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Use thermal paste or grease where a laptop CPU or GPU die makes direct contact with its heatsink. Use the laptop’s specified thermal putty, putty pad, or conventional thermal pad where VRAM, VRM components, or another device sits below a measurable gap. Paste and putty are not interchangeable simply because both transfer heat.
The correct replacement is determined by the original interface, the heatsink’s contact geometry, and the laptop manufacturer’s service instructions. A material with a higher advertised conductivity can still perform worse if it has the wrong thickness, spreads poorly, is electrically unsuitable, or prevents the heatsink from seating correctly.
Thermal paste and thermal putty solve different contact problems
A laptop cooling assembly rarely uses one identical thermal interface everywhere. The CPU and discrete GPU usually have exposed silicon dies that press directly against flat portions of a heatsink or vapor-chamber plate. Microscopic surface imperfections remain between those two surfaces, so a very thin layer of paste or grease fills the imperfections and reduces air gaps.
VRAM chips, voltage-regulator components, and other nearby packages often do not sit at the same height as the processor die. The heatsink may span all of them, but some components need a compressible material to bridge a real clearance. A pad or putty can deform to fill that space while maintaining contact. AMD describes grease, putty, and paste as ways to couple a device thermally to a heatsink, while pads are useful when a gap exists or several devices must meet one cooling solution (AMD, Types of TIM Material – XAPP1377, revision 2.0, released June 27, 2025).
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That geometry is the practical answer to “thermal putty or thermal paste?”: identify what the heatsink is contacting, then replace the original interface with the same category and specified dimensions. Do not spread paste across every chip under the heatsink, and do not substitute a thick putty layer for paste on a direct-die surface unless the laptop’s service documentation explicitly calls for it.
Where each material normally belongs
| Repair location or condition | Likely material category | What must be verified |
|---|---|---|
| CPU or GPU die touching a flat heatsink surface | Thermal paste, grease, or an OEM-specified phase-change interface | The laptop service procedure and the cooler’s contact design |
| VRAM or VRM package separated from the heatsink by a clearance | OEM-specified thermal pad, putty pad, or thermal putty | Original interface type, gap geometry, and replacement instructions |
| Several components at different heights under one heatsink | Often a combination of paste and gap-filling material | Component locations, compressibility, and every stated thickness or application area in the service guide |
| Unknown layout after disassembly | Do not choose by a generic thickness chart | The exact model’s maintenance manual, parts information, or a qualified repair reference |
The table describes common layouts, not a universal laptop standard. Some systems use a manufacturer-specific phase-change sheet, unusually thick paste, or a molded pad in places where another design would use putty. Photograph the assembly before removing anything and record which material was on each contact area.
How to identify the original interface before buying anything
Start with the exact model and revision
Write down the complete model designation, not just the product family. A laptop sold under one family name can have different motherboards, GPU options, heatsinks, and memory arrangements. Search the manufacturer’s maintenance or hardware service manual for that exact designation and board configuration. If the manual provides a parts diagram, use it to distinguish the processor die, memory packages, and power circuitry.
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After loosening the heatsink in the documented order, inspect both the cooler and the motherboard without scraping immediately. A thin, spread-out film centered over a die is consistent with paste or grease. A thicker, compressible piece that retains a shaped impression is a gap filler. A silicone-like sheet with a defined outline is a pad. These observations help, but they do not establish the required replacement thickness by themselves.
Measure only when the service information permits it
Manufacturers may specify a pad thickness, a putty type, or a quantity pattern. Follow those instructions exactly. A caliper measurement taken after compression can understate the original gap, while an uncompressed measurement can overstate the thickness needed during assembly. Do not infer a specification from a generic online table. The available evidence does not establish one universal laptop pad thickness or putty gap range.
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Check whether the material is electrically safe
AMD lists electrical conductivity, spreading characteristics, stability, ease of application, thermal conductivity, and applied pressure as selection factors for a thermal interface material (AMD, Guidelines for Thermal Interface Materials – AM013, revision 1.10, released July 31, 2026). A material that can conduct electricity is risky near exposed contacts unless the manufacturer designed for it. Keep any compound inside the intended contact area and use the OEM-specified material where electrical isolation is required.
