Alphacool

Alphacool Apex Thermal Pad Soft 18W/mK

Expert rating6.8 / 10

View on Alphacool Shop (EU)View on alphacool.com

Compound Type:: Silicone-Based Pad
Thermal Conductivity:: 17.8 W/mK
Electrical Conductivity:: Non-Conductive
Recommended Use:: High-end CPU/GPU
Package Size:: 120 x 20 x 1.5mm

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Manufacturer: Alphacool Last updated: 2026-09-15

Where to buy

Alphacool Shop (EU)Go to store

Alphacool Apex Thermal Pad Soft 18W/mK Review

The Alphacool Apex Thermal Pad Soft is Alphacool's highest officially-rated thermal pad, a silicone-based sheet rated 18 W/mK for high-end CPU and GPU cooling as well as VRM and memory-module use.

Alphacool officially measures this pad at 17.8 W/mK per the ASTM D5470 standard, one of the highest independently-standardized figures for a pad in this catalog, and it's electrically non-conductive with a documented 6x10^12 Ohm-m volume resistance and 4 KV/mm dielectric breakdown rating. The silicone-based pad is deliberately ultra-soft (Shore 00 65 hardness) for optimal compressibility against uneven surfaces, is rated for a wide -50 to +150C working range, and carries a UL94 V-0 flame rating with under 1% outgassing weight loss, giving it a genuinely lab-tested spec sheet rather than marketing round numbers. Against Alphacool's own Eisschicht pad also in this catalog, the Apex Thermal Pad Soft delivers meaningfully higher officially-measured conductivity (17.8 W/mK vs 11.0 W/mK) at a similar 1.5mm thickness.

Thermal Performance and Conductivity

Alphacool measures this pad at 17.8 W/mK (±10%) via the ASTM D5470 standard test method, among the highest independently-standardized figures in this catalog's pad lineup.

Composition

The Apex Thermal Pad Soft is a silicone-based pad engineered for ultra-soft compressibility, with a light grey color and Shore 00 65 hardness rating (±5).

Application and Consistency

The pad ships as a 120 x 20 x 1.5mm sheet with 20% elongation (ASTM D412) and can be cut to size, sold for CPU/GPU, VRM/MOSFET, memory module, and networking-hardware cooling per Alphacool's own guidance.

Electrical Safety

The pad is non-conductive with a documented volume resistance of 6x10^12 Ohm-m (ASTM D257) and a 4 KV/mm dielectric breakdown voltage (ASTM D149), both independently standardized test figures rather than marketing claims.

Longevity and Pump-Out Resistance

Alphacool's own outgassing test (ASTM E595) shows under 1% weight loss, and the pad carries a UL94 V-0 flame rating alongside a wide -50 to +150C working range.

Comparison to Alternatives

Against Alphacool's own Eisschicht pad also in this catalog, the Apex Thermal Pad Soft delivers meaningfully higher officially-measured conductivity (17.8 W/mK vs 11.0 W/mK) at a similar thickness, at some cost in the paste-like conforming softness Eisschicht is built around.

Our verdict

Reviewed by Burooj Alam. Rated by us, not by users.

Expert rating6.8 / 10

A soft, high-conductivity pad aimed at high-end builds, though it lacks the independent review base of the paste side of Alphacool's lineup.

Best for

High-end CPU/GPU, VRM/MOSFET, and memory-module cooling wanting the highest independently-measured W/mK figure among this catalog's pads
Builds needing a documented electrical safety spec sheet (volume resistance, dielectric breakdown) rather than a generic non-conductive claim

Not for

Buyers who specifically want Eisschicht's softer, more paste-like conforming fit for delicate uneven surfaces
Anyone needing a large single sheet, since this SKU ships as a narrow 120x20mm strip

Specifications

What these specs mean

Identity and form

Brand	Alphacool
Model	Alphacool Apex Thermal Pad Soft 18W/mK
Material Class	Silicone, ultra-soft with high compressibility

Thermal performance

Conductivity Source	https://shop.alphacool.com/en/shop/thermal-conductant/thermal-pads/waem-alphacool-apex-thermal-pad-soft-18w/mk-120x20x1mm

Electrical and board risk

Paste Segment	Pad

Application

Viscosity	0 Pa-s

Operating envelope

Min Operating Temperature	-50 C
Max Operating Temperature	150 C

Quantity, volume versus weight

Density	3.5 g/cm3

Compound Type	Silicone-Based Pad
Thermal Conductivity	17.8 W/mK (ASTM D5470)
Electrical Conductivity	Insulating
Package Size	120 x 20 x 1.5mm sheet
Recommended Use	High-end CPU/GPU

FAQs

What are the key specifications of the Alphacool Apex Thermal Pad Soft 18W/mK (Silicone-Based Pad/Non-Conductive/High-end CPU/GPU)?

Key specs for the Alphacool Apex Thermal Pad Soft 18W/mK: Thermal Conductivity Tolerance ±10%, Thermal Conductivity 17.8 W/mK (ASTM D5470), Thermal Conductivity Source https://shop.alphacool.com/en/shop/thermal-conductant/thermal-pads/waem-alphacool-apex-thermal-pad-soft-18w/mk-120x20x1mm, Compound Type Silicone-Based Pad, Electrical Conductivity Insulating, Material Silicone, ultra-soft with high compressibility.

Will the Alphacool Apex Thermal Pad Soft 18W/mK (Silicone-Based Pad/Non-Conductive/High-end CPU/GPU) work with my current setup?

The Alphacool Apex Thermal Pad Soft 18W/mK (Silicone-Based Pad/Non-Conductive/High-end CPU/GPU) lists Thermal Conductivity is 17.8 W/mK (ASTM D5470). Check that against the hardware you already own before buying, since this is the field that most often decides whether a part fits.

Who is the Alphacool Apex Thermal Pad Soft 18W/mK (Silicone-Based Pad/Non-Conductive/High-end CPU/GPU) best suited to?

Best suited to: High-end CPU/GPU, VRM/MOSFET, and memory-module cooling wanting the highest independently-measured W/mK figure among this catalog's pads; Builds needing a documented electrical safety spec sheet (volume resistance, dielectric breakdown) rather than a generic non-conductive claim.

What are the drawbacks of the Alphacool Apex Thermal Pad Soft 18W/mK (Silicone-Based Pad/Non-Conductive/High-end CPU/GPU)?

Not the best fit for: Buyers who specifically want Eisschicht's softer, more paste-like conforming fit for delicate uneven surfaces; Anyone needing a large single sheet, since this SKU ships as a narrow 120x20mm strip.