How It Compares
Indigo Xtreme™ is a precision engineered Phase Change Metal Alloy (PCMA) for professional, high-end applications pushing the heat flux envelope.
With its excellent surface wetting and high bulk conductivity (as much as 3 times better than the best aluminum and silver-filled greases), Indigo Xtreme™ offers dramatically lower thermal resistance than competing products.
The graph below illustrates increasing CPU wattage and corresponding junction temperature rise with the highest performance thermal interface solutions available today.
The Professional Choice
Indigo Xtreme™ is the professional's choice for the most demanding cooling challenges, and is highly recommended for CPU applications of 150 watts and above. If you operate your CPU at stock wattages and frequencies, Indigo Xtreme™ may not provide significant advantage, and a legacy solution may be adequate for your needs. The extraordinary cooling power of Indigo Xtreme™ is specifically designed for serious overclocking or other challenging applications. With increasing wattage or heat flux, the temperature difference between simple polymeric (grease) solutions and the extra cooling ability of Indigo Xtreme™ increases sharply.
The chart below highlights the performance advantage of Indigo Xtreme™ at only 130 watts of dissipated power with an Intel Core™ i7 CPU. Junction-to-sink temperature rise of Indigo Xtreme™ is almost 4 degrees better than that achieved by Arctic Silver 5.
As dissipated power increases, Indigo Xtreme ™ achieves even greater cooling performance.
ASTM D5470, a standard industry test for quantifying the thermal impedance (resistance) of thermal interface solutions, was used to obtain both thermal contact resistance and bulk thermal resistance values for Indigo Xtreme™ and for the former industry leaders seen in the table and chart below.
| Indigo Xtreme™ | Shin Etsu X23-7762 | Arctic Silver 5 | Coollabs MetalPad | |
| Composition | PCMA composite | Aluminum-filled Polymer | Silver-filled Polymer | Low Melt Alloy |
| Shimmed Bondline Thickness (mils) | ~2 | ~11 | ~11 | ~1 |
| Bulk Resistance | 0.028 | 0.0631 | 0.2301 | 0.015 |
| Contact Resistance | 0.012 | 0.0631 | 0.0791 | 0.305 |
| Overall Resistance | 0.04 | 0.1261 | 0.3091 | 0.320 |
Notes:
1. S. Narumanchi, “Thermal
Interface Materials for Power Electronics Applicationsâ€, ITherm Proceedings, 2008
2. R. Russo, et al.,
“Thermal Performance Differences Between ASTM D5470 and “Overclocker†Methodsâ€, IMAPS Thermal Advanced
Technology Workshop (ATW) Proceedings, 2007
An optimal thermal interface solution possesses both a low contact resistance and a low bulk resistance (the inverse of bulk thermal conductivity). Indigo Xtreme™ achieves high thermal performance through the optimized deployment of molten, oxide-free PCMA, thereby yielding low contact resistance and high bulk conductivity.
Total thermal resistance is the combination of bulk and contact resistances.
Additionally, bulk thermal conductivity was measured (by the cited US government and universary labs above) for the polymeric grease compounds (Shin Etsu X23-7762 and Arctic Silver 5). The Shin Etsu product tested in line with the manufacturer specifications (within measurement accuracy).
Interestingly, the labs measured Arctic Silver 5's bulk thermal conductivity to be 0.941 and 1.12 W/mK, figures which are far lower than the manufacturer's claim of >8 W/mk (>350,000W/m2 °C at 0.001 inch layer).
The increased contact resistance of Coollab's MetalPad may be due to inadequate pad thickness to accommodate a 1 mil BLT and surface asperities of the test blocks.