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High Heat Transfer Thin Powder Sintered Heatpipe for Heatsink

1.

INTRODUCTION

Recently, micro processing units (MPU) mounted on information terminal equipments, personal computers etc.,
continue to increase in density of electronic chips, inorder to adapt multi-core application and integration ofgraphic and memory control functions. As a consequence, electronic chips generate more heat andincrease heat density. On the other hand, from designingand portability aspects, not only high cooling performance but also further downsizing and thinner types arerequested for mounted cooling devices, fan type heatsinketc..
To meet this technological trend, Furukawa Electric hasdeveloped and commercialized the new product of The
Thin Powder Sintered Heatpipe. This product is a extrahigh thermal conduction device and has a maximum heattransfer rate twice more than the maximum of the conventional company product heatpipe with thickness of 2 mm.
Furukawa Electric has established the production systemof 2 million sets of the new product heatpipe per month,out of total 5 million sets of the heatpipe production
capacity, and has commercialized the thin type heatpine
mounted with heatsink of high heat transfer rate.

2.

FEATURES

In general, a vapor phase path, which transfers evaporated working fluid from heating section to cooling section
as shown in Figure 1, is placed in the center of a heatpipe. Wick structures are set at the inner periphery of acontainer. Wick structures get capillary force to flow backworking fluid, which is condensed at low temperature section, to heating section.
With this conventional structure, press flattening narrows
the space for the vapor phase path of the heatpipe andthe heat transfer rate is significantly reduced. Thinnedwick structures ensure vapor phase path, but reduce heattransfer rate due to the reduction of the capillary force.
This new product heatpipe solves this problem by applying a special wick structure specialized for a flat shaped
container. Figure 3 shows the structure. A semicircularshaped metallic powder sintered wick (a) is mounted on
top and bottom of a flat container and these wicks makecontact with each other in a sharp angle (b). This structure gives capillary force induced by surface tension ofworking fluid at the sharp angle contact part of the wickstructure. At the same time the vapor phase path (c) withthe equivalent space to conventional heatpipe is ensured
at the right and left of inner periphery of the container, andthe nonconventional high heat transfer thin heatpipe isachieved. Furthermore, by reducing the volume of themetallic powder sintered wick, the weight is reduced by
10% from the conventional heatpipe.
Figure 4 shows the maximum heat transfer ratio of thethin powder sintered heatpipe and the conventional heatpipe with φ6 mm diameter and 200 mm length of container. At 2 mm of thickness, the new product heatpipe
has twice more heat transfer rate than the conventional
powder sintered heatpipe.
Table 1 shows lineup of thin powder sintered heatpipe(dimension and approximate heat transfer rate).

Vapor phase pathContainer

Wick

Figure 1

Conventional heatpipe structure and flattened shape.

Vapor phase
ﬂow

Heat out

Heating(evaporation)sectionHeat
insulatedsectionCooling(condensation)sectionWick

Heat inContainer
Flow back of condensed working ﬂuid
Pressure reduction

Figure 2

Working ﬂuid ﬂow

Heat transfer method of heatpipe.

（b）

（c）

（a）

Figure 3

Structure of thin powder sintered heatpipe.

Furukawa Review, No. 38

2010

1

The maximum Heat transfer rate (W)High Heat Transfer Thin Powder Sintered Heatpipe for Heatsink

70

Thin powder sintered heatpipe

60

Conventional powder sintered heatpipe

50
40
30
20
Twice more thanconventional type

10
000.5

1

1.5

2

2.5

3

3.5

4

4.5

Heatpipe thickness (mm)Figure 4

Comparison of the maximum heat transfer rate.

3.1 Fin Heatsink For Notebook Computer
Thinned heatpipe gives additional merits to heatsink.
Figure 5 shows thin heatsink with heatpipe and fin.
Reduced heatpipe thickness is utilized as fin height andhigher radiation efficiency is attained.
Figure 6 shows a relation between the fan input voltage
and the computer processing unit (CPU) temperature(input 35 W, ambient temperature 25°C) on heatsink models: one is applied with thin powder sintered heatpipe(thickness 2 mm), the other is a conventional heatpipe(thickness 4 mm). Here, thin powder sintered model has
2 mm higher fin, than common model, utilizing thickness
reduction. In this case, CPU temperature is significantly
reduced by the increased fin radiation area, and by thermal resistance reduction effect between the CPU heatreceiving plate and the heatpipe, caused by the increased
heatpipe width. In addition, at the reduced fan voltage
and its rotation speed, the heat radiation performance isequivalent to a heatsink mounted with conventional heatpipe, allowing for a design of fan with lower power consumption and lower fan noise.
3.2 Blade Server
Figure 7 shows a heatsink with a heatpipe for the blade
type server. Typically, a plate type heatsink as represented
by vapor chamber, has been mounted onto the heatsink
for server. Parallel use of thin heatpipe gives equivalentheat radiation performance to conventional models, making the heatsink thin and affordable in price.

Figure 5Thin heatsink with heatpipe and fin. (Two heatpipeswith thickness of 2 mm are used, for 50 W CPU.)

Thin powder sintered heatpipe(2 mm thickness)

75

CPU temp（℃）

Assembling drawing

Conventional powder sintered heatpipe(4 mm thickness)

70

Sectional drawing
Radiation fin

65
60
55
2.5

3

3.5

4

4.5

5

5.5

Heatpipe

Fan voltage (v)Figure 63.

Comparison of CPU temperature and fan voltage.

APPLICATION TO HEATSINK

Furukawa Electric applies the new product heatpipe toheatsinks and commercializes it. Examples are shown inthe followings.

Heat receiving
plateFigure 7Heatsink with heatpipe for the blade type sever.
(Six heatpipes with thickness of 1.5 mm are used,for 140 W CPU.)

Furukawa Review, No. 38

2010

2High Heat Transfer Thin Powder Sintered Heatpipe for Heatsink

4.

IN CONCLUSION

The new product heatpipe with 2 mm thickness has twice
as much heat transfer performance as conventional products, and contribute to a thinner design of cooling devices. At the same time, the new product contributes toenergy saving, low noise etc. providing various coolingsolutions that are environmentally responsible.
For more information, please contact
ELC Administrative Unit, Electronics and Automotive
Systems Company
TEL: +81-3-3286-2423
FAX: +81-3-3286-3707

Furukawa Review, No. 3820103