Why a higher conductivity number is not enough
Thermal conductivity is only one property in a real laptop assembly. The interface must spread across the intended area, remain stable through repeated heating and cooling, tolerate the mounting pressure, and fill the actual surface irregularities or gap. AMD’s thermal-interface guidance explains the function directly: “Thermal interface material fill gaps and transfer heat between the Versal device die and the heat sink.” That sentence concerns Versal devices rather than laptops, but it accurately describes the basic purpose of an interface layer.
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Paste is optimized for a thin layer between surfaces that can be clamped closely together. A thick layer adds thermal resistance and can squeeze out of the contact zone. Putty is designed to remain in a thicker, compressible gap and accommodate variation in component height. If putty is used where the heatsink should contact a die directly, the cooler may sit higher or apply pressure unevenly. If paste is used in a large gap, it may not bridge the space, leaving air pockets or an unsupported heatsink section.
Mounting pressure is part of the design. Screws, spring tension, the order of tightening, and the flatness of the cooler determine how an interface compresses and spreads. Replacing the compound without restoring the specified mounting sequence can create poor contact even when the material itself is appropriate.
What OEM documentation can and cannot tell you
Manufacturer instructions take priority over generic repair advice. Lenovo’s Gap pad/Putty pad identification and location documentation for the ThinkSystem SD665 V3 distinguishes gap pads from putty pads, instructs technicians to replace putty pads with new ones during component replacement, and warns against using expired putty pads. That is server documentation, so it establishes Lenovo’s service practice for that platform; it is not a universal rule for every Lenovo or other laptop.
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Likewise, an iFixit laptop thermal-interface guide identifies thermal paste for CPU/GPU die areas and pads or thick paste such as thermal putty for VRAM chips. Treat that as practical repair guidance, not a substitute for the service manual for your machine. The same manufacturer can change materials between generations.
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- Shut down and isolate the laptop. Power it off, disconnect the charger, and follow the model’s battery-disconnection procedure before touching the heatsink. Work on a clean, static-aware surface and keep screws organized by location.
- Document the original layout. Take clear photographs of every interface before removal. Mark which areas are die paste, pads, putty, or another sheet material. Record any printed thickness or part number visible on a pad package.
- Obtain the model-specific specification. Use the exact service manual or an authoritative parts reference to confirm the interface category, thickness, coverage area, and whether the material must be replaced rather than reused.
- Remove the heatsink in the stated sequence. Loosen spring-loaded screws gradually and in the numbered order, if one is provided. Twisting or lifting a cooler while material is still adhered can disturb components or tear a pad.
- Clean only the surfaces receiving paste. Remove old paste from the CPU/GPU die and its mating heatsink surface with an appropriate electronics-safe cleaning method. Do not scrape silicon or use force that can damage tiny components around the die.
- Leave gap fillers in their intended locations until replacement is ready. Do not smear putty from one component across another area, and do not stack random pads to approximate a missing thickness. If a pad tears or a putty section is contaminated, replace it with the specified material.
- Apply the paste or grease according to the service instructions. Use the stated pattern and quantity if provided. If no laptop-specific quantity is documented, avoid treating a generic “pea-sized” rule as authoritative; the required amount depends on die size and the cooler’s spreading design.
- Place putty or pads precisely. Match the original footprints and keep material away from connectors and exposed contacts. Putty should fill the designed gap without creating a mound that holds the heatsink off the die.
- Reinstall the heatsink without sliding it sideways. Lower it straight onto the assembly so paste spreads in the intended plane and gap fillers stay aligned. Tighten screws in the documented order and gradually to preserve even pressure.
- Reconnect the battery and inspect before final closure. Check that no pad edge is folded, no putty has migrated into a connector, and every screw and cable is accounted for. Reassemble the bottom cover only after the cooler is seated correctly.
- Verify operation. Boot the laptop, confirm that the operating system detects the CPU and GPU, and watch for abnormal fan behavior, shutdowns, artifacts, or rapid temperature escalation. A functional check cannot prove the interface is perfect, but it can reveal a gross contact or assembly error.
Common mistakes and how to recover
Applying paste to VRAM or VRM gaps
Paste may not hold the heatsink at the height required by surrounding components. The result can be inadequate contact on memory or power circuitry, or a cooler that no longer sits flat on the processor. Remove the assembly, identify the original gap filler, and install the specified pad or putty rather than trying to compensate with a thicker paste layer.
