Substrateless Optical Sensor Packaging With LDS Vias and RDL
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Solution Overview
Problem
Conventional packaging configurations for optical integrated circuit sensor devices face issues such as cracks in the optical element and delamination due to thermal expansion mismatch, along with a large form factor, which affect the device's reliability and performance.
Innovation Solution
The use of laser direct structuring (LDS) encapsulating material with activated trace regions and conductive vias, combined with a redistribution layer (RDL), to create a more compact and stress-reduced packaging configuration that minimizes thermal expansion mismatch and optimizes electrical and optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional packaging configurations with support substrates and encapsulating materials are used, then electrical connections and device support are achieved, but thermal expansion mismatch causes cracks and delamination
Solution Approach 1:
The patent removes the support substrate from the packaging configuration, eliminating the source of thermal expansion mismatch. The optical sensor device is directly mounted on the carrier board with electrical connections achieved through conductive vias in the encapsulating material, rather than through a separate substrate that would create stress during thermal cycling.
Solution Approach 2:
The patent combines the encapsulating material with the electrical interconnection function by forming conductive vias directly through the encapsulating material. This merges the protective encapsulation function with the electrical connection function, eliminating the need for a separate substrate that would cause thermal stress.
2Ease of operation
If conventional packaging with bonding wires and substrates is used, then electrical connections are established, but the form factor becomes large
Solution Approach 1:
The patent replaces the mechanical bonding wire system with direct conductive vias through the encapsulating material. This substitution eliminates the need for wire bonds and associated routing space, significantly reducing the package footprint while maintaining electrical connection functionality.
Solution Approach 2:
The patent transitions electrical connections from a planar routing approach (through substrate traces) to a three-dimensional approach (vertical vias through the encapsulating material). This dimensional change allows for more compact packaging by utilizing the vertical dimension for electrical interconnections.
3Reliability
If spacer rings and underfill materials are used to protect the optical sensor, then optical sensor protection is achieved, but the package complexity and form factor increase
Solution Approach 1:
The patent combines the protective encapsulation function with the electrical interconnection function by forming conductive vias directly through the encapsulating material. This eliminates the need for separate spacer rings and underfill materials, reducing packaging complexity while maintaining optical sensor protection.
Solution Approach 2:
The patent removes the spacer ring and underfill material components from the packaging structure. The encapsulating material alone provides both mechanical protection and electrical connectivity through integrated conductive vias, simplifying the overall packaging structure.
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
The LDS encapsulation and RDL configuration reduces the form factor, minimizes stress, and enhances optical, electrical, and thermal performance, addressing the issues of cracks and delamination, and providing a more reliable and efficient packaging solution.
Implementation Method 1
a body of laser direct structuring (LDS) encapsulating material which encapsulates the integrated circuit device and the optical element
Data Source
AI summary
A body of laser direct structuring (LDS) encapsulating material encapsulates an integrated circuit device and an optical element mounted thereto. Laser activated trace regions and via openings at a first surface of the body are plated to form first conductive lines and first conductive vias. A first passivation layer covers the first conductive lines, the first surface of the body and a portion of the optical element. A second passivation layer covers a thinned backside of the body and integrated circuit device where distal ends of the first conductive vias are exposed. A redistribution layer (RDL) at the second passivation layer includes second conductive lines, pads, and second conductive vias which extend through the second passivation layer to electrically connect the second conductive lines to the distal ends of the first conductive vias. A solder mask layer on the second passivation layer includes openings at the pads of the RDL.