ASIC Heatsink Attach & Thermal-Interface Reference: Glue, Gel or Soldered?

Quick answer

Bitmain hashboards do not all use a thermal pad — and on several generations there is no pad at all. The attachment changes by generation: S9/L3 and the 17-series use a thermosetting thermal ADHESIVE where the glue is also the mechanical retention; the S19 family, S19 XP, S21 and T21 use a non-adhesive thermal GEL under a heatsink that is mechanically locked down; and at least one S19K Pro board (BHB56902) has the heatsink SOLDERED to a copper-plated chip surface. Treating one as another is how boards get destroyed: prying a soldered sink rips the chip, and bonding a mechanically-retained sink tears pads off the next time a chip comes out.

Identify the board part number before you apply heat or force — the attach method follows the board revision, not the model name on the box. Use a bonding compound only where the sink is adhesive-retained, a non-adhesive gel where it is mechanically retained, and hot air (not leverage) on soldered assemblies. And be skeptical of any chart quoting per-model pad thickness, durometer or torque: nobody publishes those numbers, so such a chart is invented.

Attach method by hashboard generation

The one table that decides whether a heatsink comes off cleanly or takes the chip with it. Every row cites its source, and cells nobody publishes are marked as such rather than filled in with a plausible-looking number.

Model family	Attach method	Heatsink style	Named interface material	Documented removal	Repair risk
Antminer S9 / S9j / S9k, L3 series	Thermal adhesive (thermosetting glue)	Small per-chip aluminium heatsinks, one per ASIC None — the adhesive IS the mechanical attachment	Thermosetting thermal adhesive; sold refrigerated, storage stated as 5–10 °C	not published	High
Glue does double duty here: heat transfer and physical retention. That is why S9-era boards shed heatsinks when the adhesive ages or is overheated, and why substituting a stronger compound is dangerous — an over-strong bond tears the pad off the board when a chip is later removed. Source: Zeus Mining thermal-adhesive product documentation (part ID 86) · confidence: medium
Antminer S17 / S17 Pro / T17 / S17+ / T17+	Thermal adhesive (thermosetting glue)	Per-chip heatsinks None — adhesive-retained	not published	not published	High
Same adhesive-retained pattern as the S9 generation. Adhesive-mount failure (heatsinks loosening or falling off) is widely reported as a dominant failure mode on this generation. Source: Zeus Mining 17-series repair guidance · confidence: medium
Antminer S19 / S19j Pro / S19 XP	Thermal gel + mechanically locked heatsink	Large heatsink spanning multiple chips Heatsink is mechanically retained; the gel is a heat-transfer medium only	Thermal gel, specified as Fujipoly SPG-30B in vendor repair guides	not published	Medium
This is the generation where techs most often go wrong by reaching for adhesive. The gel is explicitly NOT a glue — vendor guidance states it "is not adhesive, please do not use it as glue." If you bond a mechanically-retained sink, the next chip-level repair fights you. Source: Zeus Mining S19 / S19 XP repair guides · confidence: medium
Antminer S21 / T21	Thermal gel + mechanically locked heatsink	Large heatsink spanning multiple chips Heatsink is mechanically retained	Thermal gel, specified as Fujipoly SPG-30B in vendor repair guides	not published	Medium
Same gel-plus-mechanical approach as the S19 family; the named gel product is identical across the S19 and S21/T21 guides, which is a useful consistency check when sourcing material. Source: Zeus Mining S21 / T21 repair guides · confidence: medium
Antminer S19K Pro (board BHB56902)	Heatsink SOLDERED to the chip with tin (BSM, copper-plated chip surface)	Soldered assembly Solder joint is the attachment	Solder (tin) — there is no paste, gel or pad at this interface	Hot-air at 400 °C, nozzle ~0.5 cm above the heatsink, ~15 seconds	High
The single most important row here. If you try to pry or twist a soldered heatsink the way you would lift a gel-mounted one, you destroy the board. Verified for board part number BHB56902 specifically — do NOT assume other K-Pro or newer board revisions share it. Check your board number first. Source: Zeus Mining S19K Pro (BHB56902) repair guide · confidence: medium

Bond-line methodology — what actually determines your thermals

Since no manufacturer publishes a thickness to hit, the useful knowledge is how to get a good joint without one. This is standard thermal-interface engineering, sourced to material manufacturers rather than to mining folklore.

