1:
The patent replaces the mechanical embedding process (thermo-compression bonding with applied stress) with a chemical bonding mechanism. The eutectic material forms intermetallic compounds through diffusion bonding at lower temperatures, eliminating the need for high mechanical stress that damages chip elements while achieving sufficient bonding strength.
Solution Approach 2:
The patent changes the bonding parameters by using eutectic material with a lower melting point than traditional solder. This allows bonding to occur at reduced temperatures where mechanical stress is minimized, preventing damage to the pad, passivation layer, and die while still forming strong metallurgical bonds through intermetallic compound formation.
2Reliability
If the width of the gold bump is increased to ensure lead embedding, then bonding reliability is improved, but channel density decreases and material cost increases
Solution Approach 1:
By replacing mechanical embedding with chemical diffusion bonding using eutectic material, the patent eliminates the requirement for wide gold bumps. The chemical bonding mechanism provides sufficient bonding strength and reliability even with narrower gold bump widths, thereby maintaining high channel density on the film substrate.
3Reliability
If the width of the gold bump is increased to ensure lead embedding, then bonding reliability is improved, but material usage increases and production cost rises
Solution Approach 1:
The patent uses eutectic material with optimized composition parameters that enable effective bonding at lower material volumes. The eutectic reaction allows complete mixing and bonding with minimal material, reducing gold and other precious material consumption while maintaining bonding reliability through intermetallic compound formation.
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 achieves non-embedded bonding with improved strength and reliability, reduces production costs, and increases packaging precision and heat dissipation capabilities.
Implementation Method 1
heating the gold bump and the lead up to a temperature range to form a eutectic material coverage between the gold bump and the lead
Implementation Method 2
heating the gold bump and the lead up to a temperature range to form a eutectic material coverage
Data Source
AI summary
A chip packaging structure includes a chip and a film substrate. The chip is formed with a gold bump, and the film substrate is formed with an inner lead, wherein the gold bump includes a first bonding surface and a plurality of side walls. The gold bump is electrically connected to the inner lead through a eutectic material coverage layer, and the first bonding surface and at least one of the plurality of side walls are covered by the eutectic material coverage layer.