Diamonds, Save Chips
Data centers are among the most controversial projects in technology infrastructure development. Their energy consumption, construction costs, and site selection issues are under close scrutiny from regulators, utility departments, and local communities where the projects are located. Amid these complex political and social considerations, one fact is universally recognized by all parties: data centers convert electrical energy into computing power and heat, and the cooling process accounts for approximately 25% to 40% of their total energy consumption.
However, people often overlook where the cooling demand is actually "set" — it is not determined by the computer room environment, but by the chip package itself.
Advanced packaging technologies enable higher power density to be concentrated on a smaller silicon wafer area. Through Chiplet, stacked High Bandwidth Memory (HBM), and kilowatt-level multi-die modules, the single-package power consumption of flagship accelerators has exceeded 1000 watts, and rack density has surpassed 100 kilowatts; even in the technology roadmaps of manufacturers, 200-kilowatt-level rack solutions have already emerged. Before heat reaches the cold plate, cooling loop or chiller, every watt of generated heat must first pass through the initial 1-millimeter space above the chip junction. If the heat cannot be efficiently dissipated when leaving the die, subsequent cooling systems cannot make up for this loss.
This is exactly why the material on top of the stack needs to be replaced. Single-crystal diamond (with a thermal conductivity exceeding 2,000 W/m·K, about five times that of copper) is used as a heat dissipation spreader layer that matches the chip size and is adjacent to the junction area; it can effectively reduce thermal diffusion resistance directly at the critical part that determines the thermal budget. While actively embracing Artificial Intelligence (AI), technology leaders are also clearly aware of a major barrier hindering its widespread application: the enormous heat and energy consumption generated at the chip level will be further amplified at the data center scale. And the entry point to solve this problem is the chip itself.
The First Millimeter Determines the Budget
The heat dissipation path from the chip junction to the ambient environment can be regarded as a superposition of a series of thermal resistances: from the chip junction to the chip surface, through the first thermal interface material, into the vapor chamber, then through the second thermal interface material into the cold plate, then into the coolant, and finally the heat is discharged through the facility circulation loop. Over the past decade, the industry has invested a lot of effort in the end of this heat dissipation chain (the side far from the chip), such as adopting direct-to-chip cold plates, immersion cooling, cabinet rear door heat exchangers, and increasing the temperature of facility cooling water. However, the top of the heat dissipation chain (the part close to the chip surface) has hardly changed.
It is precisely at this top end that the laws of physics are the most stringent. Modern computing chips do not generate heat uniformly; compute tiles, SerDes modules and power supply areas generate local heat flux that can be several times the average heat flux of the chip — in the most severe hot spot areas, the heat flux is even as high as hundreds of watts per square centimeter. The copper vapor chamber with a thermal conductivity of about 400 W/m·K does not have a sufficient lateral heat conduction speed to smooth out these heat peaks. As a result, what the cold plate "sees" is a highly concentrated mapping of the chip's heat distribution; the upper limit of the chip junction temperature depends on the peak heat flux, not the average heat flux.
These consequences will spread to the entire facility. Every degree of temperature rise caused by thermal diffusion impedance must be "offset" at a cost in downstream links — and the cost of this downstream compensation is extremely high. This means that a lower coolant temperature needs to be set, resulting in chillers having to be put into operation (free cooling cannot be utilized), increasing the energy consumption of pumps and fans, requiring a smaller approach temperature, and requiring a larger-scale mechanical refrigeration system. At the equipment level, the efficiency loss caused by just a few degrees of temperature difference will be silently amplified and apportioned at the gigawatt (GW) scale of infrastructure.
In addition, there is a second, more direct "cost": throttling. Chips have self-protection mechanisms — when a certain hot spot area exceeds the temperature threshold, the chip will automatically reduce the operating frequency, even if the average temperature of the chip seems to be within a "comfortable" range. In AI data centers, throttling is not just a thermal management issue, but a problem that directly affects revenue. Because those Tokens (model output units) that should have been generated but failed to be generated cannot be converted into commercial benefits.
Integrating Diamond at the Die Level
Diamond thermal spreaders are not a new concept, and what has really changed is their manufacturability. Chemical Vapor Deposition (CVD) technology has realized the industrial production of semiconductor-grade artificial single-crystal diamond; at the same time, various forms and metallization processes required for packaging integration have matured and are applied in current production practices.
