Study of silver–palladium thick film conductor for metallisation of aluminium nitride substrate

Abstract

conductivity 110-208 W m -1 K -1 (RT ); thermal expansion coeYcient 4•1Ö 10 -6 K -1 (from RT to around 400°C); T he processing of A g-20Pd thick lm metallisation volume resistivity 10 1 4 V cm; dielectric strength 15 kV conductors on A lN substrates has been investigated. mm -1 ; dielectric constant 8•7; bending strength 300 MPa. T he conductor lms performed almost as well on theSurface roughness R a was 0•405 mm. A lN substrate as on an Al 2 O 3 substrate. During sinter-A thick lm paste was prepared from the conductor ing, the glass f rit melts and ows towards the substrate, powders, additive agent powders, and organic vehicles. The while the A g-Pd powder sinters to form a porous chemical composition of the conductor was 80 wt-%Agstructure. A s a result an intricate physical bond forms 20 wt-%Pd. Most of the particles were 0•5 mm in diameter. between the A g-Pd conductor layer and the glass, andThe additive agent was a lead oxide glass frit. Table 1 lists the glass wets and bonds rmly to the A lN substrate.the major components and the physical properties of the In order to achieve this microstructure at the conductor/ glass powders. The composition of the glass frit was adjusted substrate interface, it is necessary for the glass to have so that its softening point changed over the range 300an optimum softening point ( 500-600°C) and to wet 700°C. The organic and inorganic constituents were blended the metal and the A lN substrate.BCT /526 at given ratios in order to provide a suitable rheology for screen printing. The rheology of the paste was maintained T he authors are in the Department of Materials at 10 Pa s. Science and Engineering, T singhua University,Screen printing was carried out on a printing machine,

Glass frit content—Property co-relation in thick films of photoimageable silver conductor paste

“…Thus, it was exposed to UV light source of 1000 W for 1 min through quartz negative photomask of desired pattern by contact printing [6]. The sample was then developed in 1% sodium carbonate (Na 2 CO 3 ) solution so as to remove the unexposed part [7]. Development was followed by firing the 'green'; pattern in a standard four-zone firing furnace (BTU Model-TFF51-4-36N26GT) having peak firing temperature of 850 • C for 10 min [7].…”