Thermoelectric Cooling Solutions

site map eng | ru

Print version

Application Tips

Thermoelectric cooler (TEC) is a semiconductor device which is characterized by unique heat pump performance with high efficiency, compactness and durability. The unique ability of TECs to heat and cool, permits them to lower temperature of an object below ambient as well as to stabilize temperature of objects in widely varying ambient conditions.

Here we mention some application tips that can help in optimal use of TECs.

PROPERTIES OF MATERIALS

Proper mounting of TECs requires taking into account properties of materials in target assembly.

  • Thermal conductivity is preferably as high as possible to minimize thermal resistance in assembly which generally reduces performance of TECs.
  • 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.
  • 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.

Some useful properties of commonly used materials regarding above mentioned are listed below.

Materials of TEC

Material Density g/cm3 CTE x10-61/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/cm3 CTE x10-61/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/cm3 CTE x10-61/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 x10-61/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