Abstract A silver metallizing paste for attachment of silicon semi-conductive devices in lead-frame packages, specifically ceramic packages, which is less expensive than a gold preform but useable in hermetic packages, and provides better electrical and thermal conductivity, and higher bond strength, than silver polyimides. From 25 to 95% of silver is blended with a low-melting glass, preferably one having 95-96% PbO, and a paste or ink is formed with a suitable vehicle at 75-85% solids. Use of the paste follows conventional practice. Selection of Ag:glass ratio depends on the type of die bonding to be used. The paste is particularly useful in MOS technology, where low contact resistance is required, and also finds applications as a solder substitute and bonding chip capacitors. It is most advantageous in attachment of larger-area integrated circuits in that stress cracking associated with the gold-silicon eutectic is avoided.
An electronic assembly comprising: a ceramic substrate; a semiconductive device attached to said substrate by a bond; said bond being a silver-filled glass consisting essentially of: 25 to 95% of silver powder; and 75 to 5% of a high-lead borosilicate substantially soduim-free glass having a softening temperature in the range of 325° to 425° C., and a coefficient of thermal expansion no higher than about 13 ppm/°C.
Claim 2
Dependent Claim
67 words
An electronic assembly comprising: a ceramic substrate; a semiconductive device attached to said substrate by a bond; said bond being a silver-filled glass consisting essentially of: 25 to 95% of silver powder; and 75 to 5% of a high-lead borosilicate substantially soduim-free glass having a softening temperature in the range of 325° to 425° C., and a coefficient of thermal expansion no higher than about 13 ppm/°C.
Claim 3
Dependent Claim
24 words
The electronic assembly as claimed in claim 1, wherein said semiconductive device is selected from the group consisting of silicon devices and chip capacitors.
Claim 4
Dependent Claim
18 words
The electronic assembly as claimed in claim 1 wherein said glass has a silver-to-glass ratio of about 80:20.
Claim 5
Dependent Claim
51 words
The electronic assembly as claimed in claim 1, wherein a portion of the silver in said glass is replaced by a metal selected from the group consisting of nickel, tin and copper, up to the following limits: ______________________________________
Ni up to 10%;
Sn up to 60%;
Cu up to 20%.
______________________________________
Claim 6
Dependent Claim
23 words
The electronic assembly as claimed in claim 1, wherein said glass consists essentially of: ______________________________________
PbO 95-96%
SiO.sub.2 0.5-2.5%
B.sub.3 O.sub.3
remainder
______________________________________
Claim 7
Dependent Claim
21 words
The electronic assembly as claimed in claim 1, and additionally comprising a conductive metallized layer between said substrate and said bond.