Interlocking Mold Package for Sensor Delamination
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Solution Overview
Problem
Mold packages used in sensor applications often delaminate at the interface with the sensor device, particularly in exposed-die packages, leading to reliability issues due to incomplete coverage, which is problematic for sensors interacting with their environment.
Innovation Solution
A trench-like structure is introduced on the substrate surface adjacent to the sensor area, providing an interlock feature that increases adhesion between the mold material and the substrate, configuring a predetermined exposed surface area for enhanced mechanical coupling and reducing delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an exposed-die package is used to allow direct environmental access for sensing, then the sensor can interact with the environment, but the mold-silicon interface is prone to delamination
Solution Approach 1:
The substrate surface is segmented into distinct regions: a sensor area that remains exposed for environmental interaction and a surrounding area that is covered by the mold package. This segmentation allows the sensor to access the environment while the mold covers the non-sensing portions for protection.
Solution Approach 2:
The solution moves from a two-dimensional planar interface between mold and substrate to a three-dimensional interlocking structure. Trenches are etched into the substrate surface, creating vertical walls that the mold material can flow into and lock onto, transforming a simple surface contact into a volumetric mechanical interlock.
2Object-affected harmful factors
If the entire substrate surface is covered by the mold package, then protection from environmental conditions is maximized, but the sensor cannot directly access the environment
Solution Approach 1:
Different regions of the substrate surface are treated differently: the sensor area is left exposed with a specific local quality for environmental interaction, while the surrounding areas are covered by the mold package for protection. This local differentiation allows each region to serve its specific function optimally.
3Reliability
If a trench-like interlock structure is introduced on the substrate surface, then adhesion between mold and substrate is increased, but the device complexity increases
Solution Approach 1:
The trenches are formed in the substrate surface before the mold packaging process. This preliminary action prepares the substrate with pre-formed interlocking features that will mechanically lock with the mold material during subsequent packaging, ensuring strong adhesion without requiring complex post-processing steps.
Data Source
Figure 1~2
Figure 3~5
Figure 6A~6B
AI summary
An electronic device includes a mold package which encapsulates a portion of the electronic device and does not encapsulate another portion of the electronic device to enable a sensing portion of the electronic device to be exposed to a condition to be sensed. In an electronic sensing device having a sensor formed by a substrate such as silicon, a sensor area is not encapsulated, but areas surrounding the sensor area are encapsulated. The area surrounding the sensor area includes one or more trenches or interlock structures formed in the surrounding substrate which receives the mold material to provide an interlock feature. The interlock feature reduces or substantially prevents the mold from delaminating at an interface of the mold and the substrate.