Proximity Sensor Packaging Using Sacrificial Studs for Channel Isolation
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Solution Overview
Problem
Existing proximity sensors face challenges in achieving precise measurements due to inadequate channel isolation between transmitters and receivers, requiring complex calibration and careful alignment, which can result in larger sensor packages when trying to combine them into a single package.
Innovation Solution
The use of sacrificial studs to prevent molding compound from encapsulating the transmitter and receiver, creating cavities that allow for improved channel isolation and precise placement, while enabling standard manufacturing processes and varied cavity sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the transmitter and receiver are placed in a single package to ensure fixed spatial relationship, then measurement precision is improved, but device complexity increases and package size increases
Solution Approach 1:
The single sensor package is segmented into two separate semiconductor dies: a first die containing the transmitter and a second die containing the receiver. This segmentation allows each component to be optimized independently while maintaining a fixed spatial relationship when mounted together on a circuit board, thus improving measurement precision without excessive complexity
Solution Approach 2:
Instead of integrating transmitter and receiver in the same planar package (2D approach), the invention moves to a three-dimensional arrangement where separate dies are mounted at different positions and orientations on a circuit board. This dimensional change allows precise spatial positioning while simplifying the packaging complexity
2Measurement precision
If the transmitter and receiver are placed in a single package to ensure fixed spatial relationship, then measurement precision is improved, but the package size increases
Solution Approach 1:
By separating the transmitter and receiver into different semiconductor dies, the invention allows for more efficient space utilization on the circuit board. Each die can be smaller and positioned optimally, reducing the overall package footprint compared to a monolithic single-package design
Solution Approach 2:
The transition from a single-plane package to a multi-die arrangement on a circuit board enables better spatial distribution and compactness, reducing the overall area occupied by the sensor system while maintaining precise relative positioning
3Ease of manufacture
If standard manufacturing processes are used instead of complex integration, then ease of manufacture is improved, but channel isolation may be insufficient
Solution Approach 1:
Sacrificial studs are attached to the circuit board before mounting the semiconductor dies. These studs create pre-formed isolation structures and cavities that ensure channel isolation is achieved during the manufacturing process itself, eliminating the need for post-assembly calibration or complex integration steps
Solution Approach 2:
The sacrificial studs act as intermediary elements during manufacturing. They are temporarily attached to define precise mounting locations and create isolation cavities, then removed after the dies are mounted. This intermediary approach enables standard manufacturing processes to achieve the isolation that would otherwise require complex integration techniques
Data Source
AI summary
A method of manufacturing a sensor device includes obtaining a semiconductor die structure comprising a transmitter and a receiver. Then, a first sacrificial stud is affixed to the transmitter and a second sacrificial stud is affixed to the receiver. The semiconductor die is affixed to a lead frame, and pads on the semiconductor die structure are wirebonded to the lead frame. The lead frame, the semiconductor die structure, and the wirebonds are encapsulated in a molding compound, while the tops of the first and second sacrificial studs are left exposed. The first and second sacrificial studs prevent the molding compound from encapsulating the transmitter and the receiver, and are removed to expose the transmitter in a first cavity and the receiver in a second cavity. In some examples, the semiconductor die structure includes a first semiconductor die comprising the transmitter and a second semiconductor die comprising the receiver.