Sandoz Building Material Ltd.

SANDOZ produces a great variety of silver-based pastes for the sector of automotive glasses. Our products are used for the production of interior rear view mirrors, tempered-glass laminated windows and windshields for supplementary alarm, radio aerials and defrost systems. Our comprehensive range of glass enamels for automotive use includes unleaded conductive silver pastes.

n recent years automobile manufacturers have offered as optional equipment rear windows which can be defrosted and/or defogged by use of an electrically conductive grid permanently attached to the window. In order to defrost quickly, the circuit must be capable of supplying large amounts of power from a low voltage power source, for example 12 volts. Furthermore, the lines of the conductive grid must be sufficiently narrow in order to maintain visibility through the rear window.

The resistance requirements of conductive patterns is on the order of 2 to 15 milliohms per square, which requirements are easily met by noble metal conductors, particularly silver, which is currently the most widely used conductor material in this application.

Heretofore, the materials used for the preparation of window defogging grids have mostly been thick film silver conductors which are prepared from paste comprising finely divided silver powder particles and glass frit dispersed in an organic medium. In a typical application, a paste containing by weight 70% silver powder, 5% glass frit and 25% organic medium is screen printed through a 180 Standard Mesh Screen onto a flat, unformed glass rear window. The printed composition is dried for at least 2 minutes at about 150 C. and the entire element is then fired in air from 2 to 5 minutes at 650 C. After firing the softened glass is shaped by pressing into a mold and then tempered by rapidly cooling. During the firing cycle the organic medium is removed by evaporation and pyrolysis. The glass and silver are sintered to form a continuous conductive path with the glass acting as binder for the silver particles.

Silver Content(%)

80

75

70

65

60

Viscosity

6025 Pas( 10 rpm, 25C0.5C)

Fineness

<20m

Solid Content

822%

802%

782%

762%

722%

Printability Silk-screen

150~250 polyester screen

Leveling Time

at room temperature,2~3minutes

Drying

150~180C /( 3 minutes)

Firing

680~710C/>10 minutes

Film Thickness (m)

8-15m