September 21, 2026
DOWSIL™ EA-9189 H is a one-part, white, alkoxy-cure room-temperature-vulcanizing (RTV) silicone adhesive from Dow. Unlike products that require mixing, heating, or rely on acetic acid-cure systems, EA-9189 H requires no mixing and no heating. It cures at room temperature simply upon exposure to ambient moisture, without exothermic heat or added solvents during cure. This feature offers clear processing advantages in electronics manufacturing environments that demand high cleanliness and operational simplicity.
Chemically, the product is a mixture whose primary component is vinyltrimethoxysilane-modified aluminum hydroxide (53%–63%), which provides its thermal conductivity. The product uses a neutral alkoxy cure system that does not corrode copper, aluminum, or other metal substrates. It is suitable for corrosion-sensitive electronic devices and applications where acetic acid-cure one-part silicones cannot be used at room temperature.
| Parameter | Value |
|---|---|
| Appearance | White paste |
| Thermal Conductivity | 0.88 W/m·K |
| Density (Cured) | 1.68 g/cm³ |
| Tack-Free Time (25°C) | ~2 minutes |
| Tensile Strength | 576 psi (3.9 MPa) |
| Elongation | 32% |
| Durometer (Shore A) | 80 |
| Volume Resistivity | 3.3 * 10¹⁵ ohm·cm |
| Dielectric Strength | 28 kV/mm |
| UL Flammability | UL 94 V-0 |
| Operating Temperature | -45°C to +200°C |
These parameters reflect a balanced combination of thermal conductivity, electrical insulation, flame retardancy, and mechanical strength. The thermal conductivity of 0.88 W/m·K represents a moderate level among one-part RTV adhesives, sufficient for thermal management needs in power modules, LED lighting, and PCB component fixation. The UL 94 V-0 rating and volume resistivity of 3.3 * 10¹⁵ ohm·cm ensure suitability in safety-critical electronic assemblies.
Notably, the uncured product exhibits a non-flowing paste consistency, meaning it will not sag or run when applied to vertical or inclined surfaces, maintaining its shape until tack-free. This rheological property offers practical value in electronic assembly processes requiring precise dispensing in confined spaces.
In power module manufacturing, high-power transistors are typically bonded to aluminum heat sinks using a thermally conductive adhesive. The conventional approach relies on screws combined with thermal grease, but screw fastening creates localized stress concentrations, and thermal grease may pump out or dry out over time. EA-9189 H forms a flexible elastomeric bond after cure, serving both as structural fixation and a continuous heat conduction path. Its tack-free time of approximately 2 minutes at 25°C helps reduce production line waiting time.
If heat generated by LED chips during operation is not effectively dissipated, junction temperature rises, leading to lumen depreciation and reduced lifespan. EA-9189 H can be used to bond LED aluminum substrates to heat sinks, providing both a thermal conduction path and long-term durability through the weatherability and thermal aging resistance of the silicone elastomer. The product exhibits excellent primerless adhesion to common heat sink materials—lap shear strength reaches 327 psi on aluminum and 343 psi on copper.
For PCB systems containing open relays, unsealed motors, and other sensitive components, the low-volatile characteristics of EA-9189 H are particularly important. The release of low-molecular-weight siloxanes can cause contact contamination and electrical failure, and EA-9189 H mitigates this risk through controlled low-siloxane content. The product can be used to fix heavier components such as inductors and capacitors on PCBs, reducing vibration-induced stress on solder joints.
Background
A power module manufacturer had long used a screw-plus-thermal-pad solution to secure MOSFETs to aluminum heat sinks in its DC-DC converter product line. This solution had two problems: first, the screw fastening process was time-consuming and required additional torque control equipment; second, the interfacial thermal resistance of the thermal pad gradually increased over time, causing some products to exceed temperature rise limits in high-temperature aging tests.
Solution Adjustment
After evaluating several thermally conductive adhesives, the manufacturer selected DOWSIL™ EA-9189 H. The revised process was as follows: dispense EA-9189 H between the back of the MOSFET and the heat sink, maintain position with a locating fixture, wait about 2 minutes at room temperature until tack-free, and then proceed to the next process step. The cure process requires no heating, avoiding the effects of high temperature on surrounding plastic parts and solder joints.
Results
After switching solutions, the assembly process eliminated the screw fastening step, reducing per-unit assembly time. In subsequent high-temperature aging tests, samples bonded with EA-9189 H showed stable temperature rise and did not exhibit the interfacial thermal resistance degradation seen with the thermal pad solution. In addition, the UL 94 V-0 flame rating of EA-9189 H met the product’s safety certification requirements.
According to the Safety Data Sheet, DOWSIL™ EA-9189 H is classified as Reproductive Toxicity Category 1B, with the hazard statement “May damage fertility or the unborn child" (H360). The following precautions should be observed during use: obtain, read, and follow all safety instructions before use; use only outdoors or in a well-ventilated area; wear protective gloves, protective clothing, and eye/face protection; store locked up; and dispose of contents/container to an approved waste disposal plant.
For storage, the product should be stored in properly labeled containers, kept closed, and stored in accordance with national-specific regulations. Avoid co-storage with strong oxidizers, organic peroxides, and similar materials.
The core value of DOWSIL™ EA-9189 H lies in integrating thermal conductivity, structural bonding, and electrical insulation into a single-component, room-temperature-cure silicone system. For applications such as power modules, LED lighting, and PCB assembly where heat dissipation and fixation must be addressed simultaneously within limited space, the product offers a processing-friendly solution with balanced performance. Its UL 94 V-0 flame rating, good primerless adhesion, and low-volatile compatibility with sensitive components make it a noteworthy thermally conductive adhesive material in electronics manufacturing.
