Research Papers

Quantification of Thermal Resistance of Transient-Liquid-Phase Bonded Cu/Al/Cu Interfaces for Assembly of Cu-Based Microchannel Heat Exchangers

[+] Author and Article Information
W. J. Meng

Department of Mechanical Engineering,
Louisiana State University,
Baton Rouge, LA 70803

Rongying Jin

Department of Physics and Astronomy,
Louisiana State University,
Baton Rouge, LA 70803

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MICRO- AND NANO-MANUFACTURING. Manuscript received September 5, 2012; final manuscript received May 1, 2013; published online July 9, 2013. Assoc. Editor: Ulf Engel.

J. Micro Nano-Manuf 1(3), 031001 (Jul 09, 2013) (10 pages) Paper No: JMNM-12-1053; doi: 10.1115/1.4024683 History: Received September 05, 2012; Revised May 01, 2013

Transient liquid phase (TLP) bonding of Cu structures with a thin elemental Al intermediate bonding layer is being used to assemble Cu-based, enclosed, microchannel heat exchangers (MHEs). The heterogeneous Cu/Al/Cu TLP bonding interface region, formed during the TLP bonding process, impacts heat transfer of the assembled MHE device. To evaluate the thermal resistance of TLP bonded Cu/Al/Cu interface regions, transient flash measurements were performed across bonding interface regions formed under various conditions, in combination with detailed structural examination and measurements of bulk mass density and specific heat. The flash method is shown to yield quantitative measurements of interfacial thermal resistance values. Our results provide guidance to developing bonding protocols for Cu-based MHEs with optimized heat transfer performance.

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Fig. 1

A cross-sectional SE image of a portion of one Cu-based, low-profile MHE

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Fig. 2

The equilibrium Al-Cu phase diagram

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Fig. 3

Schematics of two different heat transfer scenarios from an external heat source to liquid flowing within a Cu MHE

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Fig. 4

A cross-sectional SE image of a portion of one double-layered Cu MHE

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Fig. 5

A schematic of the procedure for preparing TLP bonded Cu/Al/Cu test specimens

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Fig. 6

(a) A schematic of the transient flash measurement and (b) a typical raw flash data set obtained from a homogeneous Cu disc. The single-headed arrow denotes the instant the light pulse is incident on the disc front surface.

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Fig. 7

Typical cross-sectional ISE images of bonding interface regions of TLP bonded Cu/Al/Cu specimens: (a) from group560, (b) from group580, and (c) from group600

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Fig. 8

XRD patterns obtained from bulk γ1-Al4Cu9 specimens after annealing at 550 °C: (a) the quenched specimen and (b) the slow-cooled specimen

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Fig. 9

γ1 thermal conductivity values extracted from flash measurements on Cu/γ1-interalyer/Cu specimens in comparison with those measured directly from bulk γ1 specimens

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Fig. 10

(a) Effective thermal conductivity values of Cu/Al/Cu bonding interface regions versus the bonding temperature and (b) effective thermal resistance of bonding interface regions versus the bonding temperature, calculated with A = 1 mm2. The solid lines are trend lines connecting data averages.

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Fig. 11

Cross-sectional ISE images of bonding interface regions of one group560 sample after a series of annealing at 580 °C for different durations: (a) as-bonded; (b) 3 min; (c) 2 h; and (d) 48 h.

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Fig. 12

Thermal properties of bonding interface regions of group560 samples versus annealing time at 580 °C: (a) effective thermal conductivity values. The solid lines connect data points obtained from the same sample; (b) effective thermal resistance calculated with A = 1 mm2. The solid line is a trend line connecting data averages.



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