Heat-conductive Silicone Composition for Semiconductor Packages
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Solution Overview
Problem
Conventional thermosetting heat-dissipating greases used in semiconductor packages cure prematurely during high-temperature reflow processes, leading to insufficient heat dissipation due to inability to compress and spread effectively over heat-generating parts.
Innovation Solution
A silicone composition comprising organopolysiloxane, aluminum and zinc oxide fillers, organohydrogenpolysiloxane, and a platinum group metal catalyst, which maintains a low storage elastic modulus ratio after curing, allowing the grease to compress and spread adequately even after high-temperature reflow processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermosetting heat-dissipating grease is used to prevent air gaps and improve heat conduction, then heat-dissipating performance is improved, but the grease cures prematurely during high-temperature reflow processes, causing insufficient compression and spreading
Solution Approach 1:
The patent modifies the chemical composition parameters of the heat-dissipating grease by using a specific silicone base oil with controlled molecular weight and viscosity, combined with a curing agent system that adjusts the curing reaction kinetics. This allows the grease to maintain stability during high-temperature reflow (200°C or higher) while still achieving proper curing after mounting, resolving the contradiction between early curing (which causes compression issues) and late curing (which causes outflow). The base oil contains silane-modified polysiloxane with controlled aliphatic unsaturation, and the curing system uses a catalyst that activates at specific temperature ranges, ensuring the grease remains workable during reflow but cures properly afterward.
2Area of stationary object
If the grease is compressed into thin layer to reduce mounting area, then mounting area is reduced, but the grease cures before compression, preventing sufficient thinning
Solution Approach 1:
The patent applies the grease to the heat-generating part before the reflow process, allowing it to be in a soft, uncured state during application and compression. The preliminary application occurs when the grease is still pliable, enabling it to be compressed to the desired thin thickness and spread to cover the entire surface area. The curing reaction is then activated during or after the reflow process, locking the grease in its compressed, thin configuration. This preliminary action sequence resolves the contradiction by enabling compression before curing, achieving both thin profile and full coverage.
3Reliability
If the grease is allowed to spread over the whole heat-generating part, then heat conduction is improved, but the grease flows out excessively during high-temperature processing
Solution Approach 1:
The patent incorporates a curing agent system that initiates the curing reaction at a controlled rate during the reflow process, creating a preliminary anti-action against the grease's natural tendency to flow out at high temperatures. The curing reaction begins to crosslink the silicone polymer chains as temperature increases, progressively reducing the grease's fluidity and preventing excessive outflow. This controlled curing progression allows the grease to spread adequately to cover the heat-generating surface while simultaneously developing enough structural integrity to resist gravitational and capillary forces that would cause outflow during high-temperature processing.
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 silicone composition ensures sufficient heat dissipation by maintaining a low storage elastic modulus ratio, enabling effective compression and spreading over heat-generating parts, thus enhancing thermal management in semiconductor packages.
Implementation Method 1
a silicone composition comprising: (A) 100 parts by mass of an organopolysiloxane having at least two aliphatic unsaturated hydrocarbon groups per molecule... (C) an organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms (i.e. SiH group) per molecule
Implementation Method 2
If there is a space between the heat-generating member and the cooling member, thermal conduction does not proceed smoothly because of the presence of air, which is poor in heat conductivity... (B) 100 to 2,000 parts by mass of a filler containing an aluminum powder and a zinc oxide powder
Implementation Method 3
a cured product of the silicone composition exhibits a ratio of a storage elastic modulus after 3,600 seconds from the start of measurement to a storage elastic modulus after 7,200 seconds from the start of measurement of 0.7 or less, the storage elastic modulus G′ being measured, by means of a viscoelasticity measurement apparatus
Data Source
AI summary
A silicone composition that contains (A) an organopolysiloxane having at least two aliphatic unsaturated hydrocarbon groups per molecule, (B) a filler containing an aluminum powder and a zinc oxide powder, (C) an organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms per molecule, and (D) a platinum group metal catalyst, in which a cured product of the silicone composition exhibits a ratio of a storage elastic modulus after 3,600 seconds from the start of measurement to a storage elastic modulus after 7,200 seconds from the start of measurement of 0.7 or less, the storage elastic modulus G′ being measured by constructing a program for holding a sample at 150° C. for 7,200 seconds after the sample is heated from 25° C. to 125° C. at a temperature increase rate of 10° C./min, from 125° C. to 145° C. at a temperature increase rate of 2° C./min, and from 145° C. to 150° C. at a temperature increase rate of 0.5° C./min.