2. Field of Invention:

The present invention is related to industrial applications and especially bonding of Silicone composite gaskets on Aluminium alloy surfaces in order to maintain required electrical continuity between the components in the avionics systems.
3. Background of Invention:

Silicone composite gasket is the combination of insulating silicone elastomer and conducting silicone elastomer, which are laid up side by side in order to maintain conductivity from inside conductive silicone elastomer portion and insulation from outside insulating silicone elastomer portion, which are to be over molded for maintaining perfect bonding with Aluminium alloy surfaces to maintain required electrical continuity, but which are required expensive tools and special facilities. For ease of manufacturing, adhesives such as Bakelite silver filled and Epoxy silver filled were tried to bond the composite gasket on Aluminium alloy surfaces, which are not resisting environmental testing effects.
4. Brief Summary of Invention:

In order to address the above issue, RTV (Room temperature vulcanization) Silicone conductive adhesive was developed to bond silicone composite gasket on Aluminium alloy surfaces.
5. Brief description of Drawings:

Silicone composite gasket is fixed on Aluminium alloy panels to maintain electrical continuity at inside surface and insulation at outside surface in avionics system.

A typical assembly for composite gasket bonding on Aluminium alloy panel is shown in Fig-1 with components are being used, in that, '1', '2' and '3' indicate Aluminium alloy panel, Conductive silicone elastomer and Insulating silicone elastomer respectively. '2' and '3' are laid up side by side as gasket in order to maintain conductivity from inside conductive silicone portion and insulation from outside insulating silicone portion, which is fixed on '1' by applying thin layer of RTV silicone conductive adhesive.

Step by step application process is mentioned in Fig-2 for RTV Silicone conductive adhesive on Aluminium alloy panel surfaces.
6. Detailed description of invention:

A. Preparation of RTV Silicone conductive adhesive:

Prepare the RTV Silicone conductive adhesive by the following contents in order to maintain electrical conductivity.

Composition to make 12 gm of RTV Silicone conductive adhesive:

Dow corning 3145 RTV silicone adhesive (RSA) .: 10 gm

Silver Powder 99.9% purity (Ag) : 2gm

Ratio RSA:Ag :: 5:1 in weight

Mix up thoroughly the components at room temperature for preparing RTV Silicone conductive adhesive; it cures in 8 hours after application.

Note: The RTV Silicone conductive adhesive after preparation has to be applied within 10 minutes (pot life).
B. Properties of RTV Silicone conductive adhesive:

Prepared RTV Silicone conductive adhesive electrical conductivity is improved due to addition of silver powder, its contact resistance between 0.7mQ and l.Smfi (milli ohm) after curing. It resists environmental testing effects such as 16 thermal cycles at temperatures -30°C to 70°C for an hour, and also resists 3 axis sine over random vibration cycles at 7.2 Kg system unit weight with 6g acceleration for 15 minutes in each axis.
C. Application of RTV Silicone conductive adhesive:

Step by step application process is mentioned in Fig-2 for RTV Silicone

conductive adhesive on Aluminium alloy panel surfaces is given below by

considering typical component as a panel.

i. Emery/abrade on the Aluminium alloy panel surface, which area to be stuck.

ii. Clean and wipe the abraded surfaces with solvent using soaked cotton.

iii. Apply thin layer of prepared RTV Silicone conductive adhesive on the panel surface.

iv. Bond the composite gasket on the panel surface at room temperature.

v. Apply uniform pressure (approximately 10 gm/cmz) on the bonded gasket to bond firmly on the metal surface cure at room temperature. If the no separation between the gasket and metal surface, no need to apply the weight or pressure.

vi. Remove and clean the excess adhesive if any glue is smeared on the surfaces. Use clean cloth.