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Proper mounting of TECs requires taking into account properties of
materials in target assembly.
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Thermal conductivity is preferably as high as possible to minimize thermal
resistance in assembly which generally reduces performance of TECs.
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Coefficient of thermal expansion (TCE) of all materials in connections must
be adjusted (to be close to each other) to minimize thermal stress, which can lead to
damage of TECs and considerable reduction of TEC lifetime.
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Thermal properties as melting point and temperature stability must be
coordinated to provide correct mounting procedures (particularly soldering
and adhesive bonding methods) and long operation of TECs.
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Some useful properties of commonly used materials regarding above mentioned
are listed below.
Materials of TEC
|
Material |
Density
g/cm ³ |
CTE х10-6
1/K |
Thermal Conductivity W/mK |
Specific Heat
J/kgK |
Ultimate Strength
MPa |
Young's Modulus
GPa |
|
Bismuth
Telluride |
7,85 |
12.9(┴ ) |
1,5 |
188 |
20-40 |
50 |
|
Ceramics Al2O3
-
100% |
3,9 |
7,2 |
30 |
800 |
150 |
280 |
|
Ceramics Al2O3
- 96% |
3,75 |
7,0 |
24 |
800 |
150 |
280 |
|
Ceramics AlN |
3,3 |
4,5 |
170 |
920 |
n/a |
350 |
|
Ceramics BeO |
3 |
7,0 |
230 |
1088 |
105 |
330 |
Commonly used materials for heat sinks and
holders for TEC mounting
|
Material |
Density
g/cm ³ |
CTE х10-6
1/K |
Thermal Conductivity W/mK |
Specific Heat
J/kgK |
Ultimate Strength
MPa |
Young's Modulus
GPa |
|
Aluminum |
2,7 |
22,5 |
237 |
900 |
50 |
70 |
|
Copper |
8,96 |
16,7 |
400 |
385 |
215 |
120 |
|
Kovar |
8,36 |
5,5 |
17 |
460 |
n/a |
n/a |
|
Cold-Rolled Steel (CRS) |
7,85 |
11,5 |
50 |
460 |
210-240 |
200-210 |
|
Stainless
Steel |
8,01 |
17,1 |
14,5 |
460 |
580 |
n/a |
|
Cu-Mo(15%-85%) |
10 |
6,9 |
190 |
280 |
540 |
280 |
|
Cu-Mo(25%-75%) |
9,8 |
8,0 |
175 |
283 |
n/a |
n/a |
|
Cu-W(10%-90%) |
17 |
6,7 |
180 |
163 |
560 |
330 |
|
Cu-W(20%-80%) |
15,65 |
8,5 |
200 |
n/a |
490 |
280 |
|
Brass |
8,49 |
18,0 |
110 |
343 |
240-400 |
102-115 |
Solders
|
Material |
Melting Point
°C |
Density
g/cm ³ |
CTE х10-6
1/K |
Thermal Conductivity
W/mK |
Specific Heat
J/kgK |
Electric Conductivity
106
1/Ohm |
|
Bi50%
Sn25% Pb25% |
94 |
9,44 |
20 |
16 |
151 |
1,7 |
|
In52%
Sn48% |
117 |
7,3 |
24 |
73 |
233 |
9,4 |
|
Bi57%
Sn43% |
138 |
8,58 |
19 |
41 |
180 |
1,7 |
|
Sn50%
Pb32% Cd18% |
145 |
8,8 |
26 |
35 |
205 |
7,5 |
|
In100% |
157 |
7,31 |
29 |
86 |
243 |
13 |
|
Sn63%
Pb37% |
183 |
9,3 |
26 |
50 |
170 |
7,2 |
|
Sn91% Zn9% |
199 |
7,27 |
25 |
61 |
256 |
3,9 |
|
Sn95% Sb5% |
230 |
7,25 |
31 |
63 |
221 |
6,9 |
Thermal Greases (typical)
|
Material |
Thermal Conductivity W/mK |
Resistivity
Ohmcm |
Temperature range °C |
Lifetime
years |
|
Silicone (ZnO) |
0,7 |
>5x1014 |
<150 |
5 years @25C |
|
Non-Silicone ( Al2O3) |
2,0 |
>1013 |
<150 |
1 year @25C |
|
Non-Silicone
(AlN) |
4,0 |
>1013 |
<150 |
1 year @25C |
Epoxies (typical)
|
Material |
Thermal Conductivity
W/mK |
Resistivity Ohmcm |
Die-Shear kg/sm2 |
CTE х10-6
1/K |
Temperature range
°C |
|
Epoxy (Ag) |
1,35 |
0,05 |
45 |
49 |
-55…+125 |
|
Epoxy (Al2O3) |
1,73 |
>1x1014 |
105 |
140 |
-20…+130 |
|
Epoxy (Al2O3) |
1,73 |
n/a |
105 |
140 |
-20…+130 |
|
Epoxy (AlN) |
3,6 |
n/a |
125 |
120 |
-25…+130 |
|
Epoxy (Ag+ceramics) |
>7,5 |
n/a |
n/a |
n/a |
-40…+150 |
|
