Thermal Management Design Resources
for Vicor ChiP Products
Written by: Gary Gill
Director, VI Chip Product Line
March 2014
Two key factors in maximizing power converter performance and successful power
system design are thermal environment and heat management. Power densities are
increasing faster than power converter efficiency; thus increased performance from
thermal management solutions is required.
Products based on Vicor’s new ChiP packaging technology are optimized for both
electrical and thermal performance. ChiP products are:
n Designed with power components on both sides of the PCB to reduce losses due to
parasitics, to spread heat evenly throughout the whole package, and to take
advantage of both top and bottom surfaces for heat removal
n Encapsulated in a thermally enhanced molding compound which reduces
temperature differentials and provides flat module top and bottom surfaces for ease
of use with thermal management accessories (heat sinks, cold plates,
heat pipes, etc.). This approach also offers increased thermal management
flexibility as either the top or bottom surfaces of the module can be used for thermal
management. For maximum performance, both surfaces can be utilized resulting in the industry’s highest power density.
To help power system designers fully leverage the thermal management benefits of
the ChiP packaging technology, Vicor offers product, online design tools, and thermal
management accessories which simplify a customer’s thermal design process.
Product Data
For every ChiP product, Vicor provides thermal de-rating curves. These curves provide
thermal de-rating guidelines for thermal management configurations in which the top
of the converter is cooled, the top plus the leads are cooled, or the top, bottom and leads
are all cooled. For example, below is the de-rating curve for Vicor’s recently announced
BCM380P475T1K2A30 380 V to 48 V BCM® (Bus Converter Module).
Figure 1.
Output Power vs. Case Temperature
derating guidelines
(see datasheet)
Output Power (W)
Case Temperature (°C)
One side cooling One side cooling and leads
Double Sided cooling and leads
Applications Engineering: 800 927.9474
Page 1
These curves indicate that the full rated power of the BCM (1200 W) can be processed
provided that the top, bottom, and leads are all held below 95°C. Similarly, if only the
top surface is thermally managed, then the top must be held below 70°C in order for
the BCM to process full power without derating. These curves highlight the benefits of
dual sided thermal management, but also demonstrate the flexibility of the Vicor ChiP
platform for customers who are limited to cooling only the top or the bottom surface.
In addition to de-rating curves, Vicor also provides estimates for the thermal resistance
between the ChiP power modules hottest internal point and the three primary thermal
interfaces (top, bottom, and leads). Again, using the BCM380P475T1K2A30 as an
example, the following thermal resistances are provided in the data sheet:
Table 1.
thermal resistances
(see datasheet)
Thermal resistance
top side
Thermal resistance leads
Thermal resistance
bottom side
Condition / Notes
Estimated thermal resistance
to maximum temperature
internal component from
isothermal top
Estimated thermal resistance
to maximum temperature
internal component from
isothermal leads
Estimated thermal resistance
to maximum temperature
internal component from
isothermal bottom
These thermal resistances can be used in the equivalent circuit model shown below to
estimate heat flows and the BCM’s internal temperature. Please see the ChiP product’s
data sheet for further details and examples.
Figure 2.
ChiP equivalent circuit
thermal model (see datasheet)
1.24°C / W
Thermal Resistance Top
1.24 °C / W
1.24°C / W
7°C / W
Thermal Resistance Bottom
1.24 °C / W
Thermal Resistance Leads
7 °C / W
Power Dissipation
44 W
100 °C
100 °C
Applications Engineering: 800 927.9474
100 °C
Page 2
Online Design Tools
In addition to the data described above, Vicor also offers online tools to help customers
evaluate and design in ChiP products. For power system architecture planning, Vicor’s
PowerBench™ Whiteboard offers an intuitive and easy to use tool for evaluating the
power dissipation and efficiency of a multi-converter power system. With a simple
and familiar schematic capture interface, the user can construct a power system, using
Vicor products, with sources, loads and distribution resistances to determine expected
power dissipations of each converter which can then be used for thermal management
planning. Below is an example of a power system architected with multiple Vicor power
modules evaluated with the PowerBench Whiteboard.
Figure 3.
Vicor PowerBench Whiteboard
While the PowerBench Whiteboard is an excellent tool for quickly architecting a power
system design, Vicor also offers a full featured online simulator which allows a customer
to evaluate a component’s electrical and thermal performance. The PowerBench
Simulator analyzes the converter under a range of situations (startup, steady state, VIN
or load steps) in a typical reference design. Figure 4 shows the simulation tool with the
BCM380P475T1K2A30 displayed. Applications Engineering: 800 927.9474
Page 3
Figure 4.
Vicor PowerBench Simulator
In the simulation tool, the input source, output load, input filter, output filter, as
well as various parasitic effects can be modified by the customer to reflect actual
design conditions. For thermal simulation, the tool allows the user to select from a
range of recommended thermal management options including top side heat sink,
top and bottom side heat sinks, or a cold plate. The user can also specify the thermal
environment by selecting ambient temperature, air velocity, and thermal interface conductivity. Applications Engineering: 800 927.9474
Page 4
Figure 5.
PowerBench Simulator Thermal
Management Configurator
(with top side
heat sink selected)
PowerBench Simulator Thermal Management Configurator
(with dual-sided heat sink selected) Applications Engineering: 800 927.9474
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Figure 6.
PowerBench Simulator Thermal
Management Configurator
(with cold plate selected)
Finally, in order to simplify customer thermal management design and evaluation, the
recommended heat sinks modeled in the simulator are available for order (along with
any associated hardware) from both Vicor and our distribution partners. Vicor provides
mechanical drawings and assembly recommendations for these accessories as well. Applications Engineering: 800 927.9474
Page 6
Vicor’s new generation of power components based on the ChiP packaging platform
offer levels of efficiency, power density and thermal management flexibility that were
previously unavailable. To assist customers in realizing the full potential of this exciting
new family of power converter modules, Vicor also offers an unmatched collection of
product data, online design tools and thermal accessories which enable customers to
quickly evaluate and implement designs built around Vicor’s power component offerings.
Converter housed in Package (ChiP) Platform
Vicor’s ChiP platform sets best-in-class standards for a new generation of scalable power
modules. Leveraging advanced magnetic structures integrated within High Density
Interconnect (HDI) substrates with power semiconductors and control ASICs, ChiPs
provide superior thermal management supporting unprecedented power density.
Thermally-adept ChiPs enable customers to achieve low cost power system solutions
with previously unattainable system size, weight and efficiency attributes; quickly and
predictably. The advent of ChiPs, embodies a modular power system design methodology
enabling designers to achieve high performance, cost-effective power systems from AC or
DC sources to the Point of Load using proven building blocks.
The Power Behind Performance
Rev 1.1
08/2014 Applications Engineering: 800 927.9474
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