Integrated Circuit Package Bond Pad Protection
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Solution Overview
Problem
The existing methods for forming integrated circuit packages, such as flip chip assemblies, often result in defects like cracking or cratering of bond pad regions due to pressure and thermosonic bonding, which can lead to inadequate bonding and electrical connectivity issues.
Innovation Solution
The method involves forming zinc-containing adhesion layers and metal-containing layers over bond pad regions, followed by the deposition of electrically conductive layers and the use of deformable underfill materials to protect the bond pads during thermosonic bonding, thereby reducing defects and enhancing bonding quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thermosonic bonding is applied to bond interconnects to bond pad regions, then bonding strength is improved, but defects such as cracking or cratering occur in bond pad regions
Solution Approach 1:
A deformable underfill material is introduced as an intermediary between the interconnect and the bond pad region. This underfill material absorbs and distributes the pressure and thermosonic energy during bonding, preventing direct transmission of harmful forces to the bond pad region while still enabling effective bonding through the deformable material.
Solution Approach 2:
The deformable underfill material is applied to the interconnect or substrate before the bonding process begins. This pre-positioned cushioning layer is specifically designed to absorb and mitigate the pressure and ultrasonic energy during thermosonic bonding, preventing defects in the bond pad regions before they can occur.
2Strength
If pressure is applied during bonding to ensure good contact, then bonding quality is improved, but cracking or other defects are induced in bond pad regions
Solution Approach 1:
The deformable underfill material serves as a pressure-distributing intermediary that allows sufficient bonding pressure to be applied while preventing concentration of stress that would cause cracking or defects in the bond pad regions.
Solution Approach 2:
The underfill material's deformable properties allow it to change its physical state under pressure, becoming more compliant during bonding to accommodate pressure variations, then returning to a stable state that protects the bond pad region from excessive stress.
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
This approach effectively minimizes defects in bond pad regions and improves the bonding process, resulting in more reliable and durable integrated circuit packages with enhanced electrical connections.
Implementation Method 1
forming zinc-containing adhesion layers and metal-containing layers over bond pad regions, followed by the deposition of electrically conductive layers
Implementation Method 2
The bonding may comprise gold-to-gold bonding between gold-containing interconnects 22 and gold-containing interconnects 18. The gold-to-gold bonding is accomplished by pressing interconnects 18 and 22 together while subjecting the interconnects to ultrasonic energy and thermal energy (so-called thermosonic bonding).
Implementation Method 3
the use of deformable underfill materials to protect the bond pads during thermosonic bonding, thereby reducing defects and enhancing bonding quality
Data Source
AI summary
Some embodiments include methods of assembling integrated circuit packages in which at least two different conductive layers are formed over a bond pad region of a semiconductor die, and in which a conductive projection associated with an interposer is bonded through a gold ball to an outermost of the at least two conductive layers. The conductive layers may comprise one or more of silver, gold, copper, chromium, nickel, palladium, platinum, tantalum, titanium, vanadium and tungsten. In some embodiments, the bond pad region may comprise aluminum, an inner of the conductive layers may comprise nickel, an outer of the conductive layers may comprise gold, the conductive projection associated with the interposer may comprise gold; and the thermosonic bonding may comprise gold-to-gold bonding of the interposer projection to a gold ball, and gold-to-gold bonding of the outer conductive layer to the gold ball. Some embodiments include integrated circuit packages.