Mounting with Thermal Conducting Adhesives

A Better Solution for Mounting Parts to the Heat Sink

Thermally conductive adhesives offer a new solution to replace traditional mechanical assembly. These adhesives allow for the permanent assembly of similar and dissimilar substrates and simplify the assembly procedure.

Advantages of thermal conducting adhesives:

  • Simple and reliable
  • Repeatable in production
  • Cost advantage over clip & screw
  • Improved reliability of power supplies
  • Applicable to a variety of packages

Typical Package Mounting Examples


Liquid adhesive

Double-sided tape

General Application Guidelines

When evaluating thermally conductive adhesive there are some basic attributes that need to be taken into account:

  1. Thermal conductivity
  2. Bond line thickness
  3. Adhesion strength
  4. Curing conditions
  5. Storage and shelf life

Adhesives with higher thermal conductivity offer better thermal performance. It is suggested to have a thermal conductivity in the range of 3-5 W/m-K.

A typical bond line is in the 2-7 mil thickness range. For improved thermal performance (lower Thermal Resistance), a thinner bond line is suggested. A thinner bond line can reduce the adhesion strength, so each application needs to be tested to find the correct balance between bond line thickness, thermal resistance and adhesion strength.

It's important to have a uniform bond line thickness for optimal adhesive performance. Good bonding strength is necessary when attaching the IC with the adhesive. A product with higher viscosity offers superior adhesion strength. Curing has to be done according to the data sheet recommendations. If the part does not get cured correctly, it can lead to higher thermal resistance of the assembly, resulting in poor thermal performance. It's also important to take into account the storage temperatures and shelf life specifications of the material selected.


Comparison of Double-Sided Tapes

Vendor MPN Tape Thickness (mm) Thermal Conductivity (W/m-K) Dielectric Strength (kV/mm) Adhesion Peel Strength (N/cm)
3M TM-670SA 0.25 0.6 24 5.5
3M TM-671SA 0.375 0.6 24 9.3
3M TM-672SA 0.5 0.6 24 11.6
3M 8805* 0.125 0.6 26 7.5
3M 8810* 0.25 0.6 26 13
3M 8815* 0.375 0.6 26 19
3M 8820* 0.5 0.6 26 26
*Operating temperature range: Short Term (Hours-Days) 125°C - 150°C; Long Term (Weeks-Months) 90°C - 100°C
  Shelf life: 2 years

Comparison of Liquid Adhesives

Vendor MPN Thermal Conductivity (W/m-K) Shelf life
(mos.)
Storage Temp. (°C) Dielectric Strength (kV/mm) Operating Temp. Range (°C) Curing Temp. (° C) Curing time (min)
Dow Corning DA-6534 6.8 4 -10 to -25 -40 to 200 150 120
DA-6524 2.1 6 -10 to-25 -40 to 200 150 60
TC-2030 2.6 12 <40 -40 to 200 130 60
Timtronics 813HTC 2.7 4 25 20.07 270 150 30
816HTC 2.7 24 25 16.53 150 25 2880
Aremco 556-HT-SP 3.5 6 25 230 177/149 60/120
Creative Materials 116-04A / B-187 2.63 12 20-25 18.7 100 30
122-07 (SP) 5.5 2 25 17.32 -55 to 230 150 60
109-12 5.65 1.5 25 19.48 121 240
Bergquist Company Hermitage 5 150/160 20/6
Springtime Blue 3 150/160 20/6

Mounting with Double-Sided Tape

1. Clean device back surface with alcohol


2. Clean heat sink surface with alcohol


3. Cut the tape according to required dimensions


4. Apply the tape to one substrate


5. Peel off the liner on other side



6. Attach the device to the heat sink and apply clamping pressure



Mounting with Liquid Adhesives

1. Clean device back surface with alcohol


2. Two part epoxy syringe


3. Two part epoxy (Part A & Part B)


4. Mix adhesive solution


5. Apply thin layer of adhesive



6. Attach device to heat sink with clamping pressure and allow sufficient time to cure



Effect of Adhesive to Thermal Resistance

The thermal conductive adhesives tend to affect the effective thermal resistance of heat sink assembly. Refer to the following table comparing the thermal resistance between junction of the device to the heat sink of different thermal conducting adhesives as compared to that mechanically mounted with the clip and screw with thermal grease. The thermal resistance of the device is calculated using the device junction temperatures, heat sink temperature and total power dissipated on the device.

Mounting Method
Device Thermal Resistance Thermal Grease with Mechanical Clip 8805
(Tape)
8810
(Tape)
Hermitage
(Epoxy)
Springtime Blue
(Epoxy)
816HTC
(Epoxy)
Thermal Resistance MOSFET Junction to Heat Sink (°C/W) 2.955 7.057 9.589 2.733 3.018 3.776
Thermal Resistance Diode Junction to Heat Sink (°C/W) 2.034 6.042 7.839 1.784 2.157 3.097

Recommended vendors:

Vendor Contact Information
Dow Corning Corporation Corporate Center
PO Box 994
MIDLAND MI 48686-0994
United States

General Inquiries/Reception
Direct Dial: +1 (989) 496-4400
Product/Price Related Inquiries
+1 (989) 496-7875
Toll Free: 1-800-248-2481
http://www.dowcorning.com

Timtronics 35 Old Dock Road
Yaphank, NY 11980 USA
+1 (631) 345-6509
info@timtronics.com
http://www.timtronics.com

Aremco Products Inc. 707 Executive Blvd.
Valley Cottage, NY 10989 USA
+1 (845) 268 0039
+1 (845) 268 0041 (FAX)
http://www.aremco.com

Creative Materials Inc. 12 Willow Road
Ayer, MA 01432 USA
Toll Free: 1-800.560.5667
+1 (978) 391-4705 (FAX)
International +1 (978) 391-4700
info@creativematerials.com
http://www.creativematerials.com

Bergquist Company Thermal Interface Material
18930 W. 78th Street
Chanhassen, MN 55317 USA
Toll-Free: (800) 347-4572
http://www.bergquistcompany.com

3M 3M Corporate Headquarters
3M Center
St. Paul, MN 55144-1000 USA
Toll-Free: 1-888-3M HELPS (1-888-364-3577)
http://solutions.3m.com