Cavity Package Vent Hole Geometry to Block Moisture Ingress
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Solution Overview
Problem
Integrated circuit packages with cavities face reliability issues due to the absence of ventilation holes, leading to overpressure, delamination, and pollution from water and particles, which can degrade optical performance and cause operational problems.
Innovation Solution
The integration of through holes with a flaring first portion in the cavity walls, where the cross-section at the first end is less than or equal to 35 micrometers, significantly reduces capillary forces, thereby minimizing the risk of external pollution, such as moisture, entering the cavity. These holes can extend through the entire thickness of the carrier substrate and may include a second portion that flares away, created using laser or mechanical drilling techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ventilation holes are provided in the cavity walls, then reliability is improved by preventing overpressure and delamination, but external pollution such as water and particles can enter the cavity through these holes
Solution Approach 1:
The through hole is designed with an asymmetric flared shape where the opening towards the cavity is larger than the opening towards the external environment. This asymmetric geometry creates a mechanical barrier that prevents external pollution from entering while allowing pressure equalization, thus resolving the contradiction between reliability and pollution prevention.
Solution Approach 2:
Instead of trying to block the hole completely to prevent pollution ingress, the invention inverts the approach by using the hole's geometry itself as a protective feature. The flared shape acts as a physical barrier that is easier to enter from the cavity side than from the external side, effectively using the ventilation opening as both a pressure relief path and a pollution barrier.
2Reliability
If the cross-section of the first portion is reduced to less than or equal to 35 micrometers, then capillary forces are reduced making them negligible compared to gravity, but the hole becomes more difficult to manufacture with precise dimensions
Solution Approach 1:
The invention replaces conventional mechanical drilling methods with laser drilling technology. This substitution enables precise control of the flared hole geometry with the specific cross-sectional dimension of less than or equal to 35 micrometers at the first end, achieving the required manufacturing precision that would be difficult to obtain with traditional mechanical tools.
Solution Approach 2:
The invention specifies a critical parameter threshold (cross-section dimension ≤ 35 micrometers) that changes the physical behavior of the system. By controlling this dimensional parameter, the capillary forces become negligible compared to gravitational forces, fundamentally changing the mechanism that prevents pollution ingress from a capillary-driven effect to a gravity-driven effect.
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 design effectively reduces or eliminates the risk of moisture and pollution entering the cavity, enhancing the reliability and performance of integrated circuit packages by balancing capillary forces with gravity, thus preventing condensation and oxidation of components.
Implementation Method 1
the capillary force becomes negligible due to the flaring effect of the first portion
Implementation Method 2
the capillary force becomes negligible due to the flaring effect of the first portion, in relation to the force of gravity
Data Source
AI summary
An integrated circuit package includes a cavity within which a circuit device is contained. At least one through hole is provided in at least one wall of the cavity. The at least one through hole includes at least one first portion flaring towards the cavity with a frustoconical shape, for example.