Open Cavity Sensor Package Without Flow-Blocking Metal Protrusions
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Solution Overview
Problem
Semiconductor sensing packages with metal walls having horizontal protrusions obstruct ingress and egress, leading to reduced flow rates and inaccurate measurements, and pose difficulties in photoresist removal during manufacturing.
Innovation Solution
A semiconductor package design featuring a metal wall with a 'half-mushroom' shape, where the upper portion has varying thicknesses and a notch to prevent horizontal protrusions, allowing free access to the sensor and easy photoresist removal, manufactured using a method involving photolithography and electroplating to create a hollow cavity aligned with the sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal walls are designed with horizontal protrusions to provide structural support, then structural strength is improved, but ingress and egress to the sensor are obstructed leading to reduced flow rates and inaccurate measurements
Solution Approach 1:
The harmful horizontal protrusions are completely removed from the metal wall structure. The patent replaces the traditional mushroom-shaped metal wall with a simplified cylindrical or conical structure that eliminates the protruding portions while maintaining the hollow cavity configuration, thereby removing the obstruction to material flow while preserving structural integrity
Solution Approach 2:
The metal wall is designed with asymmetric thickness distribution, featuring varying wall thicknesses around its circumference. This asymmetric design allows the wall to maintain structural strength in critical areas while creating open pathways and eliminating horizontal protrusions in other areas, thus resolving the contradiction between strength and flow rate
2Stability of the object's composition
If metal walls are designed with horizontal protrusions to maintain structural integrity, then structural stability is improved, but photoresist removal during manufacturing becomes difficult
Solution Approach 1:
The horizontal protrusions that trap photoresist are completely extracted from the metal wall design. By adopting a smooth cylindrical or conical shape without protruding features, the patent eliminates the areas where photoresist would become trapped, making removal straightforward while maintaining structural stability through alternative design features
Solution Approach 2:
Instead of adding protrusions to provide structural support, the patent inverts the approach by using recesses and varying wall thicknesses to achieve the same structural stability. The hollow cavity configuration with asymmetric wall thickness provides structural integrity without the need for outward protrusions that would complicate manufacturing
3Ease of manufacture
If metal walls are designed with varying thicknesses to prevent horizontal protrusions, then ease of photoresist removal is improved, but manufacturing precision requirements increase
Solution Approach 1:
The metal wall is designed with locally varied thicknesses, where different sections of the wall have different thickness values. This local quality variation allows the structure to maintain adequate strength and stability while eliminating horizontal protrusions. The thickness varies smoothly in specific local areas rather than uniformly throughout, making the design both manufacturable and functionally effective
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
Ensures unobstructed ingress and egress of materials to the sensor, improving measurement accuracy and simplifying the manufacturing process by eliminating horizontal protrusions and ensuring proper retention of the mold compound.
Implementation Method 1
using a photolithography reticle mask to alter the photoresist layer to form a first photoresist member
Implementation Method 2
plating a metal member having lower and upper portions, the lower portion filling the circular gap
Data Source
AI summary
In examples, a semiconductor package comprises a semiconductor die including a device side having circuitry formed therein. The device side includes a sensor. The package includes a metal member creating a hollow cavity extending through the metal member, the hollow cavity vertically aligned with the sensor, the metal member including a lower portion having a first wall thickness and an upper portion having varying wall thicknesses greater than and less than the first wall thickness, an intersection of the upper and lower portions forming a notch on an outer side of the metal member opposing the hollow cavity. The package also includes a mold compound covering portions of the semiconductor die and contacting the metal member.