Bond-line thickness beats the W/mK number on the box

Thermal resistance across the joint is driven mainly by the bond-line thickness (BLT) achieved after compression, not by the headline conductivity figure. A thinner, fully-wetted joint in a mediocre material usually outperforms a thick joint in a premium one. Chasing a bigger W/mK while leaving a fat bond line is the classic mistake.

Source: TIM manufacturer datasheets (Parker Chomerics THERM-A-GAP, Modus Advanced, Stockwell)

Soft gap materials are meant to be compressed

Gap-filling pads are specified with a working compression range — commonly around 10–50 percent, with soft pads typically in the 20–40 percent band. A pad installed with no compression is not doing its job; one crushed past its range stresses the component and the board.

Source: TIM manufacturer datasheets

Shore 00 is the right hardness scale here

Gels and soft gap pads are measured on the Shore 00 scale, not Shore A. If a spec sheet quotes Shore A for a soft gap filler, treat the number with suspicion or assume it is a different class of material.

Source: TIM manufacturer datasheets

Thickness is controlled by tooling, not by a published number

In practice, hashboard shops control application thickness with a stencil and a scraper — spread evenly from the centre outward to a thin, even coating — rather than by measuring to a specified millimetre value. Stencils are sold for this purpose. If you want repeatable results, buy or make the stencil; do not try to hit an imagined thickness spec.

Source: Zeus Mining application guidance and hashboard heatsink stencils

Match the material class to the attach method, not to a brand

Adhesive-retained generations need a bonding compound; mechanically-retained generations need a non-adhesive gel. Vendor guidance warns that swapping in a different colloid changes hardness and conductivity, and that an over-strong bond will tear the hashboard when a chip is later removed. Pick by function first.

Source: Zeus Mining material guidance

Specs nobody publishes — and why we leave them blank

This section exists because the alternative is fabrication. These are the values people most want in a table, and they are the values no manufacturer or vendor actually publishes. We would rather show you an honest gap than a convincing invention.

Spec people expect	What we actually found
Per-model thermal pad / TIM thickness in millimetres	Not published by Bitmain or by any parts vendor we could find. Every model-specific repair guide we checked says "apply evenly" or "a thin coating" and never gives a dimension.
Per-model durometer (Shore hardness) of the applied material	Never published. Vendors acknowledge that hardness differs between compounds but publish no value for any specific product.
Heatsink fastener torque specifications	Not published anywhere we could find. The guides do not even consistently state fastener type. Any torque table for an Antminer heatsink is invented.
Vendor part specifications	Largely absent. Heatsink and adhesive listings we examined carry no dimensions, no W/mK, no hardness and no cure schedule — buyers are directed to contact sales. Parts in this market are sold essentially spec-free.

⚠️ A note on circular sourcing. Some very precise-sounding figures circulate for this topic — specific conductivity ratings, heat-gun temperatures, cure times. When we traced them, several led back to D-Central's own older articles, where they had been published without a primary source. We have deliberately excluded our own prior content as evidence here. If you find a number quoted confidently across several mining sites, check whether they are all quoting each other.

Sources, limits & related references

Per-model attach methods and named materials come from vendor repair guides — principally Zeus Mining, who sell these materials and publish per-model procedures. We credit them plainly: this reference organizes and cross-checks their published guidance, it does not replace it. Generic bond-line engineering is drawn from thermal-interface manufacturer datasheets (Parker Chomerics, Modus Advanced, Stockwell). Limits: the per-model rows are single-vendor sourced, so confidence is marked medium throughout; attach methods track board revisions rather than marketing names; and the soldered-heatsink finding is verified for board BHB56902 only. Identify your board before acting on any row.

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Last reviewed July 20, 2026.