{
    "meta": {
        "title": "D-Central — ASIC Heatsink Attach & Thermal-Interface Reference",
        "description": "How the heatsink is actually attached to the ASIC on each Bitmain hashboard generation — thermal adhesive, thermal gel under a mechanically-locked sink, or a soldered BSM assembly — across 5 model families, with the bond-line methodology that matters and an explicit list of the specs no manufacturer publishes.",
        "generated": "2026-07-20T16:16:20+00:00",
        "as_of": "2026-07-20",
        "version": "1.0",
        "license": "https://creativecommons.org/licenses/by/4.0/",
        "license_name": "CC BY 4.0",
        "source": "https://d-central.tech/fr/asic-heatsink-attach-reference/",
        "method": "Attach methods and named TIM products are taken from model-specific vendor repair guides (principally Zeus Mining, who sell the materials and publish per-model procedures). Generic bond-line engineering is taken from thermal-interface manufacturer datasheets. Cells that could not be sourced are published as \"not published\" rather than estimated. D-Central's own earlier articles were deliberately EXCLUDED as evidence: several precise-sounding figures circulating for this topic trace back to our own unsourced prior content, and citing them would launder a guess into a reference.",
        "provenance": "Zeus Mining per-model repair guides; thermal-interface manufacturer datasheets (Parker Chomerics, Modus Advanced, Stockwell). Vendor-sourced, single-vendor for the per-model rows — confidence is marked medium accordingly.",
        "disclaimer": "Attach methods vary by board revision, not just by marketing model name. The soldered-heatsink finding is verified for board BHB56902 specifically and must not be extrapolated to other board numbers. Always identify your board part number before applying heat or force. Not a substitute for your own inspection."
    },
    "families": [
        {
            "family": "Antminer S9 / S9j / S9k, L3 series",
            "attach": "Thermal adhesive (thermosetting glue)",
            "sink_style": "Small per-chip aluminium heatsinks, one per ASIC",
            "mechanical": "None — the adhesive IS the mechanical attachment",
            "tim_named": "Thermosetting thermal adhesive; sold refrigerated, storage stated as 5–10 °C",
            "removal": "not published",
            "risk": "high",
            "note": "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"
        },
        {
            "family": "Antminer S17 / S17 Pro / T17 / S17+ / T17+",
            "attach": "Thermal adhesive (thermosetting glue)",
            "sink_style": "Per-chip heatsinks",
            "mechanical": "None — adhesive-retained",
            "tim_named": "not published",
            "removal": "not published",
            "risk": "high",
            "note": "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"
        },
        {
            "family": "Antminer S19 / S19j Pro / S19 XP",
            "attach": "Thermal gel + mechanically locked heatsink",
            "sink_style": "Large heatsink spanning multiple chips",
            "mechanical": "Heatsink is mechanically retained; the gel is a heat-transfer medium only",
            "tim_named": "Thermal gel, specified as Fujipoly SPG-30B in vendor repair guides",
            "removal": "not published",
            "risk": "medium",
            "note": "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"
        },
        {
            "family": "Antminer S21 / T21",
            "attach": "Thermal gel + mechanically locked heatsink",
            "sink_style": "Large heatsink spanning multiple chips",
            "mechanical": "Heatsink is mechanically retained",
            "tim_named": "Thermal gel, specified as Fujipoly SPG-30B in vendor repair guides",
            "removal": "not published",
            "risk": "medium",
            "note": "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"
        },
        {
            "family": "Antminer S19K Pro (board BHB56902)",
            "attach": "Heatsink SOLDERED to the chip with tin (BSM, copper-plated chip surface)",
            "sink_style": "Soldered assembly",
            "mechanical": "Solder joint is the attachment",
            "tim_named": "Solder (tin) — there is no paste, gel or pad at this interface",
            "removal": "Hot-air at 400 °C, nozzle ~0.5 cm above the heatsink, ~15 seconds",
            "risk": "high",
            "note": "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"
        }
    ],
    "methodology": [
        {
            "principle": "Bond-line thickness beats the W/mK number on the box",
            "detail": "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)"
        },
        {
            "principle": "Soft gap materials are meant to be compressed",
            "detail": "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"
        },
        {
            "principle": "Shore 00 is the right hardness scale here",
            "detail": "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"
        },
        {
            "principle": "Thickness is controlled by tooling, not by a published number",
            "detail": "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"
        },
        {
            "principle": "Match the material class to the attach method, not to a brand",
            "detail": "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"
        }
    ],
    "unpublished": [
        {
            "spec": "Per-model thermal pad / TIM thickness in millimetres",
            "state": "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."
        },
        {
            "spec": "Per-model durometer (Shore hardness) of the applied material",
            "state": "Never published. Vendors acknowledge that hardness differs between compounds but publish no value for any specific product."
        },
        {
            "spec": "Heatsink fastener torque specifications",
            "state": "Not published anywhere we could find. The guides do not even consistently state fastener type. Any torque table for an Antminer heatsink is invented."
        },
        {
            "spec": "Vendor part specifications",
            "state": "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."
        }
    ]
}