Bonding Frits For Near-Zero And Negative Expansion Substrates

Several frit systems were developed and characterized for bonding to materials with negative, or near-zero coefficient of thermal expanison (CTE). The basis of each system is a low temperature base glass (Tg=300-325 deg C), to which one or more fillers are added to lower overall CTE. The base glasses employed were selected from the Sn0-Zn0-P205 and Pb0-Zn0-B203 systems. The major filler used was a crystalline Co-Mg pyrophosphate, which is capable of undergoing a controlled phase inversion with an associated volume change. The expansion compatibility of the frits with fused silica was characterized by polarimetric measurement of expansion mismatch versus temperature using a butt seal test sample.