Thinned Flip-Chip Die with Cavity for Optical Sensors
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Solution Overview
Problem
The thick silicon handle layer in silicon on insulator (SOI) substrates used in flip-chip dies attenuates or obstructs light/thermal signals, leading to slow response and low efficiency of optical/thermal sensors, limiting their performance in detecting applications.
Innovation Solution
A microelectronics package design featuring a thinned flip-chip die with a device layer and integrated sensor structure, where the sensor is positioned below a first surface portion and not below a second surface portion, and a mold compound component is formed over the second surface portion to create a cavity, allowing for superior light/thermal signal detection without the obstruction of a silicon handle layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick silicon handle layer is used in SOI substrates for flip-chip dies, then the structural integrity and mechanical strength are improved, but the optical/thermal signal transmission is attenuated or obstructed, leading to slow response and low efficiency of sensors
Solution Approach 1:
The flip-chip die is divided into two distinct surface portions: a first surface portion without a silicon handle layer for optimal sensor signal transmission, and a second surface portion with a silicon handle layer for providing mechanical strength and structural support. This segmentation allows each region to fulfill its specific function without compromise.
Solution Approach 2:
The silicon handle layer is selectively removed from the first surface portion where sensors are located to optimize optical and thermal signal transmission, while being retained in the second surface portion to provide structural integrity. This local quality modification ensures that material presence is optimized for the specific functional requirements of each region.
2Reliability
If the silicon handle layer is completely removed to improve sensor performance, then the optical/thermal signal transmission is improved, but the mechanical strength and structural stability of the flip-chip die are compromised
Solution Approach 1:
The die is segmented into a sensor region (first surface portion) where the silicon handle layer is removed for optimal signal transmission, and a support region (second surface portion) where the silicon handle layer is retained for mechanical stability. This spatial segmentation resolves the contradiction between sensor performance and structural integrity.
Solution Approach 2:
The silicon handle layer presence is locally optimized: absent in regions requiring signal transmission and present in regions requiring structural support. This local quality approach allows the die to simultaneously achieve both high sensor efficiency and adequate mechanical strength.
3Ease of manufacture
If traditional mold compound encapsulation is used over the entire die surface, then the protection and packaging are simplified, but the optical/thermal signals are blocked from reaching the sensors
Solution Approach 1:
The mold compound encapsulation is segmented to exclude the first surface portion containing the sensors, creating a cavity that exposes the sensor region. The mold compound is applied only to the second surface portion and peripheral regions, providing protection while maintaining signal transmission pathways to the sensors.
Solution Approach 2:
The mold compound is extracted or omitted from the first surface portion area to create an open cavity that allows optical and thermal signals to reach the sensors without obstruction. This selective exclusion of mold compound from the sensor region resolves the conflict between encapsulation and signal transmission.
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 enhances the response speed and efficiency of optical/thermal sensors by eliminating signal attenuation, maintaining the advantages of flip-chip assembly while reducing package size and improving heat dissipation through high thermal conductivity mold compounds.
Implementation Method 1
the thick silicon handle layer will attenuate or obstruct light/thermal signals passing towards optical/thermal sensors
Implementation Method 2
the thick silicon handle layer will attenuate or obstruct light/thermal signals passing towards optical/thermal sensors
Implementation Method 3
improving heat dissipation through high thermal conductivity mold compounds
Data Source
AI summary
The present disclosure relates to a microelectronics package with optical sensors and/or thermal sensors. The disclosed microelectronics package includes a module substrate, a thinned flip-chip die with an upper surface that includes a first surface portion and a second surface portion surrounding the first surface portion, and a first mold compound component. The thinned flip-chip die is attached to the module substrate and includes a device layer with sensor structure integrated at a top portion of the device layer. Herein, the sensor structure is below the first surface portion and not below the second surface portion. The first mold compound component is formed over the second surface portion to define a first cavity over the upper surface of the thinned flip-chip die. The first mold compound component is not over the first surface portion, and the first surface portion is exposed at the bottom of the first cavity.