Alphacool

Alphacool Apex Thermal Pad Soft 18W/mK

Thermal PasteView 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

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Alphacool Apex Thermal Pad Soft 18W/mK (Silicone-Based Pad/Non-Conductive/High-end CPU/GPU) 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 Sibling Products

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.

Specifications

Identity and form

Brand	Alphacool
Model	Alphacool Apex Thermal Pad Soft 18W/mK

Quantity, volume versus weight

Density	3.5 g/cm3

Compound Type	Silicone-Based Pad
Thermal Conductivity	17.8 W/mK
Electrical Conductivity	Insulating
Package Size	120 x 20 x 1.5mm sheet
Recommended Use	High-end CPU/GPU
Material	Silicone, ultra-soft with high compressibility
Thermal Conductivity Tolerance	±10%
Test Standard	ASTM D5470
Marketed Rating	18 W/mK
Volume Resistance	6×10^12 Ohm-m (ASTM D257)
Dielectric Breakdown	4 KV/mm (ASTM D149)
Also Suitable For	VRM/MOSFET, memory modules, access-point and communications hardware
Operating Temperature	-50 to +150 °C
Consistency	Shore 00 65 hardness (±5, ASTM D2240), 20% elongation (ASTM D412)
Flame Rating	UL94 V-0
Outgassing	Under 1% weight loss (ASTM E595)
Paste Segment	Pad
Min Operating Temp	-50 C
Max Operating Temp	150 C

Expert Review

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

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

FAQs

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

The Alphacool Apex Thermal Pad Soft 18W/mK (Silicone-Based Pad/Non-Conductive/High-end CPU/GPU) is a thermal paste from Alphacool. Key specs: Compound Type Silicone-Based Pad, Form Pad, Material Silicone, ultra-soft with high compressibility, Thermal Conductivity 17.8, Thermal Conductivity Tolerance ±10%.

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. 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?

It suits 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)?

It is a poor 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.