Encapsulated Image Sensor Housing With Outward Glue Degassing
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Solution Overview
Problem
Hermetic electronic component housings in aerospace applications face issues with gas condensation on transparent windows due to degassing of materials during thermal cycles, leading to reliability and production concerns, as existing measures to limit gas release are insufficient.
Innovation Solution
A modified relief structure on the upper surface of the housing peripheral wall isolates the glue bead from the interior cavity and exposes it to the exterior atmosphere, forcing degassing of the closing glue towards the outside, thereby preventing gas condensation on the internal window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bead of sealing adhesive is used to hermetically seal the closure plate to the housing wall, then hermetic sealing is achieved, but gas molecules are released during thermal cycles causing condensation on the transparent window
Solution Approach 1:
The harmful function of the adhesive (gas release into cavity) is extracted by creating a dedicated vent path. The adhesive bead is configured with its outer surface exposed to the external environment, allowing gas molecules to escape outward rather than condensing on the transparent window. This separates the sealing function from the gas containment function.
Solution Approach 2:
The adhesive bead's outer surface acts as an intermediary interface between the adhesive material and the external atmosphere. This intermediate surface provides a controlled pathway for gas release, mediating between the hermetic sealing requirement and the gas venting requirement without compromising either function.
2Reliability
If the adhesive bead is placed between the closure plate and housing wall for sealing, then hermetic seal is formed, but the adhesive surface is trapped inside the housing exposing gas to the transparent window
Solution Approach 1:
The adhesive bead configuration transitions from a fully internal placement to a partially external exposure. By allowing the outer surface of the adhesive bead to be accessible from the external environment, a new spatial dimension is created for gas venting, separating the gas release pathway from the optical path to the transparent window.
3Productivity
If standard degassing measures are implemented before sealing, then some gas is removed, but insufficient gas release prevention occurs during thermal cycles
Solution Approach 1:
The adhesive bead is pre-configured with an external exposure surface before the hermetic sealing process. This preliminary structural arrangement ensures that during subsequent thermal cycles, gas molecules have a predetermined escape route, eliminating the need for complex active degassing systems while maintaining reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively reduces the presence of gas condensates on the transparent window, enhancing the reliability and longevity of hermetic electronic components by ensuring that degassing occurs externally, thus preventing the formation of stains and maintaining the component's operational integrity.
Implementation Method 1
the outer surface of the bead of adhesive is exposed to an external atmosphere of the housing, so that gaseous species can escape from inside the housing to the outside through this outer surface of the adhesive bead
Implementation Method 2
The upper surface of the peripheral wall has a relief such that the glue bead is isolated on the inner side of the cavity, and on the outer side of the housing, presents a surface for exchange with the external atmosphere of the housing
Data Source
Figure 1~3
Figure 4~6
Figure 7~8
AI summary
In a hermetically sealed integrated circuit package, the peripheral wall that delimits the cavity 2 containing the integrated circuit has a surface with a relief defined by a raised flat area z1 along the entire length of the peripheral wall, on the inner side of the cavity package, and a stepped area z2 outside the raised flat area. The flat area is in direct contact with the package's closing plate 6, without the interposition of adhesive, along the entire length of the peripheral wall, except where flatness defects prevent contact. The stepped area is not in direct contact with the closing plate and contains an adhesive bead that connects the closing plate and the upper part of the peripheral wall along its entire peripheral length. The adhesive bead 9 has an exposed surface Se between the closing plate and the stepped area, on the outer side of the package.This surface serves as an exchange surface with the external atmosphere of the casing, in case of glue outgassing.