The key basic unit to realize this application is the diamond thermal spreader that matches the size of the chip. Through single-crystal diamond with a maximum size of 25 × 25 mm — its area is large enough to cover reticle-class computing chips without the need for multiple pieces to be spliced, thus eliminating bonding gaps in the heat conduction path. The surface of these thermal spreaders is metallized with Ti/Pt/Au (titanium/platinum/gold) — this is a standard adhesion layer-barrier layer-surface layer structure, which enables diamond to directly adapt to existing chip connection processes: it can use sintered silver to obtain an extremely low thermal resistance interface, or use AuSn (gold-tin), SAC (tin-silver-copper) or indium alloy for reflow soldering according to the needs of the assembly process. There is no need to introduce new tool sets or special process modules, and the existing chip mounting and reflow soldering equipment on the production line can be directly used.
From an architectural perspective, the thermal spreader is placed in the position where it can perform best: as a lid-integrated insert in the TIM1 (first layer thermal interface material) layer between the chip and the lid; or in a lidless design, directly placed under the cold plate. The Coefficient of Thermal Expansion (CTE) issue can be properly solved through design means — the CTE of diamond is about 1 ppm/K, which is closer to silicon than copper; in addition, adopting compliant bond-line engineering for the connection layer is already a standard industry practice, not a rare process.
The advantages of this solution are reflected in modeling analysis. In the Computational Fluid Dynamics (CFD) simulation conducted for the current kilowatt-level accelerator package (the relevant results are currently being evaluated by the thermal management team of the Original Equipment Manufacturer (OEM)), without making any changes to the cooling loop, placing a single-crystal diamond thermal spreader near the junction can reduce the case temperature and junction temperature by 8–10°C.
A temperature drop of 8 to 10 degrees Celsius may sound trivial, but at the data center scale, its significance is extraordinary.
The Arithmetic Problem of "One Gigawatt"
Industry forecasts show that in 2027 alone, about 30 gigawatts (GW) of new data center capacity in the United States will be under construction. To understand the significance of near-junction diamond technology at this scale, we can take a 1-gigawatt (1 GW) Artificial Intelligence (AI) facility as an example for analysis.
Assume that the facility deploys about 600,000 accelerator packages (including GPUs and custom ASICs). After deducting the power consumption budget occupied by host CPUs, network equipment and cooling systems, these accelerators are comparable to today's kilowatt (kW)-level hardware specifications. If each package integrates a diamond heat spreader (at a mass production scale, each costs about 600 US dollars), then the material cost of diamond alone for the entire facility is as high as 360 million US dollars.
It should be noted that this cost is not reflected in the construction budget of hyperscalers. Diamond is integrated during the packaging manufacturing stage — this is a component decision made by chip manufacturers when producing accelerators priced at 30,000 to 50,000 US dollars. At the packaging level, diamond only increases the material cost of flagship products by 1% to 2%; even if this part of the cost is fully passed on to the selling price of the accelerator, it only accounts for 1% to 2% of the total investment (about 35 billion to 50 billion US dollars) for a hyperscaler to build a 1-gigawatt facility.
When these 600,000 accelerator packages are put into operation, what benefits can the 8 to 10 degrees Celsius temperature difference bring?
The first is in terms of energy consumption. The lower the chip junction temperature, the smaller the leakage current — the leakage current will decrease significantly as the temperature drops. In addition, the cooler package allows the use of a higher-temperature cooling medium, thus converting the period that originally required chiller operation into a "free-cooling" period, and reducing the energy consumption of pumps and fans.
According to model calculations, for a 1-gigawatt facility, about 250 to 300 gigawatt-hours (GWh) of electricity can be saved every year — which is equivalent to the annual electricity consumption of about 28,000 American households, that is, the total annual electricity consumption of all households in a city the size of Palo Alto or Greenwich. Calculated at an electricity price of 0.10 US dollars per kilowatt-hour (kWh), this is equivalent to saving about 250 million US dollars in electricity bills over the 10-year life cycle of the facility. The use of smaller cooling devices (chillers) and heat dissipation systems not only saves cooling-related Capital Expenditure (Capex), but also saves an additional about 150 million US dollars during the construction phase; the total cost savings of various items are about 400 million US dollars.
In terms of revenue, the gains are even more considerable. When the chip runs at a lower temperature, its performance is less affected by thermal throttling, and the aging rate is slower — for every 10°C drop in temperature, the safety margin corresponding to the "temperature-related failure mechanism" that determines the service life of the accelerator can be approximately doubled. A stable clock frequency and longer service life mean that more salable Tokens (computing output units) can be generated under the same capital investment; according to scenario modeling estimates, the resulting incremental revenue is about 1 billion US dollars over the ten-year life cycle of the facility.
Overall view: With an investment of only 360 million US dollars in "diamond materials", it can create about 1.4 billion to 1.7 billion US dollars in value for the operator. Converted to each packaging unit, an investment of 600 US dollars in component cost can create more than 2300 US dollars in value.
Who Pays the Bill and Who Benefits
This separation between "payer" and "beneficiary" — that is, the chip manufacturer bears the cost of diamond materials, while the hyperscaler enjoys the operational benefits brought by it — is exactly the crux of why many promising packaging technologies often stagnate. When component manufacturers are required to absorb costs on their own so that downstream links can save expenses, such technologies are often difficult to survive; in the history of thermal management materials, there is no shortage of excellent solutions that died prematurely due to this misalignment of interests.
However, advanced packaging technologies have rewritten these rules. Chip manufacturers no longer just sell bare silicon wafers, but provide integrated systems differentiated through packaging — such as different memory capacity levels, slot-type or modular form factors, liquid-cooled versions, and frequency specifications screened through binning.
Heat dissipation capability has become a key dimension of product definition. The product Stock Keeping Unit (SKU) using diamond materials is exactly a new step on this advanced path: on the same silicon wafer basis, through a more excellent heat dissipation stack, higher continuous operating frequency and longer service life are achieved, and pricing is carried out according to the value it releases.
This pricing logic is very profitable. If a 600-dollar heat dissipation component can bring more than 2300 US dollars in value to the operator, the manufacturer can increase its own profit margin through a premium — and the component itself does not require the manufacturer to carry out additional design or tape-out — at the same time, the operator's Total Cost of Ownership (TCO) can still be significantly optimized. Diamond materials achieve "double payback": it is reflected in the Average Selling Price (ASP) of chip manufacturers, and also in the energy cost savings of operators. The lower junction temperature also provides manufacturers with solid product endorsements — such as longer rated service life and stronger continuous performance indicators, which are unmatched by competitors who lack heat dissipation margin.
For the growing number of hyperscalers that have begun to design their own accelerators, the above problems are easily solved. When the chip designer and the data center operator belong to the same enterprise, the problem of interest misalignment no longer exists: diamond materials are directly included in the Total Cost of Ownership (TCO) model, and all the value brought by this packaging solution eventually goes to the party that bears the cost.
What Can Packaging Architects Get
For engineers responsible for thermal management architecture, these temperature control indicators can be converted into more intuitive performance and design advantages. Thermal headroom can be converted into frequency margin: the chip die can run at the boost clock for a longer time without throttling due to hitting the hot-spot limit. It can also be converted into reliability margin: problems such as electromigration, Bias Temperature Instability (BTI) and interconnection fatigue are all closely related to temperature. It also brings design freedom: if the packaging heat dissipation speed is increased to five times the original, it can support a more compact chip layout, relax the specification requirements for Thermal Interface Materials (TIM), and even allow data center facility architects to increase the cooling water temperature — which is the most effective means to reduce cooling energy consumption. In addition, it can realize product differentiation: forming specification advantages in continuous performance and rated service life, which can be converted into market competitiveness.
The influence of this topic goes beyond the scope of data centers. Due to energy consumption issues, communities and utility departments are resisting the expansion of AI infrastructure; therefore, the industry cannot just rely on increasing power generation to cope, but must also commit to reducing waste. The most effective entry point to reduce waste is the chip itself — saving one watt of power consumption at the chip junction temperature can save several times more energy in the entire back-end cooling chain.
The Frontier Area Above the Package Lid
Over the past decade, the data center thermal engineering field has optimized all links behind the package lid with remarkable results — liquid cooling technology has become the mainstream, and facility energy efficiency has steadily improved. However, the chip technology roadmap is extremely stringent: each generation of products integrates higher power in a smaller area, and the hot spot problem is becoming more and more prominent. The next stage of energy efficiency improvement will no longer rely on larger-sized cold plates, but will depend on material innovation — that is, changing the physical properties of the initial 1-millimeter area above the chip junction temperature, and chip manufacturers will convert this physical property into actual products.
Diamond materials are no longer rare. Today, it can be artificially synthesized through reactors, metallized using standard processes, packaged and connected through conventional metallurgical methods, and has been put into mass production with specifications up to 25 × 25 mm. Heat dissipation has become the core constraint in packaging design. This is exactly the way packaging technology "strikes back".
This article is from the WeChat official account "Semiconductor Industry Watch" (ID: icbank), author: Dhrumil Rangani, published with authorization from 36Kr.