Dispensing RTV Silicone

Room Temperature Vulcanizing (RTV) Silicone

RTV silicone is a rubber that cures when exposed to air at room temperature. It is used as an adhesive sealant in automotive, consumer, industrial, avionics, aerospace, and military electronics RTV staking applications to ensure reliability.

What is RTV Staking?

RTV staking is a dispensing method that ruggedizes and protects electronic components. When you ruggedize something, you strengthen it to resist wear, stress, and abuse. Ruggedization is essential for electronics applications because it protects fragile electrical connections to ensure reliability when exposed to extreme temperatures, mechanical stress, shock, vibration, or wet and dusty conditions. Although a beneficial application, there are common challenges and a few things you should be aware of when dispensing RTV silicone. So read on.

RTV staking is beneficial for automotive, consumer, industrial, avionics, aerospace, military electronics, and more.

RTV Staking Applications a Brief Overview

Here are key details that you can expect to see when working with RTV staking applications:

RTV silicones are condensation-cure materials.
The cross-linking process begins when the material is exposed to humidity in ambient air. A curing oven is not required, with no added manufacturing cost or thermal cycles.

Thawing is not required.
Airtight ready-to-use ten-ounce cartridges and 5-gallon pails are standard, with automated production environments commonly using 5-gallon pails.

Slumping and flow-out are limited.
High viscosity ensures the material holds its shape, limiting slumping and flow-out.

RTV silicones do not shrink when cured.
Some flexibility is retained after cure, allowing the material to withstand mechanical and thermal stress without cracking or hardening.

RTV silicones must be applied quickly.
After being exposed to air, apply the material quickly to prevent it from curing in the needle tip.

Material thickness determines the cure time.
The cure time is directly related to the thickness of the material. Cross-linking and strengthening can continue for several days or 1-2 weeks.

RTV silicones are electrical insulators.
When cured, the material resists high temperatures.

Common Dispensing Challenges

Medium to high-viscosity RTV silicones are commonly used to ensure dispensed silicone stays in place, limiting slumping and flow-out. Although higher viscosities help to address those concerns, there are a couple of challenges:

Higher viscosity RTV silicones do not break off easily from the needle tip.
However, this can be managed using suck-back, thoughtful programming, and dispense settings to control break-off.

Fast cure and short “tack-free” times can lead to clogged needles.
The term “tack-free” is used to describe the condition of the material when it is completely dry with little or no moisture left after application. Fast curing materials achieve a “tack-free” state quickly. Fast curing is advantageous in some applications because it lowers the probability of dirt and other contaminants adhering to or being pushed into the surface of soft material. However, short “tack-free” time can lead to clogged needles during the dispensing process. Fortunately, you can address this by setting a purge timer to ensure the material does not cure in the needle during idle time.

Our Solutions

The Nordson Helios® SD-960 Series large-volume dispensing platform is ideal for dispensing RTV silicone. The Helios can efficiently address break-off and needle clogging concerns, and it delivers process control, easy programming, reduced material waste, angled dispensing, suck-back, and durable high-pressure dispensing.

Recommended Products
Helios SD-960 Series – single or batch-drawer
Rhino™ XD3 5-Gallon Pail Unloader
Tilt and Rotate for angled dispensing
DV-03HPA Dispense Valve