| IMPORTANT:
When two or more thermoelectric devices are mounted
between a common plate, the thermoelectric devices thicknesses
should vary no more than 0.0015-inches. Contact our Engineering
Department for more information on close tolerance lapped
thermoelectric devices.
Step 1. Prepare cold
plate and heat sink surfaces as follows:
A) Grind or lap flat
within +/- 0.001" in module area.
B) Locate bolt holes as close
as possible to opposite edges of module (1/8" clearance
recommended, 1/2" maximum), in the same plane line
as the heat exchanger fins. This orientation utilizes
the additional structural strength of the fins to prevent
bowing. Drill clearance holes on one surface and drill
and tap opposite surface accordingly (see
sketch). If a spacer block is used to increase distance
between surfaces, performance is greater if the spacer
block is on cold side of system.
C) Remove all burrs, chips and foreign matter
in thermoelectric module area.
Step 2. Thoroughly
clean and degrease thermoelectric module, heat exchanger
and cold surface.
Step 3. Apply a thin
continuous film of thermal grease (Wakefield Engineering
Type 120 or Dow Type 340) to module hot side surface and
to module area on heat exchanger.
Step 4. Locate module
on heat exchanger, hot side down.
Step 5. Gently oscillate
module back and forth, exerting uniform downward pressure,
noting efflux of thermal compound around edges of module.
Continue motion until resistance is felt.
Step 6. Repeat Step
#3 for cold side surface and cold plate.
Step 7. Position cold
plate on module.
Step 8. Repeat Step
#5, sliding cold plate instead of module. Be particularly
careful to maintain uniform pressure. Keep the module centered
between the screws, or uneven compression will result.
Step 9. Before bolting,
best results are obtained by preloading in compression the
cold plate/heat exchanger/module assembly, applying a light
load in line with center of module, using clamp or weights.
For two module assemblies, use 3 screws located on module
center line, with middle screw located between modules.
To preload, torque middle screw first. Bolt carefully, by
applying torque in small increments, alternating between
screws. Use a torque limiting screw driver. The recommended
compression for a TEC assembly is 150 to 300 pounds per
square inch of module surface area. Using the following
equation you can solve for torque per screw:
-
| T = (C x D x F x in2)
/ (# of screws) |
T = torque per screw (in-lbs)
C = torque coefficient (0.20 as received, 0.15 lubricated)
D = nominal screw size (4/40 = 0.112, 6/32 = 0.138,
8/32 = 0.164)
F = Force (lbs / in2)
in2 = Module surface area (length x width)
Check torque after one hour and retighten
if necessary. Use Stainless Steel
Screws, fiber insulating shoulder washers, and steel spring
(Belleville or split lock type) washers (see sketch
in Assembly Tips).
CAUTION
1. To assure good thermal grease interfaces
there should be no bowing of either surface due to torquing.
To prevent bowing, apply less torque if one or both surfaces
are less than 1/8 inch thick copper or 1/4 inch thick aluminum.
2. Lead wires are soldered to module tabs
with bismuth/tin solder (136°C). If lead wire replacement
is necessary, use bismuth/tin solder.
use lead /
tin solder (180°C).
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