Knife-Edge Temporary Bonding for Inspectable Die Stacking
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Solution Overview
Problem
Current microelectronic packaging and integration manufacturing requires high pressures and temperatures for thermocompression bonding, which is not suitable for temporary or reworkable bonding processes, especially for components with surface roughness and oxides, limiting the ability for inspection and adjustment before permanent bonding.
Innovation Solution
The use of knife-edge microstructures that can plastically deform at room temperature to form temporary or permanent bonds between microelectronic components, allowing for initial alignment and inspection before applying higher pressures and temperatures for final bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high pressure and high temperature are used for thermocompression bonding, then bonding strength and yield are improved, but the process becomes unsuitable for temporary bonding and rework operations
Solution Approach 1:
The bonding process is segmented into two distinct stages: temporary bonding at low pressure/room temperature using knife-edge microstructures, and permanent bonding at high pressure/temperature. This segmentation allows each stage to have optimized parameters suitable for its specific purpose, resolving the contradiction between reliability and adaptability.
Solution Approach 2:
Temporary bonding is performed as a preliminary action before final permanent bonding. The temporary bond enables alignment and inspection activities, and can be reversed if rework is needed. The knife-edge microstructures are designed to form these preliminary temporary bonds that can be later removed without damage.
2Manufacturing precision
If high pressure is applied to overcome surface asperities and oxides, then intimate atomic-level contact is achieved, but the process requires high temperature to soften metal
Solution Approach 1:
The knife-edge microstructures concentrate the bonding action to localized regions where high pressure is applied precisely at the knife-edge contact points. This local quality approach allows sufficient pressure to be applied to overcome surface asperities and oxides without requiring high temperature to soften the entire metal surface.
Solution Approach 2:
The invention changes the pressure parameter distribution by using sharp knife-edge microstructures that create highly localized high pressure zones. This parameter change allows room temperature bonding by concentrating force at the contact point, eliminating the need for high temperature metal softening.
3Ease of operation
If knife-edge microstructures are used for temporary bonding, then room temperature operation and rework capability are enabled, but the contact area is reduced
Solution Approach 1:
The knife-edge microstructures use sharp curved edges rather than flat surfaces. This curvature concentrates the contact force to a very small area, creating high local pressure that enables room temperature bonding without requiring large contact areas. The curved knife-edge geometry is essential for achieving the necessary pressure concentration.
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
Enables temporary aligned attachment and inspection of microelectronic components with minimal damage, allowing for multiple bond/debond cycles and high yield processes, while accommodating surface topography and reducing the need for high forces and temperatures.
Implementation Method 1
knife-edge microstructures that can plastically deform at room temperature to form temporary or permanent bonds
Implementation Method 2
applying a relatively low compressive force or pressure between the two electronic devices
Data Source
AI summary
A method for bonding two confronting electronic devices together wherein the two electronic devices are initially temporarily coupled together using a room temperature process with a plurality of knife-edge microstructures on at least a first one of the electronic devices engaging portions of the a second one of the electronic devices. The room temperature process involves applying a relatively low compressive force or pressure between the two electronic devices compared to the forces or pressures used in convention flip-chip bonding. The first one of the electronic devices and the second one of the electronic devices also have traditional contact pads that are spaced from each other by a standoff distance when the devices are initially coupled together using the room temperature process. This allows for inspection of the two electronic devices while they are initially temporarily coupled together. In need be, the two can be separated at this stage for re-work After passing inspection, a relatively higher compressive force or pressure is applied between the two electronic devices to cause the standoff distance to decrease to zero and for the contact pads confronting each other on the confronting two electronic devices to weld thereby permanently bonding the two electronic devices together.