Silver thick film paste hermetically sealed by surface thin film multilayer

A ceramic substrate comprising:

• a plurality of ceramic sheets stacked one on top of another, the ceramic sheets including a top ceramic sheet;
• a plurality of inner conductive layers forming electrically conductive features on an upper surface of each ceramic sheet excluding the top ceramic sheet, each inner conductive layer formed from electrically conductive material;
• a plurality of vias formed in each of the ceramic sheets, each via filled with electrically conductive material;
• a plurality of caps positioned on the upper surface of the top ceramic sheet, each cap formed from electrically conductive material and covering one via in the top ceramic sheet;
• and
• an upper conductive layer forming electrically conductive features on an upper surface of the top ceramic sheet, the upper conductive layer constructed from a stack of sublayers including a first sublayer formed from titanium, a second sublayer formed from copper, a third sublayer formed from platinum, and a fourth sublayer formed from gold, wherein the first sublayer contacts the upper surface of the top ceramic sheet and hermetically seals the caps in the top ceramic sheet and the fourth sublayer is configured to receive electrical connectors from electronic circuitry placed on the ceramic substrate.

A ceramic substrate comprising:

• a plurality of ceramic sheets stacked one on top of another, the ceramic sheets including a top ceramic sheet;
• a plurality of inner conductive layers forming electrically conductive features on an upper surface of each ceramic sheet excluding the top ceramic sheet, each inner conductive layer formed from electrically conductive material;
• a plurality of vias formed in each of the ceramic sheets, each via filled with electrically conductive material;
• a plurality of caps positioned on the upper surface of the top ceramic sheet, each cap formed from electrically conductive material and covering one via in the top ceramic sheet;
• and
• an upper conductive layer forming electrically conductive features on an upper surface of the top ceramic sheet, the upper conductive layer constructed from a stack of sublayers including:
• a first sublayer formed from titanium having a thickness ranging from 0 micrometers (μm) to approximately 0.4 μm,
• a second sublayer formed from copper having a thickness ranging from 1 μm to approximately 18 μm,
• a third sublayer formed from platinum having a thickness ranging from 1 μm to approximately 4 μm, and
• a fourth sublayer formed from gold having a thickness ranging from 0.1 μm to approximately 0.5 μm,
• wherein the first sublayer contacts the upper surface of the top ceramic sheet and hermetically seals the caps in the top ceramic sheet and the fourth sublayer is configured to receive electrical connectors from electronic circuitry placed on the ceramic substrate.