Chip Package Structure With Twinned Layer for Void-Free Heat Transfer
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Solution Overview
Problem
Existing thermal interface materials fail to address the challenges of thermal interface materials in electronic components, leading to void formation and reduced heat dissipation performance.
Innovation Solution
A package structure with a twinned layer between the thermal interface material and the chip and/or heat sink, which reduces void formation and improves heat dissipation by using a twinned layer to enhance bonding and eliminate the need for organic adhesives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional thermal grease is used to fill contact gaps, then thermal impedance is reduced, but the material cannot completely fill gaps due to high viscosity and requires high pressure (300 kPa)
Solution Approach 1:
The patent changes the physical state of the thermal interface material from high-viscosity grease to low-melting-point alloy that transitions from solid to liquid at operating temperature. This parameter change allows the material to naturally flow and fill gaps without requiring high assembly pressure, resolving the contradiction between heat dissipation performance and ease of manufacture.
Solution Approach 2:
The patent uses composite low-melting-point alloy materials combining metals such as indium, bismuth, tin, and silver. These composite materials achieve both excellent thermal conductivity for heat dissipation and low melting points for easy processing, eliminating the need for high pressure during assembly while maintaining superior heat transfer properties.
2Reliability
If polymer-based thermal grease is used, then thermal impedance is reduced, but the material experiences pump-out effect due to inability to withstand relative displacement
Solution Approach 1:
The patent transitions from polymer-based grease to metal alloy-based material that remains in solid or liquid state without polymer breakdown. This parameter change eliminates the pump-out effect as the alloy maintains structural integrity under displacement while providing superior thermal conductivity and stability.
Solution Approach 2:
The patent employs low-melting-point alloys that can be re-melted and re-applied if needed, providing easier reworkability compared to polymer-based greases that degrade over time. The alloy materials offer long service life without the pump-out issues that plague polymer-based solutions.
3Reliability
If thermal grease is exposed to high temperatures for long time, then thermal impedance is initially reduced, but polymer materials undergo chemical reactions and separate from fillers causing dry-out
Solution Approach 1:
The patent changes the material composition from temperature-sensitive polymers to thermally stable metal alloys. This parameter change allows the thermal interface material to withstand prolonged high-temperature exposure without chemical decomposition or separation, eliminating the dry-out phenomenon and extending service life.
Solution Approach 2:
The patent uses low-melting-point alloys with high thermal stability that maintain their properties throughout the operational temperature range. These materials do not undergo the chemical reactions that cause polymer-based greases to fail, providing long-lasting reliable heat dissipation performance.
4Ease of manufacture
If elastomeric thermal pads are used instead of thermal grease, then ease of assembly is improved, but thermal impedance increases significantly (1-3 K·cm2/W)
Solution Approach 1:
The patent changes the material state from room-temperature solid elastomers to low-melting-point alloys that become liquid at operating temperature. This parameter change enables the material to flow into and completely fill contact gaps, achieving thermal impedance levels comparable to or better than thermal grease while maintaining the ease of assembly advantages of elastomeric pads.
Solution Approach 2:
The patent employs composite low-melting-point alloy formulations that combine multiple metals to achieve optimal balance between melting point, thermal conductivity, and wetting properties. These composite materials provide excellent heat dissipation performance (thermal impedance < 0.2 K·cm2/W) while remaining easy to assemble without requiring high pressure.
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 twinned layer improves heat dissipation performance and reliability by ensuring complete coverage of the thermal interface material, reducing voids and simplifying the manufacturing process.
Implementation Method 1
the heat generated during the operation of the electronic components may melt the low-melting-point alloy into a liquid state, allowing it to fill the gaps at the bonding site
Implementation Method 2
Phase change materials combine the excellent thermal conductivity of thermal grease with the ease of processing of elastomeric thermal pads, providing good thermal conductivity both above and below its melting point
Implementation Method 3
The main function of TIM is to fill the contact gaps between two materials, increase the heat dissipation performance of the system, and effectively reduce the thermal impedance
Data Source
AI summary
A package structure includes a substrate; a chip disposed on the substrate and having a backside surface away from the substrate; a fin heat sink having a surface facing the chip disposed above the substrate; a thermal interface material disposed between the chip and the fin heat sink; and a twinned layer disposed on at least one side of the thermal interface material and in direct contact with the thermal interface material. A method for forming the package structure is also provided.