Patterned Surface Conductive Structure for Flip-Chip Warpage Reduction
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Solution Overview
Problem
The reflow process in flip-chip packaging often causes chip warpage due to the reliability issues with bumps, leading to potential damage and reduced packaging efficiency.
Innovation Solution
A connector structure with a patterned surface conductive structure that includes a metal portion and a supporting portion, where the supporting portion is made of materials like silicon dioxide or polyimide, and the metal portion is made of Sn, Ag, or Cu, which is formed over a semiconductor substrate with an under-bump metallurgy layer, reducing stress during reflowing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a bump is processed through the reflow process to improve reliability and attachment, then the attachment strength to the metal pad is improved, but chip warpage occurs due to thermal stress
Solution Approach 1:
The conductive structure is divided into multiple functional portions: a metal portion for electrical connection and soldering, and a supporting portion (made of materials like silicon dioxide or polyimide) that provides mechanical support and stress distribution. This segmentation allows the bump to maintain strong attachment while reducing thermal stress-induced warpage during reflow processing.
Solution Approach 2:
The conductive structure uses composite material composition, combining metal materials (Sn, Ag, Cu, or alloys) with supporting materials (silicon dioxide, silicon nitride, titanium dioxide, aluminum oxide, polyimide, or PBO). This composite structure enables simultaneous achievement of strong attachment strength and reduced thermal stress, preventing chip warpage during reflow while maintaining reliable electrical connection.
2Ease of manufacture
If the bump structure is simplified for ease of manufacture, then manufacturing complexity is reduced, but reliability during reflow process deteriorates
Solution Approach 1:
The supporting portion is formed as part of the conductive structure before the reflow process. This preliminary formation of the stress-distributing supporting structure ensures that when thermal stress occurs during reflow, the damage is already mitigated, maintaining reliability without complicating the manufacturing process.
Solution Approach 2:
The conductive structure employs composite materials combining metal and supporting materials, which can be integrated into existing manufacturing workflows. The metal portion provides solderability and electrical connection, while the supporting portion (made of materials like silicon dioxide, silicon nitride, titanium dioxide, aluminum oxide, polyimide, or PBO) ensures reliability during reflow, achieving both manufacturability and reliability.
3Strength
If a larger bump size is used to improve connection reliability, then the connection strength between substrate and chip is improved, but the stress during reflow increases causing more warpage
Solution Approach 1:
The conductive structure is segmented into a metal portion for connection and a supporting portion for stress management. This segmentation allows the bump to achieve strong connection while the supporting portion distributes and reduces thermal stress during reflow, preventing excessive warpage even with larger bump sizes.
Solution Approach 2:
The conductive structure uses composite materials where the metal portion (Sn, Ag, Cu, or alloys) provides strong connection strength, while the supporting portion (silicon dioxide, silicon nitride, titanium dioxide, aluminum oxide, polyimide, or PBO) has properties that reduce thermal stress. This composite approach enables larger bumps to maintain strong connections without proportionally increasing reflow stress and warpage.
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 patterned surface structure reduces chip warpage, enhances reliability, and lowers overall warpage levels by mitigating stress during the reflow process, thereby preventing chip cracks and improving packaging reliability.
Implementation Method 1
the supporting portion of the patterned surface structure is made of at least one inorganic material such as silicon dioxide, silicon nitride, titanium dioxide, aluminum oxide, or at least one organic material such as polyimide, polybenzoxazole (PBO), or a combination thereof
Implementation Method 2
In the reflow process, the entire assembly of the circuit board and bump is under a thermal treatment, such as by annealing. The thermal treatment may be accomplished by passing the assembly through a reflow oven or under an infrared lamp.
Data Source
AI summary
A connector structure and a manufacturing method thereof are provided. The connector structure includes a semiconductor substrate, a metal layer, a passivation layer, and a conductive structure. The metal layer is over the semiconductor substrate. The passivation layer is over the metal layer and includes an opening. The conductive structure is in contact with the metal layer in a patterned surface structure of the conductive structure through the opening of the passivation layer.