Thermoelectric Cooler Installation Guide
Contents
An Overview of the Methods for Mounting Your Thermoelectric Cooler ............................................... 2
Preparing Surfaces ............................................................................................................................... 2
Mounting with Adhesive Bonding .......................................................................................................... 2
Mounting with the Compression Method ............................................................................................... 2
Mounting with Solder ............................................................................................................................ 3
Connecting Lead Wire to Header .......................................................................................................... 3
Final Cleaning and Inspection ............................................................................................................... 4
Preventing Problems ............................................................................................................................. 4
Document Number: 017-0007
Revision: C
Page: 1 of 4
An Overview of the Methods for Mounting
Your Thermoelectric Cooler
COLD SIDE
conductivity is required.
Step One:
Because of the short amount of time needed
for epoxy to set up, be certain to have your TECs
cleaned and ready to mount before mixing epoxy. Clean
and prepare mounting surfaces on both the TEC and
heat sink using IPA, acetone or a general-use solvent.
NOTE:
It is recommended that acetone and cotton
swabs be available so that any excess or spilled epoxy
(uncured) may be quickly removed.
NEG (-)
POS (+)
Step Two:
Use commercially available Thermally
Conductive Epoxy.
Follow the instructions on the
package carefully. Follow all Safety Precautions.
Step Three:
Coat the ceramic of the TEC with
approximately a .05 mm (.002-inch) thick layer of epoxy.
Step Four:
Place the TEC on the heat sink and gently
rotate the TEC back and forth, squeezing out the excess
epoxy.
Step Five:
Using a clamp or weight, apply light
pressure, and cure per manufacturer recommendation.
Thermoelectric coolers (TECs) are mounted using one of
three methods: adhesive bonding, compression using
thermal grease or solder.
In general, for a TEC with a ceramic base of 19 mm or
less, you can solder or adhesive bond without fear of
failure due to thermal stresses. If the TEC base is larger
than 19 mm, we recommend the compression method
because thermal grease is not rigid and does not
transfer thermal stresses.
A thin layer of copper metallization on the hot and/or
cold ceramic allows soldering as a means of attachment.
Keep in mind that a TEC without metallization cannot be
mounted using solder. Remember also that adhesives
and greases are prone to outgassing, so they are not as
appropriate for use in a vacuum package.
The following methods are recommendations only, it is
the customer responsibility to verify in their application.
Mounting with the Compression Method
When to Use:
When a permanent bond is not desired;
When multiple TECs are used; When your TEC is larger
than 19 mm.
Step One:
Prepare heat sink and cold sink surfaces by
machining the module area to within +/- 0.02 mm (.001
inch).
Step Two:
Locate bolt holes in your assembly such that
they are at opposite sides of the cooler between from 3.2
to 12.7 mm (.13 to .50 in.) the sides of the
thermoelectric. The bolt holes should be in the same
plane line as the heat sink fins to minimize any bowing
that might occur.
Step Three:
The recommended hardware that should
be used are: M3 or M4 (#4-40 or #6-32) stainless steel
screw, Bellville or Split Lock type washers, as well as a
Fiber insulated washer to insulate the screw head from
the heat sink.
Step Four:
Clean and prepare mounting surfaces with
either methanol, acetone or general use solvents.
Remove all burrs.
Step Five:
Apply a thin 0.05 mm (0.002 inch) layer of
Thermal grease to the hot side of the TEC's. Place the
TEC on the heat sink and rotate the TEC's back and
forth, squeezing out the excess thermal grease until
resistance is felt.
Revision: C
Page: 2 of 4
Preparing Surfaces
Surface preparation is important when using any of the
assembly methods. No matter which method is used,
the mounting surface should be flat to less than .003-
inch over the TEC mounting area. In addition, the
surface should be clean and free from oil, nicks and
burrs. When multiple TECs are placed in parallel,
thermally between common plates, the TEC thicknesses
should vary no more than .05 mm (.002-inch).
Mounting with Adhesive Bonding
When to Use:
When you want to permanently attach the
TEC to your heat sink; When mounting with solder is not
an option; When the TECs need to be lapped to the
same height after mounting; When moderate thermal
Document Number: 017-0007
Step Six:
Repeat step 5, but for the cold side and rotate
cold plate back and forth, squeezing out the excess
thermal grease.
Step Seven:
In a two module system torque the middle
screw first.
Be careful to apply torque in small
increments, alternating between screws. In general,
apply 1034 kPa (150 psi) force to the TEC area.
Step Two:
With a soldering iron and a new tip, pre-tin
the bottom of the TEC (the side with lead wires) using
Solder In52/Sn48 (117°C) and General Purpose Hallide
Free Flux with an activity of ORHO or less. Use small
amounts. You can heat the soldering iron up to a
maximum of 150°C.
CAUTION:
Do not mix solders. Use a separate
soldering iron (or a new tip) for each solder.
Step Three:
With soldering iron, pre-tin the header or
heat sink with the same solder and flux as used in pre-
tinning the TEC. Use small amounts.
Step Four:
To minimize flux residue, clean both the
header and TEC. Rinse them first in hot water, brushing
away any excess flux residue. Finally, wash with IPA
and use forced air to blow dry.
Step Five:
Prior to mounting the TEC to the header,
add a small amount of Flux as identified in Step 2 to the
mounting site on the header.
Step Six:
Hold TEC with tweezers and align on header.
While doing this, maintain a steady, downward pressure.
Step Seven:
While holding the TEC in place, put the
soldering iron to the header near the solder seam.
When the solder junction flows, remove the soldering
iron. The downward pressure on the TEC will expel
excess solder.
REMEMBER:
If the solder which holds the TEC
together flows at 138°C, and you are using the 117°C
solder do not leave the soldering iron on the header
surface too long, or you will melt the TEC solder as well.
NOTE: Graphite pads may also be used as a thermal
interface and require a higher clamping pressure
depending on system set up. Please check thermal
interface manufacturer instructions.
Step Eight:
Continue holding the TEC in place until the
solder solidifies.
Step Nine:
Check along all four edges of the TEC,
looking for voids, cracks or bubbles. A smooth seam
insures that there will be proper thermal conduction.
Mounting with Solder
When to Use:
When you need minimal outgassing;
When the TEC is smaller than 19 mm; When you need a
high-strength junction; when high thermal conductivity is
required.
IMPORTANT:
The device to which the TEC is being
soldered should be placed on a heated surface. This will
allow the device to become hot enough to reflow the
solder. The device may be placed on a hot plate set at
100°C to help heat it to the solder melting point.
Step One:
Clean the surfaces to be soldered with
methanol, acetone or a general use solvent, removing
oils and residues which would prevent soldering.
Document Number: 017-0007
Connecting Lead Wire to Header
Step One:
Trim the excess wire from the TEC. Wrap
the lead wires 3/4 of a turn around the connector posts
on the header.
Step Two:
Using solder and a Hallide Free Flux, solder
the lead wires to the wire posts. You should be able to
see outlines of the wires, but they should be well
covered. Wick off any excess solder with the soldering
iron.
Revision: C
Page: 3 of 4
Final Cleaning and Inspection
Step One:
Rinse both the header and TEC in hot water,
brushing away any excess flux residue around the pins.
Wash with hot water and dry with forced air. To insure
complete removal of moisture, dry the entire assembly in
an oven for 30 minutes at 60°C. If an oven is not
available, forced-air should be adequate.
Step Three:
Check the solder joints, looking for cracks
or bubbles.
Preventing Problems
1. Do not use excessive amounts of solder. This
can short the power leads and/or inhibit a good
thermal interface.
2. Use the proper solder and flux activity.
3. Be sure to clean the TEC thoroughly to prevent
outgassing.
4. Do not overheat the TEC with the soldering iron.
Because of the narrow temperature differential
between the mounting solder (117°C) and the
solder used in the TEC (138°C), care must be
taken not to overheat the TEC and reflow the
solder.
5. During soldering, be sure the surface on which
the soldering is being done is composed of a low
thermal conductivity material. This will prevent
the solder iron heat from being drawn away,
which can cause difficulties with reflowing the
solder.
6. When pre-tinning a large area of the TEC, pre-
tin in small sections or buy the coolers pretinned
by II-VI Marlow.
7. If a TEC is being soldered to a large header, it
may require that the header be placed on a
100°C hot plate.
This will minimize heat
conduction away from the solder joint.
For further information or assistance, contact:
Marlow Industries, Inc.
10451 Vista Park Road
Dallas, TX 75238-1645
214-340-4900 (tel)
214-341-5212 (fax)
www.marlow.com
Document Number: 017-0007
Revision: C
Page: 4 of 4
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