LOCTITE 3873
Harmonization Code : 3506.10.00.00 | Prepared glues and other prepared adhesives, not elsewhere specified or included; products suitable for use as glues or adhesives, put up for retail sale as glues or adhesives, not exceeding a net weight of 1 kg
Main features
- Controlled 0.127 mm Thermal Bondline
- Thermally Conductive Permanent Attachment
- Activator-Cure Power-Device Bonding
Product Description
LOCTITE 3873 uses a one-part, high-viscosity acrylic ester formulation with 0.127 mm glass spheres to create a controlled thermal bondline. It cures with separately applied LOCTITE Activator 7387 and develops a high-modulus thermoset bond for power-device attachment. Typical cured thermal conductivity is 1.25 W/(m K), with Shore D 72 hardness and a 49 deg C glass transition temperature under the stated cure conditions. The self-shimming format is suited to bonding heat-generating devices to thermal spreaders where controlled bondline thickness and permanent attachment are required.
Key features
- Controlled 0.127 mm Bondline: Solid glass spheres establish the self-shimming bondline thickness.
- Thermally Conductive Attachment: Typical cured thermal conductivity is 1.25 W/(m K).
- Activator-Cure Power Bonding: LOCTITE Activator 7387 initiates cure for power-device attachment.
Applications
Applications include bonding heat-generating and power devices to thermal spreaders or similar heat-management structures.
TDS, SDS & Technical Documents
Technical Specifications
General Properties
Appearance
Light grey opaque thixotropic fluid with no visible bubbles
Appearance at room temperature.
Chemistry Type
Acrylic ester
Specific Gravity
2.08
Specific gravity (SG) is the ratio of the density of a substance to the density of a reference substance; equivalently, it is the ratio of the mass of a substance to the mass of a reference substance for the same given volume.
For liquids, the reference substance is almost always water (1), while for gases, it is air (1.18) at room temperature. Specific gravity is unitless.
Physical Properties
Viscosity
750,000 to 2,000,000 mPa.s
Viscosity is a measurement of a fluid’s resistance to flow.
Viscosity is commonly measured in centiPoise (cP). One cP is defined as
the viscosity of water and all other viscosities are derived from this base. MPa is another common unit with a 1:1 conversion to cP.
A product like honey would have a much higher viscosity -around 10,000 cPs-
compared to water. As a result, honey would flow much slower out of a tipped glass than
water would.
The viscosity of a material can be decreased with an increase in temperature in
order to better suit an application
Other Properties
Storage Temperature
2°C to 8 °C
Thermal Properties
Glass Transition Temperature (Tg)
49 °C
The glass transition temperature for organic adhesives is a temperature region where the polymers change from glassy and brittle to soft and rubbery. Increasing the temperature further continues the softening process as the viscosity drops too. Temperatures between the glass transition temperature and below the decomposition point of the adhesive are the best region for bonding.
The glass-transition temperature Tg of a material characterizes the range of temperatures over which this glass transition occurs.
Thermal Conductivity
1.25 W/m.K
Thermal conductivity describes the ability of a material to conduct heat. It is required by power packages in order to dissipate heat and maintain stable electrical performance.
Thermal conductivity units are [W/(m K)] in the SI system and [Btu/(hr ft °F)] in the Imperial system.
Mechanical Properties
Elongation
3.2 %
Elongation is the process of lengthening something.
It is a percentage that measures the initial, unstressed, length compared to the length of the material right before it breaks.
It is commonly referred to as Ultimate Elongation or Tensile Elongation at break.
Electrical Properties
Volume Resistivity
4.3×10¹⁴ Ohms⋅cm
Volume resistivity, also called volume resistance, bulk resistance or bulk resistivity is a thickness dependent measurement of the resistivity of a material perpendicular to the plane of the surface.
Additional Information
Technical properties
As-Supplied Properties
| Property | Value | Unit | Method / condition |
|---|---|---|---|
| Appearance | Light grey opaque thixotropic fluid with no visible bubbles | - | Uncured |
| Specific gravity | 2.08 | - | 25 deg C |
| Viscosity | 750,000 to 2,000,000 | mPa s | Brookfield HBT, spindle TB, 0.5 rpm, helipath, 25 deg C |
| Viscosity | 200,000 to 600,000 | mPa s | Brookfield HBT, spindle TB, 5.0 rpm, helipath, 25 deg C |
| Spacer sphere diameter | 0.127 | mm | Solid glass spheres |
Technical properties
Final-State Properties
| Property | Value | Unit | Method / condition |
|---|---|---|---|
| Coefficient of thermal expansion | 76 x 10^-6 | K^-1 | ISO 11359-2; cured 24 h at 70 deg C, then 2 days at room temperature |
| Glass transition temperature | 49 | deg C | Cured 24 h at 70 deg C, then 2 days at room temperature |
| Thermal conductivity | 1.25 | W/(m K) | ISO 8302; cured 24 h at 70 deg C, then 7 days at room temperature |
| Hardness | 72 | Shore D | ISO 868; cured 24 h at 70 deg C, then 7 days at room temperature |
| Elongation at break | 3.2 | % | ISO 527-3; cured 24 h at 70 deg C, then 7 days at room temperature |
| Tensile strength at break | 9.7 | N/mm^2 | ISO 527-3; cured 24 h at 70 deg C, then 7 days at room temperature |
| Young's modulus | 850 | N/mm^2 | Cured 24 h at 70 deg C, then 7 days at room temperature |
| Dielectric breakdown strength | 23.62 | kV/mm | IEC 60243-1; cured at room temperature |
