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Thermal interface materials
requirements
As a basic overview, thermal engineers
are looking for a single choice of thermal
interface material that can:

• Be applied in a simple process at
room temperature with minimal
capital expenditure;
• Give a consistent result over
increasingly dissimilar die heights
and heterogeneous surfaces subject
to warpage and height differences;
• Reliably remove heat at high heat
densities;
• Be applied to bare silicon die (without
requiring die backside metallization)
with no reliability issues; and
• Be applied over multiple larger die
Figure 3: Some of the 3D challenges for HPC modules.
with significantly larger surface area.
thermal conductivity of silicon itself issues in compute intensity, multi-die
(around 1.4W/cm.K at room temperature) integration, and other factors of increasing Bulk thermal conductivity and
can become a performance impediment. relevance to HPC modules and systems. thermal resistance
The complications of HPC modules are One critical factor in HPC module thermal When considering a potential TIM
already well-delineated in industry roadmap and packaging design is the selection of the solution, the key performance metric
workshops, such as those from IEEE [6] and materials used to gain the most efficient heat is the overall thermal resistance (units
iNEMI. These roadmaps outline emerging transfer, internally and externally. K/W). Bulk thermal conductivity is
usually an important consideration for
thicker bondlines, but as the bondline
thick ness of the TI M decreases,
interfacial resistances dominate the
system’s thermal performance (Figure 4).

Figure 4: Diagram of heat flow.

Generalized TIM types
There are three general types of TIM,
each relevant to the semiconductor package
design and the packaging level where the
TIM is to be applied as noted below.
TIM 0. In these applications, which are
increasingly being used in HPC modules,
the TIM0 contacts the die backside
E-Tec Interconnect AG, Mr. Pablo Rodriguez, Lengnau Switzerland
Phone : +41 32 654 15 50, E-mail: p.rodriguez@e-tec.com surface and transfers heat directly to the
heat sink base (Figure 5). This is usually
a machined copper surface compressed

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