Package-on-Package Proximity Sensor Module with IR Cut Filter
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Solution Overview
Problem
The challenge lies in manufacturing smaller, more complex proximity sensors with high production costs and reliability issues in a mass production environment, as existing sensors face difficulties in maintaining performance and reliability due to their increased complexity and size reduction.
Innovation Solution
A package-on-package proximity sensor module is developed, featuring an infrared transmitter and receiver package disposed on a half-etched lead frame, covered by an IR cut mold compound to minimize optical cross-talk and interference, and assembled using surface mount technology to reduce heat damage and manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If proximity sensors are made smaller to reduce package size, then the package size is reduced, but manufacturing complexity increases and production costs rise
Solution Approach 1:
The patent implements a package-on-package structure where the infrared receiver package is mounted directly on top of the infrared transmitter package, creating a nested vertical arrangement. This nesting approach allows both functional packages to be integrated within a compact footprint while maintaining their individual structural integrity and optical pathways, thereby reducing overall package size without significantly increasing manufacturing complexity
Solution Approach 2:
The patent transitions from a horizontal side-by-side arrangement of transmitter and receiver packages to a vertical stacked configuration. By utilizing the vertical dimension (Z-axis) instead of horizontal space, the design achieves compact footprint dimensions while keeping the manufacturing process relatively simple, as each package maintains its standard form factor and mounting procedures remain conventional
2Area of stationary object
If proximity sensors are made smaller to reduce footprint, then the footprint is reduced, but production costs increase due to manufacturing difficulties
Solution Approach 1:
By nesting the receiver package on the transmitter package in a vertical stack, the design achieves a small footprint while using standard surface mount technology for both packages. This approach avoids the need for custom miniaturized components, allowing manufacturers to use existing production lines and processes, thereby controlling production costs despite the reduced footprint
Solution Approach 2:
The package-on-package structure uses universal mounting techniques and standard component packages that can be produced using existing manufacturing infrastructure. The design leverages widely-available infrared LED and photodetector packages, maintaining compatibility with standard surface mount assembly processes, which keeps production costs manageable while achieving a compact footprint
3Ease of manufacture
If traditional assembly methods are used, then manufacturing is simpler, but heat damage occurs and reliability decreases
Solution Approach 1:
The patent replaces traditional mechanical assembly methods (such as through-hole mounting or high-temperature soldering) with surface mount technology. This substitution allows for lower-temperature, more controlled assembly processes that reduce thermal stress on the infrared LEDs and photodetectors, thereby improving reliability while maintaining ease of manufacture through automated surface mount assembly lines
4Volume of moving object
If packages are placed close together to reduce size, then package size is reduced, but optical cross-talk and interference increase
Solution Approach 1:
The patent extracts and removes the harmful optical cross-talk between transmitter and receiver packages by using an IR-cut filter layer positioned between the two packages. This filter selectively blocks infrared wavelengths that would cause cross-talk while allowing visible light to pass through, effectively eliminating the harmful optical interference that would otherwise occur in a compact stacked arrangement
Solution Approach 2:
The patent introduces an intermediary IR-cut filter layer and reflective surfaces between the infrared transmitter and receiver packages. This intermediary structure acts as an optical barrier that prevents direct infrared light from the transmitter from reaching the receiver, thereby eliminating cross-talk while maintaining the compact vertical stacking configuration and small overall package size
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 solution results in a lightweight, low-profile proximity sensor with reduced production costs and higher reliability, minimizing defects and simplifying the fabrication process while maintaining performance, even in bright environments.
Implementation Method 1
an infrared transmitter package (102), an infrared receiver package (104)
Implementation Method 2
covered by an IR cut mold compound to minimize optical cross-talk and interference
Data Source
AI summary
A package-on-package proximity sensor module including a infrared transmitter package and a infrared receiver package is presented. The proximity sensor module may include a fully-assembled infrared transmitter package and a fully-assembled infrared receiver package disposed on a quad flat pack no-lead (QFN) lead frame molded with an IR cut compound housing. A bottom surface of the QFN lead frame may be etched and covered with the IR cut compound to provide a locking feature between the QFN lead frame and the IR cut compound housing.