Embedded structures for high glass strength and robust packaging
View Patent ↗A sensor device is constructed to maintain a high glass strength to avoid the glass failure at low burst pressure, resulting from the sawing defects located in the critical high stress area of the glass pedestal as one of the materials used for construction of the sensor. This is achieved by forming polished recess structures in the critical high stress areas of the sawing street area. The sensor device is also constructed to have a robust bonding with the die attach material by creating a plurality of micro-posts on the mounting surface of the glass pedestal.
1. An apparatus, comprising:
a pressure sensing element;
a pedestal having an aperture;
a first bonding interface, the pressure sensing element bonded to the pedestal at the first bonding interface;
a cavity formed as part of the pressure sensing element;
a cap bonded to the pressure sensing element at a second bonding interface;
a cavity formed as part of the cap; and
a plurality of polished smooth areas, a portion of the plurality of polished smooth areas formed as part of the pressure sensing element adjacent the bonding interface prior to the pressure sensing element and the pedestal being partitioned from a wafer stack, and a portion of the plurality of polished smooth areas formed as part of the pedestal adjacent the bonding interface prior to the pressure sensing element and the pedestal being partitioned from the wafer stack;
wherein a portion of the pressure sensing element deflects when pressure is applied to the pressure sensing element in the cavity from the aperture.
2. The apparatus of claim 1 , the plurality of polished smooth areas further comprising:
at least one angled polished smooth area formed as part of the pressure sensing element adjacent the first bonding interface;
at least one upper polished smooth area formed as part of the pedestal adjacent the first bonding interface; and
at least one lower polished smooth area formed as part of the pedestal;
wherein the at least one angled polished smooth area and the at least one upper polished smooth area reduce the stress concentration in proximity to the first bonding interface, and the at least one lower polished smooth area reduces stress concentration in the pedestal when the pedestal is connected to a housing substrate.
3. The apparatus of claim 2 , further comprising:
a plurality of rough areas, at least one of the plurality of rough areas formed as part of the pressure sensing element adjacent the at least one angled polished smooth area, and at least one of the plurality of rough areas formed as part of the pedestal adjacent the at least one upper polished smooth area;
wherein the plurality of rough areas are formed when the pressure sensing element and the pedestal are partitioned from the wafer stack.
4. The apparatus of claim 3 , the plurality of rough areas further comprising:
a first rough area formed as part of the pressure sensing element adjacent the at least one angled polished smooth area;
a second rough area formed as part of the pedestal adjacent the at least one upper polished smooth area and the at least one lower polished smooth area;
wherein the first rough area and the second rough area are formed during a partitioning process, when the pressure sensor is partitioned from the wafer stack.
5. The apparatus of claim 2 , the plurality of polished smooth areas further comprising:
at least one outer polished smooth area formed as part of the cap in proximity to the second bonding interface;
wherein the at least one outer polished smooth area formed as part of the cap reduces thermal stress and bending stress at the second bonding interface.
6. The apparatus of claim 5 , further comprising:
at least one outer rough area formed as part of the cap in proximity to the at least one outer polished smooth area;
wherein the at least one outer rough area is formed during the partitioning process, when the pressure sensor is partitioned from a wafer stack.
7. The apparatus of claim 2 , further comprising:
a plurality of micro-posts formed as part of the pedestal; and
at least one venting area formed as part of the pedestal in proximity to the plurality of micro-posts;
wherein air and vapor are vented around the plurality of micro-posts and out of the venting area as the pedestal is bonded to the housing substrate with a mounting material.