Ultra-High Viscosity Paste Degassing: Defoaming Thermal Grease at 0.2 kPa

High-performance thermal interface materials (TIM), including thermal greases, phase-change compounds, and structural gap fillers, are formulated with extreme solid filler loadings.
To reach thermal conductivities from 3.0 to over 12.0 W/m·K, formulators pack up to 85% by weight of alumina, boron nitride, or zinc oxide powders into reactive silicone or polyurethane polymers.
The resulting slurries exhibit paste-like viscosities frequently exceeding 500,000 to 1,000,000 mPa·s.
At these extreme rheological thresholds, entrained microscopic air bubbles remain trapped permanently under normal gravity, acting as severe thermal insulators that cause device overheating.
SMIDA manufactures planetary centrifugal vacuum mixers engineered to achieve 0.2 kPa ultimate vacuum while subjecting containers to hundreds of Gs of centrifugal acceleration.

In power electronics, microprocessors, and electric vehicle battery packs, even a single 50-micron air void in a thermal interface layer increases thermal resistance exponentially and triggers high-voltage arc breakdown.
Traditional degassing methods — such as static vacuum ovens, ultrasonic baths, or low-vacuum rotor mixers — fail completely on high-viscosity pastes.
Static vacuum only expands surface bubbles, while ultrasonics generate destructive localized heat without overcoming viscous drag.
This engineering guide explains the physical mechanics of dual-axis centrifugal vacuum deaeration at 0.2 kPa and outlines best practices for zero-void paste production.

The Physics of Bubble Entrapment in Dense Pastes

According to Stokes' law, the terminal rise velocity of an air bubble in a fluid is directly proportional to gravitational acceleration and bubble diameter squared, and inversely proportional to dynamic viscosity.
When paste viscosity jumps from 1,000 mPa·s to 1,000,000 mPa·s, a 10-micron micro-bubble's natural rise velocity drops by a factor of one thousand.
Under standard 1G Earth gravity, that bubble would take weeks or months to travel a single millimeter toward the surface.
Relying on ambient buoyancy or static vacuum chambers simply does not provide sufficient upward force to overcome viscous resistance.

Centrifugal Acceleration: Multiplying Buoyancy by Hundreds of Gs

A SMIDA planetary centrifugal mixer rotates sealed containers along two independent axes simultaneously.
Primary revolution around the central machine axis generates centrifugal accelerations exceeding 400 Gs.
Because the density of entrapped air (approx. 1.2 kg/m³) is orders of magnitude lower than dense thermal paste (often 2,000 to 3,000 kg/m³), the effective buoyancy force driving the bubble upward is multiplied over 400 times.
Simultaneously, container rotation induces a rolling 3D convection flow that continually churns deep paste layers up toward the surface film.

0.2 kPa Ultimate Vacuum: Expanding Micro-Bubbles for Rapid Rupture

Centrifugal buoyancy brings air bubbles near the surface, but sub-micron bubbles still possess high surface tension that resists bursting.
This is where SMIDA's 0.2 kPa deep vacuum capability becomes decisive.
Under 0.2 kPa (a 500-fold pressure reduction from standard atmospheric pressure of 101.3 kPa), Boyle's law dictates that entrapped air bubbles expand by hundreds of times in volume.
As bubble volume expands, its buoyant rise velocity accelerates exponentially, forcing it through the surface film where it bursts instantly.
Within a 90 to 180-second cycle, paste density reaches 100% of theoretical limits with zero residual voids.

Degassing Technology Comparison for Thermal Interface Materials

Frequently Asked Questions

Will pulling a 0.2 kPa vacuum boil volatile solvents out of my paste?

Vacuum lowers solvent boiling points, but SMIDA planetary mixers feature programmable multi-stage vacuum profiles.
Operators can execute high-speed mixing at moderate pressure, followed by a brief, controlled 0.2 kPa finishing pulse to extract air without stripping essential diluents.

How does temperature control preserve thermal grease properties?

High-shear centrifugal motion naturally generates frictional warmth.
SMIDA's TTC temperature-controlled series stabilizes chamber temperatures between -15 °C and 25 °C, keeping reactive silicones and moisture-sensitive resins completely stable.

Eliminate Voids with SMIDA Vacuum Technology

SMIDA is an established manufacturer with an ISO 9001 certified 6,800 square-meter facility in Shenzhen, 80+ patents, and full CE compliance.
Our planetary centrifugal vacuum mixers handle batches from 1 g up to 100 kg+ (equipment capacity 150 g to 100 kg+), delivering reproducible void-free pastes to world-leading electronics innovators.
Contact our Shenzhen engineering staff to schedule a free degassing evaluation on your thermal paste samples.