“We clearly specified low-volatility silicone oil — but after one week of aging at 85°C, the potting compound cracked!”
An electronics packaging manufacturer traced the failure to a raw material mix-up: the supplier delivered low-viscosity silicone oil instead of low-volatility silicone oil. Though the terms sound similar, they represent fundamentally different molecular structures and performance characteristics.
This kind of terminology confusion is common — and costly.
In electronic devices such as LED modules, power supplies, and sensors, silicone oil volatilization under long-term heat exposure can lead to material shrinkage and cracking. Worse, evaporated siloxanes may condense onto optical components, forming haze that reduces light output or causes signal distortion.
The critical differences:
Low viscosity (e.g., 50 cSt): Achieved through low molecular weight. Excellent flowability — but inherently higher volatility.
Low volatility: Achieved through higher molecular weight and narrow molecular weight distribution. Even at moderate viscosity (e.g., 1000 cSt), the material can remain thermally stable.
The true gold standard for defining “low volatility” is thermal weight loss testing — typically 150°C for 3 hours (or similar conditions).
Industry benchmarks commonly require:
Volatile content ≤ 1%
Automotive-grade applications may demand ≤ 0.5%
By comparison, ordinary industrial silicone oils often show 3–8% weight loss under these conditions — far above acceptable limits.
“Many customers focus only on viscosity charts and overlook the ‘volatile content’ data in the COA,” an application engineer admitted. “We once helped a client switch from a ‘50 cSt low-viscosity’ oil to a ‘1000 cSt low-volatility’ grade. Although viscosity increased, the longer and more uniform molecular chains improved dispersion within the encapsulation system and significantly enhanced long-term reliability.”
For electronics applications, we recommend clarifying three key points during procurement:
Do not simply request “low viscosity.” Specify ‘Volatile content < 1% at 150°C for 3 hours.’
Request thermogravimetric analysis (TGA) or standardized oven-test reports.
Prioritize high-purity linear silicone oils that have undergone deep devolatilization and contain no residual cyclic siloxanes such as D4/D5.
As a manufacturer focused on electronic-grade silicone oils, all our low-volatility products are tested according to international standards such as IEC 60216 or ASTM E1131. We also support customized molecular weight distribution design to balance flowability and thermal stability.
In electronic encapsulation, the greatest risks are often the ones you cannot see — volatility is one of them.