Using a pad that is too thick
An oversized pad can prevent the heatsink from reaching the CPU or GPU die, leaving a visible or functional gap at the most important contact. Never compress a pad by guessing how much thinner it will become. Use the manufacturer’s stated thickness and compression behavior.
Using a pad that is too thin
A thin pad may not touch the component after the screws are tightened. Air remains in the gap, and the part receives little heat transfer even though the heatsink appears installed. Replace it with the documented thickness instead of stacking unrelated materials.
Reusing damaged or contaminated putty
Putty can pick up dust, fibers, and metal fragments during disassembly. It can also lose its original shape. If the service instruction calls for new putty or a new putty pad, follow that requirement; Lenovo’s ThinkSystem guidance specifically calls for replacement during component replacement and cautions against expired putty pads.
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Choosing by conductivity marketing alone
A high conductivity claim does not guarantee suitable spreading, electrical behavior, stability, or pressure response. Compare those properties with the laptop’s geometry and the manufacturer’s material requirement. If the original interface is a proprietary phase-change product, ordinary paste may not be an equivalent replacement.
Ignoring screw order and pressure
Uneven tightening can tilt a heatsink, squeeze material away from one area, or leave one device unsupported. Reopen the assembly and follow the numbered sequence and any torque guidance in the service documentation. Do not improvise a tightening pattern when the manual provides one.
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If you cannot find a service manual, use the physical evidence conservatively. Preserve the original material long enough to photograph its footprints and compression marks. Search for an authoritative repair reference for the exact model and board revision rather than a generic “laptop thermal pad thickness” chart. A qualified technician can also identify the gap geometry without forcing a guessed material into place.
When several heights are present, assume the laptop may require more than one interface type. A common arrangement is paste on the CPU/GPU dies and separate pads or putty on VRAM and VRM components, but the arrangement must be confirmed for the specific cooler. If the heatsink has a stepped or machined contact surface, the shape itself may explain why different materials are used.
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Paste versus putty: a practical comparison
| Characteristic | Thermal paste or grease | Thermal putty or putty pad |
|---|---|---|
| Primary job | Fill microscopic irregularities in a close, direct interface | Bridge and conform to a larger or variable clearance |
| Typical laptop location | CPU/GPU die to heatsink | VRAM, VRM, or other packages below the heatsink plane |
| Thickness behavior | Intended to be a thin film after mounting | Designed to remain as a compressible gap filler |
| Main application risk | Too much material or contamination can reduce contact quality | Wrong thickness, footprint, or compression can hold the heatsink off the die |
| Selection priority | OEM compound or phase-change specification and die-contact design | OEM material, gap geometry, replacement rule, and usable life |
Neither column is inherently “better.” They are solutions for different mechanical conditions. The best material is the one that reproduces the interface the laptop was designed to use.
Questions readers commonly ask
Can I use thermal putty instead of thermal paste on the CPU?
Only when the laptop’s service documentation specifies putty or a thick gap-filling interface at that die. For a normal direct die-to-heatsink contact, use the specified paste, grease, or phase-change material. Substituting putty changes the contact thickness and mounting pressure.
Can I use thermal paste on VRAM?
Do not assume so. VRAM usually needs a pad or putty when it sits below the heatsink’s main contact plane. Paste is suitable only if the manufacturer designed that location as a direct, close interface and documents it accordingly.
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Is thermal putty electrically conductive?
Properties vary by formulation. Check the material’s technical documentation and the laptop’s service requirement rather than assuming it is insulating. Keep any interface material away from exposed electrical contacts.
Should I replace every thermal interface when opening the laptop?
Replace the interfaces required by the service procedure and any material that is torn, contaminated, displaced, expired, or no longer able to fill its intended gap. Do not remove intact gap fillers merely to apply a different product without a documented reason.
What if the laptop has no published thickness information?
Do not guess from a generic chart. Preserve the original pieces, use an exact-model repair reference, or have a qualified technician identify the interface. The evidence available for laptops does not support a universal thickness or putty quantity.
Bottom line
Choose thermal paste for a documented direct CPU/GPU die interface and thermal putty or a pad for a documented gap around VRAM, VRM, or other components. Confirm the exact laptop’s layout, material type, thickness, coverage, and mounting procedure before ordering supplies. Correct geometry and pressure matter as much as thermal conductivity